Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “slicing”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Development of methods of producing large areas of silicon sheet by the slicing of silicon ingots using Inside Diameter (I.D.) saws

Modifications to a 16 inch STC automated saw included: a programmable feed system; a crystal rotating system; and a STC dynatrack blade boring and control system. By controlling the plating operation and by grinding the cutting edge, 16 inch I.D. blades were produced with a cutting edge thickness of .22 mm. Crystal rotation mechanism was used to slice 100 mm diameter crystals with a 16 inch blade down to a thickness of .20 mm. Cutting rates with crystal rotation were generally slower than with standard plunge I.D. slicing techniques. Using programmed feeds and programmed rotation, maximum cutting rates were from 0.3 to 1.0 inches per minute.

Aharonyan, P.↗
NASA NTRS1982

System for slicing wafers

A newly patented process for slicing silicon wafers that has distinct advantages over methods now widely used is described. The primary advantage of the new system is that it allows the efficient slicing of a number of ingots simultaneously at high speed. The cutting action is performed mechanically, most often with diamond particles that are transported to the cutting zone by a fluid vehicle or have been made an integral part of the blade by plating or impregnation. The new system uses a multiple or ganged band saw, arranged and spaced so that each side, or length, segment of a blade element, or loop, provides a cutting function. Each blade is maintained precisely in position by guides as it enters and leaves each ingot. The cutting action is performed with a conventional abrasive slurry composed of diamond grit suspended in an oil- or water-based vehicle. The distribution system draws the slurry from the supply reservoir and pumps it to the injection tubes to supply it to each side of each ingot. A flush system is provided at the outer end of the work-station zone. In order to reduce potential damage, a pneumatically driven flushing fluid is provided.

Source record↗
NASA NTRS1982

ID slicing and the automated factory

The automation of the slicing system utilizing internal-diameter saws for the production of the silicon wafers used in solar arrays is discussed. It is argued that saw productivity can be increased by reducing silicon waste, decreasing usage of consumables, keeping the saw slicing, and increasing the cutting speed. Several machine enhancements utilizing automatic control are discussed. The need for record keeping to anticipate maintenance operations is noted, and a digital serial communication interface with the microprocessor-based saws is recommended. Distributed control of the manufacturing process is discussed in detail, and is recommended as a method for increasing productivity.

Lewandowski, T.↗
NASA NTRS1980

Development of methods of producing large areas of silicon sheet by the slicing of silicon ingots using Inside-Diameter (I.D.) saws

Inside diametar wafering equipment, blades and processes were used to develop methods to produce large areas of silicon sheet. Modifications to a 16 inch STC automated saw included: programmable feed system, crystal rotating system, and STC dynatrack blade monitoring and control system. By controlling the plating operation and by grinding of the cutting edge, 16 inch ID blades with a cutting edge thickness of .22 mm can be produced. Crystal rotation mechanism was used to slice 100 mm diameter crystals with a 16 inch blade down to a thickness of .20 mm. Cutting rates with crystal rotation were generally slower than with standard plunge ID slicing techniques. Using programmed feeds and programmed rotation, maximum cutting rates were from 0.3 to 1.0 inches per minute.

Aharonyan, P.↗
NASA NTRS1984

X-radiography of slices of the Allende Meteorite

A 2.2 kg fragment of the Allende Meteorite was derinded and sliced by bandsawing. Several X-radiographs were made of all slices. The following features are resolved: grains of blocky troilite (bright spots), troilite rimmed chondrules (bright halos), chondrules with central vugs (dim halos), white aggregates (dark patches), and dark inclusions (medium dark patches). The number of FeS grains larger than about 0.5 mm is one per 6 + or - 1 gram of this fragment. Their concentration appears to be uniform at the 1 kg weight level, but is not uniform at the 100 g level. The number of FeS rimmed chondrules is one per 10 g. Their concentration is also nonuniform at the 100 g weight level. The number of white aggregates is roughly one per 20 g. These disc shaped objects show a distinct preferred orientation of the axis orthogonal to the plane of the disc. Chondrules with central vugs are numerous. Linear and curved arrays of chondrules, up to a few cm long, were observed. An interpretation of the observed features is given.

Smith, M. J.↗
NASA NTRS1988

The mean density and two-point correlation function for the CfA redshift survey slices

The effect of large-scale inhomogeneities on the determination of the mean number density and the two-point spatial correlation function were investigated for two complete slices of the extension of the Center for Astrophysics (CfA) redshift survey (de Lapparent et al., 1986). It was found that the mean galaxy number density for the two strips is uncertain by 25 percent, more so than previously estimated. The large uncertainty in the mean density introduces substantial uncertainty in the determination of the two-point correlation function, particularly at large scale; thus, for the 12-deg slice of the CfA redshift survey, the amplitude of the correlation function at intermediate scales is uncertain by a factor of 2. The large uncertainties in the correlation functions might reflect the lack of a fair sample.

De Lapparent, Valerie↗
NASA NTRS1989

Eight-Bit-Slice GaAs General Processor Circuit

Novel GaAs 8-bit slice enables quick and efficient implementation of variety of fast GaAs digital systems ranging from central processing units of computers to special-purpose processors for communications and signal-processing applications. With GaAs 8-bit slice, designers quickly configure and test hearts of many digital systems that demand fast complex arithmetic, fast and sufficient register storage, efficient multiplexing and routing of data words, and ease of control.

Weissman, John↗
NASA NTRS1988

Emission-line galaxies in the Slice of the Universe

The relative spatial distributions of emission-line galaxies (ELGs) and normal galaxies that lie in the sky area covered by the 'Slice' survey (de Lapparent et al., 1986) are considered. ELGs follow the same spatial distribution as found for the Slice galaxies, with the exception that they avoid the Coma cluster. It is pointed out that although the present ELGs are not shown to occur in regions of very low density, the luminosity distribution of the sample is such that luminosity/mass-dependent effects on the spatial distribution would not be noticeable.

Salzer, John J.↗
NASA NTRS1989

On the generation of a bubbly universe - A quantitative assessment of the CfA slice

A first attempt is made to calculate the properties of the matter distribution in a universe filled with overlapping bubbles produced by multiple explosions. Each spherical shell follows the cosmological Sedov-Taylor solution until it encounters another shell. Thereafter, mergers are allowed to occur in pairs on the basis of N-body results. At the final epoch, the matrix of overlapping shells is populated with 'galaxies' and the properties of slices through the numerically constructed cube compare well with CfA survey results for specified initial conditions. A statistic is found which measures the distance distribution from uniformly distributed points to the nearest galaxies on the projected plane which appears to provide a good measure of the bubbly character of the galaxy distribution. In a quantitative analysis of the CfA 'slice of the universe', a very good match is found between simulation and the real data for final average bubble radii of (13.5 + or - 1.5)/h Mpc with formal filling factor 1.0-1.5 or actual filling factor of 65-80 percent.

Ostriker, J. P.↗
NASA NTRS1990

IRAS galaxies and the large-scale structure in the CfA slice

The spatial distributions of the IRAS and the optical galaxies in the first CfA slice are compared. The IRAS galaxies are generally less clustered than optical ones, but their distribution is essentially identical to that of late-type optical galaxies. The discrepancy between the clustering properties of the IRAS and optical samples in the CfA slice region is found to be entirely due to the paucity of IRAS galaxies in the core of the Coma cluster. The spatial distributions of the IRAS and the optical galaxies, both late and early types, outside the dense core of the Coma cluster are entirely consistent with each other. This conflicts with the prediction of the linear biasing scenario.

Babul, Arif↗
NASA NTRS1990

Redshifts for fainter galaxies in the first CfA survey slice. II

Redshifts were measured for 96 galaxies in right ascension alpha between 8h and 17h declination delta between 30 and 31 deg, and with m(Zwicky) in the range 15.6-15.7. These correspond to 94 of the 96 entries in the Zwicky-Nilson merged catalog. The declination range delta between 29 deg and 31 deg is now complete to m(Zwicky) = 15.7. The structures in the first 6-deg-wide slice of the Center for Astrophysics redshift survey slice (delta between 26.5 and 32.5 deg are clearly defined in the 2-deg-wide slightly deeper sample; the fainter galaxies trace the structures defined by the brighter ones.

Wegner, Gary↗
NASA NTRS1989

Tryptophan availability modulates serotonin release from rat hypothalamic slices

The relationship between the tryptophan availability and serononin release from rat hypothalamus was investigated using a new in vitro technique for estimating rates at which endogenous serotonin is released spontaneously or upon electrical depolarization from hypothalamic slices superfused with a solution containing various amounts of tryptophan. It was found that the spontaneous, as well as electrically induced, release of serotonin from the brain slices exhibited a dose-dependent relationship with the tryptophan concentration of the superfusion medium.

Schaechter, Judith D.↗
NASA NTRS2001

"Cloud Slicing": A New Technique to Derive Upper Tropospheric Ozone from Satellite Measurements

A new technique called "cloud slicing" is introduced in this study to determine tropospheric ozone profile information. This method is unique because all previous methods incorporating satellite data were only capable of estimating the total column of ozone in the troposphere. Cloud slicing takes advantage of the opaque property of water vapor clouds to ultraviolet wavelength radiation. Measurements of above-cloud column ozone from the Nimbus 7 total ozone mapping spectrometer (TOMS) instrument are combined together with Nimbus 7 temperature humidity and infrared radiometer (THIR) cloud-top pressure data to derive ozone column amounts in the upper troposphere. In this study, tropical TOMS and THIR data for the period 1979-1984 are analyzed. Our investigation examines several case studies and illustrates the robust nature of this new technique for future satellite missions.

Chandra, Sushil↗
NASA NTRS2002

Upper Tropospheric Ozone Between Latitudes 60S and 60N Derived from Nimbus 7 TOMS/THIR Cloud Slicing

This study evaluates the spatial distributions and seasonal cycles in upper tropospheric ozone (pressure range 200-500 hPa) from low to high latitudes (60S to 60N) derived from the satellite retrieval method called "Cloud Slicing." Cloud Slicing is a unique technique for determining ozone profile information in the troposphere by combining co-located measurements of cloud-top, pressure and above-cloud column ozone. For upper tropospheric ozone, co-located measurements of Nimbus 7 Total Ozone Mapping Spectrometer (TOMS) above-cloud column ozone, and Nimbus 7 Temperature Humidity Infrared Radiometer (THIR) cloud-top pressure during 1979-1984 were incorporated. In the tropics, upper tropospheric ozone shows year-round enhancement in the Atlantic region and evidence of a possible semiannual variability. Upper tropospheric ozone outside the tropics shows greatest abundance in winter and spring seasons in both hemispheres with largest seasonal and largest amounts in the NH. These characteristics are similar to lower stratospheric ozone. Comparisons of upper tropospheric column ozone with both stratospheric ozone and a proxy of lower stratospheric air mass (i.e., tropopause pressure) from National Centers for Environmental Prediction (NCEP) suggest that stratosphere-troposphere exchange (STE) may be a significant source for the seasonal variability of upper tropospheric ozone almost everywhere between 60S and 60N except in low latitudes around 10S to 25N where other sources (e.g., tropospheric transport, biomass burning, aerosol effects, lightning, etc.) may have a greater role.

Ziemke, Jerald R.↗
NASA NTRS2004

A Long Data Record (1979-2003) of Stratospheric Ozone Derived from TOMS Cloud Slicing: Comparison with SAGE and Implications for Ozone Recovery

It is generally recognized that Stratospheric Aerosols and Gas Experiment (SAGE) stratospheric ozone data have become a standard long-record reference field for comparison with other stratospheric ozone measurements. This study demonstrates that stratospheric column ozone (SCO) derived from total ozone mapping spectrometer (TOMS) Cloud Slicing may be used to supplement SAGE data as a stand-alone long- record reference field in the tropics extending to middle and high latitudes over the Pacific. Comparisons of SAGE I1 version 6.2 SCO and TOMS version 8 Cloud Slicing SCO for 1984-2003 exhibit remarkable agreement in monthly ensemble means to within 1-3 DU (1 - 1.5% of SCO) despite being independently-calibrated measurements. An important component of our study is to incorporate these column ozone measurements to investigate long-term trends for the period 1979-2003. Our study includes Solar Backscatter Ultraviolet (SBW) version 8 measurements of upper stratospheric column ozone (i.e., zero to 32 hPa column ozone) to characterize seasonal cycles and seasonal trends in this region, as well as the lower stratosphere and troposphere when combined with TOMS SCO and total column ozone. The trend analyses suggest that most ozone reduction in the atmosphere since 1979 in mid-to-high latitudes has occurred in the Lower stratosphere below approx. 25 km. The delineation of upper and lower stratospheric column ozone indicate that trends in the upper stratosphere during the latter half of the 1979-2003 period have reduced to near zero globally, while trends in the lower stratosphere have become larger by approx. 5 DU decade%om the tropics extending to mid-latitudes in both hemispheres. For TCO, the trend analyses suggest moderate increases over the 25-year time record in the extra-tropics of both hemispheres of around 4-6 DU (Northern Hemisphere) and 6-8 DU (Southern Hemisphere).

Ziemke, Jerry R.↗
NASA NTRS2008

The Cloud Slicing Technique-Measuring the Unmeasureable

In satellite remote sensing clouds are usually considered an annoying interference. Satellite investigators go to unusual lengths to try to avoid clouds or to correct for their effects, and satellite data users routinely exclude cloudy data from analysis. Yet it was shown about a decade ago using TOMS data that for the study of tropospheric constituents, such as ozone, clouds can play a very beneficial role by allowing one to measure what otherwise cannot be directly measured from space. We call this technique "cloud Slicing". The so-called Convective Cloud Differential (CCD) method is one particular application of cloud slicing that has been applied successfully to data from TOMS and other similar satellite instruments to study the behavior of tropical tropospheric ozone at variety of spatial and temporal scales. However, there has been considerable confusion in the literature as to what exactly one measures from reflected sunlight instruments such as TOMS in cloudy atmospheres. We will discuss recently completed analysis of data taken by the Ozone Monitoring Instrument (OMI) on the Aura satellite in conjunction with several other instruments on the A-train satellite constellation to present new insight on how clouds affect absorption by aerosols and trace gases at reflected wavelengths (UV-SWIR). We will show several examples to illustrate how this insight is helping us to study the behavior of trace gases and aerosols in the atmosphere that cannot be studied by focusing only on cloud-free scenes.

Bhartia, P.↗
DOE OSTI2020

Multichannel dynamics in the OH+ n -butane reaction revealed by crossed-beam slice imaging and quasiclassical trajectory calculations

Multidimensional reactions present various channels that can exhibit very different dynamics and give products of varying subsequent reactivity. Here, we present a combination of experiment and theory to reveal the dynamics of hydrogen abstraction by OH radical at primary and secondary sites in n-butane at a collision energy of 8 kcal/mol. Crossed molecular beam slice imaging experiments unequivocally probe the secondary abstraction channel showing backward angular distributions with mild energy release to product translation, which are accurately captured by trajectory calculations using a specific-reaction-parameter Hamiltonian. Additionally, experiments containing both reaction channels indicate a less marked backward character in the angular distribution, whose origin is shown by trajectory calculations to appear as an evolution toward more sideways scattering from the secondary to primary channel. While the two channels have markedly different angular distributions, their energy release is largely comparable, showing ample energy release into the water product. The synergistic combination of crossed-beam imaging and trajectories opens the door to detailed reaction-dynamics studies of chemical reactions with ever-increasing complexity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Constructing Hubbard models for the hydrogen chain using sliced-basis density matrix renormalization group

Sliced-basis DMRG(sb-DMRG) is used to simulate a chain of hydrogen atoms and to construct low-energy effective Hubbard-like models. The downfolding procedure first involves a change of basis to a set of atom-centered Wannier functions constructed from the natural orbitals of the exact DMRG one-particle density matrix. The Wannier function model is then reduced to a fewer-parameter Hubbard-like model, whose parameters are determined by minimizing the expectation value of the Wannier Hamiltonian in the ground state of the Hubbard Hamiltonian. This indirect variational procedure not only yields compact and simple models for the hydrogen chain, but also allows us to explore the importance of constraints in the effective Hamiltonian, such as the restricting the range of the single-particle hopping and two-particle interactions, and to assess the reliability of more conventional downfolding. The entanglement entropy for a model's ground state, cut in the middle, is an important property determining the ability of DMRG and tensor networks to simulate the model, and here we study its variation with the range of the interactions. Counterintuitively, we find that shorter ranged interactions often have larger entanglement.

36 MATERIALS SCIENCE↗