Treasures @ UT Dallas
Not a member yet
7697 research outputs found
Sort by
Extended-gate MOSFET for High Sensitivity Photodetectors and pH Sensors
No full textOver the past years, semiconductors have been greatly used in sensors. With the development
semiconductor technology, the semiconductor sensors showed high sensitivity, large integration
and reliable stability. Ion-Sensitive Field Effect Transistor (ISFET) changed the gate electrode
of Metal-oxide-semiconductor Field Effect Transistor (MOSFET) from metals to electrolyte. In
this dissertation, the perovskite, which is a kind of material with large light absorption
coefficient, is used to replace the electrolyte in ISFET based on the structure of ISFET to create
high sensitivity photodetector. The perovskite is deposited on a silicon wafer and physically
separated with MOSFET. Besides taking both advantages of perovskite with excellent
optoelectrical property and silicon as a single crystal with good electrical property to get high
responsivity, this extended-gate structure provides convenience for changing the capacitance of
perovskite and removing the influence of light on MOSFET. The frequency of electrical signal
on perovskite can modulate the capacitance of perovskite, which can be used when the
capacitance of perovskite is too high compared with MOSFET. The ionic movement influence,
which degrees the performance of this photodetector, can be reduced by adding another
MOSFET served as current source at the gate of original MOSFET.
Inspired by the ionic movement of perovskite, this dissertation also proves ionic movement in
pH electrolyte deteriorates the sensitivity of ISFET by electrical measurement. The extended
gate structure is utilized to separate the MOSFET and pH capacitance so the MOSFET is free
from changing of temperature. Low temperature can decrease the mobility of ions in pH
electrolyte especially after the phase change from liquid to solid. The ions in electrolyte can’t
follow the high frequency bias voltage so the ionic movement is less at high frequency. Our
results show that the ISFETs have larger sensitivity in low temperature and high frequency since
the ionic movement can be suppressed by low temperature and high frequency
Unlocking the Transformative Potential of Health Information Technology (Health IT): Institutional, Ecological & Contextual Influences Shaping Health IT Adoption Regionally
No full textSince the 1960s, health IT has evolved into a variety of forms and functions, embedded in all
aspects of hospital care. This innovation explosion paved the ways for new ways of delivering
care, including wearable and portal technologies that empower the individual to be more
knowledgeable of, and involved in their own care. At the same time, adoption of these
technologies has been slower than anticipated -- or desired -- among healthcare leaders. In
response, President Obama signed into law the Health Information Technology for Economic
and Clinical Health (HITECH) Act as part of the American Recovery and Reinvestment Act of
2009 “to promote the adoption and meaningful use of health information technology”
(HHS.gov). While this federal policy was undoubtedly successful in spurring adoption and
implementation of health IT, some hospitals did so more rapidly than others. Knowing what we
know about innovation characteristics and given promising outcomes of health IT adoption, it is
reasonable to assume that we may not have yet witnessed the full extent of health IT’s potential
and are likely just at the cusp of its explosive growth. It is therefore important to understand the
barriers to, and facilitators of, health IT adoption, so we can ensure a nurturing environment for
innovation adoption and implementation.
Review of the literature shows that overall focus has been on factors that emanate from within
the hospital, while few have focused on factors external to hospitals. This study utilizes cross-sectional data to build and test models of the hypothesized influence of hospital-related regional
factors on the adoption of computer practitioner order entry (CPOE) technology across
metropolitan regions, while controlling for the influence of hospital ecosystem, regional health
IT support, regional economic, regional social demographic, regional vitality-impacting, regional
healthcare access and population health factors. This study aims to answer the question, “What
factors influence the adoption of health information technology?”
Part 1 of the analysis examined the influence of static physical capital (measured as average
hospital size within the region) on the adoption of CPOE by 2012 (DV1). It revealed that this
dimension of hospital-related regional factors, had a positive effect, meaning that as average
hospital size for the region increased, adoption of CPOE technology among hospitals in the
region also increased. In contrast, Part II analyses, which focused on the next five years (2012-
2017), revealed that hospitals’ health IT investment decision-making across the region was
negatively influenced by the region’s growth in physician ranks perhaps because a national
Medicaid expansion policy in 2014 signaled growing healthcare utilization. Modeling for DV1
also demonstrated that health IT decision-making by hospitals in the region is exposed to a wider
variety of external influences beyond those emanating from the hospital alone, such as the
healthcare ecology of a region, regional economic performance, and healthcare access. For
healthcare sector and government leaders, this is important to be aware of because it helps define
likely patterns of health IT adoption from a regional perspective and the likely regional profiles
of healthcare transformation
Existential Baudelaire in Fondane, Benjamin, and Sartre
No full textThis dissertation reconstructs a philosophical trialogue that might have been expected to take
place between Jean-Paul Sartre, Walter Benjamin, and Benjamin Fondane over their
philosophical readings of Charles Baudelaire, an exchange preempted by the untimely deaths of
two of the interlocutors. Their projects are motivated by the perceived problem of 20th century
nihilism’s imbrication within the fabric of mental life. Despite decades of attempts to relegate
existential nihilism to obsolescence, we remain within Nietzsche’s projected two-century
window in which nihilism was expected to be paramount as the motif within cultural history. To
draw out ways in which the experience of existential nihilism threatened to annihilate the
conceptual tools of the 20th century, I analyze this trialogue’s key images for nihilism: the abyss,
the flâneur’s turtle, the eternal return, the fall into freedom, and the dandy’s church
Carbon Nanofibers Derived From Polymer Blends as Electrodes for High Performance Supercapacitors
No full textNowadays, generation and storage of energy is vital in our life. Supercapacitors as one the energy storage devices are safe and can store high amount of energy and deliver it in a fast manner. Also, they can be used in a wide range of temperatures and show a high cyclability, which make them proper candidates for broad range of applications. However, compared to other common energy storage systems such as batteries, their energy density is low. Carbon materials are known as the most common materials for making electrodes for supercapacitors. To achieve supercapacitors with high energy density it is important to use the right materials as electrodes with proper morphologies. Two main energy storage mechanisms include electric double layer capacitance which energy is stored electrostatically, in the interface of electrode and electrolyte and pseudocapacitance, in which fast redox reactions occur at or near surface of electrodes. In double layer capacitors, high surface area and controlled pore size and pore distribution is required hence, choice of carbon precursors to obtain these properties is essential. Chapter 1 gives basic information about energy storage systems and mechanisms involved in supercapacitors. Also, carbon nanofibers as one of the popular materials for making electrodes are introduced and how they are made is explained. Chapter 2 introduces polymer blends derived from polyacrylonitrile (PAN) and polymethacrylic acid (PMAA) as suitable candidates for making high surface area carbon fibers with high performance. It shows PMAA can be used as a new degrading polymer which, blended with PAN, can result in phase-separation in carbon fibers. Chapter 3 describes fabricating hybrid materials as electrodes for supercapacitors using PANPMAA blend as carbon source and cobalt oxide. It is shown how using PMAA as a chelating polymer can enhance the distribution and uniformity of metal oxide nanoparticles on the carbon fibers which improve the performance of supercapacitors compared to the ones that are made only with PAN
Risk-associated Inferences in Survival Analysis: a Study on Adequacy of the Cox Model and Isotonic Proportional Hazard Models
No full textSurvival analysis is a powerful statistical methodology utilized in various disciplines to study
time-to-event data, particularly when the time to the event of interest is censored. The Cox
model proposed by (Cox, 1972), also called the proportional hazards model, has been one
of the most frequently used models for survival analysis due to its flexibility without specifying error distribution. However, the proportionality and log-linearity assumptions limit
the use of the model and therefore have led to the development of more adaptable models,
such as the isotonic proportional hazards model proposed by (Chung et al., 2018), which
relaxes the log linearity to the more flexible monotonicity assumption. This dissertation
proposes goodness-of-fit tests for the Cox model under the constraints that the hazard func-
tion is monotonic with respect to continuous covariates. The proposed tests are diagnostics
for the log-linearity assumption for the Cox model, while the minor assumption about the
monotonicity relationship between the hazard and the covariate is satisfied. Three popular
scenarios regarding the continuous covariate of interest are discussed to develop the test,
including time-independent univariate covariate, time-independent univariate covariate together with additional linear-effect covariates, and time-dependent univariate covariate. We
proposed partial-likelihood-ratio-based tests with bootstrapped critical values for the Cox
model versus the isotonic proportional hazards model. Simulation studies under each scenario show the controlled type-I error and the consistency of the test. Several data examples
have been discussed to apply the goodness-of-fit tests, including the heart failure clinical
records data, lung cancer data from North Central Cancer Treatment Group, breast cancer
data from the German Breast Cancer Study Group, monoclonal gammopathy data and the
AIDS Clinical Trials Grup 175 dataset
Dystopian Literary Channels Between Arabic And Western Literature
No full textIn this dissertation, I seek to reveal a double-edged aspect of Arabic dystopian fiction, namely,
how it manifests Western influence and engages with the status quo in several Middle Eastern and
North African countries. The dystopian novel is a relatively new development in Arabic literature,
having emerged as a result of recent events, such as the American-led invasion of Iraq in 2003,
and the waves of Arab Spring, which hit many regions in the Arab-speaking world, starting in the
late of 2010 and continuing until now. I argue that this genre has arisen partly due to its roots in
the translation of Western classical dystopian fiction and partly due to its relevance to the ongoing
state of affairs in many parts of the Arab-speaking world. In a post-colonial context, this genre is
both borrowed from the West to confront bitter realities as well as to critique the Western
hegemony, given that it comprises of both colonial and anti-colonial elements in its dynamic
manifestation. I also attempt to demonstrate how literature as such changes and transforms as it
moves between languages and cultures. In addition, translation plays a crucial role in influencing
and spreading Arabic dystopian novels. In this vein, translation serves a two-edged sword: 1)- as
a means of incorporating Western ideology on Arabic literature; and 2) as a part of an intellectual
movement that protests against ongoing circumstances and the hegemonic power of the
West. Therefore, the double refraction of Arabic dystopian fiction is not merely an index of
Western reflection, but also a tool of resistance against Western hegemony, thus calling for a new
era of independence
Do We Really Know That the WTO Increases Trade?
No full textThis paper estimates the effect of World Trade Organization (WTO) membership on
international trade. I use an augmented version of international trade’s baseline gravity equation
model for my model specification. I also use the dataset for six-nine (69) years and 175
countries. I replicate the study of Rose (2004) and extend the study to cover more years. This
study reveals how model specification bias, omitted variable bias, undermined WTO institutional
reach and wrong technique of data analysis have made WTO’s influence on international trade
statistically insignificant
Adversarial Machine Learning for Social Good
No full textThe deployment of Machine learning (ML) techniques to automate critical decision-making
in healthcare, employment, finance, and crime prevention has played a huge role in im-
proving these systems. However, an incorrect decision can lead to potentially life-changing
consequences. In addition, these deployed ML models are also highly vulnerable to test-time
adversarial attacks. Thus these ML models need to be made trustworthy and reliable. This
dissertation deals with these problems and presents work to make the model more robust,
fair, and reliable by using adversarial machine learning techniques.
In this dissertation, we start with the problem of whether ML-based deception detection
systems are generalizable to real-life scenarios. We perform experiments to examine whether
multimodal aspects such as facial expressions, eye movements, and video cues can be used
as deception detection features. We develop three different datasets based on real-life lying
scenarios (e.g., for a reward, duress, and speaking white lies) and use them as deception
detection features. We also study state-of-the-art deception detection systems and algorithms
and try to extend them to our deception scenarios. We show that deception detection is not
generalizable to real-life scenarios, and more subject matter knowledge and better models
are needed to make such a claim.
We also address the issue of using adversarial examples to protect user security and privacy
and make the black-box models more advantageous to the end-user, specifically in the vision
and tabular data domain. In the vision domain, we consider the problems of protecting a
sensitive attribute (e.g., gender) using an adversarial artifact like adversarial glasses on the
image. In the tabular data domain, we provide adversarial recommendations to the user in
their loan application data to change the black-box loan application model from bad credit to
good credit. Thus, we demonstrate that we can craft adversarial examples to help end-users
protect their privacy and ensure they do not get unfair treatment.
Finally, we tackle the problem of multi-concept adversarial examples. We show that the
state-of-the-art adversarial attack of a particular classifier, e.g., gender, reduces the accuracy
of a different classifier, e.g., age trained independently on the same data pool. Combining
the loss functions of the attacked model and the protected model in our loss formulation
shows that we can create targeted adversarial attacks. These custom adversarial attacks not
only successfully attack the target classifiers, but also cause no drop in the accuracy of the
other classifiers in the protected set
Secrecy and covertness in the presence of multi-casting, channel state information, and cooperative jamming
No full textWe study secret communication over multi-transmitter multicast problem in the presence of
an eavesdropper, wherein weak and strong secrecy regimes are studied. For the weak secrecy
regime, the method of Chia and El Gamal is extended to two transmitters. We show that the
achievable region calculated for the weak secrecy regime in this channel configuration is no
bigger than the one calculated under strong secrecy. Two examples are presented in which
the inner and outer bounds of secrecy region meet. In the process, we also characterize the
minimum amount of randomness necessary to achieve secrecy in the multiple-access wiretap
channel.
We consider the problem of covert communication over a state-dependent channel when
the Channel State Information (CSI) is available either non-causally, causally, or strictly
causally, either at the transmitter alone, or at both transmitter and receiver. In contrast to
previous work, we do not assume the availability of a large shared key at the transmitter and
legitimate receiver. Instead, we only require a secret key with negligible rate to bootstrap
the communication and our scheme extracts shared randomness from the CSI in a manner
that keeps it secret from the warden, despite the influence of the CSI on the warden’s output.
When CSI is available at the transmitter and receiver, we derive the covert capacity region.
When CSI is only available at the transmitter, we derive inner and outer bounds on the covert capacity. We also provide examples for which the covert capacity is positive with
knowledge of CSI but is zero without it.
We consider the problem of covert communication in the presence of a cooperative jammer.
It is known that in general, a transmitter and a receiver can communicate only O(
√
n)
covert bits over n channel uses, i.e., zero rate. Here, we show that a cooperative jammer
can facilitate the communication of positive covert rates, subject to the presence of friendly
jammer in the environment. We consider various scenarios in which it is possible to achieve
positive rate for covert communication. For these scenarios, we derive inner and outer bounds
on the covert capacity region, and also we characterize the covert capacity region for some
of these scenarios
Grid Forming Energy Router: A utility interface for Renewable Energy Sources and Energy Storage Grid Integration Applications
No full textLarge scale integration of Renewable Energy Sources (RES) (Solar/Photovoltaic (PV), Fuel
Cells (FC), wind) with smart devices into the grid is becoming an attractive concept to
meet increasing energy demand and to reduce stress on the conventional grid. Smart grid
which is an advanced automated power grid is a fascinating idea of bringing RES closer
to centralized generation with smart sensing devices, advanced control and integrated communications. This convergence provides more reliable and efficient renewable power while
reducing the carbon footprint, with reduction in power transmission distance, cost and associated transmission losses. However, intermittent nature of RES impacts power quality, grid
stability and reliability, which makes it imperative to integrate RES with Energy Storage
(ES) for their widespread adoption. Also, real-time control of data, information exchange,
and energy management in smart grid are crucial for a fast, reliable, and secure system.
Thus, the design of a utility interface known as Energy router (ER) for RES, ES, and grid
integration application, which is smart, intelligent, portable, resilient and easy to operate
was the primary source of motivation for this research.
This dissertation discusses the design and development of ER architecture and control for
RES, ES, and grid integration application. To ensure seamless interaction and power transfer
(bidirectional, if required) among the RES, ES, grid, and load, in ER a compact and efficient
Multi-Port Converter (MPC) is required. Apart from selection of suitable MPC and hence,
the structure for ER, the ER control also needs attention. Due to the presence of inverterbased RES with zero/low inertia, the ER does not respond dynamically to frequency changes
and leads to frequency swings during load disturbances which can cause load tripping issues.
This dissertation discusses the development of control for ER, which enables ER to synchronize autonomously with the grid and emulate the behavior of Synchronous Machine (SM) to
stabilize and regulate the voltage and frequency of the system during disturbances. This is
done by adding virtual inertia and damping into the system and the control is known as Grid
Forming (GFM) droop control. To harvest maximum performance efficiency, real-time and
dynamic control with energy management from ER in the smart-grid network this dissertation also explores the development of a dedicated communication module to be integrated
with the ER.
First, the proposed ER architecture and it’s control were simulated in MATLAB/Plecs and
various operating scenarios were evaluated. Simulation results prove the viability of the ER,
and its control algorithm for various operating scenarios involving RES and ES systems.
Subsequently, the ER blocks were implemented using GaN devices and experimentally verified. Measurements indicate that this small-scale laboratory prototype is able to transfer
around 1.2kW of power in both directions between battery and dc bus