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Gan Nanostructuring For The Fabrication Of Thin Membranes And Emerging Applications, Ion Tiginyanu, Veaceslav Ursaki

Turkish Journal of Physics

We present a review of technological methods developed in recent years for the purpose of gallium nitride nanostructuring, with the main focus on fabrication of thin GaN membranes. In particular, we report on traditional methods of wet etching undercutting for membrane manufacturing, technologies applied for the fabrication of photonic crystal structures based on GaN nanomembranes, double side processing, and surface charge lithography. Prospects of membrane applications in photonic devices, sensors, and microoptoelectromechanical and nanoelectromechanical systems are discussed, taking into account the advantageous piezoelectric, optical, and mechanical properties of GaN and related III-V nitride materials.

Self-Assembled Nanocrystalline Zno Thin Film Transistor Performance Optimization For High Speed Applications, Burhan Bayraktaroglu, Kevin Leedy

Turkish Journal of Physics

ZnO nanocrystals grown at relatively low temperatures using various vacuum deposition techniques can yield semiconducting thin films of self-assembled nanocolumns 20-50 nm in diameter. Such films are suitable for the fabrication of high speed and transparent thin film transistors (TFTs). Unlike amorphous TFTs, the performance of ZnO transistors depends both on the crystal quality of nanocrystals and the electrical properties of boundary layers between them. We investigated the use of radio frequency sputtering, atomic layer deposition, and pulsed laser deposition techniques to fabricate self-assembled nanocrystalline thin films and determined the influence of deposition conditions on the performance of transistors. Device …

Optical Properties Of Zno/(Zn, Mg)O Quantum Wells, Thierry Bretagnon

Turkish Journal of Physics

This paper reviews the optical properties of ZnO/(Zn, Mg)O single quantum wells grown by molecular beam epitaxy. Both heteroepitaxial quantum well growth along the polar c-direction and homoepitaxial quantum well growth on the nonpolar M plane cases are considered. The optical properties of these quantum wells are investigated by using reflectance, continuous wave photoluminescence, and time-resolved photoluminescence spectroscopies. The quantum-confined Stark effect dominates the properties of the excitons for polar quantum wells. The magnitude of the internal electric field that is induced by both spontaneous and piezoelectric polarizations is determined by comparing the experimental results with a variational calculation of …

The Influence Of Tio_2 Nanostructure Properties On The Performance Of Tio_2-Based Anodes In Lithium Ion Battery Applications, Xiang Liu, Qian Sun, Fangzhou Liu, Aleksandra B. Djurisic, Alan Man Ching Ng, Maohai Xie, Tom Wood, Juan Antonio Zapien, Changzhong Liao, Kaiming Shih

Turkish Journal of Physics

We investigated the properties of 7 different titanium dioxide nanostructures with different crystal structures (3 anatase, 2 rutile, and 2 mixed anatase--rutile phase). Nanoparticle samples and mesoporous sphere samples were investigated. Even for the same crystal structure, significant variations in performance were observed for anatase titania samples, while 2 rutile samples exhibited similar performance inferior to anatase-based anodes. Mixed-phase samples also exhibited lower specific capacity compared to the best performing anatase samples, and in this case a significant difference in performance was observed between nanoparticles and mesoporous spheres.

Optical And Magnetic Properties Of (Er, F) Co-Doped Sno_2 Nanocrystals, Vinod Kumar, Sitharaman Uma, Rajamani Nagarajan

Turkish Journal of Physics

Uniformly (Er, F) co-doped SnO_2 nanocrystals, obtained by a low-temperature solution-based method, were characterized by a variety of analytical techniques. The structure, morphology, and ratio of the elements were confirmed by PXRD, SEM, and TEM analysis, respectively. From XPS analysis, atomic concentrations of Sn, O, and F were quantified. Interparticle pore size increased significantly (with a mean pore diameter of 25.82 nm) in the co-doped sample. Higher in-plane oxygen vacancies and bands due to multiphonon scattering were observed in the Raman spectrum of the sample. The defect traps in the sample were experimentally determined using TL spectroscopy. A broad intense …

Processing Of Germanium For Integrated Circuits, Ray Duffy, Maryam Shayesteh, Ran Yu

Turkish Journal of Physics

In this review paper the authors will focus on Ge processing for integrated circuits. The key areas that require the most attention are substrates and integration, gate dielectrics, and access resistance. We will discuss each of these topics in turn, while also reviewing the most scaled Ge field-effect-transistor devices, and consider how modelling activities have matured for Ge in recent years.

Two-Dimensional Mos_2 As A New Material For Electronic Devices, Natalia Izyumskaya, Denis O. Demchenko, Vitaliy Avrutin, Ümi̇t Özgür, Hadis Morkoç

Turkish Journal of Physics

We overview fundamental properties, preparation techniques, and potential device applications of single- and few-monolayer-thick molybdenum disulfide MoS_2 belonging to a new emerging class of materials: 2-dimensional semiconductors. To a large extent, the interest in the 2-dimensional materials is fueled by the quest for alternatives to graphene, which is hardly suitable for electronic devices because of the lack of a band gap. A unique combination of physical properties, including flexibility, high electron mobility, and optical transparency combined with a large band gap tunable from indirect 1.2 eV for bulk to direct 1.9 eV for a monolayer, make MoS_2 attractive for a …

Device Architectures In Organic Photovoltaics, James T. Mcleskey Jr

Turkish Journal of Physics

The various device structures used in organic polymer solar cells are reviewed. The operating principles behind these devices are explained in order to provide the reasoning behind the different structures. The incorporation of nanostructures into both bilayer and bulk heterojunction devices to improve exciton separation, charge transport, and light absorption is discussed. Novel ideas such as electrospun fibers and supramolecules are also covered. Finally, the impact of these structures on overall efficiency is evaluated.

Amorphous And Micromorph Si Solar Cells: Current Status And Outlook, Vitaliy Avrutin, Natalia Izyumskaya, Hadis Morkoç

Turkish Journal of Physics

An overview of the current status and prospects of thin-film Si photovoltaics, including both hydrogenated amorphous and microcrystalline Si as well their combination known as micromorph solar cells, with a major focus on the technological development is given. Although thin-film Si solar cells have been one of the first commercially successful photovoltaic devices, today they face a tremendous challenge from variety of bulk Si technologies (mono- and multicrystalline Si) and compound-semiconductor thin-film solar cells, both of which have managed to substantially reduce the production cost and improve power conversion efficiency. Thin-film Si photovoltaics benefiting from the mighty mainstream Si industry …

Electron Field Emission From Nanostructured Semiconductors Under Photo Illumination, Oktay Yilmazoglu, Anatoli Evtukh, Shihab Al-Daffaie, Jens-Peter Biethan, Dimitris Pavlidis, Vladimir Litovchenko, Hans L. Hartnagel

Turkish Journal of Physics

New device concepts and materials for the fabrication of compact high-frequency vacuum sources and micro-nano-integrated X-ray sources are of particular interest for broadband communication, security screening of packages and chemical materials, biomedical examination, and other applications. This article integrates results on GaN- and ZnO-based nano and self-assembled structures. They were used as field emitter tips for cold electron emission at high local electric fields as well as for photoassisted field emitters to generate bunched electrons directly from the emitter tip. The results on functional field emitters as cold electron sources will be presented. They are key elements for building, among …

Nanosphere Lithography - Exploiting Self-Assembly On The Nanoscale For Sophisticated Nanostructure Fabrication, Eser Metin Akinoglu, Anthony John Morfa, Michael Giersig

Turkish Journal of Physics

We demonstrate the fabrication of sophisticated nanostructures using nanosphere lithography (NSL). These include periodic triangular and pyramidal islands as well as periodically perforated thin films and cavities on the nano- and microscale. Furthermore, periodic arrays of vertically standing multiwalled carbon nanotubes are grown by plasma enhanced chemical vapor deposition from catalyst islands that were prepatterned by NSL. Moreover, we discuss the applicability of NSL to rough surfaces and show that the ratio between nanosphere size and roughness is determinant of the resulting nanostructure produced. Excellent, limited, and bad applicability of NSL are shown for smooth, rough, and very rough surfaces, …

Economic And Environmental Comparison Of Different Ordering Policies For An Integrated Inventory Control And Supplier Selection Problem, Sepideh Almasi Monfared

Masters Theses

"This study analyzes an integrated inventory control and supplier selection problem in stochastic demand environment under carbon emissions regulations. In particular, a continuous review inventory model with multiple suppliers is investigated under carbon taxing and carbon trading regulations. We analyze and compare the optimal supplier selection and order splitting decisions with single sourcing and two alternative delivery structures for multi-sourcing, namely, sequential ordering and sequential delivery. For each of the three ordering policies, a solution method is proposed and these policies are compared in terms of their economic as well as environmental performances. A numerical study is conducted to demonstrate …

Statistical Analysis Of Sleep Patterns In Drosophila Melanogaster, Luyang Wang

Masters Theses

“Sleep is one of the most preserved and restorative behaviors of animals and is important in human health. Lack of sleep may cause numerous diseases. So the study of sleep rhythms is very essential and complicated. In order to simplify the process of studying sleep, the fruit fly Drosophila melanogaster, is utilized as a model organism for several reasons. Some of the molecular mechanisms that contribute to the circadian clock in the fruit fly were also found to generate similar cycles in mammals. In order to study sleep patterns in the fruit fly, experiments were designed and performed to …

Emi Investigation And Modeling Of A Flat Panel Display, Satyajeet Shinde

Masters Theses

"It is often important to carry out EMI analysis in the design phase of an electronic product to predict the radiated emissions. An EMI analysis is important to predict if the product complies with the FCC regulations as well as to gain an understanding of the noise coupling and radiation mechanisms. EMI analysis and prediction of radiated emissions in electronic products that have an electrically large chassis, pose a challenge due to the presence of multiple resonant structures and noise-coupling mechanisms.

The study focusses on the investigation of the main noise coupling mechanisms, the approach and methods used for the …

Characterization Of A Plant Gene Family Expanded In Glycine Max, Lisa Snoderly-Foster

Masters Theses

"Glycine max, commonly named the cultivated soybean, is one of the oldest and most important food crops in the world. The study of the G. max genome provides valuable insight into the molecular mechanisms that govern its reproduction and environmental responsiveness, key factors in maximizing crop yield. Since the complete sequencing of the genome in 2010, the analysis has become faster and easier, especially with the development of numerous web-based, publically accessible bioinformatics tools.

This research effort utilizes these tools to characterize a small, unannotated G. max gene family. Although no definitive evidence was uncovered for the production of a …

Corrosion Resistance Of Enamel Coating Modified By Calcium Silicate And Sand Particle For Steel Reinforcement In Concrete, Fujian Tang

Masters Theses

"Porcelain enamel has stable chemical property in harsh environments such as high temperature, acid and alkaline, and it can also chemically react with substrate reinforcing steel resulting in improved adherence strength. In this study, the corrosion resistances of enamel coating modified by calcium silicate and sand particles, which are designed for improved bond strength with surrounding concrete, were investigated in 3.5 wt% NaCl solution. It consists of two papers that describe the results of the study.

The first paper investigates the corrosion behavior of enamel coating modified by calcium silicate applied to reinforcing steel bar in 3.5 wt% NaCl solution …

Investigation Of Angiogenic Effects Of Bioactive Borate Glass Microfibers And Beads In A Rodent Model, Richard Jeffrey Watters

Masters Theses

"The primary objective of this research project was to evaluate the effects of three different compositions of bioactive glass microfibers (45S5, 13-93B3, and 13-93B3Cu) and bioactive glass beads (13-93, 13-93B3, and 13-93B3Cu) on angiogenesis in subcutaneous tissue in the SKH1 'hairless' mouse. Microvascular responses to the bioactive glass implants were investigated via three experimental approaches: noninvasive vital imaging of microvasculature in dorsal skin windows; quantitative histomorphometry of microvascular densities; and quantitative PCR measurements of mRNA expression of pro-angiogenic cytokines VEGF and FGF-2. The live imaging of dorsal skin window preparations in the hairless SKH1 showed the formation of a halo-like …

Computational Fluid Dynamics (Cfd) Modeling Of Proppant Transport In A Plug-And-Perf Completion With Different Perforation Phasing, Jinlin Zhang

Masters Theses

"Perf-and-plug is a completion technique commonly used in multistage fracturing. Fracture performance modeling assumes that fluid and proppant distributes uniformly among all perforations along the length of the wellbore in a plug and perf completion Crespo et al. (2012) has conducted a limited proppant flow experiment using a 63 foot stage, and three 0.42 inch, zero phased simulated perforations. His work demonstrates proppant does not distribute evenly, but the work is limited to a single perforation scheme.

In this study, Computational Fluid Dynamics (CFD) software has been used to simulate proppant transport and distribution in a single stage of a …

A Receiver Function Study Of Crust Thickness And Composition Beneath The Southwestern United States, Si Wu

Masters Theses

"Over the past decades, the seismic structure of the crust and upper mantle of the southwestern United States was examined using an array of different methods. The structure and composition of crust received special attentions, most due to the hydrocarbon reserves in this area. Here new constraints on crustal evolution and structure models are provide by systematically analyzing 37,402 receiver functions recorded at 234 seismic stations on the southwestern United States. The results reveal that the Transitional Crust is characterized by a thin (29.0±1.0 km) crust, a low Vp/Vs ratio of 1.76±0.016 and a high amplitude (R) of P-to-S converted …

A Remote Sensing Investigation Of Elevated Sub-Horizontal Topographic Surfaces In The Wichita Mountains, Oklahoma, Liang Xue

Masters Theses

"Multiple elevated horizontal to sub-horizontal topographic surfaces are present in the Wichita Mountains, Oklahoma. Elevated topographic surfaces, developed primarily on granite bedrock with gentle slopes of 0.5 to 7⁰,were investigated using 1) Digital Elevation Models (DEMs) extracted from NAD 27 UTM coordinates, 2) Google Earth imagery, and 3) USGS topographic maps. In the western Wichita Mountains prominent topographic surfaces at elevations of 720 ± 5 m, 685 ± 5 m, and 660 ± 5 m are well preserved on at least four different mountains (e.g., Solder's Peak, King Mt.) and can be correlated with similar surfaces on at least seven …

Access Control Delegation In The Clouds, Pavani Gorantla

Masters Theses

"Current market trends need solutions/products to be developed at high speed. To meet those requirements sometimes it requires collaboration between the organizations. Modern workforce is increasingly distributed, mobile and virtual which will incur hurdles for communication and effective collaboration within organizations. One of the greatest benefits of cloud computing has to do with improvements to organizations communication and collaboration, both internally and externally. Because of the efficient services that are being offered by the cloud service providers today, many business organizations started taking advantage of cloud services. Specifically, Cloud computing enables a new form of service in that a service …

An Empirical Study On Symptoms Of Heavier Internet Usage Among Young Adults, Saipreethi Vishwanathan

Masters Theses

"Understanding negative consequences of heavy Internet use on mental health is a topic that is gaining significant traction recently. A number of studies have investigated heavy Internet usage, especially among young adults in relation to online games, social media and email. While such studies do provide valuable insights, Internet usage so far has been characterized by means of self-reported surveys only that may suffer from errors and biases. In this paper, we report the findings of a two month empirical study on heavy Internet usage among students conducted at a college campus. The novelty of the study is that it …

Analysis Of A Ventilation Network In A Multiple Fans Limestone Mine, Ali Haghighat

Masters Theses

"As mining progresses the total resistance of an excavation is increased, the mine characteristic curve becomes steeper, and the operating point moves up the fan curve, reducing the total air quantity and increasing the system pressure. For multi-level ventilation networks with a number of fans the process can be tedious, and on a count of numerous dependent factors the optimal combination of fans is very hard to be achieved. The design of a ventilation network in conjunction with multi surface fans and booster fans entails a complex procedure.

The objective of this study is to provide a plan to improve …

Dephosphorylation Of Iqg1 By Cdc14 Temporally Regulates Actin Ring Formation, Daniel Patrick Miller

Masters Theses

"Cytokinesis is the final step in cell division when the cell separates the cytoplasm by contracting a ring composed of filamentous actin (F-actin) and type II myosin. Iqg1, an IQGAP family member, is an essential scaffolding protein in budding yeast (S. cerevisiae) required for actin recruitment to, and contraction of, the actomyosin ring. Actin is recruited by the calponin homology domain (CHD) in anaphase after Iqg1 is localized to the bud neck. Consensus sites for the cyclin-dependent kinase (CDK) Cdc28 were identified flanking the CHD. This led us to the hypothesis that phosphorylation of Iqg1 by Cdc28 negatively regulates actin …

Determination Of Minor And Trace Elements Concentration In Kidney Stones Using Elemental Analysis Techniques, Anjali Srivastava

Masters Theses

"The determination of accurate material composition of a kidney stone is crucial for understanding the formation of the kidney stone as well as for preventive therapeutic strategies. Radiations probing instrumental activation analysis techniques are excellent tools for identification of involved materials present in the kidney stone. The X-ray fluorescence (XRF) and neutron activation analysis (NAA) experiments were performed and different kidney stones were analyzed. The interactions of X-ray photons and neutrons with matter are complementary in nature, resulting in distinctly different materials detection. This is the first approach to utilize combined X-ray fluorescence and neutron activation analysis for a comprehensive …

Effect And Interactions Of Commercial Additives And Chloride Ion In Copper Electrowinning, Wenyuan Cui

Masters Theses

"This thesis is to understand and compare the effects and interactions of modified polysaccharide (HydroStar), polyacrylamide (Cyquest N-900) and chloride ion on copper electrowinning. A study of the nucleation and growth was conducted in a synthetic electrolyte (40 g/L Cu, 160 g/L H₂SO₄, 20 mg/L Cl-) with the addition of HydroStar or Cyquest N-900 using potential step measurements. The current responses generated were compared to theoretical models of nucleation and growth mechanisms. The nucleation and growth mechanism changed as function of potential and the presence of organic additives. The nucleation and growth mechanisms were confirmed using scanning electron microscopy (SEM). …

Performance Analysis Of Zero Forcing And Minimum Mean Square Error Equalizers On Multiple Input Multiple Output System On A Spinning Vehicle, Aditya Kulkarni

Masters Theses

"Channel equalizers based on minimum mean square error (MMSE) and zero forcing (ZF) criteria have been formulated for a general scalable multiple input multiple output (MIMO) system and implemented for a 2x2 MIMO system with spatial multiplexing (SM) for Rayleigh channel associated with additive white Gaussian noise. A model to emulate transmitters and receivers on a spinning vehicle has been developed. A transceiver based on the BLAST architecture is developed in this work. A mathematical framework to explain the behavior of the ZF and MMSE equalizers is formulated. The performance of the equalizers has been validated for a case with …

Pn Anisotropy Tomography Of The Colorado Plateau And Adjacent Areas, Shengyao Cheng

Masters Theses

"The Pn tomography method utilizes seismic waves that refract along the Moho interface to perform inversion in order to investigate velocity anomalies and seismic anisotropy in the uppermost mantle. Results from Pn tomography can provide important information about the composition, temperature, and tectonic processes beneath the study area. Over the past decades, numerous seismic and geologic studies have been conducted in the Colorado Plateau and its adjacent areas to reveal crustal and mantle structures and processes responsible for the diverse surface geological features and tectonic events that have occurred in this area. To investigate lateral variations in the uppermost mantle …

Shielding Effectiveness (Se) Measurement For Maxair Waveguide Panel, Lossy Material Evaluation By Laptop Application, Xiao Li

Masters Theses

"The first part of the thesis presents the EM shielding effectiveness (SE) measurement of new kind of waveguide panel, MaxAir, which based on metal coating technology. SE Measurement tell the SE performance of MaxAir compared to the traditional metal waveguide panel. In terms of good features such as lower price, less weight, MaxAir could replace traditional waveguide panel in some applications by its SE results. There are two SE measurement methods are performed for MaxAir panel, both of them based on reverberation chamber. Measured SE for several MaxAir panel samples in different cell dimension and coating configuration. By the Measured …

Modeling Of Multi-Terminal Vsc-Based Hvdc Systems, Mohammed Mabrook Alharbi

Masters Theses

"Improving the efficiency and operation of power transmission is important due to the continual increase in demand for electric power. In addition, many remote areas throughout the world lack sufficient access to electricity. Unfortunately, utilities cannot satisfy the high demand of power by building new power stations because of economic and environmental reasons. However, utilities can increase generation and transmission line efficiencies by controlling the power flow through their systems. One new attractive technology that enables the control of power flow in the system is Voltage-Source-Converter High Voltage Direct Current (VSC-HVDC) transmission.

Multi-terminal-HVDC (M-HVDC) can be built using VSC technology. …