Science.gov

Sample records for higher spatial resolution

  1. Prospects for higher spatial resolution quantitative X-ray analysis using transition element L-lines

    NASA Astrophysics Data System (ADS)

    Statham, P.; Holland, J.

    2014-03-01

    Lowering electron beam kV reduces electron scattering and improves spatial resolution of X-ray analysis. However, a previous round robin analysis of steels at 5 - 6 kV using Lα-lines for the first row transition elements gave poor accuracies. Our experiments on SS63 steel using Lα-lines show similar biases in Cr and Ni that cannot be corrected with changes to self-absorption coefficients or carbon coating. The inaccuracy may be caused by different probabilities for emission and anomalous self-absorption for the La-line between specimen and pure element standard. Analysis using Ll(L3-M1)-lines gives more accurate results for SS63 plausibly because the M1-shell is not so vulnerable to the atomic environment as the unfilled M4,5-shell. However, Ll-intensities are very weak and WDS analysis may be impractical for some applications. EDS with large area SDD offers orders of magnitude faster analysis and achieves similar results to WDS analysis with Lα-lines but poorer energy resolution precludes the use of Ll-lines in most situations. EDS analysis of K-lines at low overvoltage is an alternative strategy for improving spatial resolution that could give higher accuracy. The trade-off between low kV versus low overvoltage is explored in terms of sensitivity for element detection for different elements.

  2. Flexible hydrological modeling - Disaggregation from lumped catchment scale to higher spatial resolutions

    NASA Astrophysics Data System (ADS)

    Tran, Quoc Quan; Willems, Patrick; Pannemans, Bart; Blanckaert, Joris; Pereira, Fernando; Nossent, Jiri; Cauwenberghs, Kris; Vansteenkiste, Thomas

    2015-04-01

    Based on an international literature review on model structures of existing rainfall-runoff and hydrological models, a generalized model structure is proposed. It consists of different types of meteorological components, storage components, splitting components and routing components. They can be spatially organized in a lumped way, or on a grid, spatially interlinked by source-to-sink or grid-to-grid (cell-to-cell) routing. The grid size of the model can be chosen depending on the application. The user can select/change the spatial resolution depending on the needs and/or the evaluation of the accuracy of the model results, or use different spatial resolutions in parallel for different applications. Major research questions addressed during the study are: How can we assure consistent results of the model at any spatial detail? How can we avoid strong or sudden changes in model parameters and corresponding simulation results, when one moves from one level of spatial detail to another? How can we limit the problem of overparameterization/equifinality when we move from the lumped model to the spatially distributed model? The proposed approach is a step-wise one, where first the lumped conceptual model is calibrated using a systematic, data-based approach, followed by a disaggregation step where the lumped parameters are disaggregated based on spatial catchment characteristics (topography, land use, soil characteristics). In this way, disaggregation can be done down to any spatial scale, and consistently among scales. Only few additional calibration parameters are introduced to scale the absolute spatial differences in model parameters, but keeping the relative differences as obtained from the spatial catchment characteristics. After calibration of the spatial model, the accuracies of the lumped and spatial models were compared for peak, low and cumulative runoff total and sub-flows (at downstream and internal gauging stations). For the distributed models, additional

  3. Particle detector spatial resolution

    DOEpatents

    Perez-Mendez, Victor

    1992-01-01

    Method and apparatus for producing separated columns of scintillation layer material, for use in detection of X-rays and high energy charged particles with improved spatial resolution. A pattern of ridges or projections is formed on one surface of a substrate layer or in a thin polyimide layer, and the scintillation layer is grown at controlled temperature and growth rate on the ridge-containing material. The scintillation material preferentially forms cylinders or columns, separated by gaps conforming to the pattern of ridges, and these columns direct most of the light produced in the scintillation layer along individual columns for subsequent detection in a photodiode layer. The gaps may be filled with a light-absorbing material to further enhance the spatial resolution of the particle detector.

  4. Particle detector spatial resolution

    DOEpatents

    Perez-Mendez, V.

    1992-12-15

    Method and apparatus for producing separated columns of scintillation layer material, for use in detection of X-rays and high energy charged particles with improved spatial resolution is disclosed. A pattern of ridges or projections is formed on one surface of a substrate layer or in a thin polyimide layer, and the scintillation layer is grown at controlled temperature and growth rate on the ridge-containing material. The scintillation material preferentially forms cylinders or columns, separated by gaps conforming to the pattern of ridges, and these columns direct most of the light produced in the scintillation layer along individual columns for subsequent detection in a photodiode layer. The gaps may be filled with a light-absorbing material to further enhance the spatial resolution of the particle detector. 12 figs.

  5. Development and assessment of a higher-spatial-resolution (4.4 km) MISR aerosol optical depth product using AERONET-DRAGON data

    NASA Astrophysics Data System (ADS)

    Garay, Michael J.; Kalashnikova, Olga V.; Bull, Michael A.

    2017-04-01

    Since early 2000, the Multi-angle Imaging SpectroRadiometer (MISR) instrument on NASA's Terra satellite has been acquiring data that have been used to produce aerosol optical depth (AOD) and particle property retrievals at 17.6 km spatial resolution. Capitalizing on the capabilities provided by multi-angle viewing, the current operational (Version 22) MISR algorithm performs well, with about 75 % of MISR AOD retrievals globally falling within 0.05 or 20 % × AOD of paired validation data from the ground-based Aerosol Robotic Network (AERONET). This paper describes the development and assessment of a prototype version of a higher-spatial-resolution 4.4 km MISR aerosol optical depth product compared against multiple AERONET Distributed Regional Aerosol Gridded Observations Network (DRAGON) deployments around the globe. In comparisons with AERONET-DRAGON AODs, the 4.4 km resolution retrievals show improved correlation (r = 0. 9595), smaller RMSE (0.0768), reduced bias (-0.0208), and a larger fraction within the expected error envelope (80.92 %) relative to the Version 22 MISR retrievals.

  6. How Attention Affects Spatial Resolution

    PubMed Central

    Carrasco, Marisa; Barbot, Antoine

    2015-01-01

    We summarize and discuss a series of psychophysical studies on the effects of spatial covert attention on spatial resolution, our ability to discriminate fine patterns. Heightened resolution is beneficial in most, but not all, visual tasks. We show how endogenous attention (voluntary, goal driven) and exogenous attention (involuntary, stimulus driven) affect performance on a variety of tasks mediated by spatial resolution, such as visual search, crowding, acuity, and texture segmentation. Exogenous attention is an automatic mechanism that increases resolution regardless of whether it helps or hinders performance. In contrast, endogenous attention flexibly adjusts resolution to optimize performance according to task demands. We illustrate how psychophysical studies can reveal the underlying mechanisms of these effects and allow us to draw linking hypotheses with known neurophysiological effects of attention. PMID:25948640

  7. High Spatial Resolution Commercial Satellite Imaging Product Characterization

    NASA Technical Reports Server (NTRS)

    Ryan, Robert E.; Pagnutti, Mary; Blonski, Slawomir; Ross, Kenton W.; Stnaley, Thomas

    2005-01-01

    NASA Stennis Space Center's Remote Sensing group has been characterizing privately owned high spatial resolution multispectral imaging systems, such as IKONOS, QuickBird, and OrbView-3. Natural and man made targets were used for spatial resolution, radiometric, and geopositional characterizations. Higher spatial resolution also presents significant adjacency effects for accurate reliable radiometry.

  8. Spatial resolution and cloud optical thickness retrievals

    NASA Technical Reports Server (NTRS)

    Feind, Rand E.; Christopher, Sundar A.; Welch, Ronald M.

    1992-01-01

    The impact of sensor spatial resolution and accurate cloud pixel identification on cloud property retrievals was investigated. Twelve fair weather cumulus (FWC) scenes of high spectral and spatial resolution Airborne Visible and Infrared Imaging Spectrometer (AVIRIS) data are analyzed. A variation of the 3-band ratio technique of Gao and Goetz is used to discriminate clouds from the background, and then a discrete ordinate radiative transfer model is used to obtain optical thickness of cloudy regions for each scene. To study the effect of spatial resolution upon retrieved optical thickness, the 20 m AVIRIS data was spatially degraded to spatial resolutions ranging from 40 to 960 m. Cloud area, scene average optical thickness, and distribution of retrieved optical thickness are determined at each spatial resolution. Finally, a comparison between the 3-band ratio technique and monospectral reflectance thresholding, using 20 m spatial resolution data, is presented.

  9. Effects of spatial resolution ratio in image fusion

    USGS Publications Warehouse

    Ling, Y.; Ehlers, M.; Usery, E.L.; Madden, M.

    2008-01-01

    In image fusion, the spatial resolution ratio can be defined as the ratio between the spatial resolution of the high-resolution panchromatic image and that of the low-resolution multispectral image. This paper attempts to assess the effects of the spatial resolution ratio of the input images on the quality of the fused image. Experimental results indicate that a spatial resolution ratio of 1:10 or higher is desired for optimal multisensor image fusion provided the input panchromatic image is not downsampled to a coarser resolution. Due to the synthetic pixels generated from resampling, the quality of the fused image decreases as the spatial resolution ratio decreases (e.g. from 1:10 to 1:30). However, even with a spatial resolution ratio as small as 1:30, the quality of the fused image is still better than the original multispectral image alone for feature interpretation. In cases where the spatial resolution ratio is too small (e.g. 1:30), to obtain better spectral integrity of the fused image, one may downsample the input high-resolution panchromatic image to a slightly lower resolution before fusing it with the multispectral image.

  10. SPATIAL AND SPECTRAL RESOLUTION IN GEOBOTANY.

    USGS Publications Warehouse

    Milton, Nancy M.; Mouat, D.A.

    1984-01-01

    Remotely sensed data are now available from a wide variety of instruments, each data set having a particular spectral and spatial resolution. The changes in vegetation associated with changes in lithology or the presence of mineral deposits can also occur at different scales. The task of geobotanical remote sensing is to choose or adapt the remotely sensed data to the appropriate geobotanical technique to solve the geological problem of interest. Examples are given of a number of applications of data sets of different spectral and spatial resolution. The relative importance of spectral and spatial resolution is discussed.

  11. Fundamental Limits of Spatial Resolution in PET

    PubMed Central

    Moses, William W.

    2010-01-01

    The fundamental limits of spatial resolution in positron emission tomography (PET) have been understood for many years. The physical size of the detector element usually plays the dominant role in determining resolution, but the combined contributions from acollinearity, positron range, penetration into the detector ring, and decoding errors in the detector modules often combine to be of similar size. In addition, the sampling geometry and statistical noise further degrade the effective resolution. This paper describes quantitatively describes these effects, discusses potential methods for reducing the magnitude of these effects, and computes the ultimately achievable spatial resolution for clinical and pre-clinical PET cameras. PMID:21804677

  12. Spatial resolution improvement of the scanning detector

    NASA Astrophysics Data System (ADS)

    Katoh, Yasuto; Ito, Yoshihiro; Tomonura, Nobuhisa; Tomioka, Satoshi; Enoto, Takeaki

    2001-04-01

    In the scanning detector we propose the new system for improving spatial resolution by making sensitivity distribution of a detecting element vary. This can be simply done by only adding the filter with sensitivity distribution in front of a detecting element without requiring the higher density of equipment. In our laboratory, the plasma electron density distribution measurement by the holographic interferometry in far-infrared region has been proceeded. As one of the infrared detection material, we chose HgCdTe, and it was used as a scanning detecting element. As a verification of this system, we added the infrared filter in the front of HgCdTe, and measured the spatial resolution using a knife edge. For the method for calculating Modulation Transfer Function (MTF) from Edge Response Function (ERF), we also propose the new technique that we name the virtual test chart method. In this technique, we simulate the response corresponded to periodic bar patterns from ERF, and calculate the contrast ratio from this response. From the result of measurement that added the infrared ray filter, the validity of this system was shown. By the simulation and the experiment, the optimum sensitivity distribution was obtained in this system.

  13. Scanning SQUID susceptometers with sub-micron spatial resolution

    SciTech Connect

    Kirtley, John R. Rosenberg, Aaron J.; Palmstrom, Johanna C.; Holland, Connor M.; Moler, Kathryn A.; Paulius, Lisa; Spanton, Eric M.; Schiessl, Daniel; Jermain, Colin L.; Gibbons, Jonathan; Fung, Y.-K.K.; Gibson, Gerald W.; Huber, Martin E.; Ralph, Daniel C.; Ketchen, Mark B.

    2016-09-15

    Superconducting QUantum Interference Device (SQUID) microscopy has excellent magnetic field sensitivity, but suffers from modest spatial resolution when compared with other scanning probes. This spatial resolution is determined by both the size of the field sensitive area and the spacing between this area and the sample surface. In this paper we describe scanning SQUID susceptometers that achieve sub-micron spatial resolution while retaining a white noise floor flux sensitivity of ≈2μΦ{sub 0}/Hz{sup 1/2}. This high spatial resolution is accomplished by deep sub-micron feature sizes, well shielded pickup loops fabricated using a planarized process, and a deep etch step that minimizes the spacing between the sample surface and the SQUID pickup loop. We describe the design, modeling, fabrication, and testing of these sensors. Although sub-micron spatial resolution has been achieved previously in scanning SQUID sensors, our sensors not only achieve high spatial resolution but also have integrated modulation coils for flux feedback, integrated field coils for susceptibility measurements, and batch processing. They are therefore a generally applicable tool for imaging sample magnetization, currents, and susceptibilities with higher spatial resolution than previous susceptometers.

  14. Scanning SQUID susceptometers with sub-micron spatial resolution

    NASA Astrophysics Data System (ADS)

    Kirtley, John R.; Paulius, Lisa; Rosenberg, Aaron J.; Palmstrom, Johanna C.; Holland, Connor M.; Spanton, Eric M.; Schiessl, Daniel; Jermain, Colin L.; Gibbons, Jonathan; Fung, Y.-K.-K.; Huber, Martin E.; Ralph, Daniel C.; Ketchen, Mark B.; Gibson, Gerald W.; Moler, Kathryn A.

    2016-09-01

    Superconducting QUantum Interference Device (SQUID) microscopy has excellent magnetic field sensitivity, but suffers from modest spatial resolution when compared with other scanning probes. This spatial resolution is determined by both the size of the field sensitive area and the spacing between this area and the sample surface. In this paper we describe scanning SQUID susceptometers that achieve sub-micron spatial resolution while retaining a white noise floor flux sensitivity of ≈2μΦ0/Hz1/2. This high spatial resolution is accomplished by deep sub-micron feature sizes, well shielded pickup loops fabricated using a planarized process, and a deep etch step that minimizes the spacing between the sample surface and the SQUID pickup loop. We describe the design, modeling, fabrication, and testing of these sensors. Although sub-micron spatial resolution has been achieved previously in scanning SQUID sensors, our sensors not only achieve high spatial resolution but also have integrated modulation coils for flux feedback, integrated field coils for susceptibility measurements, and batch processing. They are therefore a generally applicable tool for imaging sample magnetization, currents, and susceptibilities with higher spatial resolution than previous susceptometers.

  15. ROLE OF SPATIAL RESOLUTION AND SPECTRAL CONTENT IN CHANGE DETECTION.

    USGS Publications Warehouse

    Milazzo, Valerie A.

    1984-01-01

    Summary form only given, as follows. Advancements in remote sensing technology have brought improvements and sophistication to modern remote sensor systems, especially those aboard earth resources satellites. These improvements have considerbly expanded the capabilities of the newer sensor systems, particularly the capability to achieve greatly increased spatial and spectral resolution levels. The debate still lingers, however, over whether future systems should maximize spatial resolution or spectral information, or both. As yet, the high costs and large volumes of data associated with even modest incremental improvements in spatial and spectral content have precluded the design of a single system that attempts to fully optimize both. Thus, the user is faced with having to choose between those systems providing high spatial resolutions but limited spectral information and those which offer a broad range of spectral data but hold spatial resolution to a less than optimum level. In this study, the contribution of both spatial resolution and spectral content to land cover change detection is examined. Ten-meter SPOT simulation imagery is compared with multispectral images acquired by the Thematic Mapper sensor system for use in the visual interpretation and mapping of changes. Several image processing and enhancement techniques are utilized to maximize the spatial and spectral data content offered by each system. Results indicate that when using visual image interpretation techniques to detect change, higher spatial resolutions are generally preferred over increased spectral content.

  16. High Spatial Resolution Thermal Satellite Technologies

    NASA Technical Reports Server (NTRS)

    Ryan, Robert

    2003-01-01

    This document in the form of viewslides, reviews various low-cost alternatives to high spatial resolution thermal satellite technologies. There exists no follow-on to Landsat 7 or ASTER high spatial resolution thermal systems. This document reviews the results of the investigation in to the use of new technologies to create a low-cost useful alternative. Three suggested technologies are examined. 1. Conventional microbolometer pushbroom modes offers potential for low cost Landsat Data Continuity Mission (LDCM) thermal or ASTER capability with at least 60-120 ground sampling distance (GSD). 2. Backscanning could produce MultiSpectral Thermal Imager performance without cooled detectors. 3. Cooled detector could produce hyperspectral thermal class system or extremely high spatial resolution class instrument.

  17. Spatial resolution considerations for urban hydrological modelling

    NASA Astrophysics Data System (ADS)

    Krebs, G.; Kokkonen, T.; Valtanen, M.; Setälä, H.; Koivusalo, H.

    2014-05-01

    Hydrological model simulations can be applied to evaluate the performance of low impact development (LID) tools in urban areas. However, the assessment for large-scale urban areas remains a challenge due to the required high spatial resolution and limited availability of field measurements for model calibration. This study proposes a methodology to parameterize a hydrological model (SWMM) with sufficiently high spatial resolution and direct accessibility of model parameters for LID performance simulation applicable to a large-scale ungauged urban area. Based on calibrated high-resolution models for three small-scale study catchments (6-12 ha), we evaluated how constraints implied by large-scale urban modelling, such as data limitations, affect the model results. The high-resolution surface representation, resulting in subcatchments of uniform surface types, reduced the number of calibration parameters. Calibration conducted independently for all catchments yielded similar parameter values for same surface types in each study catchment. These results suggest the applicability of the parameter values calibrated for high resolution models to be regionalized to larger, ungauged urban areas. The accessibility of surface specific model parameters for LID simulation is then also retained. Conducted perturbations in spatial resolution through sewer network truncation showed that while the runoff volume was mostly unaffected by resolution perturbations, lower resolutions resulted in over-simulation of peak flows due to excessively rapid catchment response to storm events. Our results suggest that a hydrological model where parameter values are adopted from high-resolution models and that is developed based on a minimum conduit diameter of 300 mm provides good simulation performance and is applicable to large-scale urban areas with reasonable effort.

  18. Improving Nano-MRI Spatial Resolution with Phase Multiplexing

    NASA Astrophysics Data System (ADS)

    Moores, Brad; Eichler, Alex; Degen, Christian

    2015-03-01

    Magnetic resonance force microscopy (MRFM) is a scanning probe technique that allows measuring nuclear spin densities with resolution better than 10nm. Detecting such small volumes of spins (less than (10nm)3 corresponds to approximately 20,000 spins) requires long averaging of signals from statistically polarized nuclei. For instance, previous work demonstrated that imaging a single isotope (1H) of a Tobacco Mosaic Virus required averaging for 2 weeks, and therefore the chemical contrast abilities of MRFM had to be forfeited to enable higher spatial resolution. In order to reconcile the chemical selectivity of MRFM along with the proven high spatial resolution, we have developed a phase multiplexing technique capable of simultaneously acquiring spin signals from multiple isotopes and from up to six spatial locations. We have demonstrated this method using a nanowire test sample, and have achieved one-dimensional imaging resolution of less than 5 nm and subnanometer positional accuracy.

  19. Enhanced spatial resolution in vector potential photoelectron microscopy.

    PubMed

    Browning, R

    2017-08-01

    The spatial resolution of the vector potential photoelectron microscope is determined by the maximum size of the cyclotron orbits of the imaged electrons at the surface of a sample. It is straightforward to calculate the spatial resolution for any imaged electron energy given the magnetic field strength. However, in low-energy secondary photoelectron images from an aluminium-calcium metal matrix alloy, we find the apparent spatial resolution is significantly higher than expected. A possible explanation for the enhanced resolution is that the low-energy cyclotron orbits are distorted when passing from one area of work function to another and the image is dependent on the surface field distribution. © 2017 The Authors Journal of Microscopy © 2017 Royal Microscopical Society.

  20. A Very High Spatial Resolution Detector for Small Animal PET

    SciTech Connect

    Kanai Shah, M.S.

    2007-03-06

    Positron Emission Tomography (PET) is an in vivo analog of autoradiography and has the potential to become a powerful new tool in imaging biological processes in small laboratory animals. PET imaging of small animals can provide unique information that can help in advancement of human disease models as well as drug development. Clinical PET scanners used for human imaging are bulky, expensive and do not have adequate spatial resolution for small animal studies. Hence, dedicated, low cost instruments are required for conducting small animal studies with higher spatial resolution than what is currently achieved with clinical as well as dedicated small animal PET scanners. The goal of the proposed project is to investigate a new all solid-state detector design for small animal PET imaging. Exceptionally high spatial resolution, good timing resolution, and excellent energy resolution are expected from the proposed detector design. The Phase I project was aimed at demonstrating the feasibility of producing high performance solid-state detectors that provide high sensitivity, spatial resolution, and timing characteristics. Energy resolution characteristics of the new detector were also investigated. The goal of the Phase II project is to advance the promising solid-state detector technology for small animal PET and determine its full potential. Detectors modules will be built and characterized and finally, a bench-top small animal PET system will be assembled and evaluated.

  1. Effects of Spatial Resolution on Image Registration

    PubMed Central

    Zhao, Can; Carass, Aaron; Jog, Amod; Prince, Jerry L.

    2016-01-01

    This paper presents a theoretical analysis of the effect of spatial resolution on image registration. Based on the assumption of additive Gaussian noise on the images, the mean and variance of the distribution of the sum of squared differences (SSD) were estimated. Using these estimates, we evaluate a distance between the SSD distributions of aligned images and non-aligned images. The experimental results show that by matching the resolutions of the moving and fixed images one can get a better image registration result. The results agree with our theoretical analysis of SSD, but also suggest that it may be valid for mutual information as well. PMID:27773960

  2. High spatial resolution restoration of IRAS images

    NASA Technical Reports Server (NTRS)

    Grasdalen, Gary L.; Inguva, R.; Dyck, H. Melvin; Canterna, R.; Hackwell, John A.

    1990-01-01

    A general technique to improve the spatial resolution of the IRAS AO data was developed at The Aerospace Corporation using the Maximum Entropy algorithm of Skilling and Gull. The technique has been applied to a variety of fields and several individual AO MACROS. With this general technique, resolutions of 15 arcsec were achieved in 12 and 25 micron images and 30 arcsec in 60 and 100 micron images. Results on galactic plane fields show that both photometric and positional accuracy achieved in the general IRAS survey are also achieved in the reconstructed images.

  3. Improved spatial resolution in PET scanners using sampling techniques

    PubMed Central

    Surti, Suleman; Scheuermann, Ryan; Werner, Matthew E.; Karp, Joel S.

    2009-01-01

    Increased focus towards improved detector spatial resolution in PET has led to the use of smaller crystals in some form of light sharing detector design. In this work we evaluate two sampling techniques that can be applied during calibrations for pixelated detector designs in order to improve the reconstructed spatial resolution. The inter-crystal positioning technique utilizes sub-sampling in the crystal flood map to better sample the Compton scatter events in the detector. The Compton scatter rejection technique, on the other hand, rejects those events that are located further from individual crystal centers in the flood map. We performed Monte Carlo simulations followed by measurements on two whole-body scanners for point source data. The simulations and measurements were performed for scanners using scintillators with Zeff ranging from 46.9 to 63 for LaBr3 and LYSO, respectively. Our results show that near the center of the scanner, inter-crystal positioning technique leads to a gain of about 0.5-mm in reconstructed spatial resolution (FWHM) for both scanner designs. In a small animal LYSO scanner the resolution improves from 1.9-mm to 1.6-mm with the inter-crystal technique. The Compton scatter rejection technique shows higher gains in spatial resolution but at the cost of reduction in scanner sensitivity. The inter-crystal positioning technique represents a modest acquisition software modification for an improvement in spatial resolution, but at a cost of potentially longer data correction and reconstruction times. The Compton scatter rejection technique, while also requiring a modest acquisition software change with no increased data correction and reconstruction times, will be useful in applications where the scanner sensitivity is very high and larger improvements in spatial resolution are desirable. PMID:19779586

  4. High spatial resolution performance of pixelated scintillators

    NASA Astrophysics Data System (ADS)

    Shigeta, Kazuki; Fujioka, Nobuyasu; Murai, Takahiro; Hikita, Izumi; Morinaga, Tomohiro; Tanino, Takahiro; Kodama, Haruhito; Okamura, Masaki

    2017-03-01

    In indirect conversion flat panel detectors (FPDs) for digital X-ray imaging, scintillating materials such as Terbiumdoped Gadolinium Oxysulfide (Gadox) convert X-ray into visible light, and an amorphous silicon (a-Si) photodiode array converts the light into electrons. It is, however, desired that the detector spatial resolution is improved because the light spreading inside scintillator causes crosstalk to next a-Si photodiode pixels and the resolution is degraded compared with direct conversion FPDs which directly convert X-ray into electrons by scintillating material such as amorphous selenium. In this study, the scintillator was pixelated with same pixel pitch as a-Si photodiode array by barrier rib structure to limit the light spreading, and the detector spatial resolution was improved. The FPD with pixelated scintillator was manufactured as follows. The barrier rib structure with 127μm pitch was fabricated on a substrate by a photosensitive organic-inorganic paste method, and a reflective layer was coated on the surface of the barrier rib, then the structure was filled up with Gadox particles. The pixelated scintillator was aligned with 127μm pixel pitch of a-Si photodiode array and set as a FPD. The FPD with pixelated scintillator showed high modulation transfer function (MTF) and 0.94 at 1cycle/mm and 0.88 at 2cycles/mm were achieved. The MTF values were almost equal to the maximum value that can be theoretically achieved in the FPD with 127μm pixel pitch of a-Si photodiode array. Thus the FPD with pixelated scintillators has great potential to apply for high spatial resolution applications such as mammography and nondestructive testing.

  5. Generating High-Temporal and Spatial Resolution TIR Image Data

    NASA Astrophysics Data System (ADS)

    Herrero-Huerta, M.; Lagüela, S.; Alfieri, S. M.; Menenti, M.

    2017-09-01

    Remote sensing imagery to monitor global biophysical dynamics requires the availability of thermal infrared data at high temporal and spatial resolution because of the rapid development of crops during the growing season and the fragmentation of most agricultural landscapes. Conversely, no single sensor meets these combined requirements. Data fusion approaches offer an alternative to exploit observations from multiple sensors, providing data sets with better properties. A novel spatio-temporal data fusion model based on constrained algorithms denoted as multisensor multiresolution technique (MMT) was developed and applied to generate TIR synthetic image data at both temporal and spatial high resolution. Firstly, an adaptive radiance model is applied based on spectral unmixing analysis of . TIR radiance data at TOA (top of atmosphere) collected by MODIS daily 1-km and Landsat - TIRS 16-day sampled at 30-m resolution are used to generate synthetic daily radiance images at TOA at 30-m spatial resolution. The next step consists of unmixing the 30 m (now lower resolution) images using the information about their pixel land-cover composition from co-registered images at higher spatial resolution. In our case study, TIR synthesized data were unmixed to the Sentinel 2 MSI with 10 m resolution. The constrained unmixing preserves all the available radiometric information of the 30 m images and involves the optimization of the number of land-cover classes and the size of the moving window for spatial unmixing. Results are still being evaluated, with particular attention for the quality of the data streams required to apply our approach.

  6. Classification of High Spatial Resolution, Hyperspectral ...

    EPA Pesticide Factsheets

    EPA announced the availability of the final report,Spatial Resolution, Hyperspectral Remote Sensing Imagery of the Little Miami River Watershed in Southwest Ohio, USA . This report and associated land use/land cover (LULC) coverage is the result of a collaborative effort among an interdisciplinary team of scientists with the U.S. Environmental Protection Agency's (U.S. EPA's) Office of Research and Development in Cincinnati, Ohio. A primary goal of this project is to enhance the use of geography and spatial analytic tools in risk assessment, and to improve the scientific basis for risk management decisions affecting drinking water and water quality. The land use/land cover classification is derived from 82 flight lines of Compact Airborne Spectrographic Imager (CASI) hyperspectral imagery acquired from July 24 through August 9, 2002 via fixed-wing aircraft.

  7. Photoplethysmographic imaging of high spatial resolution

    PubMed Central

    Kamshilin, Alexei A.; Miridonov, Serguei; Teplov, Victor; Saarenheimo, Riku; Nippolainen, Ervin

    2011-01-01

    We present a new method of formation photoplethysmographic images with high spatial resolution from video recordings of a living body in the reflection geometry. The method (patent pending) is based on lock-in amplification of every pixel of the recorded video frames. A reference function required for synchronous detection of cardiovascular pulse waves is formed from the same frames. The method is featured by ability to visualize dynamic changes in cardiovascular pulse wave during the cardiac (or respiratory) cycle. We demonstrate that the system is capable to detect the minimal irritations of the body such as gentle scratching of the skin by own finger. PMID:21483621

  8. Spatial resolution in plantar pressure measurement revisited.

    PubMed

    Pataky, Todd C

    2012-08-09

    Plantar pressures are typically measured using sensors of finite area, so the accuracy with which one can measure true maximum pressure is dependent on sensor size. Measurement accuracy has been modeled previously for one patient's metatarsals (Lord, 1997), but has not been modeled either for general subjects or for other parts of the foot. The purposes of this study were (i) to determine whether Lord's (1997) model is also valid for heel and hallux pressures, and (ii) to examine how sensor size relates to measurement accuracy in the context of four factors common to many measurement settings: pressure pulse size, foot positioning, pressure change quantification, and gross pressure redistribution. Lord's (1997) model was first generalized and was then validated using 10 healthy walking subjects, with relatively low RMSE values on the order of 20 kPa. Next, postural data were used to show that gross pressure redistributions can be accurately quantified (p<0.002), even with rather gross sensor sizes of 30 mm. Finally, numerical analyses revealed that the relation between sensor size and measurement accuracy is highly complex, with deep dependency on the measurement context. In particular, the critical sensor widths required to achieve 90% accuracy ranged from 1.7 mm to 17.4 mm amongst the presently investigated scenarios. Since measurement accuracy varies so extensively with so many factors, the current results cannot yield specific recommendations regarding spatial resolution. It is concluded simply that no particular spatial resolution can yield a constant measurement accuracy across common plantar pressure measurement tasks.

  9. Development of a large-area Multigap RPC with adequate spatial resolution for muon tomography

    NASA Astrophysics Data System (ADS)

    Wang, J.; Wang, Y.; Wang, X.; Zeng, M.; Xie, B.; Han, D.; Lyu, P.; Wang, F.; Li, Y.

    2016-11-01

    We study the performance of a large-area 2-D Multigap Resistive Plate Chamber (MRPC) designed for muon tomography with high spatial resolution. An efficiency up to 98% and a spatial resolution of around 270 μ m are obtained in cosmic ray and X-ray tests. The performance of the MRPC is also investigated for two working gases: standard gas and pure Freon. The result shows that the MRPC working in pure Freon can provide higher efficiency and better spatial resolution.

  10. Evolution of spatial resolution in breast CT at UC Davis

    SciTech Connect

    Gazi, Peymon M.; Yang, Kai; Burkett, George W.; Aminololama-Shakeri, Shadi; Anthony Seibert, J.; Boone, John M.

    2015-04-15

    Purpose: Dedicated breast computed tomography (bCT) technology for the purpose of breast cancer screening has been a focus of research at UC Davis since the late 1990s. Previous studies have shown that improvement in spatial resolution characteristics of this modality correlates with greater microcalcification detection, a factor considered a potential limitation of bCT. The aim of this study is to improve spatial resolution as characterized by the modulation transfer function (MTF) via changes in the scanner hardware components and operational schema. Methods: Four prototypes of pendant-geometry, cone-beam breast CT scanners were designed and developed spanning three generations of design evolution. To improve the system MTF in each bCT generation, modifications were made to the imaging components (x-ray tube and flat-panel detector), system geometry (source-to-isocenter and detector distance), and image acquisition parameters (technique factors, number of projections, system synchronization scheme, and gantry rotational speed). Results: Characterization of different generations of bCT systems shows these modifications resulted in a 188% improvement of the limiting MTF properties from the first to second generation and an additional 110% from the second to third. The intrinsic resolution degradation in the azimuthal direction observed in the first generation was corrected by changing the acquisition from continuous to pulsed x-ray acquisition. Utilizing a high resolution detector in the third generation, along with modifications made in system geometry and scan protocol, resulted in a 125% improvement in limiting resolution. An additional 39% improvement was obtained by changing the detector binning mode from 2 × 2 to 1 × 1. Conclusions: These results underscore the advancement in spatial resolution characteristics of breast CT technology. The combined use of a pulsed x-ray system, higher resolution flat-panel detector and changing the scanner geometry and image

  11. Positron Emission Tomography with improved spatial resolution

    SciTech Connect

    Drukier, A.K.

    1990-04-01

    Applied Research Corporation (ARC) proposed the development of a new class of solid state detectors called Superconducting Granular Detectors (SGD). These new detectors permit considerable improvements in medical imaging, e.g. Positron Emission Tomography (PET). The biggest impact of this technique will be in imaging of the brain. It should permit better clinical diagnosis of such important diseases as Altzheimer's or schizophrenia. More specifically, we will develop an improved PET-imager; a spatial resolution 2 mm may be achievable with SGD. A time-of-flight capability(t {approx} 100 psec) will permit better contrast and facilitate 3D imaging. In the following, we describe the results of the first 9 months of the development.

  12. Spatial resolution limits for synchrotron-based infrared spectromicroscopy

    SciTech Connect

    Levenson, Erika; Lerch, Philippe; Martin, Michael C.

    2007-10-15

    Detailed spatial resolution tests were performed on beamline 1.4.4 at the Advanced Light Source synchrotron facility in Berkeley, CA. The high-brightness synchrotron source is coupled at this beamline to a Thermo-Electron Continumum XL infrared microscope. Two types of resolution tests in both the mid-IR (using a KBr beamsplitter and an MCT-A* detector) and in the near-IR (using a CaF2 beamsplitter and an InGaAS detector) were performed and compared to a simple diffraction-limited spot size model. At the shorter wavelengths in the near-IR the experimental results begin to deviate from only diffraction-limited. The entire data set is fit using a combined diffraction-limit and demagnified electron beam source size model. This description experimentally verifies how the physical electron beam size of the synchrotron source demagnified to the sample stage on the endstation begins to dominate the focussed spot size and therefore spatial resolution at higher energies. We discuss how different facilities, beamlines, and microscopes will affect the achievable spatial resolution.

  13. High Spatial Resolution Spectroscopy of Semiconductor Nanostructures

    NASA Astrophysics Data System (ADS)

    Harris, Timothy D.; Gershoni, David; Pfeiffer, Loren N.

    1996-03-01

    Several recent reports employing high spatial resolution have revealed the dominance of exciton localization in the low temperature luminescence of semiconductor quantum structures.^[1-3] Understanding this localization is of critical importance for the reliable studies of low dimensional structures such as quantum wells, quantum wires and quantum dots. We report on low temperature and high spatial resolution photoluminescence and photoluminescence excitation studies of cleaved edge overgrown (CEO) single quantum wires. These samples permit the direct and unambiguous comparison between the optical properties of a (100) oriented quantum well, a (110) oriented quantum well, and the quantum wire which is formed at their intersection. Using low temperature near field optical spectroscopy, and a novel diffraction limited far field apparatus, we determine the carrier diffusion length dependence on pump wavelength and sample temperature in both the 2d systems and the genuinely 1D wire system. We also measure the absorption strength of the 1D system and find it to be a factor of 3 stronger than the absorption of the associated 2D systems.^[2] Using low temperature near field optical spectroscopy, and a novel diffraction limited far field apparatus, we also determine the carrier diffusion length dependence on pump wavelength and sample temperature. ^[1] H. F. Hess, E. Betzig, T. D. Harris, L. N. Pfeiffer, and K. W. West, Science 264, 1740 (1994). ^[2] T. D. Harris, D. Gershoni, R. D. Grober, L. Pfeiffer, K. West, and N. Chand, Appl. Phys. Lett, in press (1996) ^[3] D. Gammon, E. S. Snow, and D. S. Katzer, Appl. Phys. Lett. 67, 2391 (1995)

  14. Improving PET spatial resolution and detectability for prostate cancer imaging

    NASA Astrophysics Data System (ADS)

    Bal, H.; Guerin, L.; Casey, M. E.; Conti, M.; Eriksson, L.; Michel, C.; Fanti, S.; Pettinato, C.; Adler, S.; Choyke, P.

    2014-08-01

    Prostate cancer, one of the most common forms of cancer among men, can benefit from recent improvements in positron emission tomography (PET) technology. In particular, better spatial resolution, lower noise and higher detectability of small lesions could be greatly beneficial for early diagnosis and could provide a strong support for guiding biopsy and surgery. In this article, the impact of improved PET instrumentation with superior spatial resolution and high sensitivity are discussed, together with the latest development in PET technology: resolution recovery and time-of-flight reconstruction. Using simulated cancer lesions, inserted in clinical PET images obtained with conventional protocols, we show that visual identification of the lesions and detectability via numerical observers can already be improved using state of the art PET reconstruction methods. This was achieved using both resolution recovery and time-of-flight reconstruction, and a high resolution image with 2 mm pixel size. Channelized Hotelling numerical observers showed an increase in the area under the LROC curve from 0.52 to 0.58. In addition, a relationship between the simulated input activity and the area under the LROC curve showed that the minimum detectable activity was reduced by more than 23%.

  15. Enhanced spatial resolution on figures versus grounds

    PubMed Central

    Hecht, Lauren N.; Cosman, Joshua D.; Vecera, Shaun P.

    2016-01-01

    Much is known about the cues that determine figure-ground assignment, but less is known about the consequences of figure-ground assignment on later visual processing. Previous work has demonstrated that regions assigned figural status are subjectively more shape-like and salient than background regions. The increase in subjective salience of figural regions could be caused by a number of processes, one of which may be enhanced perceptual processing (e.g., an enhanced neural representation) of figures relative to grounds. We explored this hypothesis by having observers perform a perceptually demanding spatial resolution task in which targets appeared either on figure or ground regions. To rule out a purely attentional account of figural salience, observers discriminated targets on the basis of a region’s color (red or green), which was equally likely to define the figure or the ground. The results of our experiments show that targets appearing on figures were discriminated more accurately than those appearing in ground regions. In addition, targets appearing on figures were discriminated better than those presented in regions considered figurally neutral, but targets appearing within ground regions were discriminated more poorly than those appearing in figurally neutral regions. Taken together, our findings suggest that when two regions share a contour, regions assigned as figure are perceptually enhanced, whereas regions assigned as grounds are perceptually suppressed. PMID:27048441

  16. High spatial resolution probes for neurobiology applications

    NASA Astrophysics Data System (ADS)

    Gunning, D. E.; Kenney, C. J.; Litke, A. M.; Mathieson, K.

    2009-06-01

    Position-sensitive biological neural networks, such as the brain and the retina, require position-sensitive detection methods to identify, map and study their behavior. Traditionally, planar microelectrodes have been employed to record the cell's electrical activity with device limitations arising from the electrode's 2-D nature. Described here is the development and characterization of an array of electrically conductive micro-needles aimed at addressing the limitations of planar electrodes. The capability of this array to penetrate neural tissue improves the electrode-cell electrical interface and allows more complicated 3-D networks of neurons, such as those found in brain slices, to be studied. State-of-the-art semiconductor fabrication techniques were used to etch and passivate conformally the metal coat and fill high aspect ratio holes in silicon. These are subsequently transformed into needles with conductive tips. This process has enabled the fabrication of arrays of unprecedented dimensions: 61 hexagonally close-packed electrodes, ˜200 μm tall with 60 μm spacing. Electroplating the tungsten tips with platinum ensure suitable impedance values (˜600 kΩ at 1 kHz) for the recording of neuronal signals. Without compromising spatial resolution of the neuronal recordings, this array adds a new and exciting dimension to the study of biological neural networks.

  17. On the creation of high spatial resolution imaging spectroscopy data from multi-temporal low spatial resolution imagery

    NASA Astrophysics Data System (ADS)

    Yao, Wei; van Aardt, Jan; Messinger, David

    2017-05-01

    The Hyperspectral Infrared Imager (HyspIRI) mission aims to provide global imaging spectroscopy data to the benefit of especially ecosystem studies. The onboard spectrometer will collect radiance spectra from the visible to short wave infrared (VSWIR) regions (400-2500 nm). The mission calls for fine spectral resolution (10 nm band width) and as such will enable scientists to perform material characterization, species classification, and even sub-pixel mapping. However, the global coverage requirement results in a relatively low spatial resolution (GSD 30m), which restricts applications to objects of similar scales. We therefore have focused on the assessment of sub-pixel vegetation structure from spectroscopy data in past studies. In this study, we investigate the development or reconstruction of higher spatial resolution imaging spectroscopy data via fusion of multi-temporal data sets to address the drawbacks implicit in low spatial resolution imagery. The projected temporal resolution of the HyspIRI VSWIR instrument is 15 days, which implies that we have access to as many as six data sets for an area over the course of a growth season. Previous studies have shown that select vegetation structural parameters, e.g., leaf area index (LAI) and gross ecosystem production (GEP), are relatively constant in summer and winter for temperate forests; we therefore consider the data sets collected in summer to be from a similar, stable forest structure. The first step, prior to fusion, involves registration of the multi-temporal data. A data fusion algorithm then can be applied to the pre-processed data sets. The approach hinges on an algorithm that has been widely applied to fuse RGB images. Ideally, if we have four images of a scene which all meet the following requirements - i) they are captured with the same camera configurations; ii) the pixel size of each image is x; and iii) at least r2 images are aligned on a grid of x/r - then a high-resolution image, with a pixel

  18. Automated Verification of Spatial Resolution in Remotely Sensed Imagery

    NASA Technical Reports Server (NTRS)

    Davis, Bruce; Ryan, Robert; Holekamp, Kara; Vaughn, Ronald

    2011-01-01

    Image spatial resolution characteristics can vary widely among sources. In the case of aerial-based imaging systems, the image spatial resolution characteristics can even vary between acquisitions. In these systems, aircraft altitude, speed, and sensor look angle all affect image spatial resolution. Image spatial resolution needs to be verified with estimators that include the ground sample distance (GSD), the modulation transfer function (MTF), and the relative edge response (RER), all of which are key components of image quality, along with signal-to-noise ratio (SNR) and dynamic range. Knowledge of spatial resolution parameters is important to determine if features of interest are distinguishable in imagery or associated products, and to develop image restoration algorithms. An automated Spatial Resolution Verification Tool (SRVT) was developed to rapidly determine the spatial resolution characteristics of remotely sensed aerial and satellite imagery. Most current methods for assessing spatial resolution characteristics of imagery rely on pre-deployed engineered targets and are performed only at selected times within preselected scenes. The SRVT addresses these insufficiencies by finding uniform, high-contrast edges from urban scenes and then using these edges to determine standard estimators of spatial resolution, such as the MTF and the RER. The SRVT was developed using the MATLAB programming language and environment. This automated software algorithm assesses every image in an acquired data set, using edges found within each image, and in many cases eliminating the need for dedicated edge targets. The SRVT automatically identifies high-contrast, uniform edges and calculates the MTF and RER of each image, and when possible, within sections of an image, so that the variation of spatial resolution characteristics across the image can be analyzed. The automated algorithm is capable of quickly verifying the spatial resolution quality of all images within a data

  19. Detector motion method to increase spatial resolution in photon-counting detectors

    NASA Astrophysics Data System (ADS)

    Lee, Daehee; Park, Kyeongjin; Lim, Kyung Taek; Cho, Gyuseong

    2017-03-01

    Medical imaging requires high spatial resolution of an image to identify fine lesions. Photon-counting detectors in medical imaging have recently been rapidly replacing energy-integrating detectors due to the former`s high spatial resolution, high efficiency and low noise. Spatial resolution in a photon counting image is determined by the pixel size. Therefore, the smaller the pixel size, the higher the spatial resolution that can be obtained in an image. However, detector redesigning is required to reduce pixel size, and an expensive fine process is required to integrate a signal processing unit with reduced pixel size. Furthermore, as the pixel size decreases, charge sharing severely deteriorates spatial resolution. To increase spatial resolution, we propose a detector motion method using a large pixel detector that is less affected by charge sharing. To verify the proposed method, we utilized a UNO-XRI photon-counting detector (1-mm CdTe, Timepix chip) at the maximum X-ray tube voltage of 80 kVp. A similar spatial resolution of a 55- μm-pixel image was achieved by application of the proposed method to a 110- μm-pixel detector with a higher signal-to-noise ratio. The proposed method could be a way to increase spatial resolution without a pixel redesign when pixels severely suffer from charge sharing as pixel size is reduced.

  20. Mapping seagrass coverage and spatial patterns with high spatial resolution IKONOS imagery

    NASA Astrophysics Data System (ADS)

    Pu, Ruiliang; Bell, Susan

    2017-02-01

    Seagrass habitats in subtidal coastal waters provide a variety of ecosystem functions and services and there is an increasing need to acquire information on spatial and temporal dynamics of this resource. Here, we explored the capability of IKONOS (IKO) data of high resolution (4 m) for mapping seagrass cover [submerged aquatic vegetation (%SAV) cover] along the mid-western coast of Florida, USA. We also compared seagrass maps produced with IKO data with that obtained using the Landsat TM sensor with lower resolution (30 m). Both IKO and TM data, collected in October 2009, were preprocessed to calculate water depth invariant bands to normalize the effect of varying depth on bottom spectra recorded by the two satellite sensors and further the textural information was extracted from IKO data. Our results demonstrate that the high resolution IKO sensor produced a higher accuracy than the TM sensor in a three-class % SAV cover classification. Of note is that the OA of %SAV cover mapping at our study area created with IKO data was 5-20% higher than that from other studies published. We also examined the spatial distribution of seagrass over a spatial range of 4-240 m using the Ripley's K function [L(d)] and IKO data that represented four different grain sizes [4 m (one IKO pixel), 8 m (2 × 2 IKO pixels), 12 m (3 × 3 IKO pixels), and 16 m (4 × 4 IKO pixels)] from moderate-dense seagrass cover along a set of six transects. The Ripley's K metric repeatedly indicated that seagrass cover representing 4 m × 4 m pixels displayed a dispersed (or slightly dispersed) pattern over distances of <4-8 m, and a random or slightly clustered pattern of cover over 9-240 m. The spatial pattern of seagrass cover created with the three additional grain sizes (i.e., 2 × 24 m IKO pixels, 3 × 34 m IKO pixels, and 4 × 4 m IKO pixels) show a dispersed (or slightly dispersed) pattern across 4-32 m and a random or slightly clustered pattern across 33-240 m. Given the first report on using

  1. Study of the spatial resolution for binary readout detectors

    NASA Astrophysics Data System (ADS)

    Yonamine, R.; Maerschalk, T.; Lentdecker, G. De

    2016-07-01

    Often the binary readout is proposed for high granularity detectors to reduce the generated data volume to be readout at the price of a somewhat reduced spatial resolution compared to an analogue readout. We have been studying single hit resolutions obtained with a binary readout using simulations as well as analytical approaches. In this note we show that the detector geometry could be optimized to offer an equivalent spatial resolution than with an analogue readout.

  2. Sub-pixel spatial resolution micro-roughness measurements with interlaced stitching

    NASA Astrophysics Data System (ADS)

    Mooney, James T.; Stahl, H. Philip

    2005-08-01

    In this paper we describe a method to increase the spatial resolution of surface micro-roughness measurements. As the surface specifications for precision optics become more demanding, the metrology instruments must cover a broad spatial frequency range. Generally, multiple instruments are used to cover the full range of the specifications. For example, an interferometer (Fizeau, Michelson, etc.) would be used to test low spatial frequency surface errors, an interferometric microscope (such as a white light interferomenter) would be used for higher spatial frequency errors, and an AFM would be used for even higher spatial frequency errors. For some precision optics, three or more instruments would be necessary. However, an increase in the resolvable spatial frequency bandwidth of a metrology instrument could reduce the number of instruments necessary to characterize the optical surface over the spatial frequency bands defined by the optical specifications. A solution to increase the resolvable spatial frequency bandwidth of micro-roughness measurements will be presented. This will be accomplished by implementing an interferometric microscope and a process called "sub-pixel spatial resolution interferometry" (SSRI) with interlaced stitching. In this process, multiple interferometric measurements are made as the optic under test (or the CCD array) is laterally shifted at sub-pixel increments. The measurements are then combined to construct a measurement with higher spatial resolution. Initial results obtained implementing a similar process used to increase the spatial resolution of measurements made with a commercially available Fizeau interferometer will be presented.

  3. Trade-off between angular and spatial resolutions in in vivo fiber tractography

    PubMed Central

    Vos, Sjoerd B.; Aksoy, Murat; Han, Zhaoying; Holdsworth, Samantha J.; Maclaren, Julian; Viergever, Max A.; Leemans, Alexander; Bammer, Roland

    2016-01-01

    Tractography is becoming an increasingly popular method to reconstruct white matter connections in vivo. The diffusion MRI data that tractography is based on requires a high angular resolution to resolve crossing fibers whereas high spatial resolution is required to distinguish kissing from crossing fibers. However, scan time increases with increasing spatial and angular resolutions, which can become infeasible in clinical settings. Here we investigated the trade-off between spatial and angular resolutions to determine which of these factors is most worth investing scan time in. We created a unique diffusion MRI dataset with 1.0 mm isotropic resolution and a high angular resolution (100 directions) using an advanced 3D diffusion-weighted multi-slab EPI acquisition. This dataset was reconstructed to create subsets of lower angular (75, 50, and 25 directions) and lower spatial (1.5, 2.0, and 2.5 mm) resolution. Using all subsets, we investigated the effects of angular and spatial resolutions in three fiber bundles—the corticospinal tract, arcuate fasciculus and corpus callosum—by analyzing the volumetric bundle overlap and anatomical correspondence between tracts. Our results indicate that the subsets of 25 and 50 directions provided inferior tract reconstructions compared with the datasets with 75 and 100 directions. Datasets with spatial resolutions of 1.0, 1.5, and 2.0 mm were comparable, while the lowest resolution (2.5 mm) datasets had discernible inferior quality. In conclusion, we found that angular resolution appeared to be more influential than spatial resolution in improving tractography results. Spatial resolutions higher than 2.0 mm only appear to benefit multi-fiber tractography methods if this is not at the cost of decreased angular resolution. PMID:26774615

  4. Trade-off between angular and spatial resolutions in in vivo fiber tractography.

    PubMed

    Vos, Sjoerd B; Aksoy, Murat; Han, Zhaoying; Holdsworth, Samantha J; Maclaren, Julian; Viergever, Max A; Leemans, Alexander; Bammer, Roland

    2016-04-01

    Tractography is becoming an increasingly popular method to reconstruct white matter connections in vivo. The diffusion MRI data that tractography is based on requires a high angular resolution to resolve crossing fibers whereas high spatial resolution is required to distinguish kissing from crossing fibers. However, scan time increases with increasing spatial and angular resolutions, which can become infeasible in clinical settings. Here we investigated the trade-off between spatial and angular resolutions to determine which of these factors is most worth investing scan time in. We created a unique diffusion MRI dataset with 1.0 mm isotropic resolution and a high angular resolution (100 directions) using an advanced 3D diffusion-weighted multi-slab EPI acquisition. This dataset was reconstructed to create subsets of lower angular (75, 50, and 25 directions) and lower spatial (1.5, 2.0, and 2.5 mm) resolution. Using all subsets, we investigated the effects of angular and spatial resolutions in three fiber bundles-the corticospinal tract, arcuate fasciculus and corpus callosum-by analyzing the volumetric bundle overlap and anatomical correspondence between tracts. Our results indicate that the subsets of 25 and 50 directions provided inferior tract reconstructions compared with the datasets with 75 and 100 directions. Datasets with spatial resolutions of 1.0, 1.5, and 2.0 mm were comparable, while the lowest resolution (2.5 mm) datasets had discernible inferior quality. In conclusion, we found that angular resolution appeared to be more influential than spatial resolution in improving tractography results. Spatial resolutions higher than 2.0 mm only appear to benefit multi-fiber tractography methods if this is not at the cost of decreased angular resolution.

  5. A 50 nm spatial resolution EUV imaging-resolution dependence on object thickness and illumination bandwidth.

    PubMed

    Wachulak, Przemyslaw W; Bartnik, Andrzej; Fiedorowicz, Henryk; Kostecki, Jerzy

    2011-05-09

    In this paper we report a desk-top microscopy reaching 50 nm spatial resolution in very compact setup using a gas-puff laser plasma EUV source. The thickness of an object and the bandwidth of illuminating radiation were studied in order to estimate their quantitative influence on the EUV microscope spatial resolution. EUV images of various thickness objects obtained by illumination with variable bandwidth EUV radiation were compared in terms of knife-edge spatial resolution to study the bandwidth/object thickness parasitic influence on spatial resolution of the EUV microscope. © 2011 Optical Society of America

  6. Solar system events at high spatial resolution

    SciTech Connect

    Baines, K H; Gavel, D T; Getz, A M; Gibbartd, S G; MacIntosh, B; Max, C E; McKay, C P; Young, E F; de Pater, I

    1999-02-19

    Until relatively recent advances in technology, astronomical observations from the ground were limited in image resolution by the blurring effects of earth's atmosphere. The blur extent, ranging typically from 0.5 to 2 seconds of arc at the best astronomical sights, precluded ground-based observations of the details of the solar system's moons, asteroids, and outermost planets. With the maturing of a high resolution image processing technique called speckle imaging the resolution limitation of the atmosphere can now be largely overcome. Over the past three years they have used speckle imaging to observe Titan, a moon of Saturn with an atmospheric density comparable to Earth's, Io, the volcanically active innermost moon of Jupiter, and Neptune, a gas giant outer planet which has continually changing planet-encircling storms. These observations were made at the world's largest telescope, the Keck telescope in Hawaii and represent the highest resolution infrared images of these objects ever taken.

  7. Higher Resolution for Water Resources Studies

    NASA Astrophysics Data System (ADS)

    Dumenil-Gates, L.

    2009-12-01

    The Earth system science community is providing an increasing range of science results for the benefit of achieving the Millennium Development Goals. In addressing questions such as reducing poverty and hunger, achieving sustainable global development, or by defining adaptation strategies for climate change, one of the key issues will be the quantitative description and understanding of the global water cycle, which will allow useful projections of available future water resources for several decades ahead. The quantities of global water cycle elements that we observe today - and deal with in hydrologic and atmospheric modeling - are already very different from the natural flows as human influence on the water cycle by storage, consumption and edifice has been going on for millennia, and climate change is expected to add more uncertainty. In this case Tony Blair’s comment that perhaps the most worrying problem is climate change does not cover the full story. We shall also have to quantify how the human demand for water resources and alterations of the various elements of the water cycle may proceed in the future: will there be enough of the precious water resource to sustain current and future demands by the various sectors involved? The topics that stakeholders and decision makers concerned with managing water resources are interested in cover a variety of human uses such as agriculture, energy production, ecological flow requirements to sustain biodiversity and ecosystem services, or human cultural aspects, recreation and human well-being - all typically most relevant at the regional or local scales, this being quite different from the relatively large-scale that the IPCC assessment addresses. Halfway through the Millennium process, the knowledge base of the global water cycle is still limited. The sustainability of regional water resources is best assessed through a research program that combines high-resolution climate and hydrologic models for expected

  8. A study of spatial resolution in pollution exposure modelling

    PubMed Central

    Stroh, Emilie; Harrie, Lars; Gustafsson, Susanna

    2007-01-01

    Background This study is part of several ongoing projects concerning epidemiological research into the effects on health of exposure to air pollutants in the region of Scania, southern Sweden. The aim is to investigate the optimal spatial resolution, with respect to temporal resolution, for a pollutant database of NOx-values which will be used mainly for epidemiological studies with durations of days, weeks or longer periods. The fact that a pollutant database has a fixed spatial resolution makes the choice critical for the future use of the database. Results The results from the study showed that the accuracy between the modelled concentrations of the reference grid with high spatial resolution (100 m), denoted the fine grid, and the coarser grids (200, 400, 800 and 1600 meters) improved with increasing spatial resolution. When the pollutant values were aggregated in time (from hours to days and weeks) the disagreement between the fine grid and the coarser grids were significantly reduced. The results also illustrate a considerable difference in optimal spatial resolution depending on the characteristic of the study area (rural or urban areas). To estimate the accuracy of the modelled values comparison were made with measured NOx values. The mean difference between the modelled and the measured value were 0.6 μg/m3 and the standard deviation 5.9 μg/m3 for the daily difference. Conclusion The choice of spatial resolution should not considerably deteriorate the accuracy of the modelled NOx values. Considering the comparison between modelled and measured values we estimate that an error due to coarse resolution greater than 1 μg/m3 is inadvisable if a time resolution of one day is used. Based on the study of different spatial resolutions we conclude that for urban areas a spatial resolution of 200–400 m is suitable; and for rural areas the spatial resolution could be coarser (about 1600 m). This implies that we should develop a pollutant database that allows

  9. Results of the spatial resolution simulation for multispectral data (resolution brochures)

    NASA Technical Reports Server (NTRS)

    1982-01-01

    The variable information content of Earth Resource products at different levels of spatial resolution and in different spectral bands is addressed. A low-cost brochure that scientists and laymen could use to visualize the effects of increasing the spatial resolution of multispectral scanner images was produced.

  10. Localization bias and spatial resolution of adaptive and non-adaptive spatial filters for MEG source reconstruction

    PubMed Central

    Sekihara, Kensuke; Sahani, Maneesh; Nagarajan, Srikantan S.

    2014-01-01

    This paper discusses the location bias and the spatial resolution in the reconstruction of a single dipole source by various spatial filtering techniques used for neuromagnetic imaging. We first analyze the location bias for several representative adaptive and non-adaptive spatial filters using their resolution kernels. This analysis theoretically validates previously reported empirical findings that standardized low-resolution electromagnetic tomography (sLORETA) has no location bias. We also find that the minimum-variance spatial filter does exhibit bias in the reconstructed location of a single source, but that this bias is eliminated by using the normalized lead field. We then focus on the comparison of sLORETA and the lead-field normalized minimum-variance spatial filter, and analyze the effect of noise on source location bias. We find that the signal-to-noise ratio (SNR) in the measurements determines whether the sLORETA reconstruction has source location bias, while the lead-field normalized minimum-variance spatial filter has no location bias even in the presence of noise. Finally, we compare the spatial resolution for sLORETA and the minimum-variance filter, and show that the minimum-variance filter attains much higher resolution than sLORETA does. The results of these analyses are validated by numerical experiments as well as by reconstructions based on two sets of evoked magnetic responses. PMID:15850724

  11. Localization bias and spatial resolution of adaptive and non-adaptive spatial filters for MEG source reconstruction.

    PubMed

    Sekihara, Kensuke; Sahani, Maneesh; Nagarajan, Srikantan S

    2005-05-01

    This paper discusses the location bias and the spatial resolution in the reconstruction of a single dipole source by various spatial filtering techniques used for neuromagnetic imaging. We first analyze the location bias for several representative adaptive and non-adaptive spatial filters using their resolution kernels. This analysis theoretically validates previously reported empirical findings that standardized low-resolution electromagnetic tomography (sLORETA) has no location bias. We also find that the minimum-variance spatial filter does exhibit bias in the reconstructed location of a single source, but that this bias is eliminated by using the normalized lead field. We then focus on the comparison of sLORETA and the lead-field normalized minimum-variance spatial filter, and analyze the effect of noise on source location bias. We find that the signal-to-noise ratio (SNR) in the measurements determines whether the sLORETA reconstruction has source location bias, while the lead-field normalized minimum-variance spatial filter has no location bias even in the presence of noise. Finally, we compare the spatial resolution for sLORETA and the minimum-variance filter, and show that the minimum-variance filter attains much higher resolution than sLORETA does. The results of these analyses are validated by numerical experiments as well as by reconstructions based on two sets of evoked magnetic responses.

  12. Analysis of DOA estimation spatial resolution using MUSIC algorithm

    NASA Astrophysics Data System (ADS)

    Guo, Yue; Wang, Hongyuan; Luo, Bin

    2005-11-01

    This paper presents a performance analysis of the spatial resolution of the direction of arrival (DOA) estimates attained by the multiple signal classification (MUSIC) algorithm for uncorrelated sources. The confidence interval of estimation angle which is much more intuitionistic will be considered as the new evaluation standard for the spatial resolution. Then, based on the statistic method, the qualitative analysis reveals the factors influencing the performance of the MUSIC algorithm. At last, quantitative simulations prove the theoretical analysis result exactly.

  13. Super Spatial Resolution (SSR) method for scintigraphic imaging

    NASA Astrophysics Data System (ADS)

    Trinci, G.; Massari, R.; Scandellari, M.; Scopinaro, F.; Soluri, A.

    2011-01-01

    This work describes an innovative patented Super Spatial Resolution (SSR) method applied to scintigraphic devices. The aim of Super Resolution (SR) techniques is to enhance the resolution of an imaging system, using information from several images. SR reconstruction may be considered as a second generation problem of Image Restoration. It combines several slightly different Low Resolution (LR) images to obtain a High Resolution (HR) image. SR techniques are, widely, described in scientific literature mainly for applications in video communication, object recognition and image compression. In this paper we focus to apply the SR task to the scintigraphic imaging. Specifically, it is described as a patented method that uses a High Resolution Scintigraphic Camera (HRSC) to collect and process a set of scintigraphic images, in view of obtaining a very high resolution image. The HRSC device, which is currently used in Medical Imaging, is based on a parallel square holes collimator and on a Hamamatsu H8500 Position Sensitive Photomultiplier Tubes (PSPMT). The SSR method is applied to the synthetic images of three different phantoms, to verify the effective spatial resolution values. The results confirm that it is possible to achieve optimal spatial resolution values at different depths, useful in small object and small animal imaging. Our study confirms the feasibility of a very high resolution system in scintigraphic imaging and the possibility to have gamma cameras using the SSR method, to perform clinical applications on patients.

  14. A broadband, high-resolution spatial heterodyne spectrometer

    NASA Astrophysics Data System (ADS)

    Lawler, J. E.; Harlander, J.; Roesler, F. L.; Labby, Z.

    2009-05-01

    Design and performance parameters of a broadband, high-resolution spatial heterodyne spectrometer (SHS) with a transmitting beamsplitter are described. This Mark 1 SHS achieves more than a factor of five in continuous wavenumber coverage with a resolving power in hundreds of thousands. Progress toward an all reflection, broadband, high-resolution Mark 2 SHS is reported.

  15. High spatial resolution passive microwave sounding systems

    NASA Technical Reports Server (NTRS)

    Staelin, D. H.; Rosenkranz, P. W.; Bonanni, P. G.; Gasiewski, A. W.

    1986-01-01

    Two extensive series of flights aboard the ER-2 aircraft were conducted with the MIT 118 GHz imaging spectrometer together with a 53.6 GHz nadir channel and a TV camera record of the mission. Other microwave sensors, including a 183 GHz imaging spectrometer were flown simultaneously by other research groups. Work also continued on evaluating the impact of high-resolution passive microwave soundings upon numerical weather prediction models.

  16. Sub-pixel Spatial Resolution Micro-roughness Measurements with Interlaced Stitching

    NASA Technical Reports Server (NTRS)

    Mooney, James T.; Stahl, H. Philip

    2005-01-01

    In this paper we describe a method to increase the spatial resolution of surface micro-roughness measurements. As the surface specifications for precision optics become more demanding, the metrology instruments must cover a broad spatial frequency range. Generally, multiple instruments are used to cover the full range of the specifications. For example, a Fizeau interferometer would be used to test low spatial frequency surface errors, a white light interferometer would be used for mid spatial frequency errors, and an AFM would be used for high spatial frequency errors. For some precision optics, three instruments would be necessary. However, in many applications, an increase in the spatial resolution of a metrology instrument could negate the need for multiple instruments. A solution to increase the spatial resolution of micro-roughness measurements obtained using white light interferometry with "interlaced stitching" will be presented. In "interlaced stitching", multiple interferometric measurements are made as the optic under test (or the CCD array) is laterally shifted at sub-pixel increments. The measurements are then combined to construct a measurement with higher spatial resolution. Initial results obtained while implementing a similar process used to increase the spatial resolution of measurements made with a commercially available Fizeau interferometer will be presented.

  17. Sub-pixel Spatial Resolution Micro-roughness Measurements with Interlaced Stitching

    NASA Technical Reports Server (NTRS)

    Mooney, James T.; Stahl, H. Philip

    2005-01-01

    In this paper we describe a method to increase the spatial resolution of surface micro-roughness measurements. As the surface specifications for precision optics become more demanding, the metrology instruments must cover a broad spatial frequency range. Generally, multiple instruments are used to cover the full range of the specifications. For example, a Fizeau interferometer would be used to test low spatial frequency surface errors, a white light interferometer would be used for mid spatial frequency errors, and an AFM would be used for high spatial frequency errors. For some precision optics, three instruments would be necessary. However, in many applications, an increase in the spatial resolution of a metrology instrument could negate the need for multiple instruments. A solution to increase the spatial resolution of micro-roughness measurements obtained using white light interferometry with "interlaced stitching" will be presented. In "interlaced stitching", multiple interferometric measurements are made as the optic under test (or the CCD array) is laterally shifted at sub-pixel increments. The measurements are then combined to construct a measurement with higher spatial resolution. Initial results obtained while implementing a similar process used to increase the spatial resolution of measurements made with a commercially available Fizeau interferometer will be presented.

  18. Attentional enhancement of spatial resolution: linking behavioural and neurophysiological evidence

    PubMed Central

    Anton-Erxleben, Katharina; Carrasco, Marisa

    2014-01-01

    Attention allows us to select relevant sensory information for preferential processing. Behaviourally, it improves performance in various visual tasks. One prominent effect of attention is the modulation of performance in tasks that involve the visual system’s spatial resolution. Physiologically, attention modulates neuronal responses and alters the profile and position of receptive fields near the attended location. Here, we develop a hypothesis linking the behavioural and electrophysiological evidence. The proposed framework seeks to explain how these receptive field changes enhance the visual system’s effective spatial resolution and how the same mechanisms may also underlie attentional effects on the representation of spatial information. PMID:23422910

  19. Progress toward accurate high spatial resolution actinide analysis by EPMA

    NASA Astrophysics Data System (ADS)

    Jercinovic, M. J.; Allaz, J. M.; Williams, M. L.

    2010-12-01

    High precision, high spatial resolution EPMA of actinides is a significant issue for geochronology, resource geochemistry, and studies involving the nuclear fuel cycle. Particular interest focuses on understanding of the behavior of Th and U in the growth and breakdown reactions relevant to actinide-bearing phases (monazite, zircon, thorite, allanite, etc.), and geochemical fractionation processes involving Th and U in fluid interactions. Unfortunately, the measurement of minor and trace concentrations of U in the presence of major concentrations of Th and/or REEs is particularly problematic, especially in complexly zoned phases with large compositional variation on the micro or nanoscale - spatial resolutions now accessible with modern instruments. Sub-micron, high precision compositional analysis of minor components is feasible in very high Z phases where scattering is limited at lower kV (15kV or less) and where the beam diameter can be kept below 400nm at high current (e.g. 200-500nA). High collection efficiency spectrometers and high performance electron optics in EPMA now allow the use of lower overvoltage through an exceptional range in beam current, facilitating higher spatial resolution quantitative analysis. The U LIII edge at 17.2 kV precludes L-series analysis at low kV (high spatial resolution), requiring careful measurements of the actinide M series. Also, U-La detection (wavelength = 0.9A) requires the use of LiF (220) or (420), not generally available on most instruments. Strong peak overlaps of Th on U make highly accurate interference correction mandatory, with problems compounded by the ThMIV and ThMV absorption edges affecting peak, background, and interference calibration measurements (especially the interference of the Th M line family on UMb). Complex REE bearing phases such as monazite, zircon, and allanite have particularly complex interference issues due to multiple peak and background overlaps from elements present in the activation

  20. Full Spatial Resolution Infrared Sounding Application in the Preconvection Environment

    NASA Astrophysics Data System (ADS)

    Liu, C.; Liu, G.; Lin, T.

    2013-12-01

    Advanced infrared (IR) sounders such as the Atmospheric Infrared Sounder (AIRS) and Infrared Atmospheric Sounding Interferometer (IASI) provide atmospheric temperature and moisture profiles with high vertical resolution and high accuracy in preconvection environments. The derived atmospheric stability indices such as convective available potential energy (CAPE) and lifted index (LI) from advanced IR soundings can provide critical information 1 ; 6 h before the development of severe convective storms. Three convective storms are selected for the evaluation of applying AIRS full spatial resolution soundings and the derived products on providing warning information in the preconvection environments. In the first case, the AIRS full spatial resolution soundings revealed local extremely high atmospheric instability 3 h ahead of the convection on the leading edge of a frontal system, while the second case demonstrates that the extremely high atmospheric instability is associated with the local development of severe thunderstorm in the following hours. The third case is a local severe storm that occurred on 7-8 August 2010 in Zhou Qu, China, which caused more than 1400 deaths and left another 300 or more people missing. The AIRS full spatial resolution LI product shows the atmospheric instability 3.5 h before the storm genesis. The CAPE and LI from AIRS full spatial resolution and operational AIRS/AMSU soundings along with Geostationary Operational Environmental Satellite (GOES) Sounder derived product image (DPI) products were analyzed and compared. Case studies show that full spatial resolution AIRS retrievals provide more useful warning information in the preconvection environments for determining favorable locations for convective initiation (CI) than do the coarser spatial resolution operational soundings and lower spectral resolution GOES Sounder retrievals. The retrieved soundings are also tested in a regional data assimilation WRF 3D-var system to evaluate the

  1. Utilizing Higher Resolution Land Surface Remote Sensing Data for Assessing Recent Trends over Asia Monsoon Region

    NASA Technical Reports Server (NTRS)

    Shen, Suhung; Leptoukh, Gregory

    2010-01-01

    The slide presentation discusses the integration of 1-kilometer spatial resolution land temperature data from the Moderate Resolution Imaging Spectroradiometer (MODIS), with 8-day temporal resolution, into the NASA Monsoon-Asia Integrated Regional Study (MAIRS) Data Center. The data will be available for analysis and visualization in the Giovanni data system. It discusses the NASA MAIRS Data Center, presents an introduction to the data access tools, and an introduction of Products available from the service, discusses the higher resolution Land Surface Temperature (LST) and presents preliminary results of LST Trends over China.

  2. Impact of spatial resolution of ocean models in depicting climate change patterns of the North Sea.

    NASA Astrophysics Data System (ADS)

    Narayan, Nikesh; Klein, Birgit; Mathis, Moritz; Klein, Holger; Mikolajewicz, Uwe

    2016-04-01

    The impact of enhanced spatial resolution of models in simulating large scale climate change has been of interest for the modeling community for quite some time. It has been noticed in previous studies that the pattern of Sea Surface Temperature anomalies are better captured by higher resolution models. Significant changes in simulating sea-ice loss associated with global warming was also noticed when the spatial resolution of climate models were enhanced. Spatial resolution is a particular important issue in climate change scenarios of shelf seas such as the North Sea. The North Sea is strongly influenced by its water mass exchanges with North Atlantic to the west and north and Baltic Sea to east. Furthermore, local forcing and changes in advected water masses significantly affect the thermodynamics and stratification patterns in the North Sea, making it a challenging area to study. Under the newly started RACE2 project we are looking at global simulations of Representative Concentration Pathway (RCP) scenarios 4.5 and 8.5 at lower and higher resolutions, performed using the Max Planck Institute Earth System Model (MPIESM). The model resolution is non uniform and achieves the highest resolution over the European Seas by shifting the model poles over Chicago and Central Europe. In the high resolution run, the grid reaches up to a spatial resolution of up to 4 km in part of the German Bight and close to 20 km in the Northern part of North Sea. The placement of model poles at specific locations enables the global model to obtain higher resolution at regional scales (North Sea), without the inherent complications of open boundary conditions. High and low resolution simulations will be compared to determine differences in spatial and temporal pattern of temperature anomalies, fresh water intrusion from the Baltic Sea to North Sea etc. Also taken into consideration will be the changes in simulating local sea level change and response to basin scale oscillations like NAO.

  3. Enhancing spatial resolution of digital holographic microscopy using speckle patterns generated from ring-slit apertures

    NASA Astrophysics Data System (ADS)

    Funamizu, Hideki; Chen, Tan Qin; Onodera, Yusei; Uozumi, Jun; Aizu, Yoshihisa

    2017-04-01

    In this study, we propose a method to enhance the spatial resolution of digital holographic microscopy with speckle-illumination. In this method, speckle patterns are generated from coherence light passing through ring-slit apertures instead of the most typical circular apertures, to obtain higher numerical aperture. The results show that a reconstructed image with the higher resolution is obtained using ring-slit apertures.

  4. High spatial resolution measurements of ram accelerator gas dynamic phenomena

    NASA Technical Reports Server (NTRS)

    Hinkey, J. B.; Burnham, E. A.; Bruckner, A. P.

    1992-01-01

    High spatial resolution experimental tube wall pressure measurements of ram accelerator gas dynamic phenomena are presented. The projectile resembles the centerbody of a ramjet and travels supersonically through a tube filled with a combustible gaseous mixture, with the tube acting as the outer cowling. Pressure data are recorded as the projectile passes by sensors mounted in the tube wall at various locations along the tube. Data obtained by using a special highly instrumented section of tube has allowed the recording of gas dynamic phenomena with a spatial resolution on the order of one tenth the projectile length. High spatial resolution tube wall pressure data from the three regimes of propulsion studied to date (subdetonative, transdetonative, and superdetonative) are presented and reveal the 3D character of the flowfield induced by projectile fins and the canting of the projectile body relative to the tube wall. Also presented for comparison to the experimental data are calculations made with an inviscid, 3D CFD code.

  5. Temporal and spatial resolution of HF ocean radars

    NASA Astrophysics Data System (ADS)

    Heron, Malcom L.; Atwater, Daniel P.

    2013-03-01

    The spatial and temporal resolutions of the two main types of HF radar are compared, with reference to the phasedarray and the crossed-loop direction-finding systems which make up the Australian Coastal Ocean radar Network. Both genres use a swept frequency "chirp" modulation to define the range of a pixel being observed but the method for determining the azimuth direction of the pixel is a strong point of differentiation. The phased-array systems produce independent maps of surface currents in about 1/7 of the time for the crossed-loop systems because of contrasting noise performance of the antennas. The use of beam-forming analysis in the phased-arrays is shown to give spatial resolutions, for vector currents, of about 10 km close to the shore, and 25 km at ranges of 150 km. The corresponding vector current spatial resolutions for the crossed-loop systems are 40 km and 60 km respectively.

  6. Duality between noise and spatial resolution in linear systems.

    PubMed

    Gureyev, Timur E; Nesterets, Yakov I; de Hoog, Frank; Schmalz, Gerd; Mayo, Sheridan C; Mohammadi, Sara; Tromba, Giuliana

    2014-04-21

    It is shown that in a broad class of linear systems, including general linear shift-invariant systems, the spatial resolution and the noise satisfy a duality relationship, resembling the uncertainty principle in quantum mechanics. The product of the spatial resolution and the standard deviation of output noise in such systems represents a type of phase-space volume that is invariant with respect to linear scaling of the point-spread function, and it cannot be made smaller than a certain positive absolute lower limit. A corresponding intrinsic "quality" characteristic is introduced and then evaluated for the cases of some popular imaging systems, including computed tomography, generic image convolution and phase-contrast imaging. It is shown that in the latter case the spatial resolution and the noise can sometimes be decoupled, potentially leading to a substantial increase in the imaging quality.

  7. Improved Spatial Resolution For Reflection Mode Infrared Spectromicroscopy

    SciTech Connect

    Bechtel, Hans A; Martin, Michael C.; May, T. E.; Lerch, Philippe

    2009-08-13

    Standard commercial infrared microscopes operating in reflection mode use a mirror to direct the reflected light from the sample to the detector. This mirror blocks about half of the incident light, however, and thus degrades the spatial resolution by reducing the numerical aperture of the objective. Here, we replace the mirror with a 50% beamsplitter to allow full illumination of the objective and retain a way to direct the reflected light to the detector. The improved spatial resolution is demonstrated using a microscope coupled to a synchrotron source.

  8. Improved Spatial Resolution For Reflection Mode Infrared Spectromicroscopy

    SciTech Connect

    Bechtel, Hans A.; Martin, Michael C.; May, T. E.; Lerch, Philippe

    2010-02-03

    Standard commercial infrared microscopes operating in reflection mode use a mirror to direct the reflected light from the sample to the detector. This mirror blocks about half of the incident light, however, and thus degrades the spatial resolution by reducing the numerical aperture of the objective. Here, we replace the mirror with a 50% beamsplitter to allow full illumination of the objective and retain a way to direct the reflected light to the detector. The improved spatial resolution is demonstrated using a microscope coupled to a synchrotron source.

  9. Spatial scales of pollution from variable resolution satellite imaging.

    PubMed

    Chudnovsky, Alexandra A; Kostinski, Alex; Lyapustin, Alexei; Koutrakis, Petros

    2013-01-01

    The Moderate Resolution Imaging Spectroradiometer (MODIS) provides daily global coverage, but the 10 km resolution of its aerosol optical depth (AOD) product is not adequate for studying spatial variability of aerosols in urban areas. Recently, a new Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm was developed for MODIS which provides AOD at 1 km resolution. Using MAIAC data, the relationship between MAIAC AOD and PM(2.5) as measured by the EPA ground monitoring stations was investigated at varying spatial scales. Our analysis suggested that the correlation between PM(2.5) and AOD decreased significantly as AOD resolution was degraded. This is so despite the intrinsic mismatch between PM(2.5) ground level measurements and AOD vertically integrated measurements. Furthermore, the fine resolution results indicated spatial variability in particle concentration at a sub-10 km scale. Finally, this spatial variability of AOD within the urban domain was shown to depend on PM(2.5) levels and wind speed. Copyright © 2012 Elsevier Ltd. All rights reserved.

  10. Modeling Spatial Dependencies in High-Resolution Overhead Imagery

    SciTech Connect

    Cheriyadat, Anil M; Bright, Eddie A; Vatsavai, Raju

    2011-01-01

    Human settlement regions with different physical and socio-economic attributes exhibit unique spatial characteristics that are often illustrated in high-resolution overhead imageries. For example- size, shape and spatial arrangements of man-made structures are key attributes that vary with respect to the socioeconomic profile of the neighborhood. Successfully modeling these attributes is crucial in developing advanced image understanding systems for interpreting complex aerial scenes. In this paper we present three different approaches to model the spatial context in the overhead imagery. First, we show that the frequency domain of the image can be used to model the spatial context [1]. The shape of the spectral energy contours characterize the scene context and can be exploited as global features. Secondly, we explore a discriminative framework based on the Conditional Random Fields (CRF) [2] to model the spatial context in the overhead imagery. The features derived from the edge orientation distribution calculated for a neighborhood and the associated class labels are used as input features to model the spatial context. Our third approach is based on grouping spatially connected pixels based on the low-level edge primitives to form support-regions [3]. The statistical parameters generated from the support-region feature distributions characterize different geospatial neighborhoods. We apply our approaches on high-resolution overhead imageries. We show that proposed approaches characterize the spatial context in overhead imageries.

  11. Chromatic and Achromatic Spatial Resolution of Local Field Potentials in Awake Cortex

    PubMed Central

    Jansen, Michael; Li, Xiaobing; Lashgari, Reza; Kremkow, Jens; Bereshpolova, Yulia; Swadlow, Harvey A.; Zaidi, Qasim; Alonso, Jose-Manuel

    2015-01-01

    Local field potentials (LFPs) have become an important measure of neuronal population activity in the brain and could provide robust signals to guide the implant of visual cortical prosthesis in the future. However, it remains unclear whether LFPs can detect weak cortical responses (e.g., cortical responses to equiluminant color) and whether they have enough visual spatial resolution to distinguish different chromatic and achromatic stimulus patterns. By recording from awake behaving macaques in primary visual cortex, here we demonstrate that LFPs respond robustly to pure chromatic stimuli and exhibit ∼2.5 times lower spatial resolution for chromatic than achromatic stimulus patterns, a value that resembles the ratio of achromatic/chromatic resolution measured with psychophysical experiments in humans. We also show that, although the spatial resolution of LFP decays with visual eccentricity as is also the case for single neurons, LFPs have higher spatial resolution and show weaker response suppression to low spatial frequencies than spiking multiunit activity. These results indicate that LFP recordings are an excellent approach to measure spatial resolution from local populations of neurons in visual cortex including those responsive to color. PMID:25416722

  12. Passive Standoff Super Resolution Imaging using Spatial-Spectral Multiplexing

    DTIC Science & Technology

    2017-08-14

    transform variable of OPD in cycles per unit length, and the constant term from Eq. (89) has been removed for clarity. The full width spectral resolution...an average spatial period of 145.8 μm, which corresponds to an average spatial frequency of fc = 6.87 cycles /mm across the SLM. This carrier was...an average frequency of fc = 6.87 cycles /mm, was modulated with randomly generated envelopes. Random angular spectra were generated in MATLAB as

  13. Solar Flares at High Spatial and Temporal Resolution

    DTIC Science & Technology

    2012-11-01

    AFRL-AFOSR-UK-TR-2012-0055 Solar Flares at High Spatial and Temporal Resolution Professor Mihalis Mathioudakis Queen’s...2012 2. REPORT TYPE Final Report 3. DATES COVERED (From – To) 20 July 2009 – 19 July 2012 4. TITLE AND SUBTITLE Solar Flares at High Spatial and...Distribution A: Approved for public release; distribution is unlimited. 13. SUPPLEMENTARY NOTES 14. ABSTRACT Solar flares vary in

  14. Spatially adaptive regularized iterative high-resolution image reconstruction algorithm

    NASA Astrophysics Data System (ADS)

    Lim, Won Bae; Park, Min K.; Kang, Moon Gi

    2000-12-01

    High resolution images are often required in applications such as remote sensing, frame freeze in video, military and medical imaging. Digital image sensor arrays, which are used for image acquisition in many imaging systems, are not dense enough to prevent aliasing, so the acquired images will be degraded by aliasing effects. To prevent aliasing without loss of resolution, a dense detector array is required. But it may be very costly or unavailable, thus, many imaging systems are designed to allow some level of aliasing during image acquisition. The purpose of our work is to reconstruct an unaliased high resolution image from the acquired aliased image sequence. In this paper, we propose a spatially adaptive regularized iterative high resolution image reconstruction algorithm for blurred, noisy and down-sampled image sequences. The proposed approach is based on a Constrained Least Squares (CLS) high resolution reconstruction algorithm, with spatially adaptive regularization operators and parameters. These regularization terms are shown to improve the reconstructed image quality by forcing smoothness, while preserving edges in the reconstructed high resolution image. Accurate sub-pixel motion registration is the key of the success of the high resolution image reconstruction algorithm. However, sub-pixel motion registration may have some level of registration error. Therefore, a reconstruction algorithm which is robust against the registration error is required. The registration algorithm uses a gradient based sub-pixel motion estimator which provides shift information for each of the recorded frames. The proposed algorithm is based on a technique of high resolution image reconstruction, and it solves spatially adaptive regularized constrained least square minimization functionals. In this paper, we show that the reconstruction algorithm gives dramatic improvements in the resolution of the reconstructed image and is effective in handling the aliased information. The

  15. Spatial resolution requirements for automated cartographic road extraction

    USGS Publications Warehouse

    Benjamin, S.; Gaydos, L.

    1990-01-01

    Ground resolution requirements for detection and extraction of road locations in a digitized large-scale photographic database were investigated. A color infrared photograph of Sunnyvale, California was scanned, registered to a map grid, and spatially degraded to 1- to 5-metre resolution pixels. Road locations in each data set were extracted using a combination of image processing and CAD programs. These locations were compared to a photointerpretation of road locations to determine a preferred pixel size for the extraction method. Based on road pixel omission error computations, a 3-metre pixel resolution appears to be the best choice for this extraction method. -Authors

  16. Quantifying mangrove chlorophyll from high spatial resolution imagery

    NASA Astrophysics Data System (ADS)

    Heenkenda, Muditha K.; Joyce, Karen E.; Maier, Stefan W.; de Bruin, Sytze

    2015-10-01

    Lower than expected chlorophyll concentration of a plant can directly limit photosynthetic activity, and resultant primary production. Low chlorophyll concentration may also indicate plant physiological stress. Compared to other terrestrial vegetation, mangrove chlorophyll variations are poorly understood. This study quantifies the spatial distribution of mangrove canopy chlorophyll variation using remotely sensed data and field samples over the Rapid Creek mangrove forest in Darwin, Australia. Mangrove leaf samples were collected and analyzed for chlorophyll content in the laboratory. Once the leaf area index (LAI) of sampled trees was estimated using the digital cover photography method, the canopy chlorophyll contents were calculated. Then, the nonlinear random forests regression algorithm was used to describe the relationship between canopy chlorophyll content and remotely sensed data (WorldView-2 satellite image bands and their spectral transformations), and to estimate the spatial distribution of canopy chlorophyll variation. The imagery was evaluated at full 2 m spatial resolution, as well as at decreased resampled resolutions of 5 m and 10 m. The root mean squared errors with validation samples were 0.82, 0.64 and 0.65 g/m2 for maps at 2 m, 5 m and 10 m spatial resolution respectively. The correlation coefficient was analyzed for the relationship between measured and predicted chlorophyll values. The highest correlation: 0.71 was observed at 5 m spatial resolution (R2 = 0.5). We therefore concluded that estimating mangrove chlorophyll content from remotely sensed data is possible using red, red-edge, NIR1 and NIR2 bands and their spectral transformations as predictors at 5 m spatial resolution.

  17. Research Relative to High Spatial Resolution Passive Microwave Sounding Systems

    NASA Technical Reports Server (NTRS)

    Staelin, D. H.; Rosenkranz, P. W.

    1984-01-01

    Methods to obtain high resolution passive microwave weather observations, and understanding of their probable impact on numerical weather prediction accuracy were investigated. The development of synthetic aperture concepts for geosynchronous passive microwave sounders were studied. The effects of clouds, precipitation, surface phenomena, and atmospheric thermal fine structure on a scale of several kilometers were examined. High resolution passive microwave sounders (e.g., AMSU) with an increased number of channels will produce initialization data for numerical weather prediction (NWP) models with both increased spatial resolution and coverage. The development of statistical models for error growth in high resolution primitive equation NWP models which permit the consequences of various observing system alternatives, including sensors and assimilation times and procedures is discussed. A high resolution three dimensional primitive equation NWP model to determine parameters in an error growth model similar to that formulated by Lorenz, but with more degrees of freedom is utilized.

  18. Higher resolution satellite remote sensing and the impact on image mapping

    USGS Publications Warehouse

    Watkins, Allen H.; Thormodsgard, June M.

    1987-01-01

    Recent advances in spatial, spectral, and temporal resolution of civil land remote sensing satellite data are presenting new opportunities for image mapping applications. The U.S. Geological Survey's experimental satellite image mapping program is evolving toward larger scale image map products with increased information content as a result of improved image processing techniques and increased resolution. Thematic mapper data are being used to produce experimental image maps at 1:100,000 scale that meet established U.S. and European map accuracy standards. Availability of high quality, cloud-free, 30-meter ground resolution multispectral data from the Landsat thematic mapper sensor, along with 10-meter ground resolution panchromatic and 20-meter ground resolution multispectral data from the recently launched French SPOT satellite, present new cartographic and image processing challenges. The need to fully exploit these higher resolution data increases the complexity of processing the images into large-scale image maps. The removal of radiometric artifacts and noise prior to geometric correction can be accomplished by using a variety of image processing filters and transforms. Sensor modeling and image restoration techniques allow maximum retention of spatial and radiometric information. An optimum combination of spectral information and spatial resolution can be obtained by merging different sensor types. These processing techniques are discussed and examples are presented. 

  19. Spatial Resolution Characterization for AWiFS Multispectral Images

    NASA Technical Reports Server (NTRS)

    Blonski, Slawomir; Ryan, Robert E.; Pagnutti, Mary; Stanley, Thomas

    2007-01-01

    This viewgraph presentation describes the spatial resolution of the AWiFS multispectral images characterized by an estimation of the Modulation Transfer Function (MTF) at Nyquist frequency. The contents include: 1) MTF Analysis; 2) Target Analysis; 3) "Pulse Target"; 4) "Pulse" Method; 5) Target Images; 6) Bridge Profiles; 7) MTF Calculation; 8) MTF Results; and 9) Results Summary.

  20. Improved Spatial Resolution for Reflection Mode Infrared Microscopy

    SciTech Connect

    Bechtel, Hans A.; Martin, Michael C.; May, T.E.; Lerch, Philippe

    2009-10-09

    Standard commercial infrared microscopes operating in reflection mode use a mirror to direct the reflected light from the sample to the detector. This mirror blocks about half of the incident light, however, and thus degrades the spatial resolution by reducing the umerical aperture of the objective. Here, we replace the mirror with a 50% beamsplitter to allow full illumination of the objective and retain a way to direct the reflected light to the detector. The improved spatial resolution is demonstrated using two different microscopes apable of diffraction-limited resolution: the first microscope is coupled to a synchrotron source and utilizes a single point detector, whereas the second microscope has a standard blackbody source and uses a focal planetarray (FPA) detector.

  1. Hyperspectral Imagery Super-Resolution by Compressive Sensing Inspired Dictionary Learning and Spatial-Spectral Regularization

    PubMed Central

    Huang, Wei; Xiao, Liang; Liu, Hongyi; Wei, Zhihui

    2015-01-01

    Due to the instrumental and imaging optics limitations, it is difficult to acquire high spatial resolution hyperspectral imagery (HSI). Super-resolution (SR) imagery aims at inferring high quality images of a given scene from degraded versions of the same scene. This paper proposes a novel hyperspectral imagery super-resolution (HSI-SR) method via dictionary learning and spatial-spectral regularization. The main contributions of this paper are twofold. First, inspired by the compressive sensing (CS) framework, for learning the high resolution dictionary, we encourage stronger sparsity on image patches and promote smaller coherence between the learned dictionary and sensing matrix. Thus, a sparsity and incoherence restricted dictionary learning method is proposed to achieve higher efficiency sparse representation. Second, a variational regularization model combing a spatial sparsity regularization term and a new local spectral similarity preserving term is proposed to integrate the spectral and spatial-contextual information of the HSI. Experimental results show that the proposed method can effectively recover spatial information and better preserve spectral information. The high spatial resolution HSI reconstructed by the proposed method outperforms reconstructed results by other well-known methods in terms of both objective measurements and visual evaluation. PMID:25608212

  2. Parameter Transferability Across Spatial and Temporal Resolutions in Hydrological Modelling

    NASA Astrophysics Data System (ADS)

    Melsen, L. A.; Teuling, R.; Torfs, P. J.; Zappa, M.; Mizukami, N.; Clark, M. P.; Uijlenhoet, R.

    2015-12-01

    Improvements in computational power and data availability provided new opportunities for hydrological modeling. The increased complexity of hydrological models, however, also leads to time consuming optimization procedures. Moreover, observations are still required to calibrate the model. Both to decrease calculation time of the optimization and to be able to apply the model in poorly gauged basins, many studies have focused on transferability of parameters. We adopted a probabilistic approach to systematically investigate parameter transferability across both temporal and spatial resolution. A Variable Infiltration Capacity model for the Thur basin (1703km2, Switzerland) was set-up and run at four different spatial resolutions (1x1, 5x5, 10x10km, lumped) and three different temporal resolutions (hourly, daily, monthly). Three objective functions were used to evaluate the model: Kling-Gupta Efficiency (KGE(Q)), Nash-Sutcliffe Efficiency (NSE(Q)) and NSE(logQ). We used a Hierarchical Latin Hypercube Sample (Vorechovsky, 2014) to efficiently sample the most sensitive parameters. The model was run 3150 times and the best 1% of the runs was selected as behavioral. The overlap in selected behavioral sets for different spatial and temporal resolutions was used as indicators for parameter transferability. There was a large overlap in selected sets for the different spatial resolutions, implying that parameters were to a large extent transferable across spatial resolutions. The temporal resolution, however, had a larger impact on the parameters; it significantly affected the parameter distributions for at least four out of seven parameters. The parameter values for the monthly time step were found to be substantially different from those for daily and hourly time steps. This suggests that the output from models which are calibrated on a monthly time step, cannot be interpreted or analysed on an hourly or daily time step. It was also shown that the selected objective

  3. Influences of temporal rainfall radar and spatial rainfall-runoff model resolution on flood prediction

    NASA Astrophysics Data System (ADS)

    Weiler, Markus; Steinbrich, Andreas

    2013-04-01

    distribution of rain intensity in higher resolution by using only the information of the hourly radar data and an assumed temporal distribution of rainfall at each radar grid cell. The methods preserves the total rainfall amount at each cell and preserves the overall rainfall pattern and movement of precipitation cells. Generally, we could improve the prediction of the model for short convective events in particular for the peak discharge. The higher temporal resolution effects the runoff generation and depends strongly on soil characteristics. On soils with high infiltration capacity the increase of temporal resolution effects the generation of fast overland runoff. This effect decreases with decreasing infiltration capacity of soils. The analysis revealed that a variable temporal resolution is needed to model convective and advective rainfall events with the same model parameterization. A "correct" spatial resolution of the distributed model, however, depends strongly on the dominant runoff generation process in a watershed and is also different for runoff generation and runoff concentration.

  4. Spatial resolution of a hard x-ray CCD detector

    SciTech Connect

    Seely, John F.; Pereira, Nino R.; Weber, Bruce V.; Schumer, Joseph W.; Apruzese, John P.; Hudson, Lawrence T.; Szabo, Csilla I.; Boyer, Craig N.; Skirlo, Scott

    2010-08-10

    The spatial resolution of an x-ray CCD detector was determined from the widths of the tungsten x-ray lines in the spectrum formed by a crystal spectrometer in the 58 to 70 keV energy range. The detector had 20{mu}m pixel, 1700 by 1200 pixel format, and a CsI x-ray conversion scintillator. The spectral lines from a megavolt x-ray generator were focused on the spectrometer's Rowland circle by a curved transmission crystal. The line shapes were Lorentzian with an average width after removal of the natural and instrumental line widths of 95{mu}m (4.75 pixels). A high spatial frequency background, primarily resulting from scattered gamma rays, was removed from the spectral image by Fourier analysis. The spectral lines, having low spatial frequency in the direction perpendicular to the dispersion, were enhanced by partially removing the Lorentzian line shape and by fitting Lorentzian curves to broad unresolved spectral features. This demonstrates the ability to improve the spectral resolution of hard x-ray spectra that are recorded by a CCD detector with well-characterized intrinsic spatial resolution.

  5. High-spatial-resolution nanoparticle x-ray fluorescence tomography

    NASA Astrophysics Data System (ADS)

    Larsson, Jakob C.; Vâgberg, William; Vogt, Carmen; Lundström, Ulf; Larsson, Daniel H.; Hertz, Hans M.

    2016-03-01

    X-ray fluorescence tomography (XFCT) has potential for high-resolution 3D molecular x-ray bio-imaging. In this technique the fluorescence signal from targeted nanoparticles (NPs) is measured, providing information about the spatial distribution and concentration of the NPs inside the object. However, present laboratory XFCT systems typically have limited spatial resolution (>1 mm) and suffer from long scan times and high radiation dose even at high NP concentrations, mainly due to low efficiency and poor signal-to-noise ratio. We have developed a laboratory XFCT system with high spatial resolution (sub-100 μm), low NP concentration and vastly decreased scan times and dose, opening up the possibilities for in-vivo small-animal imaging research. The system consists of a high-brightness liquid-metal-jet microfocus x-ray source, x-ray focusing optics and an energy-resolving photon-counting detector. By using the source's characteristic 24 keV line-emission together with carefully matched molybdenum nanoparticles the Compton background is greatly reduced, increasing the SNR. Each measurement provides information about the spatial distribution and concentration of the Mo nanoparticles. A filtered back-projection method is used to produce the final XFCT image.

  6. Spatially resolved and observer-free experimental quantification of spatial resolution in tomographic images

    SciTech Connect

    Tsekenis, S. A.; McCann, H.; Tait, N.

    2015-03-15

    We present a novel framework and experimental method for the quantification of spatial resolution of a tomography system. The framework adopts the “black box” view of an imaging system, considering only its input and output. The tomography system is locally stimulated with a step input, viz., a sharp edge. The output, viz., the reconstructed images, is analysed by Fourier decomposition of their spatial frequency components, and the local limiting spatial resolution is determined using a cut-off threshold. At no point is an observer involved in the process. The framework also includes a means of translating the quantification region in the imaging space, thus creating a spatially resolved map of objectively quantified spatial resolution. As a case-study, the framework is experimentally applied using a gaseous propane phantom measured by a well-established chemical species tomography system. A spatial resolution map consisting of 28 regions is produced. In isolated regions, the indicated performance is 4-times better than that suggested in the literature and varies by 57% across the imaging space. A mechanism based on adjacent but non-interacting beams is hypothesised to explain the observed behaviour. The mechanism suggests that, as also independently concluded by other methods, a geometrically regular beam array maintains maximum objectivity in reconstructions. We believe that the proposed framework, methodology, and findings will be of value in the design and performance evaluation of tomographic imaging arrays and systems.

  7. High-Temporal-Resolution High-Spatial-Resolution Spaceborne SAR Based on Continuously Varying PRF.

    PubMed

    Men, Zhirong; Wang, Pengbo; Li, Chunsheng; Chen, Jie; Liu, Wei; Fang, Yue

    2017-07-25

    Synthetic Aperture Radar (SAR) is a well-established and powerful imaging technique for acquiring high-spatial-resolution images of the Earth's surface. With the development of beam steering techniques, sliding spotlight and staring spotlight modes have been employed to support high-spatial-resolution applications. In addition to this strengthened high-spatial-resolution and wide-swath capability, high-temporal-resolution (short repeat-observation interval) represents a key capability for numerous applications. However, conventional SAR systems are limited in that the same patch can only be illuminated for several seconds within a single pass. This paper considers a novel high-squint-angle system intended to acquire high-spatial-resolution spaceborne SAR images with repeat-observation intervals varying from tens of seconds to several minutes within a single pass. However, an exponentially increased range cell migration would arise and lead to a conflict between the receive window and 'blind ranges'. An efficient data acquisition technique for high-temporal-resolution, high-spatial-resolution and high-squint-angle spaceborne SAR, in which the pulse repetition frequency (PRF) is continuously varied according to the changing slant range, is presented in this paper. This technique allows echo data to remain in the receive window instead of conflicting with the transmitted pulse or nadir echo. Considering the precision of hardware, a compromise and practical strategy is also proposed. Furthermore, a detailed performance analysis of range ambiguities is provided with respect to parameters of TerraSAR-X. For strong point-like targets, the range ambiguity of this technique would be better than that of uniform PRF technique. For this innovative technique, a resampling strategy and modified imaging algorithm have been developed to handle the non-uniformly sampled echo data. Simulations are performed to validate the efficiency of the proposed technique and the associated

  8. A Climate Record of Enhanced Spatial Resolution Radiometer Data (Invited)

    NASA Astrophysics Data System (ADS)

    Paget, A. C.; Long, D. G.; Brodzik, M.

    2013-12-01

    Satellite radiometers, such SMMR, SSM/I, SSMIS, and AMSR, provide a multi-decadal time series of observations of the globe to support studies of climate change. Unfortunately, spatial resolution and sampling characteristics differ between sensors, which complicate compiling a single climate record. Resolution concerns can be ameliorated by reconstructing radiometer brightness temperature measurement (Tb) data onto daily-averaged compatible grids. We consider and contrast two widely used methods for image reconstruction: a radiometer version of the scatterometer image reconstruction (SIR) algorithm and Backus-Gilbert (BG). Both require detailed information about the spatial response function (antenna gain pattern) and the sampling geometry. We discuss considerations for an optimum gridding scheme based on the EASE-Grid 2.0 map projection. The EASE-Grid 2.0 simplifies the application of the Tb images in derived products since the reconstruction for each radiometer channel is implement on the same grid. This has the effect of optimally interpolating low-resolution measurements to locations of the highest resolution measurements. By employing reconstruction techniques rather than 'drop in the bucket' (dib) gridding, the effective resolution of the images is spatially enhanced compared to dib images, at the expense of additional computation required for the reconstruction processing. We evaluate the sensitivity of the radiometric accuracy of the resulting Tb images to uncertainties in the antenna gain pattern as well as variations in local-time-of-day. We briefly consider a number of applications of reconstructed Tb images. As part of the NASA-MEASUREs project 'An improved, enhanced-resolution, gridded passive microwave ESDR for monitoring cryospheric and hydrologic time series' we are processing all available satellite radiometer data to generate a consistently calibrated and processed time series of gridded images spanning from the 1970's to the present.

  9. Enhancement of spatial resolution in digital holographic microscopy using speckle field generated from ring-slit apertures

    NASA Astrophysics Data System (ADS)

    Funamizu, Hideki; Onodera, Yusei; Uozumi, Jun; Aizu, Yoshihisa

    2017-06-01

    In this study, we propose a method to enhance the spatial resolution of digital holographic microscopy with speckle illuminations. In this method, speckle patterns are generated from coherence light passing through ringslit apertures instead of the most typical circular apertures, to obtain higher numerical aperture. The results show that a reconstructed image with the higher resolution is obtained using ring-slit apertures.

  10. Subcell resolution in simplex stochastic collocation for spatial discontinuities

    SciTech Connect

    Witteveen, Jeroen A.S.; Iaccarino, Gianluca

    2013-10-15

    Subcell resolution has been used in the Finite Volume Method (FVM) to obtain accurate approximations of discontinuities in the physical space. Stochastic methods are usually based on local adaptivity for resolving discontinuities in the stochastic dimensions. However, the adaptive refinement in the probability space is ineffective in the non-intrusive uncertainty quantification framework, if the stochastic discontinuity is caused by a discontinuity in the physical space with a random location. The dependence of the discontinuity location in the probability space on the spatial coordinates then results in a staircase approximation of the statistics, which leads to first-order error convergence and an underprediction of the maximum standard deviation. To avoid these problems, we introduce subcell resolution into the Simplex Stochastic Collocation (SSC) method for obtaining a truly discontinuous representation of random spatial discontinuities in the interior of the cells discretizing the probability space. The presented SSC–SR method is based on resolving the discontinuity location in the probability space explicitly as function of the spatial coordinates and extending the stochastic response surface approximations up to the predicted discontinuity location. The applications to a linear advection problem, the inviscid Burgers’ equation, a shock tube problem, and the transonic flow over the RAE 2822 airfoil show that SSC–SR resolves random spatial discontinuities with multiple stochastic and spatial dimensions accurately using a minimal number of samples.

  11. Subcell resolution in simplex stochastic collocation for spatial discontinuities

    NASA Astrophysics Data System (ADS)

    Witteveen, Jeroen A. S.; Iaccarino, Gianluca

    2013-10-01

    Subcell resolution has been used in the Finite Volume Method (FVM) to obtain accurate approximations of discontinuities in the physical space. Stochastic methods are usually based on local adaptivity for resolving discontinuities in the stochastic dimensions. However, the adaptive refinement in the probability space is ineffective in the non-intrusive uncertainty quantification framework, if the stochastic discontinuity is caused by a discontinuity in the physical space with a random location. The dependence of the discontinuity location in the probability space on the spatial coordinates then results in a staircase approximation of the statistics, which leads to first-order error convergence and an underprediction of the maximum standard deviation. To avoid these problems, we introduce subcell resolution into the Simplex Stochastic Collocation (SSC) method for obtaining a truly discontinuous representation of random spatial discontinuities in the interior of the cells discretizing the probability space. The presented SSC-SR method is based on resolving the discontinuity location in the probability space explicitly as function of the spatial coordinates and extending the stochastic response surface approximations up to the predicted discontinuity location. The applications to a linear advection problem, the inviscid Burgers' equation, a shock tube problem, and the transonic flow over the RAE 2822 airfoil show that SSC-SR resolves random spatial discontinuities with multiple stochastic and spatial dimensions accurately using a minimal number of samples.

  12. Ameliorating the spatial resolution of Hyperion hyperspectral data

    NASA Astrophysics Data System (ADS)

    Nikolakopoulos, Konstantinos G.; Tsombos, Panagiotis I.; Skianis, George A.; Vaiopoulos, Dimitrios A.

    2009-09-01

    In this study seven fusion techniques and more especially the Ehlers, Gram-Schmidt, High Pass Filter, Local Mean Matching (LMM), Local Mean and Variance Matching (LMVM), Pansharp and PCA, were used for the fusion of Hyperion hyperspectral data with ALI panchromatic data. Both sensors are onboard on EO-1 satellite and the data are collected simultaneously. The panchromatic data has a spatial resolution of 10m while the hyperspectral data has a spatial resolution of 30m. All the fusion techniques are designed for use with classical multispectral data. Thus, it is quite interesting to investigate the assessment of the common used fusion algorithms with the hyperspectral data. The area of study is the broader area of North Western Athens near to Thrakomakedones village.

  13. A multipinhole small animal SPECT system with submillimeter spatial resolution

    SciTech Connect

    Funk, Tobias; Despres, Philippe; Barber, William C.; Shah, Kanai S.; Hasegawa, Bruce H.

    2006-05-15

    Single photon emission computed tomography (SPECT) is an important technology for molecular imaging studies of small animals. In this arena, there is an increasing demand for high performance imaging systems that offer improved spatial resolution and detection efficiency. We have designed a multipinhole small animal imaging system based on position sensitive avalanche photodiode (PSAPD) detectors with the goal of submillimeter spatial resolution and high detection efficiency, which will allow us to minimize the radiation dose to the animal and to shorten the time needed for the imaging study. Our design will use 8x24 mm{sup 2} PSAPD detector modules coupled to thallium-doped cesium iodide [CsI(Tl)] scintillators, which can achieve an intrinsic spatial resolution of 0.5 mm at 140 keV. These detectors will be arranged in rings of 24 modules each; the animal is positioned in the center of the 9 stationary detector rings which capture projection data from the animal with a cylindrical tungsten multipinhole collimator. The animal is supported on a bed which can be rocked about the central axis to increase angular sampling of the object. In contrast to conventional SPECT pinhole systems, in our design each pinhole views only a portion of the object. However, the ensemble of projection data from all of the multipinhole detectors provide angular sampling that is sufficient to reconstruct tomographic data from the object. The performance of this multipinhole PSAPD imaging system was simulated using a ray tracing program that models the appropriate point spread functions and then was compared against the performance of a dual-headed pinhole SPECT system. The detection efficiency of both systems was simulated and projection data of a hot rod phantom were generated and reconstructed to assess spatial resolution. Appropriate Poisson noise was added to the data to simulate an acquisition time of 15 min and an activity of 18.5 MBq distributed in the phantom. Both sets of data

  14. Imaging metals in biology: balancing sensitivity, selectivity and spatial resolution.

    PubMed

    Hare, Dominic J; New, Elizabeth J; de Jonge, Martin D; McColl, Gawain

    2015-10-07

    Metal biochemistry drives a diverse range of cellular processes associated with development, health and disease. Determining metal distribution, concentration and flux defines our understanding of these fundamental processes. A comprehensive analysis of biological systems requires a balance of analytical techniques that inform on metal quantity (sensitivity), chemical state (selectivity) and location (spatial resolution) with a high degree of certainty. A number of approaches are available for imaging metals from whole tissues down to subcellular organelles, as well as mapping metal turnover, protein association and redox state within these structures. Technological advances in micro- and nano-scale imaging are striving to achieve multi-dimensional and in vivo measures of metals while maintaining the native biochemical environment and physiological state. This Tutorial Review discusses state-of-the-art imaging technology as a guide to obtaining novel insight into the biology of metals, with sensitivity, selectivity and spatial resolution in focus.

  15. HIGH SPATIAL RESOLUTION OBSERVATIONS OF LOOPS IN THE SOLAR CORONA

    SciTech Connect

    Brooks, David H.; Ugarte-Urra, Ignacio; Warren, Harry P.; Winebarger, Amy R.

    2013-08-01

    Understanding how the solar corona is structured is of fundamental importance to determine how the Sun's upper atmosphere is heated to high temperatures. Recent spectroscopic studies have suggested that an instrument with a spatial resolution of 200 km or better is necessary to resolve coronal loops. The High Resolution Coronal Imager (Hi-C) achieved this performance on a rocket flight in 2012 July. We use Hi-C data to measure the Gaussian widths of 91 loops observed in the solar corona and find a distribution that peaks at about 270 km. We also use Atmospheric Imaging Assembly data for a subset of these loops and find temperature distributions that are generally very narrow. These observations provide further evidence that loops in the solar corona are often structured at a scale of several hundred kilometers, well above the spatial scale of many proposed physical mechanisms.

  16. Advanced Remote-Sensing Imaging Emission Spectrometer (ARIES): AIRS Spectral Resolution with MODIS Spatial Resolution

    NASA Technical Reports Server (NTRS)

    Pagano, Thomas S.; Chahine, Moustafa T.; Aumann, Hartmut H.; OCallaghan, Fred

    2006-01-01

    The Advanced Remote-sensing Imaging Emission Spectrometer (ARIES) will measure a wide range of earth quantities fundamental to the study of global climate change. It will build upon the success of the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Atmospheric Infrared Sounder (AIRS) instruments currently flying on the EOS Aqua Spacecraft. Both instruments are facility instruments for NASA providing data to thousands of scientists investigating land, ocean and atmospheric Earth System processes. ARIES will meet all the requirements of AIRS and MODIS in a single compact instrument, while providing the next-generation capability of improved spatial resolution for AIRS and improved spectral resolution for MODIS.

  17. Dripping faucet in extreme spatial and temporal resolution

    NASA Astrophysics Data System (ADS)

    Sack, Achim; Pöschel, Thorsten

    2017-09-01

    Besides its importance for science and engineering, the process of drop formation from a homogeneous jet or at a nozzle is of great aesthetic appeal. In this paper, we introduce a low-cost setup for classroom use to produce quasi-high-speed recordings with high temporal and spatial resolution of the formation of drops at a nozzle. The visualization of the process can be used for quantitative analysis of the underlying physical phenomena.

  18. Sub-pixel spatial resolution wavefront phase imaging

    NASA Technical Reports Server (NTRS)

    Stahl, H. Philip (Inventor); Mooney, James T. (Inventor)

    2012-01-01

    A phase imaging method for an optical wavefront acquires a plurality of phase images of the optical wavefront using a phase imager. Each phase image is unique and is shifted with respect to another of the phase images by a known/controlled amount that is less than the size of the phase imager's pixels. The phase images are then combined to generate a single high-spatial resolution phase image of the optical wavefront.

  19. Spatial and spectral resolution necessary for remotely sensed vegetation studies

    NASA Technical Reports Server (NTRS)

    Rock, B. N.

    1982-01-01

    An outline is presented of the required spatial and spectral resolution needed for accurate vegetation discrimination and mapping studies as well as for determination of state of health (i.e., detection of stress symptoms) of actively growing vegetation. Good success was achieved in vegetation discrimination and mapping of a heterogeneous forest cover in the ridge and valley portion of the Appalachians using multispectral data acquired with a spatial resolution of 15 m (IFOV). A sensor system delivering 10 to 15 m spatial resolution is needed for both vegetation mapping and detection of stress symptoms. Based on the vegetation discrimination and mapping exercises conducted at the Lost River site, accurate products (vegetation maps) are produced using broad-band spectral data ranging from the .500 to 2.500 micron portion of the spectrum. In order of decreasing utility for vegetation discrimination, the four most valuable TM simulator VNIR bands are: 6 (1.55 to 1.75 microns), 3 (0.63 to 0.69 microns), 5 (1.00 to 1.30 microns) and 4 (0.76 to 0.90 microns).

  20. Pushing the boundaries of diagnostic CT systems for high spatial resolution imaging tasks

    NASA Astrophysics Data System (ADS)

    Cruz-Bastida, Juan P.; Gomez-Cardona, Daniel; Garrett, John W.; Szczykutowicz, Timothy P.; Chen, Guang-Hong; Li, Ke

    2017-03-01

    In a previous work [Cruz-Bastida et al Med. Phys. 43, 2399 (2016)], the spatial resolution performance of a new High-Resolution (Hi-Res) multi-detector row CT (MDCT) scan mode and the associated High Definition (HD) reconstruction kernels was systematically characterized. The purpose of the present work was to study the noise properties of the Hi-Res scan mode and the joint impact of spatial resolution and noise characteristics on high contrast and high spatial resolution imaging tasks. Using a physical phantom and a diagnostic MDCT system, equipped with both Hi-Res and conventional scan modes, noise power spectrum (NPS) measurements were performed at 8 off-centered positions (0 to 14 cm with an increment of 2 cm) for 8 non-HD kernels and 7 HD kernels. An in vivo rabbit experiment was then performed to demonstrate the potential clinical value of the Hi-Res scan mode. Without the HD kernels, the Hi-Res scan mode preserved the shape of the NPS and slightly increased noise magnitude across all object positions. The combined use of the Hi-Res scan mode and HD kernels led to a greater noise increase and pushed the NPS towards higher frequencies, particularly for those edge-preserving or edge-enhancing HD kernels. Results of the in vivo rabbit study demonstrate important trade-offs between spatial resolution and noise characteristics. Overall, for a given high contrast and high spatial resolution imaging task (bronchi imaging), the benefit of spatial resolution improvement introduced by the Hi-Res scan mode outweighs the potential noise amplification, leading to better overall imaging performance for both centered and off-centered positions.

  1. A Comparison of Spatial and Spectral Image Resolution for Mapping Invasive Plants in Coastal California

    NASA Astrophysics Data System (ADS)

    Underwood, Emma C.; Ustin, Susan L.; Ramirez, Carlos M.

    2007-01-01

    We explored the potential of detecting three target invasive species: iceplant ( Carpobrotus edulis), jubata grass ( Cortaderia jubata), and blue gum ( Eucalyptus globulus) at Vandenberg Air Force Base, California. We compared the accuracy of mapping six communities (intact coastal scrub, iceplant invaded coastal scrub, iceplant invaded chaparral, jubata grass invaded chaparral, blue gum invaded chaparral, and intact chaparral) using four images with different combinations of spatial and spectral resolution: hyperspectral AVIRIS imagery (174 wavebands, 4 m spatial resolution), spatially degraded AVIRIS (174 bands, 30 m), spectrally degraded AVIRIS (6 bands, 4 m), and both spatially and spectrally degraded AVIRIS (6 bands, 30 m, i.e., simulated Landsat ETM data). Overall success rates for classifying the six classes was 75% (kappa 0.7) using full resolution AVIRIS, 58% (kappa 0.5) for the spatially degraded AVIRIS, 42% (kappa 0.3) for the spectrally degraded AVIRIS, and 37% (kappa 0.3) for the spatially and spectrally degraded AVIRIS. A true Landsat ETM image was also classified to illustrate that the results from the simulated ETM data were representative, which provided an accuracy of 50% (kappa 0.4). Mapping accuracies using different resolution images are evaluated in the context of community heterogeneity (species richness, diversity, and percent species cover). Findings illustrate that higher mapping accuracies are achieved with images possessing high spectral resolution, thus capturing information across the visible and reflected infrared solar spectrum. Understanding the tradeoffs in spectral and spatial resolution can assist land managers in deciding the most appropriate imagery with respect to target invasives and community characteristics.

  2. A comparison of spatial and spectral image resolution for mapping invasive plants in coastal california.

    PubMed

    Underwood, Emma C; Ustin, Susan L; Ramirez, Carlos M

    2007-01-01

    We explored the potential of detecting three target invasive species: iceplant (Carpobrotus edulis), jubata grass (Cortaderia jubata), and blue gum (Eucalyptus globulus) at Vandenberg Air Force Base, California. We compared the accuracy of mapping six communities (intact coastal scrub, iceplant invaded coastal scrub, iceplant invaded chaparral, jubata grass invaded chaparral, blue gum invaded chaparral, and intact chaparral) using four images with different combinations of spatial and spectral resolution: hyperspectral AVIRIS imagery (174 wavebands, 4 m spatial resolution), spatially degraded AVIRIS (174 bands, 30 m), spectrally degraded AVIRIS (6 bands, 4 m), and both spatially and spectrally degraded AVIRIS (6 bands, 30 m, i.e., simulated Landsat ETM data). Overall success rates for classifying the six classes was 75% (kappa 0.7) using full resolution AVIRIS, 58% (kappa 0.5) for the spatially degraded AVIRIS, 42% (kappa 0.3) for the spectrally degraded AVIRIS, and 37% (kappa 0.3) for the spatially and spectrally degraded AVIRIS. A true Landsat ETM image was also classified to illustrate that the results from the simulated ETM data were representative, which provided an accuracy of 50% (kappa 0.4). Mapping accuracies using different resolution images are evaluated in the context of community heterogeneity (species richness, diversity, and percent species cover). Findings illustrate that higher mapping accuracies are achieved with images possessing high spectral resolution, thus capturing information across the visible and reflected infrared solar spectrum. Understanding the tradeoffs in spectral and spatial resolution can assist land managers in deciding the most appropriate imagery with respect to target invasives and community characteristics.

  3. Spatial resolution requirements for urban land cover mapping from space

    NASA Technical Reports Server (NTRS)

    Todd, William J.; Wrigley, Robert C.

    1986-01-01

    Very low resolution (VLR) satellite data (Advanced Very High Resolution Radiometer, DMSP Operational Linescan System), low resolution (LR) data (Landsat MSS), medium resolution (MR) data (Landsat TM), and high resolution (HR) satellite data (Spot HRV, Large Format Camera) were evaluated and compared for interpretability at differing spatial resolutions. VLR data (500 m - 1.0 km) is useful for Level 1 (urban/rural distinction) mapping at 1:1,000,000 scale. Feature tone/color is utilized to distinguish generalized urban land cover using LR data (80 m) for 1:250,000 scale mapping. Advancing to MR data (30 m) and 1:100,000 scale mapping, confidence in land cover mapping is greatly increased, owing to the element of texture/pattern which is now evident in the imagery. Shape and shadow contribute to detailed Level II/III urban land use mapping possible if the interpreter can use HR (10-15 m) satellite data; mapping scales can be 1:25,000 - 1:50,000.

  4. Spatial resolution requirements for urban land cover mapping from space

    NASA Technical Reports Server (NTRS)

    Todd, William J.; Wrigley, Robert C.

    1986-01-01

    Very low resolution (VLR) satellite data (Advanced Very High Resolution Radiometer, DMSP Operational Linescan System), low resolution (LR) data (Landsat MSS), medium resolution (MR) data (Landsat TM), and high resolution (HR) satellite data (Spot HRV, Large Format Camera) were evaluated and compared for interpretability at differing spatial resolutions. VLR data (500 m - 1.0 km) is useful for Level 1 (urban/rural distinction) mapping at 1:1,000,000 scale. Feature tone/color is utilized to distinguish generalized urban land cover using LR data (80 m) for 1:250,000 scale mapping. Advancing to MR data (30 m) and 1:100,000 scale mapping, confidence in land cover mapping is greatly increased, owing to the element of texture/pattern which is now evident in the imagery. Shape and shadow contribute to detailed Level II/III urban land use mapping possible if the interpreter can use HR (10-15 m) satellite data; mapping scales can be 1:25,000 - 1:50,000.

  5. Science with High Spatial Resolution Far-Infrared Data

    NASA Technical Reports Server (NTRS)

    Terebey, Susan (Editor); Mazzarella, Joseph M. (Editor)

    1994-01-01

    The goal of this workshop was to discuss new science and techniques relevant to high spatial resolution processing of far-infrared data, with particular focus on high resolution processing of IRAS data. Users of the maximum correlation method, maximum entropy, and other resolution enhancement algorithms applicable to far-infrared data gathered at the Infrared Processing and Analysis Center (IPAC) for two days in June 1993 to compare techniques and discuss new results. During a special session on the third day, interested astronomers were introduced to IRAS HIRES processing, which is IPAC's implementation of the maximum correlation method to the IRAS data. Topics discussed during the workshop included: (1) image reconstruction; (2) random noise; (3) imagery; (4) interacting galaxies; (5) spiral galaxies; (6) galactic dust and elliptical galaxies; (7) star formation in Seyfert galaxies; (8) wavelet analysis; and (9) supernova remnants.

  6. Photoacoustic lymphatic imaging with high spatial-temporal resolution

    NASA Astrophysics Data System (ADS)

    Martel, Catherine; Yao, Junjie; Huang, Chih-Hsien; Zou, Jun; Randolph, Gwendalyn J.; Wang, Lihong V.

    2014-11-01

    Despite its critical function in coordinating the egress of inflammatory and immune cells out of tissues and maintaining fluid balance, the causative role of lymphatic network dysfunction in pathological settings is still understudied. Engineered-animal models and better noninvasive high spatial-temporal resolution imaging techniques in both preclinical and clinical studies will help to improve our understanding of different lymphatic-related pathologic disorders. Our aim was to take advantage of our newly optimized noninvasive wide-field fast-scanning photoacoustic (PA) microcopy system to coordinately image the lymphatic vasculature and its flow dynamics, while maintaining high resolution and detection sensitivity. Here, by combining the optical-resolution PA microscopy with a fast-scanning water-immersible microelectromechanical system scanning mirror, we have imaged the lymph dynamics over a large field-of-view, with high spatial resolution and advanced detection sensitivity. Depending on the application, lymphatic vessels (LV) were spectrally or temporally differentiated from blood vessels. Validation experiments were performed on phantoms and in vivo to identify the LV. Lymphatic flow dynamics in nonpathological and pathological conditions were also visualized. These results indicate that our newly developed PA microscopy is a promising tool for lymphatic-related biological research.

  7. Ameliorating the spatial resolution of GeoEye data

    NASA Astrophysics Data System (ADS)

    Nikolakopoulos, Konstantinos G.; Vaiopoulos, A. D.; Tsombos, P. I.

    2010-10-01

    GeoEye-1 is the first commercial satellite that collects images at nadir with 0.41m panchromatic and 1.65m multispectral resolution (panchromatic imagery sold to commercial customers is resampled to 0.5m resolution). In this study nine fusion techniques and more especially the Ehlers, Gram-Schmidt, High Pass Filter, Local Mean Matching (LMM), Local Mean and Variance Matching (LMVM), Modified IHS (ModIHS), Pansharp, PCA and Wavelet were used for the fusion of Geoeye panchromatic and multispectral data. The panchromatic data have a spatial resolution of 0.5m while the multispectral data have a spatial resolution of 2.0m. The optical result, the statistical parameters and different quality indexes such as ERGAS, Q and entropy were examined and the results are presented. The broader area of Agrinio city in Western Greece was selected for this comparison. It has a complex geomorphology. At the west the area is flat and the elevation ranges between 5 and 20 meters. At the east there are many hills and the elevation rises to more than 450 meters. The area combines at the same time the characteristics of an urban and a rural area thus it is suitable for a comparison of different fusion algorithms.

  8. Spatial resolution effects of CARS in turbulent premixed combustion thermometry

    SciTech Connect

    Shepherd, I.G. . Applied Science Div.); Porter, F.M.; Greenhalgh, D.A. )

    1990-10-01

    Coherent Anti-Stokes Raman Scattering CARS nitrogen thermometry has proved to be a successful technique to obtain point temperature measurements with high temporal resolution in hot reactive gases. It has significant advantages over other probe methods, such as thermocouples, where access, physical and/or chemical perturbation and a lack of sufficient temperature range may create problems. The longitudinal or axial resolution of a CARS measurement, in the preferred BOXCARS geometry, is determined by the zone of perfect overlap of the intersecting laser beams (typically 1-5 mm). The length squared dependence of the CARS signal, however, can limit the spatial resolution if usable signal-to-noise rations are to be obtained. This can be a particular problem when probing systems where steep temperature gradients exist. In this numerical study of a premixed turbulent flame zone the effect of spatial resolution on CARS temperature probability density functions (pdfs) and mean temperature profile measurements is assessed, and possible means to overcome this problem are presented.

  9. Advanced Remote-sensing Imaging Emission Spectrometer (ARIES): AIRS Spectral Resolution with MODIS Spatial Resolution

    NASA Technical Reports Server (NTRS)

    Pagano, Thomas S.; Chahine, Moustafa T.; Aumann, Hartmut H.; OCallaghan, Fred G.; Broberg, Steve E.

    2006-01-01

    This paper describes a space based instrument concept that will provide scientists with data needed to support key ongoing and future Earth System Science investigations. The measurement approach builds on the observations made by AIRS and MODIS and exceeds their capability with improved spatial and spectral resolution. This paper describes the expected products and the instrument concept that can meet those requirements.

  10. Spatially adaptive block-based super-resolution.

    PubMed

    Su, Heng; Tang, Liang; Wu, Ying; Tretter, Daniel; Zhou, Jie

    2012-03-01

    Super-resolution technology provides an effective way to increase image resolution by incorporating additional information from successive input images or training samples. Various super-resolution algorithms have been proposed based on different assumptions, and their relative performances can differ in regions of different characteristics within a single image. Based on this observation, an adaptive algorithm is proposed in this paper to integrate a higher level image classification task and a lower level super-resolution process, in which we incorporate reconstruction-based super-resolution algorithms, single-image enhancement, and image/video classification into a single comprehensive framework. The target high-resolution image plane is divided into adaptive-sized blocks, and different suitable super-resolution algorithms are automatically selected for the blocks. Then, a deblocking process is applied to reduce block edge artifacts. A new benchmark is also utilized to measure the performance of super-resolution algorithms. Experimental results with real-life videos indicate encouraging improvements with our method.

  11. Simulation Study of Spatial Resolution and Sensitivity for Tapered Depth of Interaction PET Detectors for Small Animal Imaging

    PubMed Central

    James, Sara St.; Yang, Yongfeng; Bowen, Spencer L.; Qi, Jinyi; Cherry, Simon R.

    2011-01-01

    Improvements to current small animal PET scanners can be made by improving the sensitivity and the spatial resolution of the scanner. In the past, efforts have been made to minimize the crystal dimensions in the axial and transaxial directions to improve the spatial resolution and to increase the crystal length to improve the sensitivity of the scanner. We have designed tapered PET detectors with the purpose of reducing the gaps between detector modules and optimizing the sensitivity of a future generation small animal PET scanner. In this work, we investigate spatial resolution and sensitivity of a scanner based on tapered detector elements using Monte Carlo simulations. For tapered detector elements more scintillation material is used per detector resulting in a higher sensitivity of the scanner. However, since the detector elements are not uniform in size, degradation in spatial resolution is also expected. To investigate characteristics of tapered PET detectors the spatial resolution and sensitivity of a one-ring scanner were simulated for a system based on traditional cuboid detectors and a scanner based on tapered detectors. Additionally, the effect of depth of interaction (DOI) resolution on the spatial resolution for the traditional and tapered detectors was evaluated. All simulations were performed using the Monte Carlo simulation package GATE. Using the tapered arrays a 64 % improvement in the sensitivity across the field of view was found compared with traditional detectors for the same ring diameter. The level of DOI encoding was found to be the dominating factor in determining the radial spatial resolution and not the detector shape. For all levels of DOI encoding, no significant difference was found for the spatial resolution when comparing the tapered and the cuboid detectors. Detectors employing the tapered crystal design along with excellent DOI resolution will lead to PET scanners with higher sensitivity and uniform spatial resolution across the

  12. Auditory spatial resolution in horizontal, vertical, and diagonal planes

    NASA Astrophysics Data System (ADS)

    Grantham, D. Wesley; Hornsby, Benjamin W. Y.; Erpenbeck, Eric A.

    2003-08-01

    Minimum audible angle (MAA) and minimum audible movement angle (MAMA) thresholds were measured for stimuli in horizontal, vertical, and diagonal (60°) planes. A pseudovirtual technique was employed in which signals were recorded through KEMAR's ears and played back to subjects through insert earphones. Thresholds were obtained for wideband, high-pass, and low-pass noises. Only 6 of 20 subjects obtained wideband vertical-plane MAAs less than 10°, and only these 6 subjects were retained for the complete study. For all three filter conditions thresholds were lowest in the horizontal plane, slightly (but significantly) higher in the diagonal plane, and highest for the vertical plane. These results were similar in magnitude and pattern to those reported by Perrott and Saberi [J. Acoust. Soc. Am. 87, 1728-1731 (1990)] and Saberi and Perrott [J. Acoust. Soc. Am. 88, 2639-2644 (1990)], except that these investigators generally found that thresholds for diagonal planes were as good as those for the horizontal plane. The present results are consistent with the hypothesis that diagonal-plane performance is based on independent contributions from a horizontal-plane system (sensitive to interaural differences) and a vertical-plane system (sensitive to pinna-based spectral changes). Measurements of the stimuli recorded through KEMAR indicated that sources presented from diagonal planes can produce larger interaural level differences (ILDs) in certain frequency regions than would be expected based on the horizontal projection of the trajectory. Such frequency-specific ILD cues may underlie the very good performance reported in previous studies for diagonal spatial resolution. Subjects in the present study could apparently not take advantage of these cues in the diagonal-plane condition, possibly because they did not externalize the images to their appropriate positions in space or possibly because of the absence of a patterned visual field.

  13. Effect of spatial resolution of radar-based inundation maps on the calibration of a spatial inundation model

    NASA Astrophysics Data System (ADS)

    Gobeyn, Sacha; Vernieuwe, Hilde; De Baets, Bernard; Bates, Paul; Verhoest Niko E., C.

    2013-04-01

    With advances in both flood mapping with satellite radar and computational science, the use of real-time spatial flood data holds the potential to support decision making during flood events. With recent improvements in satellite radar technology, current and future radar images are/will be delivered with higher spatial resolution. It is expected that these higher resolutions should improve the accuracy of the calibration and the prediction through data assimilation as more detailed information is available. However, these finer resolution data will result in an increased computational cost. Still, radar data of coarser resolution will remain available, and the question may then arise whether the calibration of a 2D-hydraulic model is significantly influenced by the resolution of the remotely-sensed inundation map. In order to answer this question, the raster-based inundation model, LISFLOOD-FP (Bates et al., 2000) is calibrated using a high resolution synthetic aperture radar image (ERS-2 SAR) of a flood event of the river Dee, Wales, in December 2006. Different radar resolutions are simulated through coarsening this image to different resolutions and retrieving the flood extent maps for the different resolutions. These flood maps are then used for calibrating the hydraulic model using the generalized likelihood uncertainty estimation (GLUE) framework presented by Aronica et al. (2002) as well as alternative calibration methods (e.g. Particle Swarm Optimization, PSO) to assess the possible impact of spatial resolution of the observed flood extent on the floodplain and channel Manning coefficient. Furthermore, the sensitivity of the calibration surface to error sources in radar measurement is evaluated by applying different magnitudes of noise to the radar image. References Aronica, G., Bates, P. D. and Horritt, M. S. (2002). Assessing the uncertainty in distributed model predictions using observed binary pattern information within GLUE. Hydrological Processes, 16

  14. Spatial Classification of Orchards and Vineyards with High Spatial Resolution Panchromatic Imagery

    SciTech Connect

    Warner, Timothy; Steinmaus, Karen L.

    2005-02-01

    New high resolution single spectral band imagery offers the capability to conduct image classifications based on spatial patterns in imagery. A classification algorithm based on autocorrelation patterns was developed to automatically extract orchards and vineyards from satellite imagery. The algorithm was tested on IKONOS imagery over Granger, WA, which resulted in a classification accuracy of 95%.

  15. Spatial resolution and information transfer in scanning transmission electron microscopy.

    PubMed

    Peng, Yiping; Oxley, Mark P; Lupini, Andrew R; Chisholm, Matthew F; Pennycook, Stephen J

    2008-02-01

    The relation between image resolution and information transfer is explored. It is shown that the existence of higher frequency transfer in the image is just a necessary but not sufficient condition for the achievement of higher resolution. Adopting a two-point resolution criterion, we suggest that a 10% contrast level between two features in an image should be used as a practical definition of resolution. In the context of scanning transmission electron microscopy, it is shown that the channeling effect does not have a direct connection with image resolution because sharp channeling peaks do not move with the scanning probe. Through a quantitative comparison between experimental image and simulation, a Fourier-space approach is proposed to estimate defocus and sample thickness. The effective atom size in Z-contrast imaging depends on the annular detector's inner angle. Therefore, an optimum angle exists for the highest resolution as a trade-off between reduced atom size and reduced signal with limited information transfer due to noise.

  16. Hi-Res scan mode in clinical MDCT systems: Experimental assessment of spatial resolution performance

    PubMed Central

    Cruz-Bastida, Juan P.; Gomez-Cardona, Daniel; Li, Ke; Sun, Heyi; Hsieh, Jiang; Szczykutowicz, Timothy P.; Chen, Guang-Hong

    2016-01-01

    Purpose: The introduction of a High-Resolution (Hi-Res) scan mode and another associated option that combines Hi-Res mode with the so-called High Definition (HD) reconstruction kernels (referred to as a Hi-Res/HD mode in this paper) in some multi-detector CT (MDCT) systems offers new opportunities to increase spatial resolution for some clinical applications that demand high spatial resolution. The purpose of this work was to quantify the in-plane spatial resolution along both the radial direction and tangential direction for the Hi-Res and Hi-Res/HD scan modes at different off-center positions. Methods: A technique was introduced and validated to address the signal saturation problem encountered in the attempt to quantify spatial resolution for the Hi-Res and Hi-Res/HD scan modes. Using the proposed method, the modulation transfer functions (MTFs) of a 64-slice MDCT system (Discovery CT750 HD, GE Healthcare) equipped with both Hi-Res and Hi-Res/HD modes were measured using a metal bead at nine different off-centered positions (0–16 cm with a step size of 2 cm); at each position, both conventional scans and Hi-Res scans were performed. For each type of scan and position, 80 repeated acquisitions were performed to reduce noise induced uncertainties in the MTF measurements. A total of 15 reconstruction kernels, including eight conventional kernels and seven HD kernels, were used to reconstruct CT images of the bead. An ex vivo animal study consisting of a bone fracture model was performed to corroborate the MTF results, as the detection of this high-contrast and high frequency task is predominantly determined by spatial resolution. Images of this animal model generated by different scan modes and reconstruction kernels were qualitatively compared with the MTF results. Results: At the centered position, the use of Hi-Res mode resulted in a slight improvement in the MTF; each HD kernel generated higher spatial resolution than its counterpart conventional kernel

  17. Hi-Res scan mode in clinical MDCT systems: Experimental assessment of spatial resolution performance.

    PubMed

    Cruz-Bastida, Juan P; Gomez-Cardona, Daniel; Li, Ke; Sun, Heyi; Hsieh, Jiang; Szczykutowicz, Timothy P; Chen, Guang-Hong

    2016-05-01

    The introduction of a High-Resolution (Hi-Res) scan mode and another associated option that combines Hi-Res mode with the so-called High Definition (HD) reconstruction kernels (referred to as a Hi-Res/HD mode in this paper) in some multi-detector CT (MDCT) systems offers new opportunities to increase spatial resolution for some clinical applications that demand high spatial resolution. The purpose of this work was to quantify the in-plane spatial resolution along both the radial direction and tangential direction for the Hi-Res and Hi-Res/HD scan modes at different off-center positions. A technique was introduced and validated to address the signal saturation problem encountered in the attempt to quantify spatial resolution for the Hi-Res and Hi-Res/HD scan modes. Using the proposed method, the modulation transfer functions (MTFs) of a 64-slice MDCT system (Discovery CT750 HD, GE Healthcare) equipped with both Hi-Res and Hi-Res/HD modes were measured using a metal bead at nine different off-centered positions (0-16 cm with a step size of 2 cm); at each position, both conventional scans and Hi-Res scans were performed. For each type of scan and position, 80 repeated acquisitions were performed to reduce noise induced uncertainties in the MTF measurements. A total of 15 reconstruction kernels, including eight conventional kernels and seven HD kernels, were used to reconstruct CT images of the bead. An ex vivo animal study consisting of a bone fracture model was performed to corroborate the MTF results, as the detection of this high-contrast and high frequency task is predominantly determined by spatial resolution. Images of this animal model generated by different scan modes and reconstruction kernels were qualitatively compared with the MTF results. At the centered position, the use of Hi-Res mode resulted in a slight improvement in the MTF; each HD kernel generated higher spatial resolution than its counterpart conventional kernel. However, the MTF along the

  18. Sensitivity of ecosystem models to the spatial resolution of the NCAR Community Climate Model CCM2

    NASA Astrophysics Data System (ADS)

    Ciret, C.; Henderson-Sellers, A.

    This study evaluates the sensitivity of ecosystem models to changes in the horizontal resolution of version 2 of the National Centre for Atmospheric Research Community Climate Model (CCM2). A previous study has shown that the distributions of natural ecosystems predicted by vegetation models using coarse resolution present-day climate simulations are poorly simulated. It is usually assumed that increasing the spatial resolution of general circulation models (GCMs) will improve the simulation of climate, and hence will increase our level of confidence in the use of GCM output for impacts studies. The principal goals of this study is to investigate this hypothesis and to identify which biomes are more affected by the changes in spatial resolution of the forcing climate. The ecosystem models used are the BIOME-1 model and a version of the Holdridge scheme. The climate simulations come from a set of experiments in which CCM2 was run with increasing horizontal resolutions. The biome distributions predicted using CCM2 climates are compared against biome distributions predicted using observed climate datasets. Results show that increasing the resolution of CCM2 produces a significant improvement of the global-scale vegetation prediction, indicating that a higher level of confidence can be vested in the global-scale prediction of natural ecosystems using medium and high resolution GCMs. However, not all biomes are equally affected by the increased spatial resolution, and although certain biome distributions are improved (e.g. hot desert, tropical seasonal forest), others remain globally poorly predicted even at high resolution (e.g. grasses and xerophytic woods). In addition, these results show that some climatic biases are enhanced with increasing resolution (e.g. in mountain ranges), resulting in the inadequate prediction of biomes.

  19. Spatial modeling for refining and predicting surface potential mapping with enhanced resolution.

    PubMed

    Zhang, Qiong; Deng, Xinwei; Qian, Peter Z G; Wang, Xudong

    2013-02-07

    Quantitatively mapping surface properties with nanometer or even subnanometer resolutions is critical for advanced scanning probe microscopy (SPM) characterization. However, the characterization performance often suffers from noises and artifacts due to instrumentation or environmental limitations. In this paper, we proposed a novel statistical approach with bivariate spatial modeling to efficiently refine and predict surface property mapping. Scanning Kelvin probe microscopy (SKPM) was selected as a representative example to test our proposed method on lateral nanowire assemblies. We revealed that the proposed method can effectively retrieve the artifact-free surface potential distribution by automatically identifying topological artifacts from surface potential maps. Furthermore, the statistical model built upon low spatial resolution was successfully used to predict the potential values from higher-resolution topography data. Compared to conventional regression model, our model is able to predict the surface potential distribution from less raw data but yields much higher accuracy. Through this means, the spatial resolution of SKPM surface potential maps can be significantly improved. This statistics-enabled predictive method opens a new route toward high-precision and high-resolution SPM characterizations without the enhancement of instrumentation capabilities.

  20. Extension of MINOTAUR to higher-order spatial functions

    SciTech Connect

    Pevey, R.E.

    1999-09-01

    MINOTAUR, a generalized multidimensional geometry discrete ordinates kernel that can be used to calculate the particle flow through a complicated geometrical arrangement of materials, has been extended to use higher-order within-node spatial flux expansions. MINOTAUR is an improved version of the CENTAUR code, which was developed at the Savannah River Site by DeHart, Pevey, and Parish for flat intranode flux distributions. CENTAUR was later extended to linear spatial flux shapes by Grove and Pevey. Both of these codes were limited to two-dimensional generalized geometries, for which the regions are bounded by arbitrarily oriented line segments.

  1. Ultra-High Spatial Resolution, Multi-Energy CT using Photon Counting Detector Technology.

    PubMed

    Leng, S; Gutjahr, R; Ferrero, A; Kappler, S; Henning, A; Halaweish, A; Zhou, W; Montoya, J; McCollough, C

    2017-02-11

    Two ultra-high-resolution (UHR) imaging modes, each with two energy thresholds, were implemented on a research, whole-body photon-counting-detector (PCD) CT scanner, referred to as sharp and UHR, respectively. The UHR mode has a pixel size of 0.25 mm at iso-center for both energy thresholds, with a collimation of 32 × 0.25 mm. The sharp mode has a 0.25 mm pixel for the low-energy threshold and 0.5 mm for the high-energy threshold, with a collimation of 48 × 0.25 mm. Kidney stones with mixed mineral composition and lung nodules with different shapes were scanned using both modes, and with the standard imaging mode, referred to as macro mode (0.5 mm pixel and 32 × 0.5 mm collimation). Evaluation and comparison of the three modes focused on the ability to accurately delineate anatomic structures using the high-spatial resolution capability and the ability to quantify stone composition using the multi-energy capability. The low-energy threshold images of the sharp and UHR modes showed better shape and texture information due to the achieved higher spatial resolution, although noise was also higher. No noticeable benefit was shown in multi-energy analysis using UHR compared to standard resolution (macro mode) when standard doses were used. This was due to excessive noise in the higher resolution images. However, UHR scans at higher dose showed improvement in multi-energy analysis over macro mode with regular dose. To fully take advantage of the higher spatial resolution in multi-energy analysis, either increased radiation dose, or application of noise reduction techniques, is needed.

  2. Ultra-high spatial resolution multi-energy CT using photon counting detector technology

    NASA Astrophysics Data System (ADS)

    Leng, S.; Gutjahr, R.; Ferrero, A.; Kappler, S.; Henning, A.; Halaweish, A.; Zhou, W.; Montoya, J.; McCollough, C.

    2017-03-01

    Two ultra-high-resolution (UHR) imaging modes, each with two energy thresholds, were implemented on a research, whole-body photon-counting-detector (PCD) CT scanner, referred to as sharp and UHR, respectively. The UHR mode has a pixel size of 0.25 mm at iso-center for both energy thresholds, with a collimation of 32 × 0.25 mm. The sharp mode has a 0.25 mm pixel for the low-energy threshold and 0.5 mm for the high-energy threshold, with a collimation of 48 × 0.25 mm. Kidney stones with mixed mineral composition and lung nodules with different shapes were scanned using both modes, and with the standard imaging mode, referred to as macro mode (0.5 mm pixel and 32 × 0.5 mm collimation). Evaluation and comparison of the three modes focused on the ability to accurately delineate anatomic structures using the high-spatial resolution capability and the ability to quantify stone composition using the multi-energy capability. The low-energy threshold images of the sharp and UHR modes showed better shape and texture information due to the achieved higher spatial resolution, although noise was also higher. No noticeable benefit was shown in multi-energy analysis using UHR compared to standard resolution (macro mode) when standard doses were used. This was due to excessive noise in the higher resolution images. However, UHR scans at higher dose showed improvement in multi-energy analysis over macro mode with regular dose. To fully take advantage of the higher spatial resolution in multi-energy analysis, either increased radiation dose, or application of noise reduction techniques, is needed.

  3. Ultra-High Spatial Resolution, Multi-Energy CT using Photon Counting Detector Technology

    PubMed Central

    Leng, S.; Gutjahr, R.; Ferrero, A.; Kappler, S.; Henning, A.; Halaweish, A.; Zhou, W.; Montoya, J.; McCollough, C.

    2017-01-01

    Two ultra-high-resolution (UHR) imaging modes, each with two energy thresholds, were implemented on a research, whole-body photon-counting-detector (PCD) CT scanner, referred to as sharp and UHR, respectively. The UHR mode has a pixel size of 0.25 mm at iso-center for both energy thresholds, with a collimation of 32 × 0.25 mm. The sharp mode has a 0.25 mm pixel for the low-energy threshold and 0.5 mm for the high-energy threshold, with a collimation of 48 × 0.25 mm. Kidney stones with mixed mineral composition and lung nodules with different shapes were scanned using both modes, and with the standard imaging mode, referred to as macro mode (0.5 mm pixel and 32 × 0.5 mm collimation). Evaluation and comparison of the three modes focused on the ability to accurately delineate anatomic structures using the high-spatial resolution capability and the ability to quantify stone composition using the multi-energy capability. The low-energy threshold images of the sharp and UHR modes showed better shape and texture information due to the achieved higher spatial resolution, although noise was also higher. No noticeable benefit was shown in multi-energy analysis using UHR compared to standard resolution (macro mode) when standard doses were used. This was due to excessive noise in the higher resolution images. However, UHR scans at higher dose showed improvement in multi-energy analysis over macro mode with regular dose. To fully take advantage of the higher spatial resolution in multi-energy analysis, either increased radiation dose, or application of noise reduction techniques, is needed. PMID:28392615

  4. Spatial-temperature high resolution map for early cancer diagnosis

    NASA Astrophysics Data System (ADS)

    Gavriloaia, Gheorghe V.; Hurduc, Anca; Ghimigean, Ana-Maria; Fumarel, Radu

    2009-02-01

    Heat is one of the most important parameters of living beings. Skin temperature is not the same on the entire body and so, a thermal signature can be got. Infrared map on serial imaging can constitute an early sign of an abnormality. Thermography detects changes in tissue that appear before and accompany many diseases including cancer. As this map has a better resolution an early cancer diagnosis can be done. The temperature of neoplasic tissue is different up to 1.5 °C than that of the healthy tissue as a result of the specific metabolic rate. The infrared camera images show very quickly the heat transferred by radiation. A lot of factors disturb the temperature conversion to pixel intensity. A sensitive temperature sensor with a 10 Mpixels video camera, showing its spatial position, and a computer fusion program were used for the map with high spatial-temperature resolution. A couple of minutes are necessary to get a high resolution map. The asymmetry and borders were the main parameters analyzed. The right cancer diagnosis was for about 78.4% of patients with thyroid cancer, and more than 89.6% from patients with breast cancer. In the near future, the medical prognosis will be improved by fractal analysis.

  5. High spatial resolution measurements in a single stage ram accelerator

    NASA Technical Reports Server (NTRS)

    Hinkey, J. B.; Burnham, E. A.; Bruckner, A. P.

    1992-01-01

    High spatial resolution experimental tube wall pressure measurements of ram accelerator gas dynamic phenomena are presented in this paper. The ram accelerator is a ramjet-in-tube device which operates in a manner similar to that of a conventional ramjet. The projectile resembles the centerbody of a ramjet and travels supersonically through a tube filled with a combustible gaseous mixture, with the tube acting as the outer cowling. Pressure data are recorded as the projectile passes by sensors mounted in the tube wall at various locations along the tube. Utilization of special highly instrumented sections of tube has allowed the recording of gas dynamic phenomena with high resolution. High spatial resolution tube wall pressure data from the three regimes of propulsion studied to date (subdetonative, transdetonative, and superdetonative) in a single stage gas mixture are presented and reveal the three-dimensional character of the flow field induced by projectile fins and the canting of the fins and the canting of the projectile body relative to the tube wall. Also presented for comparison to the experimental data are calculations made with an inviscid, three-dimensional CFD code. The knowledge gained from these experiments and simulations is useful in understanding the underlying nature of ram accelerator propulsive regimes, as well as assisting in the validation of three-dimensional CFD coded which model unsteady, chemically reactive flows.

  6. High resolution spatial map imaging of a gaseous target

    NASA Astrophysics Data System (ADS)

    Stei, Martin; von Vangerow, Johannes; Otto, Rico; Kelkar, Aditya H.; Carrascosa, Eduardo; Best, Thorsten; Wester, Roland

    2013-06-01

    Electrostatic ion imaging with the velocity map imaging mode is a widely used method in atomic and molecular physics and physical chemistry. In contrast, the spatial map imaging (SMI) mode has received very little attention, despite the fact that it has been proposed earlier [A. T. J. B. Eppink and D. H. Parker, Rev. Sci. Instrum. 68, 3477 (1997)], 10.1063/1.1148310. Here, we present a detailed parametric characterization of SMI both by simulation and experiment. One-, two- and three-dimensional imaging modes are described. The influence of different parameters on the imaging process is described by means of a Taylor expansion. To experimentally quantify elements of the Taylor expansion and to infer the spatial resolution of our spectrometer, photoionization of toluene with a focused laser beam has been carried out. A spatial resolution of better than 4 μm out of a focal volume of several mm in diameter has been achieved. Our results will be useful for applications of SMI to the characterization of laser beams, the overlap control of multiple particle or light beams, and the determination of absolute collision cross sections.

  7. Proceedings of the 2004 High Spatial Resolution Commercial Imagery Workshop

    NASA Technical Reports Server (NTRS)

    2006-01-01

    Topics covered include: NASA Applied Sciences Program; USGS Land Remote Sensing: Overview; QuickBird System Status and Product Overview; ORBIMAGE Overview; IKONOS 2004 Calibration and Validation Status; OrbView-3 Spatial Characterization; On-Orbit Modulation Transfer Function (MTF) Measurement of QuickBird; Spatial Resolution Characterization for QuickBird Image Products 2003-2004 Season; Image Quality Evaluation of QuickBird Super Resolution and Revisit of IKONOS: Civil and Commercial Application Project (CCAP); On-Orbit System MTF Measurement; QuickBird Post Launch Geopositional Characterization Update; OrbView-3 Geometric Calibration and Geopositional Accuracy; Geopositional Statistical Methods; QuickBird and OrbView-3 Geopositional Accuracy Assessment; Initial On-Orbit Spatial Resolution Characterization of OrbView-3 Panchromatic Images; Laboratory Measurement of Bidirectional Reflectance of Radiometric Tarps; Stennis Space Center Verification and Validation Capabilities; Joint Agency Commercial Imagery Evaluation (JACIE) Team; Adjacency Effects in High Resolution Imagery; Effect of Pulse Width vs. GSD on MTF Estimation; Camera and Sensor Calibration at the USGS; QuickBird Geometric Verification; Comparison of MODTRAN to Heritage-based Results in Vicarious Calibration at University of Arizona; Using Remotely Sensed Imagery to Determine Impervious Surface in Sioux Falls, South Dakota; Estimating Sub-Pixel Proportions of Sagebrush with a Regression Tree; How Do YOU Use the National Land Cover Dataset?; The National Map Hazards Data Distribution System; Recording a Troubled World; What Does This-Have to Do with This?; When Can a Picture Save a Thousand Homes?; InSAR Studies of Alaska Volcanoes; Earth Observing-1 (EO-1) Data Products; Improving Access to the USGS Aerial Film Collections: High Resolution Scanners; Improving Access to the USGS Aerial Film Collections: Phoenix Digitizing System Product Distribution; System and Product Characterization: Issues Approach

  8. Proceedings of the 2004 High Spatial Resolution Commercial Imagery Workshop

    NASA Technical Reports Server (NTRS)

    2006-01-01

    Topics covered include: NASA Applied Sciences Program; USGS Land Remote Sensing: Overview; QuickBird System Status and Product Overview; ORBIMAGE Overview; IKONOS 2004 Calibration and Validation Status; OrbView-3 Spatial Characterization; On-Orbit Modulation Transfer Function (MTF) Measurement of QuickBird; Spatial Resolution Characterization for QuickBird Image Products 2003-2004 Season; Image Quality Evaluation of QuickBird Super Resolution and Revisit of IKONOS: Civil and Commercial Application Project (CCAP); On-Orbit System MTF Measurement; QuickBird Post Launch Geopositional Characterization Update; OrbView-3 Geometric Calibration and Geopositional Accuracy; Geopositional Statistical Methods; QuickBird and OrbView-3 Geopositional Accuracy Assessment; Initial On-Orbit Spatial Resolution Characterization of OrbView-3 Panchromatic Images; Laboratory Measurement of Bidirectional Reflectance of Radiometric Tarps; Stennis Space Center Verification and Validation Capabilities; Joint Agency Commercial Imagery Evaluation (JACIE) Team; Adjacency Effects in High Resolution Imagery; Effect of Pulse Width vs. GSD on MTF Estimation; Camera and Sensor Calibration at the USGS; QuickBird Geometric Verification; Comparison of MODTRAN to Heritage-based Results in Vicarious Calibration at University of Arizona; Using Remotely Sensed Imagery to Determine Impervious Surface in Sioux Falls, South Dakota; Estimating Sub-Pixel Proportions of Sagebrush with a Regression Tree; How Do YOU Use the National Land Cover Dataset?; The National Map Hazards Data Distribution System; Recording a Troubled World; What Does This-Have to Do with This?; When Can a Picture Save a Thousand Homes?; InSAR Studies of Alaska Volcanoes; Earth Observing-1 (EO-1) Data Products; Improving Access to the USGS Aerial Film Collections: High Resolution Scanners; Improving Access to the USGS Aerial Film Collections: Phoenix Digitizing System Product Distribution; System and Product Characterization: Issues Approach

  9. The Grayscale/Spatial Resolution Trade-Off and Its Impact on Display System Design

    NASA Technical Reports Server (NTRS)

    Gille, Jennifer; Larimer, Jim; Martin, Russel; Statler, Irving C. (Technical Monitor)

    1994-01-01

    We examine technology trade-offs related to the grayscale/spatial resolution trade-off for AMLCD-based display systems. We present new empirical results from our study of the human grayscale/spatial resolution trade-off.

  10. Regional spatially adaptive total variation super-resolution with spatial information filtering and clustering.

    PubMed

    Yuan, Qiangqiang; Zhang, Liangpei; Shen, Huanfeng

    2013-06-01

    Total variation is used as a popular and effective image prior model in the regularization-based image processing fields. However, as the total variation model favors a piecewise constant solution, the processing result under high noise intensity in the flat regions of the image is often poor, and some pseudoedges are produced. In this paper, we develop a regional spatially adaptive total variation model. Initially, the spatial information is extracted based on each pixel, and then two filtering processes are added to suppress the effect of pseudoedges. In addition, the spatial information weight is constructed and classified with k-means clustering, and the regularization strength in each region is controlled by the clustering center value. The experimental results, on both simulated and real datasets, show that the proposed approach can effectively reduce the pseudoedges of the total variation regularization in the flat regions, and maintain the partial smoothness of the high-resolution image. More importantly, compared with the traditional pixel-based spatial information adaptive approach, the proposed region-based spatial information adaptive total variation model can better avoid the effect of noise on the spatial information extraction, and maintains robustness with changes in the noise intensity in the super-resolution process.

  11. High spatial resolution soft-x-ray microscopy

    SciTech Connect

    Meyer-Ilse, W.; Medecki, H.; Brown, J.T.

    1997-04-01

    A new soft x-ray microscope (XM-1) with high spatial resolution has been constructed by the Center for X-ray Optics. It uses bending magnet radiation from beamline 6.1 at the Advanced Light Source, and is used in a variety of projects and applications in the life and physical sciences. Most of these projects are ongoing. The instrument uses zone plate lenses and achieves a resolution of 43 nm, measured over 10% to 90% intensity with a knife edge test sample. X-ray microscopy permits the imaging of relatively thick samples, up to 10 {mu}m thick, in water. XM-1 has an easy to use interface, that utilizes visible light microscopy to precisely position and focus the specimen. The authors describe applications of this device in the biological sciences, as well as in studying industrial applications including structured polymer samples.

  12. Temporal and spatial resolution of pump sampling systems

    NASA Astrophysics Data System (ADS)

    Mackas, D. L.; Owen, R. W.

    1982-07-01

    A simple empirical method is described for determining the fine-scale resolution of continuous flow-through sampling systems. An input delta function is provided by injection of fluorescent dye into the sampler intake. The output fluorescent signal provides time-domain estimates of delay and signal spread; Fourier transformation of the output provides the frequency domain transfer function of the system. Systems with direct intakes (hose or through-hull fitting) can resolve features of 30-s duration or less; however, sea chest intakes cause substantial blurring of the input signal. Attempts to increase vertical spatial resolution by slow lowering rates can result in profiles characterized by appearent micropatchiness and multiple layering, artifacts of the procedure.

  13. EBSD spatial resolution for detecting sigma phase in steels.

    PubMed

    Bordín, S Fernandez; Limandri, S; Ranalli, J M; Castellano, G

    2016-12-01

    The spatial resolution of the electron backscatter diffraction signal is explored by Monte Carlo simulation for the sigma phase in steel at a typical instrumental set-up. In order to estimate the active volume corresponding to the diffracted electrons, the fraction of the backscattered electrons contributing to the diffraction signal was inferred by extrapolating the Kikuchi pattern contrast measured by other authors, as a function of the diffracted electron energy. In the resulting estimation, the contribution of the intrinsic incident beam size and the software capability to deconvolve patterns were included. A strong influence of the beam size on the lateral resolution was observed, resulting in 20nm for the aperture considered. For longitudinal and depth directions the resolutions obtained were 75nm and 16nm, respectively. The reliability of this last result is discussed in terms of the survey of the last large-angle deflection undergone by the backscattered electrons involved in the diffraction process. Bearing in mind the mean transversal resolution found, it was possible to detect small area grains of sigma phase by EBSD measurements, for a stabilized austenitic AISI 347 stainless steel under heat treatments, simulating post welding (40h at 600°C) and aging (284h at 484°C) effects-as usually occurring in nuclear reactor pressure vessels. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. Metadevice for intensity modulation with sub-wavelength spatial resolution

    PubMed Central

    Cencillo-Abad, Pablo; Zheludev, Nikolay I.; Plum, Eric

    2016-01-01

    Effectively continuous control over propagation of a beam of light requires light modulation with pixelation that is smaller than the optical wavelength. Here we propose a spatial intensity modulator with sub-wavelength resolution in one dimension. The metadevice combines recent advances in reconfigurable nanomembrane metamaterials and coherent all-optical control of metasurfaces. It uses nanomechanical actuation of metasurface absorber strips placed near a mirror in order to control their interaction with light from perfect absorption to negligible loss, promising a path towards dynamic diffraction and focusing of light as well as holography without unwanted diffraction artefacts. PMID:27857221

  15. SQUID-NDE of semiconductor samples with high spatial resolution

    NASA Astrophysics Data System (ADS)

    Beyer, J.; Schurig, Th; Lüdge, A.; Riemann, H.

    2000-05-01

    We developed a SQUID-based, noninvasive method for the investigation of semiconductor wafers. It is based on the detection of excited photocurrents via their magnetic field by means of a highly sensitive SQUID system. Our method allows the visualization of small growth-related fluctuations of the doping level of the semiconductor with a spatial resolution of a few tens of a micrometre determined by the excitation spot size. Numerical simulations of the magnetic signals have been performed, the results of which show a reasonable agreement with the experiments.

  16. Spatial and frequency-based super-resolution of ultrasound images.

    PubMed

    Wu, Mon-Ju; Karls, Joseph; Duenwald-Kuehl, Sarah; Vanderby, Ray; Sethares, William

    2014-07-01

    Modern ultrasound systems can output video images containing more spatial and temporal information than still images. Super-resolution techniques can exploit additional information but face two challenges: image registration and complex motion. In addition, information from multiple available frequencies is unexploited. Herein, we utilised these information sources to create better ultrasound images and videos, extending existing technologies for image capture. Spatial and frequency-based super-resolution processing using multiple motion estimation and frequency combination was applied to ultrasound videos of deforming models. Processed images are larger, have greater clarity and detail, and less variability in intensity between frames. Significantly, strain measurements are more accurate and precise than those from raw videos, and have a higher contrast ratio between 'tumour' and 'surrounding tissue' in a phantom model. We attribute improvements to reduced noise and increased resolution in processed images. Our methods can significantly improve quantitative and qualitative assessments of ultrasound images when compared assessments of standard images.

  17. Fourier domain design of microgrid imaging polarimeters with improved spatial resolution

    NASA Astrophysics Data System (ADS)

    Hirakawa, Keigo; LeMaster, Daniel A.

    2014-05-01

    Microgrid polarimetric imagers sacrifice spatial resolution for sensitivity to states of linear polarization. We have recently shown that a 2 × 4 microgrid analyzer pattern sacrifices less spatial resolution than the conventional 2× 2 case without compromising polarization sensitivity. In this paper, we discuss the design strategy that uncovered the spatial resolution benefits of the 2 × 4 array.

  18. Multi-storm, multi-catchment investigation of rainfall spatial resolution requirements for urban hydrological applications

    NASA Astrophysics Data System (ADS)

    Ochoa Rodriguez, Susana; ten Veldhuis, Marie-Claire; Bruni, Guendalina; Gires, Auguste; van Assel, Johan; Wang, Lipen; Reinoso-Rodinel, Ricardo; Ichiba, Abdellah; Kroll, Stefan; Schertzer, Daniel; Onof, Christian; Willems, Patrick

    2014-05-01

    Rainfall estimates of the highest possible resolution are required for urban hydrological applications, given the small size and fast response which characterise urban catchments. While significant progress has been made over the last few decades in high resolution measurement of rainfall at urban scales and in the modelling of urban runoff processes, a number of questions as to the actual resolution requirements for input data and models remain to be answered. With the aim of answering some of these questions, this work investigates the impact of rainfall estimates of different spatial resolutions and structures on the hydraulic outputs of models of several urban catchments with different characteristics. For this purpose multiple storm events, including convective and stratiform ones, measured by a polarimetric X-band radar located in Cabauw (NL) were selected for analysis. The original radar estimates, at 100 m and 1 min resolutions, were aggregated to coarser spatial resolutions of up to 1000 m. These estimates were then applied to the high-resolution semi distributed hydraulic models of four urban catchments of similar size (approx. 7 km2), but different morphological and land use characteristics; these are: the Herent catchment (Belgium), the Cranbrook catchment (UK), the Morée Sausset catchment (France) and the Kralingen District of Rotterdam (The Netherlands). When doing so, methodologies for standardising rainfall inputs and making results comparable were implemented. Moreover, the results were analysed considering different points at each catchment, while also taking into account the particular storm and catchment characteristics. The results obtained for the storms used in this study show that flat and less compact catchments (e.g. polder areas) may be more sensitive to the spatial resolution of rainfall estimates, as compared to catchments with higher slopes and compactness, which in general show little sensitivity to changes in spatial resolution

  19. A Method of Spatial Mapping and Reclassification for High-Spatial-Resolution Remote Sensing Image Classification

    PubMed Central

    Wang, Guizhou; Liu, Jianbo; He, Guojin

    2013-01-01

    This paper presents a new classification method for high-spatial-resolution remote sensing images based on a strategic mechanism of spatial mapping and reclassification. The proposed method includes four steps. First, the multispectral image is classified by a traditional pixel-based classification method (support vector machine). Second, the panchromatic image is subdivided by watershed segmentation. Third, the pixel-based multispectral image classification result is mapped to the panchromatic segmentation result based on a spatial mapping mechanism and the area dominant principle. During the mapping process, an area proportion threshold is set, and the regional property is defined as unclassified if the maximum area proportion does not surpass the threshold. Finally, unclassified regions are reclassified based on spectral information using the minimum distance to mean algorithm. Experimental results show that the classification method for high-spatial-resolution remote sensing images based on the spatial mapping mechanism and reclassification strategy can make use of both panchromatic and multispectral information, integrate the pixel- and object-based classification methods, and improve classification accuracy. PMID:24453808

  20. The effects of spatial resolution on integral field spectrograph surveys at different redshifts - The CALIFA perspective

    NASA Astrophysics Data System (ADS)

    Mast, D.; Rosales-Ortega, F. F.; Sánchez, S. F.; Vílchez, J. M.; Iglesias-Paramo, J.; Walcher, C. J.; Husemann, B.; Márquez, I.; Marino, R. A.; Kennicutt, R. C.; Monreal-Ibero, A.; Galbany, L.; de Lorenzo-Cáceres, A.; Mendez-Abreu, J.; Kehrig, C.; del Olmo, A.; Relaño, M.; Wisotzki, L.; Mármol-Queraltó, E.; Bekeraitè, S.; Papaderos, P.; Wild, V.; Aguerri, J. A. L.; Falcón-Barroso, J.; Bomans, D. J.; Ziegler, B.; García-Lorenzo, B.; Bland-Hawthorn, J.; López-Sánchez, Á. R.; van de Ven, G.

    2014-01-01

    Context. Over the past decade, 3D optical spectroscopy has become the preferred tool for understanding the properties of galaxies and is now increasingly used to carry out galaxy surveys. Low redshift surveys include SAURON, DiskMass, ATLAS3D, PINGS, and VENGA. At redshifts above 0.7, surveys such as MASSIV, SINS, GLACE, and IMAGES have targeted the most luminous galaxies to study mainly their kinematic properties. The on-going CALIFA survey (z ~ 0.02) is the first of a series of upcoming integral field spectroscopy (IFS) surveys with large samples representative of the entire population of galaxies. Others include SAMI and MaNGA at lower redshift and the upcoming KMOS surveys at higher redshift. Given the importance of spatial scales in IFS surveys, the study of the effects of spatial resolution on the recovered parameters becomes important. Aims: We explore the capability of the CALIFA survey and a hypothetical higher redshift survey to reproduce the properties of a sample of objects observed with better spatial resolution at lower redshift. Methods: Using a sample of PINGS galaxies, we simulated observations at different redshifts. We then studied the behaviour of different parameters as the spatial resolution degrades with increasing redshift. Results: We show that at the CALIFA resolution, we are able to measure and map common observables in a galaxy study: the number and distribution of H ii regions (Hα flux structure), the gas metallicity (using the O3N2 method), the gas ionization properties (through the [N ii]/Hα and [O iii]/Hβ line ratios), and the age of the underlying stellar population (using the D4000 index). This supports the aim of the survey to characterise the observable properties of galaxies in the Local Universe. Our analysis of simulated IFS data cubes at higher redshifts highlights the importance of the projected spatial scale per spaxel as the most important figure of merit in the design of an integral field survey.

  1. Electrophysiological measures of temporal resolution, contrast sensitivity and spatial resolving power in sharks.

    PubMed

    Ryan, Laura A; Hemmi, Jan M; Collin, Shaun P; Hart, Nathan S

    2017-03-01

    In most animals, vision plays an important role in detecting prey, predators and conspecifics. The effectiveness of vision in assessing cues such as motion and shape is influenced by the ability of the visual system to detect changes in contrast in both space and time. Understanding the role vision plays in shark behaviour has been limited by a lack of knowledge about their temporal resolution, contrast sensitivity and spatial resolution. In this study, an electrophysiological approach was used to compare these measures across five species of sharks: Chiloscyllium punctatum, Heterodontus portusjacksoni, Hemiscyllium ocellatum, Mustelus mustelus and Haploblepharus edwardsii. All shark species were highly sensitive to brightness contrast and were able to detect contrast differences as low as 1.6%. Temporal resolution of flickering stimuli ranged from 28 to 44 Hz. Species that inhabit brighter environments were found to have higher temporal resolution. Spatial resolving power was estimated in C. punctatum, H. portusjacksoni and H. ocellatum and ranged from 0.10 to 0.35 cycles per degree, which is relatively low compared to other vertebrates. These results suggest that sharks have retinal adaptations that enhance contrast sensitivity at the expense of temporal and spatial resolution, which is beneficial for vision in dimly lit and/or low contrast aquatic environments.

  2. Spatial Resolution Characterization for AWiFS Multispectral Images

    NASA Technical Reports Server (NTRS)

    Blonski, Slawomir; Ryan, Robert E.; Pagnutti, Mary; Stanley, Thomas

    2006-01-01

    Within the framework of the Joint Agency Commercial Imagery Evaluation program, the National Aeronautics and Space Administration, the National Geospatial-Intelligence Agency, and the U.S. Geological Survey cooperate in the characterization of high-to-moderate-resolution commercial imagery of mutual interest. One of the systems involved in this effort is the Advanced Wide Field Sensor (AWiFS) onboard the Indian Remote Sensing (IRS) Reourcesat-1 satellite, IRS-P6. Spatial resolution of the AWiFS multispectral images was characterized by estimating the value of the system Modulation Transfer Function (MTF) at the Nyquist spatial frequency. The Nyquist frequency is defined as half the sampling frequency, and the sampling frequency is equal to the inverse of the ground sample distance. The MTF was calculated as a ratio of the Fourier transform of a profile across an AWiFS image of the Lake Pontchartrain Causeway Bridge and the Fourier transform of a profile across an idealized model of the bridge for each spectral band evaluated. The mean MTF value for the AWiFS imagery evaluated was estimated to be 0.1.

  3. Spatial and temporal resolution of fluid flows: LDRD final report

    SciTech Connect

    Tieszen, S.R.; O`Hern, T.J.; Schefer, R.W.; Perea, L.D.

    1998-02-01

    This report describes a Laboratory Directed Research and Development (LDRD) activity to develop a diagnostic technique for simultaneous temporal and spatial resolution of fluid flows. The goal is to obtain two orders of magnitude resolution in two spatial dimensions and time simultaneously. The approach used in this study is to scale up Particle Image Velocimetry (PIV) and Planar Laser Induced Fluorescence (PLIF) to acquire meter-size images at up to 200 frames/sec. Experiments were conducted in buoyant, fully turbulent, non-reacting and reacting plumes with a base diameter of one meter. The PIV results were successful in the ambient gas for all flows, and in the plume for non-reacting helium and reacting methane, but not reacting hydrogen. No PIV was obtained in the hot combustion product region as the seed particles chosen vaporized. Weak signals prevented PLIF in the helium. However, in reacting methane flows, PLIF images speculated to be from Poly-Aromatic-Hydrocarbons were obtained which mark the flame sheets. The results were unexpected and very insightful. A natural fluorescence from the seed particle vapor was also noted in the hydrogen tests.

  4. Efficiency and spatial resolution of the CASCADE thermal neutron detector

    NASA Astrophysics Data System (ADS)

    Köhli, M.; Allmendinger, F.; Häußler, W.; Schröder, T.; Klein, M.; Meven, M.; Schmidt, U.

    2016-08-01

    We report on the CASCADE project - a detection system, which has been designed for the purposes of neutron Spin Echo spectroscopy and which is continuously further developed and adapted to various applications. It features 2D spatially resolved detection of thermal neutrons at high rates. The CASCADE detector is composed of a stack of solid 10B coated Gas Electron Multiplier foils, which serve both as a neutron converter and as an amplifier for the primary ionization deposited in the standard counting gas environment. This multi-layer setup efficiently increases the detection efficiency and by extracting the signal of the charge traversing the stack the conversion layer can be identified allowing a precise determination of the time-of-flight. The spatial resolution is found by optical contrast determination to be σ =(1.39 ± 0.05) mm and by divergence corrected aperture measurements σ =(1.454 ± 0.007) mm , which is in agreement with the simulated detector model. Furthermore this enabled to investigate and describe the non-Gaussian resolution function. At the HEiDi diffractometer the absolute detection efficiency has been studied. At 0.6 Å for the 6 layer detector, which is currently part of the RESEDA spectrometer, an efficiency of 7.8% has been measured, which by means of Monte Carlo simulations translates to (21.0±1.5)% for thermal neutrons at 1.8 Å and (46.9±3.3)% at 5.4 Å.

  5. Dynamic Raman imaging system with high spatial and temporal resolution

    NASA Astrophysics Data System (ADS)

    Wang, Lei; Dai, Yinzhen; He, Hao; Lv, Ruiqi; Zong, Cheng; Ren, Bin

    2017-09-01

    There is an increasing need to study dynamic changing systems with significantly high spatial and temporal resolutions. In this work, we integrated point-scanning, line-scanning, and wide-field Raman imaging techniques into a single system. By using an Electron Multiplying CCD (EMCCD) with a high gain and high frame rate, we significantly reduced the time required for wide-field imaging, making it possible to monitor the electrochemical reactions in situ. The highest frame rate of EMCDD was ˜50 fps, and the Raman images for a specific Raman peak can be obtained by passing the signal from the sample through the Liquid Crystal Tunable Filter. The spatial resolutions of scanning imaging and wide-field imaging with a 100× objective (NA = 0.9) are 0.5 × 0.5 μm2 and 0.36 × 0.36 μm2, respectively. The system was used to study the surface plasmon resonance of Au nanorods, the surface-enhanced Raman scattering signal distribution for Au Nanoparticle aggregates, and dynamic Raman imaging of an electrochemical reacting system.

  6. Role of color and spatial resolution in digital imaging colposcopy

    NASA Astrophysics Data System (ADS)

    Craine, Eric R.; Engel, John R.; Craine, Brian L.

    1990-07-01

    We have developed a practical digital imaging colposcope for use in research on early detection of cancerous and pre-cancerous tissue in the cervix. Several copies of the system have now been used in a variety of clinical and research environments. Two issues of considerable interest which emerged early in our work involved the roles of color and spatial resolution as they applied to digital imaging colposcopy. In each instance these qualities potentially have a significant impact on the diagnostic efficacy of the system. In order to evaluate the role of these parameters we devised and conducted a receiver operating characteristic (ROC) evaluation of the system. It is apparent from these tests that a spatial resolution of 512 x 480 pixel with 7 or 8 bits of contrast is adequate for the task. The more interesting result arises from the study of the use of color in these examinations; it appears that in general, contrary to the widely held perception of the physicians involved, color apparently provides the clinician with little or no diagnostic information. Indeed, in some instances, access to color seemed to confuse the physician and resulted in an elevated rate of false positives. Results of the ROC tests are presented in this paper along with their implications for further development of this imaging modality.

  7. Contrast and spatial resolution in MREIT using low amplitude current.

    PubMed

    Birgul, Ozlem; Hamamura, Mark J; Muftuler, L Tugan; Nalcioglu, Orhan

    2006-10-07

    Magnetic resonance-electrical impedance tomography employs low amplitude currents injected or induced inside an object. The additional magnetic field due to these currents results in a phase in the MR images. In this study, a modified fast spin-echo sequence was used to measure this magnetic field, which is obtained by scaling the MR phase image. A finite element method with first order triangular elements was used for the solution of the forward problem. An iterated sensitivity matrix-based algorithm was developed for the inverse problem. The resulting ill-conditioned matrix equation was regularized using the Tikhonov method and solved using a conjugate gradient solver. The spatial and contrast resolution of the technique was tested using agarose gel phantoms. A circular phantom with 7 cm diameter and 1 cm thickness is used in the phantom experiments. The amplitude of the injected current was 1 mA. 3, 5 and 8 mm diameter insulators and high conductor objects are used for the spatial resolution study and an average full-width half-maximum value of 4.7 mm is achieved for the 3 mm insulator case. For the contrast analysis, the conductivity of a 15 mm object is varied between 44% and 500% with respect to the background and results are compared to the ideal reconstruction.

  8. Using a high spatial resolution tactile sensor for intention detection.

    PubMed

    Castellini, Claudio; Koiva, Risto

    2013-06-01

    Intention detection is the interpretation of biological signals with the aim of automatically, reliably and naturally understanding what a human subject desires to do. Although intention detection is not restricted to disabled people, such methods can be crucial in improving a patient's life, e.g., aiding control of a robotic wheelchair or of a self-powered prosthesis. Traditionally, intention detection is done using, e.g., gaze tracking, surface electromyography and electroencephalography. In this paper we present exciting initial results of an experiment aimed at intention detection using a high-spatial-resolution, high-dynamic-range tactile sensor. The tactile image of the ventral side of the forearm of 9 able-bodied participants was recorded during a variable-force task stimulated at the fingertip. Both the forces at the fingertip and at the forearm were synchronously recorded. We show that a standard dimensionality reduction technique (Principal Component Analysis) plus a Support Vector Machine attain almost perfect detection accuracy of the direction and the intensity of the intended force. This paves the way for high spatial resolution tactile sensors to be used as a means for intention detection.

  9. A High Spatial Resolution Depth Sensing Method Based on Binocular Structured Light.

    PubMed

    Yao, Huimin; Ge, Chenyang; Xue, Jianru; Zheng, Nanning

    2017-04-08

    Depth information has been used in many fields because of its low cost and easy availability, since the Microsoft Kinect was released. However, the Kinect and Kinect-like RGB-D sensors show limited performance in certain applications and place high demands on accuracy and robustness of depth information. In this paper, we propose a depth sensing system that contains a laser projector similar to that used in the Kinect, and two infrared cameras located on both sides of the laser projector, to obtain higher spatial resolution depth information. We apply the block-matching algorithm to estimate the disparity. To improve the spatial resolution, we reduce the size of matching blocks, but smaller matching blocks generate lower matching precision. To address this problem, we combine two matching modes (binocular mode and monocular mode) in the disparity estimation process. Experimental results show that our method can obtain higher spatial resolution depth without loss of the quality of the range image, compared with the Kinect. Furthermore, our algorithm is implemented on a low-cost hardware platform, and the system can support the resolution of 1280 × 960, and up to a speed of 60 frames per second, for depth image sequences.

  10. A High Spatial Resolution Depth Sensing Method Based on Binocular Structured Light

    PubMed Central

    Yao, Huimin; Ge, Chenyang; Xue, Jianru; Zheng, Nanning

    2017-01-01

    Depth information has been used in many fields because of its low cost and easy availability, since the Microsoft Kinect was released. However, the Kinect and Kinect-like RGB-D sensors show limited performance in certain applications and place high demands on accuracy and robustness of depth information. In this paper, we propose a depth sensing system that contains a laser projector similar to that used in the Kinect, and two infrared cameras located on both sides of the laser projector, to obtain higher spatial resolution depth information. We apply the block-matching algorithm to estimate the disparity. To improve the spatial resolution, we reduce the size of matching blocks, but smaller matching blocks generate lower matching precision. To address this problem, we combine two matching modes (binocular mode and monocular mode) in the disparity estimation process. Experimental results show that our method can obtain higher spatial resolution depth without loss of the quality of the range image, compared with the Kinect. Furthermore, our algorithm is implemented on a low-cost hardware platform, and the system can support the resolution of 1280 × 960, and up to a speed of 60 frames per second, for depth image sequences. PMID:28397759

  11. COMPLEX ORGANIC MOLECULES AT HIGH SPATIAL RESOLUTION TOWARD ORION-KL. I. SPATIAL SCALES

    SciTech Connect

    Widicus Weaver, Susanna L.; Friedel, Douglas N. E-mail: friedel@astro.illinois.edu

    2012-08-01

    Here we present high spatial resolution (<1'') observations of molecular emission in Orion-KL conducted using the Combined Array for Research in Millimeter-wave Astronomy. This work was motivated by recent millimeter continuum imaging studies of this region conducted at a similarly high spatial resolution, which revealed that the bulk of the emission arises from numerous compact sources, rather than the larger-scale extended structures typically associated with the Orion Hot Core and Compact Ridge. Given that the spatial extent of molecular emission greatly affects the determination of molecular abundances, it is important to determine the true spatial scale for complex molecules in this region. Additionally, it has recently been suggested that the relative spatial distributions of complex molecules in a source might give insight into the chemical mechanisms that drive complex chemistry in star-forming regions. In order to begin to address these issues, this study seeks to determine the spatial distributions of ethyl cyanide [C{sub 2}H{sub 5}CN], dimethyl ether [(CH{sub 3}){sub 2}O], methyl formate [HCOOCH{sub 3}], formic acid [HCOOH], acetone [(CH{sub 3}){sub 2}CO], SiO, methanol [CH{sub 3}OH], and methyl cyanide [CH{sub 3}CN] in Orion-KL at {lambda} = 3 mm. We find that for all observed molecules, the molecular emission arises from multiple components of the cloud that include a range of spatial scales and physical conditions. Here, we present the results of these observations and discuss the implications for studies of complex molecules in star-forming regions.

  12. Mapping Spatial Variability in Health and Wealth Indicators in Accra, Ghana Using High Spatial Resolution Imagery

    NASA Astrophysics Data System (ADS)

    Engstrom, R.; Ashcroft, E.

    2014-12-01

    There has been a tremendous amount of research conducted that examines disparities in health and wealth of persons between urban and rural areas however, relatively little research has been undertaken to examine variations within urban areas. A major limitation to elucidating differences with urban areas is the lack of social and demographic data at a sufficiently high spatial resolution to determine these differences. Generally the only available data that contain this information are census data which are collected at most every ten years and are often difficult to obtain at a high enough spatial resolution to allow for examining in depth variability in health and wealth indicators at high spatial resolutions, especially in developing countries. High spatial resolution satellite imagery may be able to provide timely and synoptic information that is related to health and wealth variability within a city. In this study we use two dates of Quickbird imagery (2003 and 2010) classified into the vegetation-impervious surface-soil (VIS) model introduced by Ridd (1995). For 2003 we only have partial coverage of the city, while for 2010 we have a mosaic, which covers the entire city of Accra, Ghana. Variations in the VIS values represent the physical variations within the city and these are compared to variations in economic, and/or sociodemographic data derived from the 2000 Ghanaian census at two spatial resolutions, the enumeration area (approximately US Census Tract) and the neighborhood for the city. Results indicate a significant correlation between both vegetation and impervious surface to type of cooking fuel used in the household, population density, housing density, availability of sewers, cooking space usage, and other variables. The correlations are generally stronger at the neighborhood level and the relationships are stable through time and space. Overall, the results indicate that information derived from high resolution satellite data is related to

  13. High Spatial Resolution Fe XII Observations of Solar Active Regions

    NASA Astrophysics Data System (ADS)

    Testa, Paola; De Pontieu, Bart; Hansteen, Viggo

    2016-08-01

    We use UV spectral observations of active regions with the Interface Region Imaging Spectrograph (IRIS) to investigate the properties of the coronal Fe xii 1349.4 Å emission at unprecedented high spatial resolution (˜0.33″). We find that by using appropriate observational strategies (i.e., long exposures, lossless compression), Fe xii emission can be studied with IRIS at high spatial and spectral resolution, at least for high-density plasma (e.g., post-flare loops and active region moss). We find that upper transition region (TR; moss) Fe xii emission shows very small average Doppler redshifts ({v}{{D}} ˜ 3 km s-1) as well as modest non-thermal velocities (with an average of ˜24 km s-1 and the peak of the distribution at ˜15 km s-1). The observed distribution of Doppler shifts appears to be compatible with advanced three-dimensional radiative MHD simulations in which impulsive heating is concentrated at the TR footpoints of a hot corona. While the non-thermal broadening of Fe xii 1349.4 Å peaks at similar values as lower resolution simultaneous Hinode Extreme Ultraviolet Imaging Spectrometer (EIS) measurements of Fe xii 195 Å, IRIS observations show a previously undetected tail of increased non-thermal broadening that might be suggestive of the presence of subarcsecond heating events. We find that IRIS and EIS non-thermal line broadening measurements are affected by instrumental effects that can only be removed through careful analysis. Our results also reveal an unexplained discrepancy between observed 195.1/1349.4 Å Fe xii intensity ratios and those predicted by the CHIANTI atomic database.

  14. Spatial Ensemble Postprocessing of Precipitation Forecasts Using High Resolution Analyses

    NASA Astrophysics Data System (ADS)

    Lang, Moritz N.; Schicker, Irene; Kann, Alexander; Wang, Yong

    2017-04-01

    Ensemble prediction systems are designed to account for errors or uncertainties in the initial and boundary conditions, imperfect parameterizations, etc. However, due to sampling errors and underestimation of the model errors, these ensemble forecasts tend to be underdispersive, and to lack both reliability and sharpness. To overcome such limitations, statistical postprocessing methods are commonly applied to these forecasts. In this study, a full-distributional spatial post-processing method is applied to short-range precipitation forecasts over Austria using Standardized Anomaly Model Output Statistics (SAMOS). Following Stauffer et al. (2016), observation and forecast fields are transformed into standardized anomalies by subtracting a site-specific climatological mean and dividing by the climatological standard deviation. Due to the need of fitting only a single regression model for the whole domain, the SAMOS framework provides a computationally inexpensive method to create operationally calibrated probabilistic forecasts for any arbitrary location or for all grid points in the domain simultaneously. Taking advantage of the INCA system (Integrated Nowcasting through Comprehensive Analysis), high resolution analyses are used for the computation of the observed climatology and for model training. The INCA system operationally combines station measurements and remote sensing data into real-time objective analysis fields at 1 km-horizontal resolution and 1 h-temporal resolution. The precipitation forecast used in this study is obtained from a limited area model ensemble prediction system also operated by ZAMG. The so called ALADIN-LAEF provides, by applying a multi-physics approach, a 17-member forecast at a horizontal resolution of 10.9 km and a temporal resolution of 1 hour. The performed SAMOS approach statistically combines the in-house developed high resolution analysis and ensemble prediction system. The station-based validation of 6 hour precipitation sums

  15. High resolution autofocus for spatial temporal biomedical research

    NASA Astrophysics Data System (ADS)

    Li, Sihong; Cui, Xiaodong; Huang, Wei

    2013-11-01

    Maintaining focus has been a critical but challenging issue in optical microscopy, particularly for microscopic imaging systems currently used in biomedical research. During live cell imaging, environmental temperature fluctuations and other factors contribute to the unavoidable focus drift. For single molecular imaging and super resolution, focus drift can be significant even over short durations. The current commercial and experimental solutions are either optically complicated, expensive, or with limited axial resolution. Here, we present a simple autofocus solution based on low cost solid state laser and imaging sensor. By improving the optical train design and using real-time data analysis, improvement in axial resolution by approximately two orders of magnitudes over the focal depth of microscope objectives can be achieved. This solution has been tested for prolonged live cell imaging for fast ramping up in environmental chamber temperature and large daily swing in room temperature. In addition, this system can be used to spatial-temporally measure the surface for three-dimensional cell culture and tissue engineering, with flexibility that exceeds commercially available systems.

  16. Spatial resolution enhancement of EO-1 ALI bands

    NASA Astrophysics Data System (ADS)

    Nikolakopoulos, Konstantinos G.

    2006-09-01

    spectral characteristics, they do not take into account the resolution ratio of the input images. Usually the spatial resolution of the panchromatic image is two (Landsat 7, Spot 1-4) or four times (Ikonos, Quickbird) better than the size of the multispectral images. This paper is an attempt to fuse high-resolution panchromatic and low-resolution multispectral bands of the EO-1 ALI sensor. ALI collects nine multispectral bands with 30m resolution and a panchromatic band with 3 times better resolution (10m). ALI has a panchromatic band narrower than the respective band of Landsat7. It has also two narrower bands in the spectral range of Landsat7 band 4. It has also an extra narrower band near the spectral range of Landsat7 band 1. In this study we compare the efficiency of seven fusion techniques and more especially the efficiency of Gram Schmidt, Modified IHS, PCA, Pansharp, Wavelet and LMM (Local Mean Matching) LMVM (Local Mean and Variance Matching) fusion techniques for the fusion of ALI data. Two ALI images collected over the same area have been used. In order to quantitatively measure the quality of the fused images we have made the following controls: Firstly, we have examined the optical qualitative result. Then, we examined the correlation between the original multispectral and the fused images and all the statistical parameters of the histograms of the various frequency bands. All the fusion techniques improve the resolution and the optical result. In contrary to the fusion of other data (ETM, Spot5, Ikonos and Quickbird) all the algorithms provoke small changes to the statistical parameters.

  17. Estuarine Modeling: Does a higher grid resolution improve model performance?

    NASA Astrophysics Data System (ADS)

    Pauer, J. J.; Feist, T. J.; Melendez, W.; Zhang, X.; Lehrter, J. C.

    2016-02-01

    Ecological models are useful tools to explore cause effect relationships, test hypothesis and perform management scenarios. A mathematical model, the Gulf of Mexico Dissolved Oxygen Model (GoMDOM), has been developed and applied to the Louisiana continental shelf of the northern Gulf of Mexico to address long-standing hypoxia issues. A computational grid of approximately 6 km x 6 km cells and 20 sigma layers for a total of 64,320 cells was used. GoMDOM was driven by hydrodynamics from the Navy's NCOM model, and comprehensive kinetic equations were used to describe nutrient, phytoplankton and oxygen dynamics. The model was able to represent the observed salinity (an indication of transport accuracy), biogeochemical processes and the concentrations and metrics including hypoxic area for 2003 and 2006. However, the scale of a model may influence the model's capabilities. Models with low grid resolution and large cells improve computational speed but may not completely capture system dynamics, while models with high grid resolution and small cells may be take a very long time to run, and require extensive computer resources, but better simulate horizontal or vertical gradients. In order to explore the impact of a higher resolution on the model performance, the model was also executed on a 2 km x 2 km modeling grid (558,880 total cells) using the same external boundaries, forcing functions and model coefficients as used in the calibrated 6km version. Here we compare the two modeling grid sizes in terms of how well they fit observations, describing biogeochemical processes, and predicting hypoxia under different nutrient scenarios.

  18. Spectral sensitivity, spatial resolution and temporal resolution and their implications for conspecific signalling in cleaner shrimp.

    PubMed

    Caves, Eleanor M; Frank, Tamara M; Johnsen, Sönke

    2016-02-01

    Cleaner shrimp (Decapoda) regularly interact with conspecifics and client reef fish, both of which appear colourful and finely patterned to human observers. However, whether cleaner shrimp can perceive the colour patterns of conspecifics and clients is unknown, because cleaner shrimp visual capabilities are unstudied. We quantified spectral sensitivity and temporal resolution using electroretinography (ERG), and spatial resolution using both morphological (inter-ommatidial angle) and behavioural (optomotor) methods in three cleaner shrimp species: Lysmata amboinensis, Ancylomenes pedersoni and Urocaridella antonbruunii. In all three species, we found strong evidence for only a single spectral sensitivity peak of (mean ± s.e.m.) 518 ± 5, 518 ± 2 and 533 ± 3 nm, respectively. Temporal resolution in dark-adapted eyes was 39 ± 1.3, 36 ± 0.6 and 34 ± 1.3 Hz. Spatial resolution was 9.9 ± 0.3, 8.3 ± 0.1 and 11 ± 0.5 deg, respectively, which is low compared with other compound eyes of similar size. Assuming monochromacy, we present approximations of cleaner shrimp perception of both conspecifics and clients, and show that cleaner shrimp visual capabilities are sufficient to detect the outlines of large stimuli, but not to detect the colour patterns of conspecifics or clients, even over short distances. Thus, conspecific viewers have probably not played a role in the evolution of cleaner shrimp appearance; rather, further studies should investigate whether cleaner shrimp colour patterns have evolved to be viewed by client reef fish, many of which possess tri- and tetra-chromatic colour vision and relatively high spatial acuity.

  19. Extended Opacity Tables with Higher Temperature-Density-Frequency Resolution

    NASA Astrophysics Data System (ADS)

    Schillaci, Mark; Orban, Chris; Delahaye, Franck; Pinsonneault, Marc; Nahar, Sultana; Pradhan, Anil

    2015-05-01

    Theoretical models for plasma opacities underpin our understanding of radiation transport in many different astrophysical objects. These opacity models are also relevant to HEDP experiments such as ignition scale experiments on NIF. We present a significantly expanded set of opacity data from the widely utilized Opacity Project, and make these higher resolution data publicly available through OSU's portal with dropbox.com. This expanded data set is used to assess how accurate the interpolation of opacity data in temperature-density-frequency dimensions must be in order to adequately model the properties of most stellar types. These efforts are the beginning of a larger project to improve the theoretical opacity models in light of experimental results at the Sandia Z-pinch showing that the measured opacity of Iron disagrees strongly with all current models.

  20. High spatial resolution mapping of folds and fractures using Unmanned Aerial Vehicle (UAV) photogrammetry

    NASA Astrophysics Data System (ADS)

    Cruden, A. R.; Vollgger, S.

    2016-12-01

    The emerging capability of UAV photogrammetry combines a simple and cost-effective method to acquire digital aerial images with advanced computer vision algorithms that compute spatial datasets from a sequence of overlapping digital photographs from various viewpoints. Depending on flight altitude and camera setup, sub-centimeter spatial resolution orthophotographs and textured dense point clouds can be achieved. Orientation data can be collected for detailed structural analysis by digitally mapping such high-resolution spatial datasets in a fraction of time and with higher fidelity compared to traditional mapping techniques. Here we describe a photogrammetric workflow applied to a structural study of folds and fractures within alternating layers of sandstone and mudstone at a coastal outcrop in SE Australia. We surveyed this location using a downward looking digital camera mounted on commercially available multi-rotor UAV that autonomously followed waypoints at a set altitude and speed to ensure sufficient image overlap, minimum motion blur and an appropriate resolution. The use of surveyed ground control points allowed us to produce a geo-referenced 3D point cloud and an orthophotograph from hundreds of digital images at a spatial resolution < 10 mm per pixel, and cm-scale location accuracy. Orientation data of brittle and ductile structures were semi-automatically extracted from these high-resolution datasets using open-source software. This resulted in an extensive and statistically relevant orientation dataset that was used to 1) interpret the progressive development of folds and faults in the region, and 2) to generate a 3D structural model that underlines the complex internal structure of the outcrop and quantifies spatial variations in fold geometries. Overall, our work highlights how UAV photogrammetry can contribute to new insights in structural analysis.

  1. High spatial resolution brain functional MRI using submillimeter balanced steady-state free precession acquisition

    SciTech Connect

    Wu, Pei-Hsin; Chung, Hsiao-Wen; Tsai, Ping-Huei; Wu, Ming-Long; Chuang, Tzu-Chao; Shih, Yi-Yu; Huang, Teng-Yi

    2013-12-15

    Purpose: One of the technical advantages of functional magnetic resonance imaging (fMRI) is its precise localization of changes from neuronal activities. While current practice of fMRI acquisition at voxel size around 3 × 3 × 3 mm{sup 3} achieves satisfactory results in studies of basic brain functions, higher spatial resolution is required in order to resolve finer cortical structures. This study investigated spatial resolution effects on brain fMRI experiments using balanced steady-state free precession (bSSFP) imaging with 0.37 mm{sup 3} voxel volume at 3.0 T. Methods: In fMRI experiments, full and unilateral visual field 5 Hz flashing checkerboard stimulations were given to healthy subjects. The bSSFP imaging experiments were performed at three different frequency offsets to widen the coverage, with functional activations in the primary visual cortex analyzed using the general linear model. Variations of the spatial resolution were achieved by removing outerk-space data components. Results: Results show that a reduction in voxel volume from 3.44 × 3.44 × 2 mm{sup 3} to 0.43 × 0.43 × 2 mm{sup 3} has resulted in an increase of the functional activation signals from (7.7 ± 1.7)% to (20.9 ± 2.0)% at 3.0 T, despite of the threefold SNR decreases in the original images, leading to nearly invariant functional contrast-to-noise ratios (fCNR) even at high spatial resolution. Activation signals aligning nicely with gray matter sulci at high spatial resolution would, on the other hand, have possibly been mistaken as noise at low spatial resolution. Conclusions: It is concluded that the bSSFP sequence is a plausible technique for fMRI investigations at submillimeter voxel widths without compromising fCNR. The reduction of partial volume averaging with nonactivated brain tissues to retain fCNR is uniquely suitable for high spatial resolution applications such as the resolving of columnar organization in the brain.

  2. Higher order harmonic detection for exploring nonlinear interactions with nanoscale resolution.

    PubMed

    Vasudevan, R K; Okatan, M Baris; Rajapaksa, I; Kim, Y; Marincel, D; Trolier-McKinstry, S; Jesse, S; Valanoor, N; Kalinin, S V

    2013-01-01

    Nonlinear dynamics underpin a vast array of physical phenomena ranging from interfacial motion to jamming transitions. In many cases, insight into the nonlinear behavior can be gleaned through exploration of higher order harmonics. Here, a method using band excitation scanning probe microscopy (SPM) to investigate higher order harmonics of the electromechanical response, with nanometer scale spatial resolution is presented. The technique is demonstrated by probing the first three harmonics of strain for a Pb(Zr(1-x)Ti(x))O₃ (PZT) ferroelectric capacitor. It is shown that the second order harmonic response is correlated with the first harmonic response, whereas the third harmonic is not. Additionally, measurements of the second harmonic reveal significant deviations from Rayleigh-type models in the form of a much more complicated field dependence than is observed in the spatially averaged data. These results illustrate the versatility of n(th) order harmonic SPM detection methods in exploring nonlinear phenomena in nanoscale materials.

  3. Assessment of the Effects of Spatial Resolutions on Daily Water Flux Simulations

    SciTech Connect

    Liang, Xu; Guo, Jianzhong; Leung, Lai R.

    2004-10-01

    Impacts of spatially distributed precipitation and soil heterogeneity on modeling water fluxes at different spatial resolutions are investigated using the Three-layer Variable Infiltration Capacity (VIC-3L) land surface model at the Blue River watershed in Oklahoma. In this study, hourly grid-based NEXRAD (Next Generation Radar) Stage III radar precipitation data approximately at 4 x 4 km2 resolution are used to compute daily precipitation at spatial resolutions of 1/32, 1/16, 1/8, 1/4, 1/2 and 1 degree based on an area weighted average method. Soil parameters at the corresponding six spatial resolutions are derived from the State Soil Geographic (STATSGO) soil data. The forcing data of daily maximum and minimum temperature, wind speed, and vegetation parameters are disaggregated/aggregated directly to finer/coarser spatial resolutions based on the University of Washington (UW) data, which are gridded at 1/8 degree spatial resolution. Our study suggests that a critical spatial resolution for the VIC-3L model may exist for the study watershed. For spatial resolutions finer than the critical resolution, one does not necessarily obtain better model performance in terms of runoff, evapotranspiration, and total zone soil moisture with increasing spatial resolution if the VIC-3L model parameters are calibrated at each spatial resolution. Also, model parameters calibrated at a coarse resolution can be applied to finer resolutions to obtain generally comparable results. However, model parameters calibrated at finer resolutions cannot result in comparable results when applied to resolutions coarser than the identified critical resolution. In addition, while soil moisture of the total zone is more sensitive to the spatial distributions of soil properties, runoff and evaporation are more sensitive to the spatial distribution of daily precipitation at the watershed being studied.

  4. Effects of spatial fMRI resolution on the classification of naturalistic movies.

    PubMed

    Mandelkow, H; de Zwart, J A; Duyn, J H

    2017-08-24

    Studies involving multivariate pattern analysis (MVPA) of BOLD fMRI data generally attribute the success of the information-theoretic approach to BOLD signal contrast on the fine spatial scale of millimeters facilitating the classification or decoding of perceptual stimuli. However, to date MVPA studies that have actually explored fMRI resolutions at less than 2 mm voxel size are rare and limited to small sets of unnatural stimuli (like visual gratings) as well as specific sub-regions of the brain, notably the primary somatosensory cortices. To investigate what spatial scale best supports high information extraction under more general conditions this study combined naturalistic movie stimuli with high-resolution fMRI at 7 T and linear discriminant analysis (LDA) of global and local BOLD signal patterns. Contrary to predictions, LDA and similar classifiers reached a maximum in classification accuracy (CA) at a smoothed resolution close to 3 mm, well above the 1.2 mm voxel size of the fMRI acquisition. Maximal CAs around 90% were contingent upon global fMRI signal patterns comprising 4 k-16 k of the most reactive voxels distributed sparsely throughout the occipital and ventro-temporal cortices. A Searchlight analysis of local fMRI patterns largely confirmed the global results, but also revealed a small subset of brain regions in early visual cortex showing limited increases in CA with higher resolution. Principal component analysis of the global and local fMRI signal patterns suggested that reproducible neuronal contributions were spatially auto-correlated and smooth, while other components of higher spatial frequency were likely related to physiological noise and responsible for the reduced CA at higher resolution. Systematic differences between experiments and subjects suggested that higher CA was significantly correlated with more consistent behavior revealed by eye tracking. Thus, the optimal resolution of fMRI data for MVPA was mainly limited by

  5. The Tate form on steroids: resolution and higher codimension fibers

    NASA Astrophysics Data System (ADS)

    Lawrie, Craig; Schäfer-Nameki, Sakura

    2013-04-01

    F-theory on singular elliptically fibered Calabi-Yau four-folds provides a setting to geometrically study four-dimensional {N}=1 supersymmetric gauge theories, includingmatter and Yukawa couplings. The gauge degrees of freedom arise from the codimension 1 singular loci, the matter and Yukawa couplings are generated at enhanced singularities in higher codimension. We construct the resolution of the singular Tate form for an elliptic Calabi-Yau four-fold with an ADE type singularity in codimension 1 and study the structure of the fibers in codimension 2 and 3. We determine the fibers in higher codimension which in general are of Kodaira type along minimal singular loci, and are thus consistent with the low energy gauge-theoretic intuition. Furthermore, we provide a complementary description of the fibers in higher codimension, which will also be applicable to non-minimal singularities. The irreducible components in the fiber in codimension 2 correspond to weights of representations of the ADE gauge group. These can split further in codimension 3 in a way that is consistent with the generation of Yukawa couplings. Applying this reasoning, we then venture out to study non-minimal singularities, which occur for A type along codimension 3, and for D and E also in codimension 2. The fibers in this case are non-Kodaira, however some insight into these singularities can be gained by considering the splitting of fiber components along higher codimension, which are shown to be consistent with matter and Yukawa couplings for the corresponding gauge groups.

  6. High spatial resolution upgrade of the electron cyclotron emission radiometer for the DIII-D tokamak

    DOE PAGES

    Truong, D. D.; Austin, M. E.

    2014-11-01

    The 40-channel DIII-D electron cyclotron emission (ECE) radiometer provides measurements of Te(r,t) at the tokamak midplane from optically thick, second harmonic X-mode emission over a frequency range of 83-130 GHz. Heterodyning divides this frequency range into three 2-18 GHz intermediate frequency (IF) bands. The frequency spacing of the radiometer’s channels results in a spatial resolution of ~1-3 cm, depending on local magnetic field and electron temperature. A new high resolution subsystem has been added to the DIII-D ECE radiometer to make sub-centimeter (0.6-0.8 cm) resolution Te measurements. The high resolution subsystem branches off from the regular channels’ IF bands andmore » consists of a microwave switch to toggle between IF bands, a switched filter bank for frequency selectivity, an adjustable local oscillator and mixer for further frequency down-conversion, and a set of eight microwave filters in the 2-4 GHz range. We achieved a higher spatial resolution through the use of a narrower (200 MHz) filter bandwidth and closer spacing between the filters’ center frequencies (250 MHz). This configuration allows for full coverage of the 83-130 GHz frequency range in 2 GHz bands. Depending on the local magnetic field, this translates into a “zoomed-in” analysis of a ~2-4 cm radial region. These high resolution channels will be most useful in the low-field side edge region where modest Te values (1-2 keV) result in a minimum of relativistic broadening. Some expected uses of these channels include mapping the spatial dependence of Alfven eigenmodes, geodesic acoustic modes, and externally applied magnetic perturbations. Initial Te measurements, which demonstrate that the desired resolution is achieved, is presented.« less

  7. High spatial resolution upgrade of the electron cyclotron emission radiometer for the DIII-D tokamak

    SciTech Connect

    Truong, D. D.; Austin, M. E.

    2014-11-01

    The 40-channel DIII-D electron cyclotron emission (ECE) radiometer provides measurements of Te(r,t) at the tokamak midplane from optically thick, second harmonic X-mode emission over a frequency range of 83-130 GHz. Heterodyning divides this frequency range into three 2-18 GHz intermediate frequency (IF) bands. The frequency spacing of the radiometer’s channels results in a spatial resolution of ~1-3 cm, depending on local magnetic field and electron temperature. A new high resolution subsystem has been added to the DIII-D ECE radiometer to make sub-centimeter (0.6-0.8 cm) resolution Te measurements. The high resolution subsystem branches off from the regular channels’ IF bands and consists of a microwave switch to toggle between IF bands, a switched filter bank for frequency selectivity, an adjustable local oscillator and mixer for further frequency down-conversion, and a set of eight microwave filters in the 2-4 GHz range. We achieved a higher spatial resolution through the use of a narrower (200 MHz) filter bandwidth and closer spacing between the filters’ center frequencies (250 MHz). This configuration allows for full coverage of the 83-130 GHz frequency range in 2 GHz bands. Depending on the local magnetic field, this translates into a “zoomed-in” analysis of a ~2-4 cm radial region. These high resolution channels will be most useful in the low-field side edge region where modest Te values (1-2 keV) result in a minimum of relativistic broadening. Some expected uses of these channels include mapping the spatial dependence of Alfven eigenmodes, geodesic acoustic modes, and externally applied magnetic perturbations. Initial Te measurements, which demonstrate that the desired resolution is achieved, is presented.

  8. Evaluation of eight high spatial resolution gridded precipitation products in Adige Basin (Italy) at multiple temporal and spatial scales.

    PubMed

    Duan, Zheng; Liu, Junzhi; Tuo, Ye; Chiogna, Gabriele; Disse, Markus

    2016-12-15

    This study provides a comprehensive evaluation of eight high spatial resolution gridded precipitation products in Adige Basin located in Italy within 45-47.1°N. The Adige Basin is characterized by a complex topography, and independent ground data are available from a network of 101 rain gauges during 2000-2010. The eight products include the Version 7 TRMM (Tropical Rainfall Measuring Mission) Multi-satellite Precipitation Analysis 3B42 product, three products from CMORPH (the Climate Prediction Center MORPHing technique), i.e., CMORPH_RAW, CMORPH_CRT and CMORPH_BLD, PCDR (Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks-Climate Data Record), PGF (Global Meteorological Forcing Dataset for land surface modelling developed by Princeton University), CHIRPS (Climate Hazards Group InfraRed Precipitation with Station data) and GSMaP_MVK (Global Satellite Mapping of Precipitation project Moving Vector with Kalman-filter product). All eight products are evaluated against interpolated rain gauge data at the common 0.25° spatial resolution, and additional evaluations at native finer spatial resolution are conducted for CHIRPS (0.05°) and GSMaP_MVK (0.10°). Evaluation is performed at multiple temporal (daily, monthly and annual) and spatial scales (grid and watershed). Evaluation results show that in terms of overall statistical metrics the CHIRPS, TRMM and CMORPH_BLD comparably rank as the top three best performing products, while the PGF performs worst. All eight products underestimate and overestimate the occurrence frequency of daily precipitation for some intensity ranges. All products tend to show higher error in the winter months (December-February) when precipitation is low. Very slight difference can be observed in the evaluation metrics and aspects between at the aggregated 0.25° spatial resolution and at the native finer resolutions (0.05°) for CHIRPS and (0.10°) for GSMaP_MVK products. This study has implications

  9. The Role of a High-Resolution Spatial Sensor in an Educational Setting.

    ERIC Educational Resources Information Center

    Kay, Leslie; And Others

    1984-01-01

    A pilot study involving 16 visually handicapped children (6-14 years old) suggested that a new high-resolution acoustic sensory aid may be useful as a training aid for developing spatial perception. Tasks in spatial location, spatial orientation, and spatial transfer were executed using the spatial sensor in a classroom program. (Author/CL)

  10. The Role of a High-Resolution Spatial Sensor in an Educational Setting.

    ERIC Educational Resources Information Center

    Kay, Leslie; And Others

    1984-01-01

    A pilot study involving 16 visually handicapped children (6-14 years old) suggested that a new high-resolution acoustic sensory aid may be useful as a training aid for developing spatial perception. Tasks in spatial location, spatial orientation, and spatial transfer were executed using the spatial sensor in a classroom program. (Author/CL)

  11. Tactile Feedback Display with Spatial and Temporal Resolutions

    NASA Astrophysics Data System (ADS)

    Vishniakou, Siarhei; Lewis, Brian W.; Niu, Xiaofan; Kargar, Alireza; Sun, Ke; Kalajian, Michael; Park, Namseok; Yang, Muchuan; Jing, Yi; Brochu, Paul; Sun, Zhelin; Li, Chun; Nguyen, Truong; Pei, Qibing; Wang, Deli

    2013-08-01

    We report the electronic recording of the touch contact and pressure using an active matrix pressure sensor array made of transparent zinc oxide thin-film transistors and tactile feedback display using an array of diaphragm actuators made of an interpenetrating polymer elastomer network. Digital replay, editing and manipulation of the recorded touch events were demonstrated with both spatial and temporal resolutions. Analog reproduction of the force is also shown possible using the polymer actuators, despite of the high driving voltage. The ability to record, store, edit, and replay touch information adds an additional dimension to digital technologies and extends the capabilities of modern information exchange with the potential to revolutionize physical learning, social networking, e-commerce, robotics, gaming, medical and military applications.

  12. Tactile Feedback Display with Spatial and Temporal Resolutions

    PubMed Central

    Vishniakou, Siarhei; Lewis, Brian W.; Niu, Xiaofan; Kargar, Alireza; Sun, Ke; Kalajian, Michael; Park, Namseok; Yang, Muchuan; Jing, Yi; Brochu, Paul; Sun, Zhelin; Li, Chun; Nguyen, Truong; Pei, Qibing; Wang, Deli

    2013-01-01

    We report the electronic recording of the touch contact and pressure using an active matrix pressure sensor array made of transparent zinc oxide thin-film transistors and tactile feedback display using an array of diaphragm actuators made of an interpenetrating polymer elastomer network. Digital replay, editing and manipulation of the recorded touch events were demonstrated with both spatial and temporal resolutions. Analog reproduction of the force is also shown possible using the polymer actuators, despite of the high driving voltage. The ability to record, store, edit, and replay touch information adds an additional dimension to digital technologies and extends the capabilities of modern information exchange with the potential to revolutionize physical learning, social networking, e-commerce, robotics, gaming, medical and military applications. PMID:23982053

  13. Tactile feedback display with spatial and temporal resolutions.

    PubMed

    Vishniakou, Siarhei; Lewis, Brian W; Niu, Xiaofan; Kargar, Alireza; Sun, Ke; Kalajian, Michael; Park, Namseok; Yang, Muchuan; Jing, Yi; Brochu, Paul; Sun, Zhelin; Li, Chun; Nguyen, Truong; Pei, Qibing; Wang, Deli

    2013-01-01

    We report the electronic recording of the touch contact and pressure using an active matrix pressure sensor array made of transparent zinc oxide thin-film transistors and tactile feedback display using an array of diaphragm actuators made of an interpenetrating polymer elastomer network. Digital replay, editing and manipulation of the recorded touch events were demonstrated with both spatial and temporal resolutions. Analog reproduction of the force is also shown possible using the polymer actuators, despite of the high driving voltage. The ability to record, store, edit, and replay touch information adds an additional dimension to digital technologies and extends the capabilities of modern information exchange with the potential to revolutionize physical learning, social networking, e-commerce, robotics, gaming, medical and military applications.

  14. [Resolution of spatial constraints during replication of peripheral chromatin].

    PubMed

    Zhironkina, O A; Kurchashova, S Yu; Bratseva, A L; Cherepanynets, V D; Strelkova, O S; Belmont, A S; Kireev, I I

    2014-01-01

    Tight association of peripheral chromatin with nuclear lamina unavoidably creates topological constraints during replication. Additional complications are associated with high stability of lamina meshwork, which may hinder an access of replication factors to the sites of DNA synthesis in highly condensed template with limited mobility. In the current work we studied structural organization and dynamics of lamina as a function of replicative status of associated peripheral heterochromatin. The studies of molecular mobility of laminas at various stages of S-phase in vivo and using super-resolution microscopy showed no correlation between lamina dynamics and replicative status of attached heterochromatin. These data support the hypothesis that lamina-chromatin interactions during S-phase are regulated at the level of adapter proteins. Ultrastructural studies have demonstrated that temporal break of lamina-chromatin connections during replication does not cause noticeable spatial separation of replicating domains from nuclear periphery.

  15. Compressed sensing for super-resolution spatial and temporal laser detection and ranging

    NASA Astrophysics Data System (ADS)

    Laurenzis, Martin; Schertzer, Stephane; Christnacher, Frank

    2016-10-01

    In the past decades, laser aided electro-optical sensing has reached high maturity and several commercial systems are available at the market for various but specific applications. These systems can be used for detection i.e. imaging as well as ranging. They cover laser scanning devices like LiDAR and staring full frame imaging systems like laser gated viewing or LADAR. The sensing capabilities of these systems is limited by physical parameter (like FPA array size, temporal band width, scanning rate, sampling rate) and is adapted to specific applications. Change of system parameter like an increase of spatial resolution implies the setup of a new sensing device with high development cost or the purchase and installation of a complete new sensor unit. Computational imaging approaches can help to setup sensor devices with flexible or adaptable sensing capabilities. Especially, compressed sensing is an emerging computational method which is a promising candidate to realize super-resolution sensing with the possibility to adapt its performance to various sensing tasks. It is possible to increase sensing capabilities with compressed sensing to gain either higher spatial and/or temporal resolution. Then, the sensing capabilities depend no longer only on the physical performance of the device but also on the computational effort and can be adapted to the application. In this paper, we demonstrate and discuss laser aided imaging using CS for super-resolution tempo-spatial imaging and ranging.

  16. Higher rates of sex evolve in spatially heterogeneous environments.

    PubMed

    Becks, Lutz; Agrawal, Aneil F

    2010-11-04

    The evolution and maintenance of sexual reproduction has puzzled biologists for decades. Although this field is rich in hypotheses, experimental evidence is scarce. Some important experiments have demonstrated differences in evolutionary rates between sexual and asexual populations; other experiments have documented evolutionary changes in phenomena related to genetic mixing, such as recombination and selfing. However, direct experiments of the evolution of sex within populations are extremely rare (but see ref. 12). Here we use the rotifer, Brachionus calyciflorus, which is capable of both sexual and asexual reproduction, to test recent theory predicting that there is more opportunity for sex to evolve in spatially heterogeneous environments. Replicated experimental populations of rotifers were maintained in homogeneous environments, composed of either high- or low-quality food habitats, or in heterogeneous environments that consisted of a mix of the two habitats. For populations maintained in either type of homogeneous environment, the rate of sex evolves rapidly towards zero. In contrast, higher rates of sex evolve in populations experiencing spatially heterogeneous environments. The data indicate that the higher level of sex observed under heterogeneity is not due to sex being less costly or selection against sex being less efficient; rather sex is sufficiently advantageous in heterogeneous environments to overwhelm its inherent costs. Counter to some alternative theories for the evolution of sex, there is no evidence that genetic drift plays any part in the evolution of sex in these populations.

  17. High spatial resolution shortwave infrared imaging technology based on time delay and digital accumulation method

    NASA Astrophysics Data System (ADS)

    Jia, Jianxin; Wang, Yueming; Zhuang, Xiaoqiong; Yao, Yi; Wang, Shengwei; Zhao, Ding; Shu, Rong; Wang, Jianyu

    2017-03-01

    Shortwave infrared (SWIR) imaging technology attracts more and more attention by its fascinating ability of penetrating haze and smoke. For application of spaceborne remote sensing, spatial resolution of SWIR is lower compared with that of visible light (VIS) wavelength. It is difficult to balance between the spatial resolution and signal to noise ratio (SNR). Some conventional methods, such as enlarging aperture of telescope, image motion compensation, and analog time delay and integration (TDI) technology are used to gain SNR. These techniques bring in higher cost of satellite, complexity of system or other negative factors. In this paper, time delay and digital accumulation (TDDA) method is proposed to achieve higher spatial resolution. The method can enhance the SNR and non-uniformity of system theoretically. A prototype of SWIR imager consists of opto-mechanical, 1024 × 128 InGaAs detector, and electronics is designed and integrated to prove TDDA method. Both of measurements and experimental results indicate TDDA method can promote SNR of system approximated of the square root of accumulative stage. The results exhibit that non-uniformity of system is also improved by this approach to some extent. The experiment results are corresponded with the theoretical analysis. Based on the experiments results, it is proved firstly that the goal of 1 m ground sample distance (GSD) in orbit of 500 km is feasible with the TDDA stage of 30 for SWIR waveband (0.9-1.7 μm).

  18. VLBI observations of single stars, spatial resolution and astrometry

    NASA Astrophysics Data System (ADS)

    Pestalozzi, M.; Benz, A. O.; Conway, J. E.; Gudel, M.; Smith, K.

    VLBI studies can both spatially resolve single dMe stars and measure their positions at submilliarcsecond accuracy. The spatial resolution gives the brightness temperature and allows us to draw co nclusions about the nature of the emitting processes. In particular it is possib le to distinguish between thermal or non-thermal emission. The position accuracy gives better knowledge about the astrometric properties (like proper motion and parallax) especially for nearby stars. In this contribution recent results of c ontinuum VLBI observations towards two dMe stars (YZ CMi and AD Leo) at 8.4 GHz are presented. For YZ CMi an estimate of the size of the coronal emission is giv en (0.98 mas in diameter or 0.7 ±0.3 Rstar above the photosphere where Rstar refers to the photospheric radius). For AD Leo an upper limit is gi ven, i.e. the emitting region is shown to be < 0.8 Rstar. The position o f YZ CMi is found to differ by 32 mas form the Hipparcos catalogue, a discrepanc y mostly due to large errors in the listed proper motion (Pestalozzi et al. 2000 ).

  19. Forest Classification Accuracy as Influenced by Multispectral Scanner Spatial Resolution. [Sam Houston National Forest, Texas

    NASA Technical Reports Server (NTRS)

    Nalepka, R. F. (Principal Investigator); Sadowski, F. E.; Sarno, J. E.

    1976-01-01

    The author has identified the following significant results. A supervised classification within two separate ground areas of the Sam Houston National Forest was carried out for two sq meters spatial resolution MSS data. Data were progressively coarsened to simulate five additional cases of spatial resolution ranging up to 64 sq meters. Similar processing and analysis of all spatial resolutions enabled evaluations of the effect of spatial resolution on classification accuracy for various levels of detail and the effects on area proportion estimation for very general forest features. For very coarse resolutions, a subset of spectral channels which simulated the proposed thematic mapper channels was used to study classification accuracy.

  20. Comparison of the spatial resolution of source imaging techniques in high-density EEG and MEG.

    PubMed

    Hedrich, T; Pellegrino, G; Kobayashi, E; Lina, J M; Grova, C

    2017-06-13

    The present study aims at evaluating and comparing electrical and magnetic distributed source imaging methods applied to high-density Electroencephalography (hdEEG) and Magnetoencephalography (MEG) data. We used resolution matrices to characterize spatial resolution properties of Minimum Norm Estimate (MNE), dynamic Statistical Parametric Mapping (dSPM), standardized Low-Resolution Electromagnetic Tomography (sLORETA) and coherent Maximum Entropy on the Mean (cMEM, an entropy-based technique). The resolution matrix provides information of the Point Spread Functions (PSF) and of the Crosstalk functions (CT), this latter being also called source leakage, as it reflects the influence of a source on its neighbors. The spatial resolution of the inverse operators was first evaluated theoretically and then with real data acquired using electrical median nerve stimulation on five healthy participants. We evaluated the Dipole Localization Error (DLE) and the Spatial Dispersion (SD) of each PSF and CT map. cMEM showed the smallest spatial spread (SD) for both PSF and CT maps, whereas localization errors (DLE) were similar for all methods. Whereas cMEM SD values were lower in MEG compared to hdEEG, the other methods slightly favored hdEEG over MEG. In real data, cMEM provided similar localization error and significantly less spatial spread than other methods for both MEG and hdEEG. Whereas both MEG and hdEEG provided very accurate localizations, all the source imaging methods actually performed better in MEG compared to hdEEG according to all evaluation metrics, probably due to the higher signal-to-noise ratio of the data in MEG. Our overall results show that all investigated methods provide similar localization errors, suggesting very accurate localization for both MEG and hdEEG when similar number of sensors are considered for both modalities. Intrinsic properties of source imaging methods as well as their behavior for well-controlled tasks, suggest an overall better

  1. Linking the Weather Generator with Regional Climate Model: Effect of Higher Resolution

    NASA Astrophysics Data System (ADS)

    Dubrovsky, Martin; Huth, Radan; Farda, Ales; Skalak, Petr

    2014-05-01

    This contribution builds on our last year EGU contribution, which followed two aims: (i) validation of the simulations of the present climate made by the ALADIN-Climate Regional Climate Model (RCM) at 25 km resolution, and (ii) presenting a methodology for linking the parametric weather generator (WG) with RCM output (aiming to calibrate a gridded WG capable of producing realistic synthetic multivariate weather series for weather-ungauged locations). Now we have available new higher-resolution (6.25 km) simulations with the same RCM. The main topic of this contribution is an anser to a following question: What is an effect of using a higher spatial resolution on a quality of simulating the surface weather characteristics? In the first part, the high resolution RCM simulation of the present climate will be validated in terms of selected WG parameters, which are derived from the RCM-simulated surface weather series and compared to those derived from weather series observed in 125 Czech meteorological stations. The set of WG parameters will include statistics of the surface temperature and precipitation series. When comparing the WG parameters from the two sources (RCM vs observations), we interpolate the RCM-based parameters into the station locations while accounting for the effect of altitude. In the second part, we will discuss an effect of using the higher resolution: the results of the validation tests will be compared with those obtained with the lower-resolution RCM. Acknowledgements: The present experiment is made within the frame of projects ALARO-Climate (project P209/11/2405 sponsored by the Czech Science Foundation), WG4VALUE (project LD12029 sponsored by the Ministry of Education, Youth and Sports of CR) and VALUE (COST ES 1102 action).

  2. Development of an Objective High Spatial Resolution Soil Moisture Index

    NASA Astrophysics Data System (ADS)

    Zavodsky, B.; Case, J.; White, K.; Bell, J. R.

    2015-12-01

    Drought detection, analysis, and mitigation has become a key challenge for a diverse set of decision makers, including but not limited to operational weather forecasters, climatologists, agricultural interests, and water resource management. One tool that is heavily used is the United States Drought Monitor (USDM), which is derived from a complex blend of objective data and subjective analysis on a state-by-state basis using a variety of modeled and observed precipitation, soil moisture, hydrologic, and vegetation and crop health data. The NASA Short-term Prediction Research and Transition (SPoRT) Center currently runs a real-time configuration of the Noah land surface model (LSM) within the NASA Land Information System (LIS) framework. The LIS-Noah is run at 3-km resolution for local numerical weather prediction (NWP) and situational awareness applications at select NOAA/National Weather Service (NWS) forecast offices over the Continental U.S. (CONUS). To enhance the practicality of the LIS-Noah output for drought monitoring and assessing flood potential, a 30+-year soil moisture climatology has been developed in an attempt to place near real-time soil moisture values in historical context at county- and/or watershed-scale resolutions. This LIS-Noah soil moisture climatology and accompanying anomalies is intended to complement the current suite of operational products, such as the North American Land Data Assimilation System phase 2 (NLDAS-2), which are generated on a coarser-resolution grid that may not capture localized, yet important soil moisture features. Daily soil moisture histograms are used to identify the real-time soil moisture percentiles at each grid point according to the county or watershed in which the grid point resides. Spatial plots are then produced that map the percentiles as proxies to the different USDM categories. This presentation will highlight recent developments of this gridded, objective soil moisture index, comparison to subjective

  3. Optoelectronic image scanning with high spatial resolution and reconstruction fidelity

    NASA Astrophysics Data System (ADS)

    Craubner, Siegfried I.

    2002-02-01

    In imaging systems the detector arrays deliver at the output time-discrete signals, where the spatial frequencies of the object scene are mapped into the electrical signal frequencies. Since the spatial frequency spectrum cannot be bandlimited by the front optics, the usual detector arrays perform a spatial undersampling and as a consequence aliasing occurs. A means to partially suppress the backfolded alias band is bandwidth limitation in the reconstruction low-pass, at the price of resolution loss. By utilizing a bilinear detector array in a pushbroom-type scanner, undersampling and aliasing can be overcome. For modeling the perception, the theory of discrete systems and multirate digital filter banks is applied, where aliasing cancellation and perfect reconstruction play an important role. The discrete transfer function of a bilinear array can be imbedded into the scheme of a second-order filter bank. The detector arrays already build the analysis bank and the overall filter bank is completed with the synthesis bank, for which stabilized inverse filters are proposed, to compensate for the low-pass characteristics and to approximate perfect reconstruction. The synthesis filter branch can be realized in a so-called `direct form,' or the `polyphase form,' where the latter is an expenditure-optimal solution, which gives advantages when implemented in a signal processor. This paper attempts to introduce well-established concepts of the theory of multirate filter banks into the analysis of scanning imagers, which is applicable in a much broader sense than for the problems addressed here. To the author's knowledge this is also a novelty.

  4. Laser Beam Filtration for High Spatial Resolution MALDI Imaging Mass Spectrometry

    PubMed Central

    Zavalin, Andre; Yang, Junhai; Caprioli, Richard

    2013-01-01

    We describe an easy and inexpensive way to provide a highly defined Gaussian shaped laser spot on target of 5 μm diameter for Imaging Mass Spectrometry using a commercial MALDI TOF instrument that is designed to produce a 20 μm diameter laser beam on target at its lowest setting. A 25 μm pinhole filter on a swivel arm was installed in the laser beam optics outside the vacuum ion source chamber so it is easily flipped into or out of the beam as desired by the operator. The resulting ion images at 5 μm spatial resolution are sharp since the satellite secondary laser beam maxima have been removed by the filter. Ion images are shown to demonstrate the performance and are compared to the method of oversampling to achieve higher spatial resolution when only a larger laser beam spot on target is available. PMID:23661425

  5. Laser beam filtration for high spatial resolution MALDI imaging mass spectrometry.

    PubMed

    Zavalin, Andre; Yang, Junhai; Caprioli, Richard

    2013-07-01

    We describe an easy and inexpensive way to provide a highly defined Gaussian shaped laser spot on target of 5 μm diameter for imaging mass spectrometry using a commercial MALDI TOF instrument that is designed to produce a 20 μm diameter laser beam on target at its lowest setting. A 25 μm pinhole filter on a swivel arm was installed in the laser beam optics outside the vacuum ion source chamber so it is easily flipped into or out of the beam as desired by the operator. The resulting ion images at 5 μm spatial resolution are sharp since the satellite secondary laser beam maxima have been removed by the filter. Ion images are shown to demonstrate the performance and are compared with the method of oversampling to achieve higher spatial resolution when only a larger laser beam spot on target is available.

  6. Spatially detailed retrievals of spring phenology from single-season high-resolution image time series

    NASA Astrophysics Data System (ADS)

    Vrieling, Anton; Skidmore, Andrew K.; Wang, Tiejun; Meroni, Michele; Ens, Bruno J.; Oosterbeek, Kees; O'Connor, Brian; Darvishzadeh, Roshanak; Heurich, Marco; Shepherd, Anita; Paganini, Marc

    2017-07-01

    Vegetation indices derived from satellite image time series have been extensively used to estimate the timing of phenological events like season onset. Medium spatial resolution (≥250 m) satellite sensors with daily revisit capability are typically employed for this purpose. In recent years, phenology is being retrieved at higher resolution (≤30 m) in response to increasing availability of high-resolution satellite data. To overcome the reduced acquisition frequency of such data, previous attempts involved fusion between high- and medium-resolution data, or combinations of multi-year acquisitions in a single phenological reconstruction. The objectives of this study are to demonstrate that phenological parameters can now be retrieved from single-season high-resolution time series, and to compare these retrievals against those derived from multi-year high-resolution and single-season medium-resolution satellite data. The study focuses on the island of Schiermonnikoog, the Netherlands, which comprises a highly-dynamic saltmarsh, dune vegetation, and agricultural land. Combining NDVI series derived from atmospherically-corrected images from RapidEye (5 m-resolution) and the SPOT5 Take5 experiment (10m-resolution) acquired between March and August 2015, phenological parameters were estimated using a function fitting approach. We then compared results with phenology retrieved from four years of 30 m Landsat 8 OLI data, and single-year 100 m Proba-V and 250 m MODIS temporal composites of the same period. Retrieved phenological parameters from combined RapidEye/SPOT5 displayed spatially consistent results and a large spatial variability, providing complementary information to existing vegetation community maps. Retrievals that combined four years of Landsat observations into a single synthetic year were affected by the inclusion of years with warmer spring temperatures, whereas adjustment of the average phenology to 2015 observations was only feasible for a few pixels

  7. A comparison of two downscaling procedures to increase the spatial resolution of mapping actual evapotranspiration

    NASA Astrophysics Data System (ADS)

    Mahour, Milad; Tolpekin, Valentyn; Stein, Alfred; Sharifi, Ali

    2017-04-01

    This research addressed the effects of downscaling cokriging Land Surface Temperature (LST) on estimation of Actual Evapotranspiration (AET) from remote sensing images. Two procedures were followed. We first applied downscaling cokriging to a coarse resolution LST product of MODIS at 1000 m. With its outcome, daily AET of a medium spatial resolution (250 m) was obtained using the Surface Energy Balance System (SEBS). Second, we downscaled a coarse AET map to medium spatial resolution (250 m). For both procedures, the 250 m resolution MODIS NDVI product was used as a co-variable. Validation was carried out using Landsat 8 images, from which LST was derived from the thermal bands. The two procedures were applied to an agricultural area with a traditional irrigation network in Iran. We obtained an average LST value of 305.8 K as compared to a downscaled LST value of 307.0 K. Reference AET estimated with SEBS using Landsat 8 data was equal to 5.756 mm day-1, as compared with a downscaled AET value of 5.571 mm day-1. The RMSE between reference AET and downscaled AET was equal to 1.26 mm day-1 (r = 0.49) and between reference and downscaled LST to 3.67 K (r = 0.48). The study showed that AET values obtained with the two downscaling procedures were similar to each other, but that AET showed a higher spatial variability if obtained with downscaled LST. We concluded that LST had a large effect on producing AET maps from Remote Sensing (RS) images, and that downscaling cokriging was helpful to provide daily AET maps at medium spatial resolution.

  8. Device for high spatial resolution chemical analysis of a sample and method of high spatial resolution chemical analysis

    DOEpatents

    Van Berkel, Gary J.

    2015-10-06

    A system and method for analyzing a chemical composition of a specimen are described. The system can include at least one pin; a sampling device configured to contact a liquid with a specimen on the at least one pin to form a testing solution; and a stepper mechanism configured to move the at least one pin and the sampling device relative to one another. The system can also include an analytical instrument for determining a chemical composition of the specimen from the testing solution. In particular, the systems and methods described herein enable chemical analysis of specimens, such as tissue, to be evaluated in a manner that the spatial-resolution is limited by the size of the pins used to obtain tissue samples, not the size of the sampling device used to solubilize the samples coupled to the pins.

  9. Spatial resolution of the pain system: a proximal-to-distal gradient of sensitivity revealed with psychophysical testing.

    PubMed

    Weissman-Fogel, Irit; Brayer-Zwi, Nurit; Defrin, Ruth

    2012-01-01

    The spatial resolution of the pain system has not been studied in depth, and results are contradictory regarding the gradient of spatial resolution. Microneurographic recordings have revealed smaller receptive fields and higher density of nociceptors in more distal than proximal leg regions, whereas histological studies report higher density of C-fibers in more proximal than distal body regions. Due to this controversy, we conducted various psychophysical tests in order to examine the nociceptive spatial resolution and its gradient. Heat-pain threshold (HPT), perceived pain intensity, spatial summation (SS) of pain, two-point discrimination (2PD) of pain, and pain localization were measured in four body regions: upper back, thigh, lower leg, and foot. The highest HPT was demonstrated in the lower leg as compared with more proximal regions (P < 0.0001). SS was observed in all the regions and was found to be smallest in the foot (P < 0.05). The smallest 2PD and localization distances were found in the foot (P < 0.01) as compared with the lower leg and upper back. It appears that the nociceptive spatial resolution has a proximal-to-distal pattern of performance, namely that the spatial resolution of pain is finer in more distal than proximal body regions, similar to that of the touch system.

  10. High spatial resolution upgrade of the electron cyclotron emission radiometer for the DIII-D tokamak

    SciTech Connect

    Truong, D. D.; Austin, M. E.

    2014-11-15

    The 40-channel DIII-D electron cyclotron emission (ECE) radiometer provides measurements of T{sub e}(r,t) at the tokamak midplane from optically thick, second harmonic X-mode emission over a frequency range of 83–130 GHz. The frequency spacing of the radiometer's channels results in a spatial resolution of ∼1–3 cm, depending on local magnetic field and electron temperature. A new high resolution subsystem has been added to the DIII-D ECE radiometer to make sub-centimeter (0.6–0.8 cm) resolution T{sub e} measurements. The high resolution subsystem branches off from the regular channels’ IF bands and consists of a microwave switch to toggle between IF bands, a switched filter bank for frequency selectivity, an adjustable local oscillator and mixer for further frequency down-conversion, and a set of eight microwave filters in the 2–4 GHz range. Higher spatial resolution is achieved through the use of a narrower (200 MHz) filter bandwidth and closer spacing between the filters’ center frequencies (250 MHz). This configuration allows for full coverage of the 83–130 GHz frequency range in 2 GHz bands. Depending on the local magnetic field, this translates into a “zoomed-in” analysis of a ∼2–4 cm radial region. Expected uses of these channels include mapping the spatial dependence of Alfven eigenmodes, geodesic acoustic modes, and externally applied magnetic perturbations. Initial T{sub e} measurements, which demonstrate that the desired resolution is achieved, are presented.

  11. Analysis of spatial inhomogeneities in cumulus clouds using high spatial resolution Landsat data

    NASA Technical Reports Server (NTRS)

    Parker, Lindsay; Welch, R. M.; Musil, D. J.

    1986-01-01

    Aircraft observations and high resolution Landsat MSS digital data are used to determine the sizes of spatial inhomogeneities ('holes') in cumulus clouds. The majority of holes are found near cloud edges, but the larger holes tend to be found in cloud interiors. Aircraft measurements show these cloud spatial inhomogeneities in the range of 100 to 500 m, while Landsat data show them in the range of 100 m to 3 km. The number of holes per cloud decreases exponentially with increasing hole diameter. Small clouds not only have smaller holes, but also fewer holes than large clouds. Large clouds have large holes in them, as well as large numbers of the smaller holes. The total cloud area occupied by holes increases with increasing cloud size.

  12. Analysis of spatial inhomogeneities in cumulus clouds using high spatial resolution Landsat data

    NASA Technical Reports Server (NTRS)

    Parker, Lindsay; Welch, R. M.; Musil, D. J.

    1986-01-01

    Aircraft observations and high resolution Landsat MSS digital data are used to determine the sizes of spatial inhomogeneities ('holes') in cumulus clouds. The majority of holes are found near cloud edges, but the larger holes tend to be found in cloud interiors. Aircraft measurements show these cloud spatial inhomogeneities in the range of 100 to 500 m, while Landsat data show them in the range of 100 m to 3 km. The number of holes per cloud decreases exponentially with increasing hole diameter. Small clouds not only have smaller holes, but also fewer holes than large clouds. Large clouds have large holes in them, as well as large numbers of the smaller holes. The total cloud area occupied by holes increases with increasing cloud size.

  13. Spatial-Resolution Improvement in Optical Frequency Domain Reflectometry System Based on Tunable Linear Fiber Laser

    NASA Astrophysics Data System (ADS)

    Li, Guoyu; Zhao, Peng; Li, Yan

    2011-02-01

    In optical frequency domain reflectometry (OFDR) system, the spatial resolution is obtained by using the total frequency-sweep span of the tunable laser. However, in practice, the spatial resolution is severely limited by nonlinearity in the lightwave-frequency sweep of the tunable laser. A closed-loop PZT modulated DBR linear fiber laser is proposed to improve the spatial resolution of the OFDR system. Experimental results show that the spatial resolution of OFDR system has improved greatly. When the frequency sweep excursion is 66GHz and the fiber under test (FUT) is 7 m, the OFDR system has a spatial resolution of 1.5 m with open-loop PZT modulated laser. But the spatial resolution increases to 35 cm with closed-loop PZT modulated laser.

  14. Polarimetry of sunspot penumbrae with high spatial resolution

    NASA Astrophysics Data System (ADS)

    Bello González, N.; Okunev, O. V.; Domínguez Cerdeña, I.; Kneer, F.; Puschmann, K. G.

    2005-04-01

    We present two-dimensional high-spatial-resolution spectropolarimetric observations of sunspot penumbrae. They were obtained in April 2002 and May 2003 with the "Göttingen" Fabry-Pérot spectrometer at the Vacuum Tower Telescope at the Observatorio del Teide (Tenerife). Speckle methods were applied for image reconstruction which resulted in a spatial resolution of 0.5 arcsec in the magnetograms of the penumbrae. We analysed Stokes I and V profiles of the Fe II 6149 Å line, which exhibits no instrumental Stokes Q/U→ V crosstalk, and of the Fe I line pair at 6302 Å. The main results are the following: 1) on scales larger than 0.5 arcsec, the intensity pattern of penumbrae stays the same in the continuum and core images of the 6301.5 Å line, which stem from 0 km and 300 km (above τ_5=1), respectively. Yet at scales of 0.5 arcsec and smaller the pattern in the two spectral features is clearly different. 2) On the limb side of sunspots the Evershed flow is carried by dark filaments and on the centre side by bright features and their somewhat weakened tails. We explain this with a picture in which the velocity of hot rising gas is best seen on the centre side, while on the limb side the horizontal outward and possibly downward flows are seen when the gas has cooled down. 3) The un-combed structure of the magnetic field is confirmed. On the limb side, the more horizontal fields coincide with dark fibrils or with diffuse intensity structures. Generally, the more horizontal fields are located at the positions of strong outflows. 4) Strong line-of-sight components of the magnetic fields are not found in bright filaments but in dark structures, somewhat displaced from the darkest parts. Their positions do not coincide with those of the strongest velocity fields. In general, our results are compatible with the picture of low lying flow channels coincident with the horizontal magnetic field, or possibly emerging and diving down into sub-photospheric layers, like a "sea

  15. Global anthropogenic heat flux database with high spatial resolution

    NASA Astrophysics Data System (ADS)

    Dong, Y.; Varquez, A. C. G.; Kanda, M.

    2017-02-01

    This study developed a top-down method for estimating global anthropogenic heat emission (AHE), with a high spatial resolution of 30 arc-seconds and temporal resolution of 1 h. Annual average AHE was derived from human metabolic heating and primary energy consumption, which was further divided into three components based on consumer sector. The first and second components were heat loss and heat emissions from industrial sectors equally distributed throughout the country and populated areas, respectively. The third component comprised the sum of emissions from commercial, residential, and transportation sectors (CRT). Bulk AHE from the CRT was proportionally distributed using a global population dataset, with a radiance-calibrated nighttime lights adjustment. An empirical function to estimate monthly fluctuations of AHE based on gridded monthly temperatures was derived from various Japanese and American city measurements. Finally, an AHE database with a global coverage was constructed for the year 2013. Comparisons between our proposed AHE and other existing datasets revealed that the problem of overestimation of AHE intensity in previous top-down models was mitigated by the separation of energy consumption sectors; furthermore, the problem of AHE underestimation at central urban areas was solved by the nighttime lights adjustment. A strong agreement in the monthly profiles of AHE between our database and other bottom-up datasets further proved the validity of the current methodology. Investigations of AHE for the 29 largest urban agglomerations globally highlighted that the share of heat emissions from CRT sectors to the total AHE at the city level was 40-95%; whereas that of metabolic heating varied with the city's level of development by a range of 2-60%. A negative correlation between gross domestic product (GDP) and the share of metabolic heating to a city's total AHE was found. Globally, peak AHE values were found to occur between December and February, while

  16. Methods of photoelectrode characterization with high spatial and temporal resolution

    SciTech Connect

    Esposito, Daniel V.; Baxter, Jason B.; John, Jimmy; Lewis, Nathan S.; Moffat, Thomas P.; Ogitsu, Tadashi; O'Neil, Glen D.; Pham, Tuan Anh; Talin, A. Alec; Velazquez, Jesus M.; Wood, Brandon C.

    2015-06-19

    Here, materials and photoelectrode architectures that are highly efficient, extremely stable, and made from low cost materials are required for commercially viable photoelectrochemical (PEC) water-splitting technology. A key challenge is the heterogeneous nature of real-world materials, which often possess spatial variation in their crystal structure, morphology, and/or composition at the nano-, micro-, or macro-scale. Different structures and compositions can have vastly different properties and can therefore strongly influence the overall performance of the photoelectrode through complex structure–property relationships. A complete understanding of photoelectrode materials would also involve elucidation of processes such as carrier collection and electrochemical charge transfer that occur at very fast time scales. We present herein an overview of a broad suite of experimental and computational tools that can be used to define the structure–property relationships of photoelectrode materials at small dimensions and on fast time scales. A major focus is on in situ scanning-probe measurement (SPM) techniques that possess the ability to measure differences in optical, electronic, catalytic, and physical properties with nano- or micro-scale spatial resolution. In situ ultrafast spectroscopic techniques, used to probe carrier dynamics involved with processes such as carrier generation, recombination, and interfacial charge transport, are also discussed. Complementing all of these experimental techniques are computational atomistic modeling tools, which can be invaluable for interpreting experimental results, aiding in materials discovery, and interrogating PEC processes at length and time scales not currently accessible by experiment. In addition to reviewing the basic capabilities of these experimental and computational techniques, we highlight key opportunities and limitations of applying these tools for the development of PEC materials.

  17. Methods of photoelectrode characterization with high spatial and temporal resolution

    DOE PAGES

    Esposito, Daniel V.; Baxter, Jason B.; John, Jimmy; ...

    2015-06-19

    Here, materials and photoelectrode architectures that are highly efficient, extremely stable, and made from low cost materials are required for commercially viable photoelectrochemical (PEC) water-splitting technology. A key challenge is the heterogeneous nature of real-world materials, which often possess spatial variation in their crystal structure, morphology, and/or composition at the nano-, micro-, or macro-scale. Different structures and compositions can have vastly different properties and can therefore strongly influence the overall performance of the photoelectrode through complex structure–property relationships. A complete understanding of photoelectrode materials would also involve elucidation of processes such as carrier collection and electrochemical charge transfer that occurmore » at very fast time scales. We present herein an overview of a broad suite of experimental and computational tools that can be used to define the structure–property relationships of photoelectrode materials at small dimensions and on fast time scales. A major focus is on in situ scanning-probe measurement (SPM) techniques that possess the ability to measure differences in optical, electronic, catalytic, and physical properties with nano- or micro-scale spatial resolution. In situ ultrafast spectroscopic techniques, used to probe carrier dynamics involved with processes such as carrier generation, recombination, and interfacial charge transport, are also discussed. Complementing all of these experimental techniques are computational atomistic modeling tools, which can be invaluable for interpreting experimental results, aiding in materials discovery, and interrogating PEC processes at length and time scales not currently accessible by experiment. In addition to reviewing the basic capabilities of these experimental and computational techniques, we highlight key opportunities and limitations of applying these tools for the development of PEC materials.« less

  18. Spatially Regularized Compressed Sensing for High Angular Resolution Diffusion Imaging

    PubMed Central

    Rathi, Yogesh; Dolui, Sudipto

    2013-01-01

    Despite the relative recency of its inception, the theory of compressive sampling (aka compressed sensing) (CS) has already revolutionized multiple areas of applied sciences, a particularly important instance of which is medical imaging. Specifically, the theory has provided a different perspective on the important problem of optimal sampling in magnetic resonance imaging (MRI), with an ever-increasing body of works reporting stable and accurate reconstruction of MRI scans from the number of spectral measurements which would have been deemed unacceptably small as recently as five years ago. In this paper, the theory of CS is employed to palliate the problem of long acquisition times, which is known to be a major impediment to the clinical application of high angular resolution diffusion imaging (HARDI). Specifically, we demonstrate that a substantial reduction in data acquisition times is possible through minimization of the number of diffusion encoding gradients required for reliable reconstruction of HARDI scans. The success of such a minimization is primarily due to the availability of spherical ridgelet transformation, which excels in sparsifying HARDI signals. What makes the resulting reconstruction procedure even more accurate is a combination of the sparsity constraints in the diffusion domain with additional constraints imposed on the estimated diffusion field in the spatial domain. Accordingly, the present paper describes an original way to combine the diffusion-and spatial-domain constraints to achieve a maximal reduction in the number of diffusion measurements, while sacrificing little in terms of reconstruction accuracy. Finally, details are provided on an efficient numerical scheme which can be used to solve the aforementioned reconstruction problem by means of standard and readily available estimation tools. The paper is concluded with experimental results which support the practical value of the proposed reconstruction methodology. PMID:21536524

  19. Selecting Adequate Spatial Resolution to Estimate Water Flow by Using SWAT Model

    NASA Astrophysics Data System (ADS)

    Kim, G. S.; Kim, T. T.; Lim, C. H.; Ryu, H.; Lee, W. K.

    2016-12-01

    Abstract:When we studying hydrological runoff and nutrient cycle of watershed, SWAT(Soil Water Assessment Tool) model is very useful model. SWAT model can be driven delicately with many other data and it has many research case and users. Therefore, SWAT model is important model for studying hydrology. SWAT model is driven with spatial data, which are DEM(Digital Elevation Model), land cover map, soil map and so on, and it simulates water yield, ET(actual evapotranspiration), PET(potential evapotranspiration), sed yield and so on. In study which require spatial data, spatial resolution must be carefully considered. Low resolution might express imprecise and uncertain result, high resolution might express skewed result. Therefore, selecting adequate spatial resolution is important for study which treats spatial data.This study is practiced for selecting adequate spatial resolution to simulating water yield result of SWAT model. Adequate spatial resolution can be different according to Area size and topographic characteristics of target area. This study chooses Taehwa river, South Korea as target area. A high percentage of mountains are located in Korea and Korea also has a lot of steep slope area which can affect to results. SWAT model is driven according to 4 different spatial resolution(30m, 50m, 100m, 300m), and Simulated results are compared with observed results. Target period is set from 2008 to 2013. First 2 years are stabilization duration and 2010 2013 are verification period. According to watershed area size, simulated water yields per spatial resolutions are compared with other results and adequate spatial resolution will be selected.20 50m and 100m 800m resolution are expected to be accurate with observed results according to other studies. It is expected that watershed area size is directly propotional to spatial resolution. Keywords: SWAT, spatial resolution, water yield, river flow Acknowledge : This work was funded by "Development of satellite based

  20. Analysis of the impact of spatial resolution on land/water classifications using high-resolution aerial imagery

    USGS Publications Warehouse

    Enwright, Nicholas M.; Jones, William R.; Garber, Adrienne L.; Keller, Matthew J.

    2014-01-01

    Long-term monitoring efforts often use remote sensing to track trends in habitat or landscape conditions over time. To most appropriately compare observations over time, long-term monitoring efforts strive for consistency in methods. Thus, advances and changes in technology over time can present a challenge. For instance, modern camera technology has led to an increasing availability of very high-resolution imagery (i.e. submetre and metre) and a shift from analogue to digital photography. While numerous studies have shown that image resolution can impact the accuracy of classifications, most of these studies have focused on the impacts of comparing spatial resolution changes greater than 2 m. Thus, a knowledge gap exists on the impacts of minor changes in spatial resolution (i.e. submetre to about 1.5 m) in very high-resolution aerial imagery (i.e. 2 m resolution or less). This study compared the impact of spatial resolution on land/water classifications of an area dominated by coastal marsh vegetation in Louisiana, USA, using 1:12,000 scale colour-infrared analogue aerial photography (AAP) scanned at four different dot-per-inch resolutions simulating ground sample distances (GSDs) of 0.33, 0.54, 1, and 2 m. Analysis of the impact of spatial resolution on land/water classifications was conducted by exploring various spatial aspects of the classifications including density of waterbodies and frequency distributions in waterbody sizes. This study found that a small-magnitude change (1–1.5 m) in spatial resolution had little to no impact on the amount of water classified (i.e. percentage mapped was less than 1.5%), but had a significant impact on the mapping of very small waterbodies (i.e. waterbodies ≤ 250 m2). These findings should interest those using temporal image classifications derived from very high-resolution aerial photography as a component of long-term monitoring programs.

  1. Thematic and spatial resolutions affect model-based predictions of tree species distribution.

    PubMed

    Liang, Yu; He, Hong S; Fraser, Jacob S; Wu, ZhiWei

    2013-01-01

    Subjective decisions of thematic and spatial resolutions in characterizing environmental heterogeneity may affect the characterizations of spatial pattern and the simulation of occurrence and rate of ecological processes, and in turn, model-based tree species distribution. Thus, this study quantified the importance of thematic and spatial resolutions, and their interaction in predictions of tree species distribution (quantified by species abundance). We investigated how model-predicted species abundances changed and whether tree species with different ecological traits (e.g., seed dispersal distance, competitive capacity) had different responses to varying thematic and spatial resolutions. We used the LANDIS forest landscape model to predict tree species distribution at the landscape scale and designed a series of scenarios with different thematic (different numbers of land types) and spatial resolutions combinations, and then statistically examined the differences of species abundance among these scenarios. Results showed that both thematic and spatial resolutions affected model-based predictions of species distribution, but thematic resolution had a greater effect. Species ecological traits affected the predictions. For species with moderate dispersal distance and relatively abundant seed sources, predicted abundance increased as thematic resolution increased. However, for species with long seeding distance or high shade tolerance, thematic resolution had an inverse effect on predicted abundance. When seed sources and dispersal distance were not limiting, the predicted species abundance increased with spatial resolution and vice versa. Results from this study may provide insights into the choice of thematic and spatial resolutions for model-based predictions of tree species distribution.

  2. What are the basic concepts of temporal, contrast, and spatial resolution in cardiac CT?

    PubMed

    Lin, Eugene; Alessio, Adam

    2009-01-01

    An imaging instrument can be characterized by its spatial resolution, contrast resolution, and temporal resolution. The capabilities of computed tomography (CT) relative to other cardiac imaging modalities can be understood in these terms. The purpose of this review is to characterize the spatial, contrast, and temporal resolutions of cardiac CT in practical terms. Copyright (c) 2009 Society of Cardiovascular Computed Tomography. Published by Elsevier Inc. All rights reserved.

  3. Role of spatial higher order derivatives in momentum space entanglement

    NASA Astrophysics Data System (ADS)

    Kumar, S. Santhosh; Shankaranarayanan, S.

    2017-03-01

    We study the momentum space entanglement between different energy modes of interacting scalar fields propagating in general (D +1 )-dimensional flat space-time. As opposed to some of the recent works [V. Balasubramanian et al., Phys. Rev. D 86, 045014 (2012), 10.1103/PhysRevD.86.045014], we use a Lorentz invariant normalized ground state to obtain the momentum space entanglement entropy. We show that the Lorenz invariant definition removes the spurious power-law behavior obtained in the earlier works. More specifically, we show that the cubic interacting scalar field in (1 +1 ) dimensions leads to logarithmic divergence of the entanglement entropy and is consistent with the results from real space entanglement calculations. We study the effects of the introduction of the Lorentz violating higher derivative terms in the presence of a nonlinear self-interacting scalar field potential and show that the divergence structure of the entanglement entropy is improved in the presence of spatial higher derivative terms.

  4. An evaluation of the spatial resolution of soil moisture information

    NASA Technical Reports Server (NTRS)

    Hardy, K. R.; Cohen, S. H.; Rogers, L. K.; Burke, H. H. K.; Leupold, R. C.; Smallwood, M. D.

    1981-01-01

    Rainfall-amount patterns in the central regions of the U.S. were assessed. The spatial scales of surface features and their corresponding microwave responses in the mid western U.S. were investigated. The usefulness for U.S. government agencies of soil moisture information at scales of 10 km and 1 km. was ascertained. From an investigation of 494 storms, it was found that the rainfall resulting from the passage of most types of storms produces patterns which can be resolved on a 10 km scale. The land features causing the greatest problem in the sensing of soil moisture over large agricultural areas with a radiometer are bodies of water. Over the mid-western portions of the U.S., water occupies less than 2% of the total area, the consequently, the water bodies will not have a significant impact on the mapping of soil moisture. Over most of the areas, measurements at a 10-km resolution would adequately define the distribution of soil moisture. Crop yield models and hydrological models would give improved results if soil moisture information at scales of 10 km was available.

  5. Mapping stress in polycrystals with sub-10 nm spatial resolution.

    PubMed

    Polop, C; Vasco, E; Perrino, A P; Garcia, R

    2017-07-07

    From aircraft to electronic devices, and even in Formula One cars, stress is the main cause of degraded material performance and mechanical failure in applications incorporating thin films and coatings. Over the last two decades, the scientific community has searched for the mechanisms responsible for stress generation in films, with no consensus in sight. The main difficulty is that most current models of stress generation, while atomistic in nature, are based on macroscopic measurements. Here, we demonstrate a novel method for mapping the stress at the surface of polycrystals with sub-10 nm spatial resolution. This method consists of transforming elastic modulus maps measured by atomic force microscopy techniques into stress maps via the local stress-stiffening effect. The validity of this approach is supported by finite element modeling simulations. Our study reveals a strongly heterogeneous distribution of intrinsic stress in polycrystalline Au films, with gradients as high as 100 MPa nm(-1) near the grain boundaries. Consequently, our study discloses the limited capacity of macroscopic stress assessments and standard tests to discriminate among models, and the great potential of nanometer-scale stress mapping.

  6. Monte Carlo code for high spatial resolution ocean color simulations.

    PubMed

    D'Alimonte, Davide; Zibordi, Giuseppe; Kajiyama, Tamito; Cunha, José C

    2010-09-10

    A Monte Carlo code for ocean color simulations has been developed to model in-water radiometric fields of downward and upward irradiance (E(d) and E(u)), and upwelling radiance (L(u)) in a two-dimensional domain with a high spatial resolution. The efficiency of the code has been optimized by applying state-of-the-art computing solutions, while the accuracy of simulation results has been quantified through benchmark with the widely used Hydrolight code for various values of seawater inherent optical properties and different illumination conditions. Considering a seawater single scattering albedo of 0.9, as well as surface waves of 5 m width and 0.5 m height, the study has shown that the number of photons required to quantify uncertainties induced by wave focusing effects on E(d), E(u), and L(u) data products is of the order of 10(6), 10(9), and 10(10), respectively. On this basis, the effects of sea-surface geometries on radiometric quantities have been investigated for different surface gravity waves. Data products from simulated radiometric profiles have finally been analyzed as a function of the deployment speed and sampling frequency of current free-fall systems in view of providing recommendations to improve measurement protocols.

  7. Influence of Elevation Data Resolution on Spatial Prediction of Colluvial Soils in a Luvisol Region.

    PubMed

    Penížek, Vít; Zádorová, Tereza; Kodešová, Radka; Vaněk, Aleš

    2016-01-01

    The development of a soil cover is a dynamic process. Soil cover can be altered within a few decades, which requires updating of the legacy soil maps. Soil erosion is one of the most important processes quickly altering soil cover on agriculture land. Colluvial soils develop in concave parts of the landscape as a consequence of sedimentation of eroded material. Colluvial soils are recognised as important soil units because they are a vast sink of soil organic carbon. Terrain derivatives became an important tool in digital soil mapping and are among the most popular auxiliary data used for quantitative spatial prediction. Prediction success rates are often directly dependent on raster resolution. In our study, we tested how raster resolution (1, 2, 3, 5, 10, 20 and 30 meters) influences spatial prediction of colluvial soils. Terrain derivatives (altitude, slope, plane curvature, topographic position index, LS factor and convergence index) were calculated for the given raster resolutions. Four models were applied (boosted tree, neural network, random forest and Classification/Regression Tree) to spatially predict the soil cover over a 77 ha large study plot. Models training and validation was based on 111 soil profiles surveyed on a regular sampling grid. Moreover, the predicted real extent and shape of the colluvial soil area was examined. In general, no clear trend in the accuracy prediction was found without the given raster resolution range. Higher maximum prediction accuracy for colluvial soil, compared to prediction accuracy of total soil cover of the study plot, can be explained by the choice of terrain derivatives that were best for Colluvial soils differentiation from other soil units. Regarding the character of the predicted Colluvial soils area, maps of 2 to 10 m resolution provided reasonable delineation of the colluvial soil as part of the cover over the study area.

  8. Influence of Elevation Data Resolution on Spatial Prediction of Colluvial Soils in a Luvisol Region

    PubMed Central

    Penížek, Vít; Zádorová, Tereza; Kodešová, Radka; Vaněk, Aleš

    2016-01-01

    The development of a soil cover is a dynamic process. Soil cover can be altered within a few decades, which requires updating of the legacy soil maps. Soil erosion is one of the most important processes quickly altering soil cover on agriculture land. Colluvial soils develop in concave parts of the landscape as a consequence of sedimentation of eroded material. Colluvial soils are recognised as important soil units because they are a vast sink of soil organic carbon. Terrain derivatives became an important tool in digital soil mapping and are among the most popular auxiliary data used for quantitative spatial prediction. Prediction success rates are often directly dependent on raster resolution. In our study, we tested how raster resolution (1, 2, 3, 5, 10, 20 and 30 meters) influences spatial prediction of colluvial soils. Terrain derivatives (altitude, slope, plane curvature, topographic position index, LS factor and convergence index) were calculated for the given raster resolutions. Four models were applied (boosted tree, neural network, random forest and Classification/Regression Tree) to spatially predict the soil cover over a 77 ha large study plot. Models training and validation was based on 111 soil profiles surveyed on a regular sampling grid. Moreover, the predicted real extent and shape of the colluvial soil area was examined. In general, no clear trend in the accuracy prediction was found without the given raster resolution range. Higher maximum prediction accuracy for colluvial soil, compared to prediction accuracy of total soil cover of the study plot, can be explained by the choice of terrain derivatives that were best for Colluvial soils differentiation from other soil units. Regarding the character of the predicted Colluvial soils area, maps of 2 to 10 m resolution provided reasonable delineation of the colluvial soil as part of the cover over the study area. PMID:27846230

  9. Virtual electrode design for increasing spatial resolution in retinal prosthesis.

    PubMed

    Loizos, Kyle; Cela, Carlos; Marc, Robert; Lazzi, Gianluca

    2016-06-01

    Retinal prostheses systems are currently used to restore partial vision to patients blinded by degenerative diseases by electrically stimulating surviving retinal cells. To obtain likely maximum resolution, electrode size is minimised, allowing for a large quantity on an array and localised stimulation regions. Besides the small size leading to fabrication difficulties and higher electrochemical charge density, there are challenges associated with the number of drivers needed for a large electrode count as well as the strategies to deliver sufficient power to these drivers wirelessly. In hopes to increase electrode resolution while avoiding these issues, the authors propose a new 'virtual electrode' design to increase locations of likely stimulation. Passive metallisation strategically placed between disk electrodes, combined with alternating surrounding stimuli, channel current into a location between electrodes, producing a virtual stimulation site. A computational study was conducted to optimise the passive metal element geometry, quantify the expected current density output, and simulate retinal ganglion cell activity due to virtual electrode stimulation. Results show that this procedure leads to array geometry that focuses injected current and achieves retinal ganglion cell stimulation in a region beneath the 'virtual electrode,' creating an alternate stimulation site without additional drivers.

  10. Higher Resolution Neutron Velocity Spectrometer Measurements of Enriched Uranium

    DOE R&D Accomplishments Database

    Rainwater, L. J.; Havens, W. W. Jr.

    1950-08-09

    The slow neutron transmission of a sample of enriched U containing 3.193 gm/cm2 was investigated with a resolution width of 1 microsec/m. Results of transmission measurements are shown graphically. (B.J.H.)

  11. Effect of spatial resolution on remote sensing estimation of total evaporation in the uMngeni catchment, South Africa

    NASA Astrophysics Data System (ADS)

    Shoko, Cletah; Clark, David; Mengistu, Michael; Dube, Timothy; Bulcock, Hartley

    2015-01-01

    This study evaluated the effect of two readily available multispectral sensors: the newly launched 30 m spatial resolution Landsat 8 and the long-serving 1000 m moderate resolution imaging spectroradiometer (MODIS) datasets in the spatial representation of total evaporation in the heterogeneous uMngeni catchment, South Africa, using the surface energy balance system model. The results showed that sensor spatial resolution plays a critical role in the accurate estimation of energy fluxes and total evaporation across a heterogeneous catchment. Landsat 8 estimates showed better spatial representation of the biophysical parameters and total evaporation for different land cover types, due to the relatively higher spatial resolution compared to the coarse spatial resolution MODIS sensor. Moreover, MODIS failed to capture the spatial variations of total evaporation estimates across the catchment. Analysis of variance (ANOVA) results showed that MODIS-based total evaporation estimates did not show any significant differences across different land cover types (one-way ANOVA; F1.924=1.412, p=0.186). However, Landsat 8 images yielded significantly different estimates between different land cover types (one-way ANOVA; F1.993=5.185, p<0.001). The validation results showed that Landsat 8 estimates were more comparable to eddy covariance (EC) measurements than the MODIS-based total evaporation estimates. EC measurement on May 23, 2013, was 3.8 mm/day, whereas the Landsat 8 estimate on the same day was 3.6 mm/day, with MODIS showing significantly lower estimates of 2.3 mm/day. The findings of this study underscore the importance of spatial resolution in estimating spatial variations of total evaporation at the catchment scale, thus, they provide critical information on the relevance of the readily available remote sensing products in water resources management in data-scarce environments.

  12. The sensitivity of landscape evolution models to spatial and temporal rainfall resolution

    NASA Astrophysics Data System (ADS)

    Coulthard, Tom J.; Skinner, Christopher J.

    2016-09-01

    Climate is one of the main drivers for landscape evolution models (LEMs), yet its representation is often basic with values averaged over long time periods and frequently lumped to the same value for the whole basin. Clearly, this hides the heterogeneity of precipitation - but what impact does this averaging have on erosion and deposition, topography, and the final shape of LEM landscapes? This paper presents results from the first systematic investigation into how the spatial and temporal resolution of precipitation affects LEM simulations of sediment yields and patterns of erosion and deposition. This is carried out by assessing the sensitivity of the CAESAR-Lisflood LEM to different spatial and temporal precipitation resolutions - as well as how this interacts with different-size drainage basins over short and long timescales. A range of simulations were carried out, varying rainfall from 0.25 h × 5 km to 24 h × Lump resolution over three different-sized basins for 30-year durations. Results showed that there was a sensitivity to temporal and spatial resolution, with the finest leading to > 100 % increases in basin sediment yields. To look at how these interactions manifested over longer timescales, several simulations were carried out to model a 1000-year period. These showed a systematic bias towards greater erosion in uplands and deposition in valley floors with the finest spatial- and temporal-resolution data. Further tests showed that this effect was due solely to the data resolution, not orographic factors. Additional research indicated that these differences in sediment yield could be accounted for by adding a compensation factor to the model sediment transport law. However, this resulted in notable differences in the topographies generated, especially in third-order and higher streams. The implications of these findings are that uncalibrated past and present LEMs using lumped and time-averaged climate inputs may be under-predicting basin sediment

  13. The dependence of model resolution on spatial co-variance patterns - Implications for pseudo proxy experiments

    NASA Astrophysics Data System (ADS)

    Wagner, S.; Zorita, E.

    2016-12-01

    A very strong assumption underlying pseudo-proxy experiments in the paleo context relates to the models' ability to realistically simulate real-world spatial co-variance patterns. For large-scale variables like temperatures this assumption may hold true but for variables related to the hydrological cycle like precipitation it might not be sufficient. On the regional scale even for temperatures, horizontally low resolved models may fail to correctly reproduce the according characteristics over regions with complex structured terrain. In this study we test the hypothesis of an independence of the spatial model resolution on the spatial (summertime, JJA) co-variance patterns for selected proxy locations over the European realm. We use three generations of the ECHAM model ranging from ECHAM3 with a T21 resolution (approx. 400km@50° N) over ECHAM6 with T63 (approx. 135km@50° N) up to a downscaled version of ECHAM5 with the regional climate model CCLM with a horizontal resolution of 40 km@50° N. For reference we use the gridded data set E-OBS with a spatial resolution of 20 km@50° N. For temperature the large-scale patterns show similar features, also for the low resolved models, although the regionally downscaled patterns are closest to the E-OBS. However, on regional scales the higher resolved regional model outperforms the global models and show greater details on small-scales within different proxy locations. For precipitation the performance is worse and the low resolved global models do not show the local-scale structure evident in E-OBS. Also the downscaled CCLM simulation with 40 km horizontal resolutions shows co-variance patterns that are different compared to E-OBS with in general too long spatial de-correlation distances with respect to the proxy locations. Our results therefore support the idea carrying out pseudo proxy experiments for testing methods with large-scale temperature fields with different horizontally resolved models including very low

  14. Spatial resolution limits for synchrotron-based spectromicroscopy in the mid- and near-infrared

    SciTech Connect

    Levenson, Erika; Lerch, Philippe; Martin, Michael C.

    2008-01-12

    Spatial resolution tests were performed on beamline 1.4.4 at the Advanced Light Source in Berkeley, CA, USA, a third-generation synchrotron light source. This beamline couples the high-brightness synchrotron source to a Thermo-Electron Continumum XL infrared microscope. Two types of resolution tests were performed in both the mid-IR and near-IR. The results are compared with a diffraction-limited spot size theory. At shorter near-IR wavelengths the experimental results begin to deviate from diffraction-limited so a combined diffraction-limit and electron-beam-source-size model is employed. This description shows how the physical electron beam size of the synchrotron source begins to dominate the focused spot size at higher energies. The transition from diffraction-limited to electron-beam-size-limited performance is a function of storage-ring parameters and the optical demagnification within the beamline and microscope optics. The discussion includes how different facilities, beamlines and microscopes will affect the achievable spatial resolution. As synchrotron light sources and other next-generation accelerators such as energy-recovery LINACs and free-electron lasers achieve smaller beam emittances, beta-functions and/or energy spreads, diffraction-limited performance can continue to higher-energy beams, perhaps ultimately into the extreme ultraviolet.

  15. Spatial resolution limits for synchrotron-based spectromicroscopy in the mid- and near-infrared.

    PubMed

    Levenson, Erika; Lerch, Philippe; Martin, Michael C

    2008-07-01

    Spatial resolution tests were performed on beamline 1.4.4 at the Advanced Light Source in Berkeley, CA, USA, a third-generation synchrotron light source. This beamline couples the high-brightness synchrotron source to a Thermo-Electron Continumicrom XL infrared microscope. Two types of resolution tests were performed in both the mid-IR and near-IR. The results are compared with a diffraction-limited spot size theory. At shorter near-IR wavelengths the experimental results begin to deviate from diffraction-limited so a combined diffraction-limit and electron-beam-source-size model is employed. This description shows how the physical electron beam size of the synchrotron source begins to dominate the focused spot size at higher energies. The transition from diffraction-limited to electron-beam-size-limited performance is a function of storage-ring parameters and the optical demagnification within the beamline and microscope optics. The discussion includes how different facilities, beamlines and microscopes will affect the achievable spatial resolution. As synchrotron light sources and other next-generation accelerators such as energy-recovery LINACs and free-electron lasers achieve smaller beam emittances, beta-functions and/or energy spreads, diffraction-limited performance can continue to higher-energy beams, perhaps ultimately into the extreme ultraviolet.

  16. THE INFLUENCE OF SPATIAL RESOLUTION ON NONLINEAR FORCE-FREE MODELING

    SciTech Connect

    DeRosa, M. L.; Schrijver, C. J.; Leka, K. D.; Barnes, G.; Amari, T.; Canou, A.; Thalmann, J. K.; Wiegelmann, T.; Malanushenko, A.; Sun, X.; Régnier, S.

    2015-10-01

    The nonlinear force-free field (NLFFF) model is often used to describe the solar coronal magnetic field, however a series of earlier studies revealed difficulties in the numerical solution of the model in application to photospheric boundary data. We investigate the sensitivity of the modeling to the spatial resolution of the boundary data, by applying multiple codes that numerically solve the NLFFF model to a sequence of vector magnetogram data at different resolutions, prepared from a single Hinode/Solar Optical Telescope Spectro-Polarimeter scan of NOAA Active Region 10978 on 2007 December 13. We analyze the resulting energies and relative magnetic helicities, employ a Helmholtz decomposition to characterize divergence errors, and quantify changes made by the codes to the vector magnetogram boundary data in order to be compatible with the force-free model. This study shows that NLFFF modeling results depend quantitatively on the spatial resolution of the input boundary data, and that using more highly resolved boundary data yields more self-consistent results. The free energies of the resulting solutions generally trend higher with increasing resolution, while relative magnetic helicity values vary significantly between resolutions for all methods. All methods require changing the horizontal components, and for some methods also the vertical components, of the vector magnetogram boundary field in excess of nominal uncertainties in the data. The solutions produced by the various methods are significantly different at each resolution level. We continue to recommend verifying agreement between the modeled field lines and corresponding coronal loop images before any NLFFF model is used in a scientific setting.

  17. Higher sensitivity secondary ion mass spectrometry of biological molecules for high resolution, chemically specific imaging.

    PubMed

    McDonnell, Liam A; Heeren, Ron M A; de Lange, Robert P J; Fletcher, Ian W

    2006-09-01

    To expand the role of high spatial resolution secondary ion mass spectrometry (SIMS) in biological studies, numerous developments have been reported in recent years for enhancing the molecular ion yield of high mass molecules. These include both surface modification, including matrix-enhanced SIMS and metal-assisted SIMS, and polyatomic primary ions. Using rat brain tissue sections and a bismuth primary ion gun able to produce atomic and polyatomic primary ions, we report here how the sensitivity enhancements provided by these developments are additive. Combined surface modification and polyatomic primary ions provided approximately 15.8 times more signal than using atomic primary ions on the raw sample, whereas surface modification and polyatomic primary ions yield approximately 3.8 and approximately 8.4 times more signal. This higher sensitivity is used to generate chemically specific images of higher mass biomolecules using a single molecular ion peak.

  18. High spatial resolution mid-infrared studies of planetary systems

    NASA Astrophysics Data System (ADS)

    Skemer, Andrew

    I present the results of six papers related the formation and evolution of planets and planetary systems, all of which are based on high-resolution, ground-based, mid-infrared observations. The first three chapters are studies of T Tauri binaries. T Tauri stars are young, low mass stars, whose disks form the building blocks of extrasolar planets. The first chapter is a study of the 0.68"/0.12" triple system, T Tauri. Our spatially resolved N-band photometry reveals silicate absorption towards one component, T Tau Sa, indicating the presence of an edge-on disk, which is in contrast to the other components. The second chapter is an adaptive optics fed N-band spectroscopy study of the 0.88" binary, UY Aur. We find that the dust grains around UY Aur A are ISM-like, while the mineralogy of the dust around UY Aur B is more uncertain, due to self-extinction. The third chapter presents a survey of spatially resolved silicate spectroscopy for nine T Tauri binaries. We find with 90%-95% confidence that the silicate features of the binaries are more similar than those of randomly paired single stars. This implies that a shared binary property, such as age or composition, is an important parameter in dust grain evolution. The fourth chapter is a study of the planetary system, 2MASS 1207. We explore the source of 2MASS 1207 b's under-luminosity, which has typically been explained as the result of an edge-on disk of large, grey-extincting dust grains. We find that the edge-on disk theory is incompatible with several lines of evidence, and suggest that 2MASS 1207 b's appearance can be explained by a thick cloudy atmosphere, which might be typical among young, planetary systems. The fifth chapter is a study of the white dwarf, Sirius B, which in the context of this thesis is being studied as a post-planetary system. Our N-band imaging demonstrates that Sirius B does not have an infrared excess, in contrast to previous results. The sixth chapter is a study of mid

  19. Assessing the spatial fidelity of resolution-enhanced imagery using Fourier analysis: a proof-of-concept study

    NASA Astrophysics Data System (ADS)

    Civco, Daniel L.; Witharana, Chandi

    2012-10-01

    Pan-sharpening of moderate resolution multispectral remote sensing data with those of a higher spatial resolution is a standard practice in remote sensing image processing. This paper suggests a method by which the spatial properties of resolution merge products can be assessed. Whereas there are several accepted metrics, such as correlation and root mean square error, for quantifying the spectral integrity of fused images, relative to the original multispectral data, there is less agreement on a means by which to assess the spatial properties, relative to the original higher-resolution, pansharpening data. In addition to qualitative, visual, and somewhat subjective evaluation, quantitative measures used have included correlations between high-pass filtered panchromatic and fused images, gradient analysis, wavelet analysis, among others. None of these methods, however, fully exploits the spatial and structural information contained in the original high resolution and fused images. This paper proposes the use of the Fourier transform as a means to quantify the degree to which a fused image preserves the spatial properties of the pan-sharpening high resolution data. A highresolution 8-bit panchromatic image was altered to produce a set of nine different test images, as well as a random image. The Fourier Magnitude (FM) image was calculated for each of the datasets and compared via FM to FM image correlation. Furthermore, the following edge detection algorithms were applied to the original and altered images: (a) Canny; (b) Sobel; and (c) Laplacian. These edge-filtered images were compared, again by way of correlation, with the original edge-filtered panchromatic image. Results indicate that the proposed method of using FTMI as a means of assessing the spatial fidelity of high-resolution imagery used in the data fusion process outperforms the correlations produced by way of comparing edge-enhanced images.

  20. Comparison of alternative spatial resolutions in the application of a spatially distributed biogeochemical model over complex terrain

    USGS Publications Warehouse

    Turner, D.P.; Dodson, R.; Marks, D.

    1996-01-01

    Spatially distributed biogeochemical models may be applied over grids at a range of spatial resolutions, however, evaluation of potential errors and loss of information at relatively coarse resolutions is rare. In this study, a georeferenced database at the 1-km spatial resolution was developed to initialize and drive a process-based model (Forest-BGC) of water and carbon balance over a gridded 54976 km2 area covering two river basins in mountainous western Oregon. Corresponding data sets were also prepared at 10-km and 50-km spatial resolutions using commonly employed aggregation schemes. Estimates were made at each grid cell for climate variables including daily solar radiation, air temperature, humidity, and precipitation. The topographic structure, water holding capacity, vegetation type and leaf area index were likewise estimated for initial conditions. The daily time series for the climatic drivers was developed from interpolations of meteorological station data for the water year 1990 (1 October 1989-30 September 1990). Model outputs at the 1-km resolution showed good agreement with observed patterns in runoff and productivity. The ranges for model inputs at the 10-km and 50-km resolutions tended to contract because of the smoothed topography. Estimates for mean evapotranspiration and runoff were relatively insensitive to changing the spatial resolution of the grid whereas estimates of mean annual net primary production varied by 11%. The designation of a vegetation type and leaf area at the 50-km resolution often subsumed significant heterogeneity in vegetation, and this factor accounted for much of the difference in the mean values for the carbon flux variables. Although area wide means for model outputs were generally similar across resolutions, difference maps often revealed large areas of disagreement. Relatively high spatial resolution analyses of biogeochemical cycling are desirable from several perspectives and may be particularly important in the

  1. Enhanced Spatial Resolution During Locomotion and Heightened Attention in Mouse Primary Visual Cortex

    PubMed Central

    Mineault, Patrick J.; Tring, Elaine; Trachtenberg, Joshua T.

    2016-01-01

    We do not fully understand how behavioral state modulates the processing and transmission of sensory signals. Here, we studied the cortical representation of the retinal image in mice that spontaneously switched between a state of rest and a constricted pupil, and one of active locomotion and a dilated pupil, indicative of heightened attention. We measured the selectivity of neurons in primary visual cortex for orientation and spatial frequency, as well as their response gain, in these two behavioral states. Consistent with prior studies, we found that preferred orientation and spatial frequency remained invariant across states, whereas response gain increased during locomotion relative to rest. Surprisingly, relative gain, defined as the ratio between the gain during locomotion and the gain during rest, was not uniform across the population. Cells tuned to high spatial frequencies showed larger relative gain compared with those tuned to lower spatial frequencies. The preferential enhancement of high-spatial-frequency information was also reflected in our ability to decode the stimulus from population activity. Finally, we show that changes in gain originate from shifts in the operating point of neurons along a spiking nonlinearity as a function of behavioral state. Differences in the relative gain experienced by neurons with high and low spatial frequencies are due to corresponding differences in how these cells shift their operating points between behavioral states. SIGNIFICANCE STATEMENT How behavioral state modulates the processing and transmission of sensory signals remains poorly understood. Here, we show that the mean firing rate and neuronal gain increase during locomotion as a result in a shift of the operating point of neurons. We define relative gain as the ratio between the gain of neurons during locomotion and rest. Interestingly, relative gain is higher in cells with preferences for higher spatial frequencies than those with low-spatial

  2. Breast density estimation from high spectral and spatial resolution MRI.

    PubMed

    Li, Hui; Weiss, William A; Medved, Milica; Abe, Hiroyuki; Newstead, Gillian M; Karczmar, Gregory S; Giger, Maryellen L

    2016-10-01

    A three-dimensional breast density estimation method is presented for high spectral and spatial resolution (HiSS) MR imaging. Twenty-two patients were recruited (under an Institutional Review Board--approved Health Insurance Portability and Accountability Act-compliant protocol) for high-risk breast cancer screening. Each patient received standard-of-care clinical digital x-ray mammograms and MR scans, as well as HiSS scans. The algorithm for breast density estimation includes breast mask generating, breast skin removal, and breast percentage density calculation. The inter- and intra-user variabilities of the HiSS-based density estimation were determined using correlation analysis and limits of agreement. Correlation analysis was also performed between the HiSS-based density estimation and radiologists' breast imaging-reporting and data system (BI-RADS) density ratings. A correlation coefficient of 0.91 ([Formula: see text]) was obtained between left and right breast density estimations. An interclass correlation coefficient of 0.99 ([Formula: see text]) indicated high reliability for the inter-user variability of the HiSS-based breast density estimations. A moderate correlation coefficient of 0.55 ([Formula: see text]) was observed between HiSS-based breast density estimations and radiologists' BI-RADS. In summary, an objective density estimation method using HiSS spectral data from breast MRI was developed. The high reproducibility with low inter- and low intra-user variabilities shown in this preliminary study suggest that such a HiSS-based density metric may be potentially beneficial in programs requiring breast density such as in breast cancer risk assessment and monitoring effects of therapy.

  3. Cumulus cloud field morphology and spatial patterns derived from high spatial resolution Landsat imagery

    NASA Technical Reports Server (NTRS)

    Sengupta, S. K.; Welch, R. M.; Navar, M. S.; Berendes, T. A.; Chen, D. W.

    1990-01-01

    Using high-spatial-resolution Landsat MSS imagery, the cumulus cloud morphology, cloud nearest-neighbor distributions, and cloud clumping scales were investigated. It is shown that the cloud-size distribution can be represented by a mixture of two power laws; clouds of diameters less than 1 km have power-law slope range of 1.4-2.3, while larger clouds have slopes from 2.1 to 4.75. The break in power-law slope occurs at the cloud size that makes the largest contribution to cloud cover. Results suggest that larger clouds grow at the expense of smaller clouds. It was also found that the cloud inhomogeneities have significant impact on radiative fluxes.

  4. HIGH SPATIAL RESOLUTION IMAGING OF INERTIAL FUSION TARGET PLASMAS USING BUBBLE NEWTRON DETECTORS

    SciTech Connect

    FISHER,RK

    2002-10-01

    OAK B202 HIGH SPATIAL RESOLUTION IMAGING OF INERTIAL FUSION TARGET PLASMAS USING BUBBLE NEWTRON DETECTORS. Bubble detectors, which can detect neutrons with a spatial resolution of 5 to 30 {micro}, are a promising approach to high-resolution imaging of NIF target plasmas. Gel bubble detectors were used in successful proof-of-principle imaging experiments on OMEGA. Until recently, bubble detectors appeared to be the only approach capable of achieving neutron images of NIF targets with the desired 5 {micro} spatial resolution in the target plane. In 2001, NIF reduced the required standoff distance from the target, so that diagnostic components can now be placed as close as 10 cm to the target plasma. This will allow neutron imaging with higher magnification and may make it possible to obtain 5 {micro}m resolution images on NIF using deuterated scintillators. Having accomplished all that they can hope to on OMEGA using gel detectors, they suggested that the 2002 NLUF shots be used to allow experimental tests of the spatial resolution of the CEA-built deuterated scintillators. The preliminary CEA data from the June 2002 run appears to show the spatial resolution using the deuterated scintillator detector array is improved over that obtained in earlier experiments using the proton-based scintillators. Gel detectors, which consist of {approx} 10 {micro}m diameter drops of bubble detector liquid suspended in an inactive support gel that occupies {approx} 99% of the detector volume, were chosen for the initial tests on OMEGA since they are easy to use. The bubbles could be photographed several hours after the neutron exposure. Imaging NIF target plasmas at neutron yields of 10{sup 15} will require a higher detection efficiency detector. Using a liquid bubble chamber detector should result in {approx} 1000 times higher neutron detection efficiency which is comparable to that possible using scintillation detectors. A pressure-cycled liquid bubble detector will require a light

  5. Improvement of spatial resolution in the longitudinal direction for isotropic imaging in helical CT

    NASA Astrophysics Data System (ADS)

    Tsukagoshi, Shinsuke; Ota, Takamasa; Fujii, Misako; Kazama, Masahiro; Okumura, Miwa; Johkoh, Takeshi

    2007-02-01

    Experiments were conducted to confirm the isotropic spatial resolution of multislice CT with a 0.5 mm slice thickness. Isotropic spatial resolution means that the spatial resolution in the transaxial plane (X-Y plane) and that in the longitudinal direction (Z direction) are equivalent. To obtain point spread function (PSF) values in the X-Y-Z directions, three-dimensional voxel data were obtained by helical scanning of a bead phantom. The modulation transfer function (MTF) values were then obtained by three-dimensional Fourier transform of the PSF. Evaluation of the spatial resolution in the X-Y-Z directions by the MTF values showed that the spatial resolution in the Z direction does not depend on the reconstruction kernel used. It was also found that the spatial resolution in the Z direction, as compared with that in the X-Y plane, is superior with the standard kernel for the abdomen and is inferior with the high-definition kernel for the ears/bones. By performing sharpening filter processing in the Z direction with a high-definition kernel, comparable spatial resolution could be obtained in the X-Y-Z directions. It was confirmed that adjusting the spatial resolution in the Z direction with the reconstruction kernel used is an effective method for isotropic imaging.

  6. Error Estimation in an Optimal Interpolation Scheme for High Spatial and Temporal Resolution SST Analyses

    NASA Technical Reports Server (NTRS)

    Rigney, Matt; Jedlovec, Gary; LaFontaine, Frank; Shafer, Jaclyn

    2010-01-01

    Heat and moisture exchange between ocean surface and atmosphere plays an integral role in short-term, regional NWP. Current SST products lack both spatial and temporal resolution to accurately capture small-scale features that affect heat and moisture flux. NASA satellite is used to produce high spatial and temporal resolution SST analysis using an OI technique.

  7. Spatial resolution in CBCT machines for dental/maxillofacial applications-what do we know today?

    PubMed

    Brüllmann, D; Schulze, R K W

    2015-01-01

    Spatial resolution is one of the most important parameters objectively defining image quality, particularly in dental imaging, where fine details often have to be depicted. Here, we review the current status on assessment parameters for spatial resolution and on published data regarding spatial resolution in CBCT images. The current concepts of visual [line-pair (lp) measurements] and automated [modulation transfer function (MTF)] assessment of spatial resolution in CBCT images are summarized and reviewed. Published measurement data on spatial resolution in CBCT are evaluated and analysed. Effective (i.e. actual) spatial resolution available in CBCT images is being influenced by the two-dimensional detector, the three-dimensional reconstruction process, patient movement during the scan and various other parameters. In the literature, the values range between 0.6 and 2.8 lp mm(-1) (visual assessment; median, 1.7 lp mm(-1)) vs MTF (range, 0.5-2.3 cycles per mm; median, 2.1 lp mm(-1)). Spatial resolution of CBCT images is approximately one order of magnitude lower than that of intraoral radiographs. Considering movement, scatter effects and other influences in real-world scans of living patients, a realistic spatial resolution of just above 1 lp mm(-1) could be expected.

  8. Spatial perception of sound fields recorded by spherical microphone arrays with varying spatial resolution.

    PubMed

    Avni, Amir; Ahrens, Jens; Geier, Matthias; Spors, Sascha; Wierstorf, Hagen; Rafaely, Boaz

    2013-05-01

    The area of sound field synthesis has significantly advanced in the past decade, facilitated by the development of high-quality sound-field capturing and re-synthesis systems. Spherical microphone arrays are among the most recently developed systems for sound field capturing, enabling processing and analysis of three-dimensional sound fields in the spherical harmonics domain. In spite of these developments, a clear relation between sound fields recorded by spherical microphone arrays and their perception with a re-synthesis system has not yet been established, although some relation to scalar measures of spatial perception was recently presented. This paper presents an experimental study of spatial sound perception with the use of a spherical microphone array for sound recording and headphone-based binaural sound synthesis. Sound field analysis and processing is performed in the spherical harmonics domain with the use of head-related transfer functions and simulated enclosed sound fields. The effect of several factors, such as spherical harmonics order, frequency bandwidth, and spatial sampling, are investigated by applying the repertory grid technique to the results of the experiment, forming a clearer relation between sound-field capture with a spherical microphone array and its perception using binaural synthesis regarding space, frequency, and additional artifacts. The experimental study clearly shows that a source will be perceived more spatially sharp and more externalized when represented by a binaural stimuli reconstructed with a higher spherical harmonics order. This effect is apparent from low spherical harmonics orders. Spatial aliasing, as a result of sound field capturing with a finite number of microphones, introduces unpleasant artifacts which increased with the degree of aliasing error.

  9. Spatial resolution dependence on spectral frequency in human speech cortex electrocorticography

    NASA Astrophysics Data System (ADS)

    Muller, Leah; Hamilton, Liberty S.; Edwards, Erik; Bouchard, Kristofer E.; Chang, Edward F.

    2016-10-01

    Objective. Electrocorticography (ECoG) has become an important tool in human neuroscience and has tremendous potential for emerging applications in neural interface technology. Electrode array design parameters are outstanding issues for both research and clinical applications, and these parameters depend critically on the nature of the neural signals to be recorded. Here, we investigate the functional spatial resolution of neural signals recorded at the human cortical surface. We empirically derive spatial spread functions to quantify the shared neural activity for each frequency band of the electrocorticogram. Approach. Five subjects with high-density (4 mm center-to-center spacing) ECoG grid implants participated in speech perception and production tasks while neural activity was recorded from the speech cortex, including superior temporal gyrus, precentral gyrus, and postcentral gyrus. The cortical surface field potential was decomposed into traditional EEG frequency bands. Signal similarity between electrode pairs for each frequency band was quantified using a Pearson correlation coefficient. Main results. The correlation of neural activity between electrode pairs was inversely related to the distance between the electrodes; this relationship was used to quantify spatial falloff functions for cortical subdomains. As expected, lower frequencies remained correlated over larger distances than higher frequencies. However, both the envelope and phase of gamma and high gamma frequencies (30-150 Hz) are largely uncorrelated (<90%) at 4 mm, the smallest spacing of the high-density arrays. Thus, ECoG arrays smaller than 4 mm have significant promise for increasing signal resolution at high frequencies, whereas less additional gain is achieved for lower frequencies. Significance. Our findings quantitatively demonstrate the dependence of ECoG spatial resolution on the neural frequency of interest. We demonstrate that this relationship is consistent across patients and

  10. High-resolution full-field spatial coherence gated optical tomography using monochromatic light source

    NASA Astrophysics Data System (ADS)

    Srivastava, Vishal; Nandy, Sreyankar; Singh Mehta, Dalip

    2013-09-01

    We demonstrate dispersion free, high-resolution full-field spatial coherence gated optical tomography using spatially incoherent monochromatic light source. Spatial coherence properties of light source were synthesized by means of combining a static diffuser and vibrating multi mode fiber bundle. Due to low spatial coherence of light source, the axial resolution of the system was achieved similar to that of conventional optical coherence tomography which utilizes low temporal coherence. Experimental results of fringe visibility versus optical path difference are presented for varying numerical apertures objective lenses. High resolution optically sectioned images of multilayer onion skin, and red blood cells are presented.

  11. Evaluating the Value of High Spatial Resolution in National Capacity Expansion Models using ReEDS

    SciTech Connect

    Krishnan, Venkat; Cole, Wesley

    2016-11-14

    Power sector capacity expansion models (CEMs) have a broad range of spatial resolutions. This paper uses the Regional Energy Deployment System (ReEDS) model, a long-term national scale electric sector CEM, to evaluate the value of high spatial resolution for CEMs. ReEDS models the United States with 134 load balancing areas (BAs) and captures the variability in existing generation parameters, future technology costs, performance, and resource availability using very high spatial resolution data, especially for wind and solar modeled at 356 resource regions. In this paper we perform planning studies at three different spatial resolutions--native resolution (134 BAs), state-level, and NERC region level--and evaluate how results change under different levels of spatial aggregation in terms of renewable capacity deployment and location, associated transmission builds, and system costs. The results are used to ascertain the value of high geographically resolved models in terms of their impact on relative competitiveness among renewable energy resources.

  12. Selecting a spatial resolution for estimation of per-field green leaf area index

    NASA Technical Reports Server (NTRS)

    Curran, Paul J.; Williamson, H. Dawn

    1988-01-01

    For any application of multispectral scanner (MSS) data, a user is faced with a number of choices concerning the characteristics of the data; one of these is their spatial resolution. A pilot study was undertaken to determine the spatial resolution that would be optimal for the per-field estimation of green leaf area index (GLAI) in grassland. By reference to empirically-derived data from three areas of grassland, the suitable spatial resolution was hypothesized to lie in the lower portion of a 2-18 m range. To estimate per-field GLAI, airborne MSS data were collected at spatial resolutions of 2 m, 5 m and 10 m. The highest accuracies of per-field GLAI estimation were achieved using MSS data with spatial resolutions of 2 m and 5 m.

  13. Current source imaging for high spatial resolution magnetocardiography in normal and abnormal rat cardiac muscles

    NASA Astrophysics Data System (ADS)

    Uchida, S.; Iramina, K.; Goto, K.; Ueno, S.

    2000-05-01

    The purpose of our study was to identify the current source produced by acute ischemia and infarction. We measured magnetocardiograms (MCG) and electrocardiograms (ECG) of five male rats using a high-resolution dc superconducting quantum interference device gradiometer in a magnetically shielded room after performing coronary artery occlusion. The spatial resolution of the detecting magnetic field of our system is higher than the typical system, thus permitting the measurement of magnetic fields in small animals. Distribution of the magnetic fields B(t) and distribution of |rot B(t)|, which corresponded to the distribution of the current source, were imaged by 12-channel MCGs. As a result, the distribution of current source changes in the affected area of the myocardium during the ST segment, and amplitude of the peak significantly increased after occlusion. Our system can be used to help clarify the mechanism of the ST shift related to severe heart disease.

  14. High spatial resolution observations of 137Cs in northern Britain and Ireland from airborne geophysical survey.

    PubMed

    Scheib, Cathy; Beamish, David

    2010-09-01

    This study reports the (137)Cs data derived from three regional and national scale High Resolution Airborne Resource and Environmental Surveys (HiRES) in northern Britain and Ireland. The detailed spatial resolution, combined with the large areas these surveys collectively cover, gives insight into large-scale deposition patterns and possible subsequent re-distribution of (137)Cs on a level that was previously not possible. The largest survey area considered covers the whole of Northern Ireland. All three data sets display some clustering of higher (137)Cs activities on high ground together with regional scale NNW-SSE and NW-SE banding features. We interpret these as representing a series of rainfall interceptions of the repeated passage of the Chernobyl plume. Our observations, obtained at 200 m flight line intervals, appear to provide significant detail in relation to existing knowledge of large scale along-wind deposition of (137)Cs.

  15. Achieving High Spatial Resolution Surface Plasmon Resonance Microscopy with Image Reconstruction.

    PubMed

    Yu, Hui; Shan, Xiaonan; Wang, Shaopeng; Tao, Nongjian

    2017-03-07

    Surface plasmon resonance microscopy (SPRM) is a powerful platform for biomedical imaging and molecular binding kinetics analysis. However, the spatial resolution of SPRM along the plasmon propagation direction (longitudinal) is determined by the decaying length of the plasmonic wave, which can be as large as tens of microns. Different methods have been proposed to improve the spatial resolution, but each at the expense of decreased sensitivity or temporal resolution. Here we present a method to achieve high spatial resolution SPRM based on deconvolution of complex field. The method does not require additional optical setup and improves the spatial resolution in the longitudinal direction. We applied the method to image nanoparticles and achieved close-to-diffraction limit resolution in both longitudinal and transverse directions.

  16. An effect of spatial resolution of remotely sensed data for vegetation analysis over an arid zone

    NASA Astrophysics Data System (ADS)

    Oguro, Y.; Tsuchiya, K.; Setoguchi, R.

    1997-05-01

    One of the recent trends in the development of an optical sensor of earth observation satellite is a great importance of spatial resolution and the order of 1 - 2 meter resolution sensor is under development. To cope with this trend analyses are made on the effect of extremely fine spatial resolution of land cover classification accuracy utilizing spatial resolution of 20 cm and 1 meter aerial multi-sensor data of an arid reddish land where desertification is taking place in small spatial scale. Applied methods are supervised classification with combination of multi-level slice(pallarelpiped classification) and the Mahalanobis distance. The result of analysis indicates that the difference is within several percentage for 3 categories of bare land, vegetation and shadow. It was also found that small dried sparse grass land which can be recognized in 20 cm resolution image is difficult to extract in 1 meter resolution image.

  17. Increasing spatial resolution and comparison of MR imaging sequences for the inner ear

    NASA Astrophysics Data System (ADS)

    Snyder, Carl J.; Bolinger, Lizann; Rubinstein, Jay T.; Wang, Ge

    2002-04-01

    The size and location of the cochlea and cochlear nerve are needed to assess the feasibility of cochlea implantation, provide information for surgical planning, and aid in construction of cochlear models. Models of implant stimulation incorporating anatomical and physiological information are likely to provide a better understanding of the biophysics of information transferred with cochlear implants and aid in electrode design and arrangement on cochlear implants. Until recently MR did not provide the necessary image resolution and suffered from long acquisition times. The purpose of this study was to optimize both Fast Spin Echo (FSE) and Steady State Free Precession (FIESTA) imaging scan parameters for the inner ear and comparatively examine both for improved image quality and increased spatial resolution. Image quality was determined by two primary measurements, signal to noise ratio (SNR), and image sharpness. Optimized parameters for FSE were 120ms, 3000ms, 64, and 32.25kHz for the TE, TR, echo train length, and bandwidth, respectively. FIESTA parameters were optimized to 2.7, 5.5ms, 70 degree(s), and 62.5kHz, for TE, TR, flip angle, and bandwidth, respectively. While both had the same in-plane spatial resolution, 0.625mm, FIESTA data shows higher SNR per acquisition time and better edge sharpness.

  18. Spatial and frequency-based super-resolution of ultrasound images

    PubMed Central

    Wu, Mon-Ju; Karls, Joseph; Duenwald-Kuehl, Sarah; Vanderby, Ray; Sethares, William

    2014-01-01

    Modern ultrasound systems can output video images containing more spatial and temporal information than still images. Super-resolution techniques can exploit additional information but face two challenges: image registration and complex motion. In addition, information from multiple available frequencies is unexploited. Herein, we utilised these information sources to create better ultrasound images and videos, extending existing technologies for image capture. Spatial and frequency-based super-resolution processing using multiple motion estimation and frequency combination was applied to ultrasound videos of deforming models. Processed images are larger, have greater clarity and detail, and less variability in intensity between frames. Significantly, strain measurements are more accurate and precise than those from raw videos, and have a higher contrast ratio between ‘tumour’ and ‘surrounding tissue’ in a phantom model. We attribute improvements to reduced noise and increased resolution in processed images. Our methods can significantly improve quantitative and qualitative assessments of ultrasound images when compared assessments of standard images. PMID:25191631

  19. Combination of high spatial resolution and low minimum detection limit using thinned specimens in cutting-edge electron probe microanalysis.

    PubMed

    Kubo, Yugo; Hamada, Kotaro

    2015-10-01

    The effect of sample thickness on the spatial resolution and minimum detection limit (MDL) has been investigated for field-emission electron probe microanalysis with wavelength dispersive X-ray spectroscopy (FE-EPMA-WDX). Indium gallium phosphide samples thinned to thicknesses of about 100, 130, 210, 310, and 430 nm provided effective thin-sample FE-EPMA-WDX in the resolution range of 40-350 nm and MDL range of 13,000-600 ppm (mass). A comparison of the FE-EPMA results for thin and bulk samples demonstrated that thin-sample FE-EPMA can achieve both higher sensitivity and better spatial resolution than is possible using bulk samples. Most of the X-rays that determine the MDL are generated in a surface region of the sample with a depth of approximately 300 nm. The spatial resolution and MDL can be tuned by the sample thickness. Furthermore, analysis of small amounts of Cl in SiO2 indicated that thin-sample FE-EPMA can realize a spatial resolution and MDL of 41 nm and 446 ppm at Iprob=50 nA, respectively, whereas bulk-sample FE-EPMA offers a resolution of only 348 nm and MDL of 426 ppm.

  20. The importance of high spatial resolution for the performance of atmospheric chemistry-transport models

    NASA Astrophysics Data System (ADS)

    Mantzius Hansen, Kaj

    2010-05-01

    We have investigated the importance of spatial resolution for the performance of the Danish Eulerian Hemispheric Model (DEHM), a state-of-the-art atmospheric chemistry-transport model covering the majority of the Northern Hemisphere with a horizontal grid resolution of 150 km X 150 km. DEHM has 29 vertical layers in terrain-following sigma-coordinates extending up to a height of 100 hPa. Two-way nesting options with a nesting factor of three can be applied with higher resolution over a limited area of the model. At present the model can be run without nests or with one, two or three nests, each with resolutions of 50 km X 50 km, 16.7 km X 16.7 km, and 5.6 km X 5.6 km, respectively. The model includes a comprehensive chemistry scheme with more than 100 reactions and 67 atmospheric constituents, of which 4 relate to primary particulates (PM2.5, PM10, TSP and sea salt), other species are SOx, NOx, NHx, VOCs, and secondary inorganic particulates. DEHM is driven by meteorological data from the numerical weather prediction model MM5v3. Three simulations were performed with DEHM: one simulation with only the mother domain, one simulation with one nest over Europe, and one simulation with an additional nest covering Denmark and surrounding countries. All three simulations cover the period from 1989 to 2006. The predicted concentrations were evaluated against measurements from the EMEP monitoring network. Only sites within the innermost nest were included in the evaluation and the evaluations of the three simulations were compared to test the influence of spatial resolution on the performance of the model.

  1. Selecting the spatial resolution of satellite sensors required for global monitoring of land transformations

    NASA Technical Reports Server (NTRS)

    Townshend, J. R. G.; Justice, C. O.

    1988-01-01

    The paper provides preliminary evidence for the spatial resolutions required to monitor land transformations at broad scales. This is obtained from simulations of imagery at various spatial resolutions between 125 and 4000 m derived from Landsat MSS imagery. Consideration is given to the various types of spatial images detectable by remotely-sensed systems, as well as to the difficulties associated in disentangling permanent land transformations from shorter term changes such as phenological and interannual changes.

  2. Use of UAS remote sensing data to estimate crop ET at high spatial resolution

    USDA-ARS?s Scientific Manuscript database

    Estimation of the spatial distribution of evapotranspiration (ET) based on remotely sensed imagery has become useful for managing water in irrigated agricultural at various spatial scales. However, data acquired by conventional satellites (Landsat, ASTER, etc.) lack the spatial resolution to capture...

  3. Spatial resolution of subsurface anthropogenic heat fluxes in cities

    NASA Astrophysics Data System (ADS)

    Benz, Susanne; Bayer, Peter; Menberg, Kathrin; Blum, Philipp

    2015-04-01

    Urban heat islands in the subsurface contain large quantities of energy in the form of elevated groundwater temperatures caused by anthropogenic heat fluxes (AHFS) into the subsurface. Hence, the objective of this study is to exemplarily quantify these AHFS and the generated thermal powers in two German cities, Karlsruhe and Cologne. A two-dimensional (2D) statistical analytical model of the vertical subsurface anthropogenic heat fluxes across the unsaturated zone was developed. The model consists of a so-called Local Monte Carlo approach that introduces a spatial representation of the following sources of AHFS: (1) elevated ground surface temperatures, (2) basements, (3) sewage systems, (4) sewage leakage, (5) subway tunnels, and (6) district heating networks. The results show that district heating networks induce the largest local AHFS with values larger than 60 W/m2 and one order of magnitude higher than the other evaluated heat sources. Only sewage pipes and basements reaching into the groundwater cause equally high heat fluxes, with maximal values of 40.37 W/m2 and 13.60 W/m2, respectively. While dominating locally, the district heating network is rather insignificant for the citywide energy budget in both urban subsurfaces. Heat from buildings (1.51 ± 1.36 PJ/a in Karlsruhe; 0.31 ± 0.14 PJ/a in Cologne) and elevated GST (0.34 ± 0.10 PJ/a in Karlsruhe; 0.42 ± 0.13 PJ/a in Cologne) are dominant contributors to the anthropogenic thermal power of the urban aquifer. In Karlsruhe, buildings are the source of 70% of the annual heat transported into the groundwater, which is mainly caused by basements reaching into the groundwater. A variance analysis confirms these findings: basement depth is the most influential factor to citywide thermal power in the studied cities with high groundwater levels. The spatial distribution of fluxes, however, is mostly influenced by the prevailing thermal gradient across the unsaturated zone. A relatively cold groundwater

  4. A simple method for determining the spatial resolution of a general inverse problem

    NASA Astrophysics Data System (ADS)

    An, Meijian

    2012-09-01

    The resolution matrix of an inverse problem defines a linear relationship in which each solution parameter is derived from the weighted averages of nearby true-model parameters, and the resolution matrix elements are the weights. Resolution matrices are not only widely used to measure the solution obtainability or the inversion perfectness from the data based on the degree to which the matrix approximates the identity matrix, but also to extract spatial-resolution or resolution-length information. Resolution matrices presented in previous spatial-resolution analysis studies can be divided into three classes: direct resolution matrix, regularized/stabilized resolution matrix and hybrid resolution matrix. The direct resolution matrix can yield resolution-length information only for ill-posed inverse problems. The regularized resolution matrix cannot give any spatial-resolution information. The hybrid resolution matrix can provide resolution-length information; however, this depends on the regularization contribution to the inversion. The computation of the matrices needs matrix operation, however, this is often a difficult problem for very large inverse problems. Here, a new class of resolution matrices, generated using a Gaussian approximation (called the statistical resolution matrices), is proposed whereby the direct determination of the matrix is accomplished via a simple one-parameter non-linear inversion performed based on limited pairs of random synthetic models and their inverse solutions. Tests showed that a statistical resolution matrix could not only measure the resolution obtainable from the data, but also provided reasonable spatial/temporal resolution or resolution-length information. The estimates were restricted to forward/inversion processes and were independent of the degree of inverse skill used in the solution inversion; therefore, the original inversion codes did not need to be modified. The absence of a requirement for matrix operations during

  5. Scalable and memory efficient implementations of the multi-resolution approximation for spatial data

    NASA Astrophysics Data System (ADS)

    Ramakrishnaiah, V. B.; Hammerling, D.; Kumar, R. R. P.; Katzfuss, M.

    2016-12-01

    High-resolution observations of spatial fields over large geographic regions from satellites are available at an increasing rate, and their analysis can lead to new insights. Traditional spatial statistical techniques are computationally infeasible for large data sets due to the need to invert a covariance matrix of the size of the data. The recently developed multi-resolution approximation (MRA) algorithm, which expresses a spatial process as a linear combination of basis functions at multiple spatial resolutions within a hierarchical framework, addresses this issue. However, the number of observations determines the overall memory footprint during execution and even if the matrix computations are feasible, a large amount of system memory is needed when the number of observations is in the millions to hundreds of millions. A natural solution is to utilize the implicit parallelization provided by MRA at each spatial resolution and across resolutions within the hierarchical framework. By having a distributed memory parallel execution, the memory needed per computing node can be reduced. We propose and analyze two implementations of distributed memory parallel algorithms. The first approach is to divide a given resolution layer into smaller parts and assign those parts to individual computing nodes. The second approach creates sub-trees of the multiple spatial resolution hierarchy, and assigns each sub-tree to a computing node. These alternative approaches are found to reduce the memory footprint of the current implementation, show good scalability, and enable statistical analysis of spatial data with over a hundred million observations.

  6. Higher throughput high resolution multi-worm tracker

    NASA Astrophysics Data System (ADS)

    Javer, Avelino; Li, Kezhi; Gyenes, Bertalan; Brown, Andre; Behavioural Genomics Team

    2015-03-01

    We have developed a high throughput imaging system for tracking multiple nematode worms at high resolution. The tracker consists of 6 cameras mounted on a motorized gantry so that up to 48 plates (each with approximately 30 worms) can be imaged without user intervention. To deal with the high data rate of the cameras we use real time processing to find worms and only save the immediately surrounding pixels. The system is also equipped with automatic oxygen and carbon dioxide control for observing stimulus response behaviour. We will describe the design and performance of the new system, some of the challenges of truly high throughput behaviour recording, and report preliminary results on inter-individual variation in behaviour as well as a quantitative analysis of C. elegans response to hypoxia, oxygen reperfusion, and carbon dioxide. Funding provided by the Medical Research Council.

  7. High-Resolution Spatial Distribution and Estimation of Access to Improved Sanitation in Kenya

    PubMed Central

    Jia, Peng; Anderson, John D.; Leitner, Michael; Rheingans, Richard

    2016-01-01

    Background Access to sanitation facilities is imperative in reducing the risk of multiple adverse health outcomes. A distinct disparity in sanitation exists among different wealth levels in many low-income countries, which may hinder the progress across each of the Millennium Development Goals. Methods The surveyed households in 397 clusters from 2008–2009 Kenya Demographic and Health Surveys were divided into five wealth quintiles based on their national asset scores. A series of spatial analysis methods including excess risk, local spatial autocorrelation, and spatial interpolation were applied to observe disparities in coverage of improved sanitation among different wealth categories. The total number of the population with improved sanitation was estimated by interpolating, time-adjusting, and multiplying the surveyed coverage rates by high-resolution population grids. A comparison was then made with the annual estimates from United Nations Population Division and World Health Organization /United Nations Children's Fund Joint Monitoring Program for Water Supply and Sanitation. Results The Empirical Bayesian Kriging interpolation produced minimal root mean squared error for all clusters and five quintiles while predicting the raw and spatial coverage rates of improved sanitation. The coverage in southern regions was generally higher than in the north and east, and the coverage in the south decreased from Nairobi in all directions, while Nyanza and North Eastern Province had relatively poor coverage. The general clustering trend of high and low sanitation improvement among surveyed clusters was confirmed after spatial smoothing. Conclusions There exists an apparent disparity in sanitation among different wealth categories across Kenya and spatially smoothed coverage rates resulted in a closer estimation of the available statistics than raw coverage rates. Future intervention activities need to be tailored for both different wealth categories and nationally

  8. High-Resolution Spatial Distribution and Estimation of Access to Improved Sanitation in Kenya.

    PubMed

    Jia, Peng; Anderson, John D; Leitner, Michael; Rheingans, Richard

    2016-01-01

    Access to sanitation facilities is imperative in reducing the risk of multiple adverse health outcomes. A distinct disparity in sanitation exists among different wealth levels in many low-income countries, which may hinder the progress across each of the Millennium Development Goals. The surveyed households in 397 clusters from 2008-2009 Kenya Demographic and Health Surveys were divided into five wealth quintiles based on their national asset scores. A series of spatial analysis methods including excess risk, local spatial autocorrelation, and spatial interpolation were applied to observe disparities in coverage of improved sanitation among different wealth categories. The total number of the population with improved sanitation was estimated by interpolating, time-adjusting, and multiplying the surveyed coverage rates by high-resolution population grids. A comparison was then made with the annual estimates from United Nations Population Division and World Health Organization /United Nations Children's Fund Joint Monitoring Program for Water Supply and Sanitation. The Empirical Bayesian Kriging interpolation produced minimal root mean squared error for all clusters and five quintiles while predicting the raw and spatial coverage rates of improved sanitation. The coverage in southern regions was generally higher than in the north and east, and the coverage in the south decreased from Nairobi in all directions, while Nyanza and North Eastern Province had relatively poor coverage. The general clustering trend of high and low sanitation improvement among surveyed clusters was confirmed after spatial smoothing. There exists an apparent disparity in sanitation among different wealth categories across Kenya and spatially smoothed coverage rates resulted in a closer estimation of the available statistics than raw coverage rates. Future intervention activities need to be tailored for both different wealth categories and nationally where there are areas of greater needs when

  9. Exploring Opportunities for Conflict Resolution in Higher Education

    ERIC Educational Resources Information Center

    Filippelli-DiManna, Leslie P.

    2012-01-01

    The purpose of this qualitative phenomenological study was to identify methods to improve conflict management skills of administrative staff in higher education. General systems, Maslow's hierarchy of needs, and (c) Burton's human needs theories served as the conceptual frameworks for the study. The lived experiences of 25 community…

  10. Exploring Opportunities for Conflict Resolution in Higher Education

    ERIC Educational Resources Information Center

    Filippelli-DiManna, Leslie P.

    2012-01-01

    The purpose of this qualitative phenomenological study was to identify methods to improve conflict management skills of administrative staff in higher education. General systems, Maslow's hierarchy of needs, and (c) Burton's human needs theories served as the conceptual frameworks for the study. The lived experiences of 25 community…

  11. Improving the spatial resolution in CZT detectors using charge sharing effect and transient signal analysis: Simulation study

    NASA Astrophysics Data System (ADS)

    Zheng, Xiaoqing; Cheng, Zeng; Deen, M. Jamal; Peng, Hao

    2016-02-01

    Cadmium Zinc Telluride (CZT) semiconductor detectors are capable of providing superior energy resolution and three-dimensional position information of gamma ray interactions in a large variety of fields, including nuclear physics, gamma-ray imaging and nuclear medicine. Some dedicated Positron Emission Tomography (PET) systems, for example, for breast cancer detection, require higher contrast recovery and more accurate event location compared with a whole-body PET system. The spatial resolution is currently limited by electrode pitch in CZT detectors. A straightforward approach to increase the spatial resolution is by decreasing the detector electrode pitch, but this leads to higher fabrication cost and a larger number of readout channels. In addition, inter-electrode charge spreading can negate any improvement in spatial resolution. In this work, we studied the feasibility of achieving sub-pitch spatial resolution in CZT detectors using two methods: charge sharing effect and transient signal analysis. We noted that their valid ranges of usage were complementary. The dependences of their corresponding valid ranges on electrode design, depth-of-interaction (DOI), voltage bias and signal triggering threshold were investigated. The implementation of these two methods in both pixelated and cross-strip configuration of CZT detectors were discussed. Our results show that the valid range of charge sharing effect increases as a function of DOI, but decreases with increasing gap width and bias voltage. For a CZT detector of 5 mm thickness, 100 μm gap and biased at 400 V, the valid range of charge sharing effect was found to be about 112.3 μm around the gap center. This result complements the valid range of the transient signal analysis within one electrode pitch. For a signal-to-noise ratio (SNR) of 17 and preliminary measurements, the sub-pitch spatial resolution is expected to be 30 μm and 250 μm for the charge sharing and transient signal analysis methods

  12. High spatial resolution magnetic resonance imaging of cystic adventitial disease of the popliteal artery.

    PubMed

    Maged, Ismaeel M; Turba, Ulku C; Housseini, Ahmed M; Kern, John A; Kron, Irving L; Hagspiel, Klaus D

    2010-02-01

    High spatial resolution magnetic resonance imaging (MRI) of patients with cystic adventitial disease can demonstrate connections between cysts in the adventitia and the adjacent joint, which is important for successful treatment. The inability to identify these during surgery can lead to a recurrence; thus, high spatial resolution MRI has the potential to affect therapy. This article presents the high spatial resolution MRI findings of cystic adventitial disease in a series of three consecutive patients and discusses the relevance of these findings to the etiology and therapy.

  13. Spatial resolution of proton tomography: Methods, initial phase space and object thickness.

    PubMed

    Schneider, Uwe; Pedroni, Eros; Hartmann, Matthias; Besserer, Jürgen; Lomax, Tony

    2012-06-01

    Proton radiography and tomography was investigated since the early 1970s because of its low radiation dose, high density resolution and ability to image directly proton stopping power. However, spatial resolution is still a limiting factor and as a consequence experimental methods and image reconstruction should be optimized to improve position resolution. Spatial resolution of proton radiography and tomography is given by multiple Coloumb scattering (MCS) of the protons in the patient. In this paper we employ an improved MCS model to study the impact of various proton tomographic set-ups on the spatial resolution, such as different combinations of entrance and exit coordinate and angle measurements, respectively, initial particle energy and angular confusion of the incident proton field. It was found that best spatial resolution is obtained by measuring in addition to the entrance and exit coordinates also the entrance and exit angles. However, by applying partial backprojection and by using a perfect proton fan beam a sufficient spatial resolution can be achieved with less experimental complexity (measuring only exit angles). It was also shown that it is essential to use the most probable proton trajectory to improve spatial resolution. A simple straight line connection for image reconstruction results in a spatial resolution which is not clinically sufficient. The percentage deterioration of spatial resolution due to the angular confusion of the incident proton field is less than the phase space in mrad. A clinically realistic proton beam with 10 mrad angular confusion results in a less than 10% loss of spatial resolution. Clinically sufficient spatial resolution can be either achieved with a full measurement of entrance and exit coordinates and angles, but also by using a fan beam with small angular confusion and an exit angle measurement. It is necessary to use the most probable proton path for image reconstruction. A simple straight line connection is in

  14. Remote Measurements of the Atmosphere with High Spatial Resolution

    NASA Astrophysics Data System (ADS)

    Weinman, J. A.; Marzano, F. S.; Mugnai, A.

    2009-09-01

    Global atmosphere-ocean models are now operating at 3.5 km resolution and mesoscale weather prediction models operating at 1.7 km resolution have been used for the analysis of hurricanes. One can expect that weather prediction models will operate at resolutions better than 5 km during the coming decade. Microwave sensors have contributed valuable information about rainfall and sea surface winds. The Precipitation Radar (PR) onboard the Tropical Rainfall Measuring Mission (TRMM) can address this need. However it may be nearing the end of its life, and its replacement by the Global Precipitation Measurement (GPM) mission is expected no earlier than 2013. Recently the four Italian Cosmo-SkyMed, and the German Terra-SAR X-band synthetic aperture radars (SAR’s) have displayed rain distributions with resolution better than 0.5 km. The Quickscat also now provides distributions of rainfall and sea surface winds with 2.5 km resolution. We will describe rainfall retrieval algorithms, show rainfall distributions retrieved from Terra-SAR, and discuss errors in those measurements. We will also describe multi-frequency radar measurements of sea surface winds and rainfall during hurricanes. Although most remotely sensed rainfall and wind data can be expected to be obtained from satellites, unmanned aerial vehicles (UAV’s) with one week cruising duration and ~180 kg payloads flying at 18 km height may become attractive platforms from which severe weather can be tracked with high resolution.

  15. Spatial Recruiting Competition in Chinese Higher Education System

    ERIC Educational Resources Information Center

    Gu, Jiafeng

    2012-01-01

    How geographical neighboring competitors influence the strategic recruiting behavior of universities is still unclear because previous studies assume spatial independence among universities. Using data of Subordinate Universities of the Ministry of Education in China, this study found that the choice of admission score level by one university was…

  16. Using remote sensing products to classify landscape. A multi-spatial resolution approach

    NASA Astrophysics Data System (ADS)

    García-Llamas, Paula; Calvo, Leonor; Álvarez-Martínez, José Manuel; Suárez-Seoane, Susana

    2016-08-01

    The European Landscape Convention encourages the inventory and characterization of landscapes for environmental management and planning actions. Among the range of data sources available for landscape classification, remote sensing has substantial applicability, although difficulties might arise when available data are not at the spatial resolution of operational interest. We evaluated the applicability of two remote sensing products informing on land cover (the categorical CORINE map at 30 m resolution and the continuous NDVI spectral index at 1 km resolution) in landscape classification across a range of spatial resolutions (30 m, 90 m, 180 m, 1 km), using the Cantabrian Mountains (NW Spain) as study case. Separate landscape classifications (using topography, urban influence and land cover as inputs) were accomplished, one per each land cover dataset and spatial resolution. Classification accuracy was estimated through confusion matrixes and uncertainty in terms of both membership probability and confusion indices. Regarding landscape classifications based on CORINE, both typology and number of landscape classes varied across spatial resolutions. Classification accuracy increased from 30 m (the original resolution of CORINE) to 90m, decreasing towards coarser resolutions. Uncertainty followed the opposite pattern. In the case of landscape classifications based on NDVI, the identified landscape patterns were geographically structured and showed little sensitivity to changes across spatial resolutions. Only the change from 1 km (the original resolution of NDVI) to 180 m improved classification accuracy. The value of confusion indices increased with resolution. We highlight the need for greater effort in selecting data sources at the suitable spatial resolution, matching regional peculiarities and minimizing error and uncertainty.

  17. Evaluating the effect of remote sensing image spatial resolution on soil exchangeable potassium prediction models in smallholder farm settings.

    PubMed

    Xu, Yiming; Smith, Scot E; Grunwald, Sabine; Abd-Elrahman, Amr; Wani, Suhas P

    2017-09-15

    Major end users of Digital Soil Mapping (DSM) such as policy makers and agricultural extension workers are faced with choosing the appropriate remote sensing data. The objective of this research is to analyze the spatial resolution effects of different remote sensing images on soil prediction models in two smallholder farms in Southern India called Kothapally (Telangana State), and Masuti (Karnataka State), and provide empirical guidelines to choose the appropriate remote sensing images in DSM. Bayesian kriging (BK) was utilized to characterize the spatial pattern of exchangeable potassium (Kex) in the topsoil (0-15 cm) at different spatial resolutions by incorporating spectral indices from Landsat 8 (30 m), RapidEye (5 m), and WorldView-2/GeoEye-1/Pleiades-1A images (2 m). Some spectral indices such as band reflectances, band ratios, Crust Index and Atmospherically Resistant Vegetation Index from multiple images showed relatively strong correlations with soil Kex in two study areas. The research also suggested that fine spatial resolution WorldView-2/GeoEye-1/Pleiades-1A-based and RapidEye-based soil prediction models would not necessarily have higher prediction performance than coarse spatial resolution Landsat 8-based soil prediction models. The end users of DSM in smallholder farm settings need select the appropriate spectral indices and consider different factors such as the spatial resolution, band width, spectral resolution, temporal frequency, cost, and processing time of different remote sensing images. Overall, remote sensing-based Digital Soil Mapping has potential to be promoted to smallholder farm settings all over the world and help smallholder farmers implement sustainable and field-specific soil nutrient management scheme. Copyright © 2017 Elsevier Ltd. All rights reserved.

  18. Spatial Resolution and Refractive Index Contrast of Resonant Photonic Crystal Surfaces for Biosensing

    PubMed Central

    Triggs, G. J.; Fischer, M.; Stellinga, D.; Scullion, M. G.; Evans, G. J. O.; Krauss, T. F.

    2015-01-01

    By depositing a resolution test pattern on top of a Si3N4 photonic crystal resonant surface, we have measured the dependence of spatial resolution on refractive index contrast Δn. Our experimental results and finite-difference time-domain (FDTD) simulations at different refractive index contrasts show that the spatial resolution of our device reduces with reduced contrast, which is an important consideration in biosensing, where the contrast may be of order 10−2. We also compare 1-D and 2-D gratings, taking into account different incidence polarizations, leading to a better understanding of the excitation and propagation of the resonant modes in these structures, as well as how this contributes to the spatial resolution. At Δn = 0.077, we observe resolutions of 2 and 6 μm parallel to and perpendicular to the grooves of a 1-D grating, respectively, and show that for polarized illumination of a 2-D grating, resolution remains asymmetrical. Illumination of a 2-D grating at 45° results in symmetric resolution. At very low index contrast, the resolution worsens dramatically, particularly for Δn < 0.01, where we observe a resolution exceeding 10 μm for our device. In addition, we measure a reduction in the resonance linewidth as the index contrast becomes lower, corresponding to a longer resonant mode propagation length in the structure and contributing to the change in spatial resolution. PMID:26356353

  19. Exploring the spatial resolution of position-sensitive microchannel plate detectors

    NASA Astrophysics Data System (ADS)

    Wiggins, Blake; Siwal, Davinder; Desouza, Romualdo

    2016-03-01

    High amplification and excellent timing make microchannel plate (MCP) detectors excellent devices for detection of photons, electrons, and ions. In addition to providing sub-nanosecond time resolution MCP detectors can also provide spatial resolution, thus making them useful in imaging applications. Use of a resistive anode (RA) is a routinely used approach to make an MCP position-sensitive. The spatial resolution of the RA associated with detection of a single incident electron was determined. Factors impacting the spatial resolution obtained with the RA will be discussed and the achieved spatial resolution of 64 μm (FWHM) will be presented. Recently, a novel approach has been developed to provide position-sensitivity for an MCP detector. In this approach, namely the induced signal approach, the position of the incident particle is determined by sensing the electron cloud emanating from a MCP stack. By utilizing the zero-crossing point of the inherently bipolar signals, a spatial resolution of 466 μm (FWHM) has been achieved. Work to improve the spatial resolution of the induced signal approach further will be presented. Supported by the US DOE NNSA under Award No. DE-NA0002012.

  20. Zoom lens design for a novel imaging spectrometer that controls spatial and spectral resolution individually.

    PubMed

    Choi, Jin; Kim, T H; Kong, H J; Lee, Jong Ung

    2006-05-20

    A novel imaging spectrometer can individually control spatial and spectral resolution by using zoom lenses as the foreoptics of the system and a focusing lens. By varying the focal length we can use the focusing lens to change the spatial and spectral dimensions; with the foreoptics, however, we can change only the spatial dimension. Therefore the spectral resolution and the spectral range are affected by the zoom ratio of the focusing lens, whereas the spatial resolution and the field of view are affected by the multiplication of the zoom ratios of the foreoptics and the focusing lens. By properly combining two zoom ratios, we can control the spectral resolution with a fixed spatial resolution or the spatial resolution with a fixed spectral resolution. For an imaging spectrometer with this novel zooming function, we used the lens module method and third-order aberration theory to design an initial four-group zoom system with an external entrance pupil for the focusing lens. Furthermore, using the optical design software CODE V, we obtained an optimized zoom lens with a focal-length range of 50 to 150 mm. Finally, the zoom system with its transmission grating in the Littrow configuration performs satisfactorily as the focusing lens of an imaging spectrometer in the wavelength range 450-900 nm.

  1. Effect of microscopic parameters on EBSD spatial resolution.

    PubMed

    Chen, Delphic; Kuo, Jui-Chao; Wu, Wen-Tuan

    2011-01-01

    In this study, a quantitative approach is proposed to understand the effect of the accelerating voltage and the probe current on the physical resolution of EBSD. The accelerating voltage was varied from 5 to 30kV and probe currents of 1, 10, and 40nA were selected. The lateral, longitudinal, and depth resolutions at 10kV and 1nA were 34.5, 44.7, and 46nm for copper, respectively. When the accelerating voltage was in the range of 5-20kV, the ratio of the longitudinal to the lateral resolution was below the theoretical ratio of 2.9. Considering the channeling effect, the best physical depth resolution of 38nm was achieved at 5kV and 10nA. The physical depth resolution in an EBSD measurement is much larger due to the channel effect than that obtained without considering this effect. Copyright © 2011 Elsevier B.V. All rights reserved.

  2. Large patch convolutional neural networks for the scene classification of high spatial resolution imagery

    NASA Astrophysics Data System (ADS)

    Zhong, Yanfei; Fei, Feng; Zhang, Liangpei

    2016-04-01

    The increase of the spatial resolution of remote-sensing sensors helps to capture the abundant details related to the semantics of surface objects. However, it is difficult for the popular object-oriented classification approaches to acquire higher level semantics from the high spatial resolution remote-sensing (HSR-RS) images, which is often referred to as the "semantic gap." Instead of designing sophisticated operators, convolutional neural networks (CNNs), a typical deep learning method, can automatically discover intrinsic feature descriptors from a large number of input images to bridge the semantic gap. Due to the small data volume of the available HSR-RS scene datasets, which is far away from that of the natural scene datasets, there have been few reports of CNN approaches for HSR-RS image scene classifications. We propose a practical CNN architecture for HSR-RS scene classification, named the large patch convolutional neural network (LPCNN). The large patch sampling is used to generate hundreds of possible scene patches for the feature learning, and a global average pooling layer is used to replace the fully connected network as the classifier, which can greatly reduce the total parameters. The experiments confirm that the proposed LPCNN can learn effective local features to form an effective representation for different land-use scenes, and can achieve a performance that is comparable to the state-of-the-art on public HSR-RS scene datasets.

  3. Music-reading expertise alters visual spatial resolution for musical notation.

    PubMed

    Wong, Yetta Kwailing; Gauthier, Isabel

    2012-08-01

    Crowding occurs when the perception of a suprathreshold target is impaired by nearby distractors, reflecting a fundamental limitation on visual spatial resolution. It is likely that crowding limits music reading, as each musical note is crowded by adjacent notes and by the five-line staff, similar to word reading, in which letter recognition is reduced by crowding from adjacent letters. Here, we tested the hypothesis that, with extensive experience, music-reading experts have acquired visual skills such that they experience a smaller crowding effect, resulting in higher music-reading fluency. Experts experienced a smaller crowding effect than did novices, but only for musical stimuli, not for control stimuli (Landolt Cs). The magnitude of the crowding effect for musical stimuli could be predicted by individual fluency in music reading. Our results highlight the role of experience in crowding: Visual spatial resolution can be improved specifically for objects associated with perceptual expertise. Music-reading rates are likely limited by crowding, and our results are consistent with the idea that experience alleviates these limitations.

  4. Investigation of spatial resolution dependent variability in transcutaneous oxygen saturation using point spectroscopy system

    NASA Astrophysics Data System (ADS)

    Philimon, Sheena P.; Huong, Audrey K. C.; Ngu, Xavier T. I.

    2017-08-01

    This paper aims to investigate the variation in one’s percent mean transcutaneous oxygen saturation (StO2) with differences in spatial resolution of data. This work required the knowledge of extinction coefficient of hemoglobin derivatives in the wavelength range of 520 - 600 nm to solve for the StO2 value via an iterative fitting procedure. A pilot study was conducted on three healthy subjects with spectroscopic data collected from their right index finger at different arbitrarily selected distances. The StO2 value estimated by Extended Modified Lambert Beer (EMLB) model revealed a higher mean StO2 of 91.1 ± 1.3% at a proximity distance of 30 mm compared to 60.83 ± 2.8% at 200 mm. The results showed a high correlation between data spatial resolution and StO2 value, and revealed a decrease in StO2 value as the sampling distance increased. The preliminary findings from this study contribute to the knowledge of the appropriate distance range for consistent and high repeatability measurement of skin oxygenation.

  5. The Galactic Centre at infrared wavelengths: towards the highest spatial resolution

    NASA Astrophysics Data System (ADS)

    Clénet, Yann; Rouan, Daniel; Léna, Pierre; Gendron, Eric; Lacombe, François

    2007-01-01

    We now know that our Galaxy harbors at its centre a supermassive 3.6×10M black hole. This result came after more than 2 decades of infrared studies of the Galactic Centre and important instrumental developments in infrared detectors and in high spatial resolution techniques. Adaptive optics, which allows diffraction-limited infrared observations and enhanced sensitivity, was actually the major breakthrough in this respect. We introduce in the first section of this article what was our knowledge of the Galactic Centre before the advent of adaptive optics. In the second section, after a reminder of the first adaptive optics observations of this region, we highlight the specificities of Galactic Centre adaptive optics observations. In the third and fourth sections, we present the major results obtained from adaptive optics observations of the Galactic Centre: the case of the supermassive black hole and the paradox of youth. In the fifth section, we introduce two main future facilities that will provide even higher spatial resolutions, Gravity—a second generation VLTI instrument—and Extremely Large Telescopes, and the improvements that we expect with these new instruments in our knowledge of the Galactic Centre region. We conclude in the last section. To cite this article: Y. Clénet et al., C. R. Physique 8 (2007).

  6. Additional studies of forest classification accuracy as influenced by multispectral scanner spatial resolution

    NASA Technical Reports Server (NTRS)

    Sadowski, F. E.; Sarno, J. E.

    1976-01-01

    First, an analysis of forest feature signatures was used to help explain the large variation in classification accuracy that can occur among individual forest features for any one case of spatial resolution and the inconsistent changes in classification accuracy that were demonstrated among features as spatial resolution was degraded. Second, the classification rejection threshold was varied in an effort to reduce the large proportion of unclassified resolution elements that previously appeared in the processing of coarse resolution data when a constant rejection threshold was used for all cases of spatial resolution. For the signature analysis, two-channel ellipse plots showing the feature signature distributions for several cases of spatial resolution indicated that the capability of signatures to correctly identify their respective features is dependent on the amount of statistical overlap among signatures. Reductions in signature variance that occur in data of degraded spatial resolution may not necessarily decrease the amount of statistical overlap among signatures having large variance and small mean separations. Features classified by such signatures may thus continue to have similar amounts of misclassified elements in coarser resolution data, and thus, not necessarily improve in classification accuracy.

  7. Centroiding algorithms and spatial resolution of photon counting detectors with cross-strip anodes

    NASA Astrophysics Data System (ADS)

    Tremsin, Anton S.; Vallerga, John V.; Siegmund, Oswald H. W.; Hull, Jeff S.

    2003-12-01

    Significant advances in readout elements of microchannel plate based sensors have led to the development of detectors with less than 10 µm spatial resolution. We have shown that cross strip (XS) anodes have spatial resolution as small as 5 µm FWHM when a simple and fast center of gravity centroiding technique is used. In this paper we investigate the variation of XS anode spatial resolution for several types of centroiding algorithms (N-finger center of gravity, Gaussian, Lorentzian, parabolic and hyperbolic cosine centroiding) and determine the optimum algorithm in terms of spatial resolution and image linearity. We found that for existing 32x32 mm2 cross strip anodes and associated electronics, the best resolution and linearity is achieved with center of gravity centroiding with properly chosen thresholds on the data set. The images of USAF resolution test target obtained with MCP's with 6 µm pores on 7.5 µm centers resolve 71.8 line pairs per mm (Group 6 element 2, with line width of only ~7 µm). Thus the ~7 µm spatial resolution of the detector with cross strip anode is indeed limited now by the size of the MCP pores, while the resolution of XS readout is on the order of only few micrometers FWHM.

  8. Crosstalk Compensation for a Rapid, Higher Resolution Impedance Spectrum Measurement

    SciTech Connect

    Jon P. Christophersen; John L. Morrison; David M. Rose; William H. Morrison; Chester G. Motloch

    2012-03-01

    Batteries and other energy storage devices are playing larger roles in various industries (e.g., military, automotive, electric utilities, etc.) as the U.S. seeks to reduce its dependence on foreign energy resources. As such, there exists a significant need for accurate, robust state-of-health assessment techniques. Present techniques tend to focus on simple, passive monitoring of voltage and current at a given ambient temperature. However, this approach has the disadvantage of ignoring key elements of health, that is, changes in resistance growth and power fade. Impedance spectroscopy is considered a useful laboratory tool in gauging changes in the resistance and power performance, but it has not been widely considered as an onboard diagnostic tool due to the length of time required to complete the measurement. Cross-Talk Compensation (CTC) is a novel approach that enables rapid, high resolution impedance spectra measurements using a hardware platform that could be designed as an embedded system. This input signal consists of a sum-of-sines excitation current that has a known frequency spread and a duration of one period of the lowest frequency. The voltage response is then captured at a sufficiently fast sample rate. Previously developed rapid impedance spectrum measurement techniques either required a longer excitation signal or a sum-of-sines signal that was separated by harmonic frequencies to reduce or eliminate, respectively, the cross-talk interference in the calculated results. The distinct advantage of CTC, however, is that non-harmonic frequencies can now be included within the excitation signal while still keeping the signal duration at one period of the lowest frequency. Since the frequency spread of the input signal is known, the crosstalk interference between sinusoidal signals within the sum-of-sines at a given frequency of interest can be pre-determined and assigned to an error matrix. Consequently, the real and imaginary components of the

  9. SHARP: A Spatially Higher-order, Relativistic Particle-in-cell Code

    NASA Astrophysics Data System (ADS)

    Shalaby, Mohamad; Broderick, Avery E.; Chang, Philip; Pfrommer, Christoph; Lamberts, Astrid; Puchwein, Ewald

    2017-05-01

    Numerical heating in particle-in-cell (PIC) codes currently precludes the accurate simulation of cold, relativistic plasma over long periods, severely limiting their applications in astrophysical environments. We present a spatially higher-order accurate relativistic PIC algorithm in one spatial dimension, which conserves charge and momentum exactly. We utilize the smoothness implied by the usage of higher-order interpolation functions to achieve a spatially higher-order accurate algorithm (up to the fifth order). We validate our algorithm against several test problems—thermal stability of stationary plasma, stability of linear plasma waves, and two-stream instability in the relativistic and non-relativistic regimes. Comparing our simulations to exact solutions of the dispersion relations, we demonstrate that SHARP can quantitatively reproduce important kinetic features of the linear regime. Our simulations have a superior ability to control energy non-conservation and avoid numerical heating in comparison to common second-order schemes. We provide a natural definition for convergence of a general PIC algorithm: the complement of physical modes captured by the simulation, i.e., those that lie above the Poisson noise, must grow commensurately with the resolution. This implies that it is necessary to simultaneously increase the number of particles per cell and decrease the cell size. We demonstrate that traditional ways for testing for convergence fail, leading to plateauing of the energy error. This new PIC code enables us to faithfully study the long-term evolution of plasma problems that require absolute control of the energy and momentum conservation.

  10. Action-Video-Game Experience Alters the Spatial Resolution of Vision

    PubMed Central

    Green, C.S.; Bavelier, D.

    2010-01-01

    Playing action video games enhances several different aspects of visual processing; however, the mechanisms underlying this improvement remain unclear. Here we show that playing action video games can alter fundamental characteristics of the visual system, such as the spatial resolution of visual processing across the visual field. To determine the spatial resolution of visual processing, we measured the smallest distance a distractor could be from a target without compromising target identification. This approach exploits the fact that visual processing is hindered as distractors are brought close to the target, a phenomenon known as crowding. Compared with nonplayers, action-video-game players could tolerate smaller target-distractor distances. Thus, the spatial resolution of visual processing is enhanced in this population. Critically, similar effects were observed in non-video-game players who were trained on an action video game; this result verifies a causative relationship between video-game play and augmented spatial resolution. PMID:17362383

  11. Definition of the Spatial Resolution of X-Ray Microanalysis in Thin Foils

    NASA Technical Reports Server (NTRS)

    Williams, D. B.; Michael, J. R.; Goldstein, J. I.; Romig, A. D., Jr.

    1992-01-01

    The spatial resolution of X-ray microanalysis in thin foils is defined in terms of the incident electron beam diameter and the average beam broadening. The beam diameter is defined as the full width tenth maximum of a Gaussian intensity distribution. The spatial resolution is calculated by a convolution of the beam diameter and the average beam broadening. This definition of the spatial resolution can be related simply to experimental measurements of composition profiles across interphase interfaces. Monte Carlo calculations using a high-speed parallel supercomputer show good agreement with this definition of the spatial resolution and calculations based on this definition. The agreement is good over a range of specimen thicknesses and atomic number, but is poor when excessive beam tailing distorts the assumed Gaussian electron intensity distributions. Beam tailing occurs in low-Z materials because of fast secondary electrons and in high-Z materials because of plural scattering.

  12. Action-video-game experience alters the spatial resolution of vision.

    PubMed

    Green, C S; Bavelier, D

    2007-01-01

    Playing action video games enhances several different aspects of visual processing; however, the mechanisms underlying this improvement remain unclear. Here we show that playing action video games can alter fundamental characteristics of the visual system, such as the spatial resolution of visual processing across the visual field. To determine the spatial resolution of visual processing, we measured the smallest distance a distractor could be from a target without compromising target identification. This approach exploits the fact that visual processing is hindered as distractors are brought close to the target, a phenomenon known as crowding. Compared with nonplayers, action-video-game players could tolerate smaller target-distractor distances. Thus, the spatial resolution of visual processing is enhanced in this population. Critically, similar effects were observed in non-video-game players who were trained on an action video game; this result verifies a causative relationship between video-game play and augmented spatial resolution.

  13. Definition of the Spatial Resolution of X-Ray Microanalysis in Thin Foils

    NASA Technical Reports Server (NTRS)

    Williams, D. B.; Michael, J. R.; Goldstein, J. I.; Romig, A. D., Jr.

    1992-01-01

    The spatial resolution of X-ray microanalysis in thin foils is defined in terms of the incident electron beam diameter and the average beam broadening. The beam diameter is defined as the full width tenth maximum of a Gaussian intensity distribution. The spatial resolution is calculated by a convolution of the beam diameter and the average beam broadening. This definition of the spatial resolution can be related simply to experimental measurements of composition profiles across interphase interfaces. Monte Carlo calculations using a high-speed parallel supercomputer show good agreement with this definition of the spatial resolution and calculations based on this definition. The agreement is good over a range of specimen thicknesses and atomic number, but is poor when excessive beam tailing distorts the assumed Gaussian electron intensity distributions. Beam tailing occurs in low-Z materials because of fast secondary electrons and in high-Z materials because of plural scattering.

  14. TDDA technology for high spatial resolution SWIR InGaAs imaging

    NASA Astrophysics Data System (ADS)

    Jia, Jianxin; Wang, Yueming; Zhuang, Xiaoqiong; Yao, Yi; Wang, Shengwei; Zhao, Ding; Shu, Rong; Wang, Jianyu

    2016-11-01

    With the development of remote sensing technology, shortwave infrared (SWIR) imaging technology has got more and more attention because of its ability through the fog and high spatial resolution. High spatial resolution SWIR imaging often requires high frame frequency. If the frame frequency is too high, it could cause the shortage of the image's signal to noise ratio (SNR), seriously affecting image quality. In order to solve the contradiction between high spatial resolution and sensitivity, time delay and digital accumulation (TDDA) technology is proposed in this paper to improve system's SNR and image quality. A prototype of SWIR imaging system based on a large format area InGaAs detector is designed, which demonstrates TDDA technology. The experiment results indicate that TDDA technology can increase system's SNR of the square root of accumulative stage and improve image's uniformity. The results in this paper are helpful for the improvement and application of high spatial resolution SWIR imaging technology.

  15. An evaluation of spatial resolution of a prototype proton CT scanner.

    PubMed

    Plautz, Tia E; Bashkirov, V; Giacometti, V; Hurley, R F; Johnson, R P; Piersimoni, P; Sadrozinski, H F-W; Schulte, R W; Zatserklyaniy, A

    2016-12-01

    To evaluate the spatial resolution of proton CT using both a prototype proton CT scanner and Monte Carlo simulations. A custom cylindrical edge phantom containing twelve tissue-equivalent inserts with four different compositions at varying radial displacements from the axis of rotation was developed for measuring the modulation transfer function (MTF) of a prototype proton CT scanner. Two scans of the phantom, centered on the axis of rotation, were obtained with a 200 MeV, low-intensity proton beam: one scan with steps of 4°, and one scan with the phantom continuously rotating. In addition, Monte Carlo simulations of the phantom scan were performed using scanners idealized to various degrees. The data were reconstructed using an iterative projection method with added total variation superiorization based on individual proton histories. Edge spread functions in the radial and azimuthal directions were obtained using the oversampling technique. These were then used to obtain the modulation transfer functions. The spatial resolution was defined by the 10% value of the modulation transfer function (MTF10%) in units of line pairs per centimeter (lp/cm). Data from the simulations were used to better understand the contributions of multiple Coulomb scattering in the phantom and the scanner hardware, as well as the effect of discretization of proton location. The radial spatial resolution of the prototype proton CT scanner depends on the total path length, W, of the proton in the phantom, whereas the azimuthal spatial resolution depends both on W and the position, u-, at which the most-likely path uncertainty is evaluated along the path. For protons contributing to radial spatial resolution, W varies with the radial position of the edge, whereas for protons contributing to azimuthal spatial resolution, W is approximately constant. For a pixel size of 0.625 mm, the radial spatial resolution of the image reconstructed from the fully idealized simulation data ranged between

  16. Multiwavelength fiber lasers based on spatial mode beating for high resolution linear and angular displacement sensing

    NASA Astrophysics Data System (ADS)

    Chen, Nan-Kuang; Chang, Yung-Hsiang; Cheng, Wood-Hi; Guo, Tuan; Guan, Bai-Ou

    2014-05-01

    We demonstrate multiwavelength fiber lasers by incorporating the micro Michelson interferometer with spatial mode beating phenomenon, which comes from the interferences among cladding modes, into ring cavity for high resolution linear and angular displacement sensing.

  17. High-Field fMRI for Human Applications: An Overview of Spatial Resolution and Signal Specificity

    PubMed Central

    Olman, Cheryl A; Yacoub, Essa

    2011-01-01

    In the last decade, dozens of 7 Tesla scanners have been purchased or installed around the world, while 3 Tesla systems have become a standard. This increased interest in higher field strengths is driven by a demonstrated advantage of high fields for available signal-to-noise ratio (SNR) in the magnetic resonance signal. Functional imaging studies have additional advantages of increases in both the contrast and the spatial specificity of the susceptibility based BOLD signal. One use of this resultant increase in the contrast to noise ratio (CNR) for functional MRI studies at high field is increased image resolution. However, there are many factors to consider in predicting exactly what kind of resolution gains might be made at high fields, and what the opportunity costs might be. The first part of this article discusses both hardware and image quality considerations for higher resolution functional imaging. The second part draws distinctions between image resolution, spatial specificity, and functional specificity of the fMRI signals that can be acquired at high fields, suggesting practical limitations for attainable resolutions of fMRI experiments at a given field, given the current state of the art in imaging techniques. Finally, practical resolution limitations and pulse sequence options for studies in human subjects are considered. PMID:22216080

  18. Doubling the resolution of spatial-light-modulator-based differential interference contrast microscopy by structured illumination.

    PubMed

    Chen, Jianling; Lv, Xiaohua; Zeng, Shaoqun

    2013-09-01

    Recently developed spatial light modulator (SLM)-based differential interference contrast (DIC) microscopy [Opt. Lett. 34, 2988 (2009)] reveals flexibility on the implementation of DIC imaging. However, its numerical aperture (spatial resolution) is limited to maintain sufficient interference contrast, because it requires two beams to interfere. We present a structured illumination (SI) SLM-based DIC microscopy to effectively improve the lateral resolution of the SLM-based DIC microscopy. The SI field is generated and controlled by an adjustable grating displayed on an SLM. The SI SLM-based DIC expands the bandwidth of the coherent transfer function of the SLM-based DIC imaging system, thus improving the spatial resolution. The reconstructed SI SLM-based DIC image exhibits lateral resolution of approximately 208 nm, doubling that of the common SLM-based DIC image (approximately 415 nm). SI SLM-based DIC microscopy has the potential for achieving high-resolution quantitative phase images.

  19. Imaging at high spatial resolution: Soft x-ray microscopy to 15nm

    SciTech Connect

    Attwood, D.; Chao, W.; Anderson, E.; Liddle, J.A.; Harteneck, B.; Fischer, P.; Schneider, G.; Le Gros, M.; Larabell, C.

    2006-04-05

    Soft x-ray microscopy has now achieved 15 nm spatial resolution with new zone plates and bending magnet radiation. Combined with elemental sensitivity and flexible sample environment (applied magnetic or electric fields, wet samples, windows, overcoatings) this emerges as a valuable tool for nanoscience and nanotechnology, complimenting common electron and scanning tip microscopies. In this presentation we describe recent advances in spatial resolution, expectations for the near future, and applications to magnetic materials, bio-tomography, etc.

  20. Atmospheric Correction Prototype Algorithm for High Spatial Resolution Multispectral Earth Observing Imaging Systems

    NASA Technical Reports Server (NTRS)

    Pagnutti, Mary

    2006-01-01

    This viewgraph presentation reviews the creation of a prototype algorithm for atmospheric correction using high spatial resolution earth observing imaging systems. The objective of the work was to evaluate accuracy of a prototype algorithm that uses satellite-derived atmospheric products to generate scene reflectance maps for high spatial resolution (HSR) systems. This presentation focused on preliminary results of only the satellite-based atmospheric correction algorithm.

  1. On spatial resolution of quasi-optical focal plane antenna array imagers

    NASA Astrophysics Data System (ADS)

    Volkov, Leonid V.; Voronko, Alexander I.; Volkova, Natalie L.

    2004-08-01

    The spatial resolution of millimeter wave (MMW), submillimeter wave (SMMW) and infrared (IR) quasi-optical imagers based on the usage of focal plane antenna arrays (FPAA) is limited by several common factors. Analytical expressions for the point spread functions (PSF) of FPAA imagers are derived for both coherent and spatially incoherent imaging. The possibility of developing advanced super-resolution imaging algorithms using PSFs determined to a high accuracy is discussed.

  2. Spatial Resolution and Detectability Limits in Thin-Film X-Ray Microanalysis

    NASA Technical Reports Server (NTRS)

    Goldstein, J. I.; Lyman, C. E.; Zhang, Jing

    1990-01-01

    The major advantages of performing x-ray microanalysis in the analytical electron microscope (AEM) are the high compositional spatial resolution and the elemental analysis sensitivity. Unfortunately, there is usually a trade-off between these two advantages. This paper discusses the factors involved in the optimization of both spatial resolution and sensitivity during x-ray microanalysis and shows the results of such optimization experiments for several AEM instruments.

  3. Resolving the spatial relationship between intracellular components by dual color super resolution optical fluctuations imaging (SOFI)

    PubMed Central

    Gallina, Maria Elena; Xu, Jianmin; Dertinger, Thomas; Aizer, Adva; Shav-Tal, Yaron; Weiss, Shimon

    2013-01-01

    Background Multi-color super-resolution (SR) imaging microscopy techniques can resolve ultrastructura relationships between- and provide co-localization information of- different proteins inside the cell or even within organelles at a higher resolution than afforded by conventional diffraction-limited imaging. While still very challenging, important SR colocalization results have been reported in recent years using STED, PALM and STORM techniques. Results In this work, we demonstrate dual-color Super Resolution Optical Fluctuations Imaging (SOFI) using a standard far-field fluorescence microscope and different color blinking quantum dots. We define the spatial relationship between hDcp1a, a processing body (P-body, PB) protein, and the tubulin cytoskeletal network. Our finding could open up new perspectives on the role of the cytoskeleton in PB formation and assembly. Further insights into PB internal organization are also reported and discussed. Conclusions Our results demonstrate the suitability and facile use of multi-color SOFI for the investigation of intracellular ultrastructures. PMID:24324919

  4. Flow Structures and Effects of Spatial Resolution on Turbulence Statistics in Rough Wall Turbulent Channel Flow

    NASA Astrophysics Data System (ADS)

    Katz, Joseph; Hong, Jiarong; Schultz, Michael

    2009-11-01

    PIV data obtained in the roughness sublayer of a turbulent channel flow is used for examining effects of spatial resolution on the magnitude, distribution, and trends of Reynolds stresses. Starting with a vector spacing of 63um (9-12 wall units), for roughness consisting of 0.45mm high pyramids at Reτ=3400-5418, spatial filtering of data causes major reduction in the magnitude of Reynolds stresses in the roughness sublayer. Although these reductions extend to well above the log layer, they increase with decreasing distance from the wall, especially for terms involving the wall-normal velocity fluctuation component, but also for the streamwise component. As expected, these effects increase with filter size, and are much higher for 2D filters in comparison to 1D ones. Consequently, trends of Reynolds stresses, and even mean flow profile vary significantly with filter properties. Spatial energy spectra and distributions of 2D swirling strength show the increasing role of small scale eddies on 2^nd order statistics as the wall is approached, which is attenuated by filtering.

  5. Neuronal nonlinearity explains greater visual spatial resolution for darks than lights

    PubMed Central

    Kremkow, Jens; Jin, Jianzhong; Komban, Stanley J.; Wang, Yushi; Lashgari, Reza; Li, Xiaobing; Jansen, Michael; Zaidi, Qasim; Alonso, Jose-Manuel

    2014-01-01

    Astronomers and physicists noticed centuries ago that visual spatial resolution is higher for dark than light stimuli, but the neuronal mechanisms for this perceptual asymmetry remain unknown. Here we demonstrate that the asymmetry is caused by a neuronal nonlinearity in the early visual pathway. We show that neurons driven by darks (OFF neurons) increase their responses roughly linearly with luminance decrements, independent of the background luminance. However, neurons driven by lights (ON neurons) saturate their responses with small increases in luminance and need bright backgrounds to approach the linearity of OFF neurons. We show that, as a consequence of this difference in linearity, receptive fields are larger in ON than OFF thalamic neurons, and cortical neurons are more strongly driven by darks than lights at low spatial frequencies. This ON/OFF asymmetry in linearity could be demonstrated in the visual cortex of cats, monkeys, and humans and in the cat visual thalamus. Furthermore, in the cat visual thalamus, we show that the neuronal nonlinearity is present at the ON receptive field center of ON-center neurons and ON receptive field surround of OFF-center neurons, suggesting an origin at the level of the photoreceptor. These results demonstrate a fundamental difference in visual processing between ON and OFF channels and reveal a competitive advantage for OFF neurons over ON neurons at low spatial frequencies, which could be important during cortical development when retinal images are blurred by immature optics in infant eyes. PMID:24516130

  6. Estimation of inter-annual winter crop area variation and spatial distribution with low resolution NDVI data by using neural networks trained on high resolution images

    NASA Astrophysics Data System (ADS)

    Atzberger, C.; Rembold, F.

    2009-09-01

    The current work aimed at testing a methodology which can be applied to low spatial resolution satellite data to assess interannual crop area variations on a regional scale. The methodology is based on the assumption that within mixed pixels such variations are reflected by changes in the related multitemporal Normalised Difference Vegetation Index (NDVI) profiles. This implies that low resolution NDVI images with high temporal frequency can be used to update land cover estimates derived from higher resolution cartography. More particularly, changes in the shape of annual NDVI profiles can be detected by a Neural Network trained by using high resolution images for a subset of the study years. By taking into account the respective proportions of the remaining land covers within a given low resolution pixel, the accuracy of the net can be further increased. The proposed methodology was applied in a study region in central Italy to estimate area changes of winter crops from low resolution NDVI profiles. The accuracy of such estimates was assessed by comparison to official agricultural statistics using a bootstrap approach. The method showed promise for estimating crop area variation on a regional scale and proved to have a significantly higher forecast capability than other methods used previously for the same study area.

  7. Enhancing effect of phase coherence factor for improvement of spatial resolution in ultrasonic imaging.

    PubMed

    Hasegawa, Hideyuki

    2016-01-01

    Spatial resolution is one of the important factors that determines ultrasound image quality. In the present study, methods using the phase variance of ultrasonic echoes received by individual transducer elements have been examined for improvement of spatial resolution. An imaging method, i.e., phase coherence imaging, which uses the phase coherence factor (PCF) obtained from the phase variance of received ultrasonic echoes, was recently proposed. Spatial resolution is improved by weighting ultrasonic RF signals obtained by delay-and-sum (DAS) beam forming using PCF. In the present study, alternative PCFs, i.e., exponential PCF, harmonic PCF, and Gaussian PCF, have been proposed and examined for further improvement of spatial resolution. Spatial resolutions realized by the proposed PCFs were evaluated by an experiment using a phantom. The full widths at half maxima of the lateral profiles of an echo from a string phantom were 2.61 mm (DAS only), 1.46 mm (conventional PCF), and 0.48-0.62 mm (proposed PCFs). The PCFs newly proposed in the present study showed better spatial resolutions than the conventional PCF. The proposed PCFs also realized better visualization of echoes from a diffuse scattering medium than the conventional PCF.

  8. Calculation of the spatial resolution in two-photon absorption spectroscopy applied to plasma diagnosis

    NASA Astrophysics Data System (ADS)

    Garcia-Lechuga, M.; Fuentes, L. M.; Grützmacher, K.; Pérez, C.; de la Rosa, M. I.

    2014-10-01

    We report a detailed characterization of the spatial resolution provided by two-photon absorption spectroscopy suited for plasma diagnosis via the 1S-2S transition of atomic hydrogen for optogalvanic detection and laser induced fluorescence (LIF). A precise knowledge of the spatial resolution is crucial for a correct interpretation of measurements, if the plasma parameters to be analysed undergo strong spatial variations. The present study is based on a novel approach which provides a reliable and realistic determination of the spatial resolution. Measured irradiance distribution of laser beam waists in the overlap volume, provided by a high resolution UV camera, are employed to resolve coupled rate equations accounting for two-photon excitation, fluorescence decay and ionization. The resulting three-dimensional yield distributions reveal in detail the spatial resolution for optogalvanic and LIF detection and related saturation due to depletion. Two-photon absorption profiles broader than the Fourier transform-limited laser bandwidth are also incorporated in the calculations. The approach allows an accurate analysis of the spatial resolution present in recent and future measurements.

  9. Study of satellite retrieved aerosol optical depth spatial resolution effect on particulate matter concentration prediction

    NASA Astrophysics Data System (ADS)

    Strandgren, J.; Mei, L.; Vountas, M.; Burrows, J. P.; Lyapustin, A.; Wang, Y.

    2014-10-01

    The Aerosol Optical Depth (AOD) spatial resolution effect is investigated for the linear correlation between satellite retrieved AOD and ground level particulate matter concentrations (PM2.5). The Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm was developed for the Moderate Resolution Imaging Spectroradiometer (MODIS) for obtaining AOD with a high spatial resolution of 1 km and provides a good dataset for the study of the AOD spatial resolution effect on the particulate matter concentration prediction. 946 Environmental Protection Agency (EPA) ground monitoring stations across the contiguous US have been used to investigate the linear correlation between AOD and PM2.5 using AOD at different spatial resolutions (1, 3 and 10 km) and for different spatial scales (urban scale, meso-scale and continental scale). The main conclusions are: (1) for both urban, meso- and continental scale the correlation between PM2.5 and AOD increased significantly with increasing spatial resolution of the AOD, (2) the correlation between AOD and PM2.5 decreased significantly as the scale of study region increased for the eastern part of the US while vice versa for the western part of the US, (3) the correlation between PM2.5 and AOD is much more stable and better over the eastern part of the US compared to western part due to the surface characteristics and atmospheric conditions like the fine mode fraction.

  10. Angular versus spatial resolution trade-offs for diffusion imaging under time constraints

    PubMed Central

    Zhan, Liang; Jahanshad, Neda; Ennis, Daniel B.; Jin, Yan; Bernstein, Matthew A.; Borowski, Bret J.; Jack, Clifford R.; Toga, Arthur W.; Leow, Alex D.; Thompson, Paul M.

    2012-01-01

    Diffusion weighted magnetic resonance imaging (DW-MRI) are now widely used to assess brain integrity in clinical populations. The growing interest in mapping brain connectivity has made it vital to consider what scanning parameters affect the accuracy, stability, and signal-to-noise of Diffusion measures. Trade-offs between scan parameters can only be optimized if their effects on various commonly derived measures are better understood. To explore angular versus spatial resolution trade-offs in standard tensor-derived measures, and in measures that use the full angular information in diffusion signal, we scanned eight subjects twice, two weeks apart, using three protocols that took the same amount of time (7 minutes). Scans with 3, 2.7, 2.5 mm isotropic voxels were collected using 48, 41, and 37 diffusion-sensitized gradients to equalize scan times. A specially designed DTI phantom was also scanned with the same protocols, and different b-values. We assessed how several diffusion measures including fractional anisotropy (FA), mean diffusivity (MD), and the full 3D orientation distribution function (ODF) depended on the spatial/angular resolution and the SNR. We also created maps of stability over time in the FA, MD, ODF, skeleton FA of 14 TBSS-derived ROIs, and an information uncertainty index derived from the tensor distribution function, which models the signal using a continuous mixture of tensors. In scans of the same duration, higher angular resolution and larger voxels boosted SNR and improved stability over time. The increased partial voluming in large voxels also led to bias in estimating FA, but this was partially addressed by using “beyond-tensor” models of diffusion. PMID:22522814

  11. Angular versus spatial resolution trade-offs for diffusion imaging under time constraints.

    PubMed

    Zhan, Liang; Jahanshad, Neda; Ennis, Daniel B; Jin, Yan; Bernstein, Matthew A; Borowski, Bret J; Jack, Clifford R; Toga, Arthur W; Leow, Alex D; Thompson, Paul M

    2013-10-01

    Diffusion weighted magnetic resonance imaging (DW-MRI) are now widely used to assess brain integrity in clinical populations. The growing interest in mapping brain connectivity has made it vital to consider what scanning parameters affect the accuracy, stability, and signal-to-noise of diffusion measures. Trade-offs between scan parameters can only be optimized if their effects on various commonly-derived measures are better understood. To explore angular versus spatial resolution trade-offs in standard tensor-derived measures, and in measures that use the full angular information in diffusion signal, we scanned eight subjects twice, 2 weeks apart, using three protocols that took the same amount of time (7 min). Scans with 3.0, 2.7, 2.5 mm isotropic voxels were collected using 48, 41, and 37 diffusion-sensitized gradients to equalize scan times. A specially designed DTI phantom was also scanned with the same protocols, and different b-values. We assessed how several diffusion measures including fractional anisotropy (FA), mean diffusivity (MD), and the full 3D orientation distribution function (ODF) depended on the spatial/angular resolution and the SNR. We also created maps of stability over time in the FA, MD, ODF, skeleton FA of 14 TBSS-derived ROIs, and an information uncertainty index derived from the tensor distribution function, which models the signal using a continuous mixture of tensors. In scans of the same duration, higher angular resolution and larger voxels boosted SNR and improved stability over time. The increased partial voluming in large voxels also led to bias in estimating FA, but this was partially addressed by using "beyond-tensor" models of diffusion.

  12. Spatial resolution limits for the isotropic-3D PET detector X’tal cube

    NASA Astrophysics Data System (ADS)

    Yoshida, Eiji; Tashima, Hideaki; Hirano, Yoshiyuki; Inadama, Naoko; Nishikido, Fumihiko; Murayama, Hideo; Yamaya, Taiga

    2013-11-01

    Positron emission tomography (PET) has become a popular imaging method in metabolism, neuroscience, and molecular imaging. For dedicated human brain and small animal PET scanners, high spatial resolution is needed to visualize small objects. To improve the spatial resolution, we are developing the X’tal cube, which is our new PET detector to achieve isotropic 3D positioning detectability. We have shown that the X’tal cube can achieve 1 mm3 uniform crystal identification performance with the Anger-type calculation even at the block edges. We plan to develop the X’tal cube with even smaller 3D grids for sub-millimeter crystal identification. In this work, we investigate spatial resolution of a PET scanner based on the X’tal cube using Monte Carlo simulations for predicting resolution performance in smaller 3D grids. For spatial resolution evaluation, a point source emitting 511 keV photons was simulated by GATE for all physical processes involved in emission and interaction of positrons. We simulated two types of animal PET scanners. The first PET scanner had a detector ring 14.6 cm in diameter composed of 18 detectors. The second PET scanner had a detector ring 7.8 cm in diameter composed of 12 detectors. After the GATE simulations, we converted the interacting 3D position information to digitalized positions for realistic segmented crystals. We simulated several X’tal cubes with cubic crystals from (0.5 mm)3 to (2 mm)3 in size. Also, for evaluating the effect of DOI resolution, we simulated several X’tal cubes with crystal thickness from (0.5 mm)3 to (9 mm)3. We showed that sub-millimeter spatial resolution was possible using cubic crystals smaller than (1.0 mm)3 even with the assumed physical processes. Also, the weighted average spatial resolutions of both PET scanners with (0.5 mm)3 cubic crystals were 0.53 mm (14.6 cm ring diameter) and 0.48 mm (7.8 cm ring diameter). For the 7.8 cm ring diameter, spatial resolution with 0.5×0.5×1.0 mm3 crystals

  13. Effects of satellite image spatial aggregation and resolution on estimates of forest land area

    Treesearch

    M.D. Nelson; R.E. McRoberts; G.R. Holden; M.E. Bauer

    2009-01-01

    Satellite imagery is being used increasingly in association with national forest inventories (NFIs) to produce maps and enhance estimates of forest attributes. We simulated several image spatial resolutions within sparsely and heavily forested study areas to assess resolution effects on estimates of forest land area, independent of other sensor characteristics. We...

  14. Spatial Resolution, Grayscale, and Error Diffusion Trade-offs: Impact on Display System Design

    NASA Technical Reports Server (NTRS)

    Gille, Jennifer L. (Principal Investigator)

    1996-01-01

    We examine technology trade-offs related to grayscale resolution, spatial resolution, and error diffusion for tessellated display systems. We present new empirical results from our psychophysical study of these trade-offs and compare them to the predictions of a model of human vision.

  15. Spatial resolution is dependent on image content for SPECT with iterative reconstruction incorporating distance dependent resolution (DDR) correction.

    PubMed

    Badger, Daniel; Barnden, Leighton

    2014-09-01

    The aim of this study is to determine the dependence of single photon emission computed tomography (SPECT) spatial resolution on the content of images for iterative reconstruction with distance dependent resolution (DDR) correction. An experiment was performed using a perturbation technique to measure change in resolution of line sources in simple and complex images with iterative reconstruction with increasing iteration. Projections of the line sources were reconstructed alone and again after the addition of projections of a uniform flood or a complex phantom. An alternative experiment used images of a realistic brain phantom and evaluated an effective spatial resolution by matching the images to the digital version of the phantom convolved with 3D Gaussian kernels. The experiments were performed using ordered subset expectation maximisation iterative reconstruction with and without the use of DDR correction. The results show a significant difference in reconstructed resolution between images of line sources depending on the content of the added image. The full width at half maximum of images of a line source reconstructed using DDR correction increased by 20-30 % when the added image was complex. Without DDR this difference was much smaller and disappeared with increasing iteration. Reported SPECT resolution should be taken as indicative only with regard to clinical imaging if the measurement is made using a point or line source alone and an iterative reconstruction algorithm is used.

  16. Spatial Covariance Reconstructive (SCORE) Super-Resolution Fluorescence Microscopy

    PubMed Central

    Deng, Yi; Sun, Mingzhai; Lin, Pei-Hui; Ma, Jianjie; Shaevitz, Joshua W.

    2014-01-01

    Super-resolution fluorescence microscopy has become a powerful tool to resolve structural information that is not accessible to traditional diffraction-limited imaging techniques such as confocal microscopy. Stochastic optical reconstruction microscopy (STORM) and photoactivation localization microscopy (PALM) are promising super-resolution techniques due to their relative ease of implementation and instrumentation on standard microscopes. However, the application of STORM is critically limited by its long sampling time. Several recent works have been focused on improving the STORM imaging speed by making use of the information from emitters with overlapping point spread functions (PSF). In this work, we present a fast and efficient algorithm that takes into account the blinking statistics of independent fluorescence emitters. We achieve sub-diffraction lateral resolution of 100 nm from 5 to 7 seconds of imaging. Our method is insensitive to background and can be applied to different types of fluorescence sources, including but not limited to the organic dyes and quantum dots that we demonstrate in this work. PMID:24788039

  17. Super Resolution from Hyperview Image Stack by Spatial Multiplexing

    NASA Astrophysics Data System (ADS)

    Grasnick, Armin

    2016-09-01

    An image stack for a hyperview representation could contain millions of different perspective views with extreme image similarity. The recording of all views from a computational 3d model implicates a lateral displacement of the virtual camera. Because of the huge number of views, the offset in between two adjoining camera positions can be very minor. If such a virtual setup reproduces a real hyperview screen setup, the offset can be below the wavelength of the visible light. But even with such small changes, there is an intrinsic probability for a measurable difference in between two neighbour images. Such image dissimilarity can be proofed successfully also in very basic 3d scenes. By using a quantity of juxtapositional images from the hyperview image stack, the resolution of the rendered images can be considerably improved, which is commonly known as super resolution. The utilisation of super resolution images in hyperview could cut the necessity of full frame computing and will reduce the effective render time.

  18. Spatial covariance reconstructive (SCORE) super-resolution fluorescence microscopy.

    PubMed

    Deng, Yi; Sun, Mingzhai; Lin, Pei-Hui; Ma, Jianjie; Shaevitz, Joshua W

    2014-01-01

    Super-resolution fluorescence microscopy has become a powerful tool to resolve structural information that is not accessible to traditional diffraction-limited imaging techniques such as confocal microscopy. Stochastic optical reconstruction microscopy (STORM) and photoactivation localization microscopy (PALM) are promising super-resolution techniques due to their relative ease of implementation and instrumentation on standard microscopes. However, the application of STORM is critically limited by its long sampling time. Several recent works have been focused on improving the STORM imaging speed by making use of the information from emitters with overlapping point spread functions (PSF). In this work, we present a fast and efficient algorithm that takes into account the blinking statistics of independent fluorescence emitters. We achieve sub-diffraction lateral resolution of 100 nm from 5 to 7 seconds of imaging. Our method is insensitive to background and can be applied to different types of fluorescence sources, including but not limited to the organic dyes and quantum dots that we demonstrate in this work.

  19. High-spatial-resolution scanning capacitance microscope using all-metal probe with quartz tuning fork

    NASA Astrophysics Data System (ADS)

    Naitou, Yuichi; Ookubo, Norio

    2004-09-01

    The scanning capacitance microscope (SCM) reported here uses a frequency modulation (FM) technique to control the distance between the sample and an all-metal probe. The probe was attached to a quartz tuning fork in a configuration minimizing the perturbation due to the probe. The FM-SCM yields two images of ∂C/∂V and ∂C/∂Z signals, where C is capacitance sensed by the probe, Z the probe-sample distance, and V a bias voltage, respectively. On a cross section of a field effect transistor, the two-dimensional p -n junction locus was observed with a spatial resolution better than 5nm in the ∂C/∂V image. The ∂C/∂Z images of polysilicon gate electrodes and highly doped source/drain regions have higher contrast than the ∂C/∂V images.

  20. Modeling Above-Ground Biomass Across Multiple Circum-Arctic Tundra Sites Using High Spatial Resolution Remote Sensing

    NASA Astrophysics Data System (ADS)

    Räsänen, Aleksi; Juutinen, Sari; Aurela, Mika; Virtanen, Tarmo

    2017-04-01

    Biomass is one of the central bio-geophysical variables in Earth observation for tracking plant productivity, and flow of carbon, nutrients, and water. Most of the satellite based biomass mapping exercises in Arctic environments have been performed by using rather coarse spatial resolution data, e.g. Landsat and AVHRR which have spatial resolutions of 30 m and >1 km, respectively. While the coarse resolution images have high temporal resolution, they are incapable of capturing the fragmented nature of tundra environment and fine-scale changes in vegetation and carbon exchange patterns. Very high spatial resolution (VHSR, spatial resolution 0.5-2 m) satellite images have the potential to detect environmental variables with an ecologically sound spatial resolution. The usage of VHSR images has, nevertheless, been modest so far in biomass modeling in the Arctic. Our objectives were to use VHSR for predicting above ground biomass in tundra landscapes, evaluate whether a common predictive model can be applied across circum-Arctic tundra and peatland sites having different types of vegetation, and produce knowledge on distribution of plant functional types (PFT) in these sites. Such model development is dependent on ground-based surveys of vegetation with the same spatial resolution and extent with the VHSR images. In this study, we conducted ground-based surveys of vegetation composition and biomass in four different arctic tundra or peatland areas located in Russia, Canada, and Finland. First, we sorted species into PFTs and developed PFT-specific models to predict biomass on the basis of non-destructive measurements (cover, height). Second, we predicted overall biomass on landscape scale by combinations of single bands and vegetation indices of very high resolution satellite images (QuickBird or WorldView-2 images of the eight sites). We compared area-specific empirical regression models and common models that were applied across all sites. We found that NDVI was

  1. Note: spatial resolution of Fuji BAS-TR and BAS-SR imaging plates.

    PubMed

    Fiksel, G; Marshall, F J; Mileham, C; Stoeckl, C

    2012-08-01

    The spatial resolution of two types of imaging plates, Fuji BAS-TR and Fuji BAS-SR, has been measured using a knife-edge x-ray source of 8-keV Cu K(α) radiation. The values for the spatial resolution, defined as the distance between 10% and 90% levels of the edge spread function, are 94 μm and 109 μm, respectively. The resolution values are important for quantitative analysis of x-ray and particle imaging and spectroscopic diagnostics.

  2. Note: Spatial resolution of Fuji BAS-TR and BAS-SR imaging plates

    NASA Astrophysics Data System (ADS)

    Fiksel, G.; Marshall, F. J.; Mileham, C.; Stoeckl, C.

    2012-08-01

    The spatial resolution of two types of imaging plates, Fuji BAS-TR and Fuji BAS-SR, has been measured using a knife-edge x-ray source of 8-keV Cu Kα radiation. The values for the spatial resolution, defined as the distance between 10% and 90% levels of the edge spread function, are 94 μm and 109 μm, respectively. The resolution values are important for quantitative analysis of x-ray and particle imaging and spectroscopic diagnostics.

  3. Note: Spatial resolution of Fuji BAS-TR and BAS-SR imaging plates

    SciTech Connect

    Fiksel, G.; Marshall, F. J.; Mileham, C.; Stoeckl, C.

    2012-08-15

    The spatial resolution of two types of imaging plates, Fuji BAS-TR and Fuji BAS-SR, has been measured using a knife-edge x-ray source of 8-keV Cu K{sub {alpha}} radiation. The values for the spatial resolution, defined as the distance between 10% and 90% levels of the edge spread function, are 94 {mu}m and 109 {mu}m, respectively. The resolution values are important for quantitative analysis of x-ray and particle imaging and spectroscopic diagnostics.

  4. Image Jitter Enhances Visual Performance when Spatial Resolution Is Impaired

    PubMed Central

    Watson, Lynne M.; Strang, Niall C.; Scobie, Fraser; Love, Gordon D.; Seidel, Dirk; Manahilov, Velitchko

    2012-01-01

    Purpose. Visibility of low–spatial frequency stimuli improves when their contrast is modulated at 5 to 10 Hz compared with stationary stimuli. Therefore, temporal modulations of visual objects could enhance the performance of low vision patients who primarily perceive images of low–spatial frequency content. We investigated the effect of retinal-image jitter on word recognition speed and facial emotion recognition in subjects with central visual impairment. Methods. Word recognition speed and accuracy of facial emotion discrimination were measured in volunteers with AMD under stationary and jittering conditions. Computer-driven and optoelectronic approaches were used to induce retinal-image jitter with duration of 100 or 166 ms and amplitude within the range of 0.5 to 2.6° visual angle. Word recognition speed was also measured for participants with simulated (Bangerter filters) visual impairment. Results. Text jittering markedly enhanced word recognition speed for people with severe visual loss (101 ± 25%), while for those with moderate visual impairment, this effect was weaker (19 ± 9%). The ability of low vision patients to discriminate the facial emotions of jittering images improved by a factor of 2. A prototype of optoelectronic jitter goggles produced similar improvement in facial emotion discrimination. Word recognition speed in participants with simulated visual impairment was enhanced for interjitter intervals over 100 ms and reduced for shorter intervals. Conclusions. Results suggest that retinal-image jitter with optimal frequency and amplitude is an effective strategy for enhancing visual information processing in the absence of spatial detail. These findings will enable the development of novel tools to improve the quality of life of low vision patients. PMID:22879420

  5. Image jitter enhances visual performance when spatial resolution is impaired.

    PubMed

    Watson, Lynne M; Strang, Niall C; Scobie, Fraser; Love, Gordon D; Seidel, Dirk; Manahilov, Velitchko

    2012-09-06

    Visibility of low-spatial frequency stimuli improves when their contrast is modulated at 5 to 10 Hz compared with stationary stimuli. Therefore, temporal modulations of visual objects could enhance the performance of low vision patients who primarily perceive images of low-spatial frequency content. We investigated the effect of retinal-image jitter on word recognition speed and facial emotion recognition in subjects with central visual impairment. Word recognition speed and accuracy of facial emotion discrimination were measured in volunteers with AMD under stationary and jittering conditions. Computer-driven and optoelectronic approaches were used to induce retinal-image jitter with duration of 100 or 166 ms and amplitude within the range of 0.5 to 2.6° visual angle. Word recognition speed was also measured for participants with simulated (Bangerter filters) visual impairment. Text jittering markedly enhanced word recognition speed for people with severe visual loss (101 ± 25%), while for those with moderate visual impairment, this effect was weaker (19 ± 9%). The ability of low vision patients to discriminate the facial emotions of jittering images improved by a factor of 2. A prototype of optoelectronic jitter goggles produced similar improvement in facial emotion discrimination. Word recognition speed in participants with simulated visual impairment was enhanced for interjitter intervals over 100 ms and reduced for shorter intervals. Results suggest that retinal-image jitter with optimal frequency and amplitude is an effective strategy for enhancing visual information processing in the absence of spatial detail. These findings will enable the development of novel tools to improve the quality of life of low vision patients.

  6. Local Optical Spectroscopies for Subnanometer Spatial Resolution Chemical Imaging

    SciTech Connect

    Weiss, Paul

    2014-01-20

    The evanescently coupled photon scanning tunneling microscopes (STMs) have special requirements in terms of stability and optical access. We have made substantial improvements to the stability, resolution, and noise floor of our custom-built visible-photon STM, and will translate these advances to our infrared instrument. Double vibration isolation of the STM base with a damping system achieved increased rigidity, giving high tunneling junction stability for long-duration and high-power illumination. Light frequency modulation with an optical chopper and phase-sensitive detection now enhance the signal-to-noise ratio of the tunneling junction during irradiation.

  7. Spatial resolution estimation of LANDSAT-4 TM and MSS data

    NASA Technical Reports Server (NTRS)

    Mcgillem, C. D.; Anuta, P. E.; Yu, K. B.

    1983-01-01

    In order to verify that the LANDSAT-4 sensors are operating within specifications, it is useful to estimate the system parameters by analysis of the measured data. One parameter of particular interest is the sensor point-spread function (PSF) which determines the resolution of the system. A method of estimating the PSF is described that utilizes data obtained during scanning of ground elements having identifiable geometric and radiometric structure. These data are then processed in such a manner as to recover either the PSF itself or to estimate the parameters of an assumed functional representation of the PSF.

  8. Compressed Sensing for Breast MRI: Resolving the Trade-Off Between Spatial and Temporal Resolution.

    PubMed

    Vreemann, Suzan; Rodriguez-Ruiz, Alejandro; Nickel, Dominik; Heacock, Laura; Appelman, Linda; van Zelst, Jan; Karssemeijer, Nico; Weiland, Elisabeth; Maas, Marnix; Moy, Linda; Kiefer, Berthold; Mann, Ritse M

    2017-10-01

    Ultrafast dynamic contrast-enhanced magnetic resonance imaging of the breast enables assessment of the contrast inflow dynamics while providing images with diagnostic spatial resolution. However, the slice thickness of common ultrafast techniques still prevents multiplanar reconstruction. In addition, some temporal blurring of the enhancement characteristics occurs in case view-sharing is used. We evaluate a prototype compressed-sensing volume-interpolated breath-hold examination (CS-VIBE) sequence for ultrafast breast MRI that improves through plane spatial resolution and avoids temporal blurring while maintaining an ultrafast temporal resolution (less than 5 seconds per volume). Image quality (IQ) of the new sequence is compared with an ultrafast view-sharing sequence (time-resolved angiography with interleaved stochastic trajectories [TWIST]), and assessment of lesion morphology is compared with a regular T1-weighted 3D Dixon sequence (VIBE-DIXON) with an acquisition time of 91 seconds. From April 2016 to October 2016, 30 women were scanned with the CS-VIBE sequence, replacing the routine ultrafast TWIST sequence in a hybrid breast MRI protocol. The need for informed consent was waived. All MRI scans were performed on a 3T MAGNETOM Skyra system (Siemens Healthcare, Erlangen, Germany) using a 16-channel bilateral breast coil. Two reader studies were conducted involving 5 readers. In the first study, overall IQ of CS-VIBE and TWIST in the axial plane was independently rated for 23 women for whom prior MRI examinations with TWIST were available. In addition, the presence of several types of artifacts was rated on a 5-point scale. The second study was conducted in women (n = 16) with lesions. In total, characteristics of 31 lesions (5 malignant and 26 benign) were described independently for CS-VIBE and VIBE-DIXON, according to the BI-RADS MRI-lexicon. In addition, a lesion conspicuity score was given. Using CS-VIBE, a much higher through-plane spatial resolution

  9. Spatializing vineyard hydric status within heterogeneous Mediterranean watershed from high spatial resolution optical remote sensing.

    NASA Astrophysics Data System (ADS)

    Galleguillos, M.; Jacob, F.; Prevot, L.; Lagacherie, P.

    2009-04-01

    Land surface evapotranspiration is one of key hydrological inputs that determine hydric status within Mediterranean vineyards. Its knowledge in a spatially distributed manner is of interest for the monitoring of vine activity throughout the cultural cycle, and for the acquainting of hydrological modeling as upper boundary conditions. Due to vineyard landscape structures, mostly including small fields, the use of remote sensing has not been extensively investigated, apart from airborne observations. Spaceborne ASTER data, collected over the optical domain at high spatial resolution, are of strong interest for the mapping of vineyard hydric status in relation with surface and soil properties, provided vine thermal and hydric status are strongly linked. The objective of this study is to assess the performances of two spatialized approaches devoted to the mapping of instantaneous surface energy fluxes from optical remote sensing. Amongst the candidate methods to be foreseen for the mapping of vineyard water status from remote sensing, we consider two single layer methods characterized by their simplicities and feasibilities, in terms of implementation and input requirements. The first method is the Simplified Surface Energy Balance Index (S-SEBI, proposed by Roerink et al., 2000) and the second is the Water Deficit Index (WDI, designed by Moran et al., 1994). They differ by the way they use the spatial information captured over the solar and thermal domains, for the differentiating based retrieving of water status and evapotranspiration. First, the spatial information can be characterized through the temperature - vegetation index triangle that is controlled by soil moisture (WDI), or through the temperature - albedo diagram that is controlled by radiative and evaporative processes (S-SEBI). Second, evaporative extremes can be determined according to theoretical considerations and related formalisms (WDI), or assigned according to variabilities captured through thermal

  10. Estimation of Orbital Neutron Detector Spatial Resolution by Systematic Shifting of Differential Topographic Masks

    NASA Technical Reports Server (NTRS)

    McClanahan, T. P.; Mitrofanov, I. G.; Boynton, W. V.; Chin, G.; Livengood, T.; Starr, R. D.; Evans, L. G.; Mazarico, E.; Smith, D. E.

    2012-01-01

    We present a method and preliminary results related to determining the spatial resolution of orbital neutron detectors using epithermal maps and differential topographic masks. Our technique is similar to coded aperture imaging methods for optimizing photonic signals in telescopes [I]. In that approach photon masks with known spatial patterns in a telescope aperature are used to systematically restrict incoming photons which minimizes interference and enhances photon signal to noise. Three orbital neutron detector systems with different stated spatial resolutions are evaluated. The differing spatial resolutions arise due different orbital altitudes and the use of neutron collimation techniques. 1) The uncollimated Lunar Prospector Neutron Spectrometer (LPNS) system has spatial resolution of 45km FWHM from approx. 30km altitude mission phase [2]. The Lunar Rennaissance Orbiter (LRO) Lunar Exploration Neutron Detector (LEND) with two detectors at 50km altitude evaluated here: 2) the collimated 10km FWHM spatial resolution detector CSETN and 3) LEND's collimated Sensor for Epithermal Neutrons (SETN). Thus providing two orbital altitudes to study factors of: uncollimated vs collimated and two average altitudes for their effect on fields-of-view.

  11. Full field spatially-variant image-based resolution modelling reconstruction for the HRRT.

    PubMed

    Angelis, Georgios I; Kotasidis, Fotis A; Matthews, Julian C; Markiewicz, Pawel J; Lionheart, William R; Reader, Andrew J

    2015-03-01

    Accurate characterisation of the scanner's point spread function across the entire field of view (FOV) is crucial in order to account for spatially dependent factors that degrade the resolution of the reconstructed images. The HRRT users' community resolution modelling reconstruction software includes a shift-invariant resolution kernel, which leads to transaxially non-uniform resolution in the reconstructed images. Unlike previous work to date in this field, this work is the first to model the spatially variant resolution across the entire FOV of the HRRT, which is the highest resolution human brain PET scanner in the world. In this paper we developed a spatially variant image-based resolution modelling reconstruction dedicated to the HRRT, using an experimentally measured shift-variant resolution kernel. Previously, the system response was measured and characterised in detail across the entire FOV of the HRRT, using a printed point source array. The newly developed resolution modelling reconstruction was applied on measured phantom, as well as clinical data and was compared against the HRRT users' community resolution modelling reconstruction, which is currently in use. Results demonstrated improvements both in contrast and resolution recovery, particularly for regions close to the edges of the FOV, with almost uniform resolution recovery across the entire transverse FOV. In addition, because the newly measured resolution kernel is slightly broader with wider tails, compared to the deliberately conservative kernel employed in the HRRT users' community software, the reconstructed images appear to have not only improved contrast recovery (up to 20% for small regions), but also better noise characteristics.

  12. Two-photon imaging of spatially extended neuronal network dynamics with high temporal resolution.

    PubMed

    Lillis, Kyle P; Eng, Alfred; White, John A; Mertz, Jerome

    2008-07-30

    We describe a simple two-photon fluorescence imaging strategy, called targeted path scanning (TPS), to monitor the dynamics of spatially extended neuronal networks with high spatiotemporal resolution. Our strategy combines the advantages of mirror-based scanning, minimized dead time, ease of implementation, and compatibility with high-resolution low-magnification objectives. To demonstrate the performance of TPS, we monitor the calcium dynamics distributed across an entire juvenile rat hippocampus (>1.5mm), at scan rates of 100 Hz, with single cell resolution and single action potential sensitivity. Our strategy for fast, efficient two-photon microscopy over spatially extended regions provides a particularly attractive solution for monitoring neuronal population activity in thick tissue, without sacrificing the signal-to-noise ratio or high spatial resolution associated with standard two-photon microscopy. Finally, we provide the code to make our technique generally available.

  13. High spatial resolution distributed sensing in optical fibers by Brillouin gain-profile tracing.

    PubMed

    Sperber, Tom; Eyal, Avishay; Tur, Moshe; Thévenaz, Luc

    2010-04-12

    A novel BOTDA technique for distributed sensing of the Brillouin frequency in optical fibers with cm-order spatial resolution is proposed. The technique is based upon a simple modulation scheme, requiring only a single long pump pulse for acoustic excitation, and no subsequent interrogating pulse. Instead, the desired spatial mapping of the Brillouin response is extracted by taking the derivative of the probe signal. As a result, the spatial resolution is limited by the fall-time of the pump modulation, and the phenomena of secondary "echo" signals, typically appearing in BOTDA sensing methods based upon pre-excitation, is mitigated. Experimental demonstration of the detection of a Brillouin frequency variation significantly smaller than the natural Brillouin linewidth, with a 2cm spatial resolution, is presented.

  14. Spatial variability of the Black Sea surface temperature from high resolution modeling and satellite measurements

    NASA Astrophysics Data System (ADS)

    Mizyuk, Artem; Senderov, Maxim; Korotaev, Gennady

    2016-04-01

    Large number of numerical ocean models were implemented for the Black Sea basin during last two decades. They reproduce rather similar structure of synoptical variability of the circulation. Since 00-s numerical studies of the mesoscale structure are carried out using high performance computing (HPC). With the growing capacity of computing resources it is now possible to reconstruct the Black Sea currents with spatial resolution of several hundreds meters. However, how realistic these results can be? In the proposed study an attempt is made to understand which spatial scales are reproduced by ocean model in the Black Sea. Simulations are made using parallel version of NEMO (Nucleus for European Modelling of the Ocean). A two regional configurations with spatial resolutions 5 km and 2.5 km are described. Comparison of the SST from simulations with two spatial resolutions shows rather qualitative difference of the spatial structures. Results of high resolution simulation are compared also with satellite observations and observation-based products from Copernicus using spatial correlation and spectral analysis. Spatial scales of correlations functions for simulated and observed SST are rather close and differs much from satellite SST reanalysis. Evolution of spectral density for modelled SST and reanalysis showed agreed time periods of small scales intensification. Using of the spectral analysis for satellite measurements is complicated due to gaps. The research leading to this results has received funding from Russian Science Foundation (project № 15-17-20020)

  15. a Kernel Method Based on Topic Model for Very High Spatial Resolution (vhsr) Remote Sensing Image Classification

    NASA Astrophysics Data System (ADS)

    Wu, Linmei; Shen, Li; Li, Zhipeng

    2016-06-01

    A kernel-based method for very high spatial resolution remote sensing image classification is proposed in this article. The new kernel method is based on spectral-spatial information and structure information as well, which is acquired from topic model, Latent Dirichlet Allocation model. The final kernel function is defined as K = u1Kspec + u2Kspat + u3Kstru, in which Kspec, Kspat, Kstru are radial basis function (RBF) and u1 + u2 + u3 = 1. In the experiment, comparison with three other kernel methods, including the spectral-based, the spectral- and spatial-based and the spectral- and structure-based method, is provided for a panchromatic QuickBird image of a suburban area with a size of 900 × 900 pixels and spatial resolution of 0.6 m. The result shows that the overall accuracy of the spectral- and structure-based kernel method is 80 %, which is higher than the spectral-based kernel method, as well as the spectral- and spatial-based which accuracy respectively is 67 % and 74 %. What's more, the accuracy of the proposed composite kernel method that jointly uses the spectral, spatial, and structure information is highest among the four methods which is increased to 83 %. On the other hand, the result of the experiment also verifies the validity of the expression of structure information about the remote sensing image.

  16. Impact of spatial resolution of the precipitation data on hydrological Forecast

    NASA Astrophysics Data System (ADS)

    Davis, M.; Bardossy, A.; Sudheer, K.

    2013-05-01

    Flooding is a devastating problem for many countries all over the world. Real time forecasting is a necessary non-structural measure to fight against the damage. Adequate quantitative forecasting of the flood is necessary to provide enough precaution for the affected population. Time lead in the forecast is also a matter of concern considering its significance in the preparedness. The time-lead of forecast depends on the computational time along with the various other issues. The computation time depends on the whether the model is data intensive or process intensive. Considering the use of spatially distributed models in the forecast, the main dynamic data involved in the rainfall runoff models are the precipitation measurement. The data intensity of that depends on the spatial and temporal resolution of the precipitation data. The spatial resolution of the precipitation has the significance in the spatially distributed hydrological models. Neither should the resolution be so less that the quantitative prediction is disturbed nor too much to affect the time lead considerably. Finer spatial resolution of precipitation data may not even yield better forecast (A.Bardossy and T.Das, 2008). So the current study focuses on the impact of spatial and temporal resolution of the hydrological forecast. The spatially distributed model of HBV and HYMOD is being used for the analysis. Spatial resolutions from 1, 4, 9 and 25 square kilometers and a temporal resolution of daily to hourly time-series is also being analysed for their respective effects on prediction. The data from rain gauges are interpolated using the External Drift Kriging Method (EDK). The calibrations of the models are carried out using the Robust Parameter Estimation (ROPE) algorithm (S.K Singh and A. Bardossy, 2010). The framework is illustrated on the Upper Neckar catchment with 13 sub-catchments located in South West Germany. Preliminary results are encouraging. The optimum spatial resolution can be

  17. SAPHIRE (scintillator avalanche photoconductor with high resolution emitter readout) for low dose x-ray imaging: Spatial resolution.

    PubMed

    Li, Dan; Zhao, Wei

    2008-07-01

    An indirect flat panel imager (FPI) with programmable avalanche gain and field emitter array (FEA) readout is being investigated for low-dose and high resolution x-ray imaging. It is made by optically coupling a structured x-ray scintillator, e.g., thallium (Tl) doped cesium iodide (CsI), to an amorphous selenium (a-Se) avalanche photoconductor called high-gain avalanche rushing amorphous photoconductor (HARP). The charge image created by the scintillator/HARP (SHARP) combination is read out by the electron beams emitted from the FEA. The proposed detector is called scintillator avalanche photoconductor with high resolution emitter readout (SAPHIRE). The programmable avalanche gain of HARP can improve the low dose performance of indirect FPI while the FEA can be made with pixel sizes down to 50 μm. Because of the avalanche gain, a high resolution type of CsI (Tl), which has not been widely used in indirect FPI due to its lower light output, can be used to improve the high spatial frequency performance. The purpose of the present article is to investigate the factors affecting the spatial resolution of SAPHIRE. Since the resolution performance of the SHARP combination has been well studied, the focus of the present work is on the inherent resolution of the FEA readout method. The lateral spread of the electron beam emitted from a 50 μm×50 μm pixel FEA was investigated with two different electron-optical designs: mesh-electrode-only and electrostatic focusing. Our results showed that electrostatic focusing can limit the lateral spread of electron beams to within the pixel size of down to 50 μm. Since electrostatic focusing is essentially independent of signal intensity, it will provide excellent spatial uniformity. © 2008 American Association of Physicists in Medicine.

  18. SAPHIRE (scintillator avalanche photoconductor with high resolution emitter readout) for low dose x-ray imaging: Spatial resolution

    PubMed Central

    Li, Dan; Zhao, Wei

    2008-01-01

    An indirect flat panel imager (FPI) with programmable avalanche gain and field emitter array (FEA) readout is being investigated for low-dose and high resolution x-ray imaging. It is made by optically coupling a structured x-ray scintillator, e.g., thallium (Tl) doped cesium iodide (CsI), to an amorphous selenium (a-Se) avalanche photoconductor called high-gain avalanche rushing amorphous photoconductor (HARP). The charge image created by the scintillator∕HARP (SHARP) combination is read out by the electron beams emitted from the FEA. The proposed detector is called scintillator avalanche photoconductor with high resolution emitter readout (SAPHIRE). The programmable avalanche gain of HARP can improve the low dose performance of indirect FPI while the FEA can be made with pixel sizes down to 50 μm. Because of the avalanche gain, a high resolution type of CsI (Tl), which has not been widely used in indirect FPI due to its lower light output, can be used to improve the high spatial frequency performance. The purpose of the present article is to investigate the factors affecting the spatial resolution of SAPHIRE. Since the resolution performance of the SHARP combination has been well studied, the focus of the present work is on the inherent resolution of the FEA readout method. The lateral spread of the electron beam emitted from a 50 μm×50 μm pixel FEA was investigated with two different electron-optical designs: mesh-electrode-only and electrostatic focusing. Our results showed that electrostatic focusing can limit the lateral spread of electron beams to within the pixel size of down to 50 μm. Since electrostatic focusing is essentially independent of signal intensity, it will provide excellent spatial uniformity. PMID:18697540

  19. SAPHIRE (scintillator avalanche photoconductor with high resolution emitter readout) for low dose x-ray imaging: spatial resolution.

    PubMed

    Li, Dan; Zhao, Wei

    2008-07-01

    An indirect flat panel imager (FPI) with programmable avalanche gain and field emitter array (FEA) readout is being investigated for low-dose and high resolution x-ray imaging. It is made by optically coupling a structured x-ray scintillator, e.g., thallium (Tl) doped cesium iodide (CsI), to an amorphous selenium (a-Se) avalanche photoconductor called high-gain avalanche rushing amorphous photoconductor (HARP). The charge image created by the scintillator/HARP (SHARP) combination is read out by the electron beams emitted from the FEA. The proposed detector is called scintillator avalanche photoconductor with high resolution emitter readout (SAPHIRE). The programmable avalanche gain of HARP can improve the low dose performance of indirect FPI while the FEA can be made with pixel sizes down to 50 microm. Because of the avalanche gain, a high resolution type of CsI (Tl), which has not been widely used in indirect FPI due to its lower light output, can be used to improve the high spatial frequency performance. The purpose of the present article is to investigate the factors affecting the spatial resolution of SAPHIRE. Since the resolution performance of the SHARP combination has been well studied, the focus of the present work is on the inherent resolution of the FEA readout method. The lateral spread of the electron beam emitted from a 50 microm x 50 microm pixel FEA was investigated with two different electron-optical designs: mesh-electrode-only and electrostatic focusing. Our results showed that electrostatic focusing can limit the lateral spread of electron beams to within the pixel size of down to 50 microm. Since electrostatic focusing is essentially independent of signal intensity, it will provide excellent spatial uniformity.

  20. SAPHIRE (scintillator avalanche photoconductor with high resolution emitter readout) for low dose x-ray imaging: Spatial resolution

    SciTech Connect

    Li Dan; Zhao Wei

    2008-07-15

    An indirect flat panel imager (FPI) with programmable avalanche gain and field emitter array (FEA) readout is being investigated for low-dose and high resolution x-ray imaging. It is made by optically coupling a structured x-ray scintillator, e.g., thallium (Tl) doped cesium iodide (CsI), to an amorphous selenium (a-Se) avalanche photoconductor called high-gain avalanche rushing amorphous photoconductor (HARP). The charge image created by the scintillator/HARP (SHARP) combination is read out by the electron beams emitted from the FEA. The proposed detector is called scintillator avalanche photoconductor with high resolution emitter readout (SAPHIRE). The programmable avalanche gain of HARP can improve the low dose performance of indirect FPI while the FEA can be made with pixel sizes down to 50 {mu}m. Because of the avalanche gain, a high resolution type of CsI (Tl), which has not been widely used in indirect FPI due to its lower light output, can be used to improve the high spatial frequency performance. The purpose of the present article is to investigate the factors affecting the spatial resolution of SAPHIRE. Since the resolution performance of the SHARP combination has been well studied, the focus of the present work is on the inherent resolution of the FEA readout method. The lateral spread of the electron beam emitted from a 50 {mu}mx50 {mu}m pixel FEA was investigated with two different electron-optical designs: mesh-electrode-only and electrostatic focusing. Our results showed that electrostatic focusing can limit the lateral spread of electron beams to within the pixel size of down to 50 {mu}m. Since electrostatic focusing is essentially independent of signal intensity, it will provide excellent spatial uniformity.

  1. Super-resolution reconstruction to increase the spatial resolution of diffusion weighted images from orthogonal anisotropic acquisitions

    PubMed Central

    Scherrer, Benoit; Gholipour, Ali; Warfield, Simon K.

    2012-01-01

    Diffusion-weighted imaging (DWI) enables non-invasive investigation and characterization of the white matter but suffers from a relatively poor spatial resolution. Increasing the spatial resolution in DWI is challenging with a single-shot EPI acquisition due to the decreased signal-to-noise ratio and T2* relaxation effect amplified with increased echo time. In this work we propose a super-resolution reconstruction (SRR) technique based on the acquisition of multiple anisotropic orthogonal DWI scans. DWI scans acquired in different planes are not typically closely aligned due to the geometric distortion introduced by magnetic susceptibility differences in each phase-encoding direction. We compensate each scan for geometric distortion by acquisition of a dual echo gradient echo field map, providing an estimate of the field inhomogeneity. We address the problem of patient motion by aligning the volumes in both space and q-space. The SRR is formulated as a maximum a posteriori problem. It relies on a volume acquisition model which describes how the acquired scans are observations of an unknown high-resolution image which we aim to recover. Our model enables the introduction of image priors that exploit spatial homogeneity and enables regularized solutions. We detail our SRR optimization procedure and report experiments including numerical simulations, synthetic SRR and real world SRR. In particular, we demonstrate that combining distortion compensation and SRR provides better results than acquisition of a single isotropic scan for the same acquisition duration time. Importantly, SRR enables DWI with resolution beyond the scanner hardware limitations. This work provides the first evidence that SRR, which employs conventional single shot EPI techniques, enables resolution enhancement in DWI, and may dramatically impact the role of DWI in both neuroscience and clinical applications. PMID:22770597

  2. A Reliable, Feasible Method to Observe Neighborhoods at High Spatial Resolution.

    PubMed

    Kepper, Maura M; Sothern, Melinda S; Theall, Katherine P; Griffiths, Lauren A; Scribner, Richard A; Tseng, Tung-Sung; Schaettle, Paul; Cwik, Jessica M; Felker-Kantor, Erica; Broyles, Stephanie T

    2017-01-01

    Systematic social observation (SSO) methods traditionally measure neighborhoods at street level and have been performed reliably using virtual applications to increase feasibility. Research indicates that collection at even higher spatial resolution may better elucidate the health impact of neighborhood factors, but whether virtual applications can reliably capture social determinants of health at the smallest geographic resolution (parcel level) remains uncertain. This paper presents a novel, parcel-level SSO methodology and assesses whether this new method can be collected reliably using Google Street View and is feasible. Multiple raters (N=5) observed 42 neighborhoods. In 2016, inter-rater reliability (observed agreement and kappa coefficient) was compared for four SSO methods: (1) street-level in person; (2) street-level virtual; (3) parcel-level in person; and (4) parcel-level virtual. Intra-rater reliability (observed agreement and kappa coefficient) was calculated to determine whether parcel-level methods produce results comparable to traditional street-level observation. Substantial levels of inter-rater agreement were documented across all four methods; all methods had >70% of items with at least substantial agreement. Only physical decay showed higher levels of agreement (83% of items with >75% agreement) for direct versus virtual rating source. Intra-rater agreement comparing street- versus parcel-level methods resulted in observed agreement >75% for all but one item (90%). Results support the use of Google Street View as a reliable, feasible tool for performing SSO at the smallest geographic resolution. Validation of a new parcel-level method collected virtually may improve the assessment of social determinants contributing to disparities in health behaviors and outcomes. Copyright © 2016 American Journal of Preventive Medicine. Published by Elsevier Inc. All rights reserved.

  3. In vivo sub-femtoliter resolution photoacoustic microscopy with higher frame rates.

    PubMed

    Lee, Szu-Yu; Lai, Yu-Hung; Huang, Kai-Chih; Cheng, Yu-Hsiang; Tseng, Tzu-Fang; Sun, Chi-Kuang

    2015-10-21

    Microscopy based on non-fluorescent absorption dye staining is widely used in various fields of biomedicine for 400 years. Unlike its fluorescent counterpart, non-fluorescent absorption microscopy lacks proper methodologies to realize its in vivo applications with a sub-femtoliter 3D resolution. Regardless of the most advanced high-resolution photoacoustic microscopy, sub-femtoliter spatial resolution is still unattainable, and the imaging speed is relatively slow. In this paper, based on the two-photon photoacoustic mechanism, we demonstrated a in vivo label free laser-scanning photoacoustic imaging modality featuring high frame rates and sub-femtoliter 3D resolution simultaneously, which stands as a perfect solution to 3D high resolution non-fluorescent absorption microscopy. Furthermore, we first demonstrated in vivo label-free two-photon acoustic microscopy on the observation of non-fluorescent melanin distribution within mouse skin.

  4. In vivo sub-femtoliter resolution photoacoustic microscopy with higher frame rates

    NASA Astrophysics Data System (ADS)

    Lee, Szu-Yu; Lai, Yu-Hung; Huang, Kai-Chih; Cheng, Yu-Hsiang; Tseng, Tzu-Fang; Sun, Chi-Kuang

    2015-10-01

    Microscopy based on non-fluorescent absorption dye staining is widely used in various fields of biomedicine for 400 years. Unlike its fluorescent counterpart, non-fluorescent absorption microscopy lacks proper methodologies to realize its in vivo applications with a sub-femtoliter 3D resolution. Regardless of the most advanced high-resolution photoacoustic microscopy, sub-femtoliter spatial resolution is still unattainable, and the imaging speed is relatively slow. In this paper, based on the two-photon photoacoustic mechanism, we demonstrated a in vivo label free laser-scanning photoacoustic imaging modality featuring high frame rates and sub-femtoliter 3D resolution simultaneously, which stands as a perfect solution to 3D high resolution non-fluorescent absorption microscopy. Furthermore, we first demonstrated in vivo label-free two-photon acoustic microscopy on the observation of non-fluorescent melanin distribution within mouse skin.

  5. Effects of voxel size and iterative reconstruction parameters on the spatial resolution of 99mTc SPECT/CT.

    PubMed

    Kappadath, S Cheenu

    2011-11-15

    The purpose of this study was to evaluate the effects of voxel size and iterative reconstruction parameters on the radial and tangential resolution for 99mTc SPECT as a function of radial distance from isocenter. SPECT/CT scans of eight coplanar point sources of size smaller than 1 mm3 containing high concentration 99mTc solution were acquired on a SPECT/CT system with 5/8 inch NaI(Tl) detector and low-energy, high-resolution collimator. The tomographic projection images were acquired in step-and-shoot mode for 360 views over 360° with 250,000 counts per view, a zoom of 2.67, and an image matrix of 256 × 256 pixels that resulted in a 0.9 × 0.9 × 0.9 mm3 SPECT voxel size over 230 mm field-of-view. The projection images were also rebinned to image matrices of 128 × 128 and 64 × 64 to yield SPECT voxel sizes of 1.8 × 1.8 × 1.8 and 3.6 × 3.6 × 3.6 mm3, respectively. The SPECT/CT datasets were reconstructed using the vendor-supplied iterative reconstruction software that incorporated collimator-specific resolution recovery, CT-based attenuation correction, and dual-energy window-based scatter correction using different combinations of iterations and subsets. SPECT spatial resolution was estimated as the full width at half maximum of the radial and tangential profiles through the center of each point source in reconstructed SPECT images. Both radial and tangential resolution improved with higher iterations and subsets, and with smaller voxel sizes. Both radial and tangential resolution also improved with radial distance further away from isocenter. The magnitude of variation decreased for smaller voxel sizes and for higher number of iterations and subsets. Tangential resolution was found not to be equal to the radial resolution, and the nature of the anisotropy depended on the distribution of the radionuclide and on the reconstruction parameters used. The tangential resolution converged faster than the radial resolution, with higher iterations and subsets

  6. Advanced Extraction of Spatial Information from High Resolution Satellite Data

    NASA Astrophysics Data System (ADS)

    Pour, T.; Burian, J.; Miřijovský, J.

    2016-06-01

    In this paper authors processed five satellite image of five different Middle-European cities taken by five different sensors. The aim of the paper was to find methods and approaches leading to evaluation and spatial data extraction from areas of interest. For this reason, data were firstly pre-processed using image fusion, mosaicking and segmentation processes. Results going into the next step were two polygon layers; first one representing single objects and the second one representing city blocks. In the second step, polygon layers were classified and exported into Esri shapefile format. Classification was partly hierarchical expert based and partly based on the tool SEaTH used for separability distinction and thresholding. Final results along with visual previews were attached to the original thesis. Results are evaluated visually and statistically in the last part of the paper. In the discussion author described difficulties of working with data of large size, taken by different sensors and different also thematically.

  7. Intercomparison of snow density measurements: bias, precision and spatial resolution

    NASA Astrophysics Data System (ADS)

    Proksch, M.; Rutter, N.; Fierz, C.; Schneebeli, M.

    2015-07-01

    Density is a fundamental property of porous media such as snow. A wide range of snow properties and physical processes are linked to density, but few studies have addressed the uncertainty in snow density measurements. No study has yet considered the recent advances in snow measurement methods such as micro-computed tomography (CT). During the MicroSnow Davos 2014 workshop different approaches to measure snow density were applied in a controlled laboratory environment and in the field. Overall, the agreement between CT and gravimetric methods (density cutters) was 5 to 9 %, with a bias of -5 to 2 %, expressed as percentage of the mean CT density. In the field, the density cutters tend to overestimate (1 to 6 %) densities below and underestimate (1 to 6 %) densities above 296 to 350 kg m-3, respectively, depending on the cutter type. Using the mean per layer of all measurement methods applied in the field (CT, box, wedge and cylinder cutter) and ignoring ice layers, the variation of layer density between the methods was 2 to 5 % with a bias of -1 to 1 %. In general, our result suggests that snow densities measured by different methods agree within 9 %. However, the density profiles resolved by the measurement methods differed considerably. In particular, the millimeter scale density variations revealed by the high resolution CT contrasted the thick layers with sharp boundaries introduced by the observer. In this respect, the unresolved variation, i.e. the density variation within a layer, which is lost by sampling with lower resolution or layer aggregation, is critical when snow density measurements are used as boundary or initial conditions in numerical simulations.

  8. Practical Considerations for High Spatial and Temporal Resolution Dynamic Transmission Electron Microscopy

    SciTech Connect

    Armstrong, M; Boyden, K; Browning, N D; Campbell, G H; Colvin, J D; DeHope, B; Frank, A M; Gibson, D J; Hartemann, F; Kim, J S; King, W E; LaGrange, T B; Pyke, B J; Reed, B W; Shuttlesworth, R M; Stuart, B C; Torralva, B R

    2006-05-01

    Although recent years have seen significant advances in the spatial resolution possible in the transmission electron microscope (TEM), the temporal resolution of most microscopes is limited to video rate at best. This lack of temporal resolution means that our understanding of dynamic processes in materials is extremely limited. High temporal resolution in the TEM can be achieved, however, by replacing the normal thermionic or field emission source with a photoemission source. In this case the temporal resolution is limited only by the ability to create a short pulse of photoexcited electrons in the source, and this can be as short as a few femtoseconds. The operation of the photo-emission source and the control of the subsequent pulse of electrons (containing as many as 5 x 10{sup 7} electrons) create significant challenges for a standard microscope column that is designed to operate with a single electron in the column at any one time. In this paper, the generation and control of electron pulses in the TEM to obtain a temporal resolution <10{sup -6} s will be described and the effect of the pulse duration and current density on the spatial resolution of the instrument will be examined. The potential of these levels of temporal and spatial resolution for the study of dynamic materials processes will also be discussed.

  9. D Geomarketing Segmentation: a Higher Spatial Dimension Planning Perspective

    NASA Astrophysics Data System (ADS)

    Suhaibah, A.; Uznir, U.; Rahman, A. A.; Anton, F.; Mioc, D.

    2016-09-01

    Geomarketing is a discipline which uses geographic information in the process of planning and implementation of marketing activities. It can be used in any aspect of the marketing such as price, promotion or geo targeting. The analysis of geomarketing data use a huge data pool such as location residential areas, topography, it also analyzes demographic information such as age, genre, annual income and lifestyle. This information can help users to develop successful promotional campaigns in order to achieve marketing goals. One of the common activities in geomarketing is market segmentation. The segmentation clusters the data into several groups based on its geographic criteria. To refine the search operation during analysis, we proposed an approach to cluster the data using a clustering algorithm. However, with the huge data pool, overlap among clusters may happen and leads to inefficient analysis. Moreover, geomarketing is usually active in urban areas and requires clusters to be organized in a three-dimensional (3D) way (i.e. multi-level shop lots, residential apartments). This is a constraint with the current Geographic Information System (GIS) framework. To avoid this issue, we proposed a combination of market segmentation based on geographic criteria and clustering algorithm for 3D geomarketing data management. The proposed approach is capable in minimizing the overlap region during market segmentation. In this paper, geomarketing in urban area is used as a case study. Based on the case study, several locations of customers and stores in 3D are used in the test. The experiments demonstrated in this paper substantiated that the proposed approach is capable of minimizing overlapping segmentation and reducing repetitive data entries. The structure is also tested for retrieving the spatial records from the database. For marketing purposes, certain radius of point is used to analyzing marketing targets. Based on the presented tests in this paper, we strongly

  10. Impact of rainfall spatial distribution and resolution on flash floods response

    NASA Astrophysics Data System (ADS)

    Zoccatelli, Davide; Marra, Francesco; Nikolopoulos, Efthymios

    2013-04-01

    Uncertainty in flash flood forecasting critically depends on the space-time monitoring resolution of the flood-triggering rainfall. Hence, it is important to better understand at what space-time scales rainfall has to be monitored, given certain catchment and storm characteristics, and what are the effects of space-time aggregations on model simulations and forecasts. This work exploits the concept of spatial moments of catchment rainfall to quantify the dependence between rainfall spatial distribution, rainfall resolution, catchment morphology, and runoff response. The spatial moments of catchment rainfall describe rainfall organization in terms of concentration and dispersion along the flow distance coordinate. Assuming that rainfall distribution at equal flow distance is averaged by runoff propagation, these statistics provide a useful metric to examine how the catchment filters out rainfall spatial variability into runoff response. The effect of a variation in spatial rainfall resolution on spatial moments of catchment rainfall should therefore explain, at least partially, the pattern of runoff model sensitivity to spatial rainfall resolution. Since these statistics can capture the interactions between rainfall distribution and basin morphology, they can also be useful to compare its influence across scales and events. High resolution radar observations and a distributed hydrological model have been used to apply these statistics in five extreme flash floods occurred in various European regions in the period 2002-2007. This application allowed to verify the assumptions and to quantify how effective are these statistics in describing the role of spatial rainfall organization and of spatial resolution for flash flood modeling. The size of the study catchments ranges between 36 to 982 km2. The timing error introduced by neglecting the rainfall spatial variability, that ranges between -30% to 72% of the corresponding catchment response time, is well explained by

  11. Clinical Assessment of Standard and Generalized Autocalibrating Partially Parallel Acquisition Diffusion Imaging: Effects of Reduction Factor and Spatial Resolution

    PubMed Central

    Andre, J.B.; Zaharchuk, G.; Fischbein, N.J.; Augustin, M.; Skare, S.; Straka, M.; Rosenberg, J.; Lansberg, M.G.; Kemp, S.; Wijman, C.A.C.; Albers, G.W.; Schwartz, N.E.; Bammer, R.

    2012-01-01

    BACKGROUND AND PURPOSE PI improves routine EPI-based DWI by enabling higher spatial resolution and reducing geometric distortion, though it remains unclear which of these is most important. We evaluated the relative contribution of these factors and assessed their ability to increase lesion conspicuity and diagnostic confidence by using a GRAPPA technique. MATERIALS AND METHODS Four separate DWI scans were obtained at 1.5T in 48 patients with independent variation of in-plane spatial resolution (1.88 mm2 versus 1.25 mm2) and/or reduction factor (R = 1 versus R = 3). A neuroradiologist with access to clinical history and additional imaging sequences provided a reference standard diagnosis for each case. Three blinded neuroradiologists assessed scans for abnormalities and also evaluated multiple imaging-quality metrics by using a 5-point ordinal scale. Logistic regression was used to determine the impact of each factor on subjective image quality and confidence. RESULTS Reference standard diagnoses in the patient cohort were acute ischemic stroke (n = 30), ischemic stroke with hemorrhagic conversion (n = 4), intraparenchymal hemorrhage (n = 9), or no acute lesion (n = 5). While readers preferred both a higher reduction factor and a higher spatial resolution, the largest effect was due to an increased reduction factor (odds ratio, 47 ± 16). Small lesions were more confidently discriminated from artifacts on R = 3 images. The diagnosis changed in 5 of 48 scans, always toward the reference standard reading and exclusively for posterior fossa lesions. CONCLUSIONS PI improves DWI primarily by reducing geometric distortion rather than by increasing spatial resolution. This outcome leads to a more accurate and confident diagnosis of small lesions. PMID:22403781

  12. Segmentation d'images a tres haute resolution spatiale basee sur l'analyse multifractale

    NASA Astrophysics Data System (ADS)

    Voorons, Matthieu

    The recent availability, in remote sensing, of very high spatial resolution images brings the texture classification of images to a higher level of complexity. The singularity content of very high spatial resolution images, such as those from IKONOS, is very important due to the high local variability of their gray level. Such images have so many details that classical classification algorithms fail to achieve good results. In the case of IKONOS images of forest areas, a texture can be so different within a same class, that it becomes very difficult, even for a human, to classify or interpret them. The study of the high frequency content of the data seems to be a good way to study those images. The multifractal analysis provides us with global and local information on the singularities which represent the high frequency content of the image. We propose a new approach which uses the singularities of the image to achieve the classification of very high spatial resolution optical forestry images. It is based on the computation of the Holder regularity exponent at each point in the image. From this parameter we can compute the local Lacunarity spectrum or the large deviation multifractal spectrum which give information about the geometric distribution of the singularities in the image. So we use global and local descriptors of the regularity of the signal as input parameters to a k-means algorithm. The two algorithms are described and applied to an IKONOS image of forestry as well as to two artificial images, one made of Brodatz textures and the other of fractional brownian motions. The classification results are compared to those obtained with the gabor filters, the laws filters, the fractal dimension, the gaussian Markov random fields and the Haralick co-occurrence parameters. The proposed methods give good results and are even able to segment the image in tree density classes. We also devised tests to see the resistance of the discrimination power of the proposed

  13. Effects of WENO flux reconstruction order and spatial resolution on reshocked two-dimensional Richtmyer-Meshkov instability

    SciTech Connect

    Latini, M; Schilling, O; Don, W S

    2006-06-12

    Weighted essentially non-oscillatory (WENO) simulations of the reshocked two-dimensional single-mode Richtmyer-Meshkov instability using third-, fifth- and ninth-order spatial flux reconstruction and uniform grid resolutions corresponding to 128, 256 and 512 points per initial perturbation wavelength are presented. The dependence of the density, vorticity, simulated density Schlieren and baroclinic production fields, mixing layer width, circulation deposition, mixing profiles, production and mixing fractions, energy spectra, statistics, probability distribution functions, numerical turbulent kinetic energy and enstrophy production/dissipation rates, numerical Reynolds numbers, and numerical viscosity on the order and resolution is investigated to long evolution times. The results are interpreted using the implicit numerical dissipation in the characteristic projection-based, finite-difference WENO method. It is shown that higher order higher resolution simulations have lower numerical dissipation. The sensitivity of the quantities considered to the order and resolution is further amplified following reshock, when the energy deposition by the second shock-interface interaction induces the formation of small-scale structures. Lower-order lower-resolution simulations preserve large-scale structures and flow symmetry to late times, while higher-order higher-resolution simulations exhibit fragmentation of the structures, symmetry breaking and increased mixing. Similar flow features are qualitatively and quantitatively captured by either approximately doubling the order or the resolution. Additionally, the computational scaling shows that increasing the order is more advantageous than increasing the resolution for the flow considered here. The present investigation suggests that the ninth-order WENO method is well-suited for the simulation and analysis of complex multi-scale flows and mixing generated by shock-induced hydrodynamic instabilities.

  14. Ultrashort microwave-induced thermoacoustic imaging: a breakthrough in excitation efficiency and spatial resolution.

    PubMed

    Lou, Cunguang; Yang, Sihua; Ji, Zhong; Chen, Qun; Xing, Da

    2012-11-21

    With theoretical prediction and experimental validation, we propose a novel approach to significantly enhance the conversion efficiency of thermoacoustic (TA) imaging by using an ultrashort microwave pulse. The implementation of the ultrashort microwave pulse leads to orders of magnitude enhancement in excitation efficiency and spatial resolution, compared to that from existing TA imaging techniques. This allows high-resolution (~ 100 micron resolution) TA imaging to be acquired noninvasively. The present work represents a major breakthrough in the conversion efficiency of the TA effect and the resolution of TA imaging, which can potentially be used for clinical imaging.

  15. Evaluating the Value of High Spatial Resolution in National Capacity Expansion Models using ReEDS

    SciTech Connect

    Krishnan, Venkat; Cole, Wesley

    2016-07-18

    This poster is based on the paper of the same name, presented at the IEEE Power & Energy Society General Meeting, July18, 2016. Power sector capacity expansion models (CEMs) have a broad range of spatial resolutions. This paper uses the Regional Energy Deployment System (ReEDS) model, a long-term national scale electric sector CEM, to evaluate the value of high spatial resolution for CEMs. ReEDS models the United States with 134 load balancing areas (BAs) and captures the variability in existing generation parameters, future technology costs, performance, and resource availability using very high spatial resolution data, especially for wind and solar modeled at 356 resource regions. In this paper we perform planning studies at three different spatial resolutions - native resolution (134 BAs), state-level, and NERC region level - and evaluate how results change under different levels of spatial aggregation in terms of renewable capacity deployment and location, associated transmission builds, and system costs. The results are used to ascertain the value of high geographically resolved models in terms of their impact on relative competitiveness among renewable energy resources.

  16. Spatial resolution of a spherical x-ray crystal spectrometer at various magnifications

    SciTech Connect

    Gao, Lan; Hill, K. W.; Bitter, M.; Efthimion, P. C.; Delgado-Aparicio, L.; Pablant, N. A.; Baronova, E. O.; Pereira, N. R.

    2016-08-23

    Here, a high spatial resolution of a few μm is often required for probing small-scale high-energy-density plasmas using high resolution x-ray imaging spectroscopy. This resolution can be achieved by adjusting system magnification to overcome the inherent limitation of the detector pixel size. Laboratory experiments on investigating the relation between spatial resolution and system magnification for a spherical crystal spectrometer are presented. Tungsten Lβ2 rays from a tungsten-target micro-focus x-ray tube were diffracted by a Ge 440 crystal, which was spherically bent to a radius of 223 mm, and imaged onto an x-ray CCD with 13-μm pixel size. The source-to-crystal (p) and crystal-to-detector (q) distances were varied to produce spatial magnifications (M = q/p) ranging from 2 to 10. The inferred instrumental spatial width reduces with increasing system magnification M. However, the experimental measurement at each M is larger than the theoretical value of pixel size divided by M. Future work will focus on investigating possible broadening mechanisms that limit the spatial resolution.

  17. Spatial resolution of a spherical x-ray crystal spectrometer at various magnifications

    NASA Astrophysics Data System (ADS)

    Gao, Lan; Hill, K. W.; Bitter, M.; Efthimion, P. C.; Delgado-Aparicio, L.; Pablant, N. A.; Baronova, E. O.; Pereira, N. R.

    2016-11-01

    A high spatial resolution of a few μm is often required for probing small-scale high-energy-density plasmas using high resolution x-ray imaging spectroscopy. This resolution can be achieved by adjusting system magnification to overcome the inherent limitation of the detector pixel size. Laboratory experiments on investigating the relation between spatial resolution and system magnification for a spherical crystal spectrometer are presented. Tungsten Lβ2 rays from a tungsten-target micro-focus x-ray tube were diffracted by a Ge 440 crystal, which was spherically bent to a radius of 223 mm, and imaged onto an x-ray CCD with 13-μm pixel size. The source-to-crystal (p) and crystal-to-detector (q) distances were varied to produce spatial magnifications (M = q/p) ranging from 2 to 10. The inferred instrumental spatial width reduces with increasing system magnification M. However, the experimental measurement at each M is larger than the theoretical value of pixel size divided by M. Future work will focus on investigating possible broadening mechanisms that limit the spatial resolution.

  18. The effect of spatial resolution upon cloud optical property retrievals. I - Optical thickness

    NASA Technical Reports Server (NTRS)

    Feind, Rand E.; Christopher, Sundar A.; Welch, Ronald M.

    1992-01-01

    High spectral and spatial resolution Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) imagery is used to study the effects of spatial resolution upon fair weather cumulus cloud optical thickness retrievals. As a preprocessing step, a variation of the Gao and Goetz three-band ratio technique is used to discriminate clouds from the background. The combination of the elimination of cloud shadow pixels and using the first derivative of the histogram allows for accurate cloud edge discrimination. The data are progressively degraded from 20 m to 960 m spatial resolution. The results show that retrieved cloud area increases with decreasing spatial resolution. The results also show that there is a monotonic decrease in retrieved cloud optical thickness with decreasing spatial resolution. It is also demonstrated that the use of a single, monospectral reflectance threshold is inadequate for identifying cloud pixels in fair weather cumulus scenes and presumably in any inhomogeneous cloud field. Cloud edges have a distribution of reflectance thresholds. The incorrect identification of cloud edges significantly impacts the accurate retrieval of cloud optical thickness values.

  19. The effect of spatial resolution upon cloud optical property retrievals. I - Optical thickness

    NASA Technical Reports Server (NTRS)

    Feind, Rand E.; Christopher, Sundar A.; Welch, Ronald M.

    1992-01-01

    High spectral and spatial resolution Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) imagery is used to study the effects of spatial resolution upon fair weather cumulus cloud optical thickness retrievals. As a preprocessing step, a variation of the Gao and Goetz three-band ratio technique is used to discriminate clouds from the background. The combination of the elimination of cloud shadow pixels and using the first derivative of the histogram allows for accurate cloud edge discrimination. The data are progressively degraded from 20 m to 960 m spatial resolution. The results show that retrieved cloud area increases with decreasing spatial resolution. The results also show that there is a monotonic decrease in retrieved cloud optical thickness with decreasing spatial resolution. It is also demonstrated that the use of a single, monospectral reflectance threshold is inadequate for identifying cloud pixels in fair weather cumulus scenes and presumably in any inhomogeneous cloud field. Cloud edges have a distribution of reflectance thresholds. The incorrect identification of cloud edges significantly impacts the accurate retrieval of cloud optical thickness values.

  20. Spatial resolution of a spherical x-ray crystal spectrometer at various magnifications.

    PubMed

    Gao, Lan; Hill, K W; Bitter, M; Efthimion, P C; Delgado-Aparicio, L; Pablant, N A; Baronova, E O; Pereira, N R

    2016-11-01

    A high spatial resolution of a few μm is often required for probing small-scale high-energy-density plasmas using high resolution x-ray imaging spectroscopy. This resolution can be achieved by adjusting system magnification to overcome the inherent limitation of the detector pixel size. Laboratory experiments on investigating the relation between spatial resolution and system magnification for a spherical crystal spectrometer are presented. Tungsten Lβ2 rays from a tungsten-target micro-focus x-ray tube were diffracted by a Ge 440 crystal, which was spherically bent to a radius of 223 mm, and imaged onto an x-ray CCD with 13-μm pixel size. The source-to-crystal (p) and crystal-to-detector (q) distances were varied to produce spatial magnifications (M = q/p) ranging from 2 to 10. The inferred instrumental spatial width reduces with increasing system magnification M. However, the experimental measurement at each M is larger than the theoretical value of pixel size divided by M. Future work will focus on investigating possible broadening mechanisms that limit the spatial resolution.

  1. Impact of spatial resolution on correlation between segmentation evaluation metrics and forest classification accuracy

    NASA Astrophysics Data System (ADS)

    Švab Lenarčič, Andreja; Ritlop, Klemen; Äńurić, Nataša.; Čotar, Klemen; Oštir, Krištof

    2015-10-01

    Slovenia is one of the most forested countries in Europe. Its forest management authorities need information about the forest extent and state, as their responsibility lies in forest observation and preservation. Together with appropriate geographic information system mapping methods the remotely sensed data represent essential tool for an effective and sustainable forest management. Despite the large data availability, suitable mapping methods still present big challenge in terms of their speed which is often affected by the huge amount of data. The speed of the classification method could be maximised, if each of the steps in object-based classification was automated. However, automation is hard to achieve, since segmentation requires choosing optimum parameter values for optimal classification results. This paper focuses on the analysis of segmentation and classification performance and their correlation in a range of segmentation parameter values applied in the segmentation step. In order to find out which spatial resolution is still suitable for forest classification, forest classification accuracies obtained by using four images with different spatial resolutions were compared. Results of this study indicate that all high or very high spatial resolutions are suitable for optimal forest segmentation and classification, as long as appropriate scale and merge parameters combinations are used in the object-based classification. If computation interval includes all segmentation parameter combinations, all segmentation-classification correlations are spatial resolution independent and are generally high. If computation interval includes over- or optimal-segmentation parameter combinations, most segmentation-classification correlations are spatial resolution dependent.

  2. Spatial resolution of a spherical x-ray crystal spectrometer at various magnifications

    DOE PAGES

    Gao, Lan; Hill, K. W.; Bitter, M.; ...

    2016-08-23

    Here, a high spatial resolution of a few μm is often required for probing small-scale high-energy-density plasmas using high resolution x-ray imaging spectroscopy. This resolution can be achieved by adjusting system magnification to overcome the inherent limitation of the detector pixel size. Laboratory experiments on investigating the relation between spatial resolution and system magnification for a spherical crystal spectrometer are presented. Tungsten Lβ2 rays from a tungsten-target micro-focus x-ray tube were diffracted by a Ge 440 crystal, which was spherically bent to a radius of 223 mm, and imaged onto an x-ray CCD with 13-μm pixel size. The source-to-crystal (p)more » and crystal-to-detector (q) distances were varied to produce spatial magnifications (M = q/p) ranging from 2 to 10. The inferred instrumental spatial width reduces with increasing system magnification M. However, the experimental measurement at each M is larger than the theoretical value of pixel size divided by M. Future work will focus on investigating possible broadening mechanisms that limit the spatial resolution.« less

  3. Spatial resolution of a spherical x-ray crystal spectrometer at various magnifications

    SciTech Connect

    Gao, Lan Hill, K. W.; Bitter, M.; Efthimion, P. C.; Delgado-Aparicio, L.; Pablant, N. A.; Baronova, E. O.; Pereira, N. R.

    2016-11-15

    A high spatial resolution of a few μm is often required for probing small-scale high-energy-density plasmas using high resolution x-ray imaging spectroscopy. This resolution can be achieved by adjusting system magnification to overcome the inherent limitation of the detector pixel size. Laboratory experiments on investigating the relation between spatial resolution and system magnification for a spherical crystal spectrometer are presented. Tungsten Lβ{sub 2} rays from a tungsten-target micro-focus x-ray tube were diffracted by a Ge 440 crystal, which was spherically bent to a radius of 223 mm, and imaged onto an x-ray CCD with 13-μm pixel size. The source-to-crystal (p) and crystal-to-detector (q) distances were varied to produce spatial magnifications (M = q/p) ranging from 2 to 10. The inferred instrumental spatial width reduces with increasing system magnification M. However, the experimental measurement at each M is larger than the theoretical value of pixel size divided by M. Future work will focus on investigating possible broadening mechanisms that limit the spatial resolution.

  4. High-spatial-resolution passive microwave sounding systems

    NASA Technical Reports Server (NTRS)

    Staelin, David H.; Barrett, J. W.; Bonanni, Pierino Gianni; Chiarchiaro, W. J., II; Rosenkranz, P. W.

    1991-01-01

    During this period the emphasis was on the following: (1) further design, construction, and testing of the improved 54-GHz portion of the 54-118 GHz microwave temperature sounder (MTS) aircraft radiometer system in preparation for ER-2 observations in July 1991; and (2) final analysis and documentation of procedures for detecting and analyzing thermal waves in our 118-GHz MTS imagery. In addition, we have new unpublished measurements of dry-air attenuation at frequencies of 54 to 66 GHz and over a temperature range of 280K to 326K; these measurements should enable us to improve further our atmospheric transmittance models. It was further noted that the proposed SSMIS conical-scanning microwave spectrometer on the military DMSP Block 5D-3 spacecraft designed to measure stratospheric and mesospheric temperature profiles will be observing the Zeeman-split oxygen lines with sufficient spectral resolution that the changing Doppler shifts with view angle will substantially degrade the potential system performance unless remedied; this was briefly studied and documented.

  5. Study of spatial resolution of coordinate detectors based on Gas Electron Multipliers

    NASA Astrophysics Data System (ADS)

    Kudryavtsev, V. N.; Maltsev, T. V.; Shekhtman, L. I.

    2017-02-01

    Spatial resolution of GEM-based tracking detectors is determined in the simulation and measured in the experiments. The simulation includes GEANT4 implemented transport of high energy electrons with careful accounting of atomic relaxation processes including emission of fluorescent photons and Auger electrons and custom post-processing with accounting of diffusion, gas amplification fluctuations, distribution of signals on readout electrodes, electronics noise and particular algorithm of final coordinate calculation (center of gravity). The simulation demonstrates that the minimum of spatial resolution of about 10 μm can be achieved with a gas mixture of Ar -CO2 (75-25 %) at a strips pitch from 250 μm to 300 μm. At a larger pitch the resolution quickly degrades reaching 80-100 μm at a pitch of 460-500 μm. Spatial resolution of low-material triple-GEM detectors for the DEUTERON facility at the VEPP-3 storage ring is measured at the extracted beam facility of the VEPP-4 M collider. One-coordinate resolution of the DEUTERON detector is measured with electron beam of 500 MeV, 1 GeV and 3.5 GeV energies. The determined value of spatial resolution varies in the range from approximately 35 μm to 50 μm for orthogonal tracks in the experiments.

  6. The Importance of High Spatial and Appropriate Spectral Resolution Spectroscopy

    NASA Technical Reports Server (NTRS)

    Gull, Theodore

    2007-01-01

    Many diverse astronomical sources are resolved with diffraction-limited large telescopes. Application of appropriate dispersion spectroscopy unveils much information on the physics of these objects ranging from gamma ray bursters in host galaxies, star-formation regions and central engines in nearby galaxies, structures in galactic nebulae, resolved binaries with mass exchange, extended winds of massive stars, protoplanetary systems, and comets, asteroids and planets within our own solar system. Active optics and interferometers coupled with spectrographs can provide near-diffraction-limited spectroscopy from the ground but only longward of one micron. Below one micron, and certainly below 6000A, we must turn to space-based large telescopes equipped with spectrographs capable of providing spatially diffraction-limited spectroscopy of astronomical sources. Examples will be presented from the HST/STIS, ground-based and other instruments on science that has been accomplished. Suggestions will be made of what might be possible, and limitations thereof, with future large monolithic, multiple mirror or interferometric telescopes equipped with spectrographs that would be matched to the diffraction limit of the telescope.

  7. Effects of configural processing on the perceptual spatial resolution for face features.

    PubMed

    Namdar, Gal; Avidan, Galia; Ganel, Tzvi

    2015-11-01

    Configural processing governs human perception across various domains, including face perception. An established marker of configural face perception is the face inversion effect, in which performance is typically better for upright compared to inverted faces. In two experiments, we tested whether configural processing could influence basic visual abilities such as perceptual spatial resolution (i.e., the ability to detect spatial visual changes). Face-related perceptual spatial resolution was assessed by measuring the just noticeable difference (JND) to subtle positional changes between specific features in upright and inverted faces. The results revealed robust inversion effect for spatial sensitivity to configural-based changes, such as the distance between the mouth and the nose, or the distance between the eyes and the nose. Critically, spatial resolution for face features within the region of the eyes (e.g., the interocular distance between the eyes) was not affected by inversion, suggesting that the eye region operates as a separate 'gestalt' unit which is relatively immune to manipulations that would normally hamper configural processing. Together these findings suggest that face orientation modulates fundamental psychophysical abilities including spatial resolution. Furthermore, they indicate that classic psychophysical methods can be used as a valid measure of configural face processing. Copyright © 2015 Elsevier Ltd. All rights reserved.

  8. Effects of Spatial Resolution on the Simulated Dust Aerosol Lifecycle: Implications for Dust Event Magnitude and Timing in the NASA GEOS-5 AGCM

    NASA Technical Reports Server (NTRS)

    Nowottnick, E.; Colarco, Peter R.; daSilva, A.

    2011-01-01

    The NASA GEOS-5 atmospheric transport model simulates global aerosol distributions with an online aerosol module. GEOS-5 may be run at various horizontal spatial resolutions depending on the research application. For example, long integration climate simulations are typically run at 2 deg or 1 deg grid spacing, whereas aerosol reanalysis and forecasting applications may be performed at O.5 deg or 0.25 deg resolutions. In this study, we assess the implications of varying spatial resolution on the simulated aerosol fields, with a particular focus on dust. Dust emissions in GEOS-5 are calculated with one of two parameterizations, one based on the Goddard Chemistry, Aerosol, Radiation, and Transport (GO CART) model and another based on the Dust Entrainment and Deposition (DEAD) model. Emission fluxes are parameterized in terms of the surface wind speed, either the 10-m (GO CART) or friction (DEAD) wind speed. We consider how surface wind speeds and thus the dust emission rates are a function of the model spatial resolution. We find that spatial resolution has a significant effect on the magnitude of dust emissions, as higher resolution versions of the model have typically higher surface wind speeds. Utilizing space-borne observations from MISR, MODIS, and CALIOP, we find that simulated Aerosol Optical Thickness (AOT) distributions respond differently to spatial resolution over the African and Asian source regions, highlighting the need to regional dust emission tuning. When compared to ground-based observations from AERONET, we found improved timing of dust events with as spatial resolution was increased. In an attempt to improve the representation of the dust aerosol lifecycle at coarse resolutions, we found that incorporating the effects of sub-grid wind variability in a course resolution simulation led to improved agreement with observed AOT magnitudes, but did not impact the timing of simulated dust events.

  9. Progressive refining of spatial and temporal resolutions in a hydrological model: how far should we go?

    NASA Astrophysics Data System (ADS)

    de Lavenne, Alban; Ficchi, Andrea; Goullet, Julien

    2017-04-01

    Choosing a modelling resolution for an hydrological model is an important preliminary question. However, it is quite often arbitrary determined by the modeller experience according to the objective, the model capacity or the available measurements. The hydrological literature provides numerous studies which focus on the effect of refining either spatial resolution or (sometimes) temporal resolution in order to better catch hydrological response. In this study, we investigate the impact of changing simultaneously both resolutions on hydrological model performance. The idea is that these resolutions are linked and should be considered together. Thus, we look for the combination of spatial and temporal resolutions fitting at best each catchment behaviour and type of rainfall events. A large data set of 240 catchments scattered all around France is used, and in particular, we benefit from a high-resolution precipitation database (ANTILOPE, Météo-France) that describes hourly precipitation at 1 km2 resolution. Data were aggregated at different time steps (1h, 3h, 6h, 12h and 24h). Streamflow simulations are performed at these different time steps using the GR5 model in its lumped and semi-distributed version (GRSD, de Lavenne et al. (2016)), with a mesh grid of 500, 250, 100 and 50 km2. Ten different indices are used to describe spatio-temporal characteristics of rainfall events, in order to analyse in which contexts refined resolutions are needed to improve the performance of the model. These indices characterise the spatial variability, localisation, movement, intensity and temporal variability of rainfall events. In addition to some indices already reported in the hydrological literature, we propose some new indices like an indice usually applied in economics. This analysis at different time steps, events and catchments demonstrates the limits for some of them and allows to propose some corrections (Goullet J., 2016). Model performances are shown to be

  10. Full-field, high-spatial-resolution detection of local structural damage from low-resolution random strain field measurements

    NASA Astrophysics Data System (ADS)

    Yang, Yongchao; Sun, Peng; Nagarajaiah, Satish; Bachilo, Sergei M.; Weisman, R. Bruce

    2017-07-01

    Structural damage is typically a local phenomenon that initiates and propagates within a limited area. As such high spatial resolution measurement and monitoring is often needed for accurate damage detection. This requires either significantly increased costs from denser sensor deployment in the case of global simultaneous/parallel measurements, or increased measurement time and labor in the case of global sequential measurements. This study explores the feasibility of an alternative approach to this problem: a computational solution in which a limited set of randomly positioned, low-resolution global strain measurements are used to reconstruct the full-field, high-spatial-resolution, two-dimensional (2D) strain field and rapidly detect local damage. The proposed approach exploits the implicit low-rank and sparse data structure of the 2D strain field: it is highly correlated without many edges and hence has a low-rank structure, unless damage-manifesting itself as sparse local irregularity-is present and alters such a low-rank structure slightly. Therefore, reconstruction of the full-field, high-spatial-resolution strain field from a limited set of randomly positioned low-resolution global measurements is modeled as a low-rank matrix completion framework and damage detection as a sparse decomposition formulation, enabled by emerging convex optimization techniques. Numerical simulations on a plate structure are conducted for validation. The results are discussed and a practical iterative global/local procedure is recommended. This new computational approach should enable the efficient detection of local damage using limited sets of strain measurements.

  11. High-spatial-resolution passive microwave sounding systems

    NASA Technical Reports Server (NTRS)

    Staelin, D. H.; Rosenkranz, P. W.

    1994-01-01

    The principal contributions of this combined theoretical and experimental effort were to advance and demonstrate new and more accurate techniques for sounding atmospheric temperature, humidity, and precipitation profiles at millimeter wavelengths, and to improve the scientific basis for such soundings. Some of these techniques are being incorporated in both research and operational systems. Specific results include: (1) development of the MIT Microwave Temperature Sounder (MTS), a 118-GHz eight-channel imaging spectrometer plus a switched-frequency spectrometer near 53 GHz, for use on the NASA ER-2 high-altitude aircraft, (2) conduct of ER-2 MTS missions in multiple seasons and locations in combination with other instruments, mapping with unprecedented approximately 2-km lateral resolution atmospheric temperature and precipitation profiles, atmospheric transmittances (at both zenith and nadir), frontal systems, and hurricanes, (3) ground based 118-GHz 3-D spectral images of wavelike structure within clouds passing overhead, (4) development and analysis of approaches to ground- and space-based 5-mm wavelength sounding of the upper stratosphere and mesosphere, which supported the planning of improvements to operational weather satellites, (5) development of improved multidimensional and adaptive retrieval methods for atmospheric temperature and humidity profiles, (6) development of combined nonlinear and statistical retrieval techniques for 183-GHz humidity profile retrievals, (7) development of nonlinear statistical retrieval techniques for precipitation cell-top altitudes, and (8) numerical analyses of the impact of remote sensing data on the accuracy of numerical weather predictions; a 68-km gridded model was used to study the spectral properties of error growth.

  12. The variation of intrinsic spatial resolution across the UFOV of scintillation cameras.

    PubMed

    Papanastassiou, Emmanouil K; Psarrakos, Kyriakos; Sioundas, Anastasios; Ballas, Apostolos; Koufogiannis, Dimitrios; Hatziioannou, Konstantinos

    2006-12-01

    The aim of the present study was to investigate in detail the variation of the intrinsic spatial resolution across the useful field of view (UFOV) of gamma-cameras and to explore whether this variation could lead to observable effects in clinical images. Two gamma-cameras were used, without their collimators, to acquire 560 (99m)Tc point source images at different points across their UFOVs, in order to measure the intrinsic spatial resolution at each point. Possible clinical effects of the resolution variation were examined on images of a thyroid phantom using a LEHR collimator, acquired at different locations on the UFOV and at various distances from the collimator. The gamma-camera intrinsic resolution varied significantly across the UFOV, being generally lower at the central region and deteriorating at the edges. Pronounced local maxima and minima were found at points corresponding to the centers of the photomultiplier tubes (PMTs) and halfway in between. Maximum differences of more than 50% were observed between the points presenting the best and worst intrinsic resolution. Differences between neighboring points reached 17%. The effects of resolution variation were clearly observable on the thyroid phantom images. It was concluded that an appropriate correction algorithm might be necessary in order to correct for the variation of the intrinsic spatial resolution across the UFOV of gamma-cameras.

  13. High spatial resolution, dynamic, and distributed fiber optic strain sensing based on phasorial Brillouin dynamic gratings reflectometry

    NASA Astrophysics Data System (ADS)

    Bergman, A.; Langer, T.; Tur, M.

    2016-05-01

    We present a novel fiber-optic sensing technique based on the distributed measurement of Brillouin-induced phase-shift in the reflection from Brillouin dynamic gratings in polarization-maintaining fibers. Subject to signal to noise considerations, the strain sensitivity of the phase-shift in the reflection of a pulsed probe, orthogonally polarized to the gratings-generating pumps, is independent of the pulse width, suggesting the potential to achieve higher spatial resolutions than those offered by slope-assisted, phasorial Brillouin sensing techniques in standard single-mode fibers. We report the measurement of 500Hz strain vibrations (at a sampling rate of 1MHz) with a spatial resolution of 20cm.

  14. Effects of WENO flux reconstruction order and spatial resolution on reshocked two-dimensional Richtmyer-Meshkov instability

    SciTech Connect

    Latini, M; Schilling, O; Don, W

    2006-03-16

    Finite-difference weighted essentially non-oscillatory (WENO) simulations of the reshocked two-dimensional single-mode Richtmyer-Meshkov instability using third-, fifth- and ninth-order spatial flux reconstruction and uniform spatial grid resolutions corresponding to 128, 256 and 512 points per initial perturbation wavelength are presented. The dependence of the density, vorticity, simulated density Schlieren and baroclinic production fields, mixing layer width, circulation deposition, mixing profiles, chemical products and mixing fractions, energy spectra, statistics, probability distribution functions, effective turbulent kinetic energy and enstrophy production/dissipation rates, numerical Reynolds numbers, and effective numerical viscosity on the order and resolution is comprehensively investigated to long evolution times. The results are interpreted using the computed implicit numerical diffusion arising from the truncation errors in the characteristic projection-based WENO method. It is quantitatively shown that simulations with higher order and higher resolution have lower numerical dissipation. The sensitivity of the quantities considered to the order and resolution is further amplified following reshock, when the energy deposition on the evolving interface by the second shock-interface interaction induces the formation of small-scale structures. Simulations using lower orders of reconstruction and on coarser grids preserve large-scale structures and flow symmetry to late times, while simulations using higher orders of reconstruction and on finer grids exhibit fragmentation of the structures, symmetry breaking and increased mixing. The investigation demonstrates that similar flow features are qualitatively and quantitatively captured by either approximately doubling the order or the resolution. Additionally, the computational scaling shows that increasing the order is more advantageous than doubling the resolution for the complex shock-driven hydrodynamic

  15. Direct Imaging of Single Cells and Tissue at Subcellular Spatial Resolution Using Transmission Geometry MALDI MS

    PubMed Central

    Zavalin, Andre; Todd, Erik M.; Rawhouser, Patrick D.; Yang, Junhai; Norris, Jeremy L.; Caprioli, Richard M.

    2012-01-01

    The need of cellular and sub-cellular spatial resolution in LDI / MALDI Imaging Mass Spectrometry (IMS) necessitates micron and sub-micron laser spot sizes at biologically relevant sensitivities, introducing significant challenges for MS technology. To this end we have developed a transmission geometry vacuum ion source that allows the laser beam to irradiate the back side of the sample. This arrangement obviates the mechanical / ion optic complications in the source by completely separating the optical lens and ion optic structures. We have experimentally demonstrated the viability of transmission geometry MALDI MS for imaging biological tissues and cells with sub-cellular spatial resolution. Furthermore, we demonstrate that in conjunction with new sample preparation protocols, the sensitivity of this instrument is sufficient to obtain molecular images at sub-micron spatial resolution. PMID:23147833

  16. Differential pulse-width pair BOTDA for high spatial resolution sensing.

    PubMed

    Li, Wenhai; Bao, Xiaoyi; Li, Yun; Chen, Liang

    2008-12-22

    A differential pulse-width pair Brillouin optical time domain analysis (DPP-BOTDA) for centimeter spatial resolution sensing using meter equivalent pulses is proposed. This scheme uses the time domain waveform subtraction at the same scanned Brillouin frequency obtained from pulse lights with different pulse-widths (e.g. 50ns and 49ns) to form the differential Brillouin gain spectrum (BGS) at each fiber location. The spatial resolution is defined by the average of the rise and fall time equivalent fiber length for a small stress section rather than the pulse-width difference equivalent length. The spatial resolution of 0.18m for the 50/49ns pulse pair and 0.15m for 20/19ns pulse pair over 1km sensing length with Brillouin frequency shift accuracy of 2.6MHz are demonstrated.

  17. Multimodality hard-x-ray imaging of a chromosome with nanoscale spatial resolution

    NASA Astrophysics Data System (ADS)

    Yan, Hanfei; Nazaretski, Evgeny; Lauer, Kenneth; Huang, Xiaojing; Wagner, Ulrich; Rau, Christoph; Yusuf, Mohammed; Robinson, Ian; Kalbfleisch, Sebastian; Li, Li; Bouet, Nathalie; Zhou, Juan; Conley, Ray; Chu, Yong S.

    2016-02-01

    We developed a scanning hard x-ray microscope using a new class of x-ray nano-focusing optic called a multilayer Laue lens and imaged a chromosome with nanoscale spatial resolution. The combination of the hard x-ray’s superior penetration power, high sensitivity to elemental composition, high spatial-resolution and quantitative analysis creates a unique tool with capabilities that other microscopy techniques cannot provide. Using this microscope, we simultaneously obtained absorption-, phase-, and fluorescence-contrast images of Pt-stained human chromosome samples. The high spatial-resolution of the microscope and its multi-modality imaging capabilities enabled us to observe the internal ultra-structures of a thick chromosome without sectioning it.

  18. Multimodality hard-x-ray imaging of a chromosome with nanoscale spatial resolution

    DOE PAGES

    Yan, Hanfei; Nazaretski, Evgeny; Lauer, Kenneth R.; ...

    2016-02-05

    Here, we developed a scanning hard x-ray microscope using a new class of x-ray nano-focusing optic called a multilayer Laue lens and imaged a chromosome with nanoscale spatial resolution. The combination of the hard x-ray's superior penetration power, high sensitivity to elemental composition, high spatial-resolution and quantitative analysis creates a unique tool with capabilities that other microscopy techniques cannot provide. Using this microscope, we simultaneously obtained absorption-, phase-, and fluorescence-contrast images of Pt-stained human chromosome samples. The high spatial-resolution of the microscope and its multi-modality imaging capabilities enabled us to observe the internal ultra-structures of a thick chromosome without sectioningmore » it.« less

  19. Study of spatial resolution of proton computed tomography using a silicon strip detector

    NASA Astrophysics Data System (ADS)

    Saraya, Y.; Izumikawa, T.; Goto, J.; Kawasaki, T.; Kimura, T.

    2014-01-01

    Proton computed tomography (CT) is an imaging technique using a high-energy proton beam penetrating the human body and shows promise for improving the quality of cancer therapy with high-energy particle beams because more accurate electron density distribution measurements can be achieved with proton CT. The deterioration of the spatial resolution owing to multiple Coulomb scattering is, however, a crucial issue. The control of the radiation dose and the long exposure time are also problems to be solved. We have developed a prototype system for proton CT with a silicon strip detector and performed a beam test for imaging. The distribution of the electron density has been measured precisely. We also demonstrated an improvement in spatial resolution by reconstructing the proton trajectory. A spatial resolution of 0.45 mm is achieved for a 25-mm-thick polyethylene object. This will be a useful result for upgrading proton CT application for practical use.

  20. High spatial resolution ZnO scintillator for an in situ imaging device in EUV region

    NASA Astrophysics Data System (ADS)

    Arita, Ren; Nakazato, Tomoharu; Shimizu, Toshihiko; Yamanoi, Kohei; Empizo, Melvin John Fernandez; Hori, Tatsuhiro; Fukuda, Kazuhito; Minami, Yuki; Sarukura, Nobuhiko; Tanaka, Momoko; Nishikino, Masaharu; Fukuda, Tsuguo

    2014-10-01

    A single shot image of a ZnO crystal excited by the EUV laser of Kansai Photon Science Institute was captured. The evaluated EUV beam waist radii from the ZnO emission pattern along the horizontal and vertical axes are 5.0 and 4.7 μm, respectively. The expected focal spot size of EUV laser and the spatial resolution of the magnifier (including the Schwarzschild objectives and lenses) are however 1 and 4 μm, respectively. The discrepancy on the spatial resolutions is attributed to exciton diffusion. We estimated the ZnO exciton diffusion length from the effective decay time which is shortened by exciton-exciton collision quenching and which is dependence on excitation energy density. Our results indicate that the short lifetime of ZnO is required to improve the spatial resolution.

  1. Improvement of range spatial resolution of medical ultrasound imaging by element-domain signal processing

    NASA Astrophysics Data System (ADS)

    Hasegawa, Hideyuki

    2017-07-01

    The range spatial resolution is an important factor determining the image quality in ultrasonic imaging. The range spatial resolution in ultrasonic imaging depends on the ultrasonic pulse length, which is determined by the mechanical response of the piezoelectric element in an ultrasonic probe. To improve the range spatial resolution without replacing the transducer element, in the present study, methods based on maximum likelihood (ML) estimation and multiple signal classification (MUSIC) were proposed. The proposed methods were applied to echo signals received by individual transducer elements in an ultrasonic probe. The basic experimental results showed that the axial half maximum of the echo from a string phantom was improved from 0.21 mm (conventional method) to 0.086 mm (ML) and 0.094 mm (MUSIC).

  2. Multimodality hard-x-ray imaging of a chromosome with nanoscale spatial resolution

    SciTech Connect

    Yan, Hanfei; Nazaretski, Evgeny; Lauer, Kenneth R.; Huang, Xiaojing; Wagner, Ulrich; Rau, Christoph; Yusuf, Mohammed; Robinson, Ian K.; Kalbfleisch, Sebastian; Li, Li; Bouet, Nathalie; Zhou, Juan; Conley, Ray; Chu, Yong S.

    2016-02-05

    Here, we developed a scanning hard x-ray microscope using a new class of x-ray nano-focusing optic called a multilayer Laue lens and imaged a chromosome with nanoscale spatial resolution. The combination of the hard x-ray's superior penetration power, high sensitivity to elemental composition, high spatial-resolution and quantitative analysis creates a unique tool with capabilities that other microscopy techniques cannot provide. Using this microscope, we simultaneously obtained absorption-, phase-, and fluorescence-contrast images of Pt-stained human chromosome samples. The high spatial-resolution of the microscope and its multi-modality imaging capabilities enabled us to observe the internal ultra-structures of a thick chromosome without sectioning it.

  3. Multimodality hard-x-ray imaging of a chromosome with nanoscale spatial resolution

    PubMed Central

    Yan, Hanfei; Nazaretski, Evgeny; Lauer, Kenneth; Huang, Xiaojing; Wagner, Ulrich; Rau, Christoph; Yusuf, Mohammed; Robinson, Ian; Kalbfleisch, Sebastian; Li, Li; Bouet, Nathalie; Zhou, Juan; Conley, Ray; Chu, Yong S.

    2016-01-01

    We developed a scanning hard x-ray microscope using a new class of x-ray nano-focusing optic called a multilayer Laue lens and imaged a chromosome with nanoscale spatial resolution. The combination of the hard x-ray’s superior penetration power, high sensitivity to elemental composition, high spatial-resolution and quantitative analysis creates a unique tool with capabilities that other microscopy techniques cannot provide. Using this microscope, we simultaneously obtained absorption-, phase-, and fluorescence-contrast images of Pt-stained human chromosome samples. The high spatial-resolution of the microscope and its multi-modality imaging capabilities enabled us to observe the internal ultra-structures of a thick chromosome without sectioning it. PMID:26846188

  4. Extended-range high-resolution dynamical downscaling over a continental-scale spatial domain with atmospheric and surface nudging

    NASA Astrophysics Data System (ADS)

    Husain, S. Z.; Separovic, L.; Yu, W.; Fernig, D.

    2014-12-01

    Extended-range high-resolution mesoscale simulations with limited-area atmospheric models when applied to downscale regional analysis fields over large spatial domains can provide valuable information for many applications including the weather-dependent renewable energy industry. Long-term simulations over a continental-scale spatial domain, however, require mechanisms to control the large-scale deviations in the high-resolution simulated fields from the coarse-resolution driving fields. As enforcement of the lateral boundary conditions is insufficient to restrict such deviations, large scales in the simulated high-resolution meteorological fields are therefore spectrally nudged toward the driving fields. Different spectral nudging approaches, including the appropriate nudging length scales as well as the vertical profiles and temporal relaxations for nudging, have been investigated to propose an optimal nudging strategy. Impacts of time-varying nudging and generation of hourly analysis estimates are explored to circumvent problems arising from the coarse temporal resolution of the regional analysis fields. Although controlling the evolution of the atmospheric large scales generally improves the outputs of high-resolution mesoscale simulations within the surface layer, the prognostically evolving surface fields can nevertheless deviate from their expected values leading to significant inaccuracies in the predicted surface layer meteorology. A forcing strategy based on grid nudging of the different surface fields, including surface temperature, soil moisture, and snow conditions, toward their expected values obtained from a high-resolution offline surface scheme is therefore proposed to limit any considerable deviation. Finally, wind speed and temperature at wind turbine hub height predicted by different spectrally nudged extended-range simulations are compared against observations to demonstrate possible improvements achievable using higher spatiotemporal

  5. Spatially explicit rangeland erosion monitoring using high-resolution digital aerial imagery

    USGS Publications Warehouse

    Gillan, Jeffrey K.; Karl, Jason W.; Barger, Nichole N.; Elaksher, Ahmed; Duniway, Michael C.

    2016-01-01

    Nearly all of the ecosystem services supported by rangelands, including production of livestock forage, carbon sequestration, and provisioning of clean water, are negatively impacted by soil erosion. Accordingly, monitoring the severity, spatial extent, and rate of soil erosion is essential for long-term sustainable management. Traditional field-based methods of monitoring erosion (sediment traps, erosion pins, and bridges) can be labor intensive and therefore are generally limited in spatial intensity and/or extent. There is a growing effort to monitor natural resources at broad scales, which is driving the need for new soil erosion monitoring tools. One remote-sensing technique that can be used to monitor soil movement is a time series of digital elevation models (DEMs) created using aerial photogrammetry methods. By geographically coregistering the DEMs and subtracting one surface from the other, an estimate of soil elevation change can be created. Such analysis enables spatially explicit quantification and visualization of net soil movement including erosion, deposition, and redistribution. We constructed DEMs (12-cm ground sampling distance) on the basis of aerial photography immediately before and 1 year after a vegetation removal treatment on a 31-ha Piñon-Juniper woodland in southeastern Utah to evaluate the use of aerial photography in detecting soil surface change. On average, we were able to detect surface elevation change of ± 8−9cm and greater, which was sufficient for the large amount of soil movement exhibited on the study area. Detecting more subtle soil erosion could be achieved using the same technique with higher-resolution imagery from lower-flying aircraft such as unmanned aerial vehicles. DEM differencing and process-focused field methods provided complementary information and a more complete assessment of soil loss and movement than any single technique alone. Photogrammetric DEM differencing could be used as a technique to

  6. Single embryo-resolution quantitative analysis of reporters permits multiplex spatial cis-regulatory analysis.

    PubMed

    Guay, Catherine L; McQuade, Sean T; Nam, Jongmin

    2017-02-15

    Cis-regulatory modules (CRMs) control spatiotemporal gene expression patterns in embryos. While measurement of quantitative CRM activities has become efficient, measurement of spatial CRM activities still relies on slow, one-by-one methods. To overcome this bottleneck, we have developed a high-throughput method that can simultaneously measure quantitative and spatial CRM activities. The new method builds profiles of quantitative CRM activities measured at single-embryo resolution in many mosaic embryos and uses these profiles as a 'fingerprint' of spatial patterns. We show in sea urchin embryos that the new method, Multiplex and Mosaic Observation of Spatial Information encoded in Cis-regulatory modules (MMOSAIC), can efficiently predict spatial activities of new CRMs and can detect spatial responses of CRMs to gene perturbations. We anticipate that MMOSAIC will facilitate systems-wide functional analyses of CRMs in embryos. Copyright © 2017 Elsevier Inc. All rights reserved.

  7. Research on the affect of differential-images technique to the resolution of infrared spatial camera

    NASA Astrophysics Data System (ADS)

    Jin, Guang; An, Yuan; Qi, Yingchun; Hu, Fusheng

    2007-12-01

    The optical system of infrared spatial camera adopts bigger relative aperture and bigger pixel size on focal plane element. These make the system have bulky volume and low resolution. The potential of the optical systems can not be exerted adequately. So, one method for improving resolution of infrared spatial camera based on multi-frame difference-images is introduced in the dissertation. The method uses more than one detectors to acquire several difference images, and then reconstructs a new high-resolution image from these images through the relationship of pixel grey value. The technique of difference-images that uses more than two detectors is researched, and it can improve the resolution 2.5 times in theory. The relationship of pixel grey value between low-resolution difference-images and high-resolution image is found by analyzing the energy of CCD sampling, a general relationship between the enhanced times of the resolution of the detected figure with differential method and the least count of CCD that will be used to detect figure is given. Based on the research of theory, the implementation process of utilizing difference-images technique to improve the resolution of the figure was simulated used Matlab software by taking a personality image as the object, and the software can output the result as an image. The result gotten from the works we have finished proves that the technique is available in high-resolution image reconstruction. The resolution of infrared spatial camera can be improved evidently when holding the size of optical structure or using big size detector by applying for difference image technique. So the technique has a high value in optical remote fields.

  8. Crowding in Visual Working Memory Reveals Its Spatial Resolution and the Nature of Its Representations.

    PubMed

    Tamber-Rosenau, Benjamin J; Fintzi, Anat R; Marois, René

    2015-09-01

    Spatial resolution fundamentally limits any image representation. Although this limit has been extensively investigated for perceptual representations by assessing how neighboring flankers degrade the perception of a peripheral target with visual crowding, the corresponding limit for representations held in visual working memory (VWM) is unknown. In the present study, we evoked crowding in VWM and directly compared resolution in VWM and perception. Remarkably, the spatial resolution of VWM proved to be no worse than that of perception. However, mixture modeling of errors caused by crowding revealed the qualitatively distinct nature of these representations. Perceptual crowding errors arose from both increased imprecision in target representations and substitution of flankers for targets. By contrast, VWM crowding errors arose exclusively from substitutions, which suggests that VWM transforms analog perceptual representations into discrete items. Thus, although perception and VWM share a common resolution limit, exceeding this limit reveals distinct mechanisms for perceiving images and holding them in mind. © The Author(s) 2015.

  9. Performance and characterization of the prototype nm-scale spatial resolution scanning multilayer Laue lenses microscope.

    PubMed

    Nazaretski, E; Kim, Jungdae; Yan, H; Lauer, K; Eom, D; Shu, D; Maser, J; Pešić, Z; Wagner, U; Rau, C; Chu, Y S

    2013-03-01

    Synchrotron based x-ray microscopy established itself as a prominent tool for noninvasive investigations in many areas of science and technology. Many facilities around the world routinely achieve sub-micrometer resolution with a few instruments capable of imaging with the spatial resolution better than 100 nm. With an ongoing effort to push the 2D/3D resolution down to 10 nm in the hard x-ray regime both fabrication of the nano-focusing optics and stability of a microscope become extremely challenging. In this work we present our approach to overcome technical challenges on the path towards high spatial resolution hard x-ray microscopy and demonstrate the performance of a scanning fluorescence microscope equipped with the multilayer Laue lenses focusing optics.

  10. Performance and characterization of the prototype nm-scale spatial resolution scanning multilayer Laue lenses microscope

    NASA Astrophysics Data System (ADS)

    Nazaretski, E.; Kim, Jungdae; Yan, H.; Lauer, K.; Eom, D.; Shu, D.; Maser, J.; Pešić, Z.; Wagner, U.; Rau, C.; Chu, Y. S.

    2013-03-01

    Synchrotron based x-ray microscopy established itself as a prominent tool for noninvasive investigations in many areas of science and technology. Many facilities around the world routinely achieve sub-micrometer resolution with a few instruments capable of imaging with the spatial resolution better than 100 nm. With an ongoing effort to push the 2D/3D resolution down to 10 nm in the hard x-ray regime both fabrication of the nano-focusing optics and stability of a microscope become extremely challenging. In this work we present our approach to overcome technical challenges on the path towards high spatial resolution hard x-ray microscopy and demonstrate the performance of a scanning fluorescence microscope equipped with the multilayer Laue lenses focusing optics.

  11. Fundamental x-ray interaction limits in diagnostic imaging detectors: spatial resolution.

    PubMed

    Hajdok, G; Battista, J J; Cunningham, I A

    2008-07-01

    The practice of diagnostic x-ray imaging has been transformed with the emergence of digital detector technology. Although digital systems offer many practical advantages over conventional film-based systems, their spatial resolution performance can be a limitation. The authors present a Monte Carlo study to determine fundamental resolution limits caused by x-ray interactions in four converter materials: Amorphous silicon (a-Si), amorphous selenium, cesium iodide, and lead iodide. The "x-ray interaction" modulation transfer function (MTF) was determined for each material and compared in terms of the 50% MTF spatial frequency and Wagner's effective aperture for incident photon energies between 10 and 150 keV and various converter thicknesses. Several conclusions can be drawn from their Monte Carlo study. (i) In low-Z (a-Si) converters, reabsorption of Compton scatter x rays limits spatial resolution with a sharp MTF drop at very low spatial frequencies (< 0.3 cycles/mm), especially above 60 keV; while in high-Z materials, reabsorption of characteristic x rays plays a dominant role, resulting in a mid-frequency (1-5 cycles/mm) MTF drop. (ii) Coherent scatter plays a minor role in the x-ray interaction MTF. (iii) The spread of energy due to secondary electron (e.g., photoelectrons) transport is significant only at very high spatial frequencies. (iv) Unlike the spread of optical light in phosphors, the spread of absorbed energy from x-ray interactions does not significantly degrade spatial resolution as converter thickness is increased. (v) The effective aperture results reported here represent fundamental spatial resolution limits of the materials tested and serve as target benchmarks for the design and development of future digital x-ray detectors.

  12. Fundamental x-ray interaction limits in diagnostic imaging detectors: Spatial resolution

    SciTech Connect

    Hajdok, G.; Battista, J. J.; Cunningham, I. A.

    2008-07-15

    The practice of diagnostic x-ray imaging has been transformed with the emergence of digital detector technology. Although digital systems offer many practical advantages over conventional film-based systems, their spatial resolution performance can be a limitation. The authors present a Monte Carlo study to determine fundamental resolution limits caused by x-ray interactions in four converter materials: Amorphous silicon (a-Si), amorphous selenium, cesium iodide, and lead iodide. The ''x-ray interaction'' modulation transfer function (MTF) was determined for each material and compared in terms of the 50% MTF spatial frequency and Wagner's effective aperture for incident photon energies between 10 and 150 keV and various converter thicknesses. Several conclusions can be drawn from their Monte Carlo study. (i) In low-Z (a-Si) converters, reabsorption of Compton scatter x rays limits spatial resolution with a sharp MTF drop at very low spatial frequencies (<0.3 cycles/mm), especially above 60 keV; while in high-Z materials, reabsorption of characteristic x rays plays a dominant role, resulting in a mid-frequency (1-5 cycles/mm) MTF drop. (ii) Coherent scatter plays a minor role in the x-ray interaction MTF. (iii) The spread of energy due to secondary electron (e.g., photoelectrons) transport is significant only at very high spatial frequencies. (iv) Unlike the spread of optical light in phosphors, the spread of absorbed energy from x-ray interactions does not significantly degrade spatial resolution as converter thickness is increased. (v) The effective aperture results reported here represent fundamental spatial resolution limits of the materials tested and serve as target benchmarks for the design and development of future digital x-ray detectors.

  13. Ultrafast laser induced breakdown spectroscopy for high spatial resolution chemical analysis

    NASA Astrophysics Data System (ADS)

    Zorba, Vassilia; Mao, Xianglei; Russo, Richard E.

    2011-02-01

    Femtosecond laser induced breakdown spectroscopy (LIBS) was used to identify the spatial resolution limitations and assess the minimal detectable mass restrictions in laser-ablation based chemical analysis. The atomic emission of sodium (Na) and potassium (K) dopants in transparent dielectric Mica matrices was studied, to find that both these elements could be detected from 450 nm diameter ablation craters, full-width-at-half-maximum (FWHM). Under optimal conditions, mass as low as 220 ag was measured, demonstrating the feasibility of using laser-ablation based chemical analysis to achieve high spatial resolution elemental analysis in real-time and at atmospheric pressure conditions.

  14. Electron-Beam Mapping of Vibrational Modes with Nanometer Spatial Resolution.

    PubMed

    Dwyer, C; Aoki, T; Rez, P; Chang, S L Y; Lovejoy, T C; Krivanek, O L

    2016-12-16

    We demonstrate that a focused beam of high-energy electrons can be used to map the vibrational modes of a material with a spatial resolution of the order of one nanometer. Our demonstration is performed on boron nitride, a polar dielectric which gives rise to both localized and delocalized electron-vibrational scattering, either of which can be selected in our off-axial experimental geometry. Our experimental results are well supported by our calculations, and should reconcile current controversy regarding the spatial resolution achievable in vibrational mapping with focused electron beams.

  15. Electron-Beam Mapping of Vibrational Modes with Nanometer Spatial Resolution

    NASA Astrophysics Data System (ADS)

    Dwyer, C.; Aoki, T.; Rez, P.; Chang, S. L. Y.; Lovejoy, T. C.; Krivanek, O. L.

    2016-12-01

    We demonstrate that a focused beam of high-energy electrons can be used to map the vibrational modes of a material with a spatial resolution of the order of one nanometer. Our demonstration is performed on boron nitride, a polar dielectric which gives rise to both localized and delocalized electron-vibrational scattering, either of which can be selected in our off-axial experimental geometry. Our experimental results are well supported by our calculations, and should reconcile current controversy regarding the spatial resolution achievable in vibrational mapping with focused electron beams.

  16. Large-scale proton radiography with micrometer spatial resolution using femtosecond petawatt laser system

    SciTech Connect

    Wang, W. P.; Shen, B. F. Zhang, H.; Lu, X. M.; Wang, C.; Liu, Y. Q.; Yu, L. H.; Chu, Y. X.; Li, Y. Y.; Xu, T. J.; Zhang, H.; Zhai, S. H.; Leng, Y. X.; Liang, X. Y.; Li, R. X.; Xu, Z. Z.

    2015-10-15

    An image of dragonfly with many details is obtained by the fundamental property of the high-energy proton source on a femtosecond petawatt laser system. Equal imaging of the dragonfly and high spatial resolution on the micrometer scale are simultaneously obtained. The head, wing, leg, tail, and even the internal tissue structures are clearly mapped in detail by the proton beam. Experiments show that image blurring caused by multiple Coulomb scattering can be reduced to a certain extent and the spatial resolution can be increased by attaching the dragonfly to the RCFs, which is consistent with theoretical assumptions.

  17. [Spatial resolution standardization of payload on board of remote sensing satellite based on application requirements].

    PubMed

    Wei, Xiang-qin; Gu, Xing-fa; Yu, Tao; Meng, Qing-yan; Li, Bin; Guo, Hong

    2012-03-01

    Remote sensing application requirements are the starting point for design of payload on board earth observation satellite. The generalization, standardization and serialization of payload are the future development trend for payload design. In the present paper, based on the analysis of remote sensing application requirements, the spatial resolution standardization of satellite remote sensing payload, which is the main concerned indicator, was investigated. The design standards of national payload spatial resolution of earth observation satellite are presented, which are important to the promotion of satellite payload production and saving in design cost.

  18. Iterative algorithm for reconstructing rotationally asymmetric surface deviation with pixel-level spatial resolution

    NASA Astrophysics Data System (ADS)

    Quan, Haiyang; Wu, Fan; Hou, Xi

    2015-10-01

    New method for reconstructing rotationally asymmetric surface deviation with pixel-level spatial resolution is proposed. It is based on basic iterative scheme and accelerates the Gauss-Seidel method by introducing an acceleration parameter. This modified Successive Over-relaxation (SOR) is effective for solving the rotationally asymmetric components with pixel-level spatial resolution, without the usage of a fitting procedure. Compared to the Jacobi and Gauss-Seidel method, the modified SOR method with an optimal relaxation factor converges much faster and saves more computational costs and memory space without reducing accuracy. It has been proved by real experimental results.

  19. Detection efficiency, spatial and timing resolution of thermal and cold neutron counting MCP detectors

    NASA Astrophysics Data System (ADS)

    Tremsin, A. S.; McPhate, J. B.; Vallerga, J. V.; Siegmund, O. H. W.; Hull, J. S.; Feller, W. B.; Lehmann, E.

    2009-06-01

    Neutron counting detectors with boron or gadolinium doped microchannel plates (MCPs) have very high detection efficiency, spatial and temporal resolution, and have a very low readout noise. In this paper we present the results of both theoretical predictions and experimental evaluations of detection efficiency and spatial resolution measured at cold and thermal neutron beamlines. The quantum detection efficiency of a detector (not fully optimized) was measured to be 43% and 16% for the cold and thermal beamlines, respectively. The experiments also demonstrate that the spatial resolution can be better than 15 μm—highest achievable with the particular MCP pore dimension used in the experiment, although more electronics development is required in order to increase the counting rate capabilities of those <15 μm resolution devices. The timing accuracy of neutron detection is on the scale of few μs and is limited by the neutron absorption depth in the detector. The good agreement between the predicted and measured performance allows the optimization of the detector parameters in order to achieve the highest spatial resolution and detection efficiency in future devices.

  20. Simulations of the temporal and spatial resolution for a compact time-resolved electron diffractometer

    NASA Astrophysics Data System (ADS)

    Robinson, Matthew S.; Lane, Paul D.; Wann, Derek A.

    2016-02-01

    A novel compact electron gun for use in time-resolved gas electron diffraction experiments has recently been designed and commissioned. In this paper we present and discuss the extensive simulations that were performed to underpin the design in terms of the spatial and temporal qualities of the pulsed electron beam created by the ionisation of a gold photocathode using a femtosecond laser. The response of the electron pulses to a solenoid lens used to focus the electron beam has also been studied. The simulated results show that focussing the electron beam affects the overall spatial and temporal resolution of the experiment in a variety of ways, and that factors that improve the resolution of one parameter can often have a negative effect on the other. A balance must, therefore, be achieved between spatial and temporal resolution. The optimal experimental time resolution for the apparatus is predicted to be 416 fs for studies of gas-phase species, while the predicted spatial resolution of better than 2 nm-1 compares well with traditional time-averaged electron diffraction set-ups.

  1. The effect of spatial resolution on water scarcity estimates in Australia

    NASA Astrophysics Data System (ADS)

    Gevaert, Anouk; Veldkamp, Ted; van Dijk, Albert; Ward, Philip

    2017-04-01

    Water scarcity is an important global issue with severe socio-economic consequences, and its occurrence is likely to increase in many regions due to population growth, economic development and climate change. This has prompted a number of global and regional studies to identify areas that are vulnerable to water scarcity and to determine how this vulnerability will change in the future. A drawback of these studies, however, is that they typically have coarse spatial resolutions. Here, we studied the effect of increasing the spatial resolution of water scarcity estimates in Australia, and the Murray-Darling Basin in particular. This was achieved by calculating the water stress index (WSI), an indicator showing the ratio of water use to water availability, at 0.5 and 0.05 degree resolution for the period 1990-2010. Monthly water availability data were based on outputs of the Australian Water Resources Assessment Landscape model (AWRA-L), which was run at both spatial resolutions and at a daily time scale. Water use information was obtained from a monthly 0.5 degree global dataset that distinguishes between water consumption for irrigation, livestock, industrial and domestic uses. The data were downscaled to 0.05 degree by dividing the sectoral water uses over the areas covered by relevant land use types using a high resolution ( 0.5km) land use dataset. The monthly WSIs at high and low resolution were then used to evaluate differences in the patterns of water scarcity frequency and intensity. In this way, we assess to what extent increasing the spatial resolution can improve the identification of vulnerable areas and thereby assist in the development of strategies to lower this vulnerability. The results of this study provide insight into the scalability of water scarcity estimates and the added value of high resolution water scarcity information in water resources management.

  2. Low-Z target optimization for spatial resolution improvement in megavoltage imaging.

    PubMed

    Connell, Tanner; Robar, James L

    2010-01-01

    Recently, several authors have shown contrast improvements in megavoltage portal imaging and cone-beam computed tomography using low atomic number (Z) targets. This work compliments previous studies by investigating the effects of varying different beam production parameters including target atomic number, target thickness, and incident electron energy on spatial resolution. Target materials of beryllium, aluminum, and tungsten were investigated over a range of thicknesses between 10% and 100% of the continuous slowing down approximation range of electrons. Incident electron kinetic energies of 4.5 and 7.0 MeV were used, in conjunction with custom targets installed above the carousel of a modern radiotherapy linear accelerator. Monte Carlo simulations of the accelerator were constructed and compared to the experimental results. The results showed that thinner targets, as well higher incident electron energies, generally produce more favorable modulation transfer function (MTF) curves. Due to an MTF dependence of the detector system on the photon energy, the experimental results showed that low-Z targets produced superior MTF curves. Simulations showed 14.5% and 21.5% increases in f50 for the 7.0 and 4.5 MeV targets (A1; 60% R% CSDA), respectively, when moved from the carousel to the location of the clinical target. f50 values for the custom targets were compared to the clinical 6 MV beam and were found to be between 10.4% lower (4.5 MeV/W) and 15.5% higher (7.0 MeV/Be). Integration of low-Z external targets into the treatment head of a medical linear was achieved with only minor modifications. It was shown that reasonably high resolution images on par or better than those acquired with the clinical 6 MV beam can be achieved using external low-Z targets.

  3. High spatial- and temporal-resolution anthropogenic heat discharge estimation in Los Angeles County, California.

    PubMed

    Zheng, Yuanfan; Weng, Qihao

    2017-07-22

    Anthropogenic heat flux (Qf), which originates through energy consumption from buildings, industrial plants, vehicle exhausts, and human metabolism releases, is an important component in the urban Surface Energy Balance (SEB) system, and is key to understanding of many urban environmental issues. The present study provided a hybrid Qf modeling approach, which combined the inventory and GIS approach to create a 365-day hourly Qf profile at 120 m spatial resolution in Los Angeles County, California, USA. Qf was estimated by separate calculation of heat release from buildings, traffics, and human metabolism, respectively. The results indicated that Qf showed different magnitudes and diurnal patterns between workdays (dual-peak shape) and weekends/holidays, and also varied with seasons, and land use types. Qf yielded the highest values in the summer workdays, with its maximum value of 7.76 w/m(2). Qf in hot summer workdays was obviously higher than that in the average summer workdays, which caused by higher demands for space cooling in buildings, and can reach 8.14 w/m(2) at maximum. Building energy consumption was identified as the dominant contributor to the Qf in Downtown Los Angeles, which was found to have the largest mean Qf throughout the year among all neighborhoods. It can be concluded that Qf in the downtown was more significant in workdays than that in non-workdays, and its maximum value can reach 100 w/m(2). It is suggested that our approach may have wider applicability for Qf estimation in large areas compared with the existing studies, as all the data used were available to the public. A high spatial and temporal Qf profile, which can readily be incorporated into urban energy balance and Urban Heat Island (UHI) studies, provides valuable data and information for pertinent government agencies and researchers. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. Eddy Fluxes and Sensitivity of the Water Cycle to Spatial Resolution in Idealized Regional Aquaplanet Model Simulations

    SciTech Connect

    Hagos, Samson M.; Leung, Lai-Yung R.; Gustafson, William I.; Singh, Balwinder

    2014-02-28

    A multi-scale moisture budget analysis is used to identify the mechanisms responsible for the sensitivity of the water cycle to spatial resolution using idealized regional aquaplanet simulations. In the higher resolution simulations, moisture transport by eddies fluxes dry the boundary layer enhancing evaporation and precipitation. This effect of eddies, which is underestimated by the physics parameterizations in the low-resolution simulations, is found to be responsible for the sensitivity of the water cycle both directly, and through its upscale effect, on the mean circulation. Correlations among moisture transport by eddies at adjacent ranges of scales provides the potential for reducing this sensitivity by representing the unresolved eddies by their marginally resolved counterparts.

  5. Optimal Spatial Resolution of Omnidirectional Imaging Systems for Pipe Inspection Applications

    NASA Astrophysics Data System (ADS)

    Dehghan Tezerjani, Abbasali; Mehrandezh, Mehran; Paranjape, Raman

    2015-10-01

    Achieving optimal spatial resolution in imaging systems plays a major role in the design of vision-based industrial inspection tools. Single-view omnidirectional imaging systems provide a cost-effective and computationally-traceable solution for real-time inspection of infrastructure with a favorable size factor. We formulate, for the first time, the spatial cylindrical resolution of omnidirectional Catadioptric and Dioptric imaging systems with the focus on pipe inspection applications. We also provide a design guideline to achieve the highest resolution in these systems. First, we deliver a comprehensive study on optimal resolution in Catadioptric imaging systems which consist of a perspective pinhole camera, a collimated laser as the light source, and a reflective surface (i.e., hyperbolic mirror). Variation of the spatial resolution in terms of the camera's focal length, the mirror curvature, and the relative position between the laser projector and the camera is fully investigated via simulation and experiments. Also, the optimal resolution in Dioptric systems, which consist of a camera with compound refractive lenses (i.e., fish-eye lens) is studied and compared with that in Catadioptric systems. Tests were conducted on a 40-cm-diameter PVC pipe in a controlled laboratory environment.

  6. The Role of Shallow Convection in Tropical Climate via Impacts of the Model Spatial Resolution

    NASA Astrophysics Data System (ADS)

    Bui, H. X.; Chou, C.

    2014-12-01

    We examine the role of shallow convection in tropical climate, using different spatial resolutions as sensitivity studies. After examining the vertical structure and spatial distribution of tropical convection, we found that a coarser resolution produces less partition of shallow convection, while a finer resolution tends to produce greater one in convective regions. We further examine the influence of shallow convection strength on precipitation by comparing the western and eastern Pacific ITCZ. In the western Pacific ITCZ, where is dominated by deep convection, the variation of precipitation among the spatial-resolution experiments is mainly due to the contribution of thermodynamic processes. The warmer climate found in coarser resolutions enhances precipitation frequency and intensity, and then the corresponding precipitation amount. In the eastern Pacific ITCZ, which has more shallow convection, shallow convection becomes the dominant factor to determine the variation of precipitation. More partition of shallow convection found in finer resolutions tends to enhance precipitation frequency and intensity, and the total precipitation amount. This provides potential evidence that shallow convection first affects the occurrence and intensity of precipitation, and then the total amount of precipitation in the region.

  7. Impact of data assimilation on high-resolution rainfall forecasts: A spatial, seasonal, and category analysis

    NASA Astrophysics Data System (ADS)

    V, Rakesh; Goswami, Prashant

    2015-01-01

    a limited area model (LAM), the impact of data assimilation is likely to depend on the background state through lateral boundary forcing; this may introduce certain seasonality in the impact of data assimilation on rainfall forecasting. It is also likely that the impact of data assimilation on forecasts will have certain spatial variability. Finally, owing to the convective nature of rainfall and the roles of parameterization scheme, the impact of data assimilation may depend on the category (intensity) of rainfall. Here these aspects for rainfall forecasts at high resolution were examined. Using a LAM (An advanced version of Weather Research and Forecasting Model), we have carried out twin simulations with and without data assimilation; the simulations without data assimilation are used as the benchmark for assessing the impact of data assimilation. Analysis of simulations for 40 sample days distributed over the years 2012-2014 over Karnataka (southern state in India) is carried out to estimate impact of data assimilation. Various statistical measures show that data assimilation improved the rainfall prediction in most cases; however, there is also strong seasonality and location dependence in impact of data assimilation. Our results also show that improvement due to data assimilation is higher/lower for lower/higher rainfall categories. Analysis shows that the cases where the initial states with data assimilation depart strongly from the first guess generally result in less or even negative impact. It is pointed out that the results have important implications in design of observation system and assessment of impact of forecasts.

  8. Spatial resolution improvement and dose reduction potential for inner ear CT imaging using a z-axis deconvolution technique.

    PubMed

    McCollough, Cynthia H; Leng, Shuai; Sunnegardh, Johan; Vrieze, Thomas J; Yu, Lifeng; Lane, John; Raupach, Rainer; Stierstorfer, Karl; Flohr, Thomas

    2013-06-01

    spatial resolution was 12 lp/cm for the FBP-zUHR images and the IR-UHR images, although visual assessment indicated a slight improvement for the IR-UHR images. Image noise was 213.0, 181.8, and 153.5 for the FBP-zUHR, IR-zUHR, and IR-UHR images, respectively. While the FWHM was essentially the same for the FBP-zUHR and IR-UHR images, the FWTM of the IR-UHR images was almost 50% smaller compared to the FBP-zUHR images (0.83 vs 1.25 mm, respectively). Images of the anthropomorphic head phantom were judged to be of higher quality for the IR-UHR images compared to the FBP-zUHR images. With use of a z-axis deconvolution technique, z-axis spatial resolution was improved for scans acquired using a comb filter only in the fan angle direction relative to FBP images acquired with a comb filter in both the fan and cone angle directions. By avoiding use of the comb filter in the cone angle direction and use of an IR algorithm, image noise was substantially reduced for the same scanner output (CTDIvol). Thus, overall image quality (spatial resolution and image noise) can be maintained relative to the FBP-zUHR technique at a lower radiation dose.

  9. Psychosocial Maturity and Conflict Resolution Management of Higher Secondary School Students

    ERIC Educational Resources Information Center

    Jaseena M.P.M., Fathima; P., Divya

    2014-01-01

    The aim of the study is to find out the extent and difference in the mean scores of Psychosocial Maturity and Conflict Resolution Management of Higher secondary school students of Kerala. A survey technique was used for the study. Sample consists of 685 higher secondary students by giving due representation other criteria. Findings revealed that…

  10. On the sensitivity of urban hydrodynamic modelling to rainfall spatial and temporal resolution

    NASA Astrophysics Data System (ADS)

    Bruni, G.; Reinoso, R.; van de Giesen, N. C.; Clemens, F. H. L. R.; ten Veldhuis, J. A. E.

    2015-02-01

    Cities are increasingly vulnerable to floods generated by intense rainfall, because of urbanisation of flood-prone areas and ongoing urban densification. Accurate information of convective storm characteristics at high spatial and temporal resolution is a crucial input for urban hydrological models to be able to simulate fast runoff processes and enhance flood prediction in cities. In this paper, a detailed study of the sensitivity of urban hydrodynamic response to high resolution radar rainfall was conducted. Rainfall rates derived from X-band dual polarimetric weather radar were used as input into a detailed hydrodynamic sewer model for an urban catchment in the city of Rotterdam, the Netherlands. The aim was to characterise how the effect of space and time aggregation on rainfall structure affects hydrodynamic modelling of urban catchments, for resolutions ranging from 100 to 2000 m and from 1 to 10 min. Dimensionless parameters were derived to compare results between different storm conditions and to describe the effect of rainfall spatial resolution in relation to storm characteristics and hydrodynamic model properties: rainfall sampling number (rainfall resolution vs. storm size), catchment sampling number (rainfall resolution vs. catchment size), runoff and sewer sampling number (rainfall resolution vs. runoff and sewer model resolution respectively). Results show that for rainfall resolution lower than half the catchment size, rainfall volumes mean and standard deviations decrease as a result of smoothing of rainfall gradients. Moreover, deviations in maximum water depths, from 10 to 30% depending on the storm, occurred for rainfall resolution close to storm size, as a result of rainfall aggregation. Model results also showed that modelled runoff peaks are more sensitive to rainfall resolution than maximum in-sewer water depths as flow routing has a damping effect on in-sewer water level variations. Temporal resolution aggregation of rainfall inputs led to

  11. Engineers' Spatial Orientation Ability Development at the European Space for Higher Education

    ERIC Educational Resources Information Center

    Carrera, C. Carbonell; Perez, J. L. Saorin; Cantero, J. de la Torre; Gonzalez, A. M. Marrero

    2011-01-01

    The aim of this research was to determine whether the new geographic information technologies, included as teaching objectives in the new European Space for Higher Education Engineering degrees, develop spatial abilities. Bearing this in mind, a first year seminar using the INSPIRE Geoportal (Infrastructure for Spatial Information in Europe) was…

  12. Engineers' Spatial Orientation Ability Development at the European Space for Higher Education

    ERIC Educational Resources Information Center

    Carrera, C. Carbonell; Perez, J. L. Saorin; Cantero, J. de la Torre; Gonzalez, A. M. Marrero

    2011-01-01

    The aim of this research was to determine whether the new geographic information technologies, included as teaching objectives in the new European Space for Higher Education Engineering degrees, develop spatial abilities. Bearing this in mind, a first year seminar using the INSPIRE Geoportal (Infrastructure for Spatial Information in Europe) was…

  13. Estimation of the high-spatial-resolution variability in extreme wind speeds for forestry applications

    NASA Astrophysics Data System (ADS)

    Venäläinen, Ari; Laapas, Mikko; Pirinen, Pentti; Horttanainen, Matti; Hyvönen, Reijo; Lehtonen, Ilari; Junila, Päivi; Hou, Meiting; Peltola, Heli M.

    2017-07-01

    The bioeconomy has an increasing role to play in climate change mitigation and the sustainable development of national economies. In Finland, a forested country, over 50 % of the current bioeconomy relies on the sustainable management and utilization of forest resources. Wind storms are a major risk that forests are exposed to and high-spatial-resolution analysis of the most vulnerable locations can produce risk assessment of forest management planning. In this paper, we examine the feasibility of the wind multiplier approach for downscaling of maximum wind speed, using 20 m spatial resolution CORINE land-use dataset and high-resolution digital elevation data. A coarse spatial resolution estimate of the 10-year return level of maximum wind speed was obtained from the ERA-Interim reanalyzed data. Using a geospatial re-mapping technique the data were downscaled to 26 meteorological station locations to represent very diverse environments. Applying a comparison, we find that the downscaled 10-year return levels represent 66 % of the observed variation among the stations examined. In addition, the spatial variation in wind-multiplier-downscaled 10-year return level wind was compared with the WAsP model-simulated wind. The heterogeneous test area was situated in northern Finland, and it was found that the major features of the spatial variation were similar, but in some locations, there were relatively large differences. The results indicate that the wind multiplier method offers a pragmatic and computationally feasible tool for identifying at a high spatial resolution those locations with the highest forest wind damage risks. It can also be used to provide the necessary wind climate information for wind damage risk model calculations, thus making it possible to estimate the probability of predicted threshold wind speeds for wind damage and consequently the probability (and amount) of wind damage for certain forest stand configurations.

  14. Numerical analysis of single pulse and differential pulse-width pair BOTDA systems in the high spatial resolution regime.

    PubMed

    Minardo, Aldo; Bernini, Romeo; Zeni, Luigi

    2011-09-26

    A numerical analysis of conventional and differential pulse-width pair Brillouin optical time domain analysis systems is reported. The tests are focused on determining the performance of these systems especially in terms of spatial resolution, as a function of the pulse characteristics. A new definition of spatial resolution is given, based on analysis of the shape of the Brillouin gain spectrum. The influence of the rise/fall time of the pulse light to the spatial resolution is also studied.

  15. The effect of spatial resolution on decoding accuracy in fMRI multivariate pattern analysis.

    PubMed

    Gardumi, Anna; Ivanov, Dimo; Hausfeld, Lars; Valente, Giancarlo; Formisano, Elia; Uludağ, Kâmil

    2016-05-15

    Multivariate pattern analysis (MVPA) in fMRI has been used to extract information from distributed cortical activation patterns, which may go undetected in conventional univariate analysis. However, little is known about the physical and physiological underpinnings of MVPA in fMRI as well as about the effect of spatial smoothing on its performance. Several studies have addressed these issues, but their investigation was limited to the visual cortex at 3T with conflicting results. Here, we used ultra-high field (7T) fMRI to investigate the effect of spatial resolution and smoothing on decoding of speech content (vowels) and speaker identity from auditory cortical responses. To that end, we acquired high-resolution (1.1mm isotropic) fMRI data and additionally reconstructed them at 2.2 and 3.3mm in-plane spatial resolutions from the original k-space data. Furthermore, the data at each resolution were spatially smoothed with different 3D Gaussian kernel sizes (i.e. no smoothing or 1.1, 2.2, 3.3, 4.4, or 8.8mm kernels). For all spatial resolutions and smoothing kernels, we demonstrate the feasibility of decoding speech content (vowel) and speaker identity at 7T using support vector machine (SVM) MVPA. In addition, we found that high spatial frequencies are informative for vowel decoding and that the relative contribution of high and low spatial frequencies is different across the two decoding tasks. Moderate smoothing (up to 2.2mm) improved the accuracies for both decoding of vowels and speakers, possibly due to reduction of noise (e.g. residual motion artifacts or instrument noise) while still preserving information at high spatial frequency. In summary, our results show that - even with the same stimuli and within the same brain areas - the optimal spatial resolution for MVPA in fMRI depends on the specific decoding task of interest. Copyright © 2016 Elsevier Inc. All rights reserved.

  16. Resolution and Brightness Characteristics of Short-Lag Spatial Coherence (SLSC) Images

    PubMed Central

    Lediju Bell, Muyinatu A.; Dahl, Jeremy J.; Trahey, Gregg E.

    2016-01-01

    We previously described a novel beamforming method that images the spatial correlation of an echo wave field with demonstrated applications to clutter reduction in high-noise environments. In this paper, several characteristics of the resolution and brightness of short-lag spatial coherence (SLSC) images formed by this method are compared with B-mode images formed by conventional delay-and-sum beamforming methods. Point target widths were measured to estimate resolution, the autocorrelation of image texture was measured to estimate texture size, and the contrast (i.e., brightness ratio) of clinically relevant targets was assessed. SLSC images demonstrate improved resolution and contrast with increasing values of channel noise and clutter, whereas B-mode resolution was degraded in the presence of high noise (i.e., > −12 dB channel noise-to-signal ratios) and high clutter magnitudes (i.e., > −21 dB relative to point target magnitude). Lateral resolution in SLSC images was improved with increasing lag value, whereas axial resolution was degraded with increasing correlation kernel length. The texture size of SLSC images was smaller than that of matched B-mode images. Results demonstrate that the resolution and contrast of coherence-based images depend on a range of parameters, but are generally superior to those of matched B-mode images under challenging imaging conditions. PMID:26168173

  17. Noise Removal with Maintained Spatial Resolution in Raman Images of Cells Exposed to Submicron Polystyrene Particles

    PubMed Central

    Ahlinder, Linnea; Wiklund Lindström, Susanne; Lejon, Christian; Geladi, Paul; Österlund, Lars

    2016-01-01

    The biodistribution of 300 nm polystyrene particles in A549 lung epithelial cells has been studied with confocal Raman spectroscopy. This is a label-free method in which particles and cells can be imaged without using dyes or fluorescent labels. The main drawback with Raman imaging is the comparatively low spatial resolution, which is aggravated in heterogeneous systems such as biological samples, which in addition often require long measurement times because of their weak Raman signal. Long measurement times may however induce laser-induced damage. In this study we use a super-resolution algorithm with Tikhonov regularization, intended to improve the image quality without demanding an increased number of collected pixels. Images of cells exposed to polystyrene particles have been acquired with two different step lengths, i.e., the distance between pixels, and compared to each other and to corresponding images treated with the super-resolution algorithm. It is shown that the resolution after application of super-resolution algorithms is not significantly improved compared to the theoretical limit for optical microscopy. However, to reduce noise and artefacts in the hyperspectral Raman images while maintaining the spatial resolution, we show that it is advantageous to use short mapping step lengths and super-resolution algorithms with appropriate regularization. The proposed methodology should be generally applicable for Raman imaging of biological samples and other photo-sensitive samples.

  18. Fast Vascular Ultrasound Imaging with Enhanced Spatial Resolution and Background Rejection.

    PubMed

    Bar-Zion, Avinoam; Tremblay-Darveau, Charles; Solomon, Oren; Adam, Dan; Eldar, Yonina

    2016-08-15

    Ultrasound super-localization microscopy techniques presented in the last few years enable non-invasive imaging of vascular structures at the capillary level by tracking the flow of ultrasound contrast agents (gas microbubbles). However, these techniques are currently limited by low temporal resolution and long acquisition times. Super-resolution optical fluctuation imaging (SOFI) is a fluorescence microscopy technique enabling sub-diffraction limit imaging with high temporal resolution by calculating high order statistics of the fluctuating optical signal. The aim of this work is to achieve fast acoustic imaging with enhanced resolution by applying the tools used in SOFI to contrast-enhance ultrasound (CEUS) plane-wave scans. The proposed method was tested using numerical simulations and evaluated using two in-vivo rabbit models: scans of healthy kidneys and VX-2 tumor xenografts. Improved spatial resolution was observed with a reduction of up to 50% in the full width half max of the point spread function. In addition, substantial reduction in the background level was achieved compared to standard mean amplitude persistence images, revealing small vascular structures within tumors. The scan duration of the proposed method is less than a second while current superlocalization techniques require acquisition duration of several minutes. As a result, the proposed technique may be used to obtain scans with enhanced spatial resolution and high temporal resolution, facilitating flow-dynamics monitoring. Our method can also be applied during a breath-hold, reducing the sensitivity to motion artifacts.

  19. Fast Vascular Ultrasound Imaging With Enhanced Spatial Resolution and Background Rejection.

    PubMed

    Bar-Zion, Avinoam; Tremblay-Darveau, Charles; Solomon, Oren; Adam, Dan; Eldar, Yonina C

    2017-01-01

    Ultrasound super-localization microscopy techniques presented in the last few years enable non-invasive imaging of vascular structures at the capillary level by tracking the flow of ultrasound contrast agents (gas microbubbles). However, these techniques are currently limited by low temporal resolution and long acquisition times. Super-resolution optical fluctuation imaging (SOFI) is a fluorescence microscopy technique enabling sub-diffraction limit imaging with high temporal resolution by calculating high order statistics of the fluctuating optical signal. The aim of this work is to achieve fast acoustic imaging with enhanced resolution by applying the tools used in SOFI to contrast-enhance ultrasound (CEUS) plane-wave scans. The proposed method was tested using numerical simulations and evaluated using two in-vivo rabbit models: scans of healthy kidneys and VX-2 tumor xenografts. Improved spatial resolution was observed with a reduction of up to 50% in the full width half max of the point spread function. In addition, substantial reduction in the background level was achieved compared to standard mean amplitude persistence images, revealing small vascular structures within tumors. The scan duration of the proposed method is less than a second while current super-localization techniques require acquisition duration of several minutes. As a result, the proposed technique may be used to obtain scans with enhanced spatial resolution and high temporal resolution, facilitating flow-dynamics monitoring. Our method can also be applied during a breath-hold, reducing the sensitivity to motion artifacts.

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

    PubMed

    Chen, Delphic; Kuo, Jui-Chao

    2013-08-01

    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.

  1. Evaluating high temporal and spatial resolution vegetation index for crop yield prediction

    NASA Astrophysics Data System (ADS)

    Gao, Feng; Anderson, Martha; Yang, Yang

    2017-04-01

    Remote sensing data have been widely used in estimating crop yield. Remote sensing derived parameters such as Leaf Area Index (LAI), fraction of Absorbed Photosynthetically Active Radiation (fAPAR), and Vegetation Index (VI) were used either directly in building empirical models or by assimilating with crop growth models to predict crop yield. The abilities of remote sensing VI in crop yield modeling were evaluated at coarse spatial resolution and showed a great potential in capturing spatial and temporal variability of yield. With the increases of satellite remote sensing data and the emergences of new techniques, high temporal and spatial resolution data are now available or can be produced through data fusion techniques. This allows mapping crop condition, crop phenology and crop water use at the field scale. There is a potential to map crop yield at the field scale using high temporal and spatial resolution data. The goal of this study is to investigate the added values of high spatial and temporal VI for crop yield estimation. The study was conducted over a rain-fed agricultural area in central Iowa USA that covers 20 counties from 2001 to 2015. Initial results show that high temporal and spatial resolution data capture spatial variability of crop yield well and are highly correlated to crop yield. However, relationships vary from year to year, which implies VI cannot capture the inter-annual variability which may be affected by water availability, seeds improvement, and changes of management, etc. More environmental variables are needed for crop modeling. The recently available evapotranspiration (ET) and evaporative stress index (ESI) at the field scale provide necessary information to capture the inter-annual variability of crop yield and will be explored in the future.

  2. The Sun at high spatial resolution: The physics of small spatial structures in a magnetized medium

    NASA Technical Reports Server (NTRS)

    Rosner, R. T.

    1986-01-01

    An attempt is made to provide a perspective on the problem of spatial structuring on scales smaller than can presently be directly and regularly observed from the ground or with which current space-based instrumentation can be anticipated. There is abundant evidence from both observations and theory that such spatial structuring of the solar outer atmosphere is ubiquitous not only on the observed scales, but also on spatial scales down to (at least) the subarcsecond range. This is not to say that the results to be obtained from observations on these small scales can be anticipated: quite the opposite. What is clear instead is that many of the classic problems of coronal and chromospheric activity - involving the basic dissipative nature of magnetized plasmas - will be seen from a novel perspective at these scales, and that there are reasons for believing that dynamical processes of importance to activity on presently-resolved scales will themselves begin to be resolved on the sub-arcsecond level. Since the Sun is the only astrophysical laboratory for which there is any hope of studying these processes in any detail, this observatioinal opportunity is an exciting prospect for any student of magnetic activity in astrophysics.

  3. Application requirement analysis of high spectral and high spatial resolution satellite for environment remote sensing monitoring

    NASA Astrophysics Data System (ADS)

    Liu, S. H.; Yang, Y. P.; Zhao, Z. H.; Yao, Y. J.; Mao, X. J.; Wu, Y. T.; Gao, Y. H.

    2016-03-01

    China's environmental situation is still grim, environmental pressure continues to increase. The demand of environmental protection work in the new era for high resolution remote sensing application will continue to increase. Environmental monitoring has multi factor, quantitative inversion and high precision as features, environment department need to use a wide spectrum of remote sensing data with high spectral resolution capability to monitor the total amount of pollutants in macro scale and long time series. The implementation of the high resolution earth observation project provides support for the improvement of the quantitative application of environmental remote sensing. On the basis of sorting out the key work of environmental protection, the application requirements of high spectral resolution and high spatial resolution satellite remote sensing in the field of environmental protection and the building needs of national environmental remote sensing application platform are put forward.

  4. High spatial resolution increases the specificity of block-design BOLD fMRI studies of overt vowel production.

    PubMed

    Soltysik, David A; Hyde, James S

    2008-06-01

    Functional MRI (fMRI) studies of tasks involving orofacial motion, such as speech, are prone to problems related to motion-induced magnetic field variations. Orofacial motion perturbs the static magnetic field, leading to signal changes that correlate with the task and corrupt activation maps with false positives or signal loss. These motion-induced signal changes represent a contraindication for the implementation of fMRI to study the neurophysiology of orofacial motion. An fMRI experiment of a structured, non-semantic vowel production task was performed using four different voxel volumes and three different slice orientations in an attempt to find a set of acquisition parameters leading to activation maps with maximum specificity. Results indicate that the use of small voxel volumes (2 x 2 x 3 mm(3)) yielded a significantly higher percentage of true positive activation compared to the use of larger voxel volumes. Slice orientation did not have as great an impact as spatial resolution, although coronal slices appeared superior at high spatial resolutions. Furthermore, it was found that combining the strategy of high spatial resolution with an optimum task duration and post-processing methods for separating true and false positives greatly improved the specificity of single-subject, block-design fMRI studies of structured, overt vowel production.

  5. [Examination of upper abdominal region in high spatial resolution diffusion-weighted imaging using 3-Tesla MRI].

    PubMed

    Terada, Masaki; Matsushita, Hiroki; Oosugi, Masanori; Inoue, Kazuyasu; Yaegashi, Taku; Anma, Takeshi

    2009-03-20

    The advantage of the higher signal-to-noise ratio (SNR) of 3-Tesla magnetic resonance imaging (3-Tesla) has the possibility of contributing to the improvement of high spatial resolution without causing image deterioration. In this study, we compared SNR and the apparent diffusion coefficient (ADC) value with 3-Tesla as the condition in the diffusion-weighted image (DWI) parameter of the 1.5-Tesla magnetic resonance imaging (1.5-Tesla) and we examined the high spatial resolution images in the imaging method [respiratory-triggering (RT) method and breath free (BF) method] and artifact (motion and zebra) in the upper abdominal region of DWI at 3-Tesla. We have optimized scan parameters based on phantom and in vivo study. As a result, 3-Tesla was able to obtain about 1.5 times SNR in comparison with the 1.5-Tesla, ADC value had few differences. Moreover, the RT method was effective in correcting the influence of respiratory movement in comparison with the BF method, and image improvement by the effective acquisition of SNR and reduction of the artifact were provided. Thus, DWI of upper abdominal region was a useful sequence for the high spatial resolution in 3-Tesla.

  6. High Spatial Resolution Increases the Specificity of Block-Design BOLD fMRI Studies of Overt Vowel Production

    PubMed Central

    Soltysik, David A.; Hyde, James S.

    2008-01-01

    Functional MRI (fMRI) studies of tasks involving orofacial motion, such as speech, are prone to problems related to motion-induced magnetic field variations. Orofacial motion perturbs the static magnetic field, leading to signal changes that correlate with the task and corrupt activation maps with false positives or signal loss. These motion-induced signal changes represent a contraindication for the implementation of fMRI to study the neurophysiology of orofacial motion. An fMRI experiment of a structured, non-semantic vowel production task was performed using four different voxel volumes and three different slice orientations in an attempt to find a set of acquisition parameters leading to activation maps with maximum specificity. Results indicate that the use of small voxel volumes (2×2×3 mm3) yielded a significantly higher percentage of true positive activation compared to the use of larger voxel volumes. Slice orientation did not have as great an impact as spatial resolution, although coronal slices appeared superior at high spatial resolutions. Furthermore, it was found that combining the strategy of high spatial resolution with an optimum task duration and post-processing methods for separating true and false positives greatly improved the specificity of single-subject, block-design fMRI studies of structured, overt vowel production. PMID:18387825

  7. Spatial Distribution of Attentional Modulation at Columnar Resolution in Macaque Area V4

    PubMed Central

    Tanigawa, Hisashi; Chen, Gang; Roe, Anna W.

    2016-01-01

    Attention to a location in a visual scene affects neuronal responses in visual cortical areas in a retinotopically specific manner. Optical imaging studies have revealed that cortical responses consist of two components of different sizes: the stimulus-nonspecific global signal and the stimulus-specific mapping signal (domain activity). It remains unclear whether either or both of these components are modulated by spatial attention. In this study, to determine the spatial distribution of attentional modulation at columnar resolution, we performed cerebral blood volume (CBV)-based optical imaging in area V4 of monkeys performing a color change detection task in which spatial attention was manipulated. We found that spatial attention enhanced global signals of the hemodynamic responses, but did not affect stimulus-selective domain activities. These results indicate the involvement of global signals in neural processing of spatial attention. We propose that global signals reflect the neural substrate of the normalization pool in normalization models of attention. PMID:28018181

  8. Improvement in spatial resolution of plasma-enhanced quantum-well intermixing by stress-inducing dielectric mask

    NASA Astrophysics Data System (ADS)

    Djie, H. S.; Mei, T.; Arokiaraj, J.

    2004-10-01

    We report the use of a stress-inducing dielectric mask to improve the spatial resolution of the proximity quantum-well intermixing process. Photoluminescence and Raman spectroscopy were used to study the band gap modification and the spatial resolution using Ar plasma in the InGaAs /InGaAsP laser structure. A spatial resolution of 2.4μm has been achieved with the presence of an SixNy annealing cap as a stress-inducing mask. The simple technique provides a promising approach of lateral band gap tuning with a high spatial resolution for high-density photonic integrated circuits.

  9. High spatial resolution X-ray and gamma ray imaging system using diffraction crystals

    DOEpatents

    Smither, Robert K [Hinsdale, IL

    2011-05-17

    A method and a device for high spatial resolution imaging of a plurality of sources of x-ray and gamma-ray radiation are provided. The device comprises a plurality of arrays, with each array comprising a plurality of elements comprising a first collimator, a diffracting crystal, a second collimator, and a detector.

  10. Real space soft x-ray imaging at 10 nm spatial resolution

    SciTech Connect

    Chao, Weilun; Fischer, Peter; Tyliszczak, T.; Rekawa, Senajith; Anderson, Erik; Naulleau, Patrick

    2011-04-24

    Using Fresnel zone plates made with our robust nanofabrication processes, we have successfully achieved 10 nm spatial resolution with soft x-ray microscopy. The result, obtained with both a conventional full-field and scanning soft x-ray microscope, marks a significant step forward in extending the microscopy to truly nanoscale studies.

  11. High spatial resolution three-dimensional mapping of vegetation spectral dynamics using computer vision

    Treesearch

    Jonathan P. Dandois; Erle C. Ellis

    2013-01-01

    High spatial resolution three-dimensional (3D) measurements of vegetation by remote sensing are advancing ecological research and environmental management. However, substantial economic and logistical costs limit this application, especially for observing phenological dynamics in ecosystem structure and spectral traits. Here we demonstrate a new aerial remote sensing...

  12. Scaling field data to calibrate and validate moderate spatial resolution remote sensing models

    USGS Publications Warehouse

    Baccini, A.; Friedl, M.A.; Woodcock, C.E.; Zhu, Z.

    2007-01-01

    Validation and calibration are essential components of nearly all remote sensing-based studies. In both cases, ground measurements are collected and then related to the remote sensing observations or model results. In many situations, and particularly in studies that use moderate resolution remote sensing, a mismatch exists between the sensor's field of view and the scale at which in situ measurements are collected. The use of in situ measurements for model calibration and validation, therefore, requires a robust and defensible method to spatially aggregate ground measurements to the scale at which the remotely sensed data are acquired. This paper examines this challenge and specifically considers two different approaches for aggregating field measurements to match the spatial resolution of moderate spatial resolution remote sensing data: (a) landscape stratification; and (b) averaging of fine spatial resolution maps. The results show that an empirically estimated stratification based on a regression tree method provides a statistically defensible and operational basis for performing this type of procedure. 

  13. On the Importance of Spatial Resolution for Flap Side Edge Noise Prediction

    NASA Technical Reports Server (NTRS)

    Mineck, Raymond E.; Khorrami, Mehdi R.

    2017-01-01

    A spatial resolution study of flap tip flow and the effects on the farfield noise signature for an 18%-scale, semispan Gulfstream aircraft model are presented. The NASA FUN3D unstructured, compressible Navier-Stokes solver was used to perform the highly resolved, time-dependent, detached eddy simulations of the flow field associated with the flap for this high-fidelity aircraft model. Following our previous work on the same model, the latest computations were undertaken to determine the causes of deficiencies observed in our earlier predictions of the steady and unsteady surface pressures and off-surface flow field at the flap tip regions, in particular the outboard tip area, where the presence of a cavity at the side-edge produces very complex flow features and interactions. The present results show gradual improvement in steady loading at the outboard flap edge region with increasing spatial resolution, yielding more accurate fluctuating surface pressures, off-surface flow field, and farfield noise with improved high-frequency content when compared with wind tunnel measurements. The spatial resolution trends observed in the present study demonstrate that the deficiencies reported in our previous computations are mostly caused by inadequate spatial resolution and are not related to the turbulence model.

  14. A system for optically controlling neural circuits with very high spatial and temporal resolution

    PubMed Central

    Pandarinath, Chethan; Carlson, Eric T.; Nirenberg, Sheila

    2015-01-01

    Optogenetics offers a powerful new approach for controlling neural circuits. It has a vast array of applications in both basic and clinical science. For basic science, it opens the door to unraveling circuit operations, since one can perturb specific circuit components with high spatial (single cell) and high temporal (millisecond) resolution. For clinical applications, it allows new kinds of selective treatments, because it provides a method to inactivate or activate specific components in a malfunctioning circuit and bring it back into a normal operating range [1–3]. To harness the power of optogenetics, though, one needs stimulating tools that work with the same high spatial and temporal resolution as the molecules themselves, the channelrhodopsins. To date, most stimulating tools require a tradeoff between spatial and temporal precision and are prohibitively expensive to integrate into a stimulating/recording setup in a laboratory or a device in a clinical setting [4, 5]. Here we describe a Digital Light Processing (DLP)-based system capable of extremely high temporal resolution (sub-millisecond), without sacrificing spatial resolution. Furthermore, it is constructed using off-the-shelf components, making it feasible for a broad range of biology and bioengineering labs. Using transgenic mice that express channelrhodopsin-2 (ChR2), we demonstrate the system’s capability for stimulating channelrhodopsin-expressing neurons in tissue with single cell and sub-millisecond precision. PMID:25699292

  15. Effect of skull resistivity on the spatial resolutions of EEG and MEG.

    PubMed

    Malmivuo, Jaakko A; Suihko, Veikko E

    2004-07-01

    The resistivity values of the different tissues of the head affect the lead fields of electroencephalography (EEG). When the head is modeled with a concentric spherical model, the different resistivity values have no effect on the lead fields of the magnetoencephalography (MEG). Recent publications indicate that the resistivity of the skull is much lower than what was estimated by Rush and Driscoll. At the moment, this information on skull resistivity is, however, slightly controversial. We have compared the spatial resolution of EEG and MEG for cortical sources by calculating the half-sensitivity volumes (HSVs) of EEG and MEG as a function of electrode and magnetometer distance, respectively, with the relative skull resistivity as a parameter. Because the spatial resolution is related to the HSV, these data give an overview of the effect of these parameters on the spatial resolution of both techniques. Our calculations show that, with the new information on the resistivity of the skull, in the spherical model for cortical sources the spatial resolution of the EEG is better than that of the MEG.

  16. The significance of spatial resolution: Identifying forest cover from satellite data

    Treesearch

    Dumitru Salajanu; Charles E. Olson

    2001-01-01

    Twenty-five years ago, a National Academy of Sciences report identified species identification as a requirement if satellite data are to reach their full potential in forest inventory and monitoring; the report suggested that improving spatial resolution to 10 meters would probably be required (Committee on Remote Sensing Programs for Earth Resource Surveys [CORSPERS]...

  17. The Effects of Spatial Resolution on Impervious Cover Classifications in Watersheds and Riparian Zones in Vermont

    EPA Science Inventory

    Impervious cover (roads, rooftops, etc.) is a known stressor on stream biota and habitat and is often used as an indicator for assessing the effects of urbanization on stream health. Understanding how spatial data resolution impacts estimates of impervious cover is important for ...

  18. Improving the quantification at high spatial resolution using a field emission electron microprobe

    NASA Astrophysics Data System (ADS)

    Pinard, P. T.; Richter, S.

    2014-03-01

    The capabilities of field emitter electron microprobes to perform quantitative measurements at high spatial resolution are discussed. Using Fe-Cr-C particles in a bearing steel (SAE 52100) as example, a generic procedure was established to find the optimal analytical conditions (beam energy, beam current and acquisition time). The influence of these parameters on the accuracy, precision and spatial resolution was evaluated using experimental measurements and Monte Carlo simulations. A quantification procedure was developed for soft X-ray lines, taking into account the overlap of high order X-ray lines and background anomalies. The accuracy of Ka- and La-lines was verified using reference materials. A relationship between experimental and simulated X-ray intensities was determined to evaluate the measurement precision. The spatial resolution of each X-ray line was calculated from the simulated lateral and depth X-ray intensity distribution using simulations integrating experimentally measured beam diameters. The optimal analytical conditions for the studied sample were found to be 5 keV, 10 nA and 10 s acquisition time. Further specialized techniques to improve the spatial resolution are presented: focused ion beam preparation of thin lamella and wedge, and Monte Carlo based reconstruction. The feasibility of the latter to quantify features smaller than the X-ray emission volume was demonstrated.

  19. Spatial resolution of tip-enhanced Raman spectroscopy - DFT assessment of the chemical effect

    NASA Astrophysics Data System (ADS)

    Latorre, Federico; Kupfer, Stephan; Bocklitz, Thomas; Kinzel, Daniel; Trautmann, Steffen; Gräfe, Stefanie; Deckert, Volker

    2016-05-01

    Experimental evidence of extremely high spatial resolution of tip-enhanced Raman scattering (TERS) has been recently demonstrated. Here, we present a full quantum chemical description (at the density functional level of theory) of the non-resonant chemical effects on the Raman spectrum of an adenine molecule mapped by a tip, modeled as a single silver atom or a small silver cluster. We show pronounced changes in the Raman pattern and its intensities depending on the conformation of the nanoparticle-substrate system, concluding that the spatial resolution of the chemical contribution of TERS can be in the sub-nm range.Experimental evidence of extremely high spatial resolution of tip-enhanced Raman scattering (TERS) has been recently demonstrated. Here, we present a full quantum chemical description (at the density functional level of theory) of the non-resonant chemical effects on the Raman spectrum of an adenine molecule mapped by a tip, modeled as a single silver atom or a small silver cluster. We show pronounced changes in the Raman pattern and its intensities depending on the conformation of the nanoparticle-substrate system, concluding that the spatial resolution of the chemical contribution of TERS can be in the sub-nm range. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr00093b

  20. Classification of high spatial resolution imagery using optimal Gabor-filters-based texture features

    NASA Astrophysics Data System (ADS)

    Zhao, Yindi; Wu, Bo

    2007-06-01

    Texture analysis has received great attention in the interpretation of high-resolution satellite images. This paper aims to find optimal filters for discriminating between residential areas and other land cover types in high spatial resolution satellite imagery. Moreover, in order to reduce the blurring border effect, inherent in texture analysis and which introduces important errors in the transition areas between different texture units, a classification procedure is designed for such high spatial resolution satellite images as follows. Firstly, residential areas are detected using Gabor texture features, and two clusters, one a residential area and the other not, are detected using the fuzzy C-Means algorithm, in the frequency space based on Gabor filters. Sequentially, a mask is generated to eliminate residential areas so that other land-cover types would be classified accurately, and not interfered with the spectrally heterogeneous residential areas. Afterwards, other objects are classified using spectral features by the MAP (maximum a posterior) - ICM (iterated conditional mode) classification algorithm designed to enforce the spatial constraints into classification. Experimental results on high spatial resolution remote sensing data confirm that the proposed algorithm provide remarkably better detection accuracy than conventional approaches in terms of both objective measurements and visual evaluation.

  1. Spatial resolution of electron backscatter diffraction in a FEG-SEM

    SciTech Connect

    Kenik, E.A.

    1996-05-01

    Crystallographic information can be determined for bulk specimens in a SEM by utilizing electron backscatter diffraction (EBSD), which is also referred to as backscatter electron Kikuchi diffraction. This technique provides similar information to that provided by selected area electron channeling (SAEC). However, the spatial resolutions of the two techniques are limited by different processes. In SAEC patterns, the spatial resolution is limited to {approximately}2 {mu}m by the motion of the beam on the specimen, which results from the angular rocking of the beam and the aberration of the probe forming lens. Therefore, smaller incident probe sizes provide no improvement in spatial resolution of SAEC patterns. In contrast, the spatial resolution for EBSD, which uses a stationary beam and an area detector, is determined by (1) the incident probe size and (2) the size of the interaction volume from which significant backscattered electrons are produced in the direction of the EBSD detector. The second factor is influenced by the accelerating voltage, the specimen tilt, and the relative orientation of scattering direction and the specimen tilt axis. This study was performed on a Philips XL30/FEG SEM equipped with a TexSEM Orientation Imaging Microscopy (OIM) system. The signal from the EBSD detector (SIT camera) is flat- fielded and enhanced in a MTI frame storage/image processor. The Schottky FEG source provides the fine probe sizes ({approximately}10 nm) desired with sufficient probe current ({approximately}1 nA) needed for image processing with the low signal/noise EBSD signal.

  2. Assessing the Utility of Satellite Imagery with Differing Spatial Resolutions for Deriving Proxy Measures of Slum Presence in Accra, Ghana.

    PubMed

    Stoler, Justin; Daniels, Dean; Weeks, John R; Stow, Douglas A; Coulter, Lloyd L; Finch, Brian Karl

    2012-01-01

    Little research has been conducted on how differing spatial resolutions or classification techniques affect image-driven identification and categorization of slum neighborhoods in developing nations. This study assesses the correlation between satellite-derived land cover and census-derived socioeconomic variables in Accra, Ghana to determine whether the relationship between these variables is altered with a change in spatial resolution or scale. ASTER and Landsat TM satellite images are each used to classify land cover using spectral mixture analysis (SMA), and land cover proportions are summarized across Enumeration Areas in Accra and compared to socioeconomic data for the same areas. Correlation and regression analyses compare the SMA results with a Slum Index created from various socio-economic data taken from the Census of Ghana, as well as to data derived from a "hard" per-pixel classification of a 2.4 m Quickbird image. Results show that the vegetation fraction is significantly correlated with the Slum Index (Pearson's r ranges from -0.33 to -0.51 depending on which image-derived product is compared), and the use of a spatial error model improves results (multivariate model pseudo-R(2) ranges from 0.37 to 0.40 by image product). We also find that SMA products derived from ASTER are a sufficient substitute for classification products derived from higher spatial resolution QB data when using land cover fractions as a proxy for slum presence, suggesting that SMA might be more cost-effective for deriving land cover fractions than the use of high-resolution imagery for this type of demographic analysis.

  3. Spatial and temporal resolution effects on urban catchments with different imperviousness degrees

    NASA Astrophysics Data System (ADS)

    Cristiano, Elena; ten Veldhuis, Marie-Claire; van de Giesen, Nick C.

    2015-04-01

    One of the main problems in urban hydrological analysis is to measure the rainfall at urban scale with high resolution and use these measurements to model urban runoff processes to predict flows and reduce flood risk. With the aim of building a semi-distribute hydrological sewer model for an urban catchment, high resolution rainfall data are required as input. In this study, the sensitivity of hydrological response to high resolution precipitation data for hydrodynamic models at urban scale is evaluated with different combinations of spatial and temporal resolutions. The aim is to study sensitivity in relation to catchment characteristics, especially drainage area size, imperviousness degree and hydraulic properties such as special structures (weirs, pumping stations). Rainfall data of nine storms are considered with 4 different spatial resolutions (3000m, 1000m, 500m and 100m) combined with 4 different temporal resolutions (10min, 5min, 3min and 1min). The dual polarimetric X-band weather radar, located in the Cabauw Experimental Site for Atmospheric Research (CESAR) provided the high resolution rainfall data of these rainfall events, used to improve the sewer model. The effects of spatial-temporal rainfall input resolution on response is studied in three Districts of Rotterdam (NL): Kralingen, Spaanse Polder and Centrum district. These catchments have different average drainage area size (from 2km2 to 7km2), and different general characteristics. Centrum district and Kralingen are, indeed, more various and include residential and commercial areas, big green areas and a small industrial area, while Spaanse Polder is a industrial area, densely urbanized, and presents a high percentage of imperviousness.

  4. Comparison of the spatial and radiometric resolution of ERS and Metop C-band radars

    NASA Astrophysics Data System (ADS)

    Elyouncha, Anis; Neyt, Xavier

    2014-10-01

    ERS-1/2 and Metop-A/B satellites carry a very similar radars operating at similar frequencies (5.3/5.255 GHz) and same polarization (VV). However, the radars on-board the satellites of these two missions differ in the pulse waveform, bandwidth and slightly in geometry. Moreover, the on-board and the on-ground processing is different. This paper investigates the spatial and radiometric resolution of these radars and the resolution enhancement between ERS (1991-2011) and Metop (2006- ) missions. The spatial resolution assessment implies the computation and the comparison of the Spatial Response Function (SRF) of both systems. The SRF involves mainly the antenna gain pattern, the pulse waveform and the different on-board filtering stages. The radiometric resolution depends mainly on the signal to noise ratio (SNR) and the number of averaged independent samples (N). Furthermore, the correlation of the measurement samples in a resolution cell is computed to assess the independence assumption. The metric used to quantify the radiometric accuracy in scatterometry is called Kp which is the relative standard deviation. A comparison of Kp parameter extracted from the nominal products of the two missions confirms the expected performance based on the SNR, N and correlation analysis.

  5. Spatial Resolution and Catchment Size Interaction of Soil Hydrological Properties for Hydrological Modeling

    NASA Astrophysics Data System (ADS)

    Libohova, Zamir; Bowling, Laura C.; Owens, Phillip R.; Schoeneberger, Philip; Wysocki, Douglas; Wills, Skye; Lindbo, David

    2016-04-01

    Spatial resolution of soil hydrologic properties is critical for distributed hydrological model streamflow simulations. Soils from US Soil Survey Geographic (SSURGO) Database are mapped at scales varying from 1:12,000 to 65,000. Related to these scales are also soil hydrological properties, which could vary spatially outside of the common SSURGO scale range. The objective of this research was to assess the role of the spatial resolution of soil depth on simulated hydrological response for various watershed sizes using the Distributed Hydrology Soil Vegetation Model (DHSVM). The study site was Hall Creek watershed a 56 km2 in size located in Dubois County in southern Indiana, USA. The watershed size was divided in 55 sub-watersheds varying in size from less than 5 km2 to 56 km2. The grid size spatial resolution of soil hydrological properties varied from 10x10, 30x30 and 90x90m. The simulated streamflow metrics were annual mean, minimum and maximum streamflow, and R-B Flashiness, which measures the variability in streamflow between successive days highlighting the fluctuation of discharge relative to total discharge. The slopes of the regression of simulated stream discharge parameters versus watershed size were used to assess the presence of interaction. In addition, the coefficient of variation was used to assess the variability for the R-B index, annual mean, annual minimum and maximum stream discharge across different model resolutions within each watershed category. The slope for 10x10 and 30x30m spatial resolution for annual mean, and minimum streamflow were not significantly different from zero across all watershed sizes indicating lack of interaction. However, slope for the R-B flashiness was significantly different from zero for the 90x90 m grid size indicating that watershed size change is sensitive at this spatial resolution. The variability of R-B index, annual mean and annual minimum hydrologic metrics decreased with increasing watershed size but

  6. High-Spatial-Resolution Thermal Infrared Satellite Images for Lake Studies

    NASA Astrophysics Data System (ADS)

    Steissberg, T. E.; Hook, S. J.; Schladow, G.

    2006-12-01

    Thermal infrared (TIR) satellite images can be used to study transport processes in lakes, such as wind-driven upwelling and surface circulation, providing a measure of spatial variability and horizontal distribution of water temperature that conventional field-based measurements cannot provide. High-spatial-resolution TIR images provide a detailed view of fine-scale processes, such as surface jets, that cannot be clearly resolved in moderate-resolution images, and they enable the accurate measurement of surface transport and circulation patterns. The surface temperature maps derived from high-resolution thermal infrared ASTER and Landsat ETM+ images, in conjunction with moderate-resolution TIR images acquired by MODIS, enabled the characterization of wind-driven upwelling and the measurement of surface currents and circulation at Lake Tahoe, California-Nevada, USA. The images, paired with in situ surface temperature and meteorological data, have shown that wind-driven partial upwelling events occur at least twice monthly throughout the spring and summer stratified period, transporting water from intermediate depths to the surface. These are important events that contribute to the patchiness and heterogeneity that characterize natural aquatic systems. The high spatial resolution of ASTER and ETM+ and the small time separation between their subsequent overpasses allow the surface currents and general circulation in lakes and coastal environments to be accurately quantified using the maximum cross-correlation method. The surface currents and circulation at Lake Tahoe were measured using a pair of cross-platform high-resolution TIR images acquired 38 minutes apart by ETM+ and ASTER. Mean currents of 5--10 cm/s were measured, with maximum currents approaching 35 cm/s. The eastward transport of a surface jet extending from an upwelling front was clearly apparent, with 15--30 cm/s currents. The vector field delineated three gyres, consistent with surface drifter

  7. Non-Invasive Measurement of Frog Skin Reflectivity in High Spatial Resolution Using a Dual Hyperspectral Approach

    PubMed Central

    Liebisch, Frank; Walter, Achim; Greven, Hartmut; Rascher, Uwe

    2013-01-01

    Background Most spectral data for the amphibian integument are limited to the visible spectrum of light and have been collected using point measurements with low spatial resolution. In the present study a dual camera setup consisting of two push broom hyperspectral imaging systems was employed, which produces reflectance images between 400 and 2500 nm with high spectral and spatial resolution and a high dynamic range. Methodology/Principal Findings We briefly introduce the system and document the high efficiency of this technique analyzing exemplarily the spectral reflectivity of the integument of three arboreal anuran species (Litoria caerulea, Agalychnis callidryas and Hyla arborea), all of which appear green to the human eye. The imaging setup generates a high number of spectral bands within seconds and allows non-invasive characterization of spectral characteristics with relatively high working distance. Despite the comparatively uniform coloration, spectral reflectivity between 700 and 1100 nm differed markedly among the species. In contrast to H. arborea, L. caerulea and A. callidryas showed reflection in this range. For all three species, reflectivity above 1100 nm is primarily defined by water absorption. Furthermore, the high resolution allowed examining even small structures such as fingers and toes, which in A. callidryas showed an increased reflectivity in the near infrared part of the spectrum. Conclusion/Significance Hyperspectral imaging was found to be a very useful alternative technique combining the spectral resolution of spectrometric measurements with a higher spatial resolution. In addition, we used Digital Infrared/Red-Edge Photography as new simple method to roughly determine the near infrared reflectivity of frog specimens in field, where hyperspectral imaging is typically difficult. PMID:24058464

  8. Using High Spatial Resolution Satellite Imagery to Map Forest Burn Severity Across Spatial Scales in a Pine Barrens Ecosystem

    NASA Technical Reports Server (NTRS)

    Meng, Ran; Wu, Jin; Schwager, Kathy L.; Zhao, Feng; Dennison, Philip E.; Cook, Bruce D.; Brewster, Kristen; Green, Timothy M.; Serbin, Shawn P.

    2017-01-01

    As a primary disturbance agent, fire significantly influences local processes and services of forest ecosystems. Although a variety of remote sensing based approaches have been developed and applied to Landsat mission imagery to infer burn severity at 30 m spatial resolution, forest burn severity have still been seldom assessed at fine spatial scales (less than or equal to 5 m) from very-high-resolution (VHR) data. We assessed a 432 ha forest fire that occurred in April 2012 on Long Island, New York, within the Pine Barrens region, a unique but imperiled fire-dependent ecosystem in the northeastern United States. The mapping of forest burn severity was explored here at fine spatial scales, for the first time using remotely sensed spectral indices and a set of Multiple Endmember Spectral Mixture Analysis (MESMA) fraction images from bi-temporal - pre- and post-fire event - WorldView-2 (WV-2) imagery at 2 m spatial resolution. We first evaluated our approach using 1 m by 1 m validation points at the sub-crown scale per severity class (i.e. unburned, low, moderate, and high severity) from the post-fire 0.10 m color aerial ortho-photos; then, we validated the burn severity mapping of geo-referenced dominant tree crowns (crown scale) and 15 m by 15 m fixed-area plots (inter-crown scale) with the post-fire 0.10 m aerial ortho-photos and measured crown information of twenty forest inventory plots. Our approach can accurately assess forest burn severity at the sub-crown (overall accuracy is 84% with a Kappa value of 0.77), crown (overall accuracy is 82% with a Kappa value of 0.76), and inter-crown scales (89% of the variation in estimated burn severity ratings (i.e. Geo-Composite Burn Index (CBI)). This work highlights that forest burn severity mapping from VHR data can capture heterogeneous fire patterns at fine spatial scales over the large spatial extents. This is important since most ecological processes associated with fire effects vary at the less than 30 m scale and

  9. Using high spatial resolution satellite imagery to map forest burn severity across spatial scales in a Pine Barrens ecosystem

    DOE PAGES

    Meng, Ran; Wu, Jin; Schwager, Kathy L.; ...

    2017-01-21

    As a primary disturbance agent, fire significantly influences local processes and services of forest ecosystems. Although a variety of remote sensing based approaches have been developed and applied to Landsat mission imagery to infer burn severity at 30 m spatial resolution, forest burn severity have still been seldom assessed at fine spatial scales (≤ 5 m) from very-high-resolution (VHR) data. Here we assessed a 432 ha forest fire that occurred in April 2012 on Long Island, New York, within the Pine Barrens region, a unique but imperiled fire-dependent ecosystem in the northeastern United States. The mapping of forest burn severitymore » was explored here at fine spatial scales, for the first time using remotely sensed spectral indices and a set of Multiple Endmember Spectral Mixture Analysis (MESMA) fraction images from bi-temporal — pre- and post-fire event — WorldView-2 (WV-2) imagery at 2 m spatial resolution. We first evaluated our approach using 1 m by 1 m validation points at the sub-crown scale per severity class (i.e. unburned, low, moderate, and high severity) from the post-fire 0.10 m color aerial ortho-photos; then, we validated the burn severity mapping of geo-referenced dominant tree crowns (crown scale) and 15 m by 15 m fixed-area plots (inter-crown scale) with the post-fire 0.10 m aerial ortho-photos and measured crown information of twenty forest inventory plots. Our approach can accurately assess forest burn severity at the sub-crown (overall accuracy is 84% with a Kappa value of 0.77), crown (overall accuracy is 82% with a Kappa value of 0.76), and inter-crown scales (89% of the variation in estimated burn severity ratings (i.e. Geo-Composite Burn Index (CBI)). Lastly, this work highlights that forest burn severity mapping from VHR data can capture heterogeneous fire patterns at fine spatial scales over the large spatial extents. This is important since most ecological processes associated with fire effects vary at the < 30 m scale and

  10. Evaluation of charge -sharing effects on the spatial resolution of the PICASSO detector

    NASA Astrophysics Data System (ADS)

    Rigon, L.; Arfelli, F.; Bergamaschi, A.; Chen, R. C.; Dreossi, D.; Longo, R.; Menk, R.-H.; Schmitt, B.; Vallazza, E.; Castelli, E.

    2010-05-01

    A double -layer "edge-on" silicon microstrip detector has been designed and realized in the frame of the PICASSO (Phase Imaging for Clinical Application with Silicon detector and Synchrotron radiatiOn) project at the SYRMEP (SYnchrotron Radiation for MEdical Physics) beamline of Elettra (Trieste, Italy). The detector meets the requirements for synchrotron radiation mammography with patients inregarding: (a) size, since it covers the full beam width (210 mm); (b) spatial resolution, determined by the 0.05 mm strip pitch; (c) single-photon counting capabilities, because it is able to handle more than 10 6 photons/(pixel×s); (d) contrast resolution, thanks to a threshold trim DAC that equalizes the channel sensitivity; (e) efficiency, due to the high absorption in the 15-20 mm sensor depth. Experimental measurements evidence charge sharing, though not compromising the spatial resolution.

  11. Photoelectron range limitations to the spatial resolution for x-rays in gas proportional chambers

    SciTech Connect

    Smith, G.C.; Fischer, J.; Radeka, V.

    1983-11-01

    Measurements have been made, for x-ray energies from a few keV to 18 keV, of the limiting spatial resolution caused by the finite range of the photoelectron, or electrons, created when an x-ray is absorbed in the gas of a proportional chamber. In hydrocarbon gases such as methane and ethane, where the photoelectron receives the bulk of the x-ray energy, the limiting spatial resolution is found to vary as a power law of x-ray energy. In argon and xenon, at an x-ray energy approximately twice that of the A/sub K/ edge and the Xe/sub L/ edge respectively, the measured limiting resolution is better than expected from an equivalent power law behavior.

  12. High-Spatial-Resolution Multichannel Thomson Scattering Measurements for Atmospheric Pressure Microdischarge

    NASA Astrophysics Data System (ADS)

    Kono, Akihiro; Iwamoto, Kazushige

    2004-08-01

    High-spatial-resolution multichannel Thomson scattering measurement scheme is applied to the diagnostics of a microplasma produced between two knife-edge electrodes separated by a 100 μm microgap and driven by 2.45 GHz microwave. The method provides spatial profile of electron density, electron temperature, and gas temperature simultaneously in a single measurement, with a spatial resolution of ˜ 25 μm; the gas temperature is derived from the spectrum of rotational Raman scattering caused by molecules contained in the discharge gas. Measurements are carried out for discharges with air and He/N2(5%) mixture gas at atmospheric pressure and the differences in the basic plasma parameters are discussed.

  13. High-resolution measurements of the spatial and temporal scalar structure of a turbulent plume

    NASA Astrophysics Data System (ADS)

    Crimaldi, J. P.; Koseff, J. R.

    Two techniques are described for measuring the scalar structure of turbulent flows. A planar laser-induced fluorescence technique is used to make highly resolved measurements of scalar spatial structure, and a single-point laser-induced fluorescence probe is used to make highly resolved measurements of scalar temporal structure. The techniques are used to measure the spatial and temporal structure of an odor plume released from a low-momentum, bed-level source in a turbulent boundary layer. For the experimental setup used in this study, a spatial resolution of 150μm and a temporal resolution of 1,000Hz are obtained. The results show a wide range of turbulent structures in rich detail; the nature of the structure varies significantly in different regions of the plume.

  14. Cyclical thinning of black phosphorus with high spatial resolution for heterostructure devices.

    PubMed

    Robbins, Matthew C; Namgung, Seon; Oh, Sang-Hyun; Koester, Steven J

    2017-03-13

    A high-spatial resolution, cyclical thinning method for realizing black phosphorus (BP) heterostructures is reported. This process utilizes a cyclic technique involving BP surface oxidation and vacuum annealing to create BP flakes as thin as 1.6 nm. The process also utilizes a spatially patternable mask created by evaporating Al that oxidizes to form Al2O3 which stabilizes the unetched BP regions and enables the formation of lateral heterostructures with spatial resolution as small as 150 nm. This thinning/patterning technique has also been used to create the first ever lateral heterostructure BP MOSFET in which half of a BP flake was thinned in order to increase its band gap. This heterostructure MOSFET showed an on-to-off current ratio improvement of 1000× compared to homojunction MOSFETs.

  15. Fusing Multi-Source Urban Maps Under Consideration of Spatial Resolution and Environmental Characteristics

    NASA Astrophysics Data System (ADS)

    Salentinig, Andreas; Gamba, Paolo

    2016-08-01

    In this work a decision level fusion algorithm incorporating multispectral- and SAR- based urban maps from different spatial resolutions is presented. A variety of urban maps from SAR as well optical EO data with spatial resolutions ranging between 12 and 75 meters are combined in order to produce accurate urban area extractions of the Chinese 'Megacities' of Beijing and Guangzhou. The influence of spatial posting of the data, climate region and season at image acquisition has been evaluated and reflected in optimized weights of the input data in the fusion process. Therefore, the weights are determined based on the assumption that the usability and reliability of EO data products depends on the intended scale of analysis as well as on the fact that their sensor-specific advantages and limitations are strongly connected to the environmental characteristics of the area under investigation. Results show that improved built-up area extractions can be achieved with the proposed method.

  16. Spatial Resolution Characterization for QuickBird Image Products 2003-2004 Season

    NASA Technical Reports Server (NTRS)

    Blonski, Slawomir

    2006-01-01

    This presentation focuses on spatial resolution characterization for QuickBird panochromatic images in 2003-2004 and presents data measurements and analysis of SSC edge target deployment and edge response extraction and modeling. The results of the characterization are shown as values of the Modulation Transfer Function (MTF) at the Nyquist spatial frequency and as the Relative Edge Response (RER) components. The results show that RER is much less sensitive to accuracy of the curve fitting than the value of MTF at Nyquist frequency. Therefore, the RER/edge response slope is a more robust estimator of the digital image spatial resolution than the MTF. For the QuickBird panochromatic images, the RER is consistently equal to 0.5 for images processed with the Cubic Convolution resampling and to 0.8 for the MTF resampling.

  17. Using higher-level inquiry to improve spatial ability in an introductory geology course

    NASA Astrophysics Data System (ADS)

    Stevens, Lacey A.

    Visuo-spatial skills, the ability to visually take in information and create a mental image are crucial for success in fields involving science, technology, engineering, and math (STEM) as well as fine arts. Unfortunately, due to a lack of curriculum focused on developing spatial skills, students enrolled in introductory college-level science courses tend to have difficulty with spatially-related activities. One of the best ways to engage students in science activities is through a learning and teaching strategy called inquiry. There are lower levels of inquiry wherein learning and problem-solving are guided by instructions and higher levels of inquiry wherein students have a greater degree of autonomy in learning and creating their own problem-solving strategy. A study involving 112 participants was conducted during the fall semester in 2014 at Bowling Green State University (BGSU) in an 1040 Introductory Geology Lab to determine if a new, high-level, inquiry-based lab would increase participants' spatial skills more than the traditional, low-level inquiry lab. The study also evaluated whether a higher level of inquiry differentially affected low versus high spatial ability participants. Participants were evaluated using a spatial ability assessment, and pre- and post-tests. The results of this study show that for 3-D to 2-D visualization, the higher-level inquiry lab increased participants' spatial ability more than the lower-level inquiry lab. For spatial rotational skills, all participants' spatial ability scores improved, regardless of the level of inquiry to which they were exposed. Low and high spatial ability participants were not differentially affected. This study demonstrates that a lab designed with a higher level of inquiry can increase students' spatial ability more than a lab with a low level of inquiry. A lab with a higher level of inquiry helped all participants, regardless of their initial spatial ability level. These findings show that curriculum

  18. On the sensitivity of urban hydrodynamic modelling to rainfall spatial and temporal resolution

    NASA Astrophysics Data System (ADS)

    Bruni, G.; Reinoso, R.; van de Giesen, N. C.; Clemens, F. H. L. R.; ten Veldhuis, J. A. E.

    2014-06-01

    Cities are increasingly vulnerable to floods generated by intense rainfall, because of their high degree of imperviousness, implementation of infrastructures, and changes in precipitation patterns due to climate change. Accurate information of convective storm characteristics at high spatial and temporal resolution is a crucial input for urban hydrological models to be able to simulate fast runoff processes and enhance flood prediction. In this paper, a detailed study of the sensitivity of urban hydrological response to high resolution radar rainfall was conducted. Rainfall rates derived from X-band dual polarimetric weather radar for four rainstorms were used as input into a detailed hydrodynamic sewer model for an urban catchment in Rotterdam, the Netherlands. Dimensionless parameters were derived to compare results between different storm conditions and to describe the effect of rainfall spatial resolution in relation to storm and hydrodynamic model properties: rainfall sampling number (rainfall resolution vs. storm size), catchment sampling number (rainfall resolution vs. catchment size), runoff and sewer sampling number (rainfall resolution vs. runoff and sewer model resolution respectively). Results show catchment smearing effect for rainfall resolution approaching half the catchment size, i.e. for catchments sampling numbers greater than 0.5 averaged rainfall volumes decrease about 20%. Moreover, deviations in maximum water depths, form 10 to 30% depending on the storm, occur for rainfall resolution close to storm size, describing storm smearing effect due to rainfall coarsening. Model results also show the sensitivity of modelled runoff peaks and maximum water depths to the resolution of the runoff areas and sewer density respectively. Sensitivity to temporal resolution of rainfall input seems low compared to spatial resolution, for the storms analysed in this study. Findings are in agreement with previous studies on natural catchments, thus the sampling

  19. Limits of a spatial resolution of the cascaded GEM based detectors

    NASA Astrophysics Data System (ADS)

    Kudryavtsev, V. N.; Maltsev, T. V.; Shekhtman, L. I.

    2017-06-01

    Spatial resolution of tracking detectors based on GEM cascades is determined in the simulation and measured. The simulation includes GEANT4 implemented transport of high energy electrons with careful accounting for atomic relaxation processes including emission of fluorescent photons and Auger electrons and custom post-processing taking into account diffusion, gas amplification fluctuations, the distribution of signals over readout electrodes, electronics noise and particular algorithm of final coordinate calculation (centre-of-gravity algorithm). The simulation demonstrates that the minimum of the spatial resolution of about 10-20 μm can be achieved with a gas mixture of Ar-CO2 (75%-25%) at a strip pitch in the range from 250 μm to 300 μm. At a larger pitch the resolution quickly degrades reaching 70-100 μm at a pitch of 450-500 μm. The reasons of such behavior are discussed and corresponding hypothesis is tested. Particularly, the effect of electron cloud modification due to a GEM operation is considered using the ANSYS and Garfield++ simulation programs. The detection efficiency and spatial resolution of low-material triple-GEM detectors for the DEUTERON facility at BINP are measured at the extracted beam facility of the VEPP-4M collider. One-coordinate resolution of two detectors for the DEUTERON facility is measured with a 2 GeV electron beam. The determined values of the detectors' spatial resolution is equal to 46.6 ± 0.1 μm and 38.5 ± 0.2 μm for orthogonal tracks in two detectors, respectively.

  20. Estimating Carbon Storage and Sequestration by Urban Trees at Multiple Spatial Resolutions

    NASA Astrophysics Data System (ADS)

    Wu, J.; Tran, A.; Liao, A.

    2010-12-01

    Urban forests are an important component of urban-suburban environments. Urban trees provide not only a full range of social and psychological benefits to city dwellers, but also valuable ecosystem services to communities, such as removing atmospheric carbon dioxide, improving air quality, and reducing storm water runoff. There is an urgent need for developing strategic conservation plans for environmentally sustainable urban-suburban development based on the scientific understanding of the extent and function of urban forests. However, several challenges remain to accurately quantify various environmental benefits provided by urban trees, among which is to deal with the effect of changing spatial resolution and/or scale. In this study, we intended to examine the uncertainties of carbon storage and sequestration associated with the tree canopy coverage of different spatial resolutions. Multi-source satellite imagery data were acquired for the City of Fullerton, located in Orange County of California. The tree canopy coverage of the study area was classified at three spatial resolutions, ranging from 30 m (Landsat-5 Thematic Mapper), 15 m (Advanced Spaceborne Thermal Emission and Reflection Radiometer), to 2.5 m (QuickBird). We calculated the amount of carbon stored in the trees represented on the individual tree coverage maps and the annual carbon taken up by the trees with a model (i.e., CITYgreen) developed by the U.S. Forest Service. The results indicate that urban trees account for significant proportions of land cover in the study area even with the low spatial resolution data. The estimated carbon fixation benefits vary greatly depending on the details of land use and land cover classification. The extrapolation of estimation from the fine-resolution stand-level to the low-resolution landscape-scale will likely not preserve reasonable accuracy.

  1. Spatial resolution of SQUID magnetometers and comparison with low noise room temperature magnetic sensors

    NASA Astrophysics Data System (ADS)

    Dolabdjian, C.; Qasimi, A.; Bloyet, D.; Mosser, V.

    2002-03-01

    Any magnetic sensor placed in a spatially inhomogeneous magnetic field delivers a signal proportional the mean field value taken over an effective area or volume which depends on the type of sensor considered. In the case of the field produced by a magnetic dipole and detected by a square or circular planar sensor, the overall measured spatial resolution ideally depends on the ratio of the mean dipole-sensor distance z0 to the square root of the effective sensor area AE. For Z 0/ A E≪1 , the spatial resolution is limited by the size of the sensor, whereas for z 0/ A E≫1 the dipole-sensor distance is the predominant factor. To compare various low noise magnetic sensors operating either at low temperature or at room temperature, we have measured their sensitivities and spatial responses to the field produced by a magnetic moment having the form of a tiny circular current loop. The sensors could be moved in all directions with respect to the current loop. The transfer of each sensor to the magnetic dipole field was compared to their response in a homogeneous field so as to deduce their effective area and compare this area to that deduced from independent spatial resolution measurements. We report the experimental results given by four types of sensors namely a dc-SQUID, a Hall effect sensor, a giant magneto-resistive sensor and a flux-gate sensor and discuss them by mean of a “figure of merit” criterion combining their spatial resolution and their sensitivity.

  2. Spatially adaptive probabilistic computation of a sub-kilometre resolution lightning climatology for New Zealand

    NASA Astrophysics Data System (ADS)

    Etherington, Thomas R.; Perry, George L. W.

    2017-01-01

    Lightning is a key component of the Earth's atmosphere and climate systems, and there is a potential positive feedback between a warming climate and increased lightning activity. In the biosphere, lightning is important as the main natural ignition source for wildfires and because of its contribution to the nitrogen cycle. Therefore, it is important to develop lightning climatologies to characterise and monitor lightning activity. While traditional methods for constructing lightning climatologies are suitable for examining lightning's influence on atmospheric processes, they are less well suited for examining questions about biosphere-lightning interactions. For example, examining the interaction between lightning and wildfires requires linking atmospheric processes to finer scale terrestrial processes and patterns. Most wildfires ignited by lightning are less than one hectare in size, and so require lightning climatologies at a comparable spatial resolution. However, such high resolution lightning climatologies cannot be derived using the traditional cell-count methodology. Here we present a novel geocomputational approach for analysing lightning data at high spatial resolutions. Our approach is based on probabilistic computational methods and is capable of producing a sub-kilometre lightning climatology that honours the spatial accuracy of the strike locations and is adaptive to underlying spatial patterns. We demonstrate our methods by applying them to the mid-latitude oceanic landmass of New Zealand, an area with geographic conditions that are under-represented in existing lightning climatologies. Our resulting lightning climatology has unparalleled spatial resolution, and the spatial and temporal patterns we observe in it are consistent with other continental and tropical lightning climatologies. To encourage further use and development of our probabilistic approach, we provide Python scripts that demonstrate the method alongside our resulting New Zealand

  3. Effects of daily, high spatial resolution a priori profiles of satellite-derived NOx emissions

    NASA Astrophysics Data System (ADS)

    Laughner, J.; Zare, A.; Cohen, R. C.

    2016-12-01

    The current generation of space-borne NO2 column observations provides a powerful method of constraining NOx emissions due to the spatial resolution and global coverage afforded by the Ozone Monitoring Instrument (OMI). The greater resolution available in next generation instruments such as TROPOMI and the capabilities of geosynchronous platforms TEMPO, Sentinel-4, and GEMS will provide even greater capabilities in this regard, but we must apply lessons learned from the current generation of retrieval algorithms to make the best use of these instruments. Here, we focus on the effect of the resolution of the a priori NO2 profiles used in the retrieval algorithms. We show that for an OMI retrieval, using daily high-resolution a priori profiles results in changes in the retrieved VCDs up to 40% when compared to a retrieval using monthly average profiles at the same resolution. Further, comparing a retrieval with daily high spatial resolution a priori profiles to a more standard one, we show that emissions derived increase by 100% when using the optimized retrieval.

  4. Improving the spatial resolution of Magnetic Resonance Inverse Imaging via the blipped-CAIPI acquisition scheme

    PubMed Central

    Chang, Wei-Tang; Setsompop, Kawin; Ahveninen, Jyrki; Belliveau, John W.; Witzel, Thomas; Lin, Fa-Hsuan

    2014-01-01

    Using simultaneous acquisition from multiple channels of a radio-frequency (RF) coil array, magnetic resonance inverse imaging (InI) achieves functional MRI acquisitions at a rate of 100 ms per whole-brain volume. InI accelerates the scan by leaving out partition encoding steps and reconstructs images by solving under-determined inverse problems using RF coil sensitivity information. Hence, the correlated spatial information available in the coil array causes spatial blurring in the InI reconstruction. Here, we propose a method that employs gradient blips in the partition encoding direction during the acquisition to provide extra spatial encoding in order to better differentiate signals from different partitions. According to our simulations, this blipped-InI (bInI) method can increase the average spatial resolution by 15.1% (1.3 mm) across the whole brain and from 32.6% (4.2 mm) in subcortical regions, as compared to the InI method. In a visual fMRI experiment, we demonstrate that, compared to InI, the spatial distribution of bInI BOLD response is more consistent with that of a conventional echo-planar imaging (EPI) at the level of individual subjects. With the improved spatial resolution, especially in subcortical regions, bInI can be a useful fMRI tool for obtaining high spatiotemporal information for clinical and cognitive neuroscience studies. PMID:24374076

  5. Spatial resolution versus data acquisition efficiency in mapping an inhomogeneous system with species diffusion.

    PubMed

    Chen, Fengxiang; Zhang, Yong; Gfroerer, T H; Finger, A N; Wanlass, M W

    2015-06-02

    Traditionally, spatially-resolved photoluminescence (PL) has been performed using a point-by-point scan mode with both excitation and detection occurring at the same spatial location. But with the availability of high quality detector arrays like CCDs, an imaging mode has become popular for performing spatially-resolved PL. By illuminating the entire area of interest and collecting the data simultaneously from all spatial locations, the measurement efficiency can be greatly improved. However, this new approach has proceeded under the implicit assumption of comparable spatial resolution. We show here that when carrier diffusion is present, the spatial resolution can actually differ substantially between the two modes, with the less efficient scan mode being far superior. We apply both techniques in investigation of defects in a GaAs epilayer - where isolated singlet and doublet dislocations can be identified. A superposition principle is developed for solving the diffusion equation to extract the intrinsic carrier diffusion length, which can be applied to a system with arbitrarily distributed defects. The understanding derived from this work is significant for a broad range of problems in physics and beyond (for instance biology) - whenever the dynamics of generation, diffusion, and annihilation of species can be probed with either measurement mode.

  6. Improving the spatial resolution of magnetic resonance inverse imaging via the blipped-CAIPI acquisition scheme.

    PubMed

    Chang, Wei-Tang; Setsompop, Kawin; Ahveninen, Jyrki; Belliveau, John W; Witzel, Thomas; Lin, Fa-Hsuan

    2014-05-01

    Using simultaneous acquisition from multiple channels of a radio-frequency (RF) coil array, magnetic resonance inverse imaging (InI) achieves functional MRI acquisitions at a rate of 100ms per whole-brain volume. InI accelerates the scan by leaving out partition encoding steps and reconstructs images by solving under-determined inverse problems using RF coil sensitivity information. Hence, the correlated spatial information available in the coil array causes spatial blurring in the InI reconstruction. Here, we propose a method that employs gradient blips in the partition encoding direction during the acquisition to provide extra spatial encoding in order to better differentiate signals from different partitions. According to our simulations, this blipped-InI (bInI) method can increase the average spatial resolution by 15.1% (1.3mm) across the whole brain and from 32.6% (4.2mm) in subcortical regions, as compared to the InI method. In a visual fMRI experiment, we demonstrate that, compared to InI, the spatial distribution of bInI BOLD response is more consistent with that of a conventional echo-planar imaging (EPI) at the level of individual subjects. With the improved spatial resolution, especially in subcortical regions, bInI can be a useful fMRI tool for obtaining high spatiotemporal information for clinical and cognitive neuroscience studies.

  7. Spatial Resolution Versus Data Acquisition Efficiency in Mapping an Inhomogeneous System with Species Diffusion

    DOE PAGES

    Chen, Fengxiang; Zhang, Yong; Gfroerer, T. H.; ...

    2015-06-02

    Traditionally, spatially-resolved photoluminescence (PL) has been performed using a point-by-point scan mode with both excitation and detection occurring at the same spatial location. But with the availability of high quality detector arrays like CCDs, an imaging mode has become popular for performing spatially-resolved PL. By illuminating the entire area of interest and collecting the data simultaneously from all spatial locations, the measurement efficiency can be greatly improved. However, this new approach has proceeded under the implicit assumption of comparable spatial resolution. We show here that when carrier diffusion is present, the spatial resolution can actually differ substantially between the twomore » modes, with the less efficient scan mode being far superior. We apply both techniques in investigation of defects in a GaAs epilayer – where isolated singlet and doublet dislocations can be identified. A superposition principle is developed for solving the diffusion equation to extract the intrinsic carrier diffusion length, which can be applied to a system with arbitrarily distributed defects. The understanding derived from this work is significant for a broad range of problems in physics and beyond (for instance biology) – whenever the dynamics of generation, diffusion, and annihilation of species can be probed with either measurement mode.« less

  8. Spatial Resolution Versus Data Acquisition Efficiency in Mapping an Inhomogeneous System with Species Diffusion

    SciTech Connect

    Chen, Fengxiang; Zhang, Yong; Gfroerer, T. H.; Finger, A. N.; Mark W. Wanlass

    2015-06-02

    Traditionally, spatially-resolved photoluminescence (PL) has been performed using a point-by-point scan mode with both excitation and detection occurring at the same spatial location. But with the availability of high quality detector arrays like CCDs, an imaging mode has become popular for performing spatially-resolved PL. By illuminating the entire area of interest and collecting the data simultaneously from all spatial locations, the measurement efficiency can be greatly improved. However, this new approach has proceeded under the implicit assumption of comparable spatial resolution. We show here that when carrier diffusion is present, the spatial resolution can actually differ substantially between the two modes, with the less efficient scan mode being far superior. We apply both techniques in investigation of defects in a GaAs epilayer – where isolated singlet and doublet dislocations can be identified. A superposition principle is developed for solving the diffusion equation to extract the intrinsic carrier diffusion length, which can be applied to a system with arbitrarily distributed defects. The understanding derived from this work is significant for a broad range of problems in physics and beyond (for instance biology) – whenever the dynamics of generation, diffusion, and annihilation of species can be probed with either measurement mode.

  9. From high spatial resolution imagery to spatial indicators : Application for hydromorphy follow-up on Bourgneuf wetland

    NASA Astrophysics Data System (ADS)

    Bailly, J. S.; Puech, C.; Lukac, F.; Massé, J.

    2003-04-01

    On Atlantic coastal wetlands, the understanding of hydrological processes may refer to hydraulic surface structures characterization as small ditches or channels networks, permanent and temporary water bodies. Moreover to improve the understanding, this characerization should be realized regarding different seasons and different spatial scales: elementary parcel, managment unit and whole wetland scales. In complement to usual observations on a few local ground points, high spatial resolution remote sensing may be a good information support for extraction and characterization on elementary objects, especially water bodies, permanents or temporary ones and ditches. To carry out a floow-up on wetlands, a seasonal image acquisition rate, reachable from most of satelite systems, is in that case informative for hydrological needs. In this work, georeferencing methods on openfield wetlands have been handled with care in order to use diachronic images or combined geographical data; lack of relief, short vegetation and well structured landscape make this preprocess easier in comparison to other landscape situations. In this presentation we focus on spatial hydromorphy parameters constructed from images with specific processes. Especially, hydromorphy indicators for parcels or managment units have been developped using an IRC winter-spring-summer metric resolution set of images: these descriptors are based on water areas evolution or hydrophyl vegetations presence traducing hydrodynamic submersion behaviour in temporary water bodies. An other example presents a surface water network circulation indicator elaborated on IRC aerial photography combined with vectorized geographic database. This indicator is based on ditches width and vegetation presence : a specific process uses vectorized geo data set to define transects across ditches on which classified image analysis is carried out (supervised classification). These first results proposing hydromorphy descriptors from very

  10. Applications of high-resolution spatial discretization scheme and Jacobian-free Newton–Krylov method in two-phase flow problems

    SciTech Connect

    Zou, Ling; Zhao, Haihua; Zhang, Hongbin

    2015-09-01

    The majority of the existing reactor system analysis codes were developed using low-order numerical schemes in both space and time. In many nuclear thermal–hydraulics applications, it is desirable to use higher-order numerical schemes to reduce numerical errors. High-resolution spatial discretization schemes provide high order spatial accuracy in smooth regions and capture sharp spatial discontinuity without nonphysical spatial oscillations. In this work, we adapted an existing high-resolution spatial discretization scheme on staggered grids in two-phase flow applications. Fully implicit time integration schemes were also implemented to reduce numerical errors from operator-splitting types of time integration schemes. The resulting nonlinear system has been successfully solved using the Jacobian-free Newton–Krylov (JFNK) method. The high-resolution spatial discretization and high-order fully implicit time integration numerical schemes were tested and numerically verified for several two-phase test problems, including a two-phase advection problem, a two-phase advection with phase appearance/disappearance problem, and the water faucet problem. Numerical results clearly demonstrated the advantages of using such high-resolution spatial and high-order temporal numerical schemes to significantly reduce numerical diffusion and therefore improve accuracy. Our study also demonstrated that the JFNK method is stable and robust in solving two-phase flow problems, even when phase appearance/disappearance exists.

  11. High Spatial Resolution X-Ray Spectroscopy of Cas A with Chandra

    NASA Astrophysics Data System (ADS)

    Yang, Xue-Juan; Lu, Fang-Jun; Chen, Li

    2008-08-01

    We present high spatial resolution X-ray spectroscopy of the supernova remnant Cassiopeia A with the Chandra observations. The X-ray emitting region of this remnant was divided into 38 × 34 pixels of 10″× 10″ each. Spectra of 960 pixels were created and fitted with an absorbed two component non-equilibrium ionization model. From the results of the spectral analysis we obtained maps of absorbing column density, temperatures, ionization ages, and the abundances of Ne, Mg, Si, S, Ca and Fe. The Si, S and possibly Ca abundance maps show obvious jet structures, while Fe does not follow the jet but seems to be distributed perpendicular to it. The abundances of Si, S and Ca show tight correlations between one another over a range of about two dex. This suggests that they are ejecta from explosive O-burning and incomplete Si-burning. Meanwhile, the Ne abundance is well correlated with that of Mg, indicating them to be the ashes of explosive C/Ne burning. The Fe abundance is positively correlated with that of Si when the latter is lower than 3 times the solar value, and is negatively correlated when higher. We suggest that such a two phase correlation is due to the different ways in which Fe was synthesized.

  12. Integrating flood modelling in a hydrological catchment model: flow approximations and spatial resolution.

    NASA Astrophysics Data System (ADS)

    van den Bout, Bastian; Jetten, Victor

    2017-04-01

    Within hydrological models, flow approximations are commonly used to reduce computation time. The validity of these approximations is strongly determined by flow height, flow velocity, the spatial resolution of the model, and by the manner in which flow routing is implemented. The assumptions of these approximations can furthermore limit emergent behavior, and influence flow behavior under space-time scaling. In this presentation, the validity and performance of the kinematic, diffusive and dynamic flow approximations are investigated for use in a catchment-based flood model. Particularly, the validity during flood events and for varying spatial resolutions is investigated. The OpenLISEM hydrological model is extended to implement these flow approximations and channel flooding based on dynamic flow. The kinematic routing uses a predefined converging flow network, the diffusive and dynamic routing uses a 2D flow solution over a DEM. The channel flow in all cases is a 1D kinematic wave approximation. The flow approximations are used to recreate measured discharge in three catchments of different size in China, Spain and Italy, among which is the hydrograph of the 2003 flood event in the Fella river basin (Italy). Furthermore, spatial resolutions are varied for the flood simulation in order to investigate the influence of spatial resolution on these flow approximations. Results show that the kinematic, diffusive and dynamic flow approximation provide least to highest accuracy, respectively, in recreating measured temporal variation of the discharge. Kinematic flow, which is commonly used in hydrological modelling, substantially over-estimates hydrological connectivity in the simulations with a spatial resolution of below 30 meters. Since spatial resolutions of models have strongly increased over the past decades, usage of routed kinematic flow should be reconsidered. In the case of flood events, spatial modelling of kinematic flow substantially over

  13. The altitude of Neptune cloud features from high-spatial-resolution near-infrared spectra

    NASA Astrophysics Data System (ADS)

    Gibbard, S. G.; de Pater, I.; Roe, H. G.; Martin, S.; Macintosh, B. A.; Max, C. E.

    2003-12-01

    We report on observations of Neptune from the 10-meter W.M. Keck II Telescope on June 17-18 (UT) 2000 and August 2-3 (UT) 2002 using the adaptive optics (AO) system to obtain a spatial resolution of 0.06 arcseconds. With this spatial resolution we can obtain spectra of individual bright features on the disk of Neptune in a filter centered near 2 microns. The use of a gas-only, simple reflecting layer radiative transfer model allows us to estimate the best fit altitudes of 18 bright features seen on these 4 nights and to set a constraint on the fraction of hydrogen in ortho/para equilibrium. On these nights there were three main types of features observed: northern hemisphere features in the range from +30 to -45 degrees; southern hemisphere features in the range from -30 to -50 degrees; and small southern features at -70 degrees. We find that the altitudes of the northern features are in the range from 0.023-0.064 bar, which places them in Neptune's stratosphere. Southern features at -30 to -50 degrees are mainly at altitudes from 0.10 to 0.14 bars. The small features at -70 degrees are somewhat deeper in the upper troposphere, at 0.17 and 0.27 bars. This pattern of features located at higher altitudes in the northern hemisphere and lower altitudes in the south has also been noted by previous observers. The best fits for all the observed spectra give a value of 1.0 for the fraction of hydrogen in ortho/para equilibrium; the value of the helium fraction is less well constrained by the data at 0.24. We suggest that the southern mid-latitude features are methane haze circulated up from below, while the -70° features may be isolated areas of upwelling in a general area of subsidence. Northern bright features may be due to subsidence of stratospheric haze material rather than upwelling and condensation of methane gas. We suggest that convection efficiently transports methane ice clouds to the tropopause in the Southern mid latitudes and thus plays a key role in the

  14. Investigation of LANDSAT follow-on thematic mapper spatial, radiometric and spectral resolution

    NASA Technical Reports Server (NTRS)

    Nalepka, R. F. (Principal Investigator); Morgenstern, J. P.; Kent, E. R.; Erickson, J. D.

    1976-01-01

    The author has identified the following significant results. Fine resolution M7 multispectral scanner data collected during the Corn Blight Watch Experiment in 1971 served as the basis for this study. Different locations and times of year were studied. Definite improvement using 30-40 meter spatial resolution over present LANDSAT 1 resolution and over 50-60 meter resolution was observed, using crop area mensuration as the measure. Simulation studies carried out to extrapolate the empirical results to a range of field size distributions confirmed this effect, showing the improvement to be most pronounced for field sizes of 1-4 hectares. Radiometric sensitivity study showed significant degradation of crop classification accuracy immediately upon relaxation from the nominally specified values of 0.5% noise equivalent reflectance. This was especially the case for data which were spectrally similar such as that collected early in the growing season and also when attempting to accomplish crop stress detection.

  15. IR-MALDESI Mass Spectrometry Imaging at 50 Micron Spatial Resolution

    NASA Astrophysics Data System (ADS)

    Bokhart, Mark T.; Manni, Jeffrey; Garrard, Kenneth P.; Ekelöf, Måns; Nazari, Milad; Muddiman, David C.

    2017-10-01

    High spatial resolution in mass spectrometry imaging (MSI) is crucial to understanding the biology dictated by molecular distributions in complex tissue systems. Here, we present MSI using infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) at 50 μm resolution. An adjustable iris, beam expander, and an aspherical focusing lens were used to reduce tissue ablation diameters for MSI at high resolution. The laser beam caustic was modeled using laser ablation paper to calculate relevant laser beam characteristics. The minimum laser spot diameter on the tissue was determined using tissue staining and microscopy. Finally, the newly constructed optical system was used to image hen ovarian tissue with and without oversampling, detailing tissue features at 50 μm resolution. [Figure not available: see fulltext.

  16. Enhancing spatial resolution of infrared imagery using overlap of sequence images

    NASA Astrophysics Data System (ADS)

    Cao, Jiahao; Li, Chunlai; Jin, Jian; Ji, Hongzhen; Zhang, Xudong; Wang, Jianyu

    2016-05-01

    The high-resolution thermal infrared image, by which the information of a scene can be described in details, is extensively used in many fields including computer vision process, medicine, and remote sensing, etc. This paper introduces a super-resolution reconstruction algorithm in combination of phase re