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Description: The saturation voltage and current characteristics of a compensated ionization chamber (Q-1045) were measured with special regard to high current and voltage ranges. The chamber can be operated at currents up to I ma with a 2000 volt power supply. (auth)
Date: May 25, 1960
Creator: Kaufman, J. L.
Partner: UNT Libraries Government Documents Department

Double Barrier Resonant Tunneling Transistor with a Fully Two Dimensional Emitter

Description: A novel planar resonant tunneling transistor is demonstrated. The growth structure is similar to that of a double-barrier resonant tunneling diode (RTD), except for a fully two-dimensional (2D) emitter formed by a quantum well. Current is fed laterally into the emitter, and the 2D--2D resonant tunneling current is controlled by a surface gate. This unique device structure achieves figures-of-merit, i.e. peak current densities and peak voltages, approaching that of state-of-the-art RTDs. Most importantly, sensitive control of the peak current and voltage is achieved by gating of the emitter quantum well subband energy. This quantum tunneling transistor shows exceptional promise for ultra-high speed and multifunctional operation at room temperature.
Date: July 13, 2000
Partner: UNT Libraries Government Documents Department

Charged Local Defects in Extended Systems

Description: The conventional approach to treating charged defects in extended systems in first principles calculations is via the supercell approximation using a neutralizing jellium background charge. I explicitly demonstrate shortcomings of this standard approach and discuss the consequences. Errors in the electrostatic potential surface over the volume of a supercell are shown to be comparable to a band gap energy in semiconductor materials, for cell sizes typically used in first principles simulations. I present an alternate method for eliminating the divergence of the Coulomb potential in supercell calculations of charged defects in extended systems that embodies a correct treatment of the electrostatic potential in the local viciniq of the a charged defect, via a mixed boundary condition approach. I present results of first principles calculations of charged vacancies in NaCl that illustrate the importance of polarization effects once an accurate representation of the local potential is obtained. These polarization effects, poorly captured in small supercells, also impact the energetic on the scale of typical band gap energies.
Date: May 25, 1999
Creator: Schultz, Peter A.
Partner: UNT Libraries Government Documents Department

Analytic electrostatic solution of an axisymmetric accelerator gap

Description: Numerous computer codes calculate beam dynamics of particles traversing an accelerating gap. In order to carry out these calculations the electric field of a gap must be determined. The electric field is obtained from derivatives of the scalar potential which solves Laplace`s equation and satisfies the appropriate boundary conditions. An integral approach for the solution of Laplace`s equation is used in this work since the objective is to determine the potential and fields without solving on a traditional spatial grid. The motivation is to quickly obtain forces for particle transport, and eliminate the need to keep track of a large number of grid point fields. The problem then becomes one of how to evaluate the appropriate integral. In this work the integral solution has been converted to a finite sum of easily computed functions. Representing the integral solution in this manner provides a readily calculable formulation and avoids a number of difficulties inherent in dealing with an integral that can be weakly convergent in some regimes, and is, in general, highly oscillatory.
Date: March 15, 1995
Creator: Boyd, J. K.
Partner: UNT Libraries Government Documents Department

Crack growth monitoring in harsh environments by electrical potential measurements

Description: Electric potential measurement (EPM) technology offers an attractive alternative to conventional nondestructive evaluation (NDE) for monitoring crack growth in harsh environments. Where conventional NDE methods typically require localized human interaction, the EPM technique developed at the Idaho National Engineering and Environmental Laboratory (INEEL) can be operated remotely and automatically. Once a crack-like defect is discovered via conventional means, EPM can be applied to monitor local crack size changes. This is of particular interest in situations where an identified structural defect is not immediately rejectable from a fitness-for-service viewpoint, but due to operational and environmental conditions may grow to an unsafe size with continuing operation. If the location is in a harsh environment where periodic monitoring by normal means is either too costly or not possible, a very expensive repair may be immediately mandated. However, the proposed EPM methodology may offer a unique monitoring capability that would allow for continuing service. INEEL has developed this methodology, supporting equipment, and calibration information to apply EPM in a field environment for just this purpose. Laboratory and pilot scale tests on full-size engineering structures (pressure vessels and piping) have been successfully performed. The technique is applicable to many severe environments because the sensitive equipment (electronics, operators) can be situated in a remote location, with only current and voltage probe electrical leads entering into the harsh environment. Experimental results showing the utility of the methodology are presented, and unique application concepts that have been examined by multiple experiments are discussed.
Date: September 19, 1999
Creator: Lloyd, W. R.; Reuter, W. G. & Weinberg, D. M.
Partner: UNT Libraries Government Documents Department


Description: Modern weld controllers typically use current to control the weld process. SRS uses a legacy voltage control method. This task was undertaken to determine if the improvements in the weld control equipment could be implemented to provide improvements to the process control. The constant current mode of operation will reduce weld variability by about a factor of 4. The constant voltage welds were slightly hotter than the constant current welds of the same nominal current. The control mode did not appear to adversely affect the weld quality, but appropriate current ranges need to be established and a qualification methodology for both welding and shunt calibrations needs to be developed and documented.
Date: October 11, 2005
Creator: Korinko, P; STANLEY, S & HOWARD, H
Partner: UNT Libraries Government Documents Department


Description: BS>Results of a study of thermodynamic properties of aqueous hydrochloric acid solutions are presented. A hydrogen electrode was used against a silver-silver chloride electrode at 25 to 275 deg C using hydrogen pressure of about 1 atm. and hydrochloric acid concentrations of 0.005 to 1.0 M. Electromotive measurement techniques are described and resulting data are tabulated. (J.R.D.)
Date: May 1, 1959
Creator: Greeley, R S
Partner: UNT Libraries Government Documents Department

Nonlinear integrable ion traps

Description: Quadrupole ion traps can be transformed into nonlinear traps with integrable motion by adding special electrostatic potentials. This can be done with both stationary potentials (electrostatic plus a uniform magnetic field) and with time-dependent electric potentials. These potentials are chosen such that the single particle Hamilton-Jacobi equations of motion are separable in some coordinate systems. The electrostatic potentials have several free adjustable parameters allowing for a quadrupole trap to be transformed into, for example, a double-well or a toroidal-well system. The particle motion remains regular, non-chaotic, integrable in quadratures, and stable for a wide range of parameters. We present two examples of how to realize such a system in case of a time-independent (the Penning trap) as well as a time-dependent (the Paul trap) configuration.
Date: October 1, 2011
Creator: Nagaitsev, S.; /Fermilab; Danilov, V. & /SNS Project, Oak Ridge
Partner: UNT Libraries Government Documents Department

Electronic Charges and Electric Potential at LaAlO3/SrTiO3 Interfaces Studied by Core-Level Photoemission Spectroscopy

Description: We studied LaAlO{sub 3}/SrTiO{sub 3} interfaces for varying LaAlO{sub 3} thickness by core-level photoemission spectroscopy. In Ti 2p spectra for conducting 'n-type' interfaces, Ti{sup 3+} signals appeared, which were absent for insulating 'p-type' interfaces. The Ti{sup 3+} signals increased with LaAlO{sub 3} thickness, but started well below the critical thickness of 4 unit cells for metallic transport. Core-level shifts with LaAlO{sub 3} thickness were much smaller than predicted by the polar catastrophe model. We attribute these observations to surface defects/adsorbates providing charges to the interface even below the critical thickness.
Date: August 19, 2011
Creator: Hwang, Harold
Partner: UNT Libraries Government Documents Department


Description: The mechanism of reduction for chromium(III) ion to chromium(II) at the mercury cathode was studied in 0.1M KNO/sub 3/. Data obtained at varying temperature and solution composition from polarograms gave values for DELTA H*, DELTA S*, and DELTA F* which indicated that two mechanisms were involved. At potentials more positive than the polarographic half-wave potential, the mechanism appeared to be simple electron transfer from the electrode to the chromium(III) ion in solution. When the potential was more negative than the half-wave, potential electron exchange between the reduced chromium ion near the electrode surface and a chromium(III) ion in solution became appreciable. Values for the heat of activation for the reduction of chromium(III) to chromium(II) in 0.1M KNO/sub 3/ for the electron transfer and exchange reaction mechanisms were determined to be 34.7 and 27.0 kcal mole/sup -1/, respectively. (auth)
Date: May 20, 1960
Creator: McLain, M.E. Jr.
Partner: UNT Libraries Government Documents Department

Mechanisms for charge-transfer processes at electrode/solid-electrolyte interfaces.

Description: This report summarizes the accomplishments of a Laboratory-Directed Research and Development (LDRD) project focused on developing and applying new x-ray spectroscopies to understand and improve electric charge transfer in electrochemical devices. Our approach studies the device materials as they function at elevated temperature and in the presence of sufficient gas to generate meaningful currents through the device. We developed hardware and methods to allow x-ray photoelectron spectroscopy to be applied under these conditions. We then showed that the approach can measure the local electric potentials of the materials, identify the chemical nature of the electrochemical intermediate reaction species and determine the chemical state of the active materials. When performed simultaneous to traditional impedance-based analysis, the approach provides an unprecedented characterization of an operating electrochemical system.
Date: November 1, 2011
Creator: Chueh, William; El Gabaly Marquez, Farid; Whaley, Josh A.; McCarty, Kevin F.; McDaniel, Anthony H. & Farrow, Roger L.
Partner: UNT Libraries Government Documents Department

CERTS Microgrid Laboratory Test Bed

Description: CERTS Microgrid concept captures the emerging potential of distributed generation using a system approach. CERTS views generation and associated loads as a subsystem or a 'microgrid'. The sources can operate in parallel to the grid or can operate in island, providing UPS services. The system can disconnect from the utility during large events (i.e. faults, voltage collapses), but may also intentionally disconnect when the quality of power from the grid falls below certain standards. CERTS Microgrid concepts were demonstrated at a full-scale test bed built near Columbus, Ohio and operated by American Electric Power. The testing fully confirmed earlier research that had been conducted initially through analytical simulations, then through laboratory emulations, and finally through factory acceptance testing of individual microgrid components. The islanding and resynchronization method met all Institute of Electrical and Electronics Engineers Standard 1547 and power quality requirements. The electrical protection system was able to distinguish between normal and faulted operation. The controls were found to be robust under all conditions, including difficult motor starts and high impedance faults.
Date: June 8, 2010
Creator: Lasseter, R. H.; Eto, J. H.; Schenkman, B.; Stevens, J.; Volkmmer, H.; Klapp, D. et al.
Partner: UNT Libraries Government Documents Department

CERTS Microgrid Laboratory Test Bed

Description: The objective of the CERTS Microgrid Test Bed project was to enhance the ease of integrating energy sources into a microgrid. The project accomplished this objective by developing and demonstrating three advanced techniques, collectively referred to as the CERTS Microgrid concept, that significantly reduce the level of custom field engineering needed to operate microgrids consisting of generating sources less than 100kW. The techniques comprising the CERTS Microgrid concept are: 1 a method for effecting automatic and seamless transitions between grid-connected and islanded modes of operation, islanding the microgrid's load from a disturbance, thereby maintaining a higher level of service, without impacting the integrity of the utility's electrical power grid; 2 an approach to electrical protection within a limited source microgrid that does not depend on high fault currents; and 3 a method for microgrid control that achieves voltage and frequency stability under islanded conditions without requiring high-speed communications between sources.
Date: June 8, 2010
Partner: UNT Libraries Government Documents Department


Description: The manufacturers' specifications for temperature coefficient of voltage and internaI impedance of the compensated avalanche diode types IN430A and IN430B appear quite promising. These devices couId be used as shunt regulators in high stability power supplies if the noise and drift rate were sufficiently small. One investigator reported the voltage did not drift more than the J-57 engin 0.002 per cent over a 7,000 hour period. Stability tests were performed on two diode samples under resonable laboratory conditions. The measured drift rate did not exceed 0.005 per cent per month, and short term noise was less than the J-57 engin 0.002 per cent. The actual diode drift rate may be even lower than the measured rate. (auth)
Date: December 31, 1958
Creator: Blankenship, J.L.
Partner: UNT Libraries Government Documents Department