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6,873 Matching Results
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Automated Controlled-Potential Coulometer for the IAEA
An automated controlled-potential coulometer has been developed at the Savannah River Site (SRS) for the determination of plutonium for use at the International Atomic Energy Agency`s (IAEA) Safeguards Analytical Laboratory in Siebersdorf, Austria. The system is functionally the same as earlier systems built for use at the Savannah River Site`s Analytical Laboratory. All electronic circuits and printed circuits boards have been upgraded with state-of-the-art components. A higher amperage potentiostat with improved control stability has been developed. The system achieves electronic calibration accuracy and linearity of better than 0.01 percent, with a precision and accuracy better than 0.1 percent has been demonstrated. This coulometer features electrical calibration of the integration system, electrolysis current background corrections, and control-potential adjustment capabilities. These capabilities allow application of the system to plutonium measurements without chemical standards, achieving traceability to the international measurement system through electrical standards and Faraday`s constant. the chemist is provided with the capability to perform measurements without depending upon chemical standards, which is a significant advantage for applications such as characterization of primary and secondary standards. Additional benefits include reducing operating cost to procure, prepare and measure calibration standards and the corresponding decrease in radioactive waste generation. The design and documentation of …
Date:
January 29, 1998
Creator:
Cordaro, J.V.; Holland, M.K. & Fields, T.
System:
The UNT Digital Library
Isotopically controlled semiconductors
A review of recent research involving isotopically controlled semiconductors is presented. Studies with isotopically enriched semiconductor structures experienced a dramatic expansion at the end of the Cold War when significant quantities of enriched isotopes of elements forming semiconductors became available for worldwide collaborations. Isotopes of an element differ in nuclear mass, may have different nuclear spins and undergo different nuclear reactions. Among the latter, the capture of thermal neutrons which can lead to neutron transmutation doping, can be considered the most important one for semiconductors. Experimental and theoretical research exploiting the differences in all the properties has been conducted and will be illustrated with selected examples. Manuel Cardona, the longtime editor-in-chief of Solid State Communications has been and continues to be one of the major contributors to this field of solid state physics and it is a great pleasure to dedicate this review to him.
Date:
November 15, 2004
Creator:
Haller, E. E.
System:
The UNT Digital Library
Are We There Yet? Toward a Workable Controlled Vocabulary for Music
This article discusses moving toward a workable controlled vocabulary for music.
Date:
July 2012
Creator:
McKnight, Mark, 1951-
System:
The UNT Digital Library
Physics with isotopically controlled semiconductors
Control of the isotopic composition of semiconductors offers a wide range of new scientific opportunities. In this paper a number of recent results obtained with isotopically pure as well as deliberately mixed diamond and Ge bulk single crystals and Ge isotope superlattices will be reviewed. Isotopic composition affects several properties such as phonon energies, bandstructure and lattice constant in subtle but theoretically well understood ways. Large effects are observed for thermal conductivity, local vibrational modes of impurities and after neutron transmutation doping (NTD). Several experiments which could profit greatly from isotope control are proposed.
Date:
August 1, 1994
Creator:
Haller, E. E.
System:
The UNT Digital Library
Technology of controlled nuclear fusion
Separate abstracts were prepared for each of the 28 included papers. Abstracts for the remaining 43 papers appeared earlier in ERA. (MOW)
Date:
January 1, 1978
Creator:
Powell, J R & Eterno, C T
System:
The UNT Digital Library
Technology of controlled nuclear fusion
Separate abstracts were prepared for 38 of the included papers. Abstracts have appeared earlier in ERA for the remaining 32 papers. (MOW)
Date:
January 1, 1978
Creator:
Powell, J R & Eterno, C T
System:
The UNT Digital Library
Computer-controlled radiation monitoring system
A computer-controlled radiation monitoring system was designed and installed at the Lawrence Livermore National Laboratory`s Multiuser Tandem Laboratory (10 MV tandem accelerator from High Voltage Engineering Corporation). The system continuously monitors the photon and neutron radiation environment associated with the facility and automatically suspends accelerator operation if preset radiation levels are exceeded. The system has proved reliable real-time radiation monitoring over the past five years, and has been a valuable tool for maintaining personnel exposure as low as reasonably achievable.
Date:
September 27, 1994
Creator:
Homann, S.G.
System:
The UNT Digital Library
Large-scale cryopumping for controlled fusion
Vacuum pumping by freezing out or otherwise immobilizing the pumped gas is an old concept. In several plasma physics experiments for controlled fusion research, cryopumping has been used to provide clean, ultrahigh vacua. Present day fusion research devices, which rely almost universally upon neutral beams for heating, are high gas throughput systems, the pumping of which is best accomplished by cryopumping in the high mass-flow, moderate-to-high vacuum regime. Cryopumping systems have been developed for neutral beam injection systems on several fusion experiments (HVTS, TFTR) and are being developed for the overall pumping of a large, high-throughput mirror containment experiment (MFTF). In operation, these large cryopumps will require periodic defrosting, some schemes for which are discussed, along with other operational considerations. The development of cryopumps for fusion reactors is begun with the TFTR and MFTF systems. Likely paths for necessary further development for power-producing reactors are also discussed.
Date:
July 25, 1977
Creator:
Pittenger, L. C.
System:
The UNT Digital Library
An investigation of a passively controlled haptic interface
Haptic interfaces enhance cooperation between humans and robotic manipulators by providing force and tactile feedback to the human user during the execution of arbitrary tasks. The use of active actuators in haptic displays presents a certain amount of risk since they are capable of providing unacceptable levels of energy to the systems upon which they operate. An alternative to providing numerous safeguards is to remove the sources of risk altogether. This research investigates the feasibility of trajectory control using passive devices, that is, devices that cannot add energy to the system. Passive actuators are capable only of removing energy from the system or transferring energy within the system. It is proposed that the utility of passive devices is greatly enhanced by the use of redundant actuators. In a passive system, once motion is provided to the system, presumably by a human user, passive devices may be able to modify this motion to achieve a desired resultant trajectory. A mechanically passive, 2-Degree-of-Freedom (D.O.F.) manipulator has been designed and built. It is equipped with four passive actuators: two electromagnetic brakes and two electromagnetic clutches. This paper gives a review of the literature on passive and robotics and describes the experimental test bed …
Date:
March 1, 1997
Creator:
Davis, J. T. & Book, W. J.
System:
The UNT Digital Library
Surface effects in controlled thermonuclear fusion
During the operation of large size plasma facilities and future controlled thermonuclear fusion reactors the surfaces of such major components as container walls, beam limiters, diverter walls and beam-dump walls of the injector region will be exposed to particle and photon bombardment from primary plasma radiations and from secondary radiations. Such radiations can cause, for example, physical and chemical sputtering, blistering, particle- and photon- impact induced desorption, secondary electron and x-ray emission, backscattering, nuclear reactions, photo-decomposition of surface compounds, photocatalysis, and vaporization. Such effects in turn can (a) seriously damage and erode the bombarded surface and (b) release major quantities of impurities which will contaminate the plasma. The effects of some of the major surface phenomena on the operation of plasma facilities and future fusion reactors are discussed. (auth)
Date:
August 1, 1975
Creator:
Kaminsky, M.
System:
The UNT Digital Library
Computer-controlled data communications test center
This paper describes the software developed for a computer-based test center used in testing and diagnosing a large network of terminal and remote processor communications links. The software runs in time-base-scheduled and on-demand interactive modes. It includes a control program, several measurement tasks, Datatrieve-11 databases, and various graphical display programs, all running under RSX11M, V4.0, on a PDP-11/70.
Date:
January 1, 1982
Creator:
Horning, R. R.; Creel, L. R. & Doll, M. A.
System:
The UNT Digital Library
Microprocessor-controlled, wide-range streak camera
Bechtel Nevada/NSTec recently announced deployment of their fifth generation streak camera. This camera incorporates many advanced features beyond those currently available for streak cameras. The arc-resistant driver includes a trigger lockout mechanism, actively monitors input trigger levels, and incorporates a high-voltage fault interrupter for user safety and tube protection. The camera is completely modular and may deflect over a variable full-sweep time of 15 nanoseconds to 500 microseconds. The camera design is compatible with both large- and small-format commercial tubes from several vendors. The embedded microprocessor offers Ethernet connectivity, and XML [extensible markup language]-based configuration management with non-volatile parameter storage using flash-based storage media. The camera’s user interface is platform-independent (Microsoft Windows, Unix, Linux, Macintosh OSX) and is accessible using an AJAX [asynchronous Javascript and XML]-equipped modem browser, such as Internet Explorer 6, Firefox, or Safari. User interface operation requires no installation of client software or browser plug-in technology. Automation software can also access the camera configuration and control using HTTP [hypertext transfer protocol]. The software architecture supports multiple-simultaneous clients, multiple cameras, and multiple module access with a standard browser. The entire user interface can be customized.
Date:
September 1, 2006
Creator:
Amy E. Lewis, Craig Hollabaugh
System:
The UNT Digital Library
Efficiency effects of variation in controlled experimental variables
When a designed experiment is conducted, the exact levels of controlled experimental variables specified by the design may not be attainable. Two different types of situations can occur in which the actual settings of the design variables deviate from the target design settings. In one case, the actual settings obtained are unknown. In the other case, the actual settings are known; however desirable design properties such as orthogonality may have been lost. This paper examines the impact of known and unknown errors in experimental variables for designed experiments in which the response is assumed to be approximately linear in the region of interest. For comparison, the well known situation where the target values of the experimental variables can actually be obtained will also be considered.
Date:
January 1, 1993
Creator:
Wendelbeger, J.R.
System:
The UNT Digital Library
Efficiency effects of variation in controlled experimental variables
When a designed experiment is conducted, the exact levels of controlled experimental variables specified by the design may not be attainable. Two different types of situations can occur in which the actual settings of the design variables deviate from the target design settings. In one case, the actual settings obtained are unknown. In the other case, the actual settings are known; however desirable design properties such as orthogonality may have been lost. This paper examines the impact of known and unknown errors in experimental variables for designed experiments in which the response is assumed to be approximately linear in the region of interest. For comparison, the well known situation where the target values of the experimental variables can actually be obtained will also be considered.
Date:
June 1, 1993
Creator:
Wendelbeger, J. R.
System:
The UNT Digital Library
On the fracture of human dentin: Is it stress- orstrain-controlled?
Despite substantial clinical interest in the fracture resistance of human dentin, there is little mechanistic information in archival literature that can be usefully used to model such fracture. In fact, although the fracture event indent in, akin to other mineralized tissues like bone, is widely believed to be locally strain-controlled, there has never been any scientific proof to support this belief. The present study seeks to address this issue through the use of a novel set of in vitro experiments in Hanks' balanced salt solution involving a double-notched bend test geometry, which is designed to discern whether the critical failure events involved in the onset of fracture are locally stress- or strain-controlled. Such experiments are further used to characterize the notion of ''plasticity'' in dentin and the interaction of cracks with the salient microstructural features. It is observed that fracture in dentin is indeed locally strain-controlled and that the presence of dentinal tubules does not substantially affect this process of crack initiation and growth. The results presented are believed to be critical steps in the development of a micromechanical model for the fracture of human dentin that takes into consideration the influence of both the microstructure and the local failure …
Date:
February 1, 2006
Creator:
Nalla, R. K.; Kinney, J. H. & Ritchie, R. O.
System:
The UNT Digital Library
On the fracture of human dentin: Is it stress- orstrain-controlled?
Despite substantial clinical interest in the fractureresistance of human dentin, there is little mechanistic information inarchival literature that can be usefully used to model such fracture. Infact, although the fracture event indent in, akin to other mineralizedtissues like bone, is widely believed to be locally strain-controlled,there has never been any scientific proof to support this belief. Thepresent study seeks to address this issue through the use of a novel setof in vitro experiments in Hanks' balanced salt solution involving adouble-notched bend test geometry, which is designed to discern whetherthe critical failure events involved in the onset of fracture are locallystress- or strain-controlled. Such experiments are further used tocharacterize the notion of "plasticity" in dentin and the interaction ofcracks with the salient microstructural features. It is observed thatfracture in dentin is indeed locally strain-controlled and that thepresence of dentinal tubules does not substantially affect this processof crack initiation and growth. The results presented are believed to becritical steps in the development ofa micromechanical model for thefracture of human dentin that takes into consideration the influence ofboth the microstructure and the local failure mode.
Date:
February 1, 2006
Creator:
Nalla, R. K.; Kinney, J. H. & Ritchie, R. O.
System:
The UNT Digital Library
Technology of Controlled Nuclear Fusion. Volume 4
Separate abstracts were prepared for the 35 included papers. (MOW)
Date:
January 1, 1976
Creator:
Kulcinski, G. L.
System:
The UNT Digital Library
International lighting in controlled environments workshop: Proceedings
Lighting is a central and critical aspect of control in environmental research for plant research and is gaining recognition as a significant factor to control carefully for animal and human research. Thus this workshop was convened to reevaluate the technology that is available today and to work toward developing guidelines for the most effective use of lighting in controlled environments with emphasis on lighting for plants but also to initiate interest in the development of improved guidelines for human and animal research. There are a number of established guidelines for lighting in human and animal environments. Development of new lighting guidelines is necessary for three reasons: (1) recent scientific discoveries show that in addition to supporting the sensation of vision, light has profound nonvisual biological and behavioral effects in both animals and humans; (2) federal regulations (EPACT 1992) are requiring all indoor environments to become more energy efficient with a specific emphasis on energy conservation in lighting; (3) lighting engineers and manufacturers have developed a wealth of new light sources and lighting products that can be applied in animal and human environments. The workshop was aimed at bringing together plant scientists and physical scientists to interact in the discussions. It …
Date:
December 31, 1994
Creator:
unknown
System:
The UNT Digital Library
Technology of Controlled Nuclear Fusion. Volume 3
Separate abstracts were prepared for each of the 30 included papers. (MOW)
Date:
January 1, 1976
Creator:
Kulcinski, G. L.
System:
The UNT Digital Library
Technology of Controlled Nuclear Fusion. Volume 1
Separate abstracts were prepared for each of the 28 included papers. (MOW)
Date:
January 1, 1976
Creator:
Kulcinski, G. L.
System:
The UNT Digital Library
TIP list
Subcontractors and vendors providing services, including the installation of purchased goods, are required to complete a TIP List. This list does not include every Environment, Safety, and Health (ES&H) related concern at LLNL. It is intended to highlight major concerns common to most on-site service activities.
Date:
June 22, 2006
Creator:
Ludwig, M E
System:
The UNT Digital Library
New advances in three-dimensional controlled-sourceelectromagnetic inversion
New techniques for improving both the computational andimaging performance of the three dimensional (3D) electromagnetic inverseproblem are presented. A non-linear conjugate gradient algorithm is theframework of the inversion scheme. Full wave equation modelling forcontrolled sources is utilized for data simulation along with anefficient gradient computation approach for the model update. Improvingthe modelling efficiency of the 3D finite difference method involves theseparation of the potentially large modelling mesh, defining the set ofmodel parameters, from the computational finite difference meshes usedfor field simulation. Grid spacings and thus overall grid sizes can bereduced and optimized according to source frequencies and source-receiveroffsets of a given input data set. Further computational efficiency isobtained by combining different levels of parallelization. While theparallel scheme allows for an arbitrarily large number of parallel tasks,the relative amount of message passing is kept constant. Imageenhancement is achieved by model parameter transformation functions,which enforce bounded conductivity parameters and thus prevent parameterovershoots. Further, a remedy for treating distorted data within theinversion process is presented. Data distortions simulated here includepositioning errors and a highly conductive overburden, hiding the desiredtarget signal. The methods are demonstrated using both synthetic andfield data.
Date:
May 19, 2007
Creator:
Commer, Michael & Newman, Gregory A.
System:
The UNT Digital Library
Design and evaluation of a microcomputer-controlled remote pipetter system
A remote pipetter has been designed and evaluated. The system is suitable for use in either a hot-cell or a glove-box environment and, therefore, is applicable in any situation where operating personnel must be separated from hazardous materials. The principle of operation for the pipetter is the displacement of liquid via a calibrated, screw-driven plunger. Variably sized aliquots of 1 to 1000 ..mu..L can be delivered. A steppng motor is used to move the plunger, and its position is verified with a linear variable differential transformer. The unit is controlled by a microcomputer. Besides the required operation sequences and error checking, a self-calibration check has been designed into the software. Measured accuracies and precisions of aliquot delivery are 0.4 and 0.2%, respectively.
Date:
January 1, 1981
Creator:
Goeringer, D. E. & Klatt, L. N.
System:
The UNT Digital Library
Controlled-air incineration of alpha-bearing solid wastes
The Los Alamos Scientific Laboratory is completing a study of controlled-air incineration (CAI) as a technique for volume reduction and stabilization of combustible transuranic-contaminated solid wastes. To demonstrate feasibility, a process has been assembled and operated on synthetic and contaminated combustibles. This paper summarizes the CAI project history, process design, provisions for radioactive operation, experimental results to date, and future plans. Achievements include operation at the design feed rate as well as combustion of separate feed compositions including cellulosics, polyethylene, polyvinyl chloride (PVC) and latex rubber. Refractory life has been satisfactory to date, with studies continuing. The offgas cleanup system has proven to be extremely effective; the final high-efficiency filters showing virtually no pressure drop increase. The ability of the system to process high concentrations of PVC has been demonstrated with no chloride-induced degradation detected. Chloride and sulfate removal from the offgas has been excellent with concentrations reaching 8 and 10 ppM maximum, respectively, in the process condensate.
Date:
January 1, 1980
Creator:
Koenig, R. A.; Draper, W. E.; Neuls, A. S. & Newmyer, J. M.
System:
The UNT Digital Library