Engineering Commons^™

Real Time Dynamic Trajectory Smoothing For Uninhabited Aerial Vehicles, Erik Anderson, Randal Beard, Timothy W. Mclain

Faculty Publications

Sponsorship: AFOSR, DARPA. This paper presents a real-time, feasible trajectory generation algorithm for unmanned air vehicles (UAVs) flying through a sequence of waypoints. The algorithm produces extremal trajectories that transition between straight-line path segments in a time-optimal fashion. In addition, the algorithm can be configured so that the dynamically feasible trajectory has the same path length as the straight-line waypoint path. Implementation issues associated with the algorithm are described in detail. Simulation studies show the effectiveness of the proposed method.

Algan/Gan Hemts - Operation In The K-Band And Above, Ioulia P. Smorchkova, M. Wojtowicz, Rajinder Sandhu, R. Tsai, M. Barsky, C. Namba, P.-S. Liu, R. Dia, Minhdao Truong, D. Ko, J. Wang, H. Wange, Asif Khan

Faculty Publications

We report on the power and microwave noise performance of AlGan/GaN high electron-mobility transistors (HEMTs) at frequencies f > 18 GHz (K- and Ka-bands). At 20 GHz, a record continuous-wave output power of 1.6 W has been achieved on an eight-finger 500-mum total gate-periphery device. At 29 GHz, a 120-mum gate-periphery device showed a pulsed output density of 1.6 W/mm with an associated gain of 6.7 dB and power-added efficiency of 26%. Minimum noise figure of 1.5 dB has been achieved on a 0.2 mum x 200 mum device at 26 GHz. The data demonstrate the viability of AlGan/GaN HEMTs for …

Corp - A Method Of Concatenation And Optimization For Resource Reservation Path In Mobile Internet, Kyounghee Lee, Myungchul Kim, Samuel T. Chanson, Chansu Yu, Jonghyun Lee

Electrical and Computer Engineering Faculty Publications

Existing research related to RSVP with mobility support has mainly focused on maintaining reservation state along the routing path, which changes continuously with the movements of mobile host (MH), without much overhead and delay. However, problems such as deepening RSVP's inherent scalability problem and requiring significant changes in the existing network infrastructure have not been adequately addressed. In this paper, we propose a new approach, known as Concatenation and Optimization for Reservation Path (CORP), which addresses these issues. In CORP, each BS pre-establishes pseudo reservations to its neighboring BSs in anticipation of the MH's movement. When the MH moves into …

An All-Digital Clock-Smoothing Technique—Counting-Prognostication, Xiaoyi Qin, Hansheng Wang, Lieguang Zeng, Fuqin Xiong

Electrical and Computer Engineering Faculty Publications

This article presents a novel universal all-digital clock-smoothing technique - counting-prognostication. Operation principles, performance analysis, and comparisons are given. Analysis and measurement results show that this technique can efficiently smooth jitter and wander for a wide pull-in range and pull-out range, and jitter accumulation is small. A cycle-varying counting-prognostication method, which decreases pull-in time, is also suggested.

Generic Implementation Of Components Of Neuro-Fuzzy Controllers Based On Fpga Technology, Mohamed Samir Ahmed Abd El Kader

Archived Theses and Dissertations

No abstract provided.

Microwave Reflection And Dielectric Properties Of Mortar Subjected To Compression Force And Cyclically Exposed To Water And Sodium Chloride Solution, Shanup Peer, Joseph Toby Case, Eric Gallaher, K. E. Kurtis, R. Zoughi

Electrical and Computer Engineering Faculty Research & Creative Works

Corrosion of the reinforcing steel is a major cause of damage and deterioration in reinforced concrete structures such as concrete bridge decks and columns. Chloride intrusion into concrete can lead to depassivation of the steel and initiation of corrosion. Thus, it is very important to be able to nondestructively detect and evaluate the free chloride content in concrete. Near-field microwave nondestructive testing techniques, using open-ended rectangular waveguide probes, have shown great potential for evaluating various properties of concrete, including the successful detection of sodium chloride added to mortar mixing water. In this study, several mortar samples are cyclically soaked in …

Power-Bus Decoupling With Embedded Capacitance In Printed Circuit Board Design, Minjia Xu, Todd H. Hubing, Juan Chen, Thomas Van Doren, James L. Drewniak, Richard E. Dubroff

Electrical and Computer Engineering Faculty Research & Creative Works

This paper experimentally investigates the effectiveness of embedded capacitance for reducing power-bus noise in high-speed printed circuit board designs. Boards with embedded capacitance employ closely spaced power-return plane pairs separated by a thin layer of dielectric material. In this paper, test boards with four embedded capacitance materials are evaluated. Power-bus input impedance measurements and power-bus noise measurements are presented for boards with various dimensions and layer stack ups. Unlike discrete decoupling capacitors, whose effective frequency range is generally limited to a few hundred megahertz due to interconnect inductance, embedded capacitance was found to efficiently reduce power-bus noise over the entire …

Network Lifetime Extension, Power Conservation And Interference Suppression For Next Generation Mobile Wireless Networks, Amer Catovic

Dissertations

Two major focus research areas related to the design of the next generation multihop wireless networks are network lifetime extension and interference suppression. In this dissertation, these two issues are addressed.

In the area of interference suppression, a new family of projection multiuser detectors, based on a generalized, two-stage design is proposed. Projection multiuser detectors provide efficient protection against undesired interference of unknown power, while preserving simple design, with closed-form solution for error probabilities. It is shown that these detectors are linearly optimal, if the interference power is unknown.

In the area of network lifetime extension, a new approach to …

Joint Buffer Management And Scheduling For Input Queued Switches, Dequan Liu

Dissertations

Input queued (IQ) switches are highly scalable and they have been the focus of many studies from academia and industry. Many scheduling algorithms have been proposed for IQ switches. However, they do not consider the buffer space requirement inside an IQ switch that may render the scheduling algorithms inefficient in practical applications.

In this dissertation, the Queue Length Proportional (QLP) algorithm is proposed for IQ switches. QLP considers both the buffer management and the scheduling mechanism to obtain the optimal allocation region for both bandwidth and buffer space according to real traffic load. In addition, this dissertation introduces the Queue …

Packet Data Communications Over Coded Cdma With Hybrid Type-Ii Arq, Seokhyun Yoon

Dissertations

This dissertation presents in-depth investigation of turbo-coded CDNIA systems in packet data communication terminology. It is divided into three parts; (1) CDMA with hybrid FEC/ARQ in deterministic environment, (2) CDMA with hybrid FEC/ARQ in random access environment and (3) an implementation issue on turbo decoding.

As a preliminary, the performance of CDMA with hybrid FEC/ARQ is investigated in deterministic environment. It highlights the practically achievable spectral efficiency of CDMA system with turbo codes and the effect of code rates on the performance of systems with MF and LMMSE receivers, respectively. For given ensemble distance spectra of punctured turbo codes, an …

Robust And Efficient Video/Image Transmission, Xi Min Zhang

Dissertations

The Internet has become a primary medium for information transmission. The unreliability of channel conditions, limited channel bandwidth and explosive growth of information transmission requests, however, hinder its further development. Hence, research on robust and efficient delivery of video/image content is demanding nowadays.

Three aspects of this task, error burst correction, efficient rate allocation and random error protection are investigated in this dissertation. A novel technique, called successive packing, is proposed for combating multi-dimensional (M-D) bursts of errors. A new concept of basis interleaving array is introduced. By combining different basis arrays, effective M-D interleaving can be realized. It has …

Deposition And Characterization Of Magnetron Sputtered Bcc Tantalum, Anamika Patel

Dissertations

The goal of this thesis was to provide scientific and technical research results for developing and characterizing tantalum (Ta) coatings on steel substrates deposited by DC magnetron sputtering. Deposition of tantalum on steel is of special interest for the protection it offers to surfaces, e.g. the surfaces of gun barrels against the erosive wear of hot propellant gases and the mechanical damage caused by the motion of launching projectiles. Electro-plated chromium is presently most commonly used for this purpose; however, it is considered to be carcinogenic in its hexavalent form. Tantalum is being investigated as non-toxic alternative to chromium and …

Vlsi Design Of Stability Routing Protocol For Sensors In Wireless Mobile Ad-Hoc Networks, Vishnu M. Mandava

Theses

This thesis gives a detailed description of the Application specific integrated circuit (ASIC) design of Stability routing protocol for sensors in mobile ad-hoc networks. The Stability routing protocol is based on the signal strength and position components during data transmission while considering sensors in an ad-hoc network. A general ad-hoc network has unpredictable and variable mobility patterns therefore the signal strength criteria is adopted for routing. Signal strength criteria has been proved to be efficient for communication between the mobile nodes without any data loss. In this thesis an architecture for a processor implementing stability routing protocol for effective communication …

Firewall Interface For Java Ftp Smtp And Http Servers, Ratan Kumar Erukulla

Theses

The objective of my thesis is to develop a firewall interface for FTP, HTTP and SMTP servers. A firewall interface is a graphical user interface (GUI) to configure the properties of the server. Using this interface, we can spy a user, block and unblock the IP address of a client, display statistics of user and server. We can track all the user actions while he is connected to the server. These actions are logged and based on the log data we can deny access to users performing illegal operations. All the servers and interfaces are written in Java. Java was …

An Interface Chip For Saw Based Sensor In An Ad-Hoc Network, Yagneshwara Ramakrishna Vadapalli

Theses

The design of a smart integrated chemical sensor system that will enhance sensor performance and compatibility to ad hoc network architecture remains a challenge. This work involves the design of an interface chip for a Surface Acoustic Wave (SAW) based chemical sensor where the sensor reflects the RF input and introduces a time delay proportional to the concentration of the vapors absorbed by it. The interface chip detects the frequency shift as a function of the chemical species absorbed by the sensor and alerts the ad hoc network controller when a monitored parameter exceeded some threshold, based on local processing …

Testing With Hostile Data Streams, Alan A. Jorgensen

Electrical Engineering and Computer Science Faculty Publications

This note describes a method of testing software for response to malicious data streams. Systems that process data streams obtained from an external source such as the Internet are vulnerable to security issues if malicious data is not processed correctly. This note describes a testing method that creates malicious data streams, applies them to a software application and checks the appropriateness of the application response. The note begins with a description of the problem: inadequate testing of software response to malicious data streams. I present a method of testing the response to malicious data streams and introduce the concepts of …

An Analysis Of The 1999 Darpa/Lincoln Laboratory Evaluation Data For Network Anomaly Detection, Matthew V. Mahoney, Philip K. Chan

Electrical Engineering and Computer Science Faculty Publications

We investigate potential simulation artifacts and their effects on the evaluation of network anomaly detection systems in the 1999 DARPA/MIT Lincoln Laboratory off-line intrusion detection evaluation data set. A statistical comparison of the simulated background and training traffic with real traffic collected from a university departmental server suggests the presence of artifacts that could allow a network anomaly detection system to detect some novel intrusions based on idiosyncrasies of the underlying implementation of the simulation, with an artificially low false alarm rate. The evaluation problem can be mitigated by mixing real traffic into the simulation. We compare five anomaly detection …

Heat: Runtime Interception Of Win32 Functions, Michael M. Andrews

Electrical Engineering and Computer Science Faculty Publications

When researching in any field, it is always important to build upon existing work. In most research disciplines, the core base is well defined and widely documented. However, the basis of innovative research in computer science, especially at the systems level, can often be proprietary information. This can be a major problem as unless you have source code available you must be granted access to the proprietary information (by usually signing non-disclosure documents) which comes with barriers on access, ownership and the ability to publish results. As an example, Microsoft's Windows operating system (all versions) can be a good base …

Learning Rules For Anomaly Detection Of Hostile Network Traffic, Matthew V. Mahoney, Philip K. Chan

Electrical Engineering and Computer Science Faculty Publications

We introduce an algorithm called LERAD that learns rules for finding rare events in nominal time-series data with long range dependencies. We use LERAD to find anomalies in network packets and TCP sessions to detect novel intrusions. LERAD outperforms the original participants in the 1999 DARPA/Lincoln Laboratory intrusion detection evaluation, and detected most attacks that eluded a firewall in a university departmental server environment.

Time-Resolved Electroluminescence Of Algan-Based Light-Emitting Diodes With Emission At 285 Nm, M. Shatalov, A. Chitnis, V. Mandavilli, R. Pachipulusu, J. P. Zhang, V. Adivarahan, S. Wu, Grigory Simin, M. Asif Khan, G. Tamulaitis, A. Sereika, I. Yilmaz, M. S. Shur, R. Gaska

Faculty Publications

We present a study on the time evolution of the electroluminescence(EL)spectra of AlGaN-based deep ultraviolet light-emitting diodes(LEDs) under pulsed current pumping. The ELspectra peaks at 285 nm and 330 nm are found to result from recombination involving band-to-band and free carriers to deep acceptor level transitions. The 330 nm long-wavelength transitions to deep acceptor levels in the p-AlGaN layer as well as the nonradiative processes significantly influence the LED internal quantum efficiency.

Long-Lasting Photoluminescence In Freestanding Gan Templates, Michael A. Reshchikov, M. Zafar Iqbal, Hadis Morkoç, S. S. Park, K. Y. Lee

Electrical and Computer Engineering Publications

We studied time-resolvedphotoluminescence(PL) over a temporal range 10−6–103 s in high-purity freestanding GaN templates. Red, yellow, green, blue, and shallow donor–acceptor emission bands can be resolved in the PLspectrum. Observation of luminescence long after the excitation is switched off is a striking feature of our study. The persistent PL observed for all above bands, except for the green band, is primarily attributed to the donor–acceptor-pair-type recombination. An unusually slow, nonexponential decay of radiative transitions from the conduction band to the shallow acceptor was also observed, pointing to some additional mechanism for the persistent PL. Possible role of the surface states …

Stimulated Emission And Ultrafast Carrier Relaxation In Algan/Gan Multiple Quantum Wells, Ü. Özgür, Henry O. Everitt, Lei He, Hadis Morkoç

Electrical and Computer Engineering Publications

Stimulated emission (SE) and ultrafast carrier relaxation dynamics were measured in two AlxGa1−xN/GaNmultiple-quantum-well(MQW) structures, grown in a Ga-rich environment with x=0.2 and 0.3, respectively. The threshold density for SE (Ith≃100 μJ/cm2) was found to be independent of x. Room-temperature, time-resolved, differential transmission measurements mapped the carrier relaxation mechanisms for above barrier energy excitation. Photoexcited carriers are observed to relax into the QWs in <1 ps, while carrier recombination times as fast as 30 ps were measured. For excitation above Ith, SE is shown to deplete carriers in the barriers through a cascaded refilling of the QW state undergoing SE. Similar behavior is seen in an Al0.3Ga0.7N/GaNMQW grown with a N-rich atmosphere, but the relaxation phenomena of all AlGaN MQWs are significantly faster than observed in InGaN MQWs of similar structure.

4h–Sic Photoconductive Switching Devices For Use In High-Power Applications, S. Doǧan, A. Teke, D. Huang, Hadis Morkoç, C. B. Roberts, J. Parish, B. Ganguly, M. Smith, R. E. Meyers, S. E. Saddow

Electrical and Computer Engineering Publications

Siliconcarbide is a wide-band-gapsemiconductor suitable for high-power high-voltage devices and it has excellent properties for use in photoconductive semiconductor switches (PCSSs). PCSS were fabricated as planar structures on high-resistivity 4H–SiC and tested at dc bias voltages up to 1000 V. The typical maximum photocurrent of the device at 1000 V was about 49.4 A. The average on-state resistance and the ratio of on-state to off-state currents were about 20 Ω and 3×1011, respectively. Photoconductivity pulse widths for all applied voltages were 8–10 ns. These excellent results are due in part to the removal of the surface damage by high-temperature H2 …

Improvement Of N-Gan Schottky Diode Rectifying Characteristics Using Koh Etching, J. Spradlin, S. Doğan, M. Mikkelson, D. Huang, L. He, D. Johnstone, Hadis Morkoç, R. J. Molnar

Electrical and Computer Engineering Publications

KOH etch was investigated as a means to improve the I–Vcharacteristics of Schottky diodes onn-type GaNgrown by molecular-beam epitaxy on sapphire, or on hydride vapor phase epitaxy templates. Atomic force microscopy images and I–Vcharacteristics are presented. After etching as-grown films in molten KOH, Schottky diodes on c-plane GaN had orders of magnitude reduction in reverse leakage current. The best devices had leakage currents less than 10−12 A (10−8 A/cm2) at −5 V, and ideality factors of 1.04. Measurements on several different sample structures indicate a correlation between surface roughness and saturation current, and an improvement in ideality …

Electric-Field-Induced Heating And Energy Relaxation In Gan, T. A. Eckhause, Ö. Süzer, Ç. Kurdak, F. Yun, Hadis Morkoç

Electrical and Computer Engineering Publications

Electric-field-induced heating is studied using noise measurements in n-type GaN grown on sapphire substrates. The measured electron temperature is found to be an order of magnitude higher than what is expected based on calculations of electron–phonon coupling via acoustic deformation potential scattering processes in GaN. The discrepancy may be explained by a large thermal boundary resistance between the GaN film and the sapphire substrate.

Current Mapping Of Gan Films By Conductive Atomic Force Microscopy, A. A. Pomarico, D. Huang, J. Dickinson, A. A. Baski, R. Cingolani, Hadis Morkoç, R. Molnar

Electrical and Computer Engineering Publications

Conductive atomic force microscopy has been used to investigate the local conductivity in hydride vapor-phase epitaxy and molecular-beam epitaxyGaN films, focusing on the effect of off-axis facet planes. We investigated two different types of samples, in which the facet planes were either present on the perimeters of as-grown islands, or on the edges of etch pits created by post-growth chemical etching. The results show that crystallographic planes tilted with respect to the c-plane growth direction show a significantly higher conductivity than surrounding areas. The n-type (or p-type) samples required a negative (or positive) sample bias for current conduction, …

Observation Of Optical Phonon Instability Induced By Drifting Electrons In Semiconductor Nanostructures, W. Liang, K. T. Tsen, Otto F. Sankey, S. M. Komirenko, K. W. Kim, V. A. Kochelap, Meng-Chyi Wu, Chong-Long Ho, Wen-Jeng Ho, Hadis Morkoç

Electrical and Computer Engineering Publications

We have experimentally proven the Cerenkov generation of optical phonons by drifting electrons in a semiconductor. We observe an instability of the polar optical phonons in nanoscale semiconductors that occurs when electrons are accelerated to very high velocities by intense electric fields. The instability is observed when the electron drift velocity is larger than the phase velocity of optical phonons and rather resembles a “sonic boom” for optical phonons. The effect is demonstrated in p–i–nsemiconductor nanostructures by using subpicosecond Raman spectroscopy.

Conductance Modulation Of Spin Interferometers, Marc Cahay, Supriyo Bandyopadhyay

Electrical and Computer Engineering Publications

We study the conductance modulation of gate controlled electron spin interferometers (also known as spin field effect transistors) based on the Rashba spin–orbit coupling effect. It is found that the modulation is dominated by Ramsauer (or Fabry-Perot) type transmission resonances rather than the Rashba effect in typical structures. These transmission resonances are due to reflections at the interferometer’s contacts caused by large interface potential barriers and effective mass mismatch between the contact material and the semiconductor. They are particularly strong in quasi-one-dimensional structures which, in fact, are preferred for spin interferometers because of the energy independence of the spin precession …

Generation–Recombination Noise In Gallium Nitride-Based Quantum Well Structures, Rolando S. Duran, Grover L. Larkins Jr., Carolyn M. Van Vliet, Hadis Morkoç

Electrical and Computer Engineering Publications

Electronic noise has been investigated in AlxGa1−xN/GaN modulation-doped field-effect transistors of submicron dimensions, grown by molecular beam epitaxy techniques. Some 20 devices were grown on a sapphire substrate. Conduction takes place in the quasi-two-dimensional (2D) layer of the junction (xy plane) which is perpendicular to the triangular quantum well (z direction). A nondoped intrinsic buffer layer separates the Si-doped donors in the AlxGa1−xN layer from the 2D transistor plane. Since all contacts must reach through the AlxGa1−xN layer to connect internally to the 2D plane, parallel conduction through this layer is a feature of all modulation-doped devices. The …

Infrared Optical Absorbance Of Intersubband Transitions In Gan/Algan Multiple Quantum Well Structures, Qiaoying Zhou, Jiayu Chen, B. Pattada, M. O. Manasreh, Faxian Xiu, Steve Putigan, K. S. Ramaiah, Hadis Morkoç

Electrical and Computer Engineering Publications

Intersubband transitions in Si-doped molecular beam epitaxygrown GaN/AlGaN multiple quantum wells on c-plane sapphire were investigated using the Fourier-transform infrared optical absorption technique. Several GaN quantum well samples were grown with either AlGaN bulk or GaN/AlGaN short period superlattice barriers. The measurements were made in a waveguide configuration utilizing a facet polished at 45° to the c plane. The integrated area of the intersubband transitions in several waveguides cut from different location of the wafer was measured, from which we estimated the two-dimensional electron gas density (σ). The measured values of σ are about two orders of magnitude larger …