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Articles 3061 - 3090 of 3180

Full-Text Articles in Engineering

Air Jet Impingement For Levitation, James Frederick Huber May 2006

Air Jet Impingement For Levitation, James Frederick Huber

Mechanical and Aerospace Engineering Theses - Archive

Traditional part acquisition methods such as vacuum cups and robotic grippers do not meet the handling needs of truly fragile materials, because both of these methods require surface contact. An alternative to these traditional approaches is the use of air jet impingement for levitation. This technique confines impinged air to a thin disk above the target to form radial diffuser. The Bernoulli Effect causes a pressure difference between the fast-moving impinged air above the surface and ambient air below it. The net pressure difference is sufficient to lift objects weighing more than one kilogram using standard shop air. This method …

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Frequency Response Approximation Methods Of The Dissipative Model Of Fluid Transmission Lines, John King May 2006

Frequency Response Approximation Methods Of The Dissipative Model Of Fluid Transmission Lines, John King

Mechanical and Aerospace Engineering Theses - Archive

This thesis introduces an accurate and efficient method of obtaining a linear approximation for a nonlinear model of a complete fluid transmission line system using Matlab® Signal Processing Toolbox and Symbolic Math Toolbox programs. This technique is then packaged in a Graphical User Interface program to streamline the process of analyzing a total system. The method of approximating the frequency response of a fluid transmission line with a rational polynomial transfer function using the Matlab® 'invfreqs' least squares curve fitting algorithm has already been introduced. This research improves the technique by applying the 'invfreqs' command to a total system rather …

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Regional Prioritization Of Corridors For Traffic Signal Retiming, Sasanka Bhushan Pulipati May 2006

Regional Prioritization Of Corridors For Traffic Signal Retiming, Sasanka Bhushan Pulipati

Civil Engineering Theses - Archive

Every three to four years, the North Central Texas Council of Governments (NCTCOG) funds signal retiming projects to improve air quality in the Dallas-Fort Worth region. As sufficient funds are not available to retime all signals in the region at the same time, the retiming must be completed in phases. To optimize the impact of the retiming projects, the candidate corridors must be rank ordered or prioritized. NCTCOG applies a ranking model, which uses variables like delay, number of stops and system type, a dummy variable based on centralized control. The weighting for each factor is based on expert input …

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Mr Susceptibility Weighted Imaging And Its Clinical Applications, Nandita R. Shetty May 2006

Mr Susceptibility Weighted Imaging And Its Clinical Applications, Nandita R. Shetty

Bioengineering Theses - Archive

Susceptibility Weighted Imaging (SWI) is a new T2* weighted Gradient Echo sequence that exploits the magnetic properties of tissues due to local inhomogeneities in the magnetic field. This technique was originally called 'High-Resolution Blood oxygen level dependent Venography' which, as the name suggests provides an increased visibility of the venous vasculature in the brain, including the minute vessels not seen on conventional imaging techniques. Since its potential is not restricted to venography, it was renamed 'Susceptibility Weighted Imaging ' due to its contrast mechanism being the susceptibility differences between two tissues. The essential feature in this technique is to tap …

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Fpga Prototyping For Fast And Efficient Verification Of Asic H.264 Decoder, Basavaraj Mudigoudar May 2006

Fpga Prototyping For Fast And Efficient Verification Of Asic H.264 Decoder, Basavaraj Mudigoudar

Electrical Engineering Theses - Archive

To improve compression efficiency, recent video compression standards such as H.264 use complex algorithms and various modes that demand more computational power. Consumer electronics industry requires a low power, compact and cost-effective implementation of video codec for most of the products. ASIC implementation of these video codecs is a logical choice to meet these requirements. Functional verification of an ASIC implementation consumes a major part of design cycle time and lot of resources. Because of large design, various modes and options, functional verification of an ASIC H.264 video codec is a challenging, resource intensive and time consuming process. In this …

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Simulation And Characterization Of Znse/Bete Resonant Tunneling Diode On Silicon, Moshe Davis May 2006

Simulation And Characterization Of Znse/Bete Resonant Tunneling Diode On Silicon, Moshe Davis

Electrical Engineering Theses - Archive

ZnSe/BeTe resonant tunneling diodes were grown on silicon with a ZnxBe1-xTe buffer layer using MBE (Molecular Beam epitaxy).These devices were processed and characterized. The devices showed multiple NDR (negative differential resistance) regions at room temperature with PVR (Peak to valley ratios) between 1.01 to 1.23. Variations to the structure were made in growth and their corresponding current-voltage characteristics were studied. The ZnSe/BeTe resonant tunneling diode showed asymmetrical current voltage characteristics for positive and negative biases. The sources of asymmetry were investigated during fabrication and with the help of simulations. The Al/ZnSe contact was confirmed to be ohmic contact when the …

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Real-Time Data Monitoring And Manipulation For Wireless Sensor Networks, Sankar Bhanu Gorthi May 2006

Real-Time Data Monitoring And Manipulation For Wireless Sensor Networks, Sankar Bhanu Gorthi

Electrical Engineering Theses - Archive

The growth of Wireless Sensor Network research has brought about the need for tools to help developers rapidly develop applications for various platforms. In the pursuit of these capabilities, this work deals with the design of a graphical approach to development of Wireless Sensor Network applications for implementation in the LabVIEW Graphical Development Environment. The work done also covers the implementation and development of the Sound and Vibration Toolkit for LabVIEW. The implementation of these tools in developing a novel test-bed at the Distributed Intelligence and Automation Laboratory at the ARRI at UT Arlington is also shown. This work is …

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Structural Similarity Based Image Quality Assessment: Pooling Strategies And Applications To Image Compression And Digit Recognition, Xinli Shang May 2006

Structural Similarity Based Image Quality Assessment: Pooling Strategies And Applications To Image Compression And Digit Recognition, Xinli Shang

Electrical Engineering Theses - Archive

This thesis studies a recently proposed perceptual image similarity measure: the structural similarity (SSIM) index. Although still in its early stage, the SSIM index has demonstrated superior performance in a large number of tests as compared to the currently most widely used image distortion/quality measures, the mean squared error (MSE) and the peak signal-to-noise-ratio (PSNR). This motivates us to further investigate the SSIM method and extend it to other image processing and pattern recognition applications. Specifically, three topics have been studied in this thesis: spatial pooling strategies for perceptual image quality assessment, structural similarity-guided perceptual image compression, and handwritten digit …

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Design And Hardware Implementation Of A Soft-Switched Converter For Fuel Cell Applications, Shiju Wang May 2006

Design And Hardware Implementation Of A Soft-Switched Converter For Fuel Cell Applications, Shiju Wang

Electrical Engineering Theses - Archive

The focus of this thesis is to design a DC-DC quasi-soft switched boost converter suitable for fuel cell applications. Study of electrical output characteristics of fuel cells was necessary for this purpose. A number of experiments were conducted to study the steady-state and transient response of fuel cell system under various load dynamics. The results of these findings were necessary for the next phase of the project which was to design a reliable and high-performance regulated DC-DC converter. The design goals were realized with a soft-switching boost converter (implementation of zero voltage switching (ZVS) and zero current switching (ZCS) schemes) …

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Design Of An Enhanced Translinear Variable Floating Resistor And Its Application In A Vga, Nithya Jagannathan May 2006

Design Of An Enhanced Translinear Variable Floating Resistor And Its Application In A Vga, Nithya Jagannathan

Electrical Engineering Theses - Archive

An improved current controlled floating resistor is designed based on translinear loops for application in a Variable Gain Amplifier (VGA). This work compares the use of two different devices and evaluates the difference based on the model parameters and circuit performance. The different architectures employed clearly demarcate the performance variations. The translinear variable resistor exhibits a dynamic range greater than 60 mV. The resistance value lies in the range of 3 K? to few Ohms. A Current Feedback Operational Amplifier (CFOA) is also designed to have an f -3dB of 250 MHz. The CFOA together with the variable resistor in …

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Generalization Of Widely Linear Filtering Concepts For Equalization And Interference Suppression In Pam/Qam Systems, Kiran Kumar Kuchi May 2006

Generalization Of Widely Linear Filtering Concepts For Equalization And Interference Suppression In Pam/Qam Systems, Kiran Kumar Kuchi

Electrical Engineering Dissertations - Archive

In PAM/QAM transmission systems, standard Minimum Mean Square Error (MMSE) linear (LE) or Decision Feedback Equalization (DFE) equalization methods are often used to suppress the detrimental effects inter-symbol and/or co-channel interference (ISI/CCI) effects of the channel. In this thesis we show the benefits of a new signal processing concept called Widely Linear (WL) filtering for equalization applications in wireless systems. In particular, we introduce generalized WL MMSE/MMSE-DFE equalization structures for both PAM systems that use real constellations and QAM (that use complex modulation alphabets) with multiple antennas and multiple co-channel interferers. In this thesis we first show that WL equalizers …

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Design And Fabrication Of Optically-Pumped Guided-Mode Resonance Surface-Emitting Lasers, Preston Phillip Young May 2006

Design And Fabrication Of Optically-Pumped Guided-Mode Resonance Surface-Emitting Lasers, Preston Phillip Young

Electrical Engineering Dissertations - Archive

This dissertation describes the design and fabrication of guided-mode resonance (GMR) structures and their applications to laser devices. These include tunable Ti:Sapphire lasers as well as semiconductor lasers with integrated light emitting layers. The resonance characteristics of GMR structures are determined by the designed and fabricated waveguide-grating parameters. The primary tool for the design and simulation analysis of GMR devices is rigorous coupled-wave analysis (RCWA). This numerical method is used to provide diffraction efficiency calculations as well as simulations of the electric fields within GMR structures. RCWA-based field analysis is used to design an optically pumped GMR surface-emitting laser (GMR-SEL) …

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A Novel Approach In The Detection Of Obstructive Sleep Apnea From Electrocardiogram Signals Using Neural Network Classification Of Textural Features Extracted From Time-Frequency Plots, Mohammad Alabed May 2006

A Novel Approach In The Detection Of Obstructive Sleep Apnea From Electrocardiogram Signals Using Neural Network Classification Of Textural Features Extracted From Time-Frequency Plots, Mohammad Alabed

Bioengineering Theses - Archive

Sleep-Disordered Breathing (SDB) is estimated to have a prevalence of 5% in middle-aged population. The population is widely thought to be under diagnosed, since the present method to detect and diagnose SDB, Nocturnal Polysomnography (NPSG), is still expensive and not accessible by most. SDB has been shown to affect the productivity and degree of life of the patient, and to have a high correlation with obesity and cognitive heart failure (CHF). Cheap and accessible means to screen the population for SDB are greatly pursued. This work presents an automatic algorithm to detect obstructive sleep apnea (OSA) events in 15-minute clips. …

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Influence Of Polymer Surface Chemistry On The Recruitment Of Stem Cells In Mice, Shwetha Kamath May 2006

Influence Of Polymer Surface Chemistry On The Recruitment Of Stem Cells In Mice, Shwetha Kamath

Bioengineering Theses - Archive

The most troublesome biological response to the implantation of bloodcontacting biomaterials is inflammation, which thereby-sets in motion a cascade of adverse host responses. If devices for therapy and drug delivery could be developed that prevent such responses from occurring altogether, a new generation of "stealth" biomaterials would be born. Such was the motivation of this project, which sought to investigate using mouse subcutaneous implantation model, the implant mediated host tissue responses to surfaces differing in their functionalities. During the course of a previous study in our laboratory, we accidentally discovered the presence of stem cells and their accumulation at the …

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Characterization Of A Noninvasive, In Vivo, Microscopic Hyperspectral Imaging System For Microvascular Visualization., Bhavesh Shah May 2006

Characterization Of A Noninvasive, In Vivo, Microscopic Hyperspectral Imaging System For Microvascular Visualization., Bhavesh Shah

Bioengineering Theses - Archive

Instrumentation with clinical implications for imaging the human oculus was developed, based upon the hyperspectral imaging modality. The novel, non invasive, microscopic multi-modal hyperspectral imaging system, which operates in the visible as well as near infrared region, is capable of generating images illustrating spatial distribution of oxyhemoglobin contributions. The device principally comprises of a liquid crystal tunable filter and a focal plane array detector that is integrated to the slit lamp microscope. A proof of principle clinical study involving ten healthy subjects was undertaken to image the microvascular structure within the dermal tissue within the near infrared region, however these …

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Design And Construction Of A Fast Spectrometer For Fourier Domain Optical Coherence Tomography, Manish Kankaria May 2006

Design And Construction Of A Fast Spectrometer For Fourier Domain Optical Coherence Tomography, Manish Kankaria

Bioengineering Theses - Archive

A fast spectrometer capable of operating at 27.8 KHz is designed and calibrated to work in the wavelength range of 700-900 nm, to perform Fourier Domain Optical Coherence Tomography (FD-OCT). The OCT system is based on fiber-based Michelson's interferometer set up utilizing the spectrometer at the detector end. In FD-OCT system no reference scanning is necessary and hence images can be acquired at a much faster rate without any penalty to signal-to-noise ratio (SNR). A broadband Ti- sapphire source is used as input to this interferometer. Data at the rate of 60 MHz is acquired from the spectrometer using a …

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Structural Optimization Using Femlab And Smooth Support Vector Regression, Divija Odapally May 2006

Structural Optimization Using Femlab And Smooth Support Vector Regression, Divija Odapally

Mechanical and Aerospace Engineering Theses - Archive

In recent years support vector machine (SVM) has been emerging as a popular tool for function approximation. Application of SVM for approximation of mathematical functions and complex engineering analysis has been represented by Palancz et al and Clarke et al, respectively. However the training of the original SVM involves the solution of a quadratic programming (QP) problem. This makes the application of SVM to large problem computationally expensive. To circumvent this difficulty, Lee et al developed a more efficient SVM formulation namely epsilon-SSVR which drastically improved the training efficiency of SVM. In this research the SSVR is used to build …

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Self-Organization And Resource Allocation In Wireless Sensor Networks, Liang Zhao May 2006

Self-Organization And Resource Allocation In Wireless Sensor Networks, Liang Zhao

Electrical Engineering Dissertations - Archive

In this dissertation, we utilize clustering to organize wireless sensors into an energy-efficient hierarchy. We propose a Medium-Contention Based ClusterHeadship Auction (MCCHA) scheme, through which sensors self-organize themselves into energy-efficient clusters by bidding for cluster headship. This scheme is based on a new criterion that can be used by each sensor node to make a distributed decision on whether electing to be a cluster head or a non-head member, which is a fully distributed approach. Although MCCHA uses only local information, it achieves better performance in terms of effective lifetime and Data/Energy Ratio compared with native LEACH, which relies on …

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A Physics Based Multi-Resolution Technique For Extraction Of Finite Duration Time Responses In Radar Images, Nancy Lanett May 2006

A Physics Based Multi-Resolution Technique For Extraction Of Finite Duration Time Responses In Radar Images, Nancy Lanett

Electrical Engineering Theses - Archive

This paper presents a wavelet multi-resolution technique for examination of scattering phenomena in radar images. Through multi-resolution frequency domain analysis, range gating is implemented for extraction of wave medium interaction phenomena. To analyze the data, a sliding range gate is implemented by applying a phase shift to the spectral domain far field data prior to wavelet analysis. A method for efficient removal of window effects, which occur due to the finite nature of the data, is demonstrated through reconstruction of the decomposed waveform following removal of the lowest resolution. A correlation of the physical meaning of the multi-resolution data to …

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Design Of A Cmos Vco And Frequency Divider For 5 Ghz Applications, Prithvi Shylendra May 2006

Design Of A Cmos Vco And Frequency Divider For 5 Ghz Applications, Prithvi Shylendra

Electrical Engineering Theses - Archive

This thesis presents the design of a new CMOS Voltage Controlled Oscillator and a frequency divider, both of which form important blocks in the design of a PLL synthesizer. These components are important because they operate at the highest frequencies within the PLL and also consume most of the power as compared to the other components. Both these circuits have been an active topic of research in recent years especially with the scaling of technology bringing hopes of complete system-on-chip (SOC) integration at RF frequencies. The circuits in this thesis are designed for 5 GHz applications, mainly for the IEEE …

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Finite Element Analysis Of Moisture And Thermal Induced Stress In Flip Chip Packages, Santanu Ghosh May 2006

Finite Element Analysis Of Moisture And Thermal Induced Stress In Flip Chip Packages, Santanu Ghosh

Mechanical and Aerospace Engineering Theses - Archive

The process of moisture absorption and subsequent hygroswelling stress development is a cause of concern in the IC packaging industry. Also thermal stresses developed during the lead free reflow process with a high peak temperature (~ 250oC) add to the problem. In Flip Chip packages, the related effects are high shear stresses at the multilayer interfaces and normal stresses in solder balls. This can lead to phenomenon like delamination at the interfaces and UBM opening. In this work we have made an attempt to simulate the moisture absorption process, subsequent hygroswelling stress development, and thermal stress generated during reflow using …

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Design And Development Of Embedded Dsp Controllers For Power Electronic Applications, Raman Nair Harish Gopala Pillai May 2006

Design And Development Of Embedded Dsp Controllers For Power Electronic Applications, Raman Nair Harish Gopala Pillai

Electrical Engineering Theses - Archive

Power applications like motor drives, inverters have complex algorithms that can be used to improve their efficiency. More often reduced manufacturing cost takes precedence over better efficiency. DSPs with their high computational power can provide reduced cost and higher efficiency. Though the cost of a standalone DSP chip has reduced, its integration to form a complete embedded product is an area often overlooked. High frequency of operation, reduced package size, and sensitivity to component placement are some of the factors that affect the interface between input/output devices and the DSP. This thesis presents the design and development of an embedded …

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Robust Airline Fleet Assignment, Venkata Pilla May 2006

Robust Airline Fleet Assignment, Venkata Pilla

Industrial, Manufacturing, and Systems Engineering Dissertations - Archive

The fleet assignment model allocates the fleet of aircraft types to the scheduled flight legs in the airline timetable published 90 days prior to the departure of the aircraft. The objective is to maximize profit. While costs associated with assigning a particular fleet type to a leg are easy to estimate, the revenues are based upon demand, which is realized close to departure. The uncertainty in demand makes it challenging to assign the right type of aircraft to each flight leg based on the forecasts taken 90 days prior to departure. Therefore, in this dissertation a two-stage stochastic programming framework …

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Registration Of Beta-Cit Dopamine Transporter Spect Images, Abhinay Dilip Joshi May 2006

Registration Of Beta-Cit Dopamine Transporter Spect Images, Abhinay Dilip Joshi

Bioengineering Theses - Archive

This work outlines a method for quantification of nigrostriatal dopaminergic neurons by means of SPECT using the cocaine derivative [123I] β-CIT (123I-labelled 2β-carbomethoxy-3β-(4-iodophenyl) tropane (β-CIT))as a radiotracer which binds with high affinity to the dopamine receptors. It has been validated (1) that the calculation of a simple ratio of specific/non-specific displaceable binding during a period of binding-equilibrium in the striatum about 20 hrs after the administration of a bolus injection of the tracer gives a strong and reliable index of the binding potential of dopamine uptake sites. Previous studies [2] have shown that the dopaminergic deficit in patients with Parkinson's …

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Phenotypic Differences In The Behavior Of Immortalized Human Bronchial Epithelial Cells In Three Dimensional Culture Systems, Anusha Sridharan May 2006

Phenotypic Differences In The Behavior Of Immortalized Human Bronchial Epithelial Cells In Three Dimensional Culture Systems, Anusha Sridharan

Bioengineering Theses - Archive

Human Bronchial Epithelial Cells (HBECS) immortalized with viral oncoproteins E6/E7, are potentially malignant due to numerous chromosomal aberrations. Recently a model system was established in which HBECS were immortalized with Cyclin-dependent-kinase-4 (Cdk4) and human Telomerase Reverse Transcriptase (hTERT). These cells were shown to have intact p53 checkpoints and had well expressed differentiation markers. HBECS are non-tumorigenic as they do not form tumors in nude mice or colonies in soft agar. The purpose of this research was to establish the differences in phenotypic behavior between HBECS immortalized with E6/E7 viral oncoproteins and HBECS immortalized with Cdk4/hTERT. A three dimensional culture model …

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Development Of A Multi-Channel Handheld Probe Designed For Near Infrared Spectroscopy And An Exploration Into Its Clinical Applications, Pradheep Raman May 2006

Development Of A Multi-Channel Handheld Probe Designed For Near Infrared Spectroscopy And An Exploration Into Its Clinical Applications, Pradheep Raman

Bioengineering Theses - Archive

Near Infrared (NIR) spectroscopy and imaging has become popular in research fields for the past 2 decades. My research focuses on the development of a handheld, multi-channel, multi-separation probe for the low-cost, compact, NIR spectroscopy (LCC-NIRS) system and also on the exploration into its possible clinical applications. The work is divided into three parts. The first part deals with the development of the multi-separation probe with source-detector separation of 3.8 cm, 3.3 cm, 3.0 cm, and 2.3 cm. The probe is designed to work as a tri-wavelength system for the LCC-NIRS, which was developed earlier, consisting of one light emitting …

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High Precision Spatial And Temporal Control Of Neural Circuitry Using Semi-Automated, Multiwavelength Nanopatterning System, Nagasandhya Mitnala May 2006

High Precision Spatial And Temporal Control Of Neural Circuitry Using Semi-Automated, Multiwavelength Nanopatterning System, Nagasandhya Mitnala

Bioengineering Theses - Archive

The ideal way to manipulate neurons would be to reversibly activate and inactivate neuronal firing and thus enable a bi-directional control. Many attempts have been made in the past to have such a tool. The traditional approach for controlling neural circuits is to generate a local electric field which has been shown to be highly effective at triggering action potentials in neurons [53]. Although the timing of the electrode stimulation is very precise, its specificity and spatial control are poor. Also, silencing neuronal activity is as important as stimulating it. Ed Boyden described a protein that switches off nerve firing …

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Optimization Of Methods For In-Vitro Expansion And Cryopreservation Of Mammalian Stem Cells, Harikrishnan Balachandran May 2006

Optimization Of Methods For In-Vitro Expansion And Cryopreservation Of Mammalian Stem Cells, Harikrishnan Balachandran

Bioengineering Theses - Archive

The recent advances in the field of Tissue Engineering have given rise to the need for a tremendous quantity of cells. The search for and use of an appropriate multipotent or pluripotent stem cells in tissue engineering is an emerging concept. Mesenchymal stem cells hold a very great deal of promise because of their capacity to self-renew and to differentiate into various lineages. These cells are very low in number in the body but their in vitro expansion capacity is very unique. Taking into consideration the lack of uniform approach for expansion of these MSCs and storing these cells for …

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Viscoplastic Finite-Element Simulation To Predict The Solder Joint Fatigue Life Of Different Flash Memory Die Stacking Architectures, Yong Je Lee Apr 2006

Viscoplastic Finite-Element Simulation To Predict The Solder Joint Fatigue Life Of Different Flash Memory Die Stacking Architectures, Yong Je Lee

Mechanical and Aerospace Engineering Theses - Archive

This thesis focuses on the viscoplastic finite-element simulation to predict the solder joint fatigue life of different die stacking architectures for flash memory products. Four different stacked package architectures were evaluated as follows: pyramid, rotated, and spacer stacking, while interconnection (solder joint) was held constant. Number of dies for all four stacking configurations were varied from three, five and seven. To keep the package height constant, the die and die attach thickness were varied and the resulting effects on the stresses were investigated. A quarter and half symmetry model of stacked flash package are generated using ANSYS APDL script. The …

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Statistical Analysis Of Compressive Strength Of Clay Brick Masonry Prisms, Saman Afqahi Aryana Apr 2006

Statistical Analysis Of Compressive Strength Of Clay Brick Masonry Prisms, Saman Afqahi Aryana

Civil Engineering Theses - Archive

The Specification for Masonry Structures section of the current governing masonry design document in the U.S., reported by the Masonry Standards Joint Committee (MSJC), contains tables that can be used to determine the compressive strength of masonry, f'm, as a function of the mortar type and the compressive strength of the unit employed to construct the masonry. The majority of the data gathered to create the current values in the MSJC Specification were generated in studies done prior to 1970. There have been significant changes in materials and procedures since this time frame, and there is a need to gather …

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