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 Degree Level: Master's
 Collection: UNT Theses and Dissertations
Effects of UE Speed on MIMO Channel Capacity in LTE

Effects of UE Speed on MIMO Channel Capacity in LTE

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Date: August 2016
Creator: Shukla, Rahul
Description: With the introduction of 4G LTE, multiple new technologies were introduced. MIMO is one of the important technologies introduced with fourth generation. The main MIMO modes used in LTE are open loop and closed loop spatial multiplexing modes. This thesis develops an algorithm to calculate the threshold values of UE speed and SNR that is required to implement a switching algorithm which can switch between different MIMO modes for a UE based on the speed and channel conditions (CSI). Specifically, this thesis provides the values of UE speed and SNR at which we can get better results by switching between open loop and closed loop MIMO modes and then be scheduled in sub-channels accordingly. Thus, the results can be used effectively to get better channel capacity with less ISI. The main objectives of this thesis are: to determine the type of MIMO mode suitable for a UE with certain speed, to determine the effects of SNR on selection of MIMO modes, and to design and implement a scheduling algorithm to enhance channel capacity.
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"Counting Out The Harvest"

"Counting Out The Harvest"

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Date: August 2016
Creator: Lischau, Carol
Description: "Counting Out The Harvest" is a collection of poems exploring intimate encounters. The poems reflect on encounters with memories, family, and the natural and cosmic worlds. In one of the poems, "Red-Throated Anole," the speaker works desperately to save a small dying lizard. In "Ice Storm, Post-Divorce," the speaker attempts to decipher a cluster of ladybugs taking refuge in her room. In the title poem, a couple wonders patiently if their crop will eventually grow. In each of these poems there is a present longing for the construction of a meaningful identity by means of the encounter, but the intersection between speaker and world falls short of satisfaction, whether the faultiness lies in the body's inability to find full sustenance, or in the ever-changing fluidity of memory to find stability. But the poems progress from pressing against this difficulty toward finding a contented resignation to the world's cyclical order. The final line of the manuscript, "disrobe a layer to begin again," indicates an arrival at satisfaction, which is found ultimately in continuation.
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Synthesis, Characterization and Catalytic Studies of Chiral Gold Acyclic Diaminocarbene Complexes

Synthesis, Characterization and Catalytic Studies of Chiral Gold Acyclic Diaminocarbene Complexes

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Date: August 2016
Creator: Zhang, Xiaofan
Description: Chiral gold complexes have been applied in homogeneous catalytic reactions since 1986, in some cases with high enantioselectivity. Acyclic diaminocarbene (ADC) ligands are acyclic analogues of N-heterocyclic carbenes (NHCs) that have larger N-CCarbene-N angles and stronger donating ability. ADCs have been developed as alternatives to phosphine and NHC ligands in homogeneous gold catalysis. In 2012, a new series of chiral gold(I) ADCs were first developed by Slaughter's group and were shown to give remarkable enantioselectivities in some reactions. Because of the hindered rotation of the N-CCarbene bonds of ADC, chiral ADC substituents can easily get close to the metal center in some conformations, although two rotameric structures are formed if the chiral amine is nonsymmetric. The selective of specific ADC conformations was the initial focus of this study. Formational selectivity of one diastereomer of an ADC ligand during synthesis was examines by measuring the relative rates of diastereomer formation in a 1H NMR kinetic study. The potential for converting multiple conformational isomers of ADCs into a single conformation, or at least a simpler mixture, was examined. This study used the analogy that anti- isomer has electronic and structural similarity with urea/thiourea, raising the possibility that 1,8-naphthyridine can be used to ...
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Quantification of Human Thermal Comfort for Residential Building's Energy Saving

Quantification of Human Thermal Comfort for Residential Building's Energy Saving

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Date: August 2016
Creator: Sharifani, Pooya
Description: Providing conditioned and fully controlled room is the final goal for having a comfortable building. But on the other hand making smart controllers to provide the required cooling or heating load depending on occupants' real time feeling is necessary. This study has emphasized on finding a meaningful and steady state parameter in human body that can be interpreted as comfort criterion which can be expressed as the general occupants' sensation through their ambient temperature. There are lots of researches on human physiological behavior in different situations and also different body parts reaction to the same ambient situation. Body parts which have the biggest reliable linear fluctuation to the changes are the best subject for this research. For these tests, wrist and palm have been selected and their temperatures on different people have been measured accurately with thermal camera to follow the temperature trend on various comfort levels. It is found that each person reaches to his own unique temperature on these two spots, when he/ she feels comfortable, or in other word each person's body temperature is a precise nominate for comfort feeling of that individual. So in future by having this unique comfort parameter and applying them to the ...
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Network Security Tool for a Novice

Network Security Tool for a Novice

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Date: August 2016
Creator: Ganduri, Rajasekhar
Description: Network security is a complex field that is handled by security professionals who need certain expertise and experience to configure security systems. With the ever increasing size of the networks, managing them is going to be a daunting task. What kind of solution can be used to generate effective security configurations by both security professionals and nonprofessionals alike? In this thesis, a web tool is developed to simplify the process of configuring security systems by translating direct human language input into meaningful, working security rules. These human language inputs yield the security rules that the individual wants to implement in their network. The human language input can be as simple as, "Block Facebook to my son's PC". This tool will translate these inputs into specific security rules and install the translated rules into security equipment such as virtualized Cisco FWSM network firewall, Netfilter host-based firewall, and Snort Network Intrusion Detection. This tool is implemented and tested in both a traditional network and a cloud environment. One thousand input policies were collected from various users such as staff from UNT departments' and health science, including individuals with network security background as well as students with a non-computer science background to analyze ...
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The Moderating Effect of Religiosity on the Relationship between Attachment and Psychological Wellbeing in a Muslim-American Sample

The Moderating Effect of Religiosity on the Relationship between Attachment and Psychological Wellbeing in a Muslim-American Sample

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Date: August 2016
Creator: Khan, Arubah
Description: Although research on attachment theory has grown exponentially in the field of psychology, few studies exist that examine this theory among young Muslim-American adults, despite the fact that Muslim-Americans represent a significant and growing segment of the U.S. population. The first goal of the current study was to replicate the results of previous studies demonstrating a strong relationship between attachment and the selected wellbeing indicators of psychological symptoms and life satisfaction. The second goal of the proposed study was to examine the relationships among maternal attachment, Islamic religiosity, and psychological wellbeing. Findings provided partial support to the direct effects of attachment and religiosity variables on particular outcome variables but did not support the moderating effect of religiosity. High maternal Control was found to be predictive of less psychological distress, whereas both maternal control and care were found to be negatively associated with an interpersonal behaviors aspect of religiosity. In addition, those who endorsed practicing Islamic rituals were found to report less life satisfaction, and individuals who viewed the world through an Islamic lens reported higher psychological distress. Discussion on the findings, limitations of the study, future research directions, and counseling implications are addressed.
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"This Fundamental Lack": Stories

"This Fundamental Lack": Stories

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Date: August 2016
Creator: Bohanan, Ronal L.
Description: This short story collection includes five original works of fiction, three of which make up a trilogy titled "The World Drops Beneath You," which follows the life of James McClellan from 1969 in Texas until roughly 2009, when he is struggling to care for his wife, who suffers from Alzheimer's disease. One of the two remaining stories, "She Loved Him When He Looked Like Elvis," prominently features James McClellan's parents and is set approximately eight years before the start of the trilogy. Each of the stories is concerned with blue-collar families trying to make their way in postindustrial America and the forces that buffet them, including some brought on by the choices they make.
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Compostable Soy-Based Polyurethane Foam with Kenaf Core Modifiers

Compostable Soy-Based Polyurethane Foam with Kenaf Core Modifiers

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Date: August 2016
Creator: Hoyt, Zachary
Description: Building waste and disposable packaging are a major component in today's landfills. Most of these are structural or thermally insulative polymer foams that do not degrade over a long period of time. Currently, there is a push to replace these foams with thermoplastic or biodegradable foams that can either be recycled or composted. We propose the use of compostable soy-based polyurethane foams (PU) with kenaf core modifiers that will offer the desired properties with the ability to choose responsible end-of-life decisions. The effect of fillers is a critical parameter in investigating the thermal and mechanical properties along with its effect on biodegradability. In this work, foams with 5%, 10%, and 15% kenaf core content were created. Two manufacturing approaches were used: the free foaming used by spray techniques and the constrained expansion complementary to a mold cavity. Structure-property relations were examined using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermal conductivity, compression values, scanning electron microscopy (SEM), x-ray micro-computed tomography (micro-CT), and automated multiunit composting system (AMCS). The results show that mechanical properties are reduced with the introduction of kenaf core reinforcement while thermal conductivity and biodegradability display a noticeable improvement. This shows that in application properties can be ...
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Hungering for Independence: The Relationship between Food and Morale in the Continental Army, 1775-1783

Hungering for Independence: The Relationship between Food and Morale in the Continental Army, 1775-1783

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Date: May 2016
Creator: Maxwell, Nancy
Description: An adequate supply of the right kinds of foods is critical to an army's success on the march and on the battlefield. Good food supplies and a dire lack of provisions have profound effects on the regulation, confidence, esprit de corps, and physical state of an army. The American War of Independence (1775-1783) provides a challenging case study of this principle. The relationship between food and troop morale has been previously discussed as just one of many factors that contributed to the success of the Continental Army, but has not been fully explored as a single issue in its own right. I argue that despite the failures of three provisioning system adopted by the Continental Congress - the Commissariat, the state system of specific supplies, and the contract system - the army did keep up its morale and achieve the victory that resulted in independence from Great Britain. The evidence reveals that despite the poor provisioning, the American army was fed in the field for eight years thanks largely to its ability to forage for its food. This foraging system, if it can be called a system, was adequate to sustain morale and perseverance.
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Highly Stretchable Miniature Strain Sensor for Large Dynamic Strain Measurement

Highly Stretchable Miniature Strain Sensor for Large Dynamic Strain Measurement

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Date: May 2016
Creator: Yao, Shulong
Description: This thesis aims to develop a new type of highly stretchable strain sensor to measure large deformation of a specimen subjected to dynamic loading. The sensor was based on the piezo-resistive response of carbon nanotube(CNT)/polydimethysiloxane (PDMS) composites thin films, some nickel particles were added into the sensor composite to improve the sensor performance. The piezo-resistive response of CNT composite gives high frequency response in strain measurement, while the ultra-soft PDMS matrix provides high flexibility and ductility for large strain measuring large strain (up to 26%) with an excellent linearity and a fast frequency response under quasi-static test, the delay time for high strain rate test is just 30 μs. This stretchable strain sensor is also able to exhibit much higher sensitivities, with a gauge factor of as high as 80, than conventional foil strain gauges.
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'My Tattooed Mind'

'My Tattooed Mind'

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Date: May 2016
Creator: Mayo, Kaleb R
Description: This thesis features a collection of nonfiction essays.
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Microstructural Phase Evolution In Laser Deposited Compositionally Graded Titanium-Chromium Alloys

Microstructural Phase Evolution In Laser Deposited Compositionally Graded Titanium-Chromium Alloys

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Date: May 2016
Creator: Thomas, Jonova
Description: A compositionally graded Ti-xCr (10≤x≤30 wt%) alloy has been fabricated using Laser Engineered Net Shaping (LENSTM) to study the microstructural phase evolution along a compositional gradient in both as-deposited and heat treated conditions (1000°C followed by furnace cooling or air cooling). The alloys were characterized by SEM BSE imaging, XRD, EBSD, TEM and micro-hardness measurements to determine processing-structure-property relations. For the as-deposited alloy, α-Ti, β-Ti, and TiCr2 (C15 Laves) phases exist in varying phase fractions, which were influential in determining hardness values. With the furnace cooled alloy, there was more homogeneous nucleation of α phase throughout the sample with a larger phase fraction of TiCr2 resulting in increased hardness values. When compared to the air cooled alloy, there was absence of wide scale nucleation of α phase and formation of ω phase within the β phase due to the quicker cooling from elevated temperature. At lower concentrations of Cr, the kinetics resulted in a diffusionless phase transformation of ω phase with increased hardness and a lower phase fraction of TiCr2. In contrast at higher Cr concentrations, α phase separation reaction occurs where the β phase is spinodally decomposed to Cr solute-lean β1 and solute-rich β2 resulting in reduced hardness.
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Social Anxiety and Non-Medical Prescription Stimulant Use among College Students

Social Anxiety and Non-Medical Prescription Stimulant Use among College Students

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Date: May 2016
Creator: Cloutier, Renee
Description: Current evidence suggests that non-medical prescription stimulant (NMPS) use is on the rise, particularly among college students. Identifying individuals at risk for regular and problematic use is a critical step towards the development of effective intervention efforts. A growing body of work has noted that individuals with elevated levels of social anxiety (SA) or social anxiety disorder are at an enhanced risk for developing substance use problems, including NMPS use disorder. Despite the relevance of SA and NMPS use among college students, no studies have attempted to examine subclinical SA or the relation between SA and NMPS use among college students specifically. Thus, the present study sought to extend this area by testing the relation of SA symptoms and NMPS use frequency among college students. A large online study of college students was conducted (N=1604) to identify 252 NMPS users (18-25 years; 68.3% female). A hierarchical linear regression was used to test the moderation of positive prescription stimulant expectancies on SA symptoms in predicting past year NMPS use frequency. A subsample of 15 participants was also brought into the lab to assess subjective (State Anxiety) and physiological (salivary cortisol) responding to a social stressor task. Overall, the current study did ...
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Adhesion and Surface Energy Profiles of Large-area Atomic Layers of Two-dimensional MoS2 on Rigid Substrates by Facile Methods

Adhesion and Surface Energy Profiles of Large-area Atomic Layers of Two-dimensional MoS2 on Rigid Substrates by Facile Methods

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Date: May 2016
Creator: Wu, Min
Description: Two-dimensional (2D) transition metal dichalcogenides (TMDs) show great potential for the future electronics, optoelectronics and energy applications. But, the studies unveiling their interactions with the host substrates are sparse and limits their practical use for real device applications. We report the facile nano-scratch method to determine the adhesion energy of the wafer scale MoS2 atomic layers attached to the SiO2/Si and sapphire substrates. The practical adhesion energy of monolayer MoS2 on the SiO2/Si substrate is 7.78 J/m2. The practical adhesion energy was found to be an increasing function of the MoS2 thickness. Unlike SiO2/Si substrates, MoS2 films grown on the sapphire possess higher bonding energy, which is attributed to the defect-free growth and less number of grain boundaries, as well as less stress and strain stored at the interface owing to the similarity of Thermal Expansion Coefficient (TEC) between MoS2 films and sapphire substrate. Furthermore, we calculated the surface free energy of 2D MoS2 by the facile contact angle measurements and Neumann model fitting. A surface free energy ~85.3 mJ/m2 in few layers thick MoS2 manifests the hydrophilic nature of 2D MoS2. The high surface energy of MoS2 helps explain the good bonding strength at MoS2/substrate interface. This simple adhesion ...
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Predicting Posttraumatic Stress Disorder Symptoms During Adolescence: A Longitudinal Study of The Role of Hypothalamic-Pituitary-Adrenal (HPA) Axis Dysfunction

Predicting Posttraumatic Stress Disorder Symptoms During Adolescence: A Longitudinal Study of The Role of Hypothalamic-Pituitary-Adrenal (HPA) Axis Dysfunction

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Date: May 2016
Creator: Liu, Keke
Description: Posttraumatic stress disorder (PTSD) is a trauma-related disorder that may develop in response to traumatic or stressful events. Dysfunction of the Hypothalamic-Pituitary-Adrenal (HPA) axis has been implicated in the disorder. Studies support such dysfunction as being a consequence of PTSD, rather than a precursor. However, most studies of the HPA are either cross-sectional or have been carried out in adults. The aim of the present study was to identify whether HPA dysregulation interacts with stressful experiences to increase the likelihood of developing PTSD symptoms in a community-recruited sample of healthy adolescent girls. Adolescent girls (N = 550) and one of their parents participated. Adolescents’ clinical symptoms were assessed at baseline and at a nine month follow-up. Saliva samples were collected from all adolescent participants at waking, 30 minutes after waking, and 8 pm on 3 consecutive days. Flattened diurnal slope of cortisol at baseline was associated with increased PTSD symptoms nine months later. Baseline cortisol awakening response (CAR) per se was not prospectively related to developing PTSD symptoms, but its interactions with stressful experience was associated with elevated PTSD symptoms at follow-up. Effects were small and need to be replicated in samples with more severe stressors, as well as more ...
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Eaten: A Novel

Eaten: A Novel

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Date: May 2016
Creator: Foster, Natalie
Description: This novel operates on two levels. First, it is a story concerning the fate of a young woman named Raven Adams, who is prompted into journeying westward after witnessing what she believes to be an omen. On another level, however, the novel is intended to be a philosophical questioning of western modes of “science-based” singular conceptualizations of reality, which argue that there is only one “real world” and anyone who deviates from this is “crazy,” “stupid,” or “wrong.” Raven as a character sees the world in terms of what might be called “magical thinking” in modern psychology; her closest relationship is with a living embodiment of a story, the ancient philosopher Diogenes, which she believes is capable of possessing others and directing her journey. As the story continues the reader comes to understand Raven’s perceptions of her reality, leading to a conceptualization of reality as being “multi-layered.” Eventually these layers are collapsed and unified in the final chapters. The novel makes use of many reference points including philosophy, classical mythology, folklore, religion, and internet social media in order to guide the reader along Raven’s story.
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Role of Combat Exposure and Insomnia in Student Veterans' Adaptation to College

Role of Combat Exposure and Insomnia in Student Veterans' Adaptation to College

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Date: May 2016
Creator: McGuffin, James J
Description: Since 2002, the number of veterans enrolled in universities has nearly doubled, although 30-40% of veterans fail to complete their degree. While research efforts to understand the challenges veterans face transitioning from military life to college has increased in recent years, few studies have looked beyond the effects of post-traumatic stress disorder (PTSD). Insomnia is the most frequently reported symptom of combat veterans and can have serious implications for college students. The purpose of this study was to examine the role of insomnia and student veteran adaptation to college relative to civilian students. College students (N = 588) were administered a Background Information Questionnaire, the Insomnia Severity Index, the Deployment Risk and Resilience Inventory, and the Student Adaptation to College Questionnaire. Results revealed that students with insomnia reported significantly lower adaptation to college than students without insomnia. Student veterans reported better academic and personal-emotional adaptation to college than civilian students, while civilians reported better social adjustment than veterans. Although combat veterans without insomnia scored consistently higher academic adjustment than non-combat veterans and civilian students, when present insomnia seemed to have a greater negative effect on combat veterans’ academic adjustment relative to civilian students. Furthermore, insomnia mediated the relationship between combat ...
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Exploring Inorganic Catalysis with Electronic Structure Simulations

Exploring Inorganic Catalysis with Electronic Structure Simulations

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Date: May 2016
Creator: Karbalaei Khani, Sarah
Description: Organometallic catalysis has attracted significant interest from both industry and academia due to its wide applications in organic synthetic transformations. Example of such transformations include the reaction of a zinc carbenoid with olefins to form cyclopropanes. The first project is a computational study using both density functional and correlated wavefunction methods of the reaction between ethylene and model zinc carbenoid, nitrenoid and oxenoid complexes (L-Zn-E-X, E = CH2, NH or O, L = X = I or Cl). It was shown that cyclopropanation of ethylene with IZnCH2I and aziridination of ethylene with IZnNHI proceed via a single-step mechanism with an asynchronous transition state. The reaction barrier for the aziridination with IZnNHI is lower than that of cyclopropanation. Changing the leaving group of IZnNHI from I to Cl, changes the mechanism of the aziridination reaction to a two-step pathway. The calculation results from the epoxidation with IZnOI and ClZnOCl oxenoids suggest a two-step mechanism for both oxenoids. Another important example of organometallic catalysis is the formation of alkyl arenes from arenes and olefins using transition metal catalysis (olefin hydroarylation). We studied with DFT methods the mechanism of a novel Rh catalyst (FlDAB)Rh(TFA)(η2–C2H4) [FlDAB = N,N’ -bis(pentafluorophenyl)-2,3-dimethyl-1,4-diaza-1,3-butadiene; TFA = trifluoroacetate] that converts ...
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Evaluating the Pulse Sensor as a Low-Cost and Portable Measurement of Blood Pulse Waveform

Evaluating the Pulse Sensor as a Low-Cost and Portable Measurement of Blood Pulse Waveform

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Date: May 2016
Creator: Smithers, Breana Gray
Description: This study was aimed at determining whether the digital volume pulse waveform using the Pulse Sensor can be used to extract features related to arterial compliance. The Pulse Sensor, a low-cost photoplethysmograph, measures green light reflection in the finger and generates output, which is indicative of blood flow and can be read by the low-cost Arduino UNO™. The Pulse Sensor code was modified to increase the sampling frequency and to capture the data in a file, which is subsequently used for waveform analysis using programs written in the R system. Waveforms were obtained using the Pulse Sensor during two 30-s periods of seated rest, in each of 44 participants, who were between the ages of 20 and 80 years. For each cardiac cycle, the first four derivatives of the waveform were calculated and low-pass filtered by convolution before every differentiation step. The program was written to extract 19 features from the pulse waveform and its derivatives. These features were selected from those that have been reported to relate to the physiopathology of hemodynamics. Results indicate that subtle features of the pulse waveform can be calculated from the fourth derivative. Feature misidentification occurred in cases of saturation or low voltage and ...
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Developing Policy for a Tech Program Based on Understanding Organizational Practices

Developing Policy for a Tech Program Based on Understanding Organizational Practices

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Date: May 2016
Creator: Machado Perez, Luis Daniel
Description: This thesis contributes to research that informs the studies of organizational management and organizational anthropology. It examines the internal hierarchy and organizational practices of a Tech Company and describes how findings contributed to policy recommendations aimed towards supporting a “guild” model for organizational success. The data collecting and research were undertaken while working as an employee of the Tech Program and subsequent analysis continued past the end of that phase of work. Methods included semi-structured interviews which captured the sentiments and understandings of employees within the organization, and a questionnaire which revealed sentiments and experiences from former employees. These were buttressed with participant observation engaged through a participatory action research methodology. Findings add to the work directed towards understanding the effect of Founder’s Syndrome within organizations. Additionally, this thesis contributes to a growing body of research centered on best practices for fostering positive organizational growth by creating lines of communication from front-line employees to management level employers.
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Learning from small data set for object recognition in mobile platforms.

Learning from small data set for object recognition in mobile platforms.

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Date: May 2016
Creator: Liu, Siyuan
Description: Did you stand at a door with a bunch of keys and tried to find the right one to unlock the door? Did you hold a flower and wonder the name of it? A need of object recognition could rise anytime and any where in our daily lives. With the development of mobile devices object recognition applications become possible to provide immediate assistance. However, performing complex tasks in even the most advanced mobile platforms still faces great challenges due to the limited computing resources and computing power. In this thesis, we present an object recognition system that resides and executes within a mobile device, which can efficiently extract image features and perform learning and classification. To account for the computing constraint, a novel feature extraction method that minimizes the data size and maintains data consistency is proposed. This system leverages principal component analysis method and is able to update the trained classifier when new examples become available . Our system relieves users from creating a lot of examples and makes it user friendly. The experimental results demonstrate that a learning method trained with a very small number of examples can achieve recognition accuracy above 90% in various acquisition conditions. In ...
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Bioinspired and biocompatible coatings of poly(butylene adipate-co-terephthalate) and layer double hydroxide composites for corrosion resistance

Bioinspired and biocompatible coatings of poly(butylene adipate-co-terephthalate) and layer double hydroxide composites for corrosion resistance

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Date: May 2016
Creator: Rizvi, Syed Hussain
Description: Hierarchical arrangement of biological composites such as nacre and bone containing high filler (ceramic) content results in high strength and toughness of the natural material. In this study we mimic the design of layered bone microstructure and fabricate an optimal multifunctional bio-nanocomposite having strength, toughness and corrosion resistance. Poly (butylene adipate-co-terephthalate) (PBAT), a biodegradable polymer was used as a substrate material with the reinforcement of LDH (Layered double hydroxide) as a nanofiller in different concentrations to achieve enhancement in mechanical properties as well as processing related thermostability. Corrosion resistance was increased by mimicking a layered structured which incorporated a tortuous diffusion path.
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Medical Comorbidity in the Course of Bipolar Disorder

Medical Comorbidity in the Course of Bipolar Disorder

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Date: May 2016
Creator: Smith, Patrick M
Description: Bipolar disorder is a serious illness affecting approximately 2-4% of the population and is one of the world’s leading causes of disability. In individuals with bipolar disorder, medical comorbidity associated with cardiovascular, respiratory and endocrine disorders is related to increased rates of mortality. Recent updates to multi-system inflammatory related conceptualizations of bipolar disorder focus on the unique power that medical illness and biological processes may play as factors associated with course and outcome in bipolar disorder. The current study examined medical comorbidity and its associations with various demographic and psychological variables in individuals with bipolar disorder, schizophrenia, and major depressive disorder with psychotic features followed for 10 years from their first hospital admission. When compared to an age, gender and race-matched control sample from the population, those with bipolar disorder had significantly higher medical comorbidity across a range of medical diagnoses both at 6 months and 10 years after first hospital admission. Ten years following initial hospitalization, individuals in all three diagnostic groups reported increased rates of diabetes (OR: 2.0 – 3.7), stroke (OR: 4.6 – 7.0) and asthma (OR: 1.9 - 3.1), and individuals with bipolar disorder reported increased rates of cancer (OR = 2.1). A number of psychological ...
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Investigation of the Effect of Particle Size and Particle Loading on Thermal Conductivity and Dielectric Strength of Thermoset Polymers

Investigation of the Effect of Particle Size and Particle Loading on Thermal Conductivity and Dielectric Strength of Thermoset Polymers

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Date: May 2016
Creator: Warner, Nathaniel Anthony
Description: Semiconductor die attach materials for high voltage, high reliability analog devices require high thermal conductivity and retention of dielectric strength. A comparative study of effective thermal conductivity and dielectric strength of selected thermoset/ceramic composites was conducted to determine the effect of ceramic particle size and ceramic particle loading on thermoset polymers. The polymer chosen for this study is bismaleimide, a common aerospace material chosen for its strength and thermal stability. The reinforcing material chosen for this study is a ceramic, hexagonal boron nitride. Thermal conductivity and dielectric breakdown strength are measured in low and high concentrations of hexagonal boron nitride. Adhesive fracture toughness of the composite is evaluated on copper to determine the composite’s adhesive qualities. SEM imaging of composite cross-sections is used to visualize particle orientation within the matrix. Micro-indentation is used to measure mechanical properties of the composites which display increased mechanical performance in loading beyond the percolation threshold of the material. Thermal conductivity of the base polymer increases by a factor of 50 in 80%wt loading of 50µm hBN accompanied by a 10% increase in composite dielectric strength. A relationship between particle size and effective thermal conductivity is established through comparison of experimental data with an empirical ...
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