Engineering Commons^™

Fuel-Saving Strategies For Dual Spacecraft Interferometry Missions, Christopher A. Bailey, Timothy W. Mclain, Randal W. Beard

Faculty Publications

Separated spacecraft interferometry missions will require that spacecraft move in a coordinated fashion to ensure minimal and balanced consumption of fuel. This paper develops strategies for determining interferometry mission plans that result in significant fuel savings over standard approaches. Simulation results demonstrate that valuable reductions in fuel consumption can be realized by combining the retargeting and imaging maneuvers required to image multiple stellar sources. Fuel-optimal imaging strategies have been developed for two-spacecraft interferometry missions similar to the proposed StarLight mission using chained local optimization methods. Based on these strategies, sampling-pattern guidelines for space-borne interferometry missions have been developed.

Pulsed Electron Heating Of Atmospheric Pressure Air Glow Discharges, Hisham Merhi

Electrical & Computer Engineering Theses & Dissertations

By applying electric field pulses of short duration (compared to the time constant for glow-to-arc transitions) to a weakly ionized gas, the electron energy distribution can be temporarily shifted to higher energies. This effect causes a nonlinear increase in the ionization rate and consequently a larger electron decay time. This effect has been demonstrated using single pulse operation.³ In order to generate plasma with semi-continuous electron density, repetitive operation is required. As a first step towards repetitive pulsed electric field operation, the temporal development of the voltage across the plasma for two subsequent pulses was measured. The dual pulse …

Co-Located Fiber Bragg Gratings For Simultaneous Measurement Of Temperature And Strain, Ronald W. Bentley

Electrical & Computer Engineering Theses & Dissertations

Fiber Bragg gratings are periodic modulations of the refractive index of the fiber core exhibiting strong reflection at specific wavelengths determined by the periodicity and magnitude of the index modulation. Due to elastic and thermo optic properties of glass, the Bragg wavelength is sensitive to temperature and axial strain. The inability to discriminate between the effects of temperature and strain on fiber Bragg gratings, however, limits their use in sensing applications. Several schemes have been proposed to overcome this problem, and one involving a dual wavelength Bragg grating sensor implemented with co-located 850 nm and 1550 nm gratings is investigated. …

Simulation Optimization Studies Of Routing And Process Flow Problems, Satish Ravichandran

Electrical & Computer Engineering Theses & Dissertations

Computer aided simulation is emerging as a powerful tool for numerical analysis and in conducting performance evaluations of complex systems that depend on a multitude of variables. The primary objective in such simulation studies is to gauge the performance of the system under a various constraints and operating conditions. The effects of changing the operating parameter space can thus be analyzed without having to implement costly changes. Simulations are also carried out for the baseline scenarios to verity and validate the basic underlying system model. In this thesis research, two practical problems were studied through numerical modeling, and optimized solutions …

The Effect Of Multiple Pulses On Bacteria, Ramy El-Sayed Aly

Electrical & Computer Engineering Theses & Dissertations

Pulsed electric fields are widely used for bacterial decontamination of water and liquid food [I]. Depending on pulse amplitude and duration, a certain percentage of the bacteria suffer irreversible damage and, consequently, cell death. We have explored the effect of microsecond pulses of 13 kV/cm and 15 kV/cm electric field amplitude on the viability of Escherlchia coli. The pulse duration was varied from 4 μs to 32 μs, and the pulse number of 4 μs pulses from one to eight, Finally, the effect of separation between pulses was studied. The pulses were generated by means of a generator where …

Abnormal Cell Detection Using The Choquet Integral, R. Joe Stanley, James M. Keller, Charles William Caldwell, Paul D. Gader

Electrical and Computer Engineering Faculty Research & Creative Works

Automated Giemsa-banded chromosome image research has been largely restricted to classification schemes associated with isolated chromosomes within metaphase spreads. In normal human metaphase spreads, there are 46 chromosomes occurring in homologous pairs for the autosomal classes 1-22 and the X chromosome for females. Many genetic abnormalities are directly linked to structural and/or numerical aberrations of chromosomes within metaphase spreads. Cells with the Philadelphia chromosome contain an abnormal chromosome for class 9 and for class 22, leaving a single normal chromosome for each class. A data-driven homologue matching technique is applied to recognizing normal chromosomes from classes 9 and 22. Homologue …

A Study Into Lack Of Product Innovation And Business Techniques At The Tricycle Workshop And Rrs Lessons To Small Companies, E Elias

Tanzania Journal of Engineering and Technology (TJET)

A study was carried out at the Tricycle Workshop (TW) which was facing the problem of !ack of orders and therefore stagnation Of business. The objective of the study was to find out reasons for this situation and to propose possible remedial solutions. The study was conducted using the principles of the Product Innovation process where internal and external issues related to the business Of the company were investigated for information. Analysis Of information obtained indicated that the bad situation of the TW had mainly been caused by the nature of the tricycles-supply system whereby users (disabled persons) are unable …

Apparatus And Method For Two Stage Hybrid Space-Time Adaptive Processing In Radar And Communication Systems, Todd B. Hale, Michael C. Wicks, Raviraj S. Adve

AFIT Patents

A Two-Stage Hybrid algorithm offers significant improvement in the false alarm rate and detection performance of Space-Time Adaptive Processing in non-homogeneous environments for both radar and digital communications. The first stage analyzes data from a range cell of interest by direct data domain processing, suppressing discrete interferers within the range cell of interest. The second stage implements a purely statistical STAP algorithm, preferably an enhanced version of the Joint-Domain Localized ("JDL") statistical algorithm. For radar this second stage estimates the interference within the range cell of interest from the surrounding range cells. For a communications system, the second stage estimates …

Greasing The Tenure Track 2, David Braun

Electrical Engineering

Some new faculty must balance the competing demands of the desire to teach effectively while maintaining a heavy teaching load. Oh, and, by the way, along the way to the tenure hurdle, research, professional development, and service duties may distract from family, friends, and real life. Based on the author’s participation in the NSF's New Century Scholars (NCS) Workshop at Stanford University as both a scholar (1999) and, subsequently, as a senior scholar (2000), this paper summarizes six useful tips for tenure-track faculty. This second paper in the series by NCS senior scholars provides the perspective of an engineering educator …

Using Lip Features For Multimodal Speaker Verification, Xiaozheng Zhang, Charles C. Broun

Electrical Engineering

With the prevalence of the information age, privacy and personalization are forefront in today's society. As such, biometrics is viewed as an essential component of current and evolving technological systems. Consumers demand unobtrusive and non-invasive approaches. In our previous work, we have demonstrated a speaker verification system that meets these criteria. However, there are additional constraints for fielded systems. The required recognition transactions are often performed in adverse environments and across diverse populations, necessitating robust solutions.

We propose a multimodal approach that builds on our current state-of-the-art speaker verification technology. In order to maintain the transparent nature of the speech …

Design And Preliminary Test On The Integration Of Weather Data In Ecdis For Marine Navigation, Shwu-Jing Chang

Journal of Marine Science and Technology–Taiwan

The incorporation of marine weather information into Electronic Chart Display and Information System (ECDIS) has become a major issue common to international organizations such as IMO, IHO, and WMO. It is believed that this will further enhance the effectiveness of ECDIS as a tool of decision support to mariners for safe and efficient navigation. This paper first identifies essential items of marine weather information to be integrated into ECDIS. The data structure, formats, and symbology for the display and updating of weather data in ECDIS are then proposed according to related international standards. Potential use of weather data in ECDIS …

Cooperative Control Of Uav Rendezvous, Timothy W. Mclain, Phillip R. Chandler, Steven Rasmussen, Meir Pachter

Faculty Publications

The cooperative control of timing and synchronization of tasks of multiple unmanned air vehicles (UAVs) represents a valuable capability for a wide range of potential multi-UAV missions. This research addresses the specific problem of cooperative rendezvous in which multiple UAVs are to arrive at their targets simultaneously. The development of a rendezvous manager state machine and a cooperative control decomposition approach are described. Simulation results demonstrating the feasibility of the approach are presented.

Human Head-Neck Response To Impact Acceleration: Comparison Of Oblique To Combined Frontal And Lateral Response, Salvadore J. Guccione Jr., Edit J. Kaminsky

Electrical Engineering Faculty Publications

This paper relates human oblique head-neck kinematics to human frontal and lateral head-neck kinematics for three subjects of varying anthropometry. Head-neck kinematic response to indirect impact acceleration for an oblique test is compared to the superposition of the head/neck behavior of appropriate frontal and lateral tests for the same subject. The results have important implications in terms of the complexity required in the design and validation of omni-directional biofidelic crash test manikins and mathematical models of human head-neck response.

Characterizing And Calibrating A Large Helmholtz Coil At Low Ac Magnetic Field Levels With Peak Magnitudes Below The Earth's Magnetic Field, Robert A. Schill, Karin V. Hoff

Electrical & Computer Engineering Faculty Research

Characterizing and calibrating a low impedance large Helmholtz coil generating 60 Hz magnetic fields with amplitudes well below the earth’s magnetic field is difficult and imprecise when coil shielding is not available and noise is an issue. Parameters influencing the calibration process such as temperature and coil impedance need to be figured in the calibration process. A simple and reliable calibration technique is developed and used to measure low amplitude fields over a spatial grid using a standard Hall effect probe gaussmeter. These low amplitude fields are typically hard or impossible to detect in the presence of background fields when …

Globally Convergent Approximate Dynamic Programming Applied To An Autolander, J.J. Murray, Richard Saeks, C.J. Cox, George G. Lendaris

Complex Systems Faculty Publications and Presentations

A globally convergent nonlinear Approximate Dynamic Programming algorithm is described, and an implementation of the algorithm in the linear case is developed. The resultant linear Approximate Dynamic Programming algorithm is illustrated via the design of an autolander for the NASA X-43 research aircraft, without a priori knowledge of the X-43's flight dynamics.

Bi-Decomposition Of Multi-Valued Relations, Alan Mishchenko, Marek Perkowski, Bernd Steinbach

Electrical and Computer Engineering Faculty Publications and Presentations

This presentation discusses an approach to decomposition of multivalued functions and relations into networks of two-input gates implementing multi-valued MIN and MAX operations. The algorithm exploits both the incompleteness of the initial specification and the flexibilities generated in the process of decomposition. Experimental results over a set of multi-valued benchmarks show that this approach outperforms other approaches in the quality of final results and CPU time.

Turbo Space-Time Coded Modulation : Principle And Performance Analysis, Dongzhe Cui

Dissertations

A breakthrough in coding was achieved with the invention of turbo codes. Turbo codes approach Shannon capacity by displaying the properties of long random codes, yet allowing efficient decoding. Coding alone, however, cannot fully address the problem of multipath fading channel. Recent advances in information theory have revolutionized the traditional view of multipath channel as an impairment. New results show that high gains in capacity can be achieved through the use of multiple antennas at the transmitter and the receiver. To take advantage of these new results in information theory, it is necessary to devise methods that allow communication systems …

Scheduling Algorithms For High-Speed Switches, Jinhui Li

Dissertations

The virtual output queued (VOQ) switching architecture was adopted for high speed switch implementation owing to its scalability and high throughput. An ideal VOQ algorithm should provide Quality of Service (QoS) with low complexity. However, none of the existing algorithms can meet these requirements.

Several algorithms for VOQ switches are introduced in this dissertation in order to improve upon existing algorithms in terms of implementation or QoS features. Initially, the earliest due date first matching (EDDFM) algorithm, which is stable for both uniform and non-uniform traffic patterns, is proposed. EDDFM has lower probability of cell overdue than other existing maximum …

2d And 3d Surface Image Processing Algorithms And Their Applications, Jianlin Gao

Dissertations

This doctoral dissertation work aims to develop algorithms for 2D image segmentation application of solar filament disappearance detection, 3D mesh simplification, and 3D image warping in pre-surgery simulation. Filament area detection in solar images is an image segmentation problem. A thresholding and region growing combined method is proposed and applied in this application. Based on the filament area detection results, filament disappearances are reported in real time. The solar images in 1999 are processed with this proposed system and three statistical results of filaments are presented.

3D images can be obtained by passive and active range sensing. An image registration …

Channel Estimation And Signal Enhancement For Ds-Cdma Systems, Kun Wang

Dissertations

This dissertation focuses on topics of Bayesian-based multiuser detection, space-time (S-T) transceiver design, and S-T channel parameter estimation for direct-sequence code-division multiple-access (DS-CDMA) systems.

Using the Bayesian framework, various linear and simplified nonlinear multiuser detectors are proposed, and their performances are analyzed. The simplified non-linear Bayesian solutions can bridge the performance gap between sub-optimal linear multiuser detectors and the optimum multiuser detector.

To further improve the system capacity and performance, S-T transceiver design approaches with complexity constraint are investigated. Novel S-T receivers of low-complexity that jointly use the temporal code-signature and the spatial signature are proposed. Our solutions, which lead …

Modeling, Design And Scheduling Of Computer Integrated Manufacturing And Demanufacturing Systems, Ying Tang

Dissertations

This doctoral dissertation work aims to provide a discrete-event system-based methodology for design, implementation, and operation of flexible and agile manufacturing and demanufacturing systems. After a review of the current academic and industrial activities in these fields, a Virtual Production Lines (VPLs) design methodology is proposed to facilitate a Manufacturing Execution System integrated with a shop floor system. A case study on a back-end semiconductor line is performed to demonstrate that the proposed methodology is effective to increase system throughput and decrease tardiness. An adaptive algorithm is proposed to deal with the machine failure and maintenance. To minimize the environmental …

Joint Source Channel Coding For Progressive Image Transmission, Minyi Zhao

Dissertations

Recent wavelet-based image compression algorithms achieve best ever performances with fully embedded bit streams. However, those embedded bit streams are very sensitive to channel noise and protections from channel coding are necessary. Typical error correcting capability of channel codes varies according to different channel conditions. Thus, separate design leads to performance degradation relative to what could be achieved through joint design. In joint source-channel coding schemes, the choice of source coding parameters may vary over time and channel conditions. In this research, we proposed a general approach for the evaluation of such joint source-channel coding scheme. Instead of using the …

Novel Multiuser Detection And Multi-Rate Schemes For Multi-Carrier Cdma, Pingping Zong

Dissertations

A large variety of services is [sic] expected for wireless systems, in particular, high data rate services, such as wireless Internet access. Users with different data rates and quality of service (QoS) requirements must be accommodated. A suitable multiple access scheme is key to enabling wireless systems to support both the high data rate and the integrated multiple data rate transmissions with satisfactory performance and flexibility. A multi-carrier code division multiple access (MC-CDMA) scheme is a promising candidate for emerging broadband wireless systems. MC-CDMA is a hybrid of orthogonal frequency division multiplexing (OFDM) and code division multiple access (CDMA). The …

Plasma Induced Damage To Si And Sige Devices And Materials, Wei Zhong

Dissertations

This thesis studied the plasma-induced damage to Si and strained Si_1-xGe_x, and the resulting change in device characteristics. The energetic particles (ions, electrons and photons) in plasma reactor present a potentially hostile environment for processing VLSI devices. An inductively coupled plasma (ICP) reactor was used to study its damage effects to thin gate oxides. Electrical characterizations by C-V, ramped voltage breakdown (RVB) and deep-level transient spectroscopy (DLTS) measurement, and x-ray photoelectron spectroscopy (XPS) analysis were employed to investigate the damages to thin gate oxides and Si/SiO₂ interface. The shift of flat band voltage, the reduction …

Performance Analysis And Resource Allocation In Cdma Wireless Networks For Multimedia Services, Sebnem Zorlu

Dissertations

The proliferation of Internet and demand for wireless services necessitate large increases in capacity and data rates in order to support different multimedia services. Wireless systems will be required to support sources with a variety of traffic characteristics and quality of service requirements. This requires algorithms for admission control and resource allocation at the session, burst and packet levels. The purpose of this research is to develop and analyze optimal resource allocation strategies to maximize throughput of wireless systems with integrated services. Given the multimedia user requirements, the problem addressed can be formulated as a constrained optimization problem. The objective …

Buffer Management And Cell Switching Management In Wireless Packet Communications, Jongho Bang

Dissertations

The buffer management and the cell switching (e.g., packet handoff) management using buffer management scheme are studied in Wireless Packet Communications.

First, a throughput improvement method for multi-class services is proposed in Wireless Packet System. Efficient traffic management schemes should be developed to provide seamless access to the wireless network. Specially, it is proposed to regulate the buffer by the "Selective- Delay Push-In (SDPI)" scheme, which is applicable to scheduling delay-tolerant non-real time traffic and delay-sensitive real time traffic. Simulation results show that the performance observed by real time traffics are improved as compared to existing buffer priority scheme in …

Design Of Traffic Shaper / Scheduler For Packet Switches And Diffserv Networks : Algorithms And Architectures, Surong Zeng

Dissertations

The convergence of communications, information, commerce and computing are creating a significant demand and opportunity for multimedia and multi-class communication services. In such environments, controlling the network behavior and guaranteeing the user's quality of service is required. A flexible hierarchical sorting architecture which can function either as a traffic shaper or a scheduler according to the requirement of the traffic load is presented to meet the requirement. The core structure can be implemented as a hierarchical traffic shaper which can support a large number of connections with a wide variety of rates and burstiness without the loss of the granularity …

Propagation And Scattering Of Collimated Beam Wave In Vegetation Using Scalar Transport Theory, Michael Yu-Chi Wu

Theses

The scalar time-dependent equation of radiative transfer is used to develop a theory of pulse beamwave propagation and scattering in a medium character ized by many random discrete scatterers which scatter energy strongly in the forward scattering direction. Applications include the scattering of highly collimated millimeter waves in vegetation and optical beams in the atmosphere. The specific problem analyzed is that of a periodic sequence of Gaussian shaped pulses normally incident from free space onto the planar boundary surface of a random medium half-space, such as a forest, that possesses a power scatter (phase) function consisting of a strong, narrow …

Optical Properties Of Photonic Crystals, Anand G. Shenoy

Theses

The ability to confine light in three dimensions has important implications for quantum optics and quantum-optical devices. Photonic crystals, the optical analog of electronic crystals, provide us a means of achieving this goal. This analogy has motivated a whole new series of experimental and theoretical searches for elusive photonic band-gap structures. Combinations of metallic and dielectric materials can be used to obtain the required three-dimensional (3D) periodic variation in the dielectric constant. This could pave the way for photonic crystal structures that have widespread applications.

The working of 3D photonic crystals into the wavelength regimes where most optoelectronic devices operate, …

Performance Of Proton Exchange Membranefuel Cell With Co/H2 Fuel, Hong-Mei Yu, Zhong-Jun Hou, Bao-Lian Yi, Ke-Wan Bi, Jing-Xin Zhang, Zhi-Yin Lin, Ming Han

Journal of Electrochemistry

Fuel of proton exchange membrane fuel cell(PEMFC) mostly comes from reformatecontains CO which will poison the fuel cell electrocatalyst. The effect of CO on the performance of PEMFC was studied in this paper. The results of the experiment show that when CO is fed inPEMFC ,the cell voltage will be decreased violently,then it will become steady with some vibration. The poison will become more serious with higher CO content and weaker at higher temperature. The adsorption of CO on the electrocatalyst is reversible. The PtRu electrocatalyst is moresuitable for the electrocatalysis of CO/H₂ than Pt electrocatalyst.