186 research outputs found
Evaluation of selected chemical processes for production of low-cost silicon
Plant construction costs and manufacturing costs were estimated for the production of solar-grade silicon by the reduction of silicon tetrachloride in a fluidized bed of seed particles, and several modifications of the iodide process using either thermal decomposition on heated filaments (rods) or hydrogen reduction in a fluidized bed of seed particles. Energy consumption data for the zinc reduction process and each of the iodide process options are given and all appear to be acceptable from the standpoint of energy pay back. Information is presented on the experimental zinc reduction of SiCl4 and electrolytic recovery of zinc from ZnCl2. All of the experimental work performed thus far has supported the initial assumption as to technical feasibility of producing semiconductor silicon by the zinc reduction or iodide processes proposed. The results of a more thorough thermodynamic evaluation of the iodination of silicon oxide/carbon mixtures are presented which explain apparent inconsistencies in an earlier cursory examination of the system
Evaluation of selected chemical processes for production of low-cost silicon, phase 2
Potential designs for an integrated fluidized-bed reactor/zinc vaporizer/SiCl4 preheater unit are being considered and heat-transfer calculations have been initiated on versions of the zinc vaporizer section. Estimates of the cost of the silicon prepared in the experimental facility have been made for projected capacities of 25, 50, 75, and 100 metric ton of silicon. A 35 percent saving is obtained in going from 25 metric ton/year to the 50 metric ton/year level. This analysis, coupled with the recognition that use of two reactors in the 50 metric ton/year version allows for continued operation (at reduced capacity) with one reactor shut down, has resulted in a recommendation for adoption of an experimental facility capacity of 50 metric ton/year or greater. At this stage, the change to a larger size facility would not increase the design costs appreciably. In the experimental support program, the effects of seed bed particle size and depth were studied, and operation of the miniplant with a new zinc vaporizer was initiated, revealing the need for modification of the latter
The Impact of Color Graphic Report Formats on Decision Performance and Learning
One of the more common themes of the information systems literature involves the desirability of using graphics and col or to enhance the useful ness of reports and di spl ays. Very 1 ittl e empi rical research, however, has been di rected toward examining the real contribution of graphics and color to decision maker effectiveness; and, the findings of the few studies that have been undertaken are, at best, inconelusive. This paper reports on a laboratory experiment (using experienced internal auditors as subjects) that examines the contributions of color graphic outputs.on decision performance and learning. Significant resul ts were observed (controlling for individual differences) with color graphic reports proving advantageous with a simple, but not a compl ex, decl si on si tuati on
LSA silicon material task closed-cycle process development
The initial effort on feasibility of the closed cycle process was begun with the design of the two major items of untested equipment, the silicon tetrachloride by product converter and the rotary drum reactor for deposition of silicon from trichlorosilane. The design criteria of the initial laboratory equipment included consideration of the reaction chemistry, thermodynamics, and other technical factors. Design and construction of the laboratory equipment was completed. Preliminary silicon tetrachloride conversion experiments confirmed the expected high yield of trichlorosilane, up to 98 percent of theoretical conversion. A preliminary solar-grade polysilicon cost estimate, including capital costs considered extremely conservative, of $6.91/kg supports the potential of this approach to achieve the cost goal. The closed cycle process appears to have a very likely potential to achieve LSA goals
Evaluation of selected chemical processes for production of low-cost silicon phase 2. silicon material task, low-cost silicon solar array project
Progress from October 1, 1977, through December 31, 1977, is reported in the design of the 50 MT/year experimental facility for the preparation of high purity silicon by the zinc vapor reduction of silicon tetrachloride in a fluidized bed of seed particles to form a free flowing granular product
Pointing Guns
The American gun debate is increasingly populated with scenes of people pointing and otherwise displaying guns. What is the legal regime governing gun displays, and how well can it address the distinct social and legal problems they pose? In this Essay, we argue that the current structure of criminal law does not supply clear rules of conduct sufficient to avoid the negative effects of gun displays, and that the rhetorical and expressive effects of Second Amendment debates threaten to make the situation worse. We also suggest how the legal rules might be improved, and how battles over norms—as much as criminal prohibitions and defenses—will continue to shape both social practice and law when it comes to displays of firearms in public and towards other persons
Development of a chromium-thoria alloy
Low temperature ductility and high temperature strength of pure chromium and chromium-thoria alloy prepared from vapor deposited powder
Macrostates vs. Microstates in the Classical Simulation of Critical Phenomena in Quench Dynamics of 1D Ising Models
We study the tractability of classically simulating critical phenomena in the
quench dynamics of one-dimensional transverse field Ising models (TFIMs) using
highly truncated matrix product states (MPS). We focus on two paradigmatic
examples: a dynamical quantum phase transition (DQPT) that occurs in
nonintegrable long-range TFIMs, and the infinite-time correlation length of the
integrable nearest-neighbor TFIM when quenched to the critical point. For the
DQPT, we show that the order parameters can be efficiently simulated with
surprisingly heavy truncation of the MPS bond dimension. This can be used to
reliably extract critical properties of the phase transition, including
critical exponents, even when the full many-body state is not simulated with
high fidelity. The long-time correlation length near the critical point is more
sensitive to the full many-body state fidelity, and generally requires a large
bond dimension MPS. Nonetheless, we find that this can still be efficiently
simulated with strongly truncated MPS because it can be extracted from the
short-time behavior of the dynamics where entanglement is low. Our results
demonstrate that while accurate calculation of the full many-body state
(microstate) is typically intractable due to the volume-law growth of
entanglement, a precise specification of an exact microstate may not be
required when simulating phases of matter of many-body systems (macrostates).
We also study the tractability of simulation using truncated MPS based on
quantum chaos and equilibration in the models. We find a counterintuitive
inverse relationship, whereby local expectation values are most easily
approximated for chaotic systems whose exact many-body state is most
intractable.Comment: 6 sections, 4 appendices, 19 figure
ALUMINA COATING OF UO SHOT BY HYDROLYSIS OF ALUMINUM CHLORIDE VAPOR
Uniform, dense coatings of alumina about 5 to 150 mu thick were applied to uranium dioxide particles 44 to 350 mu in diameter by hydrolysis of aluminum chloride vapor in a fluidized bed of the particles at 1830 deg F. The coated particles were resistant to nitric acid leaching, to oxidation in 1830 deg F air, and to thermal cycling from 6OO to 2500 deg F. After low neutron exposures, the coated particles showed excellent fission-gas retention at temperatures up to 2400 deg F in inert gas. Although not optimized in the study, the coating process appears to have commercial feasibility. (auth
A Cross-Sectional Study of People with Epilepsy and Neurocysticercosis in Tanzania: Clinical Characteristics and Diagnostic Approaches.
Neurocysticercosis (NCC) is a major cause of epilepsy in regions where pigs are free-ranging and hygiene is poor. Pork production is expected to increase in the next decade in sub-Saharan Africa, hence NCC will likely become more prevalent. In this study, people with epilepsy (PWE, n=212) were followed up 28.6 months after diagnosis of epilepsy. CT scans were performed, and serum and cerebrospinal fluid (CSF) of selected PWE were analysed. We compared the demographic data, clinical characteristics, and associated risk factors of PWE with and without NCC. PWE with NCC (n=35) were more likely to be older at first seizure (24.3 vs. 16.3 years, p=0.097), consumed more pork (97.1% vs. 73.6%, p=0.001), and were more often a member of the Iraqw tribe (94.3% vs. 67.8%, p=0.005) than PWE without NCC (n=177). PWE and NCC who were compliant with anti-epileptic medications had a significantly higher reduction of seizures (98.6% vs. 89.2%, p=0.046). Other characteristics such as gender, seizure frequency, compliance, past medical history, close contact with pigs, use of latrines and family history of seizures did not differ significantly between the two groups. The number of NCC lesions and active NCC lesions were significantly associated with a positive antibody result. The electroimmunotransfer blot, developed by the Centers for Disease Control and Prevention, was more sensitive than a commercial western blot, especially in PWE and cerebral calcifications. This is the first study to systematically compare the clinical characteristics of PWE due to NCC or other causes and to explore the utility of two different antibody tests for diagnosis of NCC in sub-Saharan Africa
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