Search NASA⌕ Search

SEARCH · Search NASA

Results for “Sharpen”

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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2021

SHARPEN: A Scheme to Restore the Distribution of Averaged Precipitation Fields

A key strategy in obtaining complete global coverage of high-resolution precipitation is to combine observations from multiple fields, such as the intermittent passive microwave observations, precipitation propagated in time using motion vectors, and geosynchronous infrared observations. These separate precipitation fields can be combined through weighted averaging, which produces estimates that are generally superior to the individual parent fields. However, the process of averaging changes the distribution of the precipitation values, leading to an increase in precipitating area and a decrease in the values of high precipitation rates, a phenomenon observed in IMERG. To mitigate this issue, we introduce a new scheme called SHARPEN (Scheme for Histogram Adjustment with Ranked Precipitation Estimates in the Neighborhood), which recovers the distribution of the averaged precipitation field based on the idea of quantile mapping applied to the local environment. When implemented in IMERG, precipitation estimates from SHARPEN exhibit a distribution that resembles that of the original instantaneous observations, with matching precipitating area and peak precipitation rates. Case studies demonstrate its improved ability in bridging between the parent precipitation fields. Evaluation against ground observations reveals a distinct improvement in precipitation detection skill, but also a slightly reduced correlation likely because of a sharper precipitation field. The increased computational demand of SHARPEN can be mitigated by striding over multiple grid boxes, which has only marginal impacts on the accuracy of the estimates. SHARPEN can be applied to any precipitation algorithm that produces an average from multiple input precipitation fields and is being considered for implementation in IMERG V07.

Jackson Tan↗
NASA NTRS1983

Image sharpening for mixed spatial and spectral resolution satellite systems

Two methods of image sharpening (reconstruction) are compared. The first, a spatial filtering technique, extrapolates edge information from a high spatial resolution panchromatic band at 10 meters and adds it to the low spatial resolution narrow spectral bands. The second method, a color normalizing technique, is based on the ability to separate image hue and brightness components in spectral data. Using both techniques, multispectral images are sharpened from 30, 50, 70, and 90 meter resolutions. Error rates are calculated for the two methods and all sharpened resolutions. The results indicate that the color normalizing method is superior to the spatial filtering technique.

Hallada, W. A.↗
NASA NTRS2005

Phase-Imaging with a Sharpened Multi-Walled Carbon Nanotube AFM Tip: Investigation of Low-k Dielectric Polymer Hybrids

Phase shift tapping mode scanning force microscopy (TMSFM) has evolved into a very powerful technique for the nanoscale surface characterization of compositional variations in heterogeneous samples. Phase shift signal measures the difference between the phase angle of the excitation signal and the phase angle of the cantilever response. The signal correlates to the tip-sample inelastic interactions, identifying the different chemical and/or physical property of surfaces. In general, the resolution and quality of scanning probe microscopic images are highly dependent on the size of the scanning probe tip. In improving AFM tip technology, we recently developed a technique for sharpening the tip of a multi-walled carbon nanotube (CNT) AFM tip, reducing the radius of curvature of the CNT tip to less than 5 nm while still maintaining the inherent stability of multi-walled CNT tips. Herein we report the use of sharpened (CNT) AFM tips for phase-imaging of polymer hybrids, a precursor for generating nanoporous low-k dielectrics for on-chip interconnect applications. Using sharpened CNT tips, we obtained phase-contrast images having domains less than 10 nm. In contrast, conventional Si tips and unsharpened CNT tips (radius greater than 15 nm) were not able to resolve the nanoscale domains in the polymer hybrid films. C1early, the size of the CNT tip contributes significantly to the resolution of phase-contrast imaging. In addition, a study on the nonlinear tapping dynamics of the multi-walled CNT tip indicates that the multi-walled CNT tip is immune to conventional imaging instabilities related to the coexistence of attractive and repulsive tapping regimes. This factor may also contribute to the phase-contrast image quality of multi-walled CNT AFM tips. This presentation will also offer data in support of the stability of the CNT tip for phase shift TMSFM.

Nguyen, Cattien V.↗
NASA NTRS1972

Image sharpening by holography.

Discussion of the physical and mathematical fundamentals, performance capabilities and potential applications of image deblurring by holography. It is shown that a blurred photograph may be deblurred and a sharpened image extracted from it because the 'blurring' in the original photograph did not irretrievably lose the imaging information, notably in the spatial-frequency regions required for faithful imaging and for high resolution. The principles of optical image deblurring are highly mathematical in nature. One of the most important applications of holographic image deblurring is shown to be the sharpening of electron micrographs of biological specimens beyond the ultimate that can be achieved with even the most powerful instruments available.

Stroke, G. W.↗
NASA NTRS1977

First observatory results with an image-sharpening telescope

Measurements of characteristic speckle change times are presented for stars observed with an image-sharpening telescope installed and operated on equatorial mounts at Leuschner Observatory in Lafayette, California, and Lick Observatory at Mount Hamilton, California. Despite the short speckle change times encountered, it was possible to record dramatically improved stellar images on nights when the speckles changes relatively slowly. Sharpened images of Sirius and Arcturus are discussed.

Buffington, A.↗
NASA NTRS1978

Sharpening stellar images

A prototype telescope system with six movable elements has been used with sharpness detection procedures to observe objects as dim as fifth magnitude. The real-time image sharpening technique does not rely on the use of a reference star. By correcting for atmospherically induced phase perturbations, the sharpening system has permitted restoration of stellar images to the diffraction limit (in one dimension) for a 30-cm telescope. Application of the system to the separation of double stars is reported.

Buffington, A.↗
NASA NTRS2011

Accurate Adaptive Level Set Method and Sharpening Technique for Three Dimensional Deforming Interfaces

In this paper, we demonstrate improved accuracy of the level set method for resolving deforming interfaces by proposing two key elements: (1) accurate level set solutions on adapted Cartesian grids by judiciously choosing interpolation polynomials in regions of different grid levels and (2) enhanced reinitialization by an interface sharpening procedure. The level set equation is solved using a fifth order WENO scheme or a second order central differencing scheme depending on availability of uniform stencils at each grid point. Grid adaptation criteria are determined so that the Hamiltonian functions at nodes adjacent to interfaces are always calculated by the fifth order WENO scheme. This selective usage between the fifth order WENO and second order central differencing schemes is confirmed to give more accurate results compared to those in literature for standard test problems. In order to further improve accuracy especially near thin filaments, we suggest an artificial sharpening method, which is in a similar form with the conventional re-initialization method but utilizes sign of curvature instead of sign of the level set function. Consequently, volume loss due to numerical dissipation on thin filaments is remarkably reduced for the test problems

Kim, Hyoungin↗
NASA NTRS2014

Chemical Sharpening, Shortening, and Unzipping of Boron Nitride Nanotubes

Boron nitride nanotubes (BNNTs), the one-dimensional member of the boron nitride nanostructure family, are generally accepted to be highly inert to oxidative treatments and can only be covalently modifi ed by highly reactive species. Conversely, it is discovered that the BNNTs can be chemically dispersed and their morphology modifi ed by a relatively mild method: simply sonicating the nanotubes in aqueous ammonia solution. The dispersed nanotubes are significantly corroded, with end-caps removed, tips sharpened, and walls thinned. The sonication treatment in aqueous ammonia solution also removes amorphous BN impurities and shortened BNNTs, resembling various oxidative treatments of carbon nanotubes. Importantly, the majority of BNNTs are at least partially longitudinally cut, or "unzipped". Entangled and freestanding BN nanoribbons (BNNRs), resulting from the unzipping, are found to be approximately 5-20 nm in width and up to a few hundred nanometers in length. This is the fi rst chemical method to obtain BNNRs from BNNT unzipping. This method is not derived from known carbon nanotube unzipping strategies, but is unique to BNNTs because the use of aqueous ammonia solutions specifi cally targets the B-N bond network. This study may pave the way for convenient processing of BNNTs, previously thought to be highly inert, toward controlling their dispersion, purity, lengths, and electronic properties.

Liao, Yunlong↗
NASA NTRS1974

Real-time correction of atmospherically degraded telescope images through image sharpening

We present a new technique for the correction of atmospheric distortion in telescope images. Most of this distortion arises from a random phase variation of the incoming light across the telescope aperture. This variation limits the resolving power of even large telescopes to about one arc second. If the sharpness of the images is defined in a suitable way, this sharpness is maximized only when the phase distortion of the incoming light is zero. We present computer simulations of a simple feedback system in which active optical elements, set to maximize the sharpness, correct most of the atmospheric distortion. Photon statistics set the limiting magnitude of the object for which a practical feedback system can work. Details in a sixth magnitude object smaller than 0.1 sec of arc should be resolvable. The system can be conveniently employed within existing telescopes.

Muller, R. A.↗
NASA NTRS1977

Sharpening ball-nose mill cutters

Economical attachment allows faster, more precise grinding. Vibrationless and rigid relation between grinding wheel and cutter allows for extremely high finish and accurate grinding. Leveling device levels flutes with respect to toolholder rotation that generates ball-nose radius. Constant relief around entire profile of cutting edge produces longer tool life.

Burch, C. F.↗
NASA NTRS1977

Process sharpens micrographic images

Photomicrographs produced by bright field illumination of surface coated with carbon deposited by ion glow discharge, are considerably sharper and reveal more detail than those made without coating or produced by scanning electron microscopy.

Eaton, A. F.↗
NASA NTRS1977

Correction of atmospheric distortion with an image-sharpening telescope

A 30 x 5 cm aperture telescope employing six movable mirrors to compensate for atmospherically induced phase distortion is built and tested. A feedback system adjusts the mirrors in real time to maximize the intensity of light passing through a narrow slit in the image plane. Essentially diffraction-limited performance is achieved when imaging both laser and white-light objects through 250 m of turbulent atmosphere. The behavior of the telescope is accurately predicted by computer simulations. The system has yet to achieve its full potential, but has already operated successfully for objects as dim as 5th magnitude.

Buffington, A.↗
NASA NTRS1983

Electrolytic Sharpening of Diode-Contact Whiskers

Phosphor bronze wire pointed without highly-toxic chemical reagents. Phosphor bronze wire to be pointed affixed to metal post held by fixture, such as pin vise. Fixture moved axially by micrometer allows precise control of position of end of wire with respect to surface of pointing solution. Solution consists of 4 weight percent sulfamic acid crystals in deionized water. Dissolution current adjusted via the autotransformer setting.

Green, G.↗
NASA NTRS2007

Infrared Imaging Sharpens View in Critical Situations

Innovative Engineering and Consulting (IEC) Infrared Systems, a leading developer of thermal imaging systems and night vision equipment, received a Glenn Alliance for Technology Exchange (GATE) award, half of which was in the form of additional NASA assistance for new product development. IEC Infrared Systems worked with electrical and optical engineers from Glenn's Diagnostics and Data Systems Branch to develop a commercial infrared imaging system that could differentiate the intensity of heat sources better than other commercial systems. The research resulted in two major thermal imaging solutions: NightStalkIR and IntrudIR Alert. These systems are being used in the United States and abroad to help locate personnel stranded in emergency situations, defend soldiers on the battlefield abroad, and protect high-value facilities and operations. The company is also applying its advanced thermal imaging techniques to medical and pharmaceutical product development with a Cleveland-based pharmaceutical company.

Source record↗
NASA NTRS2013

Interferometers Sharpen Measurements for Better Telescopes

Over the last decade, there have been a number of innovations that have made possible the largest and most powerful telescope of its time: the James Webb Space Telescope (JWST). Scheduled to launch in 2018, JWST will provide insight into what the oldest, most distant galaxies look like. When engineers build a first-of-its-kind instrument like the JWST, they often must make new tools to construct the new technology. Throughout the decades of planning, development, and construction of the JWST, NASA has worked with numerous partners to spur innovations that have enabled the telescope s creation. Though the JWST s launch date is still several years away, a number of these innovations are spinning off to provide benefits here on Earth. One of these spinoffs has emerged from the extensive testing the JWST must undergo to ensure it will function in the extreme environment of space. In order to test the JWST instruments in conditions that closely resemble those in space, NASA uses a cryogenic vacuum chamber. By dropping the temperatures down to -400 F and employing powerful pumps to remove air from the chamber, engineers can test whether the JWST instruments will function once the spacecraft leaves Earth. Traditionally, a phase-shifting interferometer is used to measure optics like the JWST s mirrors to verify their precise shape, down to tens of nanometers, during manufacturing. However, the large size of the mirrors, coupled with vibration induced by the cryo-pumps, prohibits the use of traditional phase-shifting interferometers to measure the mirrors within the chamber environment. Because the JWST will be located in deep space, far from any possible manned service mission, it was essential to find a robust solution to guarantee the performance of the mirrors.

Source record↗
NASA NTRS2014

The Lunar Magma Ocean: Sharpening the Focus on Process and Composition

The currently accepted model for the formation of the lunar anorthositic crust is by flotation from a crystallizing lunar magma ocean (LMO) shortly following lunar accretion. Anorthositic crust is globally distributed and old, whereas the mare basalts are younger and derived from a source region that has experienced plagioclase extraction. Several attempts at modelling such a crystallization sequence have been made [e.g. 1, 2], but our ever-increasing knowledge of the lunar samples and surface have raised as many questions as these models have answered. This abstract presents results from our ongoing ex-periments simulating LMO crystallization and address-ing a range of variables. We investigate two bulk com-positions, which span most of the range of suggested lunar bulk compositions, from the refractory element enriched Taylor Whole Moon (TWM) [3] to the more Earth-like Lunar Primitive Upper Mantle (LPUM) [4]. We also investigate two potential crystallization mod-els: Fully fractional, where crystallizing phases are separated from the magma as they form and sink (or float in the case of plagioclase) throughout magma ocean solidification; and a two-step process suggested by [1, 5] with an initial stage of equilibrium crystalliza-tion, where crystals remain entrained in the magma before the crystal burden increases viscosity enough that convection slows and the crystals settle, followed by fractional crystallization. Here we consider the frac-tional crystallization part of this process; the equilibri-um cumulates having been determined by [6].

Rapp, J. F.↗