Physical Sciences and Mathematics Commons^™

Efficient Rtl Coverage Metric For Functional Test Selection, Jian Kang, Sharad C. Seth, Vijay Gangaram

CSE Conference and Workshop Papers

For performance-critical microprocessors, efficient test-selection methods are needed for reusing a subset of functional validation tests to detect manufacturing defects. Our new input/output transition fault-coverage metric (TRIO) at the register-transfer level is shown to perform much better than current metric in test selection at only an incrementally higher computational cost. TRIO may also be used for testability analysis early in the design cycle.

Keyrev: An Efficient Key Revocation Scheme For Wireless Sensor Networks, Yong Wang, Byrav Ramamurthy, Xukai Zou

CSE Conference and Workshop Papers

Key management is a core mechanism to ensure the security of applications and network services in wireless sensor networks. It includes two aspects: key distribution and key revocation. Key distribution has been extensively studied in the context of sensor networks. However, key revocation has received relatively little attention. Existing key revocation schemes can be divided into two categories: centralized key revocation scheme and distributed key revocation scheme. In this paper, we first summarize the current key revocation schemes for sensor networks. Then, we propose an efficient centralized key revocation scheme, KeyRev, for wireless sensor networks. Unlike most proposed key revocation …

Group Rekeying Schemes For Secure Group Communication In Wireless Sensor Networks, Yong Wang, Byrav Ramamurthy

CSE Conference and Workshop Papers

Wireless sensor networks are promising solutions for many applications. However, wireless sensor nodes suffer from many constraints such as low computation capability, small memory, limited energy resources, and so on. Grouping is an important technique to localize computation and reduce communication overhead in wireless sensor networks. In this paper, we use grouping to refer to the process of combining a set of sensor nodes with similar properties. We propose two centralized group rekeying (CGK) schemes for secure group communication in sensor networks. The lifetime of a group is divided into three phases, i.e., group formation, group maintenance, and group dissolution. …

Helping End-User Programmers “Engineer” Software: An Opportunity For Empirical Researchers, Gregg Rothermel

CSE Conference and Workshop Papers

While much of the software that people depend on is written by professional software engineers, increasingly, important applications are being created by non-professional (end-user) programmers. Using tools such as spreadsheet environments and web authoring tools, these programmers are creating software that is being used to support significant activities and inform decisions. Such software needs to work dependably and increase user productivity, but evidence shows that it frequently does not. For example, studies have shown that a large percentage of the spreadsheets created by end-users contain faults, and data suggests that time spent maintaining web macros may actually impede their users’ …

An Interactive Constraint-Based Approach To Sudoku, Christopher G. Reeson, Kai-Chen Huang, Ken Bayer, Berthe Y. Choueiry

CSE Conference and Workshop Papers

We present SOLVER, a Java applet that uses Constraint Processing (CP) techniques to assist human users in solving Sudoku puzzles. We also showcase CONSTRUCTOR, another applet that allows users to enter and store puzzles, which they can then load in SOLVER. These applets are available from sudoku.unl.edu/Solver and sudoku. unl.edu/Constructor. Our goals are as follows:

• To the public: Illustrate the power of CP techniques in the context of a popular easily approachable puzzle.

• For the research: Investigate how to use CP to interactively support and guide human players.

• For education: Use the Sudoku puzzle as a means …

An Interactive Constraint-Based Approach To Sudoku, Christopher Reeson, Kai-Chen Huang, Ken Bayer, Berthe Y. Choueiry

CSE Conference and Workshop Papers

• To the public:

– Illustrate the power of CP

• For the research:

– Investigate the use of CP to interactively support & guide human players

• For education:

– Teach basic and advanced CP techniques

• For insight into human reasoning:

– Understand how it differs from algorithmic approaches

On Comparability Of Random Permutations, Adam J. Hammett

Faculty Dissertations

No abstract provided.

Numerical Methods For The Stochastic Landau-Lifshitz Navier-Stokes Equations, Alejandro Garcia, J. B. Bell, S. Williams

Faculty Publications

The Landau-Lifshitz Navier-Stokes (LLNS) equations incorporate thermal fluctuations into macroscopic hydrodynamics by using stochastic fluxes. This paper examines explicit Eulerian discretizations of the full LLNS equations. Several computational fluid dynamics approaches are considered (including MacCormack’s two-step Lax-Wendroff scheme and the piecewise parabolic method) and are found to give good results for the variance of momentum fluctuations. However, neither of these schemes accurately reproduces the fluctuations in energy or density. We introduce a conservative centered scheme with a third-order Runge-Kutta temporal integrator that does accurately produce fluctuations in density, energy, and momentum. A variety of numerical tests, including the random walk …

On Cosmall Abelian Groups, Brendan Goldsmith, O. Kolman

Articles

It is a well-known homological fact that every Abelian group G has the property that Hom(G,−) commutes with direct products. Here we investigate the ‘dual’ property: an Abelian group G is said to be cosmall if Hom(−,G) commutes with direct products. We show that cosmall groups are cotorsion-free and that no group of cardinality less than a strongly compact cardinal can be cosmall. In particular, if there is a proper class of strongly compact cardinals, then there are no cosmall groups.

Value-At-Risk In It Services Contracts, Robert J. Kauffman, Ryan Sougstad

Research Collection School Of Computing and Information Systems

As information systems (IS) and technology solutions become increasingly service-driven, managers are faced with the task of choosing parameters such as service-levels, pricing, and contract duration. Information technology (IT) services vendors manage portfolios of contracts in which parameters, decided at inception, are often subject to future risks. The contract profit maximization decision may adversely affect the risk position of the firm's portfolio of services contracts. We propose a model to inform vendors on setting optimal parameters for IS contracts subject to acceptable levels of risk. The analytic model presented draws from IS economics research and the principles of value-at-risk (VaR) …

Mesoporous Matrices For Quantum Computation With Improved Response Through Redundance, T. E. Hodgson, Massimo F. Bertino, Nicholas Leventis, Irena D'Amico

Physics Faculty Research & Creative Works

We present a solid state implementation of quantum computation, which improves previously proposed optically driven schemes. Our proposal is based on vertical arrays of quantum dots embedded in a mesoporous material which can be fabricated with present technology. The redundant encoding typical of the chosen hardware protects the computation against gate errors and the effects of measurement induced noise. The system parameters required for quantum computation applications are calculated for II-VI and III-V materials and found to be within the experimental range. The proposed hardware may help minimize errors due to polydispersity of dot sizes, which is at present one …

Electronic Band Structure And Carrier Effective Mass In Calcium Aluminates, Julia E. Medvedeva, E. N. Teasley, M. D. Hoffman

Physics Faculty Research & Creative Works

First-principles electronic band structure investigations of five compounds of the CaO-Al2O3 family, 3CaO·Al2O3, 12CaO·7Al2O3, CaO·Al2O3, CaO·2Al2O3, and CaO·6Al2O3, as well as CaO and alpha-, theta-, and kappa-Al2O3 are performed. We find that the conduction band in the complex oxides is formed from the oxygen antibonding p states and, although the band gap in Al2O3 is almost twice larger than in CaO, the s states of both cations. Such a hybrid nature of the conduction band leads to isotropic electron effective masses which are nearly the same for all compounds investigated. This insensitivity of the effective mass to variations in the …

Screened-Exchange Determination Of The Electronic Properties Of Monoclinic, Tetragonal And Cubic Zirconia, Julia E. Medvedeva, C. B. Geller, D. M. Rishel, Arthur J. Freeman

Physics Faculty Research & Creative Works

First-principles electronic band structure investigations of monoclinic, tetragonal, and cubic ZrO2 reveal the highly anisotropic nature of the conduction and valence band topologies in the monoclinic phase with electron and hole effective masses differing by over an order of magnitude in perpendicular directions. The planes of relatively high implied electron and hole mobilities intersect along a single crystallographic direction, making this the only direction readily available for exciton motion. Conversely, in the tetragonal and cubic phases, charge carrier effective masses are more isotropic and exciton motion is less restricted. These findings may explain recent experimental observations suggesting that exciton production …

Spatial Distribution And Magnetism In Poly-Cr-Doped Gan From First Principles, X. Y. Cui, Julia E. Medvedeva, B. Delley, C. Stampfl, Arthur J. Freeman

Physics Faculty Research & Creative Works

Large scale density-functional theory calculations have been performed to understand the spatial distribution and magnetic coupling of Cr-doped GaN, in which exhaustive structural and magnetic configurations have been investigated by doping of up to five Cr atoms in large supercells. Our results provide direct evidence that the distribution of the doped magnetic ions is neither homogeneous nor random as widely assumed previously. Rather, under both Ga-rich and N-rich growth conditions, the Cr atoms have a strong tendency to form substitutional, embedded clusters with short-range magnetic interactions maintaining the wurtzite structure. Significantly, while the ferromagnetic state is favored for pair doping, …

Photon Angular Distribution And Nuclear-State Alignment In Nuclear Excitation By Electron Capture, Adriana Palffy, Zoltan Harman, Andrey S. Surzhykov, Ulrich D. Jentschura

Physics Faculty Research & Creative Works

The alignment of nuclear states resonantly formed in nuclear excitation by electron capture (NEEC) is studied by means of a density matrix technique. The vibrational excitations of the nucleus are described by a collective model and the electrons are treated in a relativistic framework. Formulas for the angular distribution of photons emitted in the nuclear relaxation are derived. We present numerical results for alignment parameters and photon angular distributions for a number of heavy elements in the case of E2 nuclear transitions. Our results are intended to help future experimental attempts to discern NEEC from radiative recombination, which is the …

Evidence Of Dynamical Spin Shielding In Ce From Spin-Resolved Photoelectron Spectroscopy, James G. Tobin, S. W. Yu, Takashi Komesu, B. W. Chung, Simon A. Morton, George Daniel Waddill

Physics Faculty Research & Creative Works

Using Fano effect measurements upon polycrystalline Ce, we have observed a phase reversal between the spectral structure at the Fermi edge and the other 4f derived feature near a binding energy of 2 eV. The Fano effect is the observation of spin polarized photoelectron emission from nonmagnetic materials, under chirally selective excitation, such as circularly polarized photons. The observation of phase reversal between the two peaks is a direct experimental proof of Kondo shielding in Ce, confirming the predictions of Gunnarsson and Shoenhammer, albeit with a small modification.

Effects Of Dissipation On A Quantum Critical Point With Disorder, Jose A. Hoyos, Chetan Kotabage, Thomas Vojta

Physics Faculty Research & Creative Works

We study the effects of dissipation on a disordered quantum phase transition with O(N) order-parameter symmetry by applying a strong-disorder renormalization group to the Landau-Ginzburg-Wilson field theory of the problem. We find that Ohmic dissipation results in a nonperturbative infinite-randomness critical point with unconventional activated dynamical scaling while super-Ohmic damping leads to conventional behavior. We discuss applications to the superconductor-metal transition in nanowires and to the Hertz theory of the itinerant antiferromagnetic transition.

Use Of The Mitsunobu Reaction In The Synthesis Of Orthogonally Protected A,B-Diaminopropionic Acids, Fintan Kelleher, Keith Ó Proinsias

Articles

Orthogonally protected a,b-diaminopropionic acids have been synthesised in good yields by the reaction of N-trityl L-serine esters with N-substituted sulfonamides under Mitsunobu reaction conditions (DEAD, PPh₃, THF). The best isolated yields were obtained when N-Boc p-toluenesulfonamide was used as the nitrogen nucleophile precursor in the Mitsunobu reaction. Subsequently, the N-trityl group was efficiently replaced with the more stable allyloxycarbonyl (alloc) group.

Synthesis And Characterisation Of Tetra-Tetrazole Macrocycles, Andrew Bond, Adrienne Fleming, Fintan Kelleher, John Mcginley, Vipa Prajapati, Signe Skovsgaard

Articles

The syntheses of tetra-tetrazole macrocycles, containing two bis-tetrazole units linked by a variety of alkyl chain lengths from four to eight carbons, are described. The crystal structures of three of these derivatives are reported, and the molecular conformation in the solid state is compared to that of one previously reported tetra-tetrazole macrocycle and to other bis- and tris(tetrazole)benzene structures. The macrocycle conformation is influenced by the length of the alkyl chain linker, the relative orientation of the tetrazole rings on the benzene ring, and by intermolecular interactions. In the macrocycles based on 1,2-bis(tetrazole)benzene, the adjacent tetrazole rings on the benzene …

A Comparison Of Print Advertisements From Egypt, Lebanon, Kuwait, Saudi Arabia, United Arab Emirates And The United States, Gilberto De Los Santos, Caroline Fisher, Salma Ghanem, Morris Kalliny, Anshu Saran

Business and Information Technology Faculty Research & Creative Works

This study examines cultural differences between the United States and the Arab world regarding low/high context, collectivism/individualism, time orientation and man's relationship with nature in print advertising. Study reveals that the main differences between the United States and the Arab world include cultural values that are embedded in religious values and beliefs.

Cultural Values Reflected In Arab And American Television Advertising, Morris Kalliny, Lance Gentry

Business and Information Technology Faculty Research & Creative Works

This study examines cultural values as reflected in U.S. And the Arab world television advertising. A total of 866 television commercials from Egypt, Kuwait, Lebanon, Saudi Arabia, United Arab Emirates and the United States were analyzed. Contrary to the common notion that the U.S. culture and the Arabic culture are vastly different, we found many similarities between the two cultures regarding TV advertising content and appeal. The findings contribute to the debate of standardization versus adaptation of international advertising.

Forecasting Consumer Adoption Of Technological Innovation: Choosing The Appropriate Diffusion Models For New Products And Services Before Launch, Roger Calantone, Lance Gentry

Business and Information Technology Faculty Research & Creative Works

There are many good articles on various forecasting models. There is consensus that no single diffusion model is best for every situation. Experts in the field have asked for studies to provide empirical-based guidelines for recommending when various models should be used. This research investigates multiple diffusion models and provides recommendations for which diffusion models are appropriate for radical and really new products and services before the launch of the innovation.

Local Defect In A Magnet With Long-Range Interactions, Jose A. Hoyos, Thomas Vojta

Physics Faculty Research & Creative Works

We investigate a single defect coupling to the square of the order parameter in a nearly critical magnet with long-range spatial interactions of the form r−(d+sigma), focusing on magnetic droplets nucleated at the defect while the bulk system is in the paramagnetic phase. To determine the static droplet profile, we solve a Landau-Ginzburg-Wilson action in the saddle-point approximation. Because of the long-range interaction, the droplet develops a power-law tail which is energetically unfavorable. However, as long as sigma>0, the tail contribution to the droplet free energy is subleading in the limit of large droplets; and the free energy becomes …

Angular Distributions From Photoionization Of H₂⁺, J. Colgan, O. Al-Hagan, Jerry Peacher, Don H. Madison, M. S. Pindzola, M. Foster

Physics Faculty Research & Creative Works

A study is made of the differential cross sections arising from the photoionization of H2+. Previous studies indicated surprising differences in the shapes of the angular distributions calculated from exterior complex scaling and 2C methods. To further explore these differences, we have calculated the angular distributions from the photoionization of H2+ using an independent two-body Coulomb function (2C) method and a distorted wave approach. As a final test, we also present calculations using a time-dependent technique. Our results confirm the discrepancies found previously and we present possible reasons for these differences.

Differential Double Capture Cross Sections In P+He Collisions, Michael Schulz, T. Vajnai, J. A. Brand

Physics Faculty Research & Creative Works

We have measured differential double capture cross sections for 15 to 150 keV p+He collisions. We also analyzed differential double to single capture ratios, where we find pronounced peak structures. An explanation of these structures probably requires a quantum-mechanical description of elastic scattering between the projectile and the target nucleus. Strong final-state correlations have a large effect on the magnitude of the double capture cross sections

Effects Of The Final-State Electron-Ion Interactions On The Fully Differential Cross Sections For Heavy-Particle-Impact Ionization Of Helium, Don H. Madison, Jerry Peacher, M. Foster, K. Bartschat, H. P. Saha, Allison L. Harris

Physics Faculty Research & Creative Works

Three-dimensional fully differential cross sections for heavy-particle-impact ionization of helium are examined. Previously, the three-body distorted-wave (3DW) model has achieved good agreement with experiment in the scattering plane for small momentum transfers, but poor agreement for large momentum transfers. Poor agreement was also observed outside the scattering plane for all momentum transfers. In particular, the 3DW calculations predicted cross sections that were too small both perpendicular to the scattering plane and for large momentum transfers. The important unanswered question concerns the physical effects that cause the significant disagreement between experiment and theory. In previous works, the role of the projectile-ion …

Evaluation Of Laser-Assisted Bremsstrahlung With Dirac-Volkov Propagators, Erik Lotstedt, Ulrich D. Jentschura, Christoph H. Keitel

Physics Faculty Research & Creative Works

We study spontaneous bremsstrahlung emission in a highly intense laser field. In this regime the interaction with the laser field has to be treated nonperturbatively by using the relativistic formalism including Dirac-Volkov propagators, while the interaction with the Coulomb field and the bremsstrahlung radiation can be treated in first-order perturbation theory. For the intermediate electron state a fully laser-dressed propagator is used, including radiative corrections to avoid singularities on the mass shell. We find that the use of the Dirac-Volkov propagator is crucial to obtain correct numerical results. The cross section of the process is evaluated for laser intensities of …

Erratum: Evaluation Of Laser-Assisted Bremsstrahlung With Dirac-Volkov Propagators (Physical Review Letters (2007) 98 (043002)), Erik Lotstedt, Ulrich D. Jentschura, Christoph H. Keitel

Physics Faculty Research & Creative Works

No abstract provided.

Reconciliation Of Measured Fully Differential Single Ionization Data With The First Born Approximation Convoluted With Elastic Scattering, Michael Schulz, M. Dürr, B. Najjari, R. Moshammer, J. D. Ullrich

Physics Faculty Research & Creative Works

An analysis of experimental fully differential data for single ionization in 100 MeV/amu C6++He collisions is reported. We present a convolution of the first Born approximation with elastic scattering by using an event generator technique. Furthermore, the calculation is convoluted with all known experimental resolutions. Our analysis shows that elastic scattering is a viable explanation for surprising structures observed in the fully differential cross sections outside the scattering plane. Furthermore, it may even explain discrepancies in the “recoil peak” frequently observed for both ion and electron impact.

Quantum-Theory Based Event Generator For The Analysis Of Kinematically Complete Experiments, M. Dürr, B. Najjari, Michael Schulz, A. Dorn, R. Moshammer, J. Ullrich

Physics Faculty Research & Creative Works

The 'reaction microscope', an electron-ion coincidence momentum imaging spectrometer, represents a unique technique to measure multiply differential ionization cross sections for ionic projectiles. Observed discrepancies with theory for singly ionizing collision of 3.6 MeV/u Au53+ and 100 MeV/u C6+ ions severely challenge theoretical models. We present a method based on event-generators, which allows to consistently incorporate instrumental effects into theory. The result of the convolution procedure suggests, that the observed discrepancies are not a result of the experimental resolution, but are of true physical nature.