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Articles 1  30 of 57
FullText Articles in Physics
UltraThin Silicon Wafer Bonding, Diyu Yan
UltraThin Silicon Wafer Bonding, Diyu Yan
Theses
In this thesis the history and recent developments on the silicon direct bonding technique are reviewed. The growing applications of this technique in SOI, SOS and MEMS areas, difficulties and disadvantages of various bonding processes are discussed. A direct bonding procedure for attaching ultrathin wafers less than 200 μm thick to substrate wafers is developed and described in detail. Difficulties in handling, aligning and annealing ultrathin wafers are reported. Wafers of different doping concentration, thickness, surface roughness and chemical characteristics are tested for bondability. Methods to minimize voids and other failure mechanisms are proposed. A photodetector is designed based on ...
Silicon Optical Fiber Pressure Sensor, Jian Pan
Silicon Optical Fiber Pressure Sensor, Jian Pan
Theses
A novel optical fiber pressure sensor based on a micromachined thin silicon diaphragm is proposed. Detail descriptions of the sensor structure, modulation principle and fabrication process are given.
The device operates on the following principle: Pressure deflects a silicon diaphragm which moves the output end of a light source fiber. The emitted light intensity is picked up and shared by two receiving fibers placed side by side. The variation of the intensity ratio in the receiving fibers caused by the relative motion of the emitting fiber can be easily converted to a linear signal versus the deflection of the silicon ...
A High Temperature Pressure Sensor Based On Magnetic Coupling And Silicon Wafer Bonding, Deguang Zhu
A High Temperature Pressure Sensor Based On Magnetic Coupling And Silicon Wafer Bonding, Deguang Zhu
Theses
In this thesis, the design and fabrication of a bulk micromachined and wafer bonded pressure sensor for high temperature applications is described. The device design is based on the magnetic coupling principle as described by the BiotSavart law. By combining the mechanical properties of single crystal silicon with magnetic coupling, the designed sensor can be operated up to 600°C. The key components within the sensor are two inductive coils, a silicon diaphragm and a hermetic vacuum cavity.
The modeling based on a nineturn single level coil device and a 300 μm x 300 diaphragm indicates an output rms voltage ...
Determination Of The Bulk Modulus Of A LennardJones Solid, Spencer A. Van Roekel Jr.
Determination Of The Bulk Modulus Of A LennardJones Solid, Spencer A. Van Roekel Jr.
Master's Theses
The quantum Monte Carlo method is used to determine the bulk modulus of a LennardJones solid. The quantum Monte Carlo method is discussed in detail and is compared with other numerical methods used previously.
The zero pressure bulk modulus of a LennardJones solid is computed at a number of different temperatures and compared with experimental data.
The Photonic Band Structure Of Dielectric Systems With A Frequency Dependent Dielectric Function, Jiezhou Liu
The Photonic Band Structure Of Dielectric Systems With A Frequency Dependent Dielectric Function, Jiezhou Liu
Master's Theses
The concepts of band theory for electrons can be employed to describe the behavior of electromagnetic waves propagaiting in periodic dielectric structures with a frequency independent dielectric function. These periodic structures can produce photonic band gaps in which the propagation of electromagnetic waves is strictly prohibited. The introduction of a frequency dependent dielectric function in such systems gives rise to strong changes of the photonic bands in the neighborhood of the frequency resonance of the dielectric function.
In my thesis, the photonic band structure of a dielectric system with a frequency dependent dielectric function which undergoes a dielectric resonance will ...
Absolute Photonic Band Gaps Of Zincblende, Ulrich Bass
Absolute Photonic Band Gaps Of Zincblende, Ulrich Bass
Master's Theses
One concept of examining the propagation of an electromagnetic wave through a periodic structure is the dispersion curve which relates the frequency of the propagating wave to its wave vector. In some cases frequency ranges occur where no propagation is possible. These ranges are called absolute photonic band gaps as far as periodic dielectric structures are concerned.
In my thesis I am interested in the dispersion curve of a Zincblende type dielectric array. Zincblende is a diamondlike structure and it has been shown that diamond structures possess absolute photonic band gaps. In studying Zincblende we want to gain deeper insight ...
An Experimental Apparatus For Studying Double Differential Scattering By LowEnergy Multiply Charged Ions From Atomic Targets, Meenatchi S. Gopinathan
An Experimental Apparatus For Studying Double Differential Scattering By LowEnergy Multiply Charged Ions From Atomic Targets, Meenatchi S. Gopinathan
Master's Theses
A new differential energygain spectrometer with a movable parallelplate electrostatic energy analyzer has been constructed and tested for the study of double differential (in energy and angle) cross sections for stateselective electron capture processes in collisions of lowenergy multiply charged ions with atomic gases. The ion beam is produced by extracting recoil ions from a primary interaction region where these ions are generated in collisions between a neutral target gas and a fast fluorine beam from the WMU tandem Van de Graaff accelerator. An einzel lens is used to focus the ion beam extracted from the recoilion source into a ...
Mbe Growth Of Inxga1Xas/Gaas/Si Heterostructure System, Jun Liu
Mbe Growth Of Inxga1Xas/Gaas/Si Heterostructure System, Jun Liu
Theses
In this work, we grew the In_{x}Ga_{1x}As/GaAs/Si (GaAs as buffer layer) by MBE technique. The surface of the buffer layer became microscopically rough as the thickness of the buffer layer increased and the growth mode of GaAs on Si underwent a change from threedimensional to twodimensional during the initial growth stage as indicated on the Reflection High Energy Electron Diffraction (RHEED) screen. The Scattering Electron Microscopy (SEM) observation of the etched surface of GaAs on Si showed that the structure of the buffer layer tended to be polycrystalline and it was possible that a ...
Measurement Of The Hall Coefficient And Electron Mobility Using Van Der Pauw Type Hall Effect Measurements, HongSheng Luo
Measurement Of The Hall Coefficient And Electron Mobility Using Van Der Pauw Type Hall Effect Measurements, HongSheng Luo
Theses
Hall effect measurement in the electrical characterization of semiconductor materials is very important. We set up the Hall effect measurement system and examined the system with a standard sample. The experimental results show that this Hall measurement system worked as well as expected. We also used this system to study the GaAs/GaAs and InGaAs/GaAs which grown by MBE. Finally, we disscussed and consided some common problems of Hall measurement. Some useful formulas and plots are presented.
Subthreshold Channel Leakage Current In Gaas Mesfet's, Wei Long
Subthreshold Channel Leakage Current In Gaas Mesfet's, Wei Long
Theses
In this thesis, a physical model including the subthreshold conpensation properties is presented. The Poisson equation is solved analytically in one dimension for GaAs MESFET's with undoped substrates in the subthreshold region. The solution is then used to derive expressions for subthreshold drain current and subshreshold swing in MESFET's with undoped substrates. Very good agreement between experimental and analytical results is achieved.
Two key parameters (Nilo and Iso) that determine the subthreshold Characteristics have been analyzed as a function of residual acceptor concentration Na, deep level EL2 concentration Nt, channel doping concentration Nd and threshold voltage Vt. It ...
Simulation Of Active Control Of Asymmetric Flows Around Slender Pointed Forebodies, Hazem Sharaf ElDin
Simulation Of Active Control Of Asymmetric Flows Around Slender Pointed Forebodies, Hazem Sharaf ElDin
Mechanical & Aerospace Engineering Theses & Dissertations
At high angles of attack, the flowfield over slender forebodies becomes asymmetric with substantial side force, which may exceed the available control capability. The unsteady compressible NavierStokes equations are used to investigate the effectiveness of different active control methods to alleviate and possibly eliminate the flow asymmetry and the subsequent side force. Although the research work focuses on active control methods, a passive control method has been investigated. The implicit, Roe fluxdifference splitting, finite volume scheme is used for the numerical computations. Both locallyconical and threedimensional solutions of the NavierStokes equations are obtained.
The asymmetric flow over fivedegree semiapex angle ...
Dosimetry Of HighEnergy HeavyIon Beams Using EnergyDependent Green's Functions, Sang Yull Chun
Dosimetry Of HighEnergy HeavyIon Beams Using EnergyDependent Green's Functions, Sang Yull Chun
Physics Theses & Dissertations
A theoretical description of the transport of highcharge and highenergy (HZE) ion bombardment of biological tissue is developed. The energydependent Green’s functions and particle fluxes are obtained for two boundary distributions  the monoenergetic and the Gaussian. Approximate energydependent Green’s functions for the collision terms are obtained for computational simplicity. As an application of the energydependent Green’s function method, dosimetric quantities, such as dose, doseequivalent, and average quality factor, for 600A MeV^{56}Fe , 517A MeV ^{40}Ar, and 625A MeV ^{20}Ne ion beams incident on a water target are obtained and compared with the values obtained ...
Asymmetric Adsorbate And Substrate Interactions In Physisorbed Systems: N2 On Graphite And Dipolar Molecules On Ionic Substrates, Teresa Ellen Burns
Asymmetric Adsorbate And Substrate Interactions In Physisorbed Systems: N2 On Graphite And Dipolar Molecules On Ionic Substrates, Teresa Ellen Burns
All Graduate Theses and Dissertations
Asymmetries in physisorbed systems give rise to interesting phases and phase transitions in twodimensional (2D) monolayer and multilayer systems. The effects of asymmetric adsorbate and substrate interactions in monolayers of dipolar molecules on ionic substrates and N_{2} on graphite are studied.
In the case of dipolar molecules on ionic substrates, 2D dielectric phase transitions using a modified BlumeEmeryGriffiths (BEG) model are determined theoretically. A dipole adsorbed vertically above a metal ion lattice site, and pointing up (down), is assigned a spin s=+1 (s=1). An empty lattice site is assigned a spin S=0. Analytic solutions for both ...
A Procedure For GMatrix Calculation From A Momentum Space Potential, Zhaohui Gao Busche
A Procedure For GMatrix Calculation From A Momentum Space Potential, Zhaohui Gao Busche
Master's Theses
In this work a numerical procedure was found to calculate the Gmatrix in momentum space with a momentum space potential. The integral equation for the Gmatrix was solved by conversion to a matrix equation. Two numerical integral methods, threepoint Simpson method and Gaussian integral method, were employed in this process to determine the more efficient method.
The resulting Gmatrix in momentum space was Fourier transformed into coordinate space. This was compared with the results of the Gmatrix calculated from coordinate space directly as well as the results from solving the BetheGoldstone equation. A 2% accuracy was achieved with both the ...
Building Of A Thermoacoustic Refrigerator And Measuring The Basic Performance, Torsten Blumreiter
Building Of A Thermoacoustic Refrigerator And Measuring The Basic Performance, Torsten Blumreiter
Dissertations and Theses
The application of thermoacoustic phenomena for cooling purposes has a comparatively short history. However, recent experiments have shown that thermoacoustic refrigeration can achieve practical significance for both every day cooling in households and cryocooling for scientific purposes due to its high reliability, environmental safety and functioning under extreme conditions. We build a thermoacoustic refrigerator driven by a commercial loudspeaker. It was equipped with a vacuum pump and an entrance port for introducing different gases under different pressures as working fluids. It contained two thermocouples and a pressure transducer for quantitative measurements of the basic performance. The resonance frequency of the ...
Interfacing A Computer To A Scanning Tunneling Microscope, Markus Jarasch
Interfacing A Computer To A Scanning Tunneling Microscope, Markus Jarasch
Dissertations and Theses
A program was written in 'C' to control the functions of an already existing Scanning Tunneling Microscope (STM). A DAS1601 data acquisition card (from Keithley Data Acquisition) was installed together with its drivers for 'C' on a computer with a 486DX motherboard. The computer was interfaced to the electronics of the STM. Images taken of HOPG (highly oriented pyrolitic graphite) were of a reasonable quality and showed atomic resolution.
Interactions Of Ruthenium Red With Phospholipid Vesicles, Dirk Voelker
Interactions Of Ruthenium Red With Phospholipid Vesicles, Dirk Voelker
Dissertations and Theses
We have studied the electrostatic and other interactions of the inorganic, hexavalent dye Ruthenium Red (RR) with phospholipid vesicles composed of phosphatidylcholine (PC) and phosphatidylserine (PS) or phosphatidylinositol (Pl) in various mixtures and concentrations. Experiments were based on spectrophotometric absorption measurements which compared RR concentrations in the presence and in the absence of liposomes at different dye concentrations. Multilamellar liposomes were obtained by handshaken preparations. Five freezeandthaw cycles of the lipidRR suspension produced an ion equilibrium distribution at the membranewater interface. Results are given in terms of the GouyChapmanStem adsorption theory with the linear partition coefficient and a newly introduced ...
Electrophoretic Studies Of Ion Adsorption To Sarcoplasmic Reticulum And Phosphatidylcholine Membranes, Andreas Schilling
Electrophoretic Studies Of Ion Adsorption To Sarcoplasmic Reticulum And Phosphatidylcholine Membranes, Andreas Schilling
Dissertations and Theses
In this study, electrophoretic mobilities of native and two types of trypsin digested sarcoplasmic reticulum vesicles have been determined by microelectrophoresis using a Doppler Electrophoretic Light Scattering Analyzer to investigate the influence of hydrodynamic drag, caused by the Ca2^{+}, Mg2^{+} ATPase protruding from the surface of native sarcoplasmic reticulum vesicles. After the prolonged digestion (protein:trypsin ratio of 20 for 3 hours at 25°C), the ATPase was cleaved and removed from the sarcoplasmic reticulum membrane as shown with SDS gel electrophoresis and an ATPase activity assay. Ionic strength and pH dependence of mobility showed a nearly pH independent increase ...
A Study Of Small Angle Differential And Integral Cross Sections For K 4s4p Transition, Peter A. Ozimba
A Study Of Small Angle Differential And Integral Cross Sections For K 4s4p Transition, Peter A. Ozimba
ETD Collection for AUC Robert W. Woodruff Library
Measured and calculated differential cross sections(DCS) are contrasted through the generalized ocsillator strength for impact energies of 16, 20, 40, 54.4, 60, 75, 100 and 200 eV. The recently constructed universal formula by Msezane and Sakmar is used to compare these results. Most of the results require renormalization and also show inaccuracy at small scattering angles. By also using the cubic spline function and the constructed formula from the universal formula, for the integral cross section by Chen and Msezane, total cross sections are calculated. These integral cross sections which serve as a good check to the measured ...
Molecular Dynamics And Simulations Studies Of Metal Surfaces, Akie M. Raphuthi
Molecular Dynamics And Simulations Studies Of Metal Surfaces, Akie M. Raphuthi
ETD Collection for AUC Robert W. Woodruff Library
Bulk phonon spectra for several noble metals have been investigated, and the results are being reported in this thesis. The parameters appearing in the semi empirical glue model, are fitted to several physical properties of the noble metals.
The calculation of the surface structure and dynamics of (100), (110), and (111) surfaces of aluminum using molecular dynamics and an empirical many body interatomic potential is presented. The multilayer relaxation of these surfaces was calculated by use of simulated annealing. Surface phonon spectra at finite, low temperatures was calculated by means of timedependent correlation functions. Results are compared with experimental measurements ...
Low Temperature Performance Of Field Effect Transistors, Wei Zhu
Low Temperature Performance Of Field Effect Transistors, Wei Zhu
Theses
The low temperature static characteristics of silicon junction fieldeffecttransistors (JFETs) have been investigated and analysed. The followingchanges were observed after cooling down the transistors: pinchoffvoltage and transconductance increases; and drain current is changedas a function of the drainsource voltage. It was found that there wasan increase in the amplifying properties and a reduction in noise voltageof cooled transistors. In addition, the temperature and voltage dependenceof leakage current have been studied. Temperatures below 77K are ofinterest in evaluating effects of impurity freezeout and temperatureabove 77K are important since actual device temperature will be aboutthe ambient. Operation of FET circuits at liquid ...
Application Of CoAdjoint Orbits To The Loop Group And The Diffeomorphism Group Of The Circle, Ralph Peter Lano
Application Of CoAdjoint Orbits To The Loop Group And The Diffeomorphism Group Of The Circle, Ralph Peter Lano
Theses and Dissertations
No abstract provided.
A Study Of Magnetic Activity Effects On The Thermospheric Winds In The Low Latitude Ionosphere, Ricardo Cruz Davila
A Study Of Magnetic Activity Effects On The Thermospheric Winds In The Low Latitude Ionosphere, Ricardo Cruz Davila
All Graduate Theses and Dissertations
The purpose of this thesis is to examine the effects of magnetic activity on the low latitude Fregion thermospheric winds. The Fregion (1201600 km) is a partially ionized medium where O^{+} and O are the major ion and neutral species, respectively. The thermospheric winds at these altitudes are driven primarily by pressure gradient forces resulting from the solar heating during the day and cooling at night. For this study, we use measured FabryPerot Interferometer (FPD winds at Arequipa (16.5°S, 71.5°W) and measured FPI and Incoherent Scatter Radar (ISR) winds at Arecibo (18.6°N, 66.8 ...
A Monte Carlo Simulation Of Coulomb Collisions And WaveParticle Interactions In Space Plasma At High Lattitudes, Imad Ahmad Barghouthi
A Monte Carlo Simulation Of Coulomb Collisions And WaveParticle Interactions In Space Plasma At High Lattitudes, Imad Ahmad Barghouthi
All Graduate Theses and Dissertations
Four studies were considered to simulate the ion behavior in the auroral region and the polar wind.
In study I, a Monte Carlo simulation was used to investigate the behavior of O^{+} ions that are E x Bdrifting through a background of neutral O, with the effect of O^{+}(Coulomb) selfcollisions included. Wide ranges of the iontoneutral density ratio n_{i}n_{n} and electrostatic field E were considered in order to investigate the change of ion behavior with respect to the solar cycle and altitude. For low altitudes and/or solar minimum (n_{i}n_{n}≤10^{5}), the ...
Flow Simulations About SteadyComplex And Unsteady Moving Configurations Using StructuredOverlapped And Unstructured Grids, James Charles Newman Iii
Flow Simulations About SteadyComplex And Unsteady Moving Configurations Using StructuredOverlapped And Unstructured Grids, James Charles Newman Iii
Mechanical & Aerospace Engineering Theses & Dissertations
The limiting factor in simulating flows past realistic configurations of interest has been the discretization of the physical domain on which the governing equations of fluid flow may be solved. In an attempt to circumvent this problem, many Computational Fluid Dynamic (CFD) methodologies that are based on different grid generation and domain decomposition techniques have been developed. However, due to the costs involved and expertise required, very few comparative studies between these methods have been performed. In the present work, the two CFD methodologies which show the most promise for treating complex threedimensional configurations as well as unsteady moving boundary ...
High Energy Coupled Nucleon Tranpsort In One Dimension, Stanley L. Lamkin
High Energy Coupled Nucleon Tranpsort In One Dimension, Stanley L. Lamkin
Physics Theses & Dissertations
The problem of energetic nucleon transport through extended bulk matter is considered in the context of the 'straight ahead' approximation. The applicable form of the Boltzmann transport equation is derived and solved in one dimension. The production term for secondary generation nucleons due to nuclear fragmentation includes 'coupling' of the flux to other types of nucleon projectiles. A physically motivated perturbation series approach is developed to enhance solution convergence. The Boltzmann operator is inverted and the flux is computed using a numerical marching scheme. The secondary production integrals are optimized for second order accuracy using a set of analytical benchmarks ...
Calibration Of Photoluminescence Experiment, Chihchuan Daniel Lee
Calibration Of Photoluminescence Experiment, Chihchuan Daniel Lee
Theses
Photoluminescence in a semiconductor at room temperature is quite difficult to distinguish from the many nonlasing optical lines from the laser, therefore, a blank test is very important. In so doing, the noises of the detector has to be taken into account. The calibration, however, mainly depends on the detector and is less dependent on other components. Instead of using blackbody radiation light source and pyroelectric detector, we use globar lamp and PbS detector; because of the difficulty in the former case in doing alignment of optical path (invisible) and operating at a lower signal level from the detector. The ...
A Theoretical Study Of The Semiconductor Laser Structures With Lateral Discontinuity In The Optical Cavity, Yi Cai
Theses
A theoretical study of the semiconductor laser structures with lateral discontinuity in the optical resonant cavity is presented in this thesis. Specifically, the lateral discontinuity is referred to the lateral expansion structure newly invented for increasing the power output of semiconductor lasers while keeping single mode operation.
In the first part of the thesis (Chapter 2 and Chapter 3), an explicit expression for calculating the lateral discontinuity problems is formulated by the incorporation of modematching method. Our approach is based on the mode expansion theory developed for lossless microwave and optical fiber waveguides, but the effect of gain in active ...
Einstein's Equations In Vacuum Spacetimes With Two Spacelinke Killing Vectors Using Affine Projection Tensor Geometry, Miles D. Lawrence
Einstein's Equations In Vacuum Spacetimes With Two Spacelinke Killing Vectors Using Affine Projection Tensor Geometry, Miles D. Lawrence
Theses and Dissertations
Einstein's equations in vacuum spacetimes with two spacelike killing vectors are explored using affine projection tensor geometry. By doing a semiconformal transformation on the metric, a new "fiducial" geometry is constructed using a projection tensor fields. This fiducial geometry provides coordinate independent information about the underlying structure of the spacetime without the use of an explicit form of the metric tensor.
External Cavity Laser Power Stabilizer, Jie Ding
External Cavity Laser Power Stabilizer, Jie Ding
Theses
In this thesis, we want to design a stabilizer which does not depend on laser sourcewith external cavity.
In the first part of the thesis ( Chapter 2 and 3 ), we discuss the wave propagation in crystals and the modulation of optical radiation. From the main two types electrooptic modulations, Phase Modulation and Transverse Modulation, we know that the transverse modulation shows an increase in the frequency limit or useful crystal length of (1c0/ncm)^{1}, and we will use this type modulation in this thesis.
The second part of the thesis is the procedure of design and experiment. Because we ...