identifier: Bastola, Binod  (2018). Optical spectroscopy investigation of fiber optic high temperature sensors.  Thèse.  Québec, Université du Québec, Institut national de la recherche scientifique, Doctorat en sciences de l'énergie et des matériaux, 139 p.

subject: Énergie et matériaux

abstract:
Optical fibers have become an integral part of our daily life in a variety of applications,
most notably in telecommunications and non-invasive medical diagnostics.
Derived products, including fiber Bragg gratings (FBGs) extend the field of applications
to e.g. temperature and strain sensors that are already beyond the laboratory
proof-of-concept level and that hold the promise to transform many areas
of industries in an ever increasing number of applications in aerospace, structural
integrity monitoring as well as in-site sensing in turbines and reactors. Especially
the latter represent a harsh environment which makes the use of electronic sensors
either completely impossible or which implies short service intervals. Often these
industries employ optical techniques to conduct measurement in the optical fibers
themselves, e.g. based on evanescent fields but only a few fiber-based techniques
allow for distributed multiplexed sensing. The idea is to operate different sensors
along the length of the fiber at different wavelengths, a concept that also capitalizes
on the fact that most optical sensors are passive so that the fiber only carries the
signal rather than the power supply. The aforementioned points translate into the
many advantages of fiber based sensors: reliability, good sensitivity, multiplexing,
and low maintenance costs so that in many industries, the technology is now already
seen as a worthwhile alternative to established electronic sensors. Optical fibers are
immune to electromagnetic field (EMI), compact and can be functionalized. This
collaborative dissertation with an industrial partner specialized in developing practical,
end–user–focused commercial sensor solutions, is based largely on fiber optic
sensing. While the overall project dealt with glass fiber and Fiber Bragg Gratings
(FBG) for temperature sensing at elevated temperature and in otherwise harsh environment,
the focus of my work is on the physics and material science of FBGs at
elevated temperatures.
As typical application example, the atmospheric re–entry, of space vessels exposes
materials to extreme thermal conditions under the influence of hypersonic velocity,
which lead to critically high temperatures that might affect the structural integrity
and thus the operational safety. These temperatures must therefore be monitored
at a high repetition rate with sufficient precision to provide real time feedback to
the crew. The reason of choosing optical fiber technology is not only because of
fibers being themselves relatively inert but also because they are the ideal choice for
long–term monitoring with embedding capability in composite structures. So, the
thesis primarily addresses the capability of FBG to track temperatures, a property
readily known and thoroughly investigated as such at low and moderate temperatures
but which holds a couple of surprises and challenges for temperatures above
300 °C.
Fiber Bragg gratings are periodic refractive index modulations in the core of a fiber
for which the Bragg condition is met at a specific wavelength referred to as the
Bragg wavelength. This wavelength is reflected and contains information about the
grating. The length of this periodic structure is typically a few millimeters while
the distance between two maxima of the refractive index modulation is in the range
of 500 nm for an FBG matching the C-band of telecom. The permanent change
in the physical characteristics with a spatial periodic modulation of the core index
of refraction is most commonly created through transversely exposing the fiber
core with a UV–beam and using a phase mask to generate an interference pattern
of UV–optical field. The temperature sensitivity of the Bragg wavelength depends
on the periodicity of the grating and on the effective refractive index of the fiber
core. The dominant contribution to this stems from the temperature dependence
of refractive index (thermo–optic effect) as compared to the thermal expansion of
silica. At high temperatures, the FBG is however unstable which leads to a loss in
reflectivity to the point that the signal becomes undetectable.
For specific conditions during the post-fabrication process of the FBG, the reflectivity
recovers after a certain time providing what is referred to as a regenerated
FBG. These regenerated FBGs have a much better temperature stability but suffer
from a substantially reduced reflectivity, typically in the range of 10 –15% of
the initial value. While this regeneration process is now widely used, it still lacks
fundamental understanding, in particular as the description of FBGs so far relies
on a single grating that, once it has been erased, should not regenerate. The fundamental
understanding of the regeneration process is furthermore complicated by
the complexity of glass as a material system so that e.g., chemical compositions,
stress relaxation phenomena, densification etc. are barely understood and models
of the underlying mechanisms are still in their infancy. Therefore, in this thesis, I
aim at correlating temperature dependent a) FBG parameters with b)in situ Raman
spectroscopy and c) photoluminescence data to characterize the optical fibers and
FBGs and the way fiber parameters (e.g., hydrogen loading, relaxation of the glass, fiber dopants and stresses) mitigate or impact the FBG regeneration process has
been investigated.
In the macroscopic study, an Erbium (Er) broadband source between 1530 –1565nm
is coupled to an optical spectrum analyzer (OSA) through different fibers containing
FBGs and their sensing capacities were investigated by monitoring wavelength
shifts with changes in temperature. Annealing behavior of gratings in standard
telecom grade fibers were investigated with a dedicated setup that allowed for temperature
cycles below 1000 °C. The linear temperature response is influenced upon
heating to 900 °C and subsequent cooling of FBGs back to ambient temperature and
the observed temperature sensitivity is determined to be approximately 13 pm/K.
The calibration curves are obtained to test the characteristics of RFBGs. This was
done through a dedicated program in MATLAB to automatically extract all relevant
experimental parameters from a time– and temperature–dependent sequence of
spectra and led to a new methodology to enhance the recovered reflectivity of FBGs
through regeneration between 700 –1000°C, exceeding the state of the art by over
400 %. The objectives of this work are thus to provide a better understanding of
the regeneration mechanism from a phenomenological and microscopic perspective
as well as suggestions on how to enhance the performance of regenerated FBGs.
Regarding the methodology, the observation of the key parameters of FBGs was
accomplished in collaboration with our industrial partner. I developed a dedicated
Matlab code to improve the precision with which critical parameters could be extracted
from the large amount of data which allowed me to systematically investigate
the peak width that provides a direct handle on the core refractive index modulation.
Still, the fundamental question remained about the mechanism of regeneration or in
other words, what provides the memory to generate a new grating after the initial
one was erased. I address this challenge through the introduction of a second grating
that coexists from the very beginning and which is of opposite phase to the first
while having a stronger thermal stability. All qualitative observations are covered
through this simple model. With respect to the microscopic identification, Raman
spectroscopy allowed me to identify fluorine as an undocumented component of the
core in GF1B fibers. A comprehensive description of the glass composition, as it
would be required to establish a complete microscopic model, is however still out of
reach. In order to push for additional indicators at the microscopic level, I exploited
the temperature dependence of a strong visible luminescence from the FBG under
excitation of a blue cw laser and report on reversible and irreversible contributions
of this luminescence. The two-grating model paves the way towards regeneration efficiencies above 100 %,
an exciting perspective worth exploring further. As far as the spectroscopic investigation
of the microstructure is concerned, two principle directions should be
followed in the near future: for one, it is worthwhile investigating if any of the
already observable properties (Raman signature and luminescence) correlates with
the regeneration process of FBGs and for the other, it should be possible to extract
thermal activation energies for these processes as a fingerprint of defects that can
then be compared with independent studies in other fibers and by other experimental
techniques.


identifier: Ben Smida, Oussama  (2017). Formation de voie collaborative distribuée robuste pour les futurs réseaux sans fil.  Mémoire.  Québec, Université du Québec, Institut national de la recherche scientifique, Maîtrise en télécommunications, 60 p.

type:
Thèse
Non évalué par les pairs

subject: coloborative beamforming distribué (DCB)

subject: erreurs de phase

subject: erreurs de localisation

subject: diffusion

subject: loi des grands nombres

abstract:
Dans ce travail, on propose une nouvelle technique de formation de voies collaborative (ou collaborative
beamforming (CB)) robuste contre toutes formes d’erreurs d’estimation.
Le premier chapitre introduit le concept de CB, explique son fonctionnement et étudie les propriétés
de son diagramme de rayonnement. Il est démontré que les erreurs d’estimation du canal peuvent
déteriorer significativement les performances du CB. Le deuxième chapitre propose alors une nouvelle
technique CB robuste non seulement contre ces erreurs mais aussi contre le phénomène de
diffusion présent dans presque tous les environnements de propagation. Il est aussi démontré que
son implementation ne nécessite aucun échange entre les terminaux indépendants, se conformant
ainsi à la nature distribuée des réseaux considérés.
L’efficacité du CB distribué (DCB) proposée est vérifiée et ses performances sont comparées avec
d’autres techniques. Il est démontré que notre solution est capable de compenser toute dégradation
causée par les erreurs d’estimation et la diffusion. Tout ces résultats obtenus sont vérifiés enfin par
simulation dans le dernier chapitre.


identifier: Bizan, Mohamed Sedigh  (2018). Ultra wideband stacked rectangular dielectric resonator antenna.  Mémoire.  Québec, Université du Québec, Institut national de la recherche scientifique, Maîtrise en télécommunications, 95 p.

subject: Télécommunications

abstract:
This thesis is a presentation of a design and fabrication of ultra-wideband
stacked rectangular dielectric resonator antenna (UWB-RDRA), where the effect of
position perturbations on the bandwidth of an aperture coupled dielectric resonator
antenna (DRA) is studied. The proposed antenna takes advantage of two low-Q modes
which have overlapping bandwidths so as to achieve an ultra-wideband operation. This
can be achieved by using two combinations of stacked DRAs for the analysis: larger
over smaller (LOS), and smaller over larger (SOL). Different position perturbations on
the transmission line (TL), LOS, and SOL are applied to widen the matching bandwidth
of the antenna.
The performance of the proposed antenna is compared with the conventional
antenna designed with no perturbations. The proposed antenna not only provides 5:1
ultra-wide matching bandwidth (from 2.7 GHz to 13.6 GHz), but also results in the
highest gain of 9 dBi, which is 2 dBi more than the antenna designed with conventional
method with no perturbation. The proposed antenna, therefore, consists of the dielectric
constant of 6.15 and 9.8 that are stacked vertically in order to acquire a bandwidth that
is more improved as compared to the conventional RDRA. A use of 50 Ω microstrip line
is required in the proposed antenna to act as a feeding mechanism. The physical
parameters of stacked RDRA are also optimized by extensive simulations using
Computer Simulation Technology (CST) software.
The parameters of this antenna are 65x50x5 mm³ and its grounded substrate
size is 108x90 mm². The prototype is fabricated and measured. The measured results
and simulated results show a good agreement. This prototype antenna is designed to
cover the band from 2.7 GHz to 13.6 GHz. This proposed antenna is therefore suitable
for wireless (Wi-MAX) and (WLAN) application bands.


identifier: Cassani Gonzalez, Raymundo  (2018). Towards an Automated Portable Electroencephalography-based System for Alzheimer’s Disease Diagnosis.  Thèse.  Québec, Université du Québec, Institut national de la recherche scientifique, Doctorat en télécommunications, 197 p.

subject:
maladie d’Alzheimer
électroencéphalographie
état de repos
modulation d’amplitude
manipulation automatisée des artefacts
EEG portable
Alzheimer’s disease
electroencephalography
resting-state
amplitude modulation
automated
artifact handing
portable EEG
enfermedad de Alzheimer
electroencefalografía
estado de reposo
modulación de amplitud
manipulación automática de artefactos
EEG portátil

abstract:
La maladie d’Alzheimer (MA) est une maladie neurodégénérative terminale qui représente près de 70%
des cas de démence. L’incidence mondiale de la démence devrait atteindre 75 millions d’individus d’ici 2030,
dont la majorité des personnes atteintes viendraient de pays à revenus faibles ou moyens. Bien qu’il n’y ait
pas de traitement curatif pour la MA, un diagnostic précoce peut améliorer la qualité de vie des patients
atteints de la MA et de leurs soignants. Actuellement, le diagnostic de la MA est effectué à l’aide de tests
d’évaluation de l’état mental, d’examens de neuroimagerie coûteux et de tests de laboratoire invasifs, ce qui
rend le diagnostic long et onéreux. Toutefois, l’électroencéphalographie (EEG), en particulier l’EEG à l’état
de repos (rsEEG), est apparue au cours de la dernière décennie comme une technique alternative pour le
diagnostic de la MA offrant des précisions comparables à celles d’outils de neuroimagerie plus coûteux, tels la
tomodensitométrie et la tomographie par émission de positrons. Cependant, l’utilisation de la rsEEG pour le
diagnostic de la MA présente deux inconvénients majeurs: (i) la dépendance à des segments «sans artefacts»,
sélectionnés manuellement et méticuleusement par des cliniciens experts, et (ii) le besoin d’appareils EEG
de qualité médicale et convenant à la recherche comportant souvent plus de 16 électrodes, ce qui les rend
difficiles à transporter et coûteux, en particulier pour les pays à revenus faibles ou intermédiaires. Dans cette
thèse de doctorat, nous présentons les étapes vers le développement d’un système automatisé basé sur la
rsEEG portable et peu coûteux pour le diagnostic de la maladie d’Alzheimer. Pour atteindre cet objectif,
trois innovations principales ont été développées.
Premièrement, nous avons exploré les effets de plusieurs méthodes de manipulation automatisée des
artefacts (MAA) sur les signaux rsEEG et nous avons étudié leurs avantages et désavantages pour le diagnostic
automatisé de la MA. Les résultats de cette exploration ont montré que le diagnostic de la MA basé sur les
signaux rsEEG améliorés par les méthodes de MAA est comparable à la performance obtenue avec les données
EEG «sans artefact», suggérant que l’intervention humaine experte et l’élimination des segments d’EEG (dûes
aux artefacts) peuvent être évités. Deuxièmement, nous avons évalué et comparé l’utilisation de dispositifs
EEG à densité basse (7 canaux) pour les protocoles expérimentaux à yeux ouverts et à yeux fermés en rsEEG
pour le diagnostic de la MA. Leur performance a été comparée à celle d’un système à densité moyenne (20
canaux), qui était en général considérablement plus élevée que les configurations à densité basse. Enfin, nous
avons montré que les traits caractéristiques conventionnels proposés dans la littérature ne sont pas seulement
sensibles aux artefacts, mais reposent sur des informations extraites de bandes de fréquences EEG qui ne
sont pas optimales pour le diagnostic de la MA. De ce fait, nous avons proposé un nouvel ensemble de traits
caractéristiques basé sur l’approche par spectrogramme de modulation. Les expériences ont montré que les
traits caractéristiques proposés étaient robustes aux artefacts, évitant ainsi le recours aux algorithmes de
MAA, tout en fournissant des informations plus précises pour le diagnostic de la MA, et potentiellement
pour la surveillance de la progression de la maladie. Ces nouveaux avantages sont inestimables pour le
développement d’appareils portables à bas coût et il est à espérer que les idées présentées ici pourront être
utilisées pour améliorer la qualité de vie des personnes atteintes de la MA, de leurs familles et de leurs
soignants.

 Alzheimer’s disease (AD) is a neurodegenerative terminal disorder that accounts for nearly 70% of dementia
cases worldwide. Global dementia incidence is projected to 75 million cases by 2030, with the majority of
the affected individuals coming from low- and medium- income countries. Although there is no cure for AD,
early diagnosis can improve the quality of life of AD patients and their caregivers. Currently, AD diagnosis is
carried out using mental status examinations, expensive neuroimaging scans, and invasive laboratory tests,
all of which render the diagnosis time-consuming and costly. Notwithstanding, over the last decade electroencephalography
(EEG), specifically resting-state EEG (rsEEG), has emerged as an alternative technique
for AD diagnosis with accuracies inline with those obtained with more expensive neuroimaging tools, such as
magnetic resonance imaging (MRI), computed tomography (CT) and positron emission tomography (PET).
However the use of rsEEG for AD diagnosis presents two major disadvantages: (i) the reliance on“artifactfree’’
segments, which are manually and meticulously selected by expert clinicians, and (ii) the need for
research- and medical-grade EEG devices often with 16+ electrodes, thus making them hard to transport
and expensive to fund, specially for low- and middle-income countries. In this doctoral thesis, we present the
steps towards the development of an automated portable and low-cost rsEEG-based system for AD diagnosis.
To achieve this goal, three main innovations have been developed.
First, we explored the effects of several fully automated artifact handling (AAH) methods on rsEEG
signals and reported their advantages and disadvantages for automated AD diagnosis. The outcome of this
exploration showed the AD diagnosis based on AAH-enhanced rsEEG signals is inline with the performance
obtained with “artifact-free” EEG data, suggesting that expert human intervention and the discard of EEG
data (due to artifacts) can be avoided. Secondly, we evaluated and compared the use of lower-density
(7-channel) EEG devices for rsEEG eyes-open and eyes-closed experimental protocols for AD diagnosis.
By comparing the diagnosis performance obtained with the low-density EEG devices to the one obtained
with a typical medium-density (20-channel) system, we found that the reduction of channels diminishes
the classification performance. Lastly, we showed that conventional features proposed in the literature are
not only sensitive to artifacts, but rely on information extracted from EEG frequency subbands that are
suboptimal for AD diagnosis. As such, we proposed a new set of features based on the modulation spectrogram
approach. Experiments showed the proposed features being robust to artifacts, thus bypassing the need for
AAH algorithms, as well as providing more discriminatory information not only for AD diagnosis, but also for
disease progression monitoring. These new benefits are invaluable for the development of low-cost portable
devices and it is hoped that the insights presented herein can be used to improve the quality-of-life of
individuals living with AD, their families, and caregivers.

 La enfermedad de Alzheimer (EA) es una enfermedad terminal neurodegenerativo que representa casi el
70% de los casos de demencia en todo el mundo. La incidencia de demencia global se calcula en 75 millones
de casos para el año 2030, con la mayoría de las personas afectadas provenientes de países de bajo y medio
ingreso. Aunque no existe una cura para la EA, un diagnóstico temprano puede mejorar la calidad de vida
de los pacientes con Alzheimer y las personas que los cuidan. Actualmente, el diagnóstico de la EA se lleva
a cabo mediante exámenes de estado mental, estudios costosos de neuroimagen y pruebas de laboratorio
que son invasivas, todo lo anterior hace que el diagnóstico lleve mucho tiempo y sea costoso. No obstante,
en la última década la electroencefalografía (EEG), específicamente el EEG en reposo (rsEEG), ha sido
considerada como una técnica alternativa para el diagnóstico de la EA con la cual se pueden obtener una
exactitud similar a las obtenidas con técnicas de neuroimagen más costosas, como la resonancia magnética
(MRI), tomografía computarizada (TC) y tomografía por emisión de positrones (PET). Sin embargo, el uso
de rsEEG para el diagnóstico de la EA presenta dos desventajas principales: (i) la dependencia en segmentos
“sin artefactos”, que son seleccionados manual y meticulosamente por médicos expertos y (ii) la necesidad
de dispositivos EEG de grado médico y de investigación, a menudo con más de 16 electrodos, aspecto que los
hace difíciles de transportar y costosos de financiar, especialmente para los países de bajo y mediano ingreso.
En esta tesis doctoral, presentamos los pasos hacia el desarrollo de un sistema automatizado portátil y de
bajo costo basado en rsEEG para el diagnóstico de la EA. Para alcanzar este objetivo, se han desarrollado
tres principales innovaciones.
Primero, exploramos los efectos de varios métodos de manipulación (totalmente) automatizada de artefactos
(MAA) en las señales de rsEEG y reportamos sus ventajas y desventajas de su uso en el diagnóstico
automático de la EA. El resultado de esta exploración mostró que el diagnóstico de EA basado en señales de
rsEEG mejoradas con MMA está en línea con el rendimiento obtenido con datos de EEG “sin artefactos”, lo
cual sugiere que se pueden evitar la intervención de humanos expertos y el desecho de señales de EEG (con
artefactos). En segundo lugar, evaluamos y comparamos el uso de dispositivos de EEG de baja densidad (7
canales) para los protocolos experimentales de ojos abiertos y ojos cerrados en rsEEG para el diagnóstico de
la EA. Su desempeño se comparó con el de un sistema típico de densidad media (20 canales). Por último,
demostramos que las características convencionales de EEG propuestas en la literatura no solo son sensibles
a artefactos, sino que, se basan en información extraída de subbandas de frecuencia de EEG que son subóptimas
para el diagnóstico de la EA. Como tal, propusimos un nuevo conjunto de características de EEG
basadas en la técnica del espectrograma de modulación. Los experimentos mostraron que las características
propuestas son robustas a artefactos, evitando así la necesidad de algoritmos de MAA, también proporcionan
información más discriminatoria no solo para el diagnóstico de la EA, sino también para el monitoreo de la
progresión de la enfermedad. Estos nuevos beneficios son invaluables para el desarrollo de dispositivos EEG
portátiles de bajo costo y se espera que las ideas presentadas en esta tesis puedan ser utilizadas para mejorar
la calidad de vida de las personas afectadas por la EA, sus familias y cuidadores.


identifier: Chowdhury, Mahfuzulhoq  (2018). Human-agent-robot teamwork coordination in FiWi based tactile internet infrastructures.  Thèse.  Québec, Université du Québec, Institut national de la recherche scientifique, Doctorat en télécommunications, 232 p.

subject: caching

subject: cloud computing

subject: computation offloading

subject: collaborative computing

subject: delay cost saving

subject: dynamic bandwidth allocation (DBA)

subject: energy efficiency

subject: failure avoidance

subject: fiber-wireless (FIWI) enhanced networks

subject: human-agent-robot teamwork (HART)

subject: human-to-robot communication (H2R)

subject: human-machine co-activity

subject: internet-of-things (IoT)

subject: mobile-edge computing (MEC)

subject: monetary cost saving

subject: tactile internet

subject: task and resource scheduling

subject: and task migration

abstract:
The demands of increasingly latency-sensitive applications create challenges for pervasive mobile
devices/robots to execute the involved computation-intensive tasks in a resource-efficient
manner. Cooperative human-agent-robot teamwork (HART) holds promise to serve as a powerful
paradigm to tackle the challenges of real-time task execution of mobile devices/robots.
Integrated fiber-wireless (FiWi) enhanced networks play a pivotal role in ensuring qualityof-
service (QoS) for several HART-centric applications due to their coverage and capacity
advantages. In this work, integrated FiWi access networks consist of optical fiber (Ethernet
passive optical network or EPON) and wireless (wireless local area network or WLAN) Ethernet
technologies, which are integrated with their cellular counterparts, namely, 4G Long Term
Evolution Advanced (LTE-A), to give rise to FiWi enhanced LTE-A heterogeneous networks
(HetNets).
To unleash the full potential of HART task coordination over FiWi enhanced 4G networks,
this thesis first provides a detailed study of recent progress, enabling technologies, and briefly
describes important open research challenges. To render the human-to-robot task allocation
process more efficient, this thesis presents a local and non-local human-to-robot task allocation
scheme for FiWi-based infrastructures according to several key design parameters such as the
availability, skill set, distance to task location, minimum task processing time, and remaining
energy of robots. To reduce failures during task execution, a neighboring robot assisted
failure reporting mechanism is also proposed. Our obtained results show that, compared with
traditional priority-based schemes, a task execution time efficiency of 18% can be achieved in
our proposed local and non-local human-to-robot task allocation scheme.
Due to limited computing, energy, and storage resources, robots can not always meet the
task execution time and energy consumption requirements of many delay-sensitive applications.
To improve the energy efficiency of the selected host robot while satisfying a given
task deadline, this thesis presents a collaborative task execution scheme, in which the sensing
sub-task is conducted by a suitable host robot and the computation sub-task is offloaded onto
one of the suitable collaborative nodes consisting of central cloud, cloudlets, and neighboring
robots. The presented results demonstrate that for a typical task input size of 240 KB, the
collaborative task execution scheme decreases the task response time by up to 8.75% and the energy consumption by up to 14.98% compared to the only host robot based non-collaborative
task execution scheme.
Taking the idea of task offloading a step further, task migration among mobile HART members
has emerged as an important research topic to improve the quality of experience (QoE)
of mobile users (MUs) by minimizing their task execution time. Task migration broadens the
scope of conventional computation task offloading by not only transferring the task from an
MU onto the cloud, but also from one cloud server to another one for execution. Note, however,
that task migration incurs an additional migration delay. Hence, for a given task migration
gain and latency overhead, the question of how and where an MU's task should migrate to is
key. After describing the key features of physical vs. cognitive tasks and collaborative robot
(cobot) vs. stand-alone robot types, this thesis next investigates the problem of whether and,
if so, when and where a HART-centric task should be best migrated to. For resource-efficient
task execution, a context-aware task migration scheme is presented, in which the suitable
task migration decision is made by taking into account given task processing capabilities of
cloud/cloudlet agents and cobots, task execution deadline, user mobility, energy consumption
of involved collaborative robots (cobots) and mobile devices, and task migration latency. Our
obtained results show that for a typical task input data size of 600 MB, the cobot-to-agent
(c2a) task migration (cloudlet near task location) scheme exhibits up to 20% task response
time and 23% energy efficiency improvements over the traditional task execution without migration
scheme. The results also indicate that in the case of an agent node failure, intra-agent
task migration offers a higher task response time gain than inter-agent migration.
Furthermore, to improve QoS for executing multiple HART tasks, the development of
real-time task scheduling mechanisms has emerged as an interesting research issue by taking
different real-time HART task properties, failure avoidance, and task processing capabilities
into account. Thus, to improve the HART task execution process, this thesis next presents a
community- and latency-aware HART task assignment scheme by using real-time information
about arriving task requests for both isolated and clustered robots/agents. More specifically,
a suitable multi-task scheduling scheme is presented for task on- and offloading based HART
task execution with task prefetching and fault tolerance capabilities. To reap the benefits from
task prefetching for executing multiple HART tasks, this thesis develops a novel prefetchingaware
bandwidth allocation scheme that copes with both conventional broadband and task
offloading data traffic at the same time. Next, a comprehensive analytical model is presented
to investigate the performance of our proposed community- and latency-aware task offloading
scheme in terms of mean task service time, delay and power saving ratio, task prefetching
time efficiency, task service time gain to overhead ratio, among others. Our obtained results show that for a typical system of 32 integrated optical network unit-mesh portal points (ONUMPPs)
and a polling cycle time of 100 ms, our proposed task offloading scheme achieves up
to 31.3% and 32.7% task completion time gain over the task onloading scheme for nearby
and remote task execution, respectively. The results demonstrate that for a typical task
offload input data size of 500 MB, our proposed community- and latency-aware task offloading
scheme with task prefetching capability offers a 11% higher task service time gain to overhead
ratio than a conventional fetching based scheme. Our findings also suggest that for failure
avoidance, the proposed fault tolerance mechanism is more effective in the considered task
offloading scheme than the alternative failure recovery mechanism.
Given human users' different preferences for real-time HART task execution, e.g., lower
delay and monetary cost, suitable HART task coordination has emerged as an important research
problem, taking dynamically changing cloud agent/robot resources, network bandwidth
utilization as well as delay-sensitive and delay-tolerant HART task properties into account.
To cope with these challenges, this thesis explores the synergy between caching, computation,
and communications for achieving cost-effective HART task execution. More precisely, to
minimize task execution delay and monetary cost, this thesis presents a user preference-aware
HART task coordination framework that selects the appropriate dedicated or non-dedicated
robot and cloud agent for given caching and computing HART task execution requirements.
To cope with varying bandwidth resources, this thesis proposes a proactive bandwidth allocation
policy for the execution of both delay-sensitive and delay-tolerant HART tasks. To
minimize the task execution delay of delay-sensitive users, our proposed delay cost saving
(DCS) based scheme selects suitable actors by using both dedicated and non-dedicated actors.
Conversely, to minimize the monetary cost for delay-tolerant policy users, our proposed
monetary cost saving (MCS) scheme selects appropriate actors only from the set of dedicated
actors. Furthermore, this thesis also presents a proactive bandwidth allocation scheme that
assigns preemptive and non-preemptive bandwidth resources to DCS and MCS policy users,
respectively. Unlike alternative approaches, our findings indicate that the maximum throughput
and minimum delay (MTMD) based resource assignment policy is useful for both DCS and
MCS policy users due to its minimum task execution time and monetary cost. Our obtained
results show that for a typical number of 10 tasks and 8 available dedicated robots, the DCS
(MTMD) policy exhibits a 30.5% higher task execution time saving ratio and a 63.6% lower
monetary cost saving ratio than the MCS (MTMD) policy. Our proposed user preference
aware HART task coordination policy thus represents a promising solution to reduce both
task execution delay and monetary cost for emerging Tactile Internet applications.


identifier: Dab, Chahinez  (2018). Amplification du champ proche par résonance plasmonique pour la spectroscopie Raman et la photocatalyse.  Thèse.  Québec, Université du Québec, Institut national de la recherche scientifique, Doctorat en sciences de l'énergie et des matériaux, 165 p.

subject:
nanostructures plasmoniques
réaction photocatalytique
F-TERS
points chauds

abstract: La spectroscopie Raman exaltée par effet de pointe (TERS) combine la haute résolution produite par la spectroscopie à force atomique (AFM) et l’étude des modes de vibration produites par la spectroscopie Raman. Il s’agit d’une technique à haute sensibilité qui permet la détection des molécules à très faibles concentrations et de fournir une riche information sur la structure ainsi que sur la composition chimique. En tant que technique polyvalente il y’a presque 40 ans de recherches, TERS peut non seulement répondre à des questions scientifiques fondamentales, mais aussi de résoudre des problèmes d'ingénierie dans de nombreuses applications. Cependant, dans tous les cas, le substrat plasmonique présente le composant le plus critique dans ce domaine. La détection de TERS est fortement dépendante du substrat, où l'excitation des plasmons de surface localisés (LSP) augmente les signaux de diffusion Raman des molécules à proximité de la surface étudiée. Dans cette thèse, nous avons d'abord utilisé la spectroscopie Raman exaltée par effet de surface (SERS) pour étudier la surface plasmonique qui est composée de différentes formes de nanostructures plasmoniques. Nous avons discuté l’ordre de grandeur de l’exaltation du champ électromagnétique et le décalage de la résonance dans des matériaux plasmoniques de base, tels que les nanoparticules métalliques, les nanobâtons, les nanotriangles préparés par des procédés de synthèse lithographiques. La corrélation entre les points chauds qui apparaissent entre les nanoparticules plasmoniques et les sites catalytiques a présenté toujours un débat dans la communauté scientifique. Comme solution, nous avons développé une technique avancée de TERS nommé Spectroscopie Raman exaltée par effet de pointe fonctionnalisée (F-TERS). Nous avons ainsi examiné expérimentalement des nanostructures plasmoniques avec des pointes en or fonctionnalisées avec des molécules de 4-nitrothiophénol active en Raman pour fournir une exaltation du champ intense en TERS. Nous avons discuté après des progrès de recherche de la cartographie chimique des nanostructures plasmoniques présentant des réactions photocatalytiques à leur surface. Nous avons trouvé une bonne corrélation entre les points chauds des nanostructures plasmoniques qui sont dues à l’effet de l’exaltation du champ électromagnétique par effet de surface et leur capacité photocatalytique.


identifier: Delegan, Nazar  (2018). The in-situ doping of sputtered titanium dioxide thin-films for their efficient visible light sensitization and use for the electro-photocatalytic degradation of pollutants in water.  Thèse.  Québec, Université du Québec, Institut national de la recherche scientifique, Doctorat en sciences de l'énergie et des matériaux, 274 p.

subject:
RF-magnetron sputtering
in-situ doping
nitrogen and tungsten codoping
TiO2:WN
photoanodes
bandgap narrowing
electronic acceptor-donor passivation
sunlight driven electrophotocatalysis
pollutant degradation

abstract:
The symbols and special characters used in the original abstract could not be transcribed due
to technical problems. Please use the PDF version to read the abstract.The purpose of this work is to develop photoactive TiO2 films for the electro-photocatalytic degradation
of water pollutants under sunlight. Radio frequency magnetron sputtering (RF-MS) was
used to synthesize in-situ N-doped TiO2:N films in order to shift their photoactivity from the UV
to visible light domain. Careful tuning of the nitrogen-to-argon mass flow rates during sputterdeposition
allowed the growth of TiO2:N films with a wide range of N-dopant contents ranging from
0 at.% to 13 at.%. These studies indicated that most of the N-doping atoms were in the desired
substitutional states (i.e. NO). UV-Vis absorption and spectroscopic ellipsometry measurements
were used to quantify the bandgap (Eg) variation of the TiO2:N thin films as a function of their N
content. This was used to point out the existence of an optimal nitrogen loading level that reduces
the bandgap from 3.2 eV for TiO2 to 2.2 eV for ~3.5 at.% nitrogen doped TiO2:N. This gain in
visible-light photosensitivity was assessed for the 1.5AM light driven electro-photocatalytic (EPC)
degradation of an emerging pollutant, chlortetracycline (CTC). Thus, TiO2:N photoanodes have
been shown to achieve CTC degradation efficiencies of up to 98% (within 2 h treatments under
simulated solar light). Moreover, the EPC performance of the TiO2:N was shown to be directly correlated
to their optoelectronic properties, sharing a common optimal point between Eg shrinkage and
EPC degradation efficiency. However, a more exhaustive analysis revealed that the increase in EPC
performance was disproportional with the photosensitization, with many photogenerated charges
seemingly lost. Further studies revealed that nitrogen doping was synonymous with the formation of
oxygen vacancy (VO) defects that can reduce the per-photon efficiency of the material by acting as
charge recombination centers. In order to circumvent this limitation, tungsten doped TiO2:W thin
films were developed, as they were theoretically proposed to increase VO defect formation energy.
To this end, RF-MS deposition was used to fabricate undoped TiO2, oxygen deficient (TiO2–x),
and tungsten doped (TiO2:W) films with varying dopant levels. The compositional analysis of the
W-dopant bonding states revealed the presence of substitutional WVI (W00
Ti) and WIV (W×
Ti) type
dopants with the total concentration in from 0 at.% to 10 at.%. Additionally, XPS studies revealed a
significant recovery of oxygen stoichiometry upon small W incorporations. On the other hand, high
frequency spectroscopy measurements (HF-DS) confirmed an optimal tungsten doping of ~2.5 at.%
associated with the lowest ε' contribution from the 2 TiIII V00
O defect pair (two orders of magnitude
reduction of the VO dielectric contribution as compared to TiO2–x). Consequently, this reduction
in VO was exploited by integrating the optimally doped TiO2:W films as photoanodes in visiblelight-
driven electro-photocatalytic degradation of atrazine (ATZ), another emerging pollutant. The
pseudo-first order degradation kinetic constants were shown to increase from 0.027 min−1 for TiO2
and VO-doped TiO2–x to 0.053 min−1 for the optimally doped TiO2:W photoanodes as a direct result
of the reduction in VO. Interestingly, it was revealed that optimally doped TiO2:W photoanodes
performed on par with the visible-light photosensitized TiO2:N ones. This confirmed that while
TiO2:N had higher EPC performance due to an increased amount of usable photons, TiO2:W had
better photocharge transport properties, resulting in higher relative per-photon efficiency. In light of these results, and guided by theoretical models, RF-MS was used to synthesize acceptor-donor
passivated, in-situ WN-codoped TiO2:WN thin films. Thus, by varying the reactive RF-MS deposition
parameters, we were able to tune the in-situ incorporation of both N and W dopants in the
TiO2:WN films over a wide concentration range. The objective of the co-doping was twofold: (i)
narrow the bandgap of the TiO2:WN films through N-doping to extend their photosensitivity as far
as possible in the visible, and (ii) passivate the N-doping induced VO defect centers through appropriate
WN-codoping. Systematic analysis by means of XPS and XRD techniques revealed that both
W and N dopants were mostly of substitutional nature. Nitrogen doping was found to be the key
component in narrowing the optical-band-gap down to 2.3 eV for both TiO2:N & TiO2:WN. Most
importantly, XPS analysis hinted that the codoping approach greatly reduced the density of VO in
the TiO2:WN films as compared to TiO2:N ones. This reduction in defects translated into improved
crystalline structure, and increased dopant solubility. The suppression of VO via the acceptor-donor
passivating approach was directly confirmed by HF-DS measurements showing a marked reduction
in the density of 2 TiIII V00
O defect pairs with the codoping of tungsten and nitrogen as compared
to N-monodoped samples. This defect reduction was shown to increase photocharge characteristic
lifetimes using visible light flash photolysis time-resolved microwave conductivity measurements
(FP-TRMC). Photocharge lifetime analysis indicated the presence of three distinct decay processes:
charge trapping, recombination, and surface reactions. These characteristic lifetimes of the codoped
TiO2:WN films (i.e. 0.08 μs, 0.75 μs, and 11.5 μs, respectively) were found to be about 2.5 times
longer than those of their nitrogen monodoped TiO2:N counterparts (i.e. 0.03 μs, 0.35 μs, and
6.8 μs). This quantitatively confirms the effective passivation of the WN-codoping approach developed
here. Finally, the developed TiO2:WN’s practicality was confirmed by integrating them as
photoanodes for the visible-light driven EPC decontamination of ATZ. A significant increase in the
degradation kinetics, resulting in up to a four-fold increase in the pseudo-first order degradation
constant k for the optimally codoped TiO2:WN photoanodes (k = 0.106 min−1), in comparison
with the undoped TiO2–x & TiO2 ones (both having a k = 0.026 min−1). Most importantly, the
optimal TiO2:WN photoanodes showed a twofold increase in degradation kinetics as compared to
TiO2:W (k = 0.057 min−1) & TiO2:N (k = 0.047 min−1) as a direct consequence of both increased
photocharge lifetimes and visible light photosensitivity.


identifier: Demirbilek, Edip  (2017). Modèles d’apprentissage automatique d’estimation de qualité perçue dans les communications en temps réel / Machine learning based perceived quality estimation models in realtime communications.  Thèse.  Québec, Université du Québec, Institut national de la recherche scientifique, Doctorat en télécommunications, 184 p.

subject: banc d’essai de la communication multimédia

subject: données de mesure de la qualité audiovisuelle

subject: modélisation de la qualité perçue

subject: apprentissage automatique

subject: forêts d’arbres décisionnels

subject: techniques de bootstrap

subject: apprentissage profond

subject: programmation génétique

subject: multimedia communication testbed

subject: audiovisual quality dataset

subject: perceived quality

subject: modeling

subject: machine learning

subject: random forests

subject: bagging

subject: deep learning

subject: genetic programming

abstract:
L’objectif de notre travail est de développer des modèles d’apprentissage automatique qui prédisent
la qualité audiovisuelle perçue. La prédiction se fait à partir d’un ensemble de paramètres
corrélés dérivés d’un ensemble de données extraits de la cible. Afin d’atteindre cet objectif, nous
avons tout d’abord développé, avec VLC, un banc d’essai de la VsD (Vidéo sur Demande) et avons
généré un ensemble de données préliminaires de la qualité audiovisuelle. Le but était d’étudier divers
algorithmes d’apprentissage automatique. Ces premières expérimentations nous ont encouragé à développer
un banc d’essai plus robuste, basé sur le framework multimédia GStreamer. Nous avons
généré, avec ce nouveau banc d’essai, un ensemble de données de qualité audiovisuelle, propre à
notre contexte. Ces données reflètent les configurations contemporaines des communications interactives
pour le taux d’image par seconde, la quantification vidéo, les paramètres de réduction du
bruit et le taux de perte des paquets du réseau. Nous avons ensuite utilisé cet ensemble de données
afin de développer divers modèles, reposant soit sur l’information média (« paramétriques »), soit
sur les données réseau (« bitstream »), d’estimation de la qualité perçue. Ces modèles sont basés
sur les méthodes des forêts d’arbres décisionnels, des techniques dites de démarrage (« bootstrap
»), de l’apprentissage profond et de la programmation génétique.
Pour les modèles paramétriques, les quatre méthodes ont atteint une précision élevée en terme
de corrélation RMSE et de Pearson. Les modèles basés sur les forêts d’arbres décisionnels et les
techniques de bootstrap montrent un petit avantage par rapport à l’apprentissage profond quant
à la précision qu’ils ont atteint. Les modèles basés sur la programmation génétique sont moins
performants même si leur précision est impressionnante. Nous avons également obtenu une précision
élevée en utilisant les autres ensembles de données sur la qualité visuelle, accessibles au public. Les
métriques de performance que nous avons calculées sont comparables aux modèles existants formés
et testés sur ces ensembles de données.
Pour les modèles bitstream, les méthodes de forêts d’arbres décisionnels ainsi que les techniques
de bootstrap ont surpassé les modèles basés sur l’apprentissage profond et la programmation génétique
ainsi que tous les modèles paramétriques. Cependant, les modèles bitstream réalisés en
programmation génétique et en apprentissage profond ont moins bien performé que les modèles paramétriques
à cause d’une augmentation significative du nombre de caractéristiques dans l’ensemble
de données bitstream. Dans l’ensemble, nous concluons que le calcul de l’information bitstream mérite
l’effort fourni pour la générer. Ce calcul aide à construire des modèles plus précis mais demeure
utile uniquement pour le déploiement de bons algorithmes.
Sur la base de nos résultats, nous concluons que les algorithmes basés sur l’arbre de décision
conviennent aux modèles paramétriques ainsi qu’aux modèles bitstream. De plus, nous savons que
l’extraction de données corrélées supplémentaires de l’ensemble de données nous aide à générer des
modèles plus précis lorsque des algorithmes d’apprentissage automatique appropriés sont déployés. L’ensemble des données, les outils et les codes d’apprentissage automatique qui ont été développés
au cours de cette recherche sont gracieusement offerts à la communauté pour des fins de
recherche et de développement.

 This research has started with the initial objective to build machine learning based models
that predict the perceived audiovisual quality directly from a set of correlated parameters that
are extracted from a target quality dataset. To reach that goal, we have first created a VideoLAN
Video-on-Demand based testbed and generated a preliminary audiovisual quality dataset that let
us experiment with various machine learning algorithms. These early experiments encouraged us
to create a more robust testbed based on the GStreamer multimedia framework. With this new
testbed, we have generated the INRS audiovisual quality dataset that reflects contemporary realtime
configurations for video frame rate, video quantization, noise reduction parameters and network
packet loss rate. Then we have utilized this INRS dataset to build several machine learning based
parametric and bitstream perceived quality estimation models based on Random Forests, Bagging,
Deep Learning and Genetic Programming methods.
For the parametric models, all four methods have achieved high accuracy in terms of RMSE and
Pearson correlation with subjective ratings. Random Forests and Bagging based models show a small
edge over Deep Learning with respect to the accuracy they have achieved. Genetic Programming
based models fell behind even though their accuracy is impressive as well. We have also obtained
high accuracy on other publicly available audiovisual quality datasets and the performance metrics
we have computed are comparable to the existing models trained and tested on these datasets.
For the bitstream models, both the Random Forests and Bagging based bitstream models have
outperformed the Deep Learning and Genetic Programming based bitstream models as well as
all of the parametric models. However, both the Genetic Programming and Deep Learning based
bitstream models fell behind the parametric models due to a significant increase in the number of
features in the bitstream dataset. Overall we conclude that computing the bitstream information
is worth the effort and helps to build more accurate models. However, it is useful only for the
deployment of the right algorithms.
In light of our results, we conclude that the Decision Trees based algorithms are well suited
to the parametric models as well as to the bitstream models. Moreover, we know that extracting
additional correlated data from the dataset helps us to generate more accurate models when suitable
machine learning algorithms are deployed.
The dataset, tools and machine learning codes that have been generated during this research
are publicly available for research and development purposes.


identifier: Drouin-Picaro, Alexandre  (2017). Modèle hiérarchique pour l’amélioration de l’évaluation de l’état mental de l’opérateur à l’aide de technologies portables / Hierarchical model for improved operator functional state assessment based on wearables.  Mémoire.  Québec, Université du Québec, Institut national de la recherche scientifique, Maîtrise en télécommunications, 122 p.

subject:
interfaces cerveau-ordinateur
charge mentale
EEG
classification inter-tâches
brain-computer interfaces
mental workload
cross-task classification

abstract:
La classification inter-tâches, c’est-à-dire la classification de la charge mentale pour plusieurs tâches
à l’aide d’un même modèle, est un problème important pour l’évaluation de l’état fonctionnel de
l’opérateur. Dans cette étude, nous proposons une nouvelle méthode afin d’améliorer la précision
de la classification inter-tâches, ainsi que des nouvelles caractéristiques de l’EEG afin d’améliorer la
précision intra-tâche et inter-tâches. Notre méthode se fie à un classificateur hiérarchique capable de
détecter la tâche à laquelle appartient un point de données, ainsi que sa difficulté. Les caractéristiques
que nous proposons sont des caractéristiques de couplage entre les fréquences, soit le couplage phaseamplitude
et le taux de changement de la modulation d’amplitude.
Nous avons recueilli de données cardiaques, respiratoires, oculométriques et électroencéphalographiques
de 16 participants, chacun exécutant trois tâches cognitives, soit la rotation mentale, le
N-Back et la recherche visuelle. Comme nous voulions évaluer la performance de notre modèle dans
un environnement réel, nous avons recueilli ces signaux à l’aide d’appareils portables. Afin de rendre
notre modèle indépendant de l’utilisateur, nous avons également recueilli des métriques objectives
et subjectives de la performance pour faciliter le processus de sélection des caractéristiques.
Nos résultats montrent que les caractéristiques de l’EEG que nous proposons améliorent la classification
intra-tâche pour la rotation mentale et la recherche visuelle. De plus, notre modèle hiérarchique
a atteint une précision de 69%, par rapport à 62% pour les méthodes traditionnelles. Ces résultats
indépendants de l’utilisateur sont comparables aux modèles adaptés à l’utilisateur publiés précédemment.
La performance relativement faible de notre modèle est due en grande partie à une mauvaise
distribution des électrodes EEG, ainsi qu’à des problèmes survenus avec les signaux de la physiologie
périphérique. Nous nous attendons à ce que notre modèle produise de bien meilleurs résultats avec
des appareils plus appropriés.

Cross-task classification, that is the ability of a single model to classify mental workload across many
different tasks, is an important problem in mental workload assessment. In this work, we propose
a novel approach to improve cross-task accuracy as well as new EEG features to improve withinand
cross-task accuracy. Our approach relies on a layered classifier to detect both the task being
performed and the difficulty condition, while the proposed features are Cross-Frequency Coupling
features that quantifiy the interactions between EEG sub-bands, namely Phase-Amplitude Coupling
and Amplitude Modulation Rate-of-Change.
To do this, we collected ECG, respiration, eye tracking and EEG data from 16 participants performing
three tasks : mental rotation, N-back and visual search. As we wanted to test in-the-field
performance of our methods, we collected physiological data using wearable devices. In an effort to
make our model user-independant, we also collected objective and subjective perfomance metrics
to help the feature selection process.
Our results show that the proposed EEG features improve within-task results for mental rotation
and visual search. Additionally, our hierarchical method achieved an accuracy of 69% compared to
62% using traditional methods. These user-independant results compare favourably to previously
published user-adapter models. The relatively low performance of our model is due mostly to poor
EEG electrode distribution and problems encountered with the signals extracted from peripheral
physiology. Our approach can be expected to perform much better given better data collection
devices.


identifier: Erfani, Elham  (2018). A V-Band High Gain Antenna System Integrated with a Six-Port Receiver for Backhaul Applications.  Thèse.  Québec, Université du Québec, Institut national de la recherche scientifique, Doctorat en télécommunications, 164 p.

subject: Télécommunications

abstract:
La prolifération récente des services de données et la demande exponentiellement croissante
pour le transfert de données mobiles ont conduit à l’émergence de la 5th génération (5G) de réseaux
cellulaires, destinée à traiter la multitude de problèmes liés au débit et de données élevées et à sa
capacité. Grâce au grand nombre de fréquences inutilisées disponibles dans le spectre de fréquences
d’ondes millimétriques (mm-wave), cette bande a été considérée comme un candidat prometteur
pour les futures communications mobiles 5G. Cependant, la propagation radio à ces fréquences
fait l’objet de pertes élevées, dues à l’absorption atmosphérique, à la pluie et au feuillage. Par
conséquent, pour compenser la perte de propagation et le blocage de la liaison, l’utilisation d’une
antenne hautement directionnelle à large bande, à faisceau balayé, s’avère nécessaire.
Dans cette thèse, on présente un nouveau récepteur frontal à ondes millimétriques, composé
d’un système d’antennes à gain élevé, intégrant un récepteur six-port bon marché, pour les réseaux
d’amenée en ondes millimétriques. Comme principale contribution de ce travail, on fait un examen
minutieux de l’application des matériaux artificiels émergents dans la conception d’un nouveau système
d’antennes dénommées antennes à réseau d’émission (TA) ou à lentille planaire (PDL), afin
de focaliser de manière efficace les signaux RF reçus/émis dans la/les direction(s) désirée(s); on
propose une structure appropriée pour les applications en ondes millimétriques et on fait une étude
analytique et expérimentale sur les performances de l’antenne. Dans cette perspective, tout d’abord,
on étudie et on développe une antenne TA basée sur des métamatériaux à un indice de réfraction
à gradient (GRIN), afin d’analyser sa faisabilité pour les applications en ondes millimétriques, avec
les moyens de fabrication disponibles. On conclut que, en raison des exigences liées aux tolérances
de fabrication, pour la construction d’une antenne TA, on devrait alternativement utiliser des matériaux
de surface sélective en fréquence (FSS). Pour répondre aux exigences de l’antenne TA, on a
conçu une cellule unitaire FSS insensible à la polarisation qui assure une réponse en phase de transmission
linéaire, ayant une plage de variation de 270 ° et une perte d’insertion inférieure à -3 dB, sur
une bande de fréquence désirée de 58 GHz à 64 dB. En outre, pour activer l’antenne TA proposée,
on présente un nouveau module de réseaux d’antennes planaires « patch » 2×4 avec de connexions
à ouverture couplée intercalées avec une structure à surface souple. La structure à surface souple
est utilisée pour améliorer les performances du réseau en termes d’efficacité (gain), de largeur de
bande et du niveau des lobes latéraux. Cette lentille discrète montre un gain maximal de 30.92 dB
avec une efficacité d’ouverture de 38.4.
Comme convertisseur abaisseur de fréquence direct, l’on a conçu un circuit six-port composé
de quelques éléments passifs et l’on en a fait une caractérisation complète, afin d’obtenir des ports
d’entrée/de sortie adaptés, une isolation inférieure à -20 dB, et une bonne réponse en amplitude
de transmission et en phase, sur toute la largeur de bande désirée. En outre, afin de récupérer
les données de bande de base, on propose un détecteur de puissance équilibré, ayant une grande
largeur de bande, de plus de 10 GHz. Par l’utilisation de la technologie d’interconnexion avec câblage filaire (bonding wire), l’antenne fabriquée avec la technologie PCB est intégrée à l’amplificateur à
faible bruit (LNA) et au récepteur à six-ports développé avec la technologie MHMIC. L’architecture
du récepteur frontal intégré est testée pour différents types de constellations et de distances entre
le récepteur et l’émetteur. Les résultats obtenus ont montré qu’on peut considérer la configuration
proposée comme une solution innovatrice pour les communications sans fil par ondes millimétriques.

Recently, the data service proliferation and explosively increased needs on mobile data traffic
have emerged the 5th generation (5G) of cellular networks that are expected to address the plethora
of high data rate and capacity. Because of the abundant amount of unused frequencies available
in millimeter-wave (mm-wave) frequency regime, this band has been considered as a prominent
candidate for future 5G mobile communication. However, radio propagation at these frequencies
suffer from high losses due to atmospheric absorption, rain, and foliage. Therefore, the use of a
wideband high directive antenna with beam scanning is necessary to overcome the propagation loss
and link blockage.
In this thesis, a new millimeter wave (mm-wave) front-end receiver composed of a high gain
antenna system integrated with a low-cost six-port receiver is demonstrated for mm-wave backhaul
networks. As the main contribution of this work, the application of emerging artificial materials
in designing a new antenna system, so-called transmit-array (TA) or planar discrete lens
(PDL)antennas to effectively focus the received/transmit RF-signals in the desired direction(s) is
thoroughly investigated, the appropriate structure for mm-wave applications is proposed, and the
antenna performances are analytically and experimentally studied. In this perspective, a TA based
on gradient-refractive-index metamaterials (GRIN) is firstly studied and developed to investigate
their feasibility for mm-wave applications based on the available fabrication facilities. It is concluded
that because of fabrication tolerance requirements, frequency selective surface (FSS) materials
should alternatively be used to construct a TA. To meet the requirements of the TA antenna, a
polarization-insensitive FSS unit-cell offering a linear transmission phase response with a variation
range of 270 ° and insertion loss less than -3 dB over a desired bandwidth of 58-64 GHz is designed.
Furthermore, to excite the proposed TA, a new planar array module composed of 2×4 aperturecoupled-
patches interleaved with a soft-surface structure is presented. Soft-surface structure is used
to improve the array performances in terms of efficiency (gain), bandwidth, and side-lobe level. This
discrete lens shows a peak gain of 30.92 dB with 38.4 aperture efficiency.
As a direct down-convertor, a six-port circuit composed of some passive elements is designed and
fully characterized to obtain matched input/output ports, isolation less than -20 dB, and a good
transmission amplitude and phase responses over the desired bandwidth. In addition, to recover
the baseband data, a balanced power detector with a reflection coefficient bandwidth of more than
10 GHz is proposed. By applying the bonding wire interconnection technology, the antenna fabricated
with PCB technology is integrated with LNA and six-port receiver built in MHMIC technology.
The integrated front-end receiver architecture is tested for different types of constellation and various
distances between receiver and transmitter. Achieved results demonstrated that the proposed
configuration can be considered as an innovative solution for long-distance millimeter-waves wireless
communications.


identifier: Ernotte, Guilmot  (2016). Optique non-linéaire dans le domaine des fréquences.  Mémoire.  Québec, Université du Québec, Institut national de la recherche scientifique, Maîtrise en sciences de l'énergie et des matériaux, 89 p.

subject:
optique non-lin éaire
optique ultra-rapide
optique de Fourier
amplificateur non-linéaire
génération de seconde harmonique
non-linear optics
ultrafast optics
Fourier optics
laser
non-linear amplifier
second harmonic generation

abstract:
L’optique non-linéaire repose sur l’interaction entre un champ électrique intense et la matière. Cette
interaction crée de nouvelles fréquences, permettant d’atteindre des régions spectrales inaccessibles
par l’optique linéaire. Un champ électrique intense peut être obtenu via l’utilisation d’impulsions ultra-brèves, de l’ordre de la femtoseconde. Cependant, la relation temps-fréquence montre que ce type
d’impulsions possède un spectre large. Il devient alors difficile de conserver toutes les propriétés
spectrales d’une impulsion dû à la nature non-linéaire des opérateurs en jeu, en particulier dans le cas
de l’amplification paramétrique optique et pour la génération de seconde harmonique. Ce mémoire
présente une nouvelle approche pour l’optique non-linéaire qui divise cet opérateur non-linéaire sur
des bandes spectrales plus étroites de façon parallèle afin de conserver toutes les propriétés spectrales
de l’impulsion. Pour ce faire, un montage 4-f est utilisé et l’interaction non-linéaire se réalise sur
un spectre dispersé spatialement. Plus particulièrement, un amplificateur paramétrique optique été
construit de cette façon et a permis d’amplifier une impulsion très large-bande de trois cycles optiques
à 1.8 µm jusqu’à 13 mJ avec 79 mJ de pompe sans aucune perte au niveau de la largeur du spectre.
De plus, un montage de génération de seconde harmonique a été construit dans un 4-f et les propriétés de l’impulsion de seconde harmonique sont comparées `a celles d’un montage conventionnel.
Il a été observé que la génération dans un 4-f annule le couplage fréquentiel et permet d’obtenir un
spectre de seconde harmonique qui a une relation avec le spectre fondamental linéaire en phase et
quadratique en amplitude, alors que le montage conventionnel utilisant l’espace temporel ne respecte
pas ces relations.

Nonlinear optics is performed by interacting an intense electric field with matter. This interaction generates
new frequencies, which are inaccessible by linear optics. Intense electric field can be obtained
by using ultrashort pulses that are in the order of the femtosecond. However, time-frequency relation
shows that this type of pulse has a large bandwidth. Hence, it becomes difficult to conserve all spectral
properties of the laser pulse due to the nonlinear nature of the operator, in particular in the case of
optical parametric amplification and second harmonic generation. This master thesis presents a new
approach for nonlinear optics which divides this operator on multiples shorter bandwidth in a parallel
manner to conserve all spectral properties. To do so, a 4-f setup was built and nonlinear propagation
is realized in a plane where the spectrum is dispersed on a spatial axis. In particular, an optical parametric
amplifier was built in this manner to amplify a three cycles bandwidth at 1.8 μm to 13 mJ with
the use of 79 mJ of pumping without losing any spectrum. Moreover, a second harmonic generation
setup was built in a 4-f and is compared with a regular setup. It will be shown that the generation in
the 4-f setup suppresses the frequency coupling during the nonlinear propagation thus the second
harmonic spectrum has a relation with the fundamental spectrum that is linear in phase and quadratic
in amplitude, while the conventional setup in the temporal domain did not conserve these properties.


identifier: Esmaeelzadeh Limodehi, Hamid  (2018). Capteurs à fibre optique pour les applications environnementales.  Thèse.  Québec, Université du Québec, Institut national de la recherche scientifique, Doctorat en sciences de l'énergie et des matériaux, 160 p.

subject: énergie matériaux

abstract:
De nos jours, le rôle des capteurs électroniques est comparable au système nerveux du corps humain. Impossible d’imaginer sa survie sans système nerveux. Dans le but de contrôler l’état de santé de notre corps, des données biologiques sont à tout moment collectées dans toutes les parties de notre corps pour être envoyées au cerveau via notre système nerveux.
La technologie des capteurs actuels repose principalement sur des systèmes électroniques, qui, dans de nombreux cas, ne sont pas assez rapides et précis et ont des limitations physiques les empêchant de fonctionner correctement en milieux non-contrôlés. A l’inverse, les capteurs à base de fibre optique sont plus rapides, plus précis et ont peu de limitations ce qui leur permet de fonctionner dans des milieux non-contrôlés ou difficiles d’accès.
Si les fibres optiques ont pu révolutionner le domaine des télécommunications, pourquoi ne le feraient-elles pas dans le domaine des capteurs, en permettant la création de réseaux interconnectés planétairement, permettant de surveiller des écosystèmes complets ou même les changements climatiques? Pour pouvoir parvenir à cet objectif, les systèmes actuels devraient être remplacés par la technologique optique. Durant les 25 dernières années, le remplacement des capteurs électroniques par leurs équivalents optiques n’a été que très partiel en raison de limitations technologiques et surtout de prix prohibitifs.
Le principal objectif de cette thèse est d'élaborer un système de capteurs environnementaux, principalement pour mesurer l’humidité, basé sur une technologie à fibre optique qui soit économiquement viable. Les facteurs qui motivent l'auteur à adopter cette approche dans le cadre de ce projet de doctorat sont décrits ci-dessous.
La première motivation est la migration des plates-formes électroniques actuelles vers des technologies photoniques, à l’image du rôle que la fibre optique a joué dans les télécommunications. Depuis l'invention des «guides d'ondes diélectriques» en 1966, les systèmes de communication à fibres optiques ont utilisé les ondes lumineuses comme porteuses pour transmettre des informations d'un endroit à un autre. De distances de quelques mètres obtenues en laboratoire, on est passé à des milliers de kilomètres dans la première décennie du XXIe siècle, avec des débits qui sont passés de quelques dizaines de Mbit/s à la fin des années 1960 à des dizaines de Tbit/s à l’heure actuelle. Grâce à cette énorme capacité de transmission, les systèmes d'émetteurs radio ont été largement remplacés par des systèmes à fibres optiques pour la transmission de données de télécommunications sur longues distances depuis le début du siècle. Par conséquent, la mise en place des réseaux à fibres optiques a conduit à des moyens de communications déployés mondialement pour l'ensemble du spectre des données, à savoir la voix et la vidéo, aussi bien en temps réel qu’en temps différé. Une partie de ces contenus pourrait être attribuée aux données collectées à partir de systèmes de détection environnementaux ou industriels connectés au réseau. Ces données de détection, acquises par des systèmes de transducteurs, pourraient contenir les informations de paramètres physico-chimiques pour être traitées puis envoyées via le réseau. Étant donné que les systèmes de communication sont à présent basés sur la photonique, les systèmes de détection peuvent être intégrés directement dans les réseaux actuels de télécommunications. Pour cela, les systèmes actuels de détection devraient migrés vers des techniques optiques afin d’être intégrés dans l’actuelle infrastructure de télécommunications.
La deuxième motivation est liée au fait que les capteurs électriques d'humidité actuellement commercialisés ne conviennent pas, en raison de la géométrie et de la construction de la sonde, à des environnements ayant des limitations strictes d’encombrement ou des conditions chimiques agressives. En revanche, les capteurs optiques ont certains avantages intrinsèques, tels que des temps de réponse rapide, une immunité au bruit électromagnétique et à la détection croisée, et fonctionnent en toute sécurité dans des endroits présentant des risques de déflagration et d’inflammabilité. En outre, les capteurs à fibre optique offrent des fonctionnalités supplémentaires telles que des capacités de détection ultra-rapides, leur légèreté, leur non-intrusivité et leur flexibilité. Par conséquent, de nombreuses études ont été menées sur l'utilisation de technologies optiques ou à fibres optiques pour des applications de détection. Il est souvent avancé que les capteurs optiques devraient largement se développer en raison de leurs nombreux avantages. Néanmoins, malgré tous les efforts déployés au cours du dernier quart de siècle, cet objectif n'a pas encore été atteint et les capteurs électriques/électroniques dominent toujours le marché des détecteurs. L'un des principaux obstacles à cette substitution est qu’actuellement le prix des capteurs optiques n’est pas concurrentiel par rapport au prix des détecteurs électriques. Par exemple, les capteurs basés sur les réseaux de fibre de Bragg (FBG) sont relativement coûteux en raison de l'utilisation de composants, tels que des sondes, des sources lumineuses et des détecteurs. À moins de réussir à réduire les coûts de ces composants, il semble fort probable que les capteurs électroniques resteront probablement la technologie de choix pour la grande majorité des applications de détection. Pour réduire le prix, il est impératif d’utiliser des composants à bas prix, notamment pour la source de lumière, le transducteur et le détecteur. L’objectif principal des travaux présentés dans cette thèse a été de développer un capteur optique d'humidité capable de concurrencer les technologies électroniques existantes.
Dans les chapitres 3 et 4, j’expose les travaux théoriques et les expériences associées, effectuées dans le but d’introduire une plate-forme optique efficace pour la détection de l'humidité. Dans la section théorique, j'ai créé une relation entre la résonance des plasmons de surface dans le guide d'ondes à fibre optique et le phénomène de condensation/évaporation des molécules d'eau, ce qui a permis d’élaborer une nouvelle méthode pour mesurer l'humidité ambiante et la température du point de rosée. Il y est également détaillé les activités expérimentales, en particulier, le processus de fabrication des capteurs et les mesures, afin de valider de la théorie mentionnée précédemment. Le chapitre 5 de cette thèse décrit la mise en oeuvre d’une solution optique efficace et peu onéreuse, un prototype de capteur optique multicanal de rosée et d'humidité (MODHS – “Multi-channel Optical Dew & Humidity Sensor”). Le MODHS développé permet de surveiller simultanément le point de rosée et l'humidité d'une série de systèmes de microclimat dans des bâtiments industriels pour des endroits difficiles d’accès, des musées, des salles d'archives, des bibliothèques, des laboratoires, etc. Ce résultat a été obtenu grâce à un design innovant, à la fois dans ses aspects techniques et conceptuels. Un avantage notable des MODHS est qu’ils utilisent des cellules photoconductives ou des photodiodes pour la détection, au lieu d'utiliser des spectromètres coûteux. Le MODHS utilise également une simple diode électroluminescente (DEL) en tant que source lumineuse, pour fournir la lumière à plusieurs canaux de fibres optiques, de façon simultanée. De plus, il ne nécessite pas l’utilisation d’une couche absorbant l'humidité, contrairement aux autres capteurs d'humidité, la nouvelle méthode de détection étant basée sur la résonance des plasmons de surface et la condensation de la vapeur d'eau. La plateforme actuelle du MODHS permet également d'intégrer d’autres transducteurs à fibre optique dans le système de capteur pour mesurer d'autres paramètres environnementaux. Cette recherche pourrait conduire à de nouvelles et importantes perspectives pour la mise en oeuvre de nouveaux systèmes de capteurs optiques avec une efficacité sans précédent, un prix compétitif et la suppression des limites imposées par les technologies électriques/électroniques actuelles.

 Present day sensing systems can draw the analogy to the central nervous system of living beings. In order to monitor the health of the system, biological data is instantly collected from all parts of the organism and sent to the brain via the nervous system. Current sensor technologies are primarily based on electronics which are not fast or accurate enough in many cases. Moreover they often can have physical limitations that prevent them from properly functioning in uncontrolled environments. As an alternative solution optical fiber-based sensors can be fast and accurate with fewer limitations, allowing them to operate in uncontrolled or difficult-to-access environments. Fiber optics have already revolutionized telecommunications, why would not they do the same with sensor technology? This technology could allow the creation of an interconnected planetary network that can control an entire ecosystem, or even climate change.
To achieve this goal, current sensor systems would need to be replaced by optical technology. Over the last 25 years this has not been feasible due to technological and economic difficulties. The main objective of this thesis is to introduce a robust and cost-effective environmental sensor based on fiber optic technologies. Motivating factors are discussed below;
First consider the migration of current electronic platforms towards photonics. Since the invention of “dielectric waveguides” in 1966 optical fiber communication systems have used light waves as carriers to transmit information from one place to the other. The distance of a few meters in laboratory was increased to thousands of kilometers in the first decade of this century with bit rates reaching from few tens of Mbit/s in late 1960s to tens of Tbit/s at present. Due to such enormous transmission capacity, radio transmitter systems have largely been replaced by fiber optic systems for long-haul telecommunication data transmission since beginning of this century. Establishment of the fiber-optic based networks has brought worldwide communications medium for the entire spectrum of data including of voice, video, and both real- time and non-real-time content. Part of this content could be used for sensing data gathered from environmental or industrial systems connected to the network. This sensing data acquired by transducers system could contain information from physical/chemical parameters to be processed and transmitted in the network. Hence, sensing systems can be integrated directly into today’s communications networks since the current network technology  is primarily based on photonics. This requires current sensing systems migrate toward optical techniques in order to integrate with existing telecom infrastructure.
The next motivating point is related to the fact that the current electrical based humidity sensors on the market are not suitable for use under environments with stringent limitations on physical space, and chemical conditions due to probe geometry and construction. Conversely, optical based sensors have some intrinsic advantages such as fast response, immunity to electromagnetic noise and related cross-sensing, and safe operation in explosive and flammable environments. In addition, fiber optic based sensors offer features such as ultra-fast response, lightweight, non-intrusive, and flexible. Numerous investigations have been conducted on the use of optical and fiber optic based technologies for sensing applications and it is argued that optical sensors will be widely deployed because of these advantageous properties. However, despite these efforts over the past quarter century optical based sensing technology has not yet been extensively realized and electrical based sensors still dominate the market. One of main obstacles is that the prices of optical based sensors are not competitive when compared to their electronic counterparts. For example Fiber Bragg Grating (FBG) based sensors are relatively expensive due to use of components such as their probes, light sources and detectors.
Unless the price point of optical sensing systems can be greatly reduced, it seems likely that electronic solutions will continue to dominate. To meet this competitive price point we must use cost-effective components including light source, transducer, and detector. The primary goal of the work presented in this thesis was to develop an optical humidity sensor capable of competing with existing electronic technologies.
Chapters 3 and 4 demonstrate the theoretical background and related experiments performed to develop an efficient platform for optical humidity sensing. In theoretical section a relationship between surface plasmon resonance in fiber optic waveguide and water molecules condensation/evaporation phenomenon was developed. This lead a novel method for measuring ambient humidity and dew point temperature. This was also demonstrated the experimentally, including sensor fabrication and measurement to examine the proposed theory. The results achieved through chapters 3 & 4 demonstrate the initial theory was valid encouraging the realization of a cost-effective optical-based environmental sensor, using a fiber optic approach.
Chapter 5 reports the work on the realization an efficient and cost-effective optical solution, a prototype Multi-channel Optical Dew & Humidity Sensor (MODHS). The developed MODHS enables simultaneous monitoring of dew point and humidity on a suite of microclimate systems in hard-to-access industrial locations, museums, archive rooms, libraries, laboratories, and etc. This achievement was thanks to the innovative design both conceptually and technologically. Notable advantages of the MODHS are that it employs simple photoconductive cells or photodiodes for detection, instead to use expensive spectrometers. Moreover the MODHS employs a simple LED as the light source to supply required measuring light on several fiber optic channels. It is also exempt from any moisture absorbent layer (in contrast with other humidity sensors) due to its novel sensing method based on surface plasmon resonance and water vapor condensation. The present platform of our introduced MODHS also allows further fiber optic transducer of other parameters to be incorporated in the sensor system. This research may open new and important perspectives for implementing other optical sensor systems with unprecedented efficiency, competitive price, and overcoming limitations of present electrical technologies.


identifier: Hassan, Eman  (2017). In Vitro Selections of Mammaglobin B and Mammaglobin A Aptamers for detecting Metastatic Breast Cancer Cells Using Terahertz Chemical Microscopy.  Thèse.  Québec, Université du Québec, Institut national de la recherche scientifique, Doctorat en sciences de l'énergie et des matériaux, 244 p.

subject: énergie matériaux

abstract:
Breast cancer is the most common cancer diagnosed in Canadian women, accounting for 26% of all newly diagnosed cancers in women. Metastatic breast cancer (MBC) is the stage of cancer where the disease has spread to distant parts of the body, further than the axillary lymph nodes. Breast cancer cells that leave the primary tumor to the blood are called circulating tumor cells (CTCs). Studying CTCs allows for better understanding of the metastases process. The detection of CTCs is a challenging task due to the heterogeneous nature of CTCs and lack of biomarkers. There is an urgent need to identify more biomarkers to help in the detection of CTCs from breast cancer.
Mammaglobin B (MGB2) and mammaglobin A (MGB1) proteins are small secretory proteins that are believed to have roles in cancer development, immune system regulation, and androgen binding. MGB2 is found at high levels in many secretions, including those from uterine, prostatic, pulmonary, and lacrimal and salivary glands, whereas MGB1 expression is exclusive to the breast tissue. Since both proteins are overexpressed in most cases of metastatic breast cancer,, MGB2 and MGB1 are very attractive biomarkers that could be used in the detection of breast cancer and breast CTCs.
Aptamers are powerful recognition elements. They are single-stranded ssDNA or RNA oligonucleotides that bind to their targets with high affinity and selectivity. Aptamers are chemically produced via a process called Systematic Evolution of Ligands by EXponential enrichment (SELEX). SELEX is an iterative in vitro processwhich enriches target-binding sequencesfrom randomized large ssDNA or RNA libraries. In each round of SELEX, target–binding sequences are eluted from target molecules, amplified, and used as the library for subsequent rounds. This process results in an aptamer with high affinity and specificity for the target.
In this work, a group of aptamers against MGB2 and MGB1 proteins were developed for the first time using a unique type of SELEX called hybrid SELEX, in which the ssDNA library was alternated between two targets that are the recombinant form of both MGB2, and MGB1 proteins and breast cancer cells MCF7 and MDA-MB-415 respectively. All selected aptamers were then tested for their affinity by determining the dissociation constant (Kd) using flow cytometry. Aptamers were tested for their selectivity by testing their affinities to other normal and cancer cell lines. Aptamers for both targets that had the highest affinity and selectivity were further tested for their binding affinity to their target cancer cell lines in plasma and whole blood lysate environments using flow cytometry. Aptamers for both targets were tested for their binding affinity in blood containing normal blood cells and spiked with different percentages of target breast cancer cells. The binding affinity of the selected aptamers was tested against their target proteins using Electrophoretic Mobility Shift Assay (EMSA). Finally, and for the first time, the selected aptamers against the two targets were tested to detect breast cancer cells using Terahertz Chemical Microscopy (TCM).
Results obtained by this study revealed the successful selection of a group of aptamers against MGB2 and MGB1 proteins. Among all the selected aptamers, mammaglobin B1 (MAMB1) against MGB2 (MCF7 cell line), and mammaglobin A2 (MAMA2) against MGB1 (MDA-MB-415 cell line) showed the highest affinities to their targets (as indicated by their Kd values). Moreover, these aptamers showed minimal binding to normal and other cancer cell lines, indicating the high selectivity to their target breast cancer cells. Plasma and whole blood lysate results showed that MAMB1 and MAMA2 aptamers bound specifically to MCF7 and MDA-MB-415 cells respectively. MAMB1 showed higher affinity to MCF7 than MAMA2 showed to MDA-MB-415 cells. Moreover, the study with spiked breast cancer cells showed an increase in the fluorescence intensity with increasing percentages of spiked cells for both aptamers, indicating the great potential to use both aptamers in the detection of breast CTCs.
TCM results showed that terahertz (THz) amplitude was higher when MAMB1 was interacting with MCF7 cells and MAMA2 with MDA-MB-415, compared to the control on the surface of the sensing plate. Moreover, TCM could detect the interaction of a low number of cells (10 cells) binding to their aptamers. MAMB1 aptamer was more selective than MAMA2 aptamer, as shown by TCM. Overall results obtained by flow cytometry and TCM were very promising and indicate the possibility of using MAMB1 and MAMA2 aptamers in the detection of breast cancer and breast CTCs.


identifier: Ren, Fuqiang  (2016). Near Infrared-Emitting Quantum Dots: Synthesis, Characterization and Biological Applications.  Thèse.  Québec, Université du Québec, Institut national de la recherche scientifique, Doctorat en sciences de l'énergie et des matériaux, 144 p.

subject: énergie matériaux

abstract:
Quantum dots (QDs) have attracted significant attention in many applications due to
their unique features, such as size-dependent optical absorption and emission, arising
from the quantum confinement effect, which the bulk material does not possess.
Among diverse QDs, near infrared (NIR) emitting QDs, such as lead-based QDs,
which can be tuned to emit from below 1000 nanometer to several thousand
nanometers are particularly interesting. Both their excitation and emission can be
easily adjusted to lie within the biological windows, highly desirable for some
demanding biological applications. Although the synthesis of NIR QDs with a
uniform and narrow size distribution is well known today, achieving QDs with high
quantum efficiency and excellent stability is still a big challenge.
QDs are tiny crystalline particles with typical dimensions in the range of 1-100 nm.
Their surface-to-volume ratio is very large, therefore the properties of QDs become
extremely sensitive to surface characteristics. In order to improve the optical
properties of these QDs, great efforts have been made in the past few decades on the
surface engineering of QDs. A passivation shell is normally grown over the QDs to
form a core/shell structure, which in turn improves the optical properties and stability.
In the first part of this thesis, the synthesis and optical properties of PbS/CdS
core/shell QDs are presented and discussed. We firstly synthesized a series of
differently sized PbS QDs by using the traditional hot injection method, then these
PbS QDs were coated with a thin CdS shell to form a PbS/CdS core/shell structure by
the cation exchange approach, finally the optical properties of these core/shell QDs were studied.
In Section I of Part I, we report the development of a reproducible and controllable
microwave-assisted cation exchange approach, for the first time, to quickly synthesize
high-quality, NIR emitting PbS/CdS core/shell QDs. These monodisperse QDs,
emitting in the range of 1300-1600 nm, show a quantum yield (QY) as high as 57%
that is ~1.4 times higher than that of QDs achieved by conventional heating in oil bath.
Meanwhile, the reaction was successfully scaled up by several times by increasing the
starting PbS concentration or by amplifying the reaction volume and the
as-synthesized core/shell QDs show similarly high QY.
We then report anomalous size-dependent photoluminescence (PL) intensity
variation of PbS QDs with the formation of a thin CdS shell via the same
microwave-assisted cation exchange approach. We found previously that thin shell
formation is an effective strategy for increasing the PL intensity of large sized PbS
QDs. Nonetheless, herein we observed an unusual PL decrease in ultrasmall QDs
upon shell formation. We attempted to understand this abnormal phenomenon from
the perspective of trap density variation and the probability of electrons and holes
reaching surface defects. To this end, QY and PL lifetime (on the ns-μs time scale) of
pristine PbS QDs and PbS/CdS core/shell QDs were measured and radiative and
non-radiative recombination rates were derived and compared. Moreover, transient
absorption (TA) analysis (on the fs-ns time scale) was performed to better understand
exciton dynamics on ultrafast time scales. These experimental results along with
theoretical calculations of electron and hole wave functions provide a complete picture of the photophysics governing the core/shell system. Ultimately, a model was
constructed to show the energy levels and trap states for various sizes.
Part II focuses on the photostability and colloidal stability of water dispersible
PbS/CdS/ZnS core/shell/shell QDs and their potential bio-applications. We report for
the first time detailed investigations of the synthesis of NIR, water dispersible,
strongly luminescent and highly stable PbS/CdS/ZnS core/shell/shell QDs, their
properties in different buffers, their cytotoxicity and further their applications in
tumor imaging. In particular, we focus on the QDs emitting at 930 and 1220 nm,
within the first and second biological windows, respectively. These QDs were
synthesized via our recently developed microwave-assisted approach to grow a ZnS
shell and to simultaneously exchange initial ligand with mercaptopropyl acid on the
PbS/CdS core/shell QDs dispersed in an organic phase. These QDs were extremely
stable in commonly used biological buffers and remarkably, they could keep their
initial morphology, dispersion status and PL in phosphate buffered saline buffer (PBS)
for as long as 14 months, which was the longest time we investigated with both
transmission electron microscopy and PL spectroscopy herein. PL images taken on the
930 nm emitting PbS/CdS/ZnS core/shell/shell QDs revealed that they could still emit
strongly after 30-month storage in PBS. Such long term stability of water dispersible
QDs is rarely reported in the literature. Their colloidal stability was further
investigated by keeping them in high ionic concentration conditions. Their PL
intensity did not show any change for at least 3 weeks at high NaCl concentration up
to 400 mM. The QDs also showed excellent photostability and could keep about 80% of their initial PL intensity after 1 hour of continuous, strong UV illumination. More
interestingly, they showed negligible toxicity to cultured cells even at high QDs
concentration (50 nM). Given these outstanding properties, the ultrastable and
biocompatible QDs were explored for the first time for in vivo tumor imaging in mice.
With one order of magnitude lower QD concentration (0.04 mg/mL), significantly
weaker laser intensity (0.04 W/cm2 vs ~1 W/cm2) and considerably shorter signal
integration time (≤ 1 ms vs several hundreds of ms) as compared to the best reported
rare earth doped nanoparticles, the QDs showed high emission intensity even at
injection depth of ~2.5 mm, hard to achieve with visible QDs and other NIR PL
probes.
We developed a QD-based imaging system based on NIR-emitting PbS/CdS/ZnS
QDs with minimal noticeable toxicity. Through careful engineering of their emission
wavelength, we obtained fluorescence imaging nanoprobes with optimal penetration
depths in biological tissue. Additionally, this new platform exhibited
multifunctionality beyond their use as pure imaging nanoprobes. The system is
capable of acting as a biological nanothermometer, based on the reliable
thermal-dependent behavior of the fluorescence signal. The PbS/CdS/ZnS QDs
studied here can easily be exploited to obtain thermal mapping of subskin areas in live
specimens, an accomplishment of great relevance for early disease detection and also
for real-time therapy monitoring. Moreover, as a result of the intense signal provided
by the NIR-emitting QDs, we are able to elucidate the real-time biodistribution of the
QDs by means of in vivo experiments in live mice. We determined the lack of detectable chemical toxicity attributed to the QDs based on cell culture assays, as well
as the lack of adverse health effects (no significant weight changes or behavior
abnormalities were found over 4 weeks) for mice injected with a low concentration of
QDs, coupled with the absence of any fluorescence signal detected in the body organs
at the end of the experiment. We can therefore ascertain that the ZnS outer shell
imparts a great deal of bio-compatibility and stability of the PbS/CdS/ZnS QDs
reported here. Also, the intense fluorescent emission of this material allows for low
doses to be used, significantly improving the current state of the art. This greatly
diminishes the likelihood of causing adverse health effects on the live specimen when
used as optical bioimaging probes.