WorldWideScience

Sample records for plates corner reflectors

  1. A better trihedral corner reflector for low grazing angles

    Science.gov (United States)

    Doerry, A. W.; Brock, B. C.

    2012-06-01

    Trihedral corner reflectors are the preferred canonical target for SAR performance evaluation for many radar development programs. The conventional trihedrals have problems with substantially reduced Radar Cross Section (RCS) at low grazing angles, unless they are tilted forward, but in which case other problems arise mainly due to multipath effects. Consequently there is a need for better low grazing angle performance for trihedrals. This is facilitated by extending the bottom plate of the trihedral reflector. A relevant analysis of RCS for an infinite ground plate is presented. Practical aspects are also discussed.

  2. High-frequency techniques for RCS prediction of plate geometries and a physical optics/equivalent currents model for the RCS of trihedral corner reflectors

    Science.gov (United States)

    Balanis, Constantine A.; Polka, Lesley A.; Polycarpou, Anastasis C.

    1993-01-01

    Part 1 of this report continues the investigation, initiated in previous reports, of scattering from rectangular plates coated with lossy dielectrics. The hard polarization coefficients given in the last report are incorporated into a model, which includes second- and third-order diffractions, for the coated plate. Computed results from this model are examined and compared to measured data. A breakdown of the contribution of each of the higher-order terms to the total radar cross section (RCS) is given. The effectiveness of the uniform theory of diffraction (UTD) model in accounting for the coating effect is investigated by examining a Physical Optics (PO) model which incorporates the equivalent surface impedance approximation used in the UTD model. The PO, UTD, and experimental results are compared. Part 2 of this report presents a RCS model, based on PO and the Method of Equivalent Currents (MEC), for a trihedral corner reflector. PO is used to account for the reflected fields, while MEC is used for the diffracted fields. Single, double, and triple reflections and first-order diffractions are included in the model. A detailed derivation of the E(sub theta)-polarization, monostatic RCS is included. Computed results are compared with finite-difference time-domain (FDTD) results for validation. The PO/MEC model of this report compares very well with the FDTD model, and it is a much faster model in terms of computational speed.

  3. High-frequency techniques for RCS prediction of plate geometries and a physical optics/equivalent currents model for the RCS of trihedral corner reflectors, parts 1 and 2

    Science.gov (United States)

    Balanis, Constantine A.; Polka, Lesley A.; Polycarpou, Anastasis C.

    Formulations for scattering from the coated plate and the coated dihedral corner reflector are included. A coated plate model based upon the Uniform Theory of Diffraction (UTD) for impedance wedges was presented in the last report. In order to resolve inaccuracies and discontinuities in the predicted patterns using the UTD-based model, an improved model that uses more accurate diffraction coefficients is presented. A Physical Optics (PO) model for the coated dihedral corner reflector is presented as an intermediary step in developing a high-frequency model for this structure. The PO model is based upon the reflection coefficients for a metal-backed lossy material. Preliminary PO results for the dihedral corner reflector suggest that, in addition to being much faster computationally, this model may be more accurate than existing moment method (MM) models. An improved Physical Optics (PO)/Equivalent Currents model for modeling the Radar Cross Section (RCS) of both square and triangular, perfectly conducting, trihedral corner reflectors is presented. The new model uses the PO approximation at each reflection for the first- and second-order reflection terms. For the third-order reflection terms, a Geometrical Optics (GO) approximation is used for the first reflection; and PO approximations are used for the remaining reflections. The previously reported model used GO for all reflections except the terminating reflection. Using PO for most of the reflections results in a computationally slower model because many integrations must be performed numerically, but the advantage is that the predicted RCS using the new model is much more accurate. Comparisons between the two PO models, Finite-Difference Time-Domain (FDTD) and experimental data are presented for validation of the new model.

  4. Scattering patterns of dihedral corner reflectors with impedance surface impedances

    Science.gov (United States)

    Balanis, Constantine A.; Griesser, Timothy; Liu, Kefeng

    The radar cross section patterns of lossy dihedral corner reflectors are calculated using a uniform geometrical theory of diffraction for impedance surfaces. All terms of up to third order reflections are considered for patterns in the principal plane. The surface waves are included whenever they exist for reactive surface impedances. The dihedral corner reflectors examined have right, obtuse, and acute interior angles, and patterns over the entire 360 deg azimuthal plane are calculated. The surface impedances can be different on the four faces of the dihedral corner reflector; however, the surface impedance must be uniform over each face. Computed cross sections are compared with a moment method technique for a dielectric/ferrite absorber coating on a metallic corner reflector. The analysis of the dihedral corner reflector is important because it demonstrates many of the important scattering contributors of complex targets including both interior and exterior wedge diffraction, half-plane diffraction, and dominant multiple reflections and diffractions.

  5. Radar polarimeter measures orientation of calibration corner reflectors

    Science.gov (United States)

    Zebker, Howard A.; Norikane, Lynne

    1987-01-01

    Radar polarimeter signals from a set of trihedral corner reflectors located in the Goldstone Dry Lake in California were analyzed, and three types of scattering behavior were observed: (1) Bragg-like slightly rough surface scattering that represents the background signal from the dry lake, (2) trihedral corner reflector scattering that returns the incident polarization, and (3) two-bounce corner reflector scattering resulting from a particular alignment of a trihedral reflector. A radar calibration approach using trihedral corner reflectors should be designed such that precise alignment of the reflectors is ensured, as three-bounce and two-bounce geometries lead to very different cross sections and hence very different inferred calibration factors.

  6. Integrated 222-GHz corner-reflector antennas

    Science.gov (United States)

    Gearhart, Steven S.; Ling, Curtis C.; Rebeiz, Gabriel M.

    1991-01-01

    A high-gain monolithic millimeter-wave antenna has been designed, fabricated, and tested at 222 GHz. The structure consists of a traveling-wave antenna integrated on a 1.2-micron dielectric membrane and suspended in a longitudinal cavity etched in a silicon wafer. A new traveling-wave antenna design yields a wideband input impedance and a low cross-polarization component in the E- and quasi-H-plane patterns. A directivity of 17.7 dB and a main-beam efficiency of 88.5 percent are calculated from the 222-GHz pattern measurements. The integrated corner-reflector antenna is well suited for millimeter- and submillimeter-wave imaging applications in large f-number systems.

  7. Backscattering reduction of corner reflectors using SCS technique

    Science.gov (United States)

    Ajaikumar, V.; Jose, K. A.; Aanandan, C. K.; Mohanan, P.; Nair, K. G.

    1992-10-01

    The paper reports the use of a simulated corrugated surface (SCS) to reduce radar cross section of dihedral corner reflectors. The focus is on 90-deg corner reflectors, since they are involved in many targets and normally show an enhancement in RCS. The backscattering cross section of the dihedral corner reflector, which is large due to the mutual perpendicularity of the two flat surfaces, is found to be greatly reduced for TE polarization. This simple method is determined to be very effective in reducing the RCS of corner reflectors for any corner angle by suitably selecting the parameters of SCS. This may find potential use in strategic RCS reduction of targets in defense and space applications.

  8. RCS analysis and reduction for lossy dihedral corner reflectors

    Science.gov (United States)

    Griesser, Timothy; Balanis, Constantine A.; Liu, Kefeng

    1989-05-01

    The radar-cross-section (RCS) patterns of lossy dihedral corner reflectors are calculated, using a uniform geometrical theory of diffraction for impedance surfaces. All terms of up to third-order reflections and diffractions are considered for patterns in the principal plane. The surface waves are included whenever they exist for reactive surface impedances. The dihedral corner reflectors examined have right, obtuse, and acute interior angles, and patterns over the entire 360 deg azimuthal plane are calculated. The surface impedances can be different on the four faces of the dihedral corner reflector; however, the surface impedance must be uniform over each face. Computed cross sections are compared with the results of a moment-method technique for a dielectric/ferrite absorber coating on a metallic corner reflector.

  9. The dihedral corner reflector as a reference target

    Science.gov (United States)

    Corona, P.; Ferrara, G.; Gennarelli, C.

    The radiation properties of a dihedral corner reflector are analyzed in detail in order to assess the effectiveness of such a device as a standard reference in experimental determinations of radar cross section. A short review of reference targets is presented, and the physical optics approach and the images method are used to develop a mathematical model for the dihedral corner. Results from a computer program implemented to evaluate the field backscattered from the corner and to compute patterns for various dihedral sizes are reported. It is concluded that the dihedral corner can be conveniently used as a reference target by scanning in a plane containing the corner wedge.

  10. Scattering characteristics computation method for corner reflectors in arbitrary illumination conditions

    OpenAIRE

    Sukharevsky, Oleg I.; Vasilets, Vitaly A.; Nechitaylo, Sergey V.

    2015-01-01

    The calculation method for obtaining scattering characteristics of corner reflectors is proposed. The method allows calculating the radar cross-section of corner reflectors for arbitrary aspect angles. The method proposes separating the smooth part of reflectors and some neighborhood of their edges (including that of inner edges). The method accounts for multiple reflections between smooth parts of the reflector surface. In addition, the reflector surface can have a radar absorbing or dielect...

  11. Floating volumetric image formation using a dihedral corner reflector array device.

    Science.gov (United States)

    Miyazaki, Daisuke; Hirano, Noboru; Maeda, Yuki; Yamamoto, Siori; Mukai, Takaaki; Maekawa, Satoshi

    2013-01-01

    A volumetric display system using an optical imaging device consisting of numerous dihedral corner reflectors placed perpendicular to the surface of a metal plate is proposed. Image formation by the dihedral corner reflector array (DCRA) is free from distortion and focal length. In the proposed volumetric display system, a two-dimensional real image is moved by a mirror scanner to scan a three-dimensional (3D) space. Cross-sectional images of a 3D object are displayed in accordance with the position of the image plane. A volumetric image is observed as a stack of the cross-sectional images. The use of the DCRA brings compact system configuration and volumetric real image generation with very low distortion. An experimental volumetric display system including a DCRA, a galvanometer mirror, and a digital micro-mirror device was constructed to verify the proposed method. A volumetric image consisting of 1024×768×400 voxels was formed by the experimental system.

  12. The selection of artificial corner reflectors based on RCS analysis

    Science.gov (United States)

    Li, Chengfan; Yin, Jingyuan; Zhao, Junjuan; Zhang, Guifang; Shan, Xinjian

    2012-02-01

    Artificial corner reflectors (ACRs) are widely applicable in monitoring terrain change via interferometric synthetic aperture radar (InSAR) remote sensing techniques. Many different types are available. The choice of the most appropriate ones has recently attracted scholarly attentions. Based on physical optics methods, via calculating the radar cross section (RCS) values (the higher the value, the better the detectability), the current study tested three ACRs, i.e., triangular pyramidal, rectangular pyramidal and square trihedral ACRs. Our calculation suggests that the square trihedral ACR produces the largest RCS but least tolerance towards incident radar ray's deviation from optimal angle. The triangular pyramidal trihedral ACR is the most geometrically stable ACR, and has the highest tolerance towards incident radar ray's deviation. Its RCS values, however, are the least of the three. Due to the high cost of deploying ACRs in the fields, the physical optics method seems to provide a viable way to choose appropriate ACRs.

  13. A physical optics/equivalent currents model for the RCS of trihedral corner reflectors

    Science.gov (United States)

    Balanis, Constantine A.; Polycarpou, Anastasis C.

    1993-07-01

    The scattering in the interior regions of both square and triangular trihedral corner reflectors is examined. The theoretical model presented combines geometrical and physical optics (GO and PO), used to account for reflection terms, with equivalent edge currents (EEC), used to account for first-order diffractions from the edges. First-order, second-order, and third-order reflection terms are included. Calculating the first-order reflection terms involves integrating over the entire surface of the illuminated plate. Calculating the second- and third-order reflection terms, however, is much more difficult because the illuminated area is an arbitrary polygon whose shape is dependent upon the incident angles. The method for determining the area of integration is detailed. Extensive comparisons between the high-frequency model, Finite-Difference Time-Domain (FDTD) and experimental data are used for validation of the radar cross section (RCS) of both square and triangular trihedral reflectors.

  14. Prediction of scattering cross-section reductions due to plate orthogonality errors in trihedral radar reflectors

    Science.gov (United States)

    Keen, K. M.

    1983-02-01

    A method is developed for the determination of the reduction in scattering cross-section levels due to nonorthogonal alignment of the plates in trihedral radar corner reflectors. This method is based on the technique for finding the effective error at any direction of incidence. The method can be applied to any regular reflector shape and is accurate for any incident ray direction in the reflector main beam zone. It is determined that this method gives good agreement with experimental results for a wide range of reflector sizes, although the analysis is not exact.

  15. The radar cross section of non-orthogonal corner reflectors, symmetrically illuminated

    Science.gov (United States)

    Williams, J. M.

    The monostatic radar cross section of a nonorthogonal corner reflector, for symmetrical illumination, is shown to be a function of a single dimensionless group at high frequency. The function is calculated for the triangular and square trihedrals and the dihedral.

  16. PO Analysis for RCS of Nonorthogonal Dihedral Corner Reflectors Coated by RAM

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The backscattering radar cross section (RCS) of nonorthogonal dihedral corner reflectors coated by RAM (radar absorbing materials) is formulated by the method of PO (physical optics), where singly, doubly, and triply reflected contributions are considered. The final expressions are analytical and allow for the incidence nonperpendicular to the fold axis of the reflector. The results are compared with ones of MoM (method of moment), which shows that the trend of backscatter patterr of the dihedral corner reflector can be well predicted by this method.

  17. Radar cross section of triangular trihedral reflector with extended bottom plate.

    Energy Technology Data Exchange (ETDEWEB)

    Brock, Billy C.; Doerry, Armin Walter

    2009-05-01

    Trihedral corner reflectors are the preferred canonical target for SAR performance evaluation for many radar development programs. The conventional trihedrals have problems with substantially reduced Radar Cross Section (RCS) at low grazing angles, unless they are tilted forward, but in which case other problems arise. Consequently there is a need for better low grazing angle performance for trihedrals. This is facilitated by extending the bottom plate. A relevant analysis of RCS for an infinite ground plate is presented. Practical aspects are also discussed.

  18. On the Design of Radar Corner Reflectors for Deformation Monitoring in Multi-Frequency InSAR

    OpenAIRE

    Garthwaite, Matthew C.

    2017-01-01

    Trihedral corner reflectors are being increasingly used as point targets in deformation monitoring studies using interferometric synthetic aperture radar (InSAR) techniques. The frequency and size dependence of the corner reflector Radar Cross Section (RCS) means that no single design can perform equally in all the possible imaging modes and radar frequencies available on the currently orbiting Synthetic Aperture Radar (SAR) satellites. Therefore, either a corner reflector design tailored to ...

  19. Some Broadband Calculated RF Scatter from the Trihedral Corner Reflector

    Science.gov (United States)

    Mokole, E. L.; Gold, B. T.; Taylor, D. J.; Sarkar, T. K.; Hansen, J. P.

    To understand the target-like artifacts in radar returns called sea spikes 1 that are induced by ocean scatter,2 the WIPL-D3 and WIPL-DP4 electromagnetics codes are used to calculate monostatic and bistatic radar cross sections (RCSs) of a trihedral comer reflector at 1.5, 3.8, and 7 GHz for vertically and horizontally polarized fields. These computations are part of a larger effort to provide theoretical comparisons for recent scatter data from a 1-m trihedral reflector that was collected over 1.9 to 11.5 GHz in the open ocean with a short-pulse ultrawideband (UWB) system. Over the last eight years, this UWB experimental radar, called the microwave microscope (MWM), has been used in a series of measurements at the Atlantic Underwater Test and Experiment Center (AUTEC) in the Bahamas to investigate the low-elevation (grazing angles less than 4°)scatter of RF signals from the open ocean in an attempt to understand and mitigate the sea-spike phenomenon.

  20. The electric drive control system of corner reflectors of the spacecraft interferometer

    Directory of Open Access Journals (Sweden)

    Langraf Sergey

    2017-01-01

    Full Text Available This paper presents the electric drive control system of corner reflectors of the infrared Fourier transform spectrometer for meteorological satellite. Limited-swing brushless DC motor with a torsional bearing is used as a drive motor. Stringent requirements are imposed to the drive control system for stabilization of moving speed of the reflectors while obtaining the interferogram and for limitation of the reverse time. Research of influence of torsion on steady-state error of speed and ways of its compensation is conducted. The obtained results are consistent with the simulation results of the drive. It is shown that the developed drive is operable in a spacecraft system.

  1. Corner reflector SAR interferometry as an element of a landslide early warning system

    Science.gov (United States)

    Singer, J.; Riedmann, M.; Lang, O.; Anderssohn, J.; Thuro, K.; Wunderlich, Th.; Heunecke, O.; Minet, Ch.

    2012-04-01

    The development of efficient and cost-effective landslide monitoring techniques is the central aim of the alpEWAS research project (www.alpewas.de). Within the scope of the project a terrestrial geosensor network on a landslide site in the Bavarian Alps has been set up, consisting of low cost GNSS with subcentimeter precision, time domain reflectometry (TDR) and video tacheometry (VTPS). To increase the spatial sampling, 16 low-cost Radar Corner Reflectors (CRs) were installed on the site in 2011. The CRs are to reflect radar signals back to the TerraSAR-X radar satellite, allowing for precise displacement measurements. The subject of this study is the application of the CR SAR Interferometry (CRInSAR) technique, and the integration of the derived motion field into an early warning system for landslide monitoring based on terrestrial measurements. An accurate validation data set is realized independently of the monitoring network using millimeter precision GNSS and tacheometer measurements. The 12 CRs from Astrium Geo-Information Services employed over the test site were specifically designed for TerraSAR-X satellite passes. They are made of concrete with integrated metal plates weighing about 80 to 100 kg. They are of triangular trihedral shape with minimal dimensions to obtain a Radar Cross Section 100 times stronger than that of the surrounding area. The concrete guarantees stability against harsh weather conditions, and robustness with respect to vandalism or theft. In addition, the Technical University of Munich (TUM) and the German Aerospace Center (DLR) installed another four CRs made entirely out of aluminum, with the TUM reflectors being of similar minimum size than the Astrium reflectors. Three CRs were placed on assumed stable ground outside the slope area and shall act as reference reflectors. Since the installation date of most CRs (25/08/2011), TerraSAR-X HighResolution SpotLight data have been repeatedly acquired from ascending orbit over the test

  2. Corner-cube retro-reflector instrument for advanced lunar laser ranging

    Science.gov (United States)

    Turyshev, Slava G.; Williams, James G.; Folkner, William M.; Gutt, Gary M.; Baran, Richard T.; Hein, Randall C.; Somawardhana, Ruwan P.; Lipa, John A.; Wang, Suwen

    2013-08-01

    Lunar laser ranging (LLR) has made major contributions to our understanding of the Moon's internal structure and the dynamics of the Earth-Moon system. Because of the recent improvements of the ground-based laser ranging facilities, the present LLR measurement accuracy is limited by the retro-reflectors currently on the lunar surface, which are arrays of small corner-cubes. Because of lunar librations, the surfaces of these arrays do not, in general, point directly at the Earth. This effect results in a spread of arrival times, because each cube that comprises the retroreflector is at a slightly different distance from the Earth, leading to the reduced ranging accuracy. Thus, a single, wide aperture corner-cube could have a clear advantage. In addition, after nearly four decades of successful operations the retro-reflectors arrays currently on the Moon started to show performance degradation; as a result, they yield still useful, but much weaker return signals. Thus, fresh and bright instruments on the lunar surface are needed to continue precision LLR measurements. We have developed a new retro-reflector design to enable advanced LLR operations. It is based on a single, hollow corner cube with a large aperture for which preliminary thermal, mechanical, and optical design and analysis have been performed. The new instrument will be able to reach an Earth-Moon range precision of 1-mm in a single pulse while being subjected to significant thermal variations present on the lunar surface, and will have low mass to allow robotic deployment. Here we report on our design results and instrument development effort.

  3. Corner-cube retro-reflector instrument for advanced lunar laser ranging

    CERN Document Server

    Turyshev, Slava G; Folkner, William M; Gutt, Gary M; Baran, Richard T; Hein, Randall C; Somawardhana, Ruwan P; Lipa, John A; Wang, Suwen

    2012-01-01

    Lunar laser ranging (LLR) has made major contributions to our understanding of the Moon's internal structure and the dynamics of the Earth-Moon system. Because of the recent improvements of the ground-based laser ranging facilities, the present LLR measurement accuracy is limited by the retro-reflectors currently on the lunar surface, which are arrays of small corner-cubes. Because of lunar librations, the surfaces of these arrays do not, in general, point directly at the Earth. This effect results in a spread of arrival times, because each cube that comprises the retroreflector is at a slightly different distance from the Earth, leading to the reduced ranging accuracy. Thus, a single, wide aperture corner-cube could have a clear advantage. In addition, after nearly four decades of successful operations the retro-reflectors arrays currently on the Moon started to show performance degradation; as a result, they yield still useful, but much weaker return signals. Thus, fresh and bright instruments on the lunar ...

  4. Theoretical analysis of solar thermal collector and flat plate bottom reflector with a gap between them

    OpenAIRE

    Hiroshi Tanaka

    2015-01-01

    Augmentation of solar radiation absorbed on a flat plate solar thermal collector by a flat plate bottom reflector was numerically determined when there was a gap between the collector and reflector. The inclination of both the collector and reflector was assumed to be adjustable according to the season. A mirror-symmetric plane of the collector to the reflector was introduced, and a graphical model was proposed to calculate the amount of solar radiation reflected by the reflector and then abs...

  5. Design of Wideband Printed Antenna Array in Corner Reflector with Cosecant Square-Shaped Beam Pattern

    Directory of Open Access Journals (Sweden)

    M. Milijić

    2016-11-01

    Full Text Available The paper presents a wideband printed antenna array with a cosecant square-shaped beam pattern. The array is with four symmetrical pentagonal dipoles as radiating elements operating at the second resonance. The apex of the corner reflector is at a distance λ0/2 from antenna array. Orchard Elliott’s methods and genetic algorithm are used for synthesizing the proposed antenna. A symmetrical tapered feed network of impedance transformers enables a required distribution. Simulated and measured results show that proposed antenna model has a 15 dBi gain and side lobe suppression around 20 dB in E-plane at the frequency of 10 GHz.

  6. Radar Cross Section (RCS) reduction techniques for square trihedral corner reflectors at 35 GHz: Measurements and theoretical simulations

    Science.gov (United States)

    Janssen, G. J. M.; Hulst, R. V. D.; Nennie, E.

    1988-03-01

    Radar cross section (RCS) measurements were performed at a square trihedral corner reflector to investigate RCS reduction techniques which use camouflage materials and changes in the construction. The results are compared with an RCS modeling technique. The measurement results show that a significant RCS reduction can be achieved.

  7. On the Design of Radar Corner Reflectors for Deformation Monitoring in Multi-Frequency InSAR

    Directory of Open Access Journals (Sweden)

    Matthew C. Garthwaite

    2017-06-01

    Full Text Available Trihedral corner reflectors are being increasingly used as point targets in deformation monitoring studies using interferometric synthetic aperture radar (InSAR techniques. The frequency and size dependence of the corner reflector Radar Cross Section (RCS means that no single design can perform equally in all the possible imaging modes and radar frequencies available on the currently orbiting Synthetic Aperture Radar (SAR satellites. Therefore, either a corner reflector design tailored to a specific data type or a compromise design for multiple data types is required. In this paper, I outline the practical and theoretical considerations that need to be made when designing appropriate radar targets, with a focus on supporting multi-frequency SAR data. These considerations are tested by performing field experiments on targets of different size using SAR images from TerraSAR-X, COSMO-SkyMed and RADARSAT-2. Phase noise behaviour in SAR images can be estimated by measuring the Signal-to-Clutter ratio (SCR in individual SAR images. The measured SCR of a point target is dependent on its RCS performance and the influence of clutter near to the deployed target. The SCR is used as a metric to estimate the expected InSAR displacement error incurred by the design of each target and to validate these observations against theoretical expectations. I find that triangular trihedral corner reflectors as small as 1 m in dimension can achieve a displacement error magnitude of a tenth of a millimetre or less in medium-resolution X-band data. Much larger corner reflectors (2.5 m or greater are required to achieve the same displacement error magnitude in medium-resolution C-band data. Compromise designs should aim to satisfy the requirements of the lowest SAR frequency to be used, providing that these targets will not saturate the sensor of the highest frequency to be used. Finally, accurate boresight alignment of the corner reflector can be critical to the overall

  8. Interferometric SAR monitoring of the Vallcebre landslide (Spain using corner reflectors

    Directory of Open Access Journals (Sweden)

    M. Crosetto

    2013-04-01

    Full Text Available This paper describes the deformation monitoring of the Vallcebre landslide (Eastern Pyrenees, Spain using the Differential Interferometric Synthetic Aperture Radar (DInSAR technique and corner reflectors (CRs. The fundamental aspects of this satellite-based deformation monitoring technique are described to provide the key elements needed to fully understand and correctly interpret its results. Several technical and logistic aspects related to the use of CRs are addressed including an analysis of the suitability of DInSAR data to monitor a specific landslide, a discussion on the choice of the type of CRs, suggestions for the installation of CRs and a description of the design of a CR network. This is followed by the description of the DInSAR data analysis procedure required to derive deformation estimates starting from the main observables of the procedure, i.e., the interferometric phases. The main observation equation is analysed, discussing the role of each phase component. A detailed discussion is devoted to the phase unwrapping problem, which has a direct impact on the deformation monitoring capability. Finally, the performance of CRs for monitoring ground displacements has been tested in the Vallcebre landslide (Eastern Pyrenees, Spain. Two different periods, which provide interesting results to monitor over time the kinematics of different parts of the considered landslide unit, are analysed and described.

  9. Interferometric SAR monitoring of the Vallcebre landslide (Spain) using corner reflectors

    Science.gov (United States)

    Crosetto, M.; Gili, J. A.; Monserrat, O.; Cuevas-González, M.; Corominas, J.; Serral, D.

    2013-04-01

    This paper describes the deformation monitoring of the Vallcebre landslide (Eastern Pyrenees, Spain) using the Differential Interferometric Synthetic Aperture Radar (DInSAR) technique and corner reflectors (CRs). The fundamental aspects of this satellite-based deformation monitoring technique are described to provide the key elements needed to fully understand and correctly interpret its results. Several technical and logistic aspects related to the use of CRs are addressed including an analysis of the suitability of DInSAR data to monitor a specific landslide, a discussion on the choice of the type of CRs, suggestions for the installation of CRs and a description of the design of a CR network. This is followed by the description of the DInSAR data analysis procedure required to derive deformation estimates starting from the main observables of the procedure, i.e., the interferometric phases. The main observation equation is analysed, discussing the role of each phase component. A detailed discussion is devoted to the phase unwrapping problem, which has a direct impact on the deformation monitoring capability. Finally, the performance of CRs for monitoring ground displacements has been tested in the Vallcebre landslide (Eastern Pyrenees, Spain). Two different periods, which provide interesting results to monitor over time the kinematics of different parts of the considered landslide unit, are analysed and described.

  10. Theoretical analysis of solar thermal collector and flat plate bottom reflector with a gap between them

    Directory of Open Access Journals (Sweden)

    Hiroshi Tanaka

    2015-11-01

    Full Text Available Augmentation of solar radiation absorbed on a flat plate solar thermal collector by a flat plate bottom reflector was numerically determined when there was a gap between the collector and reflector. The inclination of both the collector and reflector was assumed to be adjustable according to the season. A mirror-symmetric plane of the collector to the reflector was introduced, and a graphical model was proposed to calculate the amount of solar radiation reflected by the reflector and then absorbed on the collector. The performance was analyzed for three typical days at a latitude of 30°N. Solar radiation absorbed on the collector can be increased by the bottom reflector even if there is a gap between the collector and reflector. The optimum inclinations of both the collector and reflector are almost the same while the gap length is less than the lengths of the collector and reflector. However, the range of inclination of the reflector that can increase the solar radiation absorbed on the collector decreases with an increase in gap length, and the solar radiation absorbed on the collector rapidly decreased with an increase in the gap length when the reflector and/or collector were not set at a proper angle.

  11. Performance Study of a Double-Pass Thermoelectric Solar Air Collector with Flat-Plate Reflectors

    Science.gov (United States)

    Lertsatitthanakorn, C.; Rungsiyopas, M.; Therdyothin, A.; Soponronnarit, S.

    2012-06-01

    In this paper the results of the influence of flat-plate reflectors made of aluminum foil on the performance of a double-pass thermoelectric (TE) solar air collector are presented. The proposed TE solar collector with reflectors was composed of transparent glass, an air gap, an absorber plate, TE modules, a rectangular fin heat sink, and two flat-plate reflectors. The flat-plate reflectors were placed on two sides of the TE solar collector (east and west directions). The TE solar collector was installed on a one-axis sun-tracking system to obtain high solar radiation. Direct and reflected incident solar radiation heats up the absorber plate so that a temperature difference is created across the TE modules to generate a direct current. Only a small part of the absorbed solar radiation is converted to electricity, while the rest increases the temperature of the absorber plate. Ambient air flows through the heat sink located in the lower channel to gain heat. The heated air then flows to the upper channel, where it receives additional heating from the absorber plate. Improvements to the thermal energy and electrical power outputs of the system can be achieved by the use of the double-pass collector system with reflectors and TE technology. It was found that the optimum position of the reflectors is 60°, which gave significantly higher thermal energy and electrical power outputs compared with the TE solar collector without reflectors.

  12. Vehicle perceptibilty : reflectorized registration plates and alternative means : function, design and application.

    NARCIS (Netherlands)

    Griep, D.J. Thoenes, E. Schreuder, D.A. & Kranenburg, A.

    1970-01-01

    In November 1967 the Minister of Transport and Waterways in the Netherlands asked the Institute for Road Safety Research SWOV to examine the advisable design of reflectorized registration plates from the aspect of perceptibility. Allowance had to be made for the identification of motor vehicles.

  13. Development and testing of the pneumatic lunar drill for the emplacement of the corner cube reflector on the Moon

    Science.gov (United States)

    Zacny, K.; Currie, D.; Paulsen, G.; Szwarc, T.; Chu, P.

    2012-10-01

    Lunar Laser Ranging provides a highly accurate measurement of the distance between ground stations on Earth and reflectors on the surface of the Moon. Since retroreflectors were initially placed during the Apollo missions, the ground stations improved the ranging accuracy by a factor of 200 and now the Apollo-era arrays on the Moon pose a significant limitation to the ranging accuracy. The new Lunar Laser Ranging Retroreflector (i.e. the Lunar Laser Ranging retroreflector for the 21st century or LLRRA-21) would provide extensive new information on the lunar interior, general relativity, and cosmology. During the day/night lunar cycle, when the thermal variation of the surface is approximately 300 °C, the regolith will rise and fall by almost 500 μm. Yet, it is estimated that the thermal variation 0.5 m to 1 m below the surface is less than much 1 °C. Thus for the lunar emplacement to support 10s of microns ranging accuracy, the reflectors must be anchored to that thermally stable mass at 0.5 m or greater depth. In this paper, we present a novel method of deploying LLRRA-21 with a Corner Cube Reflector (CCR) on the Moon. The emplacement approach uses a gas-powered drill consisting of a >50 cm long, slim, hollow rod with a perforated anchor-cone at its lower end and the CCR mounted to the top. Gas supplied from a small tank is directed into and down the rod and out through the cone, lofting the soil out of the hole and allowing the rod to sink under its own weight to a depth of 0.5 m. To determine the system performance, we conducted several tests in compacted JSC-1a lunar soil simulant and inside a vacuum chamber. In several tests, the rod successfully sunk under its own weight of 16 N to a depth of 50 cm in 4-6 min. The pneumatic system is the game-changer for subsurface access. The extremely low mass and volume required to reach 50 cm, along with very simple penetration method allow the CCR to remain in a variety of payload architectures.

  14. High frequency scattering from trihedral corner reflectors and other benchmark targets - SBR versus experiment

    Science.gov (United States)

    Baldauf, John; Lee, Shung-Wu; Lin, Luke; Jeng, Shyh-Kang; Scarborough, Steven M.; Yu, C. L.

    1991-09-01

    A general method for calculating the radar cross section (RCS) from a three-dimensional target is described. The target is first constructed by using a solid-geometry-modeling computer-aided design (CAD) package. Following the shooting and bouncing ray (SBR) method, a very dense grid of rays is launched from the incident direction toward the target. Each ray is traced according to the geometrical optics theory including the effect of ray tube divergence, polarization, and material reflection coefficient. At the point where the ray exits the target, a physical optics-type integration is performed to obtain the scattered far fields. This method is tested using several simple examples involving interaction among plates, cylinders, and spheres. The theoretical results are generally in good agreement with measured data.

  15. Cascadia subducting plate fluids channelled to fore-arc mantle corner: ETS and silica deposition

    Science.gov (United States)

    Hyndman, R. D.; McCrory, P. A.; Wech, A.; Kao, H.; Ague, J.

    2015-06-01

    In this study we first summarize the constraints that on the Cascadia subduction thrust, there is a 70 km gap downdip between the megathrust seismogenic zone and the Episodic Tremor and Slip (ETS) that lies further landward; there is not a continuous transition from unstable to conditionally stable sliding. Seismic rupture occurs mainly offshore for this hot subduction zone. ETS lies onshore. We then suggest what does control the downdip position of ETS. We conclude that fluids from dehydration of the downgoing plate, focused to rise above the fore-arc mantle corner, are responsible for ETS. There is a remarkable correspondence between the position of ETS and this corner along the whole margin. Hydrated mineral assemblages in the subducting oceanic crust and uppermost mantle are dehydrated with downdip increasing temperature, and seismic tomography data indicate that these fluids have strongly serpentinized the overlying fore-arc mantle. Laboratory data show that such fore-arc mantle serpentinite has low permeability and likely blocks vertical expulsion and restricts flow updip within the underlying permeable oceanic crust and subduction shear zone. At the fore-arc mantle corner these fluids are released upward into the more permeable overlying fore-arc crust. An indication of this fluid flux comes from low Poisson's Ratios (and Vp/Vs) found above the corner that may be explained by a concentration of quartz which has exceptionally low Poisson's Ratio. The rising fluids should be silica saturated and precipitate quartz with decreasing temperature and pressure as they rise above the corner.

  16. Corner Reflector Mathematics

    Science.gov (United States)

    Popelka, Susan R.

    2011-01-01

    Tiny prisms in reflective road signs and safety vests have interesting geometrical properties that can be discussed at any level of high school mathematics. At the beginning of the school year, the author teaches a unit on these reflective materials in her precalculus class so that students can review and strengthen their geometry and trigonometry…

  17. Corner Reflector Mathematics

    Science.gov (United States)

    Popelka, Susan R.

    2011-01-01

    Tiny prisms in reflective road signs and safety vests have interesting geometrical properties that can be discussed at any level of high school mathematics. At the beginning of the school year, the author teaches a unit on these reflective materials in her precalculus class so that students can review and strengthen their geometry and trigonometry…

  18. Corner reflector deployment for X-band SAR interferometry to monitor the landslide of Carlantino, Daunia Region (Italy)

    Science.gov (United States)

    Bovenga, F.; Refice, A.; Pasquariello, G.

    2012-04-01

    case, for instance, of the Municipality of Carlantino, where PS targets detected by both C- and X-band data correspond to urban structures or peri-urban walls and guard rails, while a large landslide, extending for about 2 km from the hilltop down to the valley, is lacking stable coherent targets, due to the vegetation cover. In order to allow stability monitoring through spaceborne SAR interferometry, a network of passive reflectors was designed and deployed on the area of interest. The Corner Reflectors (CR) were designed for TerraSAR-X stripmap acquisitions, and consist of three triangular metal panels welded perpendicular to each others to form a trihedral shape which ensures that the radar signal is scattered back to the sensor. A small size is preferred to minimize the curvature of the side panels, the effect of wind, the exposition to vandalism, and to allow easier transportation and deployment in the harsh terrain setting. To design the CR network, different factors were taken into account: the visibility of the CR by the satellite in terms of geometry and radiometry, the accessibility of the location on the ground, and the relative distance between CR. The work discusses the problematic aspects of designing and deployment of the CR network and presents preliminary results.

  19. S/Ka Dichroic Plate with Rounded Corners for NASA's 34-m Beam-Waveguide Antenna

    Science.gov (United States)

    Veruttipong, W.; Khayatian, B.; Imbriale, W.

    2016-02-01

    An S-/Ka-band frequency selective surface (FSS) or a dichroic plate is designed, manufactured, and tested for use in NASA's Deep Space Network (DSN) 34-m beam-waveguide (BWG) antennas. Due to its large size, the proposed dichroic incorporates a new design feature: waveguides with rounded corners to cut cost and allow ease of manufacturing the plate. The dichroic is designed using an analysis that combines the finite-element method (FEM) for arbitrarily shaped guides with the method of moments and Floquet mode theory for periodic structures. The software was verified by comparison with previously measured and computed dichroic plates. The large plate was manufactured with end-mill machining. The RF performance was measured and is in excellent agreement with the analytical results. The dichroic has been successfully installed and is operational at DSS-24, DSS-34, and DSS-54.

  20. Cascadia subducting plate fluids channelled to fore-arc mantle corner: ETS and silica deposition

    Science.gov (United States)

    Hyndman, Roy D; McCrory, Patricia A.; Wech, Aaron; Kao, Han; Ague, Jay j

    2015-01-01

    In this study we first summarize the constraints that on the Cascadia subduction thrust, there is a 70 km gap downdip between the megathrust seismogenic zone and the Episodic Tremor and Slip (ETS) that lies further landward; there is not a continuous transition from unstable to conditionally stable sliding. Seismic rupture occurs mainly offshore for this hot subduction zone. ETS lies onshore. We then suggest what does control the downdip position of ETS. We conclude that fluids from dehydration of the downgoing plate, focused to rise above the fore-arc mantle corner, are responsible for ETS. There is a remarkable correspondence between the position of ETS and this corner along the whole margin. Hydrated mineral assemblages in the subducting oceanic crust and uppermost mantle are dehydrated with downdip increasing temperature, and seismic tomography data indicate that these fluids have strongly serpentinized the overlying fore-arc mantle. Laboratory data show that such fore-arc mantle serpentinite has low permeability and likely blocks vertical expulsion and restricts flow updip within the underlying permeable oceanic crust and subduction shear zone. At the fore-arc mantle corner these fluids are released upward into the more permeable overlying fore-arc crust. An indication of this fluid flux comes from low Poisson's Ratios (and Vp/Vs) found above the corner that may be explained by a concentration of quartz which has exceptionally low Poisson's Ratio. The rising fluids should be silica saturated and precipitate quartz with decreasing temperature and pressure as they rise above the corner.

  1. Deployment and design of bi-directional corner reflectors for op-timal ground motion monitoring using InSAR

    NARCIS (Netherlands)

    Caro Cuenca, M.; Dheenathayalan, P.; Rossum, W.L. van; Hoogeboom, P.

    2014-01-01

    SAR interferometry (InSAR) requires coherent radar reflections to measure ground displacements. Howev-er, natural coherent reflectors are not always available due to changes in the scattering properties of the ground, e.g., growing vegetation. Furthermore, the opportunistic nature of InSAR measureme

  2. Flat plate collector with external reflectors (RefleC). Experiences withthe development; Flachkollektor mit externen Reflektoren (RefleC). Entwicklungserfahrungen

    Energy Technology Data Exchange (ETDEWEB)

    Hess, S.; Oliva, A.; Di Lauro, P.; Klemke, M.; Hermann, M.; Stryi-Hipp, G. [Fraunhofer-Institut fuer Solare Energiesysteme ISE, Freiburg (Germany); Kallwellis, V.; Kramp, G.; Eisenmann, W. [Wagner und Co. Solartechnik GmbH, Coelbe (Germany); Hanby, V. [DMU Leicester (United Kingdom). Inst. of Energy and Sustainable Development

    2010-07-01

    In cooperation with the Fraunhofer Institute for Solar Energy Systems (Freiburg, Federal Republic of Germany), the company Wagner and Co. Solar Technology (Coelbe, Federal Republic of Germany) developed a stationary concentrated, double-covered flat plate collector with an external reflector for generating process heat up to a temperature of 150 C. This prototype has a half-CPC reflector which is approximated by three flat segments. The reflectors use the distance between the collectors and serves simultaneously as a supporting structure. The collector is designed so that the aperture is not shaded. The authors of the contribution under consideration present the WKI curves and the IAM curves as a test pattern as well as a simulation of the annual energy yield. According to the simulation, the Reflec-collector has an annual energy yield which is greater by 64 % than that of the double-covered base-collector.

  3. High frequency scattering from trihedral corner reflectors and other benchmark targets - SBR versus experiment. [Shooting and Bouncing Ray method

    Science.gov (United States)

    Baldauf, John; Lee, Shung-Wu; Lin, Luke; Jeng, Shyh-Kang; Scarborough, Steven M.; Yu, C. L.

    1991-01-01

    A general method for calculating the radar cross section (RCS) from a three-dimensional target is described. The target is first constructed by using a solid-geometry-modeling computer-aided design (CAD) package. Following the shooting and bouncing ray (SBR) method, a very dense grid of rays is launched from the incident direction toward the target. Each ray is traced according to the geometrical optics theory including the effect of ray tube divergence, polarization, and material reflection coefficient. At the point where the ray exits the target, a physical optics-type integration is performed to obtain the scattered far fields. This method is tested using several simple examples involving interaction among plates, cylinders, and spheres. The theoretical results are generally in good agreement with measured data.

  4. Analysis, Design and Fabrication of centimeter-wave Dielectric Fresnel Zone Plate Lens and reflector

    CERN Document Server

    Mahmoudi, A; Mahmoudi, Ali; Azalzadeh, Reza

    2005-01-01

    Fresnel lens has a long history in optics. This concept at non-optical wavelengths is also applicable. In this paper we report design and fabrication of a half and quarter wave dielectric Fresnel lens made of Plexiglas, and a Fresnel reflector at 11.1 GHz frequency. We made two lenses and one reflector at same frequency and compare their gain and radiation pattern to simulated results. Some methods for better focusing action will be introduced.

  5. 定日镜反射板力学模型及设计方法%MECHANICAL MODEL AND DESIGN METHOD FOR REFLECTOR PLATE OF HELIOSTAT

    Institute of Scientific and Technical Information of China (English)

    王昱涵; 余小孔

    2011-01-01

    该文在文献[1]的基础上,通过对太阳能定日镜反射板的实际工作状况及有限元分析,分别采用薄板大、小挠度弯曲理论研究反射板的挠度及应力规律,给出定日镜反射板周边固支矩形薄板弯曲力学模型;经理论分析及算例验证表明:太阳能定日镜反射板的合理力学模型应为周边固支矩形薄板小挠度弯曲力学模型;并根据反射板结构的受力情况及材料特性,从刚度和强度条件出发,提出反射板厚度的设计方法.%On the basis of the paper of " Deflection for Reflector Plate of Heliostat Based on Thin Plate Flexure Theory" , the model of rectangular plate with periphery fixed was proposed according to the actual working condition of reflector plate. The deflection and stress of reflector plate were respectively studied on the basis of large-deflection and small-deflection thin plate flexure theory. Theoretical and instantial analysis indicated; clamped rectangular plate based on small-deflection thin plate flexure theory was the reasonable model for reflector plate; thickness of reflector plate could be rationally designed in reference to the stiffness and intensity conditions of material properties and stress characteristics.

  6. Effects of the shape of the foil corners on the irradiation performance of U10Mo alloy based monolithic mini-plates

    Energy Technology Data Exchange (ETDEWEB)

    Ozaltun, Hakan [Idaho National Laboratory; Medvedev, Pavel G [Idaho National Laboratory

    2015-06-01

    Monolithic plate-type fuel is a fuel form being developed for high performance research and test reactors to minimize the use of enriched material. These fuel elements are comprised of a high density, low enrichment, U-Mo alloy based fuel foil, sandwiched between Zirconium liners and encapsulated in Aluminum cladding. The use of a high density fuel in a foil form presents a number of fabrication and operational concerns, such as: foil centering, flatness of the foil, fuel thickness variation, geometrical tilting, foil corner shape etc. To benchmark this new design, effects of various geometrical and operational variables on irradiation performance have been evaluated. As a part of these series of sensitivity studies, the shape of the foil corners were studied. To understand the effects of the corner shapes of the foil on thermo-mechanical performance of the plates, a behavioral model was developed for a selected plate from RERTR-12 experiments (Plate L1P785). Both fabrication and irradiation processes were simulated. Once the thermo-mechanical behavior the plate is understood for the nominal case, the simulations were repeated for two additional corner shapes to observe the changes in temperature, displacement and stress-strain fields. The results from the fabrication simulations indicated that the foil corners do not alter the post-fabrication stress-strain magnitudes. Furthermore, the irradiation simulations revealed that post-fabrication stresses of the foil would be relieved very quickly in operation. While, foils with chamfered and filleted corners yielded stresses with comparable magnitudes, they are slightly lower in magnitudes, and provided a more favorable mechanical response compared with the foil with sharp corners.

  7. Detection for transverse corner cracks of steel plates' surface using wavelet

    Institute of Scientific and Technical Information of China (English)

    Qiong ZHOU; Qi AN

    2009-01-01

    An algorithm is presented for detecting transverse comer cracks at a steel plate surface using wavelet transform. According to characteristics of trans-verse comer crack images, the wavelet transform is used for the multi-scale analysis of detecting the image edges and disintegrating the image into four directions at the same time. The proper threshold value is chosen to segment the image into vertical components to obtain the final detection result. The experiment shows that transverse comer cracks of steel plates can be more effectively extracted by the proposed method than the other two common methods.

  8. RCS Analysis of Plate Geometries, parts 1 and 2

    Science.gov (United States)

    Balanis, Constantine A.; Polka, Lesley A.; Polycarpou, Anastasis C.

    1993-01-01

    High-frequency techniques for Radar Cross Section (RCS) prediction of plate geometries and a physical optics/equivalent currents model for the RCS of trihedral corner reflectors are addressed. In part 1, a Uniform Theory of Diffraction (UTD) model for the principal-plane radar cross section (RCS) of a perfectly conducting, rectangular plate coated on one side with an electrically thin, lossy dielectric is presented. In part 2, the scattering in the interior regions of both square and triangular trihedral corner reflectors are examined.

  9. corner: Corner plots

    Science.gov (United States)

    Foreman-Mackey, Daniel

    2017-02-01

    corner uses matplotlib to visualize multidimensional samples using a scatterplot matrix. In these visualizations, each one- and two-dimensional projection of the sample is plotted to reveal covariances. corner was originally conceived to display the results of Markov Chain Monte Carlo simulations and the defaults are chosen with this application in mind but it can be used for displaying many qualitatively different samples. An earlier version of corner was known as triangle.py.

  10. Analysis of the effect of blocking mass at corner interface of two plates at arbitrary angles on transmission of plane bending waves

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Vibration energy transmission at corner interface of two infinite plates rigidly jointed at arbitrary angles was studied by wave approach so as to investigate the effect of blocking mass used for reducing plane bending wave transmission. Two local coordinate systems were introduced and six new non-dimensional coefficients implying corresponding ratio governing characteristic impedances of plates or blocking mass were introduced to simplify formulations of transmission and reflection coefficients. Five samples were tested in experiment.Discussions were carried out based on the comparison between prediction and experiment in terms of insertion loss. It is concluded that blocking mass at corner interface acts like a "lowpass filter", effective for vibration attenuation above certain frequency. The value of TL and IL in "attenuation band" depends mainly on mass per unit length and band width of "attenuation band" on mass moment of inertia per unit length of the blocking mass.

  11. Reflectors for SAR performance testing.

    Energy Technology Data Exchange (ETDEWEB)

    Doerry, Armin Walter

    2008-01-01

    Synthetic Aperture Radar (SAR) performance testing and estimation is facilitated by observing the system response to known target scene elements. Trihedral corner reflectors and other canonical targets play an important role because their Radar Cross Section (RCS) can be calculated analytically. However, reflector orientation and the proximity of the ground and mounting structures can significantly impact the accuracy and precision with which measurements can be made. These issues are examined in this report.

  12. Lamp with a truncated reflector cup

    Science.gov (United States)

    Li, Ming; Allen, Steven C.; Bazydola, Sarah; Ghiu, Camil-Daniel

    2013-10-15

    A lamp assembly, and method for making same. The lamp assembly includes first and second truncated reflector cups. The lamp assembly also includes at least one base plate disposed between the first and second truncated reflector cups, and a light engine disposed on a top surface of the at least one base plate. The light engine is configured to emit light to be reflected by one of the first and second truncated reflector cups.

  13. Partial Melt Systems in Plate-Driven Corner Flow: Evaluating the Formation of Porosity Bands as a Mechanism for Magma Focusing at Mid-Ocean Ridges

    Science.gov (United States)

    Gebhardt, D.; Butler, S. L.

    2015-12-01

    The imposition of an external shear on a system of partial melt will result in compaction of the solid matrix and concentration of the interstitial liquid melt leading to the formation of regions of contrasting high and low porosity. In experiments, direct and torsional shear geometries have demonstrated that these regions of varying porosity form in bands orientated at low angles relative to the shear plane. A variety of numerical models have been employed to recreate these experimental results. Simple shear, pure shear and torsional shear geometries have been used in both linear and nonlinear numerical settings to model the formation of the porosity bands. In this contribution the numerical models utilize a shear geometry derived from the velocity field of the plate-driven corner flow of a mid-ocean ridge. Motivation for using the velocity field of a mid-ocean ridge comes from evidence that suggests the existence of lateral melt channeling from either side of the ridge axis. Imposing the shear from a mid-ocean ridge corner flow allows for the evaluation of the resulting porosity bands in terms of suitability for channeling melt laterally toward the ridge axis. This is done using both slow and fast spreading ridge geometries. The degree of similarity between previous numerical and experimental results has been found to be greatly influenced by the imposed viscosity law of the solid matrix phase. In order to keep this in mind, the numerical models in this contribution use three different matrix viscosity laws: strain-rate independent, strain-rate dependent and anisotropic. Of these rheologies, strain-rate independence results in the poorest orientation for channeling melt directly to the ridge axis. The strain-rate dependent and anisotropic viscosities present more favorable direct-channeling orientations for the fastest growing porosity bands, but in both cases the background flow will rotate bands to less ideal orientations over time. However, these less

  14. Multi-Step Ka/Ka Dichroic Plate with Rounded Corners for NASA's 34m Beam Waveguide Antenna

    Science.gov (United States)

    Veruttipong, Watt; Khayatian, Behrouz; Hoppe, Daniel; Long, Ezra

    2013-01-01

    A multi-step Ka/Ka dichroic plate Frequency Selective Surface (FSS structure) is designed, manufactured and tested for use in NASA's Deep Space Network (DSN) 34m Beam Waveguide (BWG) antennas. The proposed design allows ease of manufacturing and ability to handle the increased transmit power (reflected off the FSS) of the DSN BWG antennas from 20kW to 100 kW. The dichroic is designed using HFSS and results agree well with measured data considering the manufacturing tolerances that could be achieved on the dichroic.

  15. Multi-Step Ka/Ka Dichroic Plate with Rounded Corners for NASA's 34m Beam Waveguide Antenna

    Science.gov (United States)

    Veruttipong, Watt; Khayatian, Behrouz; Hoppe, Daniel; Long, Ezra

    2013-01-01

    A multi-step Ka/Ka dichroic plate Frequency Selective Surface (FSS structure) is designed, manufactured and tested for use in NASA's Deep Space Network (DSN) 34m Beam Waveguide (BWG) antennas. The proposed design allows ease of manufacturing and ability to handle the increased transmit power (reflected off the FSS) of the DSN BWG antennas from 20kW to 100 kW. The dichroic is designed using HFSS and results agree well with measured data considering the manufacturing tolerances that could be achieved on the dichroic.

  16. Solar thermal collectors using planar reflector

    Science.gov (United States)

    Espy, P. N.

    1978-01-01

    Specular reflectors have been used successfully with flat-plate collectors to achieve exceptionally high operating temperatures and high delivered energy per unit collector area. Optimal orientation of collectors and reflectors can result in even higher performance with an improved relationship between energy demand and supply. This paper reports on a study providing first order optimization of collector-reflector arrays in which single- and multiple-faceted reflectors in fixed or singly adjustable configurations provide delivered energy maxima in either summer or winter.

  17. Language Corner

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Dear Readers,It’s December once more, and time for the Language Corner annual "examination. " Questions have been taken from column exercises throughout the year. The test will give you an idea of your progress in Chinese, and also help us to see what changes could be made to improve the column. So give it a try!There will be one super prize, two first prizes, five second prizes, and ten third prizes.We appreciate your participation, and wish you success.-Ed.Please mail your answers to the following address by the end of February 2003:News Center, China Today24 Baiwanzhuang Street, Xicheng District, Beijing, China 100037

  18. Reflector homogenization

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez, R.; Ragusa, J.; Santandrea, S. [Commissariat a l' Energie Atomique, Direction de l' Energie Nucleaire, Service d' Etudes de Reacteurs et de Modelisation Avancee, CEA de Saclay, DM2S/SERMA 91 191 Gif-sur-Yvette cedex (France)]. e-mail: richard.sanchez@cea.fr

    2004-07-01

    The problem of the determination of a homogeneous reflector that preserves a set of prescribed albedo is considered. Duality is used for a direct estimation of the derivatives needed in the iterative calculation of the optimal homogeneous cross sections. The calculation is based on the preservation of collapsed multigroup albedo obtained from detailed reference calculations and depends on the low-order operator used for core calculations. In this work we analyze diffusion and transport as low-order operators and argue that the P{sub 0} transfers are the best choice for the unknown cross sections to be adjusted. Numerical results illustrate the new approach for SP{sub N} core calculations. (Author)

  19. LOCATING VEHICLE LICENSE PLATE BASED ON CORNER DETECTION AND REGIONAL COLOUR COHERENCE%基于角点检测与颜色连贯性分析的车牌定位算法

    Institute of Scientific and Technical Information of China (English)

    胡振邦; 蔡之华

    2012-01-01

    针对低分辨率视频图像,提出一种基于角点检测与颜色连贯性分析的快速车牌定位算法.考虑到车牌具备固定的颜色连贯性特点,首先由车牌背景颜色与车牌字体颜色得出分析掩膜;然后使用较小的阈值和最小角点间距计算得出掩膜内角点;最后对角点进行颜色加权,选择权值最大的分析区域.该方法对图像噪声具有极好的抗干扰性,适用于分辨率较低的视频图像数据.实验表明与其他方法相比,该方法的车牌定位准确率高,平均耗时短.%Considering the problems with regard to low resolution video images, a vehicle license plate locating method based on comer detection and regional colour coherence is put forward. First, taking into acount the characteristic of fixed colour coherence the vehicle license plate has, the analysis mask is obtained from background colour and fonts colour of the license plate, and then the smaller threshold and minimum corner points spacing are employed to calculate comer points within the mask. At last, the corner points are weighted with colour, and the analysis region with largest weights is chosen. This method has excellent performance for image noise in anti-jamming and is suitable for low resolution video image data. Experimental results show that, comparing with other methods, this one locates the vehicle plates with higher accuracy and less time cost.

  20. Reflectors for SAR performance testing-second edition

    Energy Technology Data Exchange (ETDEWEB)

    Doerry, Armin Walter

    2014-02-01

    Synthetic Aperture Radar (SAR) performance testing and estimation is facilitated by observing the system response to known target scene elements. Trihedral corner reflectors and other canonical targets play an important role because their Radar Cross Section (RCS) can be calculated analytically. However, reflector orientation and the proximity of the ground and mounting structures can significantly impact the accuracy and precision with which measurements can be made. These issues are examined in this report.

  1. Fifteen Years of Synthetic Aperture Radar Calibration Using Trihedral Reflectors at the Alaska Satellite Facility

    Science.gov (United States)

    Albright, W.; Atwood, D.; Lawlor, O. S.; Utley, P.; Slater, C.

    2006-12-01

    For the past 15 years, the Alaska Satellite Facility (ASF) has provided calibration support for singly polarized SAR datasets in C-band (ERS-1, ERS-2, and RADARSAT-1 and L-Band (JERS-1. Passive point targets like trihedral corner reflectors offer a reliable and well established means to perform radiometric, geometric, and impulse response measurements for SAR calibration. Routine support of an array of corner reflectors in interior Alaska has permitted ASF an opportunity to monitor satellite health, calibrate SAR processors, and experiment with new reflector designs. Corner reflectors offer the advantages of low maintenance and low cost compared to active devices such as transponders. In order to maintain radar cross section, as the microwave wavelength get longer, so too does the size of the reflector. Increased size means decreased portability, exacerbating the difficulty of providing calibration support in remote locations. In response, ASF is developing low cost, light weight corner reflectors that can be deployed with minimal effort and no maintenance. These efforts will help to extend our present calibration efforts to more remote locations. But more importantly, these designs are expected to play an important role in Permanent Scatterer InSAR (PS-InSAR) methodology. The use of corner reflector arrays in support PS-InSAR may provide new means for monitoring terrain displacements in regions of heavy vegetation. This paper presents some long term measurements from ASF's array of corner reflectors, outlines improvements performed on trihedral corner reflectors, and describes current efforts at ASF to support the next generation of SAR missions and techniques.

  2. Advanced Manufacture of Reflectors

    Energy Technology Data Exchange (ETDEWEB)

    Angel, Roger [University of Arizona

    2014-12-17

    The main project objective has been to develop an advanced gravity sag method for molding large glass solar reflectors with either line or point focus, and with long or short focal length. The method involves taking standard sized squares of glass, 1.65 m x 1.65 m, and shaping them by gravity sag into precision steel molds. The method is designed for high volume manufacture when incorporated into a production line with separate pre-heating and cooling. The performance objectives for the self-supporting glass mirrors made by this project include mirror optical accuracy of 2 mrad root mean square (RMS), requiring surface slope errors <1 mrad rms, a target not met by current production of solar reflectors. Our objective also included development of new methods for rapidly shaping glass mirrors and coating them for higher reflectivity and soil resistance. Reflectivity of 95% for a glass mirror with anti-soil coating was targeted, compared to the present ~94% with no anti-soil coating. Our mirror cost objective is ~$20/m2 in 2020, a significant reduction compared to the present ~$35/m2 for solar trough mirrors produced for trough solar plants. During the first year a custom batch furnace was built to develop the method with high power radiative heating to simulate transfer of glass into a hot slumping zone in a production line. To preserve the original high polish of the float glass on both front and back surfaces, as required for a second surface mirror, the mold surface is machined to the required shape as grooves which intersect the glass at cusps, reducing the mold contact area to significantly less than 1%. The mold surface is gold-plated to reflect thermal radiation. Optical metrology of glass replicas made with the system has been carried out with a novel, custom-built test system. This test provides collimated, vertically-oriented parallel beams from a linear array of co-aligned lasers translated in a perpendicular direction across the reflector. Deviations of

  3. Consequences of nonorthogonality on the scattering properties of dihedral reflectors

    Science.gov (United States)

    Anderson, W. C.

    1987-10-01

    Small deviations from orthogonality can reduce drastically the backscattering radar cross section (RCS) of dihedral corner reflectors. The method of physical optics is used to calculate the magnitude of the reductions in RCS which result from modest departures from orthogonality. The theoretical results are then compared with experimental measurements which are found to be in very good agreement.

  4. Physical property and Textural transition across the Unconformity and Major Seismic Reflectors in the Upper plate of the Costa Rica Subduction zone offshore Osa Peninsula

    Science.gov (United States)

    Hamahashi, M.; Screaton, E.; Tanikawa, W.; Hashimoto, Y.; Martin, K. M.; Saito, S.; Kimura, G.

    2014-12-01

    At the Costa Rica subduction zone offshore Osa Peninsula, the Cocos plate and Cocos Ridge subduct under the Caribbean plate along the Middle America Trench, creating active seismicity. In this region, the Caribbean plate is characterized by a well-consolidated, high velocity framework material beneath the slope sediments, but the nature of the upper plate material is yet unknown. During Integrated Ocean Drilling Program (IODP) Expedition 334 and 344, the unconformity between the slope sediments (Unit 1) and upper plate material (Units 2 and 3) consisting of lithic sedimentary units was penetrated at mid-slope Site 1380. In the current study, to characterize the compaction behavior of the upper plate material, we investigate the physical properties, texture and composition of the sediments at Site 1380 by conducting microstructural observations, resistivity measurements, particle size analyses, X-ray fluorescence and X-ray diffraction analyses. The microstructures of sediments observed through the microscope tend to develop dense and cohesive textures in low porosity sediments, and particle size changes across several unconformities. In particular, the small particle-sized lithic fragments compose larger bodies and form cohesive structures. The cross correlation between measured particle size and shipboard porosity show negative correlation especially at Unit 2, indicating that larger sized particles form smaller or fewer pores. From the results of XRF and XRD analyses, we found that Al, K, Ti tend to concentrate in the higher porosity sediments of Unit 1, whereas Si, Ca, P, Mg, Na, and Mn concentrate in the lower porosity sediments of Unit 2 and 3. The higher concentration in Mg, Na, Mn, Si may be due to minerals such as chlorite, serpentine, amphibole, and sodium manganese. The crossplots between porosity and element concentration show negative correlations in Mg, Na, and Mn with porosity, suggesting that the minerals rich in these elements may relate with the

  5. Cherenkov radiation oscillator without reflectors

    Science.gov (United States)

    Li, D.; Wang, Y.; Hangyo, M.; Wei, Y.; Yang, Z.; Miyamoto, S.

    2014-05-01

    This Letter presents a Cherenkov radiation oscillator with an electron beam travelling over a finitely thick plate made of negative-index materials. In such a scheme, the external reflectors required in the traditional Cherenkov oscillators are not necessary, since the electromagnetic energy flows backward in the negative-index materials, leading to inherent feedback. We theoretically analyzed the interaction between the electron beam and the electromagnetic wave, and worked out the growth rate and start current through numerical calculations. With the help of particle-in-cell simulation, the theoretical predictions are well demonstrated.

  6. Coupling in reflector arrays

    DEFF Research Database (Denmark)

    Appel-Hansen, Jørgen

    1968-01-01

    In order to reduce the space occupied by a reflector array, it is desirable to arrange the array antennas as close to each other as possible; however, in this case coupling between the array antennas will reduce the reflecting properties of the reflector array. The purpose of the present communic...

  7. Core shroud corner joints

    Science.gov (United States)

    Gilmore, Charles B.; Forsyth, David R.

    2013-09-10

    A core shroud is provided, which includes a number of planar members, a number of unitary corners, and a number of subassemblies each comprising a combination of the planar members and the unitary corners. Each unitary corner comprises a unitary extrusion including a first planar portion and a second planar portion disposed perpendicularly with respect to the first planar portion. At least one of the subassemblies comprises a plurality of the unitary corners disposed side-by-side in an alternating opposing relationship. A plurality of the subassemblies can be combined to form a quarter perimeter segment of the core shroud. Four quarter perimeter segments join together to form the core shroud.

  8. Leaky-Wave Slot Array Antenna Fed by a Dual Reflector System

    NARCIS (Netherlands)

    Maci, S.; Ettorre, M.; Neto, A.; Gerini, G.

    2008-01-01

    A leaky-wave slot array antenna fed by a dual offset Gregorian reflector system is realized by pins in a parallel plate waveguide. The radiating part of the antenna is composed by parallel slots etched on one side of the same parallel plate waveguide. The dual offset Gregorian reflector system is fe

  9. PLATE

    DEFF Research Database (Denmark)

    Kling, Joyce; Hjulmand, Lise-Lotte

    2008-01-01

    ’s level of English is sufficient for the increasing number of courses offered in English each semester. This paper addresses these concerns and describes a pilot project initiated in 2003 at CBS to gauge the overall English language proficiency of those teaching content courses in English. Through......Copenhagen Business School (CBS) finds itself needing to address the issue of English-medium instruction for its increasing number of foreign exchange and full degree students. With internationalisation as a main pillar of the institution’s agenda, there are concerns whether the teaching faculty...... the Project in Language Assessment for Teaching in English (PLATE) language professionals from CBS’s Language Center observe teachers and provide feedback using evaluation criteria from the Common European Framework for Reference (CEFR) supplemented by some additional criteria which take the LSP nature...

  10. PLATE

    DEFF Research Database (Denmark)

    Kling, Joyce; Hjulmand, Lise-Lotte

    2008-01-01

    Copenhagen Business School (CBS) finds itself needing to address the issue of English-medium instruction for its increasing number of foreign exchange and full degree students. With internationalisation as a main pillar of the institution’s agenda, there are concerns whether the teaching faculty......’s level of English is sufficient for the increasing number of courses offered in English each semester. This paper addresses these concerns and describes a pilot project initiated in 2003 at CBS to gauge the overall English language proficiency of those teaching content courses in English. Through...... the Project in Language Assessment for Teaching in English (PLATE) language professionals from CBS’s Language Center observe teachers and provide feedback using evaluation criteria from the Common European Framework for Reference (CEFR) supplemented by some additional criteria which take the LSP nature...

  11. Square Van Atta reflector with conducting mounting flame

    DEFF Research Database (Denmark)

    Nielsen, Erik Dragø

    1970-01-01

    the antenna elements and the reradiation from the elements as well as from the conducting plate have been taken into account. The influence of the conducting plate on the induced dipole currents has been treated using the theory of images. The scattering cross section of Van Atta reflectors with or without......A theoretical and numerical analysis of square Van Atta reflectors has been carried out with or without a conducting plate, used for mounting of the antenna elements. The Van Atta reflector investigated has antenna elements which are parallel half-wave dipoles interconnected in pairs...... by transmission lines of equal electrical length. The dipoles are placed in a plane which is parallel to the conducting plate when this is present. In the theory, each pair of antenna elements with the interconnecting transmission line is represented by an equivalent circuit. The mutual impedance between...

  12. Fast algorithm for the exact determination of the mapped effective areas of trihedral radar reflectors

    Science.gov (United States)

    Keen, K. M.

    1983-11-01

    There is currently interest in the use of trihedral radar corner reflectors as ground targets for the calibration of synthetic aperture radars and scatterometers carried by remote sensing satellites. Keen (1983) has described a new technique for the evaluation of the scattering cross-sections of radar corner reflectors. This method, which uses computer evaluation, is briefly discussed. On the basis of new experience related to the employment of the scattering cross-section prediction method, a more efficient and exact way for carrying out the evaluation of mapped effective areas has been developed. The present investigation is concerned with this alternative technique.

  13. CNGS Reflector installed

    CERN Multimedia

    2006-01-01

    A major component that will help target the CNGS neutrino beam for its 732km journey through the earth's crust, from CERN to the Gran Sasso laboratory in Italy, has been installed in its final position. The transport of the huge magnetic horn reflector through the CNGS access gallery. A team from CNGS and TS/IC, and the contractors DBS, transported the magnetic horn reflector on 5th December, in a carefully conducted operation that took just under two hours. The reflector is 7m long, 1.6m in diameter and 1.6 tonnes in weight. With only a matter of centimetres to spare on either side, the reflector was transported through the CNGS access gallery, before being installed in the experiment's target chamber. The larger of two magnetic horns, the reflector will help refocus sprays of high energy pions and kaons emitted after a 0.5MW stream of protons from the Super Proton Synchrotron (SPS) strikes nucleons in a graphite target. The horns are toroidal magnetic lenses and work with high pulsed currents: 150 kA f...

  14. Corner Detection of Hand Gesture

    Directory of Open Access Journals (Sweden)

    Lili Zhang

    2012-12-01

    Full Text Available This paper studies the methods of corner detection of hand gesture, and mainly introduces the orthogonal three-direction chain code (3OT and uses it in corner detection of hand gesture. The study is discussed from four aspects: the techniques used in corner detection, the techniques of Freeman chain code, the main idea of 3OT, the process of corner detection with 3OT and the experiments on corner detectors used for hand gesture images of 26 letters in American Sign Language are described in detail. Experiment results show that the 3OT has well performance with exact corner detection rate and least false corner’s number.

  15. Under Wind Load Numerical Simulation of Internal Force and Distortion on Curtain Wall Corner Type Aluminum Plate%转角型幕墙铝板风荷载作用下内力和变形的数值模拟

    Institute of Scientific and Technical Information of China (English)

    崔传芹

    2015-01-01

    阐述了转角型铝板和加劲肋构成的铝板幕墙的内力及变形计算,采用ANSYS软件,对板块由转角型铝板与5条加劲肋组成的复合结构的内力和变形进行计算,研究了加劲肋与铝板转角处由于局部铆钉松脱由刚结点变成铰接点后,其计算模型发生改变的应力及位移计算,最后介绍实际应用。%Using the ANSYS software, the internal force and displacement of the corner type plate structure which are composed of the trough type aluminum plate and 5 stiffening ribs are calculated. The stiffening rib and the aluminum plate corner partial rivet loosens by the rigid joint turns the hinge point is studied. The computation model is built and its biggest internal force and displacement are obtained. Finally,the practical application is introduced.

  16. Ombuds' Corner: Social exclusion

    CERN Multimedia

    CERN bulletin

    2012-01-01

    In this special video edition of the Ombuds' Corner, Ombudsman Vincent Vuillemin takes a look at a social exclusion at CERN. Please note that the characters and situations appearing in this work are fictitious, and any resemblance to real persons or events is purely coincidental.

  17. Ombuds' Corner: Social exclusion

    CERN Multimedia

    Vincent Vuillemin

    2012-01-01

    In this special video edition of the Ombuds' Corner, Vincent Vuillemin takes a look at a social exclusion at CERN. Please note that the characters and situations appearing in this work are fictitious, and any resemblance to real persons or events is purely coincidental.   Contact the Ombuds Early!

  18. On manifolds with corners

    CERN Document Server

    Joyce, Dominic

    2009-01-01

    Manifolds without boundary, and manifolds with boundary, are universally known in Differential Geometry, but manifolds with corners (locally modelled on [0,\\infty)^k x R^{n-k}) have received comparatively little attention. The basic definitions in the subject are not agreed upon, there are several inequivalent definitions in use of manifolds with corners, of boundary, and of smooth map, depending on the applications in mind. We present a theory of manifolds with corners which includes a new notion of smooth map f : X --> Y. Compared to other definitions, our theory has the advantage of giving a category Man^c of manifolds with corners which is particularly well behaved as a category: it has products and direct products, boundaries behave in a functorial way, and there are simple conditions for the existence of fibre products X x_Z Y in Man^c. Our theory is tailored to future applications in Symplectic Geometry, and is part of a project to describe the geometric structure on moduli spaces of J-holomorphic curv...

  19. Ombud's Corner: holiday time!

    CERN Multimedia

    Sudeshna Datta-Cockerill

    2014-01-01

    In July and August, the Ombud’s Corner articles will be taking a holiday. They will resume in September. Meanwhile, the respect@CERN campaign continues so please keep on sending us your suggestions.   As announced in the last Bulletin, "We want these initiatives to belong to you. For this reason, we would like to ask you to suggest the messages you would like to see included in the posters. What does a “respectful workplace” mean for you? Send your suggestions to respect@cern.ch – and of course we will reward the authors with exclusively designed Respect@CERN-branded items. So, whether it's respect in relation to interpersonal interactions, noise, safety, the environment or anything else, we look forward to receiving your ideas. Do not hesitate – send that e-mail now!" As a reminder, all previous Ombud's Corners can be accessed in the Ombud's blog.

  20. Reflectors to Focus Wave Energy

    DEFF Research Database (Denmark)

    Kramer, Morten; Frigaard, Peter

    2005-01-01

    Wave Energy Converters (WEC’s) extract wave energy from a limited area, often a single point or line even though the wave energy is generally spread out along the wave crest. By the use of wave reflectors (reflecting walls) the wave energy is effectively focused and increased by approximately 30......-50%. Clearly longer wave reflectors will focus more wave energy than shorter wave reflectors. Thus the draw back is the increased wave forces for the longer wave reflectors. In the paper a procedure for calculating the energy efficiency and the wave forces on the reflectors are described, this by use of a 3D...... boundary element method. The calculations are verified by laboratory experiments and a very good agreement is found. The paper gives estimates of possible power benefit for different wave reflector geometries and optimal geometrical design parameters are specified. On this basis inventors of WEC’s can...

  1. Scaphoid excision with four-corner fusion.

    Science.gov (United States)

    Enna, Matthew; Hoepfner, Peter; Weiss, Arnold-Peter C

    2005-11-01

    The scaphoid plays a critical role in maintain-ing normal carpal kinematics. SLAC and SNAC wrist arthritis demonstrate the ramifications ofscaphoid pathology on wrist biomechanics. In the past, symptomatic SLAC or SNAC pathology spelled total wrist arthrodesis. Over the past 20 years there has been a movement toward limited wrist arthrodesis in the treatment of SLAC/SNAC wrists. In the long-term follow-up of four-corner fusions, patient satisfaction is high, patients are able to return to their previous vocation, and wrist function averages 60%-70% of the contralateral wrist. The Spider plate is a recent advancement in the four-corner fusion armamentarium that has thus far shown great promise in respect to fusion rates (100% in the first documented series [36]),functional range of motion, intercarpal stability[37], and patient satisfaction.

  2. The Planck Telescope reflectors

    Science.gov (United States)

    Stute, Thomas

    2004-09-01

    The mechanical division of EADS-Astrium GmbH, Friedrichshafen is currently engaged with the development, manufacturing and testing of the advanced dimensionally stable composite reflectors for the ESA satellite borne telescope Planck. The objective of the ESA mission Planck is to analyse the first light that filled the universe, the cosmic microwave background radiation. Under contract of the Danish Space Research Institute and ESA EADS-Astrium GmbH is developing the all CFRP primary and secondary reflectors for the 1.5-metre telescope which is the main instrument of the Planck satellite. The operational frequency ranges from to 25 GHz to 1000 GHz. The demanding high contour accuracy and surface roughness requirements are met. The design provides the extreme dimensional stability required by the cryogenic operational environment at around 40 K. The elliptical off-axis reflectors display a classical lightweight sandwich design with CFRP core and facesheets. Isostatic mounts provide the interfaces to the telescope structure. Protected VDA provides the reflecting surface. The manufacturing is performed at the Friedrichshafen premises of EADS-Space Transportation GmbH, the former Dornier composite workshops. Advanced manufacturing technologies like true angle lay-up by CNC fibre placement and filament winding are utilized. The protected coating is applied at the CAHA facilities at the Calar Alto Observatory, Spain. The exhaustive environmental testing is performed at the facilities of IABG, Munich (mechanical testing) and for the cryo-optical tests at CSL Liege. The project is in advanced state with both Qualification Models being under environmental testing. The flight models will be delivered in 2004. The paper gives an overview over the requirements and the main structural features how these requirements are met. Special production aspects and available test results are reported.

  3. Advanced Manufacture of Reflectors

    Energy Technology Data Exchange (ETDEWEB)

    Angel, Roger [Univ. of Arizona, Tucson, AZ (United States)

    2014-12-17

    The main project objective has been to develop an advanced gravity sag method for molding large glass solar reflectors with either line or point focus, and with long or short focal length. The method involves taking standard sized squares of glass, 1.65 m x 1.65 m, and shaping them by gravity sag into precision steel molds. The method is designed for high volume manufacture when incorporated into a production line with separate pre-heating and cooling. The performance objectives for the self-supporting glass mirrors made by this project include mirror optical accuracy of 2 mrad root mean square (RMS), requiring surface slope errors less than 1 mrad rms, a target not met by current production of solar reflectors. Our objective also included development of new methods for rapidly shaping glass mirrors and coating them for higher reflectivity and soil resistance. Reflectivity of 95% for a glass mirror with anti-soil coating was targeted, compared to the present ~94% with no anti-soil coating. Our mirror cost objective is ~$20/m2 in 2020, a significant reduction compared to the present ~$35/m2 for solar trough mirrors produced for trough solar plants.

  4. Freeform reflectors for architectural lighting.

    Science.gov (United States)

    Zhu, Ruidong; Hong, Qi; Zhang, Hongxia; Wu, Shin-Tson

    2015-12-14

    We propose an improved method to design freeform reflectors for architectural lighting: one for accent lighting and another for large area wall washing. The designed freeform reflectors effectively distribute light fluxes over the target surfaces, and generate appropriate illumination patterns for comfortable visual environments, which provides greater flexibility for lighting designs, allows many challenging designs, and improves energy-efficiency simultaneously.

  5. Environmental Degradation of Solar Reflectors

    Science.gov (United States)

    Bouquet, F. L.

    1985-01-01

    Report presents results of study of atmospheric degradation of large solar reflectors for power generators. Three general types of reflective surfaces investigated. Report also describes computer buildup and removal (by rain and dew) of contamination from reflectors. Data used to determine effects of soil buildup and best method and frequency of washing at various geographic locations.

  6. Cold Crystal Reflector Filter Concept

    CERN Document Server

    Muhrer, G

    2014-01-01

    In this paper the theoretical concept of a cold crystal reflector filter will be presented. The aim of this concept is to balance the shortcoming of the traditional cold polycrystalline reflector filter, which lies in the significant reduction of the neutron flux right above (in energy space) or right below (wavelength space) the first Bragg edge.

  7. Reflector Surface Error Compensation in Dual-Reflector Antennas

    Science.gov (United States)

    Jamnejad, Vahraz; Imbriale, William

    2010-01-01

    By probing the field on a small subreflector at a minimal number of points, the main reflector surface errors can be obtained and subsequently used to design a phase-correction subreflector that can compensate for main reflector errors. The compensating phase-error profile across the subreflector can be achieved either by a surface deformation or by the use of an array of elements such as patch antennas that can cause a phase shift between the incoming and outgoing fields. The second option is of primary interest here, but the methodology can be applied to either case. The patch array is most easily implemented on a planar surface. Therefore, the example of a flat subreflector and a parabolic main reflector (a Newtonian dual reflector system) is considered in this work. The subreflector is assumed to be a reflector array covered with patch elements. The phase variation on a subreflector can be detected by a small number of receiving patch elements (probes). By probing the phase change at these few selected positions on the subreflector, the phase error over the entire surface can be recovered and used to change the phase of all the patch elements covering the subreflector plane to compensate for main reflector errors. This is accomplished by using a version of sampling theorem on the circular aperture. The sampling is performed on the phase-error function on the circular aperture of the main reflector by a method developed using Zernike polynomials. This method is based upon and extended from a theory previously proposed and applied to reflector aperture integration. This sampling method provides for an exact retrieval of the coefficients of up to certain orders in the expansion of the phase function, from values on a specifically calculated set of points in radial and azimuthal directions in the polar coordinate system, on the circular reflector aperture. The corresponding points on the subreflector are then obtained and, by probing the fields at these points, a

  8. Active Reflectors: Possible Solutions Based on Reflectarrays and Fresnel Reflectors

    Directory of Open Access Journals (Sweden)

    Lorena Cabria

    2009-01-01

    Full Text Available An overview about some of the recent Spanish developments on active reflectors is presented. In the first part, a novel beamsteering active reflectarray is deeply studied. It is based on implementing in each elementary radiator an IQ modulator structure, in which amplitude and phase control of the scattered field is achieved. Finally, a special effort is made in offering solutions to overcome the active antenna integration problems. In the second part, the active concept is firstly extended to Fresnel reflectors. Thanks to the development of a proper simulator, this special structure can be easily analysed. This simulator allows the study of performance of this kind of reflectors and, applying evolutionary algorithms, to find optimal configurations of reflector in accordance with the given specifications for the conformal radiation pattern.

  9. A Novel Offset Fresnel Zone Plate Antenna

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A novel offset Fresnel Zone Plate reflector Antenna (FZPA) is proposed, the phase correcting zone of this FZPA is elliptic. Based on Physical Optics Method, the focusing characteristics of the reflector are analyzed. The comparison of this new FZPA with the circular FZPA and Mawzones FZPA is made.

  10. PCM Heat Storage Charged with a Double-Reflector Solar System

    Directory of Open Access Journals (Sweden)

    Amos Veremachi

    2016-01-01

    Full Text Available A “Solar Salt” (NaNO3–KNO3 60 : 40 molar mixture latent heat storage has been charged by direct solar illumination. Solar Salt as a Phase Change Material (PCM can be an attractive small scale heat storage solution, as the melting temperature of about 220°C can be suitable for cooking purposes. The tests were made with a double-reflector setup. In this setup a secondary reflector positioned above the focal point of the primary reflector directs the rays onto a heat storage positioned below a hole in the primary reflector. The reflectors are tracking the sun, but the storage is stationary. The direct illumination of the absorber top plate during the tracking of the sun melted the salt in the storage through conducting fins. This is a system where portable heat batteries can be charged, during sunshine hours, and then provide heat for cooking during evening times.

  11. Three Heavy Reflector Experiments in the IPEN/MB-01 Reactor: Stainless Steel, Carbon Steel, and Nickel

    Science.gov (United States)

    dos Santos, A.; de Andrade e Silva, G. S.; Mura, L. F.; Fuga, R.; Jerez, R.; Mendonça, A. G.

    2014-04-01

    The heavy reflector experiments performed in the IPEN/MB-01 research reactor facility comprise a set of critical configurations employing the standard 28×26-fuel-rod configuration. The heavy reflector, either Stainless Steel, Carbon Steel or Nickel plates, was placed at the west face of this reactor. 32 plates around 3.0 mm thick were used in all the experiments. The aim was to provide high quality experimental data for the interpretation and validation of the SS-304 heavy reflector calculation methods. The experiments of Carbon Steel, which is composed mainly of iron, and Nickel were performed to provide a consistent and an interpretative check to the SS-304 reflector measurements. The experimental data comprise a set of critical control bank positions, temperatures and reactivities as a function of the number of the plates. The competition between the effect of thermal neutron capture in the heavy reflector and the effect of fast neutrons back scattering to the core is highlighted by varying the reflector thickness. For the Carbon Steel case the reactivity gain when all the 32 plates are inserted is the smallest one, thus demonstrating that Carbon Steel or essentially iron does not have the same reflector properties as the Stainless Steel or Nickel plates do. Nickel has the highest reactivity gain, thus demonstrating that this material is better reflector than Iron and Stainless Steel. The theoretical analysis was performed by MCNP-5 with the nuclear data library ENDF/B-VII.0. It was shown that this library has a very good performance up to thirteen plates and overestimates the reactivity for higher number of plates independently of the type of the reflector.

  12. Terrace retro-reflector array for poloidal polarimeter on ITER.

    Science.gov (United States)

    Imazawa, R; Kawano, Y; Ono, T; Kusama, Y

    2011-02-01

    A new concept of a terrace retro-reflector array (TERRA) as part of the poloidal polarimeter for ITER is proposed in this paper. TERRA reflects a laser light even from a high incident angle in the direction of the incident-light path, while a conventional retro-reflector array cannot. Besides, TERRA can be installed in a smaller space than a corner-cube retro-reflector. In an optical sense, TERRA is equivalent to a Littrow grating, the blaze angle of which varies, depending on the incident angle. The reflected light generates a bright and dark fringe, and the bright fringe is required to travel along the incident-light path to achieve the objects of laser-aided diagnostics. In order to investigate the propagation properties of laser light reflected by TERRA, we have developed a new diffraction formula. Conditions for the propagation of the bright fringe in the direction of the incident light have been obtained using the Littrow grating model and have been confirmed in a simulation applying the new diffraction formula. Finally, we have designed laser transmission optics using TERRA for the ITER poloidal polarimeter and have calculated the light propagation of the system. The optical design obtains a high transmission efficiency, with 88.6% of the incident power returned. These results demonstrate the feasibility of applying TERRA to the ITER poloidal polarimeter.

  13. GPCA vs. PCA in Recognition and 3-D Localization of Ultrasound Reflectors

    Directory of Open Access Journals (Sweden)

    Carlos A. Luna

    2010-05-01

    Full Text Available In this paper, a new method of classification and localization of reflectors, using the time-of-flight (TOF data obtained from ultrasonic transducers, is presented. The method of classification and localization is based on Generalized Principal Component Analysis (GPCA applied to the TOF values obtained from a sensor that contains four ultrasound emitters and 16 receivers. Since PCA works with vectorized representations of TOF, it does not take into account the spatial locality of receivers. The GPCA works with two-dimensional representations of TOF, taking into account information on the spatial position of the receivers. This report includes a detailed description of the method of classification and localization and the results of achieved tests with three types of reflectors in 3-D environments: planes, edges, and corners. The results in terms of processing time, classification and localization were very satisfactory for the reflectors located in the range of 50–350 cm.

  14. Supercritical flows past a square cylinder with rounded corners

    Science.gov (United States)

    Cao, Yong; Tamura, Tetsuro

    2017-08-01

    Large-eddy simulations were used to investigate the supercritical aerodynamics of a square cylinder with rounded corners in comparison with those in the subcritical regime. First, the numerical methods, especially the dynamic mixed model, were validated on the basis of their prediction of supercritical flows past a circular cylinder. Then, the supercritical flows past a rounded-corner square cylinder were simulated and systematically clarified. Strong Reynolds number (Re) effects existed in the forces and local pressures as Re increased from o(104) to o(106). Changeover of flow patterns occurred as Re increased. At the supercritical Re, the free stream overall flowed along the cross sections of the cylinder, separated from the leeward corners and generated Karman vortices behind the cylinder. This pattern resulted in a much smaller recirculation region behind the cylinder compared with the subcritical flow. At the micro level, the flow experienced laminar separation and flow reattachment near the frontal corners, followed by the spatial development of turbulent boundary layers (TBLs) on the side faces and turbulent separation near the leeward corners. The feedback by large-scale primary vortex shedding and the small-scale turbulent motions in the high-frequency region with a slope of -5/3 were detected in the TBL. Their interaction affected the spanwise correlations of wall pressure fluctuations. The TBL on the side face differed from the zero-pressure-gradient flat-plate one; it was subjected to pressure gradients varying in space and time.

  15. Posteromedial Corner Reconstruction

    Science.gov (United States)

    Ferrer, Gonzalo; Leon, Agustín; Wirth, Hans; Mena, Adolfo; Tuca, María José; Espinoza, Gonzalo

    2017-01-01

    Objective: Report the experience, after 1-year follow-up, of 30 patients who underwent anatomical knee reconstruction of posteromedial corner (PMC) injuries, using La Prade´s Technique. Methods: Retrospective cohort study of 30 consecutive patients with PMC injuries operated between November 2010 and May 2014 by the same surgical team. Inclusion criteria: patients with clinical presentation and images (stress radiographs and MRI) compatible with PMC injury, who maintained a grade III chronic instability in spite of at least 3 months of orthopedic treatment, who were reconstructed using La Prade’s anatomical technique, and completed at least 12 months of follow-up. Exclusion criteria: discordance between clinical and image studies, grade I or II medial instability, and surgery performed through a different technique. Data was collected by reviewing the electronic files and images. Functional scores (IKDC and Lysholm) were applied and registered in the preoperative evaluation, and then 6 and 12 months after surgery. Results: Thirty patients (28 men and 2 women) met the inclusion criteria. Mean age was 43 years (24-69). The vast majority (28 patients) had a high-energy mechanism of injury. Twenty patients were diagnosed in the acute setting, while 10 had a delayed diagnosis after poor results of concomitant ligament reconstructions. With the exception of 2 patients, who presented with isolated PMC injury, the majority had associated injuries as detailed: 11 cases had PMC + anterior cruciate ligament (ACL) injury, 3 patients had PMC + posterior cruciate ligament (PCL) injury, 3 patients had PMC + meniscal tears, 9 patients had PMC + ACL + PCL injuries, and there were 2 cases of PMC + ACL + PCL + lateral collateral ligament injuries. Mean time for PMC reconstruction surgery was 5 months (range 2-32). Lysholm and IKDC scores were 18,2 (2-69) and 24,3 (9,2-52,9) respectively in the preoperative setting, improving to 76,7 (44-94) and 70,7 (36,8-95,4) after 1-year follow

  16. Jet screech reduction with perforated flat reflector

    Science.gov (United States)

    Khan, Md. Tawhidul Islam; Teramoto, Kenbu; Matsuo, Shigeru; Setoguchi, Toshiaki

    2008-09-01

    In the present experimental study, investigations have been carried out to evaluate the performance of the new control technique of jet screech with different perforated flat reflectors. Mainly two types of porous flat reflectors had been used in the experiment. One reflector (reflector-V) designed for placing the reflector surface vertical to the jet axis, when, another type of reflector (reflector-H) designed for placing the reflecting surface horizontal to the jet axis. In both cases the reflectors had been placed at the nozzle (base tube with uniform cross-sectional area) exit. The diameter of the reflector-V was 15D when the diameter of the reflector-H was 10D. The porous area of the reflector-V was 6D and 4.5D for reflector-H where D indicated the diameter of the nozzle exit. The placement of the reflector at the exit of the nozzle reduces the sound pressure at the nozzle exit. Thus the muted sound can not excite the unstable disturbance at the nozzle exit and the loop of the feedback mechanism disappeared, finally, the generation of jet screech be cancelled. The suction space located at the back side of the porous surface of the reflector-V improves the efficiency of the screech control technique. However, in the case of reflector-H, the receptivity process of feedback loop had been controlled by reducing the disturbances at the effective shock fronts as well as at the nozzle exit. The performance of the proposed method was verified with a flat reflector concept and good performance in jet screech suppression has been confirmed in the case of porous reflector.

  17. Jet Screech Reduction with Perforated Flat Reflector

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    In the present experimental study, investigations have been carried out to evaluate the performance of the new control technique of jet screech with different perforated flat reflectors. Mainly two types of porous flat reflectors had been used in the experiment. One reflector (reflector-V) designed for placing the reflector surface vertical to the jet axis, when, another type of reflector (reflector-H) designed for placing the reflecting surface horizontal to the jet axis. In both cases the reflectors had been placed at the nozzle (base tube with uniform cross-sectional area)exit. The diameter of the reflector-V was 15D when the diameter of the reflector-H was 10D. The porous area of the reflector-V was 6D and 4.5D for reflector-H where D indicated the diameter of the nozzle exit. The placement of the reflector at the exit of the nozzle reduces the sound pressure at the nozzle exit. Thus the muted sound can not excite the unstable disturbance at the nozzle exit and the loop of the feedback mechanism disappeared, finally,the generation of jet screech be cancelled. The suction space located at the back side of the porous surface of the reflector-V improves the efficiency of the screech control technique. However, in the case of reflector-H, the receptivity process of feedback loop had been controlled by reducing the disturbances at the effective shock fronts as well as at the nozzle exit. The performance of the proposed method was verified with a flat reflector concept and good performance in jet screech suppression has been confirmed in the case of porous reflector.

  18. Surface Optimization Techniques for Deployable Reflectors Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Under this and several other programs, CTD has developed TEMBOREG deployable solid-surface reflectors (TEMBOREG Reflectors) to provide future NASA and Air Force...

  19. Transport of the CNGS reflector.

    CERN Multimedia

    Maximilien Brice

    2005-01-01

    The CNGS magnetic horn reflectorwas transported on 5 December 2005 through the facility's access gallery. The reflector - a major component that will help target the CNGS neutrino beam for its 732km journey through the earth's crust, from CERN to the Gran Sasso laboratory in Italy - is 7m long, 1.6m in diameter and 1.6 tonnes in weight.

  20. Membrane Shell Reflector Segment Antenna

    Science.gov (United States)

    Fang, Houfei; Im, Eastwood; Lin, John; Moore, James

    2012-01-01

    The mesh reflector is the only type of large, in-space deployable antenna that has successfully flown in space. However, state-of-the-art large deployable mesh antenna systems are RF-frequency-limited by both global shape accuracy and local surface quality. The limitations of mesh reflectors stem from two factors. First, at higher frequencies, the porosity and surface roughness of the mesh results in loss and scattering of the signal. Second, the mesh material does not have any bending stiffness and thus cannot be formed into true parabolic (or other desired) shapes. To advance the deployable reflector technology at high RF frequencies from the current state-of-the-art, significant improvements need to be made in three major aspects: a high-stability and highprecision deployable truss; a continuously curved RF reflecting surface (the function of the surface as well as its first derivative are both continuous); and the RF reflecting surface should be made of a continuous material. To meet these three requirements, the Membrane Shell Reflector Segment (MSRS) antenna was developed.

  1. Polarization losses in reflector antennas

    Science.gov (United States)

    Safak, M.; Yazgan, E.

    1985-08-01

    Various definitions for polarization-loss efficiency of Cassegrainian and front-fed reflectors are compared. The effects of flare angle, feed taper and the feed pattern asymmetry on the polarization-loss efficiency are investigated. The definitions based on aperture fields are shown to be inadequate and far fields must be used for calculating the polarization losses.

  2. Magnetohydrodynamic (MHD) channel corner seal

    Science.gov (United States)

    Spurrier, Francis R.

    1980-01-01

    A corner seal for an MHD duct includes a compressible portion which contacts the duct walls and an insulating portion which contacts the electrodes, sidewall bars and insulators. The compressible portion may be a pneumatic or hydraulic gasket or an open-cell foam rubber. The insulating portion is segmented into a plurality of pieces of the same thickness as the electrodes, insulators and sidewall bars and aligned therewith, the pieces aligned with the insulator being of a different size from the pieces aligned with the electrodes and sidewall bars to create a stepped configuration along the corners of the MHD channel.

  3. Tunable reflector with active magnetic metamaterials.

    Science.gov (United States)

    Deng, Tianwei; Huang, Ruifeng; Tang, Ming-Chun; Tan, Peng Khiang

    2014-03-24

    We placed active magnetic metamaterials on metallic surface to implement a tunable reflector with excellent agile performance. By incorporating active elements into the unit cells of the magnetic metamaterial, this active magnetic metamaterial can be tuned to switch function of the reflector among a perfect absorber, a perfect reflector and a gain reflector. This brings about DC control lines to electrically tune the active magnetic metamaterial with positive loss, zero loss and even negative loss. The design, analytical and numerical simulation methods, and experimental results of the tunable reflector are presented.

  4. VT NAD27 Orthophoto Boundaries - corner points

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) RF 5000 scale orthophoto edge lines (4000 x 4000 meter grid cells) were generated automatically from the known corner locations. These corners...

  5. Superconductivity in domains with corners

    DEFF Research Database (Denmark)

    Bonnaillie-Noel, Virginie; Fournais, Søren

    2007-01-01

    We study the two-dimensional Ginzburg-Landau functional in a domain with corners for exterior magnetic field strengths near the critical field where the transition from the superconducting to the normal state occurs. We discuss and clarify the definition of this field and obtain a complete...... asymptotic expansion for it in the large $\\kappa$ regime. Furthermore, we discuss nucleation of superconductivity at the boundary....

  6. Study and simulation for the sharp-corner of silicon-on-insulator waveguides

    Science.gov (United States)

    Sun, De-Gui; Li, Xiaoqi; Wong, Dongxia; Hall, Trevor

    2008-04-01

    The semiconductor industry appears to be encouraging the photonic industry to make highly integrated low-cost optical systems. Planar lightwave circuit (PLC) technology is widely accepted for manufacturing photonic components and Silicon-on-insulator (SOI) waveguides have attracted much research for implementing the highly integrated PLC-based devices. In this work, starting with the guided-mode conversion process and the principle of transportation waves, we mathematically model the structure of corner mirrors of SOI waveguides with a model of effective reflecting interface (ERI). Then we simulate the transfer efficiencies with FDTD method and testify the simulation results with commercial FDTD software tool. Further, we analyze the simulation results and conclude that the conversion efficiency of a corner mirror is determined by several parameters including the geometrical structure, the index-difference of waveguide-reflector materials and the roughness of waveguide-reflector interface. For the corner structure from 90-120°, the optimal transfer efficiency can be achieved more than 98% and the access loss is less than 0.1 dB if the scattering loss of waveguide is not taken into account, but they become 95% and 0.2 dB if the scattering loss is taken into account. For some important PLC components, the deflection angle of 90-120° is good enough for implementing the compact design of highly integrated PLC-based devices.

  7. Nearest Neighbour Corner Points Matching Detection Algorithm

    Directory of Open Access Journals (Sweden)

    Zhang Changlong

    2015-01-01

    Full Text Available Accurate detection towards the corners plays an important part in camera calibration. To deal with the instability and inaccuracies of present corner detection algorithm, the nearest neighbour corners match-ing detection algorithms was brought forward. First, it dilates the binary image of the photographed pictures, searches and reserves quadrilateral outline of the image. Second, the blocks which accord with chess-board-corners are classified into a class. If too many blocks in class, it will be deleted; if not, it will be added, and then let the midpoint of the two vertex coordinates be the rough position of corner. At last, it precisely locates the position of the corners. The Experimental results have shown that the algorithm has obvious advantages on accuracy and validity in corner detection, and it can give security for camera calibration in traffic accident measurement.

  8. Investigations of Bragg reflectors in nanowire lasers

    CERN Document Server

    Svendsen, Guro Kristin; Skaar, Johannes

    2011-01-01

    The reflectivity of various Bragg reflectors in connection to waveguide structures, including nanowires, has been investigated using modal reflection and transmission matrices. A semi-analytical model was applied yielding increased understanding of the diffraction effects present in such gratings. Planar waveguides and nanowire lasers are considered in particular. Two geometries are compared; Bragg reflectors within the waveguides are shown to have significant advantages compared to Bragg reflectors in the substrate, when diffraction effects are significant.

  9. Springback-Compensated, Submillimeter Reflectors Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Inconsistent radius of curvature of replicated, composite reflector panels limit application of composites to large, segmented telescope apertures. This project...

  10. Performance Study of Thermoelectric Solar-Assisted Heat Pump with Reflectors

    Science.gov (United States)

    Lertsatitthanakorn, C.; Soponronnarit, S.; Jamradloedluk, J.; Rungsiyopas, M.; Sarachitti, R.

    2014-06-01

    The simultaneous conversion of solar radiation into thermal and electrical energy in a thermoelectric (TE) solar-assisted heat pump is, for the purposes of this study, referred to as hybrid conversion. To capture more thermal and electrical energy, flat-plate reflectors have been mounted on a TE solar collector. To obtain higher solar radiation intensity on the TE solar collector, the position of the reflectors has been changed and the optimal position of the reflectors determined by both experimental measurements and numerical calculation so as to obtain maximal concentration of solar radiation intensity. The calculated values have been found to be in good agreement with measured ones. Improvements to the thermal energy and electrical power outputs of the system can be achieved by the use of the TE solar-assisted heat pump with reflectors. For the optimum position of the reflectors, the coefficient of performance (COP) of the system formed from a TE solar collector integrated with a heat pump (TESC-HP) was 5.60. The power output and conversion efficiency of the TE modules can reach 10.09 W and 2.40%, respectively, being improved by 34.5% and 18.2%, respectively, compared with the TESC-HP without reflectors.

  11. Corner stores: the perspective of urban youth.

    Science.gov (United States)

    Sherman, Sandra; Grode, Gabrielle; McCoy, Tara; Vander Veur, Stephanie S; Wojtanowski, Alexis; Sandoval, Brianna Almaguer; Foster, Gary D

    2015-02-01

    We examined the perspectives of low-income, urban youth about the corner store experience to inform the development of corner store interventions. Focus groups were conducted to understand youth perceptions regarding their early shopping experiences, the process of store selection, reasons for shopping in a corner store, parental guidance about corner stores, and what their ideal, or "dream corner store" would look like. Thematic analysis was employed to identify themes using ATLAS.ti (version 6.1, 2010, ATLAS.ti GmbH) and Excel (version 2010, Microsoft Corp). Focus groups were conducted in nine kindergarten-through-grade 8 (K-8) public schools in low-income neighborhoods with 40 fourth- to sixth-graders with a mean age of 10.9±0.8 years. Youth report going to corner stores with family members at an early age. By second and third grades, a growing number of youth reported shopping unaccompanied by an older sibling or adult. Youth reported that the products sold in stores were the key reason they choose a specific store. A small number of youth said their parents offered guidance on their corner store purchases. When youth were asked what their dream corner store would look like, they mentioned wanting a combination of healthy and less-healthy foods. These data suggest that, among low-income, urban youth, corner store shopping starts at a very young age and that product, price, and location are key factors that affect corner store selection. The data also suggest that few parents offer guidance about corner store purchases, and youth are receptive to having healthier items in corner stores. Corner store intervention efforts should target young children and their parents/caregivers and aim to increase the availability of affordable, healthier products. Copyright © 2015 Academy of Nutrition and Dietetics. Published by Elsevier Inc. All rights reserved.

  12. Wall shear stress measurement in blade end-wall corner region

    Science.gov (United States)

    Bhargava, R.; Raj, R.; Boldman, D. R.

    1987-01-01

    The magnitude and the direction of wall shear stress and surface pressure in the blade end-wall corner region were investigated. The measurements were obtained on a specially designed Preston tube, the tip of which could be concentrically rotated about its axis of rotation at the measurement location. The magnitude of wall shear stress in the vicinity of the corner was observed to increase significantly (170 percent) compared to its far-upstream value; the increase was consistently higher on the blade surface compared to the value on the plate surface of the blade end-wall corner. On both surfaces in the blade end-wall corner, the variation of the wall shear stress direction was found to be more predominant in the vicinity of the blade leading-edge location. The trend of the measured wall shear stress direction showed good agreement with the limiting streamline directions obtained from the flow visualization studies.

  13. Mueller calculus of polarization change in the cube-corner retroreflector.

    Science.gov (United States)

    Segre, Sergio E; Zanza, Vincenzo

    2003-09-01

    The optical ray properties of the cube-corner retroreflector (CCR) are first recalled. The change of polarization of the radiation due to CCR reflection is then derived by use of the Mueller matrix calculus. It is found that, in general, when the faces are not ideal reflectors, the useful cross section of the CCR consists of six zones, each of which produces a different change of polarization, i.e., it gives a different Mueller matrix. All the Mueller matrices depend on wavelength. The results are quite general and can be used directly also for partially polarized radiation.

  14. Monolithic resonant optical reflector laser diodes

    Science.gov (United States)

    Hirata, T.; Suehiro, M.; Maeda, M.; Hihara, M.; Hosomatsu, H.

    1991-10-01

    The first monolithic resonant optical reflector laser diode that has a waveguide directional coupler and two DBR reflectors integrated by compositional disordering of quantum-well heterostructures is described. A linewidth of 440 kHz was obtained, and this value is expected to be greatly decreased by reducing the propagation loss in the integrated waveguide.

  15. Shaped cassegrain reflector antenna. [design equations

    Science.gov (United States)

    Rao, B. L. J.

    1973-01-01

    Design equations are developed to compute the reflector surfaces required to produce uniform illumination on the main reflector of a cassegrain system when the feed pattern is specified. The final equations are somewhat simple and straightforward to solve (using a computer) compared to the ones which exist already in the literature. Step by step procedure for solving the design equations is discussed in detail.

  16. Posteromedial corner injuries of the knee

    Energy Technology Data Exchange (ETDEWEB)

    House, C.V. [Royal National Orthopaedic Hospital NHS Trust, Stanmore, Middlesex (United Kingdom) and Institute of Orthopaedics and Musculoskeletal Sciences, Stanmore (United Kingdom)]. E-mail: charles.house@uclh.nhs.uk; Connell, D.A. [Royal National Orthopaedic Hospital NHS Trust, Stanmore, Middlesex (United Kingdom); Institute of Orthopaedics and Musculoskeletal Sciences, Stanmore (United Kingdom); Saifuddin, A. [Royal National Orthopaedic Hospital NHS Trust, Stanmore, Middlesex (United Kingdom); Institute of Orthopaedics and Musculoskeletal Sciences, Stanmore (United Kingdom)

    2007-06-15

    Magnetic resonance imaging (MRI) depicts in exquisite detail the supporting structures of the posteromedial corner of the knee. This musculoligamentous unit plays a central role as a dynamic stabilizer of the knee joint and the recognition of injury to the posteromedial corner carries important implications in terms of management and prognosis, most particularly in the anterior cruciate ligament-deficient knee. This article provides a resume of the functional anatomy of the posteromedial corner of the knee as seen with MRI and follows with a review of the MRI appearances of injury to the posteromedial corner.

  17. Numerical results for extended field method applications. [thin plates

    Science.gov (United States)

    Donaldson, B. K.; Chander, S.

    1973-01-01

    This paper presents the numerical results obtained when a new method of analysis, called the extended field method, was applied to several thin plate problems including one with non-rectangular geometry, and one problem involving both beams and a plate. The numerical results show that the quality of the single plate solutions was satisfactory for all cases except those involving a freely deflecting plate corner. The results for the beam and plate structure were satisfactory even though the structure had a freely deflecting corner.

  18. Corner Flow of Power Law Fluids

    DEFF Research Database (Denmark)

    Henriksen, P.; Hassager, Ole

    1989-01-01

    A local analysis of the flow of power law fluids near corners is performed. The equation for the stream function is shown to allow separated solutions in plane polar coordinates. The radial behavior is shown to be algebraic and results are given for the exponent for different values of corner ang...

  19. 3D-Nanomachining using corner lithography

    NARCIS (Netherlands)

    Berenschot, Johan W.; Tas, Niels Roelof; Jansen, Henricus V.; Elwenspoek, Michael Curt

    2008-01-01

    We present a fabrication method to create 3D nano structures without the need for nano lithography. The method, named "corner lithography" is based on conformal deposition and subsequent isotropic thinning of a thin film. The material that remains in sharp concave corners is either used as a mask or

  20. Curiosity Corner. What Works Clearinghouse Intervention Report

    Science.gov (United States)

    What Works Clearinghouse, 2009

    2009-01-01

    "Curiosity Corner" is an early childhood curriculum emphasizing children's language and literacy skills. It comprises two sets of 38 weekly thematic units--one for three-year-olds and one for four-year-olds. Program staff conduct daily lessons using sequential daily activities. One study of "Curiosity Corner" meets the What…

  1. Calculation of thermal noise in grating reflectors

    CERN Document Server

    Heinert, Daniel; Friedrich, Daniel; Hild, Stefan; Kley, Ernst-Bernhard; Leavey, Sean; Martin, Iain W; Nawrodt, Ronny; Tünnermann, Andreas; Vyatchanin, Sergey P; Yamamoto, Kazuhiro

    2013-01-01

    Grating reflectors have been repeatedly discussed to improve the noise performance of metrological applications due to the reduction or absence of any coating material. So far, however, no quantitative estimate on the thermal noise of these reflective structures exists. In this work we present a theoretical calculation of a grating reflector's noise. We further apply it to a proposed 3rd generation gravitational wave detector. Depending on the grating geometry, the grating material and the temperature we obtain a thermal noise decrease by up to a factor of ten compared to conventional dielectric mirrors. Thus the use of grating reflectors can substantially improve the noise performance in metrological applications.

  2. Recovery of a supersonic turbulent boundary layer after an expansion corner

    Science.gov (United States)

    Sun, Ming-bo; Hu, Zhiwei; Sandham, Neil D.

    2017-07-01

    Supersonic turbulent flows at Mach 2.7 over expansion corners with deflection angles of 0° (flat plate), 2°, and 4° have been studied using direct numerical simulation. Distributions of skin friction, pressure, velocity, and boundary layer growth show that the turbulent boundary layer experiences a recovery from a non-equilibrium to an equilibrium state downstream of the expansion corner. Analysis of velocity profiles indicates that the streamwise velocity undergoes a reduction in the near-wall region even though the velocity in the core part of the boundary layer is accelerated after the expansion corner. Growth of the boundary layer was evaluated and a higher shape factor was found in the expansion cases. Turbulence was found to be mostly suppressed downstream of the corner, and throughout the recovery region, even though turbulence is regenerated in the near-wall region. The expansion ramp increases the near-wall streak spacing compared to a flat plate, and turbulent kinetic energy profiles and budgets exhibit a characteristic two-layer structure. Near-wall turbulence recovers to a balance between the local production and dissipation equilibrium more quickly in the inner layer than in the outer layer. The two-layer structure is due to a history effect of turbulence decay in the outer part of the boundary layer downstream of the expansion corner, with limited momentum and energy exchange between the inner layer and the main stream.

  3. Perfect Multi-Channel Flat Reflectors

    CERN Document Server

    Asadchy, V S; Elsakka, A; Albooyeh, M; Tretyakov, S A

    2016-01-01

    Recent advances in engineered gradient metasurfaces have enabled unprecedented opportunities for light manipulation using optically thin sheets, such as anomalous refraction, reflection, or focusing of an incident beam. Here we introduce a concept of multi-channel functional metasurfaces, which are able to control incoming and outgoing waves in a number of propagation directions or polarization states simultaneously and independently. In particular, we reveal a possibility to create perfect multi-channel reflectors. Under the assumption of reciprocity and energy conservation, we find that there exist three fundamental classes of multi-channel mirrors. Together they form a basis of all possible reflection functionalities achievable with flat periodically modulated reflectors. To demonstrate the potential of the introduced concept, we design and experimentally test one of the basis multi-channel reflectors, confirming the desired multi-channel response. Furthermore, by extending the concept to reflectors suppor...

  4. Efficient Wave Energy Amplification with Wave Reflectors

    DEFF Research Database (Denmark)

    Kramer, Morten Mejlhede; Frigaard, Peter Bak

    2002-01-01

    Wave Energy Converters (WEC's) extract wave energy from a limited area, often a single point or line even though the wave energy is generally spread out along the wave crest. By the use of wave reflectors (reflecting walls) the wave energy is effectively focused and increased to approximately 130......-140%. In the paper a procedure for calculating the efficiency and optimizing the geometry of wave reflectors are described, this by use of a 3D boundary element method. The calculations are verified by laboratory experiments and a very good agreement is found. The paper gives estimates of possible power benifit...... for different geometries of the wave reflectors and optimal geometrical design parameters are specified. On this basis inventors of WEC's can evaluate whether a specific WEC possible could benefit from wave reflectors....

  5. Flexible-Robotic Reflector for Aerospace Applications

    Directory of Open Access Journals (Sweden)

    Nir Shvalb

    2015-01-01

    Full Text Available Existing dish based antennas tend to have geometric morphologic distortion in the surface due to drastic thermal changes common in the space environment. In this paper we present a new concept for a dynamic antenna specially designed for communication satellites. The suggested flexible-robotic antenna is based on a dual-reflector structure, where the subreflector has a complex surface shaping robotic mechanism allowing it to fix most of the morphologic errors in the main reflector. We have implemented a set of searching algorithms allowing the hyper redundant robotic subreflector to adapt its surface to the morphologic distortions in the main reflector. The suggested new antenna was constructed and tested in an RF room in which it was able to fix the loss caused by distortion in the main reflector to the original gain in less than an hour.

  6. Handbook of reflector antennas and feed systems v.3 applications of reflectors

    CERN Document Server

    Rao, Sudhakar; Sharma, Satish K

    2013-01-01

    This is the first truly comprehensive and most up-to-date handbook available on modern reflector antennas and feed sources for diversified space and ground applications. There has never been such an all-encompassing reflector handbook in print, and no currently available title offers coverage of such recent research developments. The Handbook consists of three volumes. Volume III focuses on the range of reflector antenna applications, including space, terrestrial, and radar. The intent of this book volume is to provide practical applications and design information on reflector antennas used fo

  7. Easily Assembled Reflector for Solar Concentrators

    Science.gov (United States)

    Bouquet, F. L.; Hasegawa, T.

    1982-01-01

    Reflectors for concentrating solar collectors are assembled quickly and inexpensively by method that employs precontoured supports, plastic film, and adhesive to form a segmented glass mirror. New method is self-focusing, and does not require skilled labor at any stage. Contoured ribs support film and mirror segments of reflector. Nine mirror segments are bonded to sheet. Combined mirror surface closely approximates a spherical surface with a radius of curvature of 36 inches (0.91 m).

  8. Solar central receiver heliostat reflector assembly

    Science.gov (United States)

    Horton, Richard H.; Zdeb, John J.

    1980-01-01

    A heliostat reflector assembly for a solar central receiver system comprises a light-weight, readily assemblable frame which supports a sheet of stretchable reflective material and includes mechanism for selectively applying tension to and positioning the sheet to stretch it to optical flatness. The frame is mounted on and supported by a pipe pedestal assembly that, in turn, is installed in the ground. The frame is controllably driven in a predetermined way by a light-weight drive system so as to be angularly adjustable in both elevation and azimuth to track the sun and efficiently continuously reflect the sun's rays to a focal zone, i.e. central receiver, which forms part of a solar energy utilization system, such as a solar energy fueled electrical power generation system. The frame may include a built-in system for testing for optical flatness of the reflector. The preferable geometric configuration of the reflector is octagonal; however, it may be other shapes, such as hexagonal, pentagonal or square. Several different embodiments of means for tensioning and positioning the reflector to achieve optical flatness are disclosed. The reflector assembly is based on the stretch frame concept which provides an extremely light-weight, simple, low-cost reflector assembly that may be driven for positioning and tracking by a light-weight, inexpensive drive system.

  9. Correlation based rotation-invariant corner detector

    Science.gov (United States)

    Mazzaferri, Javier; Ledesma, Silvia

    2008-04-01

    In this work we introduce a new approach for corner extraction. The method that allows the corner extraction with rotation invariance is composed by a spiral phase function and a binary amplitude. The designed function can be easily implemented as a filter for a Vander Lugt-like optical correlator. A final image obtained with the detector presents intensity peaks in each corner location. Numerical simulation has been performed on a set of synthetic scenes, modulated either in amplitude or phase. Results that show the very good performance of the method are shown.

  10. VT NAD83 Orthophoto Boundaries - corner points

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) RF 5000 NAD83 orthophoto edge lines (4000 x 4000 meter grid cells) were generated automatically from the known corner locations (generated by Gary...

  11. 3Corners of the World / Joosep Sang

    Index Scriptorium Estoniae

    Sang, Joosep

    2009-01-01

    Arvustused : Robert Jürjendal, Petri Kuljuntausta, David Rothenberg. 3Corners of the World. [Tallinn] : Terra Nova Music, 2008. Nadia ja Fragile. Uhke ali. [Tallinn] : Nadia & Fragile, 2008. UMA. Civitas Soli. [Tallinn] : Elwood, 2008. Uutest heliplaatidest

  12. 3Corners of the World / Joosep Sang

    Index Scriptorium Estoniae

    Sang, Joosep

    2009-01-01

    Arvustused : Robert Jürjendal, Petri Kuljuntausta, David Rothenberg. 3Corners of the World. [Tallinn] : Terra Nova Music, 2008. Nadia ja Fragile. Uhke ali. [Tallinn] : Nadia & Fragile, 2008. UMA. Civitas Soli. [Tallinn] : Elwood, 2008. Uutest heliplaatidest

  13. Establishment of a corner turning test capability

    Energy Technology Data Exchange (ETDEWEB)

    Ashcraft, R.W.; West, G.T.

    1978-11-01

    A corner turning test capability has been established. While the test is not suited to be the sole criterion for lot qualification, it provides valuable information regarding explosive behavior near failure. Light enhancement and film record analysis techniques are discussed.

  14. Numerical and Experimental Estimation of Heat Conductivity for Space Antenna Reflector Material

    Directory of Open Access Journals (Sweden)

    Denisov Oleg V.

    2015-01-01

    Full Text Available This article devoted for experimental method of contact heating thin carbon plates. Thermal tests provided non-stationary temperature field with gradient, which is co-directional plane reinforcement in sample. New plane reinforcement thermal conductivity data were obtained within temperature gap between 295 and 375 K. Modern thermal conductivity data could be applied for development projects of space precision antenna reflectors.

  15. Predominance of sperm motion in corners

    Science.gov (United States)

    Nosrati, Reza; Graham, Percival J.; Liu, Qiaozhi; Sinton, David

    2016-05-01

    Sperm migration through the female tract is crucial to fertilization, but the role of the complex and confined structure of the fallopian tube in sperm guidance remains unknown. Here, by confocal imaging microchannels head-on, we distinguish corner- vs. wall- vs. bulk-swimming bull sperm in confined geometries. Corner-swimming dominates with local areal concentrations as high as 200-fold that of the bulk. The relative degree of corner-swimming is strongest in small channels, decreases with increasing channel size, and plateaus for channels above 200 μm. Corner-swimming remains predominant across the physiologically-relevant range of viscosity and pH. Together, boundary-following sperm account for over 95% of the sperm distribution in small rectangular channels, which is similar to the percentage of wall swimmers in circular channels of similar size. We also demonstrate that wall-swimming sperm travel closer to walls in smaller channels (~100 μm), where the opposite wall is within the hydrodynamic interaction length-scale. The corner accumulation effect is more than the superposition of the influence of two walls, and over 5-fold stronger than that of a single wall. These findings suggest that folds and corners are dominant in sperm migration in the narrow (sub-mm) lumen of the fallopian tube and microchannel-based sperm selection devices.

  16. Analysis of ICPP fuel storage rack inner tie and corner tie substructures

    Energy Technology Data Exchange (ETDEWEB)

    Nitzel, M.E.; Rahl, R.G.

    1996-01-01

    Finite element models were developed and analyses performed for the tie plate, inner tie block assembly, and corner tie block assembly of a 25 port fuel rack assembly designed for installation in Pool 1 of Building 666 at the Idaho Chemical Processing Plant. These models were specifically developed to investigate the adequacy of certain welds joining components of the fuel storage rack assembly. The work scope for the task was limited to an investigation of the stress levels in the subject subassemblies when subjected to seismic loads. Structural acceptance criteria used for the elastic calculations performed were as found in the overall rack design report as issued by the rack`s designer, Holtec International. Structural acceptance criteria used for the plastic calculations performed as part of this effort were as defined in Subsection NF and Appendix F of the ASME Boiler & Pressure Vessel Code. The results of the analyses will also apply to the 30 port fuel storage rack design that is also scheduled for installation in Pool 1 of ICPP 666. The results obtained from the analyses performed for this task indicate that the welds joining the inner tie block and corner tie block to the surrounding rack structure meet the acceptance criteria. Further, the structural members (plates and blocks) were also found to be within the allowable stress limits established by the acceptance criteria. The separate analysis performed on the inner tie plate confirmed the structural adequacy for both the inner tie plate, corner tie plate, and tie block bolts. The analysis results verified that the inner tie and corner tie block should be capable of transferring the expected seismic load without structural failure.

  17. The Effect of Booster-Mirror Reflector on the Thermal Performance of a Truncated Pyramid Solar Thermal Cooker

    Directory of Open Access Journals (Sweden)

    I. L. Mohammed

    2014-05-01

    Full Text Available In this paper, the results and analysis of the performance of a truncated pyramid solar thermal cooker under two conditions are presented: booster-mirror reflector covered with black cloth, and booster-mirror reflector exposed to solar radiation. Results of the thermal performance tests show respective stagnation absorber plate temperatures of 145 oC and 137 oC. First/Second Figures of Merit are 0.120/0.346 and 0.125/0.400 respectively. The total heating times of 5.2 kg of water when reflector is covered with black cloth and when exposed to solar radiation are respectively 195 and 190 minutes. There is a nominal time reduction of 5 minutes in favour of the case when reflector is exposed to solar radiation, but in reality the time reduction could be as high as 30.5 minutes. In a similar vein, the difference in pot wall temperatures for corresponding water temperatures during sensible heating could be about 6 oC higher, and at boiling point this could be up to 11.6 oC. Thus, the overall thermal performance of the cooker when reflector is exposed to solar radiation is superior to its thermal performance when reflector is covered with black cloth. This superiority is manifested in improved values of the First and Second Figures of Merit, reduction in the overall heating and boiling times, and higher values of pot wall temperatures.

  18. Near wall flow parameters in the blade end-wall corner region

    Science.gov (United States)

    Bhargava, R. K.; Raj, R.

    The effects of secondary end-wall corner flows on near wall flow parameters in turbomachinary are studied. Important near wall flow parameters such as the wall shear stress vector, the mean wall pressure, the wall pressure fluctuations, and the correlation of the wall pressure fluctuation with the velocity fluctuation in three-dimensional turbulent flows are first experimentally investigated. The blade end-wall corner region is simulated by mounting airfoil section of symmetric blades on both sides of the flat plate with semicircular leading edge. Observed changes in the maximum values of the wall shear stress and its location from the corner line could be associated with the streching and attenuation of the horseshoe vortex. The values of wall pressure fluctuation intensity in the blade end-wall corner region are found to be influenced by the changes of the strength of the horseshoe vortex. The correlation of the wall pressure fluctuation with the velocity fluctuation indicated higher values of correlation coefficient in the inner region as compared to the outer region of the shear layer. The values of wall pressure-velocity correlation coefficient in the blade end-wall corner region also decrease in the streamwise direction while increasing in the presence of favorable and adverse pressure gradients.

  19. Advanced deployable reflectors for communications satellites

    Science.gov (United States)

    Lowe, Elvin; Josephs, Michael; Hedgepeth, John

    1993-02-01

    This paper discusses a concept for a deployable mesh reflector for large spacecraft antennas and the processes used in design, fabrication and testing. A set of overall reflector requirements such as stowed volume, deployed diameter and RF loss derived from system specifications are presented. The development of design and analysis tools to allow parametric studies such as facet size, number of ribs and number of rib segments is discussed. CATIA (a commercially available three-dimensional design and analysis tool) is used to perform kinematic analyses as well as to establish the database to be used by the several groups participating in the development is examined. Results of trade studies performed to reduce cost with minimum risk to product delivery are included. A thirty foot reflector has been built and tested.

  20. New principle for unpolarized wideband reflectors

    CERN Document Server

    Niraula, Manoj

    2016-01-01

    There is immense scientific interest in the properties of resonant thin films embroidered with periodic nanoscale features. This device class possesses considerable innovation potential. Accordingly, we report unpolarized broadband reflectors enabled by a serial arrangement of a pair of polarized subwavelength gratings. Optimized with numerical methods, our elemental gratings consist of a partially-etched crystalline-silicon film on a quartz substrate. The resulting reflectors exhibit extremely wide spectral reflection bands in one polarization. By arranging two such reflectors sequentially with orthogonal periodicities, there results an unpolarized spectral band that exceeds those of the individual polarized bands. In the experiments reported herein, we achieve zero-order reflectance exceeding 97% under unpolarized light incidence over a 500-nm-wide wavelength band in the near-infrared domain. Moreover, the resonant unpolarized broadband accommodates an ultra-high-reflection band spanning ~85 nm and exceedin...

  1. Broadband Multilayered Array Antenna with EBG Reflector

    Directory of Open Access Journals (Sweden)

    P. Chen

    2013-01-01

    Full Text Available Most broadband microstrip antennae are implemented in the form of slot structure or laminate structure. The impedance bandwidth is broadened, but meanwhile, the sidelobe of the directivity pattern and backlobe level are enlarged. A broadband stacked slot coupling microstrip antenna array with EBG structure reflector is proposed. Test results indicate that the proposed reflector structure can effectively improve the directivity pattern of stacked antenna and aperture coupled antenna, promote the front-to-back ratio, and reduce the thickness of the antenna. Therefore, it is more suitable to be applied as an airborne antenna.

  2. Surface roughness estimation of a parabolic reflector

    CERN Document Server

    Casco, Nicolás A

    2010-01-01

    Random surface deviations in a reflector antenna reduce the aperture efficiency. This communication presents a method for estimating the mean surface deviation of a parabolic reflector from a set of measured points. The proposed method takes into account systematic measurement errors, such as the offset between the origin of reference frame and the vertex of the surface, and the misalignment between the surface rotation axis and the measurement axis. The results will be applied to perform corrections to the surface of one of the 30 m diameter radiotelescopes at the Instituto Argentino de Radioastronom\\'ia (IAR).

  3. Handbook of reflector antennas and feed systems v.1 theory and design of reflectors

    CERN Document Server

    Sharma, Satish K; Shafai, Lotfollah

    2013-01-01

    This is the first truly comprehensive and most up-to-date handbook available on modern reflector antennas and feed sources for diversified space and ground applications. There has never been such an all-encompassing reflector handbook in print, and no currently available title offers coverage of such recent research developments. The Handbook consists of three volumes. Volume I provides a unique combination of theoretical underpinnings with design considerations and techniques. The need for knowledge in reflector antennas has grown steadily over the last two decades due to increased use in spa

  4. The geometrical theory of diffraction for axially symmetric reflectors

    DEFF Research Database (Denmark)

    Rusch, W.; Sørensen, O.

    1975-01-01

    The geometrical theory of diffraction (GTD) (cf. [1], for example) may be applied advantageously to many axially symmetric reflector antenna geometries. The material in this communication presents analytical, computational, and experimental results for commonly encountered reflector geometries...

  5. Autocollimation system for measuring angular deformations with reflector designed by quaternionic method

    Science.gov (United States)

    Hoang, Phong V.; Konyakhin, Igor A.

    2017-06-01

    Autocollimators are widely used for angular measurements in instrument-making and the manufacture of elements of optical systems (wedges, prisms, plane-parallel plates) to check their shape parameters (rectilinearity, parallelism and planarity) and retrieve their optical parameters (curvature radii, measure and test their flange focusing). Autocollimator efficiency is due to the high sensitivity of the autocollimation method to minor rotations of the reflecting control element or the controlled surface itself. We consider using quaternions to optimize reflector parameters during autocollimation measurements as compared to the matrix technique. Mathematical model studies have demonstrated that the orthogonal positioning of the two basic unchanged directions of the tetrahedral reflector of the autocollimator is optimal by the criterion of reducing measurement errors where the axis of actual rotation is in a bisecting position towards them. Computer results are presented of running quaternion models that yielded conditions for diminishing measurement errors provided apriori information is available on the position of rotation axis. A practical technique is considered for synthesizing the parameters of the tetrahedral reflector that employs the newly-retrieved relationships. Following the relationships found between the angles of the tetrahedral reflector and the angles of the parameters of its initial orientation, an applied technique was developed to synthesize the control element for autocollimation measurements in case apriori information is available on the axis of actual rotation during monitoring measurements of shaft or pipeline deformation.

  6. Prominent reflector beneath around the segmentation boundary between Tonankai-Nankai earthquake area

    Science.gov (United States)

    Nakanishi, A.; Shimomura, N.; Fujie, G.; Kodaira, S.; Obana, K.; Takahashi, T.; Yamamoto, Y.; Yamashita, M.; Takahashi, N.; Kaneda, Y.; Mochizuki, K.; Kato, A.; Iidaka, T.; Kurashimo, E.; Shinohara, M.; Takeda, T.; Shiomi, K.

    2013-12-01

    In the Nankai Trough subduction seismogenic zone, the Nankai and Tonankai earthquakes had often occurred simultaneously, and caused a great event. In most cases, first break of such large events of Nankai Trough usually begins from southwest off the Kii Peninsula so far. The idea of split Philippine Sea plate between the Kii Peninsula and the Shikoku Island, which explains seismicity, tectonic background, receiver function image and historical plate motion, was previously suggested. Moreover, between the Kii Peninsula and the Shikoku Island, there is a gap of deep low-frequency events observed in the belt-like zone along the strike of the subducting Philippine Sea plate. In 2010 and 2011, we conducted the large-scale high-resolution wide-angle and reflection (MCS) seismic study, and long-term observation from off Shikoku and Kii Peninsula. Marine active source seismic data have been acquired along grid two-dimensional profiles having the total length of ~800km/year. A three-dimensional seismic tomography using active and passive seismic data observed both land and ocean bottom stations have been also performed. From those data, we found a possible prominent reflector imaged in the offshore side in the Kii channel at the depth of ~18km. The velocity just beneath the reflector cannot be determined due to the lack of ray paths. Based of the amplitude information, we interpret the reflector as the forearc Moho based on the velocity gap (from ~6.4km/s to ~7.4km/s). However, the reflector is shallower than the forearc Moho of other area along the Nankai Trough. Similar reflectors are recognized along other seismic profiles around the Kii channel. In this presentation, we will show the result of structure analysis to understand the peculiar structure including the prominent reflector around the Kii channel. Relation between the structure and the existence of the segmentation of the Nankai megathrust earthquake or seismic gap of the deep low-frequency events will be also

  7. Probabilistic Parsing Using Left Corner Language Models

    CERN Document Server

    Manning, C D; Manning, Christopher D.; Carpenter, Bob

    1997-01-01

    We introduce a novel parser based on a probabilistic version of a left-corner parser. The left-corner strategy is attractive because rule probabilities can be conditioned on both top-down goals and bottom-up derivations. We develop the underlying theory and explain how a grammar can be induced from analyzed data. We show that the left-corner approach provides an advantage over simple top-down probabilistic context-free grammars in parsing the Wall Street Journal using a grammar induced from the Penn Treebank. We also conclude that the Penn Treebank provides a fairly weak testbed due to the flatness of its bracketings and to the obvious overgeneration and undergeneration of its induced grammar.

  8. Vertical reflector for bifacial PV-panels

    DEFF Research Database (Denmark)

    Jakobsen, Michael Linde; Thorsteinsson, Sune; Poulsen, Peter Behrensdorff;

    2016-01-01

    Bifacial solar modules offer an interesting price/performance ratio, and much work has been focused on directing the ground albedo to the back of the solar cells. In this work we design and develop a reflector for a vertical bifacial panel, with the objective to optimize the energy harvest...

  9. Collapsible structure for an antenna reflector

    Science.gov (United States)

    Trubert, M. R. (Inventor)

    1973-01-01

    A collapsible support for an antenna reflector for use in supporting spacecraft antennas is described. The support has a regid base and a number of struts which are pivoted at the base. The deployment of the struts and their final configuration for supporting the antenna are illustrated.

  10. Hybrid grating reflectors: Origin of ultrabroad stopband

    DEFF Research Database (Denmark)

    Park, Gyeong Cheol; Taghizadeh, Alireza; Chung, Il-Sug

    2016-01-01

    Hybrid grating (HG) reflectors with a high-refractive-index cap layer added onto a high contrast grating (HCG) provide a high reflectance close to 100% over a broader wavelength range than HCGs. The combination of a cap layer and a grating layer brings a strong Fabry-Perot (FP) resonance as well...

  11. Vertical reflector for bifacial PV-panels

    DEFF Research Database (Denmark)

    Jakobsen, Michael Linde; Thorsteinsson, Sune; Poulsen, Peter Behrensdorff

    2016-01-01

    Bifacial solar modules offer an interesting price/performance ratio, and much work has been focused on directing the ground albedo to the back of the solar cells. In this work we design and develop a reflector for a vertical bifacial panel, with the objective to optimize the energy harvest...

  12. Reflector Surface Modelling : A European Collaboration

    NARCIS (Netherlands)

    Albani, M; Balling, P.; Ettorre, M.; Gerini, G.; Maci, S.; Pontoppidan, K.; Sipus, Z.; Sjöberg, D.; Vecchi, G.; Vipiana, F.

    2007-01-01

    The topic of this paper is the work carried out in Work Package 2.3-2 of the EU network ACE. This work package is concerned with the modelling of the surfaces of modern reflector antennas. In particular the problems associated with homogenisation of periodic structures are described together with an

  13. Development of NRU reflector wall inspection system

    Energy Technology Data Exchange (ETDEWEB)

    Lumsden, R.H.; Luloff, B.V.; Zahn, N.; Simpson, N., E-mail: lumsdenr@aecl.ca [Atomic Energy of Canada Limited, Chalk River, Ontario (Canada)

    2013-06-15

    In 2009 May, the National Research Universal (NRU) calandria leaked. During the next year, the calandria was inspected with six new Non-Destructive Evaluation (NDE) techniques to determine the extent of the corrosion, repaired, and finally the repair was inspected with four additional new NDE techniques before the reactor was returned to service. The calandria is surrounded by a light-water reflector vessel fabricated from the same material as the calandria vessel. Concerns that the same corrosion mechanism had damaged the reflector vessel led to the development of a system to inspect the full circumference of the reflector wall for corrosion damage. The inspection region could only be accessed through 64 mm diameter ports, was 10 m below the port, and had to be inspected from the corroded surface. The ultrasonic technique was designed to produce a closely spaced wall thickness (WT) grid over an area of approximately 5 m2 on the corroded surface using a very small probe holder. This paper describes the Reflector Wall Inspection (RWI) development project and the system that resulted. (author)

  14. Multimode Analysis of Bragg Reflectors for Cyclotron Maser Applications

    Science.gov (United States)

    1991-02-16

    exponentially with distance in the reflector. The spatial dependance of the TMI I mode is oscillatory. Figure 3 shows the frequency dependence of the...mode reflector for a CARM oscillator resonator. Figure 4 shows the frequency dependance of the reflection and mode conversion in the reflector. In order

  15. A New Reflector Antenna Based on the Fresnel Principle

    Institute of Scientific and Technical Information of China (English)

    DUHui-ping

    2001-01-01

    A new type of reflector antenne is proposed, which applies the 1-D Fresnel zone phase correction to the classical parabolic cylindrical reflector, providing an alternative to the dval parabolic cylindrical ones discussed by Sanad and Shafai[1].The focusing characteristics of the new reflector are analyzed by physical optics method, and numerical results are illustrated to evaluate its applicability.

  16. A New Reflector Antenna Based on the Fresnel Principle

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A new type of reflector antenne is proposed, which applies the 1-D Fresnel zone phase correction to the classical parabolic cylindrical reflector, providing an alternative to the dual parabolic cylindrical ones discussed by Sanad and Shafai[1]. The focusing characteristics of the new reflector are analyzed by physical optics method, and numerical results are illustrated to evaluate its applicability.

  17. Spring-forward in composite plate elements

    NARCIS (Netherlands)

    Wijskamp, Sebastiaan; Lamers, E.A.D.; Akkerman, Remko; Banabic, D.

    2005-01-01

    Spring-forward is a distortion of corner sections in continuous fibre reinforced composite products. The linear thermoelastic prediction for the spring-forward of single curved geometries is incorporated in a FE formulation for plate elements in order to simulate the spring-forward of doubly curved

  18. Spring-forward in composite plate elements

    NARCIS (Netherlands)

    Wijskamp, S.; Lamers, E.A.D.; Akkerman, R.

    2005-01-01

    Spring-forward is a distortion of corner sections in continuous fibre reinforced composite products. The linear thermoelastic prediction for the spring-forward of single curved geometries is incorporated in a FE formulation for plate elements in order to simulate the spring-forward of doubly curved

  19. APPLICATION OF QUATERNIONS FOR REFLECTOR PARAMETER

    Directory of Open Access Journals (Sweden)

    I. A. Konyakhin

    2016-09-01

    Full Text Available Subject of Research. The paper deals with application of quaternions for optimization of reflector parameters at autocollimation measurements in comparison with a matrix method. Computer-based results on the quaternionic models are presented that have given the possibility to determine conditions of measurement error reduction in view of apriori information on the rotation axis position. The practical synthesis technique for tetrahedron reflector parameters using found ratios is considered. Method. Originally, received conditions for reduction of autocollimation system measurement error are determined with the use of a matrix method for definition of an angular object position as a set of three equivalent consecutive turns about coordinate axes. At realization of these conditions the numerous recalculation of orientation parameters between various systems of coordinates is necessary that increases complexity and reduces resulting accuracy of autocollimation system at practical measurements. The method of quaternions gives the possibility to analyze the change of an absolute angular position in space, thus, there are conditions of accuracy increase regardless of the used systems of coordinates. Main Results. Researches on the mathematical model have shown, that the orthogonal arrangement of two basic constant directions for autocollimator tetrahedron reflector is optimal with respect to criterion of measurement error reduction at bisection arrangement of actual turn axis against them. Practical Relevance. On the basis of the found ratios between tetrahedron reflector angles and angles of its initial orientation parameters we have developed a practical method of reflector synthesis for autocollimation measurements in case of apriori information on an actual turn axis at monitoring measurements of the shaft or pipelines deformations.

  20. Universal corner entanglement from twist operators

    CERN Document Server

    Bueno, Pablo; Witczak-Krempa, William

    2015-01-01

    The entanglement entropy in three-dimensional conformal field theories (CFTs) receives a logarithmic contribution characterized by a regulator-independent function $a(\\theta)$ when the entangling surface contains a sharp corner with opening angle $\\theta$. In the limit of a smooth surface ($\\theta\\rightarrow\\pi$), this corner contribution vanishes as $a(\\theta)=\\sigma\\,(\\theta-\\pi)^2$. In arXiv:1505.04804, we provided evidence for the conjecture that for any $d=3$ CFT, this corner coefficient $\\sigma$ is determined by $C_T$, the coefficient appearing in the two-point function of the stress tensor. Here, we argue that this is a particular instance of a much more general relation connecting the analogous corner coefficient $\\sigma_n$ appearing in the $n$th R\\'enyi entropy and the scaling dimension $h_n$ of the corresponding twist operator. In particular, we find the simple relation $h_n/\\sigma_n=(n-1)\\pi$. We show how it reduces to our previous result as $n\\rightarrow 1$, and explicitly check its validity for f...

  1. Delamination of Compressed Thin Layers at Corners

    DEFF Research Database (Denmark)

    Sørensen, Kim D.; Jensen, Henrik Myhre; Clausen, Johan

    2008-01-01

    An analysis of delamination for a thin elastic layer under compression, attached to a substrate at a corner is carried out. The analysis is performed by combining results from interface fracture mechanics and the theory of thin shells. In contrast with earlier results for delamination on a flat...... layers, Fracture mechanics, Crack closure, Steady state crack propagation....

  2. Delamination of Compressed Thin Layers at Corners

    DEFF Research Database (Denmark)

    Sørensen, Kim Dalsten; Jensen, Henrik Myhre; Clausen, Johan

    2008-01-01

    An analysis of delamination for a thin elastic layer under compression, attached to a substrate at a corner is carried out. The analysis is performed by combining results from interface fracture mechanics and the theory of thin shells. In contrast with earlier results for delamination on a flat...

  3. Corner diffraction coefficients for the quarter plane

    DEFF Research Database (Denmark)

    Hansen, Thorkild B.

    1991-01-01

    The current near a right-angled corner on a perfectly conducting flat scatterer illuminated by a plane wave is expressed as a sum of three currents. The first is the physical optics current, which describes the surface effect. The second is the fringe wave current, which is found from the half-pl...

  4. Delamination of Compressed thin Layers at Corners

    DEFF Research Database (Denmark)

    Clausen, Johan; Jensen, Henrik Myhre; Sørensen, Kim Dalsten

    2008-01-01

    An analysis of delamination for a thin elastic film, attached to a substrate with a corner, is carried out. The film is in compression and the analysis is performed by combining results from fracture mechanics and the theory of thin shells. The results show a very strong dependency of the angle...

  5. FNS Research Corner: Summary of Research

    Science.gov (United States)

    Berman, Danielle; Burdg, Jinee

    2017-01-01

    The FNS Research Corner provides a continuing series to summarize recently completed and current research conducted by the U.S. Department of Agriculture's Food and Nutrition Service (FNS) in the area of child nutrition. For further information, contact the Office of Policy Support (OPS) at (703) 305-2117. Links to published studies and reports as…

  6. Composition: Around Corners (2006-08)

    DEFF Research Database (Denmark)

    Bergstrøm-Nielsen, Carl

    2010-01-01

    Around Corners is an open composition to be realised by improvising musicians. See more about my composition practise in the entry "Composition - General Introduction". Caution: streaming the sound/video files will in some cases only provide a few minutes' sample, or the visuals will not appear...

  7. Homology Parameters for Large Axisymmetric Shaped Dual-Reflector Antennas

    Science.gov (United States)

    Ban, You; Duan, Baoyan; Wang, Congsi; Wang, Wei; Feng, Shufei; Xiang, Binbin

    2017-05-01

    We extend the concept of best-fitting paraboloids for large single and dual reflectors with conic-section surfaces to best-fit shaped surface for large dual reflectors shaped for uniform amplitude distribution. The point focus of the paraboloidal main reflector is replaced by focal lines for the main reflector and the primary subreflector focus, whereas the secondary subreflector point focus at the feed is kept. The reflector surfaces are shaped, and all rays from the main-reflector aperture to the feed meet an equal-path-length condition. This condition may be represented by a set of "homology parameters" determined by a least-squares method. Finally, we calculate the homology parameters and the root mean square of surface errors for an 8-m dual-reflector system including gravity effects for the antenna pointed toward zenith and the horizon.

  8. Silicon reflectors for external cavity lasers based on ring resonators

    Science.gov (United States)

    Wang, Chao; Li, Xia; Jin, Hao; Yu, Hui; Yang, Jianyi; Jiang, Xiaoqing

    2017-01-01

    We propose and experimentally investigate types of silicon ring reflectors on Silicon-On-Insulator (SOI) platform. These reflectors are used for realizing the silicon hybrid external cavity lasers. A suspended edge coupler is used to connect the reflective semiconductor optical amplifier (RSOA) chip and the reflectors. The properties of the reflectors and the hybrid external cavity lasers with these reflectors are illustrated. The experimental results show that all of those reflectors have a high reflectivity and the highest reflectivity can up to be 95%. The lowest insertion loss can be as low as 0.4 dB. The output power of the hybrid external cavity lasers with these reflectors can reach mW magnitude and the highest output power is 6.1 mW. Over 30 dB side mode suppression ratio is obtained.

  9. Locking Corners Speed Solar-Array Frame Assembly

    Science.gov (United States)

    Olah, S.; Sampson, W. J.

    1984-01-01

    Mitered corners of solar-array frames joined together by single angle brace and two springs. Locking corner braces and mating frame members pushed together by hand or assembled automatically. Fastening system used to assemble window screens and picture frames.

  10. Ellisoidal reflector for measuring otoacoustic emissions

    DEFF Research Database (Denmark)

    Epp, Bastian; Heiskanen, Vesa; Pulkki, Ville Topias

    2016-01-01

    Otoacoustic emissions (OAEs) are low-intensity sounds present in the ear canal, generated by mechanical processing in the cochlear in the inner ear. OAEs provide a noninvasive technique to sense the mechanical processing of sound in the inner ear. These signals are commonly measured by placing......, and especially SOAE at these low frequencies. In addition, blocking of the ear canal changes the impedance of the middle ear, potentially changing the transmission of acoustical energy from the inner ear to the ear canal, hampering the interpretation of the data in terms of normal listening conditions with open...... ear canal. This study presents the design and evaluation of a truncated prolate ellipsoidal reflector in combination with a large-diaphragm low-noise microphone to measure OAEs in the open ear canal of human listeners. The reflector was designed to gain information about BM processing at low...

  11. Numerical simulation of residual stresses at holes near edges and corners in tempered glass: A parametric study

    DEFF Research Database (Denmark)

    Pourmoghaddam, Navid; Nielsen, Jens Henrik; Schneider, Jens

    2016-01-01

    This work presents 3D results of the thermal tempering simulation by the Finite Element Method in order to calculate the residual stresses in the area of the holes near edges and corners of a tem-pered glass plate. A viscoelastic material behavior of the glass is considered for the tempering...... the influence of the hole and edge distances on the minimal residual compressive stress-es at holes after the tempering process. The residual stresses in the area of the holes are calculat-ed varying the following parameters: the hole diameter, the plate thickness and the interaction between holes and edges...... and corners. Furthermore a comparison between the minimal residual stresses at holes and the residual stresses at other areas of the glass plate (edge, chamfer and far-field stresses) is made....

  12. Simulation of parabolic reflectors for ultraviolet phototherapy

    Science.gov (United States)

    Grimes, David Robert

    2016-08-01

    Ultraviolet (UVR) phototherapy is widely used to treat an array of skin conditions, including psoriasis, eczema and vitiligo. For such interventions, a quantified dose is vital if the treatment is to be both biologically effective and to avoid the detrimental effects of over-dosing. As dose is absorbed at surface level, the orientation of patient site with respect to the UVR lamps modulates effective dose. Previous investigations have modelled this behaviour, and examined the impact of shaped anodized aluminium reflectors typically placed around lamps in phototherapy cabins. These mirrors are effective but tend to yield complex patterns of reflection around the cabin which can result in substantial dose inhomogeneity. There has been some speculation over whether using the reflective property of parabolic mirrors might improve dose delivery or homogeneity through the treatment cabin. In this work, the effects of parabolic mirrors are simulated and compared with standard shaped mirrors. Simulation results strongly suggest that parabolic reflectors reduce total irradiance relative to standard shaped reflectors, and have a negligible impact on dose homogeneity.

  13. Simulation of parabolic reflectors for ultraviolet phototherapy.

    Science.gov (United States)

    Robert Grimes, David

    2016-08-21

    Ultraviolet (UVR) phototherapy is widely used to treat an array of skin conditions, including psoriasis, eczema and vitiligo. For such interventions, a quantified dose is vital if the treatment is to be both biologically effective and to avoid the detrimental effects of over-dosing. As dose is absorbed at surface level, the orientation of patient site with respect to the UVR lamps modulates effective dose. Previous investigations have modelled this behaviour, and examined the impact of shaped anodized aluminium reflectors typically placed around lamps in phototherapy cabins. These mirrors are effective but tend to yield complex patterns of reflection around the cabin which can result in substantial dose inhomogeneity. There has been some speculation over whether using the reflective property of parabolic mirrors might improve dose delivery or homogeneity through the treatment cabin. In this work, the effects of parabolic mirrors are simulated and compared with standard shaped mirrors. Simulation results strongly suggest that parabolic reflectors reduce total irradiance relative to standard shaped reflectors, and have a negligible impact on dose homogeneity.

  14. 49 CFR 231.29 - Road locomotives with corner stairways.

    Science.gov (United States)

    2010-10-01

    ... ADMINISTRATION, DEPARTMENT OF TRANSPORTATION RAILROAD SAFETY APPLIANCE STANDARDS § 231.29 Road locomotives with corner stairways. After September 30, 1979, road locomotives with corner stairway openings must be... 49 Transportation 4 2010-10-01 2010-10-01 false Road locomotives with corner stairways....

  15. Corner Detection Based on Human Visual System Model

    Institute of Scientific and Technical Information of China (English)

    LU Xiaoguang; ZHOU Jie

    2001-01-01

    Corners are useful features in computer vision tasks.In this paper,we present an algorithm for corner detection based on a human visual system model.Experimental results proved that it ismore effective than conventional corner detector under uneven illumination conditions.

  16. The exact evaluation of the corner-to-corner resistance of an M x N resistor network: asymptotic expansion

    Energy Technology Data Exchange (ETDEWEB)

    Essam, J W [Department of Mathematics, Royal Holloway College, University of London, Egham, Surrey TW20 0EX (United Kingdom); Wu, F Y [Department of Physics, Northeastern University, Boston, MA 02115 (United States)

    2009-01-16

    We study the corner-to-corner resistance of an M x N resistor network with resistors r and s in the two spatial directions and obtain an asymptotic expansion of its exact expression for large M and N.

  17. Edge and corner detection by color invariants

    Science.gov (United States)

    Chu, Jun; Miao, Jun; Zhang, Guimei; Wang, Lu

    2013-02-01

    Gray-based features are widely used in computer vision applications, while image color is a very important source, which can provide more feature information. To fully exploit color data, a color saturation invariant based on dichromatic reflection model is first constructed. The invariant is an object reflectance property independent of viewpoint and illumination direction. The saturation invariant is then synthesized with existing hue invariant to detect edge and corner features in color image. Experiments show that the detection method proposed here can more effectively tap into color information and achieve true target features due to its lower sensitivity to shadow, shading and highlight. Moreover, when comparing with many other existing edges and corners detecting methods, experimental results demonstrate that the proposed method performs better in detection accurate and effective.

  18. Modeling interconnect corners under double patterning misalignment

    Science.gov (United States)

    Hyun, Daijoon; Shin, Youngsoo

    2016-03-01

    Publisher's Note: This paper, originally published on March 16th, was replaced with a corrected/revised version on March 28th. If you downloaded the original PDF but are unable to access the revision, please contact SPIE Digital Library Customer Service for assistance. Interconnect corners should accurately reflect the effect of misalingment in LELE double patterning process. Misalignment is usually considered separately from interconnect structure variations; this incurs too much pessimism and fails to reflect a large increase in total capacitance for asymmetric interconnect structure. We model interconnect corners by taking account of misalignment in conjunction with interconnect structure variations; we also characterize misalignment effect more accurately by handling metal pitch at both sides of a target metal independently. Identifying metal space at both sides of a target metal.

  19. Universal corner contributions to entanglement negativity

    CERN Document Server

    Kim, Keun-Young; Pang, Da-Wei

    2016-01-01

    It has been realised that corners in entangling surfaces can induce new universal contributions to the entanglement entropy and R\\'enyi entropy. In this paper we study universal corner contributions to entanglement negativity in three- and four-dimensional CFTs using both field theory and holographic techniques. We focus on the quantity $\\chi$ defined by the ratio of the universal part of the entanglement negativity over that of the entanglement entropy, which may characterise the amount of distillable entanglement. We find that for most of the examples $\\chi$ takes bigger values for singular entangling regions, which may suggest increase in distillable entanglement. However, there also exist counterexamples where distillable entanglement decreases for singular surfaces. We also explore the behaviour of $\\chi$ as the coupling varies and observe that for singular entangling surfaces, the amount of distillable entanglement is mostly largest for free theories, while counterexample exists for free Dirac fermion i...

  20. Metal nanoparticles with sharp corners: Universal properties of plasmon resonances

    CERN Document Server

    Sturman, B; Gorkunov, M

    2012-01-01

    We predict the simultaneous occurrence of two fundamental phenomena for metal nanoparticles possessing sharp corners: First, the main plasmonic dipolar mode experiences strong red shift with decreasing corner curvature radius; its resonant frequency is controlled by the apex angle of the corner and the normalized (to the particle size) corner curvature. Second, the split-off plasmonic mode experiences strong localization at the corners. Altogether, this paves the way for tailoring of metal nano-structures providing wavelength-selective excitation of localized plasmons and a strong near-field enhancement of linear and nonlinear optical phenomena.

  1. Brilliant Corners: Approaches to Jazz and Comics

    Directory of Open Access Journals (Sweden)

    Nicolas Pillai

    2016-08-01

    Full Text Available The call for papers Brilliant Corners: Approaches to Jazz and Comics was published on 30 July 2015. In it, the editors made a public invitation for scholarship that proposed meeting points between the disciplines of jazz studies and comics studies. This editorial discusses the motivations for the collection, the editorial methodology, and the research articles included. Finally, the editors suggest some areas in which jazz studies and comics scholarship might address under-researched and fertile topics.

  2. Sharp contact corners, fretting and cracks

    Directory of Open Access Journals (Sweden)

    D. A. Hills

    2013-07-01

    Full Text Available Contacts with sharp edges subject to oscillatory loading are likely to nucleate cracks from the corners, if the loading is sufficiently severe. To a first approximation, the corners behave like notches, where the local elastic behaviour is relieved by plasticity, and which in turn causes irreversibilities that give rise to crack nucleation, but also by frictional slip. One question we aim to answer here is; when is the frictional slip enveloped by plastic slip, so that the corner is effectively a notch in a monolithic material? We do this by employing the classical Williams asymptotic solution to model the contact corner, and, in doing so, we render the solution completely general in the sense that it is independent of the overall geometry of the components. We then re-define the independent parameters describing the properties of the Williams solution by using the inherent length scale, a procedure that was described at the first IJFatigue and FFEMS joint workshop [1]. By proceeding in this way, we can provide a self-contained solution that can be ‘pasted in’ to any complete contact problem, and hence the likelihood of crack nucleation, and the circumstances under which it might occur, can be classified. Further, this reformulation of Williams' solution provides a clear means of obtaining the strength (defined by crack nucleation conditions of a material pair with a particular contact angle. This means that the results from a test carried out using a laboratory specimen may easily be carried over to any complicated contact problem found in engineering practice, and a mechanical test of the prototypical geometry, which may often be quite difficult, is avoided.

  3. Capillary Flow in an Interior Corner

    Science.gov (United States)

    Weislogel, Mark Milton

    1996-01-01

    The design of fluids management processes in the low-gravity environment of space requires an accurate model and description of capillarity-controlled flow in containers of irregular geometry. Here we consider the capillary rise of a fluid along an interior corner of a container following a rapid reduction in gravity. The analytical portion of the work presents an asymptotic formulation in the limit of a slender fluid column, slight surface curvature along the corner, small inertia, and low gravity. New similarity solutions are found and a list of closed form expressions is provided for flow rate and column length. In particular, it is found that the flow is proportional to t(exp 1/2) for a constant height boundary condition, t(exp 2/5) for a spreading drop, and t(exp 3/5) for constant flow. In the experimental portion of the work, measurements from a 2.2s drop tower are reported. An extensive data set, collected over a previously unexplored range of flow parameters, includes estimates of repeatability and accuracy, the role of inertia and column slenderness, and the effects of corner angle, container geometry, and fluid properties. Comprehensive comparisons are made which illustrate the applicability of the analytic results to low-g fluid systems design.

  4. Optimization of a clamped plate silencer.

    Science.gov (United States)

    Wang, Chunqi; Han, Jun; Huang, Lixi

    2007-02-01

    A previous theoretical study [L. Huang, J. Acoust. Soc. Am. 119, 2628-2638 (2006)] shows that, in a duct, a simply supported plate covering a side-branch rigid cavity can function effectively as a wave reflector over a broad range of low to medium frequencies. In this study, analytical formulation is extended to the boundary condition of clamped plate, which is easier to implement in practice. The theoretical model is tested experimentally using balsawood, which has a very high stiffness to mass ratio. The spectral peaks and shapes of the measured TL are in agreement with those calculated theoretically, attempts are also made to account for the considerable sound absorption in the rig. Further numerical studies based on the validated model show that, for a uniform plate, the optimal stopband is narrower and the lower band limit is worse than that of the simply supported configuration. However, a wave reflector using nonuniform, clamped plates with thinner ends out-performs the simply supported configuration in every aspect. Analyses show that the improvement is attributed to the increased acoustic radiation efficiency over the bulk length of the nonuniform plate, which behaves more like a rigid plate.

  5. Properties of wideband resonant reflectors under fully conical light incidence

    Science.gov (United States)

    Ko, Yeong Hwan; Niraula, Manoj; Lee, Kyu Jin; Magnusson, Robert

    2016-03-01

    Applying numerical modeling coupled with experiments, we investigate the properties of wideband resonant reflectors under fully conical light incidence. We show that the wave vectors pertinent to resonant first-order diffraction under fully conical mounting vary less with incident angle than those associated with reflectors in classical mounting. Therefore, as the evanescent diffracted waves drive the leaky modes responsible for the resonance effects, fully-conical mounting imbues reflectors with larger angular tolerance than their classical counterparts. We quantify the angular-spectral performance of representative resonant wideband reflectors in conic and classic mounts by numerical calculations with improved spectra found for fully conic incidence. Moreover, these predictions are verified experimentally for wideband reflectors fashioned in crystalline and amorphous silicon in distinct spectral regions spanning the 1200-1600-nm and 1600-2400-nm spectral bands. These results will be useful in various applications demanding wideband reflectors that are efficient and materially sparse.

  6. Preliminary design of large reflectors with flat facets

    Science.gov (United States)

    Agrawal, P. K.; Anderson, M. S.; Card, M. F.

    1981-01-01

    A concept for approximating curved antenna surfaces using flat facets is discussed. A preliminary design technique for determining the size of the reflector surface facets necessary to meet antenna surface accuracy requirements is presented. A proposed large microwave radiometer satellite (MRS) is selected as an application, and the far-field electromagnetic response of a faceted reflector surface is compared with that from a spherical reflector surface.

  7. Ray Tracing Modelling of Reflector for Vertical Bifacial Panel

    DEFF Research Database (Denmark)

    Jakobsen, Michael Linde; Thorsteinsson, Sune; Poulsen, Peter Behrensdorff

    2016-01-01

    Bifacial solar panels have recently become a new attractive building block for PV systems. In this work we propose a reflector system for a vertical bifacial panel, and use ray tracing modelling to model the performance. Particularly, we investigate the impact of the reflector volume being filled...... with a refractive medium, and shows the refractive medium improves the reflector performance since it directs almost all the light incident on the incoming plane into the PV panel....

  8. Inflatable Reflector For Solar Power And Radio Communication

    Science.gov (United States)

    Sercel, Joel; Gilchriest, Carl; Ewell, Rich; Herman, Martin; Rascoe, Daniel L.; Nesmith, Bill J.

    1995-01-01

    Report proposes installation of lightweight inflatable reflector structure aboard spacecraft required to both derive power from sunlight and communicate with Earth by radio when apparent position of Earth is at manageably small angle from line of sight to Sun. Structure contains large-aperture paraboloidal reflector aimed toward Sun and concentrates sunlight onto photovoltaic power converter and acts as main reflector of spacecraft radio-communication system.

  9. Thermal distortion analysis of a deployable parabolic reflector

    Science.gov (United States)

    Bruck, L. R.; Honeycutt, G. H.

    1973-01-01

    A thermal distortion analysis of the ATS-6 Satellite parabolic reflector was performed using NASTRAN level 15.1. The same NASTRAN finite element method was used to conduct a one g static load analysis and a dynamic analysis of the reflector. In addition, a parametric study was made to determine which parameters had the greatest effect on the thermal distortions. The method used to model the construction of the reflector is described and the results of the analyses are presented.

  10. Properties of wideband resonant reflectors under fully conical light incidence

    OpenAIRE

    Ko, Yeong Hwan; Niraula, Manoj; Lee, Kyu Jin; Magnusson, Robert

    2016-01-01

    Applying numerical modeling coupled with experiments, we investigate the properties of wideband resonant reflectors under fully conical light incidence. We show that the wave vectors pertinent to resonant first-order diffraction under fully conical mounting vary less with incident angle than those associated with reflectors in classical mounting. Therefore, as the evanescent diffracted waves drive the leaky modes responsible for the resonance effects, fully-conical mounting imbues reflectors ...

  11. The Long-Term Outcome of Four-Corner Fusion

    Science.gov (United States)

    Trail, Ian A.; Murali, Raj; Stanley, John Knowles; Hayton, Michael John; Talwalkar, Sumedh; Sreekumar, Ramankutty; Birch, Ann

    2015-01-01

    Introduction Four-corner arthrodesis with excision of the scaphoid is an accepted salvage procedure for scapholunate advanced collapse (SLAC) and scaphoid nonunion advanced collapse (SNAC) and has been performed in our unit for over 20 years. We have undertaken a retrospective review of 116 of these procedures performed in 110 patients between 1992 and 2009. Fifty-eight patients attended for a clinical evaluation, and 29 responded by postal questionnaire. Methods The surgical technique undertaken was standard. That is, through a dorsal approach the scaphoid and tip of the radial styloid were excised. The capitate, lunate, triquetrum, and hamate articular surfaces were then prepared down to bleeding bone. Bone grafts from the scaphoid and radial styloid were then inserted and fixation undertaken. For the latter, various methods were used, including Kirschner (K-)wires, staples, bone screws, but predominantly the Spider plate (Integra Life Sciences, USA). Thereafter the wrist was immobilized for a minimum period of 2 weeks prior to rehabilitation. Results Follow-up was done at a mean of 9 years and 4 months (range 3–19 years). All patients reported a significant improvement in pain relief and ∼50% of flexion extension, although only 40% of radioulnar deviation. Grip strength was again ∼50% of the contralateral side. Most patients reported a significant improvement in function with 87% returning to work. In addition, radiologic evaluation identified 28 patients (31%) who demonstrated ongoing signs of nonunion, particularly around the triquetrum. Fourteen of these (15%) underwent a further procedure, generally with success. Finally, none of the patients demonstrated any arthritic changes in the lunate fossa on follow-up X-ray, and all secondary procedures were undertaken within 2 years of the primary. Discussion This research has demonstrated that four-corner fusion fixed with a circular plate can result in a satisfactory outcome with a reduction in pain

  12. Lightweight Thermally Stable Multi-Meter Aperture Submillimeter Reflectors Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Future astrophysics missions will require lightweight, thermally stable, submillimeter reflectors in sizes of 4m and greater. To date, graphite fiber reinforced...

  13. Jacobi-Bessel analysis of reflector antennas with elliptical apertures

    Science.gov (United States)

    Rahmat-Samii, Yahya

    1987-01-01

    Although many reflector antennas possess circular projected apertures, there are recent satellite and ground antenna applications for which it is desirable to employ reflectors with elliptical apertures. Here a modification of the Jacobi-Bessel expansion is presented for the diffraction analysis of reflectors with elliptical apertures. A comparative study is also performed between this modified Jacobi-Bessel algorithm and the one which uses the Jacobi-Bessel expansion over a circumscribing circular region. Numerical results are presented for offset reflectors with elliptical and circular apertures and the improved convergence properties of the modified algorithm are highlighted.

  14. Solgel grating waveguides for distributed Bragg reflector lasers.

    Science.gov (United States)

    Fardad, M A; Luo, H; Beregovski, Y; Fallahi, M

    1999-04-01

    Solgel grating waveguides and their application to the fabrication of external-cavity distributed Bragg reflector (DBR) lasers are demonstrated. A new composition of aluminosilicate material is developed for the fabrication of single-mode waveguides and Bragg reflectors. An average loss of <0.2 dB/cm is measured in the single-mode waveguides at 1550 nm. The reflectors show filtering greater than 97% near 1530 nm, with a bandwidth of ~0.6 nm . The Bragg reflectors are used as feedback resonators for DBR lasers. Single-mode lasing with a sidemode suppression of better than 25 dB is demonstrated.

  15. Design and Optimization of a Compact Wideband Hat-Fed Reflector Antenna for Satellite Communications

    Science.gov (United States)

    Geterud, Erik G.; Yang, Jian; Ostling, Tomas; Bergmark, Pontus

    2013-01-01

    We present a new design of the hat-fed reflector antenna for satellite communications, where a low reflection coefficient, high gain, low sidelobes and low cross-polar level are required over a wide frequency band. The hat feed has been optimized by using the Genetic Algorithm through a commercial FDTD solver, QuickWave-V2D, together with an own developed optimization code. The Gaussian vertex plate has been applied at the center of the reflector in order to improve the reflection coefficient and reduce the far-out sidelobes. A parabolic reflector with a ring-shaped focus has been designed for obtaining nearly 100% phase efficiency. The antenna's reflection coefficient is below -17 dB and the radiation patterns satisfy the M-x standard co- and cross-polar sidelobe envelopes for satellite ground stations over a bandwidth of 30%. A low-cost monolayer radome has been designed for the antenna with satisfactory performance. The simulations have been verified by measurements; both of them are presented in the paper.

  16. Bright color reflective displays with interlayer reflectors

    Science.gov (United States)

    Kitson, Stephen; Geisow, Adrian; Rudin, John; Taphouse, Tim

    2011-08-01

    A good solution to the reflective display of color has been a major challenge for the display industry, with very limited color gamuts demonstrated to date. Conventional side-by-side red, green and blue color filters waste two-thirds of incident light. The alternative of stacking cyan, magenta and yellow layers is also challenging -- a 10% loss per layer compounds to nearly 50% overall. Here we demonstrate an architecture that interleaves absorbing-to-clear shutters with matched wavelength selective reflectors. This increases color gamut by reducing losses and more cleanly separating the color channels, and gives much wider choice of electro-optic colorants.

  17. Manufacturing of neutron reflector frame for JMTR

    OpenAIRE

    2010-01-01

    Beryllium has been used as the neutron reflector in the Japan Materials Testing Reactor (JMTR). A beryllium frame is arranged in the JMTR core and the frame consists of 3 sections (North, East and West). Each section has 7 stories of the beryllium blocks. Each block is connected by the aluminum joints. The capsule or the beryllium plug is located in the inside of the beryllium frame. The first criticality achieved in 1968 and the frame has been replaced 6 times and now the 7th frame is being ...

  18. Hybrid grating reflectors: Origin of ultrabroad stopband

    Energy Technology Data Exchange (ETDEWEB)

    Park, Gyeong Cheol; Taghizadeh, Alireza; Chung, Il-Sug, E-mail: ilch@fotonik.dtu.dk [DTU Fotonik, Department of Photonics Engineering, Technical University of Denmark, DK-2800 Kgs. Lyngby (Denmark)

    2016-04-04

    Hybrid grating (HG) reflectors with a high-refractive-index cap layer added onto a high contrast grating (HCG) provide a high reflectance close to 100% over a broader wavelength range than HCGs. The combination of a cap layer and a grating layer brings a strong Fabry-Perot (FP) resonance as well as a weak guided mode (GM) resonance. Most of the reflected power results from the FP resonance, while the GM resonance plays a key role in achieving a reflectance close to 100% as well as broadening the stopband. An HG sample with 7 InGaAlAs quantum wells included in the cap layer has been fabricated by directly wafer-bonding a III-V cap layer onto a Si grating layer. Its reflection property has been characterized. This heterogeneously integrated HG reflector may allow for a hybrid III-V on Si laser to be thermally efficient, which has promising prospects for silicon photonics light sources and high-speed operation.

  19. Optical Reflectance Measurements for Commonly Used Reflectors

    Science.gov (United States)

    Janecek, Martin; Moses, William W.

    2008-08-01

    When simulating light collection in scintillators, modeling the angular distribution of optical light reflectance from surfaces is very important. Since light reflectance is poorly understood, either purely specular or purely diffuse reflectance is generally assumed. In this paper we measure the optical reflectance distribution for eleven commonly used reflectors. A 440 nm, output power stabilized, un-polarized laser is shone onto a reflector at a fixed angle of incidence. The reflected light's angular distribution is measured by an array of silicon photodiodes. The photodiodes are movable to cover 2pi of solid angle. The light-induced current is, through a multiplexer, read out with a digital multimeter. A LabVIEW program controls the motion of the laser and the photodiode array, the multiplexer, and the data collection. The laser can be positioned at any angle with a position accuracy of 10 arc minutes. Each photodiode subtends 6.3deg, and the photodiode array can be positioned at any angle with up to 10 arc minute angular resolution. The dynamic range for the current measurements is 10 5:1. The measured light reflectance distribution was measured to be specular for several ESR films as well as for aluminum foil, mostly diffuse for polytetrafluoroethylene (PTFE) tape and titanium dioxide paint, and neither specular nor diffuse for Lumirrorreg, Melinexreg and Tyvekreg. Instead, a more complicated light distribution was measured for these three materials.

  20. Dielectric rod feed for compact range reflector

    CERN Document Server

    Balabukha, Nikolay P; Shapkina, Natalia E

    2014-01-01

    A dielectric rod feed with a special radiation pattern of a tabletop form used for the compact range reflector is developed and analyzed. Application of this feed increases the size of the compact range quiet zone generated by the reflector. The feed consists of the dielectric rod made of polystyren, the rod is inserted into the circular waveguide with a corrugated flange. The waveguide is excited by the H11-mode. The rod is covered by the textolite biconical bushing and has a fluoroplastic insert in the vicinity of the bushing. Mathematical modeling was used to obtain the parameters of the feed for the optimal tabletop form of the radiation pattern. The problem of the electromagnetic radiation was solved for metal-dielectric bodies of rotation by method of integral equations with further solving of the problem of the synthesis for feed parameters. The dielectric rod feed was fabricated for the X-frequency range. Feed amplitude and phase patterns were measured in the frequency range 8.2-12.5 GHz. Presented re...

  1. Seaward dipping reflectors along the SW continental margin of India: Evidence for volcanic passive margin

    Digital Repository Service at National Institute of Oceanography (India)

    Ajay, K.K.; Chaubey, A.K.; Krishna, K.S.; Rao, D.G.; Sar, D.

    of the Chagos-Laccadive Ridge system. Velocity structure, seismic character, 2D gravity model and geographic locations of the dipping reflectors suggest that these reflectors are volcanic in origin, which are interpreted as Seaward Dipping Reflectors (SDRs...

  2. Composition: Around Corners (2006-08)

    DEFF Research Database (Denmark)

    Bergstrøm-Nielsen, Carl

    2010-01-01

    Around Corners is an open composition to be realised by improvising musicians. See more about my composition practise in the entry "Composition - General Introduction". Caution: streaming the sound/video files will in some cases only provide a few minutes' sample, or the visuals will not appear...... at all. Please DOWNLOAD them to see/hear them in full length! This work is licensed under a Creative Commons "by-nc" License. You may for non-commercial purposes use and distribute it, performance instructions as well as specially designated recordings, as long as the author(s) is (are) mentioned. Please...

  3. Corner Transfer Matrices and Quantum Affine Algebras

    CERN Document Server

    Foda, O E; Foda, Omar; Miwa, Tetsuji

    1992-01-01

    Let H be the corner-transfer-matrix Hamiltonian for the six-vertex model in the anti-ferroelectric regime. It acts on the infinite tensor product W = V . V . V ....., where is the 2-dimensional irreducible representation of the quantum affine sl(2). We observe that H is the derivation of quantum affine sl(2), and conjecture that the eigenvectors of H form the level-1 vacuum representation of quantum affine sl(2). We report on checks in support of our conjecture.

  4. Study variants of hard CFRP reflector for intersatellite communication

    Science.gov (United States)

    Prosuntsov, PV; Reznik, SV; Mikhailovsky, KV; Novikov, AD; Aung, Zaw Ye

    2016-10-01

    The paper deals with the justification of space antennas reflector layout for advanced telecommunication satellites. The selection of design decisions is based on numerical simulations of heat transfer and mechanics processes characteristic of the geostationary orbit conditions. The advantages of parabolic shell of small thickness reflector scheme reinforced with star-shaped ribs on the convex side are demonstrated.

  5. Ray Tracing Modelling of Reflector for Vertical Bifacial Panel

    DEFF Research Database (Denmark)

    Jakobsen, Michael Linde; Thorsteinsson, Sune; Poulsen, Peter Behrensdorff

    2016-01-01

    Bifacial solar panels have recently become a new attractive building block for PV systems. In this work we propose a reflector system for a vertical bifacial panel, and use ray tracing modelling to model the performance. Particularly, we investigate the impact of the reflector volume being filled...

  6. Ellipsoidal reflector for measuring oto-acoustic emissions

    DEFF Research Database (Denmark)

    Epp, Bastian; Pulkki, Ville; Heiskanen, Vesa

    2014-01-01

    A truncated prolate ellipsoidal reflector having the ear canal of a listener at one focal point and large- diaphragm low-noise microphone at the other focal point is proposed for free-field recordings of oto-acoustic emissions. A prototype reflector consisting of three pieces is presented, which ...

  7. A distributed optical fiber sensing system for dynamic strain measurement based on artificial reflector

    Science.gov (United States)

    Sun, Zhenhong; Shan, Yuanyuan; Li, Yanting; Zhang, Yixin; Zhang, Xuping

    2016-10-01

    Phase sensitive optical time domain reflectometry (Φ-OTDR) has been widely used in many applications for its distributed sensing ability on weak disturbance all along the sensing fiber. However, traditional Φ-OTDR cannot make quantitative measurement on the external disturbance due to the randomly distributed position and reflectivity of scatters within the optical fiber. Recently, some methods have been proposed to realize quantitative measurement of dynamic strain. In these literatures, the fiber with or without FBGs in practice was easily damaged and with difficulty of maintenance. PZT is employed to generate strain event in the fiber. There is a large gap compared with the real detecting environment, which will not reveal the full performance of the sensing system. In this paper, a distributed optical fiber sensing (DOFS) system for dynamic strain measurement based on artificial reflector is proposed and demonstrated experimentally. The fiber under test (FUT) is composed by four 20-meter long single mode optical fiber patch cords (OFPCs), which are cascaded with ferrule contactor/physical contact (FC/PC) connectors via fiber flanges. The fiber facet of FC/PC connector forms an artificial reflector. When the interval between the two reflectors is changed, the phase of the interference signal will also be changed. A symmetric 3×3 coupler with table-look-up scheme is introduced to discriminate the phase change through interference intensity. In our experiment, the center 10m section of the second OFPC is attached to the bottom of an aluminum alloy plate. An ordinary loudspeaker box was located on the top of the aluminum alloy plate. The dynamic strain generated by the loudspeaker box is transmitted from the aluminum alloy plate to the OFPC. Experimental results show that the proposed method has a good frequency response characteristic up to 3.2 kHz and a linear intensity response of R2=0.9986 while the optical probe pulse width and repetition rate were 100ns

  8. Properties of wideband resonant reflectors under fully conical light incidence

    CERN Document Server

    Ko, Yeong Hwan; Lee, Kyu Jin; Magnusson, Robert

    2016-01-01

    Applying numerical modeling coupled with experiments, we investigate the properties of wideband resonant reflectors under fully conical light incidence. We show that the wave vectors pertinent to resonant first-order diffraction under fully conical mounting vary less with incident angle than those associated with reflectors in classical mounting. Therefore, as the evanescent diffracted waves drive the leaky modes responsible for the resonance effects, fully-conical mounting imbues reflectors with larger angular tolerance than their classical counterparts. We quantify the angular-spectral performance of representative resonant wideband reflectors in conic and classic mounts by numerical calculations with improved spectra found for fully conic incidence. Moreover, these predictions are verified experimentally for wideband reflectors fashioned in crystalline and amorphous silicon in distinct spectral regions spanning the 1200-1600-nm and 1600-2400-nm spectral bands. These results will be useful in various applic...

  9. Broad spectrum moderators and advanced reflector filters using 208Pb

    DEFF Research Database (Denmark)

    Schönfeldt, Troels; Batkov, K.; Klinkby, Esben Bryndt

    2015-01-01

    thermalizing property of 208Pb to design a broad spectrum moderator, i.e. a moderator which emits thermal and cold neutrons from the same position. Using 208Pb as a reflector filter material is shown to be slightly less efficient than a conventional beryllium reflector filter. However, when surrounding...... the reflector filter by a cold moderator it is possible to regain the neutrons with wavelengths below the Bragg edge, which are suppressed in the beryllium reflector filter. In both the beryllium and lead case surrounding the reflector filter with a cold moderator increases the cold brightness significantly......Cold and thermal neutrons used in neutrons scattering experiments are produced in nuclear reactors and spallation sources. The neutrons are cooled to thermal or cold temperatures in thermal and cold moderators, respectively. The present study shows that it is possible to exploit the poor...

  10. Universal corner contributions to entanglement negativity

    Science.gov (United States)

    Kim, Keun-Young; Niu, Chao; Pang, Da-Wei

    2016-09-01

    It has been realised that corners in entangling surfaces can induce new universal contributions to the entanglement entropy and Rényi entropy. In this paper we study universal corner contributions to entanglement negativity in three- and four-dimensional CFTs using both field theory and holographic techniques. We focus on the quantity χ defined by the ratio of the universal part of the entanglement negativity over that of the entanglement entropy, which may characterise the amount of distillable entanglement. We find that for most of the examples χ takes bigger values for singular entangling regions, which may suggest increase in distillable entanglement. However, there also exist counterexamples where distillable entanglement decreases for singular surfaces. We also explore the behaviour of χ as the coupling varies and observe that for singular entangling surfaces, the amount of distillable entanglement is mostly largest for free theories, while counterexample exists for free Dirac fermion in three dimensions. For holographic CFTs described by higher derivative gravity, χ may increase or decrease, depending on the sign of the relevant parameters. Our results may reveal a more profound connection between geometry and distillable entanglement.

  11. Triadophilia: A Special Corner in the Landscape

    CERN Document Server

    Candelas, Philip; He, Yang-Hui; Szendroi, Balazs

    2007-01-01

    It is well known that there are a great many apparently consistent vacua of string theory. We draw attention to the fact that there appear to be very few Calabi--Yau manifolds with the Hodge numbers h^{11} and h^{21} both small. Of these, the case (h^{11}, h^{21})=(3,3) corresponds to a manifold on which a three generation heterotic model has recently been constructed. We point out also that there is a very close relation between this manifold and several familiar manifolds including the `three-generation' manifolds with \\chi=-6 that were found by Tian and Yau, and by Schimmrigk, during early investigations. It is an intriguing possibility that we may live in a naturally defined corner of the landscape. The location of these three generation models with respect to a corner of the landscape is so striking that we are led to consider the possibility of transitions between heterotic vacua. The possibility of these transitions, that we here refer to as transgressions, is an old idea that goes back to Witten. Here...

  12. Properties of the Ising magnet confined in a corner geometry

    Science.gov (United States)

    Albano, Ezequiel V.; de Virgiliis, Andres; Müller, Marcus; Binder, Kurt

    2007-10-01

    The properties of Ising square lattices with nearest neighbor ferromagnetic exchange confined in a corner geometry, are studied by means of Monte Carlo simulations. Free boundary conditions at which boundary magnetic fields ±h are applied, i.e., at the two boundary rows ending at the lower left corner a field +h acts, while at the two boundary rows ending at the upper right corner a field -h acts. For temperatures T less than the critical temperature T of the bulk, this boundary condition leads to the formation of two domains with opposite orientation of the magnetization direction, separated by an interface which for T larger than the filling transition temperature T(h) runs from the upper left corner to the lower right corner, while for Tinterface is localized either close to the lower left corner or close to the upper right corner. It is shown that for T=T(h) the magnetization profile m(z) in the z-direction normal to the interface simply is linear and the interfacial width scales as w∝L, while for T>T(h) it scales as w∝√{L}. The distribution P(ℓ) of the interface position ℓ (measured along the z-direction from the corners) decays exponentially for TT(h). Unlike the findings for critical wetting in the thin film geometry of the Ising model, the Monte Carlo results for corner wetting are in very good agreement with the theoretical predictions.

  13. Corner wetting transition in the two-dimensional Ising model

    Science.gov (United States)

    Lipowski, Adam

    1998-07-01

    We study the interfacial behavior of the two-dimensional Ising model at the corner of weakened bonds. Monte Carlo simulations results show that the interface is pinned to the corner at a lower temperature than a certain temperature Tcw at which it undergoes a corner wetting transition. The temperature Tcw is substantially lower than the temperature of the ordinary wetting transition with a line of weakened bonds. A solid-on-solid-like model is proposed, which provides a supplementary description of the corner wetting transition.

  14. Measuring the effect of rounding the corners of scattering structures

    Science.gov (United States)

    Markowskei, Audrey J.; Smith, Paul D.

    2017-05-01

    In studying acoustic or electromagnetic wave diffraction, the choice of an appropriate canonical structure to model the dominant features of a scattering scenario can be very illuminating. A common approach used when dealing with domains with corners is to round the corners, producing a smooth surface, eliminating the singularities introduced by the corners. In order to quantify the effect of corner rounding, this paper examines the diffraction from cylindrical scatterers which possess corners, that is, points at which the normal changes discontinuously. We develop a numerical method for the scattering of a plane wave normally incident on such cylindrical structures with soft, hard, or impedance loaded boundary conditions. We then examine the difference between various test structures with corners and with the corners rounded to assess the impact on near- and far-field scattering, as a function of the radius of curvature in the vicinity of the rounded corner point. We then examine the nature of the differences in the far field between the cornered and rounded scatterers as well as the effect on the differences as the frequency of the plane wave increases and obtain precise quantitative estimates for the rate of convergence of the maximum difference between the far-field solutions as the radius of curvature of the rounded scatterer approaches zero.

  15. Metal nanoparticles with sharp corners: Universal properties of plasmon resonances

    Science.gov (United States)

    Sturman, B.; Podivilov, E.; Gorkunov, M.

    2013-03-01

    We predict the simultaneous occurrence of two fundamental phenomena for metal nanoparticles possessing sharp corners with variable curvature: First, the main dipolar plasmonic mode experiences a strong red shift with increasing corner curvature; for large values of the curvature, the resonant frequency is controlled by the apex angle of the corner. Second, the split-off plasmonic mode experiences a strong localization at the corners. Altogether, this paves the way for the tailoring of metal nanostructures providing a wavelength-selective excitation of localized plasmons and a strong near-field enhancement of linear and nonlinear optical phenomena.

  16. Composite technology in radar equipment. Dopler Meteo radar reflector device

    Directory of Open Access Journals (Sweden)

    A. V. Shumov

    2014-01-01

    Full Text Available The article is devoted features of the application composite materials in radar technology for example adjustment of the development technology of the reflector antenna device DMRL-S - radar for monitoring meteorological conditions.Russian and foreign analogues DMRL-S are made of aluminum, which no longer meets modern requirements for strength and weight. Also aluminum reflectors are not temperature stable. Composite materials are characterized by higher values of specific characteristics: temporary resistance, endurance limit, stiffness, elastic modulus, and less prone to cracking. The use of such materials improves the strength, rigidity and durability.For the manufacture of the DMRL-C reflector used composite materials based on epoxy resins reinforced with fiberglass (both unidirectional and woven. To increase the rigidity and weight reflector is made in the form of three-layer sandwich fiberglass panels with honeycomb core variable height. Design work was carried out in a CAD Siemens NX8.0 / Unigraphics, through which was established mathematical model layered reflector, as well as all accessories used in the manufacture. With the program NX Nastran was held strength calculation and analysis of stiffness on the finite element method.After the manufacture of the product, we measured the standard deviation of the working surface of the reflector from the theoretical surface using a three-dimensional laser scanner. Measurements were made at different angular positions of the reflector, and when loading. It is shown that the maximum strain in the operating modes of operation across the surface of the product does not exceed 4%, which will provide the most accurate operation of the product in any position of the antenna system.As a result of this work reflector design was developed, created and verified by experimental data calculation model. Reflector antenna device of the DMRL-S was manufactured and tested. The reflector was made of reinforced

  17. Deployment simulation of a deployable reflector for earth science application

    Science.gov (United States)

    Wang, Xiaokai; Fang, Houfei; Cai, Bei; Ma, Xiaofei

    2015-10-01

    A novel mission concept namely NEXRAD-In-Space (NIS) has been developed for monitoring hurricanes, cyclones and other severe storms from a geostationary orbit. It requires a space deployable 35-meter diameter Ka-band (35 GHz) reflector. NIS can measure hurricane precipitation intensity, dynamics and its life cycle. These information is necessary for predicting the track, intensity, rain rate and hurricane-induced floods. To meet the requirements of the radar system, a Membrane Shell Reflector Segment (MSRS) reflector technology has been developed and several technologies have been evaluated. However, the deployment analysis of this large size and high-precision reflector has not been investigated. For a pre-studies, a scaled tetrahedral truss reflector with spring driving deployment system has been made and tested, deployment dynamics analysis of this scaled reflector has been performed using ADAMS to understand its deployment dynamic behaviors. Eliminating the redundant constraints in the reflector system with a large number of moving parts is a challenging issue. A primitive joint and flexible struts were introduced to the analytical model and they can effectively eliminate over constraints of the model. By using a high-speed camera and a force transducer, a deployment experiment of a single-bay tetrahedral module has been conducted. With the tested results, an optimization process has been performed by using the parameter optimization module of ADAMS to obtain the parameters of the analytical model. These parameters were incorporated to the analytical model of the whole reflector. It is observed from the analysis results that the deployment process of the reflector with a fixed boundary experiences three stages. These stages are rapid deployment stage, slow deployment stage and impact stage. The insight of the force peak distributions of the reflector can help the optimization design of the structure.

  18. Impact of HFIR LEU Conversion on Beryllium Reflector Degradation Factors

    Energy Technology Data Exchange (ETDEWEB)

    Ilas, Dan [ORNL

    2013-10-01

    An assessment of the impact of low enriched uranium (LEU) conversion on the factors that may cause the degradation of the beryllium reflector is performed for the High Flux Isotope Reactor (HFIR). The computational methods, models, and tools, comparisons with previous work, along with the results obtained are documented and discussed in this report. The report documents the results for the gas and neutronic poison production, and the heating in the beryllium reflector for both the highly enriched uranium (HEU) and LEU HFIR configurations, and discusses the impact that the conversion to LEU may have on these quantities. A time-averaging procedure was developed to calculate the isotopic (gas and poisons) production in reflector. The sensitivity of this approach to different approximations is gauged and documented. The results show that the gas is produced in the beryllium reflector at a total rate of 0.304 g/cycle for the HEU configuration; this rate increases by ~12% for the LEU case. The total tritium production rate in reflector is 0.098 g/cycle for the HEU core and approximately 11% higher for the LEU core. A significant increase (up to ~25%) in the neutronic poisons production in the reflector during the operation cycles is observed for the LEU core, compared to the HEU case, for regions close to the core s horizontal midplane. The poisoning level of the reflector may increase by more than two orders of magnitude during long periods of downtime. The heating rate in the reflector is estimated to be approximately 20% lower for the LEU core than for the HEU core. The decrease is due to a significantly lower contribution of the heating produced by the gamma radiation for the LEU core. Both the isotopic (gas and neutronic poisons) production and the heating rates are spatially non-uniform throughout the beryllium reflector volume. The maximum values typically occur in the removable reflector and close to the midplane.

  19. Inline microring reflector for photonic applications

    Science.gov (United States)

    Kang, Young Mo

    The microring is a compact resonator that is used as a versatile building block in photonic circuits ranging from filters, modulators, logic gates, sensors, switches, multiplexers, and laser cavities. The Bragg grating is a periodic structure that allows the selection of a narrow bandwidth of spectrum for stable lasing operation. In this dissertation, we study analysis and simulations of a compact microring based reflector assembled by forming a Bragg grating into a loop. With the appropriate design, the microring resonance can precisely align with the reflection peak of the grating while all other peaks are suppressed by reflection nulls of the grating. The field buildup at the resonance effectively amplifies small reflection of the grating, thereby producing significant overall reflection from the ring, and it is possible to achieve a stable narrow linewidth compact laser by forming a single mode laser cavity. The device operation principle is studied from two distinct perspectives; the first looks at coupling of two contra-directional traveling waves within the ring whereas the second aspect investigates relative excitation of the two competing microring resonant modes. In the former method, we relate the steady state amplitudes of the two traveling waves to the reflection spectrum of the grating and solve for the reflection and transmission response for each wavelength of interest. In the latter approach, we expand the field in terms of the resonant modes of the ring cavity and derive transfer functions for reflection and transmission from the nearby mode frequencies. The angular periodicity of the reflective microring geometry allows us to effectively simulate the resonant modes from a computational domain of a single period grating when the continuity boundary condition is applied. We successfully predict the reflection and transmission response of a Si3N 4/SiO2 microring reflector using this method---otherwise too large to carry out full-wave simulation

  20. Efficient video panoramic image stitching based on an improved selection of Harris corners and a multiple-constraint corner matching.

    Directory of Open Access Journals (Sweden)

    Minchen Zhu

    Full Text Available Video panoramic image stitching is extremely time-consuming among other challenges. We present a new algorithm: (i Improved, self-adaptive selection of Harris corners. The successful stitching relies heavily on the accuracy of corner selection. We fragment each image into numerous regions and select corners within each region according to the normalized variance of region grayscales. Such a selection is self-adaptive and guarantees that corners are distributed proportional to region texture information. The possible clustering of corners is also avoided. (ii Multiple-constraint corner matching. The traditional Random Sample Consensus (RANSAC algorithm is inefficient, especially when handling a large number of images with similar features. We filter out many inappropriate corners according to their position information, and then generate candidate matching pairs based on grayscales of adjacent regions around corners. Finally we apply multiple constraints on every two pairs to remove incorrectly matched pairs. By a significantly reduced number of iterations needed in RANSAC, the stitching can be performed in a much more efficient manner. Experiments demonstrate that (i our corner matching is four times faster than normalized cross-correlation function (NCC rough match in RANSAC and (ii generated panoramas feature a smooth transition in overlapping image areas and satisfy real-time human visual requirements.

  1. Laser Ranging to the Lost Lunokhod~1 Reflector

    CERN Document Server

    Murphy, T W; Battat, J B R; Hoyle, C D; Johnson, N H; McMillan, R J; Michelsen, E L; Stubbs, C W; Swanson, H E

    2011-01-01

    In 1970, the Soviet Lunokhod 1 rover delivered a French-built laser reflector to the Moon. Although a few range measurements were made within three months of its landing, these measurements---and any that may have followed---are unpublished and unavailable. The Lunokhod 1 reflector was, therefore, effectively lost until March of 2010 when images from the Lunar Reconnaissance Orbiter (LRO) provided a positive identification of the rover and determined its coordinates with uncertainties of about 100 m. This allowed the Apache Point Observatory Lunar Laser-ranging Operation (APOLLO) to quickly acquire a laser signal. The reflector appears to be in excellent condition, delivering a signal roughly four times stronger than its twin reflector on the Lunokhod 2 rover. The Lunokhod 1 reflector is especially valuable for science because it is closer to the Moon's limb than any of the other reflectors and, unlike the Lunokhod 2 reflector, we find that it is usable during the lunar day. We report the selenographic positi...

  2. Cornering diphoton resonance models at the LHC

    CERN Document Server

    Backović, Mihailo; Mariotti, Alberto; Sessolo, Enrico Maria; Spannowsky, Michael

    2016-01-01

    We explore the ability of the high luminosity LHC to test models which can explain the 750 GeV diphoton excess. We focus on a wide class of models where a 750 GeV singlet scalar couples to Standard Model gauge bosons and quarks, as well as dark matter. Including both gluon and photon fusion production mechanisms, we show that LHC searches in channels correlated with the diphoton signal will be able to probe wide classes of diphoton models with $\\mathcal{L} \\sim 3000\\, \\text{fb}^{-1}$ of data. Furthermore, models in which the scalar is a portal to the dark sector can be cornered with as little as $\\mathcal{L} \\sim 30\\, \\text{fb}^{-1}$.

  3. Cornering diphoton resonance models at the LHC

    Energy Technology Data Exchange (ETDEWEB)

    Backović, Mihailo [Center for Cosmology, Particle Physics and Phenomenology (CP3),Universite Catholique de Louvain, B-1348 Louvain-la-Neuve (Belgium); Kulkarni, Suchita [Institute of High Energy Physics, Austrian Academy of Sciences,Nikolsdorfergasse 18, 1050 Vienna (Austria); Mariotti, Alberto [Theoretische Natuurkunde and IIHE/ELEM, Vrije Universiteit Brussel,and International Solvay Institutes, Pleinlaan 2, B-1050 Brussels (Belgium); Sessolo, Enrico Maria [National Centre for Nuclear Research,Hoża 69, 00-681 Warsaw (Poland); Spannowsky, Michael [Institute for Particle Physics Phenomenology, Department of Physics,Durham University, Durham, DH13LE (United Kingdom)

    2016-08-02

    We explore the ability of the high luminosity LHC to test models which can explain the 750 GeV diphoton excess. We focus on a wide class of models where a 750 GeV singlet scalar couples to Standard Model gauge bosons and quarks, as well as dark matter. Including both gluon and photon fusion production mechanisms, we show that LHC searches in channels correlated with the diphoton signal will be able to probe wide classes of diphoton models with L∼3000 fb{sup −1} of data. Furthermore, models in which the scalar is a portal to the dark sector can be cornered with as little as L∼30 fb{sup −1}.

  4. Standing wave acoustic levitation on an annular plate

    Science.gov (United States)

    Kandemir, Mehmet Hakan; Çalışkan, Mehmet

    2016-11-01

    In standing wave acoustic levitation technique, a standing wave is formed between a source and a reflector. Particles can be attracted towards pressure nodes in standing waves owing to a spring action through which particles can be suspended in air. This operation can be performed on continuous structures as well as in several numbers of axes. In this study an annular acoustic levitation arrangement is introduced. Design features of the arrangement are discussed in detail. Bending modes of the annular plate, known as the most efficient sound generation mechanism in such structures, are focused on. Several types of bending modes of the plate are simulated and evaluated by computer simulations. Waveguides are designed to amplify waves coming from sources of excitation, that are, transducers. With the right positioning of the reflector plate, standing waves are formed in the space between the annular vibrating plate and the reflector plate. Radiation forces are also predicted. It is demonstrated that small particles can be suspended in air at pressure nodes of the standing wave corresponding to a particular bending mode.

  5. Noncontact ultrasonic transportation of small objects over long distances in air using a bending vibrator and a reflector.

    Science.gov (United States)

    Koyama, Daisuke; Nakamura, Kentaro

    2010-05-01

    Ultrasonic manipulation of small particles, including liquid droplets, over long distances is discussed. It is well known that particles can be trapped at the nodal points of an acoustic standing wave if the particles are much smaller than the wavelength of the standing wave. We used an experimental setup consisting of a 3-mm-thick, 605-mm-long duralumin bending vibrating plate and a reflector. A bolt-clamped Langevin transducer with horn was attached to each end of the vibrating plate to generate flexural vibrations along the plate. A plane reflector with the same dimensions as the vibrating plate was installed parallel to the plate at a distance of approximately 17 mm to generate an ultrasonic standing wave between them and to trap the small particles at the nodal lines. The acoustic field and acoustic radiation force between the vibrator and reflector were calculated by finite element analysis to predict the positions of the trapped particles. The sound pressure distribution was measured experimentally using a scanning laser Doppler vibrometer. By controlling the driving phase difference between the two transducers, a flexural traveling wave can be generated along the vibrating plate, and the vertical nodal lines of the standing wave and the trapped particles can be moved. The flexural wave was excited along the vibrator at 22.5 kHz. A lattice standing wave with a wavelength of 35 mm in the length direction could be excited between the vibrator and the reflector, and polystyrene spheres with diameters of several millimeters could be trapped at the nodal lines of the standing wave. The experimental and calculated results showed good agreement for the relationship between the driving phase difference and the positions of the trapped particles. Noncontact transportation of the trapped particles over long distances could be achieved by changing the driving phase difference. The position of the trapped particles could be controlled to an accuracy of 0.046 mm/deg. An

  6. Diseño y estudio de “Corner-reflectors” para sistemas radar utilizando la herramienta software POFACETS

    OpenAIRE

    Corredor Pedrero, Antonio

    2016-01-01

    El Trabajo Fin de Grado se centrará en el diseño y estudio de Corner-Reflectors (CR) de aluminio en forma de triedro para su posterior uso en procesos de calibración y georreferenciación de sistemas SAR (SyntheticAperture Radar). El estudio del diseño se realizará analizando la RCS (Radar Cross Section) producida por los cambios en los parámetros de diseño del CR. Las características de diseño que se estudiarán son la longitud de las aristas, ángulo de canteo de las aristas, radio del orifici...

  7. Performance of a PV module augmented by a plane reflector

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, G. E; Hussein, H. M. S; Mohamad, M. A [Dokki, Giza (Egypt)

    2000-07-01

    This paper presents a comparative experimental study on the performance of a PV module augmented by a south facing titled plane reflector and another identical one without reflector. The tilt angles of the two PV modules and reflector overhang are selected to be according to a previous theoretical study by the authors. The reflector tilt angle has been changed once a month so that the reflected beams from the plane reflector cover the total surface area of the PV module all days of every month during the high solar radiation period (i.e. three hours before and after solar noon). The study has been carried out on the two PV modules for a complete year under the actual atmospheric conditions of Cairo, Egypt. The measuring system used in the study comprises a data acquisition system, a computer, an electronic load and weather station. The experimental results indicate that the plane reflector enhances the yearly output energy of the PV module y about 22%. [Spanish] Este articulo presenta un estudio comparativo experimental sobre el rendimiento de un modulo de PV aumentado por un reflector plano inclinado mirando hacia el sur y otro identico sin reflector. Los angulos de inclinacion de los dos modulos y el reflector sobresaliente se seleccionan para que esten de acuerdo con un estudio teorico previo hecho por los autores. El angulo de inclinacion del reflector se cambio una vez al mes de manera que los rayos reflejados por el reflector plano cubrieran el area total de la superficie del modulo de PV todos los dias de cada mes durante el periodo de radiacion alto (o sea tres horas antes y despues del medio dia solar). El estudio ha sido llevado a cabo en dos modulos de PV durante un ano completo bajo condiciones atmosfericas reales de El Cairo, Egipto. El sistema de medicion usado en el estudio comprende un sistema de adquisicion de datos, una computadora, una memoria electronica y una estacion climatologica. Los resultados experimentales indican que el reflector plano

  8. Incidental Reflector Comparison of Containerized Dry Fire Extinguishing Agents

    Energy Technology Data Exchange (ETDEWEB)

    Chapman, Bryan Scott [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Wysong, Andrew Russell [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-12-14

    This document addresses the incidental reflector reactivity worth of containerized fire extinguishing agents authorized for use in PF-4 at Los Alamos National Laboratory (LANL). The intent of the document is to analyze dry fire extinguishing agent that remains in a container and is not actively being used in a fire emergency. The incidental reflector reactivity worth is determined by comparison to various thicknesses of close fitting water reflection which is commonly used to bound incidental reflectors in criticality safety evaluations. The conclusion is that even in unlimited quantities, when containerized the authorized dry fire extinguishing agents are bound by 0.4 inches of close fitting water.

  9. Identifying Reflectors in Seismic Images via Statistic and Syntactic Methods

    Directory of Open Access Journals (Sweden)

    Carlos A. Perez

    2010-04-01

    Full Text Available In geologic interpretation of seismic reflection data, accurate identification of reflectors is the foremost step to ensure proper subsurface structural definition. Reflector information, along with other data sets, is a key factor to predict the presence of hydrocarbons. In this work, mathematic and pattern recognition theory was adapted to design two statistical and two syntactic algorithms which constitute a tool in semiautomatic reflector identification. The interpretive power of these four schemes was evaluated in terms of prediction accuracy and computational speed. Among these, the semblance method was confirmed to render the greatest accuracy and speed. Syntactic methods offer an interesting alternative due to their inherently structural search method.

  10. Intervjuu James Corneriga = Interview with James Corner / James Corner ; interv. Andres Sevtshuk

    Index Scriptorium Estoniae

    Corner, James

    2006-01-01

    Büroo Field Operations maastikuarhitekt ning Pennsylvania Ülikooli maastikuarhitektuuri osakonna juhataja James Corner oma büroost, maastikust kui "instrumendist", postindustriaalsete aladega seotud projektidest (New Yorgi High Line'i muutmine pargiks ja promenaadiks), tööst suuremahuliste maastikega (Fresh Kills'i soo, endise prügila muutmine pargialaks), maastikuarhitektuurist ja linnakujundusest (maastiku urbanism), õpetamise tähtsusest oma töös ja maastikuarhitektuuri ideede arendamisel. Bibl. lk. 24

  11. Intervjuu James Corneriga = Interview with James Corner / James Corner ; interv. Andres Sevtshuk

    Index Scriptorium Estoniae

    Corner, James

    2006-01-01

    Büroo Field Operations maastikuarhitekt ning Pennsylvania Ülikooli maastikuarhitektuuri osakonna juhataja James Corner oma büroost, maastikust kui "instrumendist", postindustriaalsete aladega seotud projektidest (New Yorgi High Line'i muutmine pargiks ja promenaadiks), tööst suuremahuliste maastikega (Fresh Kills'i soo, endise prügila muutmine pargialaks), maastikuarhitektuurist ja linnakujundusest (maastiku urbanism), õpetamise tähtsusest oma töös ja maastikuarhitektuuri ideede arendamisel. Bibl. lk. 24

  12. Space Reflector Materials for Prometheus Application

    Energy Technology Data Exchange (ETDEWEB)

    J. Nash; V. Munne; LL Stimely

    2006-01-31

    The two materials studied in depth which appear to have the most promise in a Prometheus reflector application are beryllium (Be) and beryllium oxide (BeO). Three additional materials, magnesium oxide (MgO), alumina (Al{sub 2}O{sub 3}), and magnesium aluminate spinel (MgAl{sub 2}O{sub 4}) were also recently identified to be of potential interest, and may have promise in a Prometheus application as well, but are expected to be somewhat higher mass than either a Be or BeO based reflector. Literature review and analysis indicates that material properties for Be are largely known, but there are gaps in the properties of Be0 relative to the operating conditions for a Prometheus application. A detailed preconceptual design information document was issued providing material properties for both materials (Reference (a)). Beryllium oxide specimens were planned to be irradiated in the JOY0 Japanese test reactor to partially fill the material property gaps, but more testing in the High Flux Isotope Reactor (HFIR) test reactor at Oak Ridge National Laboratory (ORNL) was expected to be needed. A key issue identified for BeO was obtaining material for irradiation testing with an average grain size of {approx}5 micrometers, reminiscent of material for which prior irradiation test results were promising. Current commercially available material has an average grain size of {approx}10 micrometers. The literature indicated that improved irradiation performance could be expected (e.g., reduced irradiation-induced swelling) with the finer grain size material. Confirmation of these results would allow the use of historic irradiated materials test results from the literature, reducing the extent of required testing and therefore the cost of using this material. Environmental, safety and health (ES&H) concerns associated with manufacturing are significant but manageable for Be and BeO. Although particulate-generating operations (e.g., machining, grinding, etc.) involving Be

  13. X-/Ka-band dichroic plate noise temperature reduction

    Science.gov (United States)

    Veruttipong, W.; Lee, P.

    1994-11-01

    The X-/Ka-band (8.4 GHz/32.0 GHz) dichroic plate installed as DSS 13 contributes an estimated 3 K to the system noise temperature at 32.0 GHz. Approximately 1 percent of the Ka-band incident field is reflected by the plate into the 300-K environment of the DSS-13 pedestal room. A low-cost, easily implemented method of reducing the noise temperature is presented. Using a curved reflector, the reflected field can be re-focused into an 80-K cold load, reducing the noise temperature contribution of the dichroic plate by about 2 K.

  14. The Novel Y-Branch With Two Reflectors

    Institute of Scientific and Technical Information of China (English)

    Ruei-Chang Lu; Yu-Pin Liao

    2003-01-01

    A novel Y-branch waveguide with two reflectors is proposed. The normalized transmitted power for the branching angle of 50°is greater than 70%, which is higher than conventional Y-branch with such wide angle.

  15. Lightweight Thermally Stable Multi-Meter Aperture Submillimeter Reflectors Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The objective of the Phase II effort will be an affordable demonstrated full-scale design for a thermally stable multi-meter submillimeter reflector. The Phase I...

  16. Thermomechanical analysis of large deployable space reflector antenna

    Directory of Open Access Journals (Sweden)

    Ponomarev Viktor S.

    2015-01-01

    Full Text Available In this article results of large reflector thermal condition forecast using modern numerical simulation methods are presented. The results of thermal analysis are complemented with stress-strain analysis results of the whole structure under thermal loads.

  17. Proton radiation effects on optical constants of Al film reflector

    Institute of Scientific and Technical Information of China (English)

    Liu Hai; Wei Qiang; He Shi-Yu; Zhao Dan

    2006-01-01

    The Al film reflectors can yield a high-reflectance over a broad wavelength region, and have been widely used in the spacecraft optical instruments for high quality optical applications. Under the irradiation of charged particles in the Earth radiation belt, the reflectors could be deteriorated. In order to reveal the deterioration mechanism, the change in optical constants of Al film reflector induced by proton radiation with 60 keV was studied in an environment of vacuum with heat sink. Experimental results showed that when the radiation damage primarily occurs in the Al reflecting film,the extinction coefficient k will gradually decrease with increasing radiation fluence, which results in the decrease of the energies of reflective light. Therefore, the proton radiation induced an obvious degradation of spectral reflectance in the wavelength region from 200 to 800 nm on the Al film reflector.

  18. Friction-Sensing Reflector Array Patches (FRAP) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Research Support Instruments, Inc. (RSI) proposes to develop the Friction-Sensing Reflector Array Patches (FRAP), a technology that will measure the shear stress...

  19. Semitransparent organic solar cells with organic wavelength dependent reflectors

    NARCIS (Netherlands)

    Galagan, Y.O.; Debije, M.G.; Blom, P.W.M.

    2011-01-01

    Semitransparent organic solar cells employing solution-processable organic wavelength dependent reflectors of chiral nematic (cholesteric) liquid crystals are demonstrated. The cholesteric liquid crystal (CLC) reflects only in a narrow band of the solar spectrum and remains transparent for the

  20. Evaluation of the Benefits of Reflectorized Sign Posts to Drivers

    Directory of Open Access Journals (Sweden)

    Erdinç Öner

    2013-03-01

    Full Text Available In United States Federal Highway Administration (FHWA provides departments of transportation (DOTs the option of using retroreflective material on sign posts when the DOTs determine that there is a need to draw attention to the sign, especially at night. The State of Ohio Department of Transportation (ODOT required all Stop, Yield, Do Not Enter, and Wrong Way sign posts to be reflectorized with RED reflective sheeting material and all Chevron, Stop Ahead, and One/Two Large Directional Arrow sign posts to be reflectorized with YELLOW (sign background color reflective sheeting material as part of ODOT Comprehensive Highway Safety Plan and FHWA' recommendations.In this study, a photometric analysis and a human factors analysis were conducted to estimate the benefits of reflectorized sign posts to driver visual perception, driver guidance and driver comprehension. The study showed that the reflectorized sign posts improve detection, recognition, and comprehension of traffic signs for drivers, especially in nighttime driving conditions.

  1. A bionic approach to mathematical modeling the fold geometry of deployable reflector antennas on satellites

    Science.gov (United States)

    Feng, C. M.; Liu, T. S.

    2014-10-01

    Inspired from biology, this study presents a method for designing the fold geometry of deployable reflectors. Since the space available inside rockets for transporting satellites with reflector antennas is typically cylindrical in shape, and its cross-sectional area is considerably smaller than the reflector antenna after deployment, the cross-sectional area of the folded reflector must be smaller than the available rocket interior space. Membrane reflectors in aerospace are a type of lightweight structure that can be packaged compactly. To design membrane reflectors from the perspective of deployment processes, bionic applications from morphological changes of plants are investigated. Creating biologically inspired reflectors, this paper deals with fold geometry of reflectors, which imitate flower buds. This study uses mathematical formulation to describe geometric profiles of flower buds. Based on the formulation, new designs for deployable membrane reflectors derived from bionics are proposed. Adjusting parameters in the formulation of these designs leads to decreases in reflector area before deployment.

  2. Study on Segmented Reflector Lamp Design Based on Error Analysis

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    This paper discusses the basic principle and design m ethod for light distribution of car lamp, introduces an important development: h igh efficient and flexible car lamp with reflecting light distribution-segmente d reflector (multi-patch) car lamp, and puts out a design method for segmented reflector based on error analysis. Unlike classical car lamp with refractive lig ht distribution, the method of reflecting light distribution gives car lamp desi gn more flexibility. In the case of guarantying the li...

  3. Measurement of small antenna reflector losses for radiometer calibration budget

    OpenAIRE

    Skou, Niels

    1997-01-01

    Antenna reflector losses play an important role in the calibration budget for a microwave radiometer. If the losses are small, they are difficult to measure by traditional means. However, they can be assessed directly by radiometric means using the sky brightness temperature as incident radiation. This paper describes how such measurements are carried out as well as a suitable experimental setup. The main reflector of the European Space Agency's MIMR system is used to demonstrate the principle

  4. Accurate antenna reflector loss measurements for radiometer calibration budget

    DEFF Research Database (Denmark)

    Skou, Niels

    1996-01-01

    Antenna reflector losses may play an important role in the calibration budget for a microwave radiometer. If the losses are small they are difficult to measure by traditional means. However, they can be assessed directly by radiometric means using the sky brightness temperature as incident radiat...... radiation. The paper describes how such measurements are carried out as well as a suitable experimental set-up. The main reflector of the European Space Agency's MIMR system is used to demonstrate the principle...

  5. Differential correction method applied to measurement of the FAST reflector

    Science.gov (United States)

    Li, Xin-Yi; Zhu, Li-Chun; Hu, Jin-Wen; Li, Zhi-Heng

    2016-08-01

    The Five-hundred-meter Aperture Spherical radio Telescope (FAST) adopts an active deformable main reflector which is composed of 4450 triangular panels. During an observation, the illuminated area of the reflector is deformed into a 300-m diameter paraboloid and directed toward a source. To achieve accurate control of the reflector shape, positions of 2226 nodes distributed around the entire reflector must be measured with sufficient precision within a limited time, which is a challenging task because of the large scale. Measurement of the FAST reflector makes use of stations and node targets. However, in this case the effect of the atmosphere on measurement accuracy is a significant issue. This paper investigates a differential correction method for total stations measurement of the FAST reflector. A multi-benchmark differential correction method, including a scheme for benchmark selection and weight assignment, is proposed. On-site evaluation experiments show there is an improvement of 70%-80% in measurement accuracy compared with the uncorrected measurement, verifying the effectiveness of the proposed method.

  6. Development of Full-Scale Ultrathin Shell Reflector

    Directory of Open Access Journals (Sweden)

    Durmuş Türkmen

    2012-01-01

    Full Text Available It is aimed that a new ultrathin shell composite reflector is developed considering different design options to optimize the stiffness/mass ratio, cost, and manufacturing. The reflector is an offset parabolic reflector with a diameter of 6 m, a focal length of 4.8 m, and an offset of 0.3 m and has the ability of folding and self-deploying. For Ku-band missions a full-scale offset parabolic reflector antenna is designed by considering different concepts of stiffening: (i reflective surface and skirt, (ii reflective surface and radial ribs, and (iii reflective surface, skirt, and radial ribs. In a preliminary study, the options are modeled using ABAQUS finite element program and compared with respect to their mass, fundamental frequency, and thermal surface errors. It is found that the option of reflective surface and skirt is more advantageous. The option is further analyzed to optimize the stiffness/mass ratio considering the design parameters of material thickness, width of the skirt, and ply angles. Using the TOPSIS method is determined the best reflector concept among thirty different designs. Accordingly, new design can be said to have some advantages in terms of mass, natural frequency, number of parts, production, and assembly than both SSBR and AstroMesh reflectors.

  7. Light Readout Optimisation using Wavelength Shifter - Reflector Combinations

    Energy Technology Data Exchange (ETDEWEB)

    Mavrokoridis, Konstantinos, E-mail: k.mavrokoridis@liverpool.ac.uk [Department of Physics, University of Liverpool, Oliver Lodge Lab, Oxford Street, Liverpool, L69 7ZE (United Kingdom)

    2011-07-25

    The use of reflectors coated with a wavelength shifter (WLS) along with standard bialkali PMTs is an economical method for an efficient readout system for vacuum ultra violet (VUV) light produced in large liquid argon detectors. Various thicknesses of tetraphenyl butadiene (TPB) were deposited by spraying and vacuum evaporation onto both specular 3M{sup TM}-foil and diffuse Tetratex{sup TM} (TTX) reflectors. 128 nm VUV light generated in 1 bar argon gas by a 5.4 MeV {alpha} source was detected by a 3-inch bialkali borosilicate PMT within a 1 m tube lined internally with a TPB coated reflector. The light collection was recorded as a function of separation between source and PMT for each combination of coating and reflector for distances up to 1m. Reflection coefficients of TPB coated reflectors were measured using a spectroradiometer. WLS coating on the PMT window was also studied. The optimum coating and reflector combination was TPB evaporated on TTX. Measurements with coating thicknesses of 0.2 mg/cm{sup 2} and 1.0 mg/cm{sup 2} yielded a similar performance. The best PMT window coating is obtained by TPB evaporation of 0.05 mg/cm{sup 2}.

  8. Large deployable reflectors for telecom and earth observation applications

    Science.gov (United States)

    Scialino, L.; Ihle, A.; Migliorelli, M.; Gatti, N.; Datashvili, L.; van `t Klooster, K.; Santiago Prowald, J.

    2013-12-01

    Large deployable antennas are one of the key components for advanced missions in the fields of telecom and earth observation. In the recent past, missions have taken on board large deployable reflector (LDR) up to 22 m of diameter and several missions have already planned embarking large reflectors, such as the 12 m of INMARSAT XL or BIOMASS. At the moment, no European LDR providers are available and the market is dominated by Northrop-Grumman and Harris. Consequently, the development of European large reflector technology is considered a key step to maintain commercial and strategic competitiveness (ESA Large Reflector Antenna Working Group Final Report, TEC-EEA/2010.595/CM, 2010). In this scenario, the ESA General Study Project RESTEO (REflector Synergy between Telecom and Earth Observation), starting from the identification of future missions needs, has identified the most promising reflector concepts based on European heritage/technology, able to cover the largest range of potential future missions for both telecom and earth observation. This paper summarizes the activities and findings of the RESTEO Study.

  9. Corner Sort for Pareto-Based Many-Objective Optimization.

    Science.gov (United States)

    Wang, Handing; Yao, Xin

    2014-01-01

    Nondominated sorting plays an important role in Pareto-based multiobjective evolutionary algorithms (MOEAs). When faced with many-objective optimization problems multiobjective optimization problems (MOPs) with more than three objectives, the number of comparisons needed in nondominated sorting becomes very large. In view of this, a new corner sort is proposed in this paper. Corner sort first adopts a fast and simple method to obtain a nondominated solution from the corner solutions, and then uses the nondominated solution to ignore the solutions dominated by it to save comparisons. Obtaining the nondominated solutions requires much fewer objective comparisons in corner sort. In order to evaluate its performance, several state-of-the-art nondominated sorts are compared with our corner sort on three kinds of artificial solution sets of MOPs and the solution sets generated from MOEAs on benchmark problems. On one hand, the experiments on artificial solution sets show the performance on the solution sets with different distributions. On the other hand, the experiments on the solution sets generated from MOEAs show the influence that different sorts bring to MOEAs. The results show that corner sort performs well, especially on many-objective optimization problems. Corner sort uses fewer comparisons than others.

  10. Differential geodetic stereo SAR with TerraSAR-X by exploiting small multi-directional radar reflectors

    Science.gov (United States)

    Gisinger, Christoph; Willberg, Martin; Balss, Ulrich; Klügel, Thomas; Mähler, Swetlana; Pail, Roland; Eineder, Michael

    2017-01-01

    In this paper, we report on the direct positioning of small multi-directional radar reflectors, so-called octahedrons, with the synthetic aperture radar (SAR) satellite TerraSAR-X. Its highest resolution imaging mode termed staring spotlight enables the use of such octahedron reflectors with a dimension of only half a meter, but still providing backscatter equivalent to 1-2 cm observation error. Four octahedrons were deployed at Wettzell geodetic observatory, and observed by TerraSAR-X with 12 acquisitions in three different geometries. By applying our least squares stereo SAR algorithm already tested with common trihedral corner reflectors (CRs), and introducing a novel differential extension using one octahedron as reference point, the coordinates of the remaining octahedrons were directly retrieved in the International Terrestrial Reference Frame (ITRF). Contrary to our standard processing, the differential approach does not require external corrections for the atmospheric path delays and the geodynamic displacements, rendering it particularly useful for joint geodetic networks employing SAR and GNSS. In this paper, we present and discuss both methods based on results when applying them to the aforementioned Wettzell data set of the octahedrons. The comparison with the independently determined reference coordinates confirms the positioning accuracy with 2-5 cm for the standard approach, and 2-3 cm for the differential processing. Moreover, we present statistical uncertainty estimates of the observations and the positioning solutions, which are additionally provided by our parameter estimation algorithms. The results also include our 1.5 m CR available at Wettzell, and the outcomes clearly demonstrate the advantage of the multi-directional octahedrons over conventional CRs for global positioning applications with SAR.

  11. Capillary surface discontinuities above reentrant corners

    Science.gov (United States)

    Korevaar, H. J.

    1982-01-01

    A particular configuration of a vertical capillary tube for which S is the equilibrium interface between two fluids in the presence of a downward pointing gravitational field was investigated. S is the graph a function u whose domain is the (horizontal) cross section gamma of the tube. The mean curvature of S is proportional to its height above a fixed reference plane and lambda is a prescribed constant and may be taken between zero and pi/2. Domains gamma for which us is a bounded function but does not extend continuously to d gamma are sought. Simple domains are found and the behavior of u in those domains is studied. An important comparison principle that has been used in the literature to derive many of the results in capillarity is reviewed. It allows one to deduce the approximate shape of a capillary surface by constructing comparison surfaces with mean curvature and contact angle close to those of the (unknown) solution surface. In the context of nonparametric problems the comparison principle leads to height estimates above and below for the function u. An example from the literature where these height estimates have been used successfully is described. The promised domains for which the bounded u does not extend continuously to the boundary are constructed. The point on the boundary at which u has a jump discontinuity will be the vertext of a re-entrant corner having any interior angle theta pi. Using the comparison principle the behavior of u near this point is studied.

  12. Wall-Corner Classification Using Sonar: A New Approach Based on Geometric Features

    Directory of Open Access Journals (Sweden)

    Ginés Benet

    2010-11-01

    Full Text Available Ultrasonic signals coming from rotary sonar sensors in a robot gives us several features about the environment. This enables us to locate and classify the objects in the scenario of the robot. Each object and reflector produces a series of peaks in the amplitude of the signal. The radial and angular position of the sonar sensor gives information about location and their amplitudes offer information about the nature of the surface. Early works showed that the amplitude can be modeled and used to classify objects with very good results at short distances—80% average success in classifying both walls and corners at distances less than 1.5 m. In this paper, a new set of geometric features derived from the amplitude analysis of the echo is presented. These features constitute a set of characteristics that can be used to improve the results of classification at distances from 1.5 m to 4 m. Also, a comparative study on classification algorithms widely used in pattern recognition techniques has been carried out for sensor distances ranging between 0.5 to 4 m, and with incidence angles ranging between 20º to 70º. Experimental results show an enhancement on the success in classification rates when these geometric features are considered.

  13. Wall-corner classification using sonar: a new approach based on geometric features.

    Science.gov (United States)

    Martínez, Milagros; Benet, Ginés

    2010-01-01

    Ultrasonic signals coming from rotary sonar sensors in a robot gives us several features about the environment. This enables us to locate and classify the objects in the scenario of the robot. Each object and reflector produces a series of peaks in the amplitude of the signal. The radial and angular position of the sonar sensor gives information about location and their amplitudes offer information about the nature of the surface. Early works showed that the amplitude can be modeled and used to classify objects with very good results at short distances-80% average success in classifying both walls and corners at distances less than 1.5 m. In this paper, a new set of geometric features derived from the amplitude analysis of the echo is presented. These features constitute a set of characteristics that can be used to improve the results of classification at distances from 1.5 m to 4 m. Also, a comparative study on classification algorithms widely used in pattern recognition techniques has been carried out for sensor distances ranging between 0.5 to 4 m, and with incidence angles ranging between 20° to 70°. Experimental results show an enhancement on the success in classification rates when these geometric features are considered.

  14. Study of hollow corner retroreflectors for use in a synchronous orbit

    Science.gov (United States)

    Yoder, P. R., Jr.

    1975-01-01

    The performance of a hollow corner cube retroreflector made up of three mutually perpendicular optically flat mirrors when undergoing the thermal-mechanical strains induced by a spacecraft environment was studied. Of particular interest was a device of 200 square centimeter optical aperture used on a satellite in a synchronous orbit. It was assumed that the reflector always faces the earth. The effects of direct solar irradiance, earthshine, and albedo were considered. The results included the maximum mirror surface temperature during the orbit as well as the worst-case loss of optical performance due to thermally-induced mirror distortions. It was concluded that a device made of three suitably coated flat ULE mirrors, optically contacted to each other and supported mechanically in a nonrigid mount, would be expected to concentrate over 80 percent of the theoretical maximum energy in the central of the far field diffraction pattern. Continued development of the device through a detailed design, fabrication, and test phase was recommended.

  15. Performance Evaluation of a Double-Glazed Box-Type Solar Oven with Reflector

    Directory of Open Access Journals (Sweden)

    Joshua Folaranmi

    2013-01-01

    Full Text Available This research paper describes the performance evaluation of a double-glazed box-type solar oven with reflector fabricated using locally available materials, compressed sawdust with binder; size of the box is 700 mm ×  700 mm × 400 mm and 10 mm thickness. The experimental solar cooker consists of an aluminium absorber plate (1 mm painted matt black and a double-glazed lid. The bottom and sides are lagged with fibreglass wool insulator, thickness = 50 mm,  W/m°C. The reflector consists of a wooden-framed commercially available specular plane mirror which is sized to form a cover for the box when not being in use. Its thermal performance was tested according to the ASAE International Test procedure and Bureau of Indian Standards (BIS for testing the thermal performance of box-type solar cooker. Thermal performance experiments were conducted in order to determine the first figure of merit (F1, the second figure of merit (F2 and standard cooking power (Ps. The obtained test results were employed to calculate the two figures of merit (F1, and F2 and the standard cooking power (P50 to be 0.11 Km2w−1, 0.31, and 23.95 W, respectively. Finally, the results illustrated that the cooker has a good reliability for cooking food and boiling water.

  16. FREE VIBRATION OF ANISOTROPIC RECTANGULAR PLATES BY GENERAL ANALYTICAL METHOD

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    According to the differential equation for transverse displacement function of anisotropic rectangular thin plates in free vibration, a general analytical solution is established. This general solution, composed of the composite solutions of trigonometric function and hyperbolic function, can satisfy the problem of arbitrary boundary conditions along four edges. The algebraic polynomial with double sine series solutions can also satisfy the problem of boundary conditions at four corners. Consequently, this general solution can be used to solve the vibration problem of anisotropic rectangular plates with arbitrary boundaries accurately. The integral constants can be determined by boundary conditions of four edges and four corners. Each natural frequency and vibration mode can be solved by the determinate of coefficient matrix from the homogeneous linear algebraic equations equal to zero. For example, a composite symmetric angle ply laminated plate with four edges clamped has been calculated and discussed.

  17. Study of back reflectors for thin film silicon solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, H.; Mai, Y. [Baoding Tianwei Solarfilms Co., Ltd., Baoding 071051 (China); Wan, M. [Department of Chemistry and Material Science, Hunan Institute of Humanities, Science and Technology, Loudi 417000 (China); Gao, J.; Wang, Y.; He, T.; Feng, Y.; Yin, J.; Du, J.; Wang, J.; Sun, R. [Baoding Tianwei Solarfilms Co., Ltd., Baoding 071051 (China); Huang, Y., E-mail: y.huang@btw-solarfilms.com [Baoding Tianwei Solarfilms Co., Ltd., Baoding 071051 (China)

    2013-07-31

    In this study, the reflection properties of transparent conductive oxide (TCO) films i.e. aluminum doped zinc oxide (ZnO:Al) and boron doped zinc oxide (ZnO:B) films plus aluminum (Al) films or white polyvinyl butyral (PVB) foils, which are usually used as the combined back reflectors of thin film silicon solar cells, are investigated. Sputtered ZnO:Al films were etched in diluted hydrochloric acid (1%) to achieve rough surface structures while textured ZnO:B films were directly prepared by a low pressure chemical vapor deposition technique. It is found that the rough TCO/Al reflectors show a low total reflection, which is mainly due to the parasitic absorption by the surface plasmons at the rough TCO/Al interfaces as well as the absorption in the TCO films. Differently, the rough TCO/white PVB foil reflectors display a slightly high light reflection regardless of the influence of the rough interface without the excitation of surface plasmons. Thus, the TCO/white PVB foil back reflectors could be a good candidate with respect to light utilization when they are applied in thin film silicon solar cells. - Highlights: • White polyvinyl butyral and transparent conductive oxide materials are used. • The reflection properties of TCO/Al and TCO/white PVB foil reflectors are studied. • The ZnO:Al and ZnO:B films are used as two types of TCO materials. • TCO/white PVB foil reflector shows a high reflection compared to TCO/Al reflector.

  18. Cadastral Surveys, SuveyedCorners, Published in 2008, Millard County.

    Data.gov (United States)

    NSGIC GIS Inventory (aka Ramona) — This Cadastral Surveys dataset, was produced all or in part from Other information as of 2008. It is described as 'SuveyedCorners'. Data by this publisher are often...

  19. Onboard autonomy on the Three Corner Sat Mission

    Science.gov (United States)

    Chien, S.; Engelhardt, B.; Knight, R.; Rabideau, G.; Sherwood, R.

    2001-01-01

    Three Corner Sat (3CS) is a mission of three university nanosatellites scheduled for launch on September 2002. The 3CS misison will utilize significan onboard autonomy to perform onboard science data validation and replanning.

  20. Fabrication of corner cube array retro-reflective structure with DLP-based 3D printing technology

    Science.gov (United States)

    Riahi, Mohammadreza

    2016-06-01

    In this article, the fabrication of a corner cube array retro-reflective structure is presented by using DLP-based 3D printing technology. In this additive manufacturing technology a pattern of a cube corner array is designed in a computer and sliced with specific software. The image of each slice is then projected from the bottom side of a reservoir, containing UV cure resin, utilizing a DLP video projector. The projected area is cured and attached to a base plate. This process is repeated until the entire part is made. The best orientation of the printing process and the effect of layer thicknesses on the surface finish of the cube has been investigated. The thermal reflow surface finishing and replication with soft molding has also been presented in this article.

  1. Searching for the corner seismic moment in worldwide data

    Energy Technology Data Exchange (ETDEWEB)

    Felgueiras, Miguel; Santos, Rui; Martins, João Paulo [CEAUL Lisbon and ESTG, Polytechnic Institute of Leiria (Portugal)

    2015-12-31

    In this paper the existence of the corner frequency value for the seismic moment distribution is investigated, analysing worldwide data. Pareto based distributions, usually considered as the most suitable to this type of data, are fitted to the most recent data, available in a global earthquake catalog. Despite the undeniable finite nature of the seismic moment data, we conclude that no corner frequency can be established considering the available data set.

  2. Effective Reflection Area of a Cube Corner Retroreflector

    Institute of Scientific and Technical Information of China (English)

    CAI Yanmin; FANG Zujie; CHEN Gang; CHEN Gaoting

    2000-01-01

    The effective reflection area of a cube corner retroreflector is defined. It is testified for a cube corner retroreflector (CCR) that the ray reflected from a CCR is not parallel with the ray incident on the CCR undersurface. The effective reflection area of CCR is calculated when the ray incident on the CCR undersurface vertically, and the effective reflection area of a CCR is two thirds of the CCR undersurface.

  3. Thermal Analysis of Thin Plates Using the Finite Element Method

    Science.gov (United States)

    Er, G. K.; Iu, V. P.; Liu, X. L.

    2010-05-01

    The isotropic thermal plate is analyzed with finite element method. The solution procedure is presented. The elementary stiffness matrix and loading vector are derived rigorously with variation principle and the principle of minimum potential energy. Numerical results are obtained based on the derived equations and tested with available exact solutions. The problems in the finite element analysis are figured out. It is found that the finite element solutions can not converge as the number of elements increases around the corners of the plate. The derived equations presented in this paper are fundamental for our further study on more complicated thermal plate analysis.

  4. Development of lightweight, glass mirror segments for the Large Deployable Reflector

    Science.gov (United States)

    Melugin, R. K.; Miller, J. H.; Angel, J. R. P.; Wangsness, P. A. A.; Parks, R. E.

    1986-01-01

    Accomplishments in the development of lightweight, honeycomb-core, sandwich mirror blanks made of borosilicate and high-silica glasses at the University of Arizona for the Large Deployable Reflector program are described. In this paper, work spanning the last 2 years is reported, highlighting a new mirror blank fabrication technique that permits the fabrication of the honeycomb core integrally with the front and back plates of the blank in a single furnace cycle. Two types of mirror blanks made by this method, an off-axis, aspheric segment and a smaller Vycor circular piece, are described. The fabrication of two off-axis, aspheric mirror segments is also described. Cryogenic test results are included on the test of a 38-cm diameter, lightweight, honeycomb core, sandwich mirror made of Pyrex.

  5. Mechanical Behavior of CFRP Lattice Core Sandwich Bolted Corner Joints

    Science.gov (United States)

    Zhu, Xiaolei; Liu, Yang; Wang, Yana; Lu, Xiaofeng; Zhu, Lingxue

    2017-02-01

    The lattice core sandwich structures have drawn more attention for the integration of load capacity and multifunctional applications. However, the connection of carbon fibers reinforced polymer composite (CFRP) lattice core sandwich structure hinders its application. In this paper, a typical connection of two lattice core sandwich panels, named as corner joint or L-joint, was investigated by experiment and finite element method (FEM). The mechanical behavior and failure mode of the corner joints were discussed. The results showed that the main deformation pattern and failure mode of the lattice core sandwich bolted corner joints structure were the deformation of metal connector and indentation of the face sheet in the bolt holes. The metal connectors played an important role in bolted corner joints structure. In order to save the calculation resource, a continuum model of pyramid lattice core was used to replace the exact structure. The computation results were consistent with experiment, and the maximum error was 19%. The FEM demonstrated the deflection process of the bolted corner joints structure visually. So the simplified FEM can be used for further analysis of the bolted corner joints structure in engineering.

  6. Detecting Seismicity Rate Transients in the Hokkaido Corner

    Science.gov (United States)

    Llenos, A. L.; McGuire, J. J.; Ogata, Y.

    2009-12-01

    Transient aseismic processes alter the stress state of a region and can cause seismicity rate anomalies in space and time detectable by models such as the Epidemic Type Aftershock Sequence (ETAS) model (Ogata, 1988). The presence of such anomalies in subduction zones can therefore indicate stress changes are occurring due to processes such as afterslip or slow slip events. The Hokkaido corner in northeastern Japan is a good region to investigate these anomalies and their relationship to frictional conditions on the plate interface. This area consists of several asperities that rupture in great earthquakes such as the 2003 M8.3 Tokachi-oki earthquake. The abundance of high quality seismic and geodetic data for that event have led to the development of detailed coseismic and postseismic slip models (e.g., Yamanaka and Kikuchi, 2003; Miyazaki et al., 2004), from which stress changes can be inferred and compared to spatial and temporal variations in seismicity rate behavior. For example, an analysis of central Japan seismicity suggests that high aftershock productivities tend to cluster on the updip boundaries of major asperities (Ogata, 2005). Elevated stressing rates due to afterslip can also cause increased levels of background seismicity on the fault patches where afterslip is occurring. Therefore, mapping where these anomalies occur can lead to a better understanding of where and how stress is accumulating on the megathrust. We have developed a method that can directly map seismicity rate anomalies to the stressing rate changes due to aseismic processes. Because aftershocks often obscure changes in the background seismicity caused by these processes, we combine two models commonly used to estimate the time dependence of underlying driving mechanisms, the stochastic ETAS model and the physically based rate- and state-dependent friction model (Dieterich, 1994), into a single seismicity rate model that can explain both aftershock activity as well as changes in

  7. Highly Accurate Photogrammetric Measurements of the Planck Reflectors

    Science.gov (United States)

    Amiri Parian, J.; Gruen, Armin; Cozzani, Alessandro

    2006-06-01

    The Planck mission of the European Space Agency (ESA) is designed to image the anisotropies of the Cosmic Background Radiation Field over the whole sky. To achieve this aim, sophisticated reflectors are used as part of the Planck telescope receiving system. The system consists of secondary and primary reflectors which are sections of two different ellipsoids of revolution with mean diameters of 1 and 1.6 meters. Deformations of the reflectors which influence the optical parameters and the gain of receiving signals are investigated in vacuum and at very low temperatures. For this investigation, among the various high accuracy measurement techniques, photogrammetry was selected. With respect to the photogrammetric measurements, special considerations had to be taken into account in design steps, measurement arrangement and data processing to achieve very high accuracies. The determinability of additional parameters of the camera under the given network configuration, datum definition, reliability and precision issues as well as workspace limits and propagating errors from different sources are considered. We have designed an optimal photogrammetric network by heuristic simulation for the flight model of the primary and the secondary reflectors with relative precisions better than 1:1000000 and 1:400000 to achieve the requested accuracies. A least squares best fit ellipsoid method was developed to determine the optical parameters of the reflectors. In this paper we will report about the procedures, the network design and the results of real measurements.

  8. Numerical Study of Concentration Characteristics of Linear Fresnel Reflector System

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hyun Jin [Kookmin Univ., Seoul (Korea, Republic of); Kim, Jong Kyu; Lee, Sang Nam [Korea Institute of Energy Research, Daejeon (Korea, Republic of)

    2015-12-15

    In this study, we numerically investigated the concentration characteristics of a linear Fresnel reflector system that can drive a solar thermal absorption refrigeration system to be installed in Saudi Arabia. Using an optical modeling program based on the Monte Carlo ray-tracing method, we simulated the concentrated solar flux, concentration efficiency, and concentrated solar energy on four representative days of the year - the vernal equinox, summer solstice, autumnal equinox, and winter solstice. Except the winter solstice, the concentrations were approximately steady from 9 AM to 15 PM, and the concentration efficiencies exceed 70%. Moreover, the maximum solar flux around the solar receiver center changes only within the range of 13.0 - 14.6 kW/m{sup 2}. When we investigated the effects of the receiver installation height, reflector width, and reflector gap, the optimal receiver installation height was found to be 5 m. A smaller reflector width had a greater concentration efficiency. However, the design of the reflector width should be based on the capacity of the refrigeration system because it dominantly affects the concentrated solar energy. The present study was an essential prerequisite for thermal analyses of the solar receiver. Thus, an optical-thermal integration study in the future will assist with the performance prediction and design of the entire system.

  9. Application of the OPTEX method for computing reflector parameters

    Energy Technology Data Exchange (ETDEWEB)

    Hebert, A. [Ecole Polytechnique de Montreal, C.P. 6079 suce. Centre-Ville, Montreal QC. H3C 3A7 (Canada); Leroyer, H. [EDF - R and D, SINETICS, 1 Avenue du General de Gaulle, 92141 Clamart (France)

    2013-07-01

    We are investigating the OPTEX reflector model for obtaining few-group reflector parameters consistent with a reference power distribution in the core. In our study, the reference power distribution is obtained using a 142,872-region calculation defined over a 2D eighth-of-core pressurized water reactor and performed with the method of characteristics. The OPTEX method is based on generalized perturbation theory and uses an optimization algorithm known as parametric linear complementarity pivoting. The proposed model leads to few-group diffusion coefficients or P1-weighted macroscopic total cross sections that can be used to represent the reflector in full-core calculations. These few-group parameters can be spatially heterogeneous in order to correctly represent steel baffles present in modern pressurized water reactors. The optimal reflector parameters are compared to those obtained with a flux-volume weighting of the reflector cross sections recovered from the reference calculation. Important improvements in full-core power distribution are observed when the optimal parameters are used. (authors)

  10. Form-finding methods for deployable mesh reflector antennas

    Institute of Scientific and Technical Information of China (English)

    Li Tuanjie; Jiang Jie; Deng Hanqing; Lin Zhanchao; Wang Zuowei

    2013-01-01

    Deployable high-frequency mesh reflector antennas for future communications and obser-vations are required to obtain high gain and high directivity. In order to support these new missions, reflectors with high surface accuracy are widely required. The form-finding analysis of deployable mesh reflector antennas becomes more vital which aims to determine the initial surface profile formed by the equilibrium prestress distribution in cables to satisfy the surface accuracy requirement. In this paper, two form-finding methods for mesh reflector antennas, both of which include two steps, are pro-posed. The first step is to investigate the prestress design only for the cable net structure as the circum-ferential nodes connected to the supporting truss are assumed fixed. The second step is to optimize the prestress distribution of the boundary cables connected directly to the supporting truss considering the elastic deformation of the antenna structure. Some numerical examples are carried out and the simu-lation results demonstrate the proposed form-finding methods can warrant the deformed antenna reflector surface matches the one by design and the cable tension forces fall in a specified range.

  11. Solar Thermal Vacuum Test of Deployable Astromesh Reflector

    Science.gov (United States)

    Stegman, Matthew D.

    2009-01-01

    On September 10, 2008, a 36-hour Solar Thermal Vacuum Test of a 5m deployable mesh reflector was completed in JPL's 25' Space Simulator by the Advanced Deployable Structures Group at JPL. The testing was performed under NASA's Innovative Partnership Program (IPP) as a risk reduction effort for two JPL Decadal Survey Missions: DESDynI and SMAP. The 5.0 m aperture Astromesh reflector was provided by Northrop Grumman Aerospace Systems (NGAS) Astro Aerospace, our IPP industry partner. The testing utilized a state-of-the-art photogrammetry system to measure deformation of the reflector under LN2 cold soak, 0.25 Earth sun, 0.5 sun and 1.0 sun. An intricate network of thermocouples (approximately 200 in total) was used to determine the localized temperature across the mesh as well as on the perimeter truss of the reflector. Half of the reflector was in a fixed shadow to maximize thermal gradients. A mobility system was built for remotely actuating the cryo-vacuum capable photogrammetry camera around the circumference of the Solar Simulator. Photogrammetric resolution of 0.025 mm RMS (0.001") was achieved over the entire 5 meter aperture for each test case. The data will be used for thermo-elastic model correlation and validation, which will benefit the planned Earth Science Missions.

  12. Energy flow in plate assembles by hierarchical version of finite element method

    DEFF Research Database (Denmark)

    Wachulec, Marcin; Kirkegaard, Poul Henning

    method has been proposed. In this paper a modified hierarchical version of finite element method is used for modelling of energy flow in plate assembles. The formulation includes description of in-plane forces so that planes lying in different planes can be modelled. Two examples considered are: L......-corner of two rectangular plates an a I-shaped plate girder made of five plates. Energy distribution among plates due to harmonic load is studied and the comparison of performance between the hierarchical and standard finite element formulation is presented....

  13. KuDGR- Dual Gridded Carbon Fiber Reinforced Plastic Reflector

    Science.gov (United States)

    Ihle, Alexander; Reichmann, O.; Lori, M.; Nathrath, N.; Pereira, C.; Linke, S.; Rinous, P.

    2014-06-01

    In the frame of an ESA-funded TRP activity HPS GmbH, together with INVENT GmbH and INEGI, has developed an advanced concept for dual gridded reflectors. The target frequency band is the Ku-band requiring high in-orbit thermo-elastic stability. It is a follow-on of the previous KaDGR [1] activity. The concept concerns the polarisation grid of the front and rear reflector. The grids are connected by a full CFRP monolithic peripheral ring. The demonstrator has an overall diameter of 1.4 x 1.2 m and a weight of only 4.23 kg. The design of this concept allows for smaller and larger reflectors.In the following we will present the results of the different development steps and current status of the TRP activity.

  14. Semitransparent Polymer Solar Cells Based on Liquid Crystal Reflectors

    Directory of Open Access Journals (Sweden)

    Shaopeng Yang

    2014-01-01

    Full Text Available The effects of liquid crystal (LC reflectors on semitransparent polymer solar cells (PSCs were investigated in this paper. By improving the cathode, we manufactured semitransparent PSCs based on the conventional PSCs. We then incorporated the LC reflector into the semitransparent PSCs, which increased the power conversion efficiency (PCE from 2.11% to 2.71%. Subsequently adjusting the concentration and spinning speed of the active layer material changed its thickness. The maximum light absorption for the active layer was obtained using the optimum thickness, and the PCE eventually reached 3.01%. These results provide a reference for selecting LC reflectors that are suitable for different active layer materials to improve the PCE of semitransparent PSCs.

  15. An active reflector antenna using a laser angle metrology system

    Institute of Scientific and Technical Information of China (English)

    Yong Zhang; Jie Zhang; De-Hua Yang; Guo-Hua Zhou; Ai-Hua Li; Guo-Ping Li

    2012-01-01

    An active reflector is one of the key technologies for constructing large telescopes,especially for millimeter/sub-millimeter radio telescopes.This article introduces a new efficient laser angle metrology system for an active reflector antenna on large radio telescopes.Our experiments concentrate on developing an active reflector for improving the detection precisions and the maintenance of the surface shape in real time on the 65-meter prototype radio telescope constructed by Nanjing Institute of Astronomical Optics and Technology (NIAOT; http://65m.shao.cas.cn/).The test results indicate that the accuracy of the surface shape segmentation and maintenance has the dimensions of microns,and the time-response can be on the order of minutes.Our efforts proved to be workable for sub-millimeter radio telescopes.

  16. Beam-Steerable Flat-Panel Reflector Antenna

    Science.gov (United States)

    Lee, Choon Sae; Lee, Chanam; Miranda, Felix A.

    2005-01-01

    Many space applications require a high-gain antenna that can be easily deployable in space. Currently, the most common high-gain antenna for space-born applications is an umbrella-type reflector antenna that can be folded while being lifted to the Earth orbit. There have been a number of issues to be resolved for this type of antenna. The reflecting surface of a fine wire mesh has to be light in weight and flexible while opening up once in orbit. Also the mesh must be a good conductor at the operating frequency. In this paper, we propose a different type of high-gain antenna for easy space deployment. The proposed antenna is similar to reflector antennas except the curved main reflector is replaced by a flat reconfigurable surface for easy packing and deployment in space. Moreover it is possible to steer the beam without moving the entire antenna system.

  17. Effect of phototherapy with alumunium foil reflectors on neonatal hyperbilirubinemia

    Directory of Open Access Journals (Sweden)

    Tony Ijong Dachlan

    2016-07-01

    Full Text Available Background Neonatal hyperbilirubinemia (NH is one of the most common problems in neonates, but it can be treated with blue light phototherapy. Developing countries with limited medical equipment and funds have difficulty providing effective phototherapy to treat NH, leading to increased risk of bilirubin encephalopathy. Phototherapy with white reflecting curtains can decrease the duration of phototherapy needed to reduce bilirubin levels. Objective To compare the duration of phototherapy needed in neonates with NH who underwent phototherapy with and without aluminum foil reflectors. Methods This open clinical trial was conducted from July to August 2013 at Dr. Hasan Sadikin Hospital, Bandung, Indonesia. The inclusion criteria were term neonates with uncomplicated NH presenting in their first week of life. Subjects were randomized into two groups, those who received phototherapy with or without aluminum foil reflectors. Serum bilirubin is taken at 12th, 24th, 48th hours, then every 24 hours if needed until phototherapy can be stopped according to American Academy of Pediatrics guidelines. The outcome measured was the duration of phototherapy using survival analysis. The difference between the two groups was tested by Gehan method. Results Seventy newborns who fulfilled the inclusion criteria and had similar characteristics were randomized into two groups. The duration of phototherapy needed was significantly less in the group with aluminum foil reflectors than in the group without reflectors [72 vs. 96 hours, respectively, (P<0.01]. Conclusion The required duration of phototherapy with aluminum foil reflectors is significantly less than that of phototherapy without reflectors, in neonates with NH.

  18. Corner rounding in EUV photoresist: tuning through molecular weight, PAG size, and development time

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, Christopher; Daggett, Joe; Naulleau, Patrick

    2009-12-31

    In this paper, the corner rounding bias of a commercially available extreme ultraviolet photoresist is monitored as molecular weight, photoacid generator (PAG) size, and development time are varied. These experiments show that PAG size influences corner biasing while molecular weight and development time do not. Large PAGs are shown to exhibit less corner biasing, and in some cases, lower corner rounding, than small PAGs. In addition, heavier resist polymers are shown to exhibit less corner rounding than lighter ones.

  19. Recent Developments of Reflectarray Antennas in Dual-Reflector Configurations

    Directory of Open Access Journals (Sweden)

    Carolina Tienda

    2012-01-01

    Full Text Available Recent work on dual-reflector antennas involving reflectarrays is reviewed in this paper. Both dual-reflector antenna with a reflectarray subreflector and dual-reflectarrays antennas with flat or parabolic main reflectarray are considered. First, a general analysis technique for these two configurations is described. Second, results for beam scanning and contoured-beam applications in different frequency bands are shown and discussed. The performance and capabilities of these antennas are shown by describing some practical design cases for radar, satellite communications, and direct broadcast satellite (DBS applications.

  20. Lunar Eclipse Observations Reveal Anomalous Thermal Performance of Apollo Reflectors

    CERN Document Server

    Murphy, T W; Johnson, N H; Goodrow, S D

    2013-01-01

    Laser ranging measurements during the total lunar eclipse on 2010 December 21 verify previously suspected thermal lensing in the retroreflectors left on the lunar surface by the Apollo astronauts. Signal levels during the eclipse far exceeded those historically seen at full moon, and varied over an order of magnitude as the eclipse progressed. These variations can be understood via a straightforward thermal scenario involving solar absorption by a ~50% covering of dust that has accumulated on the front surfaces of the reflectors. The same mechanism can explain the long-term degradation of signal from the reflectors as well as the acute signal deficit observed near full moon.

  1. Tensile-strained germanium microdisks with circular Bragg reflectors

    Science.gov (United States)

    El Kurdi, M.; Prost, M.; Ghrib, A.; Elbaz, A.; Sauvage, S.; Checoury, X.; Beaudoin, G.; Sagnes, I.; Picardi, G.; Ossikovski, R.; Boeuf, F.; Boucaud, P.

    2016-02-01

    We demonstrate the combination of germanium microdisks tensily strained by silicon nitride layers and circular Bragg reflectors. The microdisks with suspended lateral Bragg reflectors form a cavity with quality factors up to 2000 around 2 μm. This represents a key feature to achieve a microlaser with a quasi-direct band gap germanium under a 1.6% biaxial tensile strain. We show that lowering the temperature significantly improves the quality factor of the quasi-radial modes. Linewidth narrowing is observed in a range of weak continuous wave excitation powers. We finally discuss the requirements to achieve lasing with these kind of structures.

  2. New Developments in Large High Performance Shaped Reflectors

    Science.gov (United States)

    Abegg, C.; Baril, S.

    2002-01-01

    The large shaped reflectors, currently designed and manufactured at EADS LAUNCH VEHICLES, belong to a new generation of highly precise, highly stable and low mass reflectors for C/Ku-band and up to Ka-band missions. The previous EADS LAUNCH VEHICLES flight proven design was the one presented in the past at IAF and especially in 1994 and 1995, which was already at his time the in-orbit largest (3.5m x 2.6m) rigid reflector in the world for C/Ku-band missions. Operators require higher and higher performances for telecommunication antenna. And since the antenna performances are very dependent on the reflector ones, several developments of a new generation of large shaped reflectors started in the late 1990's. The first development consists in a new concept which particularly enhances the manufacturing easiness, the manufacturing distortion performances, the in-orbit distortion performances, the mass, the versatility versus a late change of coverage and versus implementation on different platforms. An extensive qualification test campaign has been successfully achieved in 2001, with outstanding performances: 30% mass gain and 50% gain of manufacturing and in-orbit accuracy with respect to previous 1995's design for the largest 3.5m x 2.6m reflectors. In parallel, developments have been led at EADS LAUNCH VEHICLES for large Ka-band mission antenna reflectors. These developments include single and dual shell reflectors with diameters up to 1.8 m. Furthermore, antenna requirements have recently led to more and more shaped profiles to fulfil RF needs. EADS LAUNCH VEHICLES has then started a development to verify the capability to manufacture very small curvature radius around 30mm, in order to provide the best product for the satellite missions. All the necessary analyses and material/processes characterisation tests have been carried out for these developments. Qualification tests have been performed or are under progress in profile measurements, sine vibration, acoustic

  3. Lunar eclipse observations reveal anomalous thermal performance of Apollo reflectors

    Science.gov (United States)

    Murphy, T. W.; McMillan, R. J.; Johnson, N. H.; Goodrow, S. D.

    2014-03-01

    Laser ranging measurements during the total lunar eclipse on 2010 December 21 verify previously suspected thermal lensing in the retroreflectors left on the lunar surface by the Apollo astronauts. Signal levels during the eclipse far exceeded those historically seen at full moon, and varied over an order of magnitude as the eclipse progressed. These variations can be understood via a straightforward thermal scenario involving solar absorption by a ∼50% covering of dust that has accumulated on the front surfaces of the reflectors. The same mechanism can explain the long-term degradation of signal from the reflectors as well as the acute signal deficit observed near full moon.

  4. Highly Enriched Uranium Metal Cylinders Surrounded by Various Reflector Materials

    Energy Technology Data Exchange (ETDEWEB)

    Bernard Jones; J. Blair Briggs; Leland Monteirth

    2007-05-01

    A series of experiments was performed at Los Alamos Scientific Laboratory in 1958 to determine critical masses of cylinders of Oralloy (Oy) reflected by a number of materials. The experiments were all performed on the Comet Universal Critical Assembly Machine, and consisted of discs of highly enriched uranium (93.3 wt.% 235U) reflected by half-inch and one-inch-thick cylindrical shells of various reflector materials. The experiments were performed by members of Group N-2, particularly K. W. Gallup, G. E. Hansen, H. C. Paxton, and R. H. White. This experiment was intended to ascertain critical masses for criticality safety purposes, as well as to compare neutron transport cross sections to those obtained from danger coefficient measurements with the Topsy Oralloy-Tuballoy reflected and Godiva unreflected critical assemblies. The reflector materials examined in this series of experiments are as follows: magnesium, titanium, aluminum, graphite, mild steel, nickel, copper, cobalt, molybdenum, natural uranium, tungsten, beryllium, aluminum oxide, molybdenum carbide, and polythene (polyethylene). Also included are two special configurations of composite beryllium and iron reflectors. Analyses were performed in which uncertainty associated with six different parameters was evaluated; namely, extrapolation to the uranium critical mass, uranium density, 235U enrichment, reflector density, reflector thickness, and reflector impurities. In addition to the idealizations made by the experimenters (removal of the platen and diaphragm), two simplifications were also made to the benchmark models that resulted in a small bias and additional uncertainty. First of all, since impurities in core and reflector materials are only estimated, they are not included in the benchmark models. Secondly, the room, support structure, and other possible surrounding equipment were not included in the model. Bias values that result from these two simplifications were determined and associated

  5. An Optical Reflector System for the CANGAROO-II Telescope

    CERN Document Server

    Kawachi, A

    1999-01-01

    We have developed light and durable mirrors made of CFRP (Carbon Fiber Reinforced Plastics) laminates for the reflector of the new CANGAROO-II 7 m telescope. The reflector has a parabolic shape (F/1.1) with a 30 m^2 effective area which consists of 60 small spherical mirrors. The attitude of each mirror can be remotely adjusted by stepping motors. After the first adjustment work, the re ector offers a point image of about 0.14 degree (FWHM) on the optic axis. The telescope has been in operation since May 1999 with an energy threshold of ~ 300 GeV.

  6. Variables Affecting Smooth Particle Hydrodynamics Simulation of High-Velocity Flyer Plate Impact Experiments

    Energy Technology Data Exchange (ETDEWEB)

    Somasundaram, Deepak S [UNLV; Trabia, Mohamed [UNLV; O' Toole, Brendan [UNLV; Hixson, Robert S [NSTec

    2014-01-23

    This paper describes our work to characterize the variables affecting the smoothed particle hydrodynamics (SPH) method in the LS-DYNA package for simulating high-velocity flyer plate impact experiments. LS-DYNA simulations are compared with one-dimensional experimental data of an oxygen-free high-conductivity (OFHC) copper flyer plate impacting another plate of the same material. The comparison is made by measuring the velocity of a point on the back surface of the impact plate using the velocity interferometer system for any reflector (VISAR) technique.

  7. Corner Rounding in Photoresists for Extreme Ultraviolet Lithography

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, Christopher N.; Naulleau, Patrick; Deng, Yunfei; Wallow, Thomas

    2008-06-01

    Deprotection blur in EUV resists fundamentally limits the smallest sized dense features that can be patterned in a single exposure and development step. Several metrics have recently been developed to explore the ways that different resist and process parameters affect the deprotection blur in EUV resists. One of these metrics is based on the imaging fidelity of a sharp corner on a large feature. As this metric has involved the close inspection of printing fidelity of corner features, it has brought attention to an interesting phenomena: corners print differently whether or not the remaining resist edge contains 270 degrees of resist or 90 degrees of resist. Here we present experimental data across a wide sampling of leading resists to show this effect is real and reproducible. They provide aerial image modeling results assuming thin and realistic mask models that show no corner bias between the aerial images in the 90-degree and 270-degree configurations. They also compare modeled patterning results assuming several resist models including the single blur, dual blur, and Prolith models, none of which reproduce the corner biasing that is observed experimentally.

  8. An evaluation of some unbraked tire cornering force characteristics

    Science.gov (United States)

    Leland, T. J. W.

    1972-01-01

    An investigation to determine the effects of pavement surface condition on the cornering forces developed by a group of 6.50x13 automobile tires of different tread design was conducted at the Langley aircraft landing loads and traction facility. The tests were made at fixed yaw angles of 3,4.5, and 6 deg at forward speeds up to 80 knots on two concrete surfaces of different texture under dry, damp, and flooded conditions. The results showed that the cornering forces were extremely sensitive to tread pattern and runway surface texture under all conditions and that under flooded conditions tire hydroplaning and complete loss of cornering force occurred at a forward velocity predicted from an existing formula based on tire inflation pressure. Futher, tests on the damp concrete with a smooth tire and a four-groove tire showed higher cornering forces at a yaw angle of 3 deg than at 4.5 deg; this indicated that maximum cornering forces are developed at extremely small steering angles under these conditions.

  9. a Novel and Fast Corner Detection Method for SAR Imagery

    Science.gov (United States)

    Jiao, N.; Kang, W.; Xiang, Y.; You, H.

    2017-09-01

    Corners play an important role on image processing, while it is difficult to detect reliable and repeatable corners in SAR images due to the complex property of SAR sensors. In this paper, we propose a fast and novel corner detection method for SAR imagery. First, a local processing window is constructed for each point. We use the local mean of a 3 x 3 mask to represent a single point, which is weighted by a Gaussian template. Then the candidate point is compared with 16 surrounding points in the processing window. Considering the multiplicative property of speckle noise, the similarity measure between the center point and the surrounding points is calculated by the ratio of their local means. If there exist more than M continuous points are different from the center point, then the candidate point is labelled as a corner point. Finally, a selection strategy is implemented by ranking the corner score and employing the non-maxima suppression method. Extreme situations such as isolated bright points are also removed. Experimental results on both simulated and real-world SAR images show that the proposed detector has a high repeatability and a low localization error, compared with other state-of-the-art detectors.

  10. The motion of a deforming capsule through a corner

    CERN Document Server

    Zhu, Lailai

    2014-01-01

    A three-dimensional deformable capsule convected through a channel/duct with a corner is studied via numerical simulations using an accelerated boundary integral method adapted to general geometries. A global spectral method is adopted to resolve the dynamics of the capsule's membrane developing elastic tensions according to the Neo-Hookean constitutive law and bending moments in an inertialess flow. The simulations show that the trajectory of the capsule closely follows the underlying streamlines and the deformation of the capsule induces an anti-clockwise rotation of its material points with respect to the travelling direction. The surface area, principle tension and elastic energy of the capsule increase around the corner. Their temporal evolutions are characterised by a clear phase delay and the loss of time-reversal symmetry of Stokes flow due to the elasticity of membrane. The capsule centroid velocity decreases approaching the corner as the mean flow does while a velocity overshoot is observed past the...

  11. Ballistic rectification of vortex domain wall chirality at nanowire corners

    Energy Technology Data Exchange (ETDEWEB)

    Omari, K.; Bradley, R. C.; Broomhall, T. J.; Hodges, M. P. P.; Hayward, T. J. [Department of Materials Science and Engineering, University of Sheffield, Sheffield S1 3JD (United Kingdom); Rosamond, M. C.; Linfield, E. H. [School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT (United Kingdom); Im, M.-Y. [Center for X-Ray Optics, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Daegu Gyeongbuk Institute of Science and Technology, Daegu 711-873 (Korea, Republic of); Fischer, P. [Materials Sciences Division, Lawrence Berkley National Laboratory, Berkeley, California 94720 (United States); Department of Physics, University of California, Santa Cruz, California 94056 (United States)

    2015-11-30

    The interactions of vortex domain walls with corners in planar magnetic nanowires are probed using magnetic soft X-ray transmission microscopy. We show that when the domain walls are propagated into sharp corners using applied magnetic fields above a critical value, their chiralities are rectified to either clockwise or anticlockwise circulation depending on whether the corners turn left or right. Single-shot focused magneto-optic Kerr effect measurements are then used to demonstrate how, when combined with modes of domain propagation that conserve vortex chirality, this allows us to dramatically reduce the stochasticity of domain pinning at artificial defect sites. Our results provide a tool for controlling domain wall chirality and pinning behavior both in further experimental studies and in future domain wall-based memory, logic and sensor technologies.

  12. Semitransparent organic solar cells with organic wavelength dependent reflectors

    NARCIS (Netherlands)

    Galagan, Y.O.; Debije, M.G.; Blom, P.W.M.

    2011-01-01

    Semitransparent organic solar cells employing solution-processable organic wavelength dependent reflectors of chiral nematic (cholesteric) liquid crystals are demonstrated. The cholesteric liquid crystal (CLC) reflects only in a narrow band of the solar spectrum and remains transparent for the remai

  13. Advanced reflector characterization with ultrasonic phased arrays in NDE applications.

    Science.gov (United States)

    Wilcox, Paul D; Holmes, Caroline; Drinkwater, Bruce W

    2007-08-01

    Ultrasonic arrays are increasingly widely used in nondestructive evaluation (NDE) due to their greater flexibility and potentially superior performance compared to conventional monolithic probes. The characterization of small defects remains a challenge for NDE and is of great importance for determining the impact of a defect on the integrity of a structure. In this paper, a technique for characterizing reflectors with subwavelength dimensions is described. This is achieved by post-processing the complete data set of time traces obtained from an ultrasonic array using two algorithms. The first algorithm is used to obtain information about reflector orientation and the second algorithm is used to distinguish between point-like reflectors that reflect uniformly in all directions and specular reflectors that have distinct orientations. Experimental results are presented using a commercial 64-element, 5-MHZ array on two aluminum test specimens that contain a number of machined slots and side-drilled holes. The results show that the orientation of 1-mm-long slots can be determined to within a few degrees and that the signals from 1-mm-long slots can be distinguished from that from a 1-mm-diameter circular hole. Techniques for quantifying both the orientation and the specularity of measured signals are presented and the effect of processing parameters on the accuracy of results is discussed.

  14. Large-scale Optimization of Contoured Beam Reflectors and Reflectarrays

    DEFF Research Database (Denmark)

    Borries, Oscar; Sørensen, Stig B.; Jørgensen, Erik;

    2016-01-01

    Designing a contoured beam reflector or performing a direct optimization of a reflectarray requires a mathematical optimization procedure to determine the optimum design of the antenna. A popular approach, used in the market-leading TICRA software POS, can result in computation times on the order...

  15. Classification of Surface Quality of Automobile Lamp—Reflector

    Institute of Scientific and Technical Information of China (English)

    袁旭军; 贺莉清; 等

    2002-01-01

    This paper introduces an installation for quickly classifying automobile's metal reflectors based on their roughness.The measuring principle and the mechanical structure are presented.Schematics of circuits and experimental results are given.Elimination and reduction of the effect of background lights or different bulbs on the measuring results are also described in detail.

  16. Leaky Wave Enhanced Feeds for Multi-Beam Reflector Systems

    NARCIS (Netherlands)

    Neto, A.; Gerini, G.; Llombart, N.; Ettorre, M.; Maagt, P. de

    2011-01-01

    Abstract—This paper discusses the use of dielectric superlayers to shape the radiation pattern of focal plane feeds of a multi-beam reflector system. The shaping of the pattern is obtained by exciting a pair (TE/TM) of leaky waves that radiate incrementally as they propagate between the ground plane

  17. Optical Phased Array Using Guided Resonance with Backside Reflectors

    Science.gov (United States)

    Horie, Yu (Inventor); Arbabi, Amir (Inventor); Faraon, Andrei (Inventor)

    2016-01-01

    Methods and systems for controlling the phase of electromagnetic waves are disclosed. A device can consist of a guided resonance grating layer, a spacer, and a reflector. A plurality of devices, arranged in a grid pattern, can control the phase of reflected electromagnetic phase, through refractive index control. Carrier injection, temperature control, and optical beams can be applied to control the refractive index.

  18. Step-Stress Accelerated Degradation Testing for Solar Reflectors: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Jones, W.; Elmore, R.; Lee, J.; Kennedy, C.

    2011-09-01

    To meet the challenge to reduce the cost of electricity generated with concentrating solar power (CSP) new low-cost reflector materials are being developed including metalized polymer reflectors and must be tested and validated against appropriate failure mechanisms. We explore the application of testing methods and statistical inference techniques for quantifying estimates and improving lifetimes of concentrating solar power (CSP) reflectors associated with failure mechanisms initiated by exposure to the ultraviolet (UV) part of the solar spectrum. In general, a suite of durability and reliability tests are available for testing a variety of failure mechanisms where the results of a set are required to understand overall lifetime of a CSP reflector. We will focus on the use of the Ultra-Accelerated Weathering System (UAWS) as a testing device for assessing various degradation patterns attributable to accelerated UV exposure. Depending on number of samples, test conditions, degradation and failure patterns, test results may be used to derive insight into failure mechanisms, associated physical parameters, lifetimes and uncertainties. In the most complicated case warranting advanced planning and statistical inference, step-stress accelerated degradation (SSADT) methods may be applied.

  19. Frequency Selective Surfaces for extended Bandwidth backing reflector functions

    NARCIS (Netherlands)

    Pasian, M.; Neto, A.; Monni, S.; Ettorre, M.; Gerini, G.

    2008-01-01

    This paper deals with the use of Frequency Selective Surfaces (FSS) to increase the Efficiency × Bandwidth product in Ultra-Wide Band (UWB) antenna arrays whose efficiency is limited by the front-to-back ratio. If the backing reflector is realized in one metal plane solution its location will be sui

  20. Semitransparent organic solar cells with organic wavelength dependent reflectors

    NARCIS (Netherlands)

    Galagan, Y.O.; Debije, M.G.; Blom, P.W.M.

    2011-01-01

    Semitransparent organic solar cells employing solution-processable organic wavelength dependent reflectors of chiral nematic (cholesteric) liquid crystals are demonstrated. The cholesteric liquid crystal (CLC) reflects only in a narrow band of the solar spectrum and remains transparent for the remai

  1. EBG Enhanced Reflector Feeds for Wide Angle Scanning Applications

    NARCIS (Netherlands)

    Neto, A.; Ettorre, M.; Gerini, G.; Maagt, P.J. de

    2008-01-01

    This work is an extension of a series of works on the use of dielectric super-layers to shape the radiation pattern of each feed composing a focal plane imaging array. Using dielectric super-layers, the spill over from the reflectors are reduced without increasing the dimensions of each aperture. Th

  2. Computer program aids dual reflector antenna system design

    Science.gov (United States)

    Firnett, P.; Gerritsen, R.; Jarvie, P.; Ludwig, A.

    1968-01-01

    Computer program aids in the design of maximum efficiency dual reflector antenna systems. It designs a shaped cassegrainian antenna which has nearly 100 percent efficiency, and accepts input parameters specifying an existing conventional antenna and produces as output the modifications necessary to conform to a shaped design.

  3. Beam spoiling a reflector antenna with conducting shim.

    Energy Technology Data Exchange (ETDEWEB)

    Doerry, Armin Walter

    2012-12-01

    A horn-fed dish reflector antenna has characteristics including beam pattern that are a function of its mechanical form. The beam pattern can be altered by changing the mechanical configuration of the antenna. One way to do this is with a reflecting insert or shim added to the face of the original dish.

  4. Application of parabolic reflector on Raman analysis of gas samples

    Science.gov (United States)

    Yu, Anlan; Zuo, Duluo; Gao, Jun; Li, Bin; Wang, Xingbing

    2016-05-01

    Studies on the application of a parabolic reflector in spontaneous Raman scattering for low background Raman analysis of gas samples are reported. As an effective signal enhancing sample cell, photonic bandgap fiber (HC-PBF) or metallined capillary normally result in a strong continuous background in spectra caused by the strong Raman/fluorescence signal from the silica wall and the polymer protective film. In order to obtain enhanced signal with low background, a specially designed sample cell with double-pass and large collecting solid angle constructed by a parabolic reflector and a planar reflector was applied, of which the optical surfaces had been processed by diamond turning and coated by silver film and protective film of high-purity alumina. The influences of optical structure, polarization characteristic, collecting solid-angle and collecting efficiency of the sample cell on light propagation and signal enhancement were studied. A Raman spectrum of ambient air with signal to background ratio of 94 was acquired with an exposure time of 1 sec by an imaging spectrograph. Besides, the 3σ limits of detection (LOD) of 7 ppm for H2, 8 ppm for CO2 and 12 ppm for CO were also obtained. The sample cell mainly based on parabolic reflector will be helpful for compact and high-sensitive Raman system.

  5. Measurement of small antenna reflector losses for radiometer calibration budget

    DEFF Research Database (Denmark)

    Skou, Niels

    1997-01-01

    Antenna reflector losses play an important role in the calibration budget for a microwave radiometer. If the losses are small, they are difficult to measure by traditional means. However, they can be assessed directly by radiometric means using the sky brightness temperature as incident radiation...

  6. Geometrically Nonlinear Finite Element Analysis of a Composite Space Reflector

    Science.gov (United States)

    Lee, Kee-Joo; Leet, Sung W.; Clark, Greg; Broduer, Steve (Technical Monitor)

    2001-01-01

    Lightweight aerospace structures, such as low areal density composite space reflectors, are highly flexible and may undergo large deflection under applied loading, especially during the launch phase. Accordingly, geometrically nonlinear analysis that takes into account the effect of finite rotation may be needed to determine the deformed shape for a clearance check and the stress and strain state to ensure structural integrity. In this study, deformation of the space reflector is determined under static conditions using a geometrically nonlinear solid shell finite element model. For the solid shell element formulation, the kinematics of deformation is described by six variables that are purely vector components. Because rotational angles are not used, this approach is free of the limitations of small angle increments. This also allows easy connections between substructures and large load increments with respect to the conventional shell formulation using rotational parameters. Geometrically nonlinear analyses were carried out for three cases of static point loads applied at selected points. A chart shows results for a case when the load is applied at the center point of the reflector dish. The computed results capture the nonlinear behavior of the composite reflector as the applied load increases. Also, they are in good agreement with the data obtained by experiments.

  7. Create Your Plate

    Medline Plus

    Full Text Available ... A A A Listen En Español Create Your Plate Create Your Plate is a simple and effective ... and that your options are endless. Create Your Plate! Click on the plate sections below to add ...

  8. Ombuds' Corner: Signs of our times?!

    CERN Multimedia

    Sudeshna Datta-Cockerill

    2014-01-01

    Do you get up in the morning and go online before getting your coffee? Do you sit down to meals with your mobile phone next to your plate? Do you get an awful feeling of complete disorientation and not knowing what to do with yourself when you disconnect from the Internet? As exaggerated as these actions may have seemed a few years ago, today they are familiar occurrences that are indeed the signs of our times.   “I connect, therefore I am” seems to be the new version of Descartes’ famous saying. The technological possibility of 24/7 worldwide connectivity is now an everyday fact of life and we all enjoy having knowledge at our fingertips and the ability to communicate across the globe quasi-instantaneously. In the work environment, this development has brought a flexibility and availability that has completely changed the way we work and interact with each other. This constant connectivity allows us to organise our lives differently, and we find ourselves worki...

  9. Corner junction as a probe of helical edge states.

    Science.gov (United States)

    Hou, Chang-Yu; Kim, Eun-Ah; Chamon, Claudio

    2009-02-20

    We propose and analyze interedge tunneling in a quantum spin Hall corner junction as a means to probe the helical nature of the edge states. We show that electron-electron interactions in the one-dimensional helical edge states result in Luttinger parameters for spin and charge that are intertwined, and thus rather different from those for a quantum wire with spin rotation invariance. Consequently, we find that the four-terminal conductance in a corner junction has a distinctive form that could be used as evidence for the helical nature of the edge states.

  10. Control of active reflector system for radio telescope

    Science.gov (United States)

    Zhou, Guo-hua; Li, Guo-ping; Zhang, Yong; Zhang, Zhen-chao

    2016-10-01

    According to the control requirements of the active reflector surface in the 110 m radio telescope at QiTai(QTT) Xinjiang, a new displacement actuator and a new displacement control system were designed and manufactured and then their characteristics were tested by a dual-frequency laser interferometer in the micro-displacement laboratory. The displacement actuator was designed by a scheme of high precision worm and roller screw structures, and the displacement control system was based on a ARM micro-processor. Finally, the S curve acceleration control methods were used to design the hardware platform and software algorithm for the active reflection surface of the control system. The test experiments were performed based on the laser metrology system on an active reflector close-loop antenna prototype for large radio telescope. Experimental results indicate that it achieves a 30 mm working stroke and 5 μm RMS motion resolution. The accuracy (standard deviation) is 3.67 mm, and the error between the determined and theoretical values is 0.04% when the rated load is 300 kg, the step is 2 mm and the stroke is 30mm. Furthermore, the active reflector integrated system was tested by the laser sensors with the accuracy of 0.25 μm RMS on 4-panel radio telescope prototype, the measurement results show that the integrated precision of the active reflector closed-loop control system is less than 5 μm RMS, and well satisfies the technical requirements of active reflector control system of the QTT radio telescope in 3 mm wavelength.

  11. Exhumation at orogenic indentor corners under long-term glacial conditions: Example of the St. Elias orogen, Southern Alaska

    Science.gov (United States)

    Spotila, James A.; Berger, Aaron L.

    2010-07-01

    Syntaxial bends in convergent plate boundaries, or indentor corners, display some of the most intriguing deformation patterns on Earth and are type localities for "aneurysms" of coupled erosion, thermal weakening, and strain. The St. Elias orogen in Alaska is a small, young convergent system that has been dominated by a glacial climate for much of its history and exhibits two prominent indentor corners that are not well understood. We have added 40 new apatite (U-Th)/He ages to the already extensive dataset for the low-temperature cooling history of this orogen to constrain the pattern of exhumation in these indentor corners. Ages from the western syntaxis show minor variation across the structural hinge, suggesting that the bend has little effect on the pattern of exhumation and that structures, including the Bagley fault, connect smoothly from the orogen core to the subduction zone to the southwest. Rock uplift on the north flank of the range appears to increase steadily towards the eastern syntaxis, which represents the apex in the right-angle bend between a transform fault in the south and the collision zone in the west. Based on age-elevation relationships, zones of relative rock uplift can be defined in which the Mt. Logan massif, or the area just north of the eastern syntaxis, experienced ˜ 4.8 km greater rock uplift than background levels northwest of the western syntaxis. A bulge in relative rock uplift is symmetric about the hinge in the eastern indentor corner. However, rates of denudation in this bulge are not as rapid as the core of the fold and thrust belt and are lower than those implied by detrital cooling ages from beneath the Seward Glacier. This implies that a large bull's eye of ultra-rapid (˜ 5 mm/yr) exhumation does not occur and that the subpopulation of young detrital ages may be sourced from a narrow transpressional zone along the Fairweather fault. Unlike the Himalayan syntaxes, it thus appears that an aneurysm of coupled erosion

  12. Design of a plasmonic back reflector for silicon nanowire decorated solar cells.

    Science.gov (United States)

    Ren, Rui; Guo, Yongxin; Zhu, Rihong

    2012-10-15

    This Letter presents a crystalline silicon thin film solar cell model with Si nanowire arrays surface decoration and metallic nanostructure patterns on the back reflector. The nanostructured Ag back reflector can significantly enhance the absorption in the near-infrared spectrum. Furthermore, by inserting a ZnO:Al layer between the silicon substrate and nanostructured Ag back reflector, the absorption loss in the Ag back reflector can be clearly depressed, contributing to a maximum J(sc) of 28.4 mA/cm(2). A photocurrent enhancement of 22% is achieved compared with a SiNW solar cell with a planar Ag back reflector.

  13. The Okhotsk Plate and the Eurasia-North America plate boundary zone.

    Science.gov (United States)

    Hindle, David; Mackey, Kevin

    2014-05-01

    The Eurasia-North America plate boundary zone transitions from spreading at rates of ~ 25mm/yr in the North Atlantic, to compression at rates of ~ 5mm/yr in the region of the Okhotsk plate. Because the pole of rotation between Eurasia and North America lies more or less on their mutual boundary, there is a linear change in rate along the boundary, and regions near the euler pole are subject to extremely low deformation rates. The Okhotsk - Eurasia - North America triple junction lies slightly south of the rotation pole, placing the Okhotsk plate entirely in a weakly contractional setting. Regions near the triple junction absorb 1mm/yr contraction. Further south, towards the shoreline of the Okhotsk sea, up to 5 mm/yr contraction may be absorbed within the plate. How shortening is accommodated across the boundary remains an open question. One possibility is wholesale extrusion of the entire Okhotsk plate (or possibly its northwestern corner) along two plate boundary strike slip faults (Eurasia-Okhostk and North America Okhotsk). The problem with this model is that the seismic record does not presently clearly support it, with the largest events distributed both within the plate interior and on its boundaries. This may suggest that instead, the Okhotsk plate, and particularly its north-western end, consists of a series of smaller blocks which shuffle against each other, partially accommodating extrusion, but also permitting some internal deformation and change of shape of the Okhotsk plate itself. We present analyses of the very sparse seismic record from the region, as well as geometric-kinematic, tectonic models of the possible deformation of northwest Okhotsk to try to better understand the different probabilities of how this slowly deforming plate boundary zone is behaving.

  14. Bone grafting in four-corner mid-carpal fusion.

    Science.gov (United States)

    McBride, T J; Jewell, D P A; Deshmukh, S C

    2012-01-01

    Four-corner fusion is an accepted surgical treatment for established SLAC and SNAC wrist. We describe a technique of bone grafting to be used in conjunction with any of the standard fusion techniques. A step by step, illustrated approach allows the easy placement of an autograft which is in contact with all surfaces of the bones involved in the fusion.

  15. Cut Costs! Not Corners! The Helping Hand Series.

    Science.gov (United States)

    Nash, Claire

    This guide is intended to help employees in the hotel and catering industry to cut costs without cutting corners by showing more concern to cost containment measures and increasing personal productivity. The first three sections discuss the importance of the individual employee's behavior to overall cost containment in the workplace, and different…

  16. Processing Academic Language through Four Corners Vocabulary Chart Applications

    Science.gov (United States)

    Smith, Sarah; Sanchez, Claudia; Betty, Sharon; Davis, Shiloh

    2016-01-01

    4 Corners Vocabulary Charts (FCVCs) are explored as a multipurpose vehicle for processing academic language in a 5th-grade classroom. FCVCs typically display a vocabulary word, an illustration of the word, synonyms associated with the word, a sentence using a given vocabulary word, and a definition of the term in students' words. The use of…

  17. An Efficient Implementation of the Head-Corner Parser

    CERN Document Server

    Van Noord, G

    1997-01-01

    This paper describes an efficient and robust implementation of a bi-directional, head-driven parser for constraint-based grammars. This parser is developed for the OVIS system: a Dutch spoken dialogue system in which information about public transport can be obtained by telephone. After a review of the motivation for head-driven parsing strategies, and head-corner parsing in particular, a non-deterministic version of the head-corner parser is presented. A memoization technique is applied to obtain a fast parser. A goal-weakening technique is introduced which greatly improves average case efficiency, both in terms of speed and space requirements. I argue in favor of such a memoization strategy with goal-weakening in comparison with ordinary chart-parsers because such a strategy can be applied selectively and therefore enormously reduces the space requirements of the parser, while no practical loss in time-efficiency is observed. On the contrary, experiments are described in which head-corner and left-corner pa...

  18. Study on electrostatic resonance of nanoprisms with sharp corners

    Science.gov (United States)

    Chan, Wai Soen; Ng, Ka Ki; Yu, Kin Wah

    2015-03-01

    We have studied the electrostatic resonance of metal nanoprisms with sharp corners numerically. We consider an infinite metal cylinder with polygonal base, e.g. square. The incident electric field lies in the plane of cross-section of the cylinder. Yu and co-workers proposed Green's function formalism (GFF) to numerically calculate the electric potential and field distribution in plasmonic systems. We will adopt the scheme to demonstrate the effect of sharp corners, particularly on the effect of electrostatic resonance spectrum, as in the spectral analysis proposed by Bergman and Milton. Hetherington and Thorpe investigated the conductivity of a sheet containing dilute inclusion with sharp corners, they made use of a conformal mapping approach to calculate the conductivity from circular inclusions. Helsing, McPhedran and Milton also investigated the optical properties of a metamaterial lattice with inclusions having sharp corners. We study the possibility of improving numerical accuracy by combining the conformal mapping approach and GFF. We may extend similar approach to investigate the properties of plasmonic systems, for examples nanoboties and nanostars.

  19. Spectrum of an Elliptic Free Fermionic Corner Transfer Matrix Hamiltonian

    CERN Document Server

    Cuerno, R

    1993-01-01

    The eigenvalues of the Corner Transfer Matrix Hamiltonian associated to the elliptic $R$ matrix of the eight vertex free fermion model are computed in the anisotropic case for magnetic field smaller than the critical value. An argument based on generating functions is given, and the results are checked numerically. The spectrum consists of equally spaced levels.

  20. Schoolyard Corner Society: Relating Membership to Reactive and Proactive Aggressiveness

    Science.gov (United States)

    Storksen, Svein; Idsoe, Thormod; Roland, Erling

    2011-01-01

    This study investigated whether secondary schools in Norway had deviant subcultures, which could be labelled "schoolyard corner society", and how gender and age were related to membership. We also studied levels of reactive and proactive aggressiveness in students, and the relationship between these types of aggressiveness and participation in…

  1. Four Corners Television History: Gallipoli and the Fall of Singapore

    Directory of Open Access Journals (Sweden)

    Kevin Blackburn

    2007-08-01

    Full Text Available This article analyses how the Australian current affairs programme, Four Corners, which follows a style modelled on the BBC programme Panorama, has represented Australian military history in two of its programmes, Gallipoli: The Fatal Shore and No Prisoners on Australian deserters at the fall of Singapore. Chris Masters was the reporter on both programmes. These historical documentaries claim to investigate Australian Anzac mythology. Four Corners is noted for its rigorous pursuit of issues in current affairs. Programmes construct argument that the journalists steadfastly pursue in order to ‘expose the truth’. Rather than neutrally representing both sides of a debate, the programmes tend to take the side that the journalists perceive to be in the public interest. Examining how Four Corners has applied its own style of investigative journalism to the Anzac mythology is explored by outlining whether the programmes follow Ken Burn’s ideas of documentary-makers as ‘tribal story-teller’ crafting stories that uphold national identity or Bill Nichols’ view that documentary is an argument that is representative of reality rather than reflects reality. Examining the history of Gallipoli and the fall of Singapore in the Four Corners programmes tends suggest that the journalists working on the programmes preferred to reaffirm the assumptions of the Anzac legend, but attack or ignore historians and evidence that questions it. The programmes appear to be a mixture of Burns’s and Nichols’ ideas of documentary making.

  2. COMPUTATION OF NONEQUILIBRIUM HYPERSONIC FLOW OVER CONCAVE CORNERS

    Institute of Scientific and Technical Information of China (English)

    Taehoon Park; You-lan Zhu

    2001-01-01

    This paper is devoted to computation of hypersonic flow of air with chemical reactions over concave corners. A technique combining smooth transformation of domain and implicit difference methods is used to overcome numerical difficulties associated with the lack of resolution behind the shock and near the body. The implicit treatment of right hand side terms is also an important part of our method.

  3. Single and dual-Gregorian reflector antenna shaped beam far-field synthesis

    Science.gov (United States)

    Mehler, M. J.

    The direct far-field G.O. synthesis of shaped beam reflector antennas has recently been treated by Mehler, Tun and Adatia (1986). These authors use a synthesis technique which exploits complex coordinates and which is based on a method originally considered by Norris and Westcott (1976). They describe the synthesis of single reflector antennas which radiate both elliptical beams and European coverage patterns. Here this technique is extended to consider a class of dual reflector antennas which possess shaped main reflectors and conic subreflectors. An example is given of a Gregorian duel reflector antenna which radiates a cross-polar field significantly smaller than that radiated by single shaped reflector antennas. In addition, the behavior of the radiation pattern as a function of the reflector diameter is investigated.

  4. A proposal to use mercury as a reflector material for decoupled moderator system

    Energy Technology Data Exchange (ETDEWEB)

    Teshigawara, Makoto; Harada, Masahide; Watanabe, Noboru; Kai, Tetsuya; Sakata, Hideaki; Ikeda, Yujiro [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    2001-03-01

    It is important for a decoupled moderator system to obtain neutron pulses of a higher intensity with a narrower pulse width and a faster decay. To satisfy these requirements we propose to use mercury as a reflector material and report the neutronic performance of a mercury reflector system. The peak intensity is almost comparable to or even higher than that of the optimized lead reflector system and higher than the optimized Be reflector one. Furthermore the pulse shape is almost the same as that of optimized Be reflector system with a decoupling energy of several tens eV. A mercury reflector system does not require decouplers with a higher decoupling energy, liners nor cooling water, since mercury has a reasonably high neutron absorption cross section and could be used also as a coolant. Thus, the idea of the mercury reflector could bring about a higher neutronic performance with some engineering merits for a decoupled moderator system. (author)

  5. Influence of Edge Rolling Reduction on Plate-Edge Stress Distribution During Finish Rolling

    Institute of Scientific and Technical Information of China (English)

    YU Hai-liang; LIU Xiang-hua; CHEN Li-qing; LI Chang-sheng; ZHI Ying; LI Xin-wen

    2009-01-01

    Dimensions of one kind of stainless steel plate before finish rolling were obtained through analysis of the rough rolling processes by finite element method and updated geometrical method.The FE models of finish rolling process with a front edge roll were built,and influences of the edge rolling reduction on-the stress change in the plate edge during finish roiling were analyzed.The results show that when the edge rolling reduction is increased from 0 mm to 2 ram,the compressive stress in plate corner clearly increases in edge rolling process,and the zone of tensile stress during whole rolling decreases;when the edge rolling reduction is increased from 2 mm to 5 mm,the compressive stress in the plate corner seldom changes,and the compressive stress decreases after the horizontal rolling.

  6. Four-corner fusion and scaphoid excision using headless compression screws for SLAC and SNAC wrist deformities.

    Science.gov (United States)

    Richards, Allison Alexander; Afifi, Ahmed M; Moneim, Moheb S

    2011-06-01

    Scapholunate advanced collapse and scaphoid nonunion advanced collapse wrist deformities are the most common causes of traumatic arthritis of the wrist. Four-corner fusion and scaphoid excision has proven to be an effective procedure for relieving pain and preserving range of motion in the wrist joint. Several methods for providing fixation of the midcarpal joint during fusion have been used, including K-wires, staples, and the Spider plate. K-wire fixation has proven effective, but requires a period of cast immobilization to protect the fusion mass. The Spider plate was promising, but has not been without complications. The development and improvements in cannulated headless compression screws has resulted in increased indications for their use, including fixation for 4-corner fusion. We review the technique and tips developed by the senior author over the last several years using headless compression screws for fixation of the midcarpal joint. Acutrak 2 Standard implants were used. This technique has allowed for early range of motion with reliable fusion rates.

  7. A millimeter-wave integrated-circuit antenna based on the Fresnel zone plate

    Science.gov (United States)

    Gouker, Mark A.; Smith, Glenn S.

    1992-05-01

    A moderate-gain, easily constructed, millimeter-wave IC antenna based on the Fresnel zone plate has been developed. The gain and beamwidth of the antenna can be varied by adjusting the diameter and focal length of the zone plate. A theory is developed which accurately predicts the on-axis gain, beamwidth, and sidelobe levels of antennas with zone-plate focal lengths greater than 8-9 lambda. Graphs are presented to aid in the design of other IC zone-plate antennas. The performance of the antenna without the reflector and lambda/4 spacer was investigated. The gain of the antenna with nothing behind the zone plate is found to approach that of the fully configured antenna with the lambda/4 spacer and reflector. The reflection from the open rings which is responsible for this phenomenon is enhanced as the dielectric constant of the substrate is increased. Thus, on substrates with high permittivity the reflector and lambda/4 spacer may not be necessary.

  8. Gratings and Random Reflectors for Near-Infrared PIN Diodes

    Science.gov (United States)

    Gunapala, Sarath; Bandara, Sumith; Liu, John; Ting, David

    2007-01-01

    Crossed diffraction gratings and random reflectors have been proposed as means to increase the quantum efficiencies of InGaAs/InP positive/intrinsic/ negative (PIN) diodes designed to operate as near-infrared photodetectors. The proposal is meant especially to apply to focal-plane imaging arrays of such photodetectors to be used for near-infrared imaging. A further increase in quantum efficiency near the short-wavelength limit of the near-infrared spectrum of such a photodetector array could be effected by removing the InP substrate of the array. The use of crossed diffraction gratings and random reflectors as optical devices for increasing the quantum efficiencies of quantum-well infrared photodetectors (QWIPs) was discussed in several prior NASA Tech Briefs articles. While the optical effects of crossed gratings and random reflectors as applied to PIN photodiodes would be similar to those of crossed gratings and random reflectors as applied to QWIPs, the physical mechanisms by which these optical effects would enhance efficiency differ between the PIN-photodiode and QWIP cases: In a QWIP, the multiple-quantum-well layers are typically oriented parallel to the focal plane and therefore perpendicular or nearly perpendicular to the direction of incidence of infrared light. By virtue of the applicable quantum selection rules, light polarized parallel to the focal plane (as normally incident light is) cannot excite charge carriers and, hence, cannot be detected. A pair of crossed gratings or a random reflector scatters normally or nearly normally incident light so that a significant portion of it attains a component of polarization normal to the focal plane and, hence, can excite charge carriers. A pair of crossed gratings or a random reflector on a PIN photodiode would also scatter light into directions away from the perpendicular to the focal plane. However, in this case, the reason for redirecting light away from the perpendicular is to increase the length of the

  9. The transient scattering mechanism of dipole array with reflector

    Institute of Scientific and Technical Information of China (English)

    Zhang Xue-Qin; Wang Jun-Hong; Li Zeng-Rui

    2008-01-01

    The transient backscattering mechanisms of a dipole array with reflector have been investigated from different aspects:time-domain,frequency-domain,and combined time-frequency domain,using 4×8 dipole arrays with reflector as an example.The data of scattering from the arrays under the incidence of Gaussian pulses are obtained by finite differential time domain method.The influences of the array structural parameters,incident wave parameters,and incident angles on the waveforms,spectrum,and time-frequency representations of the backseattered fields of the arrays are analysed and conclusions are drawn.From these characteristics and conclusions,it is possible to deduce the array structure inversely from the backscattered field.

  10. RATAN-600 - The world's biggest reflector at the 'cross roads'

    Science.gov (United States)

    Parijskij, Yurij N.

    1993-08-01

    The RATAN-600 new-technology telescope (NTT), which supplies about one-quarter of the observational material in Russia in the field of radio astronomy and more than 80 percent in the central, centimeter-decimeter range, is described. The RATAN-600 is the first multielement reflector radio telescope without any structure linking the surface elements. The functions normally performed by such structure are executed by the earth's surface. It is also the first radio telescope with a controlled-shape surface. In observations at different elevations about the horizon, the shape of its surface varies, remaining in the family of second-order surfaces. The RATAN-600 is also the first aperture-synthesis reflector-type telescope. The location of the radio telescope, its design, its modes of operation, and its future prospects are discussed.

  11. Conceptual Design of the Aluminum Reflector Antenna for DATE5

    Science.gov (United States)

    Qian, Yuan; Kan, Frank W.; Sarawit, Andrew T.; Lou, Zheng; Cheng, Jing-Quan; Wang, Hai-Ren; Zuo, Ying-Xi; Yang, Ji

    2016-08-01

    DATE5, a 5 m telescope for terahertz exploration, was proposed for acquiring observations at Dome A, Antarctica. In order to observe the terahertz spectrum, it is necessary to maintain high surface accuracy in the the antenna when it is exposed to Antarctic weather conditions. Structural analysis shows that both machined aluminum and carbon fiber reinforced plastic (CFRP) panels can meet surface accuracy requirements. In this paper, one design concept based on aluminum panels is introduced. This includes panel layout, details on panel support, design of a CFRP backup structure, and detailed finite element analysis. Modal, gravity and thermal analysis are all performed and surface deformations of the main reflector are evaluated for all load cases. At the end of the paper, the manufacture of a prototype panel is also described. Based on these results, we found that using smaller aluminum reflector panels has the potential to meet the surface requirements in the harsh Dome A environment.

  12. Finite Element Analysis of Reinforced Concrete Plate Impacted by Block

    Institute of Scientific and Technical Information of China (English)

    LUO Xiaoyang; Pascal PERROTIN; YAN Quansheng

    2006-01-01

    A new concept of structurally dissipating rock-shed (SDR) was developed by the lab of Tonello IC and LOCIE-ESIGEC (France).To decide the dimension of the plate used in SDR,an ANSYS model which could simulate the impact of rock in the centre of the plate was established by Fabien Delhomme.By using this model,some finite element analyses are carried out in the present paper Firstly,a plate impacted by a block is numerically simulated,the numerical results obtained from different mesh sizes are compared and the accuracy of the finite element model is verified.Then,the dynamic response of the plate impacted at the boundary and in the medium part is computed.By analyzing the stress in rebar,the most dangerous region of impact of plate was found.For a rectangular plate,the most dangerous region is at the corner of the plate when a block drops in.Finally,the whole deformation process of the plate under dropping block was simulated and a simplified definition (effect zone) to describe the deformation process in different positions of plate was given.From this study,it is found that the impact only affects heavily within the effect zone.

  13. Prestack exploding reflector modeling and migration in TI media

    KAUST Repository

    Wang, H.

    2014-01-01

    Prestack depth migration in anisotropic media, especially those that exhibit tilt, can be costly using reverse time migration (RTM). We present two-way spectral extrapolation of prestack exploding reflector modeling and migration (PERM) in acoustic transversely isotropic (TI) media. We construct systematic ways to evaluate phase angles and phase velocities in dip oriented TI (DTI), vertical TI (VTI) and tilted TI (TTI) media. Migration results from the Marmousi VTI model and the BP2007 TTI model show the feasibility of our approach.

  14. Parabolic dish reflectors for solar applications approximated by simple surfaces

    OpenAIRE

    Broman, Lars; Broman, Arne

    1996-01-01

    Two different concentrating mirrors have been constructed that resemble parabolic dish reflectors. Both mirrors are made of slightly curved strips of flat, bendable material. The strips of the most simplified mirror have only large-radius circles and straight lines as boundaries. The necessary equations for making the mirrors have been derived. Also a simple way to make a stiff, lightweight frame and support for the mirror strips has been developed. Models of the mirrors have been built and s...

  15. Grating-assisted silicon-on-insulator racetrack resonator reflector.

    Science.gov (United States)

    Boeck, Robert; Caverley, Michael; Chrostowski, Lukas; Jaeger, Nicolas A F

    2015-10-05

    We experimentally demonstrate a grating-assisted silicon-on-insulator (SOI) racetrack resonator reflector with a reflect port suppression of 10.3 dB and no free spectral range. We use contra-directional grating couplers within the coupling regions of the racetrack resonator to enable suppression of all but one of the peaks within the reflect port spectrum as well as all but one of the notches within the through port spectrum.

  16. Design and testing for novel joint for wave reflectors

    Energy Technology Data Exchange (ETDEWEB)

    Tedd, J. [SPOK ApS, Copenhagen (Denmark); Friis-Madsen, E. [Loewenmark, Copenhagen (Denmark); Frigaard, P. [Aalborg Univ., Aalborg (Denmark)

    2005-07-01

    Construction of a novel joint between the main platform and the wave reflectors of the Wave Dragon has begun. This paper describes the design and testing process behind this. Tests conducted in the facilities at Aalborg University highlighted large motions, and similar force magnitudes to the previous design. This testing has influenced the design and allowed construction to begin on refitting the joint to the 1:4.5 scale prototype Wave Dragon. (au)

  17. Theoretical analysis of a parabolic torus reflector antenna with multibeam

    Institute of Scientific and Technical Information of China (English)

    杜彪; 杨可忠; 钟顺时

    1995-01-01

    The parametric equations and the formulas of unit normal vector and surface element for aparabolic torus reflector antenna are derived and the mechanism of producing multibeam is proposed, Based on physical optics, the radiation pattern formulas for the antenna are given, with which the effects of geometric parameters on the antenna are studied. The good agreement between the calculated patterns and the measured ones shows that the theory is helpful for designing parabolic torus antennas.

  18. A SAW resonator with two-dimensional reflectors.

    Science.gov (United States)

    Solal, Marc; Gratier, Julien; Kook, Taeho

    2010-01-01

    It is known that a part of the loss of leaky SAW resonators is due to radiation of acoustic energy in the bus-bars. Many researchers are working on so-called phononic crystals. A 2-D grating of very strong reflectors allows these devices to fully reflect, for a given frequency band, any incoming wave. A new device based on the superposition of a regular SAW resonator and a 2-D periodic grating of reflectors is proposed. Several arrangements and geometries of the reflectors were studied and compared experimentally on 48 degrees rotated Y-cut lithium tantalate. In particular, a very narrow aperture (7.5 lambda) resonator was manufactured in the 900 MHz range. Because of its small size, this resonator has a resonance Q of only 575 when using the standard technology, whereas a resonance Q of 1100 was obtained for the new device without degradation of the other characteristics. Because of the narrow aperture, the admittance of the standard resonator showed a very strong parasitic above the resonance frequency, whereas this effect is drastically reduced for the new device. These results demonstrate the feasibility of the new approach.

  19. Reflector cells in the skin of Octopus dofleini.

    Science.gov (United States)

    Brocco, S L; Cloney, R A

    1980-01-01

    The cells that form the reflecting layer beneath the chromatophore organs of the octopus are conspicuous elements of its dermal chromatic system. Each flattened, ellipsoidal reflector cell in this layer bears thousands of peripherally radiating, discoidal, reflecting lamellae. Each lamella consists of a proteinaceous reflecting platelet enveloped by the plasmalemma. The lamellae average 90 nm in thickness and have variable diameters with a maximum of about 1.7 micrometer. Sets of reflecting lamellae are organized into functional units called reflectosomes. The lamellae in each reflectosome form a parallel array - similar to a stack of coins. The average number of lamellae in a reflectosome is 11. Adjacent lamellae are uniformly separated by an extracellular gap of about 60 nm in embedded specimens. The reflectosomes are randomly disposed over the surface of the reflector cell. The observed organization of the reflectosomes is compatible with its role as a quarter-wave thin-film interference device. The alternating reflecting lamellae and intelamellar spaces constitute layers of high and low refractive indices. Using measurements of the thicknesses and refractive indices of the platelets and interlamellar spaces, we have calculated that the color of reflected light should be blue - green, as seen in vivo. The sequence of events leading to the definitive arrangement of the reflectosomes is uncertain. The reflector cells of O. dofleini are compared and contrasted with the iridophores of squid.

  20. Shape control of distributed parameter reflectors using sliding mode control

    Science.gov (United States)

    Andoh, Fukashi; Washington, Gregory N.; Utkin, Vadim

    2001-08-01

    Sliding mode control has become one of the most powerful control methods for variable structure systems, a set of continuous systems with an appropriate switching logic. Its robustness properties and order reduction capability have made sliding mode control one of the most efficient tools for relatively higher order nonlinear plants operating under uncertain conditions. Piezo-electric materials possess the property of creating a charge when subjected to a mechanical strain, and of generating a strain when subjected to an electric field. Piezo-electric actuators are known to have a hysteresis due to the thermal motion and Coulomb interaction of Weiss domains. Because of the thermal effect the hysteresis of piezo-electric actuators is reproducible only with some uncertainty in experiments. The robustness of sliding mode control under uncertain conditions has an advantage in handling the hysteresis of piezo-electric actuators. In this research sliding mode control is used to control the shape of one- and two-dimensionally curved adaptive reflectors with piezo-electric actuators. Four discrete linear actuators for the one-dimensionally curved reflector and eight actuators for the two-dimensionally curved reflector are assumed.

  1. Design of Ring-Focus Elliptical Beam Reflector Antenna

    Directory of Open Access Journals (Sweden)

    Jun-Mo Wu

    2016-01-01

    Full Text Available A new method for the design of elliptical beam reflector antenna is presented in this paper. By means of the basic principles of ring-focus antenna, a circularly symmetric feed and two specially shaped reflectors are used to form an elliptical beam antenna. Firstly, the design process of this ring-focus elliptical beam antenna is studied in detail. Transition function is defined and used in the design process. Then, combining the needs of practical engineering, a ring-focus elliptical beam reflector antenna is manufactured and tested. The gain at center frequency (12 GHz is 37.7 dBi with an aperture efficiency of 74.6%. 3 dB beam-width in φ=0° and φ=90° plane is 2.6° and 1.4°, respectively. Ratio of the elliptical beam (ratio of 3 dB beam-width in φ=0° and φ=90° plane is 2.6/1.4=1.85, substantially equal to designed ratio 2. Simulating and testing results match well, which testify the effectiveness of this design method.

  2. A Slice Algorithm for Corners and Hilbert-Poincaré Series of Monomial Ideals

    DEFF Research Database (Denmark)

    Roune, Bjarke Hammersholt

    2010-01-01

    We present an algorithm for computing the corners of a monomial ideal. The corners are a set of multidegrees that support the numerical information of a monomial ideal such as Betti numbers and Hilbert-Poincaré series. We show an experiment using corners to compute Hilbert-Poincaré series...

  3. 40 CFR 81.121 - Four Corners Interstate Air Quality Control Region.

    Science.gov (United States)

    2010-07-01

    ... Quality Control Regions § 81.121 Four Corners Interstate Air Quality Control Region. The Four Corners Interstate Air Quality Control Region (Colorado-New Mexico-Utah) has been revised to consist of the... 40 Protection of Environment 17 2010-07-01 2010-07-01 false Four Corners Interstate Air...

  4. Models, modules and abelian groups in memory of A.L.S.Corner

    CERN Document Server

    Goldsmith, Brendan

    2008-01-01

    This is a memorial volume dedicated to A. L. S. Corner, previously Professor in Oxford, who published important results on algebra, especially on the connections of modules with endomorphism algebras. The volume contains refereed contributions which are related to the work of Corner.It contains also an unpublished extended paper of Corner himself. A memorial volume with important contributions related to algebra.

  5. IMPROVED REAL-TIME SCAN MATCHING USING CORNER FEATURES

    Directory of Open Access Journals (Sweden)

    H. A. Mohamed

    2016-06-01

    Full Text Available The automation of unmanned vehicle operation has gained a lot of research attention, in the last few years, because of its numerous applications. The vehicle localization is more challenging in indoor environments where absolute positioning measurements (e.g. GPS are typically unavailable. Laser range finders are among the most widely used sensors that help the unmanned vehicles to localize themselves in indoor environments. Typically, automatic real-time matching of the successive scans is performed either explicitly or implicitly by any localization approach that utilizes laser range finders. Many accustomed approaches such as Iterative Closest Point (ICP, Iterative Matching Range Point (IMRP, Iterative Dual Correspondence (IDC, and Polar Scan Matching (PSM handles the scan matching problem in an iterative fashion which significantly affects the time consumption. Furthermore, the solution convergence is not guaranteed especially in cases of sharp maneuvers or fast movement. This paper proposes an automated real-time scan matching algorithm where the matching process is initialized using the detected corners. This initialization step aims to increase the convergence probability and to limit the number of iterations needed to reach convergence. The corner detection is preceded by line extraction from the laser scans. To evaluate the probability of line availability in indoor environments, various data sets, offered by different research groups, have been tested and the mean numbers of extracted lines per scan for these data sets are ranging from 4.10 to 8.86 lines of more than 7 points. The set of all intersections between extracted lines are detected as corners regardless of the physical intersection of these line segments in the scan. To account for the uncertainties of the detected corners, the covariance of the corners is estimated using the extracted lines variances. The detected corners are used to estimate the transformation parameters

  6. Improved Real-Time Scan Matching Using Corner Features

    Science.gov (United States)

    Mohamed, H. A.; Moussa, A. M.; Elhabiby, M. M.; El-Sheimy, N.; Sesay, Abu B.

    2016-06-01

    The automation of unmanned vehicle operation has gained a lot of research attention, in the last few years, because of its numerous applications. The vehicle localization is more challenging in indoor environments where absolute positioning measurements (e.g. GPS) are typically unavailable. Laser range finders are among the most widely used sensors that help the unmanned vehicles to localize themselves in indoor environments. Typically, automatic real-time matching of the successive scans is performed either explicitly or implicitly by any localization approach that utilizes laser range finders. Many accustomed approaches such as Iterative Closest Point (ICP), Iterative Matching Range Point (IMRP), Iterative Dual Correspondence (IDC), and Polar Scan Matching (PSM) handles the scan matching problem in an iterative fashion which significantly affects the time consumption. Furthermore, the solution convergence is not guaranteed especially in cases of sharp maneuvers or fast movement. This paper proposes an automated real-time scan matching algorithm where the matching process is initialized using the detected corners. This initialization step aims to increase the convergence probability and to limit the number of iterations needed to reach convergence. The corner detection is preceded by line extraction from the laser scans. To evaluate the probability of line availability in indoor environments, various data sets, offered by different research groups, have been tested and the mean numbers of extracted lines per scan for these data sets are ranging from 4.10 to 8.86 lines of more than 7 points. The set of all intersections between extracted lines are detected as corners regardless of the physical intersection of these line segments in the scan. To account for the uncertainties of the detected corners, the covariance of the corners is estimated using the extracted lines variances. The detected corners are used to estimate the transformation parameters between the

  7. The Position and Attitude of Sub-reflector Modeling for TM65 m Radio Telescope

    Science.gov (United States)

    Sun, Z. X.; Chen, L.; Wang, J. Q.

    2016-01-01

    In the course of astronomical observations, with changes in angle of pitch, the large radio telescope will have different degrees of deformation in the sub-reflector support, back frame, main reflector etc, which will lead to the dramatic decline of antenna efficiency in both high and low elevation. A sub-reflector system of the Tian Ma 65 m radio telescope has been installed in order to compensate for the gravitational deformations of the sub-reflector support and the main reflector. The position and attitude of the sub-reflector are variable in order to improve the pointing performance and the efficiency at different elevations. In this paper, it is studied that the changes of position and attitude of the sub-reflector have influence on the efficiency of antenna in the X band and Ku band. A model has been constructed to determine the position and attitude of the sub-reflector with elevation, as well as the point compensation model, by observing the radio source. In addition, antenna efficiency was tested with sub-reflector position adjusted and fixed. The results show that the model of sub-reflector can effectively improve the efficiency of the 65 m radio telescope. In X band, the aperture efficiency of the radio telescope reaches more than 60% over the entire elevation range.

  8. Large networks of artificial radar reflectors to monitor land subsidence in natural lowlying coastal areas

    Science.gov (United States)

    Tosi, Luigi; Strozzi, Tazio; Teatini, Pietro

    2014-05-01

    Deltas, lagoons, estuaries are generally much prone to land subsidence. They are also very sensitive to land lowering due to their small elevation with respect to the mean sea level, also in view of the expected eustatic sea rise due to climate changes. Land subsidence can be presently monitored with an impressive accuracy by Persistent Scatterer Interferometry (PSI) on the large megacities that are often located on lowlying coastlands, e.g., Shanghai (China) on the Yangtze River delta, Dhaka (Bangladesh) on the Gange River delta, New Orleans (Louisiana) on the Mississippi river delta. Conversely, the land movements of the portions of these transitional coastlands where natural environments still persist are very challenging to be measured. The lack of anthropogenic structures strongly limits the use of PSI and the difficult accessibility caused by the presence of marshlands, tidal marshes, channels, and ponds yield traditional methodologies, such as levelling and GPS, both time-consuming and costly. In this contribution we present a unique experimental study aimed at using a large network of artificial radar reflectors to measure land subsidence in natural coastal areas. The test site is the 60-km long, 10-15 km wide lagoon of Venice, Italy, where previous PSI investigations revealed the lack of radar reflectors in large portions of the northern and southern lagoon basins (e.g., Teatini et al., 2011). A network of 57 trihedral corner reflectors (TCRs) were established between the end of 2006 and the beginning of 2007 and monitored by ENVISAT ASAR and TerraSAR-X acquisitions covering the time period from 2007 to 2011 (Strozzi et al., 2012). The application has provided general important insights on the possibility of controlling land subsidence using this approach. For example: (i) relatively small-size (from 0.5 to 1.0 m edge length) and cheap (few hundred euros) TCRs suffice to be clearly detectable from the radar sensors because of the low backscattering

  9. Edge and corner identification for tracking the line of sight Edge and corner identification for tracking the line of sight

    OpenAIRE

    María S Orozco; Uwe Jasnoch; Oscar Eduardo Ruiz Salguero

    2005-01-01

    This article presents an edge-corner detector, implemented in the realm of the GEIST project (an Computer Aided Touristic Information System) to extract the information of straight edges and their intersections (image corners) from camera-captured (real world) and computer-generated images (from the database of Historical Monuments, using ob- server position and orientation data). Camera and computer-generated images are processed for reduction of detail, skeletonization and corner-edge detec...

  10. Thermal Performance Evaluation of Friction Stir Welded and Bolted Cold Plates with Al/Cu Interface

    Science.gov (United States)

    Lakshminarayanan, A. K.; Suresh, M.; Sibi Varshan, M.

    2015-05-01

    An attempt is made to design and fabricate a cold plate with aluminum-copper dissimilar interface joined by friction stir welding. Optimum welding conditions for obtaining sound-quality corner and T joints with an aluminum-copper interface were established. Welded cross sections of the friction stir welded cold plate were analyzed to understand the bonding characteristics. Computational fluid dynamics (CFD) was used to evaluate the fluid-flow characteristics and thermal resistance of friction stir welded cold plate and the resulted are compared with the conventional bolted cold plate configuration. For CFD modeling of a cold plate with a dissimilar interface, a new methodology is proposed. From the CFD analysis and experimental results, it is observed that friction stir welded cold plate offered better thermal performance compared to the bolted cold plate and it is due to the metallurgical bonding at the aluminum-copper interface with the dispersion of copper particles.

  11. Formative Evaluation for a Healthy Corner Store Initiative in Pitt County, North Carolina: Engaging Stakeholders for a Healthy Corner Store Initiative, Part 2

    Directory of Open Access Journals (Sweden)

    Katherine K. Lawton, MPH

    2013-07-01

    Full Text Available Introduction We examined the feasibility of increasing access to healthful food in corner stores to inform a Communities Putting Prevention to Work (CPPW initiative by engaging stakeholders (corner store owners and customers in a formative evaluation. Methods Qualitative interviews were conducted with corner store owners and managers (n = 11. Customer intercept surveys (n = 179 were also conducted with customers of 9 stores. Corner stores were located in rural food deserts (municipalities without a chain supermarket and in low-income, urban municipalities in eastern North Carolina. Interviews were transcribed verbatim and double-coded. Qualitative themes related to feasibility of increasing access to healthful foods were extracted. Shopping patterns of rural and urban customers were compared by using t tests. Results Corner store owners were willing to stock more healthful foods, but they perceived that customer demand for these foods was low. Rural customers reported more frequently shopping at corner stores than urban customers and more frequently stated that the reason they do not eat more fruits and vegetables is that the stores in which they shop do not sell them. Most customers reported they would be very or somewhat likely to purchase fresh produce at a corner store. Conclusion Corner stores may be an important source of food for rural and low-income residents and thus a good place in which to intervene. The results of this formative evaluation were used to plan and evaluate a CPPW healthy corner store initiative.

  12. Universality of corner entanglement in conformal field theories

    CERN Document Server

    Bueno, Pablo; Witczak-Krempa, William

    2015-01-01

    We study the contribution to the entanglement entropy of (2+1)-dimensional conformal field theories coming from a sharp corner in the entangling surface. This contribution is encoded in a function $a(\\theta)$ of the corner opening angle, and was recently proposed as a measure of the degrees of freedom in the underlying CFT. We show that the ratio $a(\\theta)/C_T$ , where $C_T$ is the central charge in the stress tensor correlator, is an almost universal quantity for a broad class of theories including various higher-curvature holographic models, free scalars and fermions, and Wilson-Fisher fixed points of the $O(N)$ models with $N=1,2,3$. Strikingly, the agreement between these different theories becomes exact in the limit $\\theta\\rightarrow \\pi$, where the entangling surface approaches a smooth curve. We thus conjecture that the corresponding ratio is universal for general CFTs in three dimensions.

  13. An improved TLD with Harris corner and color moment

    Science.gov (United States)

    Li, Ling; Liu, Kai; Cheng, Fei; Bao, Di

    2017-02-01

    Video tracking is a main field of computer vision, and TLD algorithm plays a key role in long-term tracking. However, the original TLD ignores the color features of patch in detection, and tracks the common points from grid, then, the tracking accuracy is limited to both of them. This paper presents a novel TLD algorithm with Harris corner and color moment to overcome this drawback. Instead of tracking common points, we screen more important points utilizing Harris corner to reject a half patches, these points are better able to show the object's textural features. In addition, the color moment classifier replaces patch variance to reduce the errors of detection. The classifier compares mine-dimensional color moment vectors so that it can keep the TLD's stable speed. Experiment has proved that our TLD tracks a more reliable position and higher ability without affecting the speed.

  14. Ship Detection and Measurement of Ship Motion by Multi-Aperture Synthetic Aperture Radar

    Science.gov (United States)

    2014-06-01

    corner act as radar corner reflectors . 4. Metal plates that are joined at right angles form radar dihedrals whose radar cross section is...angles to metal plates form a dihedral known as a top-hat reflector whose radar cross section is independent of the radar aspect angle (for a circular...heading and radar cross section . From the data set used in this study for ships that are longer

  15. Communities Putting Prevention to Work: The Healthy Corner Store Initiative

    Centers for Disease Control (CDC) Podcasts

    2013-07-18

    This podcast is an interview with Dr. Stephanie Jilcott Pitts, Associate Professor in the Department of Public Health at East Carolina University. Dr. Pitts answers questions about her study involving a healthy corner store initiative in North Carolina.  Created: 7/18/2013 by Preventing Chronic Disease (PCD), National Center for Chronic Disease Prevention and Health Promotion (NCCDPHP).   Date Released: 7/18/2013.

  16. Suppressing rippling with minimized corner rounding through OPC fragmentation optimization

    Science.gov (United States)

    Wang, Jingyu; Wei, Alexander; Wilkinson, William; Chen, Norman

    2016-10-01

    As technology shrinks, the requirements placed on the post-OPC solution become so exacting that even small residual optical effects are significant. Simultaneously minimizing rippling and corner rounding cannot be accom- plished in parallel in wafer patterning especially when complex asymmetric pixelated sources are used. While either effect can be moderated by accurate application of optical proximity correction, they are both charac- teristic of unfiltered diffraction due to asymmetric illumination or design geometry and will remain inherent. Corrections that over emphasize reduced corner-rounding necessarily sacrifice edge convergence, resulting in a standing wave or unacceptable rippling along an entire edge. OPC can be used to reduce the magnitude of this rippling, but fragment placing is extremely critical. In this paper, we discuss optimized OPC fragmentation that offers balanced consideration to suppressing rippling and minimizing corner rounding. Specifically, we correlate design shapes with simulated post-OPC contours to account for design geometry-dependent rippling signature given existing illumination conditions. In contrast to adaptive fragmentation that relies on multiple iterations of simulation of intensity extrema redistribution, our method predicts the optimum contour as allowed by process and fragments the mask accordingly. The maximum imaging curvature resolvable by process coupled with the rippling signature, gives rise to the exact locations of the inflection points of the wafer contour. From there we achieve the best correction results by segmenting edges at the inflection points.

  17. Corner block list representation and its application with boundary constraints

    Institute of Scientific and Technical Information of China (English)

    HONG Xianlong; MA Yuchun; DONG Sheqin; CAI Yici; Chung-Kuan Cheng; GU Jun

    2004-01-01

    Floorplanning is a critical phase in physical design of VLSI circuits. The stochastic optimization method is widely used to handle this NP-hard problem. The key to the floorplanning algorithm based on stochastic optimization is to encode the floorplan structure properly. In this paper, corner block list (CBL)-a new efficient topological representation for non-slicing floorplan-is proposed with applications to VLSI floorplan.Given a corner block list, it takes only linear time to construct the floorplan. In floorplanning of typical VLSI design, some blocks are required to satisfy some constraints in the final packing. Boundary constraint is one kind of those constraints to pack some blocks along the pre-specified boundaries of the final chip so that the blocks are easier to be connected to certain I/O pads. We implement the boundary constraint algorithm for general floorplan by extending CBL. Our contribution is to find the necessary and sufficient characterization of the blocks along the boundary represented by CBL. We can check the boundary constraints by scanning the intermediate solutions in linear time during the simulated annealing process and fix the corner block list in case the constraints are violated. The experiment results are demonstrated by several examples of MCNC benchmarks and the performance is remarkable.

  18. ANALISIS PERBANDINGAN OUTPUT DAYA LISTRIK PANEL SURYA SISTEM TRACKING DENGAN SOLAR REFLECTOR

    Directory of Open Access Journals (Sweden)

    I B Kd Surya Negara

    2016-03-01

    Full Text Available Indonesia merupakan negara beriklim tropis yang memiliki intensitas radiasi matahari yang sangat besar dan intensitas radiasi tersebut berpotensi untuk dikembangkan menjadi Pembangkit Listrik Tenaga Surya. Efisiensi dari panel surya saat ini masih perlu pertimbangan lebih lanjut. Efisiensi panel surya yang rendah ini, berpengaruh pada hasil output daya listrik yang dihasilkan. Upaya untuk meningkatkan output daya listrik panel surya, yaitu dengan sistem tracking dan solar reflector. Penelitian ini bertujuan untuk mengetahui output daya listrik yang lebih maksimal. Metode dalam penelitian ini menggunakan sistem tracking yang pergerakannya berdasarkan waktu dan menggunakan solar reflector dengan cermin datar dan sudut reflector yang berbeda. Hasil dari perbandingan sistem tracking dengan solar reflector yaitu solar reflector menghasilkan output daya listrik lebih besar dibandingan dengan sistem tracking, dimana solar reflector menghasilkan output daya listrik sebesar 0.1224 Watt dan sistem tracking sebesar 0.1136 Watt.

  19. Demonstration of a single-crystal reflector-filter for enhancing slow neutron beams

    DEFF Research Database (Denmark)

    Muhrer, G.; Schonfeldt, T.; Iverson, E. B.

    2016-01-01

    The cold polycrystalline beryllium reflector-filter concept has been used to enhance the cold neutron emission of cryogenic hydrogen moderators, while suppressing the intermediate wavelength and fast neutron emission at the same time. While suppressing the fast neutron emission is often desired......, the suppression of intermediate wavelength neutrons is often unwelcome. It has been hypothesized that replacing the polycrystalline reflector-filter concept with a single-crystal reflector-filter concept would overcome the suppression of intermediate wavelength neutrons and thereby extend the usability...... of the reflector-filter concept to shorter but still important wavelengths. In this paper we present the first experimental data on a single-crystal reflector-filter at a reflected neutron source and compare experimental results with hypothesized performance. We find that a single-crystal reflector-filter retains...

  20. Impact of beryllium reflector ageing on Safari–1 reactor core parameters / L.E. Moloko

    OpenAIRE

    Moloko, Lesego Ernest

    2011-01-01

    The build–up of 6Li and 3He, that is, the strong thermal neutron absorbers or the so called "neutron poisons", in the beryllium reflector changes the physical characteristics of the reactor, such as reactivity, neutron spectra, neutron flux level, power distribution, etc.; furthermore,gaseous isotopes such as 3H and 4He induce swelling and embrittlement of the reflector. The SAFARI–1 research reactor, operated by Necsa at Pelindaba in South Africa, uses a beryllium reflector on...

  1. Neutronic optimization of premoderator and reflector for decoupled hydrogen moderator in 1 MW spallation neutron source

    CERN Document Server

    Harada, M; Kai, T; Sakata, H; Watanabe, N; Ikeda, Y

    2002-01-01

    For a decoupled liquid-hydrogen moderator, optimization studies have been performance on a premoderator and reflector materials (Pb, Be, Fe and Hg) together with several decoupling energies to realize a higher neutronic performance. The result indicated that, among four reflector materials mentioned above, the best neutronic performance could be obtained by adopting a Pb reflector with an optimized premoderator and an appropriate decoupling energy. (author)

  2. Analysis and Design of a New Shaped Spherical Reflector Antenna with a Horn Feed

    Institute of Scientific and Technical Information of China (English)

    LIN Yan; HUANG Bin; ZHU Quan-fu; YUAN Yuan

    2009-01-01

    A design method of a new shaped spherical reflector antenna with a horn feed for wide-angle scanning is presented, in which the horn's phase center need not be found out and its optimal position can be determined. It is found from numerical calculation that the shaped spherical reflector antenna has better electrical performance than that of the spherical reflector antenna, at the maximum gain value under the conditions of the same feed and reflector aperture, and can be used as a wide angle searching antenna.

  3. Characterization of a Bifacial Photovoltaic Panel Integrated with External Diffuse and Semimirror Type Reflectors

    Directory of Open Access Journals (Sweden)

    P. Ooshaksaraei

    2013-01-01

    Full Text Available Silicon wafer accounts for almost one-half the cost of a photovoltaic (PV panel. A bifacial silicon solar cell is attractive due to its potential of enhancing power generation from the same silicon wafer in comparison with a conventional monofacial solar cell. The bifacial PV cell is able to capture solar radiation by back surface. This ability requires a suitable reflector appropriately oriented and separated from the cell’s rear surface. In order to optimize the bifacial solar cell performance with respect to an external back surface reflector, diffuse and semimirror reflectors were investigated at various angles and separations from the back surface. A simple bifacial solar panel, consisting of four monocrystalline Si solar cells, was designed and built. Reflection from the rear surface was provided by an extended semimirror and a white-painted diffuse reflector. Maximum power generation was observed at 30° with respect to ground for the semimirror reflector and 10° for diffuse reflector at an optimized reflector-panel separation of 115 mm. Output power enhancement of 20% and 15% from semimirror and diffuse reflectors, respectively, were observed. This loss from diffuse reflector is attributed to scattering of light beyond the rear surface capture cross-section of the bifacial solar panel.

  4. Demonstration of a single-crystal reflector-filter for enhancing slow neutron beams

    Science.gov (United States)

    Muhrer, G.; Schönfeldt, T.; Iverson, E. B.; Mocko, M.; Baxter, D. V.; Hügle, Th.; Gallmeier, F. X.; Klinkby, E. B.

    2016-09-01

    The cold polycrystalline beryllium reflector-filter concept has been used to enhance the cold neutron emission of cryogenic hydrogen moderators, while suppressing the intermediate wavelength and fast neutron emission at the same time. While suppressing the fast neutron emission is often desired, the suppression of intermediate wavelength neutrons is often unwelcome. It has been hypothesized that replacing the polycrystalline reflector-filter concept with a single-crystal reflector-filter concept would overcome the suppression of intermediate wavelength neutrons and thereby extend the usability of the reflector-filter concept to shorter but still important wavelengths. In this paper we present the first experimental data on a single-crystal reflector-filter at a reflected neutron source and compare experimental results with hypothesized performance. We find that a single-crystal reflector-filter retains the long-wavelength benefit of the polycrystalline reflector-filter, without suffering the same loss of important intermediate wavelength neutrons. This finding extends the applicability of the reflector-filter concept to intermediate wavelengths, and furthermore indicates that the reflector-filter benefits arise from its interaction with fast (background) neutrons, not with intermediate wavelength neutrons of potential interest in many types of neutron scattering.

  5. Demonstration of a single-crystal reflector-filter for enhancing slow neutron beams

    Energy Technology Data Exchange (ETDEWEB)

    Muhrer, G. [European Spallation Source, Lund (Sweden); Los Alamos Neutron Science Center, Los Alamos National Laboratory, Los Alamos, NM (United States); Schönfeldt, T. [Center for Nuclear Technologies, Technical University of Denmark, Roskilde (Denmark); European Spallation Source, Lund (Sweden); Iverson, E.B., E-mail: iversoneb@ornl.gov [Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN (United States); Mocko, M. [Los Alamos Neutron Science Center, Los Alamos National Laboratory, Los Alamos, NM (United States); Baxter, D.V. [Center for the Exploration of Energy and Matter, Indiana University, Bloomington, IN (United States); Hügle, Th.; Gallmeier, F.X. [Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN (United States); Klinkby, E.B. [Center for Nuclear Technologies, Technical University of Denmark, Roskilde (Denmark); European Spallation Source, Lund (Sweden)

    2016-09-11

    The cold polycrystalline beryllium reflector-filter concept has been used to enhance the cold neutron emission of cryogenic hydrogen moderators, while suppressing the intermediate wavelength and fast neutron emission at the same time. While suppressing the fast neutron emission is often desired, the suppression of intermediate wavelength neutrons is often unwelcome. It has been hypothesized that replacing the polycrystalline reflector-filter concept with a single-crystal reflector-filter concept would overcome the suppression of intermediate wavelength neutrons and thereby extend the usability of the reflector-filter concept to shorter but still important wavelengths. In this paper we present the first experimental data on a single-crystal reflector-filter at a reflected neutron source and compare experimental results with hypothesized performance. We find that a single-crystal reflector-filter retains the long-wavelength benefit of the polycrystalline reflector-filter, without suffering the same loss of important intermediate wavelength neutrons. This finding extends the applicability of the reflector-filter concept to intermediate wavelengths, and furthermore indicates that the reflector-filter benefits arise from its interaction with fast (background) neutrons, not with intermediate wavelength neutrons of potential interest in many types of neutron scattering.

  6. Reflector and Shield Material Properties for Project Prometheus

    Energy Technology Data Exchange (ETDEWEB)

    J. Nash

    2005-11-02

    This letter provides updated reflector and shield preliminary material property information to support reactor design efforts. The information provided herein supersedes the applicable portions of Revision 1 to the Space Power Program Preliminary Reactor Design Basis (Reference (a)). This letter partially answers the request in Reference (b) to provide unirradiated and irradiated material properties for beryllium, beryllium oxide, isotopically enriched boron carbide ({sup 11}B{sub 4}C) and lithium hydride. With the exception of {sup 11}B{sub 4}C, the information is provided in Attachments 1 and 2. At the time of issuance of this document, {sup 11}B{sub 4}C had not been studied.

  7. A Van Atta reflector consisting of half-wave dipoles

    DEFF Research Database (Denmark)

    Appel-Hansen, Jørgen

    1966-01-01

    The reradiation pattern of a passive Van Atta reflector consisting of half-wave dipoles is investigated. The character of the reradiation pattern first is deduced by qualitative and physical considerations. Various types of array elements are considered and several geometrical configurations...... of these elements are outlined. Following this, an analysis is made of the reradiation pattern of a linear Van Atta array consisting of four equispaced half-wave dipoles. The general form of the reradiation pattern is studied analytically. The influence of scattering and coupling is determined and the dependence...

  8. Q-switched distributed-Bragg-reflector ytterbium laser

    Science.gov (United States)

    Ouslimani, H.; Bastard, L.; Broquin, J.-E.

    2013-03-01

    A passively Q-switched distributed-Bragg-reflector laser made in glass integrated optics technology, and operating around 1030 nm, is designed, realized and investigated. The laser is formed by an ion-exchanged single mode waveguide realized in an Ytterbium doped phosphate glass. The Q-switching behavior is obtained by hybridizing a saturable absorber film on the waveguides. This allows the realization of a short and simple laser cavity having both pulsed and a narrow linewidth emission. Its experimental characterization leads to the observation of a stable repetition rate of 12.5 kHz and a stable pulse duration of 9.2 ns FWHM.

  9. Photoluminescence and X-ray Diffraction of Distributed Bragg Reflector

    Institute of Scientific and Technical Information of China (English)

    LI Lin; LI Yong-da; LIU Wen-li; LU Bin; JU Guo-xian; ZHANG Yong-ming; HAO Yong-qin; SU Wei; ZHONG Jing-chang

    2004-01-01

    Spectral and structural characteristics of distributed Bragg reflector (DBR) in vertical-cavity surface-emitting lasers were studied with photoluminescence and double- crystal X- ray diffraction measurement. The expected high quality epitaxial DBR structure was verified. In the X- ray double- crystal rocking curves of DBR the zeroth- order peak, the first and second order satellite peaks were measured.Splitting of diffraction peak appeared in the rocking curves was analyzed. The effects of introduced deep energy levels on the structural perfection and optical properties were discussed.

  10. VSHOT: a tool for characterizing large, imprecise reflectors

    Energy Technology Data Exchange (ETDEWEB)

    Jones, S.A.; Neal, D.R.; Gruetzner, J.K.; Houser, R.M.; Edgar, R.M. [Sandia National Labs., Albuquerque, NM (United States); Wendelin, T.J. [National Renewable Energy Lab., Golden, CO (United States)

    1996-11-01

    A prototype Video Scanning Hartmann Optical Tester (VSHOT) has been developed to characterize the optics of dish-type solar concentrators. VSHOT is a flexible platform that may characterize any large reflector with a focal length over diameter ratio (f{number_sign}) greater than 0. 45, and RMS optical error in the 0. I - I 0 milliradian range. The VSHOT hardware, software, and operation are described. Measurement uncertainty and preliminary test results are discussed. Another potential application being explored for the VSHOT is the quality assurance of slumped-glass automobile windshields. Preliminary test results from a reference optic and a section of a windshield are presented.

  11. Processless offset printing plates

    Directory of Open Access Journals (Sweden)

    Sanja Mahović Poljaček

    2015-06-01

    Full Text Available With the implementation of platesetters in the offset printing plate making process, imaging of the printing plate became more stable and ensured increase of the printing plate quality. But as the chemical processing of the printing plates still highly influences the plate making process and the graphic reproduction workflow, development of printing plates that do not require chemical processing for offset printing technique has been one of the top interests in graphic technology in the last few years. The main reason for that came from the user experience, where majority of the problems with plate making process could be connected with the chemical processing of the printing plate. Furthermore, increased environmental standards lead to reducing of the chemicals used in the industrial processes. Considering these facts, different types of offset printing plates have been introduced to the market today. This paper presents some of the processless printing plates.

  12. Stress fields of the overriding plate at convergent margins and beneath active volcanic arcs.

    Science.gov (United States)

    Apperson, K D

    1991-11-01

    Tectonic stress fields in the overriding plate at convergent plate margins are complex and vary on local to regional scales. Volcanic arcs are a common element of overriding plates. Stress fields in the volcanic arc region are related to deformation generated by subduction and to magma generation and ascent processes. Analysis of moment tensors of shallow and intermediate depth earthquakes in volcanic arcs indicates that the seismic strain field in the arc region of many convergent margins is subhorizontal extension oriented nearly perpendicular to the arc. A process capable of generating such a globally consistent strain field is induced asthenospheric corner flow below the arc region.

  13. Design constraints on Cherenkov telescopes with Davies-Cotton reflectors

    CERN Document Server

    Bretz, Thomas

    2013-01-01

    This paper discusses the construction of high-performance ground-based gamma-ray Cherenkov telescopes with a Davies-Cotton reflector. For the design of such telescopes, usually physics constrains the field-of-view, while the photo-sensor size is defined by limited options. Including the effect of light-concentrators in front of the photo sensor, it is demonstrated that these constraints are enough to mutually constrain all other design parameters. The dependability of the various design parameters naturally arises once a relationship between the value of the point-spread functions at the edge of the field-of-view and the pixel field-of-view is introduced. To be able to include this constraint into a system of equations, an analytical description for the point-spread function of a tessellated Davies-Cotton reflector is derived from Taylor developments and ray-tracing simulations. Including higher order terms renders the result precise on the percent level. Design curves are provided within the typical phase sp...

  14. Soiling and Cleaning of Polymer Film Solar Reflectors

    Directory of Open Access Journals (Sweden)

    Christopher Sansom

    2016-11-01

    Full Text Available This paper describes the accelerated ageing of commercially available silvered polymer film by contact cleaning using brushes and water in the presence of soiling created by dust and sand particles. These conditions represent cleaning regimes in real concentrating solar power (CSP solar fields in arid environments, where contact cleaning using brushes and water is often required to clean the reflecting surfaces. Whilst suitable for glass reflectors, this paper discusses the effects of these established cleaning processes on the optical and visual characteristics of polymer film surfaces, and then describes the development of a more benign but effective contact cleaning process for cleaning polymer reflectors. The effects of a range of cleaning brushes are discussed, with and without the presence of water, in the presence of sand and dust particles from selected representative locations. The experiments were repeated using different experimental equipment at Plataforma Solar de Almería (PSA in Spain and Cranfield University in the UK. The results highlight differences that are attributable to the experimental methods used. Reflectance measurements and visual inspection show that a soft cleaning brush with a small amount of water, used in a cleaning head with both linear and rotational motion, can clean polymer film reflecting surfaces without inflicting surface damage or reducing specular reflectance.

  15. Iterative alignment of reflector segments using a laser tracker

    Science.gov (United States)

    Cabrera Cuevas, Lizeth; Lucero Alvarez, Maribel; Leon-Huerta, Andrea; Hernandez Rios, Emilio; Hernandez Lázaro, Josefina; Tzile Torres, Carlos; Castro Santos, David; Gale, David M.; Wilson, Grant; Narayanan, Gopal; Smith, David R.

    2013-04-01

    The Large Millimeter Telescope (LMT) is a 50m diameter millimetre-wave radio telescope situated on the summit of Sierra Negra, Puebla, at an altitude of 4600 meters. The reflector surface of the LMT currently employs84 segments arranged in three annular rings. Each segment is comprised of 8 precision composite subpanels located on five threaded adjusters. During the current primary surface refurbishment, individual segments are aligned in the telescope basement using a laser tracker. This allows increased spatial resolution in shorter timescales, resulting in the opportunity for improved logistics and increased alignment precision. To perform segment alignment an iterative process is carried out whereby the surface is measured and subpanel deformations are corrected with the goal of 40 microns RMS. In practice we have been able to achieve RMS errors of almost 20 microns, with 35 microns typical. The number of iterations varies from around ten to over 20, depending mainly on the behaviour of the mechanical adjusters that support the individual subpanels. Cross marks scribed on the reflector surface are used as fiducials, because their positions on the paraboloid are well known. Measurement data is processed using a robust curve fitting algorithm which provides a map of the surface showing the subpanel deviations. From this map the required subpanel adjuster movements are calculated allowing surface improvement in a stepwise manner.

  16. Ultraviolet reflector materials for solar detoxification of hazardous waste

    Energy Technology Data Exchange (ETDEWEB)

    Jorgensen, G.; Govindarajan, R.

    1991-07-01

    Organic waste detoxification requires cleavage of carbon bonds. Such reactions can be photo-driven by light that is energetic enough to disrupt such bonds. Alternately, light can be used to activate catalyst materials, which in turn can break organic bonds. In either case, photons with wavelengths less than 400 nm are required. Because the terrestrial solar resource below 400 nm is so small (roughly 3% of the available spectrum), highly efficient optical concentrators are needed that can withstand outdoor service conditions. In the past, optical elements for solar application have been designed to prevent ultraviolet (uv) radiation from reaching the reflective layer to avoid the potentially harmful effects of such light on the collector materials themselves. This effectively forfeits the uv part of the spectrum in return for some measure of protection against optical degradation. To optimize the cost/performance benefit of photochemical reaction systems, optical materials must be developed that are not only highly efficient but also inherently stable against the radiation they are designed to concentrate. The requirements of uv optical elements in terms of appropriate spectral bands and level of reflectance are established based upon the needs of photochemical applications. Relevant literature on uv reflector materials is reviewed which, along with discussions with industrial contacts, allows the establishment of a data base of currently available materials. Although a number of related technologies exist that require uv reflectors, to date little attention has been paid to achieving outdoor durability required for solar applications. 49 refs., 3 figs.

  17. Key technologies for high-accuracy large mesh antenna reflectors

    Science.gov (United States)

    Meguro, Akira; Harada, Satoshi; Watanabe, Mitsunobu

    2003-12-01

    Nippon Telephone and Telegram Corporation (NTT) continues to develop the modular mesh-type deployable antenna. Antenna diameter can be changed from 5 m to about 20 m by changing the number of modules used with surface accuracy better than 2.4 mm RMS (including all error factors) with sufficient deployment reliability. Key technologies are the antenna's structural design, the deployment mechanism, the design tool, the analysis tool, and modularized testing/evaluation methods. This paper describes our beam steering mechanism. Tests show that it yields a beam pointing accuracy of better than 0.1°. Based on the S-band modular mesh antenna reflector, the surface accuracy degradation factors that must be considered in designing the new antenna are partially identified. The influence of modular connection errors on surface accuracy is quantitatively estimated. Our analysis tool SPADE is extended to include the addition of joint gaps. The addition of gaps allows non-linear vibration characteristics due to gapping in deployment hinges to be calculated. We intend to design a new type of mesh antenna reflector. Our new goal is an antenna for Ku or Ka band satellite communication. For this mission, the surface shape must be 5 times more accurate than is required for an S-band antenna.

  18. Temperature Knowledge and Model Correlation for the Soil Moisture Active and Passive (SMAP) Reflector Mesh

    Science.gov (United States)

    Mikhaylov, Rebecca; Dawson, Douglas; Kwack, Eug

    2014-01-01

    NASA's Earth observing Soil Moisture Active & Passive (SMAP) Mission is scheduled to launch in November 2014 into a 685 km near-polar, sun synchronous orbit. SMAP will provide comprehensive global mapping measurements of soil moisture and freeze/thaw state in order to enhance understanding of the processes that link the water, energy, and carbon cycles. The primary objectives of SMAP are to improve worldwide weather and flood forecasting, enhance climate prediction, and refine drought and agriculture monitoring during its 3 year mission. The SMAP instrument architecture incorporates an L-band radar and an L-band radiometer which share a common feed horn and parabolic mesh reflector. The instrument rotates about the nadir axis at approximately 15 rpm, thereby providing a conically scanning wide swath antenna beam that is capable of achieving global coverage within 3 days. In order to make the necessary precise surface emission measurements from space, a temperature knowledge of 60 deg C for the mesh reflector is required. In order to show compliance, a thermal vacuum test was conducted using a portable solar simulator to illuminate a non flight, but flight-like test article through the quartz window of the vacuum chamber. The molybdenum wire of the antenna mesh is too fine to accommodate thermal sensors for direct temperature measurements. Instead, the mesh temperature was inferred from resistance measurements made during the test. The test article was rotated to five separate angles between 10 deg and 90 deg via chamber breaks to simulate the maximum expected on-orbit solar loading during the mission. The resistance measurements were converted to temperature via a resistance versus temperature calibration plot that was constructed from data collected in a separate calibration test. A simple thermal model of two different representations of the mesh (plate and torus) was created to correlate the mesh temperature predictions to within 60 deg C. The on-orbit mesh

  19. Subpixel accuracy for extracting groove center based on corner detection

    Institute of Scientific and Technical Information of China (English)

    Liu Suyi; Wang Guorong; Shi Yonghua

    2006-01-01

    Subpixel accuracy for V-groove center in robot welding is researched and a software measure to increase the accuracy of seam tracking by laser is presented.LOG( Laplacian of Gaussian ) operator is adopted to detect image edge.Vgroove center is extracted by corner detection of extremum curvature.Subpixel position is obtained by Lagarange polynomial interpolation algorithm.Experiment results show that the method is brief and applied, and is sufficient for the real time of robot welding by laser sensors.

  20. Constructing an optimal decision tree for FAST corner point detection

    KAUST Repository

    Alkhalid, Abdulaziz

    2011-01-01

    In this paper, we consider a problem that is originated in computer vision: determining an optimal testing strategy for the corner point detection problem that is a part of FAST algorithm [11,12]. The problem can be formulated as building a decision tree with the minimum average depth for a decision table with all discrete attributes. We experimentally compare performance of an exact algorithm based on dynamic programming and several greedy algorithms that differ in the attribute selection criterion. © 2011 Springer-Verlag.

  1. Corner contribution to percolation cluster numbers in three dimensions

    Science.gov (United States)

    Kovács, István A.; Iglói, Ferenc

    2014-05-01

    In three-dimensional critical percolation we study numerically the number of clusters NΓ which intersect a given subset of bonds Γ. If Γ represents the interface between a subsystem and the environment, then NΓ is related to the entanglement entropy of the critical diluted quantum Ising model. Due to corners in Γ there are singular corrections to NΓ, which scale as bΓlnLΓ, with LΓ being the linear size of Γ and the prefactor bΓ is found to be universal. This result indicates that logarithmic finite-size corrections exist in the free energy of three-dimensional critical systems.

  2. Technology Corner: Dating of Electronic Hardware for Prior Art Investigations

    Directory of Open Access Journals (Sweden)

    Sellam Ismail

    2012-03-01

    Full Text Available In many legal matters, specifically patent litigation, determining and authenticating the date of computer hardware or other electronic products or components is often key to establishing the item as legitimate evidence of prior art. Such evidence can be used to buttress claims of technologies available or of events transpiring by or at a particular date.In 1945, the Electronics Industry Association published a standard, EIA 476-A, standardized in the reference Source and Date Code Marking (Electronic Industries Association, 1988.(see PDF for full tech corner

  3. Contour tracking and corner detection in a logic programming environment

    DEFF Research Database (Denmark)

    Bell, Benjamin; Pau, L. F.

    1990-01-01

    The added functionality such as contour tracking and corner detection which logic programming lends to standard image operators is described. An environment for implementing low-level imaging operations with Prolog predicates is considered. Within this environment, higher-level image predicates...... has been very good in many more complex images, as it allows for feedback both ways between sensor input and symbolic models. More important is the parameter selection capability in a dynamic version where background properties change. The authors present examples of Prolog predicates for performing...

  4. Polarization properties of a metal corner-cube retroreflector

    Energy Technology Data Exchange (ETDEWEB)

    Bieg, B., E-mail: b.bieg@am.szczecin.pl

    2015-10-15

    The cube-corner retroreflector, an optical element consisting of three orthogonal mirrors, reflects incident beam in the exactly opposite direction. The change in the polarization state of the infrared beam, reflected from CCR constructed of three metal surfaces with complex reflexion coefficient, is discussed theoretically with ray tracing and the Jones matrices formalism. It is found that the final polarization state is modified according to the angle of incidence, the ray path through the retroreflector as well as the beam wavelength and its initial polarization. The main point is that under the specified conditions polarization changes could be minimized, what is essential for the CCR practical application at tokamak polarimetric systems.

  5. Remarks on the stability of Cartesian PMLs in corners

    CERN Document Server

    Bécache, Eliane

    2011-01-01

    This work is a contribution to the understanding of the question of stability of Perfectly Matched Layers (PMLs) in corners, at continuous and discrete levels. First, stability results are presented for the Cartesian PMLs associated to a general first-order hyperbolic system. Then, in the context of the pressure-velocity formulation of the acoustic wave propagation, an unsplit PML formulation is discretized with spectral mixed finite elements in space and finite differences in time. It is shown, through the stability analysis of two different schemes, how a bad choice of the time discretization can deteriorate the CFL stability condition. Some numerical results are finally presented to illustrate these stability results.

  6. Novel boundary element method for resolving plate bending problems

    Institute of Scientific and Technical Information of China (English)

    陈颂英; 王乐勤; 焦磊

    2003-01-01

    This paper discusses the application of the boundary contour method for resolving plate bending problems. The exploitation of the integrand divergence free property of the plate bending boundary integral equation based on the Kirchhoff hypothesis and a very useful application of Stokes' Theorem are presented to convert surface integrals on boundary elements to the computation of bending potential functions on the discretized boundary points, even for curved surface elements of arbitrary shape. Singularity and treatment of the discontinued corner point are not needed at all. The evaluation of the physics variant at internal points is also shown in this article. Numerical results are presented for some plate bending problems and compared against analytical and previous solutions.

  7. The Location Algorithm of the Inclined License Plates Based on Mathematical Morphology and Orientation Field

    Institute of Scientific and Technical Information of China (English)

    LIANGDong; GAOJun; CAOWei; FUQizhong; ZHAOJing

    2003-01-01

    The license plate recognition (LPR), as an important measure of traffic controlling and information management, is being paid more and more attention. The location and detection of the inclined license plate is an important problem in the License Plate Recognition Sys-tem. But now most of the proposed location algorithms are based on the condition of the horizontal license. These methods don't work well on inclined license plate. At the same time, the method based on Hough Transform is pro-posed to detect the inclined angle of the license plate, but it has many limitations. In order to solve this problem,we propose a new method to locate the inclined plate region using Mathematical Morphology and Orientation Field. The algorithm consists of preprocessing, inclined an-gel detecting and license plate location modules. Firstly,we adopt the gray extension method to improve the ob-serving quality of the images and study the intrinsic char-acteristic of texture and shape of vehicle license, such as the size, space and height of characters, then we construct the morphologic operator to make a series of morphologicoperations and locate the plate region roughly in the pre-processed image; secondly we make the horizontal and ver-tical projection, get the coordinate of the down left corner and top right corner in the license plate, and detect the inclined angle of the license plate with Orientation Field;lastly, the results of projecting and Orientation Field cal-culating are used to locate the license plate precisely. We practise our method on images under different illumination condition, and the experimental results show that the accu-racy of inclined angel detection and license plate extraction based on Mathematical Morphology and Orientation Field is significant.

  8. The effects of stainless steel radial reflector on core reactivity for small modular reactor

    Science.gov (United States)

    Kang, Jung Kil; Hah, Chang Joo; Cho, Sung Ju; Seong, Ki Bong

    2016-01-01

    Commercial PWR core is surrounded by a radial reflector, which consists of a baffle and water. Radial reflector is designed to reflect neutron back into the core region to improve the neutron efficiency of the reactor and to protect the reactor vessels from the embrittling effects caused by irradiation during power operation. Reflector also helps to flatten the neutron flux and power distributions in the reactor core. The conceptual nuclear design for boron-free small modular reactor (SMR) under development in Korea requires to have the cycle length of 4˜5 years, rated power of 180 MWth and enrichment less than 5 w/o. The aim of this paper is to analyze the effects of stainless steel radial reflector on the performance of the SMR using UO2 fuels. Three types of reflectors such as water, water/stainless steel 304 mixture and stainless steel 304 are selected to investigate the effect on core reactivity. Additionally, the thickness of stainless steel and double layer reflector type are also investigated. CASMO-4/SIMULATE-3 code system is used for this analysis. The results of analysis show that single layer stainless steel reflector is the most efficient reflector.

  9. Three-dimensional photonic crystal intermediate reflectors for enhanced light-trapping in tandem solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Uepping, Johannes; Bielawny, Andreas; Wehrspohn, Ralf B. [Institute of Physics, Martin-Luther-Universitaet Halle-Wittenberg, Halle (Germany); Fraunhofer-Institute for Mechanics of Materials, Halle (Germany); Beckers, Thomas; Carius, Reinhard; Rau, Uwe [Institute of Energy and Climate Research 5 - Photovoltaics, Forschungszentrum Juelich GmbH, Juelich (Germany); Fahr, Stefan; Rockstuhl, Carsten; Lederer, Falk [Institute of Condensed Matter Theory and Solid State Optics and Abbe Center of Photonics, Friedrich-Schiller-Universitaet Jena (Germany); Kroll, Matthias; Pertsch, Thomas [Institute of Applied Physics, Friedrich-Schiller-Universitaet Jena (Germany); Steidl, Lorenz; Zentel, Rudolf [Institute of Organic Chemistry, Johannes Gutenberg-Universitaet Mainz (Germany)

    2011-09-08

    A three-dimensional photonic crystal intermediate reflector for enhanced light trapping in tandem solar cells is presented. The intermediate reflector consists of a transparent and conductive ZnO:Al inverted opal sandwiched in between the top amorphous silicon and bottom microcrystalline silicon cell. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. The role of oxide interlayers in back reflector configurations for amorphous silicon solar cells

    NARCIS (Netherlands)

    Demontis, V.; Sanna, C.; Melskens, J.; Santbergen, R.; Smets, A.H.M.; Damiano, A.; Zeman, M.

    2013-01-01

    Thin oxide interlayers are commonly added to the back reflector of thin-film silicon solar cells to increase their current. To gain more insight in the enhancement mechanism, we tested different back reflector designs consisting of aluminium-doped zinc oxide (ZnO:Al) and/or hydrogenated silicon oxid

  11. Self-Mixing Fringes of Vertical-Cavity Surface-Emitting Lasers under Dual Reflector Feedback

    Institute of Scientific and Technical Information of China (English)

    CHENG Xiang; ZHANG Shu-Lian; ZHANG Lian-Qing; TAN Yi-Dong

    2006-01-01

    The self-mixing fringes which shift due to every one-twentieth wavelength displacement of the target are observed.Taking advantage of the dual reflectors in the external cavity of lasers, the resolution of the sensors has been improved by 10 times. The role of the each reflector has been discussed in detail.

  12. 16 CFR Figure 8 to Part 1512 - Reflectorized Bicycle Wheel Rim Abrasion Test Device

    Science.gov (United States)

    2010-01-01

    ... 16 Commercial Practices 2 2010-01-01 2010-01-01 false Reflectorized Bicycle Wheel Rim Abrasion... HAZARDOUS SUBSTANCES ACT REGULATIONS REQUIREMENTS FOR BICYCLES Pt. 1512, Fig. 8 Figure 8 to Part 1512—Reflectorized Bicycle Wheel Rim Abrasion Test Device EC03OC91.074...

  13. Theoretical modeling of the dynamics of a semiconductor laser subject to double-reflector optical feedback

    Science.gov (United States)

    Bakry, A.; Abdulrhmann, S.; Ahmed, M.

    2016-06-01

    We theoretically model the dynamics of semiconductor lasers subject to the double-reflector feedback. The proposed model is a new modification of the time-delay rate equations of semiconductor lasers under the optical feedback to account for this type of the double-reflector feedback. We examine the influence of adding the second reflector to dynamical states induced by the single-reflector feedback: periodic oscillations, period doubling, and chaos. Regimes of both short and long external cavities are considered. The present analyses are done using the bifurcation diagram, temporal trajectory, phase portrait, and fast Fourier transform of the laser intensity. We show that adding the second reflector attracts the periodic and perioddoubling oscillations, and chaos induced by the first reflector to a route-to-continuous-wave operation. During this operation, the periodic-oscillation frequency increases with strengthening the optical feedback. We show that the chaos induced by the double-reflector feedback is more irregular than that induced by the single-reflector feedback. The power spectrum of this chaos state does not reflect information on the geometry of the optical system, which then has potential for use in chaotic (secure) optical data encryption.

  14. Concepts for polarising sheets & "dual-gridded" reflectors for circular polarisation

    NARCIS (Netherlands)

    Albani, M.; Balling, P.; Datashvili, L.; Gerini, G.; Ingvarson, P.; Pontoppidan, K.; Sabbadini, M.; Sjöberg, D.; Skokic, S.; Vecchi, G.

    2010-01-01

    C-, Ku- and Ka-band communications and broadcast satellites use so-called dual-gridded reflector antennas for linear polarisation to provide independent reflector surfaces and/or independent feeds for the two orthogonal polarisations. This paper describes initial work to extend this concept to circu

  15. Flexible, angle-independent, structural color reflectors inspired by morpho butterfly wings.

    Science.gov (United States)

    Chung, Kyungjae; Yu, Sunkyu; Heo, Chul-Joon; Shim, Jae Won; Yang, Seung-Man; Han, Moon Gyu; Lee, Hong-Seok; Jin, Yongwan; Lee, Sang Yoon; Park, Namkyoo; Shin, Jung H

    2012-05-08

    Thin-film color reflectors inspired by Morpho butterflies are fabricated. Using a combination of directional deposition, silica microspheres with a wide size distribution, and a PDMS (polydimethylsiloxane) encasing, a large, flexible reflector is created that actually provides better angle-independent color characteristics than Morpho butterflies and which can even be bent and folded freely without losing its Morpho-mimetic photonic properties.

  16. Leaky wave enhanced feeds for multibeam reflectors to be used for telecom satellite based links

    NARCIS (Netherlands)

    Neto, A.; Ettorre, M.; Gerini, G.; Maagt, P. de

    2012-01-01

    The use of dielectric super-layers for shaping the radiation pattern of focal plane feeds of a multibeam reflector system is discussed. Using the super-layers, it is possible to reduce the spillover from the reflectors without increasing the dimension of each aperture. The effect has been demonstrat

  17. Shaped reflector antenna analysis using the Jacobi-Bessel series. [design for space and satellite communication

    Science.gov (United States)

    Rahmat-Samii, Y.; Galindo-Israel, V.

    1980-01-01

    A vector radiation integral is derived for an offset shaped reflector illuminated by an arbitrarily located and oriented source. A procedure for expressing the integral in terms of a series of the Fourier transforms of an effective aperture distribution is discussed. The Jacobi-Bessel series is used to evaluate the Fourier transforms. Numerical results are presented for different reflector configurations and source locations.

  18. Theoretical modeling of the dynamics of a semiconductor laser subject to double-reflector optical feedback

    Energy Technology Data Exchange (ETDEWEB)

    Bakry, A. [King Abdulaziz University, 80203, Department of Physics, Faculty of Science (Saudi Arabia); Abdulrhmann, S. [Jazan University, 114, Department of Physics, Faculty of Sciences (Saudi Arabia); Ahmed, M., E-mail: mostafa.farghal@mu.edu.eg [King Abdulaziz University, 80203, Department of Physics, Faculty of Science (Saudi Arabia)

    2016-06-15

    We theoretically model the dynamics of semiconductor lasers subject to the double-reflector feedback. The proposed model is a new modification of the time-delay rate equations of semiconductor lasers under the optical feedback to account for this type of the double-reflector feedback. We examine the influence of adding the second reflector to dynamical states induced by the single-reflector feedback: periodic oscillations, period doubling, and chaos. Regimes of both short and long external cavities are considered. The present analyses are done using the bifurcation diagram, temporal trajectory, phase portrait, and fast Fourier transform of the laser intensity. We show that adding the second reflector attracts the periodic and perioddoubling oscillations, and chaos induced by the first reflector to a route-to-continuous-wave operation. During this operation, the periodic-oscillation frequency increases with strengthening the optical feedback. We show that the chaos induced by the double-reflector feedback is more irregular than that induced by the single-reflector feedback. The power spectrum of this chaos state does not reflect information on the geometry of the optical system, which then has potential for use in chaotic (secure) optical data encryption.

  19. The role of oxide interlayers in back reflector configurations for amorphous silicon solar cells

    NARCIS (Netherlands)

    Demontis, V.; Sanna, C.; Melskens, J.; Santbergen, R.; Smets, A.H.M.; Damiano, A.; Zeman, M.

    2013-01-01

    Thin oxide interlayers are commonly added to the back reflector of thin-film silicon solar cells to increase their current. To gain more insight in the enhancement mechanism, we tested different back reflector designs consisting of aluminium-doped zinc oxide (ZnO:Al) and/or hydrogenated silicon oxid

  20. Modulation of Transmission Spectra of Anodized Alumina Membrane Distributed Bragg Reflector by Controlling Anodization Temperature

    Directory of Open Access Journals (Sweden)

    Zheng WenJun

    2009-01-01

    Full Text Available Abstract We have successfully prepared anodized alumina membrane distributed Bragg reflector (DBR using electrochemical anodization method. The transmission peak of this distributed Bragg reflector could be easily and effectively modulated to cover almost any wavelength range of the whole visible spectrum by adjusting anodization temperature.

  1. Effect of disc reflectors on radiation impedance of short-backfire antenna

    Science.gov (United States)

    Marougi, S. D.

    1982-02-01

    Using near-field analysis, the influence of large and small disc reflectors used in short-backfire antennas on the radiation impedance of a dipole feed element has been investigated. The effect of each reflector is evaluated separately, and the overall change in the radiation impedance of the dipole is predicted.

  2. The effects of stainless steel radial reflector on core reactivity for small modular reactor

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Jung Kil, E-mail: jkkang@email.kings.ac.kr; Hah, Chang Joo, E-mail: changhah@kings.ac.kr [KINGS, 658-91, Haemaji-ro, Seosaeng-myeon, Ulju-gun, Ulsan, 689-882 (Korea, Republic of); Cho, Sung Ju, E-mail: sungju@knfc.co.kr; Seong, Ki Bong, E-mail: kbseong@knfc.co.kr [KNFC, Daedeok-daero 989beon-gil, Yuseong-gu, Daejeon, 305-353 (Korea, Republic of)

    2016-01-22

    Commercial PWR core is surrounded by a radial reflector, which consists of a baffle and water. Radial reflector is designed to reflect neutron back into the core region to improve the neutron efficiency of the reactor and to protect the reactor vessels from the embrittling effects caused by irradiation during power operation. Reflector also helps to flatten the neutron flux and power distributions in the reactor core. The conceptual nuclear design for boron-free small modular reactor (SMR) under development in Korea requires to have the cycle length of 4∼5 years, rated power of 180 MWth and enrichment less than 5 w/o. The aim of this paper is to analyze the effects of stainless steel radial reflector on the performance of the SMR using UO{sub 2} fuels. Three types of reflectors such as water, water/stainless steel 304 mixture and stainless steel 304 are selected to investigate the effect on core reactivity. Additionally, the thickness of stainless steel and double layer reflector type are also investigated. CASMO-4/SIMULATE-3 code system is used for this analysis. The results of analysis show that single layer stainless steel reflector is the most efficient reflector.

  3. Electronic Brake-Force Distribution Control Methods of ABS-Equipped Vehicles During Cornering Braking

    Institute of Scientific and Technical Information of China (English)

    WANG Guo-ye; LIU Zhao-du; MA Yue-feng; QI Zhi-quan

    2007-01-01

    Based on the dynamics of ABS-equipped vehicles during cornering braking,the electronic brakeforce distribution (EBD) control methods of ABS-equipped vehicles during cornering braking are proposed.According to the dynamics and the tire model under tire adhesion limit,the stability acceptance criteria of vehicles during cornering braking are proposed.According to the stability acceptance criteria and the ABS control,the EBD control methods of ABS-equipped vehicles during cornering braking are implemented by adjusting the threshold values of tires slip independently.The vehicle states during cornering braking at two typical initial velocities of the vehicle are analyzed by the EBD control methods,whose results indicate the EBD control methods can improve the braking performances of the vehicle during cornering braking comparing with the ABS control.

  4. Design and Fabrication of Integrated Fabry-Perot Type Color Reflector for Reflective Displays.

    Science.gov (United States)

    Cho, Seong M; Cheon, Sang Hoon; Kim, Tae-Youb; Ah, Chil Seong; Song, Juhee; Ryu, Hojun; Chu, Hye Yong

    2016-05-01

    A Fabry-Perot type integrated color reflector, with red/blue/green colors as subpixels, was designed and fabricated with Si substrate. Ag films were used as reflective mirror layers, SiO2 films were used as Fabry-Perot cavity layers and W films were used as partially reflective layers for the cavity. To minimize the effects of the thickness variation of the oxide cavity layers, the structure of the color reflector was optimized, and the differential deposition scheme was devised and applied in the fabrication process. The integrated color reflector was successfully fabricated with the proposed fabrication scheme. The measured white reflectance was > 45% in the visible spectrum range and -49% at 550 nm wavelength. The fabricated reflector had moderate color gamut of 17% of the National Television System Committee (NTSC) standard and it showed very high white reflectivity. The fabricated color reflector is expected to be applicable to reflective displays.

  5. Generation of XS library for the reflector of VVER reactor core using Monte Carlo code Serpent

    Science.gov (United States)

    Usheva, K. I.; Kuten, S. A.; Khruschinsky, A. A.; Babichev, L. F.

    2017-01-01

    A physical model of the radial and axial reflector of VVER-1200-like reactor core has been developed. Five types of radial reflector with different material composition exist for the VVER reactor core and 1D and 2D models were developed for all of them. Axial top and bottom reflectors are described by the 1D model. A two-group XS library for diffusion code DYN3D has been generated for all types of reflectors by using Serpent 2 Monte Carlo code. Power distribution in the reactor core calculated in DYN3D is flattened in the core central region to more extent in the 2D model of the radial reflector than in its 1D model.

  6. Weighted SAW reflector gratings for orthogonal frequency coded SAW tags and sensors

    Science.gov (United States)

    Puccio, Derek (Inventor); Malocha, Donald (Inventor)

    2011-01-01

    Weighted surface acoustic wave reflector gratings for coding identification tags and sensors to enable unique sensor operation and identification for a multi-sensor environment. In an embodiment, the weighted reflectors are variable while in another embodiment the reflector gratings are apodized. The weighting technique allows the designer to decrease reflectively and allows for more chips to be implemented in a device and, consequently, more coding diversity. As a result, more tags and sensors can be implemented using a given bandwidth when compared with uniform reflectors. Use of weighted reflector gratings with OFC makes various phase shifting schemes possible, such as in-phase and quadrature implementations of coded waveforms resulting in reduced device size and increased coding.

  7. Positive focal shift of gallium nitride high contrast grating focusing reflectors

    Science.gov (United States)

    He, Shumin; Wang, Zhenhai; Liu, Qifa

    2016-09-01

    We design a type of metasurfaces capable of serving as a visible-light focusing reflector based on gallium nitride (GaN) high contrast gratings (HCGs). The wavefront of the reflected light is precisely manipulated by spatial variation of the grating periods along the subwavelength ridge array to achieve light focusing. Different from conventional negative focal shift effect, a positive focal shift is observed in such focusing reflectors. Detailed investigations of the influence of device size on the focusing performance, especially the focal length, are preformed via a finite element method . The results show that all performance parameters are greatly affected by the reflector size. A more concentrated focal point, or a better focusing capability, can be achieved by larger size. With increasing reflector size, the achieved focal length decreases and gradually approaches to the design, thus the corresponding positive focal shift decreases. Our results are helpful for understanding the visible-light control of the planar HCG-based focusing reflectors.

  8. [Four corner fusion in patients with wrist arthritis].

    Science.gov (United States)

    Vázquez-Alonso, María Francisca; Viñas-Silva, Alberto

    2016-01-01

    Scapholunate advance collapse (SLAC) and Scaphoid nonunion advance collapse (SNAC), are the two most common patterns of postraumatic wrist arthritis. SLAC wrist develops after attenuation, either traumatically or atraumatically, of the scapholunate ligament. Atraumatic causes of SLAC wrist include calcium pyrophosphate dehydrate deposition disease, reumathoid arthritis, neuropathic diseases, and b2-microglobulin asociated amyloid deposition diseases. On the other hand, SNAC wrist develops following a scahpoid fracture that has progressed to a nonunion. Both of these processes lead to abnormal joint kinematics, since the lunate is unrestrained by the distal scaphoid and, therefore, assumes an extended posture. Over time, this may result in Dorsal intercalated segment instability (DISI) deformity, which invariably progresses to degenerative arthritis of the radioescaphoid articulation, followed by carpal collapse and midcarpal arthritis. The purpose of this retrospective study is to evaluate the functional outcome and pain relief in SLAC/SNAC wrist, after four corner fusion. This study was made in 52 patients of the Hospital de Traumatología y Ortopedia Lomas Verdes, these patients undergone four corner fusion surgery, in a period january 2007 to december 2014. We used Quick Dash Questionary to evaluate functional outcome and pain relief in these patients.

  9. Faster and better: a machine learning approach to corner detection

    CERN Document Server

    Rosten, Edward; Drummond, Tom

    2008-01-01

    The repeatability and efficiency of a corner detector determines how likely it is to be useful in a real-world application. The repeatability is importand because the same scene viewed from different positions should yield features which correspond to the same real-world 3D locations [Schmid et al 2000]. The efficiency is important because this determines whether the detector combined with further processing can operate at frame rate. Three advances are described in this paper. First, we present a new heuristic for feature detection, and using machine learning we derive a feature detector from this which can fully process live PAL video using less than 5% of the available processing time. By comparison, most other detectors cannot even operate at frame rate (Harris detector 115%, SIFT 195%). Second, we generalize the detector, allowing it to be optimized for repeatability, with little loss of efficiency. Third, we carry out a rigorous comparison of corner detectors based on the above repeatability criterion a...

  10. OPERATORS ON CORNER MANIFOLDS WITH EXIT TO INFINITY

    Institute of Scientific and Technical Information of China (English)

    D. Calvo; B. W. Schulze

    2006-01-01

    We study (pseudo-)differential operators on a manifold with edge Z,locally modelled on a wedge with model cone that has itself a base manifold W with smooth edge Y. The typical operators A are corner degenerate in a specific way. They (σψ (A), σ∧ (A), σ∧ (A)), where σψ is the interior symbol and σ∧ (A)(y, η), (y, η) ∈ T*Y\\0,weighted Sobolev spaces on the infinite cone with base W. Since such a cone has edges with exit to infinity, the calculus has the problem to understand the behaviour of operators on a manifold of that kind.We show the continuity of corner-degenerate operators in weighted edge Sobolev spaces, and we investigate the ellipticity of edge symbols of second generation. Starting from parameter-dependent elliptic families of edge operators of first generation, we obtain the Fredholm property of higher edge symbols on the corresponding singular infinite model cone.

  11. Corner-turning characteristics of TATB/HMX/Kel-F mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Stallings, T.L.; Osborn, A.G.; West, G.T.

    1983-01-01

    A factorial experiment was conducted to determine the effects of HMX content, HMX particle size and TATB particle size in TATB/HMX-Kel-F formulations containing 5% by weight Kel-F 800 binder on corner-turning performance at ambient and -54 C. TATB and HMX particle-size variations did not significantly affect differences in corner-turning performance between the two temperatures. With increasing HMX contents the effect of temperature on corner turning became less and at the maximum HMX content studied, 25%, the corner turning levels were almost equal at ambient and -54 C.

  12. Features of draws of corner kicks in games of teams of high qualification

    Directory of Open Access Journals (Sweden)

    Andrii Pertsukhov

    2016-04-01

    Full Text Available Purpose: to define quantity and efficiency of corner kicks in games of teams-participants of the World Championship of 2014. Material &Methods: analysis of scientific and methodical literature, registration of technical and tactical actions, methods of mathematical statistics. The research of the competitive activity was carried out with teams-participants of the World Championship of 2014. Results: quantitative and quality indicators of draws of corner kicks in games of teams of high qualification are presented. Conclusions: teams-participants of the World Cup of 2014 carried out 5,2 corner kicks. The efficiency of draw of corner kicks made 44,5% on average for a game.

  13. Photogrammetry research for FAST eleven-meter reflector panel surface shape measurement

    Science.gov (United States)

    Zhou, Rongwei; Zhu, Lichun; Li, Weimin; Hu, Jingwen; Zhai, Xuebing

    2010-10-01

    In order to design and manufacture the Five-hundred-meter Aperture Spherical Radio Telescope (FAST) active reflector measuring equipment, measurement on each reflector panel surface shape was presented, static measurement of the whole neutral spherical network of nodes was performed, real-time dynamic measurement at the cable network dynamic deformation was undertaken. In the implementation process of the FAST, reflector panel surface shape detection was completed before eleven-meter reflector panel installation. Binocular vision system was constructed based on the method of binocular stereo vision in machine vision, eleven-meter reflector panel surface shape was measured with photogrammetry method. Cameras were calibrated with the feature points. Under the linearity camera model, the lighting spot array was used as calibration standard pattern, and the intrinsic and extrinsic parameters were acquired. The images were collected for digital image processing and analyzing with two cameras, feature points were extracted with the detection algorithm of characteristic points, and those characteristic points were matched based on epipolar constraint method. Three-dimensional reconstruction coordinates of feature points were analyzed and reflective panel surface shape structure was established by curve and surface fitting method. The error of reflector panel surface shape was calculated to realize automatic measurement on reflector panel surface shape. The results show that unit reflector panel surface inspection accuracy was 2.30mm, within the standard deviation error of 5.00mm. Compared with the requirement of reflector panel machining precision, photogrammetry has fine precision and operation feasibility on eleven-meter reflector panel surface shape measurement for FAST.

  14. Study on differences between high contrast grating reflectors for TM and TE polarizations and their impact on VCSEL designs

    DEFF Research Database (Denmark)

    Chung, Il-Sug

    2015-01-01

    A theoretical study of differences in broadband high-indexcontrast grating (HCG) reflectors for TM and TE polarizations is presented, covering various grating parameters and properties of HCGs. It is shown that the HCG reflectors for TM polarization (TM HCG reflectors) have much thicker grating...

  15. Create Your Plate

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    Full Text Available ... steps to get started: Using your dinner plate, put a line down the middle of the plate. ... vegetables . Now in one of the small sections, put grains and starchy foods. See this list of ...

  16. Create Your Plate

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    Full Text Available ... Your Plate It's simple and effective for both managing diabetes and losing weight. Creating your plate lets ... 2016 Articles from Diabetes Forecast® magazine: wcie-meal-planning, In this section Food Planning Meals Diabetes Meal ...

  17. Create Your Plate

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    Full Text Available ... Your Plate Gluten Free Diets Meal Planning for Vegetarian Diets Cook with Heart-Healthy Foods Holiday Meal ... Healthy Diet Create Your Plate Meal Planning for Vegetarian Diets Gluten Free Diets Holiday Meal Planning Cook ...

  18. Food guide plate

    Science.gov (United States)

    ... chips or cookies. VEGETABLES: MAKE HALF OF YOUR PLATE FRUITS AND VEGETABLES Vegetables can be raw, fresh, ... as a snack. FRUITS: MAKE HALF OF YOUR PLATE FRUITS AND VEGETABLES Fruits can be fresh, canned, ...

  19. Growth Plate Fractures

    Science.gov (United States)

    ... the most widely used by doctors is the Salter-Harris system, described below. Type I Fractures These ... incidence of growth plate fractures peaks in adolescence. Salter-Harris classification of growth plate fractures. AAOS does ...

  20. Create Your Plate

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    Full Text Available ... Planning Meals Diabetes Meal Plans Create Your Plate Gluten Free Diets Meal Planning for Vegetarian Diets Cook ... Create Your Plate Meal Planning for Vegetarian Diets Gluten Free Diets Holiday Meal Planning Cook with Heart- ...

  1. Create Your Plate

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    Full Text Available ... Planning Meals Diabetes Meal Plans Create Your Plate Gluten Free Diets Meal Planning for Vegetarian Diets Cook ... Create Your Plate Meal Planning for Vegetarian Diets Gluten Free Diets Holiday Meal Planning Cook with Heart- ...

  2. Create Your Plate

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    Full Text Available ... Your Plate It's simple and effective for both managing diabetes and losing weight. Creating your plate lets you still choose the foods you want, but changes the portion sizes so you are getting larger ...

  3. Create Your Plate

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    Full Text Available ... Your Plate It's simple and effective for both managing diabetes and losing weight. Creating your plate lets ... Sleeve Custom jerseys for your Tour de Cure team benefits the cause. Ask the Experts: Learn to ...

  4. Study of the Dynamics of Large Reflector Antennas with Accelerometers

    CERN Document Server

    Snel, R C; Baars, J W M

    2007-01-01

    The Atacama Large Millimeter Array (ALMA) will consist of up to 64 state-of-the-art sub-mm telescopes, subject to stringent performance specifications which will push the boundaries of the technology, and makes testing of antenna performance a likewise challenging task. Two antenna prototypes were evaluated at the ALMA Test Facility at the Very Large Array site in New Mexico, USA. The dynamic behaviour of the antennas under operational conditions was investigated with the help of an accelerometer system capable of measuring rigid body motion of the elevation structure of the antenna, as well as a few low-order deformation modes, resulting in dynamic performance numbers for pointing stability, reflector surface stability, path length stability, and structure flexure. Special emphasis was given to wind effects, one of the major factors affecting performance on timescales of seconds to tens of minutes. This paper describes the accelerometer system, its capabilities and limitations, and presents the dynamic perfo...

  5. Photoacoustic imaging using acoustic reflectors to enhance planar arrays.

    Science.gov (United States)

    Ellwood, Robert; Zhang, Edward; Beard, Paul; Cox, Ben

    2014-12-01

    Planar sensor arrays have advantages when used for photoacoustic imaging: they do not require the imaging target to be enclosed, and they are easier to manufacture than curved arrays. However, planar arrays have a limited view of the acoustic field due to their finite size; therefore, not all of the acoustic waves emitted from a photoacoustic source can be recorded. This loss of data results in artifacts in the reconstructed photoacoustic image. A detection array configuration which combines a planar Fabry–Pérot sensor with perpendicular acoustic reflectors is described and experimentally implemented. This retains the detection advantages of the planar sensor while increasing the effective detection aperture in order to improve the reconstructed photoacoustic image.

  6. Multiphysics modeling and uncertainty quantification for an active composite reflector

    Science.gov (United States)

    Peterson, Lee D.; Bradford, S. C.; Schiermeier, John E.; Agnes, Gregory S.; Basinger, Scott A.

    2013-09-01

    A multiphysics, high resolution simulation of an actively controlled, composite reflector panel is developed to extrapolate from ground test results to flight performance. The subject test article has previously demonstrated sub-micron corrected shape in a controlled laboratory thermal load. This paper develops a model of the on-orbit performance of the panel under realistic thermal loads, with an active heater control system, and performs an uncertainty quantification of the predicted response. The primary contribution of this paper is the first reported application of the Sandia developed Sierra mechanics simulation tools to a spacecraft multiphysics simulation of a closed-loop system, including uncertainty quantification. The simulation was developed so as to have sufficient resolution to capture the residual panel shape error that remains after the thermal and mechanical control loops are closed. An uncertainty quantification analysis was performed to assess the predicted tolerance in the closed-loop wavefront error. Key tools used for the uncertainty quantification are also described.

  7. Dual-Band Feed for a Microwave Reflector Antenna

    Science.gov (United States)

    Hoppe, Daniel; Reilly, Harry

    2005-01-01

    A waveguide feed has been designed to provide specified illumination patterns for a dual-reflector antenna in two wavelength bands: 8 to 9 GHz and 30 to 40 GHz. The feed (see figure) has a coaxial configuration: A wider circular tube surrounds a narrower circular tube that serves as a waveguide for the signals in the 30-to-40-GHz band. The annular space between the narrower and the wider tube serves as a coaxial waveguide for the signals in the 8-to-9-GHz band. The nominal design frequencies of the outer and inner waveguides are 8.45 and 32 GHz, respectively. Each of the two waveguides is terminated in a component that is sized and shaped to help focus the radiation in its respective frequency band into the specified illumination pattern. For the outer waveguide, the beam-shaping termination is a corrugated horn; for the inner waveguide, the beam-shaping termination is a dielectric rod insert.

  8. Compact Single-Mode Distributed Bragg Reflector Fiber Laser

    Institute of Scientific and Technical Information of China (English)

    XUE Yi-Yuan; AN Hong-Lin; FU Li-Bin; LIN Xiang-Zhi; LIU Hong-Du

    2000-01-01

    A compact single-mode distributed Bragg reflector (DBR) fiber laser with narrow spectral linewidth is investigated. Firstly, based on our theoretical analysis the single longitudinal mode operation domain is obtained. Then, a single-mode DBR fiber laser of 7.9cm long with master oscillator power amplifier (MOPA) configuration is designed and constructed to operate in the single-mode domain. The fiber laser is pumped by a semiconductor laser at 975.5nm. The master oscillator operates at 1556.91 nm with a cw output power of 1.43mW for a pump power of 55.35 mW. Its slope efficiency is 2.7% and the spectral linewidth is less than 1.2MHz (instrument resolution limited). With the MOPA configuration the laser output power and slope efficiency are increased to 7.8mW and 16.9%, respectively.

  9. Investigation of Flexible Textile Antennas and AMC Reflectors

    Directory of Open Access Journals (Sweden)

    M. Mantash

    2012-01-01

    Full Text Available In this paper, two different methods for fabric characterization are presented: a single frequency method and a broadband method. Felt and denim fabrics are characterized, and patch antennas are designed using these substrates to test both methods. Prototypes of the antennas on felt and denim are manufactured using conductive textile (called electrotextile aiming to obtain fully flexible antennas. The prototypes are characterized in anechoic chamber to be compared and obtain conclusions related to the characterization methods. A new dual-band hexagonal AMC reflector combinable with antennas is also proposed to improve their performance and reduce the backward radiation to the human body. A novel broadband CPW-fed monopole antenna is designed to be combined with the AMC. The resulted prototype is characterized and compared with the performance of the CPW-fed antenna alone.

  10. Large Deployable Reflector (LDR) Requirements for Space Station Accommodations

    Science.gov (United States)

    Crowe, D. A.; Clayton, M. J.; Runge, F. C.

    1985-01-01

    Top level requirements for assembly and integration of the Large Deployable Reflector (LDR) Observatory at the Space Station are examined. Concepts are currently under study for LDR which will provide a sequel to the Infrared Astronomy Satellite and the Space Infrared Telescope Facility. LDR will provide a spectacular capability over a very broad spectral range. The Space Station will provide an essential facility for the initial assembly and check out of LDR, as well as a necessary base for refurbishment, repair and modification. By providing a manned platform, the Space Station will remove the time constraint on assembly associated with use of the Shuttle alone. Personnel safety during necessary EVA is enhanced by the presence of the manned facility.

  11. Accelerated plate tectonics.

    Science.gov (United States)

    Anderson, D L

    1975-03-21

    The concept of a stressed elastic lithospheric plate riding on a viscous asthenosphere is used to calculate the recurrence interval of great earthquakes at convergent plate boundaries, the separation of decoupling and lithospheric earthquakes, and the migration pattern of large earthquakes along an arc. It is proposed that plate motions accelerate after great decoupling earthquakes and that most of the observed plate motions occur during short periods of time, separated by periods of relative quiescence.

  12. System overview on electromagnetic compensation for reflector antenna surface distortion

    Science.gov (United States)

    Acosta, R. J.; Zaman, A. J.; Terry, J. D.

    1993-01-01

    The system requirements and hardware implementation for electromagnetic compensation of antenna performance degradations due to thermal effects was investigated. Future commercial space communication antenna systems will utilize the 20/30 GHz frequency spectrum and support very narrow multiple beams (0.3 deg) over wide angle field of view (15-20 beamwidth). On the ground, portable and inexpensive very small aperture terminals (VSAT) for transmitting and receiving video, facsimile and data will be employed. These types of communication system puts a very stringent requirement on spacecraft antenna beam pointing stability (less than .01 deg), high gain (greater than 50 dB) and very lowside lobes (less than -25 dB). Thermal analysis performed on the advanced communication technology satellite (ACTS) has shown that the reflector surfaces, the mechanical supporting structures and metallic surfaces on the spacecraft body will distort due thermal effects from a varying solar flux. The antenna performance characteristics (e.g., pointing stability, gain, side lobe, etc.) will degrade due to thermal distortion in the reflector surface and supporting structures. Specifically, antenna RF radiation analysis has shown that pointing error is the most sensitive antenna performance parameter to thermal distortions. Other antenna parameters like peak gain, cross polarization level (beam isolation), and side lobe level will also degrade with thermal distortions. In order to restore pointing stability and in general antenna performance several compensation methods were proposed. In general these compensation methods can be classified as being either of mechanical or electromagnetic type. This paper will address only the later one. In this approach an adaptive phased array antenna feed is used to compensate for the antenna performance degradation. Extensive work has been devoted to demonstrate the feasibility of adaptive feed compensation on space communication antenna systems. This

  13. Create Your Plate

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    Full Text Available ... Reset Plate Share Create Your Plate ! Share: Seven Simple Steps to Create Your Plate It's simple and effective for both managing diabetes and losing ... en.html Have Type 2 Diabetes? Our free program will help you live well. More from diabetes. ...

  14. Obliquity along plate boundaries

    Science.gov (United States)

    Philippon, Mélody; Corti, Giacomo

    2016-12-01

    Most of the plate boundaries are activated obliquely with respect to the direction of far field stresses, as roughly only 8% of the plate boundaries total length shows a very low obliquity (ranging from 0 to 10°, sub-orthogonal to the plate displacement). The obliquity along plate boundaries is controlled by (i) lateral rheological variations within the lithosphere and (ii) consistency with the global plate circuit. Indeed, plate tectonics and magmatism drive rheological changes within the lithosphere and consequently influence strain localization. Geodynamical evolution controls large-scale mantle convection and plate formation, consumption, and re-organization, thus triggering plate kinematics variations, and the adjustment and re-orientation of far field stresses. These geological processes may thus result in plate boundaries that are not perpendicular but oblique to the direction of far field stresses. This paper reviews the global patterns of obliquity along plate boundaries. Using GPlate, we provide a statistical analysis of present-day obliquity along plate boundaries. Within this framework, by comparing natural examples and geological models, we discuss deformation patterns and kinematics recorded along oblique plate boundaries.

  15. Comparison of electrohydraulic lithotripters with rigid and pressure-release ellipsoidal reflectors. II. Cavitation fields.

    Science.gov (United States)

    Bailey, M R; Blackstock, D T; Cleveland, R O; Crum, L A

    1999-08-01

    Dramatically different cavitation was produced by two separate acoustic pulses that had different shapes but similar duration, frequency content, and peak positive and negative pressure. Both pulses were produced by a Dornier HM-3 style lithotripter: one pulse when the ellipsoidal reflector was rigid, the other when the reflector was pressure release. The cavitation, or bubble action, generated by the conventional rigid-reflector pulse was nearly 50 times longer lived and 3-13 times stronger than that produced by the pressure-release-reflector pulse. Cavitation durations measured by passive acoustic detection and high-speed video agreed with calculations based on the Gilmore equation. Cavitation intensity, or destructive potential, was judged (1) experimentally by the size of pits in aluminum foil detectors and (2) numerically by the calculated amplitude of the shock wave emitted by a collapsing bubble. The results indicate that the trailing positive spike in the pressure-release-reflector waveform stifles bubble growth and mitigates the collapse, whereas the trough after the positive spike in the rigid-reflector waveform triggers inertially driven growth and collapse. The two reflectors therefore provide a tool to compare effects in weakly and strongly cavitating fields and thereby help assess cavitation's role in lithotripsy.

  16. The Effect of Reflector with Sound-Absorbing Material on Supersonic Jet Noise

    Institute of Scientific and Technical Information of China (English)

    Y.-H. KWEON; M. TSUCHIDA; Y. MIYAZATO; T. AOKI; H.-D. KIM; T. SETOGUCHI

    2005-01-01

    This paper describes an experimental work to investigate the effect of a reflector on supersonic jet noise radiated from a convergent-divergent nozzle with a design Mach number 2.0. In the present study, a metal reflector and reflectors made of three different sound-absorbing materials (grass wool and polyurethane foam) were employed,and the reflector size was varied. Acoustic measurement is carried out to obtain the acoustic characteristics such as frequency, amplitude of screech tone and overall sound pressure level (OASPL). A high-quality schlieren optical system is used to visualize the detailed structure of supersonic jet. The results obtained show that the acoustic characteristics of supersonic jet noise are strongly dependent upon the jet pressure ratio and the reflector size. It is also found that the reflector with sound-absorbing material reduces the screech tone amplitude by about 5-13dB and the overall sound pressure levels by about 2-5dB, compared with those of the metal reflector.

  17. Optimization design of an adaptive CFRC reflector for high order wave-front error control

    Science.gov (United States)

    Lan, Lan; Fang, Houfei; Wu, Ke; Jiang, Shuidong; Zhou, Yang

    2017-04-01

    The trend in future space high precision reflectors is going towards large aperture, lightweight and actively controlled deformable antennas. An adaptive shape control system for a Carbon Fiber Reinforced Composite (CFRC) reflector is conducted by Piezoelectric Ceramic Transducer (PZT) actuators. This adaptive shape control system has been shown to effectively mitigate common low order wave-front error, but it is inevitably plagued by high order wave-front error control. In order to improve the controllability of the adaptive CFRC reflector control system for high order wave-front error, the design of adaptive CFRC reflector requires optimizing further. According to numerical and experimental results, the print-through error induced by manufacturing and PZT actuators actuation is a type of predominant high order wave-front error. This paper describes a design which some secondary rib elements are embedded within the triangular cells of the primary ribs. These small secondary ribs are designed to support the reflector surface's weak region. Controllability of this new adaptive CFRC reflector control system with small secondary ribs is evaluated by generalized Zernike functions. This new design scheme can reduce high order residual error and suppress the high order wave-front error such as print-through error. Finally, design parameters of the adaptive CFRC reflector control system with small secondary ribs, such as primary rib height, secondary rib height, cut-out height of primary rib, are optimized.

  18. Angular shear plate

    Science.gov (United States)

    Ruda, Mitchell C [Tucson, AZ; Greynolds, Alan W [Tucson, AZ; Stuhlinger, Tilman W [Tucson, AZ

    2009-07-14

    One or more disc-shaped angular shear plates each include a region thereon having a thickness that varies with a nonlinear function. For the case of two such shear plates, they are positioned in a facing relationship and rotated relative to each other. Light passing through the variable thickness regions in the angular plates is refracted. By properly timing the relative rotation of the plates and by the use of an appropriate polynomial function for the thickness of the shear plate, light passing therethrough can be focused at variable positions.

  19. Asymptotic modelling of a thermopiezoelastic anisotropic smart plate

    Science.gov (United States)

    Long, Yufei

    Motivated by the requirement of modelling for space flexible reflectors as well as other applications of plate structures in engineering, a general anisotropic laminated thin plate model and a monoclinic Reissner-Mindlin plate model with thermal deformation, two-way coupled piezoelectric effect and pyroelectric effect is constructed using the variational asymptotic method, without any ad hoc assumptions. Total potential energy contains strain energy, electric potential energy and energy caused by temperature change. Three-dimensional strain field is built based on the concept of warping function and decomposition of the rotation tensor. The feature of small thickness and large in-plane dimension of plate structure helped to asymptotically simplify the three-dimensional analysis to a two-dimensional analysis on the reference surface and a one-dimensional analysis through the thickness. For the zeroth-order approximation, the asymptotically correct expression of energy is derived into the form of energetic equation in classical laminated plate theory, which will be enough to predict the behavior of plate structures as thin as a space flexible reflector. A through-the-thickness strain field can be expressed in terms of material constants and two-dimensional membrane and bending strains, while the transverse normal and shear stresses are not predictable yet. In the first-order approximation, the warping functions are further disturbed into a high order and an asymptotically correct energy expression with derivatives of the two-dimensional strains is acquired. For the convenience of practical use, the expression is transformed into a Reissner-Mindlin form with optimization implemented to minimize the error. Transverse stresses and strains are recovered using the in-plane strain variables. Several numerical examples of different laminations and shapes are studied with the help of analytical solutions or shell elements in finite element codes. The constitutive relation is

  20. Heat Transfer in Conical Corner and Short Superelliptical Transition Ducts

    Science.gov (United States)

    Poinsatte, Philip; Thurman, Douglas; Hippensteele, Steven

    2008-01-01

    Local surface heat transfer measurements were experimentally mapped using a transient liquid-crystal heat-transfer technique on the surface of two circular-to-rectangular transition ducts. One has a transition cross section defined by conical corners (Duct 1) and the other by an elliptical equation with changing coefficients (Duct 2). Duct 1 has a length-to-diameter ratio of 0.75 and an exit plane aspect ratio of 1.5. Duct 2 has a length-to-diameter ratio of 1.0 and an exit plane aspect ratio of 2.9. Test results are reported for various inlet-diameter-based Reynolds numbers ranging from 0.45 106 to 2.39 106 and two freestream turbulence intensities of about 1 percent, which is typical of wind tunnels, and up to 16 percent, which may be more typical of real engine conditions.

  1. Cornering Gapless Quantum States via Their Torus Entanglement

    Science.gov (United States)

    Witczak-Krempa, William; Hayward Sierens, Lauren E.; Melko, Roger G.

    2017-02-01

    The entanglement entropy (EE) has emerged as an important window into the structure of complex quantum states of matter. We analyze the universal part of the EE for gapless systems on tori in 2D and 3D, denoted by χ . Focusing on scale-invariant systems, we derive general nonperturbative properties for the shape dependence of χ and reveal surprising relations to the EE associated with corners in the entangling surface. We obtain closed-form expressions for χ in 2D and 3D within a model that arises in the study of conformal field theories (CFTs), and we use them to obtain Ansätze without fitting parameters for the 2D and 3D free boson CFTs. Our numerical lattice calculations show that the Ansätze are highly accurate. Finally, we discuss how the torus EE can act as a fingerprint of exotic states such as gapless quantum spin liquids, e.g., Kitaev's honeycomb model.

  2. Optically lightweight tracking of objects around a corner

    CERN Document Server

    Klein, Jonathan; Martín, Jaime; Laurenzis, Martin; Hullin, Matthias B

    2016-01-01

    The observation of objects located in inaccessible regions is a recurring challenge in a wide variety of important applications. Recent work has shown that indirect diffuse light reflections can be used to reconstruct objects and two-dimensional (2D) patterns around a corner. However, these prior methods always require some specialized setup involving either ultrafast detectors or narrowband light sources. Here we show that occluded objects can be tracked in real time using a standard 2D camera and a laser pointer. Unlike previous methods based on the backprojection approach, we formulate the problem in an analysis-by-synthesis sense. By repeatedly simulating light transport through the scene, we determine the set of object parameters that most closely fits the measured intensity distribution. We experimentally demonstrate that this approach is capable of following the translation of unknown objects, and translation and orientation of a known object, in real time.

  3. Optimization and improvement of FOA corner cube algorithm

    Science.gov (United States)

    McClay, Wilbert A., III; Awwal, Abdul A. S.; Burkhart, Scott C.; Candy, James V.

    2004-11-01

    Alignment of laser beams based on video images is a crucial task necessary to automate operation of the 192 beams at the National Ignition Facility (NIF). The final optics assembly (FOA) is the optical element that aligns the beam into the target chamber. This work presents an algorithm for determining the position of a corner cube alignment image in the final optics assembly. The improved algorithm was compared to the existing FOA algorithm on 900 noise-simulated images. While the existing FOA algorithm based on correlation with a synthetic template has a radial standard deviation of 1 pixel, the new algorithm based on classical matched filtering (CMF) and polynomial fit to the correlation peak improves the radial standard deviation performance to less than 0.3 pixels. In the new algorithm the templates are designed from real data stored during a year of actual operation.

  4. Three-corner wrist fusion using memory staples.

    Science.gov (United States)

    van Riet, Roger P; Bain, Gregory I

    2006-12-01

    Scapholunate dissociation with advanced collapse (SLAC), scaphoid nonunion advanced collapse (SNAC), and lunotriquetral advanced collapse (LTAC) of the carpus are challenging problems. Various treatment options have been described. We describe a technique of 3-corner wrist fusion, using memory staples. The scaphoid and triquetrum are resected, and the capitate is fused to the lunate. Articular cartilage is removed from the capitolunate joint, and the bones are shaped to conforming surfaces. Bone graft from the resected triquetrum and scaphoid is used to increase fusion rate and a dynamic compressive fixation force is applied due to the unique properties of the memory staples. The main advantages of this procedure include the following: retained anatomical articulation between the lunate and the lunate fossa on the radius, improved ulnar deviation due to the resection of the triquetrum, and an excellent fusion rate between the lunate and capitate due to the dynamic fixation, the conforming surfaces, and the use of autologous bone graft.

  5. Boundary and Corner Terms in the Action for General Relativity

    CERN Document Server

    Jubb, Ian; Sorkin, Rafael; Surya, Sumati

    2016-01-01

    We revisit the action principle for general relativity motivated by the path integral approach to quantum gravity. We consider a spacetime region whose boundary has piecewise $C^2$ components, each of which can be spacelike, timelike or null and consider metric variations in which only the pullback of the metric to the boundary is held fixed. Allowing all such metric variations we present a unified treatment of the spacelike, timelike and null boundary components using Cartan's tetrad formalism. Apart from its computational simplicity, this formalism gives us a simple way of identifying corner terms. We also discuss "creases" which occur when the boundary is the event horizon of a black hole. Our treatment is geometric and intrinsic and we present our results both in the computationally simpler tetrad formalism as well as the more familiar metric formalism. We recover known results from a simpler and more general point of view and find some new ones.

  6. Simulation of Interfacial Corner Cracks in Bimaterial Systems

    DEFF Research Database (Denmark)

    Veluri, Badrinath; Jensen, Henrik Myhre

    2012-01-01

    . The crack propagation is investigated by estimating the fracture mechanics parameters that include the strain energy release rate, crack front profiles and the three-dimensional mode-mixity along the crack front. A numerical approach is then applied for coupling the far field solutions utilizing......, a custom quantitative approach was formulated based on the finite element method with iterative adjustment of the crack front to estimate the critical delamination stress as a function of the fracture criterion and corner angles. The implication of the results on the delamination is discussed in terms...... of crack front profiles and the critical stresses, which can then be used as the framework for modeling reliability of advanced interconnects system....

  7. Posterolateral Corner of the Knee:Current Concepts

    Directory of Open Access Journals (Sweden)

    Jorge Chahla

    2016-04-01

    Full Text Available Injuries to the posterolateral corner (PLC comprise a significant portion of knee ligament injuries. A high index of suspicion is necessary when evaluating the injured knee to detect these sometimes occult injuries. Moreover, a thorough physical examination and a comprehensive review of radiographic studies are necessary to identify these injuries. In this sense, stress radiographs can help to objectively determine the extent of these lesions. Non-operative and operative treatment options have been reported depending on the extent of the injury. Complete PLC lesions rarely heal with non-operative treatment, and are therefore most often treated surgically. The purpose of this article was to review the anatomy and clinically relevant biomechanics, diagnosis algorithms, treatment and rehabilitation protocols for PLC injuries.

  8. Boundary and corner terms in the action for general relativity

    Science.gov (United States)

    Jubb, Ian; Samuel, Joseph; Sorkin, Rafael D.; Surya, Sumati

    2017-03-01

    We revisit the action principle for general relativity, motivated by the path integral approach to quantum gravity. We consider a spacetime region whose boundary has piecewise C 2 components, each of which can be spacelike, timelike or null and consider metric variations in which only the pullback of the metric to the boundary is held fixed. Allowing all such metric variations we present a unified treatment of the spacelike, timelike and null boundary components using Cartan’s tetrad formalism. Apart from its computational simplicity, this formalism gives us a simple way of identifying corner terms. We also discuss ‘creases’ which occur when the boundary is the event horizon of a black hole. Our treatment is geometric and intrinsic and we present our results both in the computationally simpler tetrad formalism as well as the more familiar metric formalism. We recover known results from a simpler and more general point of view and find some new ones.

  9. Optimization and Improvement of FOA Corner Cube Algorithm

    Energy Technology Data Exchange (ETDEWEB)

    McClay, W A; Awwal, A S; Burkhart, S C; Candy, J V

    2004-10-01

    Alignment of laser beams based on video images is a crucial task necessary to automate operation of the 192 beams at the National Ignition Facility (NIF). The final optics assembly (FOA) is the optical element that aligns the beam into the target chamber. This work presents an algorithm for determining the position of a corner cube alignment image in the final optics assembly. The improved algorithm was compared to the existing FOA algorithm on 900 noise-simulated images. While the existing FOA algorithm based on correlation with a synthetic template has a radial standard deviation of 1 pixel, the new algorithm based on classical matched filtering (CMF) and polynomial fit to the correlation peak improves the radial standard deviation performance to less than 0.3 pixels. In the new algorithm the templates are designed from real data stored during a year of actual operation.

  10. Energy flow in plate assembles by hierarchical version of finite element method

    DEFF Research Database (Denmark)

    Wachulec, Marcin; Kirkegaard, Poul Henning

    method has been proposed. In this paper a modified hierarchical version of finite element method is used for modelling of energy flow in plate assembles. The formulation includes description of in-plane forces so that planes lying in different planes can be modelled. Two examples considered are: L......The dynamic analysis of structures in medium and high frequencies are usually focused on frequency and spatial averages of energy of components, and not the displacement/velocity fields. This is especially true for structure-borne noise modelling. For the analysis of complicated structures......-corner of two rectangular plates an a I-shaped plate girder made of five plates. Energy distribution among plates due to harmonic load is studied and the comparison of performance between the hierarchical and standard finite element formulation is presented....

  11. Methodical Specifics of Thermal Experiments with Thin Carbon Reinforced Plates

    Directory of Open Access Journals (Sweden)

    O. V. Denisov

    2015-01-01

    Full Text Available Polymer composite materials (CM are widely used in creation of large space constructions, especially reflectors of space antennas. Composite materials should provide high level of specific stiffness and strength for space structures. Thermal conductivity in reinforcement plane is a significant factor in case of irregular heating space antennas. Nowadays, data on CM reinforcement plane thermal conductivity are limited and existing methods of its defining are imperfect. Basically, traditional methods allow us to define thermal conductivity in perpendicular direction towards the reinforcement plane on the samples of round or rectangular plate. In addition, the thickness of standard samples is larger than space antenna thickness. Consequently, new methods are required. Method of contact heating, which was developed by BMSTU specialists with long hollow carbon beam, could be a perspective way. This article is devoted to the experimental method of contact heating on the thin carbon plates.Thermal tests were supposed to provide a non-stationary temperature field with a gradient being co-directional with the plane reinforcement in the material sample. Experiments were conducted in vacuum chamber to prevent unstructured convection. Experimental thermo-grams processing were calculated by 1-d thermal model for a thin plate. Influence of uncertainty of experimental parameters, such as (radiation emission coefficients of sample surface, glue, temperature sensors and uncertainty of sensors placement on the result of defined thermal conductivity has been estimated. New data on the thermal conductivity in reinforcement plane were obtained within 295 - 375 K temperature range, which can be used to design and develop reflectors of precision space antennas. In the future it is expedient to conduct tests of thin-wall plates from carbon fiber-reinforced plastic in wide temperature range, especially in the low-range temperatures.

  12. High-resolution seismic attenuation structures beneath Hokkaido corner, northeastern Japan

    Science.gov (United States)

    Kita, S.; Nakajima, J.; Okada, T.; Hasegawa, A.; Katsumata, K.; Asano, Y.; Uchida, N.

    2013-12-01

    1. Introduction In the Hokkaido corner, the Kuril fore-arc sliver collides with the northeastern Japan arc. Using data from the nationwide Kiban seismic network and a temporary seismic network, Kita et al. [2012] determined high-resolution 3D seismic velocity structure beneath this area for deeper understanding of the collision process of two fore-arcs. The results show that a broad low-V zone (crust material) anomalously descends into the mantle wedge at depths of 30-90 km in the west of the Hidaka main thrust. On the other hand, several high-velocity zones having velocities of mantle materials are distributed in the crust at depths of 10-35 km. These high-velocity zones are inclined eastward, being nearly parallel to each other. Two of the western boundaries of these high-V zones correspond to the fault planes of the 1970 Mj 6.7 Hidaka and the 1982 Mj 7.1 Urakawa-oki earthquakes, respectively. In this study, we merged waveform data from the Kiban-network and from a dense temporary seismic network [Katsumata et al., 2002], and estimated the seismic attenuation structure to compare with the seismic velocity images of Kita et al. [2012]. 2. Data and method We estimated corner frequency for each earthquake by the spectral ratio method using the coda waves [e.g. Mayeda et al., 2007]. Then, we simultaneously determined values of t* and the amplitude level at lower frequencies from the observed spectra after correcting for the source spectrum. Seismic attenuation (Q-1 value) structure was obtained, inverting t* values with the tomographic code of Zhao et al. [1992]. We adopted the geometry of the Pacific plate which was precisely estimated by Kita et al. [2010b]. The study region covers an area of 41-45N, 140.5-146E, and a depth range of 0-200 km. We obtained 131,958 t* from 6,186 events (M>2.5) that occurred during the period from Aug. 1999 to Dec. 2012. The number of stations used is 353. Horizontal and vertical grid nodes were set with spacing of 0.10-0.3 degree and

  13. Electrically switchable polymer stabilised broadband infrared reflectors and their potential as smart windows for energy saving in buildings

    Science.gov (United States)

    Khandelwal, Hitesh; Loonen, Roel C. G. M.; Hensen, Jan L. M.; Debije, Michael G.; Schenning, Albertus P. H. J.

    2015-07-01

    Electrically switchable broadband infrared reflectors that are relatively transparent in the visible region have been fabricated using polymer stabilised cholesteric liquid crystals. The IR reflectors can change their reflection/transmission properties by applying a voltage in response to changes in environmental conditions. Simulations predict that a significant amount of energy can be saved on heating, cooling and lighting of buildings in places such as Madrid by using this switchable IR reflector. We have also fabricated a switchable IR reflector which can also generate electricity. These polymer based switchable IR reflectors are of high potential as windows of automobiles and buildings to control interior temperatures and save energy.

  14. The Science, Engineering and Technology Career Library Corner. Final report, February 1, 1995--January 31, 1996

    Energy Technology Data Exchange (ETDEWEB)

    Cole, P.R.

    1996-03-01

    A grant was made to install and pilot-test the Science, Engineering and Technology (SET) Career Library Corner at the New York Hall of Science. The SET Career Library Corner is located in a multi-media library setting where visitors can explore careers in a quiet, uninterrupted environment, in contrast to the original installation designed as a museum floor exhibit.

  15. Method for protecting chip corners in wet chemical etching of wafers

    Science.gov (United States)

    Hui, Wing C.

    1994-01-01

    The present invention is a corner protection mask design that protects chip corners from undercutting during anisotropic etching of wafers. The corner protection masks abut the chip corner point and extend laterally from segments along one or both corner sides of the corner point, forming lateral extensions. The protection mask then extends from the lateral extensions, parallel to the direction of the corner side of the chip and parallel to scribe lines, thus conserving wafer space. Unmasked bomb regions strategically formed in the protection mask facilitate the break-up of the protection mask during etching. Corner protection masks are useful for chip patterns with deep grooves and either large or small chip mask areas. Auxiliary protection masks form nested concentric frames that etch from the center outward are useful for small chip mask patterns. The protection masks also form self-aligning chip mask areas. The present invention is advantageous for etching wafers with thin film windows, microfine and micromechanical structures, and for forming chip structures more elaborate than presently possible.

  16. Optimization of a dielectric radome for a dual-reflector omnidirectional antenna

    DEFF Research Database (Denmark)

    Kim, Oleksiy S.

    2001-01-01

    In the millimetre-wave range, cylindrical dielectric insertions are employed to support a subreflector and, at the same time, as a radome of a dual-reflector omnidirectional antenna. Such a dielectric discontinuity can substantially degrade both matching and radiation characteristics of the antenna....... Until recently, the problem of optimization of a dielectric radome was solved experimentally due to a lack of methods that allow the VSWR of a dual-reflector omnidirectional antenna to be calculated taking into account the dielectric insertions. This paper presents a numerical approach to select...... the parameters of a dielectric radome for a dual-reflector omnidirectional antenna....

  17. A Study of the Fitting Accuracy of the Active Reflector for a Large Spherical Radio Telescope

    Institute of Scientific and Technical Information of China (English)

    Xiao-Qiang Tang; Jin-Song Wang; Qi-Ming Wang

    2003-01-01

    We propose a spatial three-degree-of-freedom (DOF) parallel mechanism combining two degrees of rotations and one degree of translation to support the active reflector units of a large spherical radio telescope. The kinematics, workspace and accuracy of the mechanism are analyzed. One-dimensional and two-dimensional fitting errors to the working region of active reflector are investigated. Dimensional parameters of the mechanism and active reflector unit are examined with respect to the requirement of fitting accuracy. The result of accuracy analysis shows the effectiveness and feasibility of the proposed mechanism, and gives a design rule to guarantee the highest working frequency required by large radio telescope.

  18. Diffraction-resistant scalar beams generated by a parabolic reflector and a source of spherical waves.

    Science.gov (United States)

    Zamboni-Rached, Michel; de Assis, Mariana Carolina; Ambrosio, Leonardo A

    2015-07-01

    In this work, we propose the generation of diffraction-resistant beams by using a parabolic reflector and a source of spherical waves positioned at a point slightly displaced from its focus (away from the reflector). In our analysis, considering the reflector dimensions much greater than the wavelength, we describe the main characteristics of the resulting beams, showing their properties of resistance to the diffraction effects. Due to its simplicity, this method may be an interesting alternative for the generation of long-range diffraction-resistant waves.

  19. Diffraction Resistant Scalar Beams Generated by a Parabolic Reflector and a Source of Spherical Waves

    CERN Document Server

    Zamboni-Rached, Michel; Ambrosio, Leonardo A

    2015-01-01

    In this work, we propose the generation of diffraction resistant beams by using a parabolic reflector and a source of spherical waves positioned at a point slightly displaced from its focus (away from the reflector). In our analysis, considering the reflector dimensions much greater than the wavelength, we describe the main characteristics of the resulting beams, showing their properties of resistance to the diffraction effects. Due to its simplicity, this method may be an interesting alternative for the generation of long range diffraction resistant waves.

  20. Observations on the linear programming formulation of the single reflector design problem.

    Science.gov (United States)

    Canavesi, Cristina; Cassarly, William J; Rolland, Jannick P

    2012-02-13

    We implemented the linear programming approach proposed by Oliker and by Wang to solve the single reflector problem for a point source and a far-field target. The algorithm was shown to produce solutions that aim the input rays at the intersections between neighboring reflectors. This feature makes it possible to obtain the same reflector with a low number of rays - of the order of the number of targets - as with a high number of rays, greatly reducing the computation complexity of the problem.

  1. Numerical Simulation of Capillary Flow in Fan-Shaped Asymmetric Interior Corner Under Microgravity

    Science.gov (United States)

    Yong-Qiang, Li; Wen-Hui, Cao; Ling, Liu

    2017-02-01

    Based on fluid mechanics theories, this research focuses on numerical simulation and analysis of capillary flow under microgravity in fan-shaped asymmetric interior corner. We analyze the effect the contact angle has on rising height in a fan-shaped asymmetric interior corner, and get the Concus-Finn condition the calculation of capillary flow needs to satisfy in fan-shaped asymmetric interior corner. Then we study the effect that different parameters of experimental medium and container configuration has on capillary flow in fan-shaped asymmetric interior corner when Concus-Finn condition is fulfilled. The conclusions of this paper has an important role in guiding the analytic solution of flow in a fan-shaped asymmetric interior corner under microgravity. We can also chose the appropriate experimental medium and design a container based on this paper.

  2. Corner forming of AZ61A magnesium alloy tube within warm hydroforming

    Institute of Scientific and Technical Information of China (English)

    HU Lan; HAN Cong; HE Zhu-bin; TANG Ze-jun; LIU Gang; YUAN Shi-jian

    2009-01-01

    The corners with small radii on cross sections are crucial for forming hydroformed components with polygonal sections. In this paper, warm hydroforming experiments of AZ61 A magnesium alloy tubes were carried out to study the forming regularity of round corners by using a demonstration part with square sections.Effects of temperature on radius forming, thinning ratio distribution and microstructure were revealed and a component with relative outer corner radius of 3.0 was obtained by warm hydroforming at 240℃. The minimum thickness of the formed square section was located in the transition position between the corner and the straight wall. The thinning ratio of the round corner increased with the increase of forming temperature. Formability of the magnesium tube was improved by raising temperature under the effect of dynamic recrystallization at 240℃.

  3. Evolution of supersonic corner vortex in a hypersonic inlet/isolator model

    Science.gov (United States)

    Huang, He-Xia; Tan, Hui-Jun; Sun, Shu; Ling, Yu

    2016-12-01

    There are complex corner vortex flows in a rectangular hypersonic inlet/isolator. The corner vortex propagates downstream and interacts with the shocks and expansion waves in the isolator repeatedly. The supersonic corner vortex in a generic hypersonic inlet/isolator model is theoretically and numerically analyzed at a freestream Mach number of 4.92. The cross-flow topology of the corner vortex flow is found to obey Zhang's theory ["Analytical analysis of subsonic and supersonic vortex formation," Acta Aerodyn. Sin. 13, 259-264 (1995)] strictly, except for the short process with the vortex core situated in a subsonic flow which is surrounded by a supersonic flow. In general, the evolution history of the corner vortex under the influence of the background waves in the hypersonic inlet/isolator model can be classified into two types, namely, from the adverse pressure gradient region to the favorable pressure gradient region and the reversed one. For type 1, the corner vortex is a one-celled vortex with the cross-sectional streamlines spiraling inwards at first. Then the Hopf bifurcation occurs and the streamlines in the outer part of the limit cycle switch to spiraling outwards, yielding a two-celled vortex. The limit cycle shrinks gradually and finally vanishes with the streamlines of the entire corner vortex spiraling outwards. For type 2, the cross-sectional streamlines of the corner vortex spiral outwards first. Then a stable limit cycle is formed, yielding a two-celled vortex. The short-lived limit cycle forces the streamlines in the corner vortex to change the spiraling trends rapidly. Although it is found in this paper that there are some defects on the theoretical proof of the limit cycle, Zhang's theory is proven useful for the prediction and qualitative analysis of the complex corner vortex in a hypersonic inlet/isolator. In addition, three conservation laws inside the limit cycle are obtained.

  4. Mapping sub-crustal reflectors in southwestern Spain

    Science.gov (United States)

    Palomeras, I.; Ayarza, P.; Carbonell, R.; Ehsan, S. A.; Afonso, J. C.; Diaz Cusi, J.

    2015-12-01

    During the last 15 years, the IBERSEIS and ALCUDIA controlled source experiments have acquired vertical incidence and wide angle seismic reflection data in southwest Spain, in the Variscan Sub-Portuguese, Ossa-Morena and Central-Iberian Zones. Apart from providing detailed information of the crust, these datasets have also imaged a conspicuous sub-crustal reflector. First identified on the IBERSEIS wide-angle reflection dataset, this interface seemed to feature a positive seismic impedance contrast. A boundary located between 61-72 km depth, with a Vp increase from 8.2 km/s to 8.3 km/s allowed us to model clear wide-angle reflections found above 180 km offsets. The fact that this reflector was not identified in the coincident vertical incidence dataset led us to interpret it as a gradient zone. A correlation with the 'Hales gradient zone', i.e. the boundary between spinel and garnet peridotites was our preferred interpretation. The ALCUDIA experiment, later acquired northwards of the IBERSEIS profiles, also shows prominent sub-crustal arrivals with the same characteristics as those observed in the IBERSEIS wide-angle data. However, these reflections also appear, locally and at 19 s TWT, in the vertical incidence dataset, further constraining the depth at which this feature is located. In addition, the ALCUDIA wide-angle dataset shows deeper sub-horizontal reflectivity (at Vred=8 km/s) that maybe preliminarily associated with mantle anisotropy or even, with the lithosphere-astenosphere boundary. Integration of the information provided by the IBERSEIS and ALCUDIA datasets with older and lower resolution data from the ILIHA project, where three sub-crustal phases were identified in SW Iberia, allows us to conclude that, in this area, mantle reflectivity is outstanding. Also, modeling of all the datasets contributes to map, at a regional scale, the Hales discontinuity or gradient zone in southwest Iberia. Further research, involving receiver function analysis is

  5. Sonographic assessment of predictors of depth of the corner pocket for ultrasound-guided supraclavicular brachial plexus block

    Directory of Open Access Journals (Sweden)

    Naveen Yadav

    2016-01-01

    Conclusion: Prescanning of supraclavicular region for estimating depth of corner pocket should be done before choosing an appropriate size needle. Furthermore, the needle should not be advanced more than the predicted corner pocket depth.

  6. Local-Global Interactions in the Transient Response of Lattice-Truss Plates.

    Science.gov (United States)

    1984-08-01

    plate model subjected to an initial out-of-plane impulse at the lower left corner. The color scale at the right of each frame represents variations of...Fiur 4. RepneapeLoain (Core ~ ~ ~ \\ and uppe sufc ebr emvdfrcaiy 23 TETRA 11 - Tranwlezt nleporave fLvtorvy 0.003 - Mrst Uccde Ix3ltial Impulse ...vidual lattice members dynamic characteristics influence the transient response charac- teristics. When the lattice members are modeled as bars. the

  7. A New Method of Designing Circularly Symmetric Shaped Dual Reflector Antennas Using Distorted Conics

    Directory of Open Access Journals (Sweden)

    Mohammad Asif Zaman

    2014-01-01

    Full Text Available A new method of designing circularly symmetric shaped dual reflector antennas using distorted conics is presented. The surface of the shaped subreflector is expressed using a new set of equations employing differential geometry. The proposed equations require only a small number of parameters to accurately describe practical shaped subreflector surfaces. A geometrical optics (GO based method is used to synthesize the shaped main reflector surface corresponding to the shaped subreflector. Using the proposed method, a shaped Cassegrain dual reflector system is designed. The field scattered from the subreflector is calculated using uniform geometrical theory of diffraction (UTD. Finally, a numerical example is provided showing how a shaped subreflector produces more uniform illumination over the main reflector aperture compared to an unshaped subreflector.

  8. Mercapto-based coupling agent for improved thermophotovoltaic device back surface reflector adhesion and reflectance

    Energy Technology Data Exchange (ETDEWEB)

    Wernsman, Bernard; Fiedor, Joseph N.; Irr, Lawrence G.; Palmisiano, Marc N.

    2016-10-04

    A back surface reflector (BSR) is described. The BSR includes a reflecting layer, a substrate and an adhesion layer between the reflecting layer and the substrate. The adhesion layer includes 3-mercaptopropyl (trimethoxy) silane (a.k.a. Merc).

  9. Realization of LOS (Line of Sight) stabilization based on reflector using carrier attitude compensation method

    Science.gov (United States)

    Mao, Yao; Tian, Jing; Ma, Jia-guang

    2015-02-01

    The techonology of LOS stabilization is widely applicated in moving carrier photoelectric systems such as shipborne, airborne and so on. In application situations with compact structure, such as LOS stabilization system of unmanned aerial vehicle, LOS stabilization based on reflector is adopted, and the detector is installed on the carrier to reduce the volume of stabilized platform and loading weight. However, the LOS deflection angle through reflector and the rotation angle of the reflector has a ratio relation of 2:1, simple reflector of stable inertial space can not make the optical axis stable. To eliminate the limitation of mirror stabilizing method, this article puts forward the carrier attitude compensation method, which uses the inertial sensor installed on the carrier to measure the attitude change of the carrier, and the stabilized platform rotating half of the carrier turbulence angle to realize the LOS stabilization.

  10. Ultra wideband reflector antenna log-periodic feed with operating frequency range 1–20 GHz.

    Directory of Open Access Journals (Sweden)

    F. F. Dubrovka

    2010-05-01

    Full Text Available Results of modeling and optimization of electric characteristics of ultra wideband reflector antenna log-periodic feed, based on two log-periodic antennas array for operating over frequency range 1 -20 GHz, are presented.

  11. Affordable Unfurlable Fan-Fold Wrapable Reflector for Small and Large Apertures Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Deployable Space Systems (DSS) will focus the proposed SBIR program on the development and concept feasibility of an innovative deployable mesh/membrane reflector...

  12. Monolithic distributed Bragg reflector cavities in Al2O3 with quality factors exceeding one million

    NARCIS (Netherlands)

    Bernhardi, Edward; van Wolferen, Hendricus A.G.M.; Worhoff, Kerstin; de Ridder, R.M.; Pollnau, Markus

    Monolithic distributed Bragg reflector (DBR) cavities with quality factors exceeding one million have been realized in aluminum oxide channel waveguides. This technology enabled the successful demonstration of the first DBR laser in this waveguide platform.

  13. High-quality distributed Bragg reflectors for resonant-cavity light-emitting diode applications

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez, S.; Naranjo, F.B.; Calle, F.; Sanchez-Garcia, M.A.; Calleja, E. [ISOM, ETSI Telecomunicacion, Universidad Politecnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid (Spain); Departamento de Ingenieria Electronica, ETSI Telecomunicacion, Universidad Politecnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid (Spain); Vennegues, P. [CHREA-CNRS, Rue Bernard Gregory, Sophia Antipolis, 06560 Valbonne (France)

    2002-08-16

    Efficient distributed Bragg reflectors based on Al{sub x}Ga{sub 1} {sub -} {sub x}N/GaN multilayer stacks have been grown by plasma-assisted molecular-beam epitaxy on GaN/Al{sub 2}O{sub 3} templates. The final goal is to incorporate these reflectors as bottom mirrors in a backside (sapphire) resonant-cavity light-emitting diode at 510 nm. The reflectors have been characterised by atomic force microscopy, high-resolution X-ray diffraction and high-resolution transmission electron microscopy. Reflectivity measurements have also been performed, obtaining values between 30% and 50%, depending on the Al content used. The incorporation of the Al{sub x}Ga{sub 1} {sub -} {sub x}N/GaN Bragg reflector as bottom mirror in a RCLED structure improves the output power by a factor of 12 compared with conventional light-emitting diodes. (Abstract Copyright[2002], Wiley Periodicals, Inc.)

  14. Multi-beaming propertieis of reflector antennas used in radio telescopes with wide field of view

    CERN Document Server

    Iupikov, O

    2016-01-01

    The given work is devoted to the modern developments in the field of radio astronomy instrumentation. In particular, the sensitivity of the multi-beam reflector radio telescope which is fed by phased array (PAF) is considered. Using PAF as reflector feed allows obtaining wide and continuous field of view (FOV) of the telescope. This has several advantages with compare to horn-cluster feeds which are described in this work. The sensitivity inside whole FOV was computed using three different beamforming schemes.

  15. Bichromatic tuning of reflection bands in integrated CLC reflectors for optical switches, gates, and logic

    Science.gov (United States)

    Wu, Shing-Trong; Fuh, Andy Ying-Guey; Ho, Shau-Jung; Li, Ming-Shian

    2015-03-01

    This study investigates the bichromatic tuning of cholesteric liquid crystal (CLC) reflection bands from reflectors containing chiral azo dopants. Because the chiral azo molecules change their helical twist power in reversible photoisomerization, the reflection bands of the CLCs are modulated using purple and green laser beams. The CLC reflectors are integrated into an optical gate that can be used to modulate output spectra. We also apply the integrated system in optical switching and logic.

  16. The optical reflector system for the CANGAROO-II imaging atmospheric Cherenkov telescope

    CERN Document Server

    Kawachi, A; Jimbo, J; Kamei, S; Kifune, T; Kubo, H; Kushida, J; Le Bohec, S; Miyawaki, K; Mori, M; Nishijima, K; Patterson, J R; Suzuki, R; Tanimori, T; Yanagita, S; Yoshikoshi, T; Yuki, A

    2001-01-01

    A new imaging atmospheric Cherenkov telescope (CANGAROO-II) with a light-weight reflector has been constructed. Light, robust, and durable mirror facets of containing CFRP (Carbon Fiber Reinforced Plastic) laminates were developed for the telescope. The attitude of each facet can be adjusted by stepping motors. In this paper, we describe the design, manufacturing, alignment procedure, and the performance of the CANGAROO-II optical reflector system.

  17. Analysis of a generalized dual reflector antenna system using physical optics

    Science.gov (United States)

    Acosta, Roberto J.; Lagin, Alan R.

    1992-01-01

    Reflector antennas are widely used in communication satellite systems because they provide high gain at low cost. Offset-fed single paraboloids and dual reflector offset Cassegrain and Gregorian antennas with multiple focal region feeds provide a simple, blockage-free means of forming multiple, shaped, and isolated beams with low sidelobes. Such antennas are applicable to communications satellite frequency reuse systems and earth stations requiring access to several satellites. While the single offset paraboloid has been the most extensively used configuration for the satellite multiple-beam antenna, the trend toward large apertures requiring minimum scanned beam degradation over the field of view 18 degrees for full earth coverage from geostationary orbit may lead to impractically long focal length and large feed arrays. Dual reflector antennas offer packaging advantages and more degrees of design freedom to improve beam scanning and cross-polarization properties. The Cassegrain and Gregorian antennas are the most commonly used dual reflector antennas. A computer program for calculating the secondary pattern and directivity of a generalized dual reflector antenna system was developed and implemented at LeRC. The theoretical foundation for this program is based on the use of physical optics methodology for describing the induced currents on the sub-reflector and main reflector. The resulting induced currents on the main reflector are integrated to obtain the antenna far-zone electric fields. The computer program is verified with other physical optics programs and with measured antenna patterns. The comparison shows good agreement in far-field sidelobe reproduction and directivity.

  18. Tilting A Small Reflector For Vernier Pointing Of A Large Antenna

    Science.gov (United States)

    Veruttipong, Watt; Bathker, Dan A.

    1995-01-01

    Simple vernier pointing technique devised to facilitate scanning beam pointing of large paraboloidal reflector so line of sight of antenna sweeps out narrow cone about fixed axis (conical scan, also known as "conscan" in art). Scan effected by one of relatively small beam-waveguide reflectors or mirrors that couple signals between antenna and distant transmitting and/or receiving electronic circuits. Easier to tilt small mirror than to tilt massive antenna structure.

  19. Generalized Fibonacci zone plates

    CERN Document Server

    Ke, Jie; Zhu, Jianqiang

    2015-01-01

    We propose a family of zone plates which are produced by the generalized Fibonacci sequences and their axial focusing properties are analyzed in detail. Compared with traditional Fresnel zone plates, the generalized Fibonacci zone plates present two axial foci with equal intensity. Besides, we propose an approach to adjust the axial locations of the two foci by means of different optical path difference, and further give the deterministic ratio of the two focal distances which attributes to their own generalized Fibonacci sequences. The generalized Fibonacci zone plates may allow for new applications in micro and nanophotonics.

  20. Experimental Validation of Plasma Metasurfaces as Tunable THz Reflectors

    Science.gov (United States)

    Colon Quinones, Roberto; Underwood, Thomas; Cappelli, Mark

    2016-10-01

    Measurements are presented which validate the use of plasma metasurfaces (PMs) as potential tunable THz reflectors. The PM considered here is an n x n array of laser produced plasma kernels generated by focusing the fundamental output from a 2 J/p Q-switched Nd:YAG laser through a multi-lens array (MLA) and into a gas of varying pressure. An M Squared Firefly-THz laser is used to generate a collimated pulse of THz light, which is then directed to the PM at varying angles of incidence. The reflected energy is measured using a Gentec-EO SDX-1187 joulemeter probe to characterize the surface impedance or reflectivity. In this presentation, we will compare the measured reflectance to values obtained from theoretical predictions and 3D finite-difference time-domain (FDTD) simulations. Work supported by the Air Force Office of Scientific Research (AFOSR). R. Colon Quinones and T. Underwood acknowledge the support of the Department of Defense (DoD) through the National Defense Science & Engineering Graduate Fellowship (NDSEG) Program.

  1. HI Survey Science with the Canadian Large Adaptive Reflector

    CERN Document Server

    Côté, S; Dewdney, P E

    2002-01-01

    The Canadian Large Adaptive Reflector (CLAR) is a proposed prototype of a new concept for large, filled-aperture radio telescopes. The prototype would have a 300-metre aperture, working up to frequencies of at least 1.4 GHz, and would be equipped with a multi-beam phased array providing a field-of-view of 0.8deg at that frequency. The largest fully-steerable radio telescope in the world, and endowed with a large field-of-view, the CLAR will be uniquely suited for deep spectral imaging over large areas of the sky. Conducted over a period of three to four years, a CLAR Northern-Sky Survey would allow us to simultaneously: survey at arcminute scales the distribution and kinematics of the faint HI in the halo of the Milky Way and High Velocity Clouds; chart the large scale distribution of galaxies in HI out to redshift close to 1; reveal the structure and dynamics of the cosmic web responsible for wide-spread Lyman $\\alpha$ absorption systems; image the signal of the reionization of the Universe over a large area...

  2. Widely Tunable Distributed Bragg Reflectors Integrated into Nanowire Waveguides.

    Science.gov (United States)

    Fu, Anthony; Gao, Hanwei; Petrov, Petar; Yang, Peidong

    2015-10-14

    Periodic structures with dimensions on the order of the wavelength of light can tailor and improve the performance of optical components, and they can enable the creation of devices with new functionalities. For example, distributed Bragg reflectors (DBRs), which are created by periodic modulations in a structure's dielectric medium, are essential in dielectric mirrors, vertical cavity surface emitting lasers, fiber Bragg gratings, and single-frequency laser diodes. This work introduces nanoscale DBRs integrated directly into gallium nitride (GaN) nanowire waveguides. Photonic band gaps that are tunable across the visible spectrum are demonstrated by precisely controlling the grating's parameters. Numerical simulations indicate that in-wire DBRs have significantly larger reflection coefficients in comparison with the nanowire's end facet. By comparing the measured spectra with the simulated spectra, the index of refraction of the GaN nanowire waveguides was extracted to facilitate the design of photonic coupling structures that are sensitive to phase-matching conditions. This work indicates the potential to design nanowire-based devices with improved performance for optical resonators and optical routing.

  3. Microtrap on a concave grating reflector for atom trapping

    Science.gov (United States)

    Zhang, Hui; Li, Tao; Yin, Ya-Ling; Li, Xing-Jia; Xia, Yong; Yin, Jian-Ping

    2016-08-01

    We propose a novel scheme of optical confinement for atoms by using a concave grating reflector. The two-dimension grating structure with a concave surface shape exhibits strong focusing ability under radially polarized illumination. Especially, the light intensity at the focal point is about 100 times higher than that of the incident light. Such a focusing optical field reflected from the curved grating structure can provide a deep potential to trap cold atoms. We discuss the feasibility of the structure serving as an optical dipole trap. Our results are as follows. (i) Van der Waals attraction potential to the surface of the structure has a low effect on trapped atoms. (ii) The maximum trapping potential is ˜ 1.14 mK in the optical trap, which is high enough to trap cold 87Rb atoms from a standard magneto-optical trap with a temperature of 120 μK, and the maximum photon scattering rate is lower than 1/s. (iii) Such a microtrap array can also manipulate and control cold molecules, or microscopic particles. Project supported by the National Natural Science Foundation of China (Grant Nos. 11374100, 91536218, and 11274114) and the Natural Science Foundation of Shanghai Municipality, China (Grant No. 13ZR1412800).

  4. Simulation of environment effects on retro-reflectors in ITER

    Energy Technology Data Exchange (ETDEWEB)

    Voitsenya, V.S.; Berezhnyj, V.L.; Konovalov, V.G.; Naidenkova, D.I.; Ryzhkov, V.I.; Solodovchenko, S.I. [NSC KIPT, Kharkov (Ukraine); Bardamid, A.F.; Vinnichenko, M.V. [Shevchenko National Univ., 03127 Kiev (Ukraine); Belyaeva, A.I. [National Technical Univ., Kharkov (Ukraine); Donne, A.J.H. [FOM-Institute for Plasma Physics Rijnhuizen (Netherlands); Gil, Ch.; Lipa, M.; Schunke, B. [Euratom-CEA, Centre d' Etudes de Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. de Recherches sur la Fusion Controlee; Malaquais, A. [International Atomic Energy Agency (IAEA), Vienna (Austria); Topkov, A.N. [National University, Kharkov (Ukraine)

    2004-07-01

    The use of retro-reflectors (RR) is considered for 2 plasma diagnostics in ITER: -) poloidal multichannel polarimetry that is supposed to operate on a single wavelength (118 {mu}m) and -) toroidal multichannel polarimetry that will use a dual frequency CO{sub 2} laser operating at 10.6 and 9.27 {mu}m. In order to shorten the time of simulation experiments, the long term sputtering effects on optical properties of RR were studied with Cu mirrors instead of Mo mirrors, results are reported in this series of slides. It was shown that the sputtering of the top 5 {mu}m layer from a poly-crystal Mo mirror would not result in a noticeable decrease of reflectance at 118 {mu}m. For the toroidal polarimetry system with much shorter wavelengths, a similar sputtering rate is absolutely inadmissible due to much longer path length of the probing beam. It was also shown that the micro-relief that will develop on the surface of RR due to long-term sputtering, can significantly change both the reflectance and the polarization angle of the reflecting beam. Polarization angle will also be changed if the surface of RR is coated with a carbon film.

  5. Dynamic single-mode semiconductor lasers with a distributed reflector

    Energy Technology Data Exchange (ETDEWEB)

    Suematsu, Y.; Arai, S.; Kishino, K.

    1983-03-01

    Recent progress in dynamic single-mode (DSM) semiconductor lasers in the wavelength of 1.5-1.6 microns are reviewed, and the basic principle of DSM operation is given. Study of the DSM laser is originated for application to wide-band optical-fiber communication in the lowest loss wavelength region of 1.5 to 1.65 microns. A DSM laser consists of a mode-selective resonator and a transverse-mode-controller waveguide, as in the narrow-striped distributed-Bragg-reflector (DBR) laser, so as to maintain a fixed axial mode under rapid direct modulation. The technology of monolithic integration for optical circuits is applied to realize some DSM lasers. Structures, static and dynamic characteristics of lasing wavelength, output power, and reliability of state-of-the-art DSM lasers are reviewed. Dynamic spectral width of 0.3 nm, output power of a few milliwatts, and reliability over a few thousand hours are reported for experimental DSM lasers. 120 references.

  6. Dynamic single-mode semiconductor lasers with a distributed reflector

    Science.gov (United States)

    Suematsu, Y.; Arai, S.; Kishino, K.

    1983-03-01

    Recent progress in dynamic single-mode (DSM) semiconductor lasers in the wavelength of 1.5-1.6 microns are reviewed, and the basic principle of DSM operation is given. Study of the DSM laser is originated for application to wide-band optical-fiber communication in the lowest loss wavelength region of 1.5 to 1.65 microns. A DSM laser consists of a mode-selective resonator and a transverse-mode-controller waveguide, as in the narrow-striped distributed-Bragg-reflector (DBR) laser, so as to maintain a fixed axial mode under rapid direct modulation. The technology of monolithic integration for optical circuits is applied to realize some DSM lasers. Structures, static and dynamic characteristics of lasing wavelength, output power, and reliability of state-of-the-art DSM lasers are reviewed. Dynamic spectral width of 0.3 nm, output power of a few milliwatts, and reliability over a few thousand hours are reported for experimental DSM lasers.

  7. Colloidal plasmonic back reflectors for light trapping in solar cells

    Science.gov (United States)

    Mendes, Manuel J.; Morawiec, Seweryn; Simone, Francesca; Priolo, Francesco; Crupi, Isodiana

    2014-04-01

    A novel type of plasmonic light trapping structure is presented in this paper, composed of metal nanoparticles synthesized in colloidal solution and self-assembled in uniform long-range arrays using a wet-coating method. The high monodispersion in size and spherical shape of the gold colloids used in this work allows a precise match between their measured optical properties and electromagnetic simulations performed with Mie theory, and enables the full exploitation of their collective resonant plasmonic behavior for light-scattering applications. The colloidal arrays are integrated in plasmonic back reflector (PBR) structures aimed for light trapping in thin film solar cells. The PBRs exhibit high diffuse reflectance (up to 75%) in the red and near-infrared spectrum, which can pronouncedly enhance the near-bandgap photocurrent generated by the cells. Furthermore, the colloidal PBRs are fabricated by low-temperature (<120 °C) processes that allow their implementation, as a final step of the cell construction, in typical commercial thin film devices generally fabricated in a superstrate configuration.

  8. A new strain based brick element for plate bending

    Directory of Open Access Journals (Sweden)

    L. Belounar

    2014-03-01

    Full Text Available This paper presents the development of a new three-dimensional brick finite element by the use of the strain based approach for the linear analysis of plate bending. The developed element has the three essential external degrees of freedom (U, V and W at each of the eight corner nodes as well as at the centroidal node. The displacement field of the developed element is based on assumed functions for the various strains satisfying the compatibility equations and the static condensation technique is used for the internal node. The performance of this element is evaluated on several problems related to thick and thin plate bending in linear analysis. The obtained results show the good performances and accuracy of the present element.

  9. Structural-electromagnetic bidirectional coupling analysis of space large film reflector antennas

    Science.gov (United States)

    Zhang, Xinghua; Zhang, Shuxin; Cheng, ZhengAi; Duan, Baoyan; Yang, Chen; Li, Meng; Hou, Xinbin; Li, Xun

    2017-10-01

    As used for energy transmission, a space large film reflector antenna (SLFRA) is characterized by large size and enduring high power density. The structural flexibility and the microwave radiation pressure (MRP) will lead to the phenomenon of structural-electromagnetic bidirectional coupling (SEBC). In this paper, the SEBC model of SLFRA is presented, then the deformation induced by the MRP and the corresponding far field pattern deterioration are simulated. Results show that, the direction of the MRP is identical to the normal of the reflector surface, and the magnitude is proportional to the power density and the square of cosine incident angle. For a typical cosine function distributed electric field, the MRP is a square of cosine distributed across the diameter. The maximum deflections of SLFRA linearly increase with the increasing microwave power densities and the square of the reflector diameters, and vary inversely with the film thicknesses. When the reflector diameter becomes 100 m large and the microwave power density exceeds 102 W/cm2, the gain loss of the 6.3 μm-thick reflector goes beyond 0.75 dB. When the MRP-induced deflection degrades the reflector performance, the SEBC should be taken into account.

  10. Direct evidence for radar reflector originating from changes in crystal-orientation fabric

    Directory of Open Access Journals (Sweden)

    O. Eisen

    2007-06-01

    Full Text Available The origin of a strong continuous radar reflector observed with airborne radio-echo sounding (RES at the EPICA deep-drilling site in Dronning Maud Land, Antarctica, is identified as a transition in crystal fabric orientation from a vertical girdle- to increased single-pole orientation seen along the ice core. The reflector is observed with a 60 ns and 600 ns long pulse at a frequency of 150 MHz, spans one pulse length, is continuous over 5 km, and occurs at a depth of about 2020–2030 m at the drill site. Changes in conductivity as reflector origin are excluded by investigating the ice-core profile and synthetic RES data. Our observations allow to extrapolate the crystal orientation feature along the reflector in space, with implications for ice-sheet dynamics. As the conductivity profile of the EPICA shows no distinctive peak at this depths, we exclude changes in conductivity as the reflector origin. This is supported by application of numerical forward modelling of electromagnetic wave propagation, based on the conductivity profile, which is able to reproduce nearby reflections, but fails to reproduce this one. Because of background noise, the permittivity profile based on dielectric does not show prominent signals at these depths. We therefore interpret the observed reflector to originate from this change in crystal fabric.

  11. New adaptive method to optimize the secondary reflector of linear Fresnel collectors

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Guangdong

    2017-03-01

    Performance of linear Fresnel collectors may largely depend on the secondary-reflector profile design when small-aperture absorbers are used. Optimization of the secondary-reflector profile is an extremely challenging task because there is no established theory to ensure superior performance of derived profiles. In this work, an innovative optimization method is proposed to optimize the secondary-reflector profile of a generic linear Fresnel configuration. The method correctly and accurately captures impacts of both geometric and optical aspects of a linear Fresnel collector to secondary-reflector design. The proposed method is an adaptive approach that does not assume a secondary shape of any particular form, but rather, starts at a single edge point and adaptively constructs the next surface point to maximize the reflected power to be reflected to absorber(s). As a test case, the proposed optimization method is applied to an industrial linear Fresnel configuration, and the results show that the derived optimal secondary reflector is able to redirect more than 90% of the power to the absorber in a wide range of incidence angles. The proposed method can be naturally extended to other types of solar collectors as well, and it will be a valuable tool for solar-collector designs with a secondary reflector.

  12. Parametric Study of Cylindrical Dielectric Resonator Antenna (CDRA Feeder with Symmetric Parabolic Reflector

    Directory of Open Access Journals (Sweden)

    S.M. Ali

    2015-06-01

    Full Text Available In this study a parabolic reflector antenna is designed and fabricated for IEEE 802.11a WLAN application. Initially, a single element circular tuning slot coupled Cylindrical Dielectric Resonator Antenna (CDRA feeder is designed and fabricated for a symmetric parabolic reflector. Subsequently, the designed feeder is integrated at the focal point of the parabolic reflector to provide unidirectional radiation pattern with improved gain and sidelobe levels. The measured fractional impedance bandwidth achieved for the proposed antenna is 1.8% for S11<-10 dB from 5.32 to 5.52 GHz. A radiation pattern with broadside radiation and low back radiation has been obtained. A good measurement gain of approximately 13 dB is achieved over the bandwidth by placing CDRA feeder at the focal point of the parabolic reflector. In addition, a comprehensive parametric study has been conducted to realize the effect of slot size and position on the resonance frequency of the designed feeder. Furthermore, a parametric study of various reflector parameters has also been performed to study the effect of size, depth and focal point of the parabolic reflector on gain of the antenna. Important design factors have been identified from the parametric study of the antenna. The experimental and measured results show that the designed antenna is suitable for IEEE WLAN 802.11a wireless application.

  13. Scanning properties of large dual-shaped offset and symmetric reflector antennas

    Science.gov (United States)

    Galindo-Israel, Victor; Veruttipong, Watt; Norrod, Roger D.; Imbriale, William A.

    1992-01-01

    Several characteristics of dual offset (DOSR) and symmetric shaped reflectors are examined. Among these is the amelioration of the added cost of manufacturing a shaped reflector antenna, particularly a doubly curved surface for the DOSR, if adjustable panels, which may be necessary for correction of gravity and wind distortions, are also used for improving gain by shaping. The scanning properties of shaped reflectors, both offset and circularly symmetric, are examined and compared to conic section scanning characteristics. Scanning of the pencil beam is obtained by lateral and axial translation of a single point-source feed. The feed is kept pointed toward the center of the subreflector. The effects of power spillover and aperture phase error as a function of beam scanning is examined for several different types of large reflector designs including DOSR, circularly symmetric large f/D and smaller f/D dual reflector antenna systems. It is graphically illustrated that the Abbe-sine condition for improving scanning of an optical system cannot, inherently, be satisfied in a dual-shaped reflector system shaped for high gain and low feed spillover.

  14. Scanning spherical tri-reflector antenna with a moving flat mirror

    Science.gov (United States)

    Shen, Bing; Stutzman, Warren L.

    1995-03-01

    Spherical reflector systems can achieve pattern scanning without rotation of the main reflector through the use of multiple subreflectors that can move. Also, two subreflectors can be shaped to correct for spherical aberration and to control the aperture distribution on the spherical main reflector. In a previous paper we introduced a method that offers both aperture phase and intensity control and scans the main beam without an accompanying movement of the illuminated area over main reflector. The method can overcome the poor aperture utilization problem common in spherical reflector antenna systems; however, it requires motion of the entire subreflector system, including the feed, during scan. In this paper we discuss a method that does not require motion of the subreflector system during scan. This method employs a flat mirror that creates a virtual image of the subreflector system. The motion of the subreflector system in the previous design is replaced by the motion of the virtual image that is controlled by the motion of the flat mirror. The new design offers simplified mechanical motion, while maintaining beam efficiency performance comparable to that of traditional spherical tri-reflector scanning antennas, but with some sacrifice in aperture efficiency and cross-polarization performance.

  15. Porous silicon as an internal reflector in thin epitaxial solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Kuzma-Filipek, I.; Duerinckx, F.; Nieuwenhuysen, K. van; Beaucarne, G.; Poortmans, J.; Mertens, R. [IMEC vzw, Leuven (Belgium)

    2007-05-15

    Thin film epitaxial silicon solar cells are considered a near future alternative to bulk silicon solar cells. However due to the limited thickness of the active layer they require efficient light trapping. Therefore we propose the development and implementation of such light confinement by means of a porous silicon (PS) intermediate reflector at the epi/substrate interface. The formation of the reflector is done by electrochemical etching of a highly doped Si substrate into a multilayer stack (Bragg-optical reflector), and is followed by epitaxial deposition of the active layer. The implementation of the PS reflector however requires detailed analysis of many problematic issues, foremost the optical optimisation of the stack for internal reflection at the Si/PS/Si interface. Other topics include the pore rearrangement during high-temperature CVD as well as the quality of the epitaxial layer grown on porous silicon. Another challenge is the resistance within the PS layers. For that purpose, SRP (Spreading Resistance Probe) and resistance measurements were performed to determine the conductive properties of rearranged PS. First cells with a 9-layer porous silicon reflector gave a very promising efficiency of 13.5% which is 1.5% higher compared to cells without internal reflector. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Assessment of irradiation effects on beryllium reflector and heavy water tank of JRR-3M

    Energy Technology Data Exchange (ETDEWEB)

    Murayama, Yoji; Kakehuda, Kazuhiro [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1998-10-01

    The JRR-3M, a swimming pool type research reactor with beryllium and heavy water reflectors, has been operated since 1990. Since the beryllium reflectors are close to fuel and receive high fast neutron fluence in a relatively short time, they may be subject to change their dimensions by swelling due mostly to entrapped helium gaseous. This may bend the reflectors to the outside and narrow gaps between the reflectors and the fuel elements. The gaps have been measured with an ultrasonic thickness gage in an annual inspection. The results in 1996 show that the maximum of expansion in the diametral directions was 0.6 mm against 1.6 mm of a managed value for replacement of the reflector. A heavy water tank of the JRR-3M is made of aluminum alloy A5052. Surveillance tests of the alloy have been conducted to evaluate irradiation effects of the heavy water tank. Five sets of specimens of the alloy have been irradiated in the beryllium reflectors where fast neutron flux is higher than that in the heavy water tank. In 1994, one set of specimens had been unloaded and carried out the post-irradiation tests. The results show that the heavy water tank preserved satisfactory mechanical properties. (author)

  17. The Effect of Boundary Support and Reflector Dimensions on Inflatable Parabolic Antenna Performance

    Science.gov (United States)

    Coleman, Michael J.; Baginski, Frank; Romanofsky, Robert R.

    2011-01-01

    For parabolic antennas with sufficient surface accuracy, more power can be radiated with a larger aperture size. This paper explores the performance of antennas of various size and reflector depth. The particular focus is on a large inflatable elastic antenna reflector that is supported about its perimeter by a set of elastic tendons and is subjected to a constant hydrostatic pressure. The surface accuracy of the antenna is measured by an RMS calculation, while the reflector phase error component of the efficiency is determined by computing the power density at boresight. In the analysis, the calculation of antenna efficiency is not based on the Ruze Equation. Hence, no assumption regarding the distribution of the reflector surface distortions is presumed. The reflector surface is modeled as an isotropic elastic membrane using a linear stress-strain constitutive relation. Three types of antenna reflector construction are considered: one molded to an ideal parabolic form and two different flat panel design patterns. The flat panel surfaces are constructed by seaming together panels in a manner that the desired parabolic shape is approximately attained after pressurization. Numerical solutions of the model problem are calculated under a variety of conditions in order to estimate the accuracy and efficiency of these antenna systems. In the case of the flat panel constructions, several different cutting patterns are analyzed in order to determine an optimal cutting strategy.

  18. Vertical Corner Feature Based Precise Vehicle Localization Using 3D LIDAR in Urban Area.

    Science.gov (United States)

    Im, Jun-Hyuck; Im, Sung-Hyuck; Jee, Gyu-In

    2016-08-10

    Tall buildings are concentrated in urban areas. The outer walls of buildings are vertically erected to the ground and almost flat. Therefore, the vertical corners that meet the vertical planes are present everywhere in urban areas. These corners act as convenient landmarks, which can be extracted by using the light detection and ranging (LIDAR) sensor. A vertical corner feature based precise vehicle localization method is proposed in this paper and implemented using 3D LIDAR (Velodyne HDL-32E). The vehicle motion is predicted by accumulating the pose increment output from the iterative closest point (ICP) algorithm based on the geometric relations between the scan data of the 3D LIDAR. The vertical corner is extracted using the proposed corner extraction method. The vehicle position is then corrected by matching the prebuilt corner map with the extracted corner. The experiment was carried out in the Gangnam area of Seoul, South Korea. In the experimental results, the maximum horizontal position error is about 0.46 m and the 2D Root Mean Square (RMS) horizontal error is about 0.138 m.

  19. Hydrodynamic analysis of flagellated bacteria swimming in corners of rectangular channels

    Science.gov (United States)

    Shum, Henry; Gaffney, Eamonn A.

    2015-12-01

    The influence of nearby solid surfaces on the motility of bacteria is of fundamental importance as these interactions govern the ability of the microorganisms to explore their environment and form sessile colonies. Reducing biofouling in medical implants and controlling the transport of bacterial cells in a microfluidic device are two applications that could benefit from a detailed understanding of swimming in microchannels. In this study, we investigate the self-propelled motion of a model bacterium, driven by rotating a single helical flagellum, in such an environment. In particular, we focus on the corner region of a large channel modeled as two perpendicular sections of no-slip planes joined with a rounded corner. We numerically solve the equations of Stokes flow using the boundary element method to obtain the swimming velocities at different positions and orientations relative to the channel corner. From these velocities, we construct many trajectories to ascertain the general behavior of the swimmers. Considering only hydrodynamic interactions between the bacterium and the channel walls, we show that some swimmers can become trapped near the corner while moving, on average, along the axis of the channel. This result suggests that such bacteria may be found at much higher densities in corners than in other parts of the channel. Another implication is that these corner accumulating bacteria may travel quickly through channels since they are guided directly along the corner and do not turn back or swim transversely across the channel.

  20. Vertical Corner Feature Based Precise Vehicle Localization Using 3D LIDAR in Urban Area

    Directory of Open Access Journals (Sweden)

    Jun-Hyuck Im

    2016-08-01

    Full Text Available Tall buildings are concentrated in urban areas. The outer walls of buildings are vertically erected to the ground and almost flat. Therefore, the vertical corners that meet the vertical planes are present everywhere in urban areas. These corners act as convenient landmarks, which can be extracted by using the light detection and ranging (LIDAR sensor. A vertical corner feature based precise vehicle localization method is proposed in this paper and implemented using 3D LIDAR (Velodyne HDL-32E. The vehicle motion is predicted by accumulating the pose increment output from the iterative closest point (ICP algorithm based on the geometric relations between the scan data of the 3D LIDAR. The vertical corner is extracted using the proposed corner extraction method. The vehicle position is then corrected by matching the prebuilt corner map with the extracted corner. The experiment was carried out in the Gangnam area of Seoul, South Korea. In the experimental results, the maximum horizontal position error is about 0.46 m and the 2D Root Mean Square (RMS horizontal error is about 0.138 m.