Engineering Commons^™

Terahertz Optical-Hall Effect Characterization Of Two-Dimensional Electron Gas Properties In Algan/Gan High Electron Mobility Transistor Structures, S. Schöche, Junxia Shi, A. Boosalis, P. Kühne, C. M. Herzinger, John A. Woollam, W. J. Schaff, L. F. Eastman, M. Schubert, Tino Hofmann

Department of Electrical and Computer Engineering: Faculty Publications

The free-charge carrier mobility, sheet density, and effective mass of a two-dimensional electron gas are exemplarily determined in the spectral range from 640 GHz to 1 THz in a AlGaN/GaN heterostructure using the optical-Hall effect at room temperature. Complementary midinfrared spectroscopic ellipsometry measurements are performed for analysis of heterostructure constituents layer thickness, phonon mode, and free-charge carrier parameters. The electron effective mass is determined to be (0.22 ± 0.04)m₀. The high-frequency sheet density and carrier mobility parameters are in good agreement with results from dc electrical Hall effect measurements, indicative for frequency-independent carrier scattering mechanisms of the …

Reprogrammed Transcriptome In Rhesus-Bovine Interspecies Somatic Cell Nuclear Transfer Embryos, Kai Wang, Hasan H. Otu, Ying Chen, Young Lee, Keith Latham, Jose B. Cibelli

Department of Electrical and Computer Engineering: Faculty Publications

Background: Global activation of the embryonic genome (EGA), one of the most critical steps in early mammalian embryo development, is recognized as the time when interspecies somatic cell nuclear transfer (iSCNT) embryos fail to thrive.

Methodology/Principal Findings: In this study, we analyzed the EGA-related transcriptome of rhesus-bovine iSCNT 8- to 16- cell embryos and dissected the reprogramming process in terms of embryonic gene activation, somatic gene silencing, and maternal RNA degradation. Compared with fibroblast donor cells, two thousand and seven genes were activated in iSCNT embryos, one quarter of them reaching expression levels comparable to those found in in vitro …

Power Controlled Multirate Multimedia Transmission In Self-Encoded Spread Spectrum Over Dynamic Fading Channels, Liang Chi, Poomathi Duraisamy, Won Mee Jang, Lim Nguyen

Department of Electrical and Computer Engineering: Faculty Publications (to 2015)

In this paper, we propose to apply power control to self-encoded spread spectrum (SESS) in multirate and multimedia applications. The transmitter employs power control to to combat dynamic channel fading and the receiver employs decorrelation to reduce interference from multiple applications. We show that iterative detection can significantly improve the system performance. The proposed approach also improves the power efficiency which is essential in battery-driven communications such as mobile cellular systems.

Self-Encoded Spread Spectrum For Multirate Multimedia Communication In Multipath Channel, Liang Chi, Won Mee Jang, Lim Nguyen

Department of Electrical and Computer Engineering: Faculty Publications (to 2015)

In this paper, we propose the self-encoded spread spectrum (SESS) with multirate multimedia communication in multipath channel. In multirate multimedia SESS system, each application has their own transmission bit rate. The signal is transmitted through multipath channels each with different channel gain and time delay. We view the main path as the signal resource and other paths as interference. At the receiver side, decorrelation scheme is employed for the main path combined signal not only to reduce the crosstalk between different applications, but also to provide a better estimation for the despreading sequence in the main path. Interference cancellation(IC) in …

Low-Complexity Image Coder/Decoder With An Approaching-Entropy Quad-Tree Search Code For Embedded Computing Platforms, Tao Ma, Pradhumna Shrestha, Michael Hempel, Dongming Peng, Hamid Sharif

Department of Electrical and Computer Engineering: Faculty Publications (to 2015)

In this paper, we propose a fast, simple and efficient image codec applicable for embedded processing systems. Among the existing image coding methods, wavelet quad-tree is a foundation leading to an efficient structure to encode images. By searching significant coefficients along quad-trees, an embedded efficient code can be obtained. In this work, we exploit hierarchical relations of the quad-tree structure in terms of searching entropy and present a quad-tree searching model that is very close to the searching entropy. By applying this model, our codec surpasses SPIHT [1] by 0.2-0.4 db over wide code rates, and its performance is comparable …

Impact Of Interference On Secrecy Capacity In A Cognitive Radio Network, Zhihui Shu, Yaoqing Lamar Yang, Yi Qian, Rose Qingyang Hu

Department of Electrical and Computer Engineering: Faculty Publications (to 2015)

In this paper, we investigate secrecy capacity of a cognitive radio network based on stochastic geometry distributions. We consider the Poisson process of both the secondary users and the eavesdroppers, and analyze how the stochastic interference from the secondary users can influence the secrecy capacity of the primary users. First, we describe a network model with primary users, secondary users and eavesdroppers in a cognitive radio communication network environment, and derive the expression of secrecy capacity in an additive white Gaussian noise channel. Then, we study the outage probability of secrecy capacity of a primary node from a secure communication …

A Secure Data Aggregation And Dispatch Scheme For Home Area Networks In Smart Grid, Yun Ye, Yi Qian, Hamid Sharif

Department of Electrical and Computer Engineering: Faculty Publications (to 2015)

Cyber security for smart grid communication systems is one of the most critical requirements need to be assured before smart grid can be operationally ready for the market. Privacy is one of a very important security services. The customer information privacy in smart grid need to be protected. Smart grid data privacy encompasses confidentiality and anonymity of the information extracted from smart devices and metering transmission in a smart grid communication system. In this paper, we consider a home area network as a basic reading data aggregation and dispatch unit in smart grid systems, and we propose a secure in-network …

A Secure And Reliable In-Network Collaborative Communication Scheme For Advanced Metering Infrastructure In Smart Grid, Yun Ye, Yi Qian, Hamid Sharif

Department of Electrical and Computer Engineering: Faculty Publications (to 2015)

We consider various security vulnerabilities of deploying Advanced Metering Infrastructure (AMI) in smart grid, and explore the issues related to confidentiality for customer privacy and customer behavior as well as message authentication for meter reading and control messages. There are only a very few research work on AMI authentications, and no work exists on confidentiality for user privacy and user behavior, from the best of our knowledge. In this paper, we propose an in-network collaborative scheme to provide secure and reliable AMI communications in smart grid, with smart meters interconnected through a multihop wireless network. In this approach, an AMI …

A Cross-Layer Parallel Handover Optimization Scheme For Wimax Networks, Ting Zhou, Hamid Sharif, Michael Hempel, Puttipong Mahasukhon, Tao Ma, Pradhumna Shrestha

Department of Electrical and Computer Engineering: Faculty Publications (to 2015)

The handover performance plays a crucial role in guaranteeing the quality of real-time applications in WiMAX networks. In general, a handover process can be divided into four stages: i) cell reselection, ii) handover preparation, iii) link layer handover, and iv) IP layer handover. A cross-layer parallel handover optimization (CPHO) scheme is proposed in this paper to reduce the handover signaling overhead and latency in each stage. The key idea of our proposed scheme is that uses the knowledge achieved from the backhaul inter-BS communications to reduce the HO control message load in wireless links and overlaps the executions of the …

A Novel Channel Probing/Scanning Scheme For Secure Fast Handoff In Ieee 802.11-Based Wireless Networks, Ye Yan, Yi Qian, Rose Qingyang Hu

Department of Electrical and Computer Engineering: Faculty Publications (to 2015)

With the proliferation of wireless networks for practical deployments in recent years, secure fast handoff has become significantly important to provide secured access while reduce the latency caused by handoff procedure. Channel probing/scanning delay has been a major contribution to the overall latency of handoff in IEEE 802.11 based wireless networks. In this paper, we present a novel secure fast handoff scheme that adopts network-assisted radio statement (NACS) to eliminate lengthy probing/scanning delay by taking advantage of the knowledge of network topology of neighboring nodes in the network. We apply an opportunistic mechanism to retrieve the channel condition from neighboring …

Mobile Wimax Throughput And Delay Measurements In Railroad Environment, Puttipong Mahasukhon, Hamid Sharif, Michael Hempel, Tao Ma, Pradhumna Shrestha

Department of Electrical and Computer Engineering: Faculty Publications (to 2015)

The railroad industry in North America is heavily involved in improving the broadband wireless connectivity of their railroad operations. We propose our approach of establishing a Mobile WiMAX test bed as a part of our collaborations with the Federal Railroad Administration (FRA) for investigating the performance of current and upcoming broadband wireless technologies in a railroad environment. The focus is on studying the impact of mobility on the wireless system throughput for moving trains at high velocities. Our goal is to provide a comprehensive measurement that will assist others in understanding Mobile WiMAX performance and guiding future network deployment. In …

Battery-Aware Multimedia Coding Optimization By Dynamic Frequency Scaling, Jianxin Sun, Xueyi Wang, Song Ci

Department of Electrical and Computer Engineering: Faculty Publications (to 2015)

Nowadays, multimedia application and video streaming have gained a great popularity because of the boasting development on mobile hardware, and battery driven devices have emerged with a tremendous speed. Due to the important issue of battery efficiency on mobile devices, many optimization algorithms have being proposed toward various of battery powered platforms and scenarios. Most of the provided solutions choose to aim at the minimization of energy usage under a given task scheduling by adjusting parameters reside in the processes of different schemes. However, the battery discharging characteristics and its instant output pattern are still ignored if the optimization is …

Impact Of Channel Estimation Errors On Effectiveness Of Eigenvector-Based Jamming For Physical Layer Security In Wireless Networks, James M. Taylor, Michael Hempel, Hamid Sharif, Shichuan Ma, Yaoqing Lamar Yang

Department of Electrical and Computer Engineering: Faculty Publications (to 2015)

In this paper, we present our study of an Eigenvector-based artificial noise-based jamming technique developed to provide increased wireless physical layer security in transmit-receive diversity systems and analyze the impact of channel estimation errors on system performance. Our simulation results showed that with knowledge of perfect channel state information, the technique provided secrecy capacity of approximately 7 bits/s/Hz for a normalized transmit power of 25 dB for a variety of transmit, receive, and eavesdropper configurations. We also describe a novel method to simulate generalized channel state information estimation errors. While other publications neglect the impact of these estimation errors, our …

Prof. Dr. Marek E. Bialkowski (1951 – 2011), Tadeusz Wysocki, Salman Durrani, Rodney A. Kennedy

Department of Electrical and Computer Engineering: Faculty Publications (to 2015)

It is our sad duty to report the untimely death of Prof. Dr. Marek E. Bialkowski, who passed away on Thursday, October 27, 2011 after a short unexpected illness caused by pneumonia. He was a remarkable researcher and a mentor and friend to many us and he will be greatly missed.

Marek was born in Sochaczew, Poland, in 1951. He received the M.Eng.Sc. degree in applied mathematics and the Ph.D. degree in electrical engineering, both from the Warsaw University of Technology, Warsaw, Poland, in 1974 and 1979, respectively. He received the Doctor of Engineering (higher doctorate) degree in computer science …

Message From The Chair Of Technical Program Committee, Tadeusz Wysocki

Department of Electrical and Computer Engineering: Faculty Publications (to 2015)

On behalf of all the members of the Organizing Committee, I would like to welcome you to the 5th International Conference on Signal Processing and Telecommunication Systems, ICSPCS’2011. The ICSPCS conferences evolved from the series of successful symposia and workshops, i.e. International Symposia on DSP and Communication Systems (DSPCS), and Workshops on the Internet, Telecommunications and Signal Processing (WITSP). As in the past, the Organizing Committee has succeeded this year in achieving an official technical co-sponsorship of the IEEE Communications Society for conference. As a result the ICSPCS’2011 conference has been listed in the IEEE database of the conferences and …

Priority Preemption For Real-Time Application Qos Guarantees In Cooperative Vehicular Networks, Ting Zhou, Hamid Sharif, Michael Hempel, Puttipong Mahasukhon, Tao Ma, Pradhumna Shrestha

Department of Electrical and Computer Engineering: Faculty Publications (to 2015)

Inter-vehicle and roadside-to-vehicle communications can contribute to a safer and more efficient driving experience by providing time-sensitive and location-aware information. However, its performance suffers from vehicle mobility, intermittent user connectivity, and wireless channel unreliability. In this paper, we propose a novel cross-layer optimization approach based on our Adaptive Distributed Cooperative Medium Access Control (ADC-MAC) protocol to guarantee the quality-of-service (QoS) of real-time applications. Markov chain based theoretical analysis show that our proposed priority preemption approach can improve the quality of a real-time application by guaranteeing its bandwidth and reducing its transmission latency.

A Building Lca Case Study Using Autodesk Ecotect And Bim Model, Endong Wang, Zhigang Shen, Charles Barryman

Department of Construction Engineering and Management: Faculty Publications

The main objective of this study is to evaluate the potential of utilizing building information model (BIM) to perform whole building Life Cycle Analysis (LCA). The research question addressed was how life cycle performance of a building was affected quantitatively by design configurations. Life cycle energy consumption and CO₂ emission of a university building in the Midwest was calculated using Autodesk® Ecotect and BIM model. The study compared life cycle performance, i.e., CO₂ emissions and energy consumptions, among different design configurations, as well as their distributions in the stages of the building’s life time. Sensitivity analysis was performed …

Achieving High Efficiency Laminated Polymer Solar Cell With Interfacial Modified Metallic Electrode And Pressure Induced Crystallization, Yongbo Yuan, Yu Bi, Jinsong Huang

Department of Mechanical and Materials Engineering: Faculty Publications

We report efficient laminated organic photovoltaic device with efficiency approach the optimized device by regular method based on Poly(3-hexylthiophene-2,5-diyl) and [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM). The high efficiency is mainly attributed to the formation of a concrete polymer/metal interface mechanically and electrically by the use of electronic-glue, and using the highly conductive and flexible silver film as anode to reduce photovoltage loss and modifying its work function for efficiency hole extraction by ultraviolet/ozone treatment, and the pressure induced crystallization of PCBM.

In Vitro Models For Glaucoma Research: Effects Of Hydrostatic Pressure, Yuan Lei, Shadi Rajabi, Ryan M. Pedrigi, Darryl R. Overby, A. Thomas Read, C. Ross Ethier

Department of Mechanical and Materials Engineering: Faculty Publications

PURPOSE. The response of cells (e.g., optic nerve head [ONH] cells) to mechanical stress is important in glaucoma. Studies have reported the biological effects of hydrostatic pressure on ONH cells cultured on a rigid substrate. An apparatus, designed to independently vary hydrostatic pressure and gas tension (including oxygen tension) in culture medium, was used to evaluate the effects of pressure and tension on cell migration, shape, and α-tubulin architecture in a transformed cell line (DITNC1 rat cortical astrocytes).

METHODS. During the assay period, cells were exposed to one of four experimental configurations: (1) control pressure and control gas tension; (2) …

Impact Of Elliptical Trainer Ergonomic Modifications On Perceptions Of Safety, Comfort, Workout, And Usability For People With Physical Disabilities And Chronic Conditions, Judith M. Burnfield, Yu Shu, Thad W. Buster, Adam P. Taylor, Carl A. Nelson

Department of Mechanical and Materials Engineering: Faculty Publications

Background The popularity of elliptical training has grown in rehabilitation, fitness, and home settings as a means for improving fitness and walking, yet many people with physical disabilities and chronic conditions experience difficulties when trying to use elliptical trainers.

Objective The purpose of this study was to compare, for people with disabilities and chronic conditions, perceptions of safety, comfort, workout, and usability of 4 elliptical trainers before and after the development of a set of low-cost adaptations.

Design This study was a quasi-experimental repeated-measures investigation.

Methods Twenty adults with diverse medical conditions and functional abilities evaluated 4 elliptical trainers for …

Missouri River Recovery Program Emergent Sandbar Habitat Annual Adaptive Management Report, Year 1, 2010)

United States Army Corps of Engineers, Omaha District

This Adaptive Management (AM) Report for Emergent Sandbar Habitat (ESH) represents the first complete iteration within the draft AM strategy being implemented for the interior least terns (Sternula antillarum) and piping plovers (Charadrius melodus) within the Missouri River Mainstem System based on the 2003 Amended Biological Opinion (BiOp). Please refer to the ESH AM Strategy - Appendix H of the Draft ESH Programmatic Environmental Impact Statement (PEIS) – and the Missouri River Recovery Program (MRRP) AM Process Framework for detailed background information on the overall scope and approach of this effort. Also note that as more …

Missouri River Recovery Program: Adaptive Management Process Framework, Joe Bonneau, Tim Fleeger, Craig Flemming, Carol Hale, Mike Anderson, Kate Buenau, Tim L. Hiller, Doug Latka, Ron Thom, Drew Tyre, Steve Fischer, Casey Kruse, Brad Thompson

United States Army Corps of Engineers, Omaha District

The purpose of this Adaptive Management (AM) Process Framework is to describe the AM process for the U.S. Army Corps of Engineers (USACE) Missouri River Recovery Program (MRRP) and explain how AM principles will be used in the MRRP to reduce uncertainty and ensure that Program objectives are achieved over time. The AM Process Framework is intended to be broad so that it can be applied to all aspects of the MRRP and be understood by a diverse audience of managers, federal and state agencies, scientists, engineers, the Missouri River Recovery Implementation Committee (MRRIC), stakeholders, Tribes, and the public.

Assessment Of Shape Memory Alloy Stent Deployment In A Stenosed Artery, Shijia Zhao, Linxia Gu, Stacey R. Froemming

Department of Mechanical and Materials Engineering: Faculty Publications

Purpose — Shape memory alloy (SMA) stents have been used increasingly for the treatment of complex arterial occlusions. There is an immediate need to quantify the mechanical performance of SMA stents to open occluded arteries.
Methods — The stent crimping and expanding process was assessed through both numerical modeling and in-vitro studies. The implantation of a SMA stent in curved arteries with eccentric stenosis were simulated to evaluate the effect of artery curvature on arterial mechanics.
Results — The crimping process stored a considerable amount of strain energy in the stent, which were then released through self-expansion until a balance …

Comparative Analysis Of The Biaxial Mechanical Behavior Of Carotid Wall Tissue And Biological And Synthetic Materials Used For Carotid Patch Angioplasty, Alexey Kamenskiy, Iraklis I. Pipinos, Jason N. Mactaggart, Syed A. Jaffar Kazmi, Yuris A. Dzenis

Department of Mechanical and Materials Engineering: Faculty Publications

Patch angioplasty is the most common technique used for the performance of carotid endarterectomy. A large number of patching materials are available for use while new materials are being continuously developed. Surprisingly little is known about the mechanical properties of these materials and how these properties compare with those of the carotid artery wall. Mismatch of the mechanical properties can produce mechanical and hemodynamic effects that may compromise the long-term patency of the endarterectomized arterial segment. The aim of this paper was to systematically evaluate and compare the biaxial mechanical behavior of the most commonly used patching materials. We compared …

It’S Not What You Think: A Theory For Understanding The Lack Of Interest Among Domestic Students In The Engineering Phd, Michelle C. Howell Smith, Amanda L. Garrett, Ellen Weissinger, Namas Chandra

Department of Mechanical and Materials Engineering: Faculty Publications

We live in a fast-paced world surrounded by technological advances. Engineers with advanced skills perform important functions in our society. However we know very little about how engineers consider obtaining advanced education and skills. The purpose of this study is to understand and develop a theory explaining the process domestic engineers undergo in developing an interest in obtaining a PhD in engineering. Our research was guided by the following central research question: What is the theory that explains the process of developing interest in doctoral-level engineering education for engineers? We used qualitative, grounded theory methods, to investigate the process of …

Frequency Shifts In Plate Crystal Resonators Induced By Electric, Magnetic, Or Mechanical Fields In Surface Films, Nan Liu, J.S. Yang, Yuantai Hu, Xuedong Chen, Wei Jiang

Department of Mechanical and Materials Engineering: Faculty Publications

We study frequency shifts in plate crystal resonators with surface films. The films are multiphysical, including the effects of inertia, stiffness, intrinsic stress, piezoelectric coupling, and piezomagnetic coupling. Mindlin’s two-dimensional equations for a crystal plate with two elastic surface films are generalized to include the multiphysical effects of the films. They are used to study thickness-shear vibrations of a rotated Y-cut quartz plate with initial fields resulting from the mechanical, electric, and magnetic fields in the surface films. Frequency shifts caused by the initial fields are calculated and examined. Results show that plate crystal resonators with multiphysical surface films may …

A Few Transient Effects In At-Cut Quartz Thickness-Shear Resonators, Runyu Zhang, Hongping Hu

Department of Mechanical and Materials Engineering: Faculty Publications

We study a few transient effects of AT-cut quartz thickness-shear resonators, including resonator turning on and turning off as well as voltage amplitude and frequency fluctuations. Mindlin’s two-dimensional plate equations are used and solved analytically. Both a sudden change and a gradual change of the driving voltage are studied. It is found that for a resonator with a frequency of 1.649430868 MHz and material quality factor of Q = 10⁵, the characteristic time scale of the transient effects is of the order of 0.1 s.

Use Of Environmental Scanning Electron Microscopy For In Situ Observation Of Interaction Of Cells With Micro- And Nanoprobes, Alexander Goponenko, B. J. Boyle, K. I. Jahan, Maxim V. Gerashchenko, Dmitri E. Fomenko, Vadim N. Gladyshev, Yuris A. Dzenis

Department of Mechanical and Materials Engineering: Faculty Publications

Precision intracellular sensing, probing and manipulation offer unprecedented opportunities for advances in biological sciences. Next-generation ultra-fine probes will be capable of targeting individual cell organelles. Development of such probes as well as probes capable of penetrating through tough cell walls requires detailed knowledge of cell-probe interaction. This Letter evaluated the applicability of environmental scanning electron microscopy (ESEM) for cell and cell-probe interaction imaging. Several types of cells (plant and yeast cells as well as mouse spermatozoa) were successfully imaged in their natural state, with mouse spermatozoa observed by ESEM for the first time. Computerized stage applied to image was tough …

Biocomposites Developed Using Water-Plasticized Wheat Gluten As Matrix And Jute Fibers As Reinforcement, Narendra Reddy, Yiqi Yang

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Biocomposites developed from wheat gluten using water without any chemicals as plasticizer and jute fibers as reinforcement have much better flexural and tensile properties than similar polypropylene composites reinforced with jute fibers. Wheat gluten is an inexpensive and abundant co-product derived from renewable resources and is biodegradable but non-thermoplastic. Previous attempts at developing biocomposites from wheat gluten have used plasticizers such as glycerol or chemical modifications to make gluten thermoplastic. However, plasticizers have a considerably negative effect on the mechanical properties of the composites and chemical modifications make wheat gluten less biodegradable, expensive and/or environmentally unfriendly. In the research reported, …

Corn Seed Spacing Uniformity As Affected By Seed Tube Condition, Michael F. Kocher, John M. Coleman, John A. Smith, Stephen D. Kachman

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Variation in corn seed spacing from a John Deere MaxEmerge^TM Plus Vacumeter planter was evaluated on the University of Nebraska Planter Test Stand in a laboratory setting for two seed tube conditions (new or worn) with two examples of corn seed shape (round or flat). Seed spacing uniformity was measured using three seed spacing uniformity parameters: Coefficient of Precision (CP3), ISO Multiples index, and ISO Miss index.

Differences were detected in all three seed spacing uniformity parameters due to the seed tube condition. The new seed tubes had better seed spacing uniformity than the worn seed tubes, within each …