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An application of mechanical leverage to microactuation
Preliminary results on the use of mechanical advantage to convert a short-displacement, high-force actuation mechanism into a long-displacement, medium-force actuator are presented. This micromechanical, mechanically-advantaged actuator is capable of relatively large displacement and force values. The target design values are lever ration of 17.5:1 leading to a {plus_minus}17.5 {mu}N of force throughout providing no less than 2.25 {mu}N of force throughout actuator`s range of motion for an applied voltage of less tan 50 volts. The basis for the mechanical advantage is simple levers with fulcrums.
Date:
December 31, 1994
Creator:
Sniegowski, J.J. & Smith, C.
Object Type:
Article
System:
The UNT Digital Library
Applications of Langevin and Molecular Dynamics methods
Computer simulation of complex nonlinear and disordered phenomena from materials science is rapidly becoming an active and new area serving as guide for experiments and for testing of theoretical concepts. This is especially true when novel massively parallel computer systems and techniques are used on these problems. In particular the Langevin dynamics simulation technique has proven useful in situations where the time evolution of a system in contact with a heat bath is to be studied. The traditional way to study systems in contact with a heat bath has been via the Monte Carlo method. While this method has indeed been used successfully in many applications, it has difficulty addressing true dynamical questions. Large systems of coupled stochastic ODEs (or Langevin equations) are commonly the end result of a theoretical description of higher dimensional nonlinear systems in contact with a heat bath. The coupling is often local in nature, because it reflects local interactions formulated on a lattice, the lattice for example represents the underlying discreteness of a substrate of atoms or discrete k-values in Fourier space. The fundamental unit of parallelism thus has a direct analog in the physical system the authors are interested in. In these lecture notes …
Date:
December 31, 1994
Creator:
Lomdahl, P.S.
Object Type:
Article
System:
The UNT Digital Library
Applications of SXPS for studying surface structure, reaction mechanisms and kinetics
Soft x-ray photoelectron spectroscopy (SXPS) from the S 2p core level has been used to study adsorbate induced reconstruction, identify reaction intermediates and study reaction kinetics on the Ni(111) surface. The S 2p binding energy is affected by the nature of the surface adsorption site. It has been determined from the number of S 2p states and their relative binding energies that adsorbed S induces a reconstruction of the Ni(111) surface and that the S adsorbs in fourfold sites on terraces and in troughs. S 2p SXPS has also been used to identify adsorbed species during the thermal decomposition of methanethiol on Ni(111). CH{sub 3}SH adsorbs as CH{sub 3}S{minus} at low temperatures. Above 200 K, the CH{sub 3}S{minus} changes adsorption site and the C-S bond begins to cleave. The relative concentrations of CH{sub 3}S{minus} in the two different sites and of atomic S have been monitored as a function of temperature and initial coverage. As a result of the sensitivity and resolution available in SXPS, reaction rates and kinetic parameters have been obtained for the decomposition of benzenethiol on Ni(111) by monitoring the changes in the surface composition continuously as a function of temperature and time.
Date:
December 31, 1994
Creator:
Mullins, D. R.; Huntley, D. R. & Overbury, S. H.
Object Type:
Article
System:
The UNT Digital Library
APS injector synchrotron low-level RF system design and test
We describe the control of the RF system for the injector synchrotron (booster) of the 7-GeV Advanced Photon Source. The rf system consists of one klystron and four 5-cell cavities of the LEP type. A block diagram of the system is shown and the low power rf circuitry is described. Voltage and phase feedback are discussed, along with accelerating the beam to 7 GeV. The accelerating voltage is programmed with a waveform generator. Although the acceleration is constant, the power at injection is almost zero and at extraction it is near 600 kW. The power increases with beam energy to replace synchrotron radiation losses. Stability of the rf phase between the two sides of the ring are discussed. Control signals are described which synchronize the bunch during injection from an accumulator ring and for extraction to the 352-MHz bucket in the storage ring. Timing for injection into any bucket in the Storage Ring is accomplished in the rf controls interface located on the VM cards. There is only one bunch accelerated in the booster at a time, so the beam loading of the cavities is negligible. Operating experience during early commissioning efforts will also be outlined.
Date:
December 31, 1994
Creator:
Stepp, J.D. & Bridges, J.F.
Object Type:
Article
System:
The UNT Digital Library
Aspects of macroscopic phase separation and interstitial oxygen ordering in oxygen doped La{sub 2}CuO{sub 4+{delta}}
NMR and neutron diffraction measurements reveal that macroscopic phase separation and the tetragonal to orthorhombic (TO) structural phase coincide at two distinct points in the temperature-doping phase plot for oxygen doped La{sub 2}CuO{sub 4+{delta}}. Thus the TO phase line coincides with the phase separation line. This is evidence that the macroscopic phase separation is inhibited in the tetragonal phase. We propose that the interstitial oxygen has higher mobility in the orthorhombic phase and that insufficient mobility suppresses macroscopic phase separation in the tetragonal phase. Neutron diffraction measurements also reveal superlattice peaks which indicate ordering of the interstitial oxygen. Our NMR measurements, have demonstrated a distribution of tilts of the CuO{sub 6} octahedra. We propose a sawtooth modulation of the octahedral tilt in which the sign of the tilt changes when the tilt reaches a maximum value can explain this distribution. The large openings in the La-O layer resulting from the abrupt switch of the sign of the tilt provide an attractive location for the interstitial oxygen. This mechanism would lead to stripe ordering of the interstitial oxygen.
Date:
December 31, 1994
Creator:
Hammel, P. C.; Fisk, Z.; Statt, B. W.; Chou, F. C.; Johnston, D. C.; Cheong, S. W. et al.
Object Type:
Article
System:
The UNT Digital Library
Assessing braze quality in the actively cooled Tore Supra Phase III outboard pump limiter
The quality of brazing of pyrolytic graphite armor brazed to copper tubes in Tore Supra`s Phase III Outboard Pump Limiter was assessed through pre-service qualification testing of individual copper/tile assemblies. The evaluation used non-destructive, hot water transient heating tests performed in the high-temperature, high-pressure flow loop at Sandia`s Plasma Materials Test Facility. Surface temperatures of tiles were monitored with an infrared camera as water at 120{degrees}C at about 2.07 MPa (300 psi) passed through a tube assembly initially at 30{degrees}C. For tiles with braze voids or cracks, the surface temperatures tagged behind those of adjacent well-bonded tiles. Temperature tags were correlated with flaw sizes observed during repairs based upon a detailed 2-D heat transfer analyses. {open_quotes}Bad{close_quotes} tiles, i.e., temperature tags of 10-20{degrees}C depending upon tile`s size, were easy to detect and, when removed, revealed braze voids of roughly 50% of the joint area. Eleven of the 14 tubes were rebrazed after bad tiles were detected and removed. Three tubes were rebrazed twice.
Date:
December 31, 1994
Creator:
Nygren, R. E.; Lutz, T. L.; Miller, J. D.; McGrath, R. & Dale, G.
Object Type:
Article
System:
The UNT Digital Library
Assessment of size-dependent mercury distribution in King Mackerel, Scomberomorus cavalla
The assessment of health risks from fish contamination and the issuance of advisories require accurate characterizations of the actual contaminant concentrations in fish of every relevant size. Such characterizations should not only contain statistical measures of location and variation, but provide a complete parameterization of the contaminant distribution for each given size class. This paper proposes two methods for determining such distributions from scatter diagrams of contaminant concentration versus fish length and illustrates them with an analysis of mercury contaminant in king mackerel, Scomberomorus cavalla. The first method consists of fitting contamination data with a family of S-distributions. This family shows trends in its defining parameter values, and these trends provide a comprehensive characterization of the measured contaminant concentrations. Each S-distribution has a rather simple mathematical structure from which one readily obtains secondary characteristics like quantiles, which are necessary for advanced simulation purposes. The second method takes into account that contaminant accumulation is the outcome of a metabolic process. When this process is modeled as a system of differential equations, it can be reformulated in such a way that it describes how the contaminant distribution changes over a given period of time. The resulting distributions have a more complicated structure …
Date:
December 31, 1994
Creator:
Voit, E. O. & Balthis, W. L.
Object Type:
Report
System:
The UNT Digital Library
Assessment of the performance of the SMERF indoor fire facility with the use of an active calorimeter
Tests with a water cooled calorimeter in the SMokE Reduction Facility (SMERF) at Sandia National Laboratories demonstrate that the facility is operational and ready for thermal regulatory testing of containers for radioactive materials. The facility is briefly described, and initial test results summarized.
Date:
December 31, 1994
Creator:
Koski, J. A.; Gill, W.; Kent, L. A. & Wix, S. D.
Object Type:
Article
System:
The UNT Digital Library
Atmospheric aerosol microphysics: Formation, characterization, and interaction. Progress report, September 1, 1991--February 28, 1994
This project conducts theoretical and computational studies of the physical transformation processes of aerosols which underlie their atmospheric formation, interaction, transport, and removal and derives results that contribute to improved capabilities for modelling aerosol physical and chemical evolution in support of the environmental component of the National Energy Strategy. The subject of study is submicrometer aerosol particles with primary focus upon the ultrafine fraction. This report summarizes technical progress during the first two and one-half years of the project. Results of calculations of equilibrium vapor pressures over adhering pairs of 50, 100, and 200 nm particles are reported showing substantial depression of equilibrium vapor pressure relative to isolated spheres. Calculations are given of collective, long-range intermolecular energies for irregular particles to be used for growth rate calculations for realistic particles. Molecular dynamic simulations of thermal collisions of small clusters with each other and with single atoms are presented as a function of cluster size in the range from 1 to 8 atoms. Calculations of aerosol condensation in which vapor depletion and heating effects are taken into account for atmospheric cloud nucleation modelling are reported.
Date:
December 31, 1994
Creator:
Marlow, W.H.
Object Type:
Report
System:
The UNT Digital Library
Atmospheric and dispersion modeling in areas of highly complex terrain employing a four-dimensional data assimilation technique
The results of this study indicate that the current data assimilation technique can have a positive impact on the mesoscale flow fields; however, care must be taken in its application to grids of relatively fine horizontal resolution. Continuous FDDA is a useful tool in producing high-resolution mesoscale analysis fields that can be used to (1) create a better initial conditions for mesoscale atmospheric models and (2) drive transport models for dispersion studies. While RAMS is capable of predicting the qualitative flow during this evening, additional experiments need to be performed to improve the prognostic forecasts made by RAMS and refine the FDDA procedure so that the overall errors are reduced even further. Despite the fact that a great deal of computational time is necessary in executing RAMS and LPDM in the configuration employed in this study, recent advances in workstations is making applications such as this more practical. As the speed of these machines increase in the next few years, it will become feasible to employ prognostic, three-dimensional mesoscale/transport models to routinely predict atmospheric dispersion of pollutants, even to highly complex terrain. For example, the version of RAMS in this study could be run in a ``nowcasting`` model that would …
Date:
December 31, 1994
Creator:
Fast, J. D. & O`Steen, B. L.
Object Type:
Article
System:
The UNT Digital Library
Atomic oxygen interaction with nickel multilayer and antimony oxide doped MoS{sub 2} films
Sputtered MoS{sub 2} is a solid lubricant capable of ultralow friction coefficients (below 0.05) load-bearing capacity. Since it exhibits low friction in vacuum, low outgassing rate, is non-migrating and lacks organic binders, this material is an attractive lubricant for space mechanisms. To exploit these new materials to their fullest potential, designers of space-based motion systems require data on the effects of atomic oxygen exposure on dense, sputtered MoS{sub 2}. This paper describes the effects of atomic oxygen in low earth orbit on the friction and surface composition of sputtered MoS{sub 2} films. Sputtered multilayer films of MoS{sub 2} with nickel (0.7 nm Ni per 10 nm MoS{sub 2}, for 1 {mu}m total film thickness), and MoS{sub 2} cosputtered with antimony oxide (nominally 2 {mu}m thick) were exposed to 2.2 to 2.5 x 10{sup 20} oxygen/cm{sup 2} over a period of 42.25 hours in earth orbit on the United States space shuttle. Identical specimens were kept as controls in desiccated storage for the duration of the mission, and another set was exposed to an equivalent fluence of atomic oxygen in the laboratory. The friction coefficient in air and vacuum, and the composition of worn surfaces, were determined prior to the shuttle …
Date:
December 31, 1994
Creator:
Dugger, M.T.
Object Type:
Article
System:
The UNT Digital Library
Atomistic study of energy and structure of surfaces in NiO
The structure and energy of surfaces in NiO have been studied by atomistic calculations employing short range Buckingham potentials fitted to properties of NiO. The polarizability of lattice anions is included by using the shell model. The results show that the surface energy depends strongly on surface orientation, and the 100 surface has the lowest energy. Surfaces with higher energy prefer to reconstruct into 100 facets to lower their energy and to stabilize their structure.
Date:
December 31, 1994
Creator:
Yan, M.; Chen, S. P.; Voter, A. F. & Mitchell, T. E.
Object Type:
Article
System:
The UNT Digital Library
Austenite to ferrite transformation kinetics during continuous cooling
The austenite decomposition has been investigated in a hypo-eutectoid plain carbon steel under continuous cooling conditions using a dilatometer and a Gleeble 1500 thermomechanical simulator. The experimental results were used to verify model calculations based on a fundamental approach for the dilute ternary systems Fe-C-Mn. The austenite to ferrite transformation start temperature can be predicted from a nucleation model for slow cooling rates. The formation of ferrite nuclei takes place with equilibrium composition on austenite grain boundaries. The nuclei are assumed to have a pill box shape in accordance with minimal interfacial energy. For higher cooling rates, early growth has to be taken into account to describe the transformation start. In contrast to nucleation, growth of the ferrite is characterized by paraequilibrium; i.e. only carbon can redistribute, whereas the diffusion of Mn is too slow to allow full equilibrium in the ternary system. However, Mn segregation to the moving ferrite-austenite interface has to be considered. The latter, in turn, exerts a solute drag effect on the boundary movement. Thus, growth kinetics is controlled by carbon diffusion in austenite modified by interfacial segregation of Mn. Employing a phenomenological segregation model, good agreement has been achieved with the measurements.
Date:
December 31, 1994
Creator:
Militzer, M.; Pandi, R. & Hawbolt, E.B.
Object Type:
Report
System:
The UNT Digital Library
Automatic differentiation: Obtaining fast and reliable derivatives -- fast
In this paper, the authors introduce automatic differentiation as a method for computing derivatives of large computer codes. After a brief discussion of methods of differentiating codes, they review automatic differentiation and introduce the ADIFOR (Automatic DIfferentiation of FORtran) tool. They highlight some applications of ADIFOR to large industrial and scientific codes (groundwater transport, CFD airfoil design, and sensitivity-enhanced MM5 mesoscale weather model), and discuss the effectiveness and performance of their approach. Finally, they discuss sparsity in automatic differentiation and introduce the SparsLinC library.
Date:
December 31, 1994
Creator:
Bischof, C. H.; Khademi, P. M.; Pusch, G. & Carle, A.
Object Type:
Article
System:
The UNT Digital Library
Autonomous, teleoperated, and shared control of robot systems
This paper illustrates how different modes of operation such as bilateral teleoperation, autonomous control, and shared control can be described and implemented using combinations of modules in the SMART robot control architecture. Telerobotics modes are characterized by different ``grids`` of SMART icons, where each icon represents a portion of run-time code that implements a passive control law. By placing strict requirements on the module`s input-output behavior and using scattering theory to develop a passive sampling technique, a flexible, expandable telerobot architecture is achieved. An automatic code generation tool for generating SMART systems is also described.
Date:
December 31, 1994
Creator:
Anderson, R.J.
Object Type:
Article
System:
The UNT Digital Library
Back surface cell structures for reducing recombination in CZ silicon solar cells
Mass-produced terrestrial CZ silicon solar cells are currently entering the domain in which bulk diffusion length is comparable to the cell thickness, so that recombination at the back surface can have a significant effect on device performance. Three manufacturable processes that address the problem of back recombination are examined here: boron diffusion from a deposited doped SiO{sub 2}, layer; Al-alloyed layers using screen-printed paste; and use of a collecting n* layer on the back interdigitated with the positive electrode. 104-cm{sup 2} cells fabricated at Siemens Solar Industries using these back surface structures are characterized by current-voltage, spectral response, photoconductivity decay, and SIMS measurements.
Date:
December 31, 1994
Creator:
King, R. R.; Mitchell, K. W. & Gee, J. M.
Object Type:
Article
System:
The UNT Digital Library
Baryon spectroscopy and the omega minus
In this report, I will mainly discuss baryon resonances with emphasis on the discovery of the {Omega}{sup {minus}}. However, for completeness, I will also present some data on the meson resonances which together with the baryons led to the uncovering of the SU(3) symmetry of particles and ultimately to the concept of quarks.
Date:
December 31, 1994
Creator:
Samios, N. P.
Object Type:
Article
System:
The UNT Digital Library
Base hydrolysis and hydrothermal processing of PBX-9404 explosive
Base hydrolysis in combination with hydrothermal processing has been proposed as an environmentally acceptable alternative to open burning/open detonation for degradation and destruction of high explosives. In this report, we examine gaseous and aqueous products of base hydrolysis of the HMX-based plastic bonded explosive, PBX-9404. We also examine products from the subsequent hydrothermal treatment of the base hydrolysate. The gases produced from hydrolysis of PBX-9404 are ammonia, nitrous oxide, and nitrogen. Major aqueous products are sodium formate, acetate, nitrate, and nitrite, but not all carbon products have been identified. Hydrothermal processing of base hydrolysate destroyed up to 98% of the organic carbon in solution, and higher destruction efficiencies are possible. Major gas products detected from hydrothermal processing were nitrogen and nitrous oxide.
Date:
December 31, 1994
Creator:
Sanchez, J. A.; Flesner, R. L.; Spontarelli, T.; Dell`Orco, P. C. & Kramer, J. F.
Object Type:
Report
System:
The UNT Digital Library
Base Program on Energy Related Research: Quarterly report, August 1-October 31, 1994
This document describes research performed at the Morgantown Energy Technology Center in the areas of oil and gas, advanced systems application, environmental technologies, applied energy science and remediation. The following subtasks are described: CROW{sup TM} Process Modeling, Development of a Portable Data Acquisition System and Coalbed Methane Simulator, Tank Bottom Waste Processing using the TaBoRR{sup TM} Process, Process Support and Development, Eastern Shale Oil Residue as an Asphalt Additive, Solid Waste Management, Remediation of Contaminated Soils, The Syn-Ag{sup TM} Process: Coal Combustion Ash Management Option, the Maxi-Acid{sup TM} Process: In- sit Amelioration of Acid Mine Drainage, Spill Test Facility Database, Heavy Oil/Plastics Co-Processing, Fossil Fuel and Hydrocarbon Conversion Using Hydrogen-Rich Plasmas, and North Site Remediation.
Date:
December 31, 1994
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library
Baseline design/economics for advanced Fischer-Tropsch technology. Quarterly report, July--September 1994
This report is Bechtel`s twelfth quarterly technical progress report and covers the period of July through September, 1994. All major tasks associated with the contract study have essentially been completed. Effort is under way in preparing various topical reports for publication. The objectives of this study are to: Develop a baseline design and two alternative designs for indirect liquefaction using advanced F-T technology. The baseline design uses Illinois No. 6 Eastern Coal and conventional refining. There is an alternative refining case using ZSM-5 treatment of the vapor stream from the slurry F-T reactor and an alternative coal case using Western coal from the Powder River Basin. Prepare the capital and operating costs for the baseline design and the alternatives. Individual plant costs for the alternative cases win be prorated on capacity, wherever possible, from the baseline case. Develop a process flowsheet simulation (PFS) model; establish the baseline design and alternatives; evaluate baseline and alternative economics; develop engineering design criteria; develop a process flowsheet simulation (PFS) model; perform sensitivity studies using the PFS model; document the PFS model and develop a DOE training session on its use; and perform project management, technical coordination and other miscellaneous support functions. Tasks 1, 2, …
Date:
December 31, 1994
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library
Beam dynamics group summary
This paper summarizes the activities of the beam dynamics working group of the LHC Collective Effects Workshop that was held in Montreux in 1994. It reviews the presentations that were made to the group, the discussions that ensued, and the consensuses that evolved.
Date:
December 31, 1994
Creator:
Peggs, S.
Object Type:
Article
System:
The UNT Digital Library
The behavior of matter under nonequilibrium conditions: Fundamental aspects and applications. Final report, April 15, 1991--July 14, 1994
The authors have introduced an extended formulation of dynamics which allows a clear distinction between temporal behavior of stable systems on one hand, chaotic and unstable systems on the other. For stable systems, the evolution is deterministic and time reversible. For chaotic and unstable systems it is probabilistic and breaks time-symmetry. The new formulation of dynamics incorporates the second law of thermodynamics and leads therefore to a great unification of physics. More precisely: (1) the authors found that unstable dynamical systems have new spectral decompositions in extended functional spaces. These spectral decompositions incorporate new characteristics of the time evolution associated with irreversibility; (2) these new spectral decompositions can be in general obtained iteratively through a well-defined algorithm; and (3) the method provides spectral decompositions of the time evolutions operator in the Liouville space of density matrices or distribution functions which cannot be implemented in the Hilbert space (wave functions) or by trajectories. In summary, they obtain an extension of classical and quantum mechanics. This extension leads to the inclusion of irreversibility into the framework of dynamics. Moreover, it also provides the theoretical basis for probabilistic predictions and control methods for complex systems, where the conventional deterministic predictions and control methods …
Date:
December 31, 1994
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library
Bench-scale demonstration of hot-gas desulfurization technology. Quarterly report, October 1 - December 31, 1994
The U.S. Department of Energy (DOE), Morgantown Energy Technology Center (METC), is sponsoring research in advanced methods for controlling contaminants in hot coal gasifier gas (coal gas) streams of integrated gasification combined-cycle (IGCC) power systems. The programs focus on hot-gas particulate removal and desulfurization technologies that match or nearly match the temperatures and pressures of the gasifier, cleanup system, and power generator. The work seeks to eliminate the need for expensive heat recovery equipment, reduce efficiency losses due to quenching, and minimize wastewater treatment costs. Hot-gas desulfurization research has focused on regenerable mixed-metal oxide sorbents which can reduce the sulfur in coal gas to less than 20 ppmv and can be regenerated in a cyclic manner with air for multicycle operation. Zinc titanate (Zn{sub 2}TiO{sub 4} or ZnTiO{sub 3}), formed by a solid-state reaction of zinc (ZnO) and titanium dioxide (TiO{sub 2}), is currently one of the leading sorbents. This report summarizes the highlights and accomplishments of the October slipstream test run of the Zinc Titanate Fluid Bed Desulfurization/Direct Sulfur Recovery Process (ZTFBD/DSRP) Mobile Laboratory at the Department of Energy`s Morgantown Energy Technology Center. Although the run had to be shortened due to mechanical problems with METC`s gasifier, there was …
Date:
December 31, 1994
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library
{beta}-Decay probing the electron bulk correlations
The theoretical approach based on the Boltzman-Langevin model is applied to study the thermal properties of the excitation phenomena in condensed matter. This approach making use of the advantages of the thermodynamic Green`s function method provides a tool for the self-consistent description of the many-body correlations. It is demonstrated that such a correlation modifies significantly the excitation strength properties of the electron gas. The resonant thermal effects in electron bulk excitation accompanying a radioactive decay in solids are discussed.
Date:
December 31, 1994
Creator:
Kondratyev, V.N. & Ayik, S.
Object Type:
Article
System:
The UNT Digital Library