Digital Commons Network^™

Origin Of Photomultiplication In C60 Based Devices, Jinsong Huang, Yang Yang

Department of Mechanical and Materials Engineering: Faculty Publications

In this manuscript, the origin of the photomultiplication effect was studied in C₆₀ based devices by evaluating the wavelength dependent external and internal quantum efficiencies under various biases. The effect of materials with disordered structures on the photomultiplication effect was determined by intentionally integrating both ordered and disordered material structures into one organic solar cell device with a configuration of indium tin oxide/poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS)/pentacene/C₆₀ fullerene/bathocuproine (BCP)/Al. Our results show that both the disordered structure of C₆₀ and the charge trapping effect at the C₆₀ /PEDOT:PSS interface contribute to the photomultiplication effect. By studying the C60-only …

Low Voltage And Fast Speed All-Polymeric Optocouplers, Yan Yao, Hsiang-Yu Chen, Jinsong Huang, Yang Yang

Department of Mechanical and Materials Engineering: Faculty Publications

An all-polymeric optocoupler has been demonstrated with a polymer light-emitting diode (PLED) as the light source (input unit) and a polymer/fullerene photodiode (PD) as the detector (output unit). The electroluminescence (EL) peak of the PLED is 560 nm, and the entire EL spectrum is within the response range of the PD. The optocoupler can work at low driving voltages, 5 V on the PLED and 0 V on the PD. The output photocurrent increases linearly with input current, and the current density transfer ratio reaches 1.5%. The frequency response of the optocoupler is at 500 kHz. With comparable performance to …

Mist Netting Bias, Species Accumulation Curves, And The Rediscovery Of Two Bats On Montserrat (Lesser Antilles), Roxanne Larsen, Karen A. Boegler, Hugh H. Genoways, Will P. Masefield, Ronan A. Kirsch, Scott C. Pedersen

University of Nebraska State Museum: Mammalogy Papers

Mist nets are commonly used to survey bat populations and to estimate bat biodiversity, but several studies have found that mist net capture data and methods are biased due to a number of factors, including size and placement of nets, and the frequency at which investigators check their nets. Despite the wealth of literature and anecdotal reports, few investigators have quantified the interactions of bats with mist nets directly. We employed night vision camcorders to monitor bat behavior when bats encountered a mist net and then utilized these data to reevaluate years of survey data collected on Montserrat, Lesser Antilles. …

Lessons From The Trademark Use Debate, Mark D. Janis, Graeme B. Dinwoodie

Articles by Maurer Faculty

In their response to our article Confusion Over Use: Contextualism in Trademark Law, Professors Dogan and Lemley discard more all-encompassing versions of the trademark use requirement. Instead, they seek to delineate and defend a "more surgical form" of trademark use doctrine. In this reply, we demonstrate that the language of the Lanham Act does not impose a trademark use requirement even when that requirement is defined "surgically" and sections 32 and 43(a) are read "fluidly," as Dogan and Lemley suggest. Moreover, their interpretation still renders section 33(b)(4) redundant and unduly limits appropriate common law development of trademark law. We also …

High-Resolution Evidence For Dynamic Transitional Geomagnetic Field Behaviour From A Miocene Reversal, Mcmurdo Sound, Ross Sea, Antarctica, Andrew P. Roberts, Anisch Bakrania, Fabio Florindo, Christopher J. Rowan, Christopher R. Fielding, Ross D. Powell

Department of Earth and Atmospheric Sciences: Faculty Publications

We report a high-resolution record of a Miocene polarity transition (probably the Chron C6r-C6n transition) from glacimarine sediments in McMurdo Sound, Ross Sea, Antarctica, which is the first transition record reported from high southern latitudes. The transition is recorded in two parallel cores through a 10.7 m stratigraphic thickness. The sediments are interpreted as having been deposited in a marine environment under the influence of floating ice or seaward of a glacier terminus from which a large sediment load was delivered to the drill site. The core was recovered using rotary drilling, which precludes azimuthal orientation of the core and …

A Method For Estimating Fractal Dimension Of Tree Crowns From Digital Images, Dongsheng Zhang, Ashok Samal, James R. Brandle

School of Computing: Faculty Publications

A new method for estimating fractal dimension of tree crowns from digital images is presented. Three species of trees, Japanese yew (Taxus cuspidata Sieb & Zucc), Hicks yew (Taxus × media), and eastern white pine (Pinus strobus L.), were studied. Fractal dimensions of Japanese yew and Hicks yew range from 2.26 to 2.70. Fractal dimension of eastern white pine range from 2.14 to 2.43. The difference in fractal dimension between Japanese yew and eastern white pine was statistically significant at 0.05 significance level as was the difference in fractal dimension between Hicks yew and eastern white …

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

School of Computing: 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

School of Computing: 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. …

Layered Clustering Communication Protocol For Wireless Sensor Networks, Yong Wang, Byrav Ramamurthy

School of Computing: Conference and Workshop Papers

In this paper, we propose a Layered Clustering Hierarchy (LCH) communication protocol for Wireless Sensor Networks (WSNs). The design of LCH has two goals: scalability and energy-efficiency. In LCH, the sensor nodes are organized as a layered clustering structure. Each layer runs a distributed clustering protocol. By randomizing the rotation of cluster heads in each layer, the energy load is distributed evenly across sensors in the network. Our simulations show that LCH is effective in densely deployed sensor networks. On average, 70% of live sensor nodes are involved directly in the clustering communication hierarchy. Moreover, the simulations also show that …

Bandit-Based Algorithms For Budgeted Learning, Kun Deng, Chris Bourke, Stephen Scott, Julie Sunderman, Yaling Zheng

School of Computing: Conference and Workshop Papers

We explore the problem of budgeted machine learning, in which the learning algorithm has free access to the training examples’ labels but has to pay for each attribute that is specified. This learning model is appropriate in many areas, including medical applications. We present new algorithms for choosing which attributes to purchase of which examples in the budgeted learning model based on algorithms for the multi-armed bandit problem. All of our approaches outperformed the current state of the art. Furthermore, we present a new means for selecting an example to purchase after the attribute is selected, instead of selecting an …

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

School of Computing: 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 …

Semantic 3d Cad And Its Applications In Construction Industry — An Outlook Of Construction Data Visualization, Zhigang Shen, Raja R. A. Issa, Linxia Gu

Department of Construction Engineering and Management: Faculty Publications

In response to the need of using electronic design data directly in construction management applications, many CAD developers have started implementing semantic data models in their CAD products using industry foundation classes (IFCs). While helpful, these semantic CAD applications have limitations when used in actual construction practices. The case studies in the thesis indicated that: 1) the semantics of the current data model (IFC as an example) is not rich enough to cover the richer details of the real trade practices; 2) the current implementation of the semantic data model lacks the mechanism to provide multiple trades views at various …

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

School of Computing: 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.

Symbolic Path Sensitization Analysis And Applications, Jian Kang, Sharad C. Seth, Shashank K. Mehta

School of Computing: Conference and Workshop Papers

A new symbolic approach models the sensitization paths to selected primary output(s) as Boolean equations, with satisfying solutions representing the set of all sources of single and multiple sensitizations in the circuit. The paper discusses two applications of this idea: model-free fault diagnosis and input sensitization analysis.

A Note On The Karp-Lipton Collapse For The Exponential Hierarchy, Chris Bourke

School of Computing: Technical Reports

We extend previous collapsing results involving the exponential hierarchy by using recent hardness-randomness trade-off results. Specifically, we show that if the second level of the exponential hierarchy has polynomial-sized circuits, then it collapses all the way down to MA.

A Simple Orthogonal Space-Time-Polarization Block Code, B. J. Wysocki, Tadeusz Wysocki, J. Seberry, S. Spence Adams, H. Sharif

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

This letter proposes a simple but highly efficient technique to jointly utilize space, time, and polarization diversities. The technique is based on extending orthogonal space-time block codes into the quaternion domain and utilizing a description of the dual-polarized signal by means of quaternions, which are a generalization of complex numbers. In the given example, the achievable performance gain for two transmit and one receive antennas is approximately 6 dB at a bit error rate of 10^-4 when compared with the Alamouti code.

A Bayesian Multilevel Modeling Approach For Data Query In Wireless Sensor Networks, Honggang Wang, Hua Fang, Kimberly A. Espy, Dongming Peng, Hamid Sharif

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

In power-limited Wireless Sensor Network (WSN), it is important to reduce the communication load in order to achieve energy savings. This paper applies a novel statistic method to estimate the parameters based on the real-time data measured by local sensors. Instead of transmitting large real-time data, we proposed to transmit the small amount of dynamic parameters by exploiting both temporal and spatial correlation within and between sensor clusters. The temporal correlation is built on the level-1 Bayesian model at each sensor to predict local readings. Each local sensor transmits their local parameters learned from historical measurement data to their cluster …

Network Architectures For Live Peer-To-Peer Media Streaming, Jagannath Ghoshal, Lisong Xu, Byrav Ramamurthy, Miao Wang

School of Computing: Technical Reports

Peer-to-Peer (P2P) media streaming networks, motivated by the huge success of P2P file downloading networks, have recently attracted a lot of research interest. However, it is challenging to design P2P media streaming networks because of the stringent time constraints on the delivered media streams, which require more efficient and resilient overlay architectures. In this paper, we focus on live P2P media streaming networks, a promising application flourishing in the Internet and which requires the distribution of live (not stored) multimedia content to subscribers. We review the architectures for live P2P media streaming networks, and consider both overlay topologies and their …

Experimenting With Software Testbeds For Evaluating New Technologies, Mikael Lindvall, Ioana Rus, Paolo Donzelli, Atif Memon, Marvin Zelkowitz, Aysu Betin-Can, Tevfik Bultan, Chris Ackermann, Bettina Anders, Sima Asgari, Victor Basili, Lorin Hochstein, Jörg Fellmann, Forrest Shull, Roseanne Tvedt, Daniel Pech, Daniel Hirschbach

School of Computing: Faculty Publications

The evolution of a new technology depends upon a good theoretical basis for developing the technology, as well as upon its experimental validation. In order to provide for this experimentation, we have investigated the creation of a software testbed and the feasibility of using the same testbed for experimenting with a broad set of technologies. The testbed is a set of programs, data, and supporting documentation that allows researchers to test their new technology on a standard software platform. An important component of this testbed is the Unified Model of Dependability (UMD), which was used to elicit dependability requirements for …

A-Mac: Adaptive Medium Access Control For Next Generation Wireless Terminals, Mehmet C. Vuran, Ian F. Akyildiz

School of Computing: Faculty Publications

Next Generation (NG) wireless networks are envisioned to provide high bandwidth to mobile users via bandwidth aggregation over heterogeneous wireless architectures. NG wireless networks, however, impose challenges due to their architectural heterogeneity in terms of different access schemes, resource allocation techniques as well as diverse quality of service requirements. These heterogeneities must be captured and handled dynamically as mobile terminals roam between different wireless architectures. However, to address these challenges, the existing proposals require either a significant modification in the network structure and in base stations or a completely new architecture, which lead to integration problems in terms of implementation …

A Two-Phase Approach For Dynamic Lightpath Scheduling In Wdm Optical Networks, Lu Shen, Xi Yang, Ajay Todimala, Byrav Ramamurthy

School of Computing: Conference and Workshop Papers

Lightpath scheduling is an important capability in next-generation wavelength-division multiplexing (WDM) optical networks to reserve resources in advance for a specified time period while provisioning end-to-end lightpaths. In a dynamic environment, the end user requests for dynamic scheduled lightpath demands (D-SLDs) need to be serviced without the knowledge of future requests. Even though the starting time of the request may be hours or days from the current time, the end-user however expects a quick response as to whether the request could be satisfied. We propose a two-phase approach to dynamically schedule and provision D-SLDs. In the first phase, termed the …

Vacuum Ultraviolet Optical Analysis Of Spin-Cast Chitosan Films Modified By Succinic Anhydride And Glycidyl Phenyl Ether, W. H. Nosal, D. W. Thompson, T. E. Tiwald, S. Sarkar, Anuradha Subramanian, John A. Woollam

John A. Woollam Publications

Optical properties of spin-cast chitosan films were determined in the vacuum ultraviolet (VUV) through visible regions of the spectrum using spectroscopic ellipsometry. The onset of absorption in the ultraviolet was determined for chitosan films modified with succinic anhydride (SA) and glycidyl phenyl ether (GPE). This absorption was accounted for by including Gaussian and Tauc– Lorentz shaped oscillators in the optical model. VUV through visible optical constants were determined for these modified films, as well as for immunoglobulin G (IgG) attached to GPE-modified samples. Several resonant oscillator structures exhibit greatly differing oscillator parameters for the as-deposited, as well as SA-and GPE-modified …

Recasting Dilemma Zone Design As A Marginal Cost-Benefit Problem, Anuj Sharma, Darcy M. Bullock, Srinivas Peeta

Department of Civil and Environmental Engineering: Faculty Publications

One control objective at high-speed isolated intersections is to provide safe phase transition by minimizing the occurrence of high-speed vehicles in the dilemma zone before the phase is terminated. An upper limit for extending the green (maximum green time) is used to avoid an indefinite extension of the main-street green. Currently, the maximum green times are chosen by using engineering judgment. This approach does not explicitly consider the trade-offs between safety and delay and hence often results in both unsafe and inefficient performance at the intersection under medium to heavy traffic volumes. The dilemma problem is recast as one of …

Limitations Of Simultaneous Gap-Out Logic, Anuj Sharma, Darcy M. Bullock, Srinivas Peeta

Department of Civil and Environmental Engineering: Faculty Publications

The current practice of specifying simultaneous gap-out logic places constraints on signal controller logic. These constraints cannot be achieved under high traffic flow conditions, and degraded signal efficiency and dilemma zone protection often result. This study documents the phenomenon described above with set-back detectors at an instrumented intersection in Noblesville, Indiana, and characterizes the problem of dilemma zone protection as being traffic-volume dependent, a factor that should be carefully considered before the simultaneous gap-out logic is applied. Implementation of simultaneous gap-out logic led to max out ranging from 3.5% to 40% of cycles per hour during peak traffic flow periods …

Event-Based Data Collection For Generating Actuated Controller Performance Measures, Edward J. Smaglik, Anuj Sharma, Darcy M. Bullock, James R. Sturdevant, Gary Duncan

Department of Civil and Environmental Engineering: Faculty Publications

Cycle-by-cycle data have been shown to be effective in the analysis of a signalized intersection with measures of effectiveness such as volume-to-capacity ratios, arrival type, and average vehicular delay. Currently, actuated traffic controllers are unable to store vehicle counts and vehicle occupancy in cycle-by-cycle bins, requiring extra equipment and personnel to collect data in these bins. The objective of this research was to develop an integrated general purpose data collection module that time stamps detector and phase state changes within a National Electrical Manufacturers Association actuated traffic signal controller and uses those data to provide quantitative graphs to assess arterial …

Evaluation Of An Adult Education Technology Program, Iwasan D. Kejawa

Theses and Dissertations

The purpose of this study was to evaluate the adult education technology program at a chartered alternative adult education center in Florida. The adult education center had a low rate of students passing the Florida Comprehensive Assessment Test (FCAT). This study examined the impact of the use of computer technology in an effort to improve student learning in mathematics, reading, and science. Computers at the institution were used by all students for tutorials to prepare them for the FCAT and to obtain a high school diploma. The research questions for this study were as follows:

1. Is the education technology program …

Evaluation Of The Streambed Leakage Concept In Analytical Models Using Data From Three Pumping Tests, Sefan J. Kollet, Vitaly A. Zlotnik

Department of Earth and Atmospheric Sciences: Faculty Publications

Two-dimensional analytical models of pumping induced drawdown and stream depletion account for the streambed properties and stream geometry. Using data from three pumping tests performed under various hydrologic conditions, the following hypotheses were tested: (1) a partially penetrating stream at a certain distance from the pumping well can be represented by the streambed leakage term in the analytical models; (2) in the streambed leakage term, the streambed conductance coefficient λ=(WK′)/m′ accounts for the average stream width W, the streambed thickness m′, and hydraulic conductivity K′. The first hypothesis was tested by comparing results from tests under flow and no-flow stream …

Stream Network Characteristics Used To Infer The Distribution Of Fold Types In The Zagros Simply Folded Belt, Iran, Caroline M. Burberry, John W. Cosgrove, Jian Guo Liu

Department of Earth and Atmospheric Sciences: Faculty Publications

Progressive deformation at a convergent margin (the Zagros Simply Folded Belt) was analysed using satellite images, digital elevation models, contour maps and artificially generated stream networks. Two end-member fold types (fault-bend folds and detachment folds) interact with streams flowing from the High Zagros Mountains into the Persian Gulf. Growing folds divert streams and create wind or water gaps in characteristic patterns which are related to the uplift histories of the two fold types. Additionally, the symmetry of minor channels reflects the inherent symmetry of the folds. The distribution of fold types is shown for the region N27°- N30°, E50°-E54° at …

Modeling Annual Extreme Precipitation In China Using The Generalized Extreme Value Distribution, Song Feng, Saralees Nadarajah, Qi Hu

Department of Earth and Atmospheric Sciences: Faculty Publications

Extreme precipitation events are the major causes of severe floods in China. In this study, four time series of daily, 2-day, 5-day, and 10-day annual maximum precipitation from 1951 to 2000 at 651 weather stations in China were analyzed. The generalized extreme value (GEV) distribution was used, to model the annual extreme precipitation events at each station. The GEV distribution was also modified to explore the linear temporal trends in the extreme events. The results showed that more than 12% of the stations have significant (p-value < 0.10) linear trends. Decreasing trends are mainly observed in northern China, and increasing trends are observed in the Yangtze River basin and northwestern China. The return periods of extreme participation have changed stations with significant temporal trends. The 50-year event observed in parts of the Yangtze River basin, and northwestern China during the 1951-60, has become a more frequent 25-year event in the 1990s. The spatial distribution of the return levels of the 651 stations are closely related to the climatic mean precipitation, and are influenced by the East Asian summer monsoon system (return levels are measures of extremity – for example, a 10 year return level is the value that can be expected to be exceeded on average once in every 10 years). The return period of extreme precipitation, that caused the 1998 severe floods in the Yangtze River basin, was also evaluated from a probabilistic perspective.

Spectropolarimetric Survey Of Hydrogen-Rich White Dwarf Stars, Adéla Kawka, Stéphane Vennes, Gary D. Schmidt, Dayal T. Wickramasinghe, Rolf Koch

Aerospace, Physics, and Space Science Faculty Publications

We have conducted a survey of 61 southern white dwarfs searching for magnetic fields using Zeeman spectropolarimetry. Our objective is to obtain a magnetic field distribution for these objects and, in particular, to find white dwarfs with weak fields. We found one possible candidate (WD 0310-688) that may have a weak magnetic field of -6.1 ±2.2 kG. Next, we determine the fraction and distribution of magnetic white dwarfs in the solar neighborhood and investigate the probability of finding more of these objects based on the current incidence of magnetism in white dwarfs within 20 pc of the Sun. We have …