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Back Contact Effects on the Electro-Optical Properties of CdTe/CdS Solar Cells

Description: Studies of junction photoluminescence (PL) in CdTe/CdS solar cells reveal that back-contact application produces a dramatic qualitative change in the junction picosecond-PL spectrum. Prior to contact application, the spectrum has two peaks at energies of 1.501 eV and 1.457 eV, corresponding to recombination in regions of CdTeS alloy with 2% and 12% sulfur content, respectively. After contact application, the spectrum consists of a single broad peak at 1.48 eV. Previous studies have shown that the nitric-phosphoric (NP) etch used in the contact procedure produces a layer of elemental tellurium (Te) on the CdTe surface. We postulate that the change in the near-junction PL spectrum is caused by a grain-boundary field effect due to perturbations of the grain-boundary conductivity and Fermi level.
Date: October 15, 1998
Creator: Levi, D. H.; Albin, D. S.; Gessert, T. A. (National Renewable Energy Laboratory) & Woods, L. M. (Department of Electrical Engineering, Colorado State University, Ft. Collins, CO)
Partner: UNT Libraries Government Documents Department

Advanced Processing of CdTe- and CuInxGa1-xSe2-Based Solar Cells: Final Report: 18 April 1995 - 31 May 1998

Description: This report summarizes work performed by the University of South Florida Department of Electrical Engineering under this subcontract. The Cadmium telluride(CdTe) portion of this project deals with the development of high-efficiency thin-filmed CdTe solar cells using fabrication techniques that are suitable for manufacturing environments.
Date: January 13, 1999
Creator: Morel, D. L.; Ferekides, C. S.; Bhatt, R.; Jayapalan, A.; Komin, V.; Lin, H. et al.
Partner: UNT Libraries Government Documents Department

Electroosmosis effect on micro permeability through rock samples

Description: It is a well known fact that a liquid flowing through a microporous media creates a potential difference between entry and exit of the sample. This phenomenon is known as streaming potential. In an other hand, when a potential difference is applied through an impregnate rock sample, a flow is induced, this is called electroosmosis effect. In this paper, we examine electroosmosis experiments made in a percolation cell in which two gold electrodes are placed in the inner and in the outer chamber. The temperature, the pressure and potential difference, the flow, the current and the chemical composition of water in chambers may be recorded. Experiment consist to the application of electric field through the sample and to observe the evolution of the flow, the electrical current and the chemical dissolution.
Date: January 24, 1996
Creator: G., Touchard; Paillat, T.; Beaufort, D. & Watanabe, S.
Partner: UNT Libraries Government Documents Department

Input Impedance of a Probe Antenna Exciting a TEM Cell

Description: Abstract: The input impedance of a probe antenna exciting a transverse electromagnetic (TEM) transmission line cell is formulated by a variational approach. The formulation also utilizes the results from a previous work on the field distribution inside a TEM cell excited by a vertical electrical Hertzian dipole. The final result of imoedance is shown to consist of two distinct terms, which are respectively contributed by the ordinary rectangular waveguide and the gap perturbation. Numerical results for both the real and imaginary parts of the impedance are given. The resistive part is found to be proportional to the square of the probe length, and the reactive part largely capacitive.
Date: April 1982
Creator: Wilson, Perry F.; Chang, David C. & Ma, Mark T.
Partner: UNT Libraries Government Documents Department

Applications of wireless sensors in monitoring Indoor Air Quality in the classroom environment [Poster]

Description: This poster discusses applications of wireless sensors in monitoring indoor air quality in the classroom environment. The focus of this research project was to investigate Indoor Air Quality monitoring technologies, government regulations and policies, and best practices to improve IAQ.
Date: 2012
Creator: Chamberlain, Blaine; Jordan, Georgette; Li, Xinrong; Thompson, Ruthanne; Borkar, Chirag & Mansour, Sahar
Partner: UNT College of Engineering

Executive Correspondence – Letter received 08/08/05 by the BRAC Commission from Princeton University Professor of Electrical Engineering Daniel C. Tsui

Description: Executive Correspondence – Letter received 08/08/05 by the BRAC Commission from Princeton University Professor of Electrical Engineering Daniel C. Tsui criticizing DoD’s recommendation to move the Army Research Office (ARO) from North Carolina to Bethesda, MD and explaining how such a move would severely compromise ARO’s ability to provide revolutionary advances to the Army.
Date: August 11, 2005
Partner: UNT Libraries Government Documents Department

Bringing real world applications for wireless sensor networks into the classroom: Telemetric monitoring of water quality in an artificial stream [2012: Poster]

Description: This poster discusses research on bringing real world applications for wireless sensor networks into the classroom and covers the use of a wireless sensor network (WSN) using the ZigBee protocol to remotely monitor an artificial aquatic ecosystem.
Date: 2012
Creator: Bunn, Zac; Guerrero, Jose; Wolf, Lori; Fu, Shengli; Hoeinghaus, David; Driver, Luke et al.
Partner: UNT College of Engineering

Demand Controlled Ventilation using CO2 Sensors in a Wireless Sensor Network [Poster]

Description: Poster presented as part of the 2013 Research Experiences for Teachers (RET) in Sensor Education, a National Science Foundation (NSF) funded grant project. This poster discusses research on demand controlled ventilation using CO₂ sensors in a wireless sensor network.
Date: 2013
Creator: Parsons, David; Jordan, Georgette; Li, Xinrong; Thompson, Ruthanne & Abraham, Sherin
Partner: UNT College of Engineering

Single Molecule Junctions: Probing Contact Chemistry and Fundamental Circuit Laws

Description: By exploiting selective link chemistry, formation of single molecule junctions with reproducible conductance has become established. Systematic studies reveal the structure-conductance relationships for diverse molecules. I will draw on experiments from my collaborators at Columbia University, atomic-scale calculations and theory to describe progress in two areas. First, I will describe a novel route to form single molecule junctions, based on SnMe3 terminated molecules, in which gold directly bonds to carbon in the molecule backbone resulting in near ideal contact resistance [1]. Second, comparison of the conductance of junctions formed with molecular species containing either one backbone or two backbones in parallel allows demonstration of the role of quantum interference in the conductance superposition law at the molecular scale [2].
Date: April 11, 2013
Creator: S., Hybertsen M.
Partner: UNT Libraries Government Documents Department

Low cost, compact, and high efficiency traction motor for electric and hybrid electric vehicles

Description: A new motor drive, the switched reluctance motor drive, has been developed for hybrid-electric vehicles. The motor drive has been designed, built and tested in the test bed at a near vehicle scale. It has been shown that the switched reluctance motor drive is more suitable for traction application than any other motor drive.
Date: October 7, 2002
Creator: Ehsani, Mark
Partner: UNT Libraries Government Documents Department

The Use of Thyristors for Repetitive Narrow Pulse, High Power Switching

Description: Inverter type thyristors were switched repetitively to failure with 1 {micro}s pulses at repetition rates of 10, 50 and 100 pps and at peak currents up to 12 kA. Millions of pulses could be obtained before failure if the peak current were held at around 6 kA.
Date: January 13, 2000
Creator: BAYNE,S.B.; PORTNOY,W.M. & ROHWEIN,G.J.
Partner: UNT Libraries Government Documents Department

Miniature Nuclear Magnetic Resonance Spectrometer For In-Situ And In-Process Analysis And Monitoring

Description: The main purpose of this research is to develop a nuclear magnetic resonance (NMR) spectrometer that is small enough to be held in the palm of a hand. Such an instrument could be used in many applications of importance to DOE as well as to industry. These applications would include in-field characterization of contaminants, monitoring and analysis of chemical processes in chemical plants and other environmental monitoring applications. In addition to having drastically reduced size and cost, a miniature NMR instrument would be ideally suited for chemical analysis of volume limited samples which frequently occur in biological, medical and drug development applications.
Date: June 1, 1999
Creator: Friemand, Gennady & Feinerman, Alan
Partner: UNT Libraries Government Documents Department

Application and Network-Cognizant Proxies - Final Report

Description: OAK B264 Application and Network-Cognizant Proxies - Final Report. Current networks show increasing heterogeneity both in terms of their bandwidths/delays and the applications they are required to support. This is a trend that is likely to intensify in the future, as real-time services, such as video, become more widely available and networking access over wireless links becomes more widespread. For this reason they propose that application-specific proxies, intermediate network nodes that broker the interactions between server and client, will become an increasingly important network element. These proxies will allow adaptation to changes in network characteristics without requiring a direct intervention of either server or client. Moreover, it will be possible to locate these proxies strategically at those points where a mismatch occurs between subdomains (for example, a proxy could be placed so as to act as a bridge between a reliable network domain and an unreliable one). This design philosophy favors scalability in the sense that the basic network infrastructure can remain unchanged while new functionality can be added to proxies, as required by the applications. While proxies can perform numerous generic functions, such as caching or security, they concentrate here on media-specific, and in particular video-specific, tasks. The goal of this project was to demonstrate that application- and network-specific knowledge at a proxy can improve overall performance especially under changing network conditions. They summarize below the work performed to address these issues. Particular effort was spent in studying caching techniques and on video classification to enable DiffServ delivery. other work included analysis of traffic characteristics, optimized media scheduling, coding techniques based on multiple description coding, and use of proxies to reduce computation costs. This work covered much of what was originally proposed but with a necessarily reduced scope.
Date: March 24, 2003
Creator: Ortega, Antonio & Lee, Daniel C.
Partner: UNT Libraries Government Documents Department

New insights into input relegation control for inverse kinematics of a redundant manipulator. Part 1, On the orthogonality of matrices B and J and comparison to the extended Jacobian method

Description: A method for kinematically modeling a constrained rigid body mechanical system and a method for controlling such a system termed input relegation control (IRC) were applied to resolve the kinematic redundancy of a serial link manipulator moving in an open chain configuration in. A set of equations was introduced to define a new vector variable parameterizing the redundant degrees of freedom (DOF) as a linear function of the joint velocities. The new set was combined with the classical kinematic velocity model of manipulator and solved to yield a well specified solution for the joint velocities as a function of the Cartesian velocities of the end effector and of the redundant DOF variable. In the previous work a technique was proposed for selecting the matrix relating the redundant DOF variable to the joint velocities which resulted in it rows being orthogonal to the rows of the Jacobian matrix. The implications for such a selection were not discussed in. In Part 1 of this report a basis for the joint space is suggested which provides considerable insight into why picking the aforementioned matrix to be orthogonal to the Jacobian is advantageous. A second objective of Part 1 is to compare the IRC method to the Extended Jacobian method of Baillieul and Martin and other related methods.
Date: July 1, 1995
Creator: Unseren, M.A. & Reister, D.B.
Partner: UNT Libraries Government Documents Department

New insights into input relegation control for inverse kinematics of a redundant manipulator. Part 2, The optimization of a secondary criteria involving self motion of the joints

Description: The input relegation control (IRC) technique for redundancy resolution is extended to solve the problem of optimizing a scalar performance criteria representing a secondary objective to be accomplished via self motion of the joints. The criteria is defined to be the error between the vector of joint velocities and a new vector of ``corrective` joint velocities, which is minimized in a Eudidean norm sense. The corrective velocities represent a `corrective` action to be applied to the system and axe projected into the null space of the Jacoblan in the solution for the joint velocities. The report demonstrates that there exists a component in the solution for the joint velocities that induces self motion of the joints but is not a function of the ``corrective action``. A technique for eliminating this undesired component is presented. The method is compared to the well known gradient projection technique and its advantages are discussed.
Date: July 1, 1995
Creator: Unseren, M.A.
Partner: UNT Libraries Government Documents Department

Nano-patterning of Co/Pt multilayers.

Description: One of the most promising new systems for both basic research and technical development are the periodic arrays of nano-magnetic elements, as shown. Such arrays show remarkably rich and novel magnetic behavior. Periodic magnetic arrays not only provide excellent opportunities for new science but also constitute a promising candidate for new applications such as high-density, patterned magnetic memory for advanced computer designs in the next decade. In the presentation they will focus on patterned [Co4 {angstrom}/Pt10 {angstrom}]n multilayers, which demonstrate an unusually strong out-of-plane magnetic anisotropy and sensitivity to structural modification. This strong out-of-plane anisotropy makes Co/Pt ML the favorite candidates for perpendicular magnetic recording. The patterned Co/Pt ML are representatives of a new generation of magnetic nanostructures with lateral dimensions in 100 nm range, and individual layer thickness approaching a monolayer scale (e.g., 4 {angstrom} of Co and 10 {angstrom} of Pt). In addition to traditional lithography, they are developing a new approach to tailoring the local magnetic properties of Co/Pt ML. In this process the local magnetic properties are modified not through conventional modulation of the chemical composition, but through structural modification induced by low energy ion implantation.
Date: July 24, 2001
Creator: Metlushko, V.; Crabtree, G.; Welp, U.; Vlasko-Vlasov, V.; Baldo, P.; Rehn, L. E. et al.
Partner: UNT Libraries Government Documents Department

Final report on characterizing the dynamics of spatio-temporal data

Description: One principal goal of the grant was to model and analyze the dynamics of spatially extended chaotic systems. One of the principal tools used in the analysis was KLTOOL, a computer package developed by the principal investigators for Karhunen-Loeve analysis. The package was used to analyze video data from a laboratory experiment on cellular flames. A second goal of the project was to analyze complex time series whose underlying dynamics may be low dimensionally chaotic. Particular emphasis was placed on systems of possible relevance to energy production and distribution. The work attempted to characterize low-dimensional aspects of the dynamics of a fluidized bed, in particular, a transition from periodic to irregular behavior. Finally, collaborators worked on aspects of targeting in chaotic dynamical systems. This work showed that it is possible to switch a moderately high-dimensional chaotic process rapidly between prespecified periodic saddle orbits embedding within the attractor. Additional work extended previously-developed algorithms for the highly accurate computation of stable manifolds of periodic saddle orbits, which is essential to the successful application of targeting algorithms.
Date: September 1, 1998
Creator: Kostelich, E.J. & Armbruster, H.D.
Partner: UNT Libraries Government Documents Department

Final report on work for Center for Gyrokinetic Particle Simulation of Turbulent Transport in Burning Plasmas — Tools for Improved Data Logistics

Description: This project focused on the use of Logistical Networking technology to address the challenges involved in rapid sharing of data from the the Center's gyrokinetic particle simulations, which can be on the order of terabytes per time step, among researchers at a number of geographically distributed locations. There is a great need to manage data on this scale in a flexible manner, with simulation code, file system, database and visualization functions requiring access. The project used distributed data management infrastructure based on Logistical Networking technology to address these issues in a way that maximized interoperability and achieved the levels of performance the required by the Center's application community. The work focused on the development and deployment of software tools and infrastructure for the storage and distribution of terascale datasets generated by simulations running at the National Center for Computational Science at Oak Ridge National Laboratory.
Date: September 14, 2008
Creator: Beck, Micah
Partner: UNT Libraries Government Documents Department

Defect Structures in Semiconducting ReSi{sub 2-x} Epitaxial Thin Films

Description: Narrow band gap semiconductors such as ReSi{sub 2{minus}x} (Eg {approximately} 0.12 eV) are potential materials for infrared detectors. Further, ReSi{sub 2{minus}x} is in thermodynamic equilibrium and has a very small lattice mismatch with Si offering the potential of developing ReSi{sub 2{minus}x} heterojunction devices where the detector element and the signal processing circuitry can be integrated on one Si chip. In a previous study, strong crystallographic alignment between ReSi{sub 2{minus}x} film and (001)Si substrate was observed by ion channeling. In this study, a transmission electron microscopy (TEM) study has been performed on ReSi{sub 2{minus}x} epitaxial films on (001) Si. Comparisons are made to our previous microscopy study on the defect structures in bulk single crystals of ReSi{sub 2{minus}x}.
Date: February 1, 1999
Creator: Mahan, J.E.; Mirsa, A. & Mitchell, T.E.
Partner: UNT Libraries Government Documents Department

The Composite OLAP-Object Data Model

Description: In this paper, we define an OLAP-Object model that combines the main characteristics of OLAP and Object data models in order to achieve their functionalities in a common framework. We classify three different object classes: primitive, regular and composite. Then, we define a query language which uses the path concept in order to facilitate data navigation and data manipulation. The main feature of the proposed language is an anchor. It allows us to fix dynamically an object class (primitive, regular or composite) along the paths over the OLAP-Object data model for expressing queries. The queries can be formulated on objects, composite objects and combination of both. The power of the proposed query language is investigated through multiple query examples. The semantic of different clauses and syntax of the proposed language are investigated.
Date: December 7, 2005
Creator: Pourabbas, Elaheh & Shoshani, Arie
Partner: UNT Libraries Government Documents Department