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Article Excerpt
Chair: S. Kant Vajpayee, University of Southern Mississippi
Vice-chair: Erdem Topsakal, Mississippi State University
THURSDAY MORNING
Bost Theater
8:00 SURPRISED! SURPRISED! CT SCANS IN MANUFACTURING PLANTS
S. Kant Vajpayee, University of Southern Mississippi, Hattiesburg, MS 39406
We associate the term CT scans usually with hospitals, physicians, and the like. Recently, CT scans have begun to enter manufacturing. They are evolving to help production engineers for the same reasons they help physicians. Like all technologies, manufacturing had to wait for CT scans until these became affordable. The CT scan technology is proving extremely useful since it fits in nicely with the modern philosophy of preventing defects, rather than inspecting it at the end of the production. The defects are identified and quantified; the associated data are used for taking timely corrective actions. X-ray computed tomography (CT) is one of the several non-destructive testing tools. However, it is the only one which can measure internal features non-destructively. It complements other inspection tools such as coordinate measuring machines (CMMs) and non-contact optical scanners that are suitable for external features. CT scans helps seeing inside a part to identify porosity, blockage, cracks, inclusions, voids, and mechanical fit. CT uses X-rays to produce cross-sectional views of the part under inspection. The CT data help create a 3-dimensional volumetric image of the part using X, Y, and Z coordinates. The CT slices yield a volume stereo lithography model (STL file) of both the internal and external features. The STL file is compared with the CAD data--the output the design process. Currently, CT technology is being used for first-part inspection and in medical-implant applications to benchmark processes. But its future lies in using the CT data as negative feedback to correct for the errors of production while the part is on the production machine. CT technology can achieve measurement accuracy as high as one-thousandth of an inch.
8:15 COMPARISON OF GENETIC ALGORITHM VERSUS PARTICLE SWARM OPTIMIZATION IN THE ADAPTIVE NULLING OF PHASED ARRAY ANTENNAS
Andy Harrison*, deciBel Research, Inc., Huntsville, AL 35806
When operating a system in the presence of one or more strong interfering sources, low sidelobe levels may not be enough to ensure adequate reception of the desired signal. A method for overcoming this problem is adaptive nulling. In this method, the amplitude and phase coefficients of each element in the phased array are adjusted in such a fashion as to place a null in the antenna pattern in the direction of the interfering sources. Many adaptive nulling algorithms calculate the adaptive weighting coefficients for each antenna element by multiplying the original coefficients by the inverse of the covariance matrix. While this method is computationally fast, quantization of the phase will result in errors in null placement. Also, it is necessary to have receiver hardware at each element of the phased array as well as an elaborate calibration technique. Genetic algorithm and particle swarm techniques are global search methods that place very deep nulls in the desired directions, while maintaining the characteristics of the antenna main beam. Since the solution space is predefined by the quantized amplitude and phase coefficients of the particular antenna system, these global methods do not require continuous amplitude and phase shifts. Additionally, these methods deal with the coherent output power of the antenna array and therefore do not require receiver hardware at each element in the antenna array.
8:30 WHY WE NEED STRING THEORY FOR THE UNIVERSE?
Amin Haque, Alcorn State University, Lorman, MS 39096
The current unsolved mysteries in physics are the birth of the Universe, the beginning of time, the cause of the Universe inflation, dark matter, dark energy, and the black holes. According to Hubble's law and other evidence, the Universe was born with a Big Bang about 14.5 billion years ago. A fraction of microsecond later, it started expanding at an extremely high rate for a brief period of time. Within billion years the galaxies began to form with the aid of dark matter, which is believed to hold them together. A mysterious force, called dark energy, is believed to be responsible for the continuous expansion of the Universe at an accelerating rate. We want to go deeper to understand why things happened the way they did. Einstein's general theory of relativity describes only large objects ? the solar system, galaxies, and the Universe. Physicists discovered new building blocks of matter and laws that govern their behavior. The standard model of particle physics was developed, which is an expansion of quantum theory and describes the behavior of elementary particles very satisfactorily. Having two different theories for one Universe is not satisfactory. It should be possible to unify the standard model and general theory of relativity into one complete and comprehensive theory that should describe the behavior of atoms as well as stars. String theory promises new insights and offers hope that answers to at least some of these puzzles may be on the horizon.
8:45 SUPERSTRING THEORY AND THE UNIVERSE
Amin Haque, Alcorn State University, Lorman, MS 39096
String theory attempts to unify all four forces of the nature--gravity, electromagnetic, weak, and strong. According to string theory, all the particles of the Universe and all the force carriers are different modes of vibration of extremely tiny fibers or strings. The observed particle properties (mass, charge, spin) are determined by the strings' oscillatory patterns. Force carriers--graviton, photons, weak gauge bosons, and gluons--are yet other patters of vibration. The units of mass, quarks and electrons (leptons) that form protons and neutrons, are actually made of still more fundamental units--Strings. According to superstring theory, to describe the motion of a string we need eleven dimensions, plus antiparticles and a mirror image of particles, called superparticles. The hidden dark matter and dark energy also may shape our Universe from these dimensions. Superstring theory also predicts that for every known matter particle to have as-yet-undiscovered corresponding "super" force carrier particle and every known force carrier particle to have corresponding "super" matter particle. The superpartners (Squark, Selectron, Sneutrino etc) are thought to be more massive than their partners (quark, electron, neutrino etc). String theory can explore what happened at the instant of the big bang, and what was before the big bang. We now believe a multiverse of universes has existed since before the big bang. At this point no experiments are possible which could prove or disprove if string theory is real or just a mathematical concept.
9:00 EFFECTS OF NONPLANARITY ON SECONDARY FLOWS IN THE SMALL BRONCHIAL TUBES
Bela Soni*, Charla Lindley, and David Thompson, Mississippi State University, Mississippi State, MS 39762
Laminar flow in the small bronchial tubes, characterized by a Reynolds number range of approximately 100 to 1000, is quite complex due to the presence of vortex-dominated secondary flows that play a critical but poorly understood role in the filtration of entrained particles from inhaled air. Contributing to the complexity of the problem is the geometry of the bronchial network, which contains nonplanar, multi-generational branching. The out-of-plane branch angles are randomly distributed in a manner that allows the bronchial network to fill the space available in the chest cavity without intersections. In this paper, we present the results of computational fluid dynamics simulations for steady-state inhalation flow in four three-generation geometries. Since the branching angles are randomly distributed in, we limit this study to only cases for which the branching occurs in the plane perpendicular to the previous branch or the plane of the previous branch. Various fluid dynamical properties are employed to describe the differences between the flows.
9:15 PARTICIPATING IN DoD RESIDENTIAL PROTON EXCANGE MEMBRANE (PEM) FUEL CELL(FC) PROJECT BY ALCORN STATE UNIVERSITY AND THE PARAMETRIC STUDY OF PEM-FC OPERATION
Sam Aceil*, Alcorn State University, Lorman, MS 39096
Distributed electric power generation is considered as a possible substitute for the current centralized power generation for certain usage. Starting 2001, the Department of Defense (DoD) funded a numbers of PEM fuel cells at various military sites with different climates. The Alcorn State University (ASU) Reserve Officers' Training Corps (ROTC) building was selected as one those sites during the 2004 Fiscal Year (FY04). The 5KW Plugpower GenSys PEM Fuel Cell arrived on campus on January of 2006 and the installation completed by March 2006 at ROTC building. The DoD contractor closely monitors the operation of the FC system remotely for one year as part of their contract with DoD. The data is also avail to ASU for their investigations. Parameters under investigation include electric and cogeneration power and efficiency, availability, unscheduled down-time, capacity factor, fuel consumption, total KWh, available KWh, electric efficiency. This paper discusses the results of the operation obtained so far.
9:30 MECHANISM OF DYNAMIC RECRYSTALLIZATION DURING THE FRICTION STIR WELD PROCESS
Lei Dong*, and Judy Schneider, Mississippi State University, Mississippi State, MS 39762
Friction Stir welding (FSW) is becoming an increasingly popular, solid state method for joining materials which are difficult to join by conventional fusion weld methods. Based on microstructural characterization of the FSW, three distinct zones can been identified: heat-affected zone (HAZ), thermo-mechanically affected zone (TMAZ), and refined zone (NZ). Many researchers attribute the formation of the ultrafine grains in the NZ to dynamic recrytallization (DRX). Although this mechanism is postulated, recovery rather than recrytallization is normally observed in alloys such aluminum with high stacking fault energy (SFE). Based on a review of the literature, there does not appear to be a consensus regarding the mechanism of grain refinement mechanism in the NZ. In our experiments, the use of metal cutting theory is being used to describe the thermo-mechanical processes the metal experiences during the FSW process. Using this analogy, a shear zone is expected to form around the weld tool. If the resulting microstructure found in machine chips can be correlated with the microstructure of the FSW in NZ, then this approach may help to quantify the thermo-mechanical conditions required for grain refinement.
9:45 Break
10:00 THE DIPOLE VORTEX
Henk Arnoldus*, Mississippi State University, Mississippi State, MS 39762
When light is observed by for instance the human eye, a camera or a photomultiplier in a laboratory, the distance between the detector and the source of the light is largely irrelevant. Light emanating from a source appears to travel in rays, e.g., it seems to propagate along straight lines from the source to the detector. This picture changes dramatically when we consider the spatial structure of the energy flow on a scale of an optical wavelength. We shall show that the light emitted by a point dipole, which is the most common source of electromagnetic radiation, emerges from the dipole in a peculiar way. The flow lines of the emitted energy form an optical vortex in the sense that the energy flow lines first swirls around the axis of the dipole before turning into an optical ray. We shall also consider the effect of such an optical vortex on the induced electrical current in a nearby interface with a conducting material. The current density, which is generated by the dipole, can have a very intricate structure, depending on the orientation of the dipole with respect to the boundary, and depending on whether it is an electric or a magnetic dipole.
10:15 SIMULATION AND PERFORMANCE EVALUATION OF BEST HOPPING SEQUENCE SELECTION PROTOCOL FOR INCREASING BATTERY LIFE OF UNMANNED AIRBONE VEHICLES
Amer Magableh*, Ibrahim Y. Abualhaol, Mustafa M. Matalgah, Atef Z. Elsherbeni, University of Mississippi, University, MS 38677
Frequency hopping (FH) is one of two basic spreading techniques used in spread spectrum communication to minimize the effectiveness of electronic warfare or jamming. The concept of FH is used in Unmanned Airborne Vehicle (UAV) transmission mainly to extend the battery life. We propose a new technique for FH, which is based on assigning multiple subchannel hops to handle the transmission. The number of subchannels and their selection are based on the required data rate and the signal-to-interference-plus-noise ratio (SINR) for each sub-channel. In our model, we assume the UAV uses adaptive modulation and coding techniques, and the transmission is carried over 16 sub-channels, each with 5 MHz bandwidth and span 80 MHz of bandwidth at the 2.4 GHz spectrum. The proposed new technique namely. Best Hopping Sequence Selection Protocol (BHSSP) is based on selecting a partial set of sub-channels based on a pre-defined minimum transmission data rate. The objective is to find a minimum number of sub-channels to be assigned to the link satisfying the minimum required data rate. Therefore, the sub-channels data rates should be determined, which are associated with the estimated SINRs. The BHSSP is implemented in simulink software package to simulate the system and evaluate its performance before going to real time implementation. The proposed simulink model for this new protocol contains a real-time estimator for the SINR of the 16 sub-channels. The BHSSP provides input to the communication system about which frequency hopping sequence to use in order to minimize power consumption and therefore increase battery life.
10:30 CIRCUIT MODEL AND FULL WAVE ANALYSIS OF A COMPACT WIDEBAND QUARDARTUE HYBRID
Adarsh Jaiswal* and Ahmed A. Kishk, University of Mississippi, University, MS 38677
A printed, compact and wideband quadrature hybrid is designed by utilizing the multi-section technique for bandwidth enhancement and equivalent transmission line technique for size reduction. The compact quadrature hybrid has a size reduction of 50% as compared with the conventional quadrature hybrid. The compact hybrid achieves over 50% bandwidth...
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