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2008

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Bee-To-Bee Contact Drives Oxalic Acid Distribution In Honey Bee Colonies, Nicholas P. Aliano, Marion D. Ellis Jan 2008

Bee-To-Bee Contact Drives Oxalic Acid Distribution In Honey Bee Colonies, Nicholas P. Aliano, Marion D. Ellis

Department of Entomology: Faculty Publications

Nine divided hives were constructed to study the distribution of oxalic acid (OA). Experimental colonies were split into two equal, queenright sections with one of three divider types. The first divider allowed trophallaxis to occur between adult bees on each side, but did not allow bee-to-bee contact. The second divider did not allow trophallaxis or bee-to-bee contact. The third divider allowed both bee-to-bee contact and trophallaxis between the two sides. All three dividers allowed gas exchange of volatile materials. The objective was to investigate factors that contribute to the distribution of OA in a hive by monitoring Varroa destructor mortality. …

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Mortalités Et Dépopulations Des Colonies D’Abeilles Aux États-Unis, Marion D. Ellis, Yves Leconte Jan 2008

Mortalités Et Dépopulations Des Colonies D’Abeilles Aux États-Unis, Marion D. Ellis, Yves Leconte

Department of Entomology: Faculty Publications

Après la France et l’Europe, les États-Unis d’Amérique subissent de plein fouet les problèmes de mortalités massives d’abeilles. Un déficit d’abeilles disponibles pour la pollinisation et les résultats d’enquêtes auprès des apiculteurs attestent clairement ce phénomène très préoccupant pour l’apiculture américaine. Y a-t-il des analogies avec ce que nous avons vécu sur nos populations d’abeilles ou bien est-ce un phénomène différent ? L’état américain débloque des fonds importants pour expliquer et lutter contre ce syndrome qui détruit leur cheptel.

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Simulations With Elaborated Worked Example Modeling: Beneficial Effects On Schema Acquisition, Debra K. Meier, Karl J. Reinhard, David O. Carter, David W. Brooks Jan 2008

Simulations With Elaborated Worked Example Modeling: Beneficial Effects On Schema Acquisition, Debra K. Meier, Karl J. Reinhard, David O. Carter, David W. Brooks

Department of Entomology: Faculty Publications

Worked examples have been effective in enhancing learning outcomes, especially with novice learners. Most of this research has been conducted in laboratory settings. This study examined the impact of embedding elaborated worked example modeling in a computer simulation practice activity on learning achievement among 39 undergraduate students within a classroom environment. The students from one introductory forensic science course were randomly assigned to one of two groups that worked through computer-based simulations containing worked example modeling conditions presented in varied order. The computer software administered the modeled simulations, prior knowledge test, pretest, posttests, and a second domain test. Findings from …

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Using Banded Sunflower Moth (Lepidoptera: Tortricidae) Egg Density To Estimate Damage And Economic Distance In Oilseed Sunflower, Kirk D. Mundal, Gary J. Brewer Jan 2008

Using Banded Sunflower Moth (Lepidoptera: Tortricidae) Egg Density To Estimate Damage And Economic Distance In Oilseed Sunflower, Kirk D. Mundal, Gary J. Brewer

Department of Entomology: Faculty Publications

The banded sunflower moth, Cochylis hospes Walsingham (Lepidoptera: Tortricidae), is an important economic pest of sunflower in the Upper Great Plains of North America. Economic losses due to reductions in seed number, weight, and quality can be significant. Previously, the potential for economic losses were estimated by sampling for adult moths. However, sampling for moths can be difficult and inaccurate. An alternative is to sample for banded sunflower moth eggs, which can be accurately counted in the field by using a binocular 3.5 headband magnifier. The egg counts are used to calculate the economic injury level (EIL): EIL …

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Levels Of Tolerance, Antibiosis, And Antixenosis Among Resistant Buffalograsses And Zoysiagrasses, Thomas E. Eickhoff, Tiffany Heng-Moss, Frederick P. Baxendale, John E. Foster Jan 2008

Levels Of Tolerance, Antibiosis, And Antixenosis Among Resistant Buffalograsses And Zoysiagrasses, Thomas E. Eickhoff, Tiffany Heng-Moss, Frederick P. Baxendale, John E. Foster

Department of Entomology: Faculty Publications

The western chinch bug, Blissus occiduus Barber, has been documented as one of the most serious pests of buffalograss, Buchloë dactyloides (Nuttall) Engelmann, and zoysiagrass, Zoysia japonica Steudel, grown for turf in midwestern states. Resistance to the western chinch bug has been identified in both buffalograsses and zoysiagrasses. Choice and no-choice studies were conducted to determine the categories (antibiosis, antixenosis, and tolerance) of three resistant buffalograsses (PX3-5-1’, 196’, and 184’) and three resistant zoysiagrasses (El Toro, Emerald, and Zorro). Antibiosis studies found no significant differences in survival, nymphal development, or fecundity among the resistant and susceptible buffalograsses or zoysiagrasses, …

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Influence Of Temperature On Rate Of Uptake And Subsequent Horizontal Transfer Of [14C]Fipronil By Eastern Subterranean Termites (Isoptera: Rhinotermitidae), Neil A. Spomer, Shripat T. Kamble, Richard A. Warriner, Robert W. Davis Jan 2008

Influence Of Temperature On Rate Of Uptake And Subsequent Horizontal Transfer Of [14C]Fipronil By Eastern Subterranean Termites (Isoptera: Rhinotermitidae), Neil A. Spomer, Shripat T. Kamble, Richard A. Warriner, Robert W. Davis

Department of Entomology: Faculty Publications

The effect of temperature on [14C]fipronil uptake and transfer from donor (D) to recipient (R) Reticulitermes flavipes (Kollar) (Isoptera: Rhinotermitidae) workers was evaluated. Test chambers used in the fipronil uptake study were constructed from petri dishes containing autoclaved soil treated with 1 ppm [14C]fipronil (1.14 μCi of total radioactivity per petri dish), distilled water, and R. flavipes workers. Test chambers were held in environmental growth chambers preset at 12, 17, 22, 27, and 32°C. For the fipronil transfer study, donor termites stained with Nile blue-A were exposed to soil treated with 1 ppm [14C]fipronil …

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An Automatic Bridge Detection Technique For Multispectral Images, D. Chaudhuri, Ashok Samal Jan 2008

An Automatic Bridge Detection Technique For Multispectral Images, D. Chaudhuri, Ashok Samal

School of Computing: Conference and Workshop Papers

Extraction of features from images has been a goal of researchers since the early days of remote sensing. While significant progress has been made in several applications, much remains to be done in the area of accurate identification of high-level features such as buildings and roads. This paper presents an approach for detecting bridges over water bodies from multispectral imagery. The multispectral image is first classified into eight land-cover types using a majority-must-be-granted logic based on the multiseed supervised classification technique. The classified image is then categorized into a trilevel image: water, concrete, and background. Bridges are then recognized in …

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Considering Operational Issues For Multiagent Conceptual Inferencing In A Distributed Information Retrieval Application, Leen-Kiat Soh Jan 2008

Considering Operational Issues For Multiagent Conceptual Inferencing In A Distributed Information Retrieval Application, Leen-Kiat Soh

School of Computing: Faculty Publications

Our system, based on a multiagent framework called collaborative understanding of distributed knowledge (CUDK), is designed with the overall goal of balancing agents’ conceptual learning and task accomplishment. The tradeoff between the two is that while conceptual learning allows an agent to improve its own concept base, it could be counter-productive: conceptual learning is time consuming and requires processing resources necessary for the agent to accomplish its tasks. In our current phase of research, we investigate the roles of resource and knowledge constraints, environmental factors (such as the frequency of queries), and learning mechanisms in a CUDK-based distributed information retrieval …

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Partial Forwarding Scheme For Dynamic Window Resizing In Live P2p Streaming Systems, Zhipeng Ouyang, Lisong Xu, Byrav Ramamurthy Jan 2008

Partial Forwarding Scheme For Dynamic Window Resizing In Live P2p Streaming Systems, Zhipeng Ouyang, Lisong Xu, Byrav Ramamurthy

School of Computing: Conference and Workshop Papers

Peer-to-peer (P2P) streaming systems, in which individual nodes or peers operated by ordinary Internet users collaborate to serve video streams, have recently aroused considerable interest in both academia and industry. An important problem in P2P streaming systems is how to reduce their consumed bandwidth, which is a major concern of Internet service providers. Our work is motivated by the fact that a user may dynamically change the size of a window displaying a video stream according to his/her personal choice, a scenario we refer to as dynamic window resizing. In this paper, we propose a scheme called the Partial Forwarding …

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A Security Framework For Wireless Sensor Networks Utilizing A Unique Session Key, Yong Wang, Byrav Ramamurthy, Yuyan Xue, Xukai Zou Jan 2008

A Security Framework For Wireless Sensor Networks Utilizing A Unique Session Key, Yong Wang, Byrav Ramamurthy, Yuyan Xue, 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. Many key management protocols have been specifically designed for wireless sensor networks. However, most of the key management protocols focus on the establishment of the required keys or the removal of the compromised keys. The design of these key management protocols does not consider the support of higher level security applications. When the applications are integrated later in sensor networks, new mechanisms must be designed. In this paper, we propose a security …

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Providing Reliable Data Transport For Dynamic Event Sensing In Wireless Sensor Networks, Yuyan Xue, Byrav Ramamurthy, Yong Wang Jan 2008

Providing Reliable Data Transport For Dynamic Event Sensing In Wireless Sensor Networks, Yuyan Xue, Byrav Ramamurthy, Yong Wang

School of Computing: Conference and Workshop Papers

In this paper, we propose a Loss Tolerant Reliable (LTR) data transport mechanism for dynamic Event Sensing (LTRES) in WSNs. In LTRES, a reliable event sensing requirement at the transport layer is dynamically determined by the sink. A distributed source rate adaptation mechanism is designed, incorporating a loss rate based lightweight congestion control mechanism, to regulate the data traffic injected into the network so that the reliability requirement can be satisfied. An equation based fair rate control algorithm is used to improve the fairness among the LTRES flows sharing the congestion path. The performance evaluations show that LTRES can provide …

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A Key Management Protocol For Wireless Sensor Networks With Multiple Base Stations, Yong Wang, Byrav Ramamurthy, Yuyan Xue Jan 2008

A Key Management Protocol For Wireless Sensor Networks With Multiple Base Stations, Yong Wang, Byrav Ramamurthy, Yuyan Xue

School of Computing: Conference and Workshop Papers

Most of the proposed key management protocols for wireless sensor networks (WSNs) in the literature assume that a single base station is used and that the base station is trustworthy. However, there are applications in which multiple base stations are used and the security of the base stations must be considered. This paper investigates a key management protocol in wireless sensor networks which include multiple base stations. We consider the situations in which both the base stations and the sensor nodes can be compromised. The proposed key management protocol, mKeying, includes two schemes, a key distribution scheme, mKeyDist, supporting multiple …

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Computation Of A Face Attractiveness Index Based On Neoclassical Canons, Symmetry, And Golden Ratios, Kendra Schmid, David Marx, Ashok Samal Jan 2008

Computation Of A Face Attractiveness Index Based On Neoclassical Canons, Symmetry, And Golden Ratios, Kendra Schmid, David Marx, Ashok Samal

School of Computing: Faculty Publications

Analysis of attractiveness of faces has long been a topic of research. Literature has identified many different factors that can be related to attractiveness. In this research we analyze the role of symmetry, neoclassical canons, and golden ratio in the determination of attractiveness of a face. We focus on the geometry of a face and use actual faces for our analysis. We find there are some differences in the criteria used by males and females to determine attractiveness. The model we have developed to predict the attractiveness of a face using its geometry is accurate with low residual errors.

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Cross-Layer Packet Size Optimization For Wireless Terrestrial, Underwater, And Underground Sensor Networks, Mehmet C. Vuran, Ian F. Akyildiz Jan 2008

Cross-Layer Packet Size Optimization For Wireless Terrestrial, Underwater, And Underground Sensor Networks, Mehmet C. Vuran, Ian F. Akyildiz

School of Computing: Conference and Workshop Papers

In this paper, a cross-layer solution for packet size optimization in wireless sensor networks (WSN) is introduced such that the effects of multi-hop routing, the broadcast nature of the physical wireless channel, and the effects of error control techniques are captured. A key result of this paper is that contrary to the conventional wireless networks, in wireless sensor networks, longer packets reduce the collision probability. Consequently, an optimization solution is formalized by using three different objective functions, i.e., packet throughput, energy consumption, and resource utilization. Furthermore, the effects of end-to-end latency and reliability constraints are investigated that may be required …

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Design Of A Wireless Vision Sensor For Object Tracking In Wireless Vision Sensor Networks, Mauricio Casarest, Mehmet C. Vuran, Senem Velipasalar Jan 2008

Design Of A Wireless Vision Sensor For Object Tracking In Wireless Vision Sensor Networks, Mauricio Casarest, Mehmet C. Vuran, Senem Velipasalar

School of Computing: Conference and Workshop Papers

The integration of CMOS cameras with embedded processors and wireless communication devices has enabled the development of distributed wireless vision systems. Wireless Vision Sensor Networks (WVSNs), which consist of wirelessly connected embedded systems with vision and sensing capabilities, provide wide variety of application areas that have not been possible to realize with the wall-powered vision systems with wired links or scalar-data based wireless sensor networks. In this paper, the design of a middleware for a wireless vision sensor node is presented for the realization of WVSNs. The implemented wireless vision sensor node is tested through a simple vision application to …

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Food Insecurity And Maternal Depression In Rural, Low-Income Families: A Longitudinal Investigation, Catherine Huddleston-Casas, Richard Charnigo, Leigh Ann Simmons Jan 2008

Food Insecurity And Maternal Depression In Rural, Low-Income Families: A Longitudinal Investigation, Catherine Huddleston-Casas, Richard Charnigo, Leigh Ann Simmons

Nebraska Center for Research on Children, Youth, Families, and Schools: Faculty Publications

Objective: The purpose of the present study was to examine the relationship between household food insecurity and maternal depression in a rural sample to determine whether food insecurity predicted mothers’ depression over time or vice versa.

Design: The study employed a prospective design using three waves of data from ‘Rural Families Speak’, a multi-state study of low-income rural families in the USA. Food insecurity was measured using the Core Food Security Module and depression was measured using the Center for Epidemiologic Studies–Depression Scale. A structural equation model was fit to the data using the AMOS software package.

Setting: Sixteen states …

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Atlantic And Pacific Sst Influences On Medieval Drought In North America Simulated By The Community Atmospheric Model, Song Feng, Robert Oglesby, Clinton M. Rowe, David B. Loope, Qi Hu Jan 2008

Atlantic And Pacific Sst Influences On Medieval Drought In North America Simulated By The Community Atmospheric Model, Song Feng, Robert Oglesby, Clinton M. Rowe, David B. Loope, Qi Hu

Department of Earth and Atmospheric Sciences: Faculty Publications

Severe drought is arguably one of the greatest recurring natural disasters that strikes North America. A synthesis of multiproxy data shows that North America was in the grip of a severe centennial-scale drought during medieval times (800–1300 AD). In this study, the Community Atmospheric Model (CAM) is used to investigate the role of sea surface temperature (SST) anomalies from the North Atlantic and the tropical Pacific Ocean on this megadrought. These anomalies are obtained from proxy reconstructions of SST. Four model experiments with prescribed SST anomalies in the tropical Pacific and/or North Atlantic Ocean were made. The CAM results captured …

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Life In A Temperate Polar Sea: A Unique Taphonomic Window On The Structure Of A Late Cretaceous Arctic Marine Ecosystem, Karen Chin, John Bloch, Arthur Sweet, Justin Tweet, Jaelyn Eberle, Stephen Cumbaa, Jakub Witowski, David M. Harwood Jan 2008

Life In A Temperate Polar Sea: A Unique Taphonomic Window On The Structure Of A Late Cretaceous Arctic Marine Ecosystem, Karen Chin, John Bloch, Arthur Sweet, Justin Tweet, Jaelyn Eberle, Stephen Cumbaa, Jakub Witowski, David M. Harwood

Department of Earth and Atmospheric Sciences: Faculty Publications

As the earth faces a warming climate, the rock record reminds us that comparable climatic scenarios have occurred before. In the Late Cretaceous, Arctic marine organisms were not subject to frigid temperatures but still contended with seasonal extremes in photoperiod. Here, we describe an unusual fossil assemblage from Devon Island, Arctic Canada, that offers a snapshot of a ca 75 MYR ago marine paleoecosystem adapted to such conditions. Thick siliceous biogenic sediments and glaucony sands reveal remarkably persistent high primary productivity along a high-latitude Late Cretaceous coastline. Abundant fossil feces demonstrate that this planktonic bounty supported benthic invertebrates and large, …

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Elevated Primary Productivity Of Calcareous Nannoplankton Associated With Ocean Anxoic Event 1b During The Aptian/Albian Transition (Early Cretaceous), Emily L. Browning, David K. Watkins Jan 2008

Elevated Primary Productivity Of Calcareous Nannoplankton Associated With Ocean Anxoic Event 1b During The Aptian/Albian Transition (Early Cretaceous), Emily L. Browning, David K. Watkins

Department of Earth and Atmospheric Sciences: Faculty Publications

Previous isotopic investigations of Aptian/Albian oceanic anoxic event (OAE) 1b from the western North Atlantic (Blake Nose) posited that increased sea surface temperatures and decreased salinity led to stratification of the upper water column, resulting in lowered dissolved oxygen and enhanced organic matter preservation. We examined calcareous nannofossils from the same site in the western North Atlantic (Blake Nose) to evaluate changes in surface water conditions prior to, during, and after the Aptian/Albian OAE1b. The results of our analysis conflict somewhat with the previous interpretation that OAE1b at Blake Nose was linked to water column stratification. The signal from calcareous …

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Seismic Facies And Stratigraphy Of The Cenozoic Succession In Mcmurdo Sound, Antarctica: Implications For Tectonic, Climatic And Glacial History, Christopher R. Fielding, Joanne Whittaker, Stuart A. Henrys, Terry J. Wilson, Timothy R. Naish Jan 2008

Seismic Facies And Stratigraphy Of The Cenozoic Succession In Mcmurdo Sound, Antarctica: Implications For Tectonic, Climatic And Glacial History, Christopher R. Fielding, Joanne Whittaker, Stuart A. Henrys, Terry J. Wilson, Timothy R. Naish

Department of Earth and Atmospheric Sciences: Faculty Publications

Integration of data from fully cored stratigraphic holes with an extensive grid of seismic reflection lines in McMurdo Sound, Antarctica, has allowed the formulation of a new model for the evolution of the Cenozoic Victoria Land Basin of the West Antarctic Rift. The Early Rift phase (Eocene to Early Oligocene) is recorded by wedges of strata confined by early extensional faults, and which contain seismic facies consistent with drainage via coarse-grained fans and deltas into discrete, actively subsiding grabens and half-grabens. The Main Rift phase (Early Oligocene to Early Miocene) is represented by a lens of strata that thickens symmetrically …

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Chloride And The Environmental Isotopes As The Indicators Of The Groundwater Recharge In The Gobi Desert, Northwest China, J. Z. Ma, Z. Ding, John B. Gates, Y. Su Jan 2008

Chloride And The Environmental Isotopes As The Indicators Of The Groundwater Recharge In The Gobi Desert, Northwest China, J. Z. Ma, Z. Ding, John B. Gates, Y. Su

Department of Earth and Atmospheric Sciences: Faculty Publications

The long term recharge in Gobi Desert from Hexi Corridor to Inner Mongolia Plateau was estimated to Be 1 mm year-1 by using the chloride mass balance method from one unsaturated zone profile, which shows that no effective modern recharge is taking place. A good rainfall database from Zhangye provides definition of the stable isotopic composition of modern rainfall. The signature of groundwater from the late Pleistocene differs markedly from that of the Holocene, shown clearly by the compositions of -10.5‰ δ18O as compared with values of -7‰ at the present day. It is apparent that the …

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Seismic Facies And Stratigraphy Of The Cenozoic Succession In Mcmurdo Sound, Antarctica: Implications For Tectonic, Climatic And Glacial History, Christopher R. Fielding, J. Whittaker, Stuart A. Henrys, T. J. Wilson, T. R. Naish Jan 2008

Seismic Facies And Stratigraphy Of The Cenozoic Succession In Mcmurdo Sound, Antarctica: Implications For Tectonic, Climatic And Glacial History, Christopher R. Fielding, J. Whittaker, Stuart A. Henrys, T. J. Wilson, T. R. Naish

Department of Earth and Atmospheric Sciences: Faculty Publications

A new stratigraphic model is presented for the evolution of the Cenozoic Victoria Land Basin of the West Antarctic Rift, based on integration of seismic reflection and drilling data. The Early Rift phase (?latest Eocene to Early Oligocene) comprises wedges of strata confined by early extensional faults, and which contain seismic facies consistent with drainage via coarse-grained fans and deltas into discrete, actively subsiding grabens and half-grabens. The Main Rift phase (Early Oligocene to Early Miocene) comprises a lens of strata that thickens symmetrically from the basin margins into a central depocenter, and in which stratal events pass continuously over …

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An Observational Analysis And Evaluation Of Land Surface Model Accuracy In The Nebraska Sand Hills, David B. Radell, Clinton M. Rowe Jan 2008

An Observational Analysis And Evaluation Of Land Surface Model Accuracy In The Nebraska Sand Hills, David B. Radell, Clinton M. Rowe

Department of Earth and Atmospheric Sciences: Faculty Publications

In this study, the influence of subsurface water on the energy budget components of three locations with heterogeneous land surfaces in the Nebraska Sand Hills are examined through observations and use of the Noah land surface model (LSM). Observations of the four primary components of the surface energy budget are compared for a wet interdunal meadow valley, a dry interdunal valley, and a dunal upland location. With similar atmospheric forcing at each site, it was determined that differences in the partitioning of the mean diurnal net radiation (Rnet) existed among the three locations due to the influence …

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Improved Algorithm For Modis Satellite Retrievals Of Aerosol Optical Depths Over Western North America, Easan Drury, Daniel J. Jacob, Jun Wang, Robert J.D. Spurr, Kelly Chance Jan 2008

Improved Algorithm For Modis Satellite Retrievals Of Aerosol Optical Depths Over Western North America, Easan Drury, Daniel J. Jacob, Jun Wang, Robert J.D. Spurr, Kelly Chance

Department of Earth and Atmospheric Sciences: Faculty Publications

Quantitative evaluation of chemical transport models (CTMs) with aerosol optical depth (AOD) products retrieved from satellite backscattered reflectances can be compromised by inconsistent assumptions of aerosol optical properties and errors in surface reflectance estimates. We present an improved AOD retrieval algorithm for the MODIS satellite instrument using locally derived surface reflectances and CTM aerosol optical properties for the 0.47, 0.65, and 2.13 μm MODIS channels. Assuming negligible atmospheric reflectance at 2.13 μm in cloud-free conditions, we derive 0.65/2.13 surface reflectance ratios at 1° X 1.25° horizontal resolution for the continental United States in summer 2004 from the subset of top-of-atmosphere …

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The Optimal Bulk Wind Differential Depth And The Utility Of The Upper-Tropospheric Storm-Relative Flow For Forecasting Supercells, Adam L. Houston, Richard L. Thompson, Roger Edwards Jan 2008

The Optimal Bulk Wind Differential Depth And The Utility Of The Upper-Tropospheric Storm-Relative Flow For Forecasting Supercells, Adam L. Houston, Richard L. Thompson, Roger Edwards

Department of Earth and Atmospheric Sciences: Faculty Publications

An analysis of 4 yr of Rapid Update Cycle-2 (RUC-2) derived soundings in proximity to radar-observed supercells and nonsupercells is conducted in an effort to answer two questions: 1) over what depth is the fixed-layer bulk wind differential (BWD; the vector difference between the wind velocity at a given level and the wind velocity at the surface) the best discriminator between supercell and nonsupercell environments and 2) does the upper-tropospheric storm-relative flow (UTSRF) discriminate between the environments of supercells and nonsupercells? Previous climatologies of sounding-based supercell forecast parameters have documented the ability of the 0–6-km BWD in delineating supercell from …

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Ex-Situ And In-Situ Selenization Of Copper-Indium And Copper-Boron Thin Films, Rodney J. Soukup, Natale J. Ianno, Chad Kamler, Martin Diaz, Shuchi Sharma, James Huguenin-Love, Jiri Olejnicek Jan 2008

Ex-Situ And In-Situ Selenization Of Copper-Indium And Copper-Boron Thin Films, Rodney J. Soukup, Natale J. Ianno, Chad Kamler, Martin Diaz, Shuchi Sharma, James Huguenin-Love, Jiri Olejnicek

Department of Electrical and Computer Engineering: Faculty Publications

It has recently been established that the ideal bandgap for terrestrial photovoltaics is 1.37 eV and the bandgap for CulnSe2 is only around 1.04 eV. Thus, a larger bandgap is needed. However, neither the substitution of Ga nor of AI has made a high efficiency solar cell absorber with a band gap of 1.37 eV possible. B, an even smaller atom, should require less atomic substitution than either Ga or AI to achieve a wider bandgap. In order to fabricate a thin film of CulnxB1-xSe2 (CIBS), Cu, In and B were deposited from a variety …

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Grid Connection Requirements And Solutions For Dfig Wind Turbines, Wei Qiao, Ronald G. Harley Jan 2008

Grid Connection Requirements And Solutions For Dfig Wind Turbines, Wei Qiao, Ronald G. Harley

Department of Electrical and Computer Engineering: Faculty Publications

As the number and size of windfarms continue to grow,many countries have established or are developing a set of specific requirements (i.e., grid codes) for operation and grid connection of windfarms. The objective of these grid codes is to ensure that wind farms do not adversely affect the power system operation with respect to security of supply, reliability and power quality. This paper reviews major grid code requirements for wind farms, and investigates various technologies developed by and solutions proposed by researchers and wind turbine manufactures in order to meet these requirements. In addition, some ofthe authors' work on these …

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Reliability-Based Stand-Alone Photovoltaic System Sizing Design- A Case Study, Haifeng Ge, Liqin Ni, Sohrab Asgarpoor Jan 2008

Reliability-Based Stand-Alone Photovoltaic System Sizing Design- A Case Study, Haifeng Ge, Liqin Ni, Sohrab Asgarpoor

Department of Electrical and Computer Engineering: Faculty Publications

This paper introduces a method for designing a standalone photovoltaic system to improve the load point reliability, extend the operation life, and minimize the design cost. This approach examines the impacts of solar panel sizes, tilt angles and battery volumes toward load point reliability, as well as the expected system life, by using real insolation data in a given location and random load burdens. The reliability evaluation incorporating solar insolation variations and load point uncertainty is performed. Life evaluation of battery is included in this paper with consideration of the battery State of Charge (SoC) history. The Economical analysis to …

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A Quantitative Study Of Mobility Impact For Real- Time Services On A Wi-Fi Multi-Hop Network, Ting Zhou, Hamid Sharif, Michael Hempel, Puttipong Mahasukhon, Wei Wang, Song Ci Jan 2008

A Quantitative Study Of Mobility Impact For Real- Time Services On A Wi-Fi Multi-Hop Network, Ting Zhou, Hamid Sharif, Michael Hempel, Puttipong Mahasukhon, Wei Wang, Song Ci

Department of Electrical and Computer Engineering: Faculty Publications

In this paper, we analyze the performance of mobile real time services in a large-scale IEEE 802.11 multi-hop network. We present our field measurements with discussion of performance bottlenecks for VoIP services under mobile scenarios. We utilized our test bed which is located in Nebraska and supported by the University of Nebraska-Lincoln (UNL), US Federal Railroads Administrations (FRA), and major US railroad companies. Our UNL-FRA test bed consists of 8 outdoor access point towers, which are deployed along 3.5 mile of BNSF railroad. Passive measurement approaches are taken to ensure the integrity of collected data and multi-layer stream based packet …

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Full-Wave Finite-Difference Time-Domain Simulation Of Electromagnetic Cloaking Structures, Yan Zhao, Christos Argyropoulos, Yang Hao Jan 2008

Full-Wave Finite-Difference Time-Domain Simulation Of Electromagnetic Cloaking Structures, Yan Zhao, Christos Argyropoulos, Yang Hao

Department of Electrical and Computer Engineering: Faculty Publications

This paper proposes a radial dependent dispersive finitedifference time-domain method for the modeling of electromagnetic cloaking structures. The permittivity and permeability of the cloak are mapped to the Drude dispersion model and taken into account in dispersive FDTD simulations. Numerical simulations demonstrate that under ideal conditions, objects placed inside the cloak are ‘invisible’ to external electromagnetic fields. However for the simplified cloak based on linear transformations, the back scattering has a similar level to the case of a PEC cylinder without any cloak, rendering the object still being ‘visible’. It is also demonstrated numerically that the simplified cloak based on …

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