Digital Commons Network^™

A Static Voltage Security Region For Centralized Wind Power Integration-Part Ii: Applications, Tao Ding, Qinglai Guo, Rui Bo, Hongbin Sun, Boming Zhang, Tianen Huang

Electrical and Computer Engineering Faculty Research & Creative Works

In Part I of this work, a static voltage security region was introduced to guarantee the safety of wind farm reactive power outputs under both base conditions and N-1 contingency. In this paper, a mathematical representation of the approximate N-1 security region has further studied to provide better coordination among wind farms and help prevent cascading tripping following a single wind farm trip. Besides, the influence of active power on the security region is studied. The proposed methods are demonstrated for N-1 contingency cases in a nine-bus system. The simulations verify that the N-1 security region is a small subset …

Magnetoelectric Dipole Antenna Arrays, Shulabh Gupta, Li (Lijun) Jun Jiang, Christophe Caloz

Electrical and Computer Engineering Faculty Research & Creative Works

A planar magnetoelectric (ME) dipole antenna array is proposed and demonstrated by both full-wave analysis and experiments. The proposed structure leverages the operation of composite right/left-handed transmission lines under balanced conditions to form high-gain magnetic radiators, combined with radial conventional electric radiators, where the overall structure is excited by a single differential feed. The traveling-wave-type nature of the proposed ME-dipole antenna enables the formation of directive arrays with high-gain characteristics and scanning capability. Peak gains of 10.84 dB and 5.73 dB are demonstrated for the electric dipole and magnetic-dipole radiation components, respectively. © 1963-2012 IEEE.

Helmholtz Decomposition Based On Integral Equation Method For Electromagnetic Analysis, Xiaoyan Y.Z. Xiong, Wei E.I. Sha, Li (Lijun) Jun Jiang

Electrical and Computer Engineering Faculty Research & Creative Works

Helmholtz decomposition (HD) is a vector analysis fundamental tool and plays an important role in electromagnetics (EM) and microwave engineering. Instead of applying HD to the EM solving process, this article proposes an integral equation based rigorous HD process to extract and analyze the known EM field. It provides much clearer insight into field coupling and radiation mechanism that is valuable to electromagnetic interference (EMI) and electromagnetic compatibility (EMC) analysis. Compared to the loop-tree based decomposition that is a quasi-HD, the proposed method is rigorous and frequency-independent. The algorithm verification and its application to coupling and resonating problems are presented. …

Assessment Of Multi-Mode Spacecraft Micropropulsion Systems, Steven P. Berg, Joshua L. Rovey

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Multi-mode spacecraft micro propulsion systems which include a high-thrust chemical mode and high-specific impulse electric mode are assessed with specific reference to cube sat-sized satellite applications. Both cold gas Freon-14 propellant and ionic liquid chemical monopropellant modes were investigated alongside pulsed plasma, electrospray, and helicon electric thruster modes. Systems involving chemical monopropellants have the highest payload mass fractions for a reference mission of a 500 m/s delta-V and 6U sized cube sat for electric propulsion usage below 55% of total delta-V. For higher electric propulsion usage, cold gas thrusters delivered a higher payload mass fraction due to lower system inert …

Adaptive Resonance Theory And Diffusion Maps For Clustering Applications In Pattern Analysis, Donald C. Wunsch, David J. Morris, Rui Xu

Electrical and Computer Engineering Faculty Research & Creative Works

Adaptive Resonance is primarily a theory that learning is regulated by resonance phenomena in neural circuits. Diffusion maps are a class of kernel methods on edge-weighted graphs. While either of these approaches have demonstrated success in image analysis, their combination is particularly effective. These techniques are reviewed and some example applications are given.

Localization And Tracking Of Objects Using Cross-Correlation Of Shadow Fading Noise, M. R. Basheer, S. Jagannathan

Electrical and Computer Engineering Faculty Research & Creative Works

Multipath and shadow fading are the primary cause for positioning errors in a Received Signal Strength Indicator (RSSI) based localization scheme. While fading, in general, is detrimental to localization accuracy, cross-correlation and divergence properties of shadow fading residuals may be utilized to improve localization and tracking accuracy of mobile IEEE 802.15.4 transmitters. Therefore, this paper begins by presenting a stochastic filter that models the fast-changing multipath fading as a mean reverting Ornstein-Uhlenbeck (OU) process followed by a Generalized Auto Regressive Conditional Heteroskedasticity (GARCH) filtering to isolate the slow changing shadow fading residuals from measured RSSI values. Subsequently, a novel wireless …

Phasor Measurement Unit Placement For Identifying Power Line Outages In Wide-Area Transmission System Monitoring, Hao Zhu, Yiyu Shi

Electrical and Computer Engineering Faculty Research & Creative Works

Phasor measurement units (PMUs) are widely recognized to be instrumental for enhancing the power system situational awareness - a key step toward the future power grid. With limited PMU resources and high installation costs, it is of great importance to develop strategic PMU deployment methods. This paper focuses on optimally selecting PMU locations for monitoring transmission line status across the wide-area grid. To bypass the combinatorial search involved, a linear programming reformulation is first developed to provide an upper bound estimate for the global optimum. Furthermore, a greedy heuristic method is adopted with the complexity only linearly in the number …

The Soft-Feedback Isi Canceller-Based Turbo Equalizer For Multilevel Modulations, Huang Lou, Chengshan Xiao

Electrical and Computer Engineering Faculty Research & Creative Works

In this paper, we investigate the soft-feedback equalizer (SFE) proposed by Lopes et al. for multilevel modulations. The SFE is based on InterSymbol interference canceller structure and is compared to both soft-decision feedback turbo equalizer (SDFE) and the exact solution of MMSE linear equalizer (Exact-MMSE-LE) by means of EXIT chart analysis and BER simulations. Interesting results reveal that, for multilevel modulations, the SFE not only exhibits the same low complexity, low SNR threshold and fast convergence as SDFE but also reaches matched filter bound after a large number of iterations. © 2013 Springer Science + Business Media New York.

Ambiguity Group Based Location Recognition For Multiple Power Line Outages In Smart Grids, Jie Wu, Jinjun Xiong, Yiyu Shi

Electrical and Computer Engineering Faculty Research & Creative Works

The efficient location recognition of multiple outage lines is critical to not only cascading failure elimination but also repair cost reduction. Most of existing methods, however, fail to handle location recognition well. This failure typically occurs because the methods cannot overcome three challenges: the very limited number of Phasor Measurement Units (PMUs), the high computational complexity, and the possibility of concurrent multiple outage lines. This paper presents an efficient algorithm inspired by the ambiguity group theory to recognize the most likely outage line locations with limited PMUs. Using IEEE 14-, 57-, and 118-bus system, the experimental study demonstrates that the …

An Online Outlier Identification And Removal Scheme For Improving Fault Detection Performance, Hasan Ferdowsi, Sarangapani Jagannathan, Maciej Jan Zawodniok

Electrical and Computer Engineering Faculty Research & Creative Works

Measured data or states for a nonlinear dynamic system is usually contaminated by outliers. Identifying and removing outliers will make the data (or system states) more trustworthy and reliable since outliers in the measured data (or states) can cause missed or false alarms during fault diagnosis. In addition, faults can make the system states nonstationary needing a novel analytical model-based fault detection (FD) framework. In this paper, an online outlier identification and removal (OIR) scheme is proposed for a nonlinear dynamic system. Since the dynamics of the system can experience unknown changes due to faults, traditional observer-based techniques cannot be …

On The Deployment Of On-Chip Noise Sensors, Tao Wang, Chun Zhang, Jinjun Xiong, Yiyu Shi

Electrical and Computer Engineering Faculty Research & Creative Works

Runtime noise management systems can enforce power integrity without significantly increasing design margins. These systems typically respond to on-chip noise sensors to accurately capture voltage emergencies. Unfortunately, it remains an open problem in the literature how to optimally place a given number of noise sensors for best voltage emergency detection, or how to best set the threshold voltage for these sensors. In this paper, we formally define the problem of noise sensor placement along with a novel sensing quality metric to be maximized. We then put forward an efficient algorithm to solve it, which is proven to attain the best …

Earnings Management And Corporate Spinoffs, Ying Chou Lin, Kenneth Yung

Economics Faculty Research & Creative Works

In this study we examine whether firms manage earnings before pursuing corporate spinoffs. Using a sample of 226 completed spinoffs between 1985 and 2005, we find strong evidence of pre-spinoff earnings management among parent firms involved in non-focus-increasing spinoffs. We also find higher levels of earnings management among parent firms that have a higher level of information asymmetry prior to spinoff announcements. Our regression results show a significant negative relation between income-increasing earnings management and the announcement period returns for non-focus-increasing spinoffs. In addition, a significant positive relation is found between income-increasing earnings management and the announcement period returns for …

Timekeeping Issues In Ultra-Quality Metering Systems, David D. Haynes, Steven M. Corns

Engineering Management and Systems Engineering Faculty Research & Creative Works

The improvements made to smart metering systems in terms of performance and accuracy have in many cases created a gap in the requirements for timekeeping performance. When clock errors accumulate in different metrology systems, data collected from one system cannot be compared to data collected from another system. This paper recommends the use of a common time base for all data gathering systems, and that systems clocks are corrected with numerous minor corrections when possible, rather than major corrections. © 2013 IEEE.

Sensor Authentication In Collaborating Sensor Networks, Jake Bielefeldt, Sriram Chellappan

Computer Science Faculty Research & Creative Works

In this paper, we address a new security problem in the realm of collaborating sensor networks. By collaborating sensor networks, we refer to the networks of sensor networks collaborating on a mission, with each sensor network is independently owned and operated by separate entities. Such networks are practical where a number of independent entities can deploy their own sensor networks in multi-national, commercial, and environmental scenarios, and some of these networks will integrate complementary functionalities for a mission. In the scenario, we address an authentication problem wherein the goal is for the Operator Oi of Sensor Network Si to correctly …

Secure K-Nearest Neighbor Query Over Encrypted Data In Outsourced Environments, Yousef Elmehdwi, Bharath K. Samanthula, Wei Jiang

Computer Science Faculty Research & Creative Works

For the past decade, query processing on relational data has been studied extensively, and many theoretical and practical solutions to query processing have been proposed under various scenarios. With the recent popularity of cloud computing, users now have the opportunity to outsource their data as well as the data management tasks to the cloud. However, due to the rise of various privacy issues, sensitive data (e.g., medical records) need to be encrypted before outsourcing to the cloud. In addition, query processing tasks should be handled by the cloud; otherwise, there would be no point to outsource the data at the …

Sensor Cloud: A Cloud Of Virtual Sensors, Sanjay Madria, Vimal Kumar, Rashmi Dalvi

Computer Science Faculty Research & Creative Works

Newer models for interacting with wireless sensors such as Internet of Things and Sensor Cloud aim to overcome restricted resources and efficiency. The Missouri S&T (science and technology) sensor cloud enables different networks, spread in a huge geographical area, to connect together and be employed simultaneously by multiple users on demand. Virtual sensors, which are at the core of this sensor cloud architecture, assist in creating a multiuser environment on top of resource-constrained physical wireless sensors and can help in supporting multiple applications. © 1984-2012 IEEE.

Thermotropic Phase Boundaries In Classic Ferroelectrics, Tom T. A. Lummen, Yijia Gu, Jianjun Wang

Materials Science and Engineering Faculty Research & Creative Works

High-performance piezoelectrics are lead-based solid solutions that exhibit a so-called morphotropic phase boundary, which separates two competing phases as a function of chemical composition; as a consequence, an intermediate low-symmetry phase with a strong piezoelectric effect arises. In search for environmentally sustainable lead-free alternatives that exhibit analogous characteristics, we use a network of competing domains to create similar conditions across thermal inter-ferroelectric transitions in simple, lead-free ferroelectrics such as BaTiO₃ and KNbO₃. Here we report the experimental observation of thermotropic phase boundaries in these classic ferroelectrics, through direct imaging of low-symmetry intermediate phases that exhibit large enhancements …

Analysis And Optimization Of A Protocol For Mobile Element Discovery In Sensor Networks, Francesco Restuccia, Giuseppe Anastasi, Marco Conti, Sajal K. Das

Computer Science Faculty Research & Creative Works

Recent studies have demonstrated that mobile elements (MEs) are an efficient solution to help decrease dramatically energy consumption in wireless sensor networks (WSNs). However, in most of cases, sensors use duty cycle schemes to save energy, and unless the ME mobility pattern is deterministic, each sensor node has to discover the presence of the ME in the nearby area before starting to exchange data with it. Therefore, in such wireless sensor networks with mobile elements (in short, WSN-MEs), the definition and analysis of a protocol for efficient ME discovery becomes of fundamental importance. In this paper, we propose an extensive …

Smart And Cooperative Sensor Networks, Hongke Zhang, Sy Yen Kuo, Sajal K. Das, Mikael Gidlund

Computer Science Faculty Research & Creative Works

No abstract provided.

Impact Of Location History Collection Schemes On Observed Human Mobility Features, Alicia Rodriguez-Carrion, Sajal K. Das, Celeste Campo, Carlos Garcia-Rubio

Computer Science Faculty Research & Creative Works

Human mobility knowledge is key for urban planning or mobility model's design. Therefore, estimating reliable mobility parameters is crucial to lay an unbiased foundation. However, most works estimating such features rely on datasets made up of the history of mobile network cells where the user is located when she makes active use of the network, known as Call Data Records (CDRs), or every time their device connects to a new cell, without taking into account cell changes not caused by movement. Could we accurately characterize human mobility with such datasets? In this work we consider three approaches to collect network-based …

Qos Aware Geographic Opportunistic Routing In Wireless Sensor Networks, Long Cheng, Jianwei Niu, Jiannong Cao, Sajal K. Das, Yu Gu

Computer Science Faculty Research & Creative Works

QoS routing is an important research issue in wireless sensor networks (WSNs), especially for mission-critical monitoring and surveillance systems which requires timely and reliable data delivery. Existing work exploits multipath routing to guarantee both reliability and delay QoS constraints in WSNs. However, the multipath routing approach suffers from a significant energy cost. In this work, we exploit the geographic opportunistic routing (GOR) for QoS provisioning with both end-to-end reliability and delay constraints in WSNs. Existing GOR protocols are not efficient for QoS provisioning in WSNs, in terms of the energy efficiency and computation delay at each hop. To improve the …

Graphite Aerogels And The Formation Mechanism Of Unusual Micron-Sized Rod And Helical Structures, Clarissa Ann Wisner

Doctoral Dissertations

"Pyrolysis at 800 ºC under argon has shown that polyimide (PI), polyacrylonitrile (PAN), polydicyclopentadiene (DCPD) and polybenzoxazine (PBO) aerogels are all viable alternatives to traditional resorcinol-formaldehyde (RF) aerogels as precursors to amorphous carbon aerogels. Subsequent high temperature pyrolysis at 2300 ºC of such carbon aerogels under helium has shown that amorphous carbon from PI and PBO yields the highest degree of graphitization, whereas from RF aerogels yields the lowest.

Those two types of graphite aerogels include also a high concentration of micron-size columnar and helical (screw-like) structures, whose formation is favored by macroporosity and high nitrogen retention in the 800 …

Information Systems User Competency: A Conceptual Foundation, Brenda Eschenbrenner, Fiona Fui-Hoon Nah

Business and Information Technology Faculty Research & Creative Works

Research has identified a variety of factors that influence people's intentions to use IS and their degree of IS use. However, what has not been well understood are the characteristics of competent IS users who are proficient in using IS and are able to achieve quality IS usage. Considering that improving IS users' abilities to more efficiently and effectively use IS has always been and remains a challenge, research that provides a comprehensive view of the characteristics associated with competent IS users is warranted. This paper addresses this research question by proposing a conceptual foundation for IS user competency. Based …

Wavefunction Methods For The Accurate Characterization Of Water Clusters, J. Coleman Howard, Gregory S. Tschumper

Chemistry Faculty Research & Creative Works

Although the first ab initio Hartree-Fock computations of the water dimer were reported more than four decades ago, the detailed characterization of water clusters with sophisticated electronic structure techniques remains an important and vibrant area of research. The field of computational quantum chemistry has made significant advances since those pioneering studies. Geometry optimizations of the water dimer can now be carried out at the CCSDTQ level, and CCSD(T) energies can be computed with the aug-cc-pVTZ basis for clusters as large as (H₂O)₁₇. Some of these high-level studies are starting to reveal that the electronic structure is …

Test Development To Determine The Feasibility Of Rubber Tractor Treads For Use As Blasting Mats, Matthew Kurtis Coy

Masters Theses

"The objective of this thesis was to determine if rubber tractor treads could be used as an alternative material for blasting mats. These treads are made from steel cable and vulcanized rubber and are very tough. However, once they reach the end of their life on mobile equipment, they are destined for a landfill, or dump site because they are too tough to recycle. A potential alternative use for them is as blasting mats.

An examination of existing mat designs was conducted to better understand the matting methods used by the blasting industry today, to learn from those designs allow …

A Driving Simulator Study To Evaluate The Impact Of Portable Changeable Message Signs (Pcms) On Driver Speed Characteristics, Bharath Kolar Venkat

Masters Theses

"This research project examined the effects of sequential Portable Changeable Message Signs (PCMS) on driver behavior in work zones. PCMS are temporary traffic control (TTC) devices, part of Intelligent Transportation Systems, which supplement static signs to provide advance warning and real-time information to drivers. Text and number based messages are displayed on the PCMS for which detailed evaluation has not been carried out before. This research fills this gap using a driving simulator (DS) supplemented by objective and subjective surveys. A work zone on I-44 in rural Missouri was replicated in the DS using video recordings and GIS (Geographical Information …

Data Classification And Forecasting Using The Mahalanobis-Taguchi Method, Adebolaji A. Jobi-Taiwo

Masters Theses

"Classification and forecasting are useful concepts in the field of condition monitoring. Condition monitoring refers to the analysis and monitoring of system characteristics to understand and identify deviations from normal operating conditions. This can be performed for prediction, diagnosis, or prognosis or a combination of any these purposes. Fault identification and diagnosis are usually achieved through data classification, while forecasting methods are usually used to accomplish the prediction objective. Data gathered from monitoring systems often consists of multiple multivariate time series and is fed into a model for data analysis using various techniques. One of the data analysis techniques used …

Effect Of Stress Concentrations On Fatigue Of Composite And Metallic Structures, Ross Henry Falen

Masters Theses

"The complex shapes of hydrokinetic turbine blades can include part features such as a fillet, step, or hole. Situations can arise where two part features, such as a hole and a fillet, may be in close proximity which can introduce stress concentrations within the blade structure, adversely affecting the structure's life. Because the interaction between the part features isn't well known, fatigue data is needed to determine the proper analysis.

In this thesis, two separate topics are discussed and investigated. The first topic deals with stress concentrations in hydrokinetic turbine blades. Several blade designs were tested and improved upon to …

Comparison Of Costs Of Personal Protective Equipment For All Workers To Avoid Costs Of Fall Accidents, Sultan Noori Al-Karawi

Masters Theses

"The construction industry is one of the most important industries in the United States. It is the biggest contributor in the growth of the U.S. economy. Despite the great achievements and prominent role for this sector in the U.S. economy, the construction industry is suffering from neglect and dereliction by related government institutions and private companies. This neglect led to formation of a negative image about the construction industry that has caused a deep impact in productivity and economic growth. One of the reasons is a high percentage of accidents that occur within the construction industry which leads to injuries …

Theoretical Analysis Of Shape Separation Of Particles Using Flow Field-Flow Fractionation, Mehrdad Alfi

Masters Theses

"Size separation of spherical and rod-like particles in Flow Field-flow Fractionation was investigated theoretically. The effect of cross flow migration and rod orientation was also investigated as a new mode of study. It has been shown that the rod local orientation makes different diffusivity values in comparison with spherical particles and helps particle separation. Additionally, a new mechanism of lift-hypelayer mode was used for rod-like particles which can be compared with steric mode of spherical particles. This mechanism is said to be due to hydrodynamic interaction of rod-like particle with wall and with other rods.

As a measure of axial …