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1

Electron backscatter diffraction (EBSD) as a tool for detection of coral diagenesis  

NASA Astrophysics Data System (ADS)

Fine-scale structures of intact modern and fossil coralline skeletons were analysed to determine alteration to secondary cements and phases using electron backscatter diffraction (EBSD). EBSD analysis revealed secondary aragonite cements in endolithic borings in the modern skeleton and whole dissepiments of the fossil skeleton replaced by calcite, despite X-ray diffraction (XRD) bulk analysis of the general area suggesting only aragonite was present. Non-destructive, in situ screening of coral samples by EBSD analysis provides a valuable tool for assessing the extent of alteration and can determine which areas may produce more reliable climate proxy data.

Cusack, M.; England, J.; Dalbeck, P.; Tudhope, A. W.; Fallick, A. E.; Allison, N.

2008-12-01

2

Advanced microstructural analysis of ferrite materials by means of electron backscatter diffraction (EBSD)  

NASA Astrophysics Data System (ADS)

The analysis of the achieved texture is of great importance for the performance of ferrite materials, either bulk or thin films. The recently developed electron backscatter diffraction (EBSD) technique enables a spatially resolved study of the crystallographic orientations by means of recording of Kikuchi patterns. To our knowledge, such a thorough EBSD analysis was not yet performed in any oxidic magnetic material, and only very recently on magnetite thin films by us. A good surface polishing/cleaning is essential for this analysis, as the method requires an undisturbed surface area for a high image quality (IQ). This information is recorded to each measured Kikuchi pattern, together with a parameter describing the quality of indexation. Here, the spatially highly resolved EBSD mappings provide additional information as compared to the standard analysis techniques, which can contribute to an optimization of the growth process. Furthermore, an analysis of the grain aspect ratio is possible which provides further insight to the microstructural dependence of the magnetic properties of ferrites.

Koblischka-Veneva, A.; Koblischka, M. R.; Mücklich, F.

2010-05-01

3

Texture analysis of melt-spun Ni-Mn-Ga tapes by means of electron backscatter diffraction (EBSD)  

NASA Astrophysics Data System (ADS)

A texture analysis is performed by means of the electron-backscatter diffraction technique (EBSD) on melt-spun ribbon-like samples of the composition Ni52.5Mn24.5Ga23 (at.-%) were prepared. A dedicated surface treatment is required in order to achieve high quality Kikuchi patterns. For this purpose, mechanical polishing plus ion polishing was employed. EBSD analysis and transmission electron microscopy revealed that the samples have a polycrystalline, granular morphology, with grain sizes around 1 - 2 ?m. Several larger grains being present in the region selected for EBSD analysis, and many small grains are found, even embedded in the larger ones. The larger grains exhibit a common direction of elongation, yielding to a specific texture.

Koblischka-Veneva, A.; Koblischka, M. R.; Schmauch, J.; Mitra, A.; Panda, A. K.

2010-01-01

4

Monte Carlo simulation of spatial resolution for electron backscattered diffraction (EBSD) with application to two-phase materials  

SciTech Connect

The study of texture and grain boundary misorientation in multiphase materials has been greatly benefited from the recent automation of the electron back-scattered diffraction (EBSD) technique. With this technique, each phase in a multiphase material can be individually sampled and analyzed. This is of great significance and interest in the study of thin films, inclusions and multiphase alloys. Spatial resolution, which depends on experimental conditions such as beam energy and specimen tilt, and the material being studied, is critical in order to determine the orientation of different phases in multiphase materials. The Monte Carlo (MC) method has been effectively used to investigate spatial resolution in single phase materials. In this paper, the MC simulation is modified and applied to two-phase geometries, specifically an Al/Au specimen, and a 750 nm thick Au film on a SiO{sub 2} substrate.

Ren, S.X.; Kenik, E.A.; Alexander, K.B.

1997-10-01

5

Application of Electron Backscattered Diffraction (EBSD) and Atomic Force Microscopy (AFM) to Determine Texture, Microtexture, and Grain Boundary Energies in Ceramics  

SciTech Connect

Crystallographic orientations in alumina (Al203) and magnesium aluminate spinel (MgAl204) were obtained using electron backscattered diffraction (EBSD) patterns. The texture and mesotexture (grain boundary misorientations) were random and no special boundaries were observed. The relative grain boundary energies were determined by thermal groove geometries using atomic force microscopy (AFM) to identify relationships between the grain boundary energies and misorientations.

Glass, S.J.; Rohrer, G.S.; Saylor, D.M.; Vedula, V.R.

1999-05-19

6

Texture analysis of monofilamentary, Ag-sheathed (Pb,Bi)2Sr2Ca2Cu3Ox tapes by electron backscatter diffraction (EBSD)  

NASA Astrophysics Data System (ADS)

Using automated orientation imaging, the grain orientations and texture of monofilamentary, Ag-sheathed (Pb,Bi)2Sr2Ca2Cu3Ox (Bi-2223) tape is analysed in detail by means of electron backscatter diffraction (EBSD). The achieved high image quality of the Kikuchi patterns enables multi-phase scans including Bi-2223, Bi2Sr2CaCu2Ox, Bi2Sr2CuOx, (Sr,Ca)14Cu24O41 and Ag to be performed. Two areas are selected for the EBSD analysis, one close to the silver sheath, the other located in the center of the sample. The grain orientation maps are presented for each phase separately allowing a new insight into the microtexture of Ag-sheathed Bi-2223 tapes. Furthermore, the EBSD analysis provides the possibility for a misorientation angle analysis within each individual phase.

Koblischka-Veneva, A.; Koblischka, M. R.; Qu, T.; Han, Z.; Mücklich, F.

2008-02-01

7

Study of ferrous corrosion products on iron archaeological objects by electron backscattered diffraction (EBSD)  

NASA Astrophysics Data System (ADS)

The corrosion of iron-based archaeomaterials in anoxic environments leads mainly to Fe(II) compounds, like the hydroxychloride ?-Fe2(OH)3Cl, chukanovite Fe2(OH)2CO3 or siderite FeCO3. The understanding of the mechanisms then necessarily implies a thorough investigation of the chemical, mechanical and morphological characteristics of the Fe(II)-based layer that develops between the metal surface and the environment. In the peculiar case of Fe(II) compounds, generally very reactive towards O2, the main concern is to prevent any transformation by air during the analysis. The EBSD technique is adapted on a scanning electron microscope (SEM) where the samples are analysed under vacuum and consequently sheltered from air. Different options offered by EBSD for phase characterisation and microstructural study were tested for the first time on the rust layers of two archaeological iron nails. Results were confronted to those obtained by micro-Raman spectroscopy, which was used as reference method. Magnetite, Fe(II) hydroxychloride ?-Fe2(OH)3Cl and siderite were analysed successfully but improvements have to be brought for the study of other compounds such as iron oxyhydroxides and chukanovite. The choice of experimental parameters in our approach as well as the potentialities and limits of the technique for this kind of application are discussed.

Azoulay, Ilanith; Conforto, Egle; Refait, Philippe; Rémazeilles, Céline

2013-02-01

8

Microtexture determination by electron back-scatter diffraction  

Microsoft Academic Search

This review describes the use of an experimental technique known as electron back-scatter diffraction (EBSD) to measure microtexture, that is, spatially specific texture measured on an individual orientation basis. Other methods of microtexture determination are briefly described and compared with EBSD. The EBSD technique itself is described in considerable detail including recent developments such as on-line automation. Those EBSD-based microtexture

D. J. Dingley; V. Randle

1992-01-01

9

Quantitative metallography by electron backscattered diffraction.  

PubMed

Although electron backscattered diffraction (EBSD) in the scanning electron microscope is used mainly to investigate the relationship between local textures and microstructures, the technique has now developed to the stage where it requires serious consideration as a tool for routine quantitative characterization of microstructures. This paper examines the application of EBSD to the characterization of phase distributions, grain and subgrain structures and also textures. Comparisons are made with the standard methods of quantitative metallography and it is shown that in many cases EBSD can produce more accurate and detailed measurements than the standard methods and that the data may sometimes be obtained more rapidly. The factors which currently limit the use of EBSD for quantitative microstructural characterization, including the speed of data acquisition and the angular and spatial resolutions, are discussed, and future developments are considered. PMID:10460682

Humphreys

1999-09-01

10

Electron backscatter diffraction: Strategies for reliable data acquisition and processing  

SciTech Connect

In electron backscatter diffraction (EBSD) software packages there are many user choices both in data acquisition and in data processing and display. In order to extract maximum scientific value from an inquiry, it is helpful to have some guidelines for best practice in conducting an EBSD investigation. The purpose of this article therefore is to address selected topics of EBSD practice, in a tutorial manner. The topics covered are a brief summary on the principles of EBSD, specimen preparation, calibration of an EBSD system, experiment design, speed of data acquisition, data clean-up, microstructure characterisation (including grain size) and grain boundary characterisation. This list is not meant to cover exhaustively all areas where EBSD is used, but rather to provide a resource consisting of some useful strategies for novice EBSD users.

Randle, Valerie, E-mail: v.randle@swansea.ac.uk [Materials Research Centre, School of Engineering, Swansea University, Swansea SA2 8PP (United Kingdom)

2009-09-15

11

Validation of three-dimensional diffraction contrast tomography reconstructions by means of electron backscatter diffraction characterization  

PubMed Central

Microstructure reconstructions resulting from diffraction contrast tomography data of polycrystalline bulk strontium titanate were reinvestigated by means of electron backscatter diffraction (EBSD) characterization. Corresponding two-dimensional grain maps from the two characterization methods were aligned and compared, focusing on the spatial resolution at the internal interfaces. The compared grain boundary networks show a remarkably good agreement both morphologically and in crystallographic orientation. Deviations are critically assessed and discussed in the context of diffraction data reconstruction and EBSD data collection techniques.

Syha, Melanie; Trenkle, Andreas; Lodermann, Barbara; Graff, Andreas; Ludwig, Wolfgang; Weygand, Daniel; Gumbsch, Peter

2013-01-01

12

Crystallographic orientation assessment by electron backscattered diffraction.  

PubMed

With an angular orientation accuracy of at least 1 , the ability of electron backscattered diffraction (EBSD) to determine and emphasise crystallographic orientation is illustrated. Using the abilities of specially developed software for computing Euler angles derived from the scanned specimen, misorientations are pointed out with acceptable flexibility and graphic output through crystallographic orientation maps or pole figures. This ability is displayed in the particular case of laser cladding of nickel-based superalloy, a process that combines the advantages of a near net-shape manufacturing and a close control of the solidification microstructure (E-LMF: epitaxial laser metal forming). PMID:10483877

Cléton, F; Jouneau, P H; Henry, S; Gäumann, M; Buffat, P A

13

Present State of Electron Backscatter Diffraction and Prospective Developments  

Microsoft Academic Search

Electron backscatter diffraction (EBSD), when employed as an additional characterization technique to a scanning electron microscope (SEM), enables individual grain orientations, local texture, point-to-point orientation correlations, and phase identification and distributions to be determined routinely on the surfaces of bulk polycrystals. The application has experienced rapid acceptance in metallurgical, materials, and geophysical laboratories within the past decade (Schwartz et al.

Robert A. Schwarzer; David P. Field; Brent L. Adams; Mukul Kumar; Adam J. Schwartz

2008-01-01

14

Electron backscatter diffraction: applications for nuclear materials.  

PubMed

The diffraction of electrons was first observed in 1928 by Kikuchi. The phenomenon results in the formation of characteristic diagrams of the crystalline lattice and the orientation of the phase. Backscattered electrons are diffracted by the different crystallographic planes (hkl) according to the Bragg angle thetab. These describe, by symmetry, two cones of axes normal to the diffracting plane. Information is collected on a phosphor screen, leading to the acquisition of a diffraction pattern called a Kikuchi diagram. Several improvements now give a wide range of applications such as phase identification (carbides or complex compounds in a (U,Zr,O) structure), analysis of materials interfaces (ZrO2/UO2), as well as solidification studies and local texture determination (molybdenum sheets). In these applications, EBSD, as a type of quantitative metallography, is a powerful tool. PMID:10460689

Medevielle; Hugon; Dugne

1999-09-01

15

Present State of Electron Backscatter Diffraction and Prospective Developments  

SciTech Connect

Electron backscatter diffraction (EBSD), when employed as an additional characterization technique to a scanning electron microscope (SEM), enables individual grain orientations, local texture, point-to-point orientation correlations, and phase identification and distributions to be determined routinely on the surfaces of bulk polycrystals. The application has experienced rapid acceptance in metallurgical, materials, and geophysical laboratories within the past decade (Schwartz et al. 2000) due to the wide availability of SEMs, the ease of sample preparation from the bulk, the high speed of data acquisition, and the access to complementary information about the microstructure on a submicron scale. From the same specimen area, surface structure and morphology of the microstructure are characterized in great detail by the relief and orientation contrast in secondary and backscatter electron images, element distributions are accessed by energy dispersive spectroscopy (EDS), wavelength dispersive spectroscopy (WDS), or cathodoluminescence analysis, and the orientations of single grains and phases can now be determined, as a complement, by EBSD.

Schwarzer, R A; Field, D P; Adams, B L; Kumar, M; Schwartz, A J

2008-10-24

16

The backscatter electron signal as an additional tool for phase segmentation in electron backscatter diffraction.  

PubMed

The advent of simultaneous energy dispersive X-ray spectroscopy (EDS) data collection has vastly improved the phase separation capabilities for electron backscatter diffraction (EBSD) mapping. A major problem remains, however, in distinguishing between multiple cubic phases in a specimen, especially when the compositions of the phases are similar or their particle sizes are small, because the EDS interaction volume is much larger than that of EBSD and the EDS spectra collected during spatial mapping are generally noisy due to time limitations and the need to minimize sample drift. The backscatter electron (BSE) signal is very sensitive to the local composition due to its atomic number (Z) dependence. BSE imaging is investigated as a complimentary tool to EDS to assist phase segmentation and identification in EBSD through examination of specimens of meteorite, Cu dross, and steel oxidation layers. The results demonstrate that the simultaneous acquisition of EBSD patterns, EDS spectra, and the BSE signal can provide new potential for advancing multiphase material characterization in the scanning electron microscope. PMID:23575349

Payton, E J; Nolze, G

2013-04-10

17

Multivariate statistical approaches for electron backscattered diffraction.  

SciTech Connect

Electron backscattered diffraction (EBSD) is a widely used technique for both identifying the crystallographic phase and for mapping the orientation of crystalline materials on the micron length scale. Often the operating conditions necessary for phase identification are not suitable for orientation mapping and vice versa. In an effort to optimize the speed involved in the mapping technique, pattern quality is sacrificed and the wealth of information present in an EBSD pattern is compressed to basically 4 values: a matched phase and three Euler angles. However, ab initio identification of phases from EBSD patterns requires high quality patterns and fairly intense computation. Spectrum imaging is an analytical approach that may offer some solutions to the aforementioned problems. Spectrum imaging consists of collecting a whole spectrum at each pixel in a mapping style measurement. This large set of data is then analyzed using multivariate statistical analysis (MSA) techniques such as principle components analysis, multivariate curve resolution, or other least squares based techniques. The result of these calculations is a set of component spectral shapes with corresponding abundances that allow the analyst to extract the greatest amount of physically relevant information from an otherwise enormous data set. Spectrum imaging has been used successfully in EDX microanalysis (both in the SEM and TEM), TOF-SIMS, WDS, and EELS. To examine the potential benefits of the spectrum imaging approach for EBSD data, a series of basic experiments and calculations were run. Test data sets (20 x 20 patterns in .jpeg format) on polycrystalline Al and on the directionally solidified eutectic oxide, CoO/ZrO{sub 2}(CaO), were collected using the HKL Channel 5 system with a Nordlys detector under normal mapping conditions. The data was collected on a FEI dual beam FIB (model DB235) and a Zeiss (Supra 55 VP) SEM at 20keV for Al and CoO/ZrO{sub 2}(CaO), respectively. The data sets were analyzed according to the schematic shown in Figure 1. Each EBSD pattern was hough transformed, unzipped into a 1-D vector of channels with intensities ranging from 0-255, and then added to an overall data matrix. A range of treatments (edge/no edge detection, spatial simplicity/spectral simplicity, etc.) were examined to determine the optimal way of treating the data. The multivariate analyses were performed using the AXSIA code developed at Sandia National Laboratories. The MSA techniques were able to correctly identify individual grains in the Al sample and individual phases in the CoO/ZrO{sub 2}(CaO) sample. For each component EBSD pattern identified from the Al data, a corresponding color map of abundance can be seen which clearly corresponds to a single grain (Figure 2). The success in the CoO/ZrO{sub 2}(CaO) sample is particularly notable due to both phases sharing the Fm-3m space group which would confuse most autoindexing routines. The range of analytical treatments identified two extremes in results: a minimal number of components (patterns) with only kikuchi line positions present or a larger number of components with full intensity information present. The further application of these results to phase mapping will be discussed.

Michael, Joseph Richard; Brewer, Luke N.; Kotula, Paul Gabriel

2005-07-01

18

Electron backscatter diffraction of grain and subgrain structures - resolution considerations.  

PubMed

Characterization of microstructures containing small grains or low-angle grain boundaries by electron backscattered diffraction (EBSD) is limited by the spatial and angular resolution limits of the technique. It was found that the best effective spatial resolution (60 nm) for aluminium alloys in a tungsten-filament scanning electron microscope (SEM) was obtained for an intermediate probe current which provided a compromise between pattern quality and specimen interaction volume. The same specimens and EBSD equipment when used with a field-emission gun SEM showed an improvement in spatial resolution by a factor of 2-3. For characterizing low-angle boundary microstructures, the precision of determining relative orientations is a limiting factor. It was found that the orientation noise was directly related to the probe current and this was interpreted in terms of the effect of probe current on the quality of the diffraction patterns. PMID:10460686

Humphreys; Huang; Brough; Harris

1999-09-01

19

Electron backscatter diffraction of plutonium-gallium alloys  

SciTech Connect

At Los Alamos National Laboratory a recent experimental technique has been developed to characterize reactive metals, including plutonium arid cerium, using electron backscatter diffraction (EBSD). Microstructural characterization of plutonium and its alloys by EBSD had been previously elusive primarily because of the extreme toxicity and rapid surface oxidation rate associated with plutonium metal. The experimental techniques, which included ion-sputtering the metal surface using a scanning auger microprobe (SAM) followed by vacuum transfer of the sample from the SAM to the scanning electron microscope (SEM), used to obtain electron backscatter diffraction Kikuchi patterns (EBSPs) and orientation maps for plutonium-gallium alloys are described and the initial microstructural observations based on the analysis are discussed. Combining the SEM and EBSD observations, the phase transformation behavior between the {delta} and {var_epsilon} structures was explained. This demonstrated sample preparation and characterization technique is expected to be a powerful means to further understand phase transformation behavior, orientation relationships, and texlure in the complicated plutonium alloy systems.

Boehlert, C. J. (Carl J.); Zocco, T. G. (Thomas G.); Schulze, R. K. (Roland K.); Mitchell, J. N. (Jeremy N.); Pereyra, R. A. (Ramiro A.)

2002-01-01

20

Electron backscatter diffraction of MgB2  

NASA Astrophysics Data System (ADS)

MgB2 is one of important new functional materials, which can play significant role in emerging Hydrogen Economy. If adopted, Hydrogen Economy would be a low-CO2 fossil-fuels-free answer to the current and future energy demands. To contribute to this economy, advanced methods of MgB2 preparation and an insight into its properties are required. This paper reports electron backscatter diffraction (EBSD) of dense polycrystalline MgB2 prepared by Hot Isostatic Pressing and Resistive Sintering. The EBSD study was performed in combination with polarised optical microscopy, scanning electron microscopy, transmission electron microscopy, atomic force microscopy and scanning conductivity probe microscopy. The superconducting properties were measured in order to select specimens with highest critical current density to associate this density with structural features of the samples. The investigation shows importance of twist grain boundaries in increasing critical current density in MgB2.

Mikheenko, P.

2012-07-01

21

Feldspar fabrics in a greenschist facies albite-rich mylonite from electron backscatter diffraction  

Microsoft Academic Search

The current database of plagioclase CPOs in naturally deformed rocks is small and is not supported by CPOs from experimentally deformed rocks or by numerical modelling so that the current understanding of plagioclase CPOs is limited. Electron backscatter diffraction (EBSD) has the potential of measuring the full crystallographic orientation of small domains of any crystalline material, including plagioclase. We generate

David J Prior; John Wheeler

1999-01-01

22

Electron backscatter diffraction microstructure investigations of electronic materials down to the nanoscale  

Microsoft Academic Search

In this paper, the application of electron backscatter diffraction (EBSD) methods to materials used for common microelectronic interconnection technologies is demonstrated with particular emphasis to lead-free soldered interfaces and thermosonic wire bond interconnects. Here, the paper focuses on the quantitative analysis of grain orientation, grain size and grain distribution of SAC as well as gold, aluminum and copper bonding wire

M. Krause; B. Ma?rz; C. Dresbach; M. Petzold

2010-01-01

23

On slip band features and crack initiation in fatigued 316L austenitic stainless steel: Part 1: Analysis by electron back-scattered diffraction and atomic force microscopy  

Microsoft Academic Search

Electron back-scattered diffraction (EBSD) and atomic force microscopy (AFM) have been used to study surface slip features on 316L austenitic stainless steel polycrystals tested in the low cycle fatigue range. EBSD investigations allow activated slip planes to be identified for each grain and the local inclination of these slip planes to the surface to be calculated. AFM allows the height

P. Villechaise; L. Sabatier; J. C. Girard

2002-01-01

24

Ultrasonic Characterization of Texture in Rolled Aluminium Correlated with Electron Backscatter Diffraction Measurements  

SciTech Connect

Electron Backscatter Diffraction (EBSD) is a microscopic technique that provides detailed crystallographic orientation and microstructural information, allowing for accurate measurement of such properties like average grain size. In order to validate and better understand what information an ultrasonic technique can give us we are correlating the ultrasonic measurements with those from EBSD. It generates an appreciation of the limitations of both techniques, and what each can reasonably deliver. We describe a technique to extrapolate the three independent orientation distribution coefficients (ODCs) for cubic structures W400, W420 and W440 from the Bunge-Euler angle data from EBSD scans. Preliminary EBSD results for thin rolled aluminium sheet are discussed and compared to the ODCs determined on the same sample using an ultrasonic EMAT-EMAT S0 Lamb wave measurement system.

Essex, S. D.; Potter, M. D. G.; Dixon, S. [University of Warwick, Dept. of Physics, Coventry. CV4 7AL (United Kingdom)

2007-03-21

25

Electron backscatter diffraction in conservation science: phase identification of pigments in paint layers.  

PubMed

Electron backscatter diffraction (EBSD) was used in Conservation Science for characterization of ancient materials collected from works of art. The results demonstrate the feasibility of EBSD analysis on heterogeneous matrices as very small samples of paint layers collected from paintings. Two reference pigments were selected from those used by artists to investigate the relationship existing between EBSD pattern quality and properties of the investigated material (i.e., average atomic number, density, and Mohs hardness). The technique was also tested to investigate the pigment phases on two real samples collected from Romanino's Santa Giustina altarpiece, an oil on wood painting dated 1514 (Civic Museum, Padova, Italy). Results show for the first time the acquisition of EBSD patterns from painting samples mounted in resin, i.e., painting cross sections, opening a new powerful tool to elucidate the pigment phases avoiding large sampling on works of arts and to further study the complex mechanisms of pigment deterioration. PMID:23663448

Gambirasi, A; Peruzzo, L; Bianchin, S; Favaro, M

2013-05-13

26

Improving Phyllosilicate Electron Backscatter Diffraction Data Using Ion Milling  

NASA Astrophysics Data System (ADS)

Phyllosilicates are difficult phases to characterize using electron backscatter diffraction (EBSD), as they tend to yield poor diffraction patterns. The underlying cause of this problem is under debate, however, prior studies point to poor sample surface preparation and problems inherent in the phyllosilicate structure. Traditional protocol for sample surface preparation for EBSD involves stepwise mechanical polishing followed by chemical mechanical polishing. Although variations of this procedure have proven relatively successful, problems still exist when preparing polyphase materials that pair soft and hard phases, i.e. mica and quartz. Ion milling is a technique ideally suited for EBSD sample preparation as it offers the ability to smooth sample surface topography and remove subsurface damage induced by mechanical polishing. We explore the viability of this method as a final step in preparing polyphase, mica-bearing geological materials for EBSD analysis. We prepared a suite of samples using a combination of mechanical and chemical mechanical polishing. The samples were collected from the Northern Mylonite Zone of the Cheyenne Belt in southern Wyoming and include mylonitic muscovite-kyanite quartzite and garnet-muscovite-biotite schist. Three thin sections of each lithology were cut in different orientations according to a kinematic reference frame in an effort to introduce orientational variability to our data and to determine whether an optimal orientation exists for acquiring electron backscatter diffraction patterns (EBSPs) from mica. EBSD data were collected on each sample using an FEI Nova 600i scanning electron microscope with an EDAX-TSL EBSD attachment. All working conditions and data collection areas were carefully noted for reproducibility. Sample surface topography, likely caused by preferential mechanical polishing of softer phases, was exaggerated in our sections and is responsible for relatively poor initial EBSD data. Ion milling, using the South Bay Technology, Inc. IBS/e ion beam sputter deposition and etching system, at high energy (600eV, 5.0mA) and low incident angle (4 degrees) while oscillating our sample for 20 minutes was used in an attempt to reduce topography. This was followed by a low energy step (250eV, 2.0mA, 20 minutes) to remove any damage imparted by prior polishing. Samples undergoing this treatment show an increase in surface topography and a decrease in the overall image quality of EBSPs. Sample surface topography was a limiting factor in our experiment, forcing us to examine before and after EBSD data within individual phases. Samples showing overall image quality improvement are those that were continuously rotated at low incident angles (4 degrees) using short, high and low energy steps regardless of orientation. Our results suggest that improvement of image quality of phyllosilicate EBSPs is possible with an ion mill but analytical limitations remain, possibly owing to phyllosilicate crystal structure and lattice defects.

Ward, D. E.; Walck, S. D.; Mahan, K. H.; Geiss, R.

2010-12-01

27

Application of electron backscatter diffraction techniques to quenched and partitioned steels.  

PubMed

Electron backscatter diffraction (EBSD) techniques were used to characterize "hot-rolled" quenched and partitioned microstructures produced via Gleeble thermal simulations representing a hot-strip cooling practice for steel. In particular, EBSD was utilized to positively identify the morphology and location of retained austenite, to qualitatively distinguish martensite from ferrite, and in an attempt to identify transition carbides. Large pools of retained austenite and some thin films were accurately indexed; however, there was some disparity between austenite volume fractions measured by EBSD and those measured by X-ray diffraction. Due to similarities between the crystal structures of martensite and ferrite (body centered tetragonal versus body centered cubic, respectively), martensite could not be distinguished from ferrite by indexing of diffraction patterns; however, martensite could qualitatively be distinguished from ferrite by regions of low image quality based on the very high dislocation density of martensite. PMID:21281538

Thomas, Grant; Speer, John; Matlock, David; Michael, Joseph

2011-01-31

28

Characterization of isothermally aged Grade 91 (9Cr–1Mo–Nb–V) steel by electron backscatter diffraction  

Microsoft Academic Search

An electron backscatter diffraction (EBSD) investigation on the effect of long-term aging on the microstructure of modified 9Cr–1Mo steel for steam piping in power plant has been carried out. EBSD has been used to determine changes in the matrix microstructure, such as the ratio of low to high angle boundaries and the total grain boundary length. Both have been shown

J. J. Sanchez-Hanton; R. C. Thomson

2007-01-01

29

Phase analysis on dual-phase steel using band slope of electron backscatter diffraction pattern.  

PubMed

A quantitative and automated phase analysis of dual-phase (DP) steel using electron backscatter diffraction (EBSD) was attempted. A ferrite-martensite DP microstructure was produced by intercritical annealing and quenching. An EBSD map of the microstructure was obtained and post-processed for phase discrimination. Band slope (BS), which was a measure of pattern quality, exhibited much stronger phase contrast than another conventional one, band contrast. Owing to high sensitivity to lattice defect and little orientation dependence, BS provided handiness in finding a threshold for phase discrimination. Its grain average gave a superior result on the discrimination and volume fraction measurement of the constituent phases in the DP steel. PMID:23920165

Kang, Jun-Yun; Park, Seong-Jun; Moon, Man-Been

2013-08-01

30

Microstructure Characterization of Magnetic-Pulse-Welded AA 6061-T6 by Electron Backscattered Diffraction  

SciTech Connect

The grain boundary crystallographic misorientations of magnetic-pulse-welded (MPW) aluminum alloy (AA) 6061-T6 in linear and tubular configurations were examined using the electron backscattered diffraction (EBSD) technique. A refined structure of heavily deformed grains with higher grain boundary angles was observed in linear welds. Significant spalling was observed away from the joints, in the interior of tubular welds. The results show the complex interaction of shock waves with the materials during this impact welding process.

Zhang, Yuan [Ohio State University; Babu, Suresh [Ohio State University; Zhang, P [Edison Welding Institute; Kenik, Edward A [ORNL; Daehn, Glenn [Ohio State University

2008-01-01

31

Electron backscatter diffraction and electron channeling contrast imaging of tilt and dislocations in nitride thin films  

SciTech Connect

In this paper we describe the use of electron backscatter diffraction (EBSD) mapping and electron channeling contrast imaging--in the scanning electron microscope--to study tilt, atomic steps and dislocations in epitaxial GaN thin films. We show results from a series of GaN thin films of increasing thickness and from a just coalesced epitaxial laterally overgrown GaN thin film. From our results we deduce that EBSD may be used to measure orientation changes of the order of 0.02 deg. , in GaN thin films. As EBSD has a spatial resolution of {approx_equal}20 nm, this means we have a powerful technique with which to quantitatively map surface tilt. We also demonstrate that electron channeling contrast images may be used to image tilt, atomic steps, and threading dislocations in GaN thin films.

Trager-Cowan, C.; Sweeney, F.; Trimby, P. W.; Day, A. P.; Gholinia, A.; Schmidt, N.-H.; Parbrook, P. J.; Wilkinson, A. J.; Watson, I. M. [SUPA, Department of Physics, University of Strathclyde, Glasgow G4 ONG, Scotland (United Kingdom); HKL TECHNOLOGY A/S, Majsmarken 1, Hobro, DK 9500 (Denmark); EPSRC National Centre for III-V Technologies, University of Sheffield (United Kingdom); Department of Materials, University of Oxford, Oxford OX1 3PH (United Kingdom); SUPA, Institute of Photonics, University of Strathclyde, Glasgow G4 ONW, Scotland (United Kingdom)

2007-02-15

32

Misorientation mapping for visualization of plastic deformation via electron back-scattered diffraction.  

PubMed

The ability to map plastic deformation around high strain gradient microstructural features is central in studying phenomena such as fatigue and stress corrosion cracking. A method for the visualization of plastic deformation in electron back-scattered diffraction (EBSD) data has been developed and is described in this article. This technique is based on mapping the intragrain misorientation in polycrystalline metals. The algorithm maps the scalar misorientation between a local minimum misorientation reference pixel and every other pixel within an individual grain. A map around the corner of a Vickers indentation in 304 stainless steel was used as a test case. Several algorithms for EBSD mapping were then applied to the deformation distributions around air fatigue and stress corrosion cracks in 304 stainless steel. Using this technique, clear visualization of a deformation zone around high strain gradient microstructural features (crack tips, indentations, etc.) is possible with standard EBSD data. PMID:17481344

Brewer, L N; Othon, M A; Young, L M; Angeliu, T M

2006-02-01

33

Direct Detection of Electron Backscatter Diffraction Patterns  

NASA Astrophysics Data System (ADS)

We report the first use of direct detection for recording electron backscatter diffraction patterns. We demonstrate the following advantages of direct detection: the resolution in the patterns is such that higher order features are visible; patterns can be recorded at beam energies below those at which conventional detectors usefully operate; high precision in cross-correlation based pattern shift measurements needed for high resolution electron backscatter diffraction strain mapping can be obtained. We also show that the physics underlying direct detection is sufficiently well understood at low primary electron energies such that simulated patterns can be generated to verify our experimental data.

Wilkinson, Angus J.; Moldovan, Grigore; Britton, T. Benjamin; Bewick, Angus; Clough, Robert; Kirkland, Angus I.

2013-08-01

34

Direct detection of electron backscatter diffraction patterns.  

PubMed

We report the first use of direct detection for recording electron backscatter diffraction patterns. We demonstrate the following advantages of direct detection: the resolution in the patterns is such that higher order features are visible; patterns can be recorded at beam energies below those at which conventional detectors usefully operate; high precision in cross-correlation based pattern shift measurements needed for high resolution electron backscatter diffraction strain mapping can be obtained. We also show that the physics underlying direct detection is sufficiently well understood at low primary electron energies such that simulated patterns can be generated to verify our experimental data. PMID:23971587

Wilkinson, Angus J; Moldovan, Grigore; Britton, T Benjamin; Bewick, Angus; Clough, Robert; Kirkland, Angus I

2013-08-08

35

Use of electropolishing for enhanced metallic specimen preparation for electron backscatter diffraction analysis  

SciTech Connect

The effects of mechanical polishing with Al{sub 2}O{sub 3} and colloidal SiO{sub 2} followed by electropolishing were studied for preparation of metal alloy specimens for Electron Backscatter Diffraction (EBSD). The alloys studied were Inconel 718, a commonly used nickel-based superalloy, and a Ti-Al-Nb alloy (nominally Ti-22Al-28Nb(at.%)). Atomic Force Microscopy was used to measure the surface topography to attempt to correlate nano-scale surface roughness with EBSD pattern quality. The results suggest that mechanically polishing with Al{sub 2}O{sub 3} followed by electropolishing for a short time can produce EBSD pattern confidence indices and image quality values that are equal to or better than those produced by mechanically polishing with colloidal SiO{sub 2} alone. The data suggests that surface roughness on the scale considered here has much less effect on EBSD pattern quality than had been previously believed. The data suggests that removing the surface damage is more critical than reduction of topography for EBSD.

Wynick, G.L. [Alfred University, School of Engineering, Alfred, NY 14802 (United States); Boehlert, C.J. [Michigan State University, Department of Chemical Engineering and Materials Science, East Lansing, MI 48824-1226 (United States)]. E-mail: boehlert@egr.msu.edu

2005-09-15

36

Combined application of electron backscatter diffraction and stereo-photogrammetry in fractography studies.  

PubMed

The main aim of this paper is to report on recent experimental developments that have succeeded in combining electron back-scatter diffraction (EBSD) with stereo-photogrammetry, compared with two other methods for study of fracture surfaces, namely visual fractography analysis in the scanning electron microscope (SEM) and EBSD directly from facets. These approaches will be illustrated with data relating to the cleavage plane orientation analysis in a ferritic and C-Mn steel. It is demonstrated that the combined use of EBSD and stereo-photogrammetry represents a significant advance in the methodology for facet crystallography analysis. The results of point counting from fractograph characterization determined that the proportions of intergranular fracture in C-Mn and ferritic steels were 10.4% and 9.4%, respectively. The crystallographic orientation was determined directly from the fracture surface of a ferritic steel sample and produced an orientation distribution with a clear trend towards the [001] plane. A stereo-photogrammetry technique was validated using the known geometry of a Vickers hardness indent. The technique was then successfully employed to measure the macroscopic orientation of individual cleavage facets in the same reference frame as the EBSD measurements. Correlating the results of these measurements indicated that the actual crystallographic orientation of every cleavage facet identified in the steel specimens is [001]. PMID:11580810

Davies, P A; Randle, V

2001-10-01

37

Advanced characterization of twins using automated electron backscatter diffraction  

SciTech Connect

This paper describes results obtained using an automated, crystallographically-based technique for twin identification. The technique is based on the automated collection of spatially specific orientation measurements by electron backscatter diffraction (EBSD) in the scanning electron microscope (SEM). The key features of the analysis are identification of potential twin boundaries by their misorientation character, identification of the distinct boundary planes among the symmetrically equivalent candidates, and validation of these boundaries through comparison with the boundary and twin plane traces in the sample cross section. Results on the application of this technique to deformation twins in zirconium are analyzed for the effect of twin type and amount and sense of uniaxial deformation. The accumulation of strain tends to increase the misorientation deviation at least to the degree of the trace deviation compared with recrystallization twins in nickel. In addition to the results on characterizing the twin character, results on extending the twin analysis to automated identification of parent and daughter material for structures exhibiting twin deformation are reported as well.

Wright, S. I. (Stuart I.); Bingert, J. F. (John F.); Mason, T. A. (Thomas A.); Larson, R. J. (Ryan J.)

2002-01-01

38

Electron Backscatter Diffraction: An Important Tool for Analyses of Structure-Property Relationships in Thin-Film Solar Cells  

NASA Astrophysics Data System (ADS)

The present work gives an overview of the application of electron backscatter diffraction (EBSD) in the field of thin-film solar cells, which consist of stacks of polycrystalline layers on various rigid or flexible substrates. EBSD provides access to grain-size and local-orientation distributions, film textures, and grain-boundary types. By evaluation of the EBSD patterns within individual grains of the polycrystalline solar cell layers, microstrain distributions also can be obtained. These microstructural properties are of considerable interest for research and development of thin-film solar cells. Moreover, EBSD may be performed three-dimensionally, by alternating slicing of cross sections in a focused ion-beam machine and EBSD acquisition. To relate the microstructural properties to the electrical properties of individual layers as well as to the device performances of corresponding solar cells, EBSD can be combined with electron-beam-induced current and cathodoluminescence measurements and with various scanning-probe microscopy methods such as Kelvin-probe force, scanning spreading resistance, or scanning capacitance microscopy on identical specimen positions. Together with standard device characterization of thin-film solar cells, these scanning microscopy measurements provide the means for extensive analysis of structure-property relationships in solar-cell stacks with polycrystalline layers.

Abou-Ras, D.; Kavalakkatt, J.; Nichterwitz, M.; Schäfer, N.; Harndt, S.; Wilkinson, A. J.; Tsyrulin, K.; Schulz, H.; Bauer, F.

2013-09-01

39

Probing Deformation and Revealing Microstructural Mechanisms with Cross-Correlation-Based, High-Resolution Electron Backscatter Diffraction  

NASA Astrophysics Data System (ADS)

High-resolution, cross-correlation-based, electron backscatter diffraction (HR-EBSD) is an emerging technique capable of measuring elastic strains, lattice rotations, and defect populations in crystalline materials. Here we briefly review development of the technique and the fundamental method. Application of HR-EBSD to metallic samples is illustrated with three examples: nickel-superalloy matrix/carbide interactions during cyclic deformation; interaction of a slip band and grain boundary; and patterning of stress and dislocation storage in deformed copper. These three examples highlight the ability of HR-EBSD to deliver new science by revealing new insights into the fundamental nature of deformation, as well as validating existing models. Application of the technique is now commonplace, and emergence of the technique is opening it up to the wider materials science community to tackle grand challenges.

Britton, T. Ben; Jiang, Jun; Karamched, Phani S.; Wilkinson, Angus J.

2013-09-01

40

Characterization of Ferrite in Tempered Martensite of Modified 9Cr-1Mo Steel Using the Electron Backscattered Diffraction Technique  

NASA Astrophysics Data System (ADS)

Ferrite was identified and characterized in tempered martensitic modified 9Cr-1Mo steel using the electron backscattered diffraction (EBSD) technique. Microstructural examination of the as-received modified 9Cr-1Mo steel revealed the presence of polycrystalline grains without lath morphology having low hardness within a predominantly tempered lath martensitic matrix. These grains were identified as the ferrite phase, and subsequent EBSD data analysis confirmed that the image quality (IQ) index of these grains is higher and boundary line length per unit area is lower than those of martensitic matrix. Therefore, it is proposed that characterization of ferrite phase in martensitic matrix can be carried out using microstructural parameters such as IQ index and boundary line length per unit area obtained from EBSD data analysis.

Das, C. R.; Albert, S. K.; Bhaduri, A. K.; Murty, B. S.

2011-12-01

41

Electron Backscatter Diffraction of CdTe Thin Films: Effects of CdCl2 Treatment  

SciTech Connect

In this work, the authors describe procedures to prepare the surface of close-spaced sublimation CdTe thin films necessary for producing good electron backscatter diffraction (EBSD) data. They found that polishing resulted in an amorphous layer on the surface and no Kikuchi pattern; however, ion-beam milling produced a relatively flat and good-quality surface, resulting in high-quality patterns and, consequently, excellent EBSD data. The authors used a combination of polishing and ion-beam milling or etching to study the crystalline structure of the CdTe film at different depths. They also used EBSD, in conjunction with other analytical techniques, to investigate the effects of the CdCl{sub 2} treatment, performed at different temperatures and times, on the recrystallization process of physical vapor deposition CdTe thin films. The authors found that the untreated films were <111> oriented, with grain sizes smaller than 1 {micro}m. The CdCl{sub 2} at 350 C produced partially recrystallized films, whereas treatments at 400 C or 420 C produced completely recrystallized films, with no texture, and grains with grain sizes varying from about 1 {micro}m to more than 40{micro}m. These films were so flat that good EBSD data could be obtained without any surface preparation. Atomic force microscopy and scanning electron microscopy showed that large grains had different morphologies than smaller grains, and EBSD showed that these large grains had <111> texture. These results indicate that the (111) surface is the lowest energy surface in these films and, consequently, <111>-oriented grains grow at the expense of grains oriented in less-favorable directions. Regardless of the deposition method and treatment, the CdTe films have a high density of 60{sup o} <111> twin boundaries.

Moutinho, H. R.; Dhere, R. G.; Romero, M. J.; Jiang, C.-S.; To, B.; Al-Jassim, M. M.

2008-07-01

42

Quantifying recrystallization by electron backscatter diffraction.  

PubMed

The use of high-resolution electron backscatter diffraction in the scanning electron microscope to quantify the volume fraction of recrystallization and the recrystallization kinetics is discussed. Monitoring the changes of high-angle grain boundary (HAGB) content during annealing is shown to be a reliable method of determining the volume fraction of recrystallization during discontinuous recrystallization, where a large increase in the percentage of high-angle boundaries occurs during annealing. The results are shown to be consistent with the standard methods of studying recrystallization, such as quantitative metallography and hardness testing. Application of the method to a highly deformed material has shown that it can be used to identify the transition from discontinuous to continuous recrystallization during which there is no significant change in the percentage of HAGB during annealing. PMID:15009691

Jazaeri, H; Humphreys, F J

2004-03-01

43

Validation of neutron texture data on GEM at ISIS using electron backscattered diffraction  

NASA Astrophysics Data System (ADS)

The high solid angular coverage of the general materials (GEM) diffractometer at the ISIS pulsed neutron source located at the UK Rutherford Appleton Laboratory offers the capability of obtaining quantitative bulk crystallographic texture data in a 'single shot' within a matter of minutes. This enables the possibility of in situ texture measurements to be made as a function of temperature to monitor and quantify texture changes during phase transformation or microstructure restoration processes like recrystallization. The purpose of this paper is to determine the quality of the texture data produced from GEM in order to define a level of confidence for subsequent texture model validation. This has been achieved by comparing textures of sections of a 200 mm diameter titanium alloy billet using data obtained from GEM with data obtained using electron backscattered diffraction (EBSD). In both cases, the data were obtained at room temperature. EBSD, unlike time-of-flight neutron diffraction analysis, obtains texture data directly from orientation measurements via backscattered Kikuchi patterns in the scanning electron microscope. In all analysed locations, both methods show near-identical textures, with regard to both the general orientation distributions and the levels of intensity of the distributions. This shows that the GEM diffractometer is capable of accurately determining bulk textures in a single shot, thus confirming its suitability for in situ high temperature experiments.

Davies, Peter; Kockelmann, Winfried; Wynne, Brad; Eccleston, Roger; Hutchinson, Bevis; Rainforth, W. Mark

2008-03-01

44

Prediction of Elastic Modulus + Anisotropy Using X-Ray and Electron Backscattered Diffraction Texture Quantification and Ultrasonic (Electromagnetic Acoustic Transducer) Measurements in Aluminum Sheets  

NASA Astrophysics Data System (ADS)

Crystallographic texture is generally measured using X-ray diffraction, performed off-line using small samples determining near-surface texture only; electron backscattered diffraction (EBSD) can also be used, but only samples relatively small areas. Ultrasonic methods determine elastic property anisotropy and texture, via orientation distribution coefficients (ODCs), and while there is substantial literature comparing ultrasonically determined properties with X-ray or neutron diffraction texture, there is little discussion about texture inhomogeneity (place to place in a sheet or through thickness) and sampling volume effects (X-ray compared to EBSD) on the accuracy of the correlations. In this article, the crystallographic texture of nominally pure aluminum and commercial aluminum alloy sheets has been determined by X-ray diffraction and EBSD and used to calculate the elastic anisotropy, which is then compared to ultrasonic electromagnetic acoustic transducer (EMAT) velocity anisotropy taking into account through-thickness texture variations. Significant and consistent spatial variability in texture occurs in the aluminum sheet samples (sheet edge to center and through thickness). Predictions of elastic anisotropy based on surface texture determination, as characterized by X-ray diffraction or surface EBSD, gave poor correlations with EMAT velocity anisotropy when the sample contained significant through thickness texture variations; however, accounting for this using multiple EBSD scans through thickness gave good correlations.

Davis, C. L.; Strangwood, M.; Potter, M.; Dixon, S.; Morris, P. F.

2008-03-01

45

Plagioclase Preferred Orientation in Anorthosite by TOF Neutron Diffraction and SEM-EBSD  

NASA Astrophysics Data System (ADS)

Preferred Orientation analysis of the triclinic mineral plagioclase has traditionally relied on the measurements of the optical indicatrix, cleavages and twins with time-consuming U-stage methods. X-ray methods that are conventionally used for texture measurements proved to be unsatisfactory because of insufficient resolution to separate the closely spaced or overlapped diffraction peaks. This study reports a Time-of-Flight (TOF) neutron diffraction texture analysis of plagioclase. Results are compared with Electron Back Scatter Diffraction (EBSD) data. The sample investigated is a highly deformed anorthositic mylonite (Grenville Province, Quebec), composed of andesine. Neutron diffraction was performed with a Kappa-geometry texture goniometer at the Intense Pulsed Neutron Source (IPNS) of Argonne National Laboratory. Spectra were recorded in 16 sample orientations with 10 detectors, with a measurement time of 2.5 hours at each orientation. The texture was investigated with a modified Rietveld method, using many pole figures (56, in the d-range 2-3.5Ĺ) and small number of sample orientations (16) with the Williams-Imhof-Matthies-Vinel (WIMV) algorithm implemented in the program package MAUD (Materials Analysis Using Diffraction). Electron Diffraction was performed by a digital SEM-EBSD system at Berkeley, relying on the Channel+ software for indexing diffraction patterns. 6561 diffraction patterns were measured. Analyses from neutron and electron diffraction data gave similar results. The principal pole figures show (010) roughly parallel to the rock foliation, (001) poles exhibiting a small angle ( ~15° ) to the pole to foliation, and (100) poles close to the Y-direction (the direction perpendicular to the lineation and foliation pole). The textures of the crystallographic directions [100], [010], and [001] were indirectly obtained by approximating the closest (hkl) poles (20-1), (010), and (-102) respectively. The [100] maximum is in the lineation direction, [010] directions concentrate near the foliation pole. The geological deformation conditions and the constructed pole figure patterns indicate that the preferred orientation could be attributed to intracrystalline slip dominantly on (010) with [100] as slip direction. The results demonstrate that neutron diffraction, as well as EBSD are reliable techniques to establish the orientation distribution of triclinic feldspars in deformed rocks.

Xie, Y.; Wenk, R.

2001-12-01

46

Characterization of multicomponent scales by electron back scattered diffraction (EBSD)  

SciTech Connect

Exposure of metals and alloys to high temperatures leads to the formation of oxide scales. Characterizing the nature of the scale is of considerable importance to the steel manufacturers, who are under continual pressure to improve surface finish. Scale properties are also of interest because of the effect on friction and heat transfer during hot working operations, and the resultant wear of tooling or work rolls. Oxidation of pure iron is well documented and has lead to the classical three layer scale characterization. Hot working operations break up the classical three layer scale and make characterization of the individual components of the scale difficult. Identification of the individual components simply by their layer position is no longer reliable since the layers have been disrupted by the hot working process. Scale microstructures become further complicated on cooling as the wuestite decomposes to magnetite at temperatures below 570 C. The resultant scale microstructures are therefore complex on a sub-micron scale. These secondary and tertiary scales must be removed before subsequent processing, such as cold rolling or wire drawing and the mechanical properties of the scale layers are important factors when considering descalability. For example, hematite is much harder than magnetite and wuestite, thus magnetite scales are more brittle and therefore easier to remove than scales containing wuestite.with this in mind it is necessary to develop a reliable technique for the characterization of these scales and their microstructures with respect to developing an ideal scale for easy removal, without sacrificing the mechanical properties of the product. Furthermore a reliable method of characterizing the scale development along the rolling mill would be useful in charting the scale growth and re-growth behavior between passes and may lead to the development of an ideal rolling schedule for the formation of an easily removed scale. This paper discusses the characterization of these scales by electron back scattered diffraction.

Burke, D.P.; Higginson, R.L.

2000-01-01

47

Electron backscatter diffraction analysis of ZnO:Al thin films  

NASA Astrophysics Data System (ADS)

Microstructural characterization and crystallographic orientation aspects of aluminium doped zinc oxide (ZnO:Al) thin films have been investigated by means of electron backscatter diffraction. ZnO:Al was produced by magnetron sputtering deposition from a ZnO ceramic target containing 2.0 wt% Al2O3 and 0.12 wt% Y2O3. Both top surface and cross-section analysis were performed. The experimental details concerning specific sample preparation procedures for EBSD investigations are presented. Crystalline texture was described by the inverse pole figure (IPF) maps. Strong texture on the basal plane orientation was observed on the analyzed thin film surface. In accordance with these results obtained from top surface investigations, a strong prismatic texture was found in cross-section analysis. From all these analyses a good description and quantification of the three dimensional configuration of the grains and of their crystallographic texture can be proposed.

Garcia, C. B.; Ariza, E.; Tavares, C. J.; Villechaise, P.

2012-10-01

48

Study of microstructure and phase evolution of hot-dipped aluminide mild steel during high-temperature diffusion using electron backscatter diffraction  

Microsoft Academic Search

Mild steel was coated by hot-dipping into a molten aluminum bath. The microstructure and phase evolution in the aluminide layer during diffusion at 750°C in static air were analyzed by electron backscatter diffraction (EBSD). The results showed that the aluminide layer of the as-coated specimen consisted of an outer aluminum topcoat, minor FeAl3 and major Fe2Al5, respectively. Also, Fe2Al5 possessed

Wei-Jen Cheng; Chaur-Jeng Wang

2011-01-01

49

Electron Backscatter Diffraction Analysis of a CZT Growth Tip from a Vertical Gradient Freeze Furnace  

SciTech Connect

Electronic backscatter diffraction (EBSD) was used to characterize the growth-tip region of a 4.2-cm diameter CdZnTe (CZT) boule grown using low-pressure Bridgman method in a vertical gradient freeze furnace. The boule was sectioned and polished and a section taken along the boule longitudinal centerline with an approximate surface area of 1-cm2 was used for optical and scanning electron microscopy. A collage was assembled using EBSD/SEM images to show morphological features, e.g., twin structure, grain structure, and overall crystal growth direction. Severely twinned regions originating from the tip and side walls were observed. The overall growth orientation was close to <110> and <112> directions. In some regions, the (001) poles of the CZT matrix aligned with the growth direction, while twins aligned such that (111) and (112) poles aligned with the growth direction. In some other areas, (112) or (011) poles of the CZT matrix aligned with the growth direction. New relationships between the CZT matrix and large Te polycrystalline particles were revealed: {11 }CZT??{1 00}Te and {001}CZT??{0 1}Te.

Sundaram, S. K.; Henager, Charles H.; Edwards, Danny J.; Schemer-Kohrn, Alan L.; Bliss, Mary; Riley, Brian J.

2011-08-15

50

Electron Backscatter Diffraction of a Ge Growth Tip from a Vertical Gradient Freeze Furnace  

SciTech Connect

The growth-tip region of a high-purity 4.2-cm diameter Ge boule grown using low-pressure Bridgman methods in a vertical gradient freeze furnace was sectioned and polished in preparation for scanning electron microscopy and was characterized using electron backscatter diffraction (EBSD). The boule had a characteristic conical tip region with cone angle of 40? of a right circular cylinder from which a section was taken along the boule longitudinal centerline with an approximate surface area of 4 cm2. The majority of this surface area was characterized using EBSD and an image collage was assembled for the tip region. The grain structure, grain boundary orientation, twin structure, and overall crystal growth direction were determined. A crystal growth direction of approximately <112> was observed, which was also identified as the growth direction of several prominent twins observed in the tip region. The grain structure of the tip region appeared to be controlled by the sidewall nucleation of a stray grain that competed for dominance during growth. Grain boundaries and triple grain junctions were identified as low-energy coincident-site-lattice (CSL) boundaries and junctions of the ?3 and ?9 types.

Henager, Charles H.; Edwards, Danny J.; Schemer-Kohrn, Alan L.; Sundaram, S. K.; Riley, Brian J.; Bliss, Mary

2008-12-15

51

EBSD analysis of the microtexture of Ba-hexaferrite samples  

NASA Astrophysics Data System (ADS)

The microtexture of differently prepared Ba-hexaferrite samples is investigated by means of electron backscatter diffraction (EBSD). Kikuchi patterns are obtained with a high image quality, enabling a spatial resolution of the EBSD maps of about 20 nm. The spatially highly resolved EBSD mappings provide additional information (individual grain orientation, misorientation angles, grain size distribution) as compared to the standard analysis techniques, which can contribute to an optimization of the growth process. Furthermore, as the crystallographic orientation of each grain is known, an exact analysis of the grain aspect ratio becomes possible which provides further insight to the microstructural dependence of the magnetic properties of ferrites.

Koblischka-Veneva, A.; Koblischka, M. R.; Schmauch, J.; Chen, Y.; Harris, V. G.

2010-01-01

52

Study of grain boundary properties in Ag-clad Bi2Sr2Ca2Cu3Ox tapes by multi-phase electron backscatter diffraction analysis  

NASA Astrophysics Data System (ADS)

The properties of grain boundaries within Ag-clad (Pb,Bi)2Sr2Ca2Cu3Ox (Bi-2223) tapes are studied by means of electron backscatter diffraction (EBSD). The achieved high image quality of the Kikuchi patterns enables multi-phase EBSD scans including Bi-2223, Bi2Sr2CaCu2Ox (Bi-2212), Bi2Sr2CuOx (Bi-2201), (Sr,Ca)14Cu24O41 and Ag to be performed. For the EBSD scans a maximum spatial resolution of 30 nm was reached enabling a detailed orientation analysis. The nature of the grain boundaries is discussed on the base of the EBSD data. While the main orientation of the tape is in [0 0 1] direction, a large number of misorientations is detected. These misorientations are visualized using crystal direction (CD) maps. Furthermore, EBSD enables the spatially resolved mapping of the misorientation angles within each phase separately. The influence of these grain boundaries on the current transport properties is discussed.

Koblischka-Veneva, A.; Koblischka, M. R.

2008-01-01

53

Electron energy loss and diffraction of backscattered electrons from silicon  

NASA Astrophysics Data System (ADS)

Electrons backscattered from crystals can show Kikuchi patterns: variations in intensity for different outgoing directions due to diffraction by the lattice. Here, we measure these effects as a function of their energy loss for 30 keV electrons backscattered from silicon. The change in diffraction contrast with energy loss depends strongly on the scattering geometry. At steep incidence on the sample, diffraction contrast in the observed Kikuchi bands decreases rapidly with energy loss. For an energy loss larger than about 150 eV the contrast is more than 5 times less than the contrast due to electrons near zero energy loss. However, for grazing incidence angles, maximum Kikuchi band contrast is observed for electrons with an energy loss near 60 eV, where the contrast is more than 2.5× larger than near zero energy loss. In addition, in this grazing incidence geometry, the Kikuchi diffraction effects stay significant even for electrons that have lost hundreds of electron volts. For the maximum measured energy loss of 440 eV, the electrons still show a contrast that is 1.5 × larger than that of the electrons near zero energy loss. These geometry-dependent observations of Kikuchi band diffraction contrast are interpreted based on the elastic and inelastic scattering properties of electrons and dynamical diffraction simulations.

Winkelmann, Aimo; Aizel, Koceila; Vos, Maarten

2010-05-01

54

Features of Transmission EBSD and its Application  

NASA Astrophysics Data System (ADS)

Features of transmission electron backscatter diffraction (EBSD) observation with a standard EBSD ( s-EBSD) detector are surveyed in this study. Heavily deformed Al and 8Cr tempered martensite transmission electron microscope (TEM) specimens were used for this study. It is shown that a specimen tilt angle of ~30°-40° in the opposite direction of the usual 70° and a smaller working distance in the range 4 mm-5 mm are recommended when using a s-EBSD detector. Specimen thickness and accelerating voltage (Acc.V) have a strong affect on the quality of transmission EBSD patterns and orientation maps. Higher Acc.Vs are generally recommended to get good quality orientation maps. In case of very thin specimens, lowering the Acc.Vs will give better results. In the observation of a thin film of an 8Cr tempered martensite steel specimen, it is confirmed that t-EBSD can provide images and detailed quantitative orientation data comparable with that obtained by TEM. It is also shown that small precipitates of Cr23C6 with sizes around 30 nm could be detected and their orientations measured.

Suzuki, Seiichi

2013-09-01

55

Limits of simulation based high resolution EBSD.  

PubMed

High resolution electron backscattered diffraction (HREBSD) is a novel technique for a relative determination of both orientation and stress state in crystals through digital image correlation techniques. Recent works have tried to use simulated EBSD patterns as reference patterns to achieve the absolute orientation and stress state of crystals. However, a precise calibration of the pattern centre location is needed to avoid the occurrence of phantom stresses. A careful analysis of the projective transformation involved in the formation of EBSD patterns has permitted to understand these phantom stresses. This geometrical analysis has been confirmed by numerical simulations. The results indicate that certain combinations of crystal strain states and sample locations (pattern centre locations) lead to virtually identical EBSD patterns. This ambiguity makes the problem of solving the absolute stress state of a crystal unfeasible in a single-detector configuration. PMID:23676453

Alkorta, Jon

2013-04-17

56

EBSD analysis of electroplated magnetite thin films  

NASA Astrophysics Data System (ADS)

By means of electron backscatter diffraction (EBSD), we analyse the crystallographic orientation of electroplated magnetite thin films on Si/copper substrates. Varying the voltage during the electroplating procedure, the resulting surface properties are differing considerably. While a high voltage produces larger but individual grains on the surface, the surfaces become smoother on decreasing voltage. Good quality Kikuchi patterns could be obtained from all samples; even on individual grains, where the surface and the edges could be measured. The spatial resolution of the EBSD measurement could be increased to about 10 nm; thus enabling a detailed analysis of single magnetite grains. The thin film samples are polycrystalline and do not exhibit a preferred orientation. EBSD reveals that the grain size changes depending on the processing conditions, while the detected misorientation angles stay similar.

Koblischka-Veneva, A.; Koblischka, M. R.; Teng, C. L.; Ryan, M. P.; Hartmann, U.; Mücklich, F.

2010-05-01

57

Application of Electron Backscatter Diffraction to Phase Identification  

SciTech Connect

The identification of crystalline phases in solids requires knowledge of two microstructural properties: crystallographic structure and chemical composition. Traditionally, this has been accomplished using X-ray diffraction techniques where the measured crystallographic information, in combination with separate chemical composition measurements for specimens of unknown pedigrees, is used to deduce the unknown phases. With the latest microstructural analysis tools for scanning electron microscopes, both the crystallography and composition can be determined in a single analysis utilizing electron backscatter diffraction and energy dispersive spectroscopy, respectively. In this chapter, we discuss the approach required to perform these experiments, elucidate the benefits and limitations of this technique, and detail via case studies how composition, crystallography, and diffraction contrast can be used as phase discriminators.

El-Dasher, B S; Deal, A

2008-07-16

58

Application of electron backscattered diffraction to cleavage fracture in duplex stainless steel  

SciTech Connect

The mechanical properties and corrosion resistance of duplex stainless steel (DSS) are generally superior to conventional austenite or ferrite grades. DSSs can have yield strengths twice the austenite grades, while retaining good ductility and toughness properties. Commercial wrought duplex stainless steels, either plates or rod, are processed by hot rolling followed by a solution annealing treatment to optimize the austenite-ferrite ratio and dissolve any pre-existing secondary phases. Processing may lead to a significant anisotropy in mechanical properties. For example, the tensile properties in cold-rolled sheet of duplex stainless steel (22Cr5Ni) reveals anisotropy of strength, i.e., the transverse direction tensile strength is 7.3% higher than tensile strength in the rolling direction (RD). It was also shown in a study of the effect of crack orientation on the impact properties of the same steel, that when the crack was oriented parallel to the direction of elongation of the austenite phase, the crack could grow along the more brittle ferrite phase for a longer distance before encountering the more ductile austenite. This decreased impact toughness. These are examples of microstructure texture. Crystallographic texture may also have an effect on properties that are related to specific crystallographic planes; such as brittle cleavage and stress corrosion cracking. This paper describes the application of electron backscattered diffraction (EBSD) to study cleavage fracture and crystal texture in age-hardened DSS.

Kim, S.; Marrow, T.J.

1999-05-21

59

Plastic strain characterization in austenitic stainless steels and nickel alloys by electron backscatter diffraction  

NASA Astrophysics Data System (ADS)

Stress corrosion cracking (SCC) is enhanced by cold work and causes many problems in components of the nuclear power plants. Besides, during manufacturing, installation, welding and service of the material, residual strains can be produced increasing the susceptibility to SCC. For this reason, it is important to characterize the degree of plastic strain due to dislocation accumulation in each crystal. Electron backscatter diffraction (EBSD), in conjunction with scanning electron microscope (SEM), has been a great advance in this field because it enables to estimate the plastic strain in a quick and easy way. Nevertheless, over the last few years, a lot of different mathematical expressions to estimate the plastic strain have appeared in the literature. This situation hinders the election of one of them by a novel scientist in this field.Therefore, in this paper some of the more common expressions used in the calculation of the angular misorientation have been presented and discussed in order to clarify their more important aspects. Then, using one of these expressions (average local misorientation), curves relating misorientation density with known levels of strain will be obtained for an austenitic stainless steel 304L and nickel base alloy 690, which have shown a linear behaviour that is in good agreement with results found in the literature. Finally, using curves obtained in previous steps, levels of plastic strain in a plate of nickel base alloy 600 welded with weld metal 182 were estimated between 8 and 10% for a high temperature mill annealing sample.

Sáez-Maderuelo, A.; Castro, L.; de Diego, G.

2011-09-01

60

Analysis of different acicular ferrite microstructures in low-carbon steels by electron backscattered diffraction. Study of their toughness behavior  

NASA Astrophysics Data System (ADS)

Acicular ferrite formation, promoted by the intragranular nucleation of ferrite plates, is well known to be beneficial for achieving a good combination of mechanical properties. However, the set of microstructures that can be obtained during the subsequent development of the transformation from the primary plates generated at particles can be quite complex and depends on a certain number of variables: steel composition, temperature range, prior austenite grain size, and particle density. In the present work, acicular ferrite microstructures have been produced by isothermal treatments in three different steels with different active particle types and densities. The morphology of the obtained intragranular microstructures has been found to depend on the steel composition, the prior austenite grain size, and the density of particles able to promote intragranular nucleation. Electron backscattered diffraction (EBSD) techniques have been used to define the microstructural unit controlling toughness in these types of microstructures.

Dáz-Fuentes, M.; Iza-Mendia, A.; Gutiérrez, I.

2003-11-01

61

Electron Backscattered Diffraction Analysis Of Narrow Copper Interconnects In Cross-View To Investigate Scale Effect On Microstructure  

SciTech Connect

In this article, we propose to use Electron Backscattered Diffraction (EBSD) to characterize microstructure of copper interconnects of thin metal level in top view and cross view. These two views give very complementary information about microstructure of copper and thus about recrystallization of copper during annealing. Moreover, for minimum width, as interconnect is two times thicker than wide; It will be easier to analyze smaller interconnect of 45 nm node technology in cross-section. We look for evolution of texture and microstructure of copper with line width in top view and in cross view. We highlight the presence of two recrystallization mechanisms and also the fact that transition from one to the other is progressive with competition of both mechanisms.

Galand, Romain [STMicroelectronics, 850 rue Jean Monnet 38926 Crolles Cedex (France); SIMaP, 1130 rue de la Piscine BP 75 38402 St Martin D'Heres Cedex (France); Clement, Laurent; Waltz, Patrice [STMicroelectronics, 850 rue Jean Monnet 38926 Crolles Cedex (France); Wouters, Yves [SIMaP, 1130 rue de la Piscine BP 75 38402 St Martin D'Heres Cedex (France)

2010-11-24

62

Epitaxial SiC Growth Morphology and Extended Defects Investigated by Electron Backscatter Diffraction and Electron Channeling Contrast Imaging  

NASA Astrophysics Data System (ADS)

Electron backscatter diffraction (EBSD) and electron channeling contrast imaging (ECCI) were employed to investigate epitaxial SiC growth on 4H-SiC mesa structures. SiC polytypes were identified by indexing Kikuchi maps recorded from various points on the mesa surfaces. Orientation contrast was observed between different polytype surfaces using ECCI by forescattered electron detection. Extended defects in 3C-SiC were imaged directly by ECCI. Additionally, the ECCI technique was utilized to correlate dislocations with atomic step morphologies for various mesa surfaces. Evidence of vertical growth enhancement in the form of additional faceting was attributed to the presence of threading screw dislocations at mesa surfaces. Atomic steps were observed very near the edges of some mesa surfaces free of dislocations.

Picard, Yoosuf N.; Twigg, Mark E.; Caldwell, Joshua D.; Eddy, Charles R.; Neudeck, Philip G.; Trunek, Andrew J.; Anthony Powell, J.

2008-05-01

63

Three-dimensional cathodoluminescence imaging and electron backscatter diffraction: tools for studying the genetic nature of diamond inclusions  

NASA Astrophysics Data System (ADS)

As a step towards resolving the genesis of inclusions in diamonds, a new technique is presented. This technique combines cathodoluminescence (CL) and electron backscatter diffraction (EBSD) using a focused ion beam-scanning electron microscope (FIB-SEM) instrument with the aim of determining, in detail, the three-dimensional diamond zonation adjacent to a diamond inclusion. EBSD reveals that mineral inclusions in a single diamond have similar crystallographic orientations to the host, within ±0.4°. The chromite inclusions record a systematic change in Mg# and Cr# from core to the rim of the diamond that corresponds with a ~80°C decrease of their formation temperature as established by zinc thermometry. A chromite inclusion, positioned adjacent to a boundary between two major diamond growth zones, is multi-faceted with preferred octahedral and cubic faces. The chromite is surrounded by a volume of non-luminescent diamond (CL halo) that partially obscures any diamond growth structures. The CL halo has apparent crystallographic morphology with symmetrically oriented pointed features. The CL halo is enriched in ~200 ppm Cr and ~80 ppm Fe and is interpreted to have a secondary origin as it overprints a major primary diamond growth structure. The diamond zonation adjacent to the chromite is complex and records both syngenetic and protogenetic features based on current inclusion entrapment models. In this specific case, a syngenetic origin is favoured with the complex form of the inclusion and growth layers indicating changes of growth rates at the diamond-chromite interface. Combined EBSD and 3D-CL imaging appears an extremely useful tool in resolving the ongoing discussion about the timing of inclusion growth and the significance of diamond inclusion studies.

Wiggers de Vries, D. F.; Drury, M. R.; de Winter, D. A. M.; Bulanova, G. P.; Pearson, D. G.; Davies, G. R.

2011-04-01

64

Three-Dimensional EBSD Analysis of YSZ, NiO-YSZ and Ni-Alloy  

SciTech Connect

In this report, a method is discussed to perform successive milling on yttria-stabilized zirconia (YSZ), NiO-YSZ and Ni-alloy at the intervals of 85 nm 50 nm and 100 nm, respectively using a focused ion beam (FIB) followed by electron backscatter diffraction (EBSD) analysis on each slice. The EBSD data is then reconstructed to generate 3D volume. The 3D-EBSD band quality data is superimposed on inverse pole figure (IPF) grain orientation analysis to get a correlation with quality of band indexing. For the NiO-YSZ case, grain orientations and band quality factors were matched for grains {approx}250 nm diameters producing a high resolution 3D-EBSD data. For this case, a pore space in 3D volume was visible due to nanocrystalline NiO-YSZ grain network. The advantages of 3D EBSD are discussed in the context of its applications to SOFC research community.

Saraf, Laxmikant V.

2012-01-03

65

Influence of Surface Preparation on Scanning Kelvin Probe Microscopy and Electron Backscatter Diffraction Analysis of Cross Sections of CdTe/CdS Solar Cells  

SciTech Connect

Electron backscatter diffraction (EBSD) provides information on the crystallographic structure of a sample, while scanning Kelvin probe microscopy (SKPM) provides information on its electrical properties. The advantage of these techniques is their high spatial resolution, which cannot be attained with any other techniques. However, because these techniques analyze the top layers of the sample, surface or cross section features directly influence the results of the measurements, and sample preparation is a main step in the analysis. In this work we investigated different methods to prepare cross sections of CdTe/CdS solar cells for EBSD and SKPM analyses. We observed that procedures used to prepare surfaces for EBSD are not suitable to prepare cross sections, and we were able to develop a process using polishing and ion-beam milling. This process resulted in very good results and allowed us to reveal important aspects of the cross section of the CdTe films. For SKPM, polishing and a light ion-beam milling resulted in cross sections that provided good data. We were able to observe the depletion region on the CdTe film and the p-n junction as well as the interdiffusion layer between CdTe and CdS. However, preparing good-quality cross sections for SKPM is not a reproducible process, and artifacts are often observed.

Moutinho, H. R.; Dhere, R. G.; Jiang, C. S.; Al-Jassim, M. M.

2011-01-01

66

EBSD characterization of cavitation during superplastic deformation of Al–Li alloy  

Microsoft Academic Search

The cavitation microstructure of an Al–Li alloy was characterized using electron backscatter diffraction (EBSD). The results showed clear evidence of the correlation between grain boundary sliding and cavity development. It is proposed that the stress concentrations arising at boundary irregularities such as second-phase particles, boundary ledges, and triple junctions were responsible for the development of cavitation at the high angle

Y. Xun; M. J. Tan; K. M. Liew

2005-01-01

67

Coupling of Electron Channeling with EBSD: Toward the Quantitative Characterization of Deformation Structures in the SEM  

NASA Astrophysics Data System (ADS)

The coupling of electron channeling contrast imaging (ECCI) with electron backscatter diffraction (EBSD) provides an efficient and fast approach to perform ECCI of crystal defects, such as dislocations, cells, and stacking faults, under controlled diffraction conditions with enhanced contrast. From a technical point of view, the ECCI technique complements two of the main electron microscopy techniques, namely, EBSD and conventional diffraction-based transmission electron microscopy. In this review, we provide several application examples of the EBSD-based ECCI approach on microstructure characterization, namely, characterization of single dislocations, measurement of dislocation densities, and characterization of dislocation substructures in deformed bulk materials. We make use of a two-beam Bloch wave approach to interpret the channeling contrast associated with crystal defects. The approach captures the main features observed in the experimental contrast associated with stacking faults and dislocations.

Gutierrez-Urrutia, I.; Zaefferer, S.; Raabe, D.

2013-09-01

68

Dependence of the Electron Beam Energy and Types of Surface to Determine EBSD Indexing Reliability in Yttria-Stabilized Zirconia  

SciTech Connect

Electron backscatter diffraction (EBSD) is a powerful technique for the surface microstructure analysis. EBSD analysis of cubic yttria-stabilized zirconia (YSZ) in two and three dimensions (2-D, 3-D) is demonstrated using sequential slicing from a focused ion beam (FIB) followed by EBSD mapping to represent 3-D reconstructed high density grain structure with random orientation. The statistics related to accuracy of EBSD band detection shows that probability of accurate grain orientation detection increased significantly when the electron beam energy is increased from 10 kV to 30 kV. As a result of better sampling with increased interaction volume, a disparity between local and average grain orientation angle also exhibited the dependence of the electron beam energy to determine the accuracy of grain orientation. To study the accuracy and quality of EBSD band detection as a function of surface roughness and over layer formation, rapid EBSD measurement tests are performed on (a) YSZ surfaces ion-polished at ion beam energies of 65 nA at 30 kV and 1 nA at 30 kV and (b) carbon coated versus uncoated YSZ surfaces. The EBSD results at both 10 kV and 30 kV electron beam energies indicate that EBSD band detection accuracy is negatively affected by surface roughness and amorphous over layer formation.

Saraf, Laxmikant V.

2012-04-01

69

Combined electron backscatter diffraction and cathodoluminescence measurements on CuInS2/Mo/glass stacks and CuInS2 thin-film solar cells  

NASA Astrophysics Data System (ADS)

Electron backscatter diffraction (EBSD) and cathodoluminescence (CL) measurements in a scanning electron microscope were performed on cross sections of CuInS2 thin films and ZnO/CdS/CuInS2/Mo/glass thin-film solar cells. The CuInS2 layers analyzed for the present study were grown by a rapid thermal process. The regions of the CuInS2 layers emitting high CL intensity of band-band luminescence are situated near the top surface (or close to the interface with ZnO/CdS). This can be attributed to an enhanced crystal quality of the thin films in this region. The phenomenon may be related to the recrystallization via solid-state reactions with CuxS phases, which is assumed to run from the top to the bottom of the growing CuInS2 layer. The distribution of CL intensities is independent of the sample temperature, the acceleration voltage of the electron beam, and of whether or not the ZnO/CdS window layers are present. When comparing CL images and EBSD maps on identical sample positions, pronounced intragrain CL contrast is found for individual grains. Also, it is shown that at random grain boundaries, the decreases in CL intensities are substantially larger than at ?3 grain boundaries.

Abou-Ras, D.; Jahn, U.; Nichterwitz, M.; Unold, T.; Klaer, J.; Schock, H.-W.

2010-01-01

70

Electron backscatter diffraction characterization of plasma immersion ion implantation effects in stainless steel  

NASA Astrophysics Data System (ADS)

In these experiments plasma immersion ion implantation is utilised to simulate some of the radiation effects in a nuclear reactor environment. Scanning electron microscopy using the angular selective backscatter detector has revealed observable changes in crystallographic contrast after irradiation with helium ions. Further studies using electron backscatter diffraction in both plan and cross section view allow us to visualize the extent and depth of damage and observe differences in the behavior of different crystalline phases present in several grades of stainless steel.

Davis, Joel; Short, Ken; Wuhrer, Richard; Phillips, Matthew R.; Lumpkin, Gregory R.; Whittle, Karl R.

2013-01-01

71

An Electron Backscatter Diffraction Investigation of Plastic Deformation in Pyrite: Microstructural Changes, Slip Systems and a Revised Deformation Mechanism map  

NASA Astrophysics Data System (ADS)

Experimentally deformed single-crystal and polycrystalline pyrite samples have been investigated using electron backscatter diffraction (EBSD). The single-crystal samples were loaded parallel to <100> or <110> and deformed at a strain rate of 10-5 s-1 and temperatures of 600°C and 700°C. Schmid factor results advocate that <110> loading activates the well established {001}<100> slip system while <100> loading activates the {110}<1-10> slip system. However, while boundary trace analysis and lattice rotation axes indicate {110}<1-10> is possible, it requires concurrent activation of a complex arrangement of slip planes and vectors. In contrast determination of 75MPa as the required critical resolved shear stress (CRSS) for {001}<100> activation, suggests crystal misalignment of ~5-15° to the loading direction in <100> loaded crystals would be sufficient to activate the {001}<100> slip system. Thus, {001}<100> is considered the most likely active slip system in deformed pyrite. This is supported by {001}<1-10> slip being uncommon in polycrystalline pyrite samples. Polycrystalline pyrite samples deformed experimentally at strain rates of 10-4 s-1 and 10-5 s-1 and temperatures between 450-700°C preserve evidence for plastic deformation, specifically dislocation creep. Similar results are recorded in naturally deformed samples (~320-610°C) suggesting dislocation creep is widespread in deformed pyrite and operates at temperatures far lower than previously anticipated (~ 425°C). Combining the EBSD results with the stress-strain curve data from experimental deformation allows construction of a revised pyrite deformation mechanism map. This map corresponds to polycrystalline pyrite with a grain size of ~35?m and suggests the brittle-plastic transition at geological strain-rates occurs at ~320°C. Pyrite trace-element geochemistry is widely used in mineral deposit characterisation, and increasingly evidence is presented documenting trace element zonation in pyrite. While such zonation may relate to growth processes, this study raises the possibility that it may rather be related to diffusion pathways facilitated by plastic deformation processes that are much more widespread in pyrite than is generally accepted.

Boyle, A. P.; Barrie, C. D.; Cox, S. F.; Pearce, M. A.; Prior, D. J.

2008-12-01

72

EBSD characterization of 8090 Al–Li alloy during dynamic and static recrystallization  

Microsoft Academic Search

The microstructures of high-temperature deformed and annealed 8090 Al–Li alloy have been characterized using electron back-scattered diffraction (EBSD). The observed structure refinement, which is attributed to the dynamic and static recrystallization (DRX and SRX, respectively) for the deformation and annealing processes, respectively, was accompanied by a shift in misorientation angle distribution from low- to high-angle side, with more significant effect

Y. Xun; M. J Tan

2004-01-01

73

Characterization of microstructural damage due to low-cycle fatigue by EBSD observation  

SciTech Connect

Electron backscatter diffraction (EBSD) in conjunction with scanning electron microscopy was used to assess the damage due to cyclic or uniform strain. Samples of Type 316 stainless steel after fatigue and tensile tests were prepared for EBSD observation and the misorientation angle between neighboring points (local misorientation) was evaluated. It was shown that the local misorientation developed due to the cyclic and uniform strain and that its spatial distribution was not uniform. In fatigue samples, the area of large local misorientation tended to form clusters, whereas it localized to the grain boundaries in the tensile samples, and the magnitude of local misorientation and the degree of the localization increased with the strain amplitude. The degree of localization was quantified via statistical processing of the measured data. It was also shown that the source of damage (cyclic or uniform strain) and the loading direction could be deduced from the EBSD observations of the damaged sample.

Kamaya, Masayuki, E-mail: kamaya@inss.co.jp [Institute of Nuclear Safety System, Inc., 64 Sata, Mihama-cho, Mikata-gun, Fukui 919-1205 (Japan)

2009-12-15

74

Zirconium deformation behavior: insights from EBSD measurements.  

SciTech Connect

The deformation of crystal-bar zirconium was investigated as a function of strain and strain rate through electron back-scattered diffraction (EBSD) characterization. The resultant data provided spatially resolved information on microstructure and texture evolution, individual twin system activity, and subsequent strain partitioning between twinned volume and parent grains. A range of deformation conditions was represented through quasi-static compression, 4-point beam bend tests at room and cryogenic temperature, and Taylor cylinder impact experiments. Effects from the interplay between slip and twinning deformation modes on anisotropic plasticity are considered in order to address the apparent trend toward isotropy at high rates. The role of various length scales on deformation behavior will be considered, along with the implications of these length scales on the assumptions typically invoked for plasticity modeling.

Bingert, J. F. (John F.); Mason, T. A. (Thomas A.); Kaschner, G. C. (George C.); Maudlin, P. J. (Paul J.); Gray, G. T. (George T.), III

2001-01-01

75

Electron backscattering diffraction analysis of an ancient wootz steel blade from central India  

SciTech Connect

The electron backscattering diffraction technique was used to analyse the nature of carbides present in an ancient wootz steel blade. Bulky carbides, pro-eutectoid carbide along the prior austenite grain boundaries and fine spheroidized carbides were detected. Electron backscattering diffraction was employed to understand the texture of these carbides. The orientations of the cementite frequently occur in clusters, which points to a common origin of the members of the cluster. For the bands of coarse cementite, the origin is probably large coarse particles formed during the original cooling of the wootz cake. Pearlite formed earlier in the forging process has led to groups of similarly oriented fine cementite particles. The crystallographic texture of the cementite is sharp whereas that of the ferrite is weak. The sharp cementite textures point to the longevity of the coarse cementite throughout the repeated forging steps and to the influence of existing textured cementite on the nucleation of new cementite during cooling.

Barnett, M.R. [Centre for Material and Fibre Innovation, Deakin University, Geelong (Australia)], E-mail: barnettm@deakin.edu.au; Sullivan, A. [Centre for Material and Fibre Innovation, Deakin University, Geelong (Australia); Balasubramaniam, R. [Depertment of Materials and Metallurgical Engineering, Indian Institute of Technology, Kanpur, Kanpur 208 016 (India)

2009-04-15

76

Microstructural evolution in adiabatic shear bands of copper at high strain rates: Electron backscatter diffraction characterization  

SciTech Connect

The microstructural evolution of adiabatic shear bands in annealed copper with different large strains at high strain rates has been investigated by electron backscatter diffraction. The results show that mechanical twinning can occur with minimal contribution to shear localization under dynamic loading. Elongated ultrafine grains with widths of 100-300 nm are observed during the evolution of the adiabatic shear bands. A rotational dynamic recrystallization mechanism is proposed to explain the formation of the elongated ultrafine grains. - Highlights: Black-Right-Pointing-Pointer The microstructural evolution of ASB is studied by electron backscatter diffraction. Black-Right-Pointing-Pointer Twinning can occur in ASB while the contribution to shear localization is slight. Black-Right-Pointing-Pointer Elongated ultrafine grains are observed during the evolution process of ASB. Black-Right-Pointing-Pointer A possible mechanism is proposed to explain the microstructure evolution of ASB.

Tang Lin [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Chen Zhiyong, E-mail: czysh@netease.com [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Zhan Congkun; Yang Xuyue; Liu Chuming [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Cai Hongnian [School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China)

2012-02-15

77

A microtexture study of eutectic carbides in white cast irons using electron back-scatter diffraction  

Microsoft Academic Search

White cast irons have a microstructure composed of a ferrous matrix with hexagonal and\\/or orthorhombic carbides, M7C3 and M3C, respectively. The US Bureau of Mines has implemented a study programme to improve microstructure and thereby wear resistance of these alloys. This work included electron back-scatter diffraction in a scanning electron microscope to identify the hexagonal and orthorhombic phases from their

V. Randle; G. Laird II

1993-01-01

78

Characterization of crystallographic texture in plasma-sprayed splats by electron-backscattered diffraction  

Microsoft Academic Search

The surface microtexture of splats deposited by atmospheric dc plasma spraying was studied by the electron-backscattered diffraction method. The examined splats were yttria-stabilized zirconia (YSZ) and nickel deposited onto a mirror-polished stainless steel substrate preheated to 500K. The YSZ splats exhibited a disk-shaped morphology and had a peculiar <111> fiber texture in their peripheral region; the fiber axes were perpendicular

Kentaro Shinoda; Masahiko Demura; Hideyuki Murakami; Seiji Kuroda; Sanjay Sampath

2010-01-01

79

Effect of the surface preparation techniques on the EBSD analysis of a friction stir welded AA1100-B{sub 4}C metal matrix composite  

SciTech Connect

Aluminum based metal matrix composites (MMCs) have been used in various automobile, aerospace and military industries. Yet characterization of the microstructure in these materials remains a challenge. In the present work, the grain structure in the matrix of B{sub 4}C particulate reinforced MMCs and their friction stir welds is characterized by using optical metallography and the electron backscatter diffraction (EBSD) technique. Optical metallography can partially reveal the grain structure in the matrix of AA1100-16 vol.% B{sub 4}C composite. The EBSD technique has been successfully applied to characterize the grain structure in the AA1100-16 vol.% B{sub 4}C friction stir welds, which provides a powerful tool to follow the microstructural evolution of MMC materials during friction stir welding (FSW). Both mechanical polishing and ion beam polishing are used for the EBSD sample preparation. The effect of the sample preparation on the EBSD data acquisition quality is studied. Some typical examples, such as the identification of grains and subgrains, grain size distribution, deformation fields and the texture components are given. - Highlights: {yields} EBSD has been used to characterize the grain structure of Al-B{sub 4}C MMCs. {yields} Mechanical and ion beam polishing are compared for EBSD sample preparation of MMCs. {yields} EBSD shows great advantages over optical microscopy for microtexture analysis of MMCs.

Guo, J., E-mail: junfeng.guo@cnrc-nrc.gc.ca [University of Quebec at Chicoutimi, Chicoutimi (QC), G7H 2B1 (Canada); Aluminium Technology Centre, National Research Council Canada, Chicoutimi (QC), G7H 8C3 (Canada); Amira, S.; Gougeon, P. [Aluminium Technology Centre, National Research Council Canada, Chicoutimi (QC), G7H 8C3 (Canada); Chen, X.-G. [University of Quebec at Chicoutimi, Chicoutimi (QC), G7H 2B1 (Canada)

2011-09-15

80

Electron Backscatter Diffraction Analysis for Polarization of SrBi2(Ta,Nb)2O9 Ferroelectric Capacitors in Submicron Small Area  

NASA Astrophysics Data System (ADS)

We investigate the size and crystal orientation of each small grain of ferroelectric SrBi2(Ta,Nb)2O9 (SBTN) films within very small areas by an electron backscatter diffraction (EBSD) analysis technique. The obtained map of the grains reveals that the size of c-axis-oriented grains increases as the average grain size of the films increases. On the other hand, the size of a-axis-oriented grains, each of which has a finite remnant polarization normal to the films, is almost unchanged. The area fraction of the a-axis-oriented grains is in good agreement with the measured polarizations of ferroelectric capacitors with different average grain sizes. This result implies that an increase in the number of relatively small a-axis-oriented grains is effective for increasing the total polarization of the ferroelectric films. The demonstrated analysis technique is very useful for the precise design of future high-density ferroelectric random access memories (FeRAMs) with very small capacitor structures, each of which consists of only a few grains.

Kaibara, Kazuhiro; Tanaka, Keisuke; Uchiyama, Kiyoshi; Kato, Yoshihisa; Shimada, Yasuhiro

2008-01-01

81

Quantification of ridging in ferritic stainless steel sheets by electron backscattered diffraction R-value maps.  

PubMed

In ferritic stainless steel (FSS), undesirable surface defects of ridging appear during deep drawing. The formation of these defects is attributed to the inhomogeneous distribution of orientations of individual grains. In the present work, a new electron backscattered diffraction R(?)-value map was introduced, and the dependence of the tensile directions on the formation of ridging in an FSS sheet was discussed using this map. The results showed that large grain colonies in the R(?)-value maps lead to the formation of severe ridging in an FSS sheet. PMID:23920166

Lee, Kye-Man; Park, Jieon; Kim, Sangseok; Park, Sooho; Huh, Moo-Young

2013-08-01

82

ARPGE: a computer program to automatically reconstruct the parent grains from electron backscatter diffraction data.  

PubMed

A computer program called ARPGE written in Python uses the theoretical results generated by the computer program GenOVa to automatically reconstruct the parent grains from electron backscatter diffraction data obtained on phase transition materials with or without residual parent phase. The misorientations between daughter grains are identified with operators, the daughter grains are identified with indexed variants, the orientations of the parent grains are determined, and some statistics on the variants and operators are established. Some examples with martensitic transformations in iron and titanium alloys were treated. Variant selection phenomena were revealed. PMID:19461849

Cayron, Cyril

2007-11-10

83

The application of electron backscatter diffraction and orientation contrast imaging in the SEM to textural problems in rocks  

Microsoft Academic Search

In a scanning electron microscope (SEM) an electron beam sets up an omni-directional source of scattered electrons within a specimen. Diffraction of these electrons will occur simultaneously on all lattice planes in the sample and the backscattered electrons (BSE), which escape from the specimen, will form a diffraction pattern that can be imaged on a phosphor screen. This is the

DAVID J. PRIOR; ALAN P. B OYLE; FRANK BRENKER; MICHAEL C. CHEADLE; AUSTIN DAY; GLORIA LOPEZ; LUCA PERUZZO; GRAHAM J. POTTS; STEVE REDDY; RICHARD SPIESS; NICK E. TIMMS; PAT TRIMBY; JOHN WHEELER; LENA ZETTERSTRÖM

1999-01-01

84

USING A MULTI-DISCIPLINARY APPROACH, THE FIRST ELECTRON BACKSCATTERED KIKUCHI PATTERNS WERE CAPTURES FOR A PU ALLOY  

SciTech Connect

Microstructural characterization of plutonium by electron backscattered diffraction (EBSD) has been previously elusive primarily because of the extreme toxicity and surface oxidation rates associated with plutonium metal. In this work, initial electron backscattered diffraction pattern (EBSP) observations of a plutonium-gallium (Pu-Ga) alloy were made. Samples were prepared using standard metallographic and electropolishing techniques that were performed inside gloveboxes and/or an open front hood to prevent spread of radioactive contamination. A scanning Auger microprobe (SAM), equipped with an ion-gun, was used to characterize and remove surface chemical impurities (in particular carbon (C) and oxygen (O)) and a specially designed vacuum transfer device was used to minimize oxidation during the sample transfer from the SAM to the scanning electron microscope (SEM). EBSD patterns of the {delta}-phase (face-centered-cubic) were captured and the experimental techniques and parameters used to perform EBSD characterization are described in detail.

C. J. BOEHLERT

2001-06-01

85

Combined electron backscatter diffraction and cathodoluminescence measurements on CuInS{sub 2}/Mo/glass stacks and CuInS{sub 2} thin-film solar cells  

SciTech Connect

Electron backscatter diffraction (EBSD) and cathodoluminescence (CL) measurements in a scanning electron microscope were performed on cross sections of CuInS{sub 2} thin films and ZnO/CdS/CuInS{sub 2}/Mo/glass thin-film solar cells. The CuInS{sub 2} layers analyzed for the present study were grown by a rapid thermal process. The regions of the CuInS{sub 2} layers emitting high CL intensity of band-band luminescence are situated near the top surface (or close to the interface with ZnO/CdS). This can be attributed to an enhanced crystal quality of the thin films in this region. The phenomenon may be related to the recrystallization via solid-state reactions with Cu{sub x}S phases, which is assumed to run from the top to the bottom of the growing CuInS{sub 2} layer. The distribution of CL intensities is independent of the sample temperature, the acceleration voltage of the electron beam, and of whether or not the ZnO/CdS window layers are present. When comparing CL images and EBSD maps on identical sample positions, pronounced intragrain CL contrast is found for individual grains. Also, it is shown that at random grain boundaries, the decreases in CL intensities are substantially larger than at {Sigma}3 grain boundaries.

Abou-Ras, D.; Nichterwitz, M.; Unold, T.; Klaer, J.; Schock, H.-W. [Helmholtz-Zentrum Berlin fuer Materialien und Energie, Glienicker Strasse 100, 14109 Berlin (Germany); Jahn, U. [Paul-Drude Institute for Solid-State Electronics, Hausvogteiplatz 5-7, 10117 Berlin (Germany)

2010-01-15

86

Ultraprecise studies of the thermal expansion coefficient of diamond using backscattering x-ray diffraction.  

SciTech Connect

The linear thermal expansion coefficient of diamond crystals of type IIa and type Ia was measured in the temperature range from 10 to 295 K. Neither negative thermal expansion nor any substantial difference in the thermal expansion coefficient in crystals of the different types were observed. An empirical expression was obtained that approximates the temperature dependence of the thermal expansion coefficient of diamond. The T{sup 3} temperature dependence of a Debye solid holds below {approx}100 K with an accuracy of {approx}10{sup -8} K{sup -1}. A slight increase in the value of the lattice parameter was found for the Ia-type crystal, which suggests lattice dilatation by nitrogen impurity. The measurements were performed using Bragg diffraction in backscattering from diamond crystals of highly monochromatic 23.7 keV x rays with the recently demonstrated high relative accuracy of 1.2 x 10{sup -8} in the determination of the lattice parameter.

Stoupin, S.; Shvyd'ko, Y. (X-Ray Science Division)

2011-03-17

87

Study of grain morphology of various magnetite samples by means of EBSD  

NASA Astrophysics Data System (ADS)

(001)- and (111)-oriented magnetite thin films were grown on MgO substrates (film thickness 200 nm) by means of oxygen-plasma-assisted molecular beam epitaxy and by laser-ablation. Further samples are electroplated magnetite thin films on Si/copper substrates and films from biogenic magnetite. The achieved grain orientations are analysed by means of the electron backscatter diffraction (EBSD) technique. The EBSD technique enables the crystallographic orientation of individual grains to be determined with a high spatial resolution of up to 40 nm on such ceramic materials. A high image quality of the recorded Kikuchi patterns was achieved enabling multi-phase scans (e.g., Fe3O4, MgO, Fe2O3). The facets of individual grains are analysed in detail.

Koblischka-Veneva, A.; Koblischka, M. R.

2010-01-01

88

Identification of dynamic ferrite formed during the deformation of super-cooled austenite by image-based analysis of an EBSD map  

Microsoft Academic Search

Differentiation of dynamically and statically transformed ferrites in SIDT (Strain-Induced Dynamic Transformation) steel was\\u000a carried out by various image-based analyses of EBSD (Electron BackScattered Diffraction) maps. Various identification methods\\u000a were tried on the basis on the grain size, and the intra- and inter-granular misorientations. The grain-size-based method\\u000a was valid only when a bimodal grain size distribution in the ferrite phase,

Yong Min Kim; Tae-Hong Ahn; Kwang Kyun Park; Kyu Hwan Oh; Heung Nam Han

2011-01-01

89

Hyperspectral Imaging at the Micro and Nanoscale using Energy-dispersive Spectroscopy (EDS) with Silicon Drift Detector (SDD) and EBSD Analysis  

Microsoft Academic Search

SDD systems have become state of the art technology in the field of EDS. The main characteristic of the SDDs is their extremely high pulse load capacity of up to 750,000 counts per second at good energy resolution (<123 eV Mn-Kalpha, <46 eV C-Kalpha at 100,000 counts per seconds). These properties in conjunction with electron backscatter diffraction (EBSD) technique and

T. Salge; D. Goran

2010-01-01

90

Effect of grain orientation on the nitriding rate of a nickel base alloy studied by electron backscatter diffraction  

Microsoft Academic Search

Electron backscatter diffraction is a rather new and powerful technique that provides local orientation. In this paper we present an investigation on cross-sections of a nickel base alloy (Inconel 690) treated by low temperature plasma assisted nitriding. The studied alloy presents non-uniform nitrided layer thickness from grain to grain. A linear relationship is found between the thickness of the nitrided

H. He; T. Czerwiec; C. Dong; H. Michel

2003-01-01

91

In situ electron backscatter diffraction investigation of recrystallization in a copper wire.  

PubMed

The microstructural evolution of a cold drawn copper wire (reduction area of 38%) during primary recrystallization and grain growth was observed in situ by electron backscatter diffraction. Two thermal treatments were performed, and successive scans were acquired on samples undergoing heating from ambient temperature to a steady state of 200°C or 215°C. During a third in situ annealing, the temperature was continuously increased up to 600°C. Nuclei were observed to grow at the expense of the deformed microstructure. This growth was enhanced by the high stored energy difference between the nuclei and their neighbors (driving energy in recrystallization) and by the presence of high-angle grain boundaries of high mobility. In the early stages of growth, the nuclei twin and the newly created orientations continue to grow to the detriment of the strained copper. At high temperatures, the disappearance of some twins was evidenced by the migration of the incoherent twin boundaries. Thermal grooving of grain boundaries is observed at these high temperatures and affects the high mobile boundaries but tends to preserve the twin boundaries of lower energy. Thus, grooving may contribute to the twin vanishing. PMID:23570697

Brisset, François; Helbert, Anne-Laure; Baudin, Thierry

2013-04-10

92

Measurement of local plastic strain distribution of stainless steel by electron backscatter diffraction  

SciTech Connect

Electron backscatter diffraction in conjunction with scanning electron microscopy was used to assess the plastic strain on a microstructural scale (local plastic strain) induced in stainless steel deformed up to a nominal strain of 19.7%. Accuracy of the measurement of misorientations was improved by a technique called the Domain Averaging Method (DAM), in which an average of crystal orientation was calculated for several data measured from the same domain. It was shown that the misorientation evaluated using the crystal orientation of which accuracy was improved by DAM showed localized plastic strain in the vicinity of grain boundaries (GB). The distribution of misorientations followed a log-normal distribution and the mean value correlated well with the macroscopic plastic strain induced. By using the correlation between the misorientation and the plastic strain, the distribution of local plastic strain could be quantified. It was shown that the plastic strain becomes more than 15% locally under a macroscopic strain of 4.9%. A procedure for confirming the accuracy of the measurement is also suggested.

Kamaya, Masayuki [Institute of Nuclear Safety System, Inc., 64 Sata, Mihama-cho, Mikata-gun, Fukui 919-1205 (Japan)], E-mail: kamaya@inss.co.jp

2009-02-15

93

Grain boundary studies of high temperature superconducting materials using electron backscatter Kikuchi diffraction  

SciTech Connect

Grain Orientation and gain boundary misorientation distributions in high critical current density, high temperature superconductors were determined using electron backscatter Kikuchi diffraction. It is found that depending on the type of superconductor and the processing method used to fabricate it, there exist different scales of biaxial texture from no biaxial texture, local biaxial texture, to complete biaxial texture. Experimentally obtained grain boundary misorientation distributions (GBMDs) were found to be skewed significantly to low angles in comparison to what is expected on the basis of macroscopic texture alone, suggesting that minimization of energy may be a driving force during the processing of high critical current density materials. In addition, a higher than expected fraction of coincident-site lattice boundaries is observed. Examination of maps of grain boundary misorientations in spatially correlated gains, i.e. the grain boundary mesotexture, suggests the presence percolative paths of high critical current density. A combination of orientation measurements, theoretical modeling of GBMDs and modeling of percolative current flow through an assemblage of gain boundaries is performed to gain an insight into the important microstructural features dictating the transport properties of high temperature superconductors. It is found that maximization of low energy, in particular, low angle boundaries is essential for higher critical currents. The combination of experimental and analytical techniques employed are applicable to other materials where physical properties are dominated by interganular characteristics.

Goyal, A.; Specht, E.D.; Wang, Z.L.; Kroeger, D.M.

1996-12-31

94

Seismic anisotropy of the crust: electron-backscatter diffraction measurements from the Basin and Range  

NASA Astrophysics Data System (ADS)

Crystal preferred orientations were measured in a suite of rocks from three locations in the Basin and Range using electron-backscatter diffraction. Anisotropic velocities were calculated for all rocks using single-crystal stiffnesses, the Christoffel equation and Voigt-Reuss-Hill averaging. Anisotropic velocities were calculated for all three crustal sections using these values combined with rock proportions as exposed in the field. One suite of rocks previously measured in the laboratory was used as a benchmark to evaluate the accuracy of the calculated velocities. Differences in the seismic anisotropy of the Funeral Mountains, Ruby Mountains and East Humboldt Range sections arise because of differences in mineralogy and strain, with the calc-silicate dominated Ruby Mountains section having higher P-wave speeds and VP/VS ratios because of the reduced quartz content. In all cases, the velocities show either transverse isotropy or nearly so, with a unique slow axis normal to the foliation. Velocity anisotropy can thus be used to infer the flow plane, but not the flow direction in typical crustal rocks. Areas with a subhorizontal foliation have minimal shear wave splitting for vertically propagating waves and are thus good places to measure mantle anisotropy using SKS-splitting.

Erdman, Monica E.; Hacker, Bradley R.; Zandt, George; Seward, Gareth

2013-11-01

95

Ultraprecise Studies of the Thermal Expansion Coefficient of Diamond using Backscattering X-ray Diffraction  

SciTech Connect

The linear thermal expansion coefficient of diamond crystals of type IIa and type Ia was measured in the temperature range from 10 to 295 K. Neither negative thermal expansion nor any substantial difference in the thermal expansion coefficient in crystals of the different types were observed. An empirical expression was obtained that approximates the temperature dependence of the thermal expansion coefficient of diamond. The T{sup 3} temperature dependence of a Debye solid holds below {approx}100 K with an accuracy of {approx}10{sup -8} K{sup -1}. A slight increase in the value of the lattice parameter was found for the Ia-type crystal, which suggests lattice dilatation by nitrogen impurity. The measurements were performed using Bragg diffraction in backscattering from diamond crystals of highly monochromatic 23.7 keV x rays with the recently demonstrated high relative accuracy of 1.2 x 10{sup -8} in the determination of the lattice parameter [S. Stoupin and Yu. Shvyd'ko Phys. Rev. Lett. 104 085901 (2010)].

S Stoupin; Y Shvydko

2011-12-31

96

Crystallographic analysis of plate martensite in Fe-28.5 at.% Ni by FE-SEM/EBSD  

SciTech Connect

Crystallographic analysis of plate martensite in an Fe-28.5 at.% Ni alloy was studied by electron backscattering diffraction (EBSD) in a scanning electron microscope equipped with a field emission gun (FE-SEM). It was shown that sound orientation mapping was possible even for the martensite having a high density of lattice defects and the FE-SEM/EBSD could be a strong tool for crystallographic/microstructural analysis of martensite in steels. It was confirmed that the martensite in this alloy held the Nishiyama-Wassermann (N-W) orientation relationship. Variant analysis of every martensite crystal was successfully done from orientation mapping data. It was clarified that a certain rule of variant selection operated within local areas. The procedures of crystallographic analysis of N-W martensite were explained in detail.

Kitahara, Hiromoto [Department of Adaptive Machine Systems, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita 565-0871 (Japan)]. E-mail: kitahara@im.ams.eng.osaka-u.ac.jp; Ueji, Rintaro [Department of Advanced Materials Science, Faculty of Engineering, Kagawa University, 2217-20 Hayashi-cho, Takamatsu 761-0396 (Japan); Ueda, Masato [Department of Materials Science and Processing, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita 565-0871 (Japan); Tsuji, Nobuhiro [Department of Adaptive Machine Systems, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita 565-0871 (Japan); Minamino, Yoritoshi [Department of Adaptive Machine Systems, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita 565-0871 (Japan)

2005-05-15

97

EBSD study of angular deviations from the Goss component in grain-oriented electrical steels.  

PubMed

The magnetic properties of grain-oriented (GO) electrical steels strongly depend on the distribution of the ? and ? angles, i.e., the deviations of the easy magnetisation ?100? from the rolling direction (RD) in the rolling plane and out of the rolling plane, respectively. However, most Electron Backscatter Diffraction (EBSD) studies consider the standard Goss deviation angle, which includes the rotation of the (110) plane about the RD. Therefore, in the present work, a new procedure is demonstrated for deriving the ? and ? angles from EBSD mappings to obtain a quantitative texture characterisation in line with the magnetic properties. This procedure is later applied to 37 GO steels after secondary recrystallisation that exhibit a wide range of permeability levels. The relation between the texture and the polarisation at 800A/m (J800) that is measured in the present study by EBSD is compared to the one that has been determined in previous papers with optical goniometers and X-ray diffraction techniques, and this relation is subsequently used to define a relevant parameter to describe the orientation quality of the grains. The results indicate that the average angle of the ? and ? deviations is a relevant deviation parameter for the characterisation of grain orientations. Finally, it is demonstrated that the combination of the quantitative correlation between polarisation and texture with the orientation imaging of EBSD offers the possibilities of both studying the crystallographic environment of highly oriented grains in the primary recrystallised matrix for the production of high-permeability steels and evaluating the spatial distribution of the angular deviations in GO steels after secondary recrystallisation. PMID:24090630

Bernier, Nicolas; Leunis, Elke; Furtado, Carlos; Van De Putte, Tom; Ban, Gabor

2013-09-12

98

Boundary identification in EBSD data with a generalization of fast multiscale clustering.  

PubMed

Electron backscatter diffraction (EBSD) studies of cellular or subgrain microstructures present problems beyond those in the study of coarse-grained polycrystalline aggregates. In particular, identification of boundaries delineating some subgrain structures, such as microbands, cannot be accomplished simply with pixel-to-pixel misorientation thresholding because many of the boundaries are gradual transitions in crystallographic orientation. Fast multiscale clustering (FMC) is an established data segmentation technique that is combined here with quaternion representation of orientation to segment EBSD data with gradual transitions. This implementation of FMC addresses a common problem with segmentation algorithms, handling data sets with both high and low magnitude boundaries, by using a novel distance function that is a modification of Mahalanobis distance. It accommodates data representations, such as quaternions, whose features are not necessarily linearly correlated but have known distance functions. To maintain the linear run time of FMC with such data, the method requires a novel variance update rule. Although FMC was originally an algorithm for two-dimensional data segmentation, it can be generalized to analyze three-dimensional data sets. As examples, several segmentations of quaternion EBSD data sets are presented. PMID:23751208

McMahon, Cullen; Soe, Brian; Loeb, Andrew; Vemulkar, Ayyappa; Ferry, Michael; Bassman, Lori

2013-05-02

99

Scanning Electron Microscopy/Electron Backscatter Diffraction-Based Observations of Martensite Variant Selection and Slip Plane Activity in Supermartensitic Stainless Steels during Plastic Deformation at Elevated, Ambient, and Subzero Temperatures  

NASA Astrophysics Data System (ADS)

The deformation-induced martensite variant selection in a supermartensitic stainless steel (SMSS) has been examined in the temperature range from -60 °C to 150 °C, using in-situ tensile testing in combination with electron backscatter diffraction (EBSD) analyses in the scanning electron microscope (SEM). In the as-received ( i.e., intercritically annealed) condition, the base material contains about 40 vol pct of retained austenite. At each testing temperature, this austenite transforms back to martensite during plastic deformation at a rate which is controlled by the accumulated plastic strain in the material. On the other hand, the applied strain rate and crystallographic orientations of the prior austenite grains do not affect the overall transformation rate. Moreover, the subsequent Schmid factor analysis reveals that the martensite variant selection is independent of the local slip activity within the austenite. Therefore, no new martensite variants, besides those already present in the parent steel, develop during the phase transformation. At the same time, their individual intensities remain approximately constant within each prior austenite grain. This means that the deformation-induced martensite variants nucleate from the same sites as those that are operative in the intercritically-annealed base material. Thus, the observed variant selection is another example of the inherent reversible nature of the martensite transformation.

Karlsen, Morten; Grong, Řystein; Sřfferud, Mario; Hjelen, Jarle; Rřrvik, Gisle; Chiron, Remi

2009-02-01

100

An analysis of the microstructures developed in experimentally deformed polycrystalline pyrite and minor sulphide phases using electron backscatter diffraction  

NASA Astrophysics Data System (ADS)

Samples of polycrystalline pyrite previously deformed in tri-axial compression tests at a confining pressure of 300 MPa and a strain rate of 2 × 10-4 s-1 but varying temperature were analysed in this study. Five samples including the original starting material have undergone analysis using forescatter orientation contrast (OC) imaging coupled with electron back scatter diffraction (EBSD) to determine how the micro-structures in pyrite and to an extent the surrounding minor phases have changed with increasing temperature. Between 550 °C and 650 °C the dominant deformation mechanism in pyrite is that of dislocation creep. Above 650 °C this mechanism becomes less apparent and few if any dislocation walls are present within pyrite grains by 700 °C. This is a result of either increased dynamic recrystallisation with temperature or a change in the dominant deformation mechanism. Dislocation creep occurs via lattice rotation, principally about a single <100> axis, but also about two separate <100> axes and more rarely about a single <110> axis. Deformation has not resulted in a crystallographic preferred orientation (CPO) within any of the samples. Shape change of pyrite grains has occurred and this can account for most if not all of the shortening applied, but dynamic recrystallisation of pyrite and grain boundary sliding accommodated along the minor phases are also likely to be important mechanisms in all of the samples.

Barrie, Craig D.; Boyle, Alan P.; Prior, David J.

2007-09-01

101

Texture and nano-scale internal microstructure of otoliths in the Atlantic molly, Poecilia mexicana: A high-resolution EBSD study.  

PubMed

Otoliths of modern bony fishes are massive polycrystalline structures consisting mainly of calcium carbonate (primarily aragonite), and 1-10% organic residuals. Unlike other biomineralisates like shells, teeth and bones, they are not optimized for mechanical loads but serve the senses of hearing and balance in the inner ear. We examined internal structural variation of otoliths through microstructural and texture analyses. Our study applied the electron backscattered diffraction technique (EBSD) to whole sections of saccular otoliths on cave- and surface-dwelling fish. Application of high spatial resolution EBSD on otoliths of the livebearing fish Poecilia mexicana allowed for an investigation of crystal orientation despite the small size (<150nm) of aragonite crystallites. Crystallites at the rims of otoliths had a higher structural organization than those situated near the center, where no dominant orientation pattern was discernible. Moreover, the medial (sulcal) face of otoliths, which makes contact with the sensory epithelium, was more structured than the lateral (antisulcal) face. PMID:23891259

Schulz-Mirbach, T; Götz, A; Griesshaber, E; Plath, M; Schmahl, W W

2013-07-10

102

Crystal preferred orientations of garnet: comparison between numerical simulations and electron back-scattered diffraction (EBSD) measurements in naturally deformed eclogites  

Microsoft Academic Search

Observations of dislocations, sub-grains and elongated crystal shapes support plastic deformation of garnet in laboratory experiments and naturally deformed eclogites. To evaluate the crystal preferred orientations (CPO) of garnet formed in axial shortening, pure shear and simple shear, we performed numerical simulations of CPO development during plastic flow using the visco-plastic self-consistent model. As input for the models we use

David Mainprice; Jérôme Bascou; Patrick Cordier; Andréa Tommasi

2004-01-01

103

Plastic deformation and creep damage evaluations of type 316 austenitic stainless steels by EBSD  

SciTech Connect

The inspection method of plastic and/or creep deformations has been required as the quantitative damage estimation procedure for structural components especially used in electric power plants. In this study, the method using electron backscatter diffraction (EBSD) was applied to the deformation and damage evaluation of austenitic stainless steels strained by tension or compression at room temperature and also tested in creep at high temperature. It was found that the value of Grain Average Misorientation (GAM) which showed the average misorientation for the whole observed area including over several dozen grains, was a very useful parameter for quantifying the microstructural change as either the plastic or creep strain increased. The unique linear correlation was obtained between GAM and plastic strain in tension and compression. For creep damage evaluation, the difference of grain average misorientation from the value of the unstrained specimen ({Delta}GAM) showed an excellent correlation with the inelastic strain below strain at which the tertiary creep began.

Yoda, Rika, E-mail: yoda.rika@kki.kobelco.com [Electronics Division, Kobelco Research Institute Inc., 1-5-5 Takatsuka-dai, Nishi-ku, Kobe, Hyogo 651-2271 (Japan); Department of Adaptive Machine Systems, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871 (Japan); Department of Materials Science and Engineering, Graduate School of Engineering, Kyoto University, Yoshida Honmachi, Sakyo-ku, Kyoto, 606-8501 (Japan); Yokomaku, Toshinori, E-mail: yokomaku.toshinori@kki.kobelco.com [Engineering Mechanics Division, Kobelco Research Institute Inc., 1-5-5 Takatsuka-dai, Nishi-ku, Kobe, Hyogo 651-2271 (Japan); Tsuji, Nobuhiro, E-mail: nobuhiro.tsuji@ky5.ecs.kyoto-u.ac.jp [Department of Materials Science and Engineering, Graduate School of Engineering, Kyoto University, Yoshida Honmachi, Sakyo-ku, Kyoto, 606-8501 (Japan)

2010-10-15

104

EBSD and TEM investigation of the hot deformation substructure characteristics of a type 316L austenitic stainless steel.  

PubMed

The evolution of crystallographic texture and deformation substructure was studied in a type 316L austenitic stainless steel, deformed in rolling at 900 degrees C to true strain levels of about 0.3 and 0.7. Electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) were used in the investigation and a comparison of the substructural characteristics obtained by these techniques was made. At the lower strain level, the deformation substructure observed by EBSD appeared to be rather poorly developed. There was considerable evidence of a rotation of the pre-existing twin boundaries from their original orientation relationship, as well as the formation of highly distorted grain boundary regions. In TEM, at this strain level, the substructure was more clearly revealed, although it appeared rather inhomogeneously developed from grain to grain. The subgrains were frequently elongated and their boundaries often approximated to traces of [111] slip planes. The corresponding misorientations were small and largely displayed a non-cumulative character. At the larger strain, the substructure within most grains became well developed and the corresponding misorientations increased. This resulted in better detection of sub-boundaries by EBSD, although the percentage of indexing slightly decreased. TEM revealed splitting of some sub-boundaries to form fine microbands, as well as the localized formation of microshear bands. The substructural characteristics observed by EBSD, in particular at the larger strain, generally appeared to compare well with those obtained using TEM. With increased strain level, the mean subgrain size became finer, the corresponding mean misorientation angle increased and both these characteristics became less dependent on a particular grain orientation. The statistically representative data obtained will assist in the development of physically based models of microstructural evolution during thermomechanical processing of austenitic stainless steels. PMID:15009696

Cizek, P; Whiteman, J A; Rainforth, W M; Beynon, J H

2004-03-01

105

Study of { 11bar{2} 1} Twinning in ?-Ti by EBSD and Laue Microdiffraction  

NASA Astrophysics Data System (ADS)

Activity of the { 11bar{2} 1} < bar{1} bar{1} 26 rangle extension twinning (T2) mode was analyzed in a commercial purity Ti sample after 2 pct tensile strain imposed by four-point bending. The sample had a moderate c-axis fiber texture parallel to the tensile axis. Compared with the many { 10bar{1} 2} < bar{1} 011 rangle extension (T1) twins that formed in 6 pct of the grains, T2 twins were identified in 0.25 pct of the grains by scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD) maps. Most of the T2 twins exhibited irregular twin boundaries (TBs) on one side of the twin. High-resolution EBSD revealed both intermediate orientations at some matrix/twin interfaces and substantial lattice rotation within some T2 twins. Interactions between matrix < c + a> dislocations 1/3 < 1bar{2} 13 rangle and a { 11bar{2} 1} T2 twin were investigated by combining SEM/EBSD slip trace characterization and Laue microdiffraction peak streak analysis. < c + a> dislocations that originally glided on a pyramidal plane in the matrix were found on other planes in both the matrix and the twin, which was attributed to extensive cross-slip of the screw component, whose Burgers vector was parallel to the twinning plane. On the other hand, thickening of the twin could engulf some pile-up edge components in front of the TB. During this process, these < c + a> dislocations transmuted from a pyramidal plane (0bar{1} 11) in the matrix to a prismatic plane (bar{1} 010)_{{T}} in the twin lattice. Finally, possible mechanisms for the nucleation and growth of T2 twins will be discussed.

Wang, Leyun; Barabash, Rozaliya; Bieler, Thomas; Liu, Wenjun; Eisenlohr, Philip

2013-08-01

106

Use of EBSD Data in Numerical Analyses  

SciTech Connect

Experimentation, theory and modeling have all played vital roles in defining what is known about microstructural evolution and the effects of microstructure on material properties. Recently, technology has become an enabling factor, allowing significant advances to be made on several fronts. Experimental evidence of crystallographic slip and the basic theory of crystal plasticity were established in the early 20th Century, and the theory and models evolved incrementally over the next 60 years. (Asaro provides a comprehensive review of the mechanisms and basic plasticity models.) During this time modeling was primarily concerned with the average response of polycrystalline aggregates. While some detailed finite element modeling (FEM) with crystal plasticity constitutive relations was done in the early 1980s, such simulations over taxed the capabilities of the available computer hardware. Advances in computer capability led to a flurry of activity in finite element modeling in the next 10 years, increasing understanding of microstructure evolution and pushing the limits of theories and material characterization. Automated Electron Back Scatter Diffraction (EBSD) has produced a similar revolution in material characterization. The data collected is extensive and many questions about the evolution of microstructure and its role in determining mechanic properties can now be addressed. It is also now possible to obtain sufficient information about lattice orientations on a fine enough scale to allow detailed quantitative comparisons of experiments and newly emerging large scale numerical simulations. The insight gained from the coupling of EBSD and FEM studies will provide impetus for further development of microstructure models and theories of microstructure evolution. Early studies connecting EBSD data to finite element models used manual measurements to define initial orientations for the simulation. In one study, manual measurements of the deformed structure were also obtained for comparison with the model predictions. More recent work has taken advantage of automated data collection on deformed specimens as a means of collecting detailed and spatially correlated data for model validation. Although it will not be discussed in detail here, another area in which EBSD data is having a great impact is on recrystallization modeling. EBSD techniques can be used to collect data for quantitative microstructural analysis. This data can be used to infer growth kinetics of specific orientations, and this information can be synthesized into more accurate grain growth or recrystallization models. Another role which EBSD techniques may play is in determining initial structures for recrystallization models. A realistic starting structure is vital for evaluating the models, and attempts at predicting realistic structures with finite element simulations are not yet successful. As methodologies and equipment resolution continue to improve, it is possible that measured structures will serve as input for recrystallization models. Simulations have already been run using information obtained manually from a TEM.

Becker, R; Wiland, H

2000-01-14

107

EBSD study of (1 1 0) orientation of iridium (Ir) coating on niobium (Nb) substrate by double glow plasma  

NASA Astrophysics Data System (ADS)

(1 1 0)-Oriented Ir coating was prepared by double glow plasma technique on (2 0 0)-oriented Nb substrate. The microstructure of the coating was observed by scanning electron microscopy (SEM). The crystal orientation of the coating was determined by X-ray diffraction (XRD) and electron backscatter diffraction (EBSD). The coating was composed of columnar grains with submicrometer size of 0.2-0.3 ?m. The thickness of the coating was approximately 6-7 ?m. The mean misorientation angles of the surface of the coating were about 38.6°. The columnar Ir coating had a preferential growth orientation of (1 1 0) crystal plane by XRD and EBSD due to the initial nuclei with preferred growth on the surface of the substrate. The vigorous bombardment from the high energy ions prevented the lower energy (1 0 0) crystal face and the lowest energy (1 1 1) crystal face from generating the orientation. Only the highest energy (1 1 0) crystal face could be formed and grew up, which resulted in the preferred (1 1 0) orientation.

Wu, Wangping; Chen, Zhaofeng; Cheng, Xingwang; Wang, Yangwei

2013-07-01

108

An investigation into the use of electron back scattered diffraction to measure recrystallized fraction  

SciTech Connect

The Electron Back-Scattered Diffraction (EBSD) technique is in its infancy and is a highly promising area of development. Use of EBSD has been predominantly for the determination of crystallographic textures. Other applications have also been considered, which include: crystal structure determination, phase determination, grain boundary studies and both elastic and plastic deformation measurement. Although it has been acknowledged that an important use of the EBSD could be in the measurement of recrystallization and its kinetics there are a number of inherent problems with such measurements using EBSD. These problems include the ability of the system to index deformed microstructures even those on a fine scale, the difficulties of analyzing patterns in the region of grain boundaries and the problems of sample preparation which is critical in the quality of the diffraction patterns obtained. The aim of the present study is to determine whether it is possible to measure the volume fraction recrystallized using EBSP of partially recrystallized stainless steel. This has been done by investigation of the quality of matching between the observed and calculated diffraction patterns, and the quality of the observed patterns measured in terms of their contrast. The material used was stainless steel 316L.

Black, M.P.; Higginson, R.L. (Univ. of Sheffield (United Kingdom). Dept. of Engineering Materials)

1999-06-18

109

EBSD Characterization of Dendrites in Synthetic and Natural Rocks  

NASA Astrophysics Data System (ADS)

Arborescent crystals in igneous rocks are associated with extreme crystallization environments: the protoplanary disk (chondrules), Earth's ultramafic Archean mantle (komatiite), and terrestrial submarine-erupted lavas (pillow basalts), although the role of morphological instabilities in more mundane settings such as magma reservoirs of modern oceanic islands is increasingly appreciated (see Welsch et al., V16). Fundamentals of dendrite formation are presumably well understood: branching morphologies belie crystal growth conditions in which the driving force for solidification produces a kinetic roughening transition, transforming an atomically smooth crystal-liquid interface into a rough, adhesive interface capable of extremely rapid advancement. However, not since photomicrograhic advances made possible close observations of snow crystals (Nakaya 1936), has there been a more promising set of analytical tools to characterize dendrites in natural and synthetic materials in pursuit of new insights. We are investigating clinopyroxene (cpx) in the quenched top of Fe-rich tholeiitic lava (Munro Township, Northeast Ontario; Fig. 1) and a synthetic basalt of similar character (Hammer 2006) with electron backscatter diffraction (EBSD), 3D reconstruction of optical serial sections, and TEM. Here we report intriguing phenomena observed with EBSD common to both samples. Severe thinning of dendrite trunks and repeated tip splitting destroys the self-similarity associated with classical dendrites and instead presages 'seaweed' morphology. Split tips manifest incremental trajectory deflections, producing gently arched trunks (Fig. 1A) as well as tightly curved (r<10 um) trunks. Crystals progressively rotate clockwise about cpx <010>, producing distinctive misorientation maps and pole figures (Fig. 1C). Parallel branches exhibit similar rotational trajectories, carving parallel arcs in the <010> pole figure. The high incidence of side branching and tip splitting is consistent with very rapid growth velocity, associated with extremely high kinetic undercooling at the dendrite tip (Mullis and Cochrane 2001). A plausible explanation for development of the lattice misorientation is engulfment of impurity particles (possibly plagioclase), a process of progressive tip deflection that has been modeled using phase field theory (Gránásy et al. 2003). The ubiquity of cpx rotation in concert with seaweed morphology suggests that not only is growth exceptionally rapid, but profoundly influenced by heterophase effects. Nakaya, U et al. (1934-1938) Investigation on Snow. J Fac Sci Hokkaido Univ, Ser II, 1-2. Hammer, JE (2006) EPSL 248, 618-637. Mullis, AM and Cochrane RF (2001) Acta Mater 49, 2205-2214. Gránásy, L et al. (2003) Nature doi:10.1038/nmat815.

Hammer, J. E.; Tiley, J.; Shiveley, A.; Knox, S.; Viswanathan, G.

2011-12-01

110

Quantitative metallography of ?-Sn dendrites in Sn3.8Ag0.7Cu ball grid array solder balls via electron backscatter diffraction and polarized light microscopy  

Microsoft Academic Search

Electron backscatter diffraction and polarized light microscopy have been used to quantify the number of crystallographically\\u000a independent ?-Sn dendrites present in near-eutectic, ball grid array Sn-Ag-Cu (SAC) solder balls as a function of cooling\\u000a rate (0.35–3.0C\\/s). Based on these data, it is estimated that a single 900-m-diameter solder ball contains on average eight\\u000a individual ?-Sn dendrites, independent of cooling rate.

A. LaLonde; D. Emelander; J. Jeannette; C. Larson; W. Rietz; D. Swenson; D. W. Henderson

2004-01-01

111

Electron backscatter diffraction as a domain analysis technique in BiFeO3-PbTiO3 single crystals  

Microsoft Academic Search

xBiFeO3-(1-x)PbTiO3 single crystals were grown via a flux method for a range of compositions. Presented here is a study of the domain configuration in the 0.5BiFeO3-0.5PbTiO3 composition using electron backscatter diffraction to demonstrate the ability of the technique to map ferroelastic domain structures at the micron and submicron scale. The micron-scale domains exhibit an angle of approximately 85deg between each

Tim L. Burnett; Tim P. Comyn; Eleanor Merson; Andrew J. Bell; Ken Mingard; Tristan Hegarty; Markys Cain

2008-01-01

112

EBSD analysis of the Shergottite Meteorites: New developments within the technique and their implication on what we know about the preferred orientation of Martian minerals  

NASA Astrophysics Data System (ADS)

What we know about the geology and mineralogy of the Martian surface has been characterised by both the use of remote sensing techniques and the analysis of Martian meteorites. Various techniques are employed to conduct these analyses including crystallographic, geochemical and spectral measurements, all of which enable us to infer a geological history for these rocks. Several references have been made to the potential for preferred orientation of crystals within the Shergottites [1] and their implication for the cooling history of the respective magmas on Mars [2]. We have already shown that a preferred orientation of the two pyroxenes, augite and pigeonite, can be seen in the Zagami meteorite using electron back-scatter diffraction (EBSD) analysis [3]. However, when compared to previous modal studies of the same meteorites [4], it becomes apparent that the current EBSD datasets for Martian meteorites are incomplete. Indexing of some minerals can be hampered by the lack of available matches within library databases for EBSD, or become difficult to resolve between minerals where crystallographic differences between similar minerals fall below the technical limitations of the instrument [3]. Recent advances in EBSD technologies combined with the simultaneous acquisition of energy-dispersive spectra (EDS) however now allow us to determine a more comprehensive set of analyses in a much shorter period of time, fully resolving even similar minerals where areas have been left with no indexing previously [5]. Preliminary investigations suggest that the new technology can successfully index >90% of the sample. The most recent EBSD analyses potentially reveals previously unseen fabrics in the meteorites alongside the EDS hyper-spectral imaging helping to resolve any unknown or questionable phases within them. In this study we will present new data from an investigation using EDS alongside EBSD analysis on 2 Shergottite meteorites, SAU 005 and Zagami, to further resolve their constituent minerals and any existing preferred orientations. [1] Stolper E. and McSween, H.Y. Jnr (1979) Geochemica et Cosomochimica Acta, 43, 1475-1498 [2] McCoy, T.J. et al. (1992) Geochimica et Cosomochimica Acta, 56, 3571-3582 [3] N.R. Stephen et al. (2010) Abstract #5008 73rd Annual Meeting of the Meteoritical Society [4] N.R. Stephen et al. (2010) Abstract #2367 Lunar & Planetary Science Conference XLI [5] J. Berlin et al. (2011) Abstract #2723 Lunar & Planetary Science Conference XLII

Stephen, N.; Benedix, G. K.; Bland, P.; Berlin, J.; Salge, T.; Goran, D.

2011-12-01

113

Microstructural characterization of autogenous laser welds on 316L stainless steel using EBSD and EDS.  

PubMed

This research is concerned with autogenous welding of 316L stainless steel and the microstructure generated by such a process. Autogenous welding does not require a filler material and in this case relies on an initial shallow melt phase to maintain a conduction limited weld. Essentially, a high power laser beam traverses the substrate, with the beam shaped by conventional optics, which produces a Gaussian irradiance distribution; or with a diffractive optical element, used to produce a uniform irradiance distribution. Initial results have shown that due to the nature of the heating cycle, complex microstructures are developed. These fine, complicated microstructures cannot be satisfactorily resolved and quantified using standard optical microscopy techniques. Electron backscatter diffraction (EBSD) and energy dispersive spectroscopy (EDS) have been carried out on a number of different microstructures prepared using a range of welding parameters. It is demonstrated that the simultaneous determination of the chemistry and crystallography is a very useful tool for rapid identification of the different phases formed on solidification as a consequence of varying welding procedures. PMID:15683414

Kell, J; Tyrer, J R; Higginson, R L; Thomson, R C

2005-02-01

114

Exploring the Distribution and Nature of Shock Deformation in an Enstatite Chondrule at Submicron Resolution by a Combination of CL, Electron Backscatter Diffraction, EDS Mapping and EPMA  

NASA Astrophysics Data System (ADS)

EBSD, CL, EDS and EPMA investigations of shock-deformed enstatite in MET 00783 (EH4, S4) reveal microstructures including heterogeneous lamellar fabrics corresponding to subtle differences in Kikuchi band contrast, and amorphous feldspathic material.

Izawa, M. R. M.; Moser, D. E.; Barker, I. R.; Flemming, R. L.; Gainsforth, Z.; Stodolna, J.; Matveev, S.; Banerjee, N. R.

2012-03-01

115

An EBSD Study of the Deformation of Service-Aged 316 Austenitic Steel  

NASA Astrophysics Data System (ADS)

Electron backscatter diffraction (EBSD) has been used to examine the plastic deformation of an ex-service 316 austenitic stainless steel at 297 K and 823 K (24 °C and 550 °C) at strain rates from 3.5 × 10-3 to 4 × 10-7 s-1. The distribution of local misorientations was found to depend on the imposed plastic strain following a lognormal distribution at true strains <0.1 and a gamma distribution at strains >0.1. At 823 K (550 °C), the distribution of misorientations depended on the applied strain rate. The evolution of lattice misorientations with increasing plastic strain of up to 0.23 was quantified using the metrics kernel average misorientation, average intragrain misorientation, and low angle misorientation fraction. For strain rate down to 10-5 s-1, all metrics were insensitive to deformation temperature, mode (tension vs compression), and orientation of the measurement plane. The strain sensitivity of the different metrics was found to depend on the misorientation ranges considered in their calculation. A simple new metric, proportion of undeformed grains, is proposed for assessing strain in both the aged and unaged materials. Lattice misorientations develop with strain faster in aged steel than in unaged material, and most of the metrics were sensitive to the effects of thermal aging. Ignoring aging effects leads to significant overestimation of the strains around welds. The EBSD results were compared with nanohardness measurements, and good agreement was established between the two techniques of assessing plastic strain in aged 316 steel.

Githinji, David N.; Northover, Shirley M.; Bouchard, P. John; Rist, Martin A.

2013-09-01

116

3D EBSD characterization of deformation structures in commercial purity aluminum  

SciTech Connect

A method to map the microstructure in deformed aluminum in three dimensions is presented. The method employs serial sectioning by mechanical polishing, and electropolishing to obtain a good surface quality, and orientation mapping of individual grains in each section by electron backscattered diffraction. Techniques to carefully align the sample and to accurately measure the thickness of the material removed in each serial section are described. A new method for stacking the two dimensional maps together to produce a three dimensional visualization of the microstructure is presented. The data are analyzed in terms of the deformation-induced orientation spread within each grain. In particular the advantage of using three dimensional data, as opposed to two dimensional data, is illustrated, by inclusion of information about the three dimensional morphology of a grain and its neighbors. - Research Highlights: The deformation structures in commercial purity aluminum were characterized in 3D. The method employs serial sectioning by mechanical polishing, and electropolishing to obtain a good surface quality, and orientation mapping of individual grains in each section by electron backscattered diffraction. Techniques to carefully align the sample and to accurately measure the thickness of the material removed in each serial section are described. A new method for stacking the two dimensional maps together to produce a three dimensional visualization of the microstructure is presented. The data are analyzed in terms of the deformation-induced orientation spread within each grain. In particular the advantage of using three dimensional data, as opposed to two dimensional data, is illustrated, by inclusion of information about the three dimensional morphology of a grain and its neighbors. The highlights of the paper include: {yields} a method to obtain 3D EBSD data over a large volume {yields} a modified method for section alignment based on characteristics of deformed grains {yields}a critical comparison of information available from 2D and 3D investigations.

Lin, F.X., E-mail: lnfe@risoe.dtu.dk [Laboratory of Advanced Materials, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Danish-Chinese Center for Nanometals, Materials Research Division, Riso National Laboratory for Sustainable Energy, Technical University of Denmark, DK-4000 Roskilde (Denmark); Godfrey, A. [Laboratory of Advanced Materials, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Jensen, D. Juul; Winther, G. [Danish-Chinese Center for Nanometals, Materials Research Division, Riso National Laboratory for Sustainable Energy, Technical University of Denmark, DK-4000 Roskilde (Denmark)

2010-11-15

117

EBSD study of crystallographic identification of Fe-Al-Si intermetallic phases in Al-Si coating on Cr-Mo steel  

NASA Astrophysics Data System (ADS)

5Cr-0.5Mo steel was coated by hot-dipping in a molten Al-10 wt.% Si bath at 700 °C for 10, 60, 120 or 180 s. The identification of the phases in the Fe-Al-Si intermetallic phases formed in the aluminide layers during hot-dipping was carried out by using a combination of scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and electron backscatter diffraction (EBSD). The EDS results show a ? 5(H)-Al 7Fe 2Si phase, which exhibited 2 distinct morphologies, small particles widely dispersed and a continuous layer. Also revealed by EDS were ? 6-Al 4FeSi and ? 4-Al 3FeSi 2 phases, which showed plate-shaped morphology, in an Al-Si topcoat. However, the XRD results show the intermetallic phases in the aluminide layer were composed of outer cubic ? 5(C)-Al 7(Fe,Cr) 2Si and inner hexagonal ? 5(H)-Al 7Fe 2Si. EBSPs and mapping functions in EBSD helped to clarify the confused phase identifications yielded by EDS and XRD. In this way, the small intermetallic particles and the continuous intermetallic layer were identified as cubic ? 5(C)-Al 7(Fe,Cr) 2Si and hexagonal ? 5(H)-Al 7Fe 2Si, respectively, and the plate-shaped intermetallic phase was identified as monoclinic ? 6-Al 4FeSi and tetragonal ? 4-Al 3FeSi 2 with the same metallographic morphology. EBSD proved to be a very effective technique for local phase identification of aluminide layers with complicated multiphase morphologies.

Cheng, Wei-Jen; Wang, Chaur-Jeng

2011-03-01

118

Structural characterization of AlGaN\\/GaN superlattices by x-ray diffraction and Rutherford backscattering  

Microsoft Academic Search

We report on structural characterization of AlGaN\\/GaN superlattices grown on sapphire. The superlattice formation is evidenced by high-resolution x-ray diffraction and transmission electron microscopy. The high resolution x-ray diffraction spectra exhibit a pattern of satellite peaks. The in-plane lattice constants of the superlattices indicate the coherent growth of the AlGaN layer onto GaN. The average Al composition in the superlattices

Shengqiang Zhou; M. F. Wu; S. D. Yao; B. S. Zhang; H. Yang

2006-01-01

119

Local orientation analysis by electron backscatter diffraction in highly textured sintered, die-upset, and hydrogenation disproportionation desorption and recombination Nd-Fe-B magnets  

NASA Astrophysics Data System (ADS)

Local texture in polycrystalline Nd-Fe-B powders produced by hydrogenation disproportionation desorption and recombination (HDDR) and by pulverization of hot deformed material (MQA-F) has been studied by electron backscatter diffraction and compared with the ideal case of a powder consisting of single-crystalline particles. The HDDR powder particles exhibited a biaxial {001}, <100> local texture, whereas the MQA-F particles showed a local <001> fiber texture. This was explained by differences in the texture mechanisms of the two materials. Resin bonded compacts were prepared from the two polycrystalline powders following alignment in an external magnetic field. The degree of texture on the global scale was determined from magnetic measurements of these compacts and the results were compared with those from a commercial Nd-Fe-B sintered magnet and hot deformed magnet.

Güth, K.; Woodcock, T. G.; Thielsch, J.; Schultz, L.; Gutfleisch, O.

2011-04-01

120

Correlating whisker growth and grain structure on Sn-Cu samples by real-time scanning electron microscopy and backscattering diffraction characterization  

SciTech Connect

Whiskers/hillocks grow out of Pb-free Sn coatings used in electronics manufacturing. To determine which grains form whiskers/hillocks, we use scanning electron microscopy and backscattering diffraction to simultaneously monitor the surface morphology and grain structure. To reduce surface roughness, we developed a ''peel-off'' method to prepare ultra-flat samples that were measured repeatedly while whiskers/hillocks formed. We find grains that form into whiskers/hillocks are present in the as-deposited film (i.e., not re-nucleated) and many have horizontal grain boundaries beneath them. Grain rotation during whisker/hillock formation means that measurements performed after the features grow do not indicate their initial grain orientations.

Pei Fei; Jadhav, Nitin; Chason, Eric [School of Engineering, Brown University, Providence, Rhode Island 02912 (United States)

2012-05-28

121

Comparison of recrystallisation kinetics determined by stress relaxation, double hit, optical metallography and EBSD approaches  

SciTech Connect

A comparison of the recrystallisation kinetics determined by stress relaxation (SR), double-hit (DH), optical metallography and scanning electron microscope/electron backscattered diffraction (SEM/EBSD) mapping experimental approaches has been conducted. Two different types of steel were used as experimental material: C-Mn and interstitial-free (IF). Tests were carried out in the austenitic region for C-Mn steel and just above the Ar{sub 1} temperature for IF steel. Both steels were investigated in static and postdynamic recrystallisation (SRx and PDRx, respectively) regions. The work indicates that some differences exist between the results given by these methods. The biggest correction to the experimental results in the SRx region has to be performed on the 'raw data' obtained by the SR method. The SR method, owing to its continually applied stress, tends to accelerate the recrystallisation kinetics. The estimation of the recrystallised fraction in the PDRx region by the DH test gives even higher error because of dynamic changes of microstructure during the second hit.

Dzubinsky, M.; Husain, Z.; Haaften, W.M. van

2004-05-15

122

Assessment of local deformation using EBSD: Quantification of local damage at grain boundaries  

SciTech Connect

Electron backscatter diffraction (EBSD) in conjunction with scanning electron microscopy was used to assess localization of the local misorientation to grain boundary. In order to quantify the degree of localization, a parameter, which was referred to as the grain boundary local misorientation, was proposed. Through crystal orientation measurements using deformed Type 316 stainless steel, it was shown that the grain boundary local misorientation increased with the applied plastic strain. Particularly, at several grain boundaries, the grain boundary local misorientation was more than 3 times the local misorientation averaged for the whole area. Surface observations revealed that the large local misorientation near the grain boundaries was attributed to the impeded slip steps rather than the number of slip steps observed on the surface. The magnitude of the grain boundary local misorientation had a week correlation with grain boundary length or grain boundary misorientation, and no correlation was found for twin boundaries. Finally, it was shown that the maximum grain boundary local misorientation could be estimated statistically, and the estimated maximum value for the specimen surface with an area of 80 mm{sup 2} was 10.6 times the averaged value. - Highlights: Black-Right-Pointing-Pointer The grain boundary local misorientation was proposed. Black-Right-Pointing-Pointer The maximum grain boundary local misorientation could be estimated statistically. Black-Right-Pointing-Pointer The large local misorientation was attributed to the impeded slip steps.

Kamaya, Masayuki, E-mail: kamaya@inss.co.jp

2012-04-15

123

An Assessment and Estimation of the Damage Progression Behavior of IN738LC under Various Applied Stress Conditions Based on EBSD Analysis  

NASA Astrophysics Data System (ADS)

In order to characterize the damage progression behavior of IN738LC and the influence of applied stress, the average misorientation within grains was evaluated using the electron backscattered diffraction (EBSD) method, by measuring over a million data points located across almost the whole zone of the tested specimens. It has been shown under various test conditions such as differing temperatures and strain rates that the average misorientation increases linearly with the increase of creep strains. As a result, it is confirmed that it is possible to assess the remaining creep fracture life from its average misorientation value regardless of the testing temperature and strain rate. In addition, the deformation and fracture mechanisms of various types of mechanical damage, such as tensile, impact, and creep conditions, were discussed by evaluating the characteristics of misorientation distribution. As a result, it has been revealed that creep damage affects a large area of the material, but it is localized near grain boundaries, which is completely different from that of tensile or impact damage. In conclusion, detailed investigation into the cross section of fracture samples using the EBSD misorientation analysis allows for the qualitative estimation of the fracture mode under various applied stress conditions, the cause of the fracture.

Kobayashi, Daisuke; Miyabe, Masamichi; Kagiya, Yukio; Sugiura, Ryuji; Yokobori, A. Toshimitsu

2013-07-01

124

Matrix grain characterisation by electron backscattering diffraction of powder metallurgy aluminum matrix composites reinforced with MoSi{sub 2} intermetallic particles  

SciTech Connect

Research highlights: Six extruded PM AA6061/MoSi{sub 2}/15p were processed with and without ball milling {yields} EBSD was used to characterise matrix grain size and grain orientation. {yields} Ball milling decreases matrix grain size to submicrometric level. {yields} Ball milling produces a more equiaxed microstructure and larger misorientation. {yields} Increasing milling time produces matrix texture randomization.

Corrochano, J., E-mail: javier.corrochano.flores@gmail.com; Hidalgo, P.; Lieblich, M.; Ibanez, J.

2010-11-15

125

Relating pore structure to activity at the subcrystal level for ZSM-5: an electron backscattering diffraction and fluorescence microscopy study.  

PubMed

The catalytic performance of microporous materials such as zeolites is determined not only by the active sites' molecular architecture, but also by the organization of the surrounding pores with varying diameter, shape, and directionality. These pores control transport of reagents and products and induce shape selectivity. Rather than being ideal single crystals, zeolites often have complex 3-dimensional morphologies, comprising intergrowths and various defect types. Here, the underlying pore architecture of the hexagonal facet of an individual zeolite ZSM-5 crystal is successfully determined by electron beam scattering diffraction and is correlated with the initial reactivity toward the acid-catalyzed oligomerization of furfuryl alcohol using polarized fluorescence microscopy. PMID:18800795

Roeffaers, Maarten B J; Ameloot, Rob; Bons, Anton-Jan; Mortier, Wilfried; De Cremer, Gert; de Kloe, René; Hofkens, Johan; De Vos, Dirk E; Sels, Bert F

2008-09-19

126

Microstructural evolution during initial stages of static recovery and recrystallization: new insights from in-situ heating experiments combined with electron backscatter diffraction analysis  

NASA Astrophysics Data System (ADS)

We present in-situ observations, performed using electron backscatter diffraction, of static recovery and recrystallization processes occurring in a plastically deformed geological material, namely rocksalt. Static heating experiments, carried out in a scanning electron microscope at temperatures of up to 450 °C, allowed direct detailed observations of grain boundary migration between substructured grains in deformed polycrystalline samples. Contrary to expectations, crystallographic orientation maps reveal that behind slowly migrating grain boundaries new subgrain boundaries form while pre-existing subgrain boundaries are sometimes inherited. Moreover, the crystallographic character, especially the preferred orientation of misorientation axes of the new substructures reflects the character of the previous deformation history. These results imply that substructural features, such as subgrain misorientation distributions, may be relatively robust indicators of deformation mechanisms and conditions, even in tectonites that have undergone late, static recrystallization. In addition, our observations suggest that the process of static grain boundary migration does not necessarily reset earlier deformation microstructures as commonly assumed. The kinematic observations of boundary migrations are inconsistent with simple models in which migration is achieved by single atoms jumping across the boundary.

Bestmann, Michel; Piazolo, Sandra; Spiers, Chris J.; Prior, David J.

2005-03-01

127

Influence of the Pt barrier on Ti/Al/Pt/Au ohmic contacts to n-GaN studied by Rutherford backscattering spectrometry and x-ray diffraction  

NASA Astrophysics Data System (ADS)

The diffusion barrier effect of Pt has been investigated in Ti/Al/Pt/Au ohmic contacts to n-GaN. Severe indiffusion, outdiffusion of Pt and outdiffusion of Ga have been found in 450 °C annealed samples according to the Rutherford backscattering spectrometry (RBS) results. At the same time, the reaction between Ga and Pt has also been identified by glancing angle synchrotron irradiation x-ray diffraction (GASIXRD) in the samples annealed at 450 °C. A higher annealing temperature causes Pt to indiffuse into GaN and react with GaN further. As a result, electrical degradation of the Ti/Al/Pt/Au metallization system was found for samples aged at 600 °C. In contrast, no obvious degradation was found for the aged Ti/Al/Ni/Au samples. According to the RBS and GASIXRD results, it is suggested that the formation of Ga3Pt5 may cause degradation in the electrical properties of the Ti/Al/Pt/Au metallization system.

Hu, C. Y.; Ding, Z. B.; Qin, Z. X.; Chen, Z. Z.; Wang, Y. J.; Yang, Z. J.; Hu, X. D.; Yu, T. J.; Yu, L. S.; Yao, S. D.; Zhang, G. Y.

2006-07-01

128

Influence of Surface Preparation on Scanning Kelvin Probe Microscopy and Electron Backscatter Diffraction Analysis of Cross Sections of CdTe/CdS Solar Cells: Preprint  

SciTech Connect

In this work we investigated different methods to prepare cross sections of CdTe/CdS solar cells for EBSD and SKPM analyses. We observed that procedures used to prepare surfaces for EBSD are not suitable to prepare cross sections, and we were able to develop a process using polishing and ion-beam milling. This process resulted in very good results and allowed us to reveal important aspects of the cross section of the CdTe film. For SKPM, polishing and a light ion-beam milling resulted in cross sections that provided good data. We were able to observe the depletion region on the CdTe film and the p-n junction as well as the interdiffusion layer between CdTe and CdS. However, preparing good-quality cross sections for SKPM is not a reproducible process, and artifacts are often observed.

Moutinho, H. R.; Dhere, R. G.; Jiang, C. S.; Al-Jassim, M. M.

2011-06-01

129

EBSD, SEM and FIB characterisation of subsurface deformation during tribocorrosion of stainless steel in sulphuric acid  

Microsoft Academic Search

The tribocorrosion behaviour of a 304L stainless steel\\/alumina contact was investigated in sulphuric acid at two imposed potentials (cathodic and passive). The metal deformation below the surface was investigated by analyzing cross sections using secondary electron microscopy (SEM) and electron back scatter diffraction (EBSD). Cross sections were also prepared using focussed ion beam (FIB) and analyzed by in situ SEM.

J. Perret; E. Boehm-Courjault; M. Cantoni; S. Mischler; A. Beaudouin; W. Chitty; J.-P. Vernot

2010-01-01

130

The Influence of Sn Orientation on Intermetallic Compound Evolution in Idealized Sn-Ag-Cu 305 Interconnects: an Electron Backscatter Diffraction Study of Electromigration  

NASA Astrophysics Data System (ADS)

Previous research showed the relationship between Sn grain orientation and the intermetallic growth rate in Sn-Ag-Cu (SAC)305 interconnects. Samples with the Sn c-axis aligned parallel to the current flow have an intermetallic compound growth rate significantly faster than samples with the c-axis perpendicular to the current flow. This study continues the previous research by investigating intermetallic growth in polygranular joints and in joints that have a thin Ni layer at the cathodic or anodic interface of the interconnect. Planar SAC305 interconnects were sandwiched between two Cu pads (sometimes incorporating a thin Ni layer at the interface) and subjected to uniaxial current. The crystallographic orientation of Sn in these samples was characterized with electron backscatter diffraction before and after electromigration testing. The results show that polycrystalline joints have relatively slow intermetallic growth rates, close to those found in single-crystal joints with the c-axis perpendicular to the current. When a Ni layer was present on the anode side, the intermetallic grew at a rate comparable to that in samples without a Ni layer. However, when the Ni layer was on the cathode side, the intermetallic growth was significantly retarded. The measured growth rates of the intermetallic, combined with literature values for the diffusion of Cu in Sn, were used to calculate values for the effective charge, z *, which is significantly smaller for samples with current parallel to the c-axis than for either polycrystalline samples or samples with the c-axis perpendicular to the electron flow.

Linares, Xioranny; Kinney, Chris; Lee, Kyu-Oh; Morris, J. W.

2013-10-01

131

A methodology to study crystal plasticity inside a compression test sample based on image correlation and EBSD  

SciTech Connect

Modified compression tests in a coarse-grained austenitic stainless steel have been carried out in order to examine the crystal plasticity behavior for large plastic deformations. The measurements of local in-plane strains provide deeper insight into the deformation process on the local scale. These measurements are performed by digital image correlation technique (DIC) in combination with local crystal orientation measurements by using the electron backscatter diffraction technique (EBSD). Split test samples are prepared to track the strong microstructural changes during deformation, which is done incrementally in 10% steps up to 60% total macroscopic strain. The clear correlation of local strains with crystal orientation changes - e.g. in the case of mechanical twinning - permits to identify the acting deformation mechanisms. Such, experimentally determined local strain maps can be used for verification of crystal plasticity finite element method simulations (CPFEM). - Research Highlights: {yields} Method to study large strain crystal plasticity inside an austenitic FeCrNi-alloy. {yields} Correlation of local strain analyses with crystal orientation measurements. {yields} Deformation mechanism changes locally from dislocation glide to mechanical twinning. {yields} Suitable to study grain-grain interactions, slip system activation and grain boundary effects. {yields} Provide essential data for crystal plasticity FEM studies.

Rehrl, C., E-mail: christian.rehrl@oeaw.ac.at [Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, Jahnstr. 12, 8700 Leoben (Austria); Kleber, S. [Boehler Edelstahl GmbH, Kapfenberg, Mariazeller Str. 25, 8605 Kapfenberg (Austria); Antretter, T. [Institute for Mechanics, Montanuniversitaet Leoben, Leoben (Austria); Pippan, R. [Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, Jahnstr. 12, 8700 Leoben (Austria)

2011-08-15

132

The Weighted Burgers Vector: a new quantity for constraining dislocation densities and types using electron backscatter diffraction on 2D sections through crystalline materials.  

PubMed

The Weighted Burgers Vector (WBV) is defined here as the sum, over all types of dislocations, of [(density of intersections of dislocation lines with a map) x (Burgers vector)]. Here we show that it can be calculated, for any crystal system, solely from orientation gradients in a map view, unlike the full dislocation density tensor, which requires gradients in the third dimension. No assumption is made about gradients in the third dimension and they may be non-zero. The only assumption involved is that elastic strains are small so the lattice distortion is entirely due to dislocations. Orientation gradients can be estimated from gridded orientation measurements obtained by EBSD mapping, so the WBV can be calculated as a vector field on an EBSD map. The magnitude of the WBV gives a lower bound on the magnitude of the dislocation density tensor when that magnitude is defined in a coordinate invariant way. The direction of the WBV can constrain the types of Burgers vectors of geometrically necessary dislocations present in the microstructure, most clearly when it is broken down in terms of lattice vectors. The WBV has three advantages over other measures of local lattice distortion: it is a vector and hence carries more information than a scalar quantity, it has an explicit mathematical link to the individual Burgers vectors of dislocations and, since it is derived via tensor calculus, it is not dependent on the map coordinate system. If a sub-grain wall is included in the WBV calculation, the magnitude of the WBV becomes dependent on the step size but its direction still carries information on the Burgers vectors in the wall. The net Burgers vector content of dislocations intersecting an area of a map can be simply calculated by an integration round the edge of that area, a method which is fast and complements point-by-point WBV calculations. PMID:19250469

Wheeler, J; Mariani, E; Piazolo, S; Prior, D J; Trimby, P; Drury, M R

2009-03-01

133

EBSD characterization of high-temperature phase transformations in an Al-Si coating on Cr-Mo steel  

SciTech Connect

5Cr-0.5Mo steel was coated by hot-dipping in a molten bath containing Al-10 wt.% Si. The phase transformation in the aluminide layer during diffusion at 750 Degree-Sign C in static air was analyzed by electron backscatter diffraction. The results show the aluminide layer of the as-coated specimen consisted of an outer Al-Si topcoat, a middle layer formed of scattered {tau}{sub 5(C)}-Al{sub 7}(Fe,Cr){sub 2}Si particles and minor plate-shaped {tau}{sub 4}-Al{sub 4}FeSi{sub 2} and {tau}{sub 6}-Al{sub 4}FeSi phases in the Al-Si matrix and an inner continuous {tau}{sub 5(H)}-Al{sub 7}Fe{sub 2}Si layer, respectively from the coating surface to the steel substrate. The formation of FeAl{sub 3} and Fe{sub 2}Al{sub 5} with {tau}{sub 1}-(Al,Si){sub 5}Fe{sub 3} precipitates can be observed with increasing exposure time at 750 Degree-Sign C. After 5 h of exposure, the Al-Si topcoat has been consumed, and the aluminide layer consisted of Fe{sub 2}Al{sub 5} and a few {tau}{sub 1}-(Al,Si){sub 5}Fe{sub 3} precipitates. The FeAl phase not only formed at the interface between Fe{sub 2}Al{sub 5} and the steel substrate, but also transformed from {tau}{sub 1}-(Al,Si){sub 5}Fe{sub 3} after diffusion for 10 h. With prolonged exposure, the aluminide layer comprised only FeAl{sub 2} and FeAl. - Highlights: Black-Right-Pointing-Pointer EBSD can differentiate phases in aluminide layer with similar chemical compositions. Black-Right-Pointing-Pointer Mapping and EBSPs functions in EBSD provide a reliable phase identification. Black-Right-Pointing-Pointer A phase transformation in the aluminide layer has been described in detail. Black-Right-Pointing-Pointer 5 Fe-Al-Si and 4 Fe-Al intermetallic phases are performed during the diffusion. Black-Right-Pointing-Pointer Cubic {tau}{sub 5(C)}-Al{sub 7} (Fe,Cr){sub 2}Si and hexagonal {tau}{sub 5(H)}-Al{sub 7}(Fe,Cr){sub 2}Si are identified.

Cheng, Wei-Jen, E-mail: d9603505@mail.ntust.edu.tw; Wang, Chaur-Jeng

2012-02-15

134

An EBSD study of texture development and hybrid deformation mechanisms in fine grained calcite aggregates deformed in direct shear  

NASA Astrophysics Data System (ADS)

Understanding of texture development and its relation to grain size sensitive (GSS) deformation mechanism is of great importance since the rheological behavior of rocks varies substantially depending on which deformation mechanisms are controlling. Recent studies on naturally and experimentally deformed calcite and olivine aggregates have demonstrated that even fine grained materials that are expected to deform by grain size sensitive (GSS) mechanisms, develop a weak but distinct LPO (texture) at high strain. To investigate this behavior we conducted new deformation experiments on Solnhofen limestone in direct shear. This study is part of a wider investigation on large strain deformation in different deformation modes from G. Trullenque, in collaboration with D.L. Kohlstedt (Minneapolis, USA), R. Heilbronner and H. Stuenitz (Basel, Switzerland) and the Utrecht group. The samples have been deformed to high strain both in the conditions of the transition between the GSS and GSI creep regime and in the GSS creep regime. We used Electron Backscatter Diffraction (EBSD) to determine the texture strength of the samples, the distribution of misorientation axes and the grain size distributions. The results show an oblique shape preferred orientation at 35° to 40° to the shear plane and a moderate LPO. The c-axis preferred orientation shows a girdle with one main maximum at a high angle to the shear plane, displaced towards the shortening direction of the imposed shear. The a-axes present a weak girdle perpendicular to the c-axis. Grain growth occurred during high deformation. The misorientation angle distribution has a main peak at low angle. This is due to the progressive subgrain formation and rotation which occurred mainly in the larger grains. Subgrain rotation with misorientations up to 10° occured but most boundaries are low angle (< 5°). This shows the formation of new high angle boundaries and grain size reduction. The formation of subgrains and subgrain rotation, along with the fact that the larger grain fraction shows a slightly stronger LPO than the fine grain fraction, suggest a component of dislocation creep in the coarser grains. We suggest therefore that the GSS regime in the fine grain aggregates may be a transient stage evolving into hybrid deformation (GSI and GSS mechanisms) at high strain. The next steps in this study will be to quantify the contribution of the GSI and GSS mechanisms through the EBSD study and develop a new flow law for the hybrid deformation of the Solnhofen limestone.

Maeder, X.; Trullenque, G.; Drury, M. R.; de Bresser, J.

2007-12-01

135

Advances in SEM-based diffraction studies of defects and strains in semiconductors  

PubMed

Two scanning electron microscope (SEM)-based diffraction techniques, i.e. electron channelling contrast imaging (ECCI) and electron back-scatter diffraction (EBSD) are used to study lattice defect and local elastic strain distributions in Si1-xGe(x) epilayers grown on Si substrates patterned with mesas. The ECCI technique allows the misfit dislocations to be imaged in bulk samples. The misfit dislocations caused plastic relaxation of the strain in planar regions between mesas and in the wider mesas. In the narrower mesas the removal of lateral constraint at the mesa side faces had reduced the stress sufficiently to suppress the propagation of dislocations parallel to the closely spaced side faces. The measurements of small changes in the positions of two zone axes in EBSD patterns caused by variations in the local strain field were used to determine the strains and rotations making up the generalized plane strain tensor describing the deformation in the long mesa structures. The strain sensitivity of the method was determined to be approximately +/- 2 x 10(-4). Distributions of strains and rotations across mesas of several dimensions are reported and differ significantly between mesa for which the mesas width to epilayer thickness is high and low. PMID:11108053

Wilkinson

2000-01-01

136

Area-preserving projections from hexagonal and triangular domains to the sphere and applications to electron back-scatter diffraction pattern simulations  

NASA Astrophysics Data System (ADS)

We construct two new area-preserving projections, which map regular hexagons and regular triangles onto circles. Combination of these projections with the inverse Lambert equal-area projection from the disc to the two hemispheres of a sphere provide bi-directional conversions between uniform planar grids with three-fold and six-fold rotational symmetry and corresponding uniform grids on the sphere. An application example is given for the representation of the channeling-modified back-scattered electron yield for hexagonal titanium.

Ro?ca, D.; De Graef, M.

2013-07-01

137

EBSD studies on the influence of texture on the surface damage mechanisms developed in cyclically loaded aged duplex stainless steels  

Microsoft Academic Search

Interrupted cyclic deformation tests up to 20% of fatigue life were performed on electropolished specimens of a thermally aged superduplex stainless steel. Crystallographic orientation results obtained by electron back-scattering diffraction analysis allowed to determine the individual orientation of each individual grain as well as the plastically active slip systems. Electron back-scattering diffraction results demonstrate the requirement for the accomplishment of

A. Girončs; P. Villechaise; A. Mateo; M. Anglada; J. Méndez

2004-01-01

138

Advanced characterization of twins using automated EBSD  

SciTech Connect

This poster describes resuns obtained using an automated, crystallographically-based technique for twin identification. The technique is based on the automated EBSD. The key features of the analysis are identification of potential twin boundaries by their misorientation character, identification of the distinct boundary planes among the symmetrically equiwlent candidates. and validation of these boundaries through comparison with the boundary and twin plane traces in the sample cross section. Results on the application of this technique to deformation twins in zirconium are analyzed for the effect of twin type and amount and sense of uniaxial deformation. The accumulation of strain tends to increase the misorientation deviation at least to the degree of the trace deviation compared with recrystalllzation twins in nickel.

Wright, S. I. (Stuart I.); Bingert, J. F. (John F.); Mason, T. A. (Thomas A.); Larsen, Ryan J.

2002-01-01

139

EBSD characterization of pre-Cambrian deformations in conglomerate pebbles (Sierra de la Demanda, Northern Spain)  

NASA Astrophysics Data System (ADS)

Pre-Cambrian and unconformable earliest Cambrian rocks from the Sierra de la Demanda (N Spain) exhibit field and microstructural relationships that attest to orogenic events recorded by concealed basement rocks. Neoproterozoic foliated slates ("Anguiano Schists") crop out under up to 300 m thick, unfoliated quartz-rich conglomerates ("Anguiano Conglomerates") and quartzites which are stratigraphically ca. 600 m below the oldest, paleontologically dated, pre-trilobitic Cambrian layers (likely older than 520 Ma). The Anguiano Conglomerates contain mm to cm grainsized well-rounded pebbles of various types including monocrystalline quartz, detrital zircon and tourmaline-bearing sandstones, black cherts and metamorphic poly-crystalline quartz aggregates. The undeformed matrix is made of much smaller (diagenetically overgrown) monocrystaline quartz grains and minor amounts of accesory zircon, tourmaline and mica. Black chert pebbles exhibit microstructural evidence of brittle deformation (microfaults and thin veins of syntaxial fibrous quartz). These and the fine-grained sandstone pebbles can also exhibit ductile deformations (microfolds with thickened hinges and axial planar continuous foliations), too. Polycrystalline quartz pebbles exhibit a variety of microstructures that resulted from syn-metamorphic ductile deformations. These are recognisable under the petrographic microscope and include continuous foliations, quartz shape fabrics, various types of subgrain or recrystallized new grain microtextures, and lattice preferred orientations (LPOs). Conventional characterization of quartz fabrics (after oriented structural sections) is challenged in conglomerate pebble thin sections by the difficulty of unraveling in them the complete structural reference framework provided by foliation (whose trace can be unraveled) and lineation orientation (which cannot be directly identified). Quartz in various metamorphic polycrystalline pebbles was studied with the Electron Back-Scatter Diffraction (EBSD) technique. The identification of quartz c-axis point maxima or girdles and their geometrical relationships with respect to -axis arrangements and pebble foliation traces enabled us to identify the operation of basal and prism- and occasionally prism-[c] intracrystalline slip systems. This points to upper-greenschists and amphibolite facies syn-metamorphic deformations. By contrast, black chert and sandstone pebbles and matrix quartz aggregates lack any LPO. The source area of the conglomerates was likely a pre-Cambrian basement that contained penetratively deformed low- to medium-grade metamorphic rocks. Radiometric dating of this metamorphism has not been accomplished so far though it is known that inherited Precambrian sources in the Iberian Peninsula relate notably to Neoproterozoic (Pan-African and Cadomian) orogens, and to a lesser extent to Paleoproterozoic (1.8-2.1 Ga) or Neoarchean (2.4-2.8 Ga) ones. Neoproterozoic (Cadomian) metamorphism of this grade has only been recognized in SW Iberia. If the fabrics here studied were Cadomian, they might be related to the arc-related igneous suites that have been detected or inferred in other realms of the northern Iberian Massif.

Puelles, Pablo; Ábalos, Benito; Fernández-Armas, Sergio

2010-05-01

140

SNS backscattering spectrometer, BASIS  

SciTech Connect

We describe the design and current performance of the backscattering silicon spectrometer (BASIS), a time-of-flight backscattering spectrometer built at the spallation neutron source (SNS) of the Oak Ridge National Laboratory (ORNL). BASIS is the first silicon-based backscattering spectrometer installed at a spallation neutron source. In addition to high intensity, it offers a high-energy resolution of about 3.5 {mu}eV and a large and variable energy transfer range. These ensure an excellent overlap with the dynamic ranges accessible at other inelastic spectrometers at the SNS.

Mamontov, Eugene [ORNL; Herwig, Kenneth W [ORNL

2011-01-01

141

EBSD Study of Delamination Fracture in Al–Li Alloy 2090  

Microsoft Academic Search

Aluminum–lithium (Al–Li) alloys offer attractive combinations of high strength and low density for aerospace structural applications.\\u000a However, a tendency for delamination fracture has limited their use. Identification of the metallurgical mechanisms controlling\\u000a delamination may suggest processing modifications to minimize the occurrence of this mode of fracture. In the current study\\u000a of Al–Li alloy 2090 plate, high quality electron backscattered diffraction

W. Tayon; R. Crooks; M. Domack; J. Wagner; A. A. Elmustafa

2010-01-01

142

A simulation of recrystallization based on EBSD orientation microscopy data  

SciTech Connect

The present paper introduces a novel stochastic two-dimensional model to simulate the evolution of microstructure and texture during recrystallization. The model is based on data derived by automated large-scale EBSD local texture analysis, i.e., by orientation microscopy. Each measured point is characterized by its coordinates x and y in the microstructure, its crystallographic orientation g and a parameter q describing the quality of the EBSD-pattern which is affected by lattice strain and hence discloses information on the dislocation density. The concurrent information on the local arrangement of orientations and dislocation densities is utilized to derive conclusions on the nucleation and subsequent growth of the new recrystallized grains. The principles of the model are outlined and three example are shown to illustrate the possibilities of the model to simulate the evolution of microstructure and texture during recrystallization.

Engler, O.

1998-12-01

143

Frequency dependence of apparent ultrasonic backscatter from human cancellous bone  

NASA Astrophysics Data System (ADS)

This study examines the frequency dependence of apparent ultrasonic backscatter from human cancellous bone as quantified by the apparent backscatter transfer function (ABTF). The term 'apparent' means that the backscatter signals are not compensated for the frequency-dependent effects of diffraction and attenuation. Backscatter measurements were performed in vitro on 22 specimens of bone using five transducers ranging in centre frequency from 1 to 10 MHz. The ABTF was measured at multiple sites and spatially averaged. The resulting spatially averaged ABTF (in dB) generally was a monotonically decreasing, quasi-linear function of frequency over the analysis bandwidth of the study (0.6-9.1 MHz). The apparent backscattered power tended to decrease with specimen density and become more strongly frequency dependent. Three parameters were determined from the spatially averaged ABTF. Apparent integrated backscatter (AIB) was determined by frequency averaging the spatially averaged ABTF. The frequency slope of apparent backscatter (FSAB) and the zero frequency intercept of apparent backscatter (FIAB) were determined from the slope and intercept of the spatially averaged ABTF, respectively. AIB and FSAB demonstrated moderate to good linear correlations with specimen density (|r| = 0.570-0.933). Correlations with density were weaker for the intercept-based parameter FIAB (|r| = 0.299-0.676).

Hoffmeister, Brent K.

2011-02-01

144

Backscattered Electron Imaging  

Microsoft Academic Search

Scanning electron microscopy (SEM) with secondary electron emissions is useful for the study of cardiomyocyte architecture, however, the information is limited from the cell surface. Whereas backscattered electron (BSE) emission can give a high-resolution image of the specimen's intracellular structure after heavy metal staining. In this study, we applied BSE imaging analysis to the study of the arrangement of cardiomyocytes

Makoto Okabe; Yumiko Kanzaki; Hiroaki Shimomura; Fumio Terasaki; Tetsuya Hayashi; Keishiro Kawamura; Yasushi Kitaura

2000-01-01

145

Tectonic history of continental crustal wedge constrained by EBSD measurements of garnet inclusion trails and thermodynamic modeling  

NASA Astrophysics Data System (ADS)

Inclusion trails in garnets represent an important but underused tool of structural geology to examine non-coaxial or polyphase coaxial deformation histories of orogens. Garnet growth with respect to deformation during prograde and retrograde orogenic evolution of a continental crustal wedge was constrained by EBSD measurements of internal garnet fabrics and petrological record from mid-crustal rocks of the ?nie?nik Massif (Western Sudetes). Textural position of metamorphic minerals and thermodynamic modeling document three main stages in the tectonic evolution. Few garnet cores show prograde MnO zoning and growth coeval with the formation of the earliest metamorphic foliation which is only rarely observed in the field. The major garnet growth occurs synchronously with the second steep S2 fabric under still prograde conditions as shown by garnet zoning and appearance of staurolite and kyanite (peak at 6,5kbar/600°C). Oppositely, garnet retrogression associated to the development of sillimanite and later andalusite indicates pressure decrease of ca. 3 kbar for the late flat and pervasive S3 fabric associated with macroscopic recumbent folding of steep S2 foliation. Electron back-scatter diffraction measurements on ilmenites platelets included in garnets help determining their crystallographic preferred orientation. Ilmenites a[100] axes define planar structures that are interpreted as included foliations. Consequently, microscopic observations and foliation intersection axes (FIA) allow to distinguish between two different records. Only few (prograde) garnet cores yield information on the orientation of the presumed first metamorphic fabric whereas most of the internal garnet foliations are straight, steep and correspond to relics of originally steep S2 fabric. Importantly, this steep attitude of internal garnet foliations is persistent in both F3 fold hinge and limb zones as well as in zones of complete transposition of S2 into flat S3. Therefore, these microstructural and petrological records bring new insights on the mechanical behaviour of this Variscan continental crustal wedge. Burial was initiated during the formation of the first flat metamorphic foliation and continued during the formation of a steep fabric while a major phase of garnet growth entrapped the orientation of this structure. This metamorphic and structural evolution is interpreted as a result of crustal thickening due to subhorizontal material influx followed by large-scale vertical folding. The following tectonic phase produces a flat fabric without any reorientation of the garnet porphyroblasts as exemplified by strong orientation consistency and good compatibility between internal records (foliations, FIA) and field data (measured or reconstructed positions of S2, F3 fold axes). Thus, the vertical D3 shortening looks like it was controlled by passive amplification of folded S2 surfaces and coaxial (non-rotational) flow in weak micaceous matrix. The homogeneous pure shear vertical shortening could be responsible for crustal thinning corresponding to the 3-4 kbar difference between peak assemblage and mineral association of horizontal S3 fabric. The latter fabric is interpreted as a result of horizontal flow related to ductile thinning of the thickened crustal wedge.

Skrzypek, E.; Schulmann, K.; Lexa, O.; Haloda, J.

2009-04-01

146

EBSD and EDX analyses of a multiphase glass-ceramic obtained by crystallizing an yttrium aluminosilicate glass.  

PubMed

A glass with the mol % composition 23.82 Y2O3·39.82 Al2O3·28.50 SiO2·2.91AlF3·4.95 ZrO2 doped with 2 mol % CeF3 is crystallized at 1250 °C for 20 h. The crystallized samples are studied using X-ray diffraction (XRD), the SEM-based methods EBSD and EDX, as well as fluorescence microscopy. Six crystalline phases are detected in the residual glass including alumina, YAG, Y-stabilized zirconia (YSZ), and three different yttrium silicates of the composition Y2Si2O7. Chemistry-assisted indexing (ChI) is successfully applied to separate YAG and YSZ in EBSD-scans. YAG displays polygon as well as dendritic growth. Some crystals show both mechanisms at opposite ends, indicating that the growth mechanism is influenced by the chemistry of the surrounding glass matrix. PMID:23848162

Keshavarzi, Ashkan; Wisniewski, Wolfgang; Rüssel, Christian

2013-08-26

147

THERMAL NEUTRON BACKSCATTER IMAGING.  

SciTech Connect

Objects of various shapes, with some appreciable hydrogen content, were exposed to fast neutrons from a pulsed D-T generator, resulting in a partially-moderated spectrum of backscattered neutrons. The thermal component of the backscatter was used to form images of the objects by means of a coded aperture thermal neutron imaging system. Timing signals from the neutron generator were used to gate the detection system so as to record only events consistent with thermal neutrons traveling the distance between the target and the detector. It was shown that this time-of-flight method provided a significant improvement in image contrast compared to counting all events detected by the position-sensitive {sup 3}He proportional chamber used in the imager. The technique may have application in the detection and shape-determination of land mines, particularly non-metallic types.

VANIER,P.; FORMAN,L.; HUNTER,S.; HARRIS,E.; SMITH,G.

2004-10-16

148

Backscatter digital holography of microparticles.  

PubMed

This work investigates a method for digital holographic imaging of microparticles. Traditional digital holographic techniques use a particle's forward scattered light to form the hologram, whereas here we use the backscattered light. Images of a particle are then computationally reconstructed from the backscatter hologram, and several examples of such reconstructions are presented. A potential advantage of this technique is that the backscatter holograms may be more sensitive to particle-surface details. PMID:23736480

Subedi, Nava R; Fowler, Nicholas B; Berg, Matthew J

2013-05-20

149

EBSD Studies of Ringwoodite Microcrystalline Fabrics in the Shocked NWA 5011 L6 Chondritic Meteorite  

NASA Astrophysics Data System (ADS)

EBSD measurements on a 2 mm × 2 mm sample of the shocked, veined NWA 5011 L6 chondrite showed that the optically homogeneous large ringwoodite minerals in the veins consist of 2-5 ?m sized, variously oriented micrograins.

Bérczi, Sz.; Nagy, Sz.; Gyollai, I.; Józsa, S.; Havancsák, K.; Dankházi, Z.; Varga, G.; Ratter, K.; Pál-Molnár, E.; Fintor, K.; Gucsik, A.

2012-03-01

150

Application of combined EBSD and 3D-SEM technique on crystallographic facet analysis of steel at low temperature.  

PubMed

Electron backscatter diffraction has been increasingly used to identify the crystallographic planes and orientation of cleavage facets with respect to the rolling direction in fracture surfaces. The crystallographic indices of cleavage planes can be determined either directly from the fracture surface or indirectly from metallographic sections perpendicular to the plane of the fracture surface. A combination of electron backscatter diffraction and 3D scanning electron microscopy imaging technique has been modified to determine crystallographic facet orientations. The main purpose of this work has been to identify the macroscopic crystallographic orientations of cleavage facets in the fracture surfaces of weld heat affected zones in a well-known steel fractured at low temperatures. The material used for the work was an American Petroleum Institute (API) X80 grade steel developed for applications at low temperatures, and typical heat affected zone microstructures were obtained by carrying out weld thermal simulation. The fracture toughness was measured at different temperatures (0°C, -30°C, -60°C and -90°C) by using Crack Tip Opening Displacement testing. Fracture surfaces and changes in microstructure were analyzed by scanning electron microscopy and light microscopy. Crystallographic orientations were identified by electron backscatter diffraction, indirectly from a polished section perpendicular to the major fracture surface of the samples. Computer assisted 3D imaging was used to measure the angles between the cleavage facets and the adjacent polished surface, and then these angles were combined with electron backscatter diffraction measurements to determine the macroscopic crystallographic planes of the facets. The crystallographic indices of the macroscopic cleavage facet planes were identified to be {100}, {110}, {211} and {310} at all temperatures. PMID:23692572

Mohseni, P; Solberg, J K; Karlsen, M; Akselsen, O M; Ostby, E

2013-05-20

151

Microstructure characterization of ZK60 magnesium alloys using TEM and HR-EBSD.  

PubMed

ZK60 (Mg-Zn-Zr) alloys exhibited a variation in precipitates with aging, and their mechanical properties also changed. Microindentation tests were carried out on two types of ZK60 alloys of solid solution (T4) and peak aging (T6). Microstructure and texture evolution during indentation was investigated using electron backscatter diffraction. Twinning occurred near the indentation marks in most grains. It was found that tensile twinning was dominant, and two twin variants were usually observed. Texture and microstructure evolution by twinning and slip activation was further examined by uniaxial compression test with strain. The initial random orientation gradually changed into basal fibers with strain. Some grains with nonbasal orientations aligned with the loading direction easily underwent twinning followed by slip deformation. Other grains near basal orientations revealed only slip deformation. PMID:23920164

Cho, Jae-Hyung; Kim, Soo-Hyun; Han, Sang-Ho; Kang, Suk-Bong

2013-08-01

152

Effect of the cortex on ultrasonic backscatter measurements of cancellous bone  

NASA Astrophysics Data System (ADS)

Ultrasonic backscatter techniques offer a promising new approach for detecting changes in bone caused by osteoporosis. However, several challenges impede clinical implementation of backscatter techniques. This study examines how the dense outer surface of bone (the cortex) affects backscatter measurements of interior regions of porous (cancellous) bone tissue. Fifty-two specimens of bone were prepared from 13 human femoral heads so that the same region of cancellous bone could be ultrasonically interrogated through the cortex or along directions that avoided the cortex. Backscatter signals were analyzed over a frequency range of 0.8-3.0 MHz to determine two ultrasonic parameters: apparent integrated backscatter (AIB) and frequency slope of apparent backscatter (FSAB). The term 'apparent' means that the parameters are sensitive to the frequency-dependent effects of diffraction and attenuation. Significant (p < 0.001) changes in AIB and FSAB indicated that measurements through the cortex decreased the apparent backscattered power and increased the frequency dependence of the power. However, the cortex did not affect the correlation of AIB and FSAB with the x-ray bone mineral density of the specimens. This suggests that results from many previous in vitro backscatter studies of specimens of purely cancellous bone may be extrapolated with greater confidence to in vivo conditions.

Hoffmeister, Brent K.; Holt, Andrew P.; Kaste, Sue C.

2011-10-01

153

Effect of the cortex on ultrasonic backscatter measurements of cancellous bone  

PubMed Central

Ultrasonic backscatter techniques offer a promising new approach for detecting changes in bone caused by osteoporosis. However, several challenges impede clinical implementation of backscatter techniques. This study examines how the dense outer surface of bone (the cortex) affects backscatter measurements of interior regions of porous (cancellous) bone tissue. Fifty-two specimens of bone were prepared from 13 human femoral heads so that the same region of cancellous bone could be ultrasonically interrogated through the cortex or along directions that avoided the cortex. Backscatter signals were analyzed over a frequency range of 0.8-3.0 MHz to determine two ultrasonic parameters: apparent integrated backscatter (AIB) and frequency slope of apparent backscatter (FSAB). The term “apparent” means that the parameters are sensitive to the frequency dependent effects of diffraction and attenuation. Significant (p < 0.001) changes in AIB and FSAB indicated that measurements through the cortex decreased the apparent backscattered power and increased the frequency dependence of the power. However, the cortex did not affect the correlation of AIB and FSAB with the x-ray bone mineral density of the specimens. This suggests that results from many previous in vitro backscatter studies of specimens of purely cancellous bone may be extrapolated with greater confidence to in vivo conditions.

Hoffmeister, Brent K.; Holt, Andrew P.; Kaste, Sue C.

2012-01-01

154

Aerosol Backscatter Studies Supporting LAWS. (Abstract Only)  

National Technical Information Service (NTIS)

Optimized Royal Signals and Radar Establishment (RSRE), Laser True Airspeed System (LATAS) algorithm for low backscatter conditions was developed. The algorithm converts backscatter intensity measurements from focused continuous-wave (CW) airborne Doppler...

J. Rothermel

1989-01-01

155

Global Backscatter Experiment Airborne Pulsed Lidar Measurements.  

National Technical Information Service (NTIS)

The Global Backscatter Experiment (GLOBE) was intended to provide data on prevailing values of atmospheric backscatter cross section. The primary intent was predicting the performance of space-borne lidar systems. A second and related goal was to understa...

J. D. Spinhirne S. Chudamani R. T. Menzies D. Tratt

1992-01-01

156

Backscatter absorption gas imaging system  

Microsoft Academic Search

A video imaging system for detecting hazardous gas leaks. Visual displays of invisible gas clouds are produced by radiation augmentation of the field of view of an imaging device by radiation corresponding to an absorption line of the gas to be detected. The field of view of an imager is irradiated by a laser. The imager receives both backscattered laser

McRae Jr

1985-01-01

157

Backscatter absorption gas imaging system  

Microsoft Academic Search

A video imaging system for detecting hazardous gas leaks. Visual displays of invisible gas clouds are produced by radiation augmentation of the field of view of an imaging device by radiation corresponding to an absorption line of the gas to be detected. The field of view of an imager is irradiated by a laser. The imager receives both backscattered laser

McRae; T. G. Jr

2009-01-01

158

Global Backscatter Assessment. (Abstract Only)  

National Technical Information Service (NTIS)

The focus of this effort is the development of a global-scale model of aerosol backscatter for laser atmospheric wind sounder (LAWS) design and performance studies. Background parameters are derived from aerosol data sets with global-scale spatial and/or ...

D. A. Bowdle

1989-01-01

159

Studies of enhanced radar backscatter  

Microsoft Academic Search

Since 1 October 1991, experimental and theoretical research has been conducted aimed at investigating ionospheric plasma disturbances which can significantly affect radio wave propagation from satellite communications systems. The efforts have developed a theory to explain reflectivity of radio waves from lightning induced plasmas. In addition, the research has focused on enhanced radar backscatter, source mechanisms for generating symmetric lower

Min-Chang Lee

1993-01-01

160

New Technique for Backscattering Analysis.  

National Technical Information Service (NTIS)

A new technique for analyzing Rutherford backscattering spectra is suggested. By determining the ratio of the range of a particle of energy E, to that of a particle whose energy is a fraction of E, two basic integral equations are converted into a pair of...

P. W. Keaton P. S. Peercy B. L. Doyle C. J. Maggiore

1979-01-01

161

Electromagnetic backscatter predictions using XPATCH  

Microsoft Academic Search

The ability to accurately identify objects solely from their electromagnetic backscatter is of continuing interest. In order for object identification to be practical, a comprehensive catalog of signatures must be generated. The prediction code XPATCH is one tool capable of generating such a catalog. It is a high frequency polarimetric code based on the shooting and bouncing ray (SBR) method,

R. O. Jernejcic; R. F. Schindel

1994-01-01

162

Decomposition of the backscattering dyadic  

Microsoft Academic Search

In polarimetric remote sensing, one can use the symmetric 2 X 2 backscattering dyadic to obtain information concerning the target. When operating at a single frequency, however, the amount of information is limited and there is an ambiguity in applying simple scattering models to the data. By extending the bandwidth in the sense of a pulse or multiple frequencies (retaining

Carl E. Baum

1997-01-01

163

Backscattering control logic component using FPGA device  

Microsoft Academic Search

The work presented in this paper contributes to the research of UHF RFID systems especially on backscattering control logic. We present backscattering control logic concept, designing backscattering control logic component based on FPGA using VHDL, and simulate the component design in the form of behavioral simulation and post-route simulation.

Silmina Ulfah; Fiftatianti Hendajani; Sunny Arief Sudiro

2011-01-01

164

Backscatter measurements for NIF ignition targets (invited)  

SciTech Connect

Backscattered light via laser-plasma instabilities has been measured in early NIF hohlraum experiments on two beam quads using a suite of detectors. A full aperture backscatter system and near backscatter imager (NBI) instrument separately measure the stimulated Brillouin and stimulated Raman scattered light. Both instruments work in conjunction to determine the total backscattered power to an accuracy of {approx}15%. In order to achieve the power accuracy we have added time-resolution to the NBI for the first time. This capability provides a temporally resolved spatial image of the backscatter which can be viewed as a movie.

Moody, J. D.; Datte, P.; Krauter, K.; Bond, E.; Michel, P. A.; Glenzer, S. H.; Divol, L.; Suter, L.; Meezan, N.; MacGowan, B. J.; Hibbard, R.; London, R.; Kilkenny, J.; Wallace, R.; Knittel, K.; Frieders, G.; Golick, B.; Ross, G.; Widmann, K.; Jackson, J. [Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94550 (United States); and others

2010-10-15

165

Backscatter absorption gas imaging system  

DOEpatents

A video imaging system for detecting hazardous gas leaks. Visual displays of invisible gas clouds are produced by radiation augmentation of the field of view of an imaging device by radiation corresponding to an absorption line of the gas to be detected. The field of view of an imager is irradiated by a laser. The imager receives both backscattered laser light and background radiation. When a detectable gas is present, the backscattered laser light is highly attenuated, producing a region of contrast or shadow on the image. A flying spot imaging system is utilized to synchronously irradiate and scan the area to lower laser power requirements. The imager signal is processed to produce a video display.

McRae, Jr., Thomas G. (Livermore, CA)

1985-01-01

166

Preferred Orientations of Pyroxene in the Zagami Shergottite: Implications for Magmatic Emplacement  

NASA Astrophysics Data System (ADS)

Electron backscatter diffraction (EBSD) techniques on the (normal) Zagami shergottite identify foliated but not lineated pyroxenes within the coarse-grained lithology. Results for fine-grained lithology will be presented.

Becker, T. E.; Reynolds, V. S.; Beane, R. J.; McCoy, T. J.

2011-03-01

167

Microstructural Characterization of Foil-Gage Haynes (register trademark) 230 (registered trademark) (Preprint).  

National Technical Information Service (NTIS)

The microstructures of foil-gage Haynes 230 with thicknesses of 125 and 500 um (5 and 20 mils, respectively) were characterized using optical, scanning electron (SEM) and electron backscattered diffraction (EBSD) microscopy. The average gamma grain size w...

I. W. Porter K. Li R. John R. J. Morrissey

2010-01-01

168

Diffracted S  

Microsoft Academic Search

Gutenberg and Richter1 commented in 1935 that diffracted S (the S wave diffracted around the Earth's core) was recorded more frequently than diffracted P, but they provided no observational data. To our knowledge, the only reference to observations of S beyond the shadow zone since that time was made by Lehmann2, who expressed doubt (on the score of amplitude) whether

J. Cleary; K. Porra; L. Read

1967-01-01

169

The effect of atomic mass on the physical spatial resolution in EBSD.  

PubMed

In this study, bicrystals of silver (Ag) and aluminum (Al) were used to investigate the physical spatial resolution of the electron backscatter diffraction system combining a digital image correlation method. Furthermore, the effect of the accelerating voltage and probe current was investigated on the physical spatial resolution of the lateral and longitudinal resolutions for Ag and Al, respectively. The lateral and longitudinal resolutions show high dependency on the accelerating voltage for a low atomic mass material of Al, In addition, these are almost independent of the accelerating voltage for a high atomic mass material of Ag. Moreover, the probe current does not play any role on both the lateral and longitudinal resolutions. The best lateral resolutions for Al and Ag are 40.5 and 12.1 nm at 10 kV and 1 nA, respectively. The best longitudinal resolutions of 23.2 and 80 nm were obtained at 10 kV and 1 nA for Al and Ag, respectively. PMID:23920163

Chen, Delphic; Kuo, Jui-Chao

2013-08-01

170

Backscattering spectroscopy at the NIST Center for Neutron Research  

NASA Astrophysics Data System (ADS)

We discuss the design of a new backscattering spectrometer that is soon to become operational at the NIST Center for Neutron Research. Both monochromator and analyzer are composed of spherically bent Si (1 1 1) crystals that focus the incident and scattered neutron beams. The bending increases the intrinsic lattice gradient of Si beyond its Darwin limit, resulting in an energy resolution of about 0.75 ?eV FWHM. The Doppler-driven monochromator should provide a wide dynamic range of +/-50 ?eV. The elastic Q-range will cover 0.15-1.8 Ĺ-1. The most novel component of this spectrometer is the phase-space-transform chopper. This device rotates at 4730 rpm while neutrons are Bragg-diffracted from sets of HOPG crystals affixed to its periphery. The process enhances the neutron flux at the backscattered energy of 2.08 meV, but at the expense of a larger horizontal divergence. This effectively reduces the divergence mismatch between primary and secondary spectrometers, a long standing problem with backscattering instruments. Simulations suggest a resultant flux increase of order 3 should be obtained.

Gehring, P. M.; Neumann, D. A.

1998-04-01

171

Crystallographic-magnetic correlations in single-crystal haemo-ilmenite: new evidence for lamellar magnetism  

Microsoft Academic Search

17 single crystals were identified by electron backscatter diffraction (EBSD) and isolated from coarse massive haemo-ilmenite ore from South Rogaland, Norway. These were studied using the EBSD results, natural remanent magnetization (NRM), and anisotropy of magnetic susceptibility (AMS), to gain a better understanding of angular relationships between crystallographic axes and magnetic properties of haemo-ilmenite in relation to lamellar magnetism. Electron

P. Robinson; F. Heidelbach; A. M. Hirt; S. A. McEnroe; L. L. Brown

2006-01-01

172

Radar backscatter analysis using fractional Fourier transform  

Microsoft Academic Search

This paper focuses on analyzing radar backscatter returns using the fractional Fourier transform. This study is motivated by two factors: first, to examine the radar backscatter mechanism of standard small targets; and second, to extract pertinent scattering features that can be used in target recognition. Radar returns have been examined using time-frequency analysis techniques, particularly those targets with dispersive scattering

Ismail I. Jouny

2004-01-01

173

[Backscattering characteristics of Amphidinium carterae Hulburt].  

PubMed

Variability of the backscattering characteristics of the alga amphidinium carterae hulburt and its interpretation were examined using the measured data performed during July 2012 in the laboratory. The results indicated that the backscattering coefficient has the characteristic of spectral variability, and was highly power correlated with the chlorophyll concentration, the minimum of the correlation coefficient reached up to 0.96; otherwise, the shape of the particulate backscattering coefficient spectra was also changed from the low chlorophyll concentration to the higher concentration because of the influence of chlorophyll absorption. At the same time, the authors got another value of the particulate backscattering ratio ranging between 0.006 4 and 0.011 6 at 620 nm, although a global increase in particulate backscattering ratio with growing chlorophyll concentration was also visible, but the regularity is not obviously especially at the higher chlorophyll concentration and unlike backscattering coefficient, the spectral shapes of the backscattering ratio remained constant. The authors also found that particle density was one of the main factors controlling the variability of particles backscattering ratio for the pure algal water, and the authors fit a power law function to them and the correlation coefficient at 620 nm was as high as 0.98. PMID:24059196

Jiang, Ling-Ling; Wang, Lin; Zhao, Dong-Zhi; Wang, Xiang

2013-07-01

174

Biomedical applications of enhanced backscattering spectroscopy  

Microsoft Academic Search

Enhanced Backscattering Spectroscopy enables minimally invasive measurement of optical properties of biological tissues by characterizing the shape of backscattered light in both angle and spectrum. The peak in scattering intensity in the retroreflection direction depends on the scattering properties of a random medium including mean free path, anisotropy, and even higher order characteristics such as mass fractal dimension. These properties

Jeremy D. Rogers; Nikhil Mutyal; Andrew Radosevich; Vladimir Turzhitsky; Hemant Roy; Vadim Backman

2011-01-01

175

Electromagnetic backscattering from aircraft propeller blades  

Microsoft Academic Search

This paper gives a theoretical solution to the problem of determining the electromagnetic backscattering and Doppler spectrum of an aircraft propeller as presented to a radar operating in the 8-12 GHz band. At this band for all practical aircraft propeller the electromagnetic backscattering regime is in the optical region. The solution proceeds by modeling the aircraft propeller as a set

S. Y. Yang; S. M. Yeh; S. S. Bor; S. R. Huang; C. C. Hwang

1997-01-01

176

Propagation Studies for Rfd. Volume II. High Frequency Backscatter Studies.  

National Technical Information Service (NTIS)

A description of several investigations concerning high frequency backscatter is presented. These deal with traveling ionospheric irregularities, topside sounder-bottomside backscatter sounder comparisons, backscatter Doppler observations, ray tracing bac...

L. H. Tveten J. C. Blair R. D. Hunsucker L. L. Melanson H. G. Moller

1966-01-01

177

Rectilinear diffraction  

NASA Astrophysics Data System (ADS)

Classical diffraction of the Fresnel, Fraunhofer, or caustic type can be described in terms of solutions of a Schroedinger equation. This equation is obtained for dispersive conservative wave systems as well as for nondispersive systems obeying the usual wave equation. For dispersive wave systems, the dispersion tensor in the Schroedinger equation can be indefinite in the sense of quadratic forms. If so, anomalous diffraction phenomena may appear. With certain orientations it may be necessary to go to a higher-order theory to describe the diffraction. Deep water waves and conical waves, examples of systems with indefinite dispersion tensors, are discussed briefly.

Hayes, W. D.

1983-11-01

178

Anisotropic enhanced backscattering induced by anisotropic diffusion.  

PubMed

The enhanced backscattering cone displaying a strong anisotropy from a material with anisotropic diffusion is reported. The constructive interference of the wave is preserved in the helicity preserving polarization channel and completely lost in the nonpreserving one. The internal reflectivity at the interface modifies the width of the backscatter cone. The reflectivity coefficient is measured by angular-resolved transmission. This interface property is found to be isotropic, simplifying the backscatter cone analysis. The material used is a macroporous semiconductor, gallium phosphide, in which pores are etched in a disordered position but with a preferential direction. PMID:15524650

Bret, B P J; Lagendijk, A

2004-09-03

179

Apparent integrated backscatter from cancellous bone in the frequency range 2.5-7.5 MHz  

NASA Astrophysics Data System (ADS)

Ultrasonic backscatter may offer useful new techniques for ultrasonic bone assessment. For this study, backscatter measurements were performed on 18 specimens of bovine cancellous bone using a 5-MHz broadband ultrasonic system operating between 2.5-7.5 MHz. Specimens were obtained from the proximal tibia, and prepared in the shape of cubes (15-mm side length) with faces oriented along principal anatomic directions (anterior, posterior, medial, lateral, superior, and inferior). A mechanical scanning system was used to acquire ultrasonic backscatter signals from 144 sites perpendicular to each face of each cube. The signals were analyzed to extract values of apparent integrated backscatter (AIB), a parameter that represents the frequency-averaged backscattered power uncompensated for the effects of attenuation and diffraction. AIB demonstrated highly significant linear correlations with bone mineral density (BMD) for both the transverse (anterior, posterior, medial, and lateral) and longitudinal (superior and inferior) directions. In all cases AIB decreased with increasing BMD. No significant anisotropy was detected. We conclude that AIB measurements performed on bovine cancellous bone in this range of frequencies correlate well with BMD.

Hoffmeister, Brent K.; Jones, Charles I.; Kaste, Sue C.

2004-10-01

180

Instrument for underwater measurement of optical backscatter  

NASA Astrophysics Data System (ADS)

A backscatter sensor has been developed for rapidly measuring, in situ, the volume scattering function (VSF) in the backward direction. The backscatter sensor uses a bistatic optical geometry to measure backscatter from a small volume of seawater over a range of scattering angles from approximately 115 degree(s) to 170 degree(s). The calibration of the sensor yields a weighted, angular averaged value of the VSF with a centroid located at a scattering angle of about 150 degree(s). The backscatter sensor design is based on a sensitive synchronous detector and pulsed, light-emitting diode that has been used at visible and near-infrared wavelengths. The entire sensor package, which includes circuitry for digitizing the signal, is contained in a compact, rugged housing. The sensor has been deployed both in towed arrays and in stationary profiling mode. Scattering profiles from two recent deployments are presented.

Maffione, Robert A.; Dana, David R.; Honey, Richard C.

1991-12-01

181

Optical Fiber Backscatter Signature Generator (OFBSG)  

NASA Astrophysics Data System (ADS)

The optical fiber backscatter signal generator (OFBSG) generates simulated optical fiber backscatter waveform signals that are used to characterize or calibrate an optical time domain reflectometer (OTDR). An OTDR is a commercially available test instrument that measures loss and length of a fiber optic cable by launching an optical signal into the cable and measuring the power that is reflected back (backscattered) into the OTDR. The OFBSG device creates a simulated optical fiber backscattered signal of a virtual cable and couples this signal into the OTDR so that length accuracy, loss accuracy, and dynamic range of the OTDR can be determined. An electrooptical section, a signal generator section and a microprocessor section that is programmable to simulate a variety of cable anomalies, provide adaptability to accommodate a wide variety of OTDRs and, by reason of its sound engineering design, it is capable of being used under adverse conditions such as those encountered in this field.

Kamikawa, Neil; Nakagawa, Arthur; Tanaka, Grant; Yamada, Ken

1990-08-01

182

An Evaluation of HF Ionospheric Backscatter Echoes.  

National Technical Information Service (NTIS)

The characteristics of HF radar echoes reflected from ionization irregularities aligned along the lines of force of the earth's magnetic field are discussed. The spatial-geographical extent of ionospheric backscatter echoes is estimated for an HF radar lo...

G. H. Millman

1975-01-01

183

On observing acoustic backscattering from salinity turbulence.  

PubMed

It has been hypothesized that at sufficiently high levels of oceanic salinity turbulence it should be possible to observe acoustic backscattering. However, there have been limited in situ measurements to confirm this hypothesis. Using an autonomous underwater vehicle equipped with upward and downward looking 1.2 MHz acoustic Doppler current profilers and with turbulence and fine scale sensors, measurements were performed in a region of intense turbulence and a strong salinity gradient. The approach taken was to correlate variations in the backscattered acoustic intensity, I, with a theoretical acoustic backscattering cross section per volume for salinity turbulence, ?(s), to obtain an estimated scattering cross section per volume, ?(e). Results indicated that of order 50% of the observed region was characterized by salinity turbulence induced backscattering. PMID:21877785

Goodman, Louis; Sastre-Cordova, Marcos M

2011-08-01

184

Complete Link Budgets for Backscatter-Radio and RFID Systems  

Microsoft Academic Search

Backscatter radio - wireless communication by modulating signals scattered from a transponder (RF tag) - is fundamentally different from conventional radio because it involves two distinct links: the power-up link for powering passive RF tags, and the backscatter link for describing backscatter communication. Because of severe power constraints on the RF tag, a thorough knowledge of the backscatter channel is

Joshua D. Griffin; Gregory D. Durgin

2009-01-01

185

X band microwave backscattering from ocean waves  

Microsoft Academic Search

Backscattering experiments at microwave frequencies were conducted off the west coast of Scotland in the summer of 1991. Using a dual-polarization, eight-frequency, X band, coherent scatterometer mounted on the bow of a boat, the authors measured time-resolved backscattering from ocean waves at a range of grazing angles from 10° to 70°. From the grazing-angle-dependent signals and their Doppler spectra, the

P. H. Y. Lee; J. D. Barter; K. L. Beach; C. L. Hindman; B. M. Lake; H. Rungaldier; J. C. Shelton; A. B. Williams; R. Yee; H. C. Yuen

1995-01-01

186

Principles and applications of ultrasound backscatter microscopy  

Microsoft Academic Search

The development of ultrasound backscatter microscopy (UBM) is described together with initial clinical and biological applications. UBM is essentially an extension of the powerful B-mode backscatter methods developed for clinical imaging in the 3-10-MHz frequency range. The development of new high sensitivity transducers in the 40-100-MHz range now permits visualization of tissue structures with resolution approaching 20 ?m and a

F. Stuart Foster; G. R. Lockwood; L. K. Ryan; K. A. Harasiewicz; L. Berube; A. M. Rauth

1993-01-01

187

Backscatter correction factor for megavoltage photon beam  

SciTech Connect

Purpose: For routine clinical dosimetry of photon beams, it is often necessary to know the minimum thickness of backscatter phantom material to ensure that full backscatter condition exists. Methods: In case of insufficient backscatter thickness, one can determine the backscatter correction factor, BCF(s,d,t), defined as the ratio of absorbed dose measured on the central-axis of a phantom with backscatter thickness of t to that with full backscatter for square field size s and forward depth d. Measurements were performed in SAD geometry for 6 and 15 MV photon beams using a 0.125 cc thimble chamber for field sizes between 10 x 10 and 30 x 30 cm at depths between d{sub max} (1.5 cm for 6 MV and 3 cm for 15 MV) and 20 cm. Results: A convolution method was used to calculate BCF using Monte-Carlo simulated point-spread kernels generated for clinical photon beams for energies between Co-60 and 24 MV. The convolution calculation agrees with the experimental measurements to within 0.8% with the same physical trend. The value of BCF deviates more from 1 for lower energies and larger field sizes. According to our convolution calculation, the minimum BCF occurs at forward depth d{sub max} and 40 x 40 cm field size, 0.970 for 6 MV and 0.983 for 15 MV. Conclusions: The authors concluded that backscatter thickness is 6.0 cm for 6 MV and 4.0 cm for 15 MV for field size up to 10 x 10 cm when BCF = 0.998. If 4 cm backscatter thickness is used, BCF is 0.997 and 0.983 for field size of 10 x 10 and 40 x 40 cm for 6 MV, and is 0.998 and 0.990 for 10 x 10 and 40 x 40 cm for 15 MV, respectively.

Hu, Yida; Zhu, Timothy C. [Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States)

2011-10-15

188

Spectral variability of the particulate backscattering ratio  

NASA Astrophysics Data System (ADS)

The spectral dependency of the particulate backscattering ratio is relevant in the fields of ocean color inversion, light field modeling, and inferring particle properties from optical measurements. Aside from theoretical predictions for spherical, homogeneous particles, we have very limited knowledge of the actual in situ spectral variability of the particulate backscattering ratio. This work presents results from five research cruises that were conducted over a three-year period. Water column profiles of physical and optical properties were conducted across diverse aquatic environments that offered a wide range of particle populations. The main objective of this research was to examine the behavior of the spectral particulate backscattering ratio in situ, both in terms of its absolute magnitude and its variability across visible wavelengths, using over nine thousand 1-meter binned data points for each of five wavelengths of the spectral particulate backscattering ratio. Our analysis reveals no spectral dependence of the particulate backscattering ratio within our measurement certainty, and a geometric mean value of 0.013 for this dataset. This is lower than the commonly used value of 0.0183 from Petzold’s integrated volume scattering data. Within the first optical depth of the water column, the mean particulate backscattering ratio was 0.010.

Whitmire, A. L.; Boss, E.; Cowles, T. J.; Pegau, W. S.

2007-05-01

189

Optimising HIFU Lesion Formation with Backscatter Attenuation Estimation (BAE)  

NASA Astrophysics Data System (ADS)

Ultrasound attenuation is an important dosimetric factor for HIFU treatments of soft tissue tumours. During clinical HIFU treatments ultrasound attenuation in the tissue overlying the focal volume leads to a loss in intensity. In clinical treatments at the Royal Marsden Hospital (UK), ultrasound attenuation is currently estimated using published tissue attenuation coefficients and the thickness of tissue layers determined from diagnostic ultrasound images. This method gives an inaccurate estimate of attenuation. Therefore to improve the delivery of HIFU, a better measurement of attenuation is required. Methods have been investigated for eventual clinical use in estimating the attenuation coefficient of the liver in vivo, immediately prior to HIFU treatment, using backscattered ultrasound pulses. Radio frequency (RF) echo signals were acquired using a clinical ultrasound scanner working with a linear array probe. The data required for diffraction correction of these estimates is a set of RF images obtained where the sample is axially translated with respect to the imaging transducer. These data were used to compute the diffraction corrected attenuation coefficient at each frequency using two methods: a substitution method and an inverse diffraction filtering process. In preliminary experiments, a homogeneous sponge material was used to test the data acquisition and processing techniques. Attenuation measurements were also made on ex vivo bovine liver tissue samples where the time since excision and the level of degassing were varied.

Civale, John; Bamber, Jeff; Rivens, Ian; Ter Haar, Gail

2006-05-01

190

Tectonic history of continental crustal wedge constrained by EBSD measurements of garnet inclusion trails and thermodynamic modeling  

Microsoft Academic Search

Inclusion trails in garnets represent an important but underused tool of structural geology to examine non-coaxial or polyphase coaxial deformation histories of orogens. Garnet growth with respect to deformation during prograde and retrograde orogenic evolution of a continental crustal wedge was constrained by EBSD measurements of internal garnet fabrics and petrological record from mid-crustal rocks of the Snieznik Massif (Western

E. Skrzypek; K. Schulmann; O. Lexa; J. Haloda

2009-01-01

191

Backscattered electron detection in environmental SEM.  

PubMed

An examination of the backscattered electron imaging status in environmental scanning electron microscopy is presented with particular attention to the testing and use of cerium doped yttrium aluminium garnet and yttrium aluminium perovskite scintillation detectors. A comparison is made with plastic scintillating backscattered electron detectors used previously (Nuclear Enterprises type NE102A scintillator). Semi-disk, strip and wedge shapes of these materials have been tested in conjunction with various light-guide geometries. These systems have been combined with two different types of photomultipliers, which also play a critical role in the total detector efficiency. The advantage of increased light output from the monocrystal materials is gained only if matched with suitable light-guides and photomultipliers. The associated problems are discussed and proposals for further work are made for the construction of most efficient backscattered electron detectors in the environmental scanning electron microscope. PMID:22044175

Danilatos, G D

2011-11-02

192

Backscattering of {alpha}-Quartz (0 6 10) for 14.4 keV Moessbauer Photons  

SciTech Connect

Backscattering of {alpha}-quartz (0 6 10) was investigated using 14.4 keV 57Fe Moessbauer photons from {alpha}-57Fe2O3 at nuclear resonant scattering beamline BL09XU, SPring-8. The {alpha}-quartz crystal was heated to around 353 K by an oven so that the Bragg angle of {alpha}-quartz 0 6 10 diffraction meats 90 degrees. Energy width of the reflection was measured by changing temperature of the oven. The measured bandwidth is 1.14(33) meV. Backscattering by a {alpha}-quartz crystal can be applied for high-energy-resolution monochromator or analyzer.

Imai, Yasuhiko; Yoda, Yoshitaka; Kikuta, Seishi [Japan Synchrotron Radiation Research Institute, SPring-8, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); Zhang Xiaowei [Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization, KEK 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan)

2007-01-19

193

Materials Science: Diffraction  

NSDL National Science Digital Library

This suite of websites from the University of Liverpool comprises a learning module that focuses on diffraction. The website features sections on diffraction, the geometry of diffraction, the intensity of diffraction, electron diffraction and X-ray diffraction. Each section features text, images and animations as well as learning exercises. These sites aid in the exploration of the various aspects of diffraction.

Goodhew, Peter; Fretwell, Ann; Tanovic, Boban; Jones, Ian; Green, Andrew; Brook, David

194

Porosity Characterization in Fiber-Reinforced Composites Using Ultrasonic Backscatter.  

National Technical Information Service (NTIS)

The use of ultrasonic backscatter to characterize anomolous states in fiber-reinforced composites has received considerable attention in recent years. Unlike monolithic materials, ultrasonic backscatter from composites with oriented fiber reinforcement di...

R. A. Roberts

1986-01-01

195

Backscatter in the rational LES model.  

SciTech Connect

This paper presents a comparison for the backscatter (the inverse transfer of energy from small to large scales) in the rational and the gradient large eddy simulation (LES) models. We applied both LES models in the numerical simulation of turbulent channel flows at Re{sub T} = 180 and 395. The rational LES model yielded improved results and was more stable numerically.

Iliescu, T.; Fischer, P.; Mathematics and Computer Science

2004-06-01

196

Backscattering echo of correlated wave packets  

NASA Astrophysics Data System (ADS)

We present an analytical theory describing a phenomenon of enhanced backscattering corresponding to the spatial refocussing of a spreadout correlated wave packet due to a brief interaction with a disordered potential. Our theory is validated by numerical simulations and explains the physics observed in recent experiments on cold atom transport in disorder.

Cherroret, Nicolas; Delande, Dominique

2013-09-01

197

Connecting forest ecosystem and microwave backscatter models  

Microsoft Academic Search

A procedure is outlined to connect data obtained from active microwave remote sensing systems with forest ecosystem models. The hierarchy of forest ecosystem models is discussed, and the levels at which microwave remote sensing data can be used as inputs are identified. In addition, techniques to utilize forest ecosystem models to assist in the validation of theoretical microwave backscatter models

ERIC S. KASISCHKE; NORMAN L. CHRISTENSEN Jr

1990-01-01

198

F Region and Magnetosphere, Backscatter Results.  

National Technical Information Service (NTIS)

The F region and the magnetosphere are under regular observation by the incoherent-backscatter radar technique at three stations near 70W longitude and ranging in magnetic latitude from the equator (Jicamarca, Peru), through 30N (Arecibo, Puerto Rico), to...

W. E. Gordon

1967-01-01

199

Terahertz backscattering behavior of various absorbing materials  

Microsoft Academic Search

The Submillimeter-Wave Technology Laboratory (STL) at the University of Massachusetts Lowell has investigated the electromagnetic scattering behavior of various broadband absorbers. Several absorbing materials were tested in a compact radar range operating at a center frequency of 160 GHz. The polarimetric radar cross section was measured at elevation angles from 15° to 75°. In addition to the backscattering behavior, the

C. Wu; A. J. Gatesman; L. Deroeck; T. Horgan; R. H. Giles; W. E. Nixon

2009-01-01

200

MEASUREMENT OF BACKSCATTERING FROM RFID TAGS  

Microsoft Academic Search

This paper presents a method for measuring signal backscattering from an RFID tag and calculating tag radar cross-section (RCS), which depends on the chip input impedance. We present a derivation of a theoretical formula for RFID tag radar cross-section and an experimental RCS measurement method using a network analyzer connected to an antenna in an anechoic chamber where the tag

Pavel V. Nikitin; K. V. S. Rao

201

Investigation of UHF RFID tag backscatter  

Microsoft Academic Search

The results of this paper show that the backscatter from an RFID tag can be strongly influenced by the presence of other tags. This occurs even if the tag spacing is not very small. In fact, for tag spacings approaching normal antenna array spacings, the group of tags appears to behave like a parasitically coupled antenna array. The change in

Justin Johnson; Robert Sainati

2007-01-01

202

QAM backscatter for passive UHF RFID tags  

Microsoft Academic Search

Traditional passive UHF RFID tags employ either ASK or PSK backscatter modulation to communicate data from memory or sensors on the tag to a remotely-located reader. These simple modulation schemes transfer data at a rate of one bit per symbol period, which for an integrated CMOS tag IC requires an on-chip oscillator with a frequency at least equal to the

Stewart Thomas; Matthew S. Reynolds

2010-01-01

203

Radar Polarimetric Backscattering Properties of Conical Graupel  

Microsoft Academic Search

Conical graupel is modeled using sphere-cone-oblate spheroidal shapes for the purpose of computing their backscattering properties at a wavelength of 10 cm in terms of the radar polarimetric observables, reflectivity factors, differential reflectivities and circular depolarization ratios. A shape distribution based on in situ measurements is used together with gamma (m=0, 2) size distributions in the computations; both wet and

K. Aydin; T. A. Seliga

1984-01-01

204

Measurement of texture using backscattered electrons  

Microsoft Academic Search

The design and development of a device to quantitatively measure surface texture using backscattered electrons (BSE) is described. Both theoretical and engineering considerations are discussed. Four BSE detectors,located at the corners of a square,centered on the illuminating beam, are used. The detector geometry and the location of the point of interrogation on the specimen surface are used in determining the

Raski

1986-01-01

205

Neutron backscattering in monitoring engineering processes  

Microsoft Academic Search

Calculations and measurements are reported on neutron backscattering (albedos) for multilayer objects and for objects with separation surfaces in some of the layers. Calculated and measured sensitivities are given for determining the distance to the scattering surfaces (heights above the surfaces) and to the boundaries (levels) on one-sided access through metal screens.

Pekarskii; G. Sh

1988-01-01

206

Subgrid-scale backscatter in turbulent and transitional flows  

Microsoft Academic Search

Direct numerical simulations of transitional and turbulent channel flow and compressible isotropic turbulence are used to study the backscatter phenomenon. In all flows considered, roughly 50 percent of the grid points were experiencing backscatter when a Fourier cutoff filter was used. The backscatter fraction was less with a Gaussian filter, and intermediate with a box filter in physical space. Moreover,

Ugo Piomelli; William H. Cabot; Parviz Moin; Sangsan Lee

1991-01-01

207

Fluctuations of Seafloor Backscatter Data From Multibeam Sonar Systems  

Microsoft Academic Search

Several theoretical models of seafloor backscatter statistics developed over recent years show a reasonable agreement with experimental measurements made with sonar systems. However, methods of data collection and processing used in modern multibeam systems are often not taken into consideration when analyzing statistical characteristics of observed backscatter data. Fluctuations of various backscatter parameters, which can be derived from raw multibeam

Alexander N. Gavrilov; Iain M. Parnum

2010-01-01

208

Design and performance measurements of an airborne aerosol backscatter lidar  

Microsoft Academic Search

The global winds measurement application of coherent Doppler lidar requires intensive study of the global climatology of atmospheric aerosol backscatter at infrared wavelengths. An airborne backscatter lidar is discussed, which has been developed to measure atmospheric backscatter profiles at CO2 laser wavelengths. The instrument characteristics and representative flight measurement results are presented.

Robert T. Menzies; David M. Tratt; Alan M. Brothers; Stephen H. Dermenjian; Carlos Esproles

1990-01-01

209

INTEGRAL BACKSCATTERING TRANSPONDERS FOR LOW COST RFID APPLICATIONS  

Microsoft Academic Search

sequential amplifier re-transmitting, and backscattering types of RFID tags is presented, with the most inexpensive type, the backsacttering tag, being considered in greater detail. The advantages of Schottky barrier diodes as backscatter elements for long read range microwave tags are shown. ASK and PSK modulation types with Schottky diodes as backscatter elements are described, and their advantages in passive and

Michael Y. Laukine; Peter H. Cole

210

Simulation of multistatic and backscattering cross sections for airborne radar  

Microsoft Academic Search

In order to determine susceptibilities of airborne radar to electronic countermeasures and electronic counter-countermeasures simulations of multistatic and backscattering cross sections were developed as digital modules in the form of algorithms. Cross section algorithms are described for prolate (cigar shape) and oblate (disk shape) spheroids. Backscattering cross section algorithms are also described for different categories of terrain. Backscattering cross section

Albert W. Biggs

1986-01-01

211

EBSD and AFM observations of the microstructural changes induced by low temperature plasma carburising on AISI 316  

NASA Astrophysics Data System (ADS)

Low temperature plasma carburising (LTPC) has been increasingly accepted as a hardening process for austenitic stainless steels because it produces a good combination of tribological and corrosion properties. The hardening mechanism is based on the supersaturation of the austenitic structure with carbon, which greatly hardens the material, significantly expands the fcc unit cell, produces high levels of compressive residual stresses and, ultimately, leads to the occurrence of deformation bands and rotation of the crystal lattice.The microstructural changes introduced during plasma carburising have a significant impact on the mechanical, tribological and corrosion performance and, for this reason, the microstructure of expanded austenite or S-phase has been extensively studied. However, modern surface characterisation techniques could provide new insights into the formation mechanism of S-phase layers.In this work, backscattered electron diffraction and atomic force microscopy were used to characterise the surface layers of expanded austenite produced by LTPC in an active screen furnace. Based on the experimental results, the plastic deformation, its dependence on crystallographic orientation, the evolution of grain boundaries, and their effects on mechanical, tribological and corrosion properties are discussed.

Corujeira Gallo, Santiago; Dong, Hanshan

2011-10-01

212

Wave shadowing and modulation of microwave backscatter from the ocean  

NASA Astrophysics Data System (ADS)

Shadowing and modulation of microwave backscatter by ocean waves are studied using coherent X-band radars. Two types of shadowing are investigated: geometric shadowing (complete blockage of incident rays) and partial shadowing (polarization-dependent diffraction combined with weak scatterers). We point out that the frequency of occurrence of zero signal-to-noise ratio samples cannot depend on the incident power level or the polarization if geometric shadowing occurs but can if partial shadowing exists. We then compare this behavior with observations, and show that the data do not support the hypothesis that geometric shadowing plays a significant role in low-grazing-angle microwave scattering from the ocean surface. Furthermore, our data indicate that partial shadowing only depends significantly on polarization for the steep waves found near shorelines. We also study the modulation of microwave backscatter by ocean waves using these data by looking at the phase differences between received power and scatterer velocity. These phase differences appear to be rather well explained by standard composite surface theory at VV polarization, having values that are positive looking up wave and negative looking down wave. For HH polarization, however, breaking effects come into play and overshadow composite surface effects of free waves. They cause the phase difference to be near zero for up wave looks and near 180° for down-wave looks. A simple model that involves both breaking and freely propagating waves but does not include any shadowing effects is shown to account for observed phase differences at both polarizations to within about 10°.

Plant, William J.; Farquharson, Gordon

213

Statistical analysis of backscatter data from 300 kHz multibeam echo sounder  

Microsoft Academic Search

The seafloor high-frequency backscatter average statistics, including the backscatter strength and the backscatter cross section, are statistically analyzed. According to Gamma distribution model of the backscatter cross section, the probability density function (PDF) of the backscatter strength is derived, and it is proved that the backscatter strength approaches a Gaussian distribution. The data recorded by a 300 kHz multibeam echo

Chao Xu; Haisen Li; Baowei Chen; Tian Zhou

2010-01-01

214

X-ray microdiffraction and EBSD study of FSP induced structural\\/phase transitions in a Ni-based superalloy  

Microsoft Academic Search

Severe plastic deformation during Friction Stir Processing (FSP) of an IN738 Ni-based superalloy was studied by means of X-ray polychromatic microdiffraction, EBSD, scanning electron and optical microscopies. Modeling of the physical properties and phase composition was also performed. Several distinct zones are formed during FSP including a stir zone (SZ), a thermal-mechanical affected zone (TMAZ) and a heat affected zone

Oleg M. Barabash; Rozaliya I. Barabash; Gene E. Ice; Zhili Feng; David Gandy

2009-01-01

215

Statistics at HF skywave ground backscatter Doppler spectra  

NASA Astrophysics Data System (ADS)

Cumulative distribution functions (CDF's) are presented for Doppler spectra from skywave (ionospherically propagated) ground backscatter measured on 17 October 1980. The variance of the CDF's is much greater than would be expected if ionospheric reflection coefficient and ground backscatter coefficient were both Gaussian random variables. In contrast, skywave echoes from the sea show a normalized variance between 2 and 3, in agreement with a model that assigns a unit normalized variance to both the ionospheric reflection coefficient and the sea-echo backscatter. Furthermore, the CDF's for skywave sea-echo backscatter spectra show qualitative agreement with the Hankel distribution that would be expected if both ionospheric reflection coefficient and sea-echo backscatter were Gaussian random variables. The large variance in skywave ground backscatter is probably caused by observed trends of ground backscatter coefficient with range and azimuth. In addition, a new method is demonstrated for estimating the CDF of an ensemble that has only a few samples.

Jones, R. M.; Riley, J. P.; Georges, T. M.

1984-05-01

216

Shallow water acoustic backscatter and reverberation measurements using a 68-kHz cylindrical array  

NASA Astrophysics Data System (ADS)

The characterization of high frequency, shallow water acoustic backscatter and reverberation is important because acoustic systems are used in many scientific, commercial, and military applications. The approach taken is to use data collected by the Toroidal Volume Search Sonar (TVSS), a 68 kHz multibeam sonar capable of 360° imaging in a vertical plane perpendicular to its direction of travel. With this unique capability, acoustic backscatter imagery of the seafloor, sea surface, and horizontal and vertical planes in the volume are constructed from data obtained in 200m deep waters in the Northeastern Gulf of Mexico when the TVSS was towed 78m below the surface, 735m astern of a towship. The processed imagery provide a quasi-synoptic characterization of the spatial and temporal structure of boundary and volume acoustic backscatter and reverberation. Diffraction, element patterns, and high sidelobe levels are shown to be the most serious problems affecting cylindrical arrays such as the TVSS, and an amplitude shading method is presented for reducing the peak sidelobe levels of irregular-line and non-coplanar arrays. Errors in the towfish's attitude and motion sensor, and irregularities in the TVSS's transmitted beampattern produce artifacts in the TVSS-derived bathymetry and seafloor acoustic backscatter imagery. Correction strategies for these problems are described, which are unique in that they use environmental information extracted from both ocean boundaries. Sea surface and volume acoustic backscatter imagery are used to explore and characterize the structure of near-surface bubble clouds, schooling fish, and zooplankton. The simultaneous horizontal and vertical coverage provided by the TVSS is shown to be a primary advantage, motivating further use of multibeam sonars in these applications. Whereas boundary backscatter fluctuations are well described by Weibull, K, and Rayleigh mixture probability distributions, those corresponding to volume backscatter are multi-modal, with the log-normal distribution providing the best fits to the centers of the distributions, and the Rayleigh mixture models providing the best fits to the tails of the distributions. The largest distribution tails result from resonant microbubbles and patchy aggregations of zooplankton. The Office of Naval Research funded this work under ONR-NRL Contract No. N00014-96-1-G9I3.

Gallaudet, Timothy Cole

2001-10-01

217

Auroral backscatter observed at HF from Ottawa  

SciTech Connect

Bistatic HF radar recordings of auroral scattering sources north of Ottawa are reported. Doppler frequency spreads over + or - 100 Hz were obtained at least 35 percent of the time. The peak of the Doppler frequency distribution was sometimes shifted from zero by as much as 50 Hz, and significant contributions often occurred at Doppler frequencies greater than 150 Hz. Signals received simultaneously on both arms of a two-arm direction-finding array were used to identify the specific elevations and bearings of the backscatter signals. A detailed study of a particular hour-long period is reported, and a large number of 'apparent' auroral backscatter sources are identified. The source regions, probably located in the F layer, were elongated mainly in the north-south direction and extended over at least 3 deg of latitude. North-south corridors were found between such sources in which echo returns were either absent or very weak. 14 references.

Montbriand, L.E.

1988-10-01

218

Nordsee radar backscatter measurements data report  

Microsoft Academic Search

Radar backscatter measurements of the ocean were made by University of Kansas (KU) investigators from the Nordsee tower to determine scattering coefficients as a function of wind speed, incidence angle and look direction at C-, X- and Ku-bands and to determine the modulation of Bragg-resonant ripples by long waves. A modified version of the KU helicopter-borne scatterometer (HELOSCAT) was used

S. Gogineni; A. H. Chaudhry; R. K. Moore

1984-01-01

219

A corrugated surface with low backscatter  

Microsoft Academic Search

A low backscatter corrugated metal surface has been designed, fabricated, and tested for H-polarized transverse electromagnetic (TEM) incident waves. The problem has been formulated using the scattering matrix approach and reflection and transmission co-efficients at the fin-air interface are determined using an integral equation approach. Hence, an expression for monostatic radar cross section (RCS) is obtained. The RCS has been

A. K. Bhattacharyya; S. K. Tandon

1984-01-01

220

Backscattering from a randomly rough dielectric surface  

Microsoft Academic Search

A backscattering model for scattering from a randomly rough dielectric surface is developed. Both like- and cross-polarized scattering coefficients are obtained. The like-polarized scattering coefficients contain single scattering terms and multiple scattering terms. The single scattering terms are shown to reduce to the first-order solutions derived from the small perturbation method when the roughness parameters satisfy the slightly rough conditions.

A. K. Fung; Z. Li; K. S. Chen

1992-01-01

221

Backscattering enhancement of random discrete scatterers  

Microsoft Academic Search

A recent laboratory-controlled optical experiment demonstrates that a sharp peak of small but finite angular width is exhibited in backscattering from a random distribution of discrete scatterers. In this paper the phenomenon is explained by using a second-order multiple-scattering theory of discrete particles. The theory gives an angular width of the order of the attenuation rate divided by the wave

Leung Tsang; Akira Ishimaru

1984-01-01

222

Estimating splash pine biomass using radar backscatter  

Microsoft Academic Search

L-band HV multiple-incidence-angle aircraft synthetic aperture radar (SAR) data were analyzed in relation to average stand biomass, basal area, and tree height for 55 slash pine plantations located in northern Florida. This information was used to develop a system of equations to predict average stand biomass as a function of L-band (24.5-cm) radar backscatter. The system of equations developed in

Yousif Ali Hussin; Robin M. Reich; Roger M. Hoffer

1991-01-01

223

Terahertz backscattering behavior of various absorbing materials  

NASA Astrophysics Data System (ADS)

The Submillimeter-Wave Technology Laboratory (STL) at the University of Massachusetts Lowell has investigated the electromagnetic scattering behavior of various broadband absorbers. Several absorbing materials were tested in a compact radar range operating at a center frequency of 160 GHz. The polarimetric radar cross section was measured at elevation angles from 15° to 75°. In addition to the backscattering behavior, the normal incidence transmittance of the materials was evaluated.

Wu, C.; Gatesman, A. J.; Deroeck, L.; Horgan, T.; Giles, R. H.; Nixon, W. E.

2009-05-01

224

Error analysis for elastic-backscattering lidar  

NASA Astrophysics Data System (ADS)

Elastic backscattering LIDAR represents one of the most promising tools for attaining remotely information about the distribution of aerosols and particulates in the atmosphere, which could lead to a better understanding of climate processes. In this paper we shall examine the uncertainties associated with such measurements and try to determine which of the LIDAR parameters need to be optimized in order to minimize the measurement errors. An optimization method of the operative characteristic associated with the LIDAR signal validation is also proposed.

Talianu, Camelia; Nicolae, Doina N.; Ciobanu, Mircea; Babin, Vasile D.; Cristescu, Constantin P.

2004-10-01

225

Backscattering improvement of UHF RFID tag efficiency  

Microsoft Academic Search

In this work, a tag-load selection methodology is proposed for optimized tag-to-reader backscatter communication. Derivation of the method is based on antenna\\/communication theory and applies to any tag-antenna, including minimum scattering antennas as a special case. In contrast to what is commonly believed, it is shown that amplitude maximization of complex reflection coefficient difference between the two states is not

Aggelos Bletsas; Antonis G. Dimitriou; John N. Sahalos

2010-01-01

226

Study of corrosion layers using backscattering ions  

Microsoft Academic Search

The backscattering technique was applied to materials of steam generator pipes of fossil fired plants in order to study the corrosion layers with respect to elemental amounts and depth structure. The samples were taken from plants and also from treatment in a laboratory device for the simulation of material stress. Using 7.6 MeV He-ions the oxide layer of a sample

H.-E Zschau; H. Baumann; K. Bethge; F. Link; G. Wachsmuth

1998-01-01

227

Mode-converted diffuse ultrasonic backscatter.  

PubMed

Diffuse ultrasonic backscatter describes the scattering of elastic waves from interfaces within heterogeneous materials. Previously, theoretical models have been developed for the diffuse backscatter of longitudinal-to-longitudinal (L-L) wave scattering within polycrystalline materials. Following a similar formalism, a mode-conversion scattering model is presented here to quantify the component of an incident longitudinal wave that scatters and is converted to a transverse (shear) wave within a polycrystalline sample. The model is then used to fit experimental measurements associated with a pitch-catch transducer configuration performed using a sample of 1040 steel. From these measurements, an average material correlation length is determined. This value is found to be in agreement with results from L-L scattering measurements and is on the order of the grain size as determined from optical micrographs. Mode-converted ultrasonic backscatter is influenced much less by the front-wall reflection than an L-L measurement and it provides additional microstructural information that is not accessible in any other manner. PMID:23927097

Hu, Ping; Kube, Christopher M; Koester, Lucas W; Turner, Joseph A

2013-08-01

228

Dosimetric characteristics of backscattered electrons in lead  

NASA Astrophysics Data System (ADS)

In electron beam therapy, tissue overdose due to electrons backscattered from lead has been profusely studied. To quantify this dose enhancement effect, an electron backscatter factor (EBF) was defined as the ratio of dose at the tissue-inhomogeneity interface with and without the scatterer present. The dependence of the EBF on energy at the scatterer surface is not well known for energies lower than 3 MeV which is the most frequent clinical situation. In this work, we have done Monte Carlo calculations with the GEANT code to study EBF in lead at this energy range. The applicability of this code and the developed procedure for dose estimation has been experimentally verified. The dependence of the EBF on the beam energy incident on the scatterer has been studied for different nominal beam energies incident at the phantom's surface. The results show a trend of increase of EBF with the beam energy incident on the scatterer between 0.5 and 1.5 MeV, keeping practically constant above this energy up to 3 MeV. Backscattered electron energy spectra and depth dose curves in the `up-stream' direction have been obtained at the various energies of the primary electron beam striking on the lead scatterer. The results of this work are compared with previously published data.

Pérez-Calatayud, José; Ballester, Facundo; Serrano, Miguel A.; Lluch, José L.; Casal, Emilio; Carmona, Vicente

2000-07-01

229

Modeling strategies of ultrasound backscattering by blood  

NASA Astrophysics Data System (ADS)

Tissue characterization using ultrasound (US) scattering can allow the identification of relevant cellular biophysical information noninvasively. The characterization of the level of red blood cell (RBC) aggregation is one of the proposed applications. Different modeling strategies have been investigated by our group to better understand the mechanisms of US backscattering by blood, and to propose relevant measurable indices of aggregation. It could be hypothesized from these studies that the microstructure formed by RBC clusters is a main determinant of US backscattered power. The structure factor, which is related to the Fourier transform of the microscopic density function of RBCs, is described and used to explain the scattering behavior for different spatial arrangements of nonaggregated and aggregated RBCs. The microscopic density function was described by the Percus-Yevick approximation (nonaggregated RBCs), and for aggregated RBCs, by the Poisson distribution, the Neyman-Scott point process, and very recently by a flow-dependent rheological model. These statistical and microrheological models allowed the study of US backscattered power as a function of the hematocrit, scatterers' size, insonification frequency, and level of RBC aggregation. Experimental results available from the literature were used to validate the different approaches. [Work supported by Canadian Institutes of Health Research (MOP-36467), HSFQ, FCAR, and FRSQ.

Guy, Cloutier; David, Savery; Isabelle, Fontaine; Beng Ghee, Teh

2002-05-01

230

Backscatter and attenuation characterization of ventricular myocardium  

NASA Astrophysics Data System (ADS)

This Dissertation presents quantitative ultrasonic measurements of the myocardium in fetal hearts and adult human hearts with the goal of studying the physics of sound waves incident upon anisotropic and inhomogeneous materials. Ultrasound has been used as a clinical tool to assess heart structure and function for several decades. The clinical usefulness of this noninvasive approach has grown with our understanding of the physical mechanisms underlying the interaction of ultrasonic waves with the myocardium. In this Dissertation, integrated backscatter and attenuation analyses were performed on midgestational fetal hearts to assess potential differences in the left and right ventricular myocardium. The hearts were interrogated using a 50 MHz transducer that enabled finer spatial resolution than could be achieved at more typical clinical frequencies. Ultrasonic data analyses demonstrated different patterns and relative levels of backscatter and attenuation from the myocardium of the left ventricle and the right ventricle. Ultrasonic data of adult human hearts were acquired with a clinical imaging system and quantified by their magnitude and time delay of cyclic variation of myocardial backscatter. The results were analyzing using Bayes Classification and ROC analysis to quantify potential advantages of using a combination of two features of cyclic variation of myocardial backscatter over using only one or the other feature to distinguish between groups of subjects. When the subjects were classified based on hemoglobin A1c, the homeostasis model assessment of insulin resistance, and the ratio of triglyceride to high-density lipoprotein-cholesterol, differences in the magnitude and normalized time delay of cyclic variation of myocardial backscatter were observed. The cyclic variation results also suggested a trend toward a larger area under the ROC curve when information from magnitude and time delay of cyclic variation is combined using Bayes classification than when each feature is analyzed individually. Ultrasound continues to be a powerful tool that enables noninvasive quantification of material properties. The studies in this Dissertation show that understanding the physical mechanisms behind the interaction of sound waves with myocardium can reveal new information about the structure, composition and overall state of the heart.

Gibson, Allyson Ann

231

Combined nano-SIMS/AFM/EBSD analysis and atom probe tomography, of carbon distribution in austenite/?-martensite high-Mn steels.  

PubMed

We introduce a new experimental approach for the identification of the atomistic position of interstitial carbon in a high-Mn binary alloy consisting of austenite and ?-martensite. Using combined nano-beam secondary ion mass spectroscopy, atomic force microscopy and electron backscatter diffraction analyses, we clearly observe carbon partitioning to austenite. Nano-beam secondary ion mass spectroscopy and atom probe tomography studies also reveal carbon trapping at crystal imperfections as identified by transmission electron microscopy. Three main trapping sites can be distinguished: phase boundaries between austenite and ?-martensite, stacking faults in austenite, and prior austenite grain boundaries. Our findings suggest that segregation and/or partitioning of carbon can contribute to the austenite-to-martensite transformation of the investigated alloy. PMID:23537886

Seol, Jae-Bok; Lee, B-H; Choi, P; Lee, S-G; Park, C-G

2013-02-24

232

Photoelectron diffraction and holography: Some new directions  

SciTech Connect

Photoelectron diffraction has by now become a versatile and powerful technique for studying surface structures, with special capabilities for resolving chemical and magnetic states of atoms and deriving direct structural information from both forward scattering along bond directions and back-scattering path length differences. Further fitting experiment to theory can lead to structural accuracies in the {plus_minus}0.03 ){Angstrom} range. Holographic inversions of such diffraction data also show considerable promise for deriving local three-dimensional structures around a given emitter with accuracies of {plus_minus}0.2--0.3 {Angstrom}. Resolving the photoelectron spin in some way and using circularly polarized radiation for excitation provide added dimensions for the study of magnetic systems and chiral experimental geometries. Synchrotron radiation with the highest brightness and energy resolution, as well as variable polarization, is crucial to the full exploitation of these techniques.

Fadley, C.S. [Lawrence Berkeley Lab., CA (United States)]|[California Univ., Davis, CA (United States). Dept. of Physics

1993-08-01

233

Observation of high-temperature phase transformation in the Si-modified aluminide coating on mild steel using EBSD  

SciTech Connect

Mild steel was coated by hot-dipping in a molten bath containing Al-10 wt.% Si. The phase transformation in the aluminide layer during diffusion at 750 deg. C in static air was analyzed by Electron Backscatter Diffraction. The results showed that the aluminide layer of the as-coated specimen consisted of an outer Al-Si eutectic topcoat and the inner Fe-Al-Si and Fe-Al intermetallic layers. The formation of {tau}{sub 5}-Al{sub 7}Fe{sub 2}Si and {tau}{sub 6}-Al{sub 4}FeSi was observed with increasing exposure time at 750 deg. C, while the {tau}{sub 1}-(Al,Si){sub 5}Fe{sub 3} phase precipitated into the Fe{sub 2}Al{sub 5} phase. After 60 min of exposure, the {tau}{sub 5}-Al{sub 7}Fe{sub 2}Si and {tau}{sub 6}-Al{sub 4}FeSi phases disappeared. The FeAl phase not only formed at the interface between Fe{sub 2}Al{sub 5} and the steel substrate, but also transformed from {tau}{sub 1}-(Al,Si){sub 5}Fe{sub 3} after diffusion for 10 h. With prolonged exposure, the growing FeAl phase decreased the thickness of Fe{sub 2}Al{sub 5} and forced the formation of FeAl{sub 2} phase. Finally, the aluminide layer comprised only FeAl{sub 2} and FeAl.

Cheng, Wei-Jen, E-mail: d9603505@mail.ntust.edu.tw [Department of Mechanical Engineering, National Taiwan University of Science and Technology, Taipei 10672, Taiwan (China); Wang, Chaur-Jeng [Department of Mechanical Engineering, National Taiwan University of Science and Technology, Taipei 10672, Taiwan (China)

2010-04-15

234

Reference modulation for calibrated measurements of tag backscatter  

Microsoft Academic Search

This paper presents an approach for calibrating backscattering measurements from 860-960MHz Ultra-High Fre- quency Radio Frequency Identification (UHF RFID) tags. An S- parameter model is formulated to relate diode switch and antenna input circuit parameters with the scattering performance o ft he calibration device. Measurements of modulated backscattered power agree with the model to within ±0.1dB. Tag backscatter measurements can

Daniel G. Kuester; David R. Novotny; Jeffrey R. Guerrieri; Randal H. Direen; Zoya Popovic

2011-01-01

235

Analytical approach to backscattering of low-energy electrons  

NASA Astrophysics Data System (ADS)

The backscattered flux and energy of electrons when a monoenergetic electron is incident in a gas at any pitch angle are calculated using an approach based on spatial yield spectra. The four-dimensional yield spectrum function is defined and the equations for calculating the backscattered flux and energy are derived. The calculated backscattered flux and energy are compared to the data of Mantas and Walker (1976) and the data correlate well.

Haider, S. A.; Singhal, R. P.

1986-12-01

236

Combining angular response classification and backscatter imagery segmentation for benthic biological habitat mapping  

Microsoft Academic Search

Backscatter information from multibeam echosounders (MBES) have been shown to contain useful information for the characterisation of benthic habitats. Compared to backscatter imagery, angular response of backscatter has shown advantages for feature discrimination. However its low spatial resolution inhibits the generation of fine scale habitat maps. In this study, angular backscatter response was combined with image segmentation of backscatter imagery

Rozaimi Che Hasan; Daniel Ierodiaconou; Laurie Laurenson

237

Crystallographic characterization of stress corrosion cracking initiation on type316L stainless steel in high temperature and high pressure water  

NASA Astrophysics Data System (ADS)

Intergranular stress corrosion cracking (IGSCC) and transgranular stress corrosion cracking (TGSCC) of Type316L stainless steel are examined by a slow strain rate test (SSRT) in a dilute sodium sulphate solution at 288 °C. Crystallographical orientation measurements on Type316L are performed by electron backscatter diffraction (EBSD) in order to grasp crack initiation during SSRT. The relationship between crystal orientation and crack initiation of IGSCC and TGSCC can be characterized using EBSD data.

Saito, Tomo; Masaki, Hiroya; Azhari Mukhlis, Fahmi; Tsuchiya, Hiroaki; Fujimoto, Shinji

2009-05-01

238

Backscattering position detection for photonic force microscopy  

SciTech Connect

An optically trapped particle is an extremely sensitive probe for the measurement of pico- and femto-Newton forces between the particle and its environment in microscopic systems (photonic force microscopy). A typical setup comprises an optical trap, which holds the probe, and a position sensing system, which uses the scattering of a beam illuminating the probe. Usually the position is accurately determined by measuring the deflection of the forward-scattered light transmitted through the probe. However, geometrical constraints may prevent access to this side of the trap, forcing one to make use of the backscattered light instead. A theory is presented together with numerical results that describes the use of the backscattered light for position detection. With a Mie-Debye approach, we compute the total (incident plus scattered) field and follow its evolution as it is collected by the condenser lenses and projected onto the position detectors and the responses of position sensitive detectors and quadrant photodetectors to the displacement of the probe in the optical trap, both in forward and backward configurations. We find out that in the case of backward detection, for both types of detectors the displacement sensitivity can change sign as a function of the probe size and is null for some critical sizes. In addition, we study the influence of the numerical aperture of the detection system, polarization, and the cross talk between position measurements in orthogonal directions. We finally discuss how these features should be taken into account in experimental designs.

Volpe, Giovanni; Kozyreff, Gregory; Petrov, Dmitri [ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, Castelldefels, Barcelona, 08860 (Spain); Optique Nonlineaire Theorique, Universite Libre de Bruxelles (U.L.B.), Code Postal 231, Campus Plaine, B-1050 Bruxelles (Belgium) and ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, Castelldefels, Barcelona, 08860 (Spain); ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, Castelldefels, Barcelona, 08860 (Spain) and ICREA--Institucio Catalana de Recerca i Estudis Avancats, Barcelona, 08010 (Spain)

2007-10-15

239

Compton backscattered collmated X-ray source  

DOEpatents

A high-intensity, inexpensive and collimated x-ray source for applications such as x-ray lithography is disclosed. An intense pulse from a high power laser, stored in a high-finesse resonator, repetitively collides nearly head-on with and Compton backscatters off a bunched electron beam, having relatively low energy and circulating in a compact storage ring. Both the laser and the electron beams are tightly focused and matched at the interaction region inside the optical resonator. The laser-electron interaction not only gives rise to x-rays at the desired wavelength, but also cools and stabilizes the electrons against intrabeam scattering and Coulomb repulsion with each other in the storage ring. This cooling provides a compact, intense bunch of electrons suitable for many applications. In particular, a sufficient amount of x-rays can be generated by this device to make it an excellent and flexible Compton backscattered x-ray (CBX) source for high throughput x-ray lithography and many other applications.

Ruth, Ronald D. (Woodside, CA); Huang, Zhirong (Stanford, CA)

2000-01-01

240

Compton backscattered collimated x-ray source  

DOEpatents

A high-intensity, inexpensive and collimated x-ray source is disclosed for applications such as x-ray lithography is disclosed. An intense pulse from a high power laser, stored in a high-finesse resonator, repetitively collides nearly head-on with and Compton backscatters off a bunched electron beam, having relatively low energy and circulating in a compact storage ring. Both the laser and the electron beams are tightly focused and matched at the interaction region inside the optical resonator. The laser-electron interaction not only gives rise to x-rays at the desired wavelength, but also cools and stabilizes the electrons against intrabeam scattering and Coulomb repulsion with each other in the storage ring. This cooling provides a compact, intense bunch of electrons suitable for many applications. In particular, a sufficient amount of x-rays can be generated by this device to make it an excellent and flexible Compton backscattered x-ray (CBX) source for high throughput x-ray lithography and many other applications. 4 figs.

Ruth, R.D.; Huang, Z.

1998-10-20

241

Compton backscattered collimated x-ray source  

DOEpatents

A high-intensity, inexpensive and collimated x-ray source for applications such as x-ray lithography is disclosed. An intense pulse from a high power laser, stored in a high-finesse resonator, repetitively collides nearly head-on with and Compton backscatters off a bunched electron beam, having relatively low energy and circulating in a compact storage ring. Both the laser and the electron beams are tightly focused and matched at the interaction region inside the optical resonator. The laser-electron interaction not only gives rise to x-rays at the desired wavelength, but also cools and stabilizes the electrons against intrabeam scattering and Coulomb repulsion with each other in the storage ring. This cooling provides a compact, intense bunch of electrons suitable for many applications. In particular, a sufficient amount of x-rays can be generated by this device to make it an excellent and flexible Compton backscattered x-ray (CBX) source for high throughput x-ray lithography and many other applications.

Ruth, Ronald D. (Woodside, CA); Huang, Zhirong (Stanford, CA)

1998-01-01

242

Compton backscattered collimated X-ray source  

SciTech Connect

A high-intensity, inexpensive and collimated x-ray source for applications such as x-ray lithography is disclosed. An intense pulse from a high power laser, stored in a high-finesse resonator, repetitively collides nearly head-on with and Compton backscatters off a bunched electron beam, having relatively low energy and circulating in a compact storage ring. Both the laser and the electron beams are tightly focused and matched at the interaction region inside the optical resonator. The laser-electron interaction not only gives rise to x-rays at the desired wavelength, but also cools and stabilizes the electrons against intrabeam scattering and Coulomb repulsion with each other in the storage ring. This cooling provides a compact, intense bunch of electrons suitable for many applications. In particular, a sufficient amount of x-rays can be generated by this device to make it an excellent and flexible Compton backscattered x-ray (CBX) source for high throughput x-ray lithography and many other applications.

Ruth, R.D.; Huang, Z.

2000-03-07

243

The Discovery of Partially Coherent Backscatter in Radar Observations of Precipitation and Its Potential Impact on Radar Hydrometeorology  

NASA Astrophysics Data System (ADS)

This work presents the discovery of radar coherent scatter in precipitation. The theory shows that the coherent scatter can be generated by spatially correlated precipitation structures acting like diffraction gratings in resonance with the radar wavelength in which the elements of the structures all moving at practically the same velocity. Such diffraction gratings are well known to produce fields of maxima and minima of back-scattered intensities. As they move through the radar beam these fields produce distinctive power oscillations of frequencies f that can not be attributed to incoherent scatter. A different kind of back-scattered power spectrum, Z(f) is then defined. This power spectrum is the distribution of the total backscattered power over the power oscillations characterized by f. This then allows us to calculate the coherent scatter contribution to the total back-scattered power. It also has the advantage that it can be computed even for incoherent radars since Doppler information is not required. Data in snow and rain were analyzed. Coherent scatter was found to be pervasive throughout these two minutes of data with only up to at most 4% of the rain observations being examples of pure incoherent scatter. We also note that when coherent scatter is present, the usual relations between the standard deviation of the observed Doppler velocities and the decorrelation time in common use are no longer valid so that signal statistics are affected. Specifically, it is also shown that these lower frequencies are associated with the increased temporal coherency and are directly linked to the Doppler spectral peaks through integer multiples of ?/2, a characteristic of coherent Bragg scatter. It seems, then, that radar coherent scatter from precipitation exists and is generated by the mechanism introduced here. Moreover, it appears to be pervasive in these data. However, because this only represents a few minutes of observations, one should not over generalize. Much work remains to be done if we are to fully explore the extent and statistical characterization of radar coherent backscatter. At a minimum, though, these findings present a challenge to the assumption that the scatter of radar waves from precipitation is always incoherent. This is important to hydrometeorology because the backscattered power for coherent scatter depends upon the square of the particle concentation, while for incoherent scatter the power depends linearly on the particle concentration. Hence, the presence of significant coherent backscatter will lead to errors in the estimates of quantities like the rainfall rate which also depend linearly on the particle concentration. Thus,if prevalent, these findings will require the reevaluation of many current approaches toward the quantitative interpretation of radar observations of precipitation.

Jameson, A. R.; Kostinski, A.

2009-12-01

244

Backscatter body scanners – A strip search by other means  

Microsoft Academic Search

Backscatter body scanners have only recently been deployed at airports across the US and used as an optional alternative to patdowns – the open hand form of body search. This paper will essentially outline the statutory law and case-law of special relevance in the US to backscatter body scanners and determine the deficiencies and dilemmas of the legal framework with

Demetrius Klitou

2008-01-01

245

Fading Characteristics of Panchromatic Radar Backscatter from Selected Agricultural Targets  

Microsoft Academic Search

An experiment was performed to determine the fading characteristics of backscattered radar signals from four agricultural targets at 9 GHz. The targets included two different row crops (corn and soybeans), a continuous canopy (alfalfa) and bare ground. After a short review of the statistics of Rayleigh fading backscatter, the data processing method and the results of the experiment are analyzed.

Thomas F. Bush; Fawwaz Uloby

1975-01-01

246

Technique for measuring antenna drive port impedance using backscatter data  

Microsoft Academic Search

This paper describes a technique for measuring the drive port impedance, denoted Z(sub D), of an antenna using radar backscatter data. It requires only that one has access to the antenna terminal ports, and the ability to attach a known load to the terminals. In the technique described here, three sets of backscatter data (amplitude and phase) are required: one

Joseph T. Mayhan; Andre R. Dion; Alan J. Simmons

1994-01-01

247

UHF passive RFID backscatter power transfer function and coverage area  

Microsoft Academic Search

The RFID tag backscatter transfer power function is estimated from various measurement results in our anechoic chamber for two brands of tags. The backscatter transfer power function turns out to not be directly proportional to input power and therefore it cannot be modeled as a constant radar cross section. Additionally it shows that the classic radar equation cannot be applied

Koon-Ting Chu; Ross D. Murch

2009-01-01

248

Analytical Approach to the Backscattering from UHF RFID Transponder  

Microsoft Academic Search

The investigation of the modulated, backscattered contribution from UHF RFID Transponders is a crucial issue for the reliable evaluation of the behavior and the performance of RFID systems. The backscattered, radiated field by a UHF Transponder is described by means of a simple and complete analytical expression. The tag radar cross section (RCS) and the bit error rate (BER) at

Franco Fuschini; Carmine Piersanti; Francesco Paolazzi; Gabriele Falciasecca

2008-01-01

249

Opposition Effect from Clementine Data and Mechanisms of Backscatter  

Microsoft Academic Search

An analysis of Clementine data obtained from a UVVIS camera and simulating laboratory photometric and polarimetric measurements is presented with the use of a new photometric three-parameter function combining the shadow-hiding and coherent backscatter mechanisms. The fit of calculated curves to the average brightness phase function of the Moon derived from Clementine data indicates that the coherent backscatter component is

Yu. G. Shkuratov; M. A. Kreslavsky; A. A. Ovcharenko; D. G. Stankevich; E. S. Zubko; C. Pieters; G. Arnold

1999-01-01

250

Raman backscattering in an electron beam-plasma system  

Microsoft Academic Search

The parametric decay of an electromagnetic pump wave into a backscattered electromagnetic wave and an electron electrostatic scatterer wave in a plasma traversed by an electron beam is investigated. A formula for the growth rate of the backscattered and scatterer waves is derived and studied numerically.

Joseph E. Willett

1982-01-01

251

Raman backscattering in an electron beam-plasma system  

NASA Astrophysics Data System (ADS)

The parametric decay of an electromagnetic pump wave into a backscattered electromagnetic wave and an electron electrostatic scatterer wave in a plasma traversed by an electron beam is investigated. A formula for the growth rate of the backscattered and scatterer waves is derived and studied numerically.

Willett, J. E.

1982-12-01

252

Fading characteristics of panchromatic radar backscatter from selected agricultural targets  

Microsoft Academic Search

An experiment was performed to empirically determine the fading characteristics of backscattered radar signals from four agricultural targets at 9 GHz. After a short review of the statistics of Rayleigh fading backscatter, the data processing method and results of the data are analyzed. Comparison with theory shows adequate agreement with the experimental results, provided of course, the targets are modeled

T. F. Bush; F. T. Ulaby

1973-01-01

253

A Backscatter Model for a Randomly Perturbed Periodic Surface  

Microsoft Academic Search

A backscatter model for a randomly perturbed periodic surface has been developed to explain backscatter measurements from a bare soil surface with row structure. It is assumed that the rowdirection effect can be included by integrating the scattering coefficient żss (ż') due to the random roughness component over the underlying periodic component of the soil surface. It is found that

Fawwaz T. Ulaby; F. Kouyate; Adrian K. Fung; Alois J. Sieber

1982-01-01

254

Rayleigh backscattering in a fiber gyroscope with limited coherence sources  

Microsoft Academic Search

Noise due to temporal fluctuations of Rayleigh baekscattered light in fiber-optical gyroscopes is studied experimentally with various sources whose coherence length is less than the fiber length. The reduction of the coherent fraction of backscattered light and its fluctuation frequencies with reduced source coherence is demonstrated and fit to an analytical model. Measured backscatter parameters for the fiber and sources

W. Burns; R. Moeller

1983-01-01

255

Use of backscattered electron detector arrays for forming backscattered electron images in the scanning electron microscope.  

PubMed

The backscattered electron (BSE) signal in the scanning electron microscope (SEM) can be used in two different ways. The first is to give a BSE image from an area that is defined by the scanning of the electron beam (EB) over the surface of the specimen. The second is to use an array of small BSE detectors to give an electron backscattering pattern (EBSP) with crystallographic information from a single point. It is also possible to utilize the EBSP detector and computer-control system to give an image from an area on the specimen--for example, to show the orientations of the grains in a polycrystalline sample ("grain orientation imaging"). Some further possibilities based on some other ways for analyzing the output from an EBSP detector array, are described. PMID:16502623

Wells, O C; Gignac, L M; Murray, C E; Frye, A; Bruley, J

256

Origin of low-coherence enhanced backscattering  

NASA Astrophysics Data System (ADS)

The origin of low-coherence enhanced backscattering (EBS) of light in random media when the spatial coherence length of illumination is much smaller than the transport mean free path has been poorly understood. We report that in weakly scattering discrete random media low-coherence EBS originates from time-reversed paths of double scattering. Low spatial coherence illumination dephases the time-reversed waves outside its finite coherence area, which isolates the minimal number of scattering events in EBS from higher-order scattering. Moreover, we show the first experimental evidence that the minimal number of scattering events in EBS is double scattering, which has been hypothesized since the first observation of EBS.

Kim, Young L.; Pradhan, Prabhakar; Subramanian, Hariharan; Liu, Yang; Kim, Min H.; Backman, Vadim

2006-05-01

257

Elements of diffractive optics  

NASA Astrophysics Data System (ADS)

Diffractive optics makes use of diffraction of light to design otpical elements and systems, which serve for imaging visual objects and transforming coherent optical beams. A diffractive structure can be computed and the pattern written using focused laser or electron beams. Phase nature of diffraction pattern is preferred. Computations involve the first and second order terms and a curvature of the substrate plate, which can be exploited for the element to be aplanatic. Diffraction grooves should have a suitable transversal saw-tooth profile to obtain the highest diffraction efficiency. An alternative method for fabrication of elements of this kind is holographic recording, which can be use mainly for off-axial components.

Miler, Miroslav

1999-12-01

258

Orientation imaging microscopy of polycrystalline sodium chloride  

SciTech Connect

A novel preparation technique is described that makes possible grain size analysis of polycrystalline NaCl using orientation imaging microscopy via electron backscatter diffraction (EBSD). The preparation methodology is specifically developed to overcome difficulties in preparing microporous NaCl for microscopy. The grain size and crystallographic texture of polycrystalline NaCl samples, prepared via solution pressure and sintered in the range of 650-780 deg. C, were able to be measured successfully with EBSD. The limitations of the preparation technique for EBSD analysis of NaCl are also discussed.

Staiger, M.P., E-mail: mark.staiger@canterbury.ac.nz [Department of Mechanical Engineering, University of Canterbury, Private Bag 4800, Christchurch, 8020 (New Zealand); Kolbeinsson, I. [Department of Mechanical Engineering, University of Canterbury, Private Bag 4800, Christchurch, 8020 (New Zealand); Newman, J. [Newman Energy Research, 2 Rose Street, Christchurch (New Zealand); Woodfield, T.; Sato, T. [Department of Mechanical Engineering, University of Canterbury, Private Bag 4800, Christchurch, 8020 (New Zealand)

2010-04-15

259

Diffraction Results from CDF.  

National Technical Information Service (NTIS)

We present final results by the CDF II collaboration on diffractive W and Z production, report on the status of ongoing analyses on diffractive dijet production and on rapidity gaps between jets, and briefly summarize results obtained on exclusive product...

K. Goulianos

2011-01-01

260

Application of electron backscattered diffraction to cleavage fracture in duplex stainless steel  

Microsoft Academic Search

The mechanical properties and corrosion resistance of duplex stainless steel (DSS) are generally superior to conventional austenite or ferrite grades. DSSs can have yield strengths twice the austenite grades, while retaining good ductility and toughness properties. Commercial wrought duplex stainless steels, either plates or rod, are processed by hot rolling followed by a solution annealing treatment to optimize the austenite-ferrite

S. Kim; T. J. Marrow

1999-01-01

261

Metallographic Preparation of Space Shuttle Reaction Control System Thruster Electron Beam Welds for Electron Backscatter Diffraction.  

National Technical Information Service (NTIS)

A Space Shuttle Reaction Control System (RCS) thruster failed during a firing test at the NASA White Sands Test Facility (WSTF), Las Cruces, New Mexico. The firing test was being conducted to investigate a previous electrical malfunction. A number of crac...

J. Martinez

2011-01-01

262

Physical modeling and measurement of fish acoustic backscatter  

NASA Astrophysics Data System (ADS)

Physical acoustic model of fish is used to explain the variability in backscatter and target size. The research has the aim to apply the theoretical physics-based acoustic scattering models of single animal and laboratory measurements of backscattering by individual fish. The scattering process was modeled using the distorted-wave Born approximation. Results showed that the acoustic backscatter strongly depended on the fish orientation. Predicted scattering over the measured distribution of orientations resulted in predictions of target strength consistent with measurements of target strength of fish.

Manik, Henry M.

2012-06-01

263

Measurement of texture using backscattered electrons  

SciTech Connect

The design and development of a device to quantitatively measure surface texture using backscattered electrons (BSE) is described. Both theoretical and engineering considerations are discussed. Four BSE detectors,located at the corners of a square,centered on the illuminating beam, are used. The detector geometry and the location of the point of interrogation on the specimen surface are used in determining the partial derivatives. To obtain surface elevations from the extracted partials, integrations in Fourier space are performed, which leads to useful averaging. A scanning electron-microscope-based device was constructed to perform texture measurements. The design and construction of the BSE detection system, using Schottky barrier diodes, and of the detection hardware is presented. Calibration procedures, a means of correcting for scan distortions and the measurement of beam position drift, are also presented. The first application has included the measurement of a roughness standard. The BSE device was shown to possess spatial resolution superior to that of the stylus tracer.

Raski, J.Z.

1986-01-01

264

Thomson Backscattered X-rays from an Intense Laser Beam.  

National Technical Information Service (NTIS)

We have formulated and obtained analytical expressions for Thomson backscattered x-ray radiation for an electron beam incident on a linearly polarized electromagnetic undulator at a small angle. The analytical expressions are valid for fundamental and har...

C. M. Tang B. Hafizi S. K. Ride

1993-01-01

265

Direction Angle Sensitivity of Agricultural Field Backscatter with AIRSAR Data.  

National Technical Information Service (NTIS)

This paper presents a study of the direction angle sensitivity of radar backscatter from agricultural fields. The direction angle is defined as the angle between the incident plane and the perpendicular to the field row direction. Previous studies have co...

P. C. Dubois E. Rignot J. J. Vanzyl

1993-01-01

266

Statistics of HF Skywave Ground Backscatter Doppler Spectra.  

National Technical Information Service (NTIS)

Cumulative distribution functions (CDF's) are presented for Doppler spectra from skywave (ionospherically propagated) ground backscatter measured on 17 October 1980. The variance of the CDF's is much greater than would be expected if ionospheric reflectio...

R. M. Jones J. P. Riley T. M. Georges

1984-01-01

267

Compton backscattering polarimeter for measuring longitudinal electron polarization.  

National Technical Information Service (NTIS)

Compton backscattering polarimetry provides a fast measurement of the polarization of an electron beam in a storage ring. Since the method is non-destructive, the polarization of the electrons can be monitored during internal target experiments. At NIKHEF...

I. Passchier D. W. Higinbotham N. Vodinas N. Papadakis K. de Jager

1997-01-01

268

UHF Radar Backscatter Enhancements from the Topside Ionosphere.  

National Technical Information Service (NTIS)

Intense (about 20 dB) enhancements of the incoherent radar backscatter spectrum from the topside ionosphere have been observed with the Millstone Hill UHF radar; enhancements occurring at the local ion acoustic frequency causing large asymmetries in the m...

K. M. Groves M. C. Lee J. C. Foster

1990-01-01

269

Raman Backscatter Measurement Research on Water Vapor Systems.  

National Technical Information Service (NTIS)

Raman backscatter techniques proved to be a useful remote sensing tool, whose full potential has not been realized. The types of information available from laser probes in atmospheric studies are reviewed. Detection levels for known Raman cross sections a...

G. L. Workman

1975-01-01

270

Phase Properties of Backscattered Fields from Thin Rods.  

National Technical Information Service (NTIS)

Numerical and analytical calculations show the phase of backscatter fields from thin perfectly conducting rods at constant distance from the scatterer to become essentially independent of aspect angle for rod lengths less than lambda/2, to approach a limi...

R. B. Mack

1970-01-01

271

Angular distribution of SRS backscatter in NIF ignition experiments  

NASA Astrophysics Data System (ADS)

Modeling the SRS backscatter from NIF hohlraums provides a path to a better understanding of the under-dense plasma conditions created within, which have yet to be measured directly. The spatial location of SRS amplification regions influences the amount of refraction that the scattered light undergoes, and thus its angular distribution exiting the hohlraum. Here we describe how we use pF3D [R. L. Berger et al., Phys. Plasmas 5, 4337 (1998); C. H. Still et al., Phys. Plasmas 7, 2023 (2000)], SLIP [P. Michel et al., Phys. Plasmas 17, 056305 (2010)] and a simple ray-tracing application to model the near-field (angular) distribution of SRS backscatter in NIF ignition experiments. We compare these results to the measurements made by the improved time-dependent NBI (Near-Backscatter Imager) and the FABS (Full-Aperture Backscatter) diagnostics [J. D. Moody et al., Rev. Sci. Instrum. 81, 10D921 (2010)].

Williams, Edward; Moody, John; Michel, Pierre; Hinkel, Denise; Langdon, A. Bruce; Langer, Steven; Divol, Laurent

2011-11-01

272

Quantitative Analysis of Venus Radar Backscatter Data in Arcgis.  

National Technical Information Service (NTIS)

Ongoing mapping of the Ganiki Planitia (V14) quadrangle of Venus and definition of material units has involved an integrated but qualitative analysis of Magellan radar backscatter images and topography using standard geomorphological mapping techniques. H...

S. M. Long E. B. Grosfils

2005-01-01

273

Directional ultrasonic backscattering in polycrystals with elongated grains  

NASA Astrophysics Data System (ADS)

An analytical solution for a three dimensional integral representation of the backscattering (BS) coefficient in polycrystals with elongated grains is obtained. The theory was applied to evaluation of experimental data in Ti alloy with duplex microstructure, which consists of micro-textured regions (MTR) and smaller crystallites. Experiment shows that for microstructure characterization there is significant advantage in using the directional ratios of backscattering coefficients instead their absolute values for data analysis.

Lobkis, O. I.; Yang, L.; Li, J.; Rokhlin, S. I.

2012-05-01

274

L-Band Radar Backscatter Modeling of Forest Stands  

Microsoft Academic Search

An L-band HH radar backscatter model of a coniferous forest stand is described and compared with SIR-B L-band image data of the Mount Shasta region of northern California. Being based upon an identification and implementation of the expected major components of forest backscattering, the model is simple in form and thus fast computationally, making possible extensive simulations of forest stands.

JOHN A. RICHARDS; Guo-Qing Sun; David Simonett

1987-01-01

275

Accurate microcrystallography using electron back-scattering patterns  

Microsoft Academic Search

A method for precise determination of the orientation of mierocrystals is described. Electron back-scattering patterns are observed on a fluorescent screen in a scanning electron microscope, and high precision is obtained by casting geo metrical shadows onto the screen to determine the point from which the back-scattered electrons are emitted. Orientational accuracy around ±0.5° can be routinely obtained. The geometrical

J. A. Venables; R. Bin-Jaya

1977-01-01

276

Ultrasonic Backscattering from Suspended Erythrocytes: Dependence on Frequency and Size.  

NASA Astrophysics Data System (ADS)

The ultrasonic scattering properties of blood have been intensively investigated since the echo signal from red blood cells carries abundant diagnostic information for the study of blood flow and blood properties in the vessels. Recently, ultrasound of frequency higher than 20 MHz has been implemented in intravascular imaging to obtain better images of the vessel wall. In this research measurements were extended to 30 MHz to better understand the effect of blood on the operation of these intravascular devices. The experimentally measured backscatter of saline suspended porcine erythrocytes for frequency up to 30 MHz agrees very well with the theoretical analysis which indicate that Rayleigh scattering is still valid below this frequency. The analysis utilize the T-matrix method to calculate the backscattering cross section of an erythrocyte modeled as a fluid sphere, disk, and biconcave disk. Measurements on the backscattering coefficients of porcine, bovine, and lamb erythrocytes reveal that the backscatter has a square dependence on cell volume. The cell size dependent backscatter is also analyzed via a continuum approach. It is found that the echo intensity of high frequency ultrasound suffers greatly from the attenuation. The dilemma may be solved by using a spherically focused transducer. An analysis of the focused beam reflected from a perfect planar reflector leads to the modification of the standard substitution method for the backscatter measurement since the "image source" theory is found to be inappropriate for the focused beam. Reflection of the focused beam near the focal point is described based on Huygens' principle. Experimental and theoretical results indicate that the backscatter is dependent upon the position of the scatterer and the geometry of the transducer if a focused beam is used. Since ultrasound velocity information is needed for scattering measurements, an innovative method for measuring the acoustic speed and the attenuation coefficient without the knowledge of the thickness of a biological specimen is developed which may provide more accurate results for the measurement of backscattering coefficient.

Kuo, Ihyuan

277

Thomson-Backscattered X Rays From Laser-Accelerated Electrons  

Microsoft Academic Search

We present the first observation of Thomson-backscattered light from laser-accelerated electrons. In a compact, all-optical setup, the ``photon collider,'' a high-intensity laser pulse is focused into a pulsed He gas jet and accelerates electrons to relativistic energies. A counterpropagating laser probe pulse is scattered from these high-energy electrons, and the backscattered x-ray photons are spectrally analyzed. This experiment demonstrates a

H. Schwoerer; B. Liesfeld; H.-P. Schlenvoigt; K.-U. Amthor; R. Sauerbrey

2006-01-01

278

THE THICKNESS DISTORTION OF Fe 57 BACKSCATTER MOSSBAUER SPECTRA  

SciTech Connect

The thickness distortion of a backscatter 14.41 keV {gamma}-ray Mossbauer spectrum is calculated for the case of isotropic {gamma}-ray re-emission in the absorber, and a method of extracting the true absorber material resonant scattering cross section from experimental data is suggested and demonstrated. Some other features of backscatter and transmission Fe{sup 57} Mossbauer spectra are compared.

Fultz, B.; Morris, Jr., J.W.

1980-08-01

279

Foliage attenuation and backscatter analysis of SAR imagery  

Microsoft Academic Search

The ability of a synthetic aperture radar (SAR) to detect targets under foliage is in part determined by the attenuation suffered by radiation propagating through the foliage and the backscatter from the foliage. MIT Lincoln Laboratory made measurements of foliage attenuation and backscatter using the NASA\\/JPL-UHF, L-, C-band fully-polarimetric SAR in July 1990. In this experiment, a 48 km 2

J. G. Fleischman; S. Ayasli; E. M. Adams; D. R. Gosselin

1996-01-01

280

Comparative determination of the {alpha}/{beta} phase fraction in {alpha}+{beta}-titanium alloys using X-ray diffraction and electron microscopy  

SciTech Connect

A comparison is made between the measured {alpha}/{beta} phase fractions in Ti-6246 using X-ray diffraction (XRD) and electron microscopy. Image analysis of SEM and TEM images was compared to the phase fraction estimate obtained using electron backscattered diffraction, lab and high-energy synchrotron XRD. There was a good agreement between the electron microscopic and diffraction techniques, provided that the microstructural parameters of grain size and texture are estimated correctly when using quantitative Rietveld refinement.

Attallah, M.M., E-mail: moataz.attallah@manchester.ac.uk [School of Materials, University of Manchester, Grosvenor St., Manchester, M1 7HS (United Kingdom); Zabeen, S., E-mail: suraiya.zabeen@manchester.ac.uk [School of Materials, University of Manchester, Grosvenor St., Manchester, M1 7HS (United Kingdom); Cernik, R.J., E-mail: b.cernik@manchester.ac.uk [School of Materials, University of Manchester, Grosvenor St., Manchester, M1 7HS (United Kingdom); Preuss, M., E-mail: michael.preuss@manchester.ac.uk [School of Materials, University of Manchester, Grosvenor St., Manchester, M1 7HS (United Kingdom)

2009-11-15

281

Investigation of Coupled Surface and Bulk Reaction Phenomena Using Combined-Backscatter-Conversion Electron and Backscatter-Photon Mossbauer Spectroscopy (CEAPS).  

National Technical Information Service (NTIS)

A combined-backscatter-conversion electron and backscatter-photon Mossbauer spectrometer has been constructed and used in conjunction with new theoretical modeling efforts to examine a number of thin-film system. The spectrometer permits nondestructive de...

B. J. Tatarchuk

1988-01-01

282

Developments in crystallographic phase analysis in the SEM: Backscattered electron Kikuchi patterns  

NASA Astrophysics Data System (ADS)

The recent development of a charge coupled device (CCD)-based detector for the acquisition of backscattered electron Kikuchi patterns has enabled on-line crystallographic phase identification studies to be conducted in the scanning electron microscope. High quality patterns have been obtained from a wide variety of materials with relatively little specimen preparation compared to electron diffraction in the transmission electron microscope (TEM). Crystallographic phase identification through a combination of BEKP and energy dispersive x-ray spectrometry is demonstrated by the identification of precipitates in a high temperature Ni-based alloy containing Cr and W. The precipitates that formed in this alloy were identified as M6C or M23C6.

Michael, J. R.; Goehner, R. P.; Hills, C. R.

283

Bomb Detection Using Backscattered X-Rays  

SciTech Connect

Bomb Detection Using Backscattered X-rays* Currently the most common method to determine the contents of a package suspected of containing an explosive device is to use transmission radiography. This technique requires that an x-ray source and film be placed on opposite sides of the package. This poses a problem if the pachge is placed so that only one side is accessible, such as against a wall. There is also a threat to persomel and property since exTlosive devices may be "booby trapped." We have developed a method to x-ray a paclage using backscattered x-rays. This procedure eliminates the use of film behind the target. All of the detection is done from the same side as the source. When an object is subjected to x-rays, some of them iare scattered back towards the source. The backscattenng of x-rays is propordoml to the atomic number (Z) of the material raised to the 4.1 power. This 24"' dependence allows us to easily distinguish between explosives, wires, timer, batteries, and other bomb components. Using transmission radiography-to image the contents of an unknown package poses some undesirable risks. The object must have an x-ray film placed on the side opposite the x-ray source; this cannot be done without moving the package if it has been placed firmly against a wall or pillar. Therefore it would be extremely usefid to be able to image the contents of a package from only one side, without ever having to disturb the package itself. where E is the energy of the incoming x-ray. The volume of x-rays absorbed is important because it is, of course, directly correlated to the intensity of x-mys that will be scattered. Most of the x-rays that scatter will do so in a genemlly forward direction; however, a small percentage do scatter in a backward direction. Figure 1 shows a diagram of the various fates of x-rays directed into an object. The package that was examined in this ex~enment was an attache case made of pressed fiberboardwith a vinyl covering. It was approxirmtely 36 cm wide by 51 cm long by 13 cm deep. The case was placed on an aluminum sheet under the x-ray source. Because of the laborato~ setup, the attache case was rastered in the y-coordinate direction, while the x-ray source mstered in the x-coordinate direction. However, for field use, the x-ray source would of course raster in both the x- and y-coordinate directions, while the object under interrogation would remain stationary and undisturbed. A mobile system for use by law enforcement agencies or bomb disposal squads needs to be portable and somewhat durable. A 300 kV x-ray source should be sufficient for the task requirements and can be mounted on a mobile system. A robotic carriage could be used to transport the x-ray source and the CCD camera to the proximity of the suspect package. The controlling and data analyzing elements of the system' could then be maintained at a &tie distance from the possible explosive. F@re 8 shows a diagram of a conceptual design of a possible system for this type of use. The use of backscattered x-rays for interrogation of packages that may contain explosive devices has been shown to be feasible inthelaboratory. Usinga 150kVx-ray source anddetectors consisting of plastic scintillating material, all bomb components including the wiring were detectable. However, at this time the process requires more time than is desirable for the situations in which it will most likely be needed. Further development of the technology using CCD cameras, rather than the plastic stint illator detectors, shows promise of leading to a much faster system, as well as one with better resolution. Mounting the x- ray source and the CCD camera on a robotic vehicle while keeping the controlling and analyzing components and the opemting personnel a safe distance away from the suspect package will allow such a package to be examined at low risk to human life.

Jacobs, J.; Lockwood, G.; Selph, M; Shope, S.; Wehlburg, J.

1998-10-01

284

Robustness of Cantor diffractals.  

PubMed

Diffractals are electromagnetic waves diffracted by a fractal aperture. In an earlier paper, we reported an important property of Cantor diffractals, that of redundancy [R. Verma et. al., Opt. Express 20, 8250 (2012)]. In this paper, we report another important property, that of robustness. The question we address is: How much disorder in the Cantor grating can be accommodated by diffractals to continue to yield faithfully its fractal dimension and generator? This answer is of consequence in a number of physical problems involving fractal architecture. PMID:23571887

Verma, Rupesh; Sharma, Manoj Kumar; Banerjee, Varsha; Senthilkumaran, Paramasivam

2013-04-01

285

Microstructure and lattice bending in polycrystalline laser–crystallized silicon thin films for photovoltaic applications  

Microsoft Academic Search

Grain size, grain boundary population, orientation distribution and lattice defects of polycrystalline silicon thin films are investigated by electron backscatter diffraction (EBSD). The silicon thin films are produced by a combination of diode laser melt-mediated crystallization of an amorphous silicon seed layer and epitaxial thickening of the seed layer by solid phase epitaxy (SPE). The combined laser-SPE process delivers grains

X. Maeder; C. Niederberger; S. Christiansen; A. Bochmann; G. Andrä; A. Gawlik; F. Falk; J. Michler

2010-01-01

286

Simulation of Deformation Twinningin Extruded AZ31 Mg AlloyBarsusing the Crystal Plasticity FEM  

Microsoft Academic Search

Uniaxial compression tests on extruded AZ31 Mg alloy bars were carried out to investigate the evolution of deformation twins and deformation texture during plastic deformation. Electron back-scattered diffraction (EBSD) analysis was used to examine the orientation of parent grains and twin bands in AZ31 Mg alloy under uniaxial compression. A crystal plasticity finite element method (CPFEM) that takes both crystallographic

S. H. Choi; N. Y. Ham; A. Jung; B. S. Seong

2011-01-01

287

3-D simulation of spatial stress distribution in an AZ31 Mg alloy sheet under in-plane compression  

Microsoft Academic Search

A complete 3-D crystal plasticity finite element method (CPFEM) that considered both crystallographic slip and deformation twinning was applied to simulate the spatial distribution of the relative amount of slip and twin activities in a polycrystalline AZ31 Mg alloy during in-plane compression. A microstructure mapping technique that considered the grain size distribution and microtexture measured by electron backscatter diffraction (EBSD)

S.-H. Choi; D. W. Kim; B. S. Seong; A. D. Rollett

2011-01-01

288

Modeling uniaxial tensile deformation of polycrystalline Al using CPFEM  

Microsoft Academic Search

The crystal plasticity finite element modeling (CPFEM) is realized in commercial finite element code ABAQUS with UMAT subroutine on the basis of the crystal plasticity theory of rate dependent polycrystal constitutive relations in the mesoscopic scale. The initial orientations obtained by electron backscatter diffraction (EBSD) are directly input into the CPFEM to simulate the mechanical response of polycrystalline 1050 pure

Huachun Pi; Jingtao Han; Chuanguo Zhang; A. Kiet Tieu; Zhengyi Jiang

2008-01-01

289

Nano-grained copper strip produced by accumulative roll bonding process  

Microsoft Academic Search

Accumulative roll bonding (ARB) process is a severe plastic deformation (SPD) process that has been used for pure copper (99.9%). The ARB process up to 8 cycles was performed at ambient temperature under unlubricated conditions. Microstructural characterizations were done by transmission electron microscopy (TEM) and electron backscattered diffraction (EBSD). It was found that continuous recrystallization resulted in microstructure covered with

Mahnoosh Shaarbaf; Mohammad Reza Toroghinejad

2008-01-01

290

Nano\\/Ultrafine Structured AA1100 by ARB Process  

Microsoft Academic Search

In this study, the effect of accumulative roll bonding process at room temperature and without any annealing among cycles on the microstructure and mechanical properties of a commercially pure aluminum AA1100 was investigated. Microstructural characterizations were done by electron backscattering diffraction (EBSD) and scanning electron microscopy (SEM). It was observed that ARB is a promising process for manufacturing nano\\/ultrafine grained

Mohammad Raei; Mohammad Reza Toroghinejad; Roohollah Jamaati

2011-01-01

291

Microstructure evolution and mechanical properties of AA1100 aluminum sheet processed by accumulative roll bonding  

Microsoft Academic Search

In this study, accumulative roll bonding (ARB) process was carried out on an AA1100 aluminum sheet up to 10 cycles. Electron backscattering diffraction (EBSD) method was utilized to investigate the microstructural evolution during the ARB process. It was observed that the ARB is a promising process for fabricating ultra-fine grained structures in aluminum sheets. The results indicate that several mechanisms

H. Pirgazi; A. Akbarzadeh; R. Petrov; L. Kestens

2008-01-01

292

Modeling the Viscous to Plastic Transition in Mid-Ocean Ridge Gabbros: Implications for Crystallographic Preferred Orientation of Plagioclase and Seismic Anisotropy  

Microsoft Academic Search

Gabbroic rocks are a key component of our understanding of the physical properties (rheology, seismic velocities and anisotropy, ...) of the oceanic crust. We have established a database of over 50 samples of crystallographic preferred orientation (CPO) in gabbroic rocks from the oceanic crust using electron backscattered diffraction EBSD. The measured samples cover magmatic flow to high temperature plastic flow

B. Ildefonse; D. Mainprice

2005-01-01

293

Robust diffraction correction method for high-frequency ultrasonic tissue characterization  

NASA Astrophysics Data System (ADS)

The computation of quantitative ultrasonic parameters such as the attenuation or backscatter coefficient requires compensation for diffraction effects. In this work a simple and accurate diffraction correction method for skin characterization requiring only a single focal zone is developed. The advantage of this method is that the transducer need not be mechanically repositioned to collect data from several focal zones, thereby reducing the time of imaging and preventing motion artifacts. Data were first collected under controlled conditions from skin of volunteers using a high-frequency system (center frequency=33 MHz, BW=28 MHz) at 19 focal zones through axial translation. Using these data, mean backscatter power spectra were computed as a function of the distance between the transducer and the tissue, which then served as empirical diffraction correction curves for subsequent data. The method was demonstrated on patients patch-tested for contact dermatitis. The computed attenuation coefficient slope was significantly (p<0.05) lower at the affected site (0.13+/-0.02 dB/mm/MHz) compared to nearby normal skin (0.2+/-0.05 dB/mm/MHz). The mean backscatter level was also significantly lower at the affected site (6.7+/-2.1 in arbitrary units) compared to normal skin (11.3+/-3.2). These results show diffraction corrected ultrasonic parameters can differentiate normal from affected skin tissues.

Raju, Balasundar

2001-05-01

294

Coherent Backscattering in Los Albedo Media  

NASA Astrophysics Data System (ADS)

The opposition effect [1] observed in phase curves of materials in the lab and on planetary surfaces is attributed to two processes: 'shadow hiding opposition effect' (SHOE) and 'coherent backscattering opposition effect' (CBOE) [2,3,4]. The relative contributions of SHOE and CBOE are studied by measuring reflectance phase curves in circularly polarized light. If single scattering predominates, the circular polarization ratio (CPR) decreases with decreasing phase angle. If multiple scattering predominates, the CPR strongly increases. We observed this increase in CPR in highly reflective media [5,6,7]. In low reflectance media most of the returned signal is singly scattered and CPR is not expected to sharply increase. We have found that most such materials indeed exhibit only a slight CPR increase. However, lunar soils show a strong CPR increase [8]. Recently we encountered another interesting counter example in Boron Carbide-a material with albedo even lower than the Moon's. We find a significant CPR increase, a result inconsistent with the conventional interpretation of CBOE [8]. This suggests that albedo alone is not the principal regulator of CBOE. This CBOE may be due to multiple scattering within individual particles [10]. Unusual particle shapes may facilitate this process. Understanding this behavior contributes to the development of models that can retrieve textural properties from remote sensing data. Work performed at JPL/PITT under NASA PG&G grants. 1.Geherels, T. Astrophys. J, 123, 331-338, 1956. 2. Hapke, B. Icarus, 67, 246-280, 1986. 3. Shkuratov, Yu. SA-A.J., 27, 581-583, 1983. 4. Hapke, B. Icarus, 88, 407-417, 1990. 5. Nelson, R., et al. Icarus 131, 223-230, 1998. 6. Nelson, R., et al Icarus, 147, 545-558, 2000. 7. Nelson, R., et al. Planet. Space Sci, 2002. 8. Hapke B. et al. Science, 260, 509-511. 9. Mishchenko, M.I. Earth, Moon and Planets, 58, 127-144, 1992. 10. Hapke, B. Icarus, 157, 534-537, 2002

Nelson, R. M.; Hapke, B. W.; Hale, A. S.; Smythe, W. D.; Piatek, J.

2002-09-01

295

Optics: Laser and Diffraction  

NSDL National Science Digital Library

This site, from the University of Massachusetts at Amherst, provides a demonstration of laser light diffraction around a pinhead. Photos illustrate the demo set-up. A photo of the diffraction pattern shows Poisson's Spot, the bright spot observed in the center of the pattern.

2007-05-23

296

Single Slit Diffraction  

NSDL National Science Digital Library

This web page includes a java illustration of single slit diffraction of light. The user can adjust the wavelength of the light and the size of the slit and observe the resultant changes in the diffraction pattern. Quantitative values for the wavelength and slit-width are given.

Kiselev, Sergey

2007-11-03

297

Phononic crystal diffraction gratings  

NASA Astrophysics Data System (ADS)

When a phononic crystal is interrogated by an external source of acoustic waves, there is necessarily a phenomenon of diffraction occurring on the external enclosing surfaces. Indeed, these external surfaces are periodic and the resulting acoustic diffraction grating has a periodicity that depends on the orientation of the phononic crystal. This work presents a combined experimental and theoretical study on the diffraction of bulk ultrasonic waves on the external surfaces of a 2D phononic crystal that consists of a triangular lattice of steel rods in a water matrix. The results of transmission experiments are compared with theoretical band structures obtained with the finite-element method. Angular spectrograms (showing frequency as a function of angle) determined from diffraction experiments are then compared with finite-element simulations of diffraction occurring on the surfaces of the crystal. The experimental results show that the diffraction that occurs on its external surfaces is highly frequency-dependent and has a definite relation with the Bloch modes of the phononic crystal. In particular, a strong influence of the presence of bandgaps and deaf bands on the diffraction efficiency is found. This observation opens perspectives for the design of efficient phononic crystal diffraction gratings.

Moiseyenko, Rayisa P.; Herbison, Sarah; Declercq, Nico F.; Laude, Vincent

2012-02-01

298

Diffraction Results from CDF  

SciTech Connect

We present final results by the CDF II collaboration on diffractive W and Z production, report on the status of ongoing analyses on diffractive dijet production and on rapidity gaps between jets, and briefly summarize results obtained on exclusive production pointing to their relevance to calibrating theoretical models used to predict exclusive Higgs-boson production at the LHC.

Goulianos, Konstantin

2012-04-01

299

Diffraction of Wind Waves.  

National Technical Information Service (NTIS)

The purpose of this study is to seek a solution of the problem of the diffraction of wind waves by a breakwater. This study was divided into several parts. First, the conventional diffraction theories were examined in detail. Secondly, the characteristics...

Shou-Shan Fan

1968-01-01

300

Optical backscattering measurements off the coast of Hawaii  

NASA Astrophysics Data System (ADS)

In a recent sea test, measurements of the volume scattering function (VSF) of clear sea water in situ at several angles were made. These measurements used the APL backscattering sensor, which measures the VSF at 170 degree(s); the SRI Beta Pi sensor, which measures the VSF from 179 degree(s) to 180 degree(s); and the SRI backscattering sensor, which measures the VSF at a mean scattering angle of 150 degree(s). The intention of the testing was to quantify the enhanced backscattering feature at 180 degree(s) relative to the scattering at more traditionally measured angles of the VSF. Measurements were made in both clear ocean water and Hawaiian coastal waters. Analysis of the data has been combined with subsequent laboratory instrument intercomparisons to demonstrate that in clear ocean water there is relatively little enhanced backscattering, whereas in more turbid coastal water the feature is pronounced and is clearly higher than the VSF at 170 degree(s). Field data, including vertical profiles of optical backscatter in clear and coastal waters, are shown.

Voss, Jeffrey M.; Smart, Jeffrey H.

1994-10-01

301

Quantitative Ultrasound Backscatter for Pulsed Cavitational Ultrasound Therapy--Histotripsy  

PubMed Central

Histotripsy is a well-controlled ultrasonic tissue ablation technology that mechanically and progressively fractionates tissue structures using cavitation. The fractionated tissue volume can be monitored with ultrasound imaging because a significant ultrasound backscatter reduction occurs. This paper correlates the ultrasound backscatter reduction with the degree of tissue fractionation characterized by the percentage of remaining normal-appearing cell nuclei on histology. Different degrees of tissue fractionation were generated in vitro in freshly excised porcine kidneys by varying the number of therapeutic ultrasound pulses from 100 to 2000 pulses per treatment location. All ultrasound pulses were 15 cycles at 1 MHz delivered at 100 Hz pulse repetition frequency and 19 MPa peak negative pressure. The results showed that the normalized backscatter intensity decreased exponentially with increasing number of pulses. Correspondingly, the percentage of normal appearing nuclei in the treated area decreased exponentially as well. A linear correlation existed between the normalized backscatter intensity and the percentage of normal appearing cell nuclei in the treated region. This suggests that the normalized backscatter intensity may be a potential quantitative real-time feedback parameter for histotripsy-induced tissue fractionation. This quantitative feedback may allow the prediction of local clinical outcomes, i.e., when a tissue volume has been sufficiently treated.

Wang, Tzu-Yin; Xu, Zhen; Winterroth, Frank; Hall, Timothy L.; Fowlkes, J. Brian; Rothman, Edward D.; Roberts, William W.; Cain, Charles A.

2011-01-01

302

Statistical properties of gas ring lasers with backscattering  

SciTech Connect

The two-mode inhomogeneously broadened ring laser with spontaneous-emission noise is investigated in the presence of backscattering. Using a linear transformation it is shown that this problem in the absence of detuning is equivalent to that of the ring laser without backscattering in the two following cases: (i) in-phase backcoupling case (/ital R//sub 1/=R/sub 2//sup */), (ii) equal pump parameters and ''symmetric'' backscattering (/vert bar//ital R//sub 1//vert bar/=/vert bar/R/sub 2//vert bar/), where /ital R//sub 1/ and /ital R//sub 2/ are complex backscattering coefficients. We recover in this way the stationary probability density obtained by Christian and Mandel (Phys. Rev. A 34, 3932 (1986)). Exact expressions for the mean values, fluctuations, and correlations of the two-mode intensities are derived. Our results show that the relative intensity fluctuations of both modes die out well above threshold. Mode-competition effects are reduced by symmetric backscattering. Exact formulas for the effective eigenvalue characterizing the initial decay of intensity correlation functions are given. These results are compared with the experimental data measured by Singh (Phys. Rep. 108, 217 (1984)).

Pesquera, L.; Blanco, R.; Rodrriaaguez, M. A.

1989-06-01

303

A backscatter difference technique for ultrasonic bone assessment.  

PubMed

Ultrasonic backscatter techniques may offer a useful approach for detecting changes in cancellous bone caused by osteoporosis and other diseases. The goal of this study was to investigate the utility of a backscatter difference technique for ultrasonic bone assessment. Measurements were performed on 22 cube-shaped specimens of human cancellous bone using four broadband transducers with center frequencies 2.25, 5, 7.5, and 10 MHz. The backscatter difference spectrum D(f) was obtained by subtracting power spectra (in dB) from two different portions of the same backscatter signal. D(f) was found to be a monotonically increasing, quasi-linear function of frequency when averaged over multiple measurement sites on multiple specimens. The frequency slope of D(f) demonstrated weak to moderate correlations with specimen density (R = 0.21-0.80). The frequency averaged mean of D(f) demonstrated moderate to good correlations with density (R = 0.70-0.95). These results suggest that parameters based on the frequency averaged mean of the backscatter difference spectrum may be useful for bone assessment purposes. PMID:23231136

Hoffmeister, Brent K; Wilson, Anne R; Gilbert, Matthew J; Sellers, Mark E

2012-12-01

304

Single-Slit Diffraction  

NSDL National Science Digital Library

The Single-Slit Diffraction model simulates the diffraction pattern of light as it travels through a slit to a screen. The diffraction pattern is due to the difference in path length of the light from different parts of the slit as the light from the slit travels to the screen. The intensity of the light that reaches the screen is related to the wavelength of light, the slit width, and the angle away from the center of the screen. In the simulation one can change the wavelength, the slit separation, and whether the pattern is shown on a screen or on a photographic plate. Single-Slit Diffraction model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_diffraction.jar file will run the program if Java is installed.

Palop, Jose I.

2010-12-12

305

Radial reflection diffraction tomography  

DOEpatents

A wave-based tomographic imaging method and apparatus based upon one or more rotating radially outward oriented transmitting and receiving elements have been developed for non-destructive evaluation. At successive angular locations at a fixed radius, a predetermined transmitting element can launch a primary field and one or more predetermined receiving elements can collect the backscattered field in a "pitch/catch" operation. A Hilbert space inverse wave (HSIW) algorithm can construct images of the received scattered energy waves using operating modes chosen for a particular application. Applications include, improved intravascular imaging, bore hole tomography, and non-destructive evaluation (NDE) of parts having existing access holes.

Lehman, Sean K.

2012-12-18

306

Decoherence in electron backscattering by kinked dislocations.  

PubMed

A model is proposed that explains the origin of the bright contrast of dislocation walls consisting of edge dislocation dipoles in electron channelling contrast images (ECCI) of fatigued crystals, when the incident beam is parallel to the edge dislocations. The model is based on the assumption that the contrast arises from the dislocation segments terminating the dipoles. These are modelled as screw-type kinks which scatter electrons. Scattering by randomly distributed kinks leads to the randomization of phase of transmitted and diffracted beams and suppresses the anomalous transmission of electrons. The predicted behaviour of electron-channeling contrast images agrees well with experimental observations.With apologies for using two beams instead of three! PMID:10927255

Dudarev; Ahmed; Hirsch; Wilkinson

1999-03-01

307

Multiple-wave diffraction in high energy resolution back-reflecting x-ray optics.  

PubMed

We have studied the effects of multiple-wave diffraction in a novel optical scheme recently published by Shvyd'ko et al. utilizing Bragg diffraction of x rays in backscattering geometry from asymmetrically cut crystals for achieving energy resolutions beyond the intrinsic width of the Bragg reflection. By numerical simulations based on dynamic x-ray diffraction and by experimentation involving two-dimensional angular scans of the back-reflecting crystal, multiple-wave diffraction was found to contribute up to several tens percent loss of efficiency but can be avoided without degrading the energy resolution of the original scheme by careful choice of azimuthal orientation of the diffracting crystal surface and by tilting of the crystal perpendicular to the dispersion plane. PMID:22107300

Stetsko, Yuri P; Keister, J W; Coburn, D S; Kodituwakku, C N; Cunsolo, A; Cai, Y Q

2011-10-07

308

Multiple-Wave Diffraction in High Energy Resolution Back-Reflecting X-Ray Optics  

SciTech Connect

We have studied the effects of multiple-wave diffraction in a novel optical scheme recently published by Shvyd'ko et al. utilizing Bragg diffraction of x rays in backscattering geometry from asymmetrically cut crystals for achieving energy resolutions beyond the intrinsic width of the Bragg reflection. By numerical simulations based on dynamic x-ray diffraction and by experimentation involving two-dimensional angular scans of the back-reflecting crystal, multiple-wave diffraction was found to contribute up to several tens percent loss of efficiency but can be avoided without degrading the energy resolution of the original scheme by careful choice of azimuthal orientation of the diffracting crystal surface and by tilting of the crystal perpendicular to the dispersion plane.

Stetsko, Yuri P.; Keister, J. W.; Coburn, D. S.; Kodituwakku, C. N.; Cunsolo, A.; Cai, Y. Q. [National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, New York 11973 (United States)

2011-10-07

309

Feasibility of bone assessment with ultrasonic backscatter signals in neonates.  

PubMed

The objective of this study was to assess the value of ultrasonic backscatter signals and the backscatter coefficient (BSC) in the analysis of bone status in neonates and to analyze the relationships between the BSC and gestational age, birth weight, length, head circumference and gender. A total of 122 neonates participated in the study, including 83 premature infants and 39 full-term infants. Their BSCs were measured by ultrasound after birth. The results revealed a significant correlation between the BSC and gestational age (R = 0.47, p < 0.001), birth weight (R = 0.47, p < 0.0001) and length at birth (R = 0.43, p < 0.001) at a frequency of 5.0 MHz. This study suggests that the use of ultrasonic backscattering and the BSC is feasible for assessment of the bone status of neonates. PMID:23932274

Zhang, Rong; Ta, Dean; Liu, Chengcheng; Chen, Chao

2013-08-09

310

Effect of Backscattered Electrons on Electron Beam Focus  

SciTech Connect

Using an induction linac, ETA-II, we are studying the interaction of a 2 kA, 6 MeV electron beam focused to a <2 mm diameter spot on high-Z foils. A focus shift was noticed when changing from 5 mil to 40 mil tantalum foil targets. This shift was subsequently attributed to the effect of a substantial fraction of the incident electron beam backscattering from the target, reducing the net beam current. This fraction varies with the thickness and density of the target. The presence and magnitude of the backscattered component was confirmed using Faraday cup collectors and beam current monitors. Calculations confirm the magnitude of the focus shift is consistent with the observed backscattered fraction.

Falabella, S; Chen, Y-J; Houck, T; McCarrick, J; Sampayan, S; Weir, J

2000-08-10

311

Backscattering properties of small layered plates: a model for iridosomes.  

PubMed

The backscattering properties of small layered plates are studied for various size parameter values with respect to the plate thickness, plate aspect ratio, number of layers, incident direction, and polarization states of the incident light. The results are compared with the analytical results for semi-infinite plates. The phase functions and the corresponding backscattering efficiencies of the small plates are computed with the Discrete Dipole Approximation method. The angular width of the reflection peak is found to depend on both the size parameter and the aspect ratio. The criteria for using the reflectance of semi-infinite plates to approximate the backscattering efficiencies of finite size plates are quantified with respect to the number of layers, incident angle, and polarization state. PMID:23187277

Gao, Meng; You, Yu; Yang, Ping; Kattawar, George W

2012-10-22

312

Investigation of lidar backscatter including depolarization and higher scattering orders  

NASA Astrophysics Data System (ADS)

A lidar signal model of the depolarization of the backscatter signal, which takes into account direct backscatter as well as other scattering phenomena of aerosol particles, was developed. Special attention was paid to pulse times. An inversion method for the determination of the particle densities from the model parameters is presented. In order to verify the model, tests were performed with a monostatic single-wavelength lidar system. The analysis of the signals shows different effective extinction coefficients, the interpretation of which requires higher scattering orders. It is shown that the approximation of aspherical particles by homogeneous spherical particles is not possible for the description of the lidar backscatter signal. The measurements are found to be in excellent agreement with the theoretical signal parameters for scattering on homogeneous spherical droplets in clouds.

Ricklefs, Ubbo

1985-12-01

313

Calculating incoherent diffraction MTF  

NASA Astrophysics Data System (ADS)

The incoherent diffraction MTF plays an increasingly important role in the range performance of imaging systems as the wavelength increases and the optical aperture decreases. Accordingly, all NVESD imager models have equations that describe the incoherent diffraction MTF of a circular entrance pupil. NVThermIP, a program which models thermal imager range performance, has built in equations which analytically model the incoherent diffraction MTF of a circular entrance pupil and has a capability to input a table that describes the MTF of other apertures. These can be calculated using CODE V, which can numerically calculate the incoherent diffraction MTF in the vertical or horizontal direction for an arbitrary aperture. However, we are not aware of any program that takes as input a description of the entrance pupil and analytically outputs equations that describe the incoherent diffraction MTF. This work explores the effectiveness of Mathematica to analytically and numerically calculate the incoherent diffraction MTF for an arbitrary aperture. In this work, Mathematica is used to analytically and numerically calculate the incoherent diffraction MTF for a variety of apertures and the results are compared with CODE V calculations.

Friedman, Melvin; Vizgaitis, Jay

2008-05-01

314

Bruce Thompson: Adventures and advances in ultrasonic backscatter  

NASA Astrophysics Data System (ADS)

Over the course of his professional career Dr. R. Bruce Thompson published several hundred articles on non-destructive evaluation, the majority dealing with topics in ultrasonics. One longtime research interest of Dr. Thompson, with applications both to microstructure characterization and defect detection, was backscattered grain noise in metals. Over a 20 year period he led a revolving team of staff members and graduate students investigating various aspects of ultrasonic backscatter. As a member of that team I had the privilege of working along side Dr. Thompson for many years, serving as a sort of Dr. Watson to Bruce's Sherlock Holmes. This article discusses Dr. Thompson's general approaches to modeling backscatter, the research topics he chose to explore to systematically elucidate a better understanding of the phenomena, and the many contributions to the field achieved under his leadership. The backscatter work began in earnest around 1990, motivated by a need to improve inspections of aircraft engine components. At that time Dr. Thompson launched two research efforts. The first led to the heuristic Independent Scatterer Model which could be used to estimate the average grain noise level that would be seen in any given ultrasonic inspection. There the contribution from the microstructure was contained in a measureable parameter known as the Figure-of-Merit or FOM. The second research effort, spearheaded by Dr. Jim Rose, led to a formal relationship between FOM and details of the metal microstructure. The combination of the Independent Scattering Model and Rose's formalism provided a powerful tool for investigating backscatter in metals. In this article model developments are briefly reviewed and several illustrative applications are discussed. These include: the determination of grain size and shape from ultrasonic backscatter; grain noise variability in engine-titanium billets and forgings; and the design of ultrasonic inspection systems to improve defect-signal-to-grain-noise ratios.

Margetan, Frank J.

2012-05-01

315

Hard diffraction in CDF  

SciTech Connect

The aim of these studies is to use hard (large Q{sup 2}) processes to investigate the partonic nature of the pomeron. We have measured events with large rapidity gaps between balancing high E{sub T} jets, events with two forward (same-side) jets and a large gap (diffractive di-jet production), diffractive W{sup {+-}} production and diffractive heavy flavor (J/{psi} and b-quark) production. Candidate events of the type double-pomeron {yields} di-jet are observed. I close with a look at the future (Run II).

Albrow, M.G.; CDF Collaboration

1997-10-01

316

Diffraction at HERA  

SciTech Connect

Diffractive phenomena are an essential component of the understanding of the proton structure and lead to stringent tests of the QCD. New results are presented in the area of inclusive diffraction, with a vast coverage of the phase space and where both H1 and ZEUS data compare and may lead to combinations and data constraints. The issue of universality of the diffractive exchange is tested using final states, for instance with jets, where new results completed the previous hints of discrepancies. The production of photons and vector mesons, all recently measured either for the first time or with improved precision, present a rich panel of tests of the QCD predictions.

Rubinskiy, I. [Notkestrasse 85, DESY, 20255 Hamburg (Germany)

2009-12-17

317

Regoliths of icy satellites: The coherent backscatter model  

NASA Astrophysics Data System (ADS)

The coherent backscatter model of radar scattering from icy satellites argues that most of the received power comes from radio waves that have been multiply scattered from numerous refractive index discontinuities randomly located under the surfaces of the regoliths. In a laboratory analog experiment the circular and linear polarizations were measured in light scattered from a suspension of polystyrene spheres in water illuminated by laser. Results confirm that coherent backscatter from particle media reproduces the large intensity and unusual polarizations observed in the radar data. The model implies that the regoliths of icy satellites consist of matrices of small reflective index containing imbedded scatterers separated by distances of the order of a wavelength.

Hapke, B.; Blewett, D.

1991-06-01

318

Thomson-Backscattered X Rays From Laser-Accelerated Electrons  

SciTech Connect

We present the first observation of Thomson-backscattered light from laser-accelerated electrons. In a compact, all-optical setup, the ''photon collider,'' a high-intensity laser pulse is focused into a pulsed He gas jet and accelerates electrons to relativistic energies. A counterpropagating laser probe pulse is scattered from these high-energy electrons, and the backscattered x-ray photons are spectrally analyzed. This experiment demonstrates a novel source of directed ultrashort x-ray pulses and additionally allows for time-resolved spectroscopy of the laser acceleration of electrons.

Schwoerer, H.; Liesfeld, B.; Schlenvoigt, H.-P.; Amthor, K.-U.; Sauerbrey, R. [Institut fuer Optik und Quantenelektronik, Friedrich-Schiller-Universitaet, Max-Wien-Platz 1, 07743 Jena (Germany)

2006-01-13

319

Thomson-backscattered x rays from laser-accelerated electrons.  

PubMed

We present the first observation of Thomson-backscattered light from laser-accelerated electrons. In a compact, all-optical setup, the "photon collider," a high-intensity laser pulse is focused into a pulsed He gas jet and accelerates electrons to relativistic energies. A counterpropagating laser probe pulse is scattered from these high-energy electrons, and the backscattered x-ray photons are spectrally analyzed. This experiment demonstrates a novel source of directed ultrashort x-ray pulses and additionally allows for time-resolved spectroscopy of the laser acceleration of electrons. PMID:16486464

Schwoerer, H; Liesfeld, B; Schlenvoigt, H-P; Amthor, K-U; Sauerbrey, R

2006-01-10

320

Beta backscatter gauging of PVD copper on 35-mm tape  

SciTech Connect

Mound has developed a Nondestructive Testing (NDT) system to perform automated thickness gauging of very thin (50-200 ..mu..in.) copper, vapor-deposited on 35-mm plastic tape using either beta backscatter or eddy current techniques. This report primarily discusses the backscatter development effort, which is currently capable of achieving a precision sigma of 1.2 ..mu..in. in a minimum time of approximately 30 sec. Also discussed are planned future efforts to significantly reduce measurement time. In addition, a comparison with results obtained with the eddy current technique is provided.

Dudley, W.A.; Harvey, E.D.

1983-09-30

321

Flux conservation in coherent backscattering and weak localization of light  

NASA Astrophysics Data System (ADS)

The standard theoretical description of coherent backscattering, according to which maximally crossed diagrams accounting for interference between counterpropagating path amplitudes are added on top of the incoherent background, violates the fundamental condition of flux conservation. In contrast to the predictions of previous theories, we show that including maximally crossed diagrams with one additional scattering event does not restore flux conservation. Instead, we propose that the latter is recovered when treating the effects of coherent backscattering and weak localization in a unified framework. On the basis of this framework, we demonstrate explicitly flux conservation in leading order of the weak disorder parameter 1/(k?).

Knothe, Angelika; Wellens, Thomas

2013-08-01

322

X-ray backscatter imaging for aerospace applications  

SciTech Connect

Scatter x-ray imaging (SXI) is a real time, digital, x-ray backscatter imaging technique that allows radiographs to be taken from one side of an object. This x-ray backscatter imaging technique offers many advantages over conventional transmission radiography that include single-sided access and extremely low radiation fields compared to conventional open source industrial radiography. Examples of some applications include the detection of corrosion, foreign object debris, water intrusion, cracking, impact damage and leak detection in a variety of material such as aluminum, composites, honeycomb structures, and titanium.

Shedlock, Daniel [Nucsafe, Inc., 601 Oak Ridge Turnpike, Oak Ridge, TN 37830 (United States); Edwards, Talion [Boeing Research and Technology, 5775 Campus Parkway, Hazelwood, MO 63042 (United States); Toh, Chin [Boeing Research and Technology, 2201 Seal Beach Blvd, Seal Beach, CA 90740 (United States)

2011-06-23

323

Lidar aerosol backscatter measurements - Systematic, modeling, and calibration error considerations  

NASA Astrophysics Data System (ADS)

Sources of systematic, modeling, and calibration errors that affect the interpretation and calibration of lidar aerosol backscatter data are discussed. The treatment pertains primarily to ground-based pulsed CO2 lidars that probe the troposphere and are calibrated using hard calibration targets. However, a large part of the analysis is relevant to other types of lidar system such as lidars operating at other wavelengths; CW focused lidars; airborne or earth-orbiting lidars; lidars measuring other regions of the atmosphere; lidars measuring nonaerosol elastic or inelastic backscatter; and lidars employing other calibration techniques.

Kavaya, M. J.; Menzies, R. T.

1985-11-01

324

X-Ray Diffraction  

NSDL National Science Digital Library

This site from the University of London presents a tutorial on several methods of X-ray diffraction, including the powder, rotating crystal, and Laue methods Each section includes interactive Java applets, exercises, and links to a glossary of terms.

Matter.org

325

Hard diffraction at CDF  

SciTech Connect

We present new evidence for events with a rapidity gap between jets in {bar p}-p collisions at {radical}s = 1.8 TeV based on data collected by triggering the Collider Detector at Fermilab on two high transverse momentum forward jets and results of a search for diffractive W{+-} and dijet production where diffraction is tagged by the rapidity gap technique. We also present the results of a search for diffractive dijets using data collected by triggering on a very forward particle in the recently installed roman-pot detectors. The dijet events exhibit additional diffractive characteristics such as rapidity gaps and boosted center of mass system, however the recoil antiproton measured in the roman-pots is in a regime in which the non- pomeron contribution is significant.

Melese, P.L. [Rockefeller Univ., New York, NY (United States); CDF Collaboration

1996-07-01

326

Core level electron diffraction.  

National Technical Information Service (NTIS)

In this article the basic elements of the theory of core level electron diffraction are given in a comprehensive form. All relevant formulas are obtained rigorously. Some approximations are then considered such as those involving single scatterings and pl...

L. Fonda

1993-01-01

327

Diffractive measurements in ATLAS  

NASA Astrophysics Data System (ADS)

Measurements made using the ATLAS detector at the LHC at s = 7 TeV incorporating diffractive processes are presented. A first measurement of the inelastic cross-section using 20 ?b-1 of data is given, yielding a result of ?inel(?>5×10-6) = 60.3+/-2.1 mb, for single (pp --> Xp) and double (pp --> Xp) diffractive processes for a kinematic range corresponding to detector acceptance ? = M2X/s calculated from the invariant mass MX of the heavier dissociation system X. Furthermore a study is made of pseudorapidity gap distributions using 7.1 +/- 0.2 ?b-1 of data collected to tune the diffractive fraction of the inelastic cross-section in Monte Carlo (MC) models, and a measurement is made of the differential cross-section for events with large gaps in pseudorapidity where diffractive processes dominate.

Shaw, K.; ATLAS Collaboration

2012-04-01

328

Diffraction and holography of photoelectrons and fluorescent x-rays  

SciTech Connect

Photoelectron diffraction is by now a powerful technique for studying surface structures, with special capabilities for resolving chemical and magnetic states of atoms and deriving direct structural information from both forward scattering and backscattering. Fitting experiment to theory can lead to structural accuracies in the 0.03 {Angstrom} range. Holographic inversions of such diffraction data also show considerable promise for deriving local three-dimensional structures around a given emitter with accuracies of 0.2--0.3 {Angstrom}. Resolving the photoelectron spin in some way and using circularly polarized radiation for excitation provide added dimensions for the study of magnetic systems and chiral experimental geometries. Synchrotron radiation with the highest brightness and energy resolution, as well as variable polarization, is crucial to the full exploitation of these techniques. X-ray fluorescence holography also has promise for structural studies, but will require intense excitation sources and multichannel detection to be feasible.

Fadley, C.S. [Lawrence Berkeley Lab., CA (United States)]|[California Univ., Davis, CA (United States). Dept. of Physics

1993-04-01

329

Hard Diffraction in QCD  

SciTech Connect

Gluon exchange between the outgoing quarks and the target spectators affects the structure functions measured in deep inelastic scattering in a profound way, leading to diffractive lepto-production processes, the shadowing and antishadowing of nuclear structure functions, and target spin asymmetries--leading-twist physics not incorporated in the light-front wavefunctions of the target computed in isolation. I also discuss the diffraction dissociation of hadrons into jets as a tool for resolving fundamental hadron substructure.

Brodsky, Stanley J.; /SLAC

2005-06-30

330

Double Slit Diffraction  

NSDL National Science Digital Library

This resource illustrates the interference patterns for diffraction through double slits. A series of sources, electrons, protons, neutrons, photons, and pions, can be chosen for the virtual experiment. The energy of the source, the slit separation, and the flux rate can all be adjusted. The diffraction patterns are built from random flashes on a screen. The screens can be saved for comparison of different experiments.

Group, Kansas S.; Zollman, Dean A.

2004-03-07

331

Anomalous diffraction approximation limits  

NASA Astrophysics Data System (ADS)

It has been reported in a recent article [Liu, C., Jonas, P.R., Saunders, C.P.R., 1996. Accuracy of the anomalous diffraction approximation to light scattering by column-like ice crystals. Atmos. Res., 41, pp. 63-69] that the anomalous diffraction approximation (ADA) accuracy does not depend on particle refractive index, but instead is dependent on the particle size parameter. Since this is at odds with previous research, we thought these results warranted further discussion.

Videen, Gorden; Chýlek, Petr

332

Multiple Slit Diffraction Model  

NSDL National Science Digital Library

The EJS Multiple Slit Diffraction model allows the user to simulate Fraunhofer diffraction through single or multiple slits. The user can modify the number of slits, the slit width, the slit separation and the wavelength of the incident light. The scale of the diffraction pattern can also be changed and a plot of the light intensity can be toggled on and off with a checkbox. A basic theoretical introduction to diffraction is included. The Multiple Slit Diffraction Model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_ntnu_optics_MultipleSlitDiffraction.jar file will run the program if Java is installed. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional Open Source Physics programs for quantum mechanics are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or EJS.

Hwang, Fu-Kwun

2008-11-22

333

Effect of Faraday rotation on stimulated Brillouin backscattering  

Microsoft Academic Search

Based on a laser-heated solenoid, the influence of Faraday rotation on stimulated Brillouin backscattering is examined. It is assumed that the long homogeneous plasma is located in a strong axial magnetic field and that the incident laser beam is linearly polarized. Values are given for the distance in which ion acoustic waves reduce their amplitude to zero due to two-wave

Z. A. Pietrzyk; R. S. Massey

1978-01-01

334

Comparison between EISCAT UHF and VHF backscattering cross section  

Microsoft Academic Search

We present a comparison between the backscattering cross sections at 224 and 933 MHz measured with European Incoherent Scatter (EISCAT) radars during the passage of a discrete arc. It shows a difference of 2 orders of magnitude which cannot simply be explained by normal thermal ionospheric density fluctuations. We claim that the observed difference in the scattering cross sections is

B. Cabrit; H. Opgenoorth; W. Kofman

1996-01-01

335

Rutherford backscattering oscillation in scanning helium-ion microscopy  

SciTech Connect

Scanning helium-ion microscopy (SHIM) yields high-resolution imaging and is capable of surface elemental analysis at the nanometer scale. Here we examine recently discovered SHIM backscattered intensity oscillations versus the target atomic number. These oscillations are contrary to the expected monotonic increase of the backscattered helium-ion (He{sup +}) rate with the atomic number of elemental samples. We explore the ion-sample interaction via numerical simulations for a variety of scattering geometries and confirm the presence of oscillations. The oscillations are attributed to the atomic rather than the nuclear structure of the target. To that end, we study the link (near anticorrelation) between backscatter rate and He{sup +} beam stopping power, both versus the target atomic number. This leads us to ascribe the origin of the backscatter oscillation to the ''Z{sub 2}-oscillations'' of the stopping power in ion-beam physics, with the latter being rooted in the valence electron configuration of elemental targets.

Kostinski, Sarah; Yao, Nan [Princeton Institute for the Science and Technology of Materials, Princeton University, Princeton, New Jersey 08544 (United States)

2011-03-15

336

Electromagnetic Backscattering from a Layer of Vegetation: A Discrete Approach  

Microsoft Academic Search

Electromagnetic backscattering from a layer of vegetation over a flat lossy ground is studied. The vegetated region is composed of leaves which are modeled by lossy circular dielectric discs with prescribed orientation statistics. The mean field in the layer is computed by using the Foldy approximation and a two-variable technique which is valid for small fractional volume. Simple expressions are

Roger H. Lang; Jagjeet S. Sighu

1983-01-01

337

Theory and measurement of backscattering from RFID tags  

Microsoft Academic Search

This paper presents a method for measuring signal backscattering from RFID tags, and for calculating a tag's radar cross section (RCS). We derive a theoretical formula for the RCS of an RFID tag with a minimum-scattering antenna. We describe an experimental measurement technique, which involves using a network analyzer connected to an anechoic chamber with and without the tag. The

Pavel V. Nikitin; K. V. S. Rao

2006-01-01

338

An overview of backscattered radio frequency identification system (RFID)  

Microsoft Academic Search

A radio frequency identification (RFID) system is a wireless communication system in which the radio link between the base station and the transponders are furnished by the modulated backscattered waves. The present paper is intended to provide a brief description of various subsystems of the RFID. The various applications of RFID are discussed. Sample results on read\\/write range for a

K. V. S. Rao

1999-01-01

339

Electromagnetic backscattering from a sparse distribution of lossy dielectric scatterers  

Microsoft Academic Search

Electromagnetic backscattering from a sparse distribution of lossy dielectric particles having random orientation and position is studied. The paper begins by using the Foldy approximation to find an equation for the mean field. From this equation, an effective permittivity for the scattering medium is obtained. The correlation of the scattered field is found by employing the distorted Born approximation, i.e.,

Roger H. Lang

1981-01-01

340

Passive geosynchronous SAR system reusing backscattered digital audio broadcasting signals  

Microsoft Academic Search

A synthetic aperture radar (SAR) is considered, located on a geosynchronous receiver, and illuminated by the backscattered energy of satellite broadcast digital audio or television signals. The principal application of such a passive system could be differential interferometry, since even low spatial resolution coupled to zero baseline would be useful; however, other imaging applications could be envisaged and even some

C. Prati; F. Rocca; D. Giancola; A. Monti Guarnieri

1998-01-01

341

Radar backscatter and biomass saturation: ramifications for global biomass inventory  

Microsoft Academic Search

Two SAR and biomass data sets of forests with different canopy architectures were examined for commonalties regarding backscatter\\/biomass saturation. The SAR data were collected using the NASA\\/JPL AIRSAR at incidence angles between 40° and 50° for tropical broadleaf evergreen forests in Hawaii and coniferous forests in North America and Europe. Radar signal saturation limits with respect to biomass for both

Marc L. Imhoff

1995-01-01

342

A general statistical model for ultrasonic backscattering from tissues  

Microsoft Academic Search

The backscattered ultrasonic echo from tissue can be described in terms of Rayleigh distribution or K distribution. Even though both generalized K distribution and homodyned K distribution can account for some of the scattering conditions that exist in tissues, the analytical complexity involved with these distributions is significant. A much simpler generalized model based on the Nakagami distribution is proposed

P. Mohana Shankar

2000-01-01

343

Ultrasonic characterization of cancellous bone using apparent integrated backscatter  

NASA Astrophysics Data System (ADS)

Apparent integrated backscatter (AIB) is a measure of the frequency-averaged (integrated) backscattered power contained in some portion of a backscattered ultrasonic signal. AIB has been used extensively to study soft tissues, but its usefulness as a tissue characterization technique for cancellous bone has not been demonstrated. To address this, we performed measurements on 17 specimens of cancellous bone over two different frequency ranges using a 1 MHz and 5 MHz broadband ultrasonic transducer. Specimens were obtained from bovine tibiae and prepared in the shape of cubes (15 mm side length) with faces oriented along transverse (anterior, posterior, medial and lateral) and longitudinal (superior and inferior) principal anatomic directions. A mechanical scanning system was used to acquire multiple backscatter signals from each direction for each cube. AIB demonstrated highly significant linear correlations with bone mineral density (BMD) for both the transverse (R2 = 0.817) and longitudinal (R2 = 0.488) directions using the 5 MHz transducer. In contrast, the correlations with density were much weaker for the 1 MHz transducer (R2 = 0.007 transverse, R2 = 0.228 longitudinal). In all cases where a significant correlation was observed, AIB was found to decrease with increasing BMD.

Hoffmeister, B. K.; Jones, C. I., III; Caldwell, G. J.; Kaste, S. C.

2006-06-01

344

Myocardial Ultrasonic Backscatter in Hypertension Relation to Aldosterone and Endothelin  

Microsoft Academic Search

A disproportionate accumulation of fibrillar collagen is a characteristic feature of hypertensive heart disease, but the extent of myocardial fibrosis may differ in different models of hypertension. In experimental studies, aldosterone and endothelins emerge as important determinants of myocardial fibrosis. Changes in myocardial extracellular matrix and collagen deposition can be estimated noninvasively by analysis of the ultrasonic backscatter signal, which

Michaela Kozŕkovŕ; Simona Buralli; Carlo Palombo; Giampaolo Bernini; Angelica Moretti; Stefania Favilla; Stefano Taddei; Antonio Salvetti

2010-01-01

345

A Compton backscattering polarimeter for measuring longitudinal electron polarization  

Microsoft Academic Search

Compton backscattering polarimetry provides a fast and accurate method to measure the polarization of an electron beam in a storage ring. Since the method is non-destructive, the polarization of the electron beam can be monitored during internal target experiments. For this reason, a Compton polarimeter has been constructed at NIKHEF to measure the polarization of the longitudinally polarized electrons which

I. Passchier; D. W. Higinbotham; C. W. de Jager; B. E. Norum; N. H. Papadakis; N. P. Vodinas

1998-01-01

346

A compton backscattering polarimeter for measuring longitudinal electron polarization  

Microsoft Academic Search

Compton backscattering polarimetry provides a fast measurement of the polarization of an electron beam in a storage ring. Since the method is non-destructive, the polarization of the electrons can be monitored during internal target experiments. At NIKHEF a Compton polarimeter has been constructed to measure the polarization of the longitudinally polarized electrons stored in the AmPS ring. First results obtained

I. Passchier; Douglas W. Higinbotham; N. Vodinas; N. Papadakis; Kees de Jager; Ricardo Alarcon; T. Bauer; D. Boersma; T. Botto; M. Bouwhuis; H. J. Bulten; L. van Buuren; Rolf Ent; D. Geurts; M. Ferro-Luzzi; M. Harvey; Peter Heimberg; Blaine Norum; H. R. Poolman; M. van der Putte; J. J. M. Steijger; D. Szczerba; H. de Vries

1997-01-01

347

A Compton backscattering polarimeter for measuring longitudinal electron polarization  

Microsoft Academic Search

Compton backscattering polarimetry provides a fast measurement of the polarization of an electron beam in a storage ring. Since the method is nondestructive, the polarization of the electrons can be monitored during internal target experiments. At NIKHEF a Compton polarimeter has been constructed to measure the polarization of the longitudinally polarized electrons stored in the AmPS ring. First results obtained

I. Passchier; D. W. Higinbotham; N. Vodinas; N. Papadakis; C. W. de Jager; R. Alarcon; T. Bauer; D. Boersma; T. Botto; M. Bouwhuis; H. J. Bulten; L. van Buuren; R. Ent; D. Geurts; M. Ferro-Luzzi; M. Harvey; P. Heimberg; B. Norum; H. R. Poolman; M. van den Putte; J. J. M. Steijger; D. Szczerba; H. de Vries

1998-01-01

348

Observations of Enhanced Radar Backscatter (ERB) from Millstone Hill  

Microsoft Academic Search

Intense enhancements of the incoherent radar backscatter spectrum from the topside ionosphere were observed with the Millstone Hill UHF radar. Enhancements occurring at the local ion acoustic frequency causing large asymmetries in the measured ion line may be produced by current driven instabilities. These enhancements pose a practical problem for space surveillance systems because their cross section and spectral width

M. C. Lee

1991-01-01

349

Backscattering grain noise modelling in ultrasonic non-destructive testing  

Microsoft Academic Search

Many materials present an internal grain microstructure. When these materials are subjected to ultrasonic non-destructive testing, the grains behave like scattering centres producing unwanted backscattered noise that can make the detection of true defects difficult. This paper is devoted to the modelling of the probability density and the spacetime correlation functions of the grain noise complex envelope. Assuming statistical independence

Luis Vergara-Dominguez; J. Manuel Paez-Borrallo

1991-01-01

350

Coherent backscattering of light by cold atoms: Theory meets experiment  

Microsoft Academic Search

Coherent backscattering (CBS) of quasi-resonant light by cold atoms presents some specific features due to the internal structure of the atomic scatterers. We present the first quantitative comparison between the experimentally observed CBS cones and Monte Carlo calculations which take into account the shape of the atomic cloud as well as the internal atomic structure.

G. Labeyrie; D. Delande; C. A. Müller; C. Miniatura; R. Kaiser

2003-01-01

351

Estimation of Mars radar backscatter from measured surface rock populations  

Microsoft Academic Search

Reanalysis of rock population data at the Mars Viking Lander sites has yielded updated values of rock fractional surface coverage (about 0.16 at both sites, including outcrops) and new estimates of rock burial depths and axial ratios. These data are combined with a finite difference time domain (FDTD) numerical scattering model to estimate diffuse backscatter due to rocks at both

J. E. Baron; R. A. Simpson; G. L. Tyler; H. J. Moore; J. K. Harmon

1998-01-01

352

Estimation of Mars radar surface rock populations backscatter from measured  

Microsoft Academic Search

Reanalysis of rock population data at the Mars Viking Lander sites has yielded updated values of rock fractional surface coverage (about 0.16 at both sites, including outcrops) and new estimates of rock burial depths and axial ratios. These data are combined wih a finite difference time domain (FDTD) numerical scattering model to estimate diffuse backscatter due to rocks at both

J. E. Baron; R. A. Simpson; G. L. Tyler; H. J. Moore

1998-01-01

353

Polyamide membrane precipitation studied by confocal backscattering microscopy  

Microsoft Academic Search

A wide variety of commercial polymeric membranes are manufactured by a non-solvent immersion precipitation process, yet the detailed mechanism and kinetics of membrane formation are poorly understood. We have used a confocal microscope, with fluorescence filters removed, to observe backscatter from precipitating nylon 6 films. Nylon 6 in formic acid\\/water solutions was spread on a glass substrate, which was then

James L. Thomas; Martina Olzog; Christin Drake; Chien-Hsieh Shih; Carl C. Gryte

2002-01-01

354

Bathymetry and acoustic backscatter-Elwha River Delta, Washington  

USGS Publications Warehouse

The surveys were conducted using the R/V Parke Snavely outfitted with an interferometric sidescan sonar for swath mapping and real-time kinematic navigation equipment for accurate shallow water operations. This report provides these data in a number of different formats, as well as a summary of the mapping mission, maps of bathymetry and backscatter, and Federal Geographic Data Committee (FGDC) metadata.

Finlayson, David P.; Miller, Ian M.; Warrick, Jonathan A.

2011-01-01

355

Applying time domain physical optics to acoustic wave backscattering problem  

Microsoft Academic Search

The interest in transient analysis of acoustic waves has been growing in recent years, due to the advance of wide-band sonars. In this paper, a transient analysis method for acoustic backscattering signals is proposed based on the time domain physical optics (TDPO). TDPO is formulated via a theoretical inverse Fourier transform of the conventional physical optics formula used in the

Kookhyun Kim; Kim Jin-Hyeong; Dae-Seung Cho; Woojae Seong

2010-01-01

356

Sonar image segmentation using the angular dependence of backscattering distributions  

Microsoft Academic Search

In high resolution sonar imaging, the K-distribution has shown interesting properties for describing the statistics of backscattered intensity. This distribution is a function of two parameters. The first one is the mean intensity which is classically angular dependent. It has been found that the second one, the shape parameter, is also angular dependent. The K-distribution shape parameter shows two types

G. Le. Chenadec; J. M. Boucher

2005-01-01

357

Terrain: Slope Influence on QuikSCAT Backscatter  

Microsoft Academic Search

Soil moisture (SM) is an important variable in determining streamflow, agricultural productivity, weather, and climate. An effective way to map SM over large areas on a regular basis is by using active microwave observations. This paper examines the influence of topography on radar backscatter measurements for a range of vegetation conditions and on the development of a normalization technique for

Iliana Mladenova; Venkat Lakshmi

2009-01-01

358

Backscatter Moessbauer Spectrometer (BaMS) for Use on Mars.  

National Technical Information Service (NTIS)

The use of Moessbauer spectroscopy for in situ analysis on the surface of Mars was proposed and the design and implementation of a backscatter Moessbauer spectrometer (BaMS) instrument suitable for planetary missions to the surfaces of Mars (MESUR), the M...

D. G. Agresti R. V. Morris E. L. Wills T. D. Shelfer M. M. Pimperl

1992-01-01

359

Breast Tumor Characterization Based on Ultrawideband Microwave Backscatter  

Microsoft Academic Search

Abstract—Characterization of architectural tissue features such as the shape, margin, and size of a suspicious lesion is commonly performed in conjunction with medical imaging to provide clues about the nature of an abnormality. In this paper, we numeri- cally investigate the feasibility of using multichannel microwave backscatter in the 1–11 GHz band to classify the salient features of a dielectric

Shakti K. Davis; Barry D. Van Veen; Susan C. Hagness; Frederick Kelcz

2008-01-01

360

Enhanced Resonant Backscattering of Excitons in Disordered Quantum Wells  

Microsoft Academic Search

A clear signature of enhanced backscattering of excitons is observed in the directional resonant Rayleigh scattering of light from localized two-dimensional excitons in disordered quantum wells. Its spectral dependence and time dynamics are measured and theoretically predicted in a quantitative way. The intensity enhancement has a large momentum span extending beyond the external light emission cone. This is a consequence

W. Langbein; E. Runge; V. Savona; R. Zimmermann

2002-01-01

361

Frequency dependence of a ring laser with backscattering  

SciTech Connect

The coupled third-order equations of motion of the two-mode ring laser with spontaneous emission noise are investigated in the presence of detuning and backscattering. The steady-state solution is obtained without linearizing approximations, and it is shown to depend on backscattering only through the sum R/sub 1/ + R/sub 2//sup */, where R/sub 1/ and R/sub 2/ are complex backscattering coefficients. Above threshold the effect of backscattering is found to be equivalent to incrementing the pump parameter of each laser mode by (1/2)chemically bondR/sub 1/ + R/sub 2//sup */chemically bond. The variations of the mean light intensities of the two modes with detuning are calculated for several different pump parameters, from well below to well above threshold. The results are compared with direct measurements of a He:Ne ring laser, and good agreement is obtained over a wide range, with the adjustment of just a single scale constant.

Christian, W.R.; Mandel, L.

1986-11-01

362

Tracking California seafloor seeps with bathymetry, backscatter and ROVs  

NASA Astrophysics Data System (ADS)

The California (USA) margin includes two different tectonic regimes: subduction north of the Mendocino Triple Junction and translation south. Both margins include seeps, and their distribution can be inferred using seafloor bathymetry and backscatter as well as subsurface seismic data. Anomalous bathymetric and backscatter features related to fluid expulsion include headless submarine canyons, fault zones, anticlines, pockmarks, and mud volcanoes. Anomalous backscatter may be caused by authigenic carbonate (related to the bacterial oxidation of methane) or cold seep clams—both have an impedance and roughness that may be higher than the surrounding seafloor. Remote-operated vehicle (ROV) dives to such suspect seep sites document the presence of extensive authigenic carbonate, areally restricted cold seep communities, carpets of chemoautotrophic bacteria, and bubbling gas. Our operations in the Monterey Bay, on the translational California margin, and the Eel River basin, on the convergent margin, indicate that bathymetric and backscatter maps of the seafloor, if sufficiently high resolution, can be used to map seep sites, and that the distribution of such seeps can be used to constrain subsurface conduits of fluid flow. ROVs, due to their combination of visualization, propulsion, manipulation, sonar, and navigation, provide an excellent platform for ground-truthing, mapping, and sampling seafloor seeps.

Orange, Daniel L.; Yun, Janet; Maher, Norman; Barry, James; Greene, Gary

2002-11-01

363

Ocean Raman scattering in satellite backscatter UV measurements  

Microsoft Academic Search

Vibrational Raman scattering by liquid water (ocean Raman scattering) significantly contributes to the filling-in of solar Fraunhofer lines observed by satellite backscatter ultraviolet (buv) instruments in the cloudless atmosphere over clear ocean waters. A radiative transfer model accounting for this effect in buv measurements has been developed and the results compared with observations from the European Space Agency's Global Ozone

Alexander P. Vasilkov; Joanna Joiner; James Gleason; Pawan K. Bhartia

2002-01-01

364

Aerosol extinction to backscatter ratio derived from passive satellite measurements  

NASA Astrophysics Data System (ADS)

Spaceborne reflectance measurements from the POLDER instrument are used to study the specific directional signature close to the backscatter direction. The data analysis makes it possible to derive the extinction to backscatter ratio (EBR) which is the invert of the scattering phase function for an angle of 180° and is needed for a quantitative interpretation of lidar observations (active measurements). In addition, the multi-directional measurements are used to quantify the scattering phase function variations close to backscatter, which also provide some indication of the aerosol particle size and shape. The spatial distributions of both parameters show consistent patterns that are consistent with the aerosol type distributions. Pollution aerosols have an EBR close to 70, desert dust values are on the order of 50, while marine aerosol's is close to 25. The scattering phase function shows an increase with the scattering angle close to backscatter. The relative increase ?lnP/? ? is close to 0.01 for dust and pollution type aerosols and 0.06 for marine type aerosols. These values are consistent with those retrieved from Mie simulations.

Bréon, F.-M.

2013-01-01

365

Backscattered electron imaging of titanium dioxide in frozen hydrated preparations  

PubMed

Backscattered electron (BSE) imaging was used to study ultrafine TiO2 crystals distribution in a test cream. The cream was fast frozen, cryofractured and observed uncoated at low temperature. The BSE detector was a microchannel plate. The results demonstrate that up-to-date photoprotective preparations can be investigated by this technique. PMID:10460678

Hallegot

1999-08-01

366

BACKSCATTERED ELECTRONS TOPOGRAPHIC MODE PROBLEMS IN THE SCANNING ELECTRON MICROSCOPE  

Microsoft Academic Search

The application of several backscattered electron (BSE) detectors makes it possible to separate topographic (TOPO) contrast and material (COMPO) contrast in a scanning electron microscope (SEM). The BSE signals from six p-i-n diodes were used to investigate some artifacts connected with the reconstruction of real topography. The location of these diodes has been predicted theoretically to obtain algebraic formulas for

Danuta Kaczmarek

1998-01-01

367

Processing Backscattered Electron Digital Images of Thin Section  

Microsoft Academic Search

Image analysis of sedimentary particles using backscatter electron (BSE) microscopy shows great promise in paleoclimatic and paleoenvironmental studies. Prior to the last few years BSE microscopy has been used primarily for compositional (provenance) studies. Our preliminary work on Paleozoic loessite, as well as previous work on recent sediments (Francus 1998; Francus and Karabanov 2000), suggests that BSE microscopy image analysis

MICHAEL J. SOREGHAN; Pierre Francus

368

Inspection of multilayer components by the neutron backscattering method  

Microsoft Academic Search

The results of calculations and experimental examination of neutron backscattering (albedo) from multilayer components are examined. The results of calculations and experimental determination of sensitivity in thickness gauging of multilayer components are presented and the optimum conditions of inspection in the conditions with one-side access are determined.

Pekarskii; G. Sh

1987-01-01

369

Error caused by using a constant extinction/backscattering ratio in the lidar solution  

NASA Astrophysics Data System (ADS)

The Bernoulli solution of the lidar equation with the assumption of a constant extinction/backscattering ratio can lead to errors in the derived aerosol extinction and backscattering profiles. This paper presents a general theoretical analysis of the errors that result from differences between the assumed and actual extinction/backscattering ratio profiles. Examples of the influence of the constant extinction/backscattering ratio assumption on the lidar derived aerosol extinction profile are presented for various laser wavelengths.

Sasano, Y.; Browell, E. V.; Ismail, S.

1985-11-01

370

Backscatter Analysis of Saturn's Icy Moons with Cassini RADAR  

NASA Astrophysics Data System (ADS)

The typical Saturn icy satellite RADAR observation occurs at large distances, usually about 100,000 km, but sometimes as far as 400,000 km. Ostro et al. (Icarus 2010) have reported 2 cm-wavelength radar albedo estimates and diffuse scattering parameters for 73 radar tracks acquired through April 2008 across eight of Saturn's moons. We reprocess this data, together with more recently acquired data (bringing the total to more than 91 tracks), using an alternative processing approach, where we project the weighted received power onto the surface rather than model the power spectral shape. This allows us to create an extensive set of consistently processed measurements that we can use to understand the distribution of 2 cm-wavelength scattering characteristics across each moon's surface, as well as between the moons. We focus on data acquired during several close targeted flybys occurring at distances smaller than 45,000 km. The targeted flyby data enable us to carefully measure the backscatter response for regions on Rhea, Iapetus, and Enceladus. We model the backscatter response with a diffuse cosine power law to estimate the backscatter parameters A and N, where A is a measure of the reflection strength and N is a measure of the directivity of the backscatter power pattern. Isotropic surfaces will have N=1, whereas Lambertian surfaces have N=2. Our close flyby measurements span the range from A=0.41 for Iapetus' dark leading hemisphere to A=3.51 for Enceladus' bright trailing hemisphere, representing some of the darkest and the brightest surfaces in the Saturnian system. The measured N values reveal that Iapetus appears more Lambertian (N=1.81) and Enceladus looks more isotropic (1.23). The Rhea measurements are in between the two extremes, but are closer to the bright end of the spectrum (A=2.14, N=1.35). The Iapetus observation exhibits a small quasispecular rise at angles less than 20 degrees, a backscatter response similar to those measured for features on Titan. We fit a Hagfors and an exponential quasispecular model to the low-angle backscatter, and the results imply a low effective dielectric constant, possibly indicative of porous solid hydrocarbons or porous carbon dioxide ice, and moderate large-scale (>>2.2 cm) facet slopes. This is the first detection of a quasispecular component on an icy moon other than Titan, indicating the presence (albeit small) of a surface scattering mechanism in addition to the more prominent diffuse volume scattering mechanism that tends to dominate the backscatter of icy surfaces. We also form low resolution real aperture backscatter images of Enceladus, Rhea, and Iapetus and compare these to co-located high resolution synthetic aperture backscatter images. We analyze the resolution effects on the appearance of the backscatter responses.

Wye, L.; Zebker, H. A.; Cassini Radar Team

2011-12-01

371

Incoherent and coherent backscattering of light beyond diffusion for subsurface reflectance spectroscopy  

Microsoft Academic Search

Backscattered snake light, which has experienced exactly two large angle scattering, is taken into account together with the diffuse light to model light backscattering. This simple modification is shown to significantly improve the agreement in the radial profile of the intensity of the backscattering light between the model and Monte Carlo simulations. The applications of the analytical model in incoherent

Min Xu

2009-01-01

372

Experimental study and theoretical model of high-resolution radar backscatter from the sea  

Microsoft Academic Search

The temporal characteristics of radar backscatter from the sea depend on the pulse width for surface resolutions less than about 20 m. While low-resolution backscatter appears continuously noiselike, as the resolution is increased, the backscatter is punctuated by substantially quieter periods. This results in a noticeably 'spikey' characteristic. Measurements at 3 cm using several different pulse widths have been made

Bernard L. Lewis; Irwin D. Olin

1980-01-01

373

Time Evolution and Dynamics of Equatorial Backscatter Plumes, 1. Growth Phase  

Microsoft Academic Search

Much of our understanding of equatorial spread-F phenomena has resulted from VHF radar studies of backscatter 'plumes,' i.e., patterns of backscatter that appear to extend from the bottomside into the top- side of the F layer. By using ALTAIR, a fully steerable backscatter radar, to map selected plumes repeat- edly, it was found that the dynamic behavior of plumes can

Roland T. Tsunoda

1981-01-01

374

Multipath Fading Measurements at 5.8 GHz for Backscatter Tags With Multiple Antennas  

Microsoft Academic Search

Multipath fading can be heavy for ultra-high frequency (UHF) and microwave backscatter radio systems used in applications such as radio frequency identification (RFID). This paper presents measurements of fading on the modulated signal backscattered from a transponder for backscatter radio systems that use multiple antennas at the interrogator and transponder. Measurements were performed at 5.8 GHz and estimates of the

Joshua D. Griffin; Gregory D. Durgin

2010-01-01

375

Magnetic-field effects on coherent backscattering of light in case of Mie spheres  

Microsoft Academic Search

Magneto-optical Faraday rotation destroys the coherent backscattering enhancement of elastically multiple scattered light. In addition, Faraday rotation has been predicted, especially for Mie scattering, to cause a shift of the coherent backscattering cone off the exact backscattering direction in case of circular polarized light, or a twin peak in case of linear polarization (see Lenke R., Maret G. 2000 Eur.

R. Lenke; R. Lehner; G. Maret

2000-01-01

376

Generalized Snell's law and its possible relation to coherent backscattering of ultrasonic waves  

Microsoft Academic Search

The cause of backscattering in the Rayleigh angle has first been explained by means of finite beam models in which there are inherently present backward traveling components that explain the backscattering effect. Later, the nature of backscattered sound was proved to consist mostly of incoherent sound due to material anomalies. The present work shows that besides the well known real

Nico F. Declercq; Joris Degrieck; Oswald Leroy

2004-01-01

377

Vector Backscattered Signals Improve Piggyback Modulation for Sensing With Passive UHF RFID Tags  

Microsoft Academic Search

We expand our “piggyback modulation” technique to integrate sensing functions with existing standard passive UHF RFID tags through wireless coupling. Instead of focusing on the scalar backscattered power that is proportional to the radar cross section (RCS), we exploit the vector backscattered signal with piggyback modulation. Measuring both amplitude and phase of the backscattered wave makes advanced demodulation possible. The

Huan-Yang Chen; Atul S. Bhadkamkar; Tzu-Han Chou; Daniel W. van der Weide

2011-01-01

378

Estimation of backscatter differential phase at X band  

NASA Astrophysics Data System (ADS)

Backscatter differential phase ? appears as a deviation from the mean trend and causes bumps in copolar differential phase shift profiles of polarimetric radars. Such indicators of Mie scattering effects are clearly visible in the X-band dual polarization radar data collected even in relatively light rain. Given the importance of reliable estimators of both the propagation differential phase shift ?dp and specific differential phase Kdp for attenuation correction and rainfall retrievals the effects of backscattering and forward propagation should be separated. In this study, we suggest to retrieve propagation differential phase ?dp from the radial profile of specific attenuation A estimated using the ZPHI method (Testud et al., 2000). The backscatter differential phase ? is obtained after the propagation component of differential phase ?dp is subtracted from the measured total differential phase ?dp. The method has been tested using the X-band polarimetric data collected by the twin radars in the Bonn area (XPol Bonn and XPol Jülich). The estimates of ? exhibit spatial and temporal continuity which attests to the reliability of the method. In this study, we examine variability of backscatter differential phase ? and its relation to differential reflectivity Zdr as well as informative content of ? and its implications for estimating the median size of raindrops. Direct measurements of ? in pure rain agree very well with theoretical predictions based on T-Matrix scattering calculations. In some cases, discrepancies between observations and predictions can be attributed to more unusual drop size distributions altered by size sorting. The impact of size sorting on the Zdr - ? relation is quantified. In addition, some results of backscatter differential phase measurements within the melting layer are presented.

Troemel, S.; Kumjian, M.; Ryzhkov, A.; Simmer, C.

2011-12-01

379

Diffractions reveal drilling hazards  

SciTech Connect

Seismic waves are diffracted where there is a sudden change of curvature or acoustic impedance along a surface such as boulders embedded in clay, across faults, the eroded edges of channels, and at the edges of shallow gas drilling hazards. Diffractions reveal these situations, especially if they are enhanced at the expense of reflections and refractions and organized as in an Offset Panel. The Offset Panel was introduced by Fulton and Darr (1981) as a powerful tool for the analysis of seismic data. Their paper described a method by which conventional exploration seismic data are used to detect shallow gas drilling hazards. The work of Berryhill indicates that boulders, which are one-half the dominant wavelength in size, can be expected to generate diffractions. Hazard seismic data from the North Sea presented here show energy in the 500-700 Hertz band corresponding to wavelengths of 11 to 8 feet. Unfortunately, the spacial sampling of the hazard data is four wavelengths, much too great to resolve boulders. A spacial sampling of 2 to 3 feet would be more appropriate for these data and may allow for the detection of individual boulders or zones containing fewer boulders. Experience with the Offset Panel to detect shallow gas drilling hazards along the line of the profile suggested the Diffraction Panel to detect gas hazards nearby. In this report the authors demonstrate the use of the Diffraction Panel to detect buried channels and shallow gas drilling hazards.

Fulton, T.K.; Hsiao, R.T.

1983-05-01

380

White light conical diffraction.  

PubMed

Conical diffraction occurs when light is incident along the optic axis of a biaxial crystal. The light spreads out into a hollow cone inside the crystal, emerging as a hollow cylinder. The intensity distribution beyond the crystal is described using an adapted paraxial wave dispersion model. We show, experimentally and theoretically, how this results in a transition from conical diffraction for wavelengths at which the crystal is aligned to double refraction for misaligned wavelengths when using a white light source. The radius of the ring and location of the focal image plane (FIP) are also observed to have a wavelength dependency. The evolution of the conically diffracted beam beyond the FIP into the far field is studied and successfully described using a theoretical model. PMID:24105584

Darcy, R T; McCloskey, D; Ballantine, K E; Jennings, B D; Lunney, J G; Eastham, P R; Donegan, J F

2013-08-26

381

Diffraction at the LHC  

NASA Astrophysics Data System (ADS)

We show that the diffractive pp (and ) data (on ? tot, d? el/ dt, proton dissociation into low-mass systems, , and high-mass dissociation, d?/ d(? ?)) in a wide energy range from CERN-ISR to LHC energies, may be described in a two-channel eikonal model with only one `effective' pomeron. By allowing the pomeron coupling to the diffractive eigenstates to depend on the collider energy (as is expected theoretically) we are able to explain the low value of measured at the LHC. We calculate the survival probability, S 2, of a rapidity gap to survive `soft rescattering'. We emphasise that the values found for S 2 are particularly sensitive to the detailed structure of the diffractive eigenstates.

Khoze, V. A.; Martin, A. D.; Ryskin, M. G.

2013-07-01

382

Semiclassical quantization using diffractive orbits  

Microsoft Academic Search

Diffraction, in the context of semiclassical mechanics, describes the manner in which quantum mechanics smooths over discontinuities in classical mechanics. Semiclassical quantization then requires the inclusion of diffractive periodic orbits in addition to classical periodic orbits. In this Letter we construct the corresponding diffractive zeta function and apply it to a scattering problem which has only diffractive periodic orbits. We

Niall D. Whelan

1996-01-01

383

Diffraction radiation generators  

NASA Astrophysics Data System (ADS)

Research in the field of diffraction radiation generators (DRG) conducted at the Radio Physics and electronics Institute of the Ukranian Academy of Sciences over the past 25 years is reviewed. The effect of diffraction radiation is analyzed in detail, and various operating regimes of DRGs are discussed. The discussion then focuses on the principal requirements for the design of packaged DRGs and their principal parameters. Finally, applications of DRGs in various fields of science and technology are reviewed, including such applications as DRG spectroscopy, diagnostics of plasma, biological specimens, and vibration, and DRG radar systems.

Shestopalov, Viktor P.; Vertii, Aleksei A.; Ermak, Gennadii P.; Skrynnik, Boris K.; Khlopov, Grigorii I.; Tsvyk, Aleksei I.

384

Diffractive Interaction of Neutrinos  

NASA Astrophysics Data System (ADS)

Interactions of high-energy neutrinos expose hadronic properties, in particular, contain a strong diffractive channel. The Adler relation (AR) between soft interactions of neutrinos and pions, might look as a manifestation of pion dominance. However, neutrinos cannot fluctuate to pions because of conservation of the lepton current, and interact via much heavier hadronic components. This fact leads to nontrivial relations between interactions of different hadronic species, in particular, it links diagonal and off-diagonal diffractive interactions of pions. Absorptive corrections break these relations making the AR impossible to hold universally, for any target and at any energy.

Kopeliovich, B. Z.; Potashnikova, I. K.; Schmidt, Iván; Siddikov, M.

2013-06-01

385

Retrieval of multi-wavelength aerosol lidar ratio profiles using Raman scattering and Mie backscattering signals  

NASA Astrophysics Data System (ADS)

We advance a novel retrieval technique that combines a Raman and multi-wavelength elastic backscattered signals to retrieve multi-wavelength lidar ratio profiles of aerosol. With profile of backscatter coefficients at 355 nm retrieved from elastic backscatter signal at 355 nm and Raman scattering signal at 387 nm, lidar ratio profiles can be calculated at 532 nm and 1064 nm from the elastic backscatter signals at these wavelengths, taking advantage that the 532 nm/355 nm and 1064 nm/355 nm backscatter ratios are generally approximately equal for two neighboring range bins. This technique has been tested using numerical simulations and applied to lidar measurements at the Hampton University, Hampton, Virginia.

Su, Jia; Liu, Zhaoyan; Wu, Yonghua; McCormick, M. Patrick; Lei, Liqiao

2013-11-01

386

Diffractive hard scattering  

SciTech Connect

I discuss events in high energy hadron collisions that contain a hard scattering, in the sense that very heavy quarks or high P/sub T/ jets are produced, yet are diffractive, in the sense that one of the incident hadrons is scattered with only a small energy loss. 8 refs.

Berger, E.L.; Collins, J.C.; Soper, D.E.; Sterman, G.

1986-03-01

387

Polarimetric vector diffraction tomography  

Microsoft Academic Search

Scalar linearized inverse scattering has recently found a unified treatment within the framework of diffraction tomography in either frequency or angular diversity. The linear inverse scattering theory can be extended to electromagnetic vector fields to include complete polarization information. Its essential feature is the formulation of a vector Porter-Bojarski integral equation to be inverted by dyadic algebra. Algorithms are discussed

Michael Brandfass; K. J. Langenberg; A. Fritsch

1994-01-01

388

Fresnel Diffraction Applet  

NSDL National Science Digital Library

This applet simulates Fresnel diffraction patterns from monochromatic light through various apertures, including circles, half-plane, slit, double slit, corner, cross and more. The aperture scale is adjustable. The page also includes source code and links to other Fresnel applets/pages.

Falstad, Paul

2004-07-13

389

X-ray Diffraction  

NSDL National Science Digital Library

A series of laboratory activities on x-ray diffraction physics using the Teltron Tel-X-Ometer System. Detailed explanations on the production and delivery of the beam is included, as well as a very complete safety protocol for conducting the experiments.

Langan, Shawn

2012-03-08

390

DO Results in Diffraction  

SciTech Connect

The first search for diffractively produced Z bosons in the muon decay channel is presented, using a data set collected by the DO detector at the Fermilab Tevatron at {radical}(s) = 1.96 TeV between April and September 2003, corresponding to an integrated luminosity of approximately 110 pb-1. The current status of the FPD commissioning is also presented.

Mundim, Luiz [High Energy and Nuclear Physics Department, State University of Rio de Janeiro, R. Sao Francisco Xavier, 524 Rio de Janeiro, RJ, 20550-900 (Brazil)

2005-10-06

391

DIFFRACTION FROM MODEL CRYSTALS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Although calculating X-ray diffraction patterns from atomic coordinates of a crystal structure is a widely available capability, calculation from non-periodic arrays of atoms has not been widely applied to cellulose. Non-periodic arrays result from modeling studies that, even though started with at...

392

Inclusive diffraction at HERA  

SciTech Connect

Results are reported on recent measurements, performed by the H1 and ZEUS Collaborations, of the cross section of the diffractive deep-inelastic process ep{yields}eXp using different experimental methods. In particular, first results using the Very Forward Proton Spectrometer of H1 are discussed.

Favart, Laurent [Universite Libre de Bruxelles, CP 230, Bd. du Triomphe, B-1040 Brussels (Belgium)

2011-07-15

393

Diffraction at collider energies  

SciTech Connect

Lessons with ``soft`` hadron physics to explain (a) feasibility to observe and to investigate color transparency, color opacity effects at colliders; (b) significant probability and specific features of hard diffractive processes; (c) feasibility to investigate components of parton wave functions of hadrons with minimal number of constituents. This new physics would be more important with increase of collision energy.

Frankfurt, L.L.

1992-12-31

394

Diffraction at collider energies  

SciTech Connect

Lessons with soft'' hadron physics to explain (a) feasibility to observe and to investigate color transparency, color opacity effects at colliders; (b) significant probability and specific features of hard diffractive processes; (c) feasibility to investigate components of parton wave functions of hadrons with minimal number of constituents. This new physics would be more important with increase of collision energy.

Frankfurt, L.L.

1992-01-01

395

Coherent backscattering under conditions of pulsed radiation trapping  

SciTech Connect

Coherent backscattering of pulsed radiation emitted by optically dense atomic ensembles is considered. The diagrammatic technique is used for deriving analytic expressions for correlation functions of scattered light, which make it possible to take into account all main factors affecting the dynamics of the process, including the hyperfine and Zeeman structure of the ground and first excited states of atoms, polarization of probe radiation, the actual shape and size of an atomic cloud, its spatial inhomogeneity, motion of atoms, and angular-momentum polarization of atoms. On the basis of these relations, the time dependence of the total intensity and the dependence of enhancement factor of backscattered light on the pulse duration, type of polarization of the polarization system of observation, optical thickness of the scattering medium, and the carrier frequency of the pulse are investigated. The calculations are performed for an ensemble of rubidium-85 atoms cooled in magnetooptical traps.

Datsyuk, V. M.; Sokolov, I. M. [St. Petersburg State Technical University (Russian Federation)], E-mail: IMS@quark.stu.neva.ru

2006-05-15

396

RFID tag modification for full depth backscatter modulation  

DOEpatents

A modulated backscatter radio frequency identification device includes a diode detector configured to selectively modulate a reply signal onto an incoming continuous wave; communications circuitry configured to provide a modulation control signal to the diode detector, the diode detector being configured to modulate the reply signal in response to be modulation control signal; and circuitry configured to increase impedance change at the diode detector which would otherwise not occur because the diode detector rectifies the incoming continuous wave while modulating the reply signal, whereby reducing the rectified signal increases modulation depth by removing the reverse bias effects on impedance changes. Methods of improving depth of modulation in a modulated backscatter radio frequency identification device are also provided.

Scott, Jeffrey Wayne [Pasco, WA; Pratt, Richard M [Richland, WA

2010-07-20

397

Electron Kinetic Effects on Raman Backscatter in Plasmas  

SciTech Connect

We augment the usual three-wave cold-fluid equations governing Raman backscatter (RBS) with a new kinetic thermal correction, proportional to an average of particle kinetic energy weighted by the ponderomotive phase. From closed-form analysis within a homogeneous kinetic three-wave model and ponderomotively averaged kinetic simulations in a more realistic pulsed case, the magnitude of these new contributions is shown to be a measure of the dynamical detuning between the pump laser, seed laser, and Langmuir wave. Saturation of RBS is analyzed, and the role of trapped particles illuminated. Simple estimates show that a small fraction of trapped particles ({approx}6%) can significantly suppress backscatter. We discuss the best operating regime of the Raman plasma amplifier to reduce these deleterious kinetic effects.

Hur, M.S.; Suk, H. [Center for Advanced Accelerators, KERI, Changwon, Kyongnam 641-120 (Korea, Republic of); Lindberg, R.R.; Charman, A.E. [Department of Physics, University of California, Berkeley, Berkeley, California 94720 (United States); Wurtele, J.S. [Department of Physics, University of California, Berkeley, Berkeley, California 94720 (United States); Center for Beam Physics, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2005-09-09

398

Stimulated brillouin backscatter of a short-pulse laser  

SciTech Connect

Stimulated Brillouin backscattering (SBBS) from a short-pulse laser, where the pulse length is short compared to the plasma length, is found to be qualitatively different than in the long pulse regime, where the pulse length is long compared to the plasma length. We find that after an initial transient of order the laser pulse length transit time, the instability reaches a steady state in the variables x{prime} = x {minus} V{sub g}t, t{prime} = t, where V{sub g} is the pulse group velocity. In contrast, SBBS in a long pulse can be absolutely unstable and grows indefinitely, or until nonlinearities intervene. We find that the motion of the laser pulse induces Doppler related effects that substantially modify the backscattered spectrum at higher intensities, where the instability is strongly coupled (i.e. , has a growth rate large compared to the ion acoustic frequency).

Hinkel, D.E.; Williams, E.A.; Berger, R.L.

1994-11-03

399

Mask defect imaging system using backscattered electron images  

NASA Astrophysics Data System (ADS)

The optical inspection system has been applied for mask inspection. The small but fatal detects on the mask can not be detected minutely by the optical system because of the limitations of optical resolution. We have developed the Defect Imaging System (DIS-05) using Backscattered Electron Images (BSI). DIS-05 is composed of 3 units: (1) SEM with a newly developed Backscattered Electron detector, (2) CAD computer to create CAD Image and, (3) Main computer to control the SEM and CAD computer. One of key technologies for DIS-05 is the technique of detecting BSI at a high contrast. Moreover, we herewith describe "Superimposed Image", which compares BSI with CAD one. Finally, we also report the possibility of detecting "haze on masks" using DIS-05.

Takahashi, Katsuyuki; Ataka, Masashi; Namae, Takao

2006-10-01

400

Short-Lag Spatial Coherence of Backscattered Echoes: Imaging Characteristics  

PubMed Central

Conventional ultrasound images are formed by delay-and-sum beamforming of the backscattered echoes received by individual elements of the transducer aperture. Although the delay-and-sum beamformer is well suited for ultrasound image formation, it is corrupted by speckle noise and challenged by acoustic clutter and phase aberration. We propose an alternative method of imaging utilizing the short-lag spatial coherence of the backscattered echoes. Compared to matched B-mode images, short-lag spatial coherence (SLSC) images demonstrate superior SNR and CNR in simulated and experimental speckle-generating phantom targets, but are shown to be challenged by limited point target conspicuity. Matched B-mode and SLSC images of a human thyroid are presented. The challenges and opportunities of real-time implementation of SLSC imaging are discussed.

Lediju, Muyinatu A.; Trahey, Gregg E.; Byram, Brett C.; Dahl, Jeremy J.

2011-01-01

401

Bathymetry and Acoustic Backscatter: Northern Santa Barbara Channel, Southern California  

USGS Publications Warehouse

In the summer of 2008, as part of the California Seafloor Mapping Program (CSMP) the U.S. Geological Survey, Coastal and Marine Geology mapped a nearshore region of the northern Santa Barbara Channel in Southern California (fig 1). The CSMP is a cooperative partnership between Federal and State agencies, Universities, and Industry to create a comprehensive coastal/marine geologic and habitat basemap series to support the Marine Life Protection Act (MLPA) inititive. The program is supported by the California Ocean Protection Council and the California Coastal Conservancy. The 2008 mapping collected high resolution bathymetry and acoustic backscatter data using a bathymetric side scan system within State waters from about the 10-m isobath out over 3-nautical miles. This Open-File Report provides these data in a number of different formats, as well as a summary of the mapping mission, maps of bathymetry and backscatter, and FGDC metadata.

Dartnell, Pete; Finlayson, David; Conrad, Jamie; Cochrane, Guy; Johnson, Samuel

2010-01-01

402

Side-looking sonar backscatter response at dual frequencies  

NASA Astrophysics Data System (ADS)

Dual-frequency side-looking sonars have the potential to be used as remote sensing tools to characterize subaqueous terrains. In one case study of the carbonate-ooze-coated Blake Plateau off-shore of Georgia, U.S.A., the difference in acoustic attenuation for 50 and 20 mm wavelengths (30 and 72 kHz frequency) permits the discrimination of sub-bottom scatterers from seabed surface textural features to reveal patchy regions where a buried hard ground had been pock-marked by karst-like depressions. In a second study of the Upper Hudson River in New York, U.S.A., related to environmental contaminates, the backscatter response at 15 and 3 mm acoustic wavelengths (100 and 500 kHz frequency) serves as a useful proxy for sediment grain size with coarser detritus distinguished from finer sediments. Sand and gravel regions inferred from the backscatter were confirmed by ground truth sampling.

Ryan, William B. F.; Flood, Roger D.

1996-12-01

403

Backscatter absorption gas imaging - A new technique for gas visualization  

Microsoft Academic Search

This paper presents a new laser-based method of gas detection that permits real-time television images of gases to be produced. The principle of this technique (which is called backscatter absorption gas imaging (BAGI)) and the operation of two instruments used to implement it are described. These instruments use 5-W and 20-W CO2 lasers to achieve gas imaging at ranges of

Thomas G. McRae; Thomas J. Kulp

1993-01-01

404

Intermediate results of radar backscatter measurements from summer sea ice  

Microsoft Academic Search

A helicopter-borne scatterometer (HELOSCAT) was used to measure radar backscatter from sea ice under summer conditions near Mould Bay, N.W.T., Canada, in June and July 1982. These measurements were made at selected frequencies between 1 and 17 GHz, and at angles between 5 deg and 60 deg with like and cross-polarizations. Multiyear ice (MYI) can be distinguished form first-year ice

S. Gogineni; R. G. Onstott; R. K. Moore; J. Chancellor

1984-01-01

405

Dependence of radar backscatter on coniferous forest biomass  

Microsoft Academic Search

Two independent experimental efforts have examined the dependence of radar backscatter on above-ground biomass of monospecie conifer forests using polarimetric airborne SAR data at P-, L- and C-bands. Plantations of maritime pines near Landes, France, range in age from 8 to 46 years with above-ground biomass between 5 and 105 tons\\/ha. Loblolly pine stands established on abandoned agricultural fields near

M. Craig Dobson; Fawwaz T. Ulaby; T. Letoan; A. Beaudoin; E. S. Kasischke; N. Christensen

1992-01-01

406

Backscattering from capillary waves with application to sea clutter  

Microsoft Academic Search

The results of measurements atX-band of backscattering from water waves of amplitude less than about 0.01 wavelength and with wavelengths of the order of the microwave length are presented and compared with theory. The measurements have been made for both vertical and horizontal polarizations for grazing angles between4degand80deg. The results both as to angular dependence and absolute magnitude are in

J. Wright

1966-01-01

407

Sharpening of enhanced backscattering peak in a disordered gain medium  

NASA Astrophysics Data System (ADS)

We study theoretically the phenomenon of enhanced backscattering (EBS) from a bulk disordered gain medium due to the presence of a dye and a pump beam. We show that the presence of the gain, in combination with the effect of saturation, can dramatically sharpen the EBS peak function. In the particular case of a point source incidence for the probe beam along with the presence of a plane-wave pump beam, the EBS approaches a ? function in angular space.

Feng, Shechao Charles; Zhang, Zhao-Quing

1996-08-01

408

Backscattering Interferometry for Low Sample Consumption Molecular Interaction Screening  

Microsoft Academic Search

Backscattering interferometry (BSI), which uses a simple optical train comprising a He—Ne laser, a microfluidic channel, and a position sensor, has now enabled the measurement of both tethered and free-solution, label-free, molecular interactions within just nanoliters of sample. The simple macro-to-micro interface allows for a highly efficient assay work flow, which has been used to interrogate molecular binding interactions between

Amanda Kussrow; Carolyn S. Enders; Ereny F. Morcos; Darryl J. Bornhop

2009-01-01

409

UHF radar-backscatter enhancements from the topside ionosphere  

Microsoft Academic Search

Intense (about 20 dB) enhancements of the incoherent radar backscatter spectrum from the topside ionosphere have been observed with the Millstone Hill UHF radar; enhancements occurring at the local ion acoustic frequency causing large asymmetries in the measured ion line may be produced by current-driven instabilities. In addition to current-driven processes, we propose the generation of intense ion acoustic turbulence

K. M. Groves; M. C. Lee; J. C. Foster

1990-01-01

410

Modulation of Coherent Microwave Backscatter by Shoaling Waves  

Microsoft Academic Search

The orbital speed of long shoaling waves and the modulation of centimetric wind-generated waves by the shoaling waves were obtained from the frequency and amplitude modulations, respectively, of the backscattered signal of a coherent CW 9.375-GHz radar operated from the end of a pier on the Outer Banks of North Carolina. Modulations anomalously large in comparison with those predicted by

W. J. Plant; W. C. Keller; J. W. Wright

1978-01-01

411

Method and apparatus for measuring lung density by Compton backscattering  

DOEpatents

The density of the lung of a patient suffering from pulmonary edema is monitored by irradiating the lung by a single collimated beam of monochromatic photons and measuring the energies of photons Compton backscattered from the lung by a single high-resolution, high-purity germanium detector. A compact system geometry and a unique data extraction scheme are utilized to monimize systematic errors due to the presence of the chestwall and multiple scattering.

Loo, Billy W. (Oakland, CA); Goulding, Frederick S. (Lafayette, CA)

1991-01-01

412

Influence of physical surface characteristics on SAR backscatter  

NASA Astrophysics Data System (ADS)

An area in the Negev desert in Israel was chosen to demonstrate the capability of the SIR-C sensor system to differentiate lithological units. In addition DAIS hyperspectral data were investigated. The area around Timna mountain is characterized by Cambrian sandstones, carbonates and alluvial fans of Pleistocene and Holocene age. The mountain itself consists of diverse magmatic rock assemblage. The whole area is mapped using conventional methods. The remote sensing data are sensitive for the mapping parameters and allow the extraction of their spectral and radar signatures. Specific areas have been classified on their lithology, mineralogy, stratigraphy, grain size distribution, surface roughness and weathering state. In addition, field measurements of the roughness of the alluvial fan's terraces and of the Cambrian rocks surrounding Mount Timna were investigated. The stereoscopic images taken were used as a basis for the height models of the different targets and the standard deviation (RMS) of the height was calculated. This was used as the parameter for the surface roughness and can be correlated with the radar backscatter. The SIR-C system offers the unique possibility of multi-frequency and multi-polarized data. The sensitivity for the surface roughness for the different wavelengths of X-, C- and L-band in accordance to their incidence angle ranges between 0,13 and 27 cm absolute RMS. The RMS measured for example in the alluvial fan ranges between 0,25 and 7, this corresponds to a smooth surface with pebble size of a few mm and a coarse terrace up to 50 cm block diameter. It can be shown that the age of the terraces corresponds to the backscatter. The more ancient the terrace the lower is the backscatter, the smoother the surface, the younger and rougher the terrace, the higher is the backscatter.

Frei, Michaela; Henkel, Jochen

2002-01-01

413

Backscattering from bioturbated sediments at very high frequency  

Microsoft Academic Search

Recent backscattering measurements made in the Gulf of La Spezia, Italy, using a sonar operating at 140 kHz combined with thorough characterization of seabed interface and volume properties illustrate the importance of seabed volume scattering. Three-dimensional fluctuation statistics of density variability and vertical density gradients, both of which are attributed to the level of bioturbation (e.g., sea shell fragments, burrows,

Eric Pouliquen; Anthony P. Lyons

2002-01-01

414

Near field modulated backscatter for in vivo biotelemetry  

Microsoft Academic Search

Fully implantable wireless biotelemetry devices have traditionally used active VHF\\/UHF transmitters or load modulation at HF frequencies. HF systems tend to be bandwidth-limited due to low frequency magnetic induction, while active VHF\\/UHF transmitters generally consume a significant amount of power in DC bias current. We show in this paper that UHF near-field backscatter can be used to achieve higher data

Jordan S. Besnoff; Matthew S. Reynolds

2012-01-01

415

Raindrop axial and backscatter ratios using a collisional probability model  

NASA Astrophysics Data System (ADS)

The steady-state distribution of oscillation energies for raindrops was computed for a balance between input energies from collisions and dissipation by viscosity. Calculations of the oscillation responses indicates that an appreciable fraction of large raindrops (? 3 mm diameter) in heavy rain showers are oscillating with axis ratio changes greater than 10%. Computations of the distribution averages for the axis ratio, backscatter ratio, and ZDR indicate increasingly significant deviations from values for static raindrop shapes with increasing rain rates.

Beard, K. V.; Johnson, D. B.

1984-01-01

416

Measurement of cloud integrated backscattering coefficient with a nephelometer  

Microsoft Academic Search

We describe the application of a nephelometer to in-situ, real-time measurement of the integrated backscattering coefficient ?bs of cloud drops. For thin and moderately thick clouds, this quantity is related to the cloud albedo A, for 0° zenith solar radiation, through the relation A=?bsL, where L is the geometric cloud thickness. The instrument was used in a field experiment on

T. Novakov; C. Rivera-Carpio; R. C. Schmidt; C. F. Rogers

1991-01-01

417

Normalization and backscatter spectral analysis of human carotid arterial data acquired using a clinical linear array ultrasound imaging system.  

PubMed

The risk of plaque rupture in carotid atherosclerotic disease is associated more closely with the composition of plaque rather than the severity of stenosis. The constituents of plaque can be determined from ultrasonic spectral parameters obtained from normalized backscatter tissue data. Calibration of the data is done using echoes off a specular reflector which removes the system response of an ultrasound transducer, Terason (Teratech Corporation), from the backscatter data. A reference spectrum study is used to compare specular reflectors based on time domain (echo) and frequency domain (power spectrum, centroid and parabola test) analysis. Nylon and a tissue-mimicking phantom (velocity = 1560 m/s, slope of attenuation = 0.7 dB/cm MHz) have an intermediate acoustic impedance with respect to water and appear good choices as specular reflectors for clinical ultrasound imaging scanners compared to Plexiglas and other higher reflecting materials. A tissue-mimicking phantom is used to correct for attenuation in plaque, diffraction and saturation of electronics of the ultrasound scanner. Autoregressive power spectrum estimation methods are used to extract spectral parameters (spectral slope, y-intercept, midband fit, maximum and minimum power with corresponding frequencies, and integrated backscatter) from calibrated tissue data and linear and quadratic discriminant rules developed for classification of carotid arterial plaque. Regions of interest (n = 64; 64 samples x 8 scan lines with 30 MHz sampling frequency) consisting of 48 fibrous-fibrofatty (Class 1), 11 thrombus-necrotic core (Class 2), and 5 dense calcium (Class 3) areas selected for analysis show that fibrosis can be differentiated from necrosis and calcification. The quadratic discriminant rule identified necrosis with a lower misclassification rate (9.1%) than the linear discriminant rule (18.2%). PMID:19163329

Sareen, Meghna; Waters, Kendall; Nair, Anuja; Vince, D Geoffrey

2008-01-01

418

Annihilation and backscattered lines in black hole candidates  

NASA Astrophysics Data System (ADS)

On May 22nd 1989, HEXAGONE observed a broad region (19°FWHM) in the direction of the center of the Galaxy, and detected a narrow 511 keV line (Durouchoux et al. 1992) and also a broad emission around 170 keV (Smith et al. 1992) interpreted as backscattered annihilation photons coming from the 1E1740.7-2942 hard X-ray source. On the other hand, the french SIGMA experiment aboard the GRANAT satellite observed the Nova Muscae source on Jan 20-21 1991 and detected in addition to a line around the annihilation energy, two features which appeared successively around 102 keV and 170 keV (Goldwurm et al. 1992). Considering a new transient source EXS1737.9-2952 (Grindlay et al. 1992) which showed a bump around 102 keV a week before the HEXAGONE observation, we are questioning here if the 170 keV bump detected by HEXAGONE was also emitted by EXS source. We present a model where 102 keV and 170 keV double and single backscattered lines are explained in terms of supercritical states occurring in the accretion disk surrounding a black hole; we verify the model with a Monte Carlo simulation which accounts for the observations and mainly their timing sequence of appearance. We conclude by indicating that not only an annihilation line but also backscattered features might be signatures for black hole candidates.

Durouchoux, Ph.; Wallyn, P.

419

Laser light backscatter from intermediate and high Z plasmas  

SciTech Connect

In experiments at the Omega Laser Facility [J. M. Soures et al., Fusion Technol. 30, 492 (1996)], stimulated Brillouin backscatter (SBS) from gasbags filled with krypton and xenon gases was ten times lower than from CO{sub 2}-filled gasbags with similar electron densities. The SBS backscatter was a 1%-5% for both 527 and 351 nm interaction beams at an intensity of {approx}10{sup 15} W/cm{sup 2}. The SRS backscatter was less than 1%. The 351 nm interaction beam is below the threshold for filamentation and the SBS occurs in the density plateau between the blast waves. Inverse bremsstrahlung absorption of the incident and SBS light account for the lower reflectivity from krypton than from CO{sub 2}. The 527 nm interaction beam filaments in the blowoff plasma before the beam propagates through the blast wave, where it is strongly absorbed. Thus, most of the 527 nm SBS occurs in the flowing plasma outside the blast waves.

Berger, R. L.; Constantin, C.; Divol, L.; Meezan, N.; Froula, D. H.; Glenzer, S. H.; Suter, L. J.; Niemann, C. [University of California, Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94551 (United States); Department of Electrical Engineering, University of California, Los Angeles, California 90095 (United States)

2006-09-15

420

Measuring Ultrasonic Backscatter in the Presence of Nonlinear Propagation  

NASA Astrophysics Data System (ADS)

A goal of medical ultrasound is the formation of quantitative ultrasound images in which contrast is determined by acoustic or physical properties of tissue rather than relative echo amplitude. Such images could greatly enhance early detection of many diseases, including breast cancer and liver cirrhosis. Accurate determination of the ultrasonic backscatter coefficient from patients remains a difficult task. One reason for this difficulty is the inherent nonlinear propagation of ultrasound at high intensities used for medical imaging. The backscatter coefficient from several tissue-mimicking samples were measured using the planar reflector method. In this method, the power spectrum from a sample is compared to the power spectrum of an optically flat sample of quartz. The results should be independent of incident pressure amplitude. Results demonstrate that backscatter coefficients can vary by more than an order of magnitude when ultrasound pressure varies from 0.1 MPa to 1.5 MPa at 5.0 MHz. A new method that incorporates nonlinear propagation is proposed to explain these discrepancies.

Stiles, Timothy; Guerrero, Quinton

2011-11-01

421

Intraluminal ultrasound intensity distribution and backscattered Doppler power.  

PubMed

Ultrasound (US) incident obliquely on a cylindrical vessel is redistributed in space when the propagation path includes walls with acoustic impedance different from that of the surrounding media. We investigated this using low-density polyethylene (PE) as the vessel wall material. Both simulations and experiments were carried out. Direct hydrophone measurements of the acoustic field were made within a half section of the PE tube, and the distribution of backscattered Doppler power along a scan line was obtained using a range-Doppler instrument. Both simulation and hydrophone results demonstrate lateral shadow regions within the lumen. In every one of various Doppler flow experiments conducted, the backscattered Doppler power, compensated for on-axis transducer behaviour, increased with depth. Simulation results for an incident continuous-wave (CW) plane wave show that it tends to be focused by the curvature of the PE tube walls. The wall interactions are, however, angle-dependent and so the behaviour of a focused US beam depends on the beam as well as the walls. This study demonstrates alterations in the spatial distribution of US within a cylindrical vessel as a result of known vessel wall properties. It also provides evidence that local intensity variations within the lumen affect the relative Doppler power backscattered from small sample volumes. PMID:15588959

Thompson, Rosemary S; Bambi, Giacomo; Steel, Robin; Tortoli, Piero

2004-11-01

422

Challenges in tissue characterization from backscattered intravascular ultrasound signals  

NASA Astrophysics Data System (ADS)

Plaque characterization through backscattered intravascular ultrasound (IVUS) signal analysis has been the subject of extensive study for the past several years. A number of algorithms to analyze IVUS images and underlying RF signals to delineate the composition of atherosclerotic plaque have been reported. In this paper, we present several realistic challenges one faces throughout the process of developing such algorithms to characterize tissue type. The basic tenet of ultrasound tissue characterization is that different tissue types imprint their own "signature" on the backscattered echo returning to the transducer. Tissue characterization is possible to the extent that these echo signals can be received, the signatures read, and uniquely attributed to a tissue type. The principal difficulty in doing tissue characterization is that backscattered RF signals originating as echoes from different groups of cells of the same tissue type exhibit no obvious commonality in appearance in the time domain. This happens even in carefully controlled laboratory experiments. We describe the method of acquisition and digitization of ultrasound radiofrequency (RF) signals from left anterior descending and left circumflex coronary arteries. The challenge of obtaining corresponding histology images to match to specific regions-of-interest on the images is discussed. A tissue characterization technique based on seven features is compared to a full spectrum based approach. The same RF and histology data sets were used to evaluate the performances of these two techniques.

Katouzian, Amin; Sathyanarayana, Shashidhar; Li, Wenguang; Thomas, Tom; Carlier, Stéphane G.

2007-03-01

423

A backscattered x-ray imager for medical applications  

NASA Astrophysics Data System (ADS)

Conventional X-ray radiographic systems rely on transmitted photons for the production of images. Backscatter imaging makes use of the more abundant scattered photons for image formation. Specifically, incoherently (Compton) scattered X-ray photons are detected and used for image formation in this modality of medical imaging. However, additional information is obtained when the transmitted X-ray photons are also detected and used. Transmission radiography produces a two-dimensional image of a three dimensional system, therefore image information from a shallower object is often contaminated by image information from underlying objects. Backscattered x-ray imaging largely overcomes this deficiency by imaging depth selectively, which reduces corruption of shallow imaging information by information from deeper objects lying under it. Backscattered x-ray imaging may be particularly useful for examining anatomical structures at shallow depths beneath the skin. Some typical applications for such imaging might be breast imaging, middle ear imaging, imaging of skin melanomas, etc. Previous investigations, by way of theoretical calculations and computational simulations into the feasibility of this kind of imaging have uncovered high-contrast and SNR parameters. Simulations indicate that this method can be used for imaging relatively high-density objects at depths of up to approximately five centimeters below the surface. This paper presents both theoretical and experimental SNR results on this new medical imaging modality.

Morris, Eric Jude L.; Dibianca, Frank A.; Shukla, Hemant; Gulabani, Daya

2005-04-01

424

Spatial occurrence of decameter midlatitude E region backscatter  

NASA Astrophysics Data System (ADS)

This paper provides a statistical analysis of the spatial occurrence of midlatitude E region decameter backscatter. Measurements were made using the Valensole HF (high frequency) radar located in southern France during the summer of 1995 when it operated simultaneously at four frequencies. On the basis of the premise that E region scattering is fully magnetic aspect sensitive, the spatial occurrence statistics show that the aspect sensitive region moves toward the radar (southward) with respect to line of sight propagation calculations, with the lower-frequency echoes being closer toward the radar than the higher frequency ones are, in agreement with refraction theory predictions. Ray tracing inside nighttime midlatitude electron density profiles augmented with dense sporadic Es layers was used to calculate the expected echoing region, and good agreement with the observed region was found. Another finding is the angular distribution of backscatter inside the wide azimuthal sector covered by the radar scan. The spatial distribution of echo occurrence has its maximum at small azimuths at and about the geomagnetic north, suggesting that statistically, the meridional direction is strongly preferred for backscatter. Under the postulation that these are secondary decameter waves, we concluded that the observed angular anisotropy in spatial occurrence is at odds with the concept of strong isotropic plasma turbulence [Sudan, 1983] but in general agreement with the two-step gradient drift instability theory of secondary-wave generation proposed by Sudan et al. [1973].

Hussey, G. C.; Haldoupis, C.; Bourdillon, A.; André, D.

1999-05-01

425

Laser transmission-backscattering through inhomogeneous cirrus clouds.  

PubMed

We have developed a two-dimensional (2D) model for inhomogeneous cirrus clouds in plane-parallel and spherical geometries for the analysis of the transmission and backscattering of high-energy laser beams. The 2D extinction-coefficient and mean effective ice-crystal size fields for cirrus clouds can be determined from a combination of the remote sensing of cirrus clouds by use of the Advanced Very High Resolution Radiometer on board National Oceanic and Atmospheric Administration satellites and the vertical profiling of ice-crystal size distributions available from limited measurements. We demonstrate that satellite remote sensing of the position and the composition of high cirrus can be incorporated directly in the computer model developed for the transmission and backscattering of high-energy laser beams in realistic atmospheres. The results of laser direct transmission, forward scattering, and backscattering are analyzed carefully with respect to aircraft height, cirrus cloud optical depth, and ice-crystal size and orientation. Uncertainty in laser transmission that is due to errors in the retrieved ice-crystal size is negligible. But uncertainty of the order of 2% can be produced if the retrieved optical depth has errors of +/-0.05. With both the aircraft and the target near the cloud top, the direct transmission decreases, owing to the propagation of the laser beam through the curved portion of the cloud top. This effect becomes more pronounced as the horizontal distance between the aircraft and the target increases. PMID:12269574

Ou, Szu-Cheng; Takano, Yoshihide; Liou, Kuo-Nan; Lefevre, Randy J; Johnson, Michael W

2002-09-20

426

Dependence of radar backscatter on coniferous forest biomass  

SciTech Connect

This paper discusses two independent experimental efforts which have examined the dependence of radar backscatter on aboveground biomass of mono specie conifer forests using polarimetric airborne SAR data at P-, L- and C-bands. Plantations of maritime pines near Landes, France range in age from 8 to 46 years with aboveground biomass between 5 and 105 tons/ha. Loblolly pine stands established on abandoned agricultural fields near Duke, NC range in age from 4 to 90 years and extend the range of aboveground biomass to 560 tons/ha for the older stands. These two experimental forests are largely complementary with respect to biomass. Radar backscatter is found to increase approximately linearly with increasing biomass until it saturates at a biomass level that depends on the radar frequency. The biomass saturation level is about 200 tons/ha at P-band and 100 tons/ha at L-band, and the C-band backscattering coefficient shows much less sensitivity to total aboveground biomass.

Dobson, M.C.; Ulaby, F.T. (Radiation Lab., Dept. of Electrical Engineering and Computer Science, Univ. of Michigan, Ann Arbor, MI (US)); LeToan, T.; Beaudoin, A. (Univ. Paul Sabatier, Toulouse (FR)); Kasischke, E.S. (Environmental Research Inst. of Michigan, Ann Arbor, MI (US)); Christensen, N. (School of Environment, Duke Univ., Durham, NC (US))

1992-03-01

427

Acoustic backscattering by Atlantic mackerel as being representative of fish that lack a swimbladder. Backscattering by individual fish  

Microsoft Academic Search

Developing acoustic methods for the identification of fish remains a long-term objective of fisheries acoustics. The accuracy of abundance estimation may be increased when the acoustic-scattering characteristics of the fish are known, including their expected variability and uncertainty. The modelling approach is valuable during the process of interpreting multi-frequency echograms. This paper attempts to improve the understanding of sound backscattering

Natalia Gorska; E ONA; Rolf Korneliussen

2005-01-01

428

Fabrication and microstructure of directionally solidified SrCe 1 ? x Y x O 3 ? ? ( x = 0.1, 0.2) high temperature proton conductors  

Microsoft Academic Search

SrCe1?xYxO3?? (x=0.1, 0.2) high temperature proton conductors (HTPC) have been fabricated by directional solidification using a laser-heated float zone (LHFZ) method. The resulting microstructures have been studied using scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD). The LHFZ method produces a cellular microstructure consisting of crystalline cells embedded in an amorphous matrix,

J. Ramírez-Rico; M. J. López-Robledo; A. R. de Arellano-López; J. Martínez-Fernández; A. Sayir

2006-01-01

429

Microstructure, tensile, and creep behavior of O+ BCC Ti 2 AlNb alloys processed using induction-float-zone melting  

Microsoft Academic Search

The microstructure, tensile, and tensile–creep behavior were studied for orthorhombic (O) plus body-centered cubic (BCC) Ti–22Al–24Nb and Ti–26Al–27Nb (at.%) alloys processed using induction-float-zone melting (IFZM). Microstructure studies were performed using scanning and transmission electron microscopy (SEM and TEM), automated electron back-scattered diffraction (EBSD), and X-ray diffraction (XRD). Upon solidification, the BCC phase evolved with [100] oriented nearly parallel to the

C. J Boehlert; J. F Bingert

2001-01-01

430

EBSD investigation of the effect of strain path changes on the microstructure and texture of duplex stainless steel during hot deformation  

NASA Astrophysics Data System (ADS)

The effect of strain path changes on the microstructure/crystallographic texture characteristics was studied in a 22Cr-6Ni-3Mo duplex stainless steel subjected to several deformation regimes comprising forward and reverse torsion, performed at a temperature of 1000 °C using a strain rate of 1 s-1. A high-resolution EBSD technique, utilising an FEI Sirion FEG SEM in conjunction with a HKL Technology EBSD attachment, was successfully implemented for precise phase and substructural characterisation of the above steel. The austenite/ferrite ratio as well as the crystallographic texture, subgrain size and misorientation angles corresponding to each phase were determined over large sample areas. The results indicated that the austenite and ferrite phases, present in approximately equal volume fractions, softened via dynamic recovery and extended dynamic recovery, respectively. The phase ratio appeared to remain stable during straining. There seemed to be generally more strain partitioned to the ferrite compared to the austenite. Twin relationships in the austenite appeared partly restored after the full strain reversal. The austenite crystallographic texture displayed a tendency to revert back to the original texture after the strain reversal whereas the ferrite texture evolution appeared more complex. The obtained subgrain characteristics indicated that the reversed torsion might have caused some dissolution (and possible re-formation) of subboundaries in both phases. Nevertheless, the effect of strain path changes on the substructure characteristics generally appeared relatively moderate.

Cizek, P.; Wynne, B. P.; Rainforth, W. M.

2006-02-01

431

Crystalline characterization by Rutherford backscattering spectrometry and electron channelling of in situ grown YBa2Cu3O7 thin films deposited on (100) MgO by d.c. sputtering or laser ablation  

Microsoft Academic Search

YBa2Cu3O7 (YBCO) superconducting thin films have been grown in situ on single-crystal (100) MgO substrates by single target d.c. sputtering or laser ablation. The films were highly textured, with full c-axis orientation, as shown by standard Theta-2Theta X-ray diffractometry. The inplane structure of the films was characterized by reflection high energy electron diffraction (RHEED), oscillating single-crystal photographs, Rutherford backscattering spectrometry

M. Kechouane; H. L'Haridon; M. Salvi; P. N. Favennec; M. Gauneau; M. Guilloux-Viry; M. G. Karkut; C. Thivet; A. Perrin

1993-01-01

432

Central diffraction at ALICE  

NASA Astrophysics Data System (ADS)

The ALICE experiment is shown to be well suited for studies of exclusive final states from central diffractive reactions. The gluon-rich environment of the central system allows detailed QCD studies and searches for exotic meson states, such as glueballs, hybrids and new charmonium-like states. It would also provide a good testing ground for detailed studies of heavy quarkonia. Due to its central barrel performance, ALICE can accurately measure the low-mass central systems with good purity. The efficiency of the Forward Multiplicity Detector (FMD) and the Forward Shower Counter (FSC) system for detecting rapidity gaps is shown to be adequate for the proposed studies. With this detector arrangement, valuable new data can be obtained by tagging central diffractive processes.

Lämsä, J. W.; Orava, R.

2011-02-01

433

Interactive Tutorial About Diffraction  

NSDL National Science Digital Library

The Interactive Tutorial About Diffraction is a joint effort by professors from Michigan State University, the University of Wuerzburg, and Ludwig-Maximilians University at Munich. A multitude of examples are used to present atom scattering, crystal structure, convolution theorem, Fourier transformations of crystal phase, and other topics. The interactive examples are simulations, using software developed by the authors, where students can input the number of atoms or atom type, etc. and view results as .gif images.

2007-12-27

434

Interactive Tutorial About Diffraction  

NSDL National Science Digital Library

The Interactive Tutorial About Diffraction is a joint effort by professors from Michigan State University, the University of Wuerzburg, and Ludwig-Maximilians University at Munich. A multitude of examples are used to present atom scattering, crystal structure, convolution theorem, Fourier transformations of crystal phase, and other topics. The interactive examples are simulations, using software developed by the authors, where students can input the number of atoms or atom type, etc. and view results as .gif images.

435

SINGLE CRYSTAL NEUTRON DIFFRACTION.  

SciTech Connect

Single-crystal neutron diffraction measures the elastic Bragg reflection intensities from crystals of a material, the structure of which is the subject of investigation. A single crystal is placed in a beam of neutrons produced at a nuclear reactor or at a proton accelerator-based spallation source. Single-crystal diffraction measurements are commonly made at thermal neutron beam energies, which correspond to neutron wavelengths in the neighborhood of 1 Angstrom. For high-resolution studies requiring shorter wavelengths (ca. 0.3-0.8 Angstroms), a pulsed spallation source or a high-temperature moderator (a ''hot source'') at a reactor may be used. When complex structures with large unit-cell repeats are under investigation, as is the case in structural biology, a cryogenic-temperature moderator (a ''cold source'') may be employed to obtain longer neutron wavelengths (ca. 4-10 Angstroms). A single-crystal neutron diffraction analysis will determine the crystal structure of the material, typically including its unit cell and space group, the positions of the atomic nuclei and their mean-square displacements, and relevant site occupancies. Because the neutron possesses a magnetic moment, the magnetic structure of the material can be determined as well, from the magnetic contribution to the Bragg intensities. This latter aspect falls beyond the scope of the present unit; for information on magnetic scattering of neutrons see Unit 14.3. Instruments for single-crystal diffraction (single-crystal diffractometers or SCDs) are generally available at the major neutron scattering center facilities. Beam time on many of these instruments is available through a proposal mechanism. A listing of neutron SCD instruments and their corresponding facility contacts is included in an appendix accompanying this unit.

KOETZLE,T.F.

2001-03-13

436

Duality and Diffraction Dissociation  

Microsoft Academic Search

We discuss diffraction dissociation in the context of a dual model. We show how direct-channel resonances in the Pomeranchukon-particle amplitude build the Pomeranchukon in the crossed channel. A result of the enforcement of the Harari-Freund conjecture for particle-particle amplitudes is that the Pomeranchukon-Pomeranchukon-Reggeon coupling is small. The model is tested phenomenologically by the analysis of pi-p-->pi-p(pi+pi- ) of Lipes, Robertson,

M. B. Einhorn; M. B. Green; M. A. Virasoro

1973-01-01

437

Backscattering channel-cut high-resolution monochromator for inelastic x-ray scattering  

NASA Astrophysics Data System (ADS)

We report on a design and on some experimental results for the performance of a new high energy resolution monochromator. It is a large channel-cut Si crystal with a 197 mm separation between the two faces designed to operate in a near-backscattering regime. The device was tested as a second monochromator on Sector 3 of the Synchrotron Radiation Instrumentation Collaborative Access Team at the Advanced Photon Source using the Si(777) reflection at a photon energy of 13.84 keV. The same monochromator can be used for other energies with reflections of the type (hhh). Special care has been taken to equalize the temperature of the two faces by employing a Peltier heat pump. A Si(111) double-crystal pre-monochromator designed to withstand the high heat load of the undulator radiation was used upstream on the beamline. The measured throughput efficiency of the Si(777) channel-cut monochromator was less than ideal by a factor of 1.9. Dynamical diffraction theory was used to calculate the throughput of an ideally perfect crystal.

Kushnir, Vladimir I.; Abbamonte, Peter M.; Macrander, Albert T.; Schwoerer-Boehning, Markus

1997-12-01

438

Back-scattering channel-cut high-resolution monochromator for inelastic x-ray scattering  

SciTech Connect

We report on a design and on some experimental results for the performance of a new high energy resolution monochromator. It is a large channel-cut Si crystal with a 197 mm separation between the two faces designed to operate in a near-backscattering regime. The device was tested as a second monochromator on Sector 3 of the Synchrotron Radiation Instrumentation Collaborative Access Team (SRI-CAT) at the Advanced Photon Source using the Si(777) reflection at a photon energy of 13.84 keV. The same monochromator can be used for other energies with reflections of the type (hhh). Special care has been taken to equalize the temperature of the two faces by employing a Peltier heat pump. A Si(111) double-crystal pre-monochromator designed to withstand the high heat load of the undulator radiation was used upstream on the beamline. The measured throughput efficiency of the Si(777) channel-cut monochromator was less ideal by a factor of 1.9. Dynamical diffraction theory was used to calculate the throughput of an ideally perfect crystal.

Kushnir, V.I.; Abbamonte, P.M.; Macrander, A.T.; Schwoerer-Boehning, M.

1997-08-01

439

The influence of backscatter material on Tc and line source responses  

Microsoft Academic Search

SPECT projections are contaminated by scatter, resulting in reduced image contrast and quantitative errors. When tissue is present behind the source, some of the detected photons backscatter via this tissue. Particularly in dual-isotope SPECT and in combined emission-transmission SPECT, backscatter constitutes a major part of the down-scatter contamination in lower-energy windows. In this paper, the effects of backscatter material were

Freek J Beekman; Michael Ljungberg; Peter P van Rijk

1999-01-01

440

Characterization of polycrystals with elongated duplex microstructure by inversion of ultrasonic backscattering data  

SciTech Connect

In this letter a simple analytical ultrasonic backscattering model is proposed for determination of characteristic microstructural scales in polycrystalline materials with elongated grains. The inversion methodology for microstructural parameters is based on backscattering coefficient ratios measured in different propagation directions. The ultrasonic backscattering measurements were performed on a Ti alloy sample with a duplex microstructure and the model was applied to experimental data inversion to size the material microtexture.

Lobkis, O. I.; Rokhlin, S. I. [Department of Materials Science and Engineering, Edison Joining Technology Center, Ohio State University, 1248 Arthur E. Adams Dr., Columbus, Ohio 43221 (United States)

2010-04-19

441

Standoff detection of hidden objects using backscattered ultra-intense laser-produced x-rays  

NASA Astrophysics Data System (ADS)

Ultra-intense laser-produced sub-ps X-ray pulses can detect backscattered signals from objects hidden in aluminium containers. Coincident measurements using primary X-rays enable differentiation among acrylic, copper, and lead blocks inside the container. Backscattering reveals the shapes of the objects, while their material composition can be identified from the modification methods of the energy spectra of backscattered X-ray beams. This achievement is an important step toward more effective homeland security.

Kuwabara, H.; Mori, Y.; Kitagawa, Y.

2013-08-01

442

Atmospheric backscatter vertical profiles at 9.2 and 10.6 microm: a comparative study.  

PubMed

We report a series of atmospheric aerosol backscatter measurements at two widely spaced CO(2) laser wavelengths: 9.25 and 10.6 microm. Comparisons are made beween backscatter coefficient profiles at these two wavelengths up to 20-km altitude. Measurements such as those reported here can be used to assess the feasibility of coherent CO(2) lidar for wind measurements, and they also provide a partial test of backscatter model predictions. PMID:20539673

Ancellet, G M; Menzies, R T; Tratt, D M

1988-12-01

443

Impact and modeling of topographic effects on P-band SAR backscatter from boreal forests  

Microsoft Academic Search

P-band SAR backscatter has been proven to be useful for forest biomass prediction. However, there is a need for further studies on effects of topography on P-band backscatter. In this paper, two prediction models for backscatter are evaluated, one using only biomass as predictor and one which also includes topographic corrections. Data from the BioSAR 2007 and BioSAR 2008 campaigns

G. Sandberg; M. J. Soja; L. M. H. Ulander

2011-01-01

444

Measurements of Green Laser-Beam Propagation and Backscatter in Long-Scale Length Plasmas  

Microsoft Academic Search

Summary form only given. We have implemented a complete set of optical diagnostics at the Omega laser to measure propagation and backscatter of a green (527 nm) high intensity laser beam (1015 W\\/cm2) in large-scale length, laser produced plasmas. The diagnostics include a transmitted beam diagnostic (TBD), a full aperture backscatter station (FABS) as well as a near backscatter imager

C. Niemann; L. Divol; D. Froula; S. Glenzer; G. Gregori; R. Kirkwood; A. Mackinnon; N. Meezan; J. Moody; C. Sorce; R. Bahr; W. Seka

2005-01-01

445

A Bayesian approach to seafloor classification using multi-beam echo-sounder backscatter data  

Microsoft Academic Search

Seafloor classification using acoustic remote sensing techniques is an attractive approach due to its high-coverage capabilities and limited costs. The multi-beam echo-sounder (MBES) system provides high-resolution bathymetry and backscatter information with 100% coverage. In this paper, we present a seafloor classification method that employs the MBES backscatter data. The method uses the averaged backscatter data per beam. It, therefore, is

Dick G. Simons; Mirjam Snellen

2009-01-01

446

Diffraction from materials  

SciTech Connect

This is a completely revised second edition and is intended as a text in diffraction. The book presents elementary topics on scattering and crystallography and expands on concepts in later chapters which focus on defects in solids, scattering from perfect solids, and crystal structure determination. The first half of the book may be used as an introductory text for juniors or seniors in college, while the second half is suitable for a graduate-level course or for use as a monograph. The new edition simplifies the introduction to crystallography, introduces concepts required by the advent of synchrotron radiation and pulsed reaction sources, and updates the subject matter dealing with defects in solids.

Schwartz, L.H.; Cohen, J.B.

1987-01-01

447

Diffraction Between Wax Blocks  

NSDL National Science Digital Library

In this optics activity, learners explore diffraction by adding wax blocks to a ripple tank. The wedge-shaped blocks act as obstacles that the wave must bend around. Learners will observe this phenomenon as well as the semicircular waves that emerge from the narrow opening between the blocks. Learners experiment by changing the size of the opening and seeing what effect it has on the emerging waves. This activity is recommended as a follow-up to "The Ripple Tank" activity and can be supplemented by the "Interference in a Ripple Tank" activity (see related resources).

Cobb, Vicki; Cobb, Josh

2008-01-01

448

Diffractive Alvarez lens  

SciTech Connect

A diffractive Alvarez lens is demonstrated that consists of two separate phase plates, each having complementary 16-level surface-relief profiles that contain cubic phase delays. Translation of these two components in the plane of the phase plates is shown to produce a variable astigmatic focus. Both spherical and cylindrical phase profiles are demonstrated with good accuracy, and the discrete surface-relief features are shown to cause less than {lambda}/10 wave-front aberration in the transmitted wave front over a 40 mmx80 mm region. (c) 2000 Optical Society of America.

Barton, Ian M.; Dixit, Sham N.; Summers, Leslie J.; Thompson, Charles A.; Avicola, Kenneth; Wilhelmsen, Julia

2000-01-01

449

Excitation of phonons in medium-energy electron diffraction  

NASA Astrophysics Data System (ADS)

The ``elastic'' backscattering of electrons from crystalline surfaces presents two regimes: a low-energy regime, in which the characteristic low-energy electron diffraction (LEED) pattern is observed, and a medium-energy regime, in which the diffraction pattern is similar to those observed in x-ray photoemission diffraction (XPD) and Auger electron diffraction (AED) experiments. We present a model for the electron scattering which, including the vibrational degrees of freedom of the crystal, contains both regimes and explains the passage from one regime to the other. Our model is based on a separation of the electron and atomic motions (adiabatic approximation) and on a cluster-type formulation of the multiple scattering of the electron. The inelastic scattering events (excitation and/or absorption of phonons) are treated as coherent processes and no break of the phase relation between the incident and the exit paths of the electron is assumed. The LEED and the medium-energy electron diffraction regimes appear naturally in this model as the limit cases of completely elastic scattering and of inelastic scattering with excitation and/or absorption of multiple phonons. Intensity patterns calculated with this model are in very good agreement with recent experiments of electron scattering on Cu(001) at low and medium energies. We show that there is a correspondence between the type of intensity pattern and the mean number of phonons excited and/or absorbed during the scattering: a LEED-like pattern is observed when this mean number is less than 2, LEED-like and XPD/AED-like features coexist when this number is 3-4, and a XPD/AED-like pattern is observed when this number is greater than 5-6.

Alvarez, M. A. Vicente; Ascolani, H.; Zampieri, G.

1996-03-01

450

Breast tumor characterization based on ultrawideband microwave backscatter.  

PubMed

Characterization of architectural tissue features such as the shape, margin, and size of a suspicious lesion is commonly performed in conjunction with medical imaging to provide clues about the nature of an abnormality. In this paper, we numerically investigate the feasibility of using multichannel microwave backscatter in the 1-11 GHz band to classify the salient features of a dielectric target. We consider targets with three shape characteristics: smooth, microlobulated, and spiculated; and four size categories ranging from 0.5 to 2 cm in diameter. The numerical target constructs are based on Gaussian random spheres allowing for moderate shape irregularities. We perform shape and size classification for a range of signal-to-noise ratios (SNRs) to demonstrate the potential for tumor characterization based on ultrawideband (UWB) microwave backscatter. We approach classification with two basis selection methods from the literature: local discriminant bases and principal component analysis. Using these methods, we construct linear classifiers where a subset of the bases expansion vectors are the input features and we evaluate the average rate of correct classification as a performance measure. We demonstrate that for 10 dB SNR, the target size is very reliably classified with over 97% accuracy averaged over 360 targets; target shape is classified with over 70% accuracy. The relationship between the SNR of the test data and classifier performance is also explored. The results of this study are very encouraging and suggest that both shape and size characteristics of a dielectric target can be classified directly from its UWB backscatter. Hence, characterization can easily be performed in conjunction with UWB radar-based breast cancer detection without requiring any special hardware or additional data collection. PMID:18232367

Davis, Shakti K; Van Veen, Barry D; Hagness, Susan C; Kelcz, Frederick

2008-01-01

451

Coherent Backscatter Opposition Effect from Scratches on Solid Surfaces  

NASA Astrophysics Data System (ADS)

Shepard and Arvidson [1] discovered that the solid surfaces of rocks exhibit an opposition effect. We have measured the phase curve of a natural surface of a piece of solid basalt between 0.05 and 5 degrees in circularly polarized light using the JPL long arm goniometer and confirmed that it has an opposition effect. The circular polarization ratio (CPR) increased with decreasing phase angle, consistent with a coherent backscatter opposition effect (CBOE) Recent laboratory investigations of the CBOE in planetary regolith analogs [2,3,4] have revealed that the width of the peak is remarkably insensitive to particle size, in strong contrast to theoretical expectations. We have hypothesized that one of the reasons for this might be that multiple scattering between irregularities, such as scratches, on the surfaces of a particle could cause coherent backscatter, in addition to scattering between particles. To test this hypothesis we ground the surface of a piece of plate glass with 5 micrometer abrasive and measured its phase curve. As the phase angle decreases, the intensity increases and the CPR decreases, consistent with specular reflection. However, near zero phase there is a nonlinear rise about 2 degrees wide superimposed on the linear specular peak accompanied by an increase in CPR, showing that coherent backscatter is occuring. A piece of commercial diffusing glass exhibited the same phenomena. These results support our hypothesis and also provide a possible explanation for the observations of opposition effects from the solid surfaces of rocks. This research was supported by a grant from NASA's PGG Program References cited: [1] Shepard and Arvidson, Icarus, 141, 172-178 (1999). [2] Nelson et al, Icarus, 147, 545-558 (2000). [3] Nelson et al, Planet. Space Sci., 50, 849-856 (2002). [4] Piatek et al, Abstract, DPS Conference (2003).

Hapke, B. W.; Piatek, J. L.; Nelson, R. M.; Smythe, W. D.; Hale, A. S.

2003-05-01

452

Computation of clear-air radar backscatter from numerical simulations of turbulence: 2. Backscatter moments throughout the lifecycle of a Kelvin-Helmholtz instability  

NASA Astrophysics Data System (ADS)

Franke et al. (2011) describe a numerical simulation of the instability and turbulent breakdown of Kelvin-Helmholtz (KH) billows at a high Reynolds number, numerical assessment of radar backscatter, and accuracies of inferred Doppler spectral moments for one test volume. Those results suggest a potential for significant measurement biases for radars that obtain backscatter from refractive index fluctuations. We present in this paper the morphology of computed radar moments throughout the KH instability lifecycle for two radar configurations in order to reveal the evolving character of radar backscatter and compare the radar velocity estimates with true velocities throughout the evolution, and to provide guidance, and cautions, for the interpretation of these dynamics in observational data. Results reveal strong variations in backscatter moments and character, and dependence on radar measurement parameters, that should be beneficial in the interpretation of such measurements in the atmosphere. Backscatter power predictions agree reasonably with observations of such events and their temporal evolutions. Our results also reveal a potential for significant measurement or sensitivity biases, some of which were predicted previously. Examples include a lack of significant backscatter power in well-mixed billow cores, suggesting possibly weak turbulence where in fact it may be strongest, maximum backscatter power in the billow exteriors, where refractive index fluctuations are large but turbulence is weak, underestimated vertical velocities within the KH billows at early times, and inferred significant vertical velocities where true vertical velocities are near zero at late stages of restratification, especially in the edge regions of the turbulence layer.

Fritts, David C.; Franke, Patricia M.; Wan, Kam; Lund, Tom; Werne, Joe

2011-06-01

453

Backscatter based projectile trajectory measurement under daylight conditions  

NASA Astrophysics Data System (ADS)

In recent years the development of a system to detect and measure the trajectory of a projectile by its backscatter using a laser light source has been presented. The used principle of the described system requires a dark environment as given at night. In the current paper techniques will be discussed to enable above projectile trajectory measurements under daylight conditions. With this a new system setup under given hardware limitations is derived and described. Experimental results for measurements under daylight conditions will be presented.

Chalupka, Uwe; Rothe, Hendrik

2012-10-01

454

Conservation of energy in coherent backscattering of light  

NASA Astrophysics Data System (ADS)

Although conservation of energy is fundamental in physics, its principles seem to be violated in the field of wave propagation in turbid media by the energy enhancement of the coherent backscattering cone. In this letter we present experimental data which show that the energy enhancement of the cone is balanced by an energy cutback at all scattering angles. Moreover, we give a theoretical description which is in good agreement with these data. The additional terms needed to enforce energy conservation in this description result from an interference effect between incident and multiply scattered waves, which is reminiscent of the optical theorem in single scattering.

Fiebig, S.; Aegerter, C. M.; Bührer, W.; Störzer, M.; Akkermans, E.; Montambaux, G.; Maret, G.

2008-03-01

455

HAB detection based on absorption and backscattering properties of phytoplankton  

NASA Astrophysics Data System (ADS)

The coastal area of East China Sea (ECS) suffers from the harmful algal blooms (HAB) frequently every year in the warm season. The most common causative phytoplankton algal species of HAB in the ECS in recent years are Prorocentrum donghaiense (dinoflagellates), Karenia mikimotoi (dinoflagellates which could produce hemolytic and ichthyotoxins) and Skeletonema costatum (diatom). The discrimination between the dinoflagellates and diatom HAB through ocean color remote sensing approach can add the knowledge of HAB events in ECS and help to the precaution. A series of in-situ measurement consisted of absorption coefficient, total scattering and particulate backscattering coefficient was conducted in the southern coast of Zhejiang Province in May 2009, and the estuary of Changjiang River in August 2009 and December 2010, which encountered two HAB events and a moderate bloom. The Inherent Optical Properties (IOPs) of the bloom waters have significant difference between phytoplankton species in absorption and backscattering properties. The chlorophyll a specific absorption coefficient (a*phy(?)) for the bloom patches (chlorophyll a concentration >6mg m-3) differ greatly from the adjacent normal seawater, with the a*phy(?) of bloom water lower than 0.03 m2 mg-1 while the a*phy(?) of the adjacent normal sea