Digital Commons Network^™

The Performance Of Elliptic Curve Based Group Diffie-Hellman Protocols For Secure Group Communication Over Ad Hoc Networks, Yong Wang, Byrav Ramamurthy, Xukai Zou

School of Computing: Conference and Workshop Papers

The security of the two party Diffie-Hellman key exchange protocol is currently based on the discrete logarithm problem (DLP). However, it can also be built upon the elliptic curve discrete logarithm problem (ECDLP). Most proposed secure group communication schemes employ the DLP-based Diffie-Hellman protocol. This paper proposes the ECDLP-based Diffie-Hellman protocols for secure group communication and evaluates their performance on wireless ad hoc networks. The proposed schemes are compared at the same security level with DLP-based group protocols under different channel conditions. Our experiments and analysis show that the Tree-based Group Elliptic Curve Diffie-Hellman (TGECDH) protocol is the best in …

Spatial Correlation-Based Collaborative Medium Access Control In Wireless Sensor Networks, Mehmet C. Vuran, Ian F. Akyildiz

School of Computing: Faculty Publications

Wireless Sensor Networks (WSN) are mainly characterized by dense deployment of sensor nodes which collectively transmit information about sensed events to the sink. Due to the spatial correlation between sensor nodes subject to observed events, it may not be necessary for every sensor node to transmit its data. This paper shows how the spatial correlation can be exploited on the Medium Access Control (MAC) layer. To the best of our knowledge, this is the first effort which exploits spatial correlation in WSN on the MAC layer. A theoretical framework is developed for transmission regulation of sensor nodes under a distortion …

Eraid: Conserving Energy In High Performance Raid Systems With Conventional Disks, Dong Li, Jun Wang

School of Computing: Technical Reports

Recently energy consumption becomes an ever critical concern for both low-end and high-end storage server and data centers. A majority of existing energy conservation solutions resort to multi-speed disks. However, current server systems are still built with conventional disks.
In this paper, we propose an energy saving policy, eRAID, for conventional disk based RAID-1 systems. eRAID saves energy by spinning down partial or entire mirror disk group with predictable performance degradation. The heart work of eRAID is to develop an accurate dynamic performance control (including disk power management) scheme. To guarantee service quality, the dynamic performance control works for two …

Helping End-User Programmers “Engineer” Dependable Software, Gregg Rothermel

School of Computing: Conference and Workshop Papers

Not long ago, most software was written by professional programmers, who could be presumed to have an interest in software engineering methodologies and in tools and techniques for improving software dependability. Today, however, a great deal of software is written not by professionals but by end-users, who create applications such as multimedia simulations, dynamic web pages, and spreadsheets. Applications such as these are often used to guide important decisions or aid in important tasks, and it is important that they be sufficiently dependable, but evidence shows that they frequently are not. For example, studies have shown that a large percentage …

Spatio-Temporal Characteristics Of Point And Field Sources In Wireless Sensor Networks, Mehmet C. Vuran, Ӧzgür B. Akan

School of Computing: Conference and Workshop Papers

Wireless Sensor Networks (WSN) are comprised of densely deployed sensor nodes collaboratively observing and communicating extracted information about a physical phenomenon. Dense deployment of sensor nodes makes the sensor observations highly correlated in the space domain. In addition, consecutive samples obtained by a sensor node are also temporally correlated for the applications involving the observation of the variation of a physical phenomenon. Based on the physical characteristics and dispersion pattern over the area, the phenomenon to be observed can be modeled as point source or field source. Clearly, understanding the spatio-temporal correlation characteristics of the point and field sources brings …

A Cross-Layer Protocol For Wireless Sensor Networks, Ian F. Akyildiz, Mehmet C. Vuran, Ӧzgür B. Akan

School of Computing: Conference and Workshop Papers

Severe energy constraints of battery-powered sensor nodes necessitate energy-efficient communication protocols in order to fulfill application objectives of wireless sensor networks (WSN). However, the vast majority of the existing solutions are based on classical layered protocols approach. It is much more resource-efficient to have a unified scheme which melts common protocol layer functionalities into a cross-layer module for resource-constrained sensor nodes. To the best of our knowledge, to date, there is no unified cross-layer communication protocol for efficient and reliable event communication which considers transport, routing, medium access functionalities with physical layer (wireless channel) effects for WSNs.
In this paper, …

Cross-Layer Analysis Of Error Control In Wireless Sensor Networks, Mehmet C. Vuran, Ian F. Akyildiz

School of Computing: Conference and Workshop Papers

Severe energy constraints and hence the low power communication requirements amplify the significance of the energy efficient and preferably cross-layer error control mechanisms in Wireless Sensor Networks (WSN). In this paper, a crosslayer methodology for the analysis of error control schemes in WSNs is presented such that the effects of multi-hop routing and the broadcast nature of the wireless channel are investigated. More specifically, the cross-layer effects of routing, medium access and physical layers are considered. This analysis enables a comprehensive comparison of forward error correction (FEC) and automatic repeat request (ARQ) in WSNs.
FEC schemes improve the error resiliency …

A Constraint-Based Approach To Solving Minesweeper, Ken Bayer, Josh Snyder, Berthe Y. Choueiry

School of Computing: Conference and Workshop Papers

·Motivate the students for the study of Constraint Processing (CP). Minesweeper is perfect to this end because it allows us to illustrate the use of CP algorithms in a familiar context and show how they operate.

·Understand and demystify humans’ fascination with puzzles.

·Discourage graduate students from losing too much time playing the game by making a program that plays the game for them.

Burrows Dug By Large Vertebrates Into Rain-Moistened Middle Jurassic Sand Dunes, David B. Loope

Department of Earth and Atmospheric Sciences: Faculty Publications

In south-central Utah, eolian cross-strata of the Escalante Member of the Entrada Sandstone contain inclined, cylindrical burrows up to 63 cm in diameter and 305 cm long. Of the 14 large tunnels located during this study, 12 descend from second- and third-order bounding surfaces that formed on the lee slopes of large dune ridges, well above the water table. The tunnels are inclined 15°–22°; one tunnel ends in an expanded chamber. Eolian cross-strata fill proximal portions of four of the tunnels and indicate that after abandonment, sand drifts migrated as much as a meter into the open shafts. Structureless sand …

The Earth All Around Us: Selected Building Stone In Lincoln, Nebraska. A Walking Tour, William J. Wayne

Department of Earth and Atmospheric Sciences: Faculty Publications

Stone has been a primary building material for millennia. Cities, therefore, are treasure troves of earth materials. A wide variety of stones from many places are used for walls, as foundations to support entire buildings, as trim, and more recently as cladding (facing, an overlay). The Earth science teacher can find, in the limited space of an urban environment, a superb collection of stones with which to introduce students to these materials. The surfaces of stones on the outsides of buildings illustrate the durability and the vulnerability of each kind of stone to the local climate. And the history of …

Understanding Farmers’ Forecast Use From Their Beliefs, Values, Social Norms, And Perceived Obstacles*, Q. Steven Hu, Lisa M. Pytlikzillig, Gary D. Lynne, Alan Tomkins, William J. Waltman, Michael J. Hayes, Kenneth Hubbard, Ikrom Artikov, Stacey Hoffman, Donald A. Wilhite

Department of Earth and Atmospheric Sciences: Faculty Publications

Although the accuracy of weather and climate forecasts is continuously improving and new information retrieved from climate data is adding to the understanding of climate variation, use of the forecasts and climate information by farmers in farming decisions has changed little. This lack of change may result from knowledge barriers and psychological, social, and economic factors that undermine farmer motivation to use forecasts and climate information. According to the theory of planned behavior (TPB), the motivation to use forecasts may arise from personal attitudes, social norms, and perceived control or ability to use forecasts in specific decisions. These attributes are …

Imse Alumni Survey Of Abet Program Educational Objectives, Paul Savory

Department of Industrial and Management Systems Engineering: Faculty Publications

This report showcases the results of the Department of Industrial and Management System Engieering's survey of alumni regarding our updated ABET Program Educational Objectives. The Program Educational Objectives represent the expected characteristics of industrial engineering graduates within three to five years of receiving a Bachelor of Science degree in Industrial and Management Systems Engineering from the University of Nebraska-Lincoln. A total of 76 responses were received. The alumni survey responses indicate strong agreement and approval for the new Program Educational Objectives. The associated comments will be used by the IMSE faculty to future refine the course curriculum to ensure that …

E(Fg)2: A New Fixed-Grid Shape Optimization Method, Florin Bobaru Ph.D., Srinivas Rachakonda

Department of Engineering Mechanics: Faculty Publications

We propose a shape optimization method over a fixed grid. Nodes at the intersection with the fixed grid lines track the domain’s boundary. These “floating” boundary nodes are the only ones that can move/appear/disappear in the optimization process. The element-free Galerkin (EFG) method, used for the analysis problem, provides a simple way to create these nodes. The fixed grid (FG) defines integration cells for EFG method. We project the physical domain onto the FG and numerical integration is performed over partially cut cells. The integration procedure converges quadratically. The performance of the method is shown with examples from shape optimization …

Modeling Dual Polarization Wireless Fading Channels Using Quaternions, B. J. Wysocki, Tadeusz Wysocki, J. Seberry

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

In the letter we describe signal transmitted between two dual-polarized antennas using a quaternion notation. The channel can then be modeled by a single quaternion gain, instead of a matrix of four complex gains as it is done in a classical approach. The model is very useful as it allows for a simple accommodation of any polarization twist between the transmit and receive antennas, as well as, modeling random fading in both polarizations with or without cross-polar scattering.

Spatial Distributions Of Perchloroethylene Reactive Transport Parameters In The Borden Aquifer, Richelle M. Allen-King, Dana Divine, Michel J. L. Robin, J. Richard Alldredge, David R. Gaylord

Conservation and Survey Division: Faculty and Staff Publications

We determined the descriptive statistical and spatial geostatistical properties of the perchloroethene ln K_d and the ln k of a 1.5 m thick by 10 m horizontal transect of the Borden aquifer near the location of the Stanford-Waterloo (SW) tracer experiment. The ln K_d distribution is not normal and is right skewed because of a few high values that occur localized in two regions of the transect. In contrast, the ln k data can be characterized by a normal distribution. A linear regression of ln K_d on ln k yields a statistically significant positive correlation, also shown …

Evaluating The Effectiveness Of Slicing For Model Reduction Of Concurrent Object-Oriented Programs, Matthew B. Dwyer, John Hatcliff, Matthew Hoosier, Venkatesh Ranganath, Robby, Todd Wallentine

School of Computing: Book Chapters

Model checking techniques have proven effective for checking a number of non-trivial concurrent object-oriented software systems. However, due to the high computational and memory costs, a variety of model reduction techniques are needed to overcome current limitations on applicability and scalability. Conventional wisdom holds that static program slicing can be an effective model reduction technique, yet anecdotal evidence is mixed, and there has been no work that has systematically studied the costs/benefits of slicing for model reduction in the context of model checking source code for realistic systems. In this paper, we present an overview of the sophisticated Indus program …

A Maximum-Likelihood Approach To Symbolic Indirect Correlation, Ashutosh Joshi, George Nagy, Daniel Lopresti, Sharad C. Seth

School of Computing: Conference and Workshop Papers

Symbolic Indirect Correlation (SIC) is a nonparametric method that offers significant advantages for recognition of ordered unsegmented signals. A previously introduced formulation of SIC based on subgraph-isomorphism requires very large reference sets in the presence of noise. In this paper, we seek to address this issue by formulating SIC classification as a maximum likelihood problem. We present experimental evidence that demonstrates that this new approach is more robust for the problem of online handwriting recognition using noisy input.

On Reoptimizing Multi-Class Classifiers, Kun Deng, Chris Bourke, Stephen Scott, Robert E. Schapire, N. V. Vinodchandran

School of Computing: Technical Reports

Significant changes in the instance distribution or associated cost function of a learning problem require one to reoptimize a previously learned classifier to work under new conditions. We study the problem of reoptimizing a multi-class classifier based on its ROC hypersurface and a matrix describing the costs of each type of prediction error. For a binary classifier, it is straightforward to find an optimal operating point based on its ROC curve and the relative cost of true positive to false positive error. However, the corresponding multi-class problem (finding an optimal operating point based on a ROC hypersurface and cost matrix) …

Optimization Of Multilayer Wear-Resistant Thin Films Using Finite Element Analysis On Stiff And Compliant Substrates, R. K. Lakkaraju, Florin Bobaru, S. L. Rohde

Department of Engineering Mechanics: Faculty Publications

Extensive research has been carried out by researchers on the growth and characterization of multilayer protective coatings, but the design of these coatings still remains largely empirical. In this regard, recent progress has been made in developing a design approach for optimizing a multilayer coating structure before deposition, which would help save time and material. In pursuit of an optimal design, finite element analysis using a plane strain Hertzian contact model was developed to investigate the stress/ strain behavior within the layers of the system. The present study looks to find the optimal thicknesses of individual layers in a multilayer …

A Model For Predicting The Evolution Of Multiple Cracks On Multiple Length Scales In Viscoelastic Composites, David H. Allen, C. R. Searcy

Department of Engineering Mechanics: Faculty Publications

A model is presented herein for predicting the evolution of numerous cracks on multiple length scales, the objective of such a model being to develop the capability to predict failure of structural components to perform their intended tasks. Such a capability would then be useful as a predictive tool for designing structural components so as not to fail, but rather to succeed in performing their intended tasks. The model developed herein is somewhat involved, being based in continuum mechanics and thermodynamics, but is nevertheless expected to be cost effective (wherever sufficient accuracy permits) when compared to more costly experimental means …

Cross-Subtype T-Cell Immune Responses Induced By A Human Immunodeficiency Virus Type 1 Group M Consensus Env Immunogen, Eric A. Weaver, Zenaido T. Camacho, Fatiha Moukdar, Hua-Xin Liao, Ben-Jiang Ma, Mark Muldoon, James Theiler, Gary J. Nabel, Norman L. Letvin, Bette T. Korber, Beatrice H. Hahn, Barton F. Haynes, Feng Gao, Zhongjing Lu

Nebraska Center for Virology: Faculty Publications

The genetic diversity among globally circulating human immunodeficiency virus type 1 (HIV-1) strains is a serious challenge for HIV-1 vaccine design. We have generated a synthetic group M consensus env gene (CON6) for induction of cross-subtype immune responses and report here a comparative study of T-cell responses to this and natural strain env immunogens in a murine model. Three different strains of mice were immunized with CON6 as well as subtype A, B, or C env immunogens, using a DNA prime-recombinant vaccinia virus boost strategy. T-cell epitopes were mapped by gamma interferon enzyme-linked immunospot analysis using five overlapping Env peptide …

Effects Of Addition Of A Bird Repellent To Fish Diets On Their Growth And Bioaccumulation, Sheenan Harpaz, Larry Clark

United States Department of Agriculture Wildlife Services: Staff Publications

The effects of adding the nonlethal bird repellent methyl anthranilate (MA), at levels of 100 and 1000 mg/kg, to fish feed on the bioaccumulation and growth of juvenile (10 g) hybrid striped bass (Morone chrysops x M. saxatilis) and juvenile (1g) African cichlid fish Aulonocara jacobfreibergi were investigated under laboratory conditions. The bird repellent did not have any effect on the fish growth or survival over a period of 6 weeks. MA residues at low levels of 11.2 ± 2.6 mg/g were found in lipophili tissues (liver) of MA-fed fish. Control fish, which had no MA added to their diet, …

Monitoring Invasive Mammalian Predator Populations Sharing Habitat With The Critically Endangered Puerto Rican Parrot Amazona Vittata, Richard M. Engeman, Desley Whisson, Jessica Quinn, Felipe Cano, Pedro Quiñones, Thomas H. White

United States Department of Agriculture Wildlife Services: Staff Publications

Critically Endangered Puerto Rican parrots Amazona vittata are one of the rarest birds in the world. Several exotic mammal species capable of preying on Puerto Rican parrots cohabit the Caribbean National Forest with the only wild population of these parrots. We used tracking plates, monitoring blocks and trapping to index black rats, small Indian mongooses and feral cats in parrot habitat and in public-use areas in the same habitat type. We had high trap success for black rats at all sites (42% of all sites combined), among the highest reported in the world. Rat response to monitoring (nontoxic bait) blocks …

Red-Winged Blackbird (Agelaius Phoeniceus) Reproduction In North Dakota, Rachel M. Bush, Mark E. Clark, Wendy L. Read, George M. Linz

United States Department of Agriculture Wildlife Services: Staff Publications

No abstract provided.

Structure And Magnetism Of Atomically Thin Fe Layers On Flat And Vicinal Pt Surfaces, D. Repetto, T. Y. Lee, S. Rusponi, Jan Honolka, K. Kuhnke, Violetta Sessi, Ulrich Starke, H. Brune, P. Gambardella, C. Carbone, Axel Enders, K. Kern

Axel Enders Publications

Ultrathin Fe films on Pt substrates have been investigated under ultrahigh vacuum conditions by scanning tunneling microscopy, low energy electron diffraction, magneto-optical Kerr effect, x-ray magnetic circular dichroism measurements, and Kerr microscopy. We present a comparison between Fe films on flat Pt(111) and stepped Pt(997), with particular focus on the magnetic anisotropy in the submonolayer thickness range below 0.2 monolayer coverage, and above the spin reorientation transition at 3 monolayer thickness. The comparison of structure and magnetism suggests that the perpendicular easy axis found for films thinner than three monolayers is due to dominating contributions from both film interfaces to …

The Electronic Structure And Band Hybridization Of Co/Ti Doped Bafe12O19, Natalie Palina, H. Modrow, R. Müller, J. Hormes, Peter A. Dowben, Yaroslav B. Losovyj

Department of Physics and Astronomy: Faculty Publications

We identify contributions to the valence band of the nanosized BaFe_12−2xCo_xTi_xO₁₉ barium ferrite particles, from the cobalt and titanium dopants. Resonant photoemission results show that cobalt and titanium dopants strongly hybridize with the barium ferrite matrix. Fano resonances are identified in the valence band region, at the Ba (5s), Ti (3p) and Co (3p) thresholds, and there are significant contributions to the density of states, residing within 2 eV of the Fermi level, from barium and/or iron.

A Three-Grating Electron Interferometer, G. Gronniger, Brett E. Barwick, Herman Batelaan

Department of Physics and Astronomy: Faculty Publications

We report the observation of fringes from a three-grating electron interferometer. Interference fringes have been observed at low energies ranging from 6 to 10 keV. Contrasts of up to 25% are recorded and exceed the maximal contrast of the classical equivalent Moiré deflectometer. This type of interferometer could serve as a separate beam Mach–Zehnder interferometer for low-energy electron interferometry experiments.

Ferromagnetism And Structure Of Epitaxial Cr-Doped Anatase Tio2 Thin Films, T. C. Kaspar, T. Droubay, V. Shutthanandan, S. M. Heald, C. M. Wang, D. E. Mccready, S. Thevuthasan, J. D. Bryan, D. R. Gamelin, A. J. Kellock, M. F. Toney, X. Hong, C. H. Ahn, S. A. Chambers

Xia Hong Publications

The materials and magnetic properties of Cr-doped anatase TiO₂ thin films deposited on LaAlO₃(001) and SrTiO₃(001) substrates by oxygen-plasma-assisted molecular beam epitaxy have been studied in detail to elucidate the origin of ferromagnetic ordering. Cr substitution for Ti in the anatase lattice, with no evidence of Cr interstitials, segregation, or secondary phases, was independently confirmed by transmission electron microscopy with energy dispersive x-ray spectroscopy, extended x-ray absorption fine structure, and Rutherford backscattering spectrometry in the channeling geometry. Epitaxial films deposited at ~0.1 Å/ s were found to have a highly defected crystalline structure, as quantified …

Effect Of Electric Field Doping On The Anisotropic Magnetoresistance In Doped Manganites, X. Hong, J.-B. Yau, J. D. Hoffman, C. H. Ahn

Xia Hong Publications

We have modulated the anisotropic magnetoresistance (AMR) in 3–4 nm manganite films using the ferroelectric field effect—a method that electrostatically varies the carrier density without affecting the lattice distortion. While significant changes have been induced in T_C and p, the AMR ratio remains the same when the magnetic state is not changed. This scaling behavior is in striking contrast to chemical doping results, where similar modulation of the carrier concentration (~0.1/Mn) changes the AMR ratio by ≥30%. The results reveal unambiguously the dominant role of chemical distortion in determining the AMR in manganites.

Regional Patterns In The Isotopic Composition Of Natural And Anthropogenic Nitrate In Groundwater, High Plains, U.S.A., P. B. Mcmahon, J. K. Bohlke

United States Geological Survey: Staff Publications

Mobilization of natural nitrate (NO₃^-) deposits in the subsoil by irrigation water in arid and semiarid regions has the potential to produce large groundwater NO₃^- concentrations. The use of isotopes to distinguish between natural and anthropogenic NO₃^- sources in these settings could be complicated by the wide range in δ¹⁵N values of natural NO₃^-. An ~10 000 year record of paleore-charge from the regionally extensive High Plains aquifer indicates that δ¹⁵N values for NO₃^- derived from natural sources ranged from 1.3 to 12.3‰ and …