Digital Commons Network^™

Synthesis Of Clock Trees With Useful Skew Based On Sparse-Graph Algorithms, Rickard Fredrik Waldemar Ewetz

Open Access Dissertations

Computer-aided design (CAD) for very large scale integration (VLSI) involves

Density-To-Potential Inversions In Density Functional Theory, Daniel Spencer Jensen

Open Access Dissertations

Density functional theory and many of its extensions are formally exact quantum many-body theories. In practice, however, implementations of these theories use approximations for all but the most trivial systems. We present a set of inversion methods to numerically compute the exact potentials corresponding to given input densities. The results of these inversions may then be used to evaluate the quality of different density functional approximations and guide the design of new approximations. The inversion methods use classical gradient-based optimization routines that are constrained to satisfy the governing partial differential equations. Numerous examples are given to illustrate the strengths and …

Cardinality Constrained Optimization Problems, Jinhak Kim

Open Access Dissertations

In this thesis, we examine optimization problems with a constraint that allows for only a certain number of variables to be nonzero. This constraint, which is called a cardinality constraint, has received considerable attention in a number of areas such as machine learning, statistics, computational finance, and operations management. Despite their practical needs, most optimization problems with a cardinality constraints are hard to solve due to their nonconvexity. We focus on constructing tight convex relaxations to such problems.

Modeling And Fundamental Design Considerations For Portable, Wearable And Implantable Electronic Biosensors, Piyush Dak

Open Access Dissertations

Chronic diseases such as cancer, diabetes, acquired immune deficiency syndrome (AIDS), etc. are leading causes of mortality all over the world. Portable, wearable and implantable biosensors can go a long way in preventing these premature deaths by frequent or continuous self-monitoring of vital health parameters.

Physics Based Supervised And Unsupervised Learning Of Graph Structure, Ayan Sinha

Open Access Dissertations

Graphs are central tools to aid our understanding of biological, physical, and social systems. Graphs also play a key role in representing and understanding the visual world around us, 3D-shapes and 2D-images alike. In this dissertation, I propose the use of physical or natural phenomenon to understand graph structure. I investigate four phenomenon or laws in nature: (1) Brownian motion, (2) Gauss's law, (3) feedback loops, and (3) neural synapses, to discover patterns in graphs.

Continuum Dislocation Dynamics Modeling Of The Deformation Of Fcc Single Crystals, Shengxu Xia

Open Access Dissertations

A continuum dislocation dynamics model was developed for simulation of the deformation of Face Centred Cubic (FCC) single crystals. In this model, dislocations are described by a set of vector fields, one per slip system, whose evolution is governed by curl-type kinetic equations describing the transport of dislocation lines. These kinetic equations are closed by specifying the velocity field in terms of a mobility law in which the driving force is obtained by solving the Cauchy¡¯s equilibrium equation for stress. The coupled kinetic equations and crystal mechanics equations are numerically solved in a staggered fashion using a custom finite element …

High Dimensional Inference For Semiparametric Models, Zhuqing Yu

Open Access Dissertations

In the literature, high dimensional inference refers to statistical inference when

On The Grain Refinement Of Aluminum Alloys, Wei Dai Vian

Open Access Dissertations

ABSTRACT

Thermoacoustic Oscillations In Supercritical Fluid Flows, Steven Hunt

Open Access Dissertations

Pressure oscillations in supercritical Jet-A fuel flowing through four parallel, heated tubes connected to common manifolds have been observed in this study. Tests were performed with fuel inlet temperatures ranging from 70F to 700F, and fuel pressures ranging from 360-700 psi. Total fuel flow rate ranged from 5-55 lb/hr. Tubes were heated by blowing 800-950F nitrogen over them. Acoustic-mode oscillations, typically ranging from 100-500 Hz, occurred only when a large temperature gradient was created inside the heated fuel tubes. Pressure oscillation amplitudes ranged from 0.1-1.0 psi. Oscillations at the inlet and outlet manifolds that were caused by a mode with …

Tools And Methods To Analyze Multimodal Data In Collaborative Design Ideation, Ramaswamy Senthil Kumaran Chandrasegaran

Open Access Dissertations

Collaborative design ideation is typically characterized by informal acts of sketching, annotation, and discussion. Designers have always used the pencil-and-paper medium for this activity, partly because of the flexibility of the medium, and partly because the ambiguous and ill-defined nature of conceptual design cannot easily be supported by computers. However, recent computational tools for conceptual design have leveraged the availability of hand-held computing devices for creating and sharing ideas. In order to provide computer support for collaborative ideation in a way that augments traditional media rather than imitates it, it is necessary to study the affordances made available by digital …

Multilingual Education And Education Policies In Taiwan Public Elementary Schools: Teachers’ Perspective And Experience, Chien-Yu Wu

Open Access Dissertations

The number of new immigrants and international marriages is increasing in Taiwan, resulting in growing interest in multicultural and multilingual education. The purpose of the present study was to explore public elementary school teachers’ perspectives and experiences regarding the implementation of education policies for new immigrants and their children through an in-depth analysis of a principal, teachers, and parent-teachers at two public elementary schools in rural Taiwan. I examined education policies that were established in response to concerns involving the new immigrants and their children in Taiwan. Using an interpretive phenomenology methodological framework, I obtained a deeper understanding of elementary …

Design, Implementation And Experiments For Moving Target Defense Framework, Norman Ahmed

Open Access Dissertations

The traditional defensive security strategy for distributed systems employs well-established defensive techniques such as; redundancy/replications, firewalls, and encryption to prevent attackers from taking control of the system. However, given sufficient time and resources, all these methods can be defeated, especially when dealing with sophisticated attacks from advanced adversaries that leverage zero-day exploits.

Processes For Identifying Important Chemistry And Biochemistry Concepts And Representations And Their Qualitative Assessment In Undergraduate Biology Courses, Rethabile Reginalda Tekane

Open Access Dissertations

Biology has become increasingly more interdisciplinary in nature. Therefore, the Association of American Medical Colleges-Howard Hughes Medical Institute, and the National Research Council have called for reform in biology curricula. In particular, the Vision and Change report emphasized the importance of integrating biology with physical sciences such as chemistry and biochemistry in order to help biology majors understand the importance of biochemistry and chemistry to biology. The report also stipulated the need to design assessments that are informed by learning objectives in order to assess if students have attained the targeted conceptual knowledge. Currently, meetings and workshops have, and are …

Size And Chemistry Selective Membranes From Block Polymer Templates, Ryan A. Mulvenna

Open Access Dissertations

The use of block polymers continues to gain attention with their myriad applications in industry for advanced applications in biology, medicine, electronics, and separations. The ability of block polymers to self assemble into ordered states on the nanometer level makes these materials suitable for applications that mandate structural order on this scale. By tuning the chemistry of these block domains, we may explore their utilization for advanced separations.

In this dossier, we detail the efforts into the controlled radical polymerization of polyisoprene-b-polystyrene-b-poly( N,N-dimethylacrylamide) (PI-PS-PDMA) via. a facile reversible addition-fragmentation chain transfer (RAFT) mechanism. For this …

Electric Power And The Global Economy: Advances In Database Construction And Sector Representation, Jeffrey C. Peters

Open Access Dissertations

The electricity sector plays a crucial role in the global economy. The sector is a major consumer of fossil fuel resources, producer of greenhouse gas emissions, and an important indicator and correlate of economic development. As such, the sector is a primary target for policy-makers seeking to address these issues. The sector is also experiencing rapid technological change in generation (e.g. renewables), primary inputs (e.g. horizontal drilling and hydraulic fracturing), and end-use efficiency. This dissertation seeks to further our understanding of the role of the electricity sector as part of the dynamic global energy-economy, which requires significant research advances in …

Prediction Of Leakage Flow Of Radial Clearance In A Rolling Piston Rotary Compressor, Geon-Woo Kim, Ki-Youl Noh, Byung-Chae Min, Sang-Jin Song, Sang-Kyung Na, Tae-Seung Yoon, Kenichiro Teshima, Jang-Sik Yang, Gyung-Min Choi, Duck-Jool Kim

International Compressor Engineering Conference

The functional formula of the flow coefficients for the radial clearance in a rolling piston rotary compressor was developed by the experiments and Computational Fluid Dynamics (CFD) to improve the accuracy of a compressor simulation program. The experiments and CFD simulation were conducted to obtain the flow coefficients at the radial clearance under the assumptions of incompressible flow and steady state. The experiments were carried out with the variation of pressure ratio (0.1 to 0.9, step 0.2) and upstream pressure using the nitrogen as a working fluid. The CFD simulation was adopted to calculate the flow coefficients at the radial …

A Numerical Investigation Of The Oil Pump Suction Behaviour In A Hermetic Reciprocating Compressor, Stefan Posch, Johann Hopfgartner, Martin Heimel, Erwin Berger, Raimund Almbauer, Peter Schöllauf

International Compressor Engineering Conference

In addition to the adequate lubrication of the moving parts, the oil flow in a hermetic reciprocating compressor has a significant influence on the thermal characteristics of a compressor. The present work is concerned with the investigation of the oil pump system of a reciprocating hermetic compressor used in household refrigeration appliances. The considered oil pump system consists of a centrifugal pump immersed in the oil sump of the hermetic compressor and a helical groove machined on the crankshaft. The focus of this work lies on the immersed part of the centrifugal oil pump and its interaction with the oil …

An Integrated Model For An Oil Free Carbon Dioxide Compressor Using Sanderson-Rocker Arm Motion Mechanism, Bin Yang, Orkan Kurtulus, Eckhard Groll

International Compressor Engineering Conference

The multi-piston axial reciprocating compressor using the Sanderson-Rocker Arm Motion (S-RAM) mechanism is expected to have high volumetric efficiencies due to the application of a new type of seal to prevent the in-cylinder refrigeration gas leaking through the clearance between piston and cylinder wall. The stroke of the compressor can be controlled by adjusting the inclination angle between the connecting shaft and machine driving shaft. This allows the control of the delivered refrigerant mass flow rate to match the capacity requirement in the field. A comprehensive simulation model for a prototype reciprocating compressor using the S-RAM mechanism has been developed. …

State-Space Modeling Of Thermal Spaces In A Multi-Zone Building, Vahid Raissi Dehkordi, José Agustín Candanedo

International High Performance Buildings Conference

A study on system identification and modeling of thermal spaces in a large institutional building is presented. The main topic of this paper is how the optimum model order associated which each thermal zone depends on factors such as the location of the zone within the building, its orientation and its exposure to outdoor space. Thermal models are essential in predictive control since they are required to predict the thermal load of a single building zone, a collection of various thermal spaces, or a whole building. The results of this study will serve as a guideline for choosing the appropriate …

Accurate Classification Of Rna Structures Using Topological Fingerprints, Jiajie Huang, Kejie Li, Michael Gribskov

Department of Biological Sciences Faculty Publications

While RNAs are well known to possess complex structures, functionally similar RNAs often have little sequence similarity. While the exact size and spacing of base-paired regions vary, functionally similar RNAs have pronounced similarity in the arrangement, or topology, of base-paired stems. Furthermore, predicted RNA structures often lack pseudoknots (a crucial aspect of biological activity), and are only partially correct, or incomplete. A topological approach addresses all of these difficulties. In this work we describe each RNA structure as a graph that can be converted to a topological spectrum (RNA fingerprint). The set of subgraphs in an RNA structure, its RNA …

A Methodology For Measuring The Air Infiltration Rates Into Refrigerated Compartments, Paula Do Vale Pereira, André Sgrott, Lucas F. Back, Débora T. Kohara, Claudio Melo

International Refrigeration and Air Conditioning Conference

This work focuses on the development of a methodology for measuring the air infiltration rates into refrigerated compartments based on the tracer gas technique. To this end an experimental apparatus was designed and constructed. The apparatus is comprised of a device to supply the tracer gas uniformly into the zone, a device to ensure a uniform concentration both in the vertical and horizontal directions, a device to collect the air samples and a gas analyzer to measure the gas concentration according to the infrared photoacoustic spectroscopy technique. Tests were carried out with three distinct refrigerators, with the compressor on and …

Low Refrigerant Algorithm Detection For Cooling Systems Relying On Trending And Data Analysis, Fadi M. Alsaleem, Amro Quedan

International High Performance Buildings Conference

A hybrid algorithm of an enhanced version of Mann-Kendall trending and data analysis is proposed to solve the limitations of current technology in detecting and diagnosing cooling system refrigerant faults in general and refrigerant leakage specifically. A data abstraction mechanism is applied over feed of temperatures and power measurement to calculate and store only the significant information for further analysis. Next, an enhanced version of Mann-Kendall trending is applied periodically over the stored data to calculate the trend strength (upward or downward) for each measurement. Finally, a harmonic mean is utilized to balance the trends contribution and evaluate the result …

Improved Prediction Of Severe Thunderstorms Over The Indian Monsoon Region Using High-Resolution Soil Moisture And Temperature Initialization, K. K. Osuri, R. Nadimpalli, U. C. Mohanty, F. Chen, M. Rajeevan, Dev Niyogi

Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications

The hypothesis that realistic land conditions such as soil moisture/soil temperature (SM/ST) can significantly improve the modeling of mesoscale deep convection is tested over the Indian monsoon region (IMR). A high resolution (3 km foot print) SM/ST dataset prepared from a land data assimilation system, as part of a national monsoon mission project, showed close agreement with observations. Experiments are conducted with (LDAS) and without (CNTL) initialization of SM/ST dataset. Results highlight the significance of realistic land surface conditions on numerical prediction of initiation, movement and timing of severe thunderstorms as compared to that currently being initialized by climatological fields …

Β-Aminopropionitrile-Induced Reduction In Enzymatic Crosslinking Causes In Vitro Changes In Collagen Morphology And Molecular Composition, Silvia P. Canelón, Joseph M. Wallace

Weldon School of Biomedical Engineering Graduate Student Publications

Type I collagen morphology can be characterized using fibril D-spacing, a metric which describes the periodicity of repeating bands of gap and overlap regions of collagen molecules arranged into collagen fibrils. This fibrillar structure is stabilized by enzymatic crosslinks initiated by lysyl oxidase (LOX), a step which can be disrupted using β-aminopropionitrile (BAPN). Murine in vivo studies have confirmed effects of BAPN on collagen nanostructure and the objective of this study was to evaluate the mechanism of these effects in vitro by measuring D-spacing, evaluating the ratio of mature to immature crosslinks, and quantifying gene expression of type I collagen …

Development Of An Adaptive Pid Controller For Superheating Control Employing Artificial Bee Colony Algorithm, Nathalie Martins Panoeiro, Ricardo Nicolau Nassar Koury, Luiz Machado, Antonio Augusto Torres Maia

International Refrigeration and Air Conditioning Conference

Electronic Expansion Valves (EEV) have been used in refrigeration systems to replace conventional expansion devices. Their quick response to changes in the operating conditions improves the steady-state superheating, what contributes to increase the system efficiency. EEV are usually used with automatic controllers in order to keep the superheating close to its optimal value. Among the controllers employed in these devices, the Proportional, Integral and Derivative (PID) controller is the most common. In general, this controller allows for adjustments in the proportional, integral, and differential gains. If these gains are not properly adjusted, the system can display a slow, oscillatory, or …

Simulink Based Transient Modeling Of A Flash Tank Vapor Injection System And Experimental Validation, Viren Bhanot, Jiazhen Ling, Vikrant Aute, Reinhard Radermacher

International Refrigeration and Air Conditioning Conference

Dynamic simulations of vapor compression system are an important field of research since they allow investigation into the behavior of a system under time-varying conditions, which is essential for development of an effective control strategy for the system. It is particularly important for advanced cycles such as a flash tank vapor injection (FTVI) cycle since additional control parameters, such as injection vapor temperature or flash tank liquid level, are involved in such systems. In this study, a mathematical model for an R410A-based FTVI cycle is developed in Simulink. The model is based on an actual system that consists of two …

Performance Evaluation Criteria & Utility Function For Analysis Of Compact Air-To-Refrigerant Heat Exchangers, Daniel Bacellar, Vikrant Aute, Reinhard Radermacher

International Refrigeration and Air Conditioning Conference

The Performance Evaluation Criteria (PEC) constitutes a set of metrics that quantifies geometrical characteristics, and performance of a Heat eXchanger (HX) under design and off-design conditions. There is a vast literature describing different PEC methods and it can be separated into two main categories: energy-based and entropy-based metrics. The first include all metrics that directly measure the thermal-hydraulic performance and geometry features such as surface density, face area and aspect ratio. The second approach entails a more fundamental perspective by employing the second law of thermodynamics to determine the best and worst heat transfer surfaces in terms of entropy generation …

The Optimization Model Of Effective Thermal Conductivity For Metal Hydride Heat Pump Of Refrigeration Cycle, Heyinan Zheng, Kuan-Ting Lin, Sang-Chul Bae, Masafumi Katsuta

International Refrigeration and Air Conditioning Conference

Answering the call for the eco-friendly energy development, the thermally driven metal hydride heat pump (MHHP) is one of the feasible approaches for its great potential in the recovery of low-grade heat without greenhouse-gas emissions, making it a leading contender among different alternate fuels. The main challenge for the practical application of MHHP is the relatively poor system performance, which is mainly considered due to the low effective thermal conductivity (ETC) of metal hydride reaction bed. Therefore, aiming for improving heat transfer performance, previous researches have proved that inserting high-conductivity sheet such as Metal Hydride (MH) sheet and Aluminum Foam …

Effect Of Inclination On Pressure Drop In Large Flattened-Tube Steam Condensers, Yu Kang, William A. Davies, Pega Hrnjak, Anthony M. Jacobi

International Refrigeration and Air Conditioning Conference

This paper presents the experimental study of the inclination effect on condensation pressure drop in a large-scale flattened tube used in an Air-Cooled Condenser (ACC) for steam. Slightly-superheated steam with mass flux of 6.8 kg m-2 s-1 was condensed inside a 10.7 m long, flattened half-tube with inclination angle varied from horizontal to 13.2Ëš. A uniform velocity profile of 2.03 ± 0.12 m s-1 was imposed on the air side to extract heat from the steam. Initial two-phase pressure drop measurements and flow visualization showed a reduction of pressure drop due to improvement in the gravity-assisted drainage of condensate inside …

Simulation Model Of An Automatic Commercial Ice Machine, Haithem Murgham, David Myszka, Vijay Bahel, Rajan Rajendran, Kurt Knapke, Suresh Shivashankar, Kyaw Wynn

International Refrigeration and Air Conditioning Conference

Automatic commercial ice making machines that produce a batch of cube ice at regular intervals are known as “cubers”. Such machines are commonly used in food service, food preservation, hotel, and health service industries.  Machines are typically rated for the weight of ice produced over a 24 hour period at ambient air temperatures of 90°F and water inlet temperature of 70°F. These cubers typically utilize an air-cooled, vapor-compression cycle to freeze circulating water flowing over an evaporator grid. Once a sufficient amount ice is formed, a valve switches to enable a harvest mode, where the compressor’s discharge gas is …