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Sample records for dynamic aperture evaluation

  1. Evaluating the dynamic aperture evaluation for the new RHIC 250 GeV polarized proton lattice

    SciTech Connect

    Gu, X.; Luo, Y.; Fischer, W.; Huang, H.; Tepikian, S.

    2011-03-28

    To increase luminosity in the Relativistic Heavy Ion Collider's (RHIC's) polarized proton 250 GeV operations, we are considering reducing {beta}* to 0.65 m at the interaction points (IPs), and increasing bunch intensity. The new working point near the 2/3 integer will used on the ramp to preserve polarization. In addition, we plan to adjust the betatron-phase advances between IP6 and IP8 to (k+1/2)*{pi} so to lower the dynamic beta-beat from the beam-beam interaction. The effects of all these changes will impact the dynamic aperture, and hence, it must be evaluated carefully. In this article, we present the results of tracking the dynamic aperture with the proposed lattices.

  2. Dynamic aperture evaluation of the proposed lattices for the RHIC 2009 polarized proton run

    SciTech Connect

    Luo,Y.; Bai, M.; Beebe-Wang, J.; Fischer, W.; Montag, C.; Robert-Demolaize, G.; Satogata, T.; Tepikian, S.; Trbojevic, D.

    2009-01-02

    In the article we evaluate the dynamic apertures of the proposed lattices for the coming Relativistic Heavy Ion Collider (RHIC) 2009 polarized proton (pp) 100 GeV and 250 GeV runs. One goal of this study is to find out the appropriate {beta}* for the coming 2009 pp runs. Another goal is to study the effect of second order chromaticity correction in the RHIC pp runs.

  3. Diagnostic for dynamic aperture

    SciTech Connect

    Morton, P.L.; Pellegrin, J.L.; Raubenheimer, T.; Rivkin, L.; Ross, M.; Ruth, R.D.; Spence, W.L.

    1985-04-01

    In large accelerators and low beta colliding beam storage rings, the strong sextupoles, which are required to correct the chromatic effects, produce strong nonlinear forces which act on particles in the beam. In addition in large hadron storage rings the superconducting magnets have significant nonlinear fields. To understand the effects of these nonlinearities on the particle motion there is currently a large theoretical effort using both analytic techniques and computer tracking. This effort is focused on the determination of the 'dynamic aperture' (the stable acceptance) of both present and future accelerators and storage rings. A great deal of progress has been made in understanding nonlinear particle motion, but very little experimental verification of the theoretical results is available. In this paper we describe 'dynamic tracking', a method being studied at the SPEAR storage ring, which can be used to obtain experimental results which are in a convenient form to be compared with the theoretical predictions.

  4. Dynamic aperture measurement on Aladdin

    SciTech Connect

    Bridges, J.; Cho, Y.; Chou, W.; Crosbie, E.; Kramer, S.; Kustom, R.; Voss, D.; Teng, L.; Kleman, K.; Otte, R.; Trzeciak, W.; Symon, K.; Wisconsin Univ., Stoughton, WI . Synchrotron Radiation Center; Wisconsin Univ., Madison, WI . Dept. of Physics)

    1989-01-01

    The sextupole-induced non-linear transverse beam dynamics in the synchrotron radiation storage ring Aladdin is studied. Specifically, the dynamic aperture is measured as function of the sextupole strength. The results agree reasonably well with computer simulations. 1 ref., 8 figs., 1 tab.

  5. PDII- Additional discussion of the dynamic aperture

    SciTech Connect

    Norman M. Gelfand

    2002-07-23

    This note is in the nature of an addition to the dynamic aperture calculations found in the report on the Proton Driver, FERMILAB-TM-2169. A extensive discussion of the Proton Driver lattice, as well as the nomenclature used to describe it can be found in TM-2169. Basically the proposed lattice is a racetrack design with the two arcs joined by two long straight sections. The straight sections are dispersion free. Tracking studies were undertaken with the objective of computing the dynamic aperture for the lattice and some of the results have been incorporated into TM-2169. This note is a more extensive report of those calculations.

  6. Dynamic metamaterial aperture for microwave imaging

    SciTech Connect

    Sleasman, Timothy; Imani, Mohammadreza F.; Gollub, Jonah N.; Smith, David R.

    2015-11-16

    We present a dynamic metamaterial aperture for use in computational imaging schemes at microwave frequencies. The aperture consists of an array of complementary, resonant metamaterial elements patterned into the upper conductor of a microstrip line. Each metamaterial element contains two diodes connected to an external control circuit such that the resonance of the metamaterial element can be damped by application of a bias voltage. Through applying different voltages to the control circuit, select subsets of the elements can be switched on to create unique radiation patterns that illuminate the scene. Spatial information of an imaging domain can thus be encoded onto this set of radiation patterns, or measurements, which can be processed to reconstruct the targets in the scene using compressive sensing algorithms. We discuss the design and operation of a metamaterial imaging system and demonstrate reconstructed images with a 10:1 compression ratio. Dynamic metamaterial apertures can potentially be of benefit in microwave or millimeter wave systems such as those used in security screening and through-wall imaging. In addition, feature-specific or adaptive imaging can be facilitated through the use of the dynamic aperture.

  7. Dynamic metamaterial aperture for microwave imaging

    NASA Astrophysics Data System (ADS)

    Sleasman, Timothy; F. Imani, Mohammadreza; Gollub, Jonah N.; Smith, David R.

    2015-11-01

    We present a dynamic metamaterial aperture for use in computational imaging schemes at microwave frequencies. The aperture consists of an array of complementary, resonant metamaterial elements patterned into the upper conductor of a microstrip line. Each metamaterial element contains two diodes connected to an external control circuit such that the resonance of the metamaterial element can be damped by application of a bias voltage. Through applying different voltages to the control circuit, select subsets of the elements can be switched on to create unique radiation patterns that illuminate the scene. Spatial information of an imaging domain can thus be encoded onto this set of radiation patterns, or measurements, which can be processed to reconstruct the targets in the scene using compressive sensing algorithms. We discuss the design and operation of a metamaterial imaging system and demonstrate reconstructed images with a 10:1 compression ratio. Dynamic metamaterial apertures can potentially be of benefit in microwave or millimeter wave systems such as those used in security screening and through-wall imaging. In addition, feature-specific or adaptive imaging can be facilitated through the use of the dynamic aperture.

  8. The saga of the LEP dynamic aperture

    NASA Astrophysics Data System (ADS)

    Verdier, A.

    1999-05-01

    The large electron-positron collider LEP at CERN provides a beautiful example of our conceptual limits concerning the problem of dynamic aperture (short term stability of the transverse oscillations of particle trajectories) in circular machines. For the operation at 45 GeV (Z0 peak) the dynamic aperture did not pose any problem although its measurement gave a value much smaller than that predicted up to the end of 1993. After this date the measurements gave the same result as predicted but it was not possible to trace back the origin of the discrepancy. At high energy (the maximum operating energy foreseen is 100 GeV) the beam emittance increases with the square of the beam energy. Therefore, low emittance optics were proposed. These optics suffer from large anharmonicities because of the increased sextupole strengths. This led to an unexpected limitation of the beam lifetime.

  9. Dynamic Aperture Measurements at the Advanced Light Source

    SciTech Connect

    Decking, W.; Robin, D.

    1999-03-12

    A large dynamic aperture for a storage ring is of importance for long lifetimes and a high injection efficiency. Measurements of the dynamic aperture of the third generation synchrotron light source Advanced Light Source (ALS) using beam excitation with kicker magnets are presented. The experiments were done for various accelerator conditions, allowing us to investigate the influence of different working points, chromaticities, insertion devices, etc.. The results are compared both with tracking calculations and a simple model for the dynamic aperture yielding good agreements. This gives us confidence in the predictability of the nonlinear accelerator model. This is especially important for future ALS upgrades as well as new storage ring designs.

  10. Optimization of Dynamic Aperture of PEP-X Baseline Design

    SciTech Connect

    Wang, Min-Huey; Cai, Yunhai; Nosochkov, Yuri; /SLAC

    2010-08-23

    SLAC is developing a long-range plan to transfer the evolving scientific programs at SSRL from the SPEAR3 light source to a much higher performing photon source. Storage ring design is one of the possibilities that would be housed in the 2.2-km PEP-II tunnel. The design goal of PEPX storage ring is to approach an optimal light source design with horizontal emittance less than 100 pm and vertical emittance of 8 pm to reach the diffraction limit of 1-{angstrom} x-ray. The low emittance design requires a lattice with strong focusing leading to high natural chromaticity and therefore to strong sextupoles. The latter caused reduction of dynamic aperture. The dynamic aperture requirement for horizontal injection at injection point is about 10 mm. In order to achieve the desired dynamic aperture the transverse non-linearity of PEP-X is studied. The program LEGO is used to simulate the particle motion. The technique of frequency map is used to analyze the nonlinear behavior. The effect of the non-linearity is tried to minimize at the given constrains of limited space. The details and results of dynamic aperture optimization are discussed in this paper.

  11. Dynamic Aperture and Tolerances for PEP-X Ultimate Storage Ring Design

    SciTech Connect

    Borland, M.; Cai, Y.; Nosochkov, Y.; Wang, M.-H.; Hettel, R.O.; /SLAC

    2011-12-13

    A lattice for the PEP-X ultimate storage ring light source, having 11 pm-rad natural emittance at a beam energy of 4.5 GeV at zero current, using 90 m of damping wiggler and fitting into the existing 2.2-km PEP-II tunnel, has been recently designed. Such a low emittance lattice requires very strong sextupoles for chromaticity correction, which in turn introduce strong non-linear field effects that limit the beam dynamic aperture. In order to maximize the dynamic aperture we choose the cell phases to cancel the third and fourth order geometric resonances in each 8-cell arc. Four families of chromatic sextupoles and six families of geometric (or harmonic) sextupoles are added to correct the chromatic and amplitude-dependent tunes. To find the best settings of the ten sextupole families, we use a Multi-Objective Genetic Optimizer employing elegant to optimize the beam lifetime and dynamic aperture simultaneously. Then we evaluate dynamic aperture reduction caused by magnetic field multipole errors, magnet fabrication errors and misalignments. A sufficient dynamic aperture is obtained for injection, as well as workable beam lifetime.

  12. CONTROL OF DYNAMIC APERTURE FOR SYNCHROTRON LIGHT SOURCES.

    SciTech Connect

    BENGTSSON, J.

    2005-05-15

    A summary of how modern analytical and numerical techniques enable one to construct a realistic model of state-of-the-art synchrotron light sources is provided. The effects of engineering tolerances and radiation are included in a self-consistent manner. An approach for utilizing these tools to develop an effective strategy for the design and control of the dynamic aperture for such dynamical systems is also outlined.

  13. Swamp plots for dynamic aperture studies of PEP-II lattices

    SciTech Connect

    Yan, Y.T.; Irwin, J.; Cai, Y.; Chen, T.; Ritson, D.

    1995-06-01

    With a newly developed algorithm using resonance basis Lie generators and their evaluation with action-angle Poisson bracket maps (nPB tracking) the authors have been able to perform fast tracking for dynamic aperture studies of PEP-II lattices as well as incorporate lattice nonlinearities in beam-beam studies. They have been able to better understand the relationship between dynamic apertures and the tune shift and resonance coefficients in the generators of the one-turn maps. To obtain swamp plots (dynamic aperture vs. working point) of the PEP-II lattices, they first compute a one-turn resonance basis map for a nominal working point and then perform nPB tracking by switching the working point while holding fixed all other terms in the map. Results have been spot-checked by comparing with element-by-element tracking.

  14. Tuned Aperture Computed Tomography to Evaluate Osseous Healing

    PubMed Central

    Nair, M.K.; Seyedain, A.; Agarwall, S.; Webber, R.L.; Nair, U.P.; Piesco, N.P.; Mooney, M.P.; Grondahl, H.-G.

    2016-01-01

    Quantification of osseous healing is a challenging task, requiring expensive advanced imaging modalities. To improve diagnostic osseous imaging, we undertook this prospective study to explore the potential of Tuned Aperture Computed Tomography®. Eighty defects in 20 rabbit mandibles, randomly carrying an osteoblast suspension or a polymer matrix or a combination thereof or no treatment, were imaged at 3, 6, 9, and 12 weeks post-surgery. TACT slices, iteratively restored TACT, and conventional digital radiographs were evaluated. Mean-gray-value distribution within regions of interest was correlated with histomorphometric data. Lesions treated with osteoblast/polymer-matrix delivery systems demonstrated the highest mean gray-value, while the diagnostic efficacy of TACT-IR was significantly better than that of other imaging modalities (p < 0.001). Thus, TACT is an accurate imaging modality for non-destructive quantification of osseous dynamics. PMID:11597021

  15. Dynamic aperture studies for the LHC high luminosity lattice

    SciTech Connect

    Maria, R. de; Giovannozzi, M.; McIntosh, E.; Nosochkov, Y. M.; Cai, Y.; Wang, M. -H.

    2015-07-14

    Since quite some time, dynamic aperture studies have been undertaken with the aim of specifying the required field quality of the new magnets that will be installed in the LHC ring in the framework of the high-luminosity upgrade. In this paper the latest results concerning the specification work will be presented, taking into account both injection and collision energies and the field quality contribution from all the magnets in the newly designed interaction regions.

  16. Computational Investigation of Dynamic Glottal Aperture Effects on Respiratory Airflow

    NASA Astrophysics Data System (ADS)

    Xi, Jinxiang; Yan, Hong; Dong, Haibo

    2008-11-01

    The periodic movement of the glottal aperture (vocal folds) during tidal breathing has been long recognized as a factor in altering the airflow dynamics in the tracheobrnchial region. The potential influence from these altered flow structures on the transport and deposition of inhaled particles is not known. However, studies devoted to this dynamic physiological feature are scarce due to the complex anatomy in of the larynx and numerical challenges in simulating dynamic geometries. In this study, a high-fidelity immersed boundary solver is used to investigate this problem. A 3D human oral-larynx-lung model is firstly reconstructed from MRI data. The role of the vocal fold movement and associated airflow characteristics such as vortex shedding, Coanda effect etc. during inhalation and exhalation are then numerically studied.

  17. Optimization of the Dynamic Aperture for SPEAR3 Low-Emittance Upgrade

    SciTech Connect

    Wang, Lanfa; Huang, Xiaobiao; Nosochkov, Yuri; Safranek, James A.; Borland, Michael; /Argonne

    2012-05-30

    A low emittance upgrade is planned for SPEAR3. As the first phase, the emittance is reduced from 10nm to 7nm without additional magnets. A further upgrade with even lower emittance will require a damping wiggler. There is a smaller dynamic aperture for the lower emittance optics due to a stronger nonlinearity. Elegant based Multi-Objective Genetic Algorithm (MOGA) is used to maximize the dynamic aperture. Both the dynamic aperture and beam lifetime are optimized simultaneously. Various configurations of the sextupole magnets have been studied in order to find the best configuration. The betatron tune also can be optimized to minimize resonance effects. The optimized dynamic aperture increases more than 15% from the nominal case and the lifetime increases from 14 hours to 17 hours. It is important that the increase of the dynamic aperture is mainly in the beam injection direction. Therefore the injection efficiency will benefit from this improvement.

  18. Study of the asymptotic dynamic aperture in the NICA collider using symplectic tracking codes

    NASA Astrophysics Data System (ADS)

    Bolshakov, A. E.; Zenkevich, P. R.; Kozlov, O. S.

    2015-12-01

    The dependence of the dynamic aperture in the NICA collider on the number of turns has been calculated by MAD-X tracking code with the two independent algorithms: a program of symplectic tracking PTC (Polymorphic technology Tracking Code) and a program of the thin-lenses tracking method. The results of the numerical integration of particle motion forecast the asymptotic dynamic aperture and the possible losses of particles in the collider.

  19. Impact of High-Order Multipole Errors in the NSLS-II Quadrupoles and Sectupoles on Dynamic and Momentum Aperture

    SciTech Connect

    Nash,B.; Guo, W.

    2009-05-04

    Successful operation of NSLS-II requires sufficient dynamic aperture for injection, as well as momentum aperture for Touschek lifetime. We explore the dependence of momentum and dynamic aperture on higher-order multipole field errors in the quadrupoles and sextupoles. We add random and systematic multipole errors to the quadrupoles and sextupoles and compute the effect on dynamic aperture. We find that the strongest effect is at negative momentum, due to larger closed orbit excursions. Adding all the errors based on the NSLS-II specifications, we find adequate dynamic and momentum aperture.

  20. Adaptive uniform grayscale coded aperture design for high dynamic range compressive spectral imaging

    NASA Astrophysics Data System (ADS)

    Diaz, Nelson; Rueda, Hoover; Arguello, Henry

    2016-05-01

    Imaging spectroscopy is an important area with many applications in surveillance, agriculture and medicine. The disadvantage of conventional spectroscopy techniques is that they collect the whole datacube. In contrast, compressive spectral imaging systems capture snapshot compressive projections, which are the input of reconstruction algorithms to yield the underlying datacube. Common compressive spectral imagers use coded apertures to perform the coded projections. The coded apertures are the key elements in these imagers since they define the sensing matrix of the system. The proper design of the coded aperture entries leads to a good quality in the reconstruction. In addition, the compressive measurements are prone to saturation due to the limited dynamic range of the sensor, hence the design of coded apertures must consider saturation. The saturation errors in compressive measurements are unbounded and compressive sensing recovery algorithms only provide solutions for bounded noise or bounded with high probability. In this paper it is proposed the design of uniform adaptive grayscale coded apertures (UAGCA) to improve the dynamic range of the estimated spectral images by reducing the saturation levels. The saturation is attenuated between snapshots using an adaptive filter which updates the entries of the grayscale coded aperture based on the previous snapshots. The coded apertures are optimized in terms of transmittance and number of grayscale levels. The advantage of the proposed method is the efficient use of the dynamic range of the image sensor. Extensive simulations show improvements in the image reconstruction of the proposed method compared with grayscale coded apertures (UGCA) and adaptive block-unblock coded apertures (ABCA) in up to 10 dB.

  1. Optical Property Enhancement and Durability Evaluation of Heat Receiver Aperture Shield Materials

    NASA Technical Reports Server (NTRS)

    deGroh, Kim K.; Jaworske, Donald A.; Smith, Daniela C.

    1998-01-01

    Under the Solar Dynamic Flight Demonstration (SDFD) program, NASA Lewis Research Center worked with AlliedSignal Aerospace, the heat receiver contractor, on the development, characterization and durability testing of refractory metals to obtain appropriate optical and thermal properties for the SDFD heat receiver aperture shield. Molybdenum and tungsten foils were grit-blasted using silicon carbide or alumina grit under various grit-blasting conditions for optical property enhancement. Black rhenium coated tungsten foil was also evaluated. Tungsten, black rhenium-coated tungsten, and grit-blasted tungsten screens of various mesh sizes were placed over the pristine and grit-blasted foils for optical property characterization. Grit-blasting was found to be effective in decreasing the specular reflectance and the absorptance/emittance ratio of the refractory foils. The placement of a screen further enhanced these optical properties, with a grit-blasted screen over a grit-blasted foil producing the best results. Based on the optical property enhancement results, samples were tested for atomic oxygen and vacuum heat treatment durability. Grit-blasted (Al2O3 grit) 2 mil tungsten foil was chosen for the exterior layer of the SDFD heat receiver aperture shield. A 0.007 in. wire diameter, 20 x 20 mesh tungsten screen was chosen to cover the tungsten foil. Based on these test results, a heat receiver aperture shield test unit has been built with the screen covered grit-blast tungsten foil exterior layers. The aperture shield was tested and verified the thermal and structural durability of the outer foil layers during an off-pointing period.

  2. Synthetic tracked aperture ultrasound imaging: design, simulation, and experimental evaluation.

    PubMed

    Zhang, Haichong K; Cheng, Alexis; Bottenus, Nick; Guo, Xiaoyu; Trahey, Gregg E; Boctor, Emad M

    2016-04-01

    Ultrasonography is a widely used imaging modality to visualize anatomical structures due to its low cost and ease of use; however, it is challenging to acquire acceptable image quality in deep tissue. Synthetic aperture (SA) is a technique used to increase image resolution by synthesizing information from multiple subapertures, but the resolution improvement is limited by the physical size of the array transducer. With a large F-number, it is difficult to achieve high resolution in deep regions without extending the effective aperture size. We propose a method to extend the available aperture size for SA-called synthetic tracked aperture ultrasound (STRATUS) imaging-by sweeping an ultrasound transducer while tracking its orientation and location. Tracking information of the ultrasound probe is used to synthesize the signals received at different positions. Considering the practical implementation, we estimated the effect of tracking and ultrasound calibration error to the quality of the final beamformed image through simulation. In addition, to experimentally validate this approach, a 6 degree-of-freedom robot arm was used as a mechanical tracker to hold an ultrasound transducer and to apply in-plane lateral translational motion. Results indicate that STRATUS imaging with robotic tracking has the potential to improve ultrasound image quality. PMID:27088108

  3. Nasal aperture shape evaluation between black and white South Africans.

    PubMed

    McDowell, Jennifer L; L'Abbé, Ericka N; Kenyhercz, Michael W

    2012-10-10

    The purpose of this study was to combine morphoscopic and metric analyses to assess variation in nasal aperture size and shape of black and white South Africans. Thirteen landmarks were digitized from the bony nasal region of 152 crania using an electromechanic instrument for geometric morphometric (general procrustes analysis) and craniometric analyses. Elliptical Fourier analysis was used to assess shape of the nasal aperture via outlines applied through photographs. Both principal component and discriminant function analyses were applied to these statistical methods. Black South Africans were classified 95-96% correctly and white South Africans were classified 91-94% correctly. In a four-way analysis of sex and ancestry, classification accuracy ranged from 56 to 70%. Most misclassifications were between the sexes within each group which suggests an absence of sexual dimorphism. This study found that there is quantifiable variation in shape of the nasal aperture between black and white South African groups using all three statistical methods. In forensic application, standard craniometrics can be used to accurately classify an unknown person. PMID:22727267

  4. Dynamic aperture and space charge effect studies for the Recycler ring for Project-X

    SciTech Connect

    Xiao, M.; Vorobiev, L.G.; Johnson, D.E.; /Fermilab

    2010-09-01

    A simplified Recycler lattice was created to fine tune injection straight, ring tune, and phase trombone. In this paper, we will present detailed modifications for further optimization of Recycler lattice which requires the investigation of tune footprint and dynamic aperture based on higher order momentum components of the magnetic fields, together with the space charge effects.

  5. Dynamics and control of a 25-meter aperture virtual structure Gossamer telescope in GEO

    NASA Technical Reports Server (NTRS)

    Mettler, E.; Quadrelli, M.; Breckenrisge, W.

    2002-01-01

    In this paper we conduct a feasibility analysis of a 25-meter aperture virtual-structure space telescope example concept based on formation control of separated free-flying optical modules orbiting the Earth at GEO. We develop a Formation Flying implementation approach, and design and analyze the dynamics, control, metrology and estimation methods.

  6. Aperture, symmetry, isotropy, and compactness analysis and their correlation in spaghetti-like nanostructure dynamics

    NASA Astrophysics Data System (ADS)

    Purqon, Acep; Sugiyama, Ayumu; Nagao, Hidemi; Nishikawa, Kiyoshi

    2007-08-01

    Spaghetti-like nanostructures are interesting due to properties such having a flexible structure, self-assembly, and complex fluids. Moreover, their flexible structure dynamics imply a richness of dynamic properties. In this study, we propose a technique to analyze flexible structure dynamics based on the concepts of aperture, symmetry, isotropy, and compactness. Each parameter has physical meaning. We found some interesting phenomena in the dynamics, density, and correlation among those parameters. Although the dynamics of those parameters exhibit random processes, they have correlation with each other. This analysis also can explain the possible shapes in biological systems such as micelle, vesicle or membrane.

  7. Off-momentum dynamic aperture for lattices in the RHIC heavy ion runs

    SciTech Connect

    Luo Y.; Bai, M.; Blaskiewicz, M.; Gu, X.; Fischer, W.; Marusic, A.; Roser, T.; Tepikian, S.; Zhang, S.

    2012-05-20

    To reduce transverse emittance growth rates from intrabeam scattering in the RHIC heavy ion runs, a lattice with an increased phase advance in the arc FODO cells was adopted in 2008-2011. During these runs, a large beam loss due to limited off-momentum dynamic aperture was observed during longitudinal RF re-bucketing and with transverse cooling. Based on the beam loss observations in the previous ion runs and the calculated off-momentum apertures, we decided to adopt the lattice used before 2008 for the 2012 U-U and Cu-Au runs. The observed beam decay and the measured momentum aperture in the 2012 U-U run are presented.

  8. Dynamic aperture extraction studies for the SSC High-Energy Booster

    SciTech Connect

    Chao, A.W.; Dutt, S.K.; Johnson, D.E.; Sen, T.; Yan, Y.

    1990-09-01

    The final booster in the injector chain for the Superconducting Super Collider is a machine approximately twice the size of the Tevatron. Its design includes approximately 450, 15+ m superconducting dipoles. The original designs specified dipoles with a 7 cm coil-winding diameter and an inner horizontal beam-pipe aperture of 55 mm. This dipole design was chosen in order to provide an adequately large good-field aperture for both the beam injection process and for the slow-extraction of high-energy test beams. With the recent decision to increase the Collider dipole coil-winding diameter to 5 cm, the question of the needed HEB aperture was raised. An argument for dipole commonality between the HEB and Collider was developed, and a preliminary examination of a 5 cm HEB dipole was undertaken. This paper reports the results of a detailed study of the injection dynamic aperture for magnet errors corresponding to both a 5 cm and 7 cm dipole. Also studied and reported are preliminary results of the resonant-extraction process for the two magnet designs in question. These studies are in the form of multiparticle computer simulations. The results of the studies indicate that the 7 cm dipole design is consistent with the desired performance requirements for the HEB, while the 5 cm dipole design is marginal. We have not studied intermediate aperture values. 8 refs., 11 figs.

  9. OPTIMIZING THE DYNAMIC APERTURE FOR TRIPLE BEND ACHROMATIC LATTICES.

    SciTech Connect

    KRAMER, S.L.; BENGTSSON, J.

    2006-06-26

    The Triple Bend Achromatic (TBA) lattice has the potential for lower natural emittance per period than the Double Bend Achromatic (DBA) lattice for high brightness light sources. However, the DBA has been chosen for 3rd generation light sources more often due to the higher number of undulator straight section available for a comparable emittance. The TBA has considerable flexibility in linear optics tuning while maintaining this emittance advantage. We have used the tune and chromaticity flexibility of a TBA lattice to minimize the lowest order nonlinearities to implement a 3rd order achromatic tune, while maintaining a constant emittance. This frees the geometric sextupoles to counter the higher order nonlinearities. This procedure is being used to improve the nonlinear dynamics of the TBA as a proposed lattice for NSLS-II facility. The flexibility of the TBA lattice will also provide for future upgrade capabilities of the beam parameters.

  10. Effect of tune modulation on the dynamic aperture of the SSC lattice

    SciTech Connect

    Sen, Tanaji; Chao, A.W.; Yan, Y.T.

    1991-05-01

    We model the effects of magnet power supply ripple on the long term dynamic aperture of the SSC lattice by modulating the tunes. The lattice is represented by a Taylor map of twelfth order in the phase space coordinates. The transverse tunes parametrizing the rotation matrix (obtained from the linear terms of the map) are sinusoidally modulated at different choices of amplitude and frequency. Particles are tracked through this modulated map for over a million turns. The tune modulation results in a decrease of the dynamic aperture. The extent of this decrease depends largely on the tune of the lattice and to a secondary extent on the amplitude and frequency of the ripple. 3 refs., 4 figs.

  11. The dependence of the dynamic aperture on the tune in RHIC

    SciTech Connect

    Parzen, G.

    1992-01-01

    This note studies the dependence of the dynamic aperture on the choice of the operating tune {nu}{sub x}, {nu}{sub y} in RHIC. Tracking studies for 1000 turns were done over the tune range {nu}{sub x} {approx equal} {nu}{sub y} = 28 to {nu}{sub x} {approx equal} {nu}{sub y} = 29.5. It was found that in each tune interval {Delta}{nu} = 0.5, e.g. {nu} = 28.5 to {nu} = 29, the dynamic aperture as a function of the tune has 5 peaks, each of which is a possible operating point. Each of these possible operating points is in a tune region free of imperfection resonances of tenth order or less, and the width of this tune region ranges from {Delta}{nu} = 0.022 to {Delta}{nu} = 0.036. Operating tunes near integer values of {nu}, which appear desirable because of the relatively large tune interval free of imperfection resonances of 10th order or less, may not be desirable because of the lower dynamic aperture in this region. Operating near integer tunes may not be desirable for heavy ions like Au, but may be desirable for the lighter ions which do not experience a large transverse growth due to intrabeam scattering. If a loss in dynamic aperture of 2 mm is regarded as significant, then the tune range of {nu} = 28 to {nu} = 28.5 does not appear as attractive as the tune range {nu} = 28.5 to {nu} = 29.5.

  12. The dependence of the dynamic aperture on the tune in RHIC

    SciTech Connect

    Parzen, G.

    1992-08-01

    This note studies the dependence of the dynamic aperture on the choice of the operating tune {nu}{sub x}, {nu}{sub y} in RHIC. Tracking studies for 1000 turns were done over the tune range {nu}{sub x} {approx_equal} {nu}{sub y} = 28 to {nu}{sub x} {approx_equal} {nu}{sub y} = 29.5. It was found that in each tune interval {Delta}{nu} = 0.5, e.g. {nu} = 28.5 to {nu} = 29, the dynamic aperture as a function of the tune has 5 peaks, each of which is a possible operating point. Each of these possible operating points is in a tune region free of imperfection resonances of tenth order or less, and the width of this tune region ranges from {Delta}{nu} = 0.022 to {Delta}{nu} = 0.036. Operating tunes near integer values of {nu}, which appear desirable because of the relatively large tune interval free of imperfection resonances of 10th order or less, may not be desirable because of the lower dynamic aperture in this region. Operating near integer tunes may not be desirable for heavy ions like Au, but may be desirable for the lighter ions which do not experience a large transverse growth due to intrabeam scattering. If a loss in dynamic aperture of 2 mm is regarded as significant, then the tune range of {nu} = 28 to {nu} = 28.5 does not appear as attractive as the tune range {nu} = 28.5 to {nu} = 29.5.

  13. Dynamic optical aberration correction with adaptive coded apertures techniques in conformal imaging

    NASA Astrophysics Data System (ADS)

    Li, Yan; Hu, Bin; Zhang, Pengbin; Zhang, Binglong

    2015-02-01

    Conformal imaging systems are confronted with dynamic aberration in optical design processing. In classical optical designs, for combination high requirements of field of view, optical speed, environmental adaption and imaging quality, further enhancements can be achieved only by the introduction of increased complexity of aberration corrector. In recent years of computational imaging, the adaptive coded apertures techniques which has several potential advantages over more traditional optical systems is particularly suitable for military infrared imaging systems. The merits of this new concept include low mass, volume and moments of inertia, potentially lower costs, graceful failure modes, steerable fields of regard with no macroscopic moving parts. Example application for conformal imaging system design where the elements of a set of binary coded aperture masks are applied are optimization designed is presented in this paper, simulation results show that the optical performance is closely related to the mask design and the reconstruction algorithm optimization. As a dynamic aberration corrector, a binary-amplitude mask located at the aperture stop is optimized to mitigate dynamic optical aberrations when the field of regard changes and allow sufficient information to be recorded by the detector for the recovery of a sharp image using digital image restoration in conformal optical system.

  14. Fast k-space-based evaluation of imaging properties of ultrasound apertures

    NASA Astrophysics Data System (ADS)

    Zapf, M.; Dapp, R.; Hardt, M.; Henning, P. A.; Ruiter, N. V.

    2011-03-01

    At the Karlsruhe Institute of Technology (KIT) a three-dimensional ultrasound computer tomography (3D USCT) system for early breast cancer diagnosis is being developed. This method promises reproducible volume images of the female breast in 3D. Initial measurements and a simulation based optimization method, which took several physical properties into account, led to a new aperture setup. Yet this simulation is computational too demanding to systematically evaluate the different 'virtual' apertures which can be achieved by rotation and lifting of the system. In optics a Fourier based approach is available to simulate imaging systems as linear systems. For the two apertures used in our project and one hypothetical linear array aperture this concept was evaluated and compared to a reference simulation. An acceptable conformity between the new approach and the reference simulation could be shown. With this approach a fast evaluation of optimal 'virtual' apertures for specific measurement objects and imaging constraints can be carried out within an acceptable time constraint.

  15. Clinical evaluation of synthetic aperture harmonic imaging for scanning focal malignant liver lesions.

    PubMed

    Brandt, Andreas Hjelm; Hemmsen, Martin Christian; Hansen, Peter Møller; Madsen, Signe Sloth; Krohn, Paul Suno; Lange, Theis; Hansen, Kristoffer Lindskov; Jensen, Jørgen Arendt; Nielsen, Michael Bachmann

    2015-09-01

    The purpose of the study was to perform a clinical comparison of synthetic aperture sequential beamforming tissue harmonic imaging (SASB-THI) sequences with a conventional imaging technique, dynamic receive focusing with THI (DRF-THI). Both techniques used pulse inversion and were recorded interleaved using a commercial ultrasound system (UltraView 800, BK Medical, Herlev, Denmark). Thirty-one patients with malignant focal liver lesions (confirmed by biopsy or computed tomography/magnetic resonance) were scanned. Detection of malignant focal liver lesions and preference of image quality were evaluated blinded off-line by eight radiologists. In total, 2,032 evaluations of 127 image sequences were completed. The sensitivity (77% SASB-THI, 76% DRF-THI, p = 0.54) and specificity (71% SASB-THI, 72% DRF-THI, p = 0.67) of detection of liver lesions and the evaluation of image quality (p = 0.63) did not differ between SASB-THI and DRF-THI. This study indicates the ability of SASB-THI in a true clinical setting. PMID:26095533

  16. Plasmonic cavity-apertures as dynamic pixels for the simultaneous control of colour and intensity

    PubMed Central

    Yun, Hansik; Lee, Seung-Yeol; Hong, Keehoon; Yeom, Jiwoon; Lee, Byoungho

    2015-01-01

    Despite steady technological progress, displays are still subject to inherent limitations in resolution improvement and pixel miniaturization because a series of colours is generally expressed by a combination of at least three primary colour pixels. Here we propose a structure comprising a metal cavity and a nanoaperture, which we refer to as a cavity-aperture, to simultaneously control the colour and intensity of transmitted light in a single pixel. The metal cavity constructs plasmonic standing waves to organize the spatial distribution of amplitudes according to wavelength, and the nanoaperture permits light with a specific wavelength and amplitude to pass through it, depending on the nanoaperature's relative position in the cavity and the polarization state of the incident light. Therefore, the cavity-aperture has the potential to function as a dynamic colour pixel. This design method may be helpful in developing various photonic devices, such as micro-imaging systems and multiplexed sensors. PMID:25990071

  17. A global sub-aperture stitching algorithm and its precision evaluation

    NASA Astrophysics Data System (ADS)

    Zhan, Guangda; Xu, Xudong; Shen, Zhengxiang; Wang, Xiaoqiang; Wang, ZhanShan; Liu, Huasong; Ji, Yiqin

    2012-10-01

    Sub-aperture stitching interferometry is a method to test the surface of the large optics, which can effectively extend the lateral range of the standard interferometer and can also enhance its lateral resolution. The stitching algorithm based on the overlapping area plays a very important role in sub-aperture stitching interferometry. Due to the misalignment in the sub-aperture test cycle, relatively tilt and shift are calibrated. And the global stitching method is applied to minimize the differences of phase distributions in the overlapping areas. The inspection of stitching quality of the overlapping area is also necessary after the interferograms which have been stitched. This paper uses the statistical principle to evaluate the quality of the overlapping area.

  18. FODO-Supercell Based Compact Ring Design with Tunable Momentum Compaction and Optimized Dynamic Aperture

    SciTech Connect

    Sun, Yipeng; /SLAC

    2012-05-11

    A storage ring with tunable momentum compaction has the advantage in achieving different RMS bunch length with similar RF capacity, which is potentially useful for many applications, such as linear collider damping ring and pre-damping ring where injected beam has a large energy spread and a large transverse emittance. A tunable bunch length also makes the commissioning and fine tuning easier in manipulating the single bunch instabilities. In this paper, a compact ring design based on a supercell is presented, which achieves a tunable momentum compaction while maintaining a large dynamic aperture.

  19. Evaluation Digital Elevation Model Generated by Synthetic Aperture Radar Data

    NASA Astrophysics Data System (ADS)

    Makineci, H. B.; Karabörk, H.

    2016-06-01

    Digital elevation model, showing the physical and topographical situation of the earth, is defined a tree-dimensional digital model obtained from the elevation of the surface by using of selected an appropriate interpolation method. DEMs are used in many areas such as management of natural resources, engineering and infrastructure projects, disaster and risk analysis, archaeology, security, aviation, forestry, energy, topographic mapping, landslide and flood analysis, Geographic Information Systems (GIS). Digital elevation models, which are the fundamental components of cartography, is calculated by many methods. Digital elevation models can be obtained terrestrial methods or data obtained by digitization of maps by processing the digital platform in general. Today, Digital elevation model data is generated by the processing of stereo optical satellite images, radar images (radargrammetry, interferometry) and lidar data using remote sensing and photogrammetric techniques with the help of improving technology. One of the fundamental components of remote sensing radar technology is very advanced nowadays. In response to this progress it began to be used more frequently in various fields. Determining the shape of topography and creating digital elevation model comes the beginning topics of these areas. It is aimed in this work , the differences of evaluation of quality between Sentinel-1A SAR image ,which is sent by European Space Agency ESA and Interferometry Wide Swath imaging mode and C band type , and DTED-2 (Digital Terrain Elevation Data) and application between them. The application includes RMS static method for detecting precision of data. Results show us to variance of points make a high decrease from mountain area to plane area.

  20. Spatial mode dynamics in wide-aperture quantum-dot lasers

    SciTech Connect

    Mukherjee, Jayanta; McInerney, John G.

    2009-05-15

    We present a systematic theoretical study of spatial mode dynamics in wide-aperture semiconductor quantum-dot lasers within the Maxwell-Bloch formalism. Our opto-electro-thermal model self-consistently captures the essential dynamical coupling between field, polarization, and carrier density in both thermal and nonthermal regimes, providing detailed description of the complex spatiotemporal modal intensity structure and spectra in these novel devices and broad area edge-emitting lasers in general. Using linear stability analysis and high resolution adaptive-grid finite element numerical simulation, we show that in the nonthermal regime, the presence of inhomogeneous broadening in quantum-dot active media leads to suppressed filamentation and enhanced spatial coherence compared to conventional quantum well devices with comparable phase-amplitude coupling (alpha parameter). Increasing the degree of inhomogeneous broadening in the active medium leads to further improvement in spatial coherence. In the thermal regime, there is further suppression of filamentation in the inhomogeneously broadened quantum-dot active medium; however, the spatial coherence aided by inhomogeneous broadening is partly lost due to the effect of temperature on cavity detuning. We propose that device designs based on optimized inhomogeneous broadening of quantum-dot gain medium could ultimately lead to diffraction-limited outputs in the quasi-cw regime which are still very difficult to achieve in conventional wide-aperture designs.

  1. Simulation study of dynamic aperture with head-on beam-beam compensation in the RHIC

    SciTech Connect

    Luo, Y.; Fischer, W.

    2010-08-01

    In this note we summarize the calculated 10{sup 6} turn dynamic apertures with the proposed head-on beam-beam compensation in the Relativistic Heavy Ion Collider (RHIC). To compensate the head-on beam-beam effect in the RHIC 250 GeV polarized proton run, we are planning to introduce a DC electron beam with the same transverse profile as the proton beam to collide with the proton beam. Such a device to provide the electron beam is called an electron lens (e-lens). In this note we first present the optics and beam parameters and the tracking setup. Then we compare the calculated dynamic apertures without and with head-on beam-beam compensation. The effects of adjusted phase advances between IP8 and the center of e-lens and second order chromaticity correction are checked. In the end we will scan the proton and electron beam parameters with head-on beam-beam compensation.

  2. Radiometric calibration method for large aperture infrared system with broad dynamic range.

    PubMed

    Sun, Zhiyuan; Chang, Songtao; Zhu, Wei

    2015-05-20

    Infrared radiometric measurements can acquire important data for missile defense systems. When observation is carried out by ground-based infrared systems, a missile is characterized by long distance, small size, and large variation of radiance. Therefore, the infrared systems should be manufactured with a larger aperture to enhance detection ability and calibrated at a broader dynamic range to extend measurable radiance. Nevertheless, the frequently used calibration methods demand an extended-area blackbody with broad dynamic range or a huge collimator for filling the system's field stop, which would greatly increase manufacturing costs and difficulties. To overcome this restriction, a calibration method based on amendment of inner and outer calibration is proposed. First, the principles and procedures of this method are introduced. Then, a shifting strategy of infrared systems for measuring targets with large fluctuations of infrared radiance is put forward. Finally, several experiments are performed on a shortwave infrared system with Φ400  mm aperture. The results indicate that the proposed method cannot only ensure accuracy of calibration but have the advantage of low cost, low power, and high motility. Hence, it is an effective radiometric calibration method in the outfield. PMID:26192499

  3. An evaluation of nasal bone and aperture shape among three South African populations.

    PubMed

    McDowell, Jennifer L; Kenyhercz, Michael W; L'Abbé, Ericka N

    2015-07-01

    Reliable and valid population specific standards are necessary to accurately develop a biological profile, which includes an estimation of peer-reported social identification (Hefner, 2009). During the last 300 years, colonialism, slavery and apartheid created geographic, physical and social divisions of population groups in South Africa. The purpose of this study was to evaluate variation in nasal bone and aperture shape in a modern population of black, white, and coloured South Africans using standard craniometric variables and geometric morphometrics, namely general Procrustes and elliptical Fourier analyses. Fourteen standard landmarks were digitally recorded or computationally derived from 310 crania using a 3D coordinate digitizer for discriminant function, principal components and generalized Procrustes analyses. For elliptical Fourier analysis, outlines of the nasal aperture were generated from standardized photographs. All classification accuracies were better than chance; the lowest accuracies were for coloured and the highest accuracies were for white South Africans. Most difficulties arose in distinguishing coloured and black South African groups from each other. Generally, misclassifications were noted between the sexes within each group rather than among groups, which suggests that sex has less influence on nasal bone and aperture shape than ancestry. Quantifiable variation in shape of the nasal aperture region between white and non-white South African groups was observed. PMID:25963274

  4. Studies of the chromatic properties and dynamic aperture of the BNL colliding-beam accelerator. [PATRICIA particle tracking code

    SciTech Connect

    Dell, G.F.

    1983-01-01

    The PATRICIA particle tracking program has been used to study chromatic effects in the Brookhaven CBA (Colliding Beam Accelerator). The short term behavior of particles in the CBA has been followed for particle histories of 300 turns. Contributions from magnet multipoles characteristic of superconducting magnets and closed orbit errors have been included in determining the dynamic aperture of the CBA for on and off momentum particles. The width of the third integer stopband produced by the temperature dependence of magnetization induced sextupoles in the CBA cable dipoles is evaluated for helium distribution systems having periodicity of one and six. The stopband width at a tune of 68/3 is naturally zero for the system having a periodicity of six and is approx. 10/sup -4/ for the system having a periodicity of one. Results from theory are compared with results obtained with PATRICIA; the results agree within a factor of slightly more than two.

  5. Closed-Form Evaluation of Mutual Coupling in a Planar Array of Circular Apertures

    NASA Technical Reports Server (NTRS)

    Bailey, M. C.

    1996-01-01

    The integral expression for the mutual admittance between circular apertures in a planar array is evaluated in closed form. Very good accuracy is realized when compared with values that were obtained by numerical integration. Utilization of this closed-form expression, for all element pairs that are separated by more than one element spacing, yields extremely accurate results and significantly reduces the computation time that is required to analyze the performance of a large electronically scanning antenna array.

  6. Saturated flow in a single fracture: Evaluation of the Reynolds equation in measured aperture fields

    SciTech Connect

    NICHOLL,M.J.; RAJARAM,H.; GLASS JR.,ROBERT J.; DETWILER,R.

    2000-01-28

    Fracture transmissivity and detailed aperture fields are measured in analog fractures specially designed to evaluate the utility of the Reynolds equation. The authors employ a light transmission technique with well-defined accuracy ({approximately}1% error) to measure aperture fields at high spatial resolution ({approximately}0.015 cm). A Hele-Shaw cell is used to confirm the approach by demonstrating agreement between experimental transmissivity, simulated transmissivity on the measured aperture field, and the parallel plate law. In the two rough-walled analog fractures considered, the discrepancy between the experimental and numerical estimates of fracture transmissivity was sufficiently large ({approximately} 22--47%) to exclude numerical and experimental errors (< 2%)as a source. They conclude that the three-dimensional character of the flow field is important for fully describing fluid flow in the two rough-walled fractures considered, and that the approach of depth averaging inherent in the formulation of the Reynolds equation is inadequate. They also explore the effects of spatial resolution, aperture measurement technique, and alternative definitions for link transmissivities in the finite-difference formulation, including some that contain corrections for tortuosity perpendicular to the mean fracture plane and Stokes flow. Various formulations for link transmissivity are shown to converge at high resolution ({approximately} 1/5 the spatial correlation length) in the smoothly varying fracture. At coarser resolutions, the solution becomes increasingly sensitive to definition of link transmissivity and measurement technique. Aperture measurements that integrate over individual grid blocks were less sensitive to measurement scale and definition of link transmissivity than point sampling techniques.

  7. Monitoring of chromosome dynamics of single yeast cells in a microfluidic platform with aperture cell traps.

    PubMed

    Jin, Si Hyung; Jang, Sung-Chan; Lee, Byungjin; Jeong, Heon-Ho; Jeong, Seong-Geun; Lee, Sung Sik; Kim, Keun Pil; Lee, Chang-Soo

    2016-04-12

    Chromosome movement plays important roles in DNA replication, repair, genetic recombination, and epigenetic phenomena during mitosis and meiosis. In particular, chromosome movement in the nuclear space is essential for the reorganization of the nucleus. However, conventional methods for analyzing the chromosome movements in vivo have been limited by technical constraints of cell trapping, cell cultivation, oxygenation, and in situ imaging. Here, we present a simple microfluidic platform with aperture-based cell trapping arrays to monitor the chromosome dynamics in single living cells for a desired period of time. Under the optimized conditions, our microfluidic platform shows a single-cell trapping efficiency of 57%. This microfluidic approach enables in situ imaging of intracellular dynamics in living cells responding to variable input stimuli under the well-controlled microenvironment. As a validation of this microfluidic platform, we investigate the fundamental features of the dynamic cellular response of the individual cells treated with different stimuli and drug. We prove the basis for dynamic chromosome movement in single yeast cells to be the telomere and nuclear envelope ensembles that attach to and move in concert with nuclear actin cables. Therefore, these results illustrate the monitoring of cellular functions and obtaining of dynamic information at a high spatiotemporal resolution through the integration of a simple microfluidic platform. PMID:26980179

  8. Coded aperture coherent scatter imaging for breast cancer detection: a Monte Carlo evaluation

    NASA Astrophysics Data System (ADS)

    Lakshmanan, Manu N.; Morris, Robert E.; Greenberg, Joel A.; Samei, Ehsan; Kapadia, Anuj J.

    2016-03-01

    It is known that conventional x-ray imaging provides a maximum contrast between cancerous and healthy fibroglandular breast tissues of 3% based on their linear x-ray attenuation coefficients at 17.5 keV, whereas coherent scatter signal provides a maximum contrast of 19% based on their differential coherent scatter cross sections. Therefore in order to exploit this potential contrast, we seek to evaluate the performance of a coded- aperture coherent scatter imaging system for breast cancer detection and investigate its accuracy using Monte Carlo simulations. In the simulations we modeled our experimental system, which consists of a raster-scanned pencil beam of x-rays, a bismuth-tin coded aperture mask comprised of a repeating slit pattern with 2-mm periodicity, and a linear-array of 128 detector pixels with 6.5-keV energy resolution. The breast tissue that was scanned comprised a 3-cm sample taken from a patient-based XCAT breast phantom containing a tomosynthesis- based realistic simulated lesion. The differential coherent scatter cross section was reconstructed at each pixel in the image using an iterative reconstruction algorithm. Each pixel in the reconstructed image was then classified as being either air or the type of breast tissue with which its normalized reconstructed differential coherent scatter cross section had the highest correlation coefficient. Comparison of the final tissue classification results with the ground truth image showed that the coded aperture imaging technique has a cancerous pixel detection sensitivity (correct identification of cancerous pixels), specificity (correctly ruling out healthy pixels as not being cancer) and accuracy of 92.4%, 91.9% and 92.0%, respectively. Our Monte Carlo evaluation of our experimental coded aperture coherent scatter imaging system shows that it is able to exploit the greater contrast available from coherently scattered x-rays to increase the accuracy of detecting cancerous regions within the breast.

  9. Dynamic aperture calculation for the RHIC 2010 100 GeV Au-Au run lattices

    SciTech Connect

    Luo, Y.; Brown, K.; Fischer, W.; Ptitsyn, V.; Roser, T.; Schoefer, V.; Tepikian, S.; Trbojevic, D.

    2010-08-01

    In this note we summarize the dynamic aperture calculation with the 2010 RHIC 100 GeV Au-Au run lattices. This study was initiated to understand the observed large beam decay in the Yellow ring after rf re-bucketing in the beginning of this run. The off-line linear lattice models and the interaction region non-linearity models are used. The large beam decay in the Yellow ring after re-bucketing was eventually eliminated by lowering the Yellow tunes to 0.21 from 0.235 with {beta}* = 0.7m lattice. In this note we only focus on the numeric simulation instead of the beam experiments.

  10. Optimization of dynamic aperture for hadron lattices in eRHIC

    SciTech Connect

    Jing, Yichao; Litvinenko, Vladimir; Trbojevic, Dejan

    2015-05-03

    The potential upgrade of the Relativistic Heavy Ion Collider (RHIC) to an electron ion collider (eRHIC) involves numerous extensive changes to the existing collider complex. The expected very high luminosity is planned to be achieved at eRHIC with the help of squeezing the beta function of the hadron ring at the IP to a few cm, causing a large rise of the natural chromaticities and thus bringing with it challenges for the beam long term stability (Dynamic aperture). We present our effort to expand the DA by carefully tuning the nonlinear magnets thus controlling the size of the footprints in tune space and all lower order resonance driving terms. We show a reasonably large DA through particle tracking over millions of turns of beam revolution.

  11. The PyZgoubi framework and the simulation of dynamic aperture in fixed-field alternating-gradient accelerators

    NASA Astrophysics Data System (ADS)

    Tygier, S.; Appleby, R. B.; Garland, J. M.; Hock, K.; Owen, H.; Kelliher, D. J.; Sheehy, S. L.

    2015-03-01

    We present PyZgoubi, a framework that has been developed based on the tracking engine Zgoubi to model, optimise and visualise the dynamics in particle accelerators, especially fixed-field alternating-gradient (FFAG) accelerators. We show that PyZgoubi abstracts Zgoubi by wrapping it in an easy-to-use Python framework in order to allow simple construction, parameterisation, visualisation and optimisation of FFAG accelerator lattices. Its object oriented design gives it the flexibility and extensibility required for current novel FFAG design. We apply PyZgoubi to two example FFAGs; this includes determining the dynamic aperture of the PAMELA medical FFAG in the presence of magnet misalignments, and illustrating how PyZgoubi may be used to optimise FFAGs. We also discuss a robust definition of dynamic aperture in an FFAG and show its implementation in PyZgoubi.

  12. Optimization Of Chromaticity Compensation And Dynamic Aperture In MEIC Collider Rings

    SciTech Connect

    Fanglei Lin, Yaroslav Derbenev, Vasiliy Morozov, Yuhong Zhang, Kevin Beard

    2012-07-01

    The conceptual design of the Medium-energy Electron-Ion Collider (MEIC) at Jefferson Lab relies on an ultra-small beta-star to achieve high luminosities of up to 10{sup 34} cm{sup -2} s{sup -1}. A low-beta insertion for interaction regions unavoidably induces large chromatic effects that demand a proper compensation. The present approach of chromatic compensation in the MEIC collider rings is based on a local correction scheme using two symmetric chromatic compensation blocks that includes families of sextupoles, and are placed in a beam extension area on both sides of a collision point. It can simultaneously compensate the first order chromaticity and chromatic beam smear at the IP without inducing significant second order aberrations. In this paper, we investigate both the momentum acceptance and dynamic aperture in the MEIC ion collider ring by considering the aberration effects up to the third order, such as amplitude dependent tune shift. We also explore the compensation of the third order effects by introducing families of octupoles in the extended beam area.

  13. Evaluation of synthetic aperture radar for oil-spill response. Final report, June 1992-September 1993

    SciTech Connect

    Hover, G.L.; Mastin, G.A.; Axline, R.M.; Bradley, J.D.

    1993-10-01

    This report provides a detailed evaluation of synthetic aperture radar (SAR) as a potential technology improvement over the Coast Guard's existing side-looking airborne radar (SLAR) for oil-spill surveillance applications. The U.S. Coast Guard Research and Development Center (RD Center), Environmental Safety Branch, sponsored a joint experiment including the U.S. Coast Guard, Sandia National Laboratories, and the National Oceanographic and Atmospheric Administration (NOAA), Hazardous Materials Division. Radar imaging missions were flown on six days over the coastal waters off Santa Barbara, CA, where there are constant natural seeps of oil. Both the Coast Guard SLAR and the Sandia National Laboratories SAR were employed to acquire simultaneous images of oil slicks and other natural sea surface features that impact oil-spill interpretation. Surface truth and other environmental data were also recorded during the experiment. The experiment data were processed at Sandia National Laboratories and delivered to the RD Center on a PC-based computer workstation for analysis by experiment participants. Synthetic aperture radar, Side looking airborne radar, Oil slicks.

  14. Dual frequency Synthetic Aperture Radar (SAR) mission for monitoring our dynamic planet

    NASA Technical Reports Server (NTRS)

    Hilland, J.; Bard, S.; Key, R.; Kim, Y.; Vaze, P.; Huneycutt, B.

    2000-01-01

    Advances in spaceborne Synthetic Aperture Radar (SAR) remote sensing technology make it possible to acquire global-scale data sets that provide unique information about the Earth's continually changing surface characteristics.

  15. Dynamic gain aperture modelocking in picosecond regime based on cascaded second-order nonlinearity.

    PubMed

    Mondal, Shyamal; Mukherjee, Shouvik; Singh, Satya Pratap; Rand, Stephen C; Bhattacharya, Sayantan; Das, Amit C; Datta, Prasanta Kumar

    2016-07-11

    The operation of a cascaded second-order mode-locked Nd:YVO4 laser has been investigated considering it as a soft-aperture Kerr lens type and using complex beam parameters. A self consistent complex beam propagation method is used to incorporate the effect of cascaded Kerr nonlinearity on radially varying gain aperturing. The analysis deduces a stable pulsewidth of ~9.5 ps which agrees well with the experimental value of 10.3 ps. PMID:27410804

  16. Beyond-laboratory-scale prediction for channeling flows through subsurface rock fractures with heterogeneous aperture distributions revealed by laboratory evaluation

    NASA Astrophysics Data System (ADS)

    Ishibashi, Takuya; Watanabe, Noriaki; Hirano, Nobuo; Okamoto, Atsushi; Tsuchiya, Noriyoshi

    2015-01-01

    The present study evaluates aperture distributions and fluid flow characteristics for variously sized laboratory-scale granite fractures under confining stress. As a significant result of the laboratory investigation, the contact area in fracture plane was found to be virtually independent of scale. By combining this characteristic with the self-affine fractal nature of fracture surfaces, a novel method for predicting fracture aperture distributions beyond laboratory scale is developed. Validity of this method is revealed through reproduction of the results of laboratory investigation and the maximum aperture-fracture length relations, which are reported in the literature, for natural fractures. The present study finally predicts conceivable scale dependencies of fluid flows through joints (fractures without shear displacement) and faults (fractures with shear displacement). Both joint and fault aperture distributions are characterized by a scale-independent contact area, a scale-dependent geometric mean, and a scale-independent geometric standard deviation of aperture. The contact areas for joints and faults are approximately 60% and 40%. Changes in the geometric means of joint and fault apertures (µm), em, joint and em, fault, with fracture length (m), l, are approximated by em, joint = 1 × 102 l0.1 and em, fault = 1 × 103 l0.7, whereas the geometric standard deviations of both joint and fault apertures are approximately 3. Fluid flows through both joints and faults are characterized by formations of preferential flow paths (i.e., channeling flows) with scale-independent flow areas of approximately 10%, whereas the joint and fault permeabilities (m2), kjoint and kfault, are scale dependent and are approximated as kjoint = 1 × 10-12 l0.2 and kfault = 1 × 10-8 l1.1.

  17. The condenser-monochromator with dynamical aperture synthesis for the TXM at an undulator beamline at BESSY II

    NASA Astrophysics Data System (ADS)

    Niemann, B.; Guttmann, P.; Hambach, D.; Schneider, G.; Weiß, D.; Schmahl, G.

    2000-05-01

    The Göttingen transmission X-ray microscope at the low emittance electron storage ring BESSY II will use the concept of dynamical aperture synthesis [1] for the condenser-monochromator. The concept is well suited as a condenser, as it can match the undulator U41 to the TXM objective and has many other advantages, too. It can use an off-axis transmission zone plate with comparatively wide zones of low aspect ratio, which therefore can be produced with almost theoretical efficiency. It will deliver a monochromaticity of 1000 to 3000. As the numerical aperture of any existing micro objective zone plate can be matched, the achievable resolution increases to the theoretical limit. Phase contrast imaging is possible with annular phase plates of extremely small width, a fast switching from amplitude contrast to phase contrast is possible. Stereo imaging with arbitrary stereo axis will be possible without tilting the object.

  18. Evaluation of the cosmic-ray induced background in coded aperture high energy gamma-ray telescopes

    NASA Technical Reports Server (NTRS)

    Owens, Alan; Barbier, Loius M.; Frye, Glenn M.; Jenkins, Thomas L.

    1991-01-01

    While the application of coded-aperture techniques to high-energy gamma-ray astronomy offers potential arc-second angular resolution, concerns were raised about the level of secondary radiation produced in a thick high-z mask. A series of Monte-Carlo calculations are conducted to evaluate and quantify the cosmic-ray induced neutral particle background produced in a coded-aperture mask. It is shown that this component may be neglected, being at least a factor of 50 lower in intensity than the cosmic diffuse gamma-rays.

  19. Four-dimensional intensity-modulated radiation therapy planning for dynamic tracking using a direct aperture deformation (DAD) method

    SciTech Connect

    Gui Minzhi; Feng Yuanming; Yi Byongyong; Dhople, Anil Arvind; Yu, Cedric

    2010-05-15

    Purpose: Planning for the delivery of intensity-modulated radiation therapy (IMRT) to a moving target, referred to as four-dimensional (4D) IMRT planning, is a crucial step for achieving the treatment objectives for sites that move during treatment delivery. The authors proposed a simplistic method that accounts for both rigid and nonrigid respiration-induced target motion based on 4D computed tomography (4DCT) data sets. Methods: A set of MLC apertures and weights was first optimized on a reference phase of a 4DCT data set. At each beam angle, the apertures were morphed from the reference phase to each of the remaining phases according to the relative shape changes in the beam's eye view of the target. Three different planning schemes were evaluated for two lung cases and one pancreas patient: (1) Individually optimizing each breathing phase; (2) optimizing the reference phase and shifting the optimized apertures to other breathing phases based on a rigid-body image registration; and (3) optimizing the reference phase and deforming the optimized apertures to the other phases based on the deformation and translation of target contours. Planning results using scheme 1 serves as the ''gold standard'' for plan quality assessment; scheme 2 is the method previously proposed in the literature; and scheme 3 is the method the authors proposed in this article. The optimization results were compared between the three schemes for all three cases. Results: The proposed scheme 3 is comparable to scheme 1 in plan quality, and provides improved target coverage and conformity with similar normal tissue dose compared with scheme 2. Conclusions: Direct aperture deformation method for 4D IMRT planning improves upon methods that only consider rigid-body motion and achieves a plan quality close to that optimized for each of the phases.

  20. Dosimetric evaluation of hybrid brass/stainless-steel apertures for proton therapy

    NASA Astrophysics Data System (ADS)

    Chen, Hao; Matysiak, Witold; Flampouri, Stella; Slopsema, Roelf; Li, Zuofeng

    2014-09-01

    In passive scattering proton therapy, patient specific collimators (apertures) are used to laterally shape the proton beam, and compensators are employed to distally conform proton dose to the target. Brass is a commonly used material for apertures and recently a hybrid brass/stainless-steel (BR/SST) aperture design has been introduced to reduce treatment cost without clinical flow change. We measured stopping power and leakage dose for apertures made of stainless steel and brass in the Proton Therapy system. The linear stopping power ratios for stainless steel (type 304) and brass to water were calculated to be 5.46 and 5.51, respectively. Measured stopping power ratios of SST and BR were 5.51  ±  0.04 and 5.56  ±  0.08, respectively, which agrees with the calculated values within 1%. Leakage dose on the downstream surface of two slabs of Ø18 cm stainless steel apertures (total thickness of 6.5 cm) for the maximum available proton energy (235 MeV) was 1.283% ± 0.004% of the prescription dose, and was smaller compared to the 1.358% ± 0.005% leakage dose measured for existing brass apertures of identical physical dimensions. Therefore, the existing beam range limits for brass aperture slabs used at our institution with safety margin allowances for material composition and delivered beam range uncertainties can be safely applied for the new BR/SST aperture design. Potential range differences in the brass and stainless steel interface regions of the hybrid design were further investigated using EBT3 GafChromic film. Film dosimetry revealed no discernible range variations across the brass and stainless steel interface regions. Neutron dose to the patient from brass and stainless steel apertures was simulated using the Monte Carlo method. The results indicate that stainless steel produces similar patient neutron dose compared to brass. Material activation dose rates of stainless steel were measured over a period of 7 d after irradiation. The

  1. Dynamic consequence evaluations

    SciTech Connect

    Peterson, V.L.

    1996-05-01

    Wastes at Rocky Flats Environmental Technology Site will be consolidated into buildings being vacated and/or into newly constructed buildings. The exact mix of waste types may not be known a priori; it will likely change over time. Building operations personnel need a method to dynamically evaluate the hazard of any proposed mix of wastes type, that is, determine a measure of the hazard without having to request a new hazard evaluation from the Safety Analysis department each time the waste mix is to be changed. This report presents such a method; the method is based on the use of a spreadsheet developed for this purpose. The spreadsheet is duser-friendly, robust, and protected so that theuser can modify only certain cells.

  2. Evaluating gambles using dynamics

    NASA Astrophysics Data System (ADS)

    Peters, O.; Gell-Mann, M.

    2016-02-01

    Gambles are random variables that model possible changes in wealth. Classic decision theory transforms money into utility through a utility function and defines the value of a gamble as the expectation value of utility changes. Utility functions aim to capture individual psychological characteristics, but their generality limits predictive power. Expectation value maximizers are defined as rational in economics, but expectation values are only meaningful in the presence of ensembles or in systems with ergodic properties, whereas decision-makers have no access to ensembles, and the variables representing wealth in the usual growth models do not have the relevant ergodic properties. Simultaneously addressing the shortcomings of utility and those of expectations, we propose to evaluate gambles by averaging wealth growth over time. No utility function is needed, but a dynamic must be specified to compute time averages. Linear and logarithmic "utility functions" appear as transformations that generate ergodic observables for purely additive and purely multiplicative dynamics, respectively. We highlight inconsistencies throughout the development of decision theory, whose correction clarifies that our perspective is legitimate. These invalidate a commonly cited argument for bounded utility functions.

  3. Evaluating gambles using dynamics.

    PubMed

    Peters, O; Gell-Mann, M

    2016-02-01

    Gambles are random variables that model possible changes in wealth. Classic decision theory transforms money into utility through a utility function and defines the value of a gamble as the expectation value of utility changes. Utility functions aim to capture individual psychological characteristics, but their generality limits predictive power. Expectation value maximizers are defined as rational in economics, but expectation values are only meaningful in the presence of ensembles or in systems with ergodic properties, whereas decision-makers have no access to ensembles, and the variables representing wealth in the usual growth models do not have the relevant ergodic properties. Simultaneously addressing the shortcomings of utility and those of expectations, we propose to evaluate gambles by averaging wealth growth over time. No utility function is needed, but a dynamic must be specified to compute time averages. Linear and logarithmic "utility functions" appear as transformations that generate ergodic observables for purely additive and purely multiplicative dynamics, respectively. We highlight inconsistencies throughout the development of decision theory, whose correction clarifies that our perspective is legitimate. These invalidate a commonly cited argument for bounded utility functions. PMID:26931584

  4. Application of image entropy evaluation function for the leveling of large aperture components in auto defects detecting

    NASA Astrophysics Data System (ADS)

    Cao, Pin; Liu, Dong; Zhao, Peng; Yang, Yong-ying; Wang, Shi-tong

    2012-10-01

    In large aperture component's dark-field scattering defects imaging system, the component's size is large and part with a wedge. When the component is in the completely level position, the surface defects image can be clearly acquired by a high magnification microscope. Otherwise, fuzzy defects image would be gained because of defocusing which makes digital identification can't be able to be done. For the problem of leveling large aperture, wedge component, this paper proposes a method that using image information entropy as focusing evaluation function for leveling large aperture components. Firstly, in three different points of component surface acquiring multi-images by the same continuous steps. Then calculating the images' entropy and fitting a curve to it. Based on minimum image information entropy value criterion, the focal plane can be found and each point's defocusingamount of the fist acquisition position can be gained. Relay on the relation model of acquisition points, adjust points and defocusingamount that has been built, each adjust point's adjustment can be got. The component's level position can be achieved by adjusting the adjust points. In the experiment that using a high magnification (of 16) microscope scans over the whole surface of the component with the size of 430mm×430mm. The image microscope is always in the depth of focus which shows that the leveling precision has achieved 20μm. Until now, this method has been successfully used in large aperture component's dark-field scattering defects imaging system.

  5. Development and evaluation of aperture-based complexity metrics using film and EPID measurements of static MLC openings

    SciTech Connect

    Götstedt, Julia; Karlsson Hauer, Anna; Bäck, Anna

    2015-07-15

    Purpose: Complexity metrics have been suggested as a complement to measurement-based quality assurance for intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT). However, these metrics have not yet been sufficiently validated. This study develops and evaluates new aperture-based complexity metrics in the context of static multileaf collimator (MLC) openings and compares them to previously published metrics. Methods: This study develops the converted aperture metric and the edge area metric. The converted aperture metric is based on small and irregular parts within the MLC opening that are quantified as measured distances between MLC leaves. The edge area metric is based on the relative size of the region around the edges defined by the MLC. Another metric suggested in this study is the circumference/area ratio. Earlier defined aperture-based complexity metrics—the modulation complexity score, the edge metric, the ratio monitor units (MU)/Gy, the aperture area, and the aperture irregularity—are compared to the newly proposed metrics. A set of small and irregular static MLC openings are created which simulate individual IMRT/VMAT control points of various complexities. These are measured with both an amorphous silicon electronic portal imaging device and EBT3 film. The differences between calculated and measured dose distributions are evaluated using a pixel-by-pixel comparison with two global dose difference criteria of 3% and 5%. The extent of the dose differences, expressed in terms of pass rate, is used as a measure of the complexity of the MLC openings and used for the evaluation of the metrics compared in this study. The different complexity scores are calculated for each created static MLC opening. The correlation between the calculated complexity scores and the extent of the dose differences (pass rate) are analyzed in scatter plots and using Pearson’s r-values. Results: The complexity scores calculated by the edge

  6. Predicting dissolution patterns in variable aperture fractures: 1. Development and evaluation of an enhanced depth-averaged computational model

    SciTech Connect

    Detwiler, R L; Rajaram, H

    2006-04-21

    Water-rock interactions within variable-aperture fractures can lead to dissolution of fracture surfaces and local alteration of fracture apertures, potentially transforming the transport properties of the fracture over time. Because fractures often provide dominant pathways for subsurface flow and transport, developing models that effectively quantify the role of dissolution on changing transport properties over a range of scales is critical to understanding potential impacts of natural and anthropogenic processes. Dissolution of fracture surfaces is controlled by surface-reaction kinetics and transport of reactants and products to and from the fracture surfaces. We present development and evaluation of a depth-averaged model of fracture flow and reactive transport that explicitly calculates local dissolution-induced alterations in fracture apertures. The model incorporates an effective mass transfer relationship that implicitly represents the transition from reaction-limited dissolution to transport-limited dissolution. We evaluate the model through direct comparison to previously reported physical experiments in transparent analog fractures fabricated by mating an inert, transparent rough surface with a smooth single crystal of potassium dihydrogen phosphate (KDP), which allowed direct measurement of fracture aperture during dissolution experiments using well-established light transmission techniques [Detwiler, et al., 2003]. Comparison of experiments and simulations at different flow rates demonstrate the relative impact of the dimensionless Peclet and Damkohler numbers on fracture dissolution and the ability of the computational model to simulate dissolution. Despite some discrepancies in the small-scale details of dissolution patterns, the simulations predict the evolution of large-scale features quite well for the different experimental conditions. This suggests that our depth-averaged approach to simulating fracture dissolution provides a useful approach for

  7. Evaluating the effect of internal aperture variability on transport in kilometer scale discrete fracture networks

    NASA Astrophysics Data System (ADS)

    Makedonska, Nataliia; Hyman, Jeffrey D.; Karra, Satish; Painter, Scott L.; Gable, Carl W.; Viswanathan, Hari S.

    2016-08-01

    The apertures of natural fractures in fractured rock are highly heterogeneous. However, in-fracture aperture variability is often neglected in flow and transport modeling and individual fractures are assumed to have uniform aperture distribution. The relative importance of in-fracture variability in flow and transport modeling within kilometer-scale field-scale fracture networks has been under a matter of debate for a long time because the flow in each single fracture is controlled not only by in-fracture variability but also by boundary conditions. Computational limitations have previously prohibited researchers from investigating the relative importance of in-fracture variability in flow and transport modeling within large-scale fracture networks. We address this question by incorporating internal heterogeneity of individual fractures into flow simulations within kilometer scale three-dimensional fracture networks, where fracture intensity, P32 (ratio between total fracture area and domain volume) is between 0.027 and 0.031 [1/m]. A recently developed discrete fracture network (DFN) simulation capability, dfnWorks, is used to generate DFNs that include in-fracture aperture variability represented by a stationary log-normal stochastic field with various correlation lengths and variances. The Lagrangian transport parameters, non-reacting travel time and cumulative retention, are calculated along particles streamlines. It is observed that due to local flow channeling early particle travel times are more sensitive to in-fracture variability than the tails of travel time distributions, where no significant effect of the in-fracture transmissivity variations and spatial correlation length is observed.

  8. Evaluating the effect of internal aperture variability on transport in kilometer scale discrete fracture networks

    DOE PAGESBeta

    Makedonska, Nataliia; Hyman, Jeffrey D.; Karra, Satish; Painter, Scott L.; Gable, Carl W.; Viswanathan, Hari S.

    2016-06-17

    The apertures of natural fractures in fractured rock are highly heterogeneous. However, in-fracture aperture variability is often neglected in flow and transport modeling and individual fractures are assumed to have uniform aperture distribution. The relative importance of in-fracture variability in flow and transport modeling within kilometer18 scale field–scale fracture networks has been under a matter of debate for a long time because the flow in each single fracture is controlled not only by in-fracture variability but also by boundary conditions. Computational limitations have previously prohibited researchers from investigating the relative importance of in-fracture variability in flow and transport modeling withinmore » large-scale fracture networks. We address this question by incorporating internal heterogeneity of individual fractures into 23 flow simulations within kilometer scale three-dimensional fracture networks, where fracture intensity, P32 (ratio between total fracture area and domain volume) is between 0.027 and 0.031 [1/m]. A recently developed discrete fracture network (DFN) simulation capability, dfnWorks, is used to generate DFNs that include in-fracture aperture variability represented by a stationary log-normal stochastic field with various correlation lengths and variances. The Lagrangian transport parameters, non-reacting travel time and cumulative retention, are calculated along particles streamlines. It is observed that due to local flow channeling early particle travel times are more sensitive to in-fracture variability than the tails of travel time distributions, where no significant effect of the in-fracture transmissivity variations and spatial correlation length is observed.« less

  9. Solar dynamic modules for Space Station Freedom: The relationship between fine-pointing control and thermal loading of the aperture plate

    NASA Technical Reports Server (NTRS)

    Quinn, Roger D.; Kerslake, Thomas W.

    1992-01-01

    Dynamic simulations of Space Station Freedom (SSF) configured with solar dynamic (SD) power modules were performed. The structure was subjected to Space Shuttle docking disturbances, while being controlled with a 'natural' vibration and tracking control approach. Three control cases were investigated for the purpose of investigating the relationship between actuator effort, SD pointing, and thermal loading on the receiver aperture plate. Transient, one-dimensional heat transfer analyses were performed to conservatively predict temperatures of the multi-layered receiver aperture plate assembly and thermal stresses in its shield layer. Results indicate that the proposed aperture plate is tolerant of concentrated flux impingement during short-lived structural disturbances. Pointing requirements may be loosened and the requirement control torques lessened from that previously specified. Downsizing and simplifying the joint drive system should result in a considerable savings mass.

  10. Observation of sea-ice dynamics using synthetic aperture radar images: Automated analysis

    NASA Technical Reports Server (NTRS)

    Vesecky, John F.; Samadani, Ramin; Smith, Martha P.; Daida, Jason M.; Bracewell, Ronald N.

    1988-01-01

    The European Space Agency's ERS-1 satellite, as well as others planned to follow, is expected to carry synthetic-aperture radars (SARs) over the polar regions beginning in 1989. A key component in utilization of these SAR data is an automated scheme for extracting the sea-ice velocity field from a time sequence of SAR images of the same geographical region. Two techniques for automated sea-ice tracking, image pyramid area correlation (hierarchical correlation) and feature tracking, are described. Each technique is applied to a pair of Seasat SAR sea-ice images. The results compare well with each other and with manually tracked estimates of the ice velocity. The advantages and disadvantages of these automated methods are pointed out. Using these ice velocity field estimates it is possible to construct one sea-ice image from the other member of the pair. Comparing the reconstructed image with the observed image, errors in the estimated velocity field can be recognized and a useful probable error display created automatically to accompany ice velocity estimates. It is suggested that this error display may be useful in segmenting the sea ice observed into regions that move as rigid plates of significant ice velocity shear and distortion.

  11. Evaluation of ultrasound synthetic aperture imaging using bidirectional pixel-based focusing: preliminary phantom and in vivo breast study.

    PubMed

    Kim, Choye; Yoon, Changhan; Park, Jong-Ho; Lee, Yuhwa; Kim, Won Hwa; Chang, Jung Min; Choi, Byung Ihn; Song, Tai-Kyong; Yoo, Yang-Mo

    2013-10-01

    In medical ultrasound imaging, lateral resolution is limited when using a fixed transmit focusing. Various synthetic aperture (SA) techniques, in which two-way dynamic focusing is enabled by utilizing prebeamformed radio-frequency (RF) data have been proposed for improving the spatial resolution. However, SA methods were not extensively evaluated in terms of their clinical performance. In this paper, a phantom and an in vivo evaluation of the SA method with bidirectional pixel-based focusing (BiPBF) is presented in comparison with the conventional beamforming. The performance of the proposed SA-BiPBF was assessed with a blind study and the established breast imaging-reporting and data system (BI-RADS), in addition to measuring contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR). Prebeamformed RF data were acquired from a tissue mimicking phantom (Model 040, CIRS Inc., Norfolk, VA, USA) and from patients with breast lesions by using a commercial ultrasound scanning system with a linear array transducer equipped with a research package and parallel data acquisition system (SonixTouch, SonixDAQ, and L14-5/38, Ultrasonix Corp., Canada). In phantom and in vivo experiments, a default setting of a breast preset was applied (e.g., the center frequency of 10 MHz and acoustic output of MI = 0.66). In phantom experiment, the SA-BiPBF method showed higher CNR and SNR values compared to the conventional method (3.4 and 23.9 dB versus 3.1 and 15.8 dB, respectively). In addition, the lateral resolution and penetration depth were increased by 95.4% and 40.3%, respectively. Consistent with the phantom experiment, in the in vivo experiment with ten patients, the CNR value for the SA method was 3.3 ± 0.5 compared to 2.8 ± 0.8 for the conventional method. Similarly, the SNR values with the SA-BiPBF and conventional methods were 34.0 ± 3.6 and 27.2 ± 3.4 dB, respectively. From the experiments, it was shown in side-by-side comparisons that the image quality of the SA

  12. Clinical Evaluation of Direct Aperture Optimization When Applied to Head-And-Neck IMRT

    SciTech Connect

    Jones, Stephen Williams, Matthew

    2008-04-01

    Direct Machine Parameter Optimization (DMPO) is a leaf segmentation program released as an optional item of the Pinnacle planning system (Philips Radiation Oncology Systems, Milpitas, CA); it is based on the principles of direct aperture optimization where the size, shape, and weight of individual segments are optimized to produce an intensity modulated radiation treatment (IMRT) plan. In this study, we compare DMPO to the traditional method of IMRT planning, in which intensity maps are optimized prior to conversion into deliverable multileaf collimator (MLC) apertures, and we determine if there was any dosimetric improvement, treatment efficiency gain, or planning advantage provided by the use of DMPO. Eleven head-and-neck patients treated with IMRT had treatment plans generated using each optimization method. For each patient, the same planning parameters were used for each optimization method. All calculations were performed using Pinnacle version 7.6c software and treatments were delivered using a step-and-shoot IMRT method on a Varian 2100EX linear accelerator equipped with a 120-leaf Millennium MLC (Varian Medical Systems, Palo Alto, CA). Each plan was assessed based on the calculation time, a conformity index, the composite objective value used in the optimization, the number of segments, monitor units (MUs), and treatment time. The results showed DMPO to be superior to the traditional optimization method in all areas. Considerable advantages were observed in the dosimetric quality of DMPO plans, which also required 32% less time to calculate, 42% fewer MUs, and 35% fewer segments than the conventional optimization method. These reductions translated directly into a 29% decrease in treatment times. While considerable gains were observed in planning and treatment efficiency, they were specific to our institution, and the impact of direct aperture optimization on plan quality and workflow will be dependent on the planning parameters, planning system, and

  13. Evaluation of aperture cover tank vent nozzles for the IRAS spacecraft

    NASA Technical Reports Server (NTRS)

    Richter, R.

    1983-01-01

    The influence of coefficients for the three axes of the Infrared Astronomical Satellite (IRAS) were established to determine the maximum allowable thrust difference between the two vent nozzles of the aperture cover tank low thrust vent system and their maximum misalignment. Test data generated by flow and torque measurements permitted the selection of two nozzles whose thrust differential was within the limit of the attitude control capability. Based on thrust stand data, a thrust vector misalignment was indicated that was slightly higher than permissible for the worst case, i.e., considerable degradation of the torque capacity of the attitude control system combined with venting of helium at its upper limit. The probability of destabilizing the IRAS spacecraft by activating the venting system appeared to be very low. The selection and mounting of the nozzles have satisfied all the requirements for the safe venting of helium.

  14. Control of vacuolar dynamics and regulation of stomatal aperture by tonoplast potassium uptake.

    PubMed

    Andrés, Zaida; Pérez-Hormaeche, Javier; Leidi, Eduardo O; Schlücking, Kathrin; Steinhorst, Leonie; McLachlan, Deirdre H; Schumacher, Karin; Hetherington, Alistair M; Kudla, Jörg; Cubero, Beatriz; Pardo, José M

    2014-04-29

    Stomatal movements rely on alterations in guard cell turgor. This requires massive K(+) bidirectional fluxes across the plasma and tonoplast membranes. Surprisingly, given their physiological importance, the transporters mediating the energetically uphill transport of K(+) into the vacuole remain to be identified. Here, we report that, in Arabidopsis guard cells, the tonoplast-localized K(+)/H(+) exchangers NHX1 and NHX2 are pivotal in the vacuolar accumulation of K(+) and that nhx1 nhx2 mutant lines are dysfunctional in stomatal regulation. Hypomorphic and complete-loss-of-function double mutants exhibited significantly impaired stomatal opening and closure responses. Disruption of K(+) accumulation in guard cells correlated with more acidic vacuoles and the disappearance of the highly dynamic remodelling of vacuolar structure associated with stomatal movements. Our results show that guard cell vacuolar accumulation of K(+) is a requirement for stomatal opening and a critical component in the overall K(+) homeostasis essential for stomatal closure, and suggest that vacuolar K(+) fluxes are also of decisive importance in the regulation of vacuolar dynamics and luminal pH that underlie stomatal movements. PMID:24733919

  15. A Geosynchronous Synthetic Aperture Provides for Disaster Management, Measurement of Soil Moisture, and Measurement of Earth-Surface Dynamics

    NASA Technical Reports Server (NTRS)

    Madsen, Soren; Komar, George (Technical Monitor)

    2001-01-01

    A GEO-based Synthetic Aperture Radar (SAR) could provide daily coverage of basically all of North and South America with very good temporal coverage within the mapped area. This affords a key capability to disaster management, tectonic mapping and modeling, and vegetation mapping. The fine temporal sampling makes this system particularly useful for disaster management of flooding, hurricanes, and earthquakes. By using a fairly long wavelength, changing water boundaries caused by storms or flooding could be monitored in near real-time. This coverage would also provide revolutionary capabilities in the field of radar interferometry, including the capability to study the interferometric signature immediately before and after an earthquake, thus allowing unprecedented studies of Earth-surface dynamics. Preeruptive volcano dynamics could be studied as well as pre-seismic deformation, one of the most controversial and elusive aspects of earthquakes. Interferometric correlation would similarly allow near real-time mapping of surface changes caused by volcanic eruptions, mud slides, or fires. Finally, a GEO SAR provides an optimum configuration for soil moisture measurement that requires a high temporal sampling rate (1-2 days) with a moderate spatial resolution (1 km or better). From a technological point of view, the largest challenges involved in developing a geosynchronous SAR capability relate to the very large slant range distance from the radar to the mapped area. This leads to requirements for large power or alternatively very large antenna, the ability to steer the mapping area to the left and right of the satellite, and control of the elevation and azimuth angles. The weight of this system is estimated to be 2750 kg and it would require 20 kW of DC-power. Such a system would provide up to a 600 km ground swath in a strip-mapping mode and 4000 km dual-sided mapping in a scan-SAR mode.

  16. SU-E-T-593: Clinical Evaluation of Direct Aperture Optimization in Head/Neck and Prostate IMRT Treatment

    SciTech Connect

    Hosini, M; GALAL, M; Emam, I; Kamal, G; Algohary, M

    2014-06-01

    Purpose: To investigate the planning and dosimetric advantages of direct aperture optimization (DAO) over beam-let optimization in IMRT treatment of head and neck (H/N) and prostate cancers. Methods: Five Head and Neck as well as five prostate patients were planned using the beamlet optimizer in Elekta-Xio ver 4.6 IMRT treatment planning system. Based on our experience in beamlet IMRT optimization, PTVs in H/N plans were prescribed to 70 Gy delivered by 7 fields. While prostate PTVs were prescribed to 76 Gy with 9 fields. In all plans, fields were set to be equally spaced. All cases were re-planed using Direct Aperture optimizer in Prowess Panther ver 5.01 IMRT planning system at same configurations and dose constraints. Plans were evaluated according to ICRU criteria, number of segments, number of monitor units and planning time. Results: For H/N plans, the near maximum dose (D2) and the dose that covers 95% D95 of PTV has improved by 4% in DAO. For organs at risk (OAR), DAO reduced the volume covered by 30% (V30) in spinal cord, right parotid, and left parotid by 60%, 54%, and 53% respectively. This considerable dosimetric quality improvement achieved using 25% less planning time and lower number of segments and monitor units by 46% and 51% respectively. In DAO prostate plans, Both D2 and D95 for the PTV were improved by only 2%. The V30 of the right femur, left femur and bladder were improved by 35%, 15% and 3% respectively. On the contrary, the rectum V30 got even worse by 9%. However, number of monitor units, and number of segments decreased by 20% and 25% respectively. Moreover the planning time reduced significantly too. Conclusion: DAO introduces considerable advantages over the beamlet optimization in regards to organs at risk sparing. However, no significant improvement occurred in most studied PTVs.

  17. Remote sensing of a dynamic sub-arctic peatland reservoir using optical and synthetic aperture radar data

    NASA Astrophysics Data System (ADS)

    Larter, Jarod Lee

    Stephens Lake, Manitoba is an example of a peatland reservoir that has undergone physical changes related to mineral erosion and peatland disintegration processes since its initial impoundment. In this thesis I focused on the processes of peatland upheaval, transport, and disintegration as the primary drivers of dynamic change within the reservoir. The changes related to these processes are most frequent after initial reservoir impoundment and decline over time. They continue to occur over 35 years after initial flooding. I developed a remote sensing approach that employs both optical and microwave sensors for discriminating land (Le. floating peatlands, forested land, and barren land) from open water within the reservoir. High spatial resolution visible and near-infrared (VNIR) optical data obtained from the QuickBird satellite, and synthetic aperture radar (SAR) microwave data obtained from the RADARSAT-1 satellite were implemented. The approach was facilitated with a Geographic Information System (GIS) based validation map for the extraction of optical and SAR pixel data. Each sensor's extracted data set was first analyzed separately using univariate and multivariate statistical methods to determine the discriminant ability of each sensor. The initial analyses were followed by an integrated sensor approach; the development of an image classification model; and a change detection analysis. Results showed excellent (> 95%) classification accuracy using QuickBird satellite image data. Discrimination and classification of studied land cover classes using SAR image texture data resulted in lower overall classification accuracies (˜ 60%). SAR data classification accuracy improved to > 90% when classifying only land and water, demonstrating SAR's utility as a land and water mapping tool. An integrated sensor data approach showed no considerable improvement over the use of optical satellite image data alone. An image classification model was developed that could be

  18. Compounding in synthetic aperture imaging.

    PubMed

    Hansen, Jens Munk; Jensen, Jørgen Arendt

    2012-09-01

    A method for obtaining compound images using synthetic aperture data is investigated using a convex array transducer. The new approach allows spatial compounding to be performed for any number of angles without reducing the frame rate or temporal resolution. This important feature is an intrinsic property of how the compound images are constructed using synthetic aperture data and an improvement compared with how spatial compounding is obtained using conventional methods. The synthetic aperture compound images are created by exploiting the linearity of delay-and-sum beamformation for data collected from multiple spherical emissions to synthesize multiple transmit and receive apertures, corresponding to imaging the tissue from multiple directions. The many images are added incoherently, to produce a single compound image. Using a 192-element, 3.5-MHz, λ-pitch transducer, it is demonstrated from tissue-phantom measurements that the speckle is reduced and the contrast resolution improved when applying synthetic aperture compound imaging. At a depth of 4 cm, the size of the synthesized apertures is optimized for lesion detection based on the speckle information density. This is a performance measure for tissue contrast resolution which quantifies the tradeoff between resolution loss and speckle reduction. The speckle information density is improved by 25% when comparing synthetic aperture compounding to a similar setup for compounding using dynamic receive focusing. The cystic resolution and clutter levels are measured using a wire phantom setup and compared with conventional application of the array, as well as to synthetic aperture imaging without compounding. If the full aperture is used for synthetic aperture compounding, the cystic resolution is improved by 41% compared with conventional imaging, and is at least as good as what can be obtained using synthetic aperture imaging without compounding. PMID:23007781

  19. Performance Evaluation of Large Aperture 'Polished Panel' Optical Receivers Based on Experimental Data

    NASA Technical Reports Server (NTRS)

    Vilnrotter, Victor

    2013-01-01

    Recent interest in hybrid RF/Optical communications has led to the development and installation of a "polished-panel" optical receiver evaluation assembly on the 34-meter research antenna at Deep-Space Station 13 (DSS-13) at NASA's Goldstone Communications Complex. The test setup consists of a custom aluminum panel polished to optical smoothness, and a large-sensor CCD camera designed to image the point-spread function (PSF) generated by the polished aluminum panel. Extensive data has been obtained via realtime tracking and imaging of planets and stars at DSS-13. Both "on-source" and "off-source" data were recorded at various elevations, enabling the development of realistic simulations and analytic models to help determine the performance of future deep-space communications systems operating with on-off keying (OOK) or pulse-position-modulated (PPM) signaling formats with photon-counting detection, and compared with the ultimate quantum bound on detection performance for these modulations. Experimentally determined PSFs were scaled to provide realistic signal-distributions across a photon-counting detector array when a pulse is received, and uncoded as well as block-coded performance analyzed and evaluated for a well-known class of block codes.

  20. Correlation of tuned aperture computed tomography with conventional computed tomography for evaluation of osseous healing in calvarial defects

    PubMed Central

    Nair, Madhu K.; Nair, Umadevi P.; Seyedain, Ali; Gassner, Robert; Piesco, Nicholas; Mooney, Mark; Ganta, Sudhakar; Agarwal, Sudha

    2016-01-01

    Objective To compare the diagnostic efficacy of iteratively restored tuned aperture computed tomography (TACT) with conventional computed tomography (CT) for evaluation of osseous healing in induced calvarial defects. Study design Fifty-six calvarial defects in 14 rabbits received 1 of 4 possible treatments: copolymer membranes with and without bone marrow stromal cells (BMSCs), BMSCs alone, or no treatment (control). Healing was measured after 2, 4, and 8 wks as remaining defect areas measured on TACT and CT images. Histomorphometric analyses were done on the specimens. Results Bone formation was minimal to none in control defects and those treated with BMSCs or polymer matrices alone. Healthy bone formation was noted in defects treated with polymers impregnated with BMSCs. Unresolved defect area measurements using TACT and CT of osseous healing showed a high positive correlation. Conclusions Potential for TACT to accurately detect osseous healing in surgical defects was demonstrated. High resolution of TACT combined with generation of information in 3D yields comparable performance to CT. PMID:17234546

  1. Alternative aperture stop position designs for SIRTF

    NASA Technical Reports Server (NTRS)

    Davis, Paul K.; Dinger, Ann S.

    1990-01-01

    Three designs of the Space Infrared Telescope Facility (SIRTF) for a 100,000 high earth orbit are considered with particular attention given to the evaluation of the aperture stop position. The choice of aperture stop position will be based on stray light considerations which are being studied concurrently. It is noted that there are advantages in cost, mass, and astronomical aperture to placing the aperture stop at or near the primary mirror, if the stray light circumstances allow.

  2. Optical sparse aperture imaging.

    PubMed

    Miller, Nicholas J; Dierking, Matthew P; Duncan, Bradley D

    2007-08-10

    The resolution of a conventional diffraction-limited imaging system is proportional to its pupil diameter. A primary goal of sparse aperture imaging is to enhance resolution while minimizing the total light collection area; the latter being desirable, in part, because of the cost of large, monolithic apertures. Performance metrics are defined and used to evaluate several sparse aperture arrays constructed from multiple, identical, circular subapertures. Subaperture piston and/or tilt effects on image quality are also considered. We selected arrays with compact nonredundant autocorrelations first described by Golay. We vary both the number of subapertures and their relative spacings to arrive at an optimized array. We report the results of an experiment in which we synthesized an image from multiple subaperture pupil fields by masking a large lens with a Golay array. For this experiment we imaged a slant edge feature of an ISO12233 resolution target in order to measure the modulation transfer function. We note the contrast reduction inherent in images formed through sparse aperture arrays and demonstrate the use of a Wiener-Helstrom filter to restore contrast in our experimental images. Finally, we describe a method to synthesize images from multiple subaperture focal plane intensity images using a phase retrieval algorithm to obtain estimates of subaperture pupil fields. Experimental results from synthesizing an image of a point object from multiple subaperture images are presented, and weaknesses of the phase retrieval method for this application are discussed. PMID:17694146

  3. SU-E-T-567: Neutron Dose Equivalent Evaluation for Pencil Beam Scanning Proton Therapy with Apertures

    SciTech Connect

    Geng, C; Schuemann, J; Moteabbed, M; Paganetti, H

    2015-06-15

    Purpose: To determine the neutron contamination from the aperture in pencil beam scanning during proton therapy. Methods: A Monte Carlo based proton therapy research platform TOPAS and the UF-series hybrid pediatric phantoms were used to perform this study. First, pencil beam scanning (PBS) treatment pediatric plans with average spot size of 10 mm at iso-center were created and optimized for three patients with and without apertures. Then, the plans were imported into TOPAS. A scripting method was developed to automatically replace the patient CT with a whole body phantom positioned according to the original plan iso-center. The neutron dose equivalent was calculated using organ specific quality factors for two phantoms resembling a 4- and 14-years old patient. Results: The neutron dose equivalent generated by the apertures in PBS is 4–10% of the total neutron dose equivalent for organs near the target, while roughly 40% for organs far from the target. Compared to the neutron dose equivalent caused by PBS without aperture, the results show that the neutron dose equivalent with aperture is reduced in the organs near the target, and moderately increased for those organs located further from the target. This is due to the reduction of the proton dose around the edge of the CTV, which causes fewer neutrons generated in the patient. Conclusion: Clinically, for pediatric patients, one might consider adding an aperture to get a more conformal treatment plan if the spot size is too large. This work shows the somewhat surprising fact that adding an aperture for beam scanning for facilities with large spot sizes reduces instead of increases a potential neutron background in regions near target. Changran Geng is supported by the Chinese Scholarship Council (CSC) and the National Natural Science Foundation of China (Grant No. 11475087)

  4. Configurable Aperture Space Telescope

    NASA Technical Reports Server (NTRS)

    Ennico, Kimberly; Bendek, Eduardo

    2015-01-01

    In December 2014, we were awarded Center Innovation Fund to evaluate an optical and mechanical concept for a novel implementation of a segmented telescope based on modular, interconnected small sats (satlets). The concept is called CAST, a Configurable Aperture Space Telescope. With a current TRL is 2 we will aim to reach TLR 3 in Sept 2015 by demonstrating a 2x2 mirror system to validate our optical model and error budget, provide straw man mechanical architecture and structural damping analyses, and derive future satlet-based observatory performance requirements. CAST provides an alternative access to visible and/or UV wavelength space telescope with 1-meter or larger aperture for NASA SMD Astrophysics and Planetary Science community after the retirement of HST

  5. Integrated electrochromic aperture diaphragm

    NASA Astrophysics Data System (ADS)

    Deutschmann, T.; Oesterschulze, E.

    2014-05-01

    In the last years, the triumphal march of handheld electronics with integrated cameras has opened amazing fields for small high performing optical systems. For this purpose miniaturized iris apertures are of practical importance because they are essential to control both the dynamic range of the imaging system and the depth of focus. Therefore, we invented a micro optical iris based on an electrochromic (EC) material. This material changes its absorption in response to an applied voltage. A coaxial arrangement of annular rings of the EC material is used to establish an iris aperture without need of any mechanical moving parts. The advantages of this device do not only arise from the space-saving design with a thickness of the device layer of 50μm. But it also benefits from low power consumption. In fact, its transmission state is stable in an open circuit, phrased memory effect. Only changes of the absorption require a voltage of up to 2 V. In contrast to mechanical iris apertures the absorption may be controlled on an analog scale offering the opportunity for apodization. These properties make our device the ideal candidate for battery powered and space-saving systems. We present optical measurements concerning control of the transmitted intensity and depth of focus, and studies dealing with switching times, light scattering, and stability. While the EC polymer used in this study still has limitations concerning color and contrast, the presented device features all functions of an iris aperture. In contrast to conventional devices it offers some special features. Owing to the variable chemistry of the EC material, its spectral response may be adjusted to certain applications like color filtering in different spectral regimes (UV, optical range, infrared). Furthermore, all segments may be switched individually to establish functions like spatial Fourier filtering or lateral tunable intensity filters.

  6. Dynamic aperture calculation for 100 GeV Au-Au and 250 GeV pp lattices with near third order resonance working point

    SciTech Connect

    Gu, X.; Luo, Y.; Fischer, W.

    2010-08-01

    In the preparation for the 2011 RHIC 250 GeV polarized proton (pp) run, both experiment and simulation were carried out to investigate the possibility to accelerate the proton beam with a vertical tune near 2/3. It had been found experimentally in Run-9 that accelerating the proton beam with a vertical tune close to 2/3 will greatly benefit the transmission of the proton polarization. In this note, we report the calculated dynamic apertures with the 100 GeV Au run and 250 GeV proton run lattices with vertical tunes close to the third order resonance. We will compare the third order resonance band width between the beam experiment and the simulation with the 100 GeV Au lattices. And we also will compare the calculated resonance band width between the 100 GeV Au and 250 GeV proton run lattices.

  7. Evaluation of Aircraft Platforms for SOFIA by Computational Fluid Dynamics

    NASA Technical Reports Server (NTRS)

    Klotz, S. P.; Srinivasan, G. R.; VanDalsem, William (Technical Monitor)

    1995-01-01

    The selection of an airborne platform for the Stratospheric Observatory for Infrared Astronomy (SOFIA) is based not only on economic cost, but technical criteria, as well. Technical issues include aircraft fatigue, resonant characteristics of the cavity-port shear layer, aircraft stability, the drag penalty of the open telescope bay, and telescope performance. Recently, two versions of the Boeing 747 aircraft, viz., the -SP and -200 configurations, were evaluated by computational fluid dynamics (CFD) for their suitability as SOFIA platforms. In each configuration the telescope was mounted behind the wings in an open bay with nearly circular aperture. The geometry of the cavity, cavity aperture, and telescope was identical in both platforms. The aperture was located on the port side of the aircraft and the elevation angle of the telescope, measured with respect to the vertical axis, was 500. The unsteady, viscous, three-dimensional, aerodynamic and acoustic flow fields in the vicinity of SOFIA were simulated by an implicit, finite-difference Navier-Stokes flow solver (OVERFLOW) on a Chimera, overset grid system. The computational domain was discretized by structured grids. Computations were performed at wind-tunnel and flight Reynolds numbers corresponding to one free-stream flow condition (M = 0.85, angle of attack alpha = 2.50, and sideslip angle beta = 0 degrees). The computational domains consisted of twenty-nine(29) overset grids in the wind-tunnel simulations and forty-five(45) grids in the simulations run at cruise flight conditions. The maximum number of grid points in the simulations was approximately 4 x 10(exp 6). Issues considered in the evaluation study included analysis of the unsteady flow field in the cavity, the influence of the cavity on the flow across empennage surfaces, the drag penalty caused by the open telescope bay, and the noise radiating from cavity surfaces and the cavity-port shear layer. Wind-tunnel data were also available to compare

  8. Uses And Characteristics Of Dynamic Tradeoff Evaluation

    NASA Technical Reports Server (NTRS)

    Schwuttke, Ursula M.

    1995-01-01

    Report discusses basic concepts, some applications, and performance characteristics of dynamic tradeoff evaluation (DTE). Basic concepts of DTE also described in "Dynamic Restructuring of Problems in Artificial Intelligence" (NPO-18488). DTE is method of enhancing real-time performance of artificial-intelligence system such as might be used to monitor data from multiple sensors in factory, aircraft, spacecraft, or other complex system of equipment. Report presents evaluation of DTE as applied to spacecraft-monitoring problems.

  9. Interferometric synthetic aperture radar study of Okmok volcano, Alaska, 1992-2003: Magma supply dynamics and postemplacement lava flow deformation

    USGS Publications Warehouse

    Lu, Zhiming; Masterlark, Timothy; Dzurisin, D.

    2005-01-01

    Okmok volcano, located in the central Aleutian arc, Alaska, is a dominantly basaltic complex topped with a 10-km-wide caldera that formed circa 2.05 ka. Okmok erupted several times during the 20th century, most recently in 1997; eruptions in 1945, 1958, and 1997 produced lava flows within the caldera. We used 80 interferometric synthetic aperture radar (InSAR) images (interferograms) to study transient deformation of the volcano before, during, and after the 1997 eruption. Point source models suggest that a magma reservoir at a depth of 3.2 km below sea level, located beneath the center of the caldera and about 5 km northeast of the 1997 vent, is responsible for observed volcano-wide deformation. The preeruption uplift rate decreased from about 10 cm yr-1 during 1992-1993 to 2 ??? 3 cm yr-1 during 1993-1995 and then to about -1 ??? -2 cm yr-1 during 1995-1996. The posteruption inflation rate generally decreased with time during 1997-2001, but increased significantly during 2001-2003. By the summer of 2003, 30 ??? 60% of the magma volume lost from the reservoir in the 1997 eruption had been replenished. Interferograms for periods before the 1997 eruption indicate consistent subsidence of the surface of the 1958 lava flows, most likely due to thermal contraction. Interferograms for periods after the eruption suggest at least four distinct deformation processes: (1) volcano-wide inflation due to replenishment of the shallow magma reservoir, (2) subsidence of the 1997 lava flows, most likely due to thermal contraction, (3) deformation of the 1958 lava flows due to loading by the 1997 flows, and (4) continuing subsidence of 1958 lava flows buried beneath 1997 flows. Our results provide insights into the postemplacement behavior of lava flows and have cautionary implications for the interpretation of inflation patterns at active volcanoes.

  10. Simultaneous displacement and slope measurement in electronic speckle pattern interferometry using adjustable aperture multiplexing.

    PubMed

    Lu, Min; Wang, Shengjia; Aulbach, Laura; Koch, Alexander W

    2016-08-01

    This paper suggests the use of adjustable aperture multiplexing (AAM), a method which is able to introduce multiple tunable carrier frequencies into a three-beam electronic speckle pattern interferometer to measure the out-of-plane displacement and its first-order derivative simultaneously. In the optical arrangement, two single apertures are located in the object and reference light paths, respectively. In cooperation with two adjustable mirrors, virtual images of the single apertures construct three pairs of virtual double apertures with variable aperture opening sizes and aperture distances. By setting the aperture parameter properly, three tunable spatial carrier frequencies are produced within the speckle pattern and completely separate the information of three interferograms in the frequency domain. By applying the inverse Fourier transform to a selected spectrum, its corresponding phase difference distribution can thus be evaluated. Therefore, we can obtain the phase map due to the deformation as well as its slope of the test surface from two speckle patterns which are recorded at different loading events. By this means, simultaneous and dynamic measurements are realized. AAM has greatly simplified the measurement system, which contributes to improving the system stability and increasing the system flexibility and adaptability to various measurement requirements. This paper presents the AAM working principle, the phase retrieval using spatial carrier frequency, and preliminary experimental results. PMID:27505365

  11. Debuncher Momentum Aperture Measurements

    SciTech Connect

    O'Day, S.

    1991-01-01

    During the November 1990 through January 1991 {bar p} studies period, the momentum aperture of the beam in the debuncher ring was measured. The momentum aperture ({Delta}p/p) was found to be 4.7%. The momentum spread was also measured with beam bunch rotation off. A nearly constant particle population density was observed for particles with {Delta}p/p of less than 4.3%, indicating virtually unobstructed orbits in this region. The population of particles with momenta outside this aperture was found to decrease rapidly. An absolute or 'cut-off' momentum aperture of {Delta}p/p = 5.50% was measured.

  12. Evaluation of groundwater dynamic regime with groundwater depth evaluation indexes.

    PubMed

    Genxu, Wang; Jian, Zhou; Kubota, Jumpei; Jianping, Su

    2008-06-01

    An accurate quantitative evaluation of anthropogenic effects on regional groundwater dynamics is critical to the rational planning, management, and use of such resources and in maintaining the sustainability of groundwater-dependent ecosystems. Based on groundwater dynamics, a series of groundwater depth evaluation indexes were created to quantitatively evaluate the effects of anthropogenic activities on the groundwater system. These indexes were based on mathematical relationships relating groundwater depth to surface runoff (gammat), precipitation (rhot), and extraction (deltat). The anthropogenic effects on these relationships were evaluated statistically, with respect to both temporal and spatial variation. The anthropogenic effects on groundwater dynamics within the arid Zhangye Basin, located in the middle reaches of northwest China's Heihe River, were investigated. River valley plains in the western portion of the basin excepted, anthropogenic activities have, since 1995, dramatically altered the basin's groundwater dynamics; in particular, in the mid-upper and lower portions of alluvial-diluvial fans and in localized northerly fine-soil plains regions, the relationship of groundwater to surface runoff and atmospheric precipitation has shifted. This and other changes indicate that anthropogenic effects on groundwater systems in this region show clear spatiotemporal variation. PMID:18686930

  13. Synthetic aperture methods for angular scatter imaging

    NASA Astrophysics Data System (ADS)

    Guenther, Drake A.; Ranganathan, Karthik; McAllister, Michael J.; Rigby, K. W.; Walker, William F.

    2004-04-01

    Angular scatter offers a new source of tissue contrast and an opportunity for tissue characterization in ultrasound imaging. We have previously described the application of the translating apertures algorithm (TAA) to coherently acquire angular scatter data over a range of scattering angles. While this approach works well at the focus, it suffers from poor depth of field (DOF) due to a finite aperture size. Furthermore, application of the TAA with large focused apertures entails a tradeoff between spatial resolution and scattering angle resolution. While large multielement apertures improve spatial resolution, they encompass many permutations of transmit/receive element pairs. This results in the simultaneous interrogation of multiple scattering angles, limiting angular resolution. We propose a synthetic aperture imaging scheme that achieves both high spatial resolution and high angular resolution. In backscatter acquisition mode, we transmit successively from single transducer elements, while receiving on the same element. Other scattering angles are interrogated by successively transmitting and receiving on different single elements chosen with the appropriate spatial separation between them. Thus any given image is formed using only transmit/receive element pairs at a single separation. This synthetic aperture approach minimizes averaging across scattering angles, and yields excellent angular resolution. Likewise, synthetic aperture methods allow us to build large effective apertures to maintain a high spatial resolution. Synthetic dynamic focusing and dynamic apodization are applied to further improve spatial resolution and DOF. We present simulation results and experimental results obtained using a GE Logiq 700MR system modified to obtain synthetic aperture TAA data. Images of wire targets exhibit high DOF and spatial resolution. We also present a novel approach for combining angular scatter data to effectively reduce grating lobes. With this approach we have

  14. Variable-aperture screen

    DOEpatents

    Savage, George M.

    1991-01-01

    Apparatus for separating material into first and second portions according to size including a plurality of shafts, a plurality of spaced disks radiating outwardly from each of the shafts to define apertures and linkage interconnecting the shafts for moving the shafts toward or away from one another to vary the size of the apertures while the apparatus is performing the separating function.

  15. Rotating Aperture System

    DOEpatents

    Rusnak, Brian; Hall, James M.; Shen, Stewart; Wood, Richard L.

    2005-01-18

    A rotating aperture system includes a low-pressure vacuum pumping stage with apertures for passage of a deuterium beam. A stator assembly includes holes for passage of the beam. The rotor assembly includes a shaft connected to a deuterium gas cell or a crossflow venturi that has a single aperture on each side that together align with holes every rotation. The rotating apertures are synchronized with the firing of the deuterium beam such that the beam fires through a clear aperture and passes into the Xe gas beam stop. Portions of the rotor are lapped into the stator to improve the sealing surfaces, to prevent rapid escape of the deuterium gas from the gas cell.

  16. Evaluation of Dynamic Methods for Earthwork Assessment

    NASA Astrophysics Data System (ADS)

    Vlček, Jozef; Ďureková, Dominika; Zgútová, Katarína

    2015-05-01

    Rapid development of road construction imposes requests on fast and quality methods for earthwork quality evaluation. Dynamic methods are now adopted in numerous civil engineering sections. Especially evaluation of the earthwork quality can be sped up using dynamic equipment. This paper presents the results of the parallel measurements of chosen devices for determining the level of compaction of soils. Measurements were used to develop the correlations between values obtained from various apparatuses. Correlations show that examined apparatuses are suitable for examination of compaction level of fine-grained soils with consideration of boundary conditions of used equipment. Presented methods are quick and results can be obtained immediately after measurement, and they are thus suitable in cases when construction works have to be performed in a short period of time.

  17. Scalar wave diffraction from a circular aperture

    SciTech Connect

    Cerjan, C.

    1995-01-25

    The scalar wave theory is used to evaluate the expected diffraction patterns from a circular aperture. The standard far-field Kirchhoff approximation is compared to the exact result expressed in terms of oblate spheroidal harmonics. Deviations from an expanding spherical wave are calculated for circular aperture radius and the incident beam wavelength using suggested values for a recently proposed point diffractin interferometer. The Kirchhoff approximation is increasingly reliable in the far-field limit as the aperture radius is increased, although significant errors in amplitude and phase persist.

  18. Sub-Aperture Interferometers

    NASA Technical Reports Server (NTRS)

    Zhao, Feng

    2010-01-01

    Sub-aperture interferometers -- also called wavefront-split interferometers -- have been developed for simultaneously measuring displacements of multiple targets. The terms "sub-aperture" and "wavefront-split" signify that the original measurement light beam in an interferometer is split into multiple sub-beams derived from non-overlapping portions of the original measurement-beam aperture. Each measurement sub-beam is aimed at a retroreflector mounted on one of the targets. The splitting of the measurement beam is accomplished by use of truncated mirrors and masks, as shown in the example below

  19. Dynamic Multicriteria Evaluation of Conceptual Hydrological Models

    NASA Astrophysics Data System (ADS)

    de Vos, N. J.; Rientjes, T. H.; Fenicia, F.; Gupta, H. V.

    2007-12-01

    Accurate and precise forecasts of river streamflows are crucial for successful management of water resources and under the threat of hydrological extremes such as floods and droughts. Conceptual rainfall-runoff models are the most popular approach in flood forecasting. However, the calibration and evaluation of such models is often oversimplified by the use of performance statistics that largely ignore the dynamic character of a watershed system. This research aims to find novel ways of model evaluation by identifying periods of hydrologic similarity and customizing evaluation within each period using multiple criteria. A dynamic approach to hydrologic model identification, calibration and testing can be realized by applying clustering algorithms (e.g., Self-Organizing Map, Fuzzy C-means algorithm) to hydrological data. These algorithms are able to identify clusters in the data that represent periods of hydrological similarity. In this way, dynamic catchment system behavior can be simplified within the clusters that are identified. Although clustering requires a number of subjective choices, new insights into the hydrological functioning of a catchment can be obtained. Finally, separate model multi-criteria calibration and evaluation is performed for each of the clusters. Such a model evaluation procedure shows to be reliable and gives much-needed feedback on exactly where certain model structures fail. Several clustering algorithms were tested on two data sets of meso-scale and large-scale catchments. The results show that the clustering algorithms define categories that reflect hydrological process understanding: dry/wet seasons, rising/falling hydrograph limbs, precipitation-driven/ non-driven periods, etc. The results of various clustering algorithms are compared and validated using expert knowledge. Calibration results on a conceptual hydrological model show that the common practice of single-criteria calibration over the complete time series fails to perform

  20. Optica aperture synthesis

    NASA Astrophysics Data System (ADS)

    van der Avoort, Casper

    2006-05-01

    attained, solely based on information from the focal plane of the set-up. Further experiments show that the approximation of exact homothesis is limited by the optical quality of the beam combiner optics. Parallel to the experiments on homothesis, a study was performed to evaluate the use of the Extended Nijboer-Zernike (ENZ) formalism for analysis of multiple aperture optical systems. It is envisaged that an aberration retrieval algorithm, provided with the common focus of a homothetic array, can be used to detect misalignment of or even aberrations in the sub-apertures of the sparse synthetic aperture. The ENZ formalism is a powerful tool to describe the focal intensity profile in an optical imaging system, imaging a monochromatic point source through a pupil that is allowed to have a certain transmission profile and phase aberration function over the pupil. Moreover, the formalism allows calculation of intensity profiles outside the best-focus plane. With the intensity information of several through-focus planes, enough information is available to reconstruct the pupil function from it. The formalism is described, including the reconstruction algorithm. Although very good results are obtained for general pupil functions, the results for synthetic pupil functions are not very promising. The detailed description of the ENZ-aberration retrieval reveals the origin of the breakdown of the retrieval process. Finally, a description of experiments on nulling interferometry is given, starting with the presentation of an experimental set-up for three-beam nulling. A novel strategy for polychromatic nulling is treated here, with the goal of relieving the tight phase constraint on the spectra in the individual beams. This theoretically allows broad band-nulling with a high rejection ratio without using achromatic phase shifters. The disappointing results led to an investigation of the spectra of the individual beams. The origin of the unsatisfactory level of the rejection ratio is

  1. Variable-aperture screen

    DOEpatents

    Savage, G.M.

    1991-10-29

    Apparatus is described for separating material into first and second portions according to size including a plurality of shafts, a plurality of spaced disks radiating outwardly from each of the shafts to define apertures and linkage interconnecting the shafts for moving the shafts toward or away from one another to vary the size of the apertures while the apparatus is performing the separating function. 10 figures.

  2. Differential Synthetic Aperture Ladar

    SciTech Connect

    Stappaerts, E A; Scharlemann, E

    2005-02-07

    We report a differential synthetic aperture ladar (DSAL) concept that relaxes platform and laser requirements compared to conventional SAL. Line-of-sight translation/vibration constraints are reduced by several orders of magnitude, while laser frequency stability is typically relaxed by an order of magnitude. The technique is most advantageous for shorter laser wavelengths, ultraviolet to mid-infrared. Analytical and modeling results, including the effect of speckle and atmospheric turbulence, are presented. Synthetic aperture ladars are of growing interest, and several theoretical and experimental papers have been published on the subject. Compared to RF synthetic aperture radar (SAR), platform/ladar motion and transmitter bandwidth constraints are especially demanding at optical wavelengths. For mid-IR and shorter wavelengths, deviations from a linear trajectory along the synthetic aperture length have to be submicron, or their magnitude must be measured to that precision for compensation. The laser coherence time has to be the synthetic aperture transit time, or transmitter phase has to be recorded and a correction applied on detection.

  3. Confocal coded aperture imaging

    DOEpatents

    Tobin, Jr., Kenneth William; Thomas, Jr., Clarence E.

    2001-01-01

    A method for imaging a target volume comprises the steps of: radiating a small bandwidth of energy toward the target volume; focusing the small bandwidth of energy into a beam; moving the target volume through a plurality of positions within the focused beam; collecting a beam of energy scattered from the target volume with a non-diffractive confocal coded aperture; generating a shadow image of said aperture from every point source of radiation in the target volume; and, reconstructing the shadow image into a 3-dimensional image of the every point source by mathematically correlating the shadow image with a digital or analog version of the coded aperture. The method can comprise the step of collecting the beam of energy scattered from the target volume with a Fresnel zone plate.

  4. Temporal Aperture Modulation

    NASA Technical Reports Server (NTRS)

    Proctor, R. J.

    1981-01-01

    The two types of modulation techniques useful to X-ray imaging are reviewed. The use of optimum coded temporal aperature modulation is shown, in certain cases, to offer an advantage over a spatial aperture modulator. Example applications of a diffuse anisotropic X-ray background experiment and a wide field of view hard X-ray imager are discussed.

  5. Coded aperture computed tomography

    NASA Astrophysics Data System (ADS)

    Choi, Kerkil; Brady, David J.

    2009-08-01

    Diverse physical measurements can be modeled by X-ray transforms. While X-ray tomography is the canonical example, reference structure tomography (RST) and coded aperture snapshot spectral imaging (CASSI) are examples of physically unrelated but mathematically equivalent sensor systems. Historically, most x-ray transform based systems sample continuous distributions and apply analytical inversion processes. On the other hand, RST and CASSI generate discrete multiplexed measurements implemented with coded apertures. This multiplexing of coded measurements allows for compression of measurements from a compressed sensing perspective. Compressed sensing (CS) is a revelation that if the object has a sparse representation in some basis, then a certain number, but typically much less than what is prescribed by Shannon's sampling rate, of random projections captures enough information for a highly accurate reconstruction of the object. This paper investigates the role of coded apertures in x-ray transform measurement systems (XTMs) in terms of data efficiency and reconstruction fidelity from a CS perspective. To conduct this, we construct a unified analysis using RST and CASSI measurement models. Also, we propose a novel compressive x-ray tomography measurement scheme which also exploits coding and multiplexing, and hence shares the analysis of the other two XTMs. Using this analysis, we perform a qualitative study on how coded apertures can be exploited to implement physical random projections by "regularizing" the measurement systems. Numerical studies and simulation results demonstrate several examples of the impact of coding.

  6. Synthetic Aperture Radar Interferometry

    NASA Technical Reports Server (NTRS)

    Rosen, P. A.; Hensley, S.; Joughin, I. R.; Li, F.; Madsen, S. N.; Rodriguez, E.; Goldstein, R. M.

    1998-01-01

    Synthetic aperture radar interferometry is an imaging technique for measuring the topography of a surface, its changes over time, and other changes in the detailed characteristics of the surface. This paper reviews the techniques of interferometry, systems and limitations, and applications in a rapidly growing area of science and engineering.

  7. Apodizer aperture for lasers

    DOEpatents

    Jorna, Siebe; Siebert, Larry D.; Brueckner, Keith A.

    1976-11-09

    An aperture attenuator for use with high power lasers which includes glass windows shaped and assembled to form an annulus chamber which is filled with a dye solution. The annulus chamber is shaped such that the section in alignment with the axis of the incident beam follows a curve which is represented by the equation y = (r - r.sub.o).sup.n.

  8. Phasing rectangular apertures.

    PubMed

    Baker, K L; Homoelle, D; Utterback, E; Jones, S M

    2009-10-26

    Several techniques have been developed to phase apertures in the context of astronomical telescopes with segmented mirrors. Phasing multiple apertures, however, is important in a wide range of optical applications. The application of primary interest in this paper is the phasing of multiple short pulse laser beams for fast ignition fusion experiments. In this paper analytic expressions are derived for parameters such as the far-field distribution, a line-integrated form of the far-field distribution that could be fit to measured data, enclosed energy or energy-in-a-bucket and center-of-mass that can then be used to phase two rectangular apertures. Experimental data is taken with a MEMS device to simulate the two apertures and comparisons are made between the analytic parameters and those derived from the measurements. Two methods, fitting the measured far-field distribution to the theoretical distribution and measuring the ensquared energy in the far-field, produced overall phase variance between the 100 measurements of less than 0.005 rad(2) or an RMS displacement of less than 12 nm. PMID:19997175

  9. Genetic apertures: an improved sparse aperture design framework.

    PubMed

    Salvaggio, Philip S; Schott, John R; McKeown, Donald M

    2016-04-20

    The majority of optical sparse aperture imaging research in the remote sensing field has been confined to a small set of aperture layouts. While these layouts possess some desirable properties for imaging, they may not be ideal for all applications. This work introduces an optimization framework for sparse aperture layouts based on genetic algorithms as well as a small set of fitness functions for incoherent sparse aperture image quality. The optimization results demonstrate the merits of existing designs and the opportunity for creating new sparse aperture layouts. PMID:27140086

  10. Evaluation of allergic response using dynamic thermography

    NASA Astrophysics Data System (ADS)

    Rokita, E.; Rok, T.; Tatoń, G.

    2015-03-01

    Skin dynamic termography supplemented by a mathematical model is presented as an objective and sensitive indicator of the skin prick test result. Termographic measurements were performed simultaneously with routine skin prick tests. The IR images were acquired every 70 s up to 910 s after skin prick. In the model histamine is treated as the principal mediator of the allergic reaction. Histamine produces vasolidation and the engorged vessels are responsible for an increase in skin temperature. The model parameters were determined by fitting the analytical solutions to the spatio-temporal distributions of the differences between measured and baseline temperatures. The model reproduces experimental data very well (coefficient of determination = 0.805÷0.995). The method offers a set of parameters to describe separately skin allergic reaction and skin reactivity. The release of histamine after allergen injection is the best indicator of allergic response. The diagnostic parameter better correlates with the standard evaluation of a skin prick test (correlation coefficient = 0.98) than the result of the thermographic planimetric method based on temperature and heated area determination (0.81). The high sensitivity of the method allows for determination of the allergic response in patients with the reduced skin reactivity.

  11. Study on test metrology of large aperture optical system wavefront

    NASA Astrophysics Data System (ADS)

    Liu, Zhiying; Fu, Yuegang; Gao, Tianyuan; Wang, Zhijian

    2009-05-01

    Large aperture optical system test has been a key problem for a long time. It could be solved by sub-aperture stitching method after the sub-apertures are tested. Sub-aperture stitching technology is a feasible method for testing large diameter optical system with small diameter interferometer sub-aperture stitching. Auto-collimating component will be needed with interferometer stitching method. Auto-collimating component is defined that the image could be kept stable when the optical component rotates about any axis in space. And the beam could be back along original optical path. By this means, auto collimation could be realized. The auto-collimating component is smaller than the test system. The whole wavefront of large aperture system could be tested through the method that the auto-collimating component moves along the guide rail and rotates about optical axis. A right angle roof prism is chosen as the auto-collimating component due to its character of easier manufacture. The active matrix, characteristic orientation and extreme axial is deduced with dynamic optics. The sub-aperture stitching testing process is simulated by ZEMAX in detail. The test result by stitching method is compared with that by directive test method for large aperture optical system. It is shown that the relative test error is less than 4.3λ 0/00. The sub -aperture stitching test method is verified.

  12. Aperture center energy showcase

    SciTech Connect

    Torres, J. J.

    2012-03-01

    Sandia and Forest City have established a Cooperative Research and Development Agreement (CRADA), and the partnership provides a unique opportunity to take technology research and development from demonstration to application in a sustainable community. A project under that CRADA, Aperture Center Energy Showcase, offers a means to develop exhibits and demonstrations that present feedback to community members, Sandia customers, and visitors. The technologies included in the showcase focus on renewable energy and its efficiency, and resilience. These technologies are generally scalable, and provide secure, efficient solutions to energy production, delivery, and usage. In addition to establishing an Energy Showcase, support offices and conference capabilities that facilitate research, collaboration, and demonstration were created. The Aperture Center project focuses on establishing a location that provides outreach, awareness, and demonstration of research findings, emerging technologies, and project developments to Sandia customers, visitors, and Mesa del Sol community members.

  13. Synthetic Aperture Radiometer Systems

    NASA Technical Reports Server (NTRS)

    LeVine, David M.

    1999-01-01

    Aperture synthesis is a new technology for passive microwave remote sensing from space which has the potential to overcome the limitations set in the past by antenna size. This is an interferometric technique in which pairs of small antennas and signal processing are used to obtain the resolution of a single large antenna. The technique has been demonstrated successfully at L-band with the aircraft prototype instrument, ESTAR. Proposals have been submitted to demonstrate this technology in space (HYDROSTAR and MIRAS).

  14. Aperture excited dielectric antennas

    NASA Technical Reports Server (NTRS)

    Crosswell, W. F.; Chatterjee, J. S.; Mason, V. B.; Tai, C. T.

    1974-01-01

    The results of a comprehensive experimental and theoretical study of the effect of placing dielectric objects over the aperture of waveguide antennas are presented. Experimental measurements of the radiation patterns, gain, impedance, near-field amplitude, and pattern and impedance coupling between pairs of antennas are given for various Plexiglas shapes, including the sphere and the cube, excited by rectangular, circular, and square waveguide feed apertures. The waveguide excitation of a dielectric sphere is modeled using the Huygens' source, and expressions for the resulting electric fields, directivity, and efficiency are derived. Calculations using this model show good overall agreement with experimental patterns and directivity measurements. The waveguide under an infinite dielectric slab is used as an impedance model. Calculations using this model agree qualitatively with the measured impedance data. It is concluded that dielectric loaded antennas such as the waveguide excited sphere, cube, or sphere-cylinder can produce directivities in excess of that obtained by a uniformly illuminated aperture of the same cross section, particularly for dielectric objects with dimensions of 2 wavelengths or less. It is also shown that for certain configurations coupling between two antennas of this type is less than that for the same antennas without dielectric loading.

  15. Measurement of Fracture Aperture Fields Using Ttransmitted Light: An Evaluation of Measurement Errors and their Influence on Simulations of Flow and Transport through a Single Fracture

    SciTech Connect

    Detwiler, Russell L.; Glass, Robert J.; Pringle, Scott E.

    1999-05-06

    Understanding of single and multi-phase flow and transport in fractures can be greatly enhanced through experimentation in transparent systems (analogs or replicas) where light transmission techniques yield quantitative measurements of aperture, solute concentration, and phase saturation fields. Here we quanti@ aperture field measurement error and demonstrate the influence of this error on the results of flow and transport simulations (hypothesized experimental results) through saturated and partially saturated fractures. find that precision and accuracy can be balanced to greatly improve the technique and We present a measurement protocol to obtain a minimum error field. Simulation results show an increased sensitivity to error as we move from flow to transport and from saturated to partially saturated conditions. Significant sensitivity under partially saturated conditions results in differences in channeling and multiple-peaked breakthrough curves. These results emphasize the critical importance of defining and minimizing error for studies of flow and transpoti in single fractures.

  16. Implementation of swept synthetic aperture imaging

    NASA Astrophysics Data System (ADS)

    Bottenus, Nick; Jakovljevic, Marko; Boctor, Emad; Trahey, Gregg E.

    2015-03-01

    Ultrasound imaging of deep targets is limited by the resolution of current ultrasound systems based on the available aperture size. We propose a system to synthesize an extended effective aperture in order to improve resolution and target detectability at depth using a precisely-tracked transducer swept across the region of interest. A Field II simulation was performed to demonstrate the swept aperture approach in both the spatial and frequency domains. The adaptively beam-formed system was tested experimentally using a volumetric transducer and an ex vivo canine abdominal layer to evaluate the impact of clutter-generating tissue on the resulting point spread function. Resolution was improved by 73% using a 30.8 degree sweep despite the presence of varying aberration across the array with an amplitude on the order of 100 ns. Slight variations were observed in the magnitude and position of side lobes compared to the control case, but overall image quality was not significantly degraded as compared by a simulation based on the experimental point spread function. We conclude that the swept aperture imaging system may be a valuable tool for synthesizing large effective apertures using conventional ultrasound hardware.

  17. Differential Optical Synthetic Aperture Radar

    DOEpatents

    Stappaerts, Eddy A.

    2005-04-12

    A new differential technique for forming optical images using a synthetic aperture is introduced. This differential technique utilizes a single aperture to obtain unique (N) phases that can be processed to produce a synthetic aperture image at points along a trajectory. This is accomplished by dividing the aperture into two equal "subapertures", each having a width that is less than the actual aperture, along the direction of flight. As the platform flies along a given trajectory, a source illuminates objects and the two subapertures are configured to collect return signals. The techniques of the invention is designed to cancel common-mode errors, trajectory deviations from a straight line, and laser phase noise to provide the set of resultant (N) phases that can produce an image having a spatial resolution corresponding to a synthetic aperture.

  18. New Aperture Partitioning Element

    NASA Astrophysics Data System (ADS)

    Griffin, S.; Calef, B.; Williams, S.

    Postprocessing in an optical system can be aided by adding an optical element to partition the pupil into a number of segments. When imaging through the atmosphere, the recorded data are blurred by temperature-induced variations in the index of refraction along the line of sight. Using speckle imaging techniques developed in the astronomy community, this blurring can be corrected to some degree. The effectiveness of these techniques is diminished by redundant baselines in the pupil. Partitioning the pupil reduces the degree of baseline redundancy, and therefore improves the quality of images that can be obtained from the system. It is possible to implement the described approach on an optical system with a segmented primary mirror, but not very practical. This is because most optical systems do not have segmented primary mirrors, and those that do have relatively low bandwidth positioning of segments due to their large mass and inertia. It is much more practical to position an active aperture partitioning element at an aft optics pupil of the optical system. This paper describes the design, implementation and testing of a new aperture partitioning element that is completely reflective and reconfigurable. The device uses four independent, annular segments that can be positioned with a high degree of accuracy without impacting optical wavefront of each segment. This mirror has been produced and is currently deployed and working on the 3.6 m telescope.

  19. Subjective evaluation of higher dynamic range video

    NASA Astrophysics Data System (ADS)

    Hanhart, Philippe; Korshunov, Pavel; Ebrahimi, Touradj

    2014-09-01

    High dynamic range (HDR) imaging is able to capture a wide range of luminance values, closer to what the human eye can perceive. However, for capture and display technologies, it is important to answer the question on the significance of higher dynamic range for user preference. This paper answers this question by investigating the added value of higher dynamic range via a rigorous set of subjective experiments using paired comparison methodology. Video sequences at four different peak luminance levels were displayed side-by-side on a Dolby Research HDR RGB backlight dual modulation display (aka `Pulsar'), which is capable of reliably displaying video content at 4000 cd=m2 peak luminance. The results of the subjective experiment demonstrate that the preference of an average viewer increases logarithmically with the increase in the maximum luminance level at which HDR content is displayed, with 4000 cd=m2 being the most attractive option.

  20. Sonovestibular symptoms evaluated by computed dynamic posturography.

    PubMed

    Teszler, C B; Ben-David, J; Podoshin, L; Sabo, E

    2000-01-01

    The investigation of stability under bilateral acoustic stimulation was undertaken in an attempt to mimic the real-life conditions of noisy environment (e.g., industry, aviation). The Tullio phenomenon evaluated by computed dynamic posturography (CDP) under acoustic stimulation is reflected in postural unsteadiness, rather than in the classic nystagmus. With such a method, the dangerous effects of noise-induced instability can be assessed and prevented. Three groups of subjects were submitted. The first (group A) included 20 patients who complained of sonovestibular symptoms (i.e., Tullio phenomenon) on the background of an inner-ear disease. The second group (B) included 20 neurootological patients without a history of Tullio phenomenon. Group C consisted of 20 patients with normal hearing, as controls. A pure-tone stimulus of 1,000 Hz at 110 dB was delivered binaurally for 20 seconds during condition 5 and condition 6 of the CDP sensory organization test. The sequence of six sensory organization conditions was performed three times with two intermissions of 15-20 minutes between the trials. The first was performed in the regular mode (quiet stance). This was followed 20 minutes by a trial carried out in quiet stance in sensory organizations tests (SOTs) 1 through 4, and with acoustic stimulation in SOT 5 and SOT 6. The last test was performed in quiet stance throughout (identical to the first trial). A significant drop in the composite equilibrium score was witnessed in group A patients upon acoustic stimulation (p < .0001). This imbalance did not disappear completely until 20 minutes later when the third sensory organization trial was performed. In fact, the composite score obtained on the last SOT was still significantly worse than the baseline. Group B and the normal subjects (group C) showed no significant change in composite score. As regards the vestibular ratio score, again, group A marked a drop on stimulation with sound (p < .004). This decrease

  1. Dynamics Explorer twin spacecraft under evaluation tests

    NASA Technical Reports Server (NTRS)

    Redmond, C.

    1981-01-01

    The Dynamics Explorer A and B satellites designed to explore the interactive processes occuring between the magnetosphere and Earth's ionosphere, upper atmosphere, and plasmasphere are described. Effects of these interactions, satellite orbits, data collecting antennas, solar power systems, axes, configurations, and Earth based command, control and data display systems are mentioned.

  2. Evaluation Team Dynamics: Intragroup Ethical Challenges

    ERIC Educational Resources Information Center

    Urias, David

    2009-01-01

    Ethical challenges associated with the relationships among members of an evaluative team/organization receive less attention. Examples of the kinds of ethical dilemmas that could occur within an evaluation team include an individual taking undeserved credit, transferring blame, making false promises, withholding information, breaching…

  3. Aperture modulated, translating bed total body irradiation

    SciTech Connect

    Hussain, Amjad; Villarreal-Barajas, Jose Eduardo; Dunscombe, Peter; Brown, Derek W.

    2011-02-15

    Purpose: Total body irradiation (TBI) techniques aim to deliver a uniform radiation dose to a patient with an irregular body contour and a heterogeneous density distribution to within {+-}10% of the prescribed dose. In the current article, the authors present a novel, aperture modulated, translating bed TBI (AMTBI) technique that produces a high degree of dose uniformity throughout the entire patient. Methods: The radiation beam is dynamically shaped in two dimensions using a multileaf collimator (MLC). The irregular surface compensation algorithm in the Eclipse treatment planning system is used for fluence optimization, which is performed based on penetration depth and internal inhomogeneities. Two optimal fluence maps (AP and PA) are generated and beam apertures are created to deliver these optimal fluences. During treatment, the patient/phantom is translated on a motorized bed close to the floor (source to bed distance: 204.5 cm) under a stationary radiation beam with 0 deg. gantry angle. The bed motion and dynamic beam apertures are synchronized. Results: The AMTBI technique produces a more homogeneous dose distribution than fixed open beam translating bed TBI. In phantom studies, the dose deviation along the midline is reduced from 10% to less than 5% of the prescribed dose in the longitudinal direction. Dose to the lung is reduced by more than 15% compared to the unshielded fixed open beam technique. At the lateral body edges, the dose received from the open beam technique was 20% higher than that prescribed at umbilicus midplane. With AMTBI the dose deviation in this same region is reduced to less than 3% of the prescribed dose. Validation of the technique was performed using thermoluminescent dosimeters in a Rando phantom. Agreement between calculation and measurement was better than 3% in all cases. Conclusions: A novel, translating bed, aperture modulated TBI technique that employs dynamically shaped MLC defined beams is shown to improve dose uniformity

  4. Dynamic fuzzy hierarchy analysis for evaluation of professionalization degree

    NASA Astrophysics Data System (ADS)

    Jin, Lin; Min, Luo; Ma, Jingxi

    2016-06-01

    This paper presents the model of dynamic fuzzy hierarchy analysis for evaluation of professionalization degree, as a combination of the dynamic fuzzy theory and the AHP, which can show the changes and trends of the value of each index of professionalization.

  5. Evaluation of dynamic programming among the existing stereo matching algorithms

    NASA Astrophysics Data System (ADS)

    Huat, Teo Chee; Manap, Nurulfajar bin Abd

    2015-05-01

    There are various types of existing stereo matching algorithms on image processing which applied on stereo vision images to get better results of disparity depth map. One of them is the dynamic programming method. On this research is to perform an evaluation on the performance between the dynamic programming with other existing method as comparison. The algorithm used on the dynamic programming is the global optimization which provides better process on stereo images like its accuracy and its computational efficiency compared to other existing stereo matching algorithms. The dynamic programming algorithm used on this research is the current method as its disparity estimates at a particular pixel and all the other pixels unlike the old methods which with scanline based of dynamic programming. There will be details on every existing methods presented on this paper with the comparison between the dynamic programming and the existing methods. This can propose the dynamic programming method to be used on many applications in image processing.

  6. Dynamic Line Rating: Research and Policy Evaluation

    SciTech Connect

    Jake P. Gentle; Kurt S. Myers; Michael R. West

    2014-07-01

    Dynamic Line Rating (DLR) is a smart grid technology that allows the rating of electrical conductors to be increased based on local weather conditions. Overhead lines are conventionally given a conservative rating based on worst case scenarios. We demonstrate that observing the conditions in real time leads to additional capacity and safer operation. This paper provides a report of a pioneering scheme in the United States of America in which DLR has been applied. Thereby, we demonstrate that observing the local weather conditions in real time leads to additional capacity and safer operation. Secondly, we discuss limitations involved. In doing so, we arrive at novel insights which will inform and improve future DLR projects. Third, we provide a policy background and discussion to clarify the technology’s potential and identifies barriers to the imminent adoption of dynamic line rating systems. We provide suggestions for regulatory bodies about possible improvements in policy to encourage adoption of this beneficial technology.

  7. Material Measurements Using Groundplane Apertures

    NASA Technical Reports Server (NTRS)

    Komisarek, K.; Dominek, A.; Wang, N.

    1995-01-01

    A technique for material parameter determination using an aperture in a groundplane is studied. The material parameters are found by relating the measured reflected field in the aperture to a numerical model. Two apertures are studied which can have a variety of different material configurations covering the aperture. The aperture cross-sections studied are rectangular and coaxial. The material configurations involved combinations of single layer and dual layers with or without a resistive exterior resistive sheet. The resistivity of the resistive sheet can be specified to simulate a perfect electric conductor (PEC) backing (0 Ohms/square) to a free space backing (infinity Ohms/square). Numerical parameter studies and measurements were performed to assess the feasibility of the technique.

  8. Peer Dynamics 1977-78 Evaluation Report.

    ERIC Educational Resources Information Center

    Shada, Marsha; Winger, Joan

    This is an evaluation of the second year of a program designed to reduce the incidence of destructive risk-taking behavior (e.g., drug-alcohol abuse and juvenile delinquency) among school-age youth. Background research indicates that peer group pressure is the single most important factor in dictating the presence or absence of juvenile…

  9. Peer Dynamics 1978-79 Evaluation Report.

    ERIC Educational Resources Information Center

    Winger, Joan

    This is an evaluation of the first year of a program designed to reduce the incidence of destructive risk-taking behavior (e.g., drug-alcohol abuse and juvenile delinquency) among school-age youth. Background research indicates that peer group pressure is the single most important factor in dictating the presence or absence of juvenile delinquency…

  10. Dynamic Evaluation of Distance Education Courses.

    ERIC Educational Resources Information Center

    Champagne, Matthew V.

    This paper focuses on the Interactive and Distance Education Assessment (IDEA) laboratory, an assessment system developed by psychology students and faculty at Rensselaer Polytechnic Institute (New York) that incorporated learning styles, teaching styles, and other measures of individual difference into the evaluation of interactive and distance…

  11. A synthetic aperture study of aperture size in the presence of noise and in vivo clutter

    NASA Astrophysics Data System (ADS)

    Bottenus, Nick; Byram, Brett C.; Trahey, Gregg E.

    2013-03-01

    Conventional wisdom in ultrasonic array design drives development towards larger arrays because of the inverse relationship between aperture size and resolution. We propose a method using synthetic aperture beamforming to study image quality as a function of aperture size in simulation, in a phantom and in vivo. A single data acquisition can be beamformed to produce matched images with a range of aperture sizes, even in the presence of target motion. In this framework we evaluate the reliability of typical image quality metrics - speckle signal-tonoise ratio, contrast and contrast-to-noise ratio - for use in in vivo studies. Phantom and simulation studies are in good agreement in that there exists a point of diminishing returns in image quality at larger aperture sizes. We demonstrate challenges in applying and interpreting these metrics in vivo, showing results in hypoechoic vasculature regions. We explore the use of speckle brightness to describe image quality in the presence of in vivo clutter and underlying tissue inhomogeneities.

  12. [Dynamic MRA in the evaluation of intracranial vascular diseases].

    PubMed

    Gauvrit, J Y; Oppenheim, C; Savage, J; Nataf, F; Reyns, N; Pruvo, J P; Meder, J F; Leclerc, X

    2005-01-01

    Conventional catheter angiography (CCA) remains the gold standard for the evaluation of most intracranial vascular malformations. MRA techniques such as Time of Flight, Phase Contrast or 3D contrast-enhanced MRA, provide anatomic evaluation but without hemodynamic information. Recently developed, dynamic MRA is based on dynamic acquisition of images and image subtraction; these two principal characteristics produce images comparable to those obtained by CCA. The purpose of this review is to explain the principles, advantages and drawbacks of this technique in the evaluation of arteriovenous malformations, arteriovenous fistulas, aneurysms and venous thrombosis. PMID:15798609

  13. Interferometric Synthetic Aperture Microscopy (ISAM)

    NASA Astrophysics Data System (ADS)

    Adie, Steven G.; Shemonski, Nathan D.; Ralston, Tyler S.; Carney, P. Scott; Boppart, Stephen A.

    The trade-off between transverse resolution and depth-of-field, and the mitigation of optical aberrations, are long-standing problems in optical imaging. The deleterious impact of these problems on three-dimensional tomography increases with numerical aperture (NA), and so they represent a significant impediment for real-time cellular resolution tomography over the typical imaging depths achieved with OCT. With optical coherence microscopy (OCM), which utilizes higher-NA optics than OCT, the depth-of-field is severely reduced, and it has been postulated that aberrations play a major role in reducing the useful imaging depth in OCM. Even at lower transverse resolution, both these phenomena produce artifacts that degrade the imaging of fine tissue structures. Early approaches to the limited depth-of-field problem in time-domain OCT utilized dynamic focusing. In spectral-domain OCT, this focus-shifting approach to data acquisition leads to long acquisition times and large datasets. Adaptive optics (AO) has been utilized to correct optical aberrations, in particular for retinal OCT, but in addition to requiring elaborate and expensive setups, the real-time optimization requirements at the time of imaging, and the correction of spatially varying effects of aberrations throughout an imaged volume, remain as significant challenges. This chapter presents computed imaging solutions for the reconstruction of sample structure when imaging with ideal and aberrated Gaussian beams.

  14. Sparse aperture endoscope

    DOEpatents

    Fitch, J.P.

    1999-07-06

    An endoscope is disclosed which reduces the volume needed by the imaging part, maintains resolution of a wide diameter optical system, while increasing tool access, and allows stereographic or interferometric processing for depth and perspective information/visualization. Because the endoscope decreases the volume consumed by imaging optics such allows a larger fraction of the volume to be used for non-imaging tools, which allows smaller incisions in surgical and diagnostic medical applications thus produces less trauma to the patient or allows access to smaller volumes than is possible with larger instruments. The endoscope utilizes fiber optic light pipes in an outer layer for illumination, a multi-pupil imaging system in an inner annulus, and an access channel for other tools in the center. The endoscope is amenable to implementation as a flexible scope, and thus increases it's utility. Because the endoscope uses a multi-aperture pupil, it can also be utilized as an optical array, allowing stereographic and interferometric processing. 7 figs.

  15. Interferometric synthetic aperture microscopy

    NASA Astrophysics Data System (ADS)

    Ralston, Tyler S.; Marks, Daniel L.; Scott Carney, P.; Boppart, Stephen A.

    2007-02-01

    State-of-the-art methods in high-resolution three-dimensional optical microscopy require that the focus be scanned through the entire region of interest. However, an analysis of the physics of the light-sample interaction reveals that the Fourier-space coverage is independent of depth. Here we show that, by solving the inverse scattering problem for interference microscopy, computed reconstruction yields volumes with a resolution in all planes that is equivalent to the resolution achieved only at the focal plane for conventional high-resolution microscopy. In short, the entire illuminated volume has spatially invariant resolution, thus eliminating the compromise between resolution and depth of field. We describe and demonstrate a novel computational image-formation technique called interferometric synthetic aperture microscopy (ISAM). ISAM has the potential to broadly impact real-time three-dimensional microscopy and analysis in the fields of cell and tumour biology, as well as in clinical diagnosis where in vivo imaging is preferable to biopsy.

  16. Interferometric synthetic aperture microscopy

    NASA Astrophysics Data System (ADS)

    Ralston, Tyler S.

    State-of-the-art interferometric microscopies have problems representing objects that lie outside of the focus because the defocus and diffraction effects are not accounted for in the processing. These problems occur because of the lack of comprehensive models to include the scattering effects in the processing. In this dissertation, a new modality in three-dimensional (3D) optical microscopy, Interferometric Synthetic Aperture Microscopy (ISAM), is introduced to account for the scattering effects. Comprehensive models for interferometric microscopy, such as optical coherence tomography (OCT) are developed, for which forward, adjoint, normal, and inverse operators are formulated. Using an accurate model for the probe beam, the resulting algorithms demonstrate accurate linear estimation of the susceptibility of an object from the interferometric data. Using the regularized least squares solution, an ISAM reconstruction of underlying object structure having spatially invariant resolution is obtained from simulated and experimental interferometric data, even in regions outside of the focal plane of the lens. Two-dimensional (2D) and 3D interferometric data is used to resolve objects outside of the confocal region with minimal loss of resolution, unlike in OCT. Therefore, high-resolution details are recovered from outside of the confocal region. Models and solutions are presented for the planar-scanned, the rotationally scanned, and the full-field illuminated geometry. The models and algorithms presented account for the effects of a finite beam width, the source spectrum, the illumination and collection fields, as well as defocus, diffraction and dispersion effects.

  17. Sparse aperture endoscope

    DOEpatents

    Fitch, Joseph P.

    1999-07-06

    An endoscope which reduces the volume needed by the imaging part thereof, maintains resolution of a wide diameter optical system, while increasing tool access, and allows stereographic or interferometric processing for depth and perspective information/visualization. Because the endoscope decreases the volume consumed by imaging optics such allows a larger fraction of the volume to be used for non-imaging tools, which allows smaller incisions in surgical and diagnostic medical applications thus produces less trauma to the patient or allows access to smaller volumes than is possible with larger instruments. The endoscope utilizes fiber optic light pipes in an outer layer for illumination, a multi-pupil imaging system in an inner annulus, and an access channel for other tools in the center. The endoscope is amenable to implementation as a flexible scope, and thus increases the utility thereof. Because the endoscope uses a multi-aperture pupil, it can also be utilized as an optical array, allowing stereographic and interferometric processing.

  18. Lucky imaging and aperture synthesis with low-redundancy apertures.

    PubMed

    Ward, Jennifer E; Rhodes, William T; Sheridan, John T

    2009-01-01

    Lucky imaging, used with some success in astronomical and even horizontal-path imaging, relies on fleeting conditions of the atmosphere that allow momentary improvements in image quality, at least in portions of an image. Aperture synthesis allows a larger aperture and, thus, a higher-resolution imaging system to be synthesized through the superposition of image spatial-frequency components gathered by cooperative combinations of smaller subapertures. A combination of lucky imaging and aperture synthesis strengthens both methods for obtaining improved images through the turbulent atmosphere. We realize the lucky imaging condition appropriate for aperture synthesis imaging for a pair of rectangular subapertures and demonstrate that this condition occurs when the signal energy associated with bandpass spatial-frequency components achieves its maximum value. PMID:19107157

  19. Long-Term Evaluation of the Scintec Boundary-Layer Scintillometer and the Wageningen Large-Aperture Scintillometer: Implications for Scintillometer Users

    NASA Astrophysics Data System (ADS)

    Van Kesteren, B.; Beyrich, F.; Hartogensis, O. K.; Braam, M.

    2015-08-01

    We compare the structure parameter of the refractive index, , measured simultaneously with two large-aperture scintillometers: the WagLAS (Wageningen University, Wageningen, the Netherlands) and the BLS900 (Scintec, Rottenburg, Germany). A 3.5-year dataset shows a bias in of about 17 % between the instruments. Analysis of these data reveals firstly that the logarithmic amplifiers in the WagLAS exhibit a strong dependence on temperature, resulting in an overestimation of of up to 35 % for temperatures 0 . Secondly, high-pass filtering of the WagLAS and BLS900 intensity data artificially reduces for crosswinds 2 (error 25 and 5 % respectively). Thirdly, the BLS900 increasingly underestimates (up to 10-15 %) with increasing signal saturation. We demonstrate that Scintec's data processing relies too heavily on the assumption that the intensity data obey a log-normal distribution, which they do not in the case of saturation. Fourthly, both instruments ignore the dissipation range of the refractive-index spectrum, which leads to an overestimation of of up to 30 % for friction velocity 0.2 . Implications of these findings are discussed and placed into perspective for other scintillometer users. Furthermore, we present a tool for revealing saturation and other violations of Rytov theory for any given scintillometer type, including microwave scintillometers.

  20. Importance of dynamic aortic evaluation in planning TEVAR

    PubMed Central

    van Herwaarden, Joost A.; Conti, Michele; Auricchio, Ferdinando; Rampoldi, Vincenzo; Trimarchi, Santi; Moll, Frans L.

    2014-01-01

    Dynamic aortic evaluation in planning thoracic endovascular aortic repair (TEVAR) is important to provide optimal stent graft sizing. Static imaging protocols do not consider normal aortic dynamics and may lead to stent graft to aorta mismatch, causing stent graft related complications, such as type I endoleak and stent graft migration. Dynamic imaging can assist in accurate stent graft selection and sizing preoperatively, and evaluate stent graft performance during follow-up. To create new imaging technologies, integration of knowledge between diverse scientific fields is essential (i.e., engineering, informatics and medicine). Different dynamic imaging modalities, such as electrocardiographic-gated computed tomography angiography (ECG-gated CTA) and four-dimensional phase-contrast MRI (4D PC-MRI), are progressively investigated and implemented into clinical practice as important instruments in preoperative planning for TEVAR. In time, further application of dynamic imaging tools for preoperative screening and follow-up after TEVAR might lead to better outcomes for patients. The advances in dynamic imaging for evaluation of the thoracic aorta using new imaging modalities and their future perspectives are addressed in this manuscript. PMID:24967170

  1. Synthetic aperture radar processing with tiered subapertures

    SciTech Connect

    Doerry, A.W.

    1994-06-01

    Synthetic Aperture Radar (SAR) is used to form images that are maps of radar reflectivity of some scene of interest, from range soundings taken over some spatial aperture. Additionally, the range soundings are typically synthesized from a sampled frequency aperture. Efficient processing of the collected data necessitates using efficient digital signal processing techniques such as vector multiplies and fast implementations of the Discrete Fourier Transform. Inherent in image formation algorithms that use these is a trade-off between the size of the scene that can be acceptably imaged, and the resolution with which the image can be made. These limits arise from migration errors and spatially variant phase errors, and different algorithms mitigate these to varying degrees. Two fairly successful algorithms for airborne SARs are Polar Format processing, and Overlapped Subaperture (OSA) processing. This report introduces and summarizes the analysis of generalized Tiered Subaperture (TSA) techniques that are a superset of both Polar Format processing and OSA processing. It is shown how tiers of subapertures in both azimuth and range can effectively mitigate both migration errors and spatially variant phase errors to allow virtually arbitrary scene sizes, even in a dynamic motion environment.

  2. Conical Rotating Aperture Geometries In Digital Radiography

    NASA Astrophysics Data System (ADS)

    Rudin, Stephen; Bednarek, Daniel R.; Wong, Roland

    1981-11-01

    Applications of conical rotating aperture (RA) geometries to digital radiography are described. Two kinds of conical RA imaging systems are the conical scanning beam and the conical scanning grid assemblies. These assemblies comprise coaxial conical surface(s) the axis of which is collinear with the x-ray focal spot. This geometry allows accurate alignment and continuous focusing of the slits or the grid lines. Image receptors which use solid state photodiode arrays are described for each type of conical RA system: multiple linear arrays for the conical scanning beam assembly and multiple area arrays for the conical scanning grid assembly. The digital rotating-aperture systems combine the wide dynamic range characteristics of solid state detectors with the superior scatter-rejection advantages of scanned beam approaches. The high scanning-beam velocities attainable by the use of rotating apertures should make it possible to obtain digital images for those procedures such as chest radiography which require large fields of view and short exposure times.

  3. Bistatic synthetic aperture radar

    NASA Astrophysics Data System (ADS)

    Yates, Gillian

    Synthetic aperture radar (SAR) allows all-weather, day and night, surface surveillance and has the ability to detect, classify and geolocate objects at long stand-off ranges. Bistatic SAR, where the transmitter and the receiver are on separate platforms, is seen as a potential means of countering the vulnerability of conventional monostatic SAR to electronic countermeasures, particularly directional jamming, and avoiding physical attack of the imaging platform. As the receiving platform can be totally passive, it does not advertise its position by RF emissions. The transmitter is not susceptible to jamming and can, for example, operate at long stand-off ranges to reduce its vulnerability to physical attack. This thesis examines some of the complications involved in producing high-resolution bistatic SAR imagery. The effect of bistatic operation on resolution is examined from a theoretical viewpoint and analytical expressions for resolution are developed. These expressions are verified by simulation work using a simple 'point by point' processor. This work is extended to look at using modern practical processing engines for bistatic geometries. Adaptations of the polar format algorithm and range migration algorithm are considered. The principal achievement of this work is a fully airborne demonstration of bistatic SAR. The route taken in reaching this is given, along with some results. The bistatic SAR imagery is analysed and compared to the monostatic imagery collected at the same time. Demonstrating high-resolution bistatic SAR imagery using two airborne platforms represents what I believe to be a European first and is likely to be the first time that this has been achieved outside the US (the UK has very little insight into US work on this topic). Bistatic target characteristics are examined through the use of simulations. This also compares bistatic imagery with monostatic and gives further insight into the utility of bistatic SAR.

  4. Superresolution and Synthetic Aperture Radar

    SciTech Connect

    DICKEY,FRED M.; ROMERO,LOUIS; DOERRY,ARMIN W.

    2001-05-01

    Superresolution concepts offer the potential of resolution beyond the classical limit. This great promise has not generally been realized. In this study we investigate the potential application of superresolution concepts to synthetic aperture radar. The analytical basis for superresolution theory is discussed. The application of the concept to synthetic aperture radar is investigated as an operator inversion problem. Generally, the operator inversion problem is ill posed. A criterion for judging superresolution processing of an image is presented.

  5. Large aperture adaptive optics for intense lasers

    NASA Astrophysics Data System (ADS)

    Deneuville, François; Ropert, Laurent; Sauvageot, Paul; Theis, Sébastien

    2015-05-01

    ISP SYSTEM has developed a range of large aperture electro-mechanical deformable mirrors (DM) suitable for ultra short pulsed intense lasers. The design of the MD-AME deformable mirror is based on force application on numerous locations thanks to electromechanical actuators driven by stepper motors. DM design and assembly method have been adapted to large aperture beams and the performances were evaluated on a first application for a beam with a diameter of 250mm at 45° angle of incidence. A Strehl ratio above 0.9 was reached for this application. Simulations were correlated with measurements on optical bench and the design has been validated by calculation for very large aperture (up to Ø550mm). Optical aberrations up to Zernike order 5 can be corrected with a very low residual error as for actual MD-AME mirror. Amplitude can reach up to several hundreds of μm for low order corrections. Hysteresis is lower than 0.1% and linearity better than 99%. Contrary to piezo-electric actuators, the μ-AME actuators avoid print-through effects and they permit to keep the mirror shape stable even unpowered, providing a high resistance to electro-magnetic pulses. The MD-AME mirrors can be adapted to circular, square or elliptical beams and they are compatible with all dielectric or metallic coatings.

  6. Sensitivity evaluation of dynamic speckle activity measurements using clustering methods

    SciTech Connect

    Etchepareborda, Pablo; Federico, Alejandro; Kaufmann, Guillermo H.

    2010-07-01

    We evaluate and compare the use of competitive neural networks, self-organizing maps, the expectation-maximization algorithm, K-means, and fuzzy C-means techniques as partitional clustering methods, when the sensitivity of the activity measurement of dynamic speckle images needs to be improved. The temporal history of the acquired intensity generated by each pixel is analyzed in a wavelet decomposition framework, and it is shown that the mean energy of its corresponding wavelet coefficients provides a suited feature space for clustering purposes. The sensitivity obtained by using the evaluated clustering techniques is also compared with the well-known methods of Konishi-Fujii, weighted generalized differences, and wavelet entropy. The performance of the partitional clustering approach is evaluated using simulated dynamic speckle patterns and also experimental data.

  7. Evaluating effectiveness of dynamic soundfield system in the classroom

    PubMed Central

    da Cruz, Aline Duarte; Alves Silvério, Kelly Cristina; Da Costa, Aline Roberta Aceituno; Moret, Adriane Lima Mortari; Lauris, José Roberto Pereira; de Souza Jacob, Regina Tangerino

    2016-01-01

    Research has reported on the use of soundfield amplification devices in the classroom. However, no study has used standardized tests to determine the potential advantages of the dynamic soundfield system for normally hearing students and for the teacher's voice. Our aim was to evaluate the impact of using dynamic soundfield system on the noise of the classroom, teacher's voice and students’ academic performance. This was a prospective cohort study in which 20 student participants enrolled in the third year of basic education were divided into two groups (i.e., control and experimental); their teacher participated. The experimental group was exposed to the dynamic soundfield system for 3 consecutive months. The groups were assessed using standardized tests to evaluate their academic performance. Further, questionnaires and statements were collected on the participants’ experience of using the soundfield system. We statistically analyzed the results to compare the academic performance of the control group with that of the experimental group. In all cases, a significance level of P < .05 was adopted. Use of the dynamic soundfield system was effective for improving the students’ academic performance on standardized tests for reading, improving the teacher's speech intelligibility, and reducing the teacher's vocal strain. The dynamic soundfield system minimizes the impact of noise in the classroom as demonstrated by the mensuration of the signal-to-noise ratio (SNR) and pupil performance on standardized tests for reading and student and teacher ratings of amplification system effectiveness. PMID:26780961

  8. Evaluating effectiveness of dynamic soundfield system in the classroom.

    PubMed

    da Cruz, Aline Duarte; Alves Silvério, Kelly Cristina; Da Costa, Aline Roberta Aceituno; Moret, Adriane Lima Mortari; Lauris, José Roberto Pereira; de Souza Jacob, Regina Tangerino

    2016-01-01

    Research has reported on the use of soundfield amplification devices in the classroom. However, no study has used standardized tests to determine the potential advantages of the dynamic soundfield system for normally hearing students and for the teacher's voice. Our aim was to evaluate the impact of using dynamic soundfield system on the noise of the classroom, teacher's voice and students' academic performance. This was a prospective cohort study in which 20 student participants enrolled in the third year of basic education were divided into two groups (i.e., control and experimental); their teacher participated. The experimental group was exposed to the dynamic soundfield system for 3 consecutive months. The groups were assessed using standardized tests to evaluate their academic performance. Further, questionnaires and statements were collected on the participants' experience of using the soundfield system. We statistically analyzed the results to compare the academic performance of the control group with that of the experimental group. In all cases, a significance level of P < .05 was adopted. Use of the dynamic soundfield system was effective for improving the students' academic performance on standardized tests for reading, improving the teacher's speech intelligibility, and reducing the teacher's vocal strain. The dynamic soundfield system minimizes the impact of noise in the classroom as demonstrated by the mensuration of the signal-to-noise ratio (SNR) and pupil performance on standardized tests for reading and student and teacher ratings of amplification system effectiveness. PMID:26780961

  9. Metamaterial Apertures for Computational Imaging

    NASA Astrophysics Data System (ADS)

    Hunt, John; Driscoll, Tom; Mrozack, Alex; Lipworth, Guy; Reynolds, Matthew; Brady, David; Smith, David R.

    2013-01-01

    By leveraging metamaterials and compressive imaging, a low-profile aperture capable of microwave imaging without lenses, moving parts, or phase shifters is demonstrated. This designer aperture allows image compression to be performed on the physical hardware layer rather than in the postprocessing stage, thus averting the detector, storage, and transmission costs associated with full diffraction-limited sampling of a scene. A guided-wave metamaterial aperture is used to perform compressive image reconstruction at 10 frames per second of two-dimensional (range and angle) sparse still and video scenes at K-band (18 to 26 gigahertz) frequencies, using frequency diversity to avoid mechanical scanning. Image acquisition is accomplished with a 40:1 compression ratio.

  10. A flat laser array aperture

    NASA Astrophysics Data System (ADS)

    Papadakis, Stergios J.; Ricciardi, Gerald F.; Gross, Michael C.; Krill, Jerry A.

    2010-04-01

    We describe a design concept for a flat (or conformal) thin-plate laser phased-array aperture. The aperture consists of a substrate supporting a grid of single-mode optical waveguides fabricated from a linear electro-optic material. The waveguides are coupled to a single laser source or detector. An arrangement of electrodes provides for two-dimensional beam steering by controlling the phase of the light entering the grid. The electrodes can also be modulated to simultaneously provide atmospheric turbulence modulation for long-range free-space optical communication. An approach for fabrication is also outlined.

  11. Mosaic of coded aperture arrays

    DOEpatents

    Fenimore, Edward E.; Cannon, Thomas M.

    1980-01-01

    The present invention pertains to a mosaic of coded aperture arrays which is capable of imaging off-axis sources with minimum detector size. Mosaics of the basic array pattern create a circular on periodic correlation of the object on a section of the picture plane. This section consists of elements of the central basic pattern as well as elements from neighboring patterns and is a cyclic version of the basic pattern. Since all object points contribute a complete cyclic version of the basic pattern, a section of the picture, which is the size of the basic aperture pattern, contains all the information necessary to image the object with no artifacts.

  12. High resolution non-iterative aperture synthesis.

    PubMed

    Kraczek, Jeffrey R; McManamon, Paul F; Watson, Edward A

    2016-03-21

    The maximum resolution of a multiple-input multiple-output (MIMO) imaging system is determined by the size of the synthetic aperture. The synthetic aperture is determined by a coordinate shift using the relative positions of the illuminators and receive apertures. Previous methods have shown non-iterative phasing for multiple illuminators with a single receive aperture for intra-aperture synthesis. This work shows non-iterative phasing with both multiple illuminators and multiple receive apertures for inter-aperture synthesis. Simulated results show that piston, tip, and tilt can be calculated using inter-aperture phasing after intra-aperture phasing has been performed. Use of a fourth illuminator for increased resolution is shown. The modulation transfer function (MTF) is used to quantitatively judge increased resolution. PMID:27136816

  13. Multibeam synthetic aperture radar for global oceanography

    NASA Technical Reports Server (NTRS)

    Jain, A.

    1979-01-01

    A single-frequency multibeam synthetic aperture radar concept for large swath imaging desired for global oceanography is evaluated. Each beam iilluminates a separate range and azimuth interval, and images for different beams may be separated on the basis of the Doppler spectrum of the beams or their spatial azimuth separation in the image plane of the radar processor. The azimuth resolution of the radar system is selected so that the Doppler spectrum of each beam does not interfere with the Doppler foldover due to the finite pulse repetition frequency of the radar system.

  14. Estimating vegetation biomass using synthetic aperture radar

    NASA Astrophysics Data System (ADS)

    Baronti, Stefano; Luciani, S.; Paloscia, Simonetta; Schiavon, G.; Sigismondi, S.; Solimini, Domenico

    1994-12-01

    A significant experiment for evaluating the potential of Synthetic Aperture Radar (SAR) in monitoring soil and vegetation parameters is being carried out on an agricultural area located in Central Italy. The site has been imaged in 1991 by NASA/JPL AIRSAR during the MAC-91 Campaign and subsequently by ESA/ERS-1 and NASDA JERS-1 in 1992. The sensitivity to vegetation biomass of backscattering coefficient measured by ERS-1 and JERS-1 radars is discussed and compared with the best results achieved using the multifrequency polarimetric AIRSAR data.

  15. Quantitative Evaluation of the Reticuloendothelial System Function with Dynamic MRI

    PubMed Central

    Liu, Ting; Choi, Hoon; Zhou, Rong; Chen, I-Wei

    2014-01-01

    Purpose To evaluate the reticuloendothelial system (RES) function by real-time imaging blood clearance as well as hepatic uptake of superparamagnetic iron oxide nanoparticle (SPIO) using dynamic magnetic resonance imaging (MRI) with two-compartment pharmacokinetic modeling. Materials and Methods Kinetics of blood clearance and hepatic accumulation were recorded in young adult male 01b74 athymic nude mice by dynamic T2* weighted MRI after the injection of different doses of SPIO nanoparticles (0.5, 3 or 10 mg Fe/kg). Association parameter, Kin, dissociation parameter, Kout, and elimination constant, Ke, derived from dynamic data with two-compartment model, were used to describe active binding to Kupffer cells and extrahepatic clearance. The clodrosome and liposome were utilized to deplete macrophages and block the RES function to evaluate the capability of the kinetic parameters for investigation of macrophage function and density. Results The two-compartment model provided a good description for all data and showed a low sum squared residual for all mice (0.27±0.03). A lower Kin, a lower Kout and a lower Ke were found after clodrosome treatment, whereas a lower Kin, a higher Kout and a lower Ke were observed after liposome treatment in comparison to saline treatment (P<0.005). Conclusion Dynamic SPIO-enhanced MR imaging with two-compartment modeling can provide information on RES function on both a cell number and receptor function level. PMID:25090653

  16. Dynamic Aperture-based Solar Loop Segmentation

    NASA Technical Reports Server (NTRS)

    Lee, Jon Kwan; Newman, Timothy S.; Gary, G. Allen

    2006-01-01

    A new method to automatically segment arc-like loop structures from intensity images of the Sun's corona is introduced. The method constructively segments credible loop structures by exploiting the Gaussian-like shape of loop cross-sectional intensity profiles. The experimental results show that the method reasonably segments most of the well-defined loops in coronal images. The method is only the second published automated solar loop segmentation method. Its advantage over the other published method is that it operates independently of supplemental time specific data.

  17. A Method for Evaluating Dynamical Friction in Linear Ball Bearings

    PubMed Central

    Fujii, Yusaku; Maru, Koichi; Jin, Tao; Yupapin, Preecha P.; Mitatha, Somsak

    2010-01-01

    A method is proposed for evaluating the dynamical friction of linear bearings, whose motion is not perfectly linear due to some play in its internal mechanism. In this method, the moving part of a linear bearing is made to move freely, and the force acting on the moving part is measured as the inertial force given by the product of its mass and the acceleration of its centre of gravity. To evaluate the acceleration of its centre of gravity, the acceleration of two different points on it is measured using a dual-axis optical interferometer. PMID:22163457

  18. Sustainable Deforestation Evaluation Model and System Dynamics Analysis

    PubMed Central

    Feng, Huirong; Lim, C. W.; Chen, Liqun; Zhou, Xinnian; Zhou, Chengjun; Lin, Yi

    2014-01-01

    The current study used the improved fuzzy analytic hierarchy process to construct a sustainable deforestation development evaluation system and evaluation model, which has refined a diversified system to evaluate the theory of sustainable deforestation development. Leveraging the visual image of the system dynamics causal and power flow diagram, we illustrated here that sustainable forestry development is a complex system that encompasses the interaction and dynamic development of ecology, economy, and society and has reflected the time dynamic effect of sustainable forestry development from the three combined effects. We compared experimental programs to prove the direct and indirect impacts of the ecological, economic, and social effects of the corresponding deforest techniques and fully reflected the importance of developing scientific and rational ecological harvesting and transportation technologies. Experimental and theoretical results illustrated that light cableway skidding is an ecoskidding method that is beneficial for the sustainable development of resources, the environment, the economy, and society and forecasted the broad potential applications of light cableway skidding in timber production technology. Furthermore, we discussed the sustainable development countermeasures of forest ecosystems from the aspects of causality, interaction, and harmony. PMID:25254225

  19. Sustainable deforestation evaluation model and system dynamics analysis.

    PubMed

    Feng, Huirong; Lim, C W; Chen, Liqun; Zhou, Xinnian; Zhou, Chengjun; Lin, Yi

    2014-01-01

    The current study used the improved fuzzy analytic hierarchy process to construct a sustainable deforestation development evaluation system and evaluation model, which has refined a diversified system to evaluate the theory of sustainable deforestation development. Leveraging the visual image of the system dynamics causal and power flow diagram, we illustrated here that sustainable forestry development is a complex system that encompasses the interaction and dynamic development of ecology, economy, and society and has reflected the time dynamic effect of sustainable forestry development from the three combined effects. We compared experimental programs to prove the direct and indirect impacts of the ecological, economic, and social effects of the corresponding deforest techniques and fully reflected the importance of developing scientific and rational ecological harvesting and transportation technologies. Experimental and theoretical results illustrated that light cableway skidding is an ecoskidding method that is beneficial for the sustainable development of resources, the environment, the economy, and society and forecasted the broad potential applications of light cableway skidding in timber production technology. Furthermore, we discussed the sustainable development countermeasures of forest ecosystems from the aspects of causality, interaction, and harmony. PMID:25254225

  20. Large aperture diffractive space telescope

    DOEpatents

    Hyde, Roderick A.

    2001-01-01

    A large (10's of meters) aperture space telescope including two separate spacecraft--an optical primary objective lens functioning as a magnifying glass and an optical secondary functioning as an eyepiece. The spacecraft are spaced up to several kilometers apart with the eyepiece directly behind the magnifying glass "aiming" at an intended target with their relative orientation determining the optical axis of the telescope and hence the targets being observed. The objective lens includes a very large-aperture, very-thin-membrane, diffractive lens, e.g., a Fresnel lens, which intercepts incoming light over its full aperture and focuses it towards the eyepiece. The eyepiece has a much smaller, meter-scale aperture and is designed to move along the focal surface of the objective lens, gathering up the incoming light and converting it to high quality images. The positions of the two space craft are controlled both to maintain a good optical focus and to point at desired targets which may be either earth bound or celestial.

  1. Future of synthetic aperture radar

    NASA Technical Reports Server (NTRS)

    Barath, F. T.

    1978-01-01

    The present status of the applications of Synthetic Aperture Radars (SARs) is reviewed, and the technology state-of-the art as represented by the Seasat-A and SIR-A SARs examined. The potential of SAR applications, and the near- and longer-term technology trends are assessed.

  2. SEASAT Synthetic Aperture Radar Data

    NASA Technical Reports Server (NTRS)

    Henderson, F. M.

    1981-01-01

    The potential of radar imagery from space altitudes is discussed and the advantages of radar over passive sensor systems are outlined. Specific reference is made to the SEASAT synthetic aperture radar. Possible applications include oil spill monitoring, snow and ice reconnaissance, mineral exploration, and monitoring phenomena in the urban environment.

  3. An Aperture Photometry Pipeline for K2 Data

    NASA Astrophysics Data System (ADS)

    Buzasi, Derek L.; Carboneau, Lindsey; Lezcano, Andy; Vydra, Ekaterina

    2016-01-01

    As part of an ongoing research program with undergraduate students at Florida Gulf Coast University, we have constructed an aperture photometry pipeline for K2 data. The pipeline performs dynamic automated aperture mask definition for all targets in the K2 fields, followed by aperture photometry and detrending. Our pipeline is currently used to support a number of projects, including studies of stellar rotation and activity, red giant asteroseismology, gyrochronology, and exoplanet searches. In addition, output is used to support an undergraduate class on exoplanets aimed at a student audience of both majors and non-majors. The pipeline is designed for both batch and single-target use, and is easily extensible to data from other missions, and pipeline output is available to the community. This paper will describe our pipeline and its capabilities and illustrate the quality of the results, drawing on all of the applications for which it is currently used.

  4. Fresnel diffraction of aperture with rough edge

    NASA Astrophysics Data System (ADS)

    Cui, Yuwei; Zhang, Wei; Wang, Junhong; Zhang, Meina; Teng, Shuyun

    2015-06-01

    The Fresnel diffraction of an aperture with a rough edge is studied in this paper. Circular and elliptical apertures with sinusoidal and random edges are chosen as examples to investigate the influence of the aperture edge on the diffraction. The numerical calculation results indicate intuitively the variations of the transverse and longitude diffraction intensity distributions with the edge parameters of the aperture. The data files of aperture models are obtained through the numerical calculations, and the aperture samples are obtained with the help of a liquid crystal light modulator (LCLM). Thus, the practical experiments of the diffractions of apertures with rough edges are carried out. The measured results are consistent with the calculated ones. The approximate analytic expressions of the diffraction by the modified aperture are deduced on the basis of the Fresnel diffraction theory and the statistic optics, and the reasonable explanations for the influence of edge parameters on the diffraction are given through the theoretical analysis.

  5. Evaluating the Dynamic Characteristics of Retrofitted RC Beams

    NASA Astrophysics Data System (ADS)

    Ghods, Amir S.; Esfahani, Mohamad R.; Moghaddasie, Behrang

    2008-07-01

    The aim of this experimental study was to investigate the relationship between the damage and changes in dynamic characteristics of reinforced concrete members strengthened with Carbon Fiber Reinforced Polymer (CFRP). Modal analysis is a popular non-destructive method for evaluating health of structural systems. A total of 8 reinforced concrete beams with similar dimensions were made using concrete with two different compressive strengths and reinforcement ratios. Monotonic loading was applied with four-point-bending setup in order to generate different damage levels in the specimens while dynamic testing was conducted to monitor the changes in dynamic characteristics of the specimens. In order to investigate the effect of CFRP on static and dynamic properties of specimens, some of the beams were loaded to half of their ultimate load carrying capacity and then were retrofitted using composite laminates with different configuration. Retrofitted specimens demonstrated elevated load carrying capacity, higher flexural stiffness and lower displacement ductility. By increasing the damage level in specimens, frequencies of the beams were decreased and after strengthening these values were improved significantly. The intensity of the damage level in each specimen affects the shape of its mode as well. Fixed points and curvatures of mode shapes of beams tend to move toward the location of the damage in each case.

  6. Evaluating the Dynamic Characteristics of Retrofitted RC Beams

    SciTech Connect

    Ghods, Amir S.; Esfahani, Mohamad R.; Moghaddasie, Behrang

    2008-07-08

    The aim of this experimental study was to investigate the relationship between the damage and changes in dynamic characteristics of reinforced concrete members strengthened with Carbon Fiber Reinforced Polymer (CFRP). Modal analysis is a popular non-destructive method for evaluating health of structural systems. A total of 8 reinforced concrete beams with similar dimensions were made using concrete with two different compressive strengths and reinforcement ratios. Monotonic loading was applied with four-point-bending setup in order to generate different damage levels in the specimens while dynamic testing was conducted to monitor the changes in dynamic characteristics of the specimens. In order to investigate the effect of CFRP on static and dynamic properties of specimens, some of the beams were loaded to half of their ultimate load carrying capacity and then were retrofitted using composite laminates with different configuration. Retrofitted specimens demonstrated elevated load carrying capacity, higher flexural stiffness and lower displacement ductility. By increasing the damage level in specimens, frequencies of the beams were decreased and after strengthening these values were improved significantly. The intensity of the damage level in each specimen affects the shape of its mode as well. Fixed points and curvatures of mode shapes of beams tend to move toward the location of the damage in each case.

  7. Dynamic simulation of tibial tuberosity realignment: model evaluation.

    PubMed

    Purevsuren, Tserenchimed; Elias, John J; Kim, Kyungsoo; Kim, Yoon Hyuk

    2015-01-01

    This study was performed to evaluate a dynamic multibody model developed to characterize the influence of tibial tuberosity realignment procedures on patellofemoral motion and loading. Computational models were created to represent four knees previously tested at 40°, 60°, and 80° of flexion with the tibial tuberosity in a lateral, medial and anteromedial positions. The experimentally loaded muscles, major ligaments of the knee, and patellar tendon were represented. A repeated measures ANOVA with post-hoc testing was performed at each flexion angle to compare data between the three positions of the tibial tuberosity. Significant experimental trends for decreased patella flexion due to tuberosity anteriorization and a decrease in the lateral contact force due to tuberosity medialization were reproduced computationally. The dynamic multibody modeling technique will allow simulation of function for symptomatic knees to identify optimal surgical treatment methods based on parameters related to knee pathology and pre-operative kinematics. PMID:25025488

  8. Multi-mesh gear dynamics program evaluation and enhancements

    NASA Technical Reports Server (NTRS)

    Boyd, L. S.; Pike, J.

    1985-01-01

    A multiple mesh gear dynamics computer program was continually developed and modified during the last four years. The program can handle epicyclic gear systems as well as single mesh systems with internal, buttress, or helical tooth forms. The following modifications were added under the current funding: variable contact friction, planet cage and ring gear rim flexibility options, user friendly options, dynamic side bands, a speed survey option and the combining of the single and multiple mesh options into one general program. The modified program was evaluated by comparing calculated values to published test data and to test data taken on a Hamilton Standard turboprop reduction gear-box. In general, the correlation between the test data and the analytical data is good.

  9. Stochastic Evaluation of Riparian Vegetation Dynamics in River Channels

    NASA Astrophysics Data System (ADS)

    Miyamoto, H.; Kimura, R.; Toshimori, N.

    2013-12-01

    Vegetation overgrowth in sand bars and floodplains has been a serious problem for river management in Japan. From the viewpoints of flood control and ecological conservation, it would be necessary to accurately predict the vegetation dynamics for a long period of time. In this study, we have developed a stochastic model for predicting the dynamics of trees in floodplains with emphasis on the interaction with flood impacts. The model consists of the following four processes in coupling ecohydrology with biogeomorphology: (i) stochastic behavior of flow discharge, (ii) hydrodynamics in a channel with vegetation, (iii) variation of riverbed topography and (iv) vegetation dynamics on the floodplain. In the model, the flood discharge is stochastically simulated using a Poisson process, one of the conventional approaches in hydrological time-series generation. The model for vegetation dynamics includes the effects of tree growth, mortality by flood impacts, and infant tree invasion. To determine the model parameters, vegetation conditions have been observed mainly before and after flood impacts since 2008 at a field site located between 23.2-24.0 km from the river mouth in Kako River, Japan. This site is one of the vegetation overgrowth locations in Kako River floodplains, where the predominant tree species are willows and bamboos. In this presentation, sensitivity of the vegetation overgrowth tendency is investigated in Kako River channels. Through the Monte Carlo simulation for several cross sections in Kako River, responses of the vegetated channels are stochastically evaluated in terms of the changes of discharge magnitude and channel geomorphology. The expectation and standard deviation of vegetation areal ratio are compared in the different channel cross sections for different river discharges and relative floodplain heights. The result shows that the vegetation status changes sensitively in the channels with larger discharge and insensitive in the lower floodplain

  10. Evaluation of GLOCK 9 mm Firing Pin Aperture Shear Mark Individuality Based On 1,632 Different Pistols by Traditional Pattern Matching and IBIS Pattern Recognition.

    PubMed

    Hamby, James E; Norris, Stephen; Petraco, Nicholas D K

    2016-01-01

    Over a period of 21 years, a number of fired GLOCK cartridge cases have been evaluated. A total of 1632 GLOCK firearms were used to generate a sample of the same size. Our research hypothesis was that no cartridge cases fired from different 9-mm semiautomatic GLOCK pistols would be mistaken as coming from the same gun. Using optical comparison microscopy, two separate experiments were carried out to test this hypothesis. A subsample of 617 test-fired cases were subjected to algorithmic comparison by the Integrated Ballistics Identification System (IBIS). The second experiment subjected the full set of 1632 cases to manual comparisons using traditional pattern matching. None of the cartridge cases were "matched" by either of these two experiments. Using these empirical findings, an established Bayesian probability model was used to estimate the chance that a 9-mm cartridge case, fired from a GLOCK, could be mistaken as coming from the same firearm when in fact it did not (i.e., the random match probability). PMID:26390232

  11. Broadband synthetic aperture geoacoustic inversion.

    PubMed

    Tan, Bien Aik; Gerstoft, Peter; Yardim, Caglar; Hodgkiss, William S

    2013-07-01

    A typical geoacoustic inversion procedure involves powerful source transmissions received on a large-aperture receiver array. A more practical approach is to use a single moving source and/or receiver in a low signal to noise ratio (SNR) setting. This paper uses single-receiver, broadband, frequency coherent matched-field inversion and exploits coherently repeated transmissions to improve estimation of the geoacoustic parameters. The long observation time creates a synthetic aperture due to relative source-receiver motion. This approach is illustrated by studying the transmission of multiple linear frequency modulated (LFM) pulses which results in a multi-tonal comb spectrum that is Doppler sensitive. To correlate well with the measured field across a receiver trajectory and to incorporate transmission from a source trajectory, waveguide Doppler and normal mode theory is applied. The method is demonstrated with low SNR, 100-900 Hz LFM pulse data from the Shallow Water 2006 experiment. PMID:23862809

  12. VSATs - Very small aperture terminals

    NASA Astrophysics Data System (ADS)

    Everett, John L.

    The present volume on very small aperture terminals (VSATs) discusses antennas, semiconductor devices, and traveling wave tubes and amplifiers for VSAT systems, VSAT low noise downconverters, and modems and codecs for VSAT systems. Attention is given to multiaccess protocols for VSAT networks, protocol software in Ku-band VSAT network systems, system design of VSAT data networks, and the policing of VSAT networks. Topics addressed include the PANDATA and PolyCom systems, APOLLO - a satellite-based information distribution system, data broadcasting within a satellite television channel, and the NEC NEXTAR VSAT system. Also discussed are small aperture military ground terminals, link budgets for VSAT systems, capabilities and experience of a VSAT service provider, and developments in VSAT regulation.

  13. Aperture masking behind AO systems

    NASA Astrophysics Data System (ADS)

    Ireland, Michael J.

    2012-07-01

    Sparse Aperture-Mask Interferometry (SAM or NRM) behind Adaptive Optics (AO) has now come of age, with more than a dozen astronomy papers published from several 5-10m class telescopes around the world. I will describe the reasons behind its success in achieving relatively high contrasts ( 1000:1 at lambda/ D) and repeatable binary astronomy at the diffraction limit, even when used behind laser-guide star adaptive optics. Placed within the context of AO calibration, the information in an image can be split into pupil-plane phase, Fourier amplitude and closure-phase. It is the closure-phase observable, or its generalisation to Kernel phase, that is immune to pupil-plane phase errors at first and second-order and has been the reason for the technique's success. I will outline the limitations of the technique and the prospects for aperture-masking and related techniques in the future.

  14. Large aperture scanning airborne lidar

    NASA Technical Reports Server (NTRS)

    Smith, J.; Bindschadler, R.; Boers, R.; Bufton, J. L.; Clem, D.; Garvin, J.; Melfi, S. H.

    1988-01-01

    A large aperture scanning airborne lidar facility is being developed to provide important new capabilities for airborne lidar sensor systems. The proposed scanning mechanism allows for a large aperture telescope (25 in. diameter) in front of an elliptical flat (25 x 36 in.) turning mirror positioned at a 45 degree angle with respect to the telescope optical axis. The lidar scanning capability will provide opportunities for acquiring new data sets for atmospheric, earth resources, and oceans communities. This completed facility will also make available the opportunity to acquire simulated EOS lidar data on a near global basis. The design and construction of this unique scanning mechanism presents exciting technological challenges of maintaining the turning mirror optical flatness during scanning while exposed to extreme temperatures, ambient pressures, aircraft vibrations, etc.

  15. Multiple aperture imager component development

    NASA Astrophysics Data System (ADS)

    Lees, David E.; Henshaw, Philip D.

    1991-03-01

    This final report presents results of an experimental and analytical effort to develop multiple aperture imagers built from unphased, direct-detection subapertures. An object was imaged using wave length shift instead of object motion to create multiple speckle pattern realizations. An analysis of subaperture geometry effects of autocorrelation estimate was performed. Experimental measurements of detector modulator transfer function were made. Finally, a new algorithm to reconstruct imagery with improved signal-to-noise ratio was developed.

  16. Coherent sub-aperture ultraviolet imagery

    NASA Astrophysics Data System (ADS)

    Morton, R. G.; Connally, W. J.; Avicola, K.; Monjo, D.; Olson, T.

    1989-09-01

    Laboratory targets have been imaged by a multi-sub-aperture, coherent receiver technique in which a common local oscillator illuminates the sub-aperture array to preserve both phase and intensity information. The target, receiver and range dimensions were chosen such that each sub-aperture was smaller than the speckle size. Various targets were illuminated by microsecond pulses from an e-beam pumped XeF power amplifier, which was seeded by a coherent ultraviolet beam generated with a frequency doubled visible dye laser. Data is presented showing comparisons between the coherent multi-sub-aperture approach and conventional, full aperture photography of the same traget(s).

  17. Dynamic testing of nuclear power plant structures: an evaluation

    SciTech Connect

    Weaver, H.J.

    1980-02-01

    Lawrence Livermore Laboratory (LLL) evaluated the applications of system identification techniques to the dynamic testing of nuclear power plant structures and subsystems. These experimental techniques involve exciting a structure and measuring, digitizing, and processing the time-history motions that result. The data can be compared to parameters calculated using finite element or other models of the test systems to validate the model and to verify the seismic analysis. This report summarizes work in three main areas: (1) analytical qualification of a set of computer programs developed at LLL to extract model parameters from the time histories; (2) examination of the feasibility of safely exciting nuclear power plant structures and accurately recording the resulting time-history motions; (3) study of how the model parameters that are extracted from the data be used best to evaluate structural integrity and analyze nuclear power plants.

  18. Controlled-aperture wave-equation migration

    SciTech Connect

    Huang, L.; Fehler, Michael C.; Sun, H.; Li, Z.

    2003-01-01

    We present a controlled-aperture wave-equation migration method that no1 only can reduce migration artiracts due to limited recording aperlurcs and determine image weights to balance the efl'ects of limited-aperture illumination, but also can improve thc migration accuracy by reducing the slowness perturbations within thc controlled migration regions. The method consists of two steps: migration aperture scan and controlled-aperture migration. Migration apertures for a sparse distribution of shots arc determined using wave-equation migration, and those for the other shots are obtained by interpolation. During the final controlled-aperture niigration step, we can select a reference slowness in c;ontrollecl regions of the slowness model to reduce slowncss perturbations, and consequently increase the accuracy of wave-equation migration inel hods that makc use of reference slownesses. In addition, the computation in the space domain during wavefield downward continuation is needed to be conducted only within the controlled apertures and therefore, the computational cost of controlled-aperture migration step (without including migration aperture scan) is less than the corresponding uncontrolled-aperture migration. Finally, we can use the efficient split-step Fourier approach for migration-aperture scan, then use other, more accurate though more expensive, wave-equation migration methods to perform thc final controlled-apertio.ee migration to produce the most accurate image.

  19. Evaluation of color encodings for high dynamic range pixels

    NASA Astrophysics Data System (ADS)

    Boitard, Ronan; Mantiuk, Rafal K.; Pouli, Tania

    2015-03-01

    Traditional Low Dynamic Range (LDR) color spaces encode a small fraction of the visible color gamut, which does not encompass the range of colors produced on upcoming High Dynamic Range (HDR) displays. Future imaging systems will require encoding much wider color gamut and luminance range. Such wide color gamut can be represented using floating point HDR pixel values but those are inefficient to encode. They also lack perceptual uniformity of the luminance and color distribution, which is provided (in approximation) by most LDR color spaces. Therefore, there is a need to devise an efficient, perceptually uniform and integer valued representation for high dynamic range pixel values. In this paper we evaluate several methods for encoding colour HDR pixel values, in particular for use in image and video compression. Unlike other studies we test both luminance and color difference encoding in a rigorous 4AFC threshold experiments to determine the minimum bit-depth required. Results show that the Perceptual Quantizer (PQ) encoding provides the best perceptual uniformity in the considered luminance range, however the gain in bit-depth is rather modest. More significant difference can be observed between color difference encoding schemes, from which YDuDv encoding seems to be the most efficient.

  20. Display Factors and Subjective Evaluation of Dynamic Text Display

    NASA Astrophysics Data System (ADS)

    So, Joey C. Y.; Chan, Alan H. S.

    2009-01-01

    Communications technology has exploded in past decades, leading to the question of which display method is the best to deliver electronic text messages. Many of these systems employ cathode ray tubes, liquid crystal displays, gas plasma displays, or light-emitting diodes as the output device. In order to overcome the limitations of screen size of the display units, numerous means of presenting dynamic display on screens have been invented. There are many factors that affect the readability of electronic text. This paper reviews some related empirical studies concerning the various display methods of dynamic text presentation, such as text display type, character type, text display direction, and text/background color combination, highlighting method and validity of highlighting. The subjective evaluation questionnaire is also discussed. According to the readability and preference ratings of the subjects given under different conditions, the best display method and color for comprehending the delivered messages were investigated. General recommendations of displaying dynamic information are made for the large display units which have been widely used for delivering important messages.

  1. Multiple-Aperture-Based Solar Seeing Profiler

    NASA Astrophysics Data System (ADS)

    Ren, Deqing; Zhao, Gang; Zhang, Xi; Dou, Jiangpei; Chen, Rui; Zhu, Yongtian; Yang, Feng

    2015-09-01

    Characterization of day-time atmospheric turbulence profiles up to 30 km above the telescope is crucial for designs and performance estimations of future solar multiconjugate adaptive optics (MCAO) systems. Recently, the S-DIMM+ method has been successfully used to measure the vertical profile of turbulence. However, to measure profile up to 30 km employing the S-DIMM+ method, a telescope with a diameter of at least 1.0 m is needed, which restricts the usage of S-DIMM+, since large telescopes are scarce and their time is limited. To solve this problem, we introduce the multiple-aperture seeing profiler (MASP), which consists of two portable small telescopes instead of a single large aperture. Numerical simulations are carried out to evaluate the performance of MASP. We find that for one layer case, MASP can retrieve the seeing with error ~5% using 800 frames of wavefront sensor (WFS) data, which is quite similar to the results of a telescope with diameter of 1120 mm. We also simulate profiles with four turbulence layers, and find that our MASP can effectively retrieve the strengths and heights of the four turbulence layers. Since previous measurements at Big Bear Solar Observatory showed that day-time turbulence profile typically consists of four layers, the MASP we introduced is sufficient for actual seeing measurement.

  2. Wide aperture seismic recording in offshore west Sicily and Bolivia

    SciTech Connect

    Tilander, N.G.; Lattimore, R.K.

    1994-12-31

    Seismic operations using the Wide Aperture Recording (WAR) technique were carried out in offshore west Sicily (16.5 km offsets) and in the Sub-Andean Cordillera of Bolivia (9.0 km offsets) where conventional offset data have traditionally proved inadequate for imaging complex subsurface structures. In both cases, noise-free wide aperture events were visible at long offsets, and were successfully stacked using both hyperbolic and linear moveout. In the Sicily datasets, the resulting seismic images disagree with earlier structural interpretations, but the lack of reliable ``calibration`` data in terms of well control or usable conventional seismic data make final evaluation and interpretation of the Sicily wide aperture data ambiguous. In Bolivia good quality seismic data are present across a portion of the WAR survey; the results show that the wide aperture technique may produce a valid structural image, provided the subsurface geometries are sufficiently broad and shallow. For tight structures, the technique is unlikely to produce valid images. In general, the authors` studies show that considerable effort is required at the data processing and interpretation stage, including full waveform and ray-trace modeling, in order to identify event arrivals and to attempt to validate the wide aperture structural images. Reliable calibration data in the form of well control or conventional seismic data are needed in order to provide an understanding of the WAR results.

  3. Interference Mitigation Effects on Synthetic Aperture Radar Coherent Data Products

    SciTech Connect

    Musgrove, Cameron

    2015-07-01

    For synthetic aperture radars radio frequency interference from sources external to the radar system and techniques to mitigate the interference can degrade the quality of the image products. Usually the radar system designer will try to balance the amount of mitigation for an acceptable amount of interference to optimize the image quality. This dissertation examines the effect of interference mitigation upon coherent data products of fine resolution, high frequency synthetic aperture radars using stretch processing. Novel interference mitigation techniques are introduced that operate on single or multiple apertures of data that increase average coherence compared to existing techniques. New metrics are applied to evaluate multiple mitigation techniques for image quality and average coherence. The underlying mechanism for interference mitigation techniques that affect coherence is revealed.

  4. Fluorescence and hybrid detection aperture of the Pierre Auger Observatory

    SciTech Connect

    Bellido, J.A.; D'Urso, D.; Geenen, H.; Guarino, F.; Perrone, L.; Petrera, Sergio; Prado, L., Jr.; Salamida, F.

    2005-07-01

    The aperture of the Fluorescence Detector (FD) of the Pierre Auger Observatory is evaluated from simulated events using different detector configurations: mono, stereo, 3-FD and 4-FD. The trigger efficiency has been modeled using shower profiles with ground impacts in the field of view of a single telescope and studying the trigger response (at the different levels) by that telescope and by its neighbors. In addition, analysis cuts imposed by event reconstruction have been applied. The hybrid aperture is then derived for the Auger final extension. Taking into account the actual Surface Detector (SD) array configuration and its trigger response, the aperture is also calculated for a typical configuration of the present phase.

  5. Permeability and dispersivity of variable-aperture fracture systems

    SciTech Connect

    Tsang, Y.W.; Tsang, C.F.

    1990-01-01

    A number of recent experiments have pointed out the need of including the effects of aperture variation within each fracture in predicting flow and transport properties of fractured media. This paper introduces a new approach in which medium properties, such as the permeability to flow and dispersivity in tracer transport, are correlated to only three statistical parameters describing the fracture aperture probability distribution and the aperture spatial correlation. We demonstrate how saturated permeability and relative permeabilities for flow, as well as dispersion for solute transport in fractures may be calculated. We are in the process of examining the applicability of these concepts to field problems. Results from the evaluation and analysis of the recent Stripa-3D field data are presented. 13 refs., 10 figs.

  6. Vision aided inertial navigation system augmented with a coded aperture

    NASA Astrophysics Data System (ADS)

    Morrison, Jamie R.

    plate aperture produces diffraction patterns that change the shape of the focal blur pattern. When used as an aperture, the Fresnel zone plate produces multiple focal planes in the scene. The interference between the multiple focal planes produce changes in the aperture that can be observed both between the focal planes and beyond the most distant focal plane. The Fresnel zone plate aperture and lens may be designed to change in the focal blur pattern at greater depths, thereby improving measurement performance of the coded aperture system. This research provides an in-depth study of the Fresnel zone plate used as a coded aperture, and the performance improvement obtained by augmenting a single camera vision aided inertial navigation system with a Fresnel zone plate coded aperture. Design and analysis of a generalized coded aperture is presented and demonstrated, and special considerations for the Fresnel zone plate are given. Also techniques to determine a continuous depth measurement from a coded image are presented and evaluated through measurement. Finally the measurement results from different aperture configurations are statistically modeled and compared with a simulated vision aided navigation environment to predict the change in performance of a vision aided inertial navigation system when augmented with a coded aperture.

  7. Simulation laboratory for evaluating dynamic traffic management systems

    SciTech Connect

    Ban-Akiva, M.E.; Mishalani, R.G.; Yang, Q.; Koutsopoulos, H.N.

    1997-08-01

    This paper presents a simulation laboratory for performance evaluation and design refinement of dynamic traffic management systems. The laboratory consists of four integrated components: (1) a traffic management simulator, which mimics the generation of route guidance and operations of traffic signals and signs; (2) a traffic flow simulator, which models individual vehicle movements and drivers` route choice decisions in the presence of real-time traffic information; (3) a surveillance system module, which collects real-time traffic data from sensors and probe vehicles in the simulated network; and (4) a control device module, which implements control strategies and route guidance generated by the traffic management system under evaluation. The simulation laboratory has been implemented in C++ using object-oriented programming and a distributed environment. It features a graphical user interface that allows users to visualize the simulation process, including animation of vehicle movements, state of surveillance sensors, traffic signals, signs, and so on. This modeling system provides a unique tool for evaluating integrated ATIS and ATMS applications in a computer-based laboratory environment.

  8. Dual aperture multispectral Schmidt objective

    NASA Technical Reports Server (NTRS)

    Minott, P. O. (Inventor)

    1984-01-01

    A dual aperture, off-axis catadioptic Schmidt objective is described. It is formed by symmetrically aligning two pairs of Schmidt objectives on opposite sides of a common plane (x,z). Each objective has a spherical primary mirror with a spherical focal plane and center of curvature aligned along an optic axis laterally spaced apart from the common plane. A multiprism beamsplitter with buried dichroic layers and a convex entrance and concave exit surfaces optically concentric to the center of curvature may be positioned at the focal plane. The primary mirrors of each objective may be connected rigidly together and may have equal or unequal focal lengths.

  9. Reconstruction of coded aperture images

    NASA Technical Reports Server (NTRS)

    Bielefeld, Michael J.; Yin, Lo I.

    1987-01-01

    Balanced correlation method and the Maximum Entropy Method (MEM) were implemented to reconstruct a laboratory X-ray source as imaged by a Uniformly Redundant Array (URA) system. Although the MEM method has advantages over the balanced correlation method, it is computationally time consuming because of the iterative nature of its solution. Massively Parallel Processing, with its parallel array structure is ideally suited for such computations. These preliminary results indicate that it is possible to use the MEM method in future coded-aperture experiments with the help of the MPP.

  10. Aperture scanning Fourier ptychographic microscopy

    PubMed Central

    Ou, Xiaoze; Chung, Jaebum; Horstmeyer, Roarke; Yang, Changhuei

    2016-01-01

    Fourier ptychographic microscopy (FPM) is implemented through aperture scanning by an LCOS spatial light modulator at the back focal plane of the objective lens. This FPM configuration enables the capturing of the complex scattered field for a 3D sample both in the transmissive mode and the reflective mode. We further show that by combining with the compressive sensing theory, the reconstructed 2D complex scattered field can be used to recover the 3D sample scattering density. This implementation expands the scope of application for FPM and can be beneficial for areas such as tissue imaging and wafer inspection. PMID:27570705

  11. TELESCOPES: Astronomers Overcome 'Aperture Envy'.

    PubMed

    Irion, R

    2000-07-01

    Many users of small telescopes are disturbed by the trend of shutting down smaller instruments in order to help fund bigger and bolder ground-based telescopes. Small telescopes can thrive in the shadow of giant new observatories, they say--but only if they are adapted to specialized projects. Telescopes with apertures of 2 meters or less have unique abilities to monitor broad swaths of the sky and stare at the same objects night after night, sometimes for years; various teams are turning small telescopes into robots, creating networks that span the globe and devoting them to survey projects that big telescopes don't have a prayer of tackling. PMID:17832960

  12. the Large Aperture GRB Observatory

    SciTech Connect

    Bertou, Xavier

    2009-04-30

    The Large Aperture GRB Observatory (LAGO) aims at the detection of high energy photons from Gamma Ray Bursts (GRB) using the single particle technique (SPT) in ground based water Cherenkov detectors (WCD). To reach a reasonable sensitivity, high altitude mountain sites have been selected in Mexico (Sierra Negra, 4550 m a.s.l.), Bolivia (Chacaltaya, 5300 m a.s.l.) and Venezuela (Merida, 4765 m a.s.l.). We report on the project progresses and the first operation at high altitude, search for bursts in 6 months of preliminary data, as well as search for signal at ground level when satellites report a burst.

  13. Molecular dynamics simulations: Parameter evaluation, application and development

    NASA Astrophysics Data System (ADS)

    Zhou, Jin

    Molecular dynamics (MD) simulation is a theoretical technique for investigating the physical properties of a wide variety of molecules. This dissertation contains my studies on three important parts of the MD simulation: evaluation of parameters in empirical energy functions widely used in MD simulations, application of MD simulation on experimentally interested biological molecules and development of new methods for constraint dynamics simulations. All the work in this thesis made use of CHARMM as an MD simulation tool. The MD simulation uses empirical energy functions parameterized by a set of parameters. These parameters play an important role in the quality of the simulations. I evaluated nine parameter sets from Harvard University and Molecular Simulations, Inc. for protein simulations by the MD simulations of hydrated form of carboxy- myoglobin and interleukin-1/beta, which are rich in two typical protein structure motifs, helix and β sheet structures respectively. It is found that some sets are good at representing helical structure proteins while others are good at β sheet proteins. But all of them need improvement on representing motions at low temperature. Experimental evidence indicates that the 1A coiled-coil domains of the Intermediate Filament (IF) proteins consisting of coiled human keratins 1 and 10 (K1 and K10) are 'hot spots' for substitutional mutations. Some of these mutations are correlated to the human skin diseases-epidermolytic hyperkeratiosis (EH) and epidermolysis bullosa simplex (EBS). The MD simulation technique is used here for the first time to model and simulate these proteins to elucidate the molecular-level effects of these mutations. Lacking the experimental crystal structures, the initial structure of 1A domain of the wild type Intermediate Filament protein and its mutants were modeled from scratch to reproduce the well- known properties of the proteins of this kind followed by identical MD simulations. The important result is

  14. Strain field of a buried oxide aperture

    NASA Astrophysics Data System (ADS)

    Kießling, F.; Niermann, T.; Lehmann, M.; Schulze, J.-H.; Strittmatter, A.; Schliwa, A.; Pohl, U. W.

    2015-02-01

    The strain field of an AlOx current aperture, fabricated by selective oxidation of an AlAs/GaAs layer buried in a circular GaAs mesa, is studied. Components of the strain tensor for a thin cross-section lamella cut out of such a structure are evaluated from dark-field electron holography, proving the validity of simulations based on linear elasticity. Simulation of the entire structure is utilized to prepare mesa surfaces with tailored strain fields for controlling the nucleation site of InGaAs quantum dots. The experimental proof of strain simulations allows estimating the magnitude of piezoelectricity, yielding for the studied mesa structures a piezoelectric potential up to 50 mV.

  15. Statistical method of evaluation of flip-flop dynamical parameters

    NASA Astrophysics Data System (ADS)

    Wieczorek, P. Z.; Opalski, L. J.

    2008-01-01

    This paper presents statistical algorithm and measurement system for precise evaluation of flip-flop dynamical parameters in asynchronous operation. The analyzed flip-flop parameters are failure probability, MTBF and propagation delay. It is shown how these parameters depend on metastable operation of flip-flops. The numerical and hardware solutions shown in article allow for precise and reliable comparison of flip-flops. Also the analysis of influence of flip-flop electrical parameters of flip-flop electrical parameters on their metastable operation is possible with use of presented statistical method. Statistical estimation of parameters of flip-flops in which metastability occurs, seems to be more reliable than standard empirical methods of flip-flop analysis. Presented method allows for showing inaccuracies in theoretical model of metastability.

  16. Lotung downhole array. 1: Evaluation of site dynamic properties

    SciTech Connect

    Elgamal, A.W.; Zeghal, M.; Tang, H.T.; Stepp, J.C.

    1995-04-01

    The Lotung large-scale seismic test (LSST) site in Taiwan was instrumented in 1985 with an array of downhole and surface accelerometers, by the Electric Power Research Institute (EPRI), Palo Alto, California, and the Taiwan Power Company (TPC), Taipei, Taiwan. A total of 18 earthquakes were recorded during the period 1985--86. Correlation and spectral analyses of the recorded downhole accelerations are performed to evaluate shear wave propagation characteristics, variation of shear wave velocity with depth, and site resonant frequencies and modal configurations. A shear-beam model, calibrated by the identified site properties, is found to represent the site dynamic response characteristics over a wide frequency range. In a companion paper, strong-motion earthquake records are utilized to investigate the Lotung site large-strain soil response characteristics.

  17. Development and Evaluation of a Dynamic Moving Storm (DMS) Builder

    NASA Astrophysics Data System (ADS)

    Fang, N. Z.; Gao, S.

    2014-12-01

    The University of Texas at Arlington (UTA) developed a design rainfall generator - Dynamic Moving Storm (DMS). DMS is a unique tool because it accounts for three major factors of real rainfall events simultaneously that other tools do not: (1) spatial variability, (2) temporal variability, and (3) directional movement. The rainfall intensity distribution with a storm is normally referred to spatial variability factor. The DMS builder takes in account storm sizes, shapes, and orientations (for non-circular storms) within the spatial variability module. Given rainfall intensity within the storm always varies with respect of time, the builder has a capability of specifying temporal distributions of rainfall intensities following linear or exponential patterns. To represent the dynamic motions of real storms, the researchers at UTA developed a movement module into DMS to handle combinations of accelerations, decelerations, pause and turns. Typically, an idealized storm generated by DMS can be presented as a circular shape in 2-D and conic shape in 3-D views. While it moves across a watershed, the rainfall pattern within the storm follows a certain temporal pattern. Once various combinations of spatial, temporal, and movement factors are input into the DMS builder, it can generate corresponding elliptical-shaped rainfall contours with rainfall hyetographs for each subbasin of a particular watershed. The resulted rainfall information can then be fed into hydrologic models to evaluate the spatiotemporal impacts for any watersheds. This paper demonstrates a case study using DMS builder to access the vulnerability for the Brays Bayou watershed in Houston, Texas.

  18. Evaluating the utility of dynamical downscaling in agricultural impacts projections

    NASA Astrophysics Data System (ADS)

    Glotter, M.; Elliott, J. W.; McInerney, D. J.; Moyer, E. J.

    2013-12-01

    The need to understand the future impacts of climate change has driven the increasing use of dynamical downscaling to produce fine-spatial-scale climate projections for impacts models. We evaluate here whether this computationally intensive approach significantly alters projections of agricultural yield. Our results suggest that it does not. We simulate U.S. maize yields under current and future CO2 concentrations with the widely-used DSSAT crop model, driven by a variety of climate inputs including two general circulation models (GCMs), each in turn downscaled by two regional climate models (RCMs). We find that no climate model output can reproduce yields driven by observed climate unless a bias correction is first applied. Once a bias correction is applied, GCM- and RCM-driven yields are essentially indistinguishable in all scenarios (<10% discrepancy in national yield, equivalent to error from observations). While RCMs correct some GCM biases related to fine-scale geographic features, errors in yield are dominated by broad-scale (100s of kms) GCM systematic errors that RCMs cannot compensate for. These results support previous suggestions that the added value of dynamically downscaling raw GCM output for impacts assessments may not justify its computational demands, and that some rethinking of downscaling methods is warranted.

  19. Evaluating the utility of dynamical downscaling in agricultural impacts projections

    PubMed Central

    Glotter, Michael; Elliott, Joshua; McInerney, David; Best, Neil; Foster, Ian; Moyer, Elisabeth J.

    2014-01-01

    Interest in estimating the potential socioeconomic costs of climate change has led to the increasing use of dynamical downscaling—nested modeling in which regional climate models (RCMs) are driven with general circulation model (GCM) output—to produce fine-spatial-scale climate projections for impacts assessments. We evaluate here whether this computationally intensive approach significantly alters projections of agricultural yield, one of the greatest concerns under climate change. Our results suggest that it does not. We simulate US maize yields under current and future CO2 concentrations with the widely used Decision Support System for Agrotechnology Transfer crop model, driven by a variety of climate inputs including two GCMs, each in turn downscaled by two RCMs. We find that no climate model output can reproduce yields driven by observed climate unless a bias correction is first applied. Once a bias correction is applied, GCM- and RCM-driven US maize yields are essentially indistinguishable in all scenarios (<10% discrepancy, equivalent to error from observations). Although RCMs correct some GCM biases related to fine-scale geographic features, errors in yield are dominated by broad-scale (100s of kilometers) GCM systematic errors that RCMs cannot compensate for. These results support previous suggestions that the benefits for impacts assessments of dynamically downscaling raw GCM output may not be sufficient to justify its computational demands. Progress on fidelity of yield projections may benefit more from continuing efforts to understand and minimize systematic error in underlying climate projections. PMID:24872455

  20. Dynamic network data envelopment analysis for university hospitals evaluation

    PubMed Central

    Lobo, Maria Stella de Castro; Rodrigues, Henrique de Castro; André, Edgard Caires Gazzola; de Azeredo, Jônatas Almeida; Lins, Marcos Pereira Estellita

    2016-01-01

    ABSTRACT OBJECTIVE To develop an assessment tool to evaluate the efficiency of federal university general hospitals. METHODS Data envelopment analysis, a linear programming technique, creates a best practice frontier by comparing observed production given the amount of resources used. The model is output-oriented and considers variable returns to scale. Network data envelopment analysis considers link variables belonging to more than one dimension (in the model, medical residents, adjusted admissions, and research projects). Dynamic network data envelopment analysis uses carry-over variables (in the model, financing budget) to analyze frontier shift in subsequent years. Data were gathered from the information system of the Brazilian Ministry of Education (MEC), 2010-2013. RESULTS The mean scores for health care, teaching and research over the period were 58.0%, 86.0%, and 61.0%, respectively. In 2012, the best performance year, for all units to reach the frontier it would be necessary to have a mean increase of 65.0% in outpatient visits; 34.0% in admissions; 12.0% in undergraduate students; 13.0% in multi-professional residents; 48.0% in graduate students; 7.0% in research projects; besides a decrease of 9.0% in medical residents. In the same year, an increase of 0.9% in financing budget would be necessary to improve the care output frontier. In the dynamic evaluation, there was progress in teaching efficiency, oscillation in medical care and no variation in research. CONCLUSIONS The proposed model generates public health planning and programming parameters by estimating efficiency scores and making projections to reach the best practice frontier. PMID:27191158

  1. Resonant Effects in Nanoscale Bowtie Apertures

    NASA Astrophysics Data System (ADS)

    Ding, Li; Qin, Jin; Guo, Songpo; Liu, Tao; Kinzel, Edward; Wang, Liang

    2016-06-01

    Nanoscale bowtie aperture antennas can be used to focus light well below the diffraction limit with extremely high transmission efficiencies. This paper studies the spectral dependence of the transmission through nanoscale bowtie apertures defined in a silver film. A realistic bowtie aperture is numerically modeled using the Finite Difference Time Domain (FDTD) method. Results show that the transmission spectrum is dominated by Fabry-Pérot (F-P) waveguide modes and plasmonic modes. The F-P resonance is sensitive to the thickness of the film and the plasmonic resonant mode is closely related to the gap distance of the bowtie aperture. Both characteristics significantly affect the transmission spectrum. To verify these numerical results, bowtie apertures are FIB milled in a silver film. Experimental transmission measurements agree with simulation data. Based on this result, nanoscale bowtie apertures can be optimized to realize deep sub-wavelength confinement with high transmission efficiency with applications to nanolithography, data storage, and bio-chemical sensing.

  2. Error analysis of sub-aperture stitching interferometry

    NASA Astrophysics Data System (ADS)

    Jia, Xin; Xu, Fuchao; Xie, Weimin; Xing, Tingwen

    2012-10-01

    Large-aperture optical elements are widely employed in high-power laser system, astronomy, and outer-space technology. Sub-aperture stitching is an effective way to extend the lateral and vertical dynamic range of a conventional interferometer. With the aim to provide the accuracy of equipment, this paper simulates the arithmetic to analyze the errors. The Selection of stitching mode and setting of the number of subaperture is given. According to the programmed algorithms simulation stitching is performed for testing the algorithm. In this paper, based on the Matlab we simulate the arithmetic of Sub-aperture stitching. The sub-aperture stitching method can also be used to test the free formed surface. The freeformed surface is created by Zernike polynomials. The accuracy has relationship with the errors of tilting, positioning. Through the stitching the medium spatial frequency of the surface can be tested. The results of errors analysis by means of Matlab are shown that how the tilting and positioning errors to influence the testing accuracy. The analysis of errors can also be used in other interferometer systems.

  3. Synthetic aperture sonar image statistics

    NASA Astrophysics Data System (ADS)

    Johnson, Shawn F.

    Synthetic Aperture Sonar (SAS) systems are capable of producing photograph quality seafloor imagery using a lower frequency than other systems of comparable resolution. However, as with other high-resolution sonar systems, SAS imagery is often characterized by heavy-tailed amplitude distributions which may adversely affect target detection systems. The constant cross-range resolution with respect to range that results from the synthetic aperture formation process provides a unique opportunity to improve our understanding of system and environment interactions, which is essential for accurate performance prediction. This research focused on the impact of multipath contamination and the impact of resolution on image statistics, accomplished through analyses of data collected during at-sea experiments, analytical modeling, and development of numerical simulations. Multipath contamination was shown to have an appreciable impact on image statistics at ranges greater than the water depth and when the levels of the contributing multipath are within 10 dB of the direct path, reducing the image amplitude distribution tails while also degrading image clarity. Image statistics were shown to depend strongly upon both system resolution and orientation to seafloor features such as sand ripples. This work contributes to improving detection systems by aiding understanding of the influences of background (i.e. non-target) image statistics.

  4. DAVINCI a Dilute Aperture Coronagraph

    NASA Astrophysics Data System (ADS)

    Shao, Michael

    2009-01-01

    The motivation for DAVINCI was originally to make use of the technology developed for space interferometers like SIM to build a coronagraph from four 1.1m telescopes that was dramatically lower in cost than a 4 5m filled aperture offaxis coronagraph. Our initial studies through team X have shown this cost savings to be real. But a more careful analysis showed that DAVINCI would have an inner working angle of 35mas a factor of 2 smaller than a 2 lambda/D 4 meter coronagraph or 70m external occulter, resulting in a 10X increase in the number of potential Earth-Clone targets. DAVINCI uses a nulling interferometer as a coronagraph, a nulling interferometer is one the few coronagraph architectures that are compatible with segmented and dilute aperture telescopes. Combined with a post coronagraph wavefront sensor several ultra-demanding tolerances of conventional coronagraphs can be relaxed by factors of 100. The post coronagraph wavefront sensor is also much less affected by local and exozodi background than wavefront sensors that use the science camera as the wavefront sensor. The post coronagraph interferometer is also used on ground based extreme AO coronagraphs, GPI, and P1640.

  5. Diffraction smoothing aperture for an optical beam

    DOEpatents

    Judd, O'Dean P.; Suydam, Bergen R.

    1976-01-01

    The disclosure is directed to an aperture for an optical beam having an irregular periphery or having perturbations imposed upon the periphery to decrease the diffraction effect caused by the beam passing through the aperture. Such apertures are particularly useful with high power solid state laser systems in that they minimize the problem of self-focusing which frequently destroys expensive components in such systems.

  6. Ion mobility spectrometer with virtual aperture grid

    DOEpatents

    Pfeifer, Kent B.; Rumpf, Arthur N.

    2010-11-23

    An ion mobility spectrometer does not require a physical aperture grid to prevent premature ion detector response. The last electrodes adjacent to the ion collector (typically the last four or five) have an electrode pitch that is less than the width of the ion swarm and each of the adjacent electrodes is connected to a source of free charge, thereby providing a virtual aperture grid at the end of the drift region that shields the ion collector from the mirror current of the approaching ion swarm. The virtual aperture grid is less complex in assembly and function and is less sensitive to vibrations than the physical aperture grid.

  7. Evaluation of WES one-dimensional dynamic soil testing procedures

    NASA Astrophysics Data System (ADS)

    Seaman, L.

    1983-06-01

    The Geomechanics Division of the Waterways Experiment Station (WES) tests soils to provide material property data for ground motion calculations in support of high explosives experiments. Thus, the validity of the ground motion predictions depends greatly on the WES material properties used. The usual WES experiments are uniaxial strain (UX) and triaxial shear (TX) tests that can be performed at static testing rates and at dynamic rates with rise times down to about one millisecond. However, in the field experiments being simulated, the measured rise times are often 0.01 ms up to 0.1 ms. Recently, an effort has been made to obtain test data in UX and TX devices with rise times of about 0.1 ms. Some of the test data obtained at these very high rates have appeared to be anomalous, suggesting that wave propagation or other effects may be invalidating the data. Because of these questions about the high rate soils test data, WES asked SRI to evaluate the testing methods used at WES and the data reduction device. This report documents an evaluation of laboratory test data obtained from the explosive-loaded uniaxial strain device developed at WES and the data analysis procedures currently being used.

  8. 3D synthetic aperture for controlled-source electromagnetics

    NASA Astrophysics Data System (ADS)

    Knaak, Allison

    Locating hydrocarbon reservoirs has become more challenging with smaller, deeper or shallower targets in complicated environments. Controlled-source electromagnetics (CSEM), is a geophysical electromagnetic method used to detect and derisk hydrocarbon reservoirs in marine settings, but it is limited by the size of the target, low-spatial resolution, and depth of the reservoir. To reduce the impact of complicated settings and improve the detecting capabilities of CSEM, I apply synthetic aperture to CSEM responses, which virtually increases the length and width of the CSEM source by combining the responses from multiple individual sources. Applying a weight to each source steers or focuses the synthetic aperture source array in the inline and crossline directions. To evaluate the benefits of a 2D source distribution, I test steered synthetic aperture on 3D diffusive fields and view the changes with a new visualization technique. Then I apply 2D steered synthetic aperture to 3D noisy synthetic CSEM fields, which increases the detectability of the reservoir significantly. With more general weighting, I develop an optimization method to find the optimal weights for synthetic aperture arrays that adapts to the information in the CSEM data. The application of optimally weighted synthetic aperture to noisy, simulated electromagnetic fields reduces the presence of noise, increases detectability, and better defines the lateral extent of the target. I then modify the optimization method to include a term that minimizes the variance of random, independent noise. With the application of the modified optimization method, the weighted synthetic aperture responses amplifies the anomaly from the reservoir, lowers the noise floor, and reduces noise streaks in noisy CSEM responses from sources offset kilometers from the receivers. Even with changes to the location of the reservoir and perturbations to the physical properties, synthetic aperture is still able to highlight targets

  9. An Evaluative Review of Simulated Dynamic Smart 3d Objects

    NASA Astrophysics Data System (ADS)

    Romeijn, H.; Sheth, F.; Pettit, C. J.

    2012-07-01

    Three-dimensional (3D) modelling of plants can be an asset for creating agricultural based visualisation products. The continuum of 3D plants models ranges from static to dynamic objects, also known as smart 3D objects. There is an increasing requirement for smarter simulated 3D objects that are attributed mathematically and/or from biological inputs. A systematic approach to plant simulation offers significant advantages to applications in agricultural research, particularly in simulating plant behaviour and the influences of external environmental factors. This approach of 3D plant object visualisation is primarily evident from the visualisation of plants using photographed billboarded images, to more advanced procedural models that come closer to simulating realistic virtual plants. However, few programs model physical reactions of plants to external factors and even fewer are able to grow plants based on mathematical and/or biological parameters. In this paper, we undertake an evaluation of plant-based object simulation programs currently available, with a focus upon the components and techniques involved in producing these objects. Through an analytical review process we consider the strengths and weaknesses of several program packages, the features and use of these programs and the possible opportunities in deploying these for creating smart 3D plant-based objects to support agricultural research and natural resource management. In creating smart 3D objects the model needs to be informed by both plant physiology and phenology. Expert knowledge will frame the parameters and procedures that will attribute the object and allow the simulation of dynamic virtual plants. Ultimately, biologically smart 3D virtual plants that react to changes within an environment could be an effective medium to visually represent landscapes and communicate land management scenarios and practices to planners and decision-makers.

  10. Large aperture Fresnel telescopes/011

    SciTech Connect

    Hyde, R.A., LLNL

    1998-07-16

    At Livermore we`ve spent the last two years examining an alternative approach towards very large aperture (VLA) telescopes, one based upon transmissive Fresnel lenses rather than on mirrors. Fresnel lenses are attractive for VLA telescopes because they are launchable (lightweight, packagable, and deployable) and because they virtually eliminate the traditional, very tight, surface shape requirements faced by reflecting telescopes. Their (potentially severe) optical drawback, a very narrow spectral bandwidth, can be eliminated by use of a second (much smaller) chromatically-correcting Fresnel element. This enables Fresnel VLA telescopes to provide either single band ({Delta}{lambda}/{lambda} {approximately} 0.1), multiple band, or continuous spectral coverage. Building and fielding such large Fresnel lenses will present a significant challenge, but one which appears, with effort, to be solvable.

  11. Multifocal interferometric synthetic aperture microscopy

    PubMed Central

    Xu, Yang; Chng, Xiong Kai Benjamin; Adie, Steven G.; Boppart, Stephen A.; Scott Carney, P.

    2014-01-01

    There is an inherent trade-off between transverse resolution and depth of field (DOF) in optical coherence tomography (OCT) which becomes a limiting factor for certain applications. Multifocal OCT and interferometric synthetic aperture microscopy (ISAM) each provide a distinct solution to the trade-off through modification to the experiment or via post-processing, respectively. In this paper, we have solved the inverse problem of multifocal OCT and present a general algorithm for combining multiple ISAM datasets. Multifocal ISAM (MISAM) uses a regularized combination of the resampled datasets to bring advantages of both multifocal OCT and ISAM to achieve optimal transverse resolution, extended effective DOF and improved signal-to-noise ratio. We present theory, simulation and experimental results. PMID:24977909

  12. Multifocal interferometric synthetic aperture microscopy.

    PubMed

    Xu, Yang; Chng, Xiong Kai Benjamin; Adie, Steven G; Boppart, Stephen A; Carney, P Scott

    2014-06-30

    There is an inherent trade-off between transverse resolution and depth of field (DOF) in optical coherence tomography (OCT) which becomes a limiting factor for certain applications. Multifocal OCT and interferometric synthetic aperture microscopy (ISAM) each provide a distinct solution to the trade-off through modification to the experiment or via post-processing, respectively. In this paper, we have solved the inverse problem of multifocal OCT and present a general algorithm for combining multiple ISAM datasets. Multifocal ISAM (MISAM) uses a regularized combination of the resampled datasets to bring advantages of both multifocal OCT and ISAM to achieve optimal transverse resolution, extended effective DOF and improved signal-to-noise ratio. We present theory, simulation and experimental results. PMID:24977909

  13. Synthetic aperture interferometry: error analysis

    SciTech Connect

    Biswas, Amiya; Coupland, Jeremy

    2010-07-10

    Synthetic aperture interferometry (SAI) is a novel way of testing aspherics and has a potential for in-process measurement of aspherics [Appl. Opt.42, 701 (2003)].APOPAI0003-693510.1364/AO.42.000701 A method to measure steep aspherics using the SAI technique has been previously reported [Appl. Opt.47, 1705 (2008)].APOPAI0003-693510.1364/AO.47.001705 Here we investigate the computation of surface form using the SAI technique in different configurations and discuss the computational errors. A two-pass measurement strategy is proposed to reduce the computational errors, and a detailed investigation is carried out to determine the effect of alignment errors on the measurement process.

  14. ABCD matrix for apertured spherical waves.

    PubMed

    Wang, S; Bernabeu, E; Alda, J

    1991-05-01

    An ABCD matrix for describing the hard aperture under a large Fresnel number is defined in this Technical Note based on Li and Wolf's formula. It is useful for analyzing focal shifts of complicated optical systems with hard apertures. PMID:20700324

  15. A systematic review of aperture shapes

    NASA Astrophysics Data System (ADS)

    Schultz, A. B.; Frazier, T. V.

    The paper discusses the application of apodization to reflecting telescopes. The diffraction pattern of a telescope, which is the image of a star, can be changed considerably by using different aperture shapes in combination with appropriately shaped occulting masks on the optical axis. Aperture shapes studied were the circular, square, and hexagonal. Polaris (α-UMin) was used as the test system.

  16. Bringing social standards into project evaluation under dynamic uncertainty.

    PubMed

    Knudsen, Odin K; Scandizzo, Pasquale L

    2005-04-01

    Society often sets social standards that define thresholds of damage to society or the environment above which compensation must be paid to the state or other parties. In this article, we analyze the interdependence between the use of social standards and investment evaluation under dynamic uncertainty where a negative externality above a threshold established by society requires an assessment and payment of damages. Under uncertainty, the party considering implementing a project or new technology must not only assess when the project is economically efficient to implement but when to abandon a project that could potentially exceed the social standard. Using real-option theory and simple models, we demonstrate how such a social standard can be integrated into cost-benefit analysis through the use of a development option and a liability option coupled with a damage function. Uncertainty, in fact, implies that both parties interpret the social standard as a target for safety rather than an inflexible barrier that cannot be overcome. The larger is the uncertainty, in fact, the greater will be the tolerance for damages in excess of the social standard from both parties. PMID:15876217

  17. Micro Ring Grating Spectrometer with Adjustable Aperture

    NASA Technical Reports Server (NTRS)

    Park, Yeonjoon (Inventor); King, Glen C. (Inventor); Elliott, James R. (Inventor); Choi, Sang H. (Inventor)

    2012-01-01

    A spectrometer includes a micro-ring grating device having coaxially-aligned ring gratings for diffracting incident light onto a target focal point, a detection device for detecting light intensity, one or more actuators, and an adjustable aperture device defining a circular aperture. The aperture circumscribes a target focal point, and directs a light to the detection device. The aperture device is selectively adjustable using the actuators to select a portion of a frequency band for transmission to the detection device. A method of detecting intensity of a selected band of incident light includes directing incident light onto coaxially-aligned ring gratings of a micro-ring grating device, and diffracting the selected band onto a target focal point using the ring gratings. The method includes using an actuator to adjust an aperture device and pass a selected portion of the frequency band to a detection device for measuring the intensity of the selected portion.

  18. Thermal emission by a subwavelength aperture

    NASA Astrophysics Data System (ADS)

    Joulain, Karl; Ezzahri, Younès; Carminati, Rémi

    2016-04-01

    We calculate, by means of fluctuational electrodynamics, the thermal emission of an aperture separating from the outside, vacuum or a material at temperature T. We show that thermal emission is very different whether the aperture size is large or small compared to the thermal wavelength. Subwavelength apertures separating vacuum from the outside have their thermal emission strongly decreased compared to classical blackbodies which have an aperture much larger than the wavelength. A simple expression of their emissivity can be calculated and their total emissive power scales as T8 instead of T4 for large apertures. Thermal emission of disk of materials with a size comparable to the wavelength is also discussed. It is shown in particular that emissivity of such a disk is increased when the material can support surface waves such as phonon polaritons.

  19. Variable aperture collimator for high energy radiation

    DOEpatents

    Hill, Ronald A.

    1984-05-22

    An apparatus is disclosed providing a variable aperture energy beam collimator. A plurality of beam opaque blocks are in sliding interface edge contact to form a variable aperture. The blocks may be offset at the apex angle to provide a non-equilateral aperture. A plurality of collimator block assemblies may be employed for providing a channel defining a collimated beam. Adjacent assemblies are inverted front-to-back with respect to one another for preventing noncollimated energy from emerging from the apparatus. An adjustment mechanism comprises a cable attached to at least one block and a hand wheel mechanism for operating the cable. The blocks are supported by guide rods engaging slide brackets on the blocks. The guide rods are pivotally connected at each end to intermediate actuators supported on rotatable shafts to change the shape of the aperture. A divergent collimated beam may be obtained by adjusting the apertures of adjacent stages to be unequal.

  20. Pressure independence of granular flow through an aperture.

    PubMed

    Aguirre, M A; Grande, J G; Calvo, A; Pugnaloni, L A; Géminard, J-C

    2010-06-11

    We experimentally demonstrate that the flow rate of granular material through an aperture is controlled by the exit velocity imposed on the particles and not by the pressure at the base, contrary to what is often assumed in previous work. This result is achieved by studying the discharge process of a dense packing of monosized disks through an orifice. The flow is driven by a conveyor belt. This two-dimensional horizontal setup allows us to independently control the velocity at which the disks escape the horizontal silo and the pressure in the vicinity of the aperture. The flow rate is found to be proportional to the belt velocity, independent of the amount of disks in the container and, thus, independent of the pressure in the outlet region. In addition, this specific configuration makes it possible to get information on the system dynamics from a single image of the disks that rest on the conveyor belt after the discharge. PMID:20867272

  1. A future large-aperture UVOIR space observatory: reference designs

    NASA Astrophysics Data System (ADS)

    Rioux, Norman; Thronson, Harley; Feinberg, Lee; Stahl, H. Philip; Redding, Dave; Jones, Andrew; Sturm, James; Collins, Christine; Liu, Alice

    2015-09-01

    Our joint NASA GSFC/JPL/MSFC/STScI study team has used community-provided science goals to derive mission needs, requirements, and candidate mission architectures for a future large-aperture, non-cryogenic UVOIR space observatory. We describe the feasibility assessment of system thermal and dynamic stability for supporting coronagraphy. The observatory is in a Sun-Earth L2 orbit providing a stable thermal environment and excellent field of regard. Reference designs include a 36-segment 9.2 m aperture telescope that stows within a five meter diameter launch vehicle fairing. Performance needs developed under the study are traceable to a variety of reference designs including options for a monolithic primary mirror.

  2. A Future Large-Aperture UVOIR Space Observatory: Reference Designs

    NASA Technical Reports Server (NTRS)

    Thronson, Harley; Rioux, Norman; Feinberg, Lee; Stahl, H. Philip; Redding, Dave; Jones, Andrew; Sturm, James; Collins, Christine; Liu, Alice

    2015-01-01

    Our joint NASA GSFC/JPL/MSFC/STScI study team has used community-provided science goals to derive mission needs, requirements, and candidate mission architectures for a future large-aperture, non-cryogenic UVOIR space observatory. We describe the feasibility assessment of system thermal and dynamic stability for supporting coronagraphy. The observatory is in a Sun-Earth L2 orbit providing a stable thermal environment and excellent field of regard. Reference designs include a 36-segment 9.2 m aperture telescope that stows within a five meter diameter launch vehicle fairing. Performance needs developed under the study are traceable to a variety of reference designs including options for a monolithic primary mirror.

  3. EVALUATION OF FIVE WASTE MINIMIZATION TECHNOLOGIES AT THE GENERAL DYNAMICS POMONA DIVISION PLANT

    EPA Science Inventory

    Five technology areas encompassing eight waste reduction technologies at the General Dynamics Pomona Division (Southern California) were technically and economically evaluated under the California/EPA Waste Reduction Innovative Technology Evaluation (WRITE) Program. valuations we...

  4. Dynamic Evaluation of Long-Term Air Quality Model Simulations Over the Northeastern U.S.

    EPA Science Inventory

    Dynamic model evaluation assesses a modeling system's ability to reproduce changes in air quality induced by changes in meteorology and/or emissions. In this paper, we illustrate various approaches to dynamic mode evaluation utilizing 18 years of air quality simulations perform...

  5. Evaluating time dynamics of topographic threshold relations for gully initiation

    NASA Astrophysics Data System (ADS)

    Hayas, Antonio; Vanwalleghem, Tom; Poesen, Jean

    2016-04-01

    Gully erosion is one of the most important soil degradation processes at global scale. However, modelling of gully erosion is still difficult. Despite advances in the modelling of gully headcut rates and incision rates, it remains difficult to predict the location of gully initiation points and trajectories. In different studies it has been demonstrated that a good method of predicting gully initiation is by using a slope (S) - area (A) threshold. Such an S-A relation is a simple way of estimating the critical discharges needed to generate a critical shear stress that can incise a particular soil and initiate a gully. As such, the simple S-A threshold will vary if the rainfall-runoff behaviour of the soil changes or if the soil's erodibility changes. Over the past decades, important agronomic changes have produced significant changes in the soil use and soil management in SW Spain. It is the objective of this research to evaluate how S-A relations for gully initiation have changed over time and for two different land uses, cereal and olive. Data was collected for a gully network in the Cordoba Province, SW Spain. From photo-interpretation of historical air photos between 1956 and 2013, the gully network and initiation points were derived. In total 10 different time steps are available (1956; 1977; 1984; 1998; 2001; 2004; 2006; 2008; 2010; 2013). Topographical thresholds were extracted by combining the digitized gully network with the DEM. Due to small differences in the alignment of ortophotos and DEM, an optimization technique was developed in GIS to extract the correct S-A value for each point. With the S-A values for each year, their dynamics was evaluated as a function of land use (olive or cereal) and in function of the following variables in each of the periods considered: • soil management • soil cover by weeds, where weed growth was modeled from the daily soil water balance • rainfall intensity • root cohesion, , where root growth was modeled from

  6. Dynamic contrast-enhanced MRI evaluation of cerebral cavernous malformations.

    PubMed

    Hart, Blaine L; Taheri, Saeid; Rosenberg, Gary A; Morrison, Leslie A

    2013-10-01

    The aim of this study is to quantitatively evaluate the behavior of CNS cavernous malformations (CCMs) using a dynamic contrast-enhanced MRI (DCEMRI) technique sensitive for slow transfer rates of gadolinium. The prospective study was approved by the institutional review board and was HIPPA compliant. Written informed consent was obtained from 14 subjects with familial CCMs (4 men and 10 women, ages 22-76 years, mean 48.1 years). Following routine anatomic MRI of the brain, DCEMRI was performed for six slices, using T1 mapping with partial inversion recovery (TAPIR) to calculate T1 values, following administration of 0.025 mmol/kg gadolinium DTPA. The transfer rate (Ki) was calculated using the Patlak model, and Ki within CCMs was compared to normal-appearing white matter as well as to 17 normal control subjects previously studied. All subjects had typical MRI appearance of CCMs. Thirty-nine CCMs were studied using DCEMRI. Ki was low or normal in 12 lesions and elevated from 1.4 to 12 times higher than background in the remaining 27 lesions. Ki ranged from 2.1E-6 to 9.63E-4 min(-1), mean 3.55E-4. Normal-appearing white matter in the CCM patients had a mean Ki of 1.57E-4, not statistically different from mean WM Ki of 1.47E-4 in controls. TAPIR-based DCEMRI technique permits quantifiable assessment of CCMs in vivo and reveals considerable differences not seen with conventional MRI. Potential applications include correlation with biologic behavior such as lesion growth or hemorrage, and measurement of drug effects. PMID:24323376

  7. Smov Fos/fgs Fine Alignment (small Apertures)

    NASA Astrophysics Data System (ADS)

    Kinney, Anne

    1994-01-01

    The goal is to measure the precise aperture locations and sizes. The analysis of the observations will result in database changes to the table of aperture locations. Precise aperture locations will be determined by performing a raster step and dwell sequence in the FOS apertures along the edges of the apertures. An aperture map is required at each step of the dwell sequence. This test has to be conducted for both the RED and BLUE detectors.

  8. Smov Fos/fgs Fine Alignment (small Apertures) Revitalized

    NASA Astrophysics Data System (ADS)

    Kinney, Anne

    1994-01-01

    The goal is to measure the precise aperture locations and sizes. The analysis of the observations will result in database changes to the table of aperture locations. Precise aperture locations will be determined by performing a raster step and dwell sequence in the FOS apertures along the edges of the apertures. An aperture map is required at each step of the dwell sequence. This test has to be conducted for both the RED and BLUE detectors.

  9. Influence of alignment error and random noise on interferometry flat sub-aperture stitching

    NASA Astrophysics Data System (ADS)

    Deng, Wantao; Wang, Kaiwei; Zhang, Jinchun

    2012-10-01

    In the flat sub-aperture stitching test, the dominant e error comes from two dimensional translation stage that carries the flat under test, which contains tilt and position error i.e., the alignment error. In order to analyze the influence of alignment error on stitching precision, we use Zemax optical software to simulate a system to detect the phase of each sub-aperture of measured flat and add tilt and position errors and random noise to sub-apertures. The simulation model was utilized in this paper to evaluate the mechanical precision of the translation stage in order to meet a required stitching precision of 1/1000λ.

  10. Connecting Research to Teaching: Evaluating and Writing Dynamic Geometry Tasks

    ERIC Educational Resources Information Center

    Trocki, Aaron

    2014-01-01

    The advent of dynamic geometry software has changed the way students draw, construct, and measure by using virtual tools instead of or along with physical tools. Use of technology in general and of dynamic geometry in particular has gained traction in mathematics education, as evidenced in the Common Core State Standards for Mathematics (CCSSI…

  11. A new method for calculating the mean aperture of fractures in rocks: The dual mean

    NASA Astrophysics Data System (ADS)

    Glover, P. W. J.; Ogilvie, S. R.; Isakov, E.

    2009-04-01

    The intrinsic permeability or hydraulic aperture of single fractures can be determined with the Local Cubic Law, LCL, F(x,y) = -∇P where, F is the vector of the flow flux, H is the separation distance or local aperture of the fracture, ∇P is the local pressure gradient applied to the fluid and μ is the dynamic viscosity of the fluid. Fracture wall roughness should cause an overestimation of this permeability if it is of the same order of magnitude as fracture aperture variation. However, in laminar flow systems (to which the majority of subsurface flow belongs), roughness will not affect the mean flow velocity or flux as viscous drag near the fracture walls dampens the effect of roughness (Reynolds Number < 1). Predictions of the LCL worsen as the fracture surfaces are brought together due to an increase in in-plane toruosity. Overestimations of fracture permeability are often due to inappropriate averaging of the separation between fracture walls, the mechanical aperture, H. All mean values depend upon the mean surface heights of the two surfaces used to define the fracture aperture. However, it is common to quote the mean aperture for the scenario where the relative mean surface heights of the two surfaces used to define the fracture aperture are such that the fracture surfaces just touch. The simple arithmetic mean aperture, Ha, is well defined, but of little practical use for fluid flow calculations. The geometric mean aperture, Hg, is well defined if the surfaces do not touch, but collapses to zero if the surfaces touch at one or more points even if the rest of the aperture is patent to flow. The harmonic mean aperture, Hh, is also well defined but again it collapses to zero if the surfaces touch. To overcome the problem, we define the dual mean, Hdm. This is the arithmetic mean of the geometric mean apertures along all fracture profiles in the direction of presumed fluid flow through the fracture. It has a physical basis, and is sensitive to anisotropy

  12. Three dimensional digital holographic aperture synthesis.

    PubMed

    Crouch, Stephen; Kaylor, Brant M; Barber, Zeb W; Reibel, Randy R

    2015-09-01

    Aperture synthesis techniques are applied to temporally and spatially diverse digital holograms recorded with a fast focal-plane array. Because the technique fully resolves the downrange dimension using wide-bandwidth FMCW linear-chirp waveforms, extremely high resolution three dimensional (3D) images can be obtained even at very long standoff ranges. This allows excellent 3D image formation even when targets have significant structure or discontinuities, which are typically poorly rendered with multi-baseline synthetic aperture ladar or multi-wavelength holographic aperture ladar approaches. The background for the system is described and system performance is demonstrated through both simulation and experiments. PMID:26368474

  13. Longwave infrared (LWIR) coded aperture dispersive spectrometer.

    PubMed

    Fernandez, C; Guenther, B D; Gehm, M E; Brady, D J; Sullivan, M E

    2007-04-30

    We describe a static aperture-coded, dispersive longwave infrared (LWIR) spectrometer that uses a microbolometer array at the detector plane. The two-dimensional aperture code is based on a row-doubled Hadamard mask with transmissive and opaque openings. The independent column code nature of the matrix makes for a mathematically well-defined pattern that spatially and spectrally maps the source information to the detector plane. Post-processing techniques on the data provide spectral estimates of the source. Comparative experimental results between a slit and coded aperture for emission spectroscopy from a CO(2) laser are demonstrated. PMID:19532832

  14. Performance Evaluation of a Dedicated Camera Suitable for Dynamic Radiopharmaceuticals Evaluation in Small Animals

    SciTech Connect

    Loudos, George; Majewski, Stanislaw; Wojcik, Randolph; Weisenberger, Andrew; Sakelios, Nikolas; Nikita, Konstantina; Uzunoglu, Nikolaos; Bouziotis, Penelope; Xanthopoulos, Stavros; Varvarigou, Alexandra

    2007-06-01

    As the result of a collaboration between the Detector and Imaging Group of Thomas Jefferson National Accelerator Facility (US), the Institute of Radioisotopes and Radiodiagnostic Products (IRRP) of N.C.S.R. ldquoDemokritosrdquo and the Biomedical Simulations and Imaging Applications Laboratory (BIOSIM) of National Technical University of Athens (Greece), a mouse sized camera optimized for Tc^99m imaging was developed. The detector was built in Jefferson Lab and transferred to Greece, where it was evaluated with phantoms and small animals. The system will be used initially for planar dynamic studies in small animals, in order to assess the performance of new radiolabeled biomolecules for oncological studies. The active area of the detector is approximately 48 mm times 96 mm. It is based on two flat-panel Hamamatsu H8500 position sensitive photomultiplier tubes (PSPMT), a pixelated NaI(Tl) scintillator and a high resolution lead parallel-hole collimator. The system was developed to optim

  15. Dynamic evaluation of CMAQ part II: Evaluation of relative response factor metrics for ozone attainment demonstrations

    NASA Astrophysics Data System (ADS)

    Foley, Kristen M.; Dolwick, Patrick; Hogrefe, Christian; Simon, Heather; Timin, Brian; Possiel, Norm

    2015-02-01

    The U.S. Environmental Protection Agency provides guidelines on the use of air quality models for projecting whether an emission reduction strategy will lead to future pollutant levels that are at or below the National Ambient Air Quality Standards (NAAQS). The EPA's guidance document for ozone attainment demonstrations recommends an attainment test for the 8-h ozone NAAQS based on using the ratio of output from "future" and "base" model simulations through the calculation of location-specific Relative Response Factors (RRF). The 2007 guidance document as well as other related studies have recommended the use of retrospective evaluation studies in order to evaluate the ability of an air quality model to represent a change in air quality (dynamic evaluation) rather than relying solely on operational evaluation of model predictions under base line conditions. Here simulations from the Community Multiscale Air Quality (CMAQ) modeling system were conducted for 2002 and 2005, a time period characterized by significant emissions reductions associated with the EPA's Nitrogen Oxides State Implementation Plan Call (NOx SIP Call) as well as mobile sources. These simulations were used to evaluate the performance of different forms of the RRF metric for projecting 2002 to 2005 against 2005 observed ozone levels. The evaluation study showed that the current form of the RRF calculation is generally well designed for predicting the future 8-hr ozone "design value" metric used for determining attainment. Specifically, the methodology of using air quality model simulations in a relative sense provided better estimates of future ozone design values than using the modeled future year simulation alone. Alternative forms of the RRF metric were found to be very similar to the current methodology in terms of evaluation metrics. However, alternative RRF metrics were sensitive to the number of days used in the calculation of the RRF. Approaches which used more days in the RRF calculation

  16. Contour-Mapping Synthetic-Aperture Radar

    NASA Technical Reports Server (NTRS)

    Goldstein, R. M.; Caro, E. R.; Wu, C.

    1985-01-01

    Airborne two-antenna synthetic-aperture-radar (SAR) interferometric system provides data processed to yield terrain elevation as well as reflectedintensity information. Relative altitudes of terrain points measured to within error of approximately 25 m.

  17. Eyeglass. 1. Very large aperture diffractive telescopes.

    PubMed

    Hyde, R A

    1999-07-01

    The Eyeglass is a very large aperture (25-100-m) space telescope consisting of two distinct spacecraft, separated in space by several kilometers. A diffractive lens provides the telescope s large aperture, and a separate, much smaller, space telescope serves as its mobile eyepiece. Use of a transmissive diffractive lens solves two basic problems associated with very large aperture space telescopes; it is inherently launchable (lightweight, packagable, and deployable) it and virtually eliminates the traditional, very tight surface shape tolerances faced by reflecting apertures. The potential drawback to use of a diffractive primary (very narrow spectral bandwidth) is eliminated by corrective optics in the telescope s eyepiece; the Eyeglass can provide diffraction-limited imaging with either single-band (Deltalambda/lambda approximately 0.1), multiband, or continuous spectral coverage. PMID:18323902

  18. Very Large Aperture Diffractive Space Telescope

    SciTech Connect

    Hyde, Roderick Allen

    1998-04-20

    A very large (10's of meters) aperture space telescope including two separate spacecraft--an optical primary functioning as a magnifying glass and an optical secondary functioning as an eyepiece. The spacecraft are spaced up to several kilometers apart with the eyepiece directly behind the magnifying glass ''aiming'' at an intended target with their relative orientation determining the optical axis of the telescope and hence the targets being observed. The magnifying glass includes a very large-aperture, very-thin-membrane, diffractive lens, e.g., a Fresnel lens, which intercepts incoming light over its full aperture and focuses it towards the eyepiece. The eyepiece has a much smaller, meter-scale aperture and is designed to move along the focal surface of the magnifying glass, gathering up the incoming light and converting it to high quality images. The positions of the two space craft are controlled both to maintain a good optical focus and to point at desired targets.

  19. Shock wave absorber having apertured plate

    DOEpatents

    Shin, Yong W.; Wiedermann, Arne H.; Ockert, Carl E.

    1985-01-01

    The shock or energy absorber disclosed herein utilizes an apertured plate maintained under the normal level of liquid flowing in a piping system and disposed between the normal liquid flow path and a cavity pressurized with a compressible gas. The degree of openness (or porosity) of the plate is between 0.01 and 0.60. The energy level of a shock wave travelling down the piping system thus is dissipated by some of the liquid being jetted through the apertured plate toward the cavity. The cavity is large compared to the quantity of liquid jetted through the apertured plate, so there is little change in its volume. The porosity of the apertured plate influences the percentage of energy absorbed.

  20. Shock wave absorber having apertured plate

    DOEpatents

    Shin, Y.W.; Wiedermann, A.H.; Ockert, C.E.

    1983-08-26

    The shock or energy absorber disclosed herein utilizes an apertured plate maintained under the normal level of liquid flowing in a piping system and disposed between the normal liquid flow path and a cavity pressurized with a compressible gas. The degree of openness (or porosity) of the plate is between 0.01 and 0.60. The energy level of a shock wave travelling down the piping system thus is dissipated by some of the liquid being jetted through the apertured plate toward the cavity. The cavity is large compared to the quantity of liquid jetted through the apertured plate, so there is little change in its volume. The porosity of the apertured plate influences the percentage of energy absorbed.

  1. Synthetic Aperture Radar Missions Study Report

    NASA Technical Reports Server (NTRS)

    Bard, S.

    2000-01-01

    This report reviews the history of the LightSAR project and summarizes actions the agency can undertake to support industry-led efforts to develop an operational synthetic aperture radar (SAR) capability in the United States.

  2. Advanced optical and thermal technologies for aperture control

    SciTech Connect

    Selkowitz, S.E.; Lampert, C.M.; Rubin, M.

    1982-09-01

    Control of heat transfer and radiant energy flow through building apertures is essential for maximizing thermal and daylighting benefits and minimizing undesired heating and cooling loads. Architectural solutions based on current technology generally add devices such as louvers, shutters, shades, or blinds to the glazing system. The objectives and initial accomplishments of a research program the goal of which is to identify and evaluate advanced optical and thermal technologies for controlling aperture energy flows, thus reducing building energy requirements are outlined. Activities are described in four program areas: (1) low-conductance, high-transmittance glazing materials (e.g., heat mirrors, aerogels); (2) optical switching materials (e.g., electrochromic, photochromic); (3) selective transmitters; and (4) daylight enhancement techniques.

  3. Advanced optical and thermal technologies for aperture control

    SciTech Connect

    Selkowitz, S.E.; Lampert, C.M.; Rubin, M.

    1983-11-01

    Control of heat transfer and radiant energy flow through building apertures is essential for maximizing thermal and daylighting benefits and minimizing undesired heating and cooling loads. Architectural solutions based on current technology generally add devices such as louvers, shutters, shades, or blinds to the glazing system. The objectives and initial accomplishments of a research program are outlined, the goal of which is to identify and evaluate advanced optical and thermal technologies for controlling aperture energy flows, thus reducing building energy requirements. Activities in four program areas are described: (1) low-conductance, high-transmittance glazing materials (e.g., heat mirrors, aerogels) (2) optical switching materials (e.g., electrochromic, photochromic) (3) selective transmitters and (4) daylight enhancement techniques.

  4. Particle-in-Cell Modeling of Magnetized Argon Plasma Flow Through Small Mechanical Apertures

    SciTech Connect

    Adam B. Sefkow and Samuel A. Cohen

    2009-04-09

    Motivated by observations of supersonic argon-ion flow generated by linear helicon-heated plasma devices, a three-dimensional particle-in-cell (PIC) code is used to study whether stationary electrostatic layers form near mechanical apertures intersecting the flow of magnetized plasma. By self-consistently evaluating the temporal evolution of the plasma in the vicinity of the aperture, the PIC simulations characterize the roles of the imposed aperture and applied magnetic field on ion acceleration. The PIC model includes ionization of a background neutral-argon population by thermal and superthermal electrons, the latter found upstream of the aperture. Near the aperture, a transition from a collisional to a collisionless regime occurs. Perturbations of density and potential, with mm wavelengths and consistent with ion acoustic waves, propagate axially. An ion acceleration region of length ~ 200-300 λD,e forms at the location of the aperture and is found to be an electrostatic double layer, with axially-separated regions of net positive and negative charge. Reducing the aperture diameter or increasing its length increases the double layer strength.

  5. Stereoscopic full aperture imaging in nuclear medicine

    NASA Astrophysics Data System (ADS)

    Strocovsky, Sergio G.; Otero, Dino

    2011-06-01

    Images of planar scintigraphy and single photon emission computerized tomography (SPECT) used in nuclear medicine are often low quality. They usually appear to be blurred and noisy. This problem is due to the low spatial resolution and poor sensitivity of the acquisition technique with the gamma camera (GC). Other techniques, such as coded aperture imaging (CAI) reach higher spatial resolutions than GC. However, CAI is not frequently used for imaging in nuclear medicine, due to the decoding complexity of some images and the difficulty in controlling the noise magnitude. Summing up, the images obtained through GC are low quality and it is still difficult to implement CAI technique. A novel technique, full aperture Imaging (FAI), also uses gamma ray-encoding to obtain images, but the coding system and the method of images reconstruction are simpler than those used in CAI. In addition, FAI also reaches higher spatial resolution than GC. In this work, the principles of FAI technique and the method of images reconstruction are explained in detail. The FAI technique is tested by means of Monte Carlo simulations with filiform and spherical sources. Spatial resolution tests of GC versus FAI were performed using two different source-detector distances. First, simulations were made without interposing any material between the sources and the detector. Then, other more realistic simulations were made. In these, the sources were placed in the centre of a rectangular prismatic region, filled with water. A rigorous comparison was made between GC and FAI images of the linear filiform sources, by means of two methods: mean fluence profile graphs and correlation tests. Finally, three-dimensional capacity of FAI was tested with two spherical sources. The results show that FAI technique has greater sensitivity (>100 times) and greater spatial resolution (>2.6 times) than that of GC with LEHR collimator, in both cases, with and without attenuating material and long and short

  6. Multiple-Aperture Based Solar Seeing Profiler

    NASA Astrophysics Data System (ADS)

    Zhao, Gang; Ren, Deqing

    2015-08-01

    Characterization of daytime atmospheric turbulence profile up to 30 km above the telescope is crucial for designs and performance estimations of solar Multi-Conjugate Adaptive Optics (MCAO) systems. To measure seeing profiles up to 30km, we introduce the Multiple Aperture Seeing Profiler (MASP). It bases on the principle of S-DIMM+ and consists of two portable small telescopes similar to SHABAR. Thus the MASP take the advantages of both S-DIMM+ and SHABAR. It is portable and can be used without big telescope, while it has ability to measure turbulence profile up to 30km. Numerical simulations are carried out to evaluate the performance of MASP. We find that for one layer case, MASP can retrieve the seeing with error ~5% using 800 frames of WFS data, which is quite similar with the results of a telescope with diameter of 1120mm. We also simulate profiles with four turbulence layers, and find that our MASP can well retrieve the strengths and heights of the four turbulence layers. Since previous measurements at BBSO showed that daytime turbulence profile typically consists of four layers, MASP we introduced is sufficient for actual seeing measurement.

  7. Motion-adaptive compressive coded apertures

    NASA Astrophysics Data System (ADS)

    Harmany, Zachary T.; Oh, Albert; Marcia, Roummel; Willett, Rebecca

    2011-09-01

    This paper describes an adaptive compressive coded aperture imaging system for video based on motion-compensated video sparsity models. In particular, motion models based on optical flow and sparse deviations from optical flow (i.e. salient motion) can be used to (a) predict future video frames from previous compressive measurements, (b) perform reconstruction using efficient online convex programming techniques, and (c) adapt the coded aperture to yield higher reconstruction fidelity in the vicinity of this salient motion.

  8. Coded apertures for efficient pyroelectric motion tracking.

    PubMed

    Gopinathan, U; Brady, D; Pitsianis, N

    2003-09-01

    Coded apertures may be designed to modulate the visibility between source and measurement spaces such that the position of a source among N resolution cells may be discriminated using logarithm of N measurements. We use coded apertures as reference structures in a pyroelectric motion tracking system. This sensor system is capable of detecting source motion in one of the 15 cells uniformly distributed over a 1.6m x 1.6m domain using 4 pyroelectric detectors. PMID:19466102

  9. Large aperture ac interferometer for optical testing.

    PubMed

    Moore, D T; Murray, R; Neves, F B

    1978-12-15

    A 20-cm clear aperture modified Twyman-Green interferometer is described. The system measures phase with an AC technique called phase-lock interferometry while scanning the aperture with a dual galvanometer scanning system. Position information and phase are stored in a minicomputer with disk storage. This information is manipulated with associated software, and the wavefront deformation due to a test component is graphically displayed in perspective and contour on a CRT terminal. PMID:20208642

  10. Multiple instrument distributed aperture sensor (MIDAS) evolved design concept

    NASA Astrophysics Data System (ADS)

    Stubbs, David; Duncan, Alan; Pitman, Joseph T.; Sigler, Robert; Kendrick, Rick; Smith, Eric H.; Mason, James

    2004-10-01

    An innovative approach to future space telescopes that enables order of magnitude increased science return for astronomical, Earth-observing and planetary science missions is described. Our concept, called Multiple Instrument Distributed Aperture Sensor (MIDAS), provides a large-aperture, wide-field, diffraction-limited telescope at a fraction of the cost, mass and volume of conventional space telescopes. MIDAS integrates many optical interferometry advances as an evolution of over a decade of technology development in distributed aperture optical imaging systems. Nine collector telescopes are integrated into MIDAS as the primary remote sensing science payload, supporting a collection of six back-end science instruments tailored to a specific mission. By interfacing to multiple science instruments, enabling sequential and concurrent functional modes, we expand the potential science return of future space science missions many fold. Passive imaging modes with MIDAS enable remote sensing at diffraction-limited resolution sequentially by each science instrument, as well as in somewhat lower resolution by multiple science instruments acting concurrently on the image, such as in different wavebands. Our MIDAS concept inherently provides nanometer-resolution hyperspectral passive imaging without the need for any moving parts in the science instruments. For Earth-observing and planetary science missions, the MIDAS optical design provides high-resolution imaging at high altitudes for long dwell times, thereby enabling real-time, wide-area remote sensing of dynamic planetary surface characteristics. In its active remote sensing modes, using an integrated solid-state laser source, MIDAS enables surface illumination, active spectroscopy, LIDAR, vibrometery, and optical communications. Our concept is directly scalable to telescope synthetic apertures of 5m, limited by launch vehicle fairing diameter, and above 5m diameter achieved by means of autonomous deployments or manned