WorldWideScience

Sample records for apertures

  1. Apertures

    CERN Document Server

    Hansen, R C

    2014-01-01

    Microwave Scanning Antennas, Volume I: Apertures is a comprehensive account of phased arrays, multiple beam arrays, time domain and synthetic apertures, and adaptive antennas. Advances in continuous apertures and near field theory are discussed. Low noise and monopulse apertures, optical scanners, and large radomes are also covered, along with radio astronomy instruments and associated theory.Comprised of five chapters, this volume begins with an overview of aperture theory as well as aperture distributions and near field theory. The second and third chapters deal with mechanically steered and

  2. Aperture area measurement facility

    Data.gov (United States)

    Federal Laboratory Consortium — NIST has established an absolute aperture area measurement facility for circular and near-circular apertures use in radiometric instruments. The facility consists of...

  3. Quantum synthetic aperture radar

    Science.gov (United States)

    Lanzagorta, Marco; Jitrik, Oliverio; Uhlmann, Jeffrey; Venegas-Andraca, Salvador E.

    2017-05-01

    Synthetic aperture radar (SAR) uses sensor motion to generate finer spatial resolution of a given target area. In this paper we explore the theoretical potential of quantum synthetic aperture quantum radar (QSAR). We provide theoretical analysis and simulation results which suggest that QSAR can provide improved detection performance over classical SAR in the high-noise low-brightness regime.

  4. Mastering Apple Aperture

    CERN Document Server

    Fitzgerald, Thomas

    2013-01-01

    Written in a conversational style, the author will share his knowledge on advanced Aperture topics with detailed discussions of advanced topics, the theory behind some of those topics and lots of hints and tips for ways to improve your workflow.Photographer's who have a basic understanding of Aperture

  5. Detailed IR aperture measurements

    CERN Document Server

    Bruce, Roderik; Garcia Morales, Hector; Giovannozzi, Massimo; Hermes, Pascal Dominik; Mirarchi, Daniele; Quaranta, Elena; Redaelli, Stefano; Rossi, Carlo; Skowronski, Piotr Krzysztof; Wretborn, Sven Joel; CERN. Geneva. ATS Department

    2016-01-01

    MD 1673 was carried out on October 5 2016, in order to investigate in more detail the available aperture in the LHC high-luminosity insertions at 6.5 TeV and β∗=40 cm. Previous aperture measurements in 2016 during commissioning had shown that the available aperture is at the edge of protection, and that the aperture bottleneck at β∗=40 cm in certain cases is found in the separation plane instead of in the crossing plane. Furthermore, the bottlenecks were consistently found in close to the upstream end of Q3 on the side of the incoming beam, and not in Q2 on the outgoing beam as expected from calculations. Therefore, this MD aimed at measuring IR1 and IR5 separately (at 6.5 TeV and β∗=40 cm, for 185 µrad half crossing angle), to further localize the bottlenecks longitudinally using newly installed BLMs, investigate the difference in aperture between Q2 and Q3, and to see if any aperture can be gained using special orbit bumps.

  6. Synthetic Aperture Sequential Beamforming

    DEFF Research Database (Denmark)

    Kortbek, Jacob; Jensen, Jørgen Arendt; Gammelmark, Kim Løkke

    2008-01-01

    A synthetic aperture focusing (SAF) technique denoted Synthetic Aperture Sequential Beamforming (SASB) suitable for 2D and 3D imaging is presented. The technique differ from prior art of SAF in the sense that SAF is performed on pre-beamformed data contrary to channel data. The objective...... is stored. The second stage applies the focused image lines from the first stage as input data. The SASB method has been investigated using simulations in Field II and by off-line processing of data acquired with a commercial scanner. The performance of SASB with a static image object is compared with DRF...

  7. Optical synthetic aperture radar

    Science.gov (United States)

    Ilovitsh, Asaf; Zach, Shlomo; Zalevsky, Zeev

    2013-06-01

    A method is proposed for increasing the resolution of an object and overcoming the diffraction limit of an optical system installed on top of a moving imaging system, such as an airborne platform or satellite. The resolution improvement is obtained via a two-step process. First, three low resolution differently defocused images are captured and the optical phase is retrieved using an improved iterative Gershberg-Saxton based algorithm. The phase retrieval allows numerical back propagation of the field to the aperture plane. Second, the imaging system is shifted and the first step is repeated. The obtained optical fields at the aperture plane are combined and a synthetically increased lens aperture is generated along the direction of movement, yielding higher imaging resolution. The method resembles a well-known approach from the microwave regime called the synthetic aperture radar in which the antenna size is synthetically increased along the platform propagation direction. The proposed method is demonstrated via Matlab simulation as well as through laboratory experiment.

  8. Survey of coded aperture imaging

    International Nuclear Information System (INIS)

    Barrett, H.H.

    1975-01-01

    The basic principle and limitations of coded aperture imaging for x-ray and gamma cameras are discussed. Current trends include (1) use of time varying apertures, (2) use of ''dilute'' apertures with transmission much less than 50%, and (3) attempts to derive transverse tomographic sections, unblurred by other planes, from coded images

  9. Congenital pyriform aperture stenosis

    International Nuclear Information System (INIS)

    Osovsky, Micky; Aizer-Danon, Anat; Horev, Gadi; Sirota, Lea

    2007-01-01

    Nasal airway obstruction is a potentially life-threatening condition in the newborn. Neonates are obligatory nasal breathers. The pyriform aperture is the narrowest, most anterior bony portion of the nasal airway, and a decrease in its cross-sectional area will significantly increase nasal airway resistance. Congenital nasal pyriform aperture stenosis (CNPAS) is a rare, unusual form of nasal obstruction. It should be considered in the differential diagnosis of any neonate or infant with signs and symptoms of upper airway compromise. It is important to differentiate this level of obstruction from the more common posterior choanal stenosis or atresia. CNPAS presents with symptoms of nasal airway obstruction, which are often characterized by episodic apnea and cyclical cyanosis. (orig.)

  10. Aperture center energy showcase

    Energy Technology Data Exchange (ETDEWEB)

    Torres, J. J.

    2012-03-01

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

  11. Black silicon integrated aperture

    Science.gov (United States)

    Liu, Tianbo; Dickensheets, David L.

    2017-10-01

    This paper describes the incorporation of nanotextured black silicon as an optical absorbing material into silicon-based micro-optoelectromechanical systems devices to reduce stray light and increase optical contrast during imaging. Black silicon is created through a maskless dry etch process and characterized for two different etch conditions, a cold etch performed at 0°C and a cryogenic etch performed at -110°C. We measure specular reflection at visible wavelengths to be black velvet paint used to coat optical baffles and compare favorably with other methods to produce black surfaces from nanotextured silicon or using carbon nanotubes. We illustrate the use of this material by integrating a black silicon aperture around the perimeter of a deformable focus-control mirror. Imaging results show a significant improvement in contrast and image fidelity due to the effective reduction in stray light achieved with the self-aligned black aperture.

  12. Congenital pyriform aperture stenosis

    Energy Technology Data Exchange (ETDEWEB)

    Osovsky, Micky [Schneider Pediatric Hospital, Department of Neonatology, Petach Tikvah (Israel); Rabin Medical Center, Department of Neonatology, Schneider Children' s Medical Center of Israel, Beilinson Campus, Petah Tikvah (Israel); Aizer-Danon, Anat; Horev, Gadi [Schneider Pediatric Hospital, Department of Pediatric Radiology, Petach Tikvah (Israel); Sirota, Lea [Schneider Pediatric Hospital, Department of Neonatology, Petach Tikvah (Israel)

    2007-01-15

    Nasal airway obstruction is a potentially life-threatening condition in the newborn. Neonates are obligatory nasal breathers. The pyriform aperture is the narrowest, most anterior bony portion of the nasal airway, and a decrease in its cross-sectional area will significantly increase nasal airway resistance. Congenital nasal pyriform aperture stenosis (CNPAS) is a rare, unusual form of nasal obstruction. It should be considered in the differential diagnosis of any neonate or infant with signs and symptoms of upper airway compromise. It is important to differentiate this level of obstruction from the more common posterior choanal stenosis or atresia. CNPAS presents with symptoms of nasal airway obstruction, which are often characterized by episodic apnea and cyclical cyanosis. (orig.)

  13. Integrated electrochromic aperture diaphragm

    Science.gov (United States)

    Deutschmann, T.; Oesterschulze, E.

    2014-05-01

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

  14. Novel large aperture EBCCD

    Science.gov (United States)

    Suzuki, Atsumu; Aoki, Shigeki; Haba, Junji; Sakuda, Makoto; Suyama, Motohiro

    2011-02-01

    A novel large aperture electron bombardment charge coupled device (EBCCD) has been developed. The diameter of its photocathode is 10 cm and it is the first EBCCD with such a large aperture. Its gain shows good linearity as a function of applied voltage up to -12 kV, where the gain is 2400. The spatial resolution was measured using ladder pattern charts. It is better than 2 line pairs/mm, which corresponds to 3.5 times the CCD pixel size. The spatial resolution was also measured with a copper foil pattern on a fluorescent screen irradiated with X-rays (14 and 18 keV) and a 60 keV gamma-ray from an americium source. The result was consistent with the measurement using ladder pattern charts. The output signal as a function of input light intensity shows better linearity than that of image intensifier tubes (IIT) as expected. We could detect cosmic rays passing through a scintillating fiber block and a plastic scintillator as a demonstration for a practical use in particle physics experiments. This kind of large aperture EBCCD can, for example, be used as an image sensor for a detector with a large number of readout channels and is expected to be additionally applied to other physics experiments.

  15. Nanolithography using nanoscale ridge apertures

    Science.gov (United States)

    Wang, Liang

    There is a continuous effort to develop techniques for nanoscale feature definition below the diffraction limit. Nanolithography has been a key technique because of its precision and cost effective. A sub-wavelength hole in an opaque screen can be used to provide a small light source with the optical resolution beyond the diffraction limit in the near field. However, a nanometer-sized hole in circular or square shapes is plagued by low transmission and poor contrast. This drawback limits the nanoscale apertures from being employed in nanolithography applications. Ridge apertures in C, H and bowtie shapes, on the other hand, have been numerically and experimentally demonstrated to show the ability of achieving both enhanced light transmission and sub-wavelength optical resolution down to nanometer domain benefiting from the existence of waveguide propagation mode confined in the gap between the ridges. In this report, the detailed field distributions in contact nanolithography are analyzed using finite difference time domain (FDTD) simulations. It was found that the high imaging contrast, which is necessary for successful lithography, is achieved close to the mask exit plane and decays quickly with the increase of the distance from the mask exit plane. Simulations are also performed for comparable regular shaped apertures and different shape bowtie apertures. Design rules are proposed to optimize the bowtie aperture for producing a sub-wavelength, high transmission field with high imaging contrast. High resolution contact nanolithography was carried on a home constructed lithography setup. It has been experimentally demonstrated that nanoscale bowtie and C apertures can be used for contact lithography to achieve nanometer scale resolution due to its intrinsic advantages of achieving enhanced optical transmission and concentrating light far beyond the diffraction limit. It also has shown the advantages of bowtie and C apertures over conventional apertures in both

  16. Diagnostic for dynamic aperture

    Energy Technology Data Exchange (ETDEWEB)

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

    1985-04-01

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

  17. Synthetic Aperture Compound Imaging

    DEFF Research Database (Denmark)

    Hansen, Jens Munk

    Medical ultrasound imaging is used for many purposes, e.g. for localizing and classifying cysts, lesions, and other processes. Almost any mass is first observed using B-mode imaging and later classified using e.g. color flow, strain, or attenuation imaging. It is therefore important that the B......, it is demonstrated through theoretical considerations that the compound effect achieved is close to a theoretical maximum for the amount of compounding attainable and using a -pitch convex array transducer, the first in-vivo images are created. The computational demands for an implementation are massive...... and the limiting factor is the amount of memory IO resources available. An equally high demand for memory throughput is found in the computer gaming industry, where a large part of the processing takes place on the graphics processing unit (GPU). Using the GPU, a framework for synthetic aperture imaging...

  18. Transionospheric synthetic aperture imaging

    CERN Document Server

    Gilman, Mikhail; Tsynkov, Semyon

    2017-01-01

    This landmark monograph presents the most recent mathematical developments in the analysis of ionospheric distortions of SAR images and offers innovative new strategies for their mitigation. As a prerequisite to addressing these topics, the book also discusses the radar ambiguity theory as it applies to synthetic aperture imaging and the propagation of radio waves through the ionospheric plasma, including the anisotropic and turbulent cases. In addition, it covers a host of related subjects, such as the mathematical modeling of extended radar targets (as opposed to point-wise targets) and the scattering of radio waves off those targets, as well as the theoretical analysis of the start-stop approximation, which is used routinely in SAR signal processing but often without proper justification. The mathematics in this volume is clean and rigorous – no assumptions are hidden or ambiguously stated. The resulting work is truly interdisciplinary, providing both a comprehensive and thorough exposition of the field,...

  19. Coded aperture tomography revisited

    International Nuclear Information System (INIS)

    Bizais, Y.; Rowe, R.W.; Zubal, I.G.; Bennett, G.W.; Brill, A.B.

    1983-01-01

    Coded aperture (CA) Tomography never achieved wide spread use in Nuclear Medicine, except for the degenerate case of Seven Pinhole tomagraphy (7PHT). However it enjoys several attractive features (high sensitivity and tomographic ability with a statis detector). On the other hand, resolution is usually poor especially along the depth axis and the reconstructed volume is rather limited. Arguments are presented justifying the position that CA tomography can be useful for imaging time-varying 3D structures, if its major drawbacks (poor longitudinal resolution and difficulty in quantification) are overcome. Poor results obtained with 7PHT can be explained by both a very limited angular range sampled and a crude modelling of the image formation process. Therefore improvements can be expected by the use of a dual-detector system, along with a better understanding of its sampling properties and the use of more powerful reconstruction algorithms. Non overlapping multipinhole plates, because they do not involve a decoding procedure, should be considered first for practical applications. Use of real CA should be considered for cases in which non overlapping multipinhole plates do not lead to satisfactory solutions. We have been and currently are carrying out theoretical and experimental works, in order to define the factors which limit CA imaging and to propose satisfactory solutions for Dynamic Emission Tomography

  20. Bistatic synthetic aperture radar

    Science.gov (United States)

    Yates, Gillian

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

  1. Tissue Harmonic Synthetic Aperture Imaging

    DEFF Research Database (Denmark)

    Rasmussen, Joachim

    The main purpose of this PhD project is to develop an ultrasonic method for tissue harmonic synthetic aperture imaging. The motivation is to advance the field of synthetic aperture imaging in ultrasound, which has shown great potentials in the clinic. Suggestions for synthetic aperture tissue...... system complexity compared to conventional synthetic aperture techniques. In this project, SASB is sought combined with a pulse inversion technique for 2nd harmonic tissue harmonic imaging. The advantages in tissue harmonic imaging (THI) are expected to further improve the image quality of SASB....... The first part of the scientific contribution investigates an implementation of pulse inversion for THI on the experimental ultrasound system SARUS. The technique is initially implemented for linear array transducers and then expanded for convex array transducers. The technique is evaluated based on spatial...

  2. Compounding in synthetic aperture imaging

    DEFF Research Database (Denmark)

    Hansen, J. M.; Jensen, J. A.

    2012-01-01

    from multiple spherical emissions to synthesize multiple transmit and receive apertures, corresponding to imaging the tissue from multiple directions. The many images are added incoherently, to produce a single compound image. Using a 192-element, 3.5-MHz, λ-pitch transducer, it is demonstrated from...... tissue-phantom measurements that the speckle is reduced and the contrast resolution improved when applying synthetic aperture compound imaging. At a depth of 4 cm, the size of the synthesized apertures is optimized for lesion detection based on the speckle information density. This is a performance...... measure for tissue contrast resolution which quantifies the tradeoff between resolution loss and speckle reduction. The speckle information density is improved by 25% when comparing synthetic aperture compounding to a similar setup for compounding using dynamic receive focusing. The cystic resolution...

  3. Large aperture optical switching devices

    International Nuclear Information System (INIS)

    Goldhar, J.; Henesian, M.A.

    1983-01-01

    We have developed a new approach to constructing large aperture optical switches for next generation inertial confinement fusion lasers. A transparent plasma electrode formed in low pressure ionized gas acts as a conductive coating to allow the uniform charging of the optical faces of an electro-optic material. In this manner large electric fields can be applied longitudinally to large aperture, high aspect ratio Pockels cells. We propose a four-electrode geometry to create the necessary high conductivity plasma sheets, and have demonstrated fast (less than 10 nsec) switching in a 5x5 cm aperture KD*P Pockels cell with such a design. Detaid modelling of Pockels cell performance with plasma electrodes has been carried out for 15 and 30 cm aperture designs

  4. Future of synthetic aperture radar

    Science.gov (United States)

    Barath, F. T.

    1978-01-01

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

  5. Ultrasound fields from triangular apertures

    DEFF Research Database (Denmark)

    Jensen, Jørgen Arendt

    1996-01-01

    The pulsed field from a triangular aperture mounted in an infinite, rigidbaffle is calculated. The approach of spatial impulse responses,as developed by Tupholme and Stepanishen, is used. By this both the emitted and received pulsed ultrasound field can be found for any transducerexcitation...

  6. Imaging with Synthetic Aperture Radar

    CERN Document Server

    Massonnet, Didier

    2008-01-01

    Describing a field that has been transformed by the recent availability of data from a new generation of space and airborne systems, the authors offer a synthetic geometrical approach to the description of synthetic aperture radar, one that addresses physicists, radar specialists, as well as experts in image processing.  

  7. Aperture measurements with AC dipole

    CERN Document Server

    Fuster Martinez, Nuria; Dilly, Joschua Werner; Nevay, Laurence James; Bruce, Roderik; Tomas Garcia, Rogelio; Redaelli, Stefano; Persson, Tobias Hakan Bjorn; CERN. Geneva. ATS Department

    2018-01-01

    During the MDs performed on the 15th of September and 29th of November 2017, we measured the LHC global aperture at injection with a new AC dipole method as well as using the Transverse Damper (ADT) blow-up method used during the 2017 LHC commissioning for benchmarking. In this note, the MD procedure is presented as well as the analysis of the comparison between the two methods. The possible benefits of the new method are discussed.

  8. Slit aperture technique for mammography

    International Nuclear Information System (INIS)

    Friedrich, M.

    1984-01-01

    Following a discussion of various principles used in the elimination of scatter, the prototype of a simple slit aperture mammography apparatus is described (modified Mammomat, Siemens). The main advantage of this technique compared with grid mammography is a halving of the radiation dose for identical image quality, using an identical film system. The technical requirements (heavy duty tube, new generator) are, however, considerable. If the film-screen systems currently in use are to remain the common systems for the future, then the development of a multi-lamellar slit diaphragm technique carries much promise for mammography. (orig.) [de

  9. Synthetic Aperture Vector Flow Imaging

    DEFF Research Database (Denmark)

    Villagómez Hoyos, Carlos Armando

    The main objective of this project was to continue the development of a synthetic aperture vector flow estimator. This type of estimator is capable of overcoming two of the major limitations in conventional ultrasound systems: 1) the inability to scan large region of interest with high temporal......, this thesis showed that novel information can be obtained with vector velocity methods providing quantitative estimates of blood flow and insight into the complexity of the hemodynamics dynamics. This could give the clinician a new tool in assessment and treatment of a broad range of diseases....

  10. Synthetic Aperture Vector Flow Imaging

    DEFF Research Database (Denmark)

    Oddershede, Niels

    2008-01-01

    of the thesis considers a method for estimating the two-dimensional velocity vector within the image plane. This method, called synthetic aperture vector flow imaging, is first shortly reviewed. The main contribution of this work is partly an analysis of the method with respect to focusing effects, motion...... estimation. The method can be used for increasing the frame rate of color flow maps or alternatively for a new imaging modality entitled quadroplex imaging, featuring a color flow map and two independent spectrograms at a high frame rate. The second is an alternative method for ultrasonic vector velocity...

  11. Aperture averaging in strong oceanic turbulence

    Science.gov (United States)

    Gökçe, Muhsin Caner; Baykal, Yahya

    2018-04-01

    Receiver aperture averaging technique is employed in underwater wireless optical communication (UWOC) systems to mitigate the effects of oceanic turbulence, thus to improve the system performance. The irradiance flux variance is a measure of the intensity fluctuations on a lens of the receiver aperture. Using the modified Rytov theory which uses the small-scale and large-scale spatial filters, and our previously presented expression that shows the atmospheric structure constant in terms of oceanic turbulence parameters, we evaluate the irradiance flux variance and the aperture averaging factor of a spherical wave in strong oceanic turbulence. Irradiance flux variance variations are examined versus the oceanic turbulence parameters and the receiver aperture diameter are examined in strong oceanic turbulence. Also, the effect of the receiver aperture diameter on the aperture averaging factor is presented in strong oceanic turbulence.

  12. 5cm aperture dipole studies

    International Nuclear Information System (INIS)

    McInturff, A.D.; Bossert, R.; Carson, J.; Fisk, H.E.; Hanft, R.; Kuchnir, M.; Lundy, R.; Mantech, P.; Strait, J.

    1986-01-01

    The results obtained during the evolution of the design, construction, and testing program of the design ''B'' dipole are presented here. Design ''B'' is one of the original three competing designs for the Superconducting Super Collider ''SSC'' arc dipoles. The final design parameters were as follows: air cored (less than a few percent of the magnetic field derived from any iron present), aluminum collared, two layered winding, 5.5T maximum operating field, and a 5 cm cold aperture. There have been fourteen 64 cm long 5 cm aperture model dipoles cold tested (at 4.3K and less) in this program so far. There was a half length full size (6m) mechanical analog (M-10) built and tested to check the cryostat's mechanical design under ramping and quench conditions. Several deviations from the ''Tevatron'' dipole fabrication technique were incorporated, for example the use of aluminum collars instead of stainless steel. The winding technique variations explored were ''dry welding,'' a technique with the cable covered with Kapton insulation only and ''wet winding'' where the Kapton was covered with a light coat of ''B'' stage epoxy. Test data include quench currents, field quality (Fourier multipole co-efficients), coil magnetization, conductor current performance, and coil loading. Quench current, loss per cycle, and harmonics were measured as a function of the magnitude and rate of change of the magnetic field, and helium bath temperature

  13. Ion mobility spectrometer with virtual aperture grid

    Science.gov (United States)

    Pfeifer, Kent B.; Rumpf, Arthur N.

    2010-11-23

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

  14. Synthetic aperture interferometry: error analysis

    Energy Technology Data Exchange (ETDEWEB)

    Biswas, Amiya; Coupland, Jeremy

    2010-07-10

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

  15. Synthetic aperture interferometry: error analysis

    International Nuclear Information System (INIS)

    Biswas, Amiya; Coupland, Jeremy

    2010-01-01

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

  16. Synthetic aperture radar: principles and applications

    International Nuclear Information System (INIS)

    Khan, N.A.; Yahya, K.M.

    2003-01-01

    In this paper an introduction to synthetic aperture radar is presented. Synthetic aperture radar is a relatively new remote sensing platform and the technology has matured a lot in the last two decades. This paper introduces the concepts behind SAR principles as well as the major areas where this new technology has shown additional information. (author)

  17. Walking through Apertures in Individuals with Stroke.

    Directory of Open Access Journals (Sweden)

    Daisuke Muroi

    Full Text Available Walking through a narrow aperture requires unique postural configurations, i.e., body rotation in the yaw dimension. Stroke individuals may have difficulty performing the body rotations due to motor paralysis on one side of their body. The present study was therefore designed to investigate how successfully such individuals walk through apertures and how they perform body rotation behavior.Stroke fallers (n = 10, stroke non-fallers (n = 13, and healthy controls (n = 23 participated. In the main task, participants walked for 4 m and passed through apertures of various widths (0.9-1.3 times the participant's shoulder width. Accidental contact with the frame of an aperture and kinematic characteristics at the moment of aperture crossing were measured. Participants also performed a perceptual judgment task to measure the accuracy of their perceived aperture passability.Stroke fallers made frequent contacts on their paretic side; however, the contacts were not frequent when they penetrated apertures from their paretic side. Stroke fallers and non-fallers rotated their body with multiple steps, rather than a single step, to deal with their motor paralysis. Although the minimum passable width was greater for stroke fallers, the body rotation angle was comparable among groups. This suggests that frequent contact in stroke fallers was due to insufficient body rotation. The fact that there was no significant group difference in the perceived aperture passability suggested that contact occurred mainly due to locomotor factors rather than perceptual factors. Two possible explanations (availability of vision and/or attention were provided as to why accidental contact on the paretic side did not occur frequently when stroke fallers penetrated the apertures from their paretic side.

  18. Fast Parametric Beamformer for Synthetic Aperture Imaging

    DEFF Research Database (Denmark)

    Nikolov, Svetoslav; Jensen, Jørgen Arendt; Tomov, Borislav Gueorguiev

    2008-01-01

    This paper describes the design and implementation of a real-time delay-and-sum synthetic aperture beamformer. The beamforming delays and apodization coefficients are described parametrically. The image is viewed as a set of independent lines that are defined in 3-D by their origin, direction....... The implementation of the beamformer is optimized with respect to the architecture of a novel synthetic aperture real-time ultrasound scanner (SARUS), in which 4 channels are processed by the same set of field-programmable gate arrays (FPGA). In synthetic transmit aperture imaging, low-resolution images are formed...

  19. ULYSSES JUPITER HISCALE COMPOSITION APERTURE ION COUNTS

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set consists of HISCALE Composition Aperture (WARTD) ion counts. These measurements were taken during the Ulysses Jupiter encounter 1991-12-31 to...

  20. Beam Combination for Sparse Aperture Telescopes Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This proposal is for funding to continue development of an alternative beam combiner for Stellar Imager (SI), a 30-aperture, interferometric telescope chosen as one...

  1. Apodised aperture assembly for high power lasers

    International Nuclear Information System (INIS)

    Bliss, E.S.; Speck, D.R.

    1975-01-01

    An apodized aperture assembly using absorbing liquid or solid to vary transmission over the cross section thereof is used to minimize deleterious diffraction effects in high power lasers. By employing, for example, an absorbing liquid of varying optical density to obtain the transmission profile, a circular aperture of this type can be used to minimize diffraction effects, thereby substantially improving the performance of a high power laser system. (U.S.)

  2. Parametric Transverse Patterns in Broad Aperture Lasers

    DEFF Research Database (Denmark)

    Grigorieva, E.V.; Kashchenko, S.A.; Mosekilde, Erik

    1998-01-01

    Parametrically generated optical patterns are investigated for finite and large-scale transverse aperture lasers. Standing and rotating patterns as well as periodic and chaotic pattern alternations are described in the framework of the amplitude equation formalism. Sensitive dependence on the geo......Parametrically generated optical patterns are investigated for finite and large-scale transverse aperture lasers. Standing and rotating patterns as well as periodic and chaotic pattern alternations are described in the framework of the amplitude equation formalism. Sensitive dependence...

  3. Large-aperture subwavelength grating couplers.

    Science.gov (United States)

    Qi, Fan; Ma, Qingyan; Wang, Yufei; Zheng, Wanhua

    2016-04-10

    Subwavelength nanostructure grating couplers fabricated on silicon-on-insulator substrates are used to simplify the fabrication process while maintaining high coupling efficiency. The main obstacle for their application in photonic integrated circuits is the small aperture size of the nanostructure when TE polarization is involved, since they are difficult to achieve with 193 nm deep-ultraviolet lithography and cause problems in inductively coupled plasma etching. A larger lateral period has been used to increase the aperture size. Here, we propose that decreasing the effective index of the nanostructure can also enlarge the aperture size. We analyze the two methods in detail with a rectangle-hole nanostructure and 220 nm thick waveguide layer, aiming at TE polarization centered at 1560 nm. We find performance degenerations for large lateral periods, and this can be simply compensated by adjusting the width of the rectangle hole. The minimum linewidth of the nanostructure can reach 240 nm, while the coupling efficiency is just slightly decreased. The backreflections of a large-aperture grating increase but stay in the same order with ordinary ones, and we also show that this can be overcome by apodizing the grating structure. Finally, we experimentally demonstrate the designed large-aperture grating couplers and the coupling efficiencies are higher than 35%, and reach a rectangle-hole width.

  4. Synthetic aperture tissue and flow ultrasound imaging

    DEFF Research Database (Denmark)

    Nikolov, Svetoslav

    imaging applied to medical ultrasound. It is divided into two major parts: tissue and blood flow imaging. Tissue imaging using synthetic aperture algorithms has been investigated for about two decades, but has not been implemented in medical scanners yet. Among the other reasons, the conventional scanning...... and beamformation methods are adequate for the imaging modalities in clinical use - the B-mode imaging of tissue structures, and the color mapping of blood flow. The acquisition time, however, is too long, and these methods fail to perform real-time three-dimensional scans. The synthetic transmit aperture......, on the other hand, can create a Bmode image with as little as 2 emissions, thus significantly speeding-up the scan procedure. The first part of the dissertation describes the synthetic aperture tissue imaging. It starts with an overview of the efforts previously made by other research groups. A classification...

  5. Solar energy apparatus with apertured shield

    Science.gov (United States)

    Collings, Roger J. (Inventor); Bannon, David G. (Inventor)

    1989-01-01

    A protective apertured shield for use about an inlet to a solar apparatus which includesd a cavity receiver for absorbing concentrated solar energy. A rigid support truss assembly is fixed to the periphery of the inlet and projects radially inwardly therefrom to define a generally central aperture area through which solar radiation can pass into the cavity receiver. A non-structural, laminated blanket is spread over the rigid support truss in such a manner as to define an outer surface area and an inner surface area diverging radially outwardly from the central aperture area toward the periphery of the inlet. The outer surface area faces away from the inlet and the inner surface area faces toward the cavity receiver. The laminated blanket includes at least one layer of material, such as ceramic fiber fabric, having high infra-red emittance and low solar absorption properties, and another layer, such as metallic foil, of low infra-red emittance properties.

  6. Multi-antenna synthetic aperture radar

    CERN Document Server

    Wang, Wen-Qin

    2013-01-01

    Synthetic aperture radar (SAR) is a well-known remote sensing technique, but conventional single-antenna SAR is inherently limited by the minimum antenna area constraint. Although there are still technical issues to overcome, multi-antenna SAR offers many benefits, from improved system gain to increased degrees-of-freedom and system flexibility. Multi-Antenna Synthetic Aperture Radar explores the potential and challenges of using multi-antenna SAR in microwave remote sensing applications. These applications include high-resolution imaging, wide-swath remote sensing, ground moving target indica

  7. High frame rate synthetic aperture duplex imaging

    DEFF Research Database (Denmark)

    Stuart, Matthias Bo; Tomov, Borislav Gueorguiev; Pihl, Michael Johannes

    2013-01-01

    aperture flow imaging as demonstrated in this paper. Synthetic aperture, directional beamforming, and cross-correlation are used to produce B-mode and vector velocity images at high frame rates. The frame rate equals the effective pulse repetition frequency of each imaging mode. Emissions for making the B...... is determined by estimating the flow velocity in all directions and choosing the one with the strongest correlation. The method works for all angles, including fully axial and fully transverse flows. Field II simulations with a 192 element, 7 MHz linear array are made of laminar, transverse flow profiles...

  8. Synthetic aperture radar capabilities in development

    Energy Technology Data Exchange (ETDEWEB)

    Miller, M. [Lawrence Livermore National Lab., CA (United States)

    1994-11-15

    The Imaging and Detection Program (IDP) within the Laser Program is currently developing an X-band Synthetic Aperture Radar (SAR) to support the Joint US/UK Radar Ocean Imaging Program. The radar system will be mounted in the program`s Airborne Experimental Test-Bed (AETB), where the initial mission is to image ocean surfaces and better understand the physics of low grazing angle backscatter. The Synthetic Aperture Radar presentation will discuss its overall functionality and a brief discussion on the AETB`s capabilities. Vital subsystems including radar, computer, navigation, antenna stabilization, and SAR focusing algorithms will be examined in more detail.

  9. Synthetic Aperture Ladar Imaging and Atmospheric Turbulence

    Science.gov (United States)

    2016-06-09

    coherence factor for every retro-pair Ladar Heater Target 0 200 400 600 800 1000 1200 1400 0 50 100 150 200 250 Time [sec] In te n s it y Heater On...c) 0 200 400 600 800 1000 1200 1400 10 -13 10 -12 10 -11 C n 2 time [sec] 0.5 m 2 m 4 m 6 m 7.5 m DISTRIBUTION A: Distribution approved for...optical synthetic aperture radar,” US6879279 B2, 12- Apr - 2005. [10] Z. W. Barber and J. R. Dahl, “Synthetic aperture ladar imaging demonstrations and

  10. Sub-aperture stitching test of a cylindrical mirror with large aperture

    Science.gov (United States)

    Xue, Shuai; Chen, Shanyong; Shi, Feng; Lu, Jinfeng

    2016-09-01

    Cylindrical mirrors are key optics of high-end equipment of national defense and scientific research such as high energy laser weapons, synchrotron radiation system, etc. However, its surface error test technology develops slowly. As a result, its optical processing quality can not meet the requirements, and the developing of the associated equipment is hindered. Computer Generated-Hologram (CGH) is commonly utilized as null for testing cylindrical optics. However, since the fabrication process of CGH with large aperture is not sophisticated yet, the null test of cylindrical optics with large aperture is limited by the aperture of the CGH. Hence CGH null test combined with sub-aperture stitching method is proposed to break the limit of the aperture of CGH for testing cylindrical optics, and the design of CGH for testing cylindrical surfaces is analyzed. Besides, the misalignment aberration of cylindrical surfaces is different from that of the rotational symmetric surfaces since the special shape of cylindrical surfaces, and the existing stitching algorithm of rotational symmetric surfaces can not meet the requirements of stitching cylindrical surfaces. We therefore analyze the misalignment aberrations of cylindrical surfaces, and study the stitching algorithm for measuring cylindrical optics with large aperture. Finally we test a cylindrical mirror with large aperture to verify the validity of the proposed method.

  11. Revolutionary Astrophysics using an Incoherent Synthetic Optical Aperture

    Science.gov (United States)

    Rafanelli, Gerard L.; Cosner, Christopher M.; Spencer, Susan B.; Wolfe, Douglas w.; Newman, Arthur M.; Polidan, Ronald S.; Chakrabarti, Supriya

    2018-01-01

    We describe a paradigm shift for astronomical observatories that would replace circular apertures with rotating synthetic apertures. Rotating Synthetic Aperture (RSA) observatories can enable high value science measurements for the lowest mass to orbit, have superior performance relative to all sparse apertures, can provide resolution of 20m to 30m apertures having the collecting area of 8m to 12m telescopes with much less mass, risk, schedule, and cost. RSA is based on current, or near term technology and can be launched on a single, current launch vehicle to L2. Much larger apertures are possible using the NASA Space Launch System.

  12. Calibration of circular aperture area using vision probe at inmetro

    Directory of Open Access Journals (Sweden)

    Costa Pedro Bastos

    2016-01-01

    Full Text Available Circular aperture areas are standards of high importance for the realization of photometric and radiometric measurements, where the accuracy of these measures is related to the accuracy of the circular aperture area calibrations. In order to attend the requirement for traceability was developed in Brazilian metrology institute, a methodology for circular aperture area measurement as requirements from the radiometric and photometric measurements. In the developed methodology apertures are measured by non-contact measurement through images of the aperture edges captured by a camera. These images are processed using computer vision techniques and then the values of the circular aperture area are determined.

  13. Optimization of Synthetic Aperture Image Quality

    DEFF Research Database (Denmark)

    Moshavegh, Ramin; Jensen, Jonas; Villagómez Hoyos, Carlos Armando

    2016-01-01

    Synthetic Aperture (SA) imaging produces high-quality images and velocity estimates of both slow and fast flow at high frame rates. However, grating lobe artifacts can appear both in transmission and reception. These affect the image quality and the frame rate. Therefore optimization of parameter...

  14. Diffraction contrast imaging using virtual apertures

    International Nuclear Information System (INIS)

    Gammer, Christoph; Burak Ozdol, V.; Liebscher, Christian H.; Minor, Andrew M.

    2015-01-01

    Two methods on how to obtain the full diffraction information from a sample region and the associated reconstruction of images or diffraction patterns using virtual apertures are demonstrated. In a STEM-based approach, diffraction patterns are recorded for each beam position using a small probe convergence angle. Similarly, a tilt series of TEM dark-field images is acquired. The resulting datasets allow the reconstruction of either electron diffraction patterns, or bright-, dark- or annular dark-field images using virtual apertures. The experimental procedures of both methods are presented in the paper and are applied to a precipitation strengthened and creep deformed ferritic alloy with a complex microstructure. The reconstructed virtual images are compared with conventional TEM images. The major advantage is that arbitrarily shaped virtual apertures generated with image processing software can be designed without facing any physical limitations. In addition, any virtual detector that is specifically designed according to the underlying crystal structure can be created to optimize image contrast. - Highlights: • A dataset containing all structural information of a given position is recorded. • The dataset allows reconstruction of virtual diffraction patterns or images. • Specific virtual apertures are designed to image precipitates in a complex alloy. • Virtual diffraction patterns from arbitrarily small regions can be established. • Using STEM diffraction to record the dataset is more efficient than TEM dark-field

  15. Automated Change Detection for Synthetic Aperture Sonar

    Science.gov (United States)

    2014-01-01

    2014 2. REPORT TYPE 3. DATES COVERED 00-00-2014 to 00-00-2014 4. TITLE AND SUBTITLE Automated Change Detection for Synthetic Aperture Sonar...R. Azimi-Sadjadi and S. Srinivasan, “Coherent Change Detection and Classification in Synthetic Aper - ture Radar Imagery Using Canonical Correlation

  16. Parametric Transverse Patterns in Broad Aperture Lasers

    DEFF Research Database (Denmark)

    Grigorieva, E.V.; Kashchenko, S.A.; Mosekilde, Erik

    1998-01-01

    Parametrically generated optical patterns are investigated for finite and large-scale transverse aperture lasers. Standing and rotating patterns as well as periodic and chaotic pattern alternations are described in the framework of the amplitude equation formalism. Sensitive dependence...... on the geometrical size of the system is demonstrated even in the case of large-scale systems....

  17. Dynamic Aperture Studies for SPEAR 3

    International Nuclear Information System (INIS)

    Nosochkov, Yuri

    1999-01-01

    The SSRL is investigating an accelerator upgrade project to replace the present 130 nm.rad FODO lattice with an 18 nm.rad double bend achromat lattice: SPEAR 3. In this paper, we review the methods used to maximize the SPEAR 3 dynamic aperture including optimization of linear optics, betatron tune, chromaticity and coupling correction, and effects of machine errors and insertion devices

  18. MD2725: 16L2 aperture measurement

    CERN Document Server

    Mirarchi, Daniele; Rossi, Roberto; CERN. Geneva. ATS Department

    2018-01-01

    Dumps induced by sudden increase of losses in the half-cell 16L2 have been a serious machine limitation during the 2017 run. The aim of this MD was to perform local aperture measurements in order to assess differences after the beam screen regeneration, compared to first measurements in 2017.

  19. Wind energy applications of synthetic aperture radar

    DEFF Research Database (Denmark)

    Badger, Merete

    Synthetic aperture radars (SAR), mounted on satellites or aircraft, have proven useful for ocean wind mapping. Wind speeds at the height 10 m may be retrieved from measurements of radar backscatter using empirical model functions. The resulting windfields are valuable in offshore wind energy...

  20. Optical trapping at low numerical aperture

    NARCIS (Netherlands)

    Stallinga, S.

    2011-01-01

    A theory of optical trapping at low Numerical Aperture (NA) is presented. The theory offers an analytical description of the competition between the stabilizing gradient and destabilizing scattering force. The trade-off can be characterized by a single dimensionless trapping parameter, which

  1. Fractal characteristics of fracture roughness and aperture data

    International Nuclear Information System (INIS)

    Kumar, S.; Boernge, J.

    1991-05-01

    In this study mathematical expressions are developed for the characteristics of apertures between rough surfaces. It has shown that the correlation between the opposite surfaces influences the aperture properties and different models are presented for these different surface correlations. Fracture and apertures profiles measured from intact fractures are evaluated and it is found that they qualitatively follow the mathematically predicted trends

  2. Synthetic aperture imaging in astronomy and aerospace: introduction.

    Science.gov (United States)

    Creech-Eakman, Michelle J; Carney, P Scott; Buscher, David F; Shao, Michael

    2017-05-01

    Aperture synthesis methods allow the reconstruction of images with the angular resolutions exceeding that of extremely large monolithic apertures by using arrays of smaller apertures together in combination. In this issue we present several papers with techniques relevant to amplitude interferometry, laser radar, and intensity interferometry applications.

  3. High Gain, Very Low Areal Density, Scalable RF Apertures Enabled by Membrane Aperture Shell Technology (MAST), Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose that the Membrane Aperture Shell Technology (MAST) approach be expanded with a specific focus on space exploration orbiting comm network RF aperture...

  4. Coded aperture imaging using imperfect detector systems

    International Nuclear Information System (INIS)

    Byard, K.; Ramsden, D.

    1994-01-01

    The imaging properties of a gamma-ray telescope which employs a coded aperture in conjunction with a modular detection plane has been investigated. Gaps in the detection plane, which arise as a consequence of the design of the position sensitive detector used, produce artifacts in the deconvolved images which reduce the signal to noise ratio for the detection of point sources. The application of an iterative image processing algorithm is shown to restore the image quality to that expected from an ideal detector. The efficiency of image processing has enabled its subsequent application to a general coded aperture system in order to gain a significant improvement in the field of view without compromising the angular resolution. (orig.)

  5. Miniature synthetic-aperture radar system

    Science.gov (United States)

    Stockton, Wayne; Stromfors, Richard D.

    1990-11-01

    Loral Defense Systems-Arizona has developed a high-performance synthetic-aperture radar (SAR) for small aircraft and unmanned aerial vehicle (UAV) reconnaissance applications. This miniature radar, called Miniature Synthetic-Aperture Radar (MSAR), is packaged in a small volume and has low weight. It retains key features of large SAR systems, including high-resolution imaging and all-weather operation. The operating frequency of MSAR can optionally be selected to provide foliage penetration capability. Many imaging radar configurations can be derived using this baseline system. MSAR with a data link provides an attractive UAV sensor. MSAR with a real-time image formation processor is well suited to installations where onboard processing and immediate image analysis are required. The MSAR system provides high-resolution imaging for short-to-medium range reconnaissance applications.

  6. Dynamic Aperture Studies for SPEAR 3

    International Nuclear Information System (INIS)

    Corbett, William

    1998-01-01

    The Stanford Synchrotron Radiation Laboratory is investigating an accelerator upgrade project that would replace the present 130 nm rad FODO lattice with an 18 nm rad double bend achromat (DBA) lattice: SPEAR 3. The low emittance design yields a high brightness beam, but the stronger focusing in the DBA lattice increases chromaticity and beam sensitivity to machine errors. To ensure efficient injection and long Touschek lifetime, an optimization of the design lattice and dynamic aperture has been performed. In this paper, we review the methods used to maximize the SPEAR 3 dynamic aperture including necessary optics modifications, choice of tune and phase advance, optimization of sextupole and coupling correction, and modeling effects of machine errors, wigglers and lattice periodicity

  7. Dynamic aperture studies for SPEAR 3

    International Nuclear Information System (INIS)

    Nosochkov, Y.; Corbett, J.

    1999-01-01

    The Stanford Synchrotron Radiation Laboratory is investigating an accelerator upgrade project that would replace the present 130 nm·rad FODO lattice with an 18 nm·rad double bend achromat (DBA) lattice: SPEAR 3. The low emittance design yields a high brightness beam, but the stronger focusing in the DBA lattice increases chromaticity and beam sensitivity to machine errors. To ensure efficient injection and long Touschek lifetime, an optimization of the design lattice and dynamic aperture has been performed. In this paper, we review the methods used to maximize the SPEAR 3 dynamic aperture including necessary optics modifications, choice of tune and phase advance, optimization of sextupole and coupling correction, and modeling effects of machine errors, wigglers and lattice periodicity

  8. IR aperture measurement at β*=40 cm

    CERN Document Server

    Bruce, Roderik; Hermes, Pascal Dominik; Kwee-Hinzmann, Regina; Mereghetti, Alessio; Mirarchi, Daniele; Redaelli, Stefano; Salvachua Ferrando, Belen Maria; Skowronski, Piotr Krzysztof; Valentino, Gianluca; Valloni, Alessandra; CERN. Geneva. ATS Department

    2015-01-01

    This note summarizes MD 307, performed on August 27 2015, during which we measured with beam the global apertures at 6.5 TeV with IR1 and IR5 squeezed to β* =40 cm and a half crossing angle of 205 rad. The measurement technique involved opening collimators in steps, while inducing beam losses at each step, until the main loss location moved from the collimators to the global bottleneck in one of the triplets. Measurements were performed in both beams and planes, and each measurement gave the minimum triplet aperture over IR1 and IR5. The results are in very good agreement with theoretical predictions. At the end of the MD, an asynchronous beam dump test was performed with all collimators moved in to so-called 2-σ retraction settings. This MD is one in a series meant to address various open points for the reach in β* in Run II.

  9. Integrated Optical Synthetic Aperture Radar Processor.

    Science.gov (United States)

    1987-09-01

    tion Processing for Aerospace Applications. II, Langley, Virginia, (1983). Appendix C I. Abramov , Y. Owechko, A. R. Tanguay, Jr., and T. J. 45...1983). 3. I. Abramov , Y. Owechko, A. R. Tanguay, Jr., and T. J. Bicknell, "Real Time Synthetic Aperture Image Formation Utilizing an Electrooptic...LIGHT MODULATOR I. Abramov , Y. Owechko, and A.R. Tanguay, Jr. Departments of Electrical Engineering and Materials Science, and Image Processing

  10. Synthetic aperture ladar concept for infrastructure monitoring

    Science.gov (United States)

    Turbide, Simon; Marchese, Linda; Terroux, Marc; Bergeron, Alain

    2014-10-01

    Long range surveillance of infrastructure is a critical need in numerous security applications, both civilian and military. Synthetic aperture radar (SAR) continues to provide high resolution radar images in all weather conditions from remote distances. As well, Interferometric SAR (InSAR) and Differential Interferometric SAR (D-InSAR) have become powerful tools adding high resolution elevation and change detection measurements. State of the art SAR systems based on dual-use satellites are capable of providing ground resolutions of one meter; while their airborne counterparts obtain resolutions of 10 cm. D-InSAR products based on these systems could produce cm-scale vertical resolution image products. Deformation monitoring of railways, roads, buildings, cellular antennas, power structures (i.e., power lines, wind turbines, dams, or nuclear plants) would benefit from improved resolution, both in the ground plane and vertical direction. The ultimate limitation to the achievable resolution of any imaging system is its wavelength. State-of-the art SAR systems are approaching this limit. The natural extension to improve resolution is to thus decrease the wavelength, i.e. design a synthetic aperture system in a different wavelength regime. One such system offering the potential for vastly improved resolution is Synthetic Aperture Ladar (SAL). This system operates at infrared wavelengths, ten thousand times smaller than radar wavelengths. This paper presents a laboratory demonstration of a scaled-down infrastructure deformation monitoring with an Interferometric Synthetic Aperture Ladar (IFSAL) system operating at 1.5 μm. Results show sub-millimeter precision on the deformation applied to the target.

  11. 47 CFR 25.134 - Licensing provisions of Very Small Aperture Terminal (VSAT) and C-band Small Aperture Terminal...

    Science.gov (United States)

    2010-10-01

    ... Terminal (VSAT) and C-band Small Aperture Terminal (CSAT) networks. 25.134 Section 25.134 Telecommunication... Applications and Licenses Earth Stations § 25.134 Licensing provisions of Very Small Aperture Terminal (VSAT) and C-band Small Aperture Terminal (CSAT) networks. (a)(1) VSAT networks operating in the 12/14 GHz...

  12. Coded-aperture imaging in nuclear medicine

    Science.gov (United States)

    Smith, Warren E.; Barrett, Harrison H.; Aarsvold, John N.

    1989-11-01

    Coded-aperture imaging is a technique for imaging sources that emit high-energy radiation. This type of imaging involves shadow casting and not reflection or refraction. High-energy sources exist in x ray and gamma-ray astronomy, nuclear reactor fuel-rod imaging, and nuclear medicine. Of these three areas nuclear medicine is perhaps the most challenging because of the limited amount of radiation available and because a three-dimensional source distribution is to be determined. In nuclear medicine a radioactive pharmaceutical is administered to a patient. The pharmaceutical is designed to be taken up by a particular organ of interest, and its distribution provides clinical information about the function of the organ, or the presence of lesions within the organ. This distribution is determined from spatial measurements of the radiation emitted by the radiopharmaceutical. The principles of imaging radiopharmaceutical distributions with coded apertures are reviewed. Included is a discussion of linear shift-variant projection operators and the associated inverse problem. A system developed at the University of Arizona in Tucson consisting of small modular gamma-ray cameras fitted with coded apertures is described.

  13. Synthetic aperture radar processing with tiered subapertures

    Science.gov (United States)

    Doerry, A. W.

    1994-06-01

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

  14. Towards Very Large Aperture Massive MIMO

    DEFF Research Database (Denmark)

    Oliveras Martínez, Àlex; De Carvalho, Elisabeth; Nielsen, Jesper Ødum

    2014-01-01

    Massive MIMO is a new technique for wireless communications that claims to offer very high system throughput and energy efficiency in multi-user scenarios. The cost is to add a very large number of antennas at the base station. Theoretical research has probed these benefits, but very few measurem......Massive MIMO is a new technique for wireless communications that claims to offer very high system throughput and energy efficiency in multi-user scenarios. The cost is to add a very large number of antennas at the base station. Theoretical research has probed these benefits, but very few...... measurements have showed the potential of Massive MIMO in practice. We investigate the properties of measured Massive MIMO channels in a large indoor venue. We describe a measurement campaign using 3 arrays having different shape and aperture, with 64 antennas and 8 users with 2 antennas each. We focus...... on the impact of the array aperture which is the main limiting factor in the degrees of freedom available in the multiple antenna channel. We find that performance is improved as the aperture increases, with an impact mostly visible in crowded scenarios where the users are closely spaced. We also test MIMO...

  15. Coded-aperture imaging in nuclear medicine

    Science.gov (United States)

    Smith, Warren E.; Barrett, Harrison H.; Aarsvold, John N.

    1989-01-01

    Coded-aperture imaging is a technique for imaging sources that emit high-energy radiation. This type of imaging involves shadow casting and not reflection or refraction. High-energy sources exist in x ray and gamma-ray astronomy, nuclear reactor fuel-rod imaging, and nuclear medicine. Of these three areas nuclear medicine is perhaps the most challenging because of the limited amount of radiation available and because a three-dimensional source distribution is to be determined. In nuclear medicine a radioactive pharmaceutical is administered to a patient. The pharmaceutical is designed to be taken up by a particular organ of interest, and its distribution provides clinical information about the function of the organ, or the presence of lesions within the organ. This distribution is determined from spatial measurements of the radiation emitted by the radiopharmaceutical. The principles of imaging radiopharmaceutical distributions with coded apertures are reviewed. Included is a discussion of linear shift-variant projection operators and the associated inverse problem. A system developed at the University of Arizona in Tucson consisting of small modular gamma-ray cameras fitted with coded apertures is described.

  16. Technical Progress in Research of Multibeam Synthetic Aperture Sonar

    Directory of Open Access Journals (Sweden)

    LI Haisen

    2017-10-01

    Full Text Available Recently, detailed underwater target detection and imaging sonar technology has become a research hotpot with the urgent need of marine research. Multibeam synthetic aperture sonar technology has been proposed combining the both technological advantages in this paper, owing to the emphatically analyses of the technology trends of multibeam bathymetric sonar and synthetic aperture sonar. The research progress in the key technologies of multibeam synthetic aperture sonar has been discussed in this paper, the effectiveness of multibeam synthetic aperture sonar detection mechanism is preliminary verified by the experiments. The potential that the multibeam synthetic aperture technique can effectively enhance the underwater target resolution has aslo been proved through the contrast experiment.

  17. Filled aperture concepts for the Terrestrial Planet Finder

    Science.gov (United States)

    Ridgway, Stephen T.

    2003-02-01

    Filled aperture telescopes can deliver a real, high Strehl image which is well suited for discrimination of faint planets in the vicinity of bright stars and against an extended exo-zodiacal light. A filled aperture offers a rich variety of PSF control and diffraction suppression techniques. Filled apertures are under consideration for a wide spectral range, including visible and thermal-IR, each of which offers a significant selection of biomarker molecular bands. A filled aperture visible TPF may be simpler in several respects than a thermal-IR nuller. The required aperture size (or baseline) is much smaller, and no cryogenic systems are required. A filled aperture TPF would look and act like a normal telescope - vendors and users alike would be comfortable with its design and operation. Filled aperture telescopes pose significant challenges in production of large primary mirrors, and in very stringent wavefront requirements. Stability of the wavefront control, and hence of the PSF, is a major issue for filled aperture systems. Several groups have concluded that these and other issues can be resolved, and that filled aperture options are competitive for a TPF precursor and/or for the full TPF mission. Ball, Boeing-SVS and TRW have recently returned architecture reviews on filled aperture TPF concepts. In this paper, I will review some of the major considerations underlying these filled aperture concepts, and suggest key issues in a TPF Buyers Guide.

  18. Fast parametric beamformer for synthetic aperture imaging.

    Science.gov (United States)

    Nikolov, Svetoslav Ivanov; Jensen, Jørgen Arendt; Tomov, Borislav Gueorguiev

    2008-08-01

    This paper describes the design and implementation of a real-time delay-and-sum synthetic aperture beamformer. The beamforming delays and apodization coefficients are described parametrically. The image is viewed as a set of independent lines that are defined in 3D by their origin, direction, and inter-sample distance. The delay calculation is recursive and inspired by the coordinate rotation digital computer (CORDIC) algorithm. Only 3 parameters per channel and line are needed for their generation. The calculation of apodization coefficients is based on a piece- wise linear approximation. The implementation of the beamformer is optimized with respect to the architecture of a novel synthetic aperture real-time ultrasound scanner (SARUS), in which 4 channels are processed by the same set of field-programmable gate arrays (FPGA). In synthetic transmit aperture imaging, low-resolution images are formed after every emission. Summing all low-resolution images produces a perfectly focused high-resolution image. The design of the beamformer is modular, and a single beamformation unit can produce 4600 low-resolution images per second, each consisting of 32 lines and 1024 complex samples per line. In its present incarnation, 3 such modules fit in a single device. The summation of low-resolution images is performed internally in the FPGA to reduce the required bandwidth. The delays are calculated with a precision of 1/16th of a sample, and the apodization coefficients with 7-bit precision. The accumulation of low-resolution images is performed with 24-bit precision. The level of the side- and grating lobes, introduced by the use of integer numbers in the calculations and truncation of intermediate results, is below -86 dB from the peak.

  19. Optimization of Spatiotemporal Apertures in Channel Sounding

    DEFF Research Database (Denmark)

    Pedersen, Troels; Pedersen, Claus; Yin, Xuefeng

    2008-01-01

    In this paper we investigate the impact of the spatio-temporal aperture of a channel sounding system equipped with antenna arrays at the transmitter and receiver on the accuracy of joint estimation of Doppler frequency and bi-direction. The contribution of this work is three-fold. Firstly, we state...... a spatiotemporal model which can describe parallel as well as switched sounding systems. The proposed model is applicable for arbitrary layouts of the spatial arrays. To simplify the derivations we investigate the special case of linear spatial arrays. However, the results obtained for linear arrays can...

  20. Tissue Harmonic Synthetic Aperture Ultrasound Imaging

    DEFF Research Database (Denmark)

    Hemmsen, Martin Christian; Rasmussen, Joachim; Jensen, Jørgen Arendt

    2014-01-01

    Synthetic aperture sequential beamforming (SASB) and tissue har- monic imaging (THI) are combined to improve the image quality of medical ultrasound imaging. The technique is evaluated in a compar- ative study against dynamic receive focusing (DRF). The objective is to investigate if SASB combined......, and data were recorded with and without pulse inversion for tissue harmonic imaging. Data were acquired using a Sound Technol- ogy 192 element convex array transducer from both a wire phantom and a tissue mimicking phantom to investigate spatial resolution and pen- etration. In-vivo scans were also...

  1. VELO aperture considerations for the LHCb Upgrade

    CERN Document Server

    Appleby, RB; Ferro-Luzzi, M; Giovannozzi, M; Holzer, B

    2012-01-01

    In Long Shutdown 2 the VELO detectors will be replaced by new modules compatible with the LHCb Upgrade 40 MHz read-out system. A smaller inner radius of the VELO RF foil and of the silicon sensor active area will allow LHCb to considerably improve the impact parameter resolution. Here, a limit of the minimum VELO aperture during physics (Stable Beams) is discussed. A value of 3.5 mm for the nominal radius of the inner edge fo the RF foil seems acceptable.

  2. Synthetic aperture radar autofocus via semidefinite relaxation.

    Science.gov (United States)

    Liu, Kuang-Hung; Wiesel, Ami; Munson, David C

    2013-06-01

    The autofocus problem in synthetic aperture radar imaging amounts to estimating unknown phase errors caused by unknown platform or target motion. At the heart of three state-of-the-art autofocus algorithms, namely, phase gradient autofocus, multichannel autofocus (MCA), and Fourier-domain multichannel autofocus (FMCA), is the solution of a constant modulus quadratic program (CMQP). Currently, these algorithms solve a CMQP by using an eigenvalue relaxation approach. We propose an alternative relaxation approach based on semidefinite programming, which has recently attracted considerable attention in other signal processing problems. Experimental results show that our proposed methods provide promising performance improvements for MCA and FMCA through an increase in computational complexity.

  3. Measurements of pore-scale flow through apertures

    Energy Technology Data Exchange (ETDEWEB)

    Chojnicki, Kirsten [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2017-09-01

    Pore-scale aperture effects on flow in pore networks was studied in the laboratory to provide a parameterization for use in transport models. Four cases were considered: regular and irregular pillar/pore alignment with and without an aperture. The velocity field of each case was measured and simulated, providing quantitatively comparable results. Two aperture effect parameterizations were considered: permeability and transmission. Permeability values varied by an order of magnitude between the cases with and without apertures. However, transmission did not correlate with permeability. Despite having much greater permeability the regular aperture case permitted less transmission than the regular case. Moreover, both irregular cases had greater transmission than the regular cases, a difference not supported by the permeabilities. Overall, these findings suggest that pore-scale aperture effects on flow though a pore-network may not be adequately captured by properties such as permeability for applications that are interested in determining particle transport volume and timing.

  4. Rotatable Aperture Coronagraph for Exoplanetary Studies (RACES)

    Science.gov (United States)

    Chakrabarti, Supriya; Mendillo, Christopher; Mukherjee, Sunip; Martel, Jason; Cook, Timothy; Polidan, Ronald S.; Rafanelli, Gerard L.; Spencer, Susan B.; Wolfe, Douglas w.

    2018-01-01

    We present the design and expected performance of RACES, a suborbital mission concept to directly image exo-Jupiters with a rotatable non-circular aperture telescope. By using a high-aspect ratio elliptical or rectangular primary mirror (2.3m x 0.6m), this mission achieves the same angular resolution and inner working angle as a 2.3m dia telescope. Such an elliptical or rectangular system would fill the volume of a cylindrical launch vehicle more efficiently and by choosing the aspect ratio one can appropriately tailor its light gathering power. RACES can therefore serve as a pathfinder for future larger missions for exoplanetary explorations. For example, the system described here approaches the collecting area of the well studied EXO-C concept and exceeds its angular resolution. The mission concept, design studies, observation strategy and expected target yield for RACES will be presented, as well as simulations of the high contrast vector vortex coronagraph operating with an un-obscured elliptical aperture.

  5. Coded aperture optimization using Monte Carlo simulations

    International Nuclear Information System (INIS)

    Martineau, A.; Rocchisani, J.M.; Moretti, J.L.

    2010-01-01

    Coded apertures using Uniformly Redundant Arrays (URA) have been unsuccessfully evaluated for two-dimensional and three-dimensional imaging in Nuclear Medicine. The images reconstructed from coded projections contain artifacts and suffer from poor spatial resolution in the longitudinal direction. We introduce a Maximum-Likelihood Expectation-Maximization (MLEM) algorithm for three-dimensional coded aperture imaging which uses a projection matrix calculated by Monte Carlo simulations. The aim of the algorithm is to reduce artifacts and improve the three-dimensional spatial resolution in the reconstructed images. Firstly, we present the validation of GATE (Geant4 Application for Emission Tomography) for Monte Carlo simulations of a coded mask installed on a clinical gamma camera. The coded mask modelling was validated by comparison between experimental and simulated data in terms of energy spectra, sensitivity and spatial resolution. In the second part of the study, we use the validated model to calculate the projection matrix with Monte Carlo simulations. A three-dimensional thyroid phantom study was performed to compare the performance of the three-dimensional MLEM reconstruction with conventional correlation method. The results indicate that the artifacts are reduced and three-dimensional spatial resolution is improved with the Monte Carlo-based MLEM reconstruction.

  6. Optical Ground Terminals Using Multi Aperture Digital Coherent Combining

    Science.gov (United States)

    2017-10-01

    advantages of a multi-aperture OGT are summarized in [4]. III. EXPERIMENTAL RESULTS A first experimental validation of multi-aperture digital coherent...Optical Ground Terminals Using Multi-Aperture Digital Coherent Combining (Invited Paper) D. J. Geisler, T. M. Yarnall, C. M. Schieler, M. L. Stevens...B. S. Robinson, and S. A. Hamilton Massachusetts Institute of Technology Lincoln Laboratory 244 Wood Street, Lexington, MA, USA 02420 Email

  7. Functionalized apertures for the detection of chemical and biological materials

    Science.gov (United States)

    Letant, Sonia E.; van Buuren, Anthony W.; Terminello, Louis J.; Thelen, Michael P.; Hope-Weeks, Louisa J.; Hart, Bradley R.

    2010-12-14

    Disclosed are nanometer to micron scale functionalized apertures constructed on a substrate made of glass, carbon, semiconductors or polymeric materials that allow for the real time detection of biological materials or chemical moieties. Many apertures can exist on one substrate allowing for the simultaneous detection of numerous chemical and biological molecules. One embodiment features a macrocyclic ring attached to cross-linkers, wherein the macrocyclic ring has a biological or chemical probe extending through the aperture. Another embodiment achieves functionalization by attaching chemical or biological anchors directly to the walls of the apertures via cross-linkers.

  8. Extended Aperture Photometry of K2 RR Lyrae stars

    Science.gov (United States)

    Plachy, Emese; Klagyivik, Péter; Molnár, László; Sódor, Ádám; Szabó, Róbert

    2017-10-01

    We present the method of the Extended Aperture Photometry (EAP) that we applied on K2 RR Lyrae stars. Our aim is to minimize the instrumental variations of attitude control maneuvers by using apertures that cover the positional changes in the field of view thus contain the stars during the whole observation. We present example light curves that we compared to the light curves from the K2 Systematics Correction (K2SC) pipeline applied on the automated Single Aperture Photometry (SAP) and on the Pre-search Data Conditioning Simple Aperture Photometry (PDCSAP) data.

  9. Extended Aperture Photometry of K2 RR Lyrae stars

    Directory of Open Access Journals (Sweden)

    Plachy Emese

    2017-01-01

    Full Text Available We present the method of the Extended Aperture Photometry (EAP that we applied on K2 RR Lyrae stars. Our aim is to minimize the instrumental variations of attitude control maneuvers by using apertures that cover the positional changes in the field of view thus contain the stars during the whole observation. We present example light curves that we compared to the light curves from the K2 Systematics Correction (K2SC pipeline applied on the automated Single Aperture Photometry (SAP and on the Pre-search Data Conditioning Simple Aperture Photometry (PDCSAP data.

  10. Enhanced Spectral Modeling of Sparse Aperture Imaging Systems

    National Research Council Canada - National Science Library

    Introne, Robert

    2005-01-01

    .... Unfortunately, spaceborne applications frequently encounter launch vehicle fairing and weight constraints that limit the size of the primarily aperture that can be utilized for a given application...

  11. Defocus morphing in real aperture images.

    Science.gov (United States)

    Chaudhuri, Subhasis

    2005-11-01

    A new concept called defocus morphing in real aperture images is introduced. View morphing is an existing example of shape-preserving image morphing based on the motion cue. It is proved that images can also be morphed based on the depth-related defocus cue. This illustrates that the morphing operation is not necessarily a geometric process alone; one can also perform a photometry-based morphing wherein the shape information is implicitly buried in the image intensity field. A theoretical understanding of the defocus morphing process is presented. It is shown mathematically that, given two observations of a three-dimensional scene for different camera parameter settings, we can obtain a virtual observation for any camera parameter setting through a simple nonlinear combination of these observations.

  12. Terahertz Imaging Systems With Aperture Synthesis Techniques

    DEFF Research Database (Denmark)

    Krozer, Viktor; Löffler, Torsten; Dall, Jørgen

    2010-01-01

    imaging systems are reviewed in terms of the employed architecture and data processing strategies. Active multichannel measurement method is found to be promising for real-time applications among the various terahertz imaging techniques and is chosen as a basis for the imaging instruments presented......This paper presents the research and development of two terahertz imaging systems based on photonic and electronic principles, respectively. As part of this study, a survey of ongoing research in the field of terahertz imaging is provided focusing on security applications. Existing terahertz...... in this paper. An active system operation allows for a wide dynamic range, which is important for image quality. The described instruments employ a multichannel high-sensitivity heterodyne architecture and aperture filling techniques, with close to real-time image acquisition time. In the case of the photonic...

  13. Large aperture nanocomposite deformable mirror technology

    Science.gov (United States)

    Chen, Peter C.; Hale, Richard D.

    2007-12-01

    We report progress in the development of deformable mirrors (DM) using nanocomposite materials. For the extremely large telescopes (ELTs) currently being planned, a new generation of DMs with unprecedented performance is a critical path item. The DMs need to have large apertures (meters), continuous surfaces, and low microroughness. Most importantly, they must have excellent static optical figures and yet be sufficiently thin (1-2 mm) and flexible to function with small, low powered actuators. Carbon fiber reinforced plastics (CFRP) have the potential to fulfill these requirements. However, CFRP mirrors made using direct optical replication have encountered a number of problems. Firstly, it is difficult if not impossible for a CFRP mirror to maintain a good static optical figure if a small number of plies are used, but adding more plies to the laminate tends to make the substrate too thick and stiff. Secondly, direct optical replication requires precision mandrels, the costs of which become prohibitive at multi-meter apertures. We report development of a new approach. By using a combination of a novel support structure, selected fibers, and binding resins infused with nanoparticles, it is possible to make millimeter thick optical mirrors that can both maintain good static optical figures and yet still have the required flexibility for actuation. Development and refinement of a non-contact, deterministic process of fine figuring permits generation of accurate optical surfaces without the need for precision optical mandrels. We present data from tests that have been carried out to demonstrate these new processes. A number of flat DMs have been fabricated, as well as concave and convex DMs in spherical, parabolic, and other forms.

  14. Common aperture multispectral spotter camera: Spectro XR

    Science.gov (United States)

    Petrushevsky, Vladimir; Freiman, Dov; Diamant, Idan; Giladi, Shira; Leibovich, Maor

    2017-10-01

    The Spectro XRTM is an advanced color/NIR/SWIR/MWIR 16'' payload recently developed by Elbit Systems / ELOP. The payload's primary sensor is a spotter camera with common 7'' aperture. The sensor suite includes also MWIR zoom, EO zoom, laser designator or rangefinder, laser pointer / illuminator and laser spot tracker. Rigid structure, vibration damping and 4-axes gimbals enable high level of line-of-sight stabilization. The payload's list of features include multi-target video tracker, precise boresight, strap-on IMU, embedded moving map, geodetic calculations suite, and image fusion. The paper describes main technical characteristics of the spotter camera. Visible-quality, all-metal front catadioptric telescope maintains optical performance in wide range of environmental conditions. High-efficiency coatings separate the incoming light into EO, SWIR and MWIR band channels. Both EO and SWIR bands have dual FOV and 3 spectral filters each. Several variants of focal plane array formats are supported. The common aperture design facilitates superior DRI performance in EO and SWIR, in comparison to the conventionally configured payloads. Special spectral calibration and color correction extend the effective range of color imaging. An advanced CMOS FPA and low F-number of the optics facilitate low light performance. SWIR band provides further atmospheric penetration, as well as see-spot capability at especially long ranges, due to asynchronous pulse detection. MWIR band has good sharpness in the entire field-of-view and (with full HD FPA) delivers amount of detail far exceeding one of VGA-equipped FLIRs. The Spectro XR offers level of performance typically associated with larger and heavier payloads.

  15. Second harmonic imaging using synthetic aperture sequential beamforming

    DEFF Research Database (Denmark)

    Du, Yigang; Rasmussen, Joachim; Jensen, Henrik

    2011-01-01

    The paper investigates Second Harmonic Imaging (SHI) using Synthetic Aperture Sequential Beamforming (SASB). The investigation is made by an experimental Synthetic Aperture Real-time Ultrasound System (SARUS). A linear array transducer is used to scan 4 wires at the image depths of f22.5, 47.5, 72...

  16. The sonar aperture and its neural representation in bats.

    Science.gov (United States)

    Heinrich, Melina; Warmbold, Alexander; Hoffmann, Susanne; Firzlaff, Uwe; Wiegrebe, Lutz

    2011-10-26

    As opposed to visual imaging, biosonar imaging of spatial object properties represents a challenge for the auditory system because its sensory epithelium is not arranged along space axes. For echolocating bats, object width is encoded by the amplitude of its echo (echo intensity) but also by the naturally covarying spread of angles of incidence from which the echoes impinge on the bat's ears (sonar aperture). It is unclear whether bats use the echo intensity and/or the sonar aperture to estimate an object's width. We addressed this question in a combined psychophysical and electrophysiological approach. In three virtual-object playback experiments, bats of the species Phyllostomus discolor had to discriminate simple reflections of their own echolocation calls differing in echo intensity, sonar aperture, or both. Discrimination performance for objects with physically correct covariation of sonar aperture and echo intensity ("object width") did not differ from discrimination performances when only the sonar aperture was varied. Thus, the bats were able to detect changes in object width in the absence of intensity cues. The psychophysical results are reflected in the responses of a population of units in the auditory midbrain and cortex that responded strongest to echoes from objects with a specific sonar aperture, regardless of variations in echo intensity. Neurometric functions obtained from cortical units encoding the sonar aperture are sufficient to explain the behavioral performance of the bats. These current data show that the sonar aperture is a behaviorally relevant and reliably encoded cue for object size in bat sonar.

  17. Shadow Enhancement in Synthetic Aperture Sonar Using Fixed Focusing

    NARCIS (Netherlands)

    Groen, J.; Hansen, R.E.; Callow, H.J.; Sabel, J.C.; Sæbø, T.O.

    2009-01-01

    Abstract—A shadow cast by an object on the seafloor is important information for target recognition in synthetic aperture sonar (SAS) images. Synthetic aperture imaging causes a fundamental limitation to shadow clarity because the illuminator is moved during the data collection. This leads to a

  18. Thermal front propagation in variable aperture fracture–matrix ...

    Indian Academy of Sciences (India)

    Keywords. Thermal front; variable aperture; rock-matrix; geothermal reservoir; numerical model, liquid dominated. Abstract. A numerical study on the effect of complex fracture aperture geometry on propagation of thermal front in a coupled single fracture-matrix system has been carried out. Sinusoidal and logarithmic ...

  19. Reconfigurable metasurface aperture for security screening and microwave imaging

    Science.gov (United States)

    Sleasman, Timothy; Imani, Mohammadreza F.; Boyarsky, Michael; Pulido-Mancera, Laura; Reynolds, Matthew S.; Smith, David R.

    2017-05-01

    Microwave imaging systems have seen growing interest in recent decades for applications ranging from security screening to space/earth observation. However, hardware architectures commonly used for this purpose have not seen drastic changes. With the advent of metamaterials a wealth of opportunities have emerged for honing metasurface apertures for microwave imaging systems. Recent thrusts have introduced dynamic reconfigurability directly into the aperture layer, providing powerful capabilities from a physical layer with considerable simplicity. The waveforms generated from such dynamic metasurfaces make them suitable for application in synthetic aperture radar (SAR) and, more generally, computational imaging. In this paper, we investigate a dynamic metasurface aperture capable of performing microwave imaging in the K-band (17.5-26.5 GHz). The proposed aperture is planar and promises an inexpensive fabrication process via printed circuit board techniques. These traits are further augmented by the tunability of dynamic metasurfaces, which provides the dexterity necessary to generate field patterns ranging from a sequence of steered beams to a series of uncorrelated radiation patterns. Imaging is experimentally demonstrated with a voltage-tunable metasurface aperture. We also demonstrate the aperture's utility in real-time measurements and perform volumetric SAR imaging. The capabilities of a prototype are detailed and the future prospects of general dynamic metasurface apertures are discussed.

  20. Thermal front propagation in variable aperture fracture–matrix system

    Indian Academy of Sciences (India)

    heat transfer from rock matrix to fracture for the case of the parallel plate model is greatly dependent on the rock thermal conductivity (λm) as compared to variable aper- ture model. Further, the thermal front propagation for both parallel plate model and variable aperture model is sensitive to changes in fracture aperture.

  1. Microfabricated high-bandpass foucault aperture for electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Glaeser, Robert; Cambie, Rossana; Jin, Jian

    2014-08-26

    A variant of the Foucault (knife-edge) aperture is disclosed that is designed to provide single-sideband (SSB) contrast at low spatial frequencies but retain conventional double-sideband (DSB) contrast at high spatial frequencies in transmission electron microscopy. The aperture includes a plate with an inner open area, a support extending from the plate at an edge of the open area, a half-circle feature mounted on the support and located at the center of the aperture open area. The radius of the half-circle portion of reciprocal space that is blocked by the aperture can be varied to suit the needs of electron microscopy investigation. The aperture is fabricated from conductive material which is preferably non-oxidizing, such as gold, for example.

  2. Influence of pressure change during hydraulic tests on fracture aperture.

    Science.gov (United States)

    Ji, Sung-Hoon; Koh, Yong-Kwon; Kuhlman, Kristopher L; Lee, Moo Yul; Choi, Jong Won

    2013-03-01

    In a series of field experiments, we evaluate the influence of a small water pressure change on fracture aperture during a hydraulic test. An experimental borehole is instrumented at the Korea Atomic Energy Research Institute (KAERI) Underground Research Tunnel (KURT). The target fracture for testing was found from the analyses of borehole logging and hydraulic tests. A double packer system was developed and installed in the test borehole to directly observe the aperture change due to water pressure change. Using this packer system, both aperture and flow rate are directly observed under various water pressures. Results indicate a slight change in fracture hydraulic head leads to an observable change in aperture. This suggests that aperture change should be considered when analyzing hydraulic test data from a sparsely fractured rock aquifer. © 2012, The Author(s). Groundwater © 2012, National Ground Water Association.

  3. X-ray lenses with large aperture

    International Nuclear Information System (INIS)

    Simon, Markus

    2010-01-01

    Up to now, most X-ray imaging setups are based on absorption contrast imaging. There is a demand for focused X-rays in many X-ray analysis applications, either to increase the resolution of an imaging system, or, to reduce the time effort of an experiment through higher photon flux. For photon energies higher than 15 keV refractive X-ray optics are more efficient in comparison to non-refractive X-ray optics. The aim of this work was to develop X-ray lenses with large apertures and high transparency. By increasing the number of refracting surfaces while removing unnecessary lens material such lenses have been developed. Utilizing this approach the overall beam deflection angle is large with respect to the lens material it propagates through and so the transparency of the lens is increased. Within this work, X-ray lenses consisting of several thousands of prisms with an edge length in the range of micrometers have been developed and fabricated by deep X-ray lithography. Deep X-ray lithography enables high precision microstrucures with smooth sidewalls and large aspect ratios. The aperture of high-transparency X-ray lenses made this way is greater than 1 mm. They are suitable for photon energies in the range of 8 keV to 24 keV and offer a focal width of smaller than 10 μm at a transparency of around 40%. Furthermore, rolled X-ray lenses have been developed, that are made out of a microstructured polyimide film, which is cut according to the requirements regarding focal length and photon energy. The microstructured film is fabricated by molding, using an anisotropically etched silicon wafer as molding tool. Its mean roughness is in the range of nanometers. The film features prismatic structures, its surface topology is similar to an asparagus field. The measured diameter of the point focus was 18 μm to 31 μm, the calculated opticla efficiency was 37%. Future work will concentrate on increasing the aspect ratio of Prism Lenses and on increasing the rolling accuracy

  4. Motion measurement for synthetic aperture radar

    Energy Technology Data Exchange (ETDEWEB)

    Doerry, Armin W. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-01-01

    Synthetic Aperture Radar (SAR) measures radar soundings from a set of locations typically along the flight path of a radar platform vehicle. Optimal focusing requires precise knowledge of the sounding source locations in 3-D space with respect to the target scene. Even data driven focusing techniques (i.e. autofocus) requires some degree of initial fidelity in the measurements of the motion of the radar. These requirements may be quite stringent especially for fine resolution, long ranges, and low velocities. The principal instrument for measuring motion is typically an Inertial Measurement Unit (IMU), but these instruments have inherent limi ted precision and accuracy. The question is %22How good does an IMU need to be for a SAR across its performance space?%22 This report analytically relates IMU specifications to parametric requirements for SAR. - 4 - Acknowledgements Th e preparation of this report is the result of a n unfunded research and development activity . Although this report is an independent effort, it draws heavily from limited - release documentation generated under a CRADA with General Atomics - Aeronautical System, Inc. (GA - ASI), and under the Joint DoD/DOE Munitions Program Memorandum of Understanding. Sandia National Laboratories is a multi - program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of En ergy's National Nuclear Security Administration under contract AC04-94AL85000.

  5. Parametric Beamformer for Synthetic Aperture Ultrasound Imaging

    DEFF Research Database (Denmark)

    Nikolov, Svetoslav; Tomov, Borislav Gueorguiev; Jensen, Jørgen Arendt

    2006-01-01

    . The beamformer consists of a number of identical beamforming blocks, each processing data from several channels and producing part of the image. A number of these blocks can be accommodated in a modern field-programmable gate array device (FPGA), and a whole synthetic aperture system can be implemented using...... several FPGAs. For the current implementation, the input data is sampled at 4 times the center frequency of the excitation pulse and is match-filtered in the frequency domain. In-phase and quadrature data are beamformed with a sub-sample precision of the focusing delays of 1/16th of the sampling period...... with 255 levels. A beamforming block uses input data from 4 elements and produces a set of 10 lines. Linear interpolation is used to implement sub-sample delays. The VHDL code for the beamformer has been synthesized for a Xilinx V4FX100 speed grade 11 FPGA, where it can operate at a maximum clock frequency...

  6. Adaptive synthetic aperture radar image enhancement

    Science.gov (United States)

    Cheng, Hua; Tian, Jinwen

    2009-10-01

    An adaptive SAR image enhancement method is presented for reducing the speckle noise and increasing the contrast of synthetic aperture radar (SAR) images. First, a fuzzy logic based filter, employing fuzzy edge to weight the contributions of pixel values in filter window, is used to filter the speckles. Second, the original SAR image is decomposed into lowfrequency component and high-frequency component. The fuzzy filtered image is viewed as the low-frequency component, and the contrast limited adaptive histogram equalization algorithm is used to increase its contrast. The highfrequency component is obtained by subtracting the low-frequency component from the original image, and its gain is controlled by fuzzy structural which employed to express the degree of a pixel belonging to structures. After processed one after the other, the two components are added together to form the final enhanced SAR image. Experimental results show the excellent effect of the proposed method by visual observation and numerical measurement. Many fine structures and little speckle noise can be seen from the enhanced SAR images.

  7. Deep Learning for Passive Synthetic Aperture Radar

    Science.gov (United States)

    Yonel, Bariscan; Mason, Eric; Yazici, Birsen

    2018-02-01

    We introduce a deep learning (DL) framework for inverse problems in imaging, and demonstrate the advantages and applicability of this approach in passive synthetic aperture radar (SAR) image reconstruction. We interpret image recon- struction as a machine learning task and utilize deep networks as forward and inverse solvers for imaging. Specifically, we design a recurrent neural network (RNN) architecture as an inverse solver based on the iterations of proximal gradient descent optimization methods. We further adapt the RNN architecture to image reconstruction problems by transforming the network into a recurrent auto-encoder, thereby allowing for unsupervised training. Our DL based inverse solver is particularly suitable for a class of image formation problems in which the forward model is only partially known. The ability to learn forward models and hyper parameters combined with unsupervised training approach establish our recurrent auto-encoder suitable for real world applications. We demonstrate the performance of our method in passive SAR image reconstruction. In this regime a source of opportunity, with unknown location and transmitted waveform, is used to illuminate a scene of interest. We investigate recurrent auto- encoder architecture based on the 1 and 0 constrained least- squares problem. We present a projected stochastic gradient descent based training scheme which incorporates constraints of the unknown model parameters. We demonstrate through extensive numerical simulations that our DL based approach out performs conventional sparse coding methods in terms of computation and reconstructed image quality, specifically, when no information about the transmitter is available.

  8. In-vivo examples of synthetic aperture vector flow imaging

    DEFF Research Database (Denmark)

    Oddershede, Niels; Hansen, Kristoffer Lindskov; Nielsen, Michael Bachmann

    2007-01-01

    are processed, and movies of full vector flow images are generated. This paper presents still frames from different time instances of these movies. The movie from the femoral data tracks the accelerating velocity in the femoral artery during systole and a backwards flow at the end of the systole. A complex flow...... would be needed. Synthetic aperture vector flow imaging could potentially provide this. The purpose of this paper is to test the synthetic aperture vector flow imaging method on challenging in-vivo data. Two synthetic aperture in-vivo data sets are acquired using a commercial linear array transducer...

  9. MD1405: Demonstration of forced dynamic aperture measurements at injection

    CERN Document Server

    Carlier, Felix Simon; Persson, Tobias Hakan Bjorn; Tomas Garcia, Rogelio; CERN. Geneva. ATS Department

    2017-01-01

    Accurate measurements of dynamic aperture become more important for the LHC as it advances into increasingly nonlinear regimes of operations, as well as for the High Luminosity LHC where machine nonlinearities will have a significantly larger impact. Direct dynamic aperture measurements at top energy in the LHC are challenging, and conventional single kick methods are not viable. Dynamic aperture measurements under forced oscillation of AC dipoles have been proposed as s possible alternative observable. A first demonstration of forced DA measurements at injections energy is presented.

  10. Adjustable off-focal aperture for x-ray tubes

    International Nuclear Information System (INIS)

    Mattson, R.A.; Levar, R.E.

    1990-01-01

    This patent describes an x-ray tube assembly for radiographic scanners. It comprises: an evacuated envelope; an anode rotatably mounted within the envelope; a housing surrounding the envelope to define a cooling fluid reservoir therebetween, the housing defining an aperture therein and having a collar surrounding the aperture; an x-ray permeable, fluid impermeable window mounted to the housing to seal the aperture; an x-ray beam defining means, an off-focal radiation attenuating means, a flexible cable means, and a first stop means

  11. Electromagnetic Formation Flight (EMFF) for Sparse Aperture Arrays

    Science.gov (United States)

    Kwon, Daniel W.; Miller, David W.; Sedwick, Raymond J.

    2004-01-01

    Traditional methods of actuating spacecraft in sparse aperture arrays use propellant as a reaction mass. For formation flying systems, propellant becomes a critical consumable which can be quickly exhausted while maintaining relative orientation. Additional problems posed by propellant include optical contamination, plume impingement, thermal emission, and vibration excitation. For these missions where control of relative degrees of freedom is important, we consider using a system of electromagnets, in concert with reaction wheels, to replace the consumables. Electromagnetic Formation Flight sparse apertures, powered by solar energy, are designed differently from traditional propulsion systems, which are based on V. This paper investigates the design of sparse apertures both inside and outside the Earth's gravity field.

  12. Dynamic Aperture Measurements at the Advanced Light Source

    International Nuclear Information System (INIS)

    Decking, W.; Robin, D.

    1999-01-01

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

  13. High-contrast imaging with an arbitrary aperture: active correction of aperture discontinuities

    Science.gov (United States)

    Pueyo, Laurent; Norman, Colin; Soummer, Rémi; Perrin, Marshall; N'Diaye, Mamadou; Choquet, Elodie

    2013-09-01

    We present a new method to achieve high-contrast images using segmented and/or on-axis telescopes. Our approach relies on using two sequential Deformable Mirrors to compensate for the large amplitude excursions in the telescope aperture due to secondary support structures and/or segment gaps. In this configuration the parameter landscape of Deformable Mirror Surfaces that yield high contrast Point Spread Functions is not linear, and non-linear methods are needed to find the true minimum in the optimization topology. We solve the highly non-linear Monge-Ampere equation that is the fundamental equation describing the physics of phase induced amplitude modulation. We determine the optimum configuration for our two sequential Deformable Mirror system and show that high-throughput and high contrast solutions can be achieved using realistic surface deformations that are accessible using existing technologies. We name this process Active Compensation of Aperture Discontinuities (ACAD). We show that for geometries similar to JWST, ACAD can attain at least 10-7 in contrast and an order of magnitude higher for future Extremely Large Telescopes, even when the pupil features a missing segment" . We show that the converging non-linear mappings resulting from our Deformable Mirror shapes actually damp near-field diffraction artifacts in the vicinity of the discontinuities. Thus ACAD actually lowers the chromatic ringing due to diffraction by segment gaps and strut's while not amplifying the diffraction at the aperture edges beyond the Fresnel regime and illustrate the broadband properties of ACAD in the case of the pupil configuration corresponding to the Astrophysics Focused Telescope Assets. Since details about these telescopes are not yet available to the broader astronomical community, our test case is based on a geometry mimicking the actual one, to the best of our knowledge.

  14. High-contrast imaging with an arbitrary aperture: Active compensation of aperture discontinuities

    International Nuclear Information System (INIS)

    Pueyo, Laurent; Norman, Colin

    2013-01-01

    We present a new method to achieve high-contrast images using segmented and/or on-axis telescopes. Our approach relies on using two sequential deformable mirrors (DMs) to compensate for the large amplitude excursions in the telescope aperture due to secondary support structures and/or segment gaps. In this configuration the parameter landscape of DM surfaces that yield high-contrast point-spread functions is not linear, and nonlinear methods are needed to find the true minimum in the optimization topology. We solve the highly nonlinear Monge-Ampere equation that is the fundamental equation describing the physics of phase-induced amplitude modulation. We determine the optimum configuration for our two sequential DM system and show that high-throughput and high-contrast solutions can be achieved using realistic surface deformations that are accessible using existing technologies. We name this process Active Compensation of Aperture Discontinuities (ACAD). We show that for geometries similar to the James Webb Space Telescope, ACAD can attain at least 10 –7 in contrast and an order of magnitude higher for both the future extremely large telescopes and on-axis architectures reminiscent of the Hubble Space Telescope. We show that the converging nonlinear mappings resulting from our DM shapes actually damp near-field diffraction artifacts in the vicinity of the discontinuities. Thus, ACAD actually lowers the chromatic ringing due to diffraction by segment gaps and struts while not amplifying the diffraction at the aperture edges beyond the Fresnel regime. This outer Fresnel ringing can be mitigated by properly designing the optical system. Consequently, ACAD is a true broadband solution to the problem of high-contrast imaging with segmented and/or on-axis apertures. We finally show that once the nonlinear solution is found, fine tuning with linear methods used in wavefront control can be applied to further contrast by another order of magnitude. Generally speaking, the

  15. Morphometric analysis of septal aperture of humerus

    Directory of Open Access Journals (Sweden)

    Raghavendra K, Anil kumar Reddy Y, Shirol VS, Daksha Dixit, Desai SP

    2014-04-01

    Full Text Available Introduction: Lower end of humerus shows olecranon and coronoid fossae separated by a thin bony septum, sometimes it may deficient and shows foramen which communicates both the fossae called Septal aperture, which is commonly referred as supratrochlear foramen (STF. Materials & Methods: We have studied 260 humeri (126 right side and 134 left side, measurements were taken by using vernier caliper, translucency septum was observed by keeping the lower end of humerus against the x-ray lobby. Results: A clear cut STF was observed in 19.2% bones, translucency septum was observed in 99 (91.6% humeri on the right side and 95 (93.1% humeri on the left sides respectively (Table – 1. Clinical significance: The presence of STF is always associated with the narrow medullary canal at the lower end of humerus, Supracondylar fracture of humerus is most common in paediatric age group, medullary nailing is done to treat the fractures in those cases the knowledge about the STF is very important for treating the fractures. It has been observed in x-ray of lower end of the humerus the STF is comparatively radiolucent, it is commonly seen as a type of ‘pseudolesions’ in an x-ray of the lower end of humerus and it may mistake for an osteolytic or cystic lesions. Conclusion: The present study can add data into anthropology and anatomy text books regarding STF and it gives knowledge of understanding anatomical variation of distal end of the humerus, which is significant for anthropologists, orthopaedic surgeons and radiologists in habitual clinical practice.

  16. The LASS [Larger Aperture Superconducting Solenoid] spectrometer

    International Nuclear Information System (INIS)

    Aston, D.; Awaji, N.; Barnett, B.

    1986-04-01

    LASS is the acronym for the Large Aperture Superconducting Solenoid spectrometer which is located in an rf-separated hadron beam at the Stanford Linear Accelerator Center. This spectrometer was constructed in order to perform high statistics studies of multiparticle final states produced in hadron reactions. Such reactions are frequently characterized by events having complicated topologies and/or relatively high particle multiplicity. Their detailed study requires a spectrometer which can provide good resolution in momentum and position over almost the entire solid angle subtended by the production point. In addition, good final state particle identification must be available so that separation of the many kinematically-overlapping final states can be achieved. Precise analyses of the individual reaction channels require high statistics, so that the spectrometer must be capable of high data-taking rates in order that such samples can be acquired in a reasonable running time. Finally, the spectrometer must be complemented by a sophisticated off-line analysis package which efficiently finds tracks, recognizes and fits event topologies and correctly associates the available particle identification information. This, together with complicated programs which perform specific analysis tasks such as partial wave analysis, requires a great deal of software effort allied to a very large computing capacity. This paper describes the construction and performance of the LASS spectrometer, which is an attempt to realize the features just discussed. The configuration of the spectrometer corresponds to the data-taking on K + and K - interactions in hydrogen at 11 GeV/c which took place in 1981 and 1982. This constitutes a major upgrade of the configuration used to acquire lower statistics data on 11 GeV/c K - p interactions during 1977 and 1978, which is also described briefly

  17. The LASS (Larger Aperture Superconducting Solenoid) spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Aston, D.; Awaji, N.; Barnett, B.; Bienz, T.; Bierce, R.; Bird, F.; Bird, L.; Blockus, D.; Carnegie, R.K.; Chien, C.Y.

    1986-04-01

    LASS is the acronym for the Large Aperture Superconducting Solenoid spectrometer which is located in an rf-separated hadron beam at the Stanford Linear Accelerator Center. This spectrometer was constructed in order to perform high statistics studies of multiparticle final states produced in hadron reactions. Such reactions are frequently characterized by events having complicated topologies and/or relatively high particle multiplicity. Their detailed study requires a spectrometer which can provide good resolution in momentum and position over almost the entire solid angle subtended by the production point. In addition, good final state particle identification must be available so that separation of the many kinematically-overlapping final states can be achieved. Precise analyses of the individual reaction channels require high statistics, so that the spectrometer must be capable of high data-taking rates in order that such samples can be acquired in a reasonable running time. Finally, the spectrometer must be complemented by a sophisticated off-line analysis package which efficiently finds tracks, recognizes and fits event topologies and correctly associates the available particle identification information. This, together with complicated programs which perform specific analysis tasks such as partial wave analysis, requires a great deal of software effort allied to a very large computing capacity. This paper describes the construction and performance of the LASS spectrometer, which is an attempt to realize the features just discussed. The configuration of the spectrometer corresponds to the data-taking on K and K interactions in hydrogen at 11 GeV/c which took place in 1981 and 1982. This constitutes a major upgrade of the configuration used to acquire lower statistics data on 11 GeV/c K p interactions during 1977 and 1978, which is also described briefly.

  18. The development of deep learning in synthetic aperture radar imagery

    CSIR Research Space (South Africa)

    Schwegmann, Colin P

    2017-05-01

    Full Text Available sensing techniques but comes at the price of additional complexities. To adequately cope with these, researchers have begun to employ advanced machine learning techniques known as deep learning to Synthetic Aperture Radar data. Deep learning represents...

  19. Ships as salient objects in synthetic aperture radar imaginary

    CSIR Research Space (South Africa)

    Schwegmann, Colin P

    2016-07-01

    Full Text Available perspective on ships in Synthetic Aperture Radar imagery by viewing them as visually salient objects. The paper introduces common methods of ship object extraction and demonstrates how salient object mapping can improve the accuracy of extracted ships...

  20. Stellwagen Bank National Marine Sanctuary - Synthetic Aperture Radar (SAR) Imagery

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This geodatabase contains Synthetic Aperture Radar images (SAR), which consist of a fine resolution (12.5-50m), two-dimensional radar backscatter map of the...

  1. CLPX-Satellite: Radarsat Synthetic Aperture Radar Imagery

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set consists of time-series spaceborne Synthetic Aperture Radar (SAR) imagery of the three Cold Land Processes Field Experiment (CLPX) Meso-cell Study...

  2. Foamed Antenna Support for Very Large Apertures, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Large aperture antennas are of interest to NASA for applications in establishing high-speed communication relays for interplanetary missions. Design goals include 20...

  3. Bistatic Synthetic Aperture Radar with Application to Moving Target Detection

    National Research Council Canada - National Science Library

    Whitewood, A. P; Mueller, B. R; Griffiths, H. D; Baker, C. J

    2005-01-01

    .... This paper describes a bistatic radar system which uses the combination of a spaceborne synthetic aperture radar transmitter on board the European Space Agency's Envisat satellite, and a low-cost...

  4. Multiple Aperture Radiation Therapy (MART) for Breast Cancer

    National Research Council Canada - National Science Library

    Li, Tianfang

    2006-01-01

    .... In this USAMRMC-supported project, we have developed a multiple-aperture radiation therapy (MART) procedure dedicated to breast irradiation, which combines the planning simplicity of the conventional OFT with the superior dose distribution of IMRT methods...

  5. Ultra-Lightweight Large Aperture Support Structures, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Ultra-lightweight membranes may prove to be very attractive for large aperture systems, but their value will be fully realized only if they are mated with equally...

  6. Foamed Antenna Support for Very Large Apertures, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The proposed Phase I program will demonstrate the feasibility of the in-space production of large aperture antenna structures. The use of a novel open cell foam,...

  7. CLPX-Airborne: Airborne Synthetic Aperture Radar (AIRSAR) Imagery

    Data.gov (United States)

    National Aeronautics and Space Administration — Airborne Synthetic Aperture Radar (AIRSAR) is a side-looking imaging radar that is able to collect data irrespective of daylight or cloud cover. The AIRSAR...

  8. Role of Sucrose in Emerging Mechanisms of Stomatal Aperture Regulation.

    Energy Technology Data Exchange (ETDEWEB)

    Outlaw, W. H.

    2000-09-15

    Focused on the second of 2 hypotheses that were proposed for testing that transpiration rate determines the extent to which suc accumulates in the GC wall providing a mechanism for regulating stomatal aperture size.

  9. Application of Linear Prediction Technique to Passive Synthetic Aperture Processing

    Directory of Open Access Journals (Sweden)

    Hou Yunshan

    2010-01-01

    Full Text Available A method for the synthesis of an aperture with improved angular resolution and array gain is described. The proposed method explores the merit of linear prediction technique to improve the performance of conventional ETAM (extended towed array measurements method. Previous efforts to improve the ETAM method generally focused on how to get more accurate estimation of overlap correlator, with an aim to reduce bearing estimation variance. In this paper, however, we discuss how to further improve the angular resolution when the effective synthetic aperture is rather limited. We resort to linear prediction technique to further extend the synthetic aperture obtained by ETAM, which produces a much longer virtual aperture. Results from simulations and lake experiment showed that the proposed LP-ETAM method achieved better angular resolution than ETAM.

  10. Application of Linear Prediction Technique to Passive Synthetic Aperture Processing

    Science.gov (United States)

    Hou, Yunshan; Huang, Jianguo; Jiang, Min; Jin, Yong

    2010-12-01

    A method for the synthesis of an aperture with improved angular resolution and array gain is described. The proposed method explores the merit of linear prediction technique to improve the performance of conventional ETAM (extended towed array measurements) method. Previous efforts to improve the ETAM method generally focused on how to get more accurate estimation of overlap correlator, with an aim to reduce bearing estimation variance. In this paper, however, we discuss how to further improve the angular resolution when the effective synthetic aperture is rather limited. We resort to linear prediction technique to further extend the synthetic aperture obtained by ETAM, which produces a much longer virtual aperture. Results from simulations and lake experiment showed that the proposed LP-ETAM method achieved better angular resolution than ETAM.

  11. Beam Combination for Sparse Aperture Telescopes, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The Stellar Imager, an ultraviolet, sparse-aperture telescope, was one of the fifteen Vision Missions chosen for a study completed last year. Stellar Imager will...

  12. Autofocus algorithm for synthetic aperture radar imaging with large curvilinear apertures

    Science.gov (United States)

    Bleszynski, E.; Bleszynski, M.; Jaroszewicz, T.

    2013-05-01

    An approach to autofocusing for large curved synthetic aperture radar (SAR) apertures is presented. Its essential feature is that phase corrections are being extracted not directly from SAR images, but rather from reconstructed SAR phase-history data representing windowed patches of the scene, of sizes sufficiently small to allow the linearization of the forward- and back-projection formulae. The algorithm processes data associated with each patch independently and in two steps. The first step employs a phase-gradient-type method in which phase correction compensating (possibly rapid) trajectory perturbations are estimated from the reconstructed phase history for the dominant scattering point on the patch. The second step uses phase-gradient-corrected data and extracts the absolute phase value, removing in this way phase ambiguities and reducing possible imperfections of the first stage, and providing the distances between the sensor and the scattering point with accuracy comparable to the wavelength. The features of the proposed autofocusing method are illustrated in its applications to intentionally corrupted small-scene 2006 Gotcha data. The examples include the extraction of absolute phases (ranges) for selected prominent point targets. They are then used to focus the scene and determine relative target-target distances.

  13. Transmission of high-power electron beams through small apertures

    International Nuclear Information System (INIS)

    Tschalär, C.; Alarcon, R.; Balascuta, S.; Benson, S.V.; Bertozzi, W.; Boyce, J.R.; Cowan, R.; Douglas, D.; Evtushenko, P.; Fisher, P.; Ihloff, E.; Kalantarians, N.; Kelleher, A.; Legg, R.; Milner, R.G.; Neil, G.R.; Ou, L.; Schmookler, B.; Tennant, C.; Williams, G.P.

    2013-01-01

    Tests were performed to pass a 100 MeV, 430 kWatt c.w. electron beam from the energy-recovery linac at the Jefferson Laboratory's FEL facility through a set of small apertures in a 127 mm long aluminum block. Beam transmission losses of 3 p.p.m. through a 2 mm diameter aperture were maintained during a 7 h continuous run

  14. Phase Centers of Subapertures in a Tapered Aperture Array.

    Energy Technology Data Exchange (ETDEWEB)

    Doerry, Armin W. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Bickel, Douglas L. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)

    2015-11-01

    Antenna apertures that are tapered for sidelobe control can also be parsed into subapertures for Direction of Arrival (DOA) measurements. However, the aperture tapering complicates phase center location for the subapertures, knowledge of which is critical for proper DOA calculation. In addition, tapering affects subaperture gains, making gain dependent on subaperture position. Techniques are presented to calculate subaperture phase center locations, and algorithms are given for equalizing subapertures’ gains. Sidelobe characteristics and mitigation are also discussed.

  15. Micro-CT image calibration to improve fracture aperture measurement

    Directory of Open Access Journals (Sweden)

    Hamed Lamei Ramandi

    2016-11-01

    Full Text Available A novel technique for the accurate measurement and adjustment of fracture apertures in digital images of fractured media is presented. We utilize X-ray micro-computed tomography to image a highly fractured coal sample and collect high-resolution scanning electron microscope (SEM images from the samples surface to facilitate segmentation of coal fractures. The gray-scale micro-CT values at the mid-point of fractures are obtained and correlated to aperture sizes measured with the higher resolution SEM data. Afterwards, the micro-CT images are upsampled to enable assignment of aperture sizes smaller than the image resolution. We initially segment the coal image, upsample the segmented image, and then re-calibrate the fracture aperture sizes. The final calibrated segmented image contains the fracture network acquired from the micro-CT data with precise aperture sizes assigned based on the high-resolution SEM data. To illustrate the importance of accurate aperture measurement, two coal subsets are tested. The permeabilities before and after applying the calibration method are measured. The results show a significant change in numerical permeabilities after applying the calibration method. This indicates that a large amount of information is potentially omitted when utilizing standard image segmentation tools to segment fractured media.

  16. Programmable Aperture with MEMS Microshutter Arrays

    Science.gov (United States)

    Moseley, Samuel; Li, Mary; Kutyrev, Alexander; Kletetschka, Gunther; Fettig, Rainer

    2011-01-01

    A microshutter array (MSA) has been developed for use as an aperture array for multi-object selections in James Webb Space Telescope (JWST) technology. Light shields, molybdenum nitride (MoN) coating on shutters, and aluminum/aluminum oxide coatings on interior walls are put on each shutter for light leak prevention, and to enhance optical contrast. Individual shutters are patterned with a torsion flexure that permits shutters to open 90 deg. with a minimized mechanical stress concentration. The shutters are actuated magnetically, latched, and addressed electrostatically. Also, micromechanical features are tailored onto individual shutters to prevent stiction. An individual shutter consists of a torsion hinge, a shutter blade, a front electrode that is coated on the shutter blade, a backside electrode that is coated on the interior walls, and a magnetic cobalt-iron coating. The magnetic coating is patterned into stripes on microshutters so that shutters can respond to an external magnetic field for the magnetic actuation. A set of column electrodes is placed on top of shutters, and a set of row electrodes on sidewalls is underneath the shutters so that they can be electrostatically latched open. A linear permanent magnet is aligned with the shutter rows and is positioned above a flipped upside-down array, and sweeps across the array in a direction parallel to shutter columns. As the magnet sweeps across the array, sequential rows of shutters are rotated from their natural horizontal orientation to a vertical open position, where they approach vertical electrodes on the sidewalls. When the electrodes are biased with a sufficient electrostatic force to overcome the mechanical restoring force of torsion bars, shutters remain latched to vertical electrodes in their open state. When the bias is removed, or is insufficient, the shutters return to their horizontal, closed positions. To release a shutter, both the electrode on the shutter and the one on the back wall where

  17. Wind energy applications of synthetic aperture radar

    Energy Technology Data Exchange (ETDEWEB)

    Bruun Christiansen, M.

    2006-11-15

    Synthetic aperture radars (SAR), mounted on satellites or aircraft, have proven useful for ocean wind mapping. Wind speeds at the height 10 m may be retrieved from measurements of radar backscatter using empirical model functions. The resulting wind fields are valuable in offshore wind energy planning as a supplement to on site measurements, which are costly and sparse, and model wind fields, which are not fully validated. Two applications of SAR measurements in offshore wind energy planning are addressed here: the study of wind farm wake effects and the potential of using SAR winds in offshore wind resource assessment. Firstly, wind wakes behind two large offshore wind farms in Denmark Horns Rev and Nysted are identified. A region of reduced wind speed is found downstream of both wind farms from the SAR wind fields. The wake extent and magnitude depends on the wind speed, the atmospheric stability, and the fraction of turbines operating. Wind farm wake effects are detected up to 20 km downwind of the last turbine. This distance is longer than predicted by state-of-the art wake models. Wake losses are typically 10-20% near the wind farms. Secondly, the potential of using SAR wind maps in offshore wind resource assessment is investigated. The resource assessment is made through Weibull fitting to frequency observations of wind speed and requires at least 100 satellite observations per year for a given site of interest. Predictions of the energy density are very sensitive to the wind speed and the highest possible accuracy on SAR wind retrievals is therefore sought. A 1.1 m s{sup -1} deviation on the mean wind speed is found through comparison with mast measurements at Horns Rev. The accuracy on mean wind speeds and energy densities found from satellite measurements varies with different empirical model functions. Additional uncertainties are introduced by the infrequent satellite sampling at fixed times of the day. The accuracy on satellite based wind resource

  18. Feature-enhanced synthetic aperture radar imaging

    Science.gov (United States)

    Cetin, Mujdat

    Remotely sensed images have already attained an important role in a wide spectrum of tasks ranging from weather forecasting to battlefield reconnaissance. One of the most promising remote sensing technologies is the imaging radar, known as synthetic aperture radar (SAR). SAR overcomes the nighttime limitations of optical cameras, and the cloud-cover limitations of both optical and infrared imagers. In current systems, techniques such as the polar format algorithm are used to form images from the collected SAR data. These images are then interpreted by human observers. However, the anticipated high data rates and the time critical nature of emerging SAR tasks motivate the use of automated processing or decision-making techniques in information extraction from the reconstructed images. The success of such automated decision-making (e.g. object recognition) depends on how well SAR images exhibit certain features of the underlying scene. Unfortunately, current SAR image formation techniques have no explicit means to highlight features useful for automatic interpretation. Furthermore, these techniques are usually not robust to reduced quality or quantity of data. We have developed a mathematical foundation and associated algorithms for feature-enhanced SAR imaging to address such challenges. Our framework is based on a regularized reconstruction of the scattering field which combines a tomographic model of the SAR observation process with prior information regarding the nature of the features of interest. We demonstrate the inclusion of prior information through a variety of non-quadratic potential functions. Efficient and robust numerical solution of the optimization problems posed in our framework is achieved through novel extensions of half-quadratic regularization methods to the complex-valued SAR problem. We have established a methodology for quantitative evaluation of a SAR image formation technique based on recognition-oriented features. Through qualitative and

  19. Adaptive coded aperture imaging: progress and potential future applications

    Science.gov (United States)

    Gottesman, Stephen R.; Isser, Abraham; Gigioli, George W., Jr.

    2011-09-01

    Interest in Adaptive Coded Aperture Imaging (ACAI) continues to grow as the optical and systems engineering community becomes increasingly aware of ACAI's potential benefits in the design and performance of both imaging and non-imaging systems , such as good angular resolution (IFOV), wide distortion-free field of view (FOV), excellent image quality, and light weight construct. In this presentation we first review the accomplishments made over the past five years, then expand on previously published work to show how replacement of conventional imaging optics with coded apertures can lead to a reduction in system size and weight. We also present a trade space analysis of key design parameters of coded apertures and review potential applications as replacement for traditional imaging optics. Results will be presented, based on last year's work of our investigation into the trade space of IFOV, resolution, effective focal length, and wavelength of incident radiation for coded aperture architectures. Finally we discuss the potential application of coded apertures for replacing objective lenses of night vision goggles (NVGs).

  20. Code aperture optimization for spectrally agile compressive imaging.

    Science.gov (United States)

    Arguello, Henry; Arce, Gonzalo R

    2011-11-01

    Coded aperture snapshot spectral imaging (CASSI) provides a mechanism for capturing a 3D spectral cube with a single shot 2D measurement. In many applications selective spectral imaging is sought since relevant information often lies within a subset of spectral bands. Capturing and reconstructing all the spectral bands in the observed image cube, to then throw away a large portion of this data, is inefficient. To this end, this paper extends the concept of CASSI to a system admitting multiple shot measurements, which leads not only to higher quality of reconstruction but also to spectrally selective imaging when the sequence of code aperture patterns is optimized. The aperture code optimization problem is shown to be analogous to the optimization of a constrained multichannel filter bank. The optimal code apertures allow the decomposition of the CASSI measurement into several subsets, each having information from only a few selected spectral bands. The rich theory of compressive sensing is used to effectively reconstruct the spectral bands of interest from the measurements. A number of simulations are developed to illustrate the spectral imaging characteristics attained by optimal aperture codes.

  1. Aperture referral in dioptric systems with stigmatic elements

    Directory of Open Access Journals (Sweden)

    W. F. Harris

    2012-12-01

    Full Text Available A previous paper develops the general theory of aperture referral in linear optics and shows how several ostensibly distinct concepts, including the blur patch on the retina, the effective corneal patch, the projective field and the field of view, are now unified as particular applications of the general theory.  The theory allows for astigmatism and heterocentricity.  Symplecticity and the generality of the approach, however, make it difficult to gain insight and mean that the material is not accessible to readers unfamiliar with matrices and linear algebra. The purpose of this paper is to examine whatis, perhaps, the most important special case, that in which astigmatism is ignored.  Symplecticity and, hence, the mathematics become greatly simplified. The mathematics reduces largely to elementary vector algebra and, in some places, simple scalar algebra and yet retains the mathematical form of the general approach.  As a result the paper allows insight into and provides a stepping stone to the general theory.  Under referral an aperture under-goes simple scalar magnification and transverse translation.  The paper pays particular attention to referral to transverse planes in the neighbourhood of a focal point where the magnification may be positive, zero or negative.  Circular apertures are treated as special cases of elliptical apertures and the meaning of referred apertures of negative radius is explained briefly. (S Afr Optom 2012 71(1 3-11

  2. Analysis of the covariance function and aperture averaged fluctuations of irradiance to calculate Cn2

    Science.gov (United States)

    Cauble, Galen D.; Wayne, David T.

    2017-09-01

    The growth of optical communication has created a need to correctly characterize the atmospheric channel. Atmospheric turbulence along a given channel can drastically affect optical communication signal quality. One means of characterizing atmospheric turbulence is through measurement of the refractive index structure parameter, Cn2. When calculating Cn2 from the scintillation index, σΙ2,the point aperture scintillation index is required. Direct measurement of the point aperture scintillation index is difficult at long ranges due to the light collecting abilities of small apertures. When aperture size is increased past the atmospheric correlation width, aperture averaging decreases the scintillation index below that of the point aperture scintillation index. While the aperture averaging factor can be calculated from theory, it does not often agree with experimental results. Direct measurement of the aperture averaging factor via the pupil plane irradiance covariance function allows conversion from the aperture averaged scintillation index to the point aperture scintillation index. Using a finite aperture, camera, and detector, the aperture averaged scintillation index and aperture averaging factor are measured in parallel and the point aperture scintillation index is calculated. A new instrument built by SSC Pacific was used to collect scintillation data at the Townes Institute Science and Technology Experimentation Facility (TISTEF). This new instrument's data was then compared to BLS900 data. The results show that direct measurement of the aperture averaging factor is achievable using a camera and matches well with groundtruth instrumentation.

  3. The roles of frequency and aperture in linac accelerator design

    International Nuclear Information System (INIS)

    Farkas, Z.D.

    1988-09-01

    Expressions for accelerating structure parameters, including those that determine the peak and average power inputs required to attain a given gradient, are given as functions of aperture to wavelength ratio for a 2π/3 mode disk-loaded guide. The value of the wavelength to aperture ratio varies over a large range, corresponding to group velocities that vary from nearly zero to nearly the speed of light. The parameters exhibit proper asymptotic behavior in both limits. These parameters are benchmark values to which parameters for other modes and for other structure shapes can be compared. For example, it will be shown that the increased peak surface field to accelerating field ratio due to increased aperture to wavelength ratio can be reduced by shaping the iris profile. Structure shapes are varied not only to show possible improvement of structure parameters, but also to improve ease of mechanical fabrication and temperature control. 4 refs., 8 figs., 1 tab

  4. Permeability and dispersivity of variable-aperture fracture systems

    International Nuclear Information System (INIS)

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

    1990-01-01

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

  5. Central obscuration effects on optical synthetic aperture imaging

    Science.gov (United States)

    Wang, Xue-wen; Luo, Xiao; Zheng, Li-gong; Zhang, Xue-jun

    2014-02-01

    Due to the central obscuration problem exists in most optical synthetic aperture systems, it is necessary to analyze its effects on their image performance. Based on the incoherent diffraction limited imaging theory, a Golay-3 type synthetic aperture system was used to study the central obscuration effects on the point spread function (PSF) and the modulation transfer function (MTF). It was found that the central obscuration does not affect the width of the central peak of the PSF and the cutoff spatial frequency of the MTF, but attenuate the first sidelobe of the PSF and the midfrequency of the MTF. The imaging simulation of a Golay-3 type synthetic aperture system with central obscuration proved this conclusion. At last, a Wiener Filter restoration algorithm was used to restore the image of this system, the images were obviously better.

  6. A twin aperture resistive quadrupole for the LHC

    CERN Document Server

    Clark, G S; de Rijk, G; Racine, M

    2000-01-01

    The European Organization for Nuclear Research (CERN) is constructing the Large Hadron Collider (LHC). The LHC's cleaning insertions require 48 twin aperture resistive quadrupoles. These 3.1 m long magnets have a gradient of 35 T/m for an inscribed circle of 46 mm diameter and an aperture separation distance of 224 mm. This magnet project is part of the Canadian contribution to the LHC. A prototype magnet was delivered in May 1998 and measured at CERN. Design changes were made based on the results. Due to the small apertures and the complicated geometry, the mechanical precision of the laminations and stacks is the main issue in the production of these quadrupoles. Series production will start in October 1999. The design and the measurement results are described in this paper. (1 refs).

  7. X-ray lenses with large aperture; Roentgenlinsen mit grosser Apertur

    Energy Technology Data Exchange (ETDEWEB)

    Simon, Markus

    2010-07-01

    Up to now, most X-ray imaging setups are based on absorption contrast imaging. There is a demand for focused X-rays in many X-ray analysis applications, either to increase the resolution of an imaging system, or, to reduce the time effort of an experiment through higher photon flux. For photon energies higher than 15 keV refractive X-ray optics are more efficient in comparison to non-refractive X-ray optics. The aim of this work was to develop X-ray lenses with large apertures and high transparency. By increasing the number of refracting surfaces while removing unnecessary lens material such lenses have been developed. Utilizing this approach the overall beam deflection angle is large with respect to the lens material it propagates through and so the transparency of the lens is increased. Within this work, X-ray lenses consisting of several thousands of prisms with an edge length in the range of micrometers have been developed and fabricated by deep X-ray lithography. Deep X-ray lithography enables high precision microstrucures with smooth sidewalls and large aspect ratios. The aperture of high-transparency X-ray lenses made this way is greater than 1 mm. They are suitable for photon energies in the range of 8 keV to 24 keV and offer a focal width of smaller than 10 {mu}m at a transparency of around 40%. Furthermore, rolled X-ray lenses have been developed, that are made out of a microstructured polyimide film, which is cut according to the requirements regarding focal length and photon energy. The microstructured film is fabricated by molding, using an anisotropically etched silicon wafer as molding tool. Its mean roughness is in the range of nanometers. The film features prismatic structures, its surface topology is similar to an asparagus field. The measured diameter of the point focus was 18 {mu}m to 31 {mu}m, the calculated opticla efficiency was 37%. Future work will concentrate on increasing the aspect ratio of Prism Lenses and on increasing the rolling

  8. Aperture determination of RHIC92 from randomly generated initial coordinates

    International Nuclear Information System (INIS)

    Dell, G.F.

    1992-01-01

    Results obtained by tracking 100 particles for 1,000 turns when initial coordinates are selected randomly, with the requirement that the total emittance be constant, are compared to results from 1,000-turn and 10 6 -turn runs when initial coordinates satisfy ε x (i) = ε y (i) and X i ' = Y i ' = 0. For studies of ten distributions of magnetic field errors, the 100-particle results given apertures equivalent to those from 10 6 -turn runs, have an aperture distribution of considerably less width, and yet require only one tenth the computer time

  9. Three dimensional fracture aperture and porosity distribution using computerized tomography

    Science.gov (United States)

    Wenning, Q.; Madonna, C.; Joss, L.; Pini, R.

    2017-12-01

    A wide range of geologic processes and geo-engineered applications are governed by coupled hydromechanical properties in the subsurface. In geothermal energy reservoirs, quantifying the rate of heat transfer is directly linked with the transport properties of fractures, underscoring the importance of fracture aperture characterization for achieving optimal heat production. In this context, coupled core-flooding experiments with non-invasive imaging techniques (e.g., X-Ray Computed Tomography - X-Ray CT) provide a powerful method to make observations of these properties under representative geologic conditions. This study focuses on quantifying fracture aperture distribution in a fractured westerly granite core by using a recently developed calibration-free method [Huo et al., 2016]. Porosity is also estimated with the X-ray saturation technique using helium and krypton gases as saturating fluids, chosen for their high transmissibility and high CT contrast [e.g., Vega et al., 2014]. The westerly granite sample (diameter: 5 cm, length: 10 cm) with a single through-going rough-walled fracture was mounted in a high-pressure aluminum core-holder and placed inside a medical CT scanner for imaging. During scanning the pore fluid pressure was undrained and constant, and the confining pressure was regulated to have the desired effective pressure (0.5, 5, 7 and 10 MPa) under loading and unloading conditions. 3D reconstructions of the sample have been prepared in terms of fracture aperture and porosity at a maximum resolution of (0.24×0.24×1) mm3. Fracture aperture maps obtained independently using helium and krypton for the whole core depict a similar heterogeneous aperture field, which is also dependent on confining pressure. Estimates of the average hydraulic aperture from CT scans are in quantitative agreement with results from fluid flow experiments. However, the latter lack of the level of observational detail achieved through imaging, which further evidence the

  10. Synthetic aperture radar processing with polar formatted subapertures

    Science.gov (United States)

    Doerry, Armin W.

    Synthetic Aperture Radar (SAR) uses the motion of a small real antenna to synthesize a larger aperture, and thereby achieve very fine azimuth resolution. Efficient SAR image formation requires modelling the radar echo and compensating (focusing) the delay and phase for various positions in the target scene. Polar-Format processing is one successful algorithm developed to process large scenes at fine resolutions, but is still limited, especially at resolutions near a wavelength. This paper shows how using tiers of subapertures can overcome the limitations of Polar-Format processing and increase the focused scene size substantially while using only efficient vector multiplies and Fast Fourier Transforms.

  11. Metrology measurements for large-aperture VPH gratings

    Science.gov (United States)

    Zheng, Jessica R.; Gers, Luke; Heijmans, Jeroen

    2013-09-01

    The High Efficiency and Resolution Multi Element Spectrograph (HERMES) for the Australian Astronomical Observatory (AAO) uses four large aperture, high angle of incidence volume phase holographic gratings (VPHG) for high resolution `Galactic archaeology' spectroscopy. The large clear aperture, the high diffraction efficiency, the line frequency homogeneity, and mosaic alignment made manufacturing and testing challenging. We developed new metrology systems at the AAO to verify the performance of these VPH gratings. The measured diffraction efficiencies and line frequency of the VPH gratings received so far meet the vendor's provided data. The wavefront quality for the Blue VPH grating is good but the Green and Red VPH gratings need to be post polishing.

  12. Synthetic Aperture Sequential Beamformation applied to medical imaging

    DEFF Research Database (Denmark)

    Hemmsen, Martin Christian; Hansen, Jens Munk; Jensen, Jørgen Arendt

    2012-01-01

    Synthetic Aperture Sequential Beamforming (SASB) is applied to medical ultrasound imaging using a multi element convex array transducer. The main motivation for SASB is to apply synthetic aperture techniques without the need for storing RF-data for a number of elements and hereby devise a system...... with a reduced system complexity. Using a 192 element, 3.5 MHz, λ-pitch transducer, it is demonstrated using tissue-phantom and wire-phantom measurements, how the speckle size and the detail resolution is improved compared to conventional imaging....

  13. Analytical estimation of the dynamic apertures of circular accelerators

    International Nuclear Information System (INIS)

    Gao, J.

    2000-02-01

    By considering delta function sextupole, octupole, and deca-pole perturbations and using difference action-angle variable equations, we find some useful analytical formulae for the estimation of the dynamic apertures of circular accelerators due to single sextupole, single octupole, single deca-pole (single 2 m pole in general). Their combined effects are derived based on the Chirikov criterion of the onset of stochastic motions. Comparisons with numerical simulations are made, and the agreement is quite satisfactory. These formulae have been applied to determine the beam-beam limited dynamic aperture in a circular collider. (author)

  14. Comparison of PSF maxima and minima of multiple annuli coded aperture (MACA) and complementary multiple annuli coded aperture (CMACA) systems

    International Nuclear Information System (INIS)

    Ratnam, Challa; Rao, Vadlamudi Lakshmana; Goud, Sivagouni Lachaa

    2006-01-01

    In the present paper, and a series of papers to follow, the Fourier analytical properties of multiple annuli coded aperture (MACA) and complementary multiple annuli coded aperture (CMACA) systems are investigated. First, the transmission function for MACA and CMACA is derived using Fourier methods and, based on the Fresnel-Kirchoff diffraction theory, the formulae for the point spread function are formulated. The PSF maxima and minima are calculated for both the MACA and CMACA systems. The dependence of these properties on the number of zones is studied and reported in this paper

  15. Comparison of PSF maxima and minima of multiple annuli coded aperture (MACA) and complementary multiple annuli coded aperture (CMACA) systems

    Science.gov (United States)

    Ratnam, Challa; Lakshmana Rao, Vadlamudi; Lachaa Goud, Sivagouni

    2006-10-01

    In the present paper, and a series of papers to follow, the Fourier analytical properties of multiple annuli coded aperture (MACA) and complementary multiple annuli coded aperture (CMACA) systems are investigated. First, the transmission function for MACA and CMACA is derived using Fourier methods and, based on the Fresnel-Kirchoff diffraction theory, the formulae for the point spread function are formulated. The PSF maxima and minima are calculated for both the MACA and CMACA systems. The dependence of these properties on the number of zones is studied and reported in this paper.

  16. Comparison of PSF maxima and minima of multiple annuli coded aperture (MACA) and complementary multiple annuli coded aperture (CMACA) systems

    Energy Technology Data Exchange (ETDEWEB)

    Ratnam, Challa [Physics Department, New Science College, Ameerpet, Hyderabad (India); Rao, Vadlamudi Lakshmana [Physics Department, New Science College, Ameerpet, Hyderabad (India); Goud, Sivagouni Lachaa [Department of Physics, Osmania University, Hyderabad (India)

    2006-10-07

    In the present paper, and a series of papers to follow, the Fourier analytical properties of multiple annuli coded aperture (MACA) and complementary multiple annuli coded aperture (CMACA) systems are investigated. First, the transmission function for MACA and CMACA is derived using Fourier methods and, based on the Fresnel-Kirchoff diffraction theory, the formulae for the point spread function are formulated. The PSF maxima and minima are calculated for both the MACA and CMACA systems. The dependence of these properties on the number of zones is studied and reported in this paper.

  17. Synthetic Aperture Sequential Beamforming using Spatial Matched Filtering

    DEFF Research Database (Denmark)

    Schou, Mikkel; di Ianni, Tommaso; Bouzari, Hamed

    2017-01-01

    Synthetic Aperture Sequential Beamforming (SASB) has shown to achieve a good resolution and high penetration depth. The low complexity at the transducer level of the beamformer makes it ideal for use with a handheld device. SASB with a low F# (≤ 0.5) can achieve even better resolution at the cost...

  18. Velocity estimation using synthetic aperture imaging [blood flow

    DEFF Research Database (Denmark)

    Nikolov, Svetoslav; Jensen, Jørgen Arendt

    2001-01-01

    Presented an approach for synthetic aperture blood flow ultrasound imaging. Estimates with a low bias and standard deviation can be obtained with as few as eight emissions. The performance of the new estimator is verified using both simulations and measurements. The results demonstrate that a fully...

  19. Aperture Valve for the Mars Organic Molecule Analyzer (MOMA)

    Science.gov (United States)

    Hakun, Claef F.; Engler, Charles D.; Barber, Willie E.; Canham, John S.

    2014-01-01

    NASA's participation in the multi-nation ExoMars 2018 Rover mission includes a critical astrobiology Mass Spectrometer Instrument on the Rover called the Mars Organic Molecule Analyzer (MOMA). The Aperture Valve is a critical electromechanical valve used by the Mass Spectrometer to facilitate the transfer of ions from Martian soil to the Mass Spectrometer for analysis. The MOMA Aperture Valve development program will be discussed in terms of the Initial valve design and subsequent improvements that resulted from prototype testing. The Initial Aperture Valve concept seemed promising, based on calculations and perceived merits. However, performance results of this design were disappointing, due to delamination of TiN and DLC coatings applied to the Titanium base metals, causing debris from the coatings to seize the valve. While peer reviews and design trade studies are important forums to vet a concept design, results from testing should not be underestimated.Despite the lack of development progress to meet requirements, valuable information from weakness discovered in the Initial Valve design was used to develop a second, more robust Aperture valve. Based on a check-ball design, the ETU flight valve design resulted in significantly less surface area to create the seal. Moreover, PVD coatings were eliminated in favor of hardened, nonmagnetic corrosion resistant alloys. Test results were impressive, with the valve achieving five orders of magnitude better sealing leak rate over end of life requirements. Cycle life was equally impressive, achieving 280,000 cycles without failure.

  20. Polarimetric synthetic aperture radar data and the complex Wishart distribution

    DEFF Research Database (Denmark)

    Nielsen, Allan Aasbjerg; Conradsen, Knut; Skriver, Henning

    2003-01-01

    When working with multi-look fully polarimetric synthetic aperture radar (SAR) data an appropriate way of representing the backscattered signal consists of the so-called covariance matrix. For each pixel this is a 3 by 3 Hermitian, positive definite matrix which follows a complex Wishart distribu...

  1. Status of the TAN aperture model in MAD-X

    CERN Document Server

    Fitterer, M; Chemli, S; De Maria, R; Giovannozzi, M

    2014-01-01

    In this paper we describe the update of the existing TAN layout and aperture model in the MAD-X sequence for IR1 and IR5. The updated model introduces new markers indicating the longitudinal layering of the absorber and the geometry of the Y-chamber.

  2. Synthetic aperture ultrasound Fourier beamformation using virtual sources

    DEFF Research Database (Denmark)

    Moghimirad, Elahe; Villagómez Hoyos, Carlos Armando; Mahloojifar, Ali

    2016-01-01

    An efficient Fourier beamformation algorithm is presented for multistatic synthetic aperture ultrasound imaging using virtual sources (FBV). The concept is based on the frequency domain wavenumber algorithm from radar and sonar and is extended to a multi-element transmit/receive configuration using...

  3. Fourier beamformation of multistatic synthetic aperture ultrasound imaging

    DEFF Research Database (Denmark)

    Moghimirad, Elahe; Villagómez Hoyos, Carlos Armando; Mahloojifar, Ali

    2015-01-01

    A new Fourier beamformation (FB) algorithm is presented for multistatic synthetic aperture ultrasound imaging. It can reduce the number of computations by a factor of 20 compared to conventional Delay-and-Sum (DAS) beamformers. The concept is based on the wavenumber algorithm from radar and sonar...

  4. Synthetic Aperture Sequential Beamforming implemented on multi-core platforms

    DEFF Research Database (Denmark)

    Kjeldsen, Thomas; Lassen, Lee; Hemmsen, Martin Christian

    2014-01-01

    This paper compares several computational ap- proaches to Synthetic Aperture Sequential Beamforming (SASB) targeting consumer level parallel processors such as multi-core CPUs and GPUs. The proposed implementations demonstrate that ultrasound imaging using SASB can be executed in real- time with ...

  5. Comparison between different encoding schemes for synthetic aperture imaging

    DEFF Research Database (Denmark)

    Nikolov, Svetoslav; Jensen, Jørgen Arendt

    2002-01-01

    Synthetic transmit aperture ultrasound (STAU) imaging can create images with as low as 2 emissions, making it attractive for 3D real-time imaging. Two are the major problems to be solved: (1) complexity of the hardware involved, and (2) poor image quality due to low signal to noise ratio (SNR). W...

  6. Large aperture components for solid state laser fusion systems

    International Nuclear Information System (INIS)

    Simmons, W.W.

    1978-01-01

    Solid state lasers for fusion experiments must reliably deliver maximum power to small (approximately .5 mm) targets from stand-off focal distances of 1 m or more. This requirement places stringent limits upon the optical quality, resistance to damage, and overall performance of the several major components--amplifiers, Faraday isolators, spatial filters--in each amplifier train. Component development centers about achieving (1) highest functional material figure of merit, (2) best optical quality, and (3) maximum resistance to optical damage. Specific examples of the performance of large aperture components will be presented within the context of the Argus and Shiva laser systems, which are presently operational at Lawrence Livermore Laboratory. Shiva comprises twenty amplifiers, each of 20 cm output clear aperture. Terawatt beams from these amplifiers are focused through two opposed, nested clusters of f/6 lenses onto such targets. Design requirements upon the larger aperture Nova laser components, up to 35 cm in clear aperture, will also be discussed; these pose a significant challenge to the optical industry

  7. Thermal front propagation in variable aperture fracture–matrix system

    Indian Academy of Sciences (India)

    Keywords. Thermal front; variable aperture; rock–matrix; geothermal reservoir; numerical model, liquid dominated. 1. Introduction. Rapid commercialization in recent years has created a considerable increase in the demand for energy. This has put excessive strain on the conventional power generation units (thermal, hydro.

  8. Exploitation of distributed scatterers in synthetic aperture radar interferometry

    NARCIS (Netherlands)

    Samiei Esfahany, S.

    2017-01-01

    During the last decades, time-series interferometric synthetic aperture radar (InSAR) has emerged as a powerful technique to measure various surface deformation phenomena of the earth. Early generations of time-series InSAR methodologies, i.e. Persistent Scatterer Interferometry (PSI), focused on

  9. New Algorithms and Sparse Regularization for Synthetic Aperture Radar Imaging

    Science.gov (United States)

    2015-10-26

    statistical analysis of one such method, the so-called MUSIC algorithm (multiple signal classification). We have a publication that mathematically justifies...called MUSIC algorithm (multiple signal classification). We have a publication that mathematically justifies the scaling of the phase transition...Demanet Department of Mathematics Massachusetts Institute of Technology. • Grant title: New Algorithms and Sparse Regularization for Synthetic Aperture

  10. Optical aperture synthesis: limitations and interest for the earth observation

    Science.gov (United States)

    Brouard, Laurent; Safa, Frederic; Crombez, Vincent; Laubier, David

    2017-11-01

    For very large telescope diameters, typically above 4 meters, monolithic telescopes can hardly be envisaged for space applications. Optical aperture synthesis can be envisaged in the future for improving the image resolution from high altitude orbits by co-phasing several individual telescopes of smaller size and reconstituting an aperture of large surface. The telescopes can be deployed on a single spacecraft or distributed on several spacecrafts in free flying formation. Several future projects are based on optical aperture synthesis for science or earth observation. This paper specifically discusses the limitations and interest of aperture synthesis technique for Earth observation from high altitude orbits, in particular geostationary orbit. Classical Fizeau and Michelson configurations are recalled, and system design aspects are investigated: synthesis of the Modulation Transfer Function (MTF), integration time and imaging procedure are first discussed then co-phasing strategies and instrument metrology are developed. The discussion is supported by specific designs made at EADS Astrium. As example, a telescope design is presented with a surface of only 6.6 m2 for the primary mirror for an external diameter of 10.6 m allowing a theoretical resolution of 1.2 m from geostationary orbit with a surface lower than 10% of the overall surface. The impact is that the integration time is increasing leading to stringent satellite attitude requirements. Image simulation results are presented. The practical implementation of the concept is evaluated in terms of system impacts in particular spacecraft attitude control, spacecraft operations and imaging capability limitations.

  11. Assessment of large aperture scintillometry for large-area surface ...

    Indian Academy of Sciences (India)

    29

    This study defines that large aperture scintillometer is robust instrument which can evaluate energy flux over a large area with a long term series time domain. Moreover, further studied should be conducted to use in crop simulation modelling, developing of new model with calibration and validation of remote sensing energy ...

  12. Motion compensated beamforming in synthetic aperture vector flow imaging

    DEFF Research Database (Denmark)

    Oddershede, Niels; Jensen, Jørgen Arendt

    2006-01-01

    In synthetic aperture imaging the beamformed data from a number of emissions are summed to create dynamic focusing in transmit. This makes the method susceptible to motion, which is especially the case for the synthetic aperture flow estimation method, where large movements are expected. In this ......In synthetic aperture imaging the beamformed data from a number of emissions are summed to create dynamic focusing in transmit. This makes the method susceptible to motion, which is especially the case for the synthetic aperture flow estimation method, where large movements are expected....... In this paper, these motion effects are considered. A number of Field II simulations of a single scatterer moving at different velocities are performed both for axial and lateral velocities from 0 to 1 m/s. Data are simulated at a pulse repetition frequency of 5 kHz. The signal-to-noise ratio (SNR......) of the beamformed response from the scatterer at all velocities is compared to that of a stationary scatterer. For lateral movement, the SNR drops almost linearly with velocity to -4 dB at I m/s, while for axial movement the SNR drop is largest, when the scatterer moves a quarter of a wavelength between emissions...

  13. In Vivo Evaluation of Synthetic Aperture Sequential Beamforming

    DEFF Research Database (Denmark)

    Hemmsen, Martin Christian; Hansen, Peter Møller; Lange, Theis

    2012-01-01

    Ultrasound in vivo imaging using synthetic aperture sequential beamformation (SASB) is compared with conventional imaging in a double blinded study using side-by-side comparisons. The objective is to evaluate if the image quality in terms of penetration depth, spatial resolution, contrast...

  14. A 10 cm aperture, high quality TEA CO2 laser

    NARCIS (Netherlands)

    Ernst, G.J.

    1982-01-01

    Experiments have been performed on a corona preionization type 10 cm aperture TEA CO2 laser. For a CO2:N2:He=1: 1: 7: mixture an output energy of 34 joule per liter and for a 1 : 1 : 10 mixture 40 joule per liter could be obtained. The overall efficiency is about 18%. The time behaviour of the

  15. Assessment of large aperture scintillometry for large-area surface ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science; Volume 126; Issue 5. Assessment of large aperture scintillometry for large-area surface energy fluxes over an irrigated cropland in north India. Abhishek Danodia V K Sehgal N R Patel R Dhakar J Mukherjee S K Saha A Senthil Kumar. Volume 126 Issue 5 July 2017 Article ...

  16. Brightness-temperature retrival methods in synthetic aperture radiometers

    OpenAIRE

    Corbella Sanahuja, Ignasi; Torres Torres, Francisco; Camps Carmona, Adriano José; Duffo Ubeda, Núria; Vall-Llossera Ferran, Mercedes Magdalena

    2009-01-01

    Bightness-temperature retrieval techniques for synthetic aperture radiometers are reviewed. Three different approaches to combine measured visibility and antenna temperatures, along with instrument characterization data, into a general equation to invert are presented. Discretization and windowing techniques are briefly discussed, and formulas for reciprocal grids using rectangular and hexagonal samplings are given. Two known techniques are used to invert the equation, namel...

  17. A circular aperture array for ultrasonic tomography and quantitative NDE

    Energy Technology Data Exchange (ETDEWEB)

    Nielsen, S.A.

    1998-08-01

    The main topics of this thesis are ultrasonic tomography and ultrasonic determination of elastic stiffness constants. Both issues are based on a synthetic array with transducer elements distributed uniformly along a circular aperture, i.e., a circular aperture array. The issues are treated both theoretically and experimentally by broadband pulse techniques. Ultrasonic tomography, UCT, from a circular aperture is a relatively new imaging technique in Non-destructive Evaluation (NDE) to acquire cross sectional images in bulk materials. A filtered back-projection algorithm is used to reconstruct images in four different experiments and results of attenuation, velocity and reflection tomograms in Plexiglas of AlSi-alloy cylinders are presented. Two kinds of ultrasonic tomography are introduced: bistatic and monostatic imaging. Both techniques are verified experimentally by Plexiglas cylinders. Different reconstruction artifacts are discussed and theoretical resolution constraints are discussed for various configurations of the circular aperture array. The monostatic technique is used in volumetric imaging. In the experimental verification artificial and real discontinuities in a cylindrical AlSi-alloy are compared with similar discontinuities in a Plexiglas specimen. Finally, some limitations to UCT are discussed. The circular aperture array is used to determine five independent elastic stiffness constants of a unidirectional glass/PET (Poly Ethylene Teraphtalate) laminate. Energy flux propagation and attenuation of ultrasonic waves are considered and velocity surfaces are calculated for different planes of interest. Relations between elastic stiffness constants and engineering constants (i.e., Young`s moduli, shear moduli and Poisson`s ratios) are discussed for an orthotropic composite. Six micromechanical theories are reviewed, and expressions predicting the elastic engineering constants are evaluated. The micromechanical predicted elastic stiffness constants for the

  18. MEGARA Optics: Sub-aperture Stitching Interferometry for Large Surfaces

    Science.gov (United States)

    Aguirre-Aguirre, Daniel; Carrasco, Esperanza; Izazaga-Pérez, Rafael; Páez, Gonzalo; Granados-Agustín, Fermín; Percino-Zacarías, Elizabeth; Gil de Paz, Armando; Gallego, Jesús; Iglesias-Páramo, Jorge; Villalobos-Mendoza, Brenda

    2018-04-01

    In this work, we present a detailed analysis of sub-aperture interferogram stitching software to test circular and elliptical clear apertures with diameters and long axes up to 272 and 180 mm, respectively, from the Multi-Espectrógrafo en GTC de Alta Resolución para Astronomía (MEGARA). MEGARA is a new spectrograph for the Gran Telescopio Canarias (GTC). It offers a resolution between 6000 and 20000 via the use of volume phase holographic gratings. It has an integral field unit and a set of robots for multi-object spectroscopy at the telescope focal plane. The output end of the fibers forms the spectrograph pseudo-slit. The fixed geometry of the collimator and camera configuration requires prisms in addition to the flat windows of the volume phase holographic gratings. There are 73 optical elements of large aperture and high precision manufactured in Mexico at the Instituto Nacional de Astrofísica, Óptica y Electrónica (INAOE) and the Centro de Investigaciones en Óptica (CIO). The principle of stitching interferometry is to divide the surface being tested into overlapping small sections, which allows an easier analysis (Kim & Wyant 1981). This capability is ideal for non-contact tests for unique and large optics as required by astronomical instruments. We show that the results obtained with our sub-aperture stitching algorithm were consistent with other methods that analyze the entire aperture. We used this method to analyze the 24 MEGARA prisms that could not be tested otherwise. The instrument has been successfully commissioned at GTC in all the spectral configurations. The fulfillment of the irregularity specifications was one of the necessary conditions to comply with the spectral requirements.

  19. Implementation of adaptive coded aperture imaging using a digital micro-mirror device for defocus deblurring

    CSIR Research Space (South Africa)

    Chiranjan, Ashill

    2016-12-01

    Full Text Available Digital image processing (DIP) and computational photography are ever growing fields with new focuses on coded aperture imaging and its real world applications. Traditional coded aperture imaging systems consisted of statically coded masks that were...

  20. Propagation of various dark hollow beams through an apertured paraxial ABCD optical system

    International Nuclear Information System (INIS)

    Cai Yangjian; Ge Di

    2006-01-01

    Propagation of a dark hollow beam (DHB) of circular, elliptical or rectangular symmetry through an apertured paraxial ABCD optical system is investigated. Approximate analytical formulas for various DHBs propagating through an apertured paraxial optical system are derived by expanding the hard-aperture function into a finite sum of complex Gaussian functions in terms of a tensor method. Some numerical results are given. Our formulas provide a convenient way for studying the propagation of various DHBs through an apertured paraxial optical system

  1. A new measurement method for effective aperture of thick pinhole

    International Nuclear Information System (INIS)

    Xie Hongwei; Zhang Jianhua; Zhang Faqiang; Li Linbo; Qi Jianmin; Chen Jinchuan; Chen Dingyang

    2014-01-01

    The Lucy-Richardson super resolution image processing technique, combined with the introduced virtual point spread function (PSF), was used to develop a measurement method of the processing precision of the superfine thick pinhole aperture. The principles of the technique were based on the known ideal image and degraded image. After the restoration and reconstruction of the degraded image with the introduced virtual point spread function (PSF), the comparison is made between the reconstructed image and the ideal image to judge the correctness of the virtual point spread function (PSF). During this process, the simulation of the effects of the point spread function (PSF) upon the image reconstruction was carried out at first. As indicated by the simulation, the ideal point spread function (PSF) used in the image restoration and reconstruction could provide ideal results of the image reconstruction. However, in the case of relatively bigger size of the point spread function (PSF), the reconstructed image would be obtained smaller than the ideal image. Besides, related experiments were carried out on the cobalt radiation sources. In the experiments, the aperture of the shielded collimator to restrict and align the radiation source was known to be l.0 mm, the thick pinholes respectively 0.7 mm and 0.45 mm in aperture were used for the imaging of the ϕl mm radiation source, and the radiation image was recorded in imaging plates 0.05 mm × O.05 mm in spatial resolution. Based on the hypothesis that the processing precision of the thick pinhole fulfill the experiment requirements, the point spread function obtained from the simulated computation was introduced into the restoration and reconstruction of the recorded images. At the area with an intensity of 50%, the thick pinhole with 0.7 mm aperture could provide homogenous image of the radiation source. However, the thick pinhole with 0.45 mm aperture provided an elliptical image with a major-minor axis ratio of 5 : 3

  2. The impact of different aperture distribution models and critical stress criteria on equivalent permeability in fractured rocks

    DEFF Research Database (Denmark)

    Bisdom, Kevin; Bertotti, Giovanni; Nick, Hamid

    2016-01-01

    Predicting equivalent permeability in fractured reservoirs requires an understanding of the fracture network geometry and apertures. There are different methods for defining aperture, based on outcrop observations (power law scaling), fundamental mechanics (sublinear length-aperture scaling......), and experiments (Barton-Bandis conductive shearing). Each method predicts heterogeneous apertures, even along single fractures (i.e., intrafracture variations), but most fractured reservoir models imply constant apertures for single fractures. We compare the relative differences in aperture and permeability...

  3. New military uses for synthetic aperture radar (SAR)

    Science.gov (United States)

    Reamer, Richard E.; Stockton, Wayne; Stromfors, Richard D.

    1993-02-01

    Loral Defense Systems-Arizona, holder of the original patent for the invention of Synthetic Aperture Radar (SAR), developed SAR to meet the military's need for an all-weather, day/night sensor that could produce high quality reconnaissance imagery in adverse weather and restricted visibility conditions. These features, and the ability to image large areas with fine resolution in a relatively short period of time make this sensor useful for many military applications. To date, however, SARs for military use have been hampered by the fact that they've been large, complex, and expensive. Additionally, they have been mounted on special purpose, single mission aircraft which are costly to operate. That situation has changed. A small, modular SAR, called Miniature Synthetic Aperture Radar (MSAR) developed by Loral can be mounted with relative ease on Unmanned Aerial Vehicles (UAV) or on multi-mission aircraft such as the F-16, F/A-18, or on the F-14.

  4. Synthetic aperture radar modeling for the Watchkeeper tactical UAV program

    Science.gov (United States)

    Jolly, Alistair D.; Thompson, Peter

    2002-07-01

    Critical to the performance of any synthetic aperture radar (SAR) system is accurate compensation for aircraft motion during the imaging aperture. This is thought to be particularly important for Unmanned Aerial Vehicles (UAVs) operating in poor weather conditions where the aircraft may be subject to pronounced turbulence effects. This paper presents some initial findings of an investigation into the effects of aircraft motion on SAR azimuth point spread function for given levels of motion spectrum suppression as supplied by the radar's motion compensation processing. With validation, this approach will allow indicative levels of SAR performance to be estimated over a wide range of operating conditions and hence provides a useful source of advice when considering procurement options.

  5. Synthetic aperture flow imaging using dual stage beamforming

    DEFF Research Database (Denmark)

    Li, Ye; Jensen, Jørgen Arendt

    2013-01-01

    A method for synthetic aperture flow imaging using dual stage beamforming has been developed. The main motivation is to increase the frame rate and still maintain a beamforming quality sufficient for flow estimation that is possible to implement in a commercial scanner. This method can generate...... continuous high frame rate flow images with lower calculation demands than the full synthetic aperture flow imaging. The performance of the approach was investigated using Field II simulations and measurements with the experimental scanner SARUS. A laminar flow with a parabolic profile was generated...... of beamformed samples are reduced by a factor of 64 times, and the frame rate is much higher than the conventional method for the same velocity estimation accuracy....

  6. Synthetic Aperture Flow Imaging Using a Dual Beamformer Approach

    DEFF Research Database (Denmark)

    Li, Ye

    . However, while the conventional ultrasound imaging of making color flow mapping provides useful information in many circumstances, the spatial velocity resolution and frame rate are limited. The entire velocity distribution consists of image lines from different directions, and each image line...... is estimated using multiple emissions. Therefore, it is very difficult to acquire a full volume of data for the blood flow in the heart in real-time. A radical break with this has been the synthetic aperture technique. This technique makes it possible to increase the frame rate, and the reconstruction also...... makes it possible to improve significantly the focusing and frame rate. However, it requires a large amount of calculations to fulfill the performance because the signal from each channel is stored and processed simultaneously. The implementation of the full synthetic aperture would be very expensive...

  7. Pressure independence of granular flow through an aperture.

    Science.gov (United States)

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

    2010-06-11

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

  8. LHC β*-reach MD: aperture measurements at small β*

    CERN Document Server

    Fuster Martinez, Nuria; Redaelli, Stefano; CERN. Geneva. ATS Department

    2017-01-01

    During this MD, performed on the 25th of July 2017, we measured the LHC aperture at top energy for β*=30 cm using the Transverse Damper (ADT) blow-up method. These measurements are part of the standard commissioning of an optics and have been performed in order to provide early on inputs for a possible change of β* later in 2017, as envisaged previously to fully profit from the additional margins introduced by the rematched phase advance between dump kickers and the TCTs (Target Collimator Tertiary). In addition to the aperture measurements, two other commissioning important tests were performed: loss maps for the nominal TCTs settings and an asynchronous dump validation with tighter TCT gaps.

  9. Performance of Synthetic Aperture Compounding for in-vivo imaging

    DEFF Research Database (Denmark)

    Hansen, Jens Munk; Jensen, Jørgen Arendt

    2011-01-01

    imaging respectively. The tissue phantom measurements show a 3.2 dB improvement of the normalized information density (NID) when comparing images formed using SAC to conventional compound images and an improvement of 2 dB for a comparison between SAC imaging and SA imaging. For the clinical images......A method for synthetic aperture compounding (SAC) is applied to data from water tank measurements, data from a tissue-mimicking phantom, and clinical data from the abdomen of a healthy 27 year old male. Further, using this method compounding can be obtained without any loss in temporal resolution....... The water tank measurements reveal an improved detail resolution of 45% when comparing SAC to conventional compounding and an improvement of 22%, when comparing to synthetic aperture (SA) imaging. The cystic resolution at 12 dB is improved by 50% and 12% when comparing SAC to conventional compounding and SA...

  10. Random mask optimization for fast neutron coded aperture imaging

    Energy Technology Data Exchange (ETDEWEB)

    McMillan, Kyle [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Univ. of California, Los Angeles, CA (United States); Marleau, Peter [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Brubaker, Erik [Sandia National Lab. (SNL-CA), Livermore, CA (United States)

    2015-05-01

    In coded aperture imaging, one of the most important factors determining the quality of reconstructed images is the choice of mask/aperture pattern. In many applications, uniformly redundant arrays (URAs) are widely accepted as the optimal mask pattern. Under ideal conditions, thin and highly opaque masks, URA patterns are mathematically constructed to provide artifact-free reconstruction however, the number of URAs for a chosen number of mask elements is limited and when highly penetrating particles such as fast neutrons and high-energy gamma-rays are being imaged, the optimum is seldom achieved. In this case more robust mask patterns that provide better reconstructed image quality may exist. Through the use of heuristic optimization methods and maximum likelihood expectation maximization (MLEM) image reconstruction, we show that for both point and extended neutron sources a random mask pattern can be optimized to provide better image quality than that of a URA.

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

    Science.gov (United States)

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

    2015-09-01

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

  12. Preliminary comparison of 3D synthetic aperture imaging with Explososcan

    DEFF Research Database (Denmark)

    Rasmussen, Morten Fischer; Hansen, Jens Munk; Ferin, Guillaume

    2012-01-01

    phased array with a pitch of 300 μm, made by Vermon. For both imaging techniques, 289 emissions are used to image a volume spanning 60 in both the azimuth and elevation direction and 150mm in depth. This results for both techniques in a frame rate of 18 Hz. The implemented synthetic aperture technique...... by four and still, generally, improve the imaging quality....

  13. Investigation on Transmission Properties of Terahertz Wave Through Semiconductor Aperture

    International Nuclear Information System (INIS)

    He Xiaoyong; Cao Juncheng

    2008-01-01

    The transmission properties of terahertz (THz) wave passing through semiconductor aperture have been investigated. The dispersion relationship for surface plasmon polariton (SPP) at different temperatures has been numerically calculated. The results show that the dispersion relationship increases with the increasing of frequency and the decreasing of temperature, the thickness of slab has to be taken into consideration because of the large skin depth for semiconductor slab. In addition, the propagation constant increases with the increasing of frequency and the decreasing of temperature.

  14. The modular design of large-aperture zoom system

    Science.gov (United States)

    Liu, Kai; Jiang, Kai; Yan, Peipei; Shan, Qiu-sha; Duan, Jing; Li, Gang

    2016-10-01

    According to the large aperture, long focal length zoom system design, the structure of the optical system based on the modular concept is proposed. The structure is constituted of an afocal compression telescope and a zoom system. The parts of each other are individually designed. The aberrations of them are independently. Because of this, the alignment of the system and the difficulty of test are greatly reduced. It is easily replaced by changing the zoom system parts, which can achieve other different focal length and ratio. Using afocal compression telescope greatly reduces the radial aperture of the zoom group, simplifies the system structure and reduces the cost. Meanwhile, the variable stop is placed in the vicinity of the primary mirror. It is instead of the zoom system used in floating variable stop. In addition, the problem about large aperture zoom system pupil matching is solved perfectly. In this article, four methods of pupil matching are given and the advantages and disadvantages of them are analyzed. Using this optical structure, a zoom system is designed, which is working in the visible wavelength band with variable focal length between 900mm and 4500mm, 500mm maximum aperture. The axial dimension of the system is less than 650mm. The maximum diameter of zoom system parts is less than 40 mm. Moreover, the distances of the zoom group and compensating group are all less than 60 mm. Besides, the motion curves of each other are given in the article. The Modulation Transfer Function (MTF) values of the system are greater than 0.3 at 48lp/mm across different focal length and field pointing on the axis. The design results show that the imaging quality is excellent, the structure is compact, and the alignment and test are easy. The imaging requirements of zoom system are all satisfied.

  15. Offshore Wind Potential in South India from Synthetic Aperture Radar

    DEFF Research Database (Denmark)

    Hasager, Charlotte Bay; Bingöl, Ferhat; Badger, Merete

    The offshore wind energy potential for pre-feasibility in South India in the area from 77° to 80° Eastern longitude and 7° to 10° Northern latitude is observed from a total of 164 ENVISAT Advanced Synthetic Aperture Radar (ASAR) satellite images during the years 2002 to 2011. All satellite scenes......-year mean and a general description of the winds and climate with monsoons in India is presented....

  16. Colloid retention mechanisms in single, saturated, variable-aperture fractures.

    Science.gov (United States)

    Rodrigues, S N; Dickson, S E; Qu, J

    2013-01-01

    The characterization of fractured aquifers is commonly limited to the methodologies developed for unconsolidated porous media aquifers, which results in many uncertainties. Recent work indicates that fractured rocks remove more particulates than they are conventionally credited for. This research was designed to quantify the number of Escherichia coli RS2-GFP retained in single, saturated, variable-aperture fractures extracted from the natural environment. Conservative solute and E. coli RS2-GFP tracer experiments were used to elucidate the relationships between dominant retention mechanisms, aperture field characteristics, and flow rate. A non-destructive method of determining a surrogate measure of a coefficient of variation (COV(S)) for each fracture was used to better understand the transport behaviour of E. coli RS2-GFP. The results from this research all point to the importance of aperture field characterization in understanding the fate and transport of contaminants in fractured aquifers. The mean aperture was a very important characteristic in determining particulate recovery, so were matrix properties, COV(s), and flow rate. It was also determined that attachment is a much more significant retention mechanism than straining under the conditions employed in this research. Finally, it was demonstrated that the dominant retention mechanism in a fracture varies depending on the specific discharge. An improved understanding of the mechanisms that influence the fate and transport of contaminants through fractures will lead to the development of better tools and methodologies for the characterization of fractured aquifers, as well as the ability to manipulate the relevant mechanisms to increase or decrease retention, depending on the application. Copyright © 2012 Elsevier Ltd. All rights reserved.

  17. Implementation of real-time duplex synthetic aperture ultrasonography

    DEFF Research Database (Denmark)

    Hemmsen, Martin Christian; Larsen, Lee; Kjeldsen, Thomas

    2015-01-01

    This paper presents a real-time duplex synthetic aperture imaging system, implemented on a commercially available tablet. This includes real-time wireless reception of ultrasound signals and GPU processing for B-mode and Color Flow Imaging (CFM). The objective of the work is to investigate the im...... and that the required bandwidth between the probe and processing unit is within the current Wi-Fi standards....

  18. Feasibility of Using Synthetic Aperture Radar to Aid UAV Navigation

    OpenAIRE

    Nitti, Davide O.; Bovenga, Fabio; Chiaradia, Maria T.; Greco, Mario; Pinelli, Gianpaolo

    2015-01-01

    This study explores the potential of Synthetic Aperture Radar (SAR) to aid Unmanned Aerial Vehicle (UAV) navigation when Inertial Navigation System (INS) measurements are not accurate enough to eliminate drifts from a planned trajectory. This problem can affect medium-altitude long-endurance (MALE) UAV class, which permits heavy and wide payloads (as required by SAR) and flights for thousands of kilometres accumulating large drifts. The basic idea is to infer position and attitude of an aeria...

  19. Digital filtering and reconstruction of coded aperture images

    International Nuclear Information System (INIS)

    Tobin, K.W. Jr.

    1987-01-01

    The real-time neutron radiography facility at the University of Virginia has been used for both transmission radiography and computed tomography. Recently, a coded aperture system has been developed to permit the extraction of three dimensional information from a low intensity field of radiation scattered by an extended object. Short wave-length radiations (e.g. neutrons) are not easily image because of the difficulties in achieving diffraction and refraction with a conventional lens imaging system. By using a coded aperture approach, an imaging system has been developed that records and reconstructs an object from an intensity distribution. This system has a signal-to-noise ratio that is proportional to the total open area of the aperture making it ideal for imaging with a limiting intensity radiation field. The main goal of this research was to develope and implement the digital methods and theory necessary for the reconstruction process. Several real-time video systems, attached to an Intellect-100 image processor, a DEC PDP-11 micro-computer, and a Convex-1 parallel processing mainframe were employed. This system, coupled with theoretical extensions and improvements, allowed for retrieval of information previously unobtainable by earlier optical methods. The effect of thermal noise, shot noise, and aperture related artifacts were examined so that new digital filtering techniques could be constructed and implemented. Results of image data filtering prior to and following the reconstruction process are reported. Improvements related to the different signal processing methods are emphasized. The application and advantages of this imaging technique to the field of non-destructive testing are also discussed

  20. Digital Beamforming Synthetic Aperture Radar (DBSAR) Polarimetric Upgrade

    Science.gov (United States)

    Rincon, Rafael F.; Perrine, Martin; McLinden, Matthew; Valett, Susan

    2011-01-01

    The Digital Beamforming Synthetic Aperture Radar (DBSAR) is a state-of-the-art radar system developed at NASA/Goddard Space Flight Center for the development and implementation of digital beamforming radar techniques. DBSAR was recently upgraded to polarimetric operation in order to enhance its capability as a science instrument. Two polarimetric approaches were carried out which will be demonstrated in upcoming flight campaigns.

  1. Limits to Clutter Cancellation in Multi-Aperture GMTI Data

    Energy Technology Data Exchange (ETDEWEB)

    Doerry, Armin W. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Bickel, Douglas L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-03-01

    Multi-aperture or multi-subaperture antennas are fundamental to Ground Moving Target Indicator (GMTI) radar systems in order to detect slow-moving targets with Doppler characteristics similar to clutter. Herein we examine the performance of several subaperture architectures for their clutter cancelling performance. Significantly, more antenna phase centers isn’t always better, and in fact is sometimes worse, for detecting targets.

  2. Inverse synthetic aperture radar imaging principles, algorithms and applications

    CERN Document Server

    Chen , Victor C

    2014-01-01

    Inverse Synthetic Aperture Radar Imaging: Principles, Algorithms and Applications is based on the latest research on ISAR imaging of moving targets and non-cooperative target recognition (NCTR). With a focus on the advances and applications, this book will provide readers with a working knowledge on various algorithms of ISAR imaging of targets and implementation with MATLAB. These MATLAB algorithms will prove useful in order to visualize and manipulate some simulated ISAR images.

  3. Application of Linear Prediction Technique to Passive Synthetic Aperture Processing

    OpenAIRE

    Yong Jin; Min Jiang; Yunshan Hou; Jianguo Huang

    2010-01-01

    A method for the synthesis of an aperture with improved angular resolution and array gain is described. The proposed method explores the merit of linear prediction technique to improve the performance of conventional ETAM (extended towed array measurements) method. Previous efforts to improve the ETAM method generally focused on how to get more accurate estimation of overlap correlator, with an aim to reduce bearing estimation variance. In this paper, however, we discuss how to further impro...

  4. The LAGO (Large Aperture GRB Observatory) in Peru

    Science.gov (United States)

    Tueros-Cuadros, E.; Otiniano, L.; Chirinos, J.; Soncco, C.; Guevara-Day, W.

    2012-07-01

    The Large Aperture GRBs Observatory is a continental-wide observatory devised to detect high energy (around 100 GeV) component of Gamma Ray Bursts (GRBs), by using the single particle technique in arrays of Water Cherenkov Detectors (WCDs) at high mountain sites of Argentina, Bolivia, Colombia, Guatemala, Mexico, Venezuela and Peru. Details of the instalation and operation of the detectors in Marcapomacocha in Peru at 4550 m.a.s.l. are given. The detector calibration method will also be shown.

  5. Metamaterial apertures for coherent computational imaging on the physical layer.

    Science.gov (United States)

    Lipworth, Guy; Mrozack, Alex; Hunt, John; Marks, Daniel L; Driscoll, Tom; Brady, David; Smith, David R

    2013-08-01

    We introduce the concept of a metamaterial aperture, in which an underlying reference mode interacts with a designed metamaterial surface to produce a series of complex field patterns. The resonant frequencies of the metamaterial elements are randomly distributed over a large bandwidth (18-26 GHz), such that the aperture produces a rapidly varying sequence of field patterns as a function of the input frequency. As the frequency of operation is scanned, different subsets of metamaterial elements become active, in turn varying the field patterns at the scene. Scene information can thus be indexed by frequency, with the overall effectiveness of the imaging scheme tied to the diversity of the generated field patterns. As the quality (Q-) factor of the metamaterial resonators increases, the number of distinct field patterns that can be generated increases-improving scene estimation. In this work we provide the foundation for computational imaging with metamaterial apertures based on frequency diversity, and establish that for resonators with physically relevant Q-factors, there are potentially enough distinct measurements of a typical scene within a reasonable bandwidth to achieve diffraction-limited reconstructions of physical scenes.

  6. Two-Sided Coded Aperture Imaging Without a Detector Plane

    International Nuclear Information System (INIS)

    Ziock, Klaus-Peter; Cunningham, Mark F.; Fabris, Lorenzo

    2008-01-01

    We introduce a novel design for a two-sided, coded-aperture, gamma-ray imager suitable for use in stand off detection of orphan radioactive sources. The design is an extension of an active-mask imager that would have three active planes of detector material, a central plane acting as the detector for two (active) coded-aperture mask planes, one on either side of the detector plane. In the new design the central plane is removed and the mask on the left (right) serves as the detector plane for the mask on the right (left). This design reduces the size, mass, complexity, and cost of the overall instrument. In addition, if one has fully position-sensitive detectors, then one can use the two planes as a classic Compton camera. This enhances the instrument's sensitivity at higher energies where the coded-aperture efficiency is decreased by mask penetration. A plausible design for the system is found and explored with Monte Carlo simulations

  7. Coded aperture material motion detection system for the ACPR

    International Nuclear Information System (INIS)

    McArthur, D.A.; Kelly, J.G.

    1975-01-01

    Single LMFBR fuel pins are being irradiated in Sandia's Annular Core Pulsed Reactor (ACPR). In these experiments single fuel pins have been driven well into the melt and vaporization regions in transients with pulse widths of about 5 ms. The ACPR is being upgraded so that it can be used to irradiate bundles of seven LMFBR fuel pins. The coded aperture material motion detection system described is being developed for this upgraded ACPR, and has for its design goals 1 mm transverse resolution (i.e., in the axial and radial directions), depth resolution of a few cm, and time resolution of 0.1 ms. The target date for development of this system is fall 1977. The paper briefly reviews the properties of coded aperture imaging, describes one possible system for the ACPR upgrade, discusses experiments which have been performed to investigate the feasibility of such a system, and describes briefly the further work required to develop such a system. The type of coded aperture to be used has not yet been fixed, but a one-dimensional section of a Fresnel zone plate appears at this time to have significant advantages

  8. SARUS: A Synthetic Aperture Real-time Ultrasound System.

    Science.gov (United States)

    Jensen, Jørgen Arendt; Holten-Lund, Hans; Nilsson, Ronnie Thorup; Hansen, Martin; Larsen, Ulrik Darling; Domsten, Rune Petter; Tomov, Borislav Gueorguiev; Stuart, Matthias Bo; Nikolov, Svetoslav Ivanov; Pihl, Michael Johannes; Du, Yigang; Rasmussen, Joachim Hee; Rasmussen, Morten Fischer

    2013-09-01

    The Synthetic Aperture Real-time Ultrasound System (SARUS) for acquiring and processing synthetic aperture (SA) data for research purposes is described. The specifications and design of the system are detailed, along with its performance for SA, nonlinear, and 3-D flow estimation imaging. SARUS acquires individual channel data simultaneously for up to 1024 transducer elements for a couple of heart beats, and is capable of transmitting any kind of excitation. The 64 boards in the system house 16 transmit and 16 receive channels each, where sampled channel data can be stored in 2 GB of RAM and processed using five field-programmable gate arrays (FPGAs). The fully parametric focusing unit calculates delays and apodization values in real time in 3-D space and can produce 350 million complex samples per channel per second for full non-recursive synthetic aperture B-mode imaging at roughly 30 high-resolution images/s. Both RF element data and beamformed data can be stored in the system for later storage and processing. The stored data can be transferred in parallel using the system's sixty-four 1-Gbit Ethernet interfaces at a theoretical rate of 3.2 GB/s to a 144-core Linux cluster.

  9. Coded aperture imaging system for nuclear fuel motion detection

    International Nuclear Information System (INIS)

    Stalker, K.T.; Kelly, J.G.

    1980-01-01

    A Coded Aperature Imaging System (CAIS) has been developed at Sandia National Laboratories to image the motion of nuclear fuel rods undergoing tests simulating accident conditions within a liquid metal fast breeder reactor. The tests require that the motion of the test fuel be monitored while it is immersed in a liquid sodium coolant precluding the use of normal optical means of imaging. However, using the fission gamma rays emitted by the fuel itself and coded aperture techniques, images with 1.5 mm radial and 5 mm axial resolution have been attained. Using an electro-optical detection system coupled to a high speed motion picture camera a time resolution of one millisecond can be achieved. This paper will discuss the application of coded aperture imaging to the problem, including the design of the one-dimensional Fresnel zone plate apertures used and the special problems arising from the reactor environment and use of high energy gamma ray photons to form the coded image. Also to be discussed will be the reconstruction techniques employed and the effect of various noise sources on system performance. Finally, some experimental results obtained using the system will be presented

  10. An implementation of synthetic aperture focusing technique in frequency domain.

    Science.gov (United States)

    Stepinski, Tadeusz

    2007-07-01

    A new implementation of a synthetic aperture focusing technique (SAFT) based on concepts used in synthetic aperture radar and sonar is presented in the paper. The algorithm, based on the convolution model of the imaging system developed in frequency domain, accounts for the beam pattern of the finite-sized transducer used in the synthetic aperture. The 2D fast Fourier transform (FFT) is used for the calculation of a 2D spectrum of the ultrasonic data. The spectrum is then interpolated to convert the polar coordinate system used for the acquisition of ultrasonic signals to the rectangular coordinates used for the presentation of imaging results. After compensating the transducer lobe amplitude profile using a Wiener filter, the transformed spectrum is subjected to the 2D inverse Fourier transform to get the time-domain image again. The algorithm is computationally attractive due to the use of 2D FFT. The performance of the proposed frequency-domain algorithm and the classical time-domain SAFT are compared in the paper using simulated and real ultrasonic data.

  11. Small aperture seismic arrays for studying planetary interiors and seismicity

    Science.gov (United States)

    Schmerr, N. C.; Lekic, V.; Fouch, M. J.; Panning, M. P.; Siegler, M.; Weber, R. C.

    2017-12-01

    Seismic arrays are a powerful tool for understanding the interior structure and seismicity across objects in the Solar System. Given the operational constraints of ground-based lander investigations, a small aperture seismic array can provide many of the benefits of a larger-scale network, but does not necessitate a global deployment of instrumentation. Here we define a small aperture array as a deployment of multiple seismometers, with a separation between instruments of 1-1000 meters. For example, small aperture seismic arrays have been deployed on the Moon during the Apollo program, the Active Seismic Experiments of Apollo 14 and 16, and the Lunar Seismic Profiling Experiment deployed by the Apollo 17 astronauts. Both were high frequency geophone arrays with spacing of 50 meters that provided information on the layering and velocity structure of the uppermost kilometer of the lunar crust. Ideally such arrays would consist of instruments that are 3-axis short period or broadband seismometers. The instruments must have a sampling rate and frequency range sensitivity capable of distinguishing between waves arriving at each station in the array. Both terrestrial analogs and the data retrieved from the Apollo arrays demonstrate the efficacy of this approach. Future opportunities exist for deployment of seismic arrays on Europa, asteroids, and other objects throughout the Solar System. Here we will present both observational data and 3-D synthetic modeling results that reveal the sensing requirements and the primary advantages of a small aperture seismic array over single station approach. For example, at the smallest apertures of < 1 m, we constrain that sampling rates must exceed 500 Hz and instrument sensitivity must extend to 100 Hz or greater. Such advantages include the improved ability to resolve the location of the sources near the array through detection of backazimuth and differential timing between stations, determination of the small-scale structure

  12. Application of a matched filter approach for finite aperture transducers for the synthetic aperture imaging of defects.

    Science.gov (United States)

    Satyanarayan, L; Muralidharan, Ajith; Krishnamurthy, Chittivenkata; Balasubramaniam, Krishnan

    2010-06-01

    The suitability of the synthetic aperture imaging of defects using a matched filter approach on finite aperture transducers was investigated. The first part of the study involved the use a finite-difference time-domain (FDTD) algorithm to simulate the phased array ultrasonic wave propagation in an aluminum block and its interaction with side-drilled hole-like defects. B-scans were generated using the FDTD method for three active aperture transducer configurations of the phased array (a) single element and (b) 16-element linear scan mode, and (c) 16-element steering mode. A matched filter algorithm (MFA) was developed using the delay laws and the spatial impulse response of a finite size rectangular phased array transducer. The conventional synthetic aperture focusing technique (SAFT) algorithm and the MFA were independently applied on the FDTD signals simulated with the probe operating at a center frequency of 5 MHz and the processed B-scans were compared. The second part of the study investigated the capability of the MFA approach to improve the SNR. Gaussian white noise was added to the FDTD generated defect signals. The noisy B-scans were then processed using the SAFT and the MFA and the improvements in the SNR were estimated. The third part of the study investigated the application of the MFA to image and size surface-crack-like defects in pipe specimens obtained using a 45 degrees steered beam from a phased array probe. These studies confirm that MFA is an alternative to SAFT with little additional computational burden. It can also be applied blindly, like SAFT, to effect synthetic focusing with distinct advantages in treating finite transducer effects, and in handling steered beam inspections. Finally, limitations of the MFA in dealing with larger-sized transducers are discussed.

  13. Influence of coma aberration on aperture averaged scintillations in oceanic turbulence

    Science.gov (United States)

    Luo, Yujuan; Ji, Xiaoling; Yu, Hong

    2018-01-01

    The influence of coma aberration on aperture averaged scintillations in oceanic turbulence is studied in detail by using the numerical simulation method. In general, in weak oceanic turbulence, the aperture averaged scintillation can be effectively suppressed by means of the coma aberration, and the aperture averaged scintillation decreases as the coma aberration coefficient increases. However, in moderate and strong oceanic turbulence the influence of coma aberration on aperture averaged scintillations can be ignored. In addition, the aperture averaged scintillation dominated by salinity-induced turbulence is larger than that dominated by temperature-induced turbulence. In particular, it is shown that for coma-aberrated Gaussian beams, the behavior of aperture averaged scintillation index is quite different from the behavior of point scintillation index, and the aperture averaged scintillation index is more suitable for characterizing scintillations in practice.

  14. Synthetic aperture ladar based on a MOPAW laser

    Science.gov (United States)

    Turbide, Simon; Marchese, Linda; Bergeron, Alain; Desbiens, Louis; Paradis, Patrick

    2016-10-01

    Long range land surveillance is a critical need in numerous military and civilian security applications, such as threat detection, terrain mapping and disaster prevention. A key technology for land surveillance, synthetic aperture radar (SAR) continues to provide high resolution radar images in all weather conditions from remote distances. State of the art SAR systems based on dual-use satellites are capable of providing ground resolutions of one meter; while their airborne counterparts obtain resolutions of 10 cm. Certain land surveillance applications such as subsidence monitoring, landslide hazard prediction and tactical target tracking could benefit from improved resolution. The ultimate limitation to the achievable resolution of any imaging system is its wavelength. State-of-the-art SAR systems are approaching this limit. The natural extension to improve resolution is to thus decrease the wavelength, i.e. design a synthetic aperture system in a different wavelength regime. One such system offering the potential for vastly improved resolution is Synthetic Aperture Ladar (SAL). This system operates at infrared wavelengths, ten thousand times smaller radar wavelengths. This paper presents a SAL platform based on the INO Master Oscillator with Programmable Amplitude Waveform (MOPAW) laser that has a wavelength sweep of Δλ=1.22 nm, a pulse repetition rate up to 1 kHz and up to 200 μJ per pulse. The results for SAL 2D imagery at a range of 10 m are presented, indicating a reflectance sensibility of 8 %, ground-range and azimuth resolution of 1.7 mm and 0.84 mm respectively.

  15. Forward imaging for obstacle avoidance using ultrawideband synthetic aperture radar

    Science.gov (United States)

    Nguyen, Lam H.; Wong, David C.; Stanton, Brian; Smith, Gregory

    2003-09-01

    In support of the Army vision for increased mobility, survivability, and lethality, we are investigating the use of ultra-wideband (UWB) synthetic aperture radar (SAR) technology to enhance unmanned ground vehicle missions. The ability of UWB radar technology to detect objects concealed by foilage could provide an important obstacle avoidance capability for robotic vehicles. This would improve the speed and maneuverability of these vehicles and consequently increase the probability of survivability of U.S. forces. This technology would address the particular challenges that confront robotic vehicles such as large rocks hidden in tall grass and voids such as ditches and bodies of water. ARL has designed and constructed an instrumentation-grade low frequency, UWB synthetic aperture radar for evaluation of the target signatures and underlying phenomenology of stationary tactical targets concealed by foilage and objects buried in the ground. The radar (named BoomSAR) is installed in teh basekt of a 30-ton boom lift and can be operated while the entire boom lift is driven forward slowly, with the boom arm extended as high as 45 m to generate a synthetic aperture. In this paper, we investigate the potential use of the UWB radar in the forward imaging configuration. The paper describes the forward imaging radar and test setup at Aberdeen Proving Ground, Maryland. We present imagery of "positive" obstacles such as trees, fences, wires, mines, etc., as well as "negative" obstacles such as ditches. Imagery of small targets such as plastic mines is also included. We provide eletromagnetic simulations of forward SAR imagery of plastic mines and compare that to the measurement data.

  16. Design of a hybrid double-sideband/single-sideband (schlieren) objective aperture suitable for electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Buijsse, Bart; Laarhoven, Frank M.H.M. van [FEI Company, PO Box 80066, 5600 KA Eindhoven (Netherlands); Schmid, Andreas K.; Cambie, Rossana; Cabrini, Stefano; Jin, Jian [Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720 (United States); Glaeser, Robert M., E-mail: rmglaeser@lbl.gov [Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720 (United States)

    2011-12-15

    A novel design is described for an aperture that blocks a half-plane of the electron diffraction pattern out to a desired scattering angle, and then - except for a narrow support beam - transmits all of the scattered electrons beyond that angle. Our proposed tulip-shaped design is thus a hybrid between the single-sideband (ssb) aperture, which blocks a full half-plane of the diffraction pattern, and the conventional (i.e. fully open) double-sideband (dsb) aperture. The benefits of this hybrid design include the fact that such an aperture allows one to obtain high-contrast images of weak-phase objects with the objective lens set to Scherzer defocus. We further demonstrate that such apertures can be fabricated from thin-foil materials by milling with a focused ion beam (FIB), and that such apertures are fully compatible with the requirements of imaging out to a resolution of at least 0.34 nm. As is known from earlier work with single-sideband apertures, however, the edge of such an aperture can introduce unwanted, electrostatic phase shifts due to charging. The principal requirement for using such an aperture in a routine data-collection mode is thus to discover appropriate materials, protocols for fabrication and processing and conditions of use such that the hybrid aperture remains free of charging over long periods of time. -- Highlights: Black-Right-Pointing-Pointer New objective-aperture design is proposed for imaging weak-phase objects. Black-Right-Pointing-Pointer Design produces single-sideband contrast at low spatial frequencies. Black-Right-Pointing-Pointer Design also retains Scherzer-defocus phase contrast at higher resolution. Black-Right-Pointing-Pointer Proof-of-concept results are presented for microfabricated apertures. Black-Right-Pointing-Pointer Charging of such apertures during use remains an experimental challenge.

  17. LAGOVirtual: A Collaborative Environment for the Large Aperture GRB Observatory

    OpenAIRE

    Camacho, R.; Chacon, R.; Diaz, G.; Guada, C.; Hamar, V.; Hoeger, H.; Melfo, A.; Nunez, L. A.; Perez, Y.; Quintero, C.; Rosales, M.; Torrens, R.; Collaboration, the LAGO

    2009-01-01

    We present the LAGOVirtual Project: an ongoing project to develop platform to collaborate in the Large Aperture GRB Observatory (LAGO). This continental-wide observatory is devised to detect high energy (around 100 GeV) component of Gamma Ray Bursts, by using the single particle technique in arrays of Water Cherenkov Detectors (WCD) at high mountain sites (Chacaltaya, Bolivia, 5300 m a.s.l., Pico Espejo, Venezuela, 4750 m a.s.l., Sierra Negra, Mexico, 4650 m a.s.l). This platform will allow L...

  18. Multielement Synthetic Transmit Aperture Imaging Using Temporal Encoding

    DEFF Research Database (Denmark)

    Gammelmark, Kim; Jensen, Jørgen Arendt

    2003-01-01

    A new method to increase the signal-to-noise ratio (SNR) of synthetic transmit aperture imaging is investigated. The approach utilizes multiple elements to emulate a spherical wave, and the conventional short excitation pulse is replaced by a linear frequency-modulated (FM) signal. The approach...... is evaluated in terms of image quality parameters in comparison to linear array imaging. Field II simulations using an 8.5-MHz linear array transducer with 128 elements show an improvement in lateral resolution of up to 30% and up to 10.75% improvement in contrast resolution for the new approach. Measurements...

  19. Apodized RFI filtering of synthetic aperture radar images

    Energy Technology Data Exchange (ETDEWEB)

    Doerry, Armin Walter

    2014-02-01

    Fine resolution Synthetic Aperture Radar (SAR) systems necessarily require wide bandwidths that often overlap spectrum utilized by other wireless services. These other emitters pose a source of Radio Frequency Interference (RFI) to the SAR echo signals that degrades SAR image quality. Filtering, or excising, the offending spectral contaminants will mitigate the interference, but at a cost of often degrading the SAR image in other ways, notably by raising offensive sidelobe levels. This report proposes borrowing an idea from nonlinear sidelobe apodization techniques to suppress interference without the attendant increase in sidelobe levels. The simple post-processing technique is termed Apodized RFI Filtering (ARF).

  20. Beaconless search and rescue using polarimetric synthetic aperture radar

    Science.gov (United States)

    McCandless, Samuel W.; Huxtable, Barton D.; Mansfield, Arthur W.; Wallace, Ronald; Larsen, Rudolph; Rais, Houra

    1996-03-01

    In developing a beaconless search and rescue capability to quickly locate small aircraft that have crashed in remote areas, NASA's Search and Rescue (S&R) Program brings together advanced polarimetric synthetic aperture radar processing, field and laboratory tests, and state-of-the-art automated target detection algorithms. This paper provides the status of this program, which began with experiments conducted in concert with the JPL DC-8 AirSAR in 1989 at the Duke University Forest. The program is being conducted by NASA's Goddard Space Flight Center (GSFC) under the auspices of the Search and Rescue Office.

  1. Multi element synthetic aperture transmission using a frequency division approach

    DEFF Research Database (Denmark)

    Gran, Fredrik; Jensen, Jørgen Arendt

    2003-01-01

    transmitted into the tissue is low. This paper describes a novel method in which the available spectrum is divided into 2N overlapping subbands. This will assure a smooth broadband high resolution spectrum when combined. The signals are grouped into two subsets in which all signals are fully orthogonal...... can therefore be used for flow imaging, unlike with Hadamard and Golay coding. The frequency division approach increases the SNR by a factor of N2 compared to conventional pulsed synthetic aperture imaging, provided that N transmission centers are used. Simulations and phantom measurements...

  2. Chinese very small aperture terminal system for ministries

    Science.gov (United States)

    Dan, Sen

    The objective and technologic approach of the Chinese very small aperture terminal (VSAT) system of data communications is described in this paper. The system is primarily designed for the management business of many governmental ministries and administrations. It consists of a centralized processing and switching facility and a number of groups of remote terminals. The network is constructed in a star configuration because of simplicity and the inherent nature of the management business. Either Intelsat of Chinese domestic communications satellite can be used for the space segment. The system performance has been verified by field trials. Some results of system analysis can be used for traffic design.

  3. Synthetic aperture lidar as a future tool for earth observation

    Science.gov (United States)

    Turbide, Simon; Marchese, Linda; Terroux, Marc; Bergeron, Alain

    2017-11-01

    Synthetic aperture radar (SAR) is a tool of prime importance for Earth observation; it provides day and night capabilities in various weather conditions. State-of-the-art satellite SAR systems are a few meters in height and width and achieve resolutions of less than 1 m with revisit times on the order of days. Today's Earth observation needs demand higher resolution imaging together with timelier data collection within a compact low power consumption payload. Such needs are seen in Earth Observation applications such as disaster management of earthquakes, landslides, forest fires, floods and others. In these applications the availability of timely reliable information is critical to assess the extent of the disaster and to rapidly and safely deploy rescue teams. Synthetic aperture lidar (SAL) is based on the same basic principles as SAR. Both rely on the acquisition of multiple electromagnetic echoes to emulate a large antenna aperture providing the ability to produce high resolution images. However, in SAL, much shorter optical wavelengths (1.5 μm) are used instead of radar ones (wavelengths around 3 cm). Resolution being related to the wavelength, multiple orders of magnitude of improvement could be theoretically expected. Also, the sources, the detector, and the components are much smaller in optical domain than those for radar. The resulting system can thus be made compact opening the door to deployment onboard small satellites, airborne platforms and unmanned air vehicles. This has a strong impact on the time required to develop, deploy and use a payload. Moreover, in combination with airborne deployment, revisit times can be made much smaller and accessibility to the information can become almost in real-time. Over the last decades, studies from different groups have been done to validate the feasibility of a SAL system for 2D imagery and more recently for 3D static target imagery. In this paper, an overview of the advantages of this emerging technology will

  4. MYRaf: An Easy Aperture Photometry GUI for IRAF

    Science.gov (United States)

    Niaei, M. S.; KiliÇ, Y.; Özeren, F. F.

    2015-07-01

    We describe the design and development of MYRaf, a GUI (Graphical User Interface) that aims to be completely open-source under General Public License (GPL). MYRaf is an easy to use, reliable, and a fast IRAF aperture photometry GUI tool for those who are conversant with text-based software and command-line procedures in GNU/Linux OSs. MYRaf uses IRAF, PyRAF, matplotlib, ginga, alipy, and SExtractor with the general-purpose and high-level programming language Python, and uses the Qt framework.

  5. A fast autofocus algorithm for synthetic aperture radar processing

    DEFF Research Database (Denmark)

    Dall, Jørgen

    1992-01-01

    High-resolution synthetic aperture radar (SAR) imaging requires the motion of the radar platform to be known very accurately. Otherwise, phase errors are induced in the processing of the raw SAR data, and bad focusing results. In particular, a constant error in the measured along-track velocity o...... of magnitude lower than that of other algorithms providing comparable accuracies is presented. The algorithm has been tested on data from the Danish Airborne SAR, and the performance is compared with that of the traditional map drift algorithm...

  6. Crossover from spherical particle Mie scattering to circular aperture diffraction.

    Science.gov (United States)

    Heinson, William R; Chakrabarti, Amitabha; Sorensen, Christopher M

    2014-11-01

    This paper demonstrates the manner in which the Mie results for light scattering by a three-dimensional sphere of arbitrary size and refractive index crosses over to Fraunhofer diffraction by a two-dimensional circular aperture of the same radius in the limit of very large radius. Demonstration is feasible only because the graphical results are plotted in the manner of the Q-space analysis that plots scattered intensity versus the logarithm of the magnitude of the scattering wave vector rather than linear versus the scattering angle.

  7. VSAT networks - An overview. [Very Small Aperture Terminals

    Science.gov (United States)

    Maggenti, Mark; Ha, Tri T.; Pratt, Timothy

    1987-01-01

    This paper examines the technology and constraints of very small aperture terminals (VSAT) networks, a special type of wide-area thin-route satellite network that represents a recent innovation in the field of satellite communications. VSAT network architectures suitable for both data and voice communications are studied in this paper. Several issues concerning the frequency of operations, that is, C-band versus Ku-band are examined, and trade-offs between nonspread spectrum and spread spectrum techniques, as well as modulation and multiple access schemes, are considered in detail. Link design examples are given to illustrate the performance of various types of VSAT networks.

  8. Convolutional neural networks for synthetic aperture radar classification

    Science.gov (United States)

    Profeta, Andrew; Rodriguez, Andres; Clouse, H. Scott

    2016-05-01

    For electro-optical object recognition, convolutional neural networks (CNNs) are the state-of-the-art. For large datasets, CNNs are able to learn meaningful features used for classification. However, their application to synthetic aperture radar (SAR) has been limited. In this work we experimented with various CNN architectures on the MSTAR SAR dataset. As the input to the CNN we used the magnitude and phase (2 channels) of the SAR imagery. We used the deep learning toolboxes CAFFE and Torch7. Our results show that we can achieve 93% accuracy on the MSTAR dataset using CNNs.

  9. Extracting spatial information from large aperture exposures of diffuse sources

    Science.gov (United States)

    Clarke, J. T.; Moos, H. W.

    1981-01-01

    The spatial properties of large aperture exposures of diffuse emission can be used both to investigate spatial variations in the emission and to filter out camera noise in exposures of weak emission sources. Spatial imaging can be accomplished both parallel and perpendicular to dispersion with a resolution of 5-6 arc sec, and a narrow median filter running perpendicular to dispersion across a diffuse image selectively filters out point source features, such as reseaux marks and fast particle hits. Spatial information derived from observations of solar system objects is presented.

  10. Resonant Transmission of Cold Atoms through Subwavelength Apertures

    International Nuclear Information System (INIS)

    Moreno, Esteban; Fernandez-Dominguez, A.I.; Garcia-Vidal, F.J.; Cirac, J. Ignacio; Martin-Moreno, L.

    2005-01-01

    Recently, it has been observed that transmission of light through subwavelength apertures, which is usually negligible, can be significantly enhanced when surface plasmons are resonantly excited. Here we introduce the idea that similar effects can be expected for cold atoms in structures supporting surface matter waves. We show that surface matter waves are possible in properly designed structures, and then we theoretically demonstrate 100% transmission of rubidium atoms through an array of slits much narrower than the de Broglie wavelength of the atoms. Our results open up the possibility of using surface matter waves to control the flow of neutral atoms

  11. In-vivo synthetic aperture flow imaging in medical ultrasound

    DEFF Research Database (Denmark)

    Nikolov, Svetoslav; Jensen, Jørgen Arendt

    2003-01-01

    A new method for acquiring flow images using synthetic aperture techniques in medical ultrasound is presented. The new approach makes it possible to have a continuous acquisition of flow data throughout the whole image simultaneously, and this can significantly improve blood velocity estimation.......2% and a mean relative bias of 3.4% using 24 pulse emissions at a flow angle of 45 degrees. The 24 emissions can be used for making a full-color flow map image. An in-vivo image of How in the carotid artery for a 29-year-old male also is presented. The full image is acquired using 24 emissions....

  12. Implementation of Synthetic Aperture Imaging in Medical Ultrasound

    DEFF Research Database (Denmark)

    Jensen, Jørgen Arendt; Kortbek, Jacob; Nikolov, Svetoslav

    2010-01-01

    The main advantage of medical ultrasound imaging is its real time capability, which makes it possible to visualize dynamic structures in the human body. Real time synthetic aperture imaging puts very high demands on the hardware, which currently cannot be met. A method for reducing the number...... of calculations and still retain the many advantages of SA imaging is described. It consists of a dual stage beamformer, where the first can be a simple fixed focus analog beamformer and the second an ordinary digital ultrasound beamformer. The performance and constrictions of the approach is described....

  13. Synthetic Aperture Interferometry: In-Process Measurement of Aspheric Optics

    Science.gov (United States)

    Tomlinson, Richard; Coupland, Jeremy M.; Petzing, Jon

    2003-02-01

    A scanning probe consisting of a source and receive fiber pair is used to measure the phase difference between wave fronts scattered from the front and rear surfaces of an aspheric optic. This system can be thought of as a classical interferometer with an aperture synthesized from the data collected along the path of the probe. If the form of either surface is known, the other can be deduced. In contrast with classical interferometers, the method does not need test or null plates and has the potential to be integrated into the manufacturing process.

  14. Singer product apertures—A coded aperture system with a fast decoding algorithm

    Energy Technology Data Exchange (ETDEWEB)

    Byard, Kevin, E-mail: kevin.byard@aut.ac.nz [School of Economics, Faculty of Business, Economics and Law, Auckland University of Technology, Auckland 1142 (New Zealand); Shutler, Paul M.E. [National Institute of Education, Nanyang Technological University, 1 Nanyang Walk, Singapore 637616 (Singapore)

    2017-06-01

    A new type of coded aperture configuration that enables fast decoding of the coded aperture shadowgram data is presented. Based on the products of incidence vectors generated from the Singer difference sets, we call these Singer product apertures. For a range of aperture dimensions, we compare experimentally the performance of three decoding methods: standard decoding, induction decoding and direct vector decoding. In all cases the induction and direct vector methods are several orders of magnitude faster than the standard method, with direct vector decoding being significantly faster than induction decoding. For apertures of the same dimensions the increase in speed offered by direct vector decoding over induction decoding is better for lower throughput apertures.

  15. Singer product apertures—A coded aperture system with a fast decoding algorithm

    International Nuclear Information System (INIS)

    Byard, Kevin; Shutler, Paul M.E.

    2017-01-01

    A new type of coded aperture configuration that enables fast decoding of the coded aperture shadowgram data is presented. Based on the products of incidence vectors generated from the Singer difference sets, we call these Singer product apertures. For a range of aperture dimensions, we compare experimentally the performance of three decoding methods: standard decoding, induction decoding and direct vector decoding. In all cases the induction and direct vector methods are several orders of magnitude faster than the standard method, with direct vector decoding being significantly faster than induction decoding. For apertures of the same dimensions the increase in speed offered by direct vector decoding over induction decoding is better for lower throughput apertures.

  16. Pattern Synthesis of Dual-band Shared Aperture Interleaved Linear Antenna Arrays

    Directory of Open Access Journals (Sweden)

    H. Guo

    2014-09-01

    Full Text Available This paper presents an approach to improve the efficiency of an array aperture by interleaving two different arrays in the same aperture area. Two sub-arrays working at different frequencies are interleaved in the same linear aperture area. The available aperture area is efficiently used. The element positions of antenna array are optimized by using Invasive Weed Optimization (IWO to reduce the peak side lobe level (PSLL of the radiation pattern. To overcome the shortness of traditional methods which can only fulfill the design of shared aperture antenna array working at the same frequency, this method can achieve the design of dual-band antenna array with wide working frequency range. Simulation results show that the proposed method is feasible and efficient in the synthesis of dual-band shared aperture antenna array.

  17. Nonparaxial propagation and focusing properties of azimuthal-variant vector fields diffracted by an annular aperture.

    Science.gov (United States)

    Gu, Bing; Xu, Danfeng; Pan, Yang; Cui, Yiping

    2014-07-01

    Based on the vectorial Rayleigh-Sommerfeld integrals, the analytical expressions for azimuthal-variant vector fields diffracted by an annular aperture are presented. This helps us to investigate the propagation behaviors and the focusing properties of apertured azimuthal-variant vector fields under nonparaxial and paraxial approximations. The diffraction by a circular aperture, a circular disk, or propagation in free space can be treated as special cases of this general result. Simulation results show that the transverse intensity, longitudinal intensity, and far-field divergence angle of nonparaxially apertured azimuthal-variant vector fields depend strongly on the azimuthal index, the outer truncation parameter and the inner truncation parameter of the annular aperture, as well as the ratio of the waist width to the wavelength. Moreover, the multiple-ring-structured intensity pattern of the focused azimuthal-variant vector field, which originates from the diffraction effect caused by an annular aperture, is experimentally demonstrated.

  18. Automated Polarimetry with Smaller Aperture Telescopes: The ROVOR Observatory

    Directory of Open Access Journals (Sweden)

    Joseph Moody

    2017-10-01

    Full Text Available To better understand possible blazar jet mechanisms and morphologies, brighter prototypical objects are regularly monitored for variability in optical broad-band light. If the monitoring filters are polarized, the position angles and polarization percentages can be measured and their evolution monitored over time. However, building up a statistically significant time base of polarization parameters requires the arduous task of monitoring sources for months or years to catch and follow interesting events such as flares. Fortunately, monitoring an object is easily done using remotely operated or robotic telescopes. The Remote Observatory for Variable Object Research (ROVOR is a small-aperture telescope that has monitored blazars in broad-band Johnson filters since 2009. Calibration data using a set of four plane-polarized filters suggest that it is suitable for polarimetric monitoring as well. We have successfully collected data on CTA 102 and are encouraged at the prospects of monitoring it and other similar objects. Long-term monitoring campaigns are a scientifically and educationally-effective use of underutilized smaller-aperture telescopes.

  19. Study of Wide Swath Synthetic Aperture Ladar Imaging Techology

    Directory of Open Access Journals (Sweden)

    Zhang Keshu

    2017-02-01

    Full Text Available Combining synthetic-aperture imaging and coherent-light detection technology, the weak signal identification capacity of Synthetic Aperture Ladar (SAL reaches the photo level, and the image resolution exceeds the diffraction limit of the telescope to obtain high-resolution images irrespective to ranges. This paper introduces SAL, including the development path, technology characteristics, and the restriction of imaging swath. On the basis of this, we propose to integrate the SAL technology for extending its swath. By analyzing the scanning-operation mode and the signal model, the paper explicitly proposes that the former mode will be the developmental trend of the SAL technology. This paper also introduces the flight demonstrations of the SAL and the imaging results of remote targets, showing the potential of the SAL in long-range, high-resolution, and scanning-imaging applications. The technology and the theory of the scanning mode of SAL compensates for the defects related to the swath and operation efficiency of the current SAL. It provides scientific foundation for the SAL system applied in wide swath, high resolution earth observation, and the ISAL system applied in space-targets imaging.

  20. Dynamic Aperture and Resonance Correction for JPARC-RCS

    CERN Document Server

    Molodojentsev, Alexander Y; Hotchi, Hideaki; Ishi, Yoshihiro; Machida, Shinji; Noda, Fumiaki; Shirakata, Masashi; Shobuda, Yoshihiro; Suzuki, Hiromitu; Yamamoto, Kazami

    2005-01-01

    Main intrinsic field nonlinearities, which are common for synchrotrons with large aperture, are the nonlinear field of the bending magnets, the fringing field of the magnets and the sextupole field nonlinearity, used for the chromaticity correction. The particle motion in the ring bending magnets has been analyzed by two methods: (1) by direct integration of the particle motion equations in the 3D magnetic field (Tosca output), based on the 4th order Runge-Kutta integrator and (2) by determination the transfer 8th order map of the bending magnet by using the Gaussian wavelet in the 3D space. The second technique allows us to use powerful tools such as the normal form analysis, to define the resonance driving terms, which can be used for the resonance correction. As the result of this study it was shown that the main limitation of the RCS dynamic aperture can be caused by the structure normal sextupole-order resonance and the normal octupole-order resonance. Other high-order resonances have smaller effects on ...

  1. Super Unit Cells in Aperture-Based Metamaterials

    Directory of Open Access Journals (Sweden)

    Dragan Tanasković

    2015-01-01

    Full Text Available An important class of electromagnetic metamaterials are aperture-based metasurfaces. Examples include extraordinary optical transmission arrays and double fishnets with negative refractive index. We analyze a generalization of such metamaterials where a simple aperture is now replaced by a compound object formed by superposition of two or more primitive objects (e.g., rectangles, circles, and ellipses. Thus obtained “super unit cell” shows far richer behavior than the subobjects that comprise it. We show that nonlocalities introduced by overlapping simple subobjects can be used to produce large deviations of spectral dispersion even for small additive modifications of the basic geometry. Technologically, some super cells may be fabricated by simple spatial shifting of the existing photolithographic masks. In our investigation we applied analytical calculations and ab initio finite element modeling to prove the possibility to tailor the dispersion including resonances for plasmonic nanocomposites by adjusting the local geometry and exploiting localized interactions at a subwavelength level. Any desired form could be defined using simple primitive objects, making the situation a geometrical analog of the case of series expansion of a function. Thus an additional degree of tunability of metamaterials is obtained. The obtained designer structures can be applied in different fields like waveguiding and sensing.

  2. A Compressed Sensing Strategy for Synthetic Transmit Aperture Ultrasound Imaging.

    Science.gov (United States)

    Liu, Jing; He, Qiong; Luo, Jianwen

    2017-04-01

    A novel beamforming technique, named compressed sensing based synthetic transmit aperture (CS-STA) is proposed to speed up the acquisition of ultrasound imaging. This technique consists of three steps. First, the ultrasound transducer transmits randomly apodized plane waves for a number of times and receives the backscattered echoes. Second, the recorded backscattered echoes are used to recover the full channel dataset of synthetic transmit aperture (STA) with a compressed sensing (CS) reconstruction algorithm. Finally, an STA image is beamformed from the recovered full STA dataset. As CS allows recovering a signal from its few linear measurements with high probability, CS-STA is capable of recovering the STA image with fewer firings (i.e., higher frame rate) and retaining the high resolution of STA. In addition, the contrast of the STA image can be improved at the same time owing to the higher energy of plane wave firing in CS-STA. Simulations demonstrate that CS-STA is capable of recovering the STA channel dataset with a smaller number of firings. The performance of CS-STA is evaluated in phantom experiments through comparisons with STA, multi-element STA, conventional focused mode and coherent plane wave imaging. The results demonstrate that, implemented with the same frame rate, CS-STA achieves higher or comparable resolution and contrast. Moreover, comparisons are conducted on the biceps brachii muscle and thyroid of a human subject, and the results demonstrate the feasibility and competitiveness of CS-STA in the in vivo conditions.

  3. Multi-Aperture CMOS Sun Sensor for Microsatellite Attitude Determination

    Directory of Open Access Journals (Sweden)

    Michele Grassi

    2009-06-01

    Full Text Available This paper describes the high precision digital sun sensor under development at the University of Naples. The sensor determines the sun line orientation in the sensor frame from the measurement of the sun position on the focal plane. It exploits CMOS technology and an original optical head design with multiple apertures. This allows simultaneous multiple acquisitions of the sun as spots on the focal plane. The sensor can be operated either with a fixed or a variable number of sun spots, depending on the required field of view and sun-line measurement precision. Multiple acquisitions are averaged by using techniques which minimize the computational load to extract the sun line orientation with high precision. Accuracy and computational efficiency are also improved thanks to an original design of the calibration function relying on neural networks. Extensive test campaigns are carried out using a laboratory test facility reproducing sun spectrum, apparent size and distance, and variable illumination directions. Test results validate the sensor concept, confirming the precision improvement achievable with multiple apertures, and sensor operation with a variable number of sun spots. Specifically, the sensor provides accuracy and precision in the order of 1 arcmin and 1 arcsec, respectively.

  4. Interferometric Synthetic Aperture Microscopy: Computed Imaging for Scanned Coherent Microscopy

    Directory of Open Access Journals (Sweden)

    Stephen A. Boppart

    2008-06-01

    Full Text Available Three-dimensional image formation in microscopy is greatly enhanced by the use of computed imaging techniques. In particular, Interferometric Synthetic Aperture Microscopy (ISAM allows the removal of out-of-focus blur in broadband, coherent microscopy. Earlier methods, such as optical coherence tomography (OCT, utilize interferometric ranging, but do not apply computed imaging methods and therefore must scan the focal depth to acquire extended volumetric images. ISAM removes the need to scan the focus by allowing volumetric image reconstruction from data collected at a single focal depth. ISAM signal processing techniques are similar to the Fourier migration methods of seismology and the Fourier reconstruction methods of Synthetic Aperture Radar (SAR. In this article ISAM is described and the close ties between ISAM and SAR are explored. ISAM and a simple strip-map SAR system are placed in a common mathematical framework and compared to OCT and radar respectively. This article is intended to serve as a review of ISAM, and will be especially useful to readers with a background in SAR.

  5. Fabrication of large aperture SiC brazing mirror

    Science.gov (United States)

    Li, Ang; Wang, Peipei; Dong, Huiwen; Wang, Peng

    2016-10-01

    The SiC brazing mirror is the mirror whose blank is made by assembling together smaller SiC pieces with brazing technique. Using such kinds of joining techniques, people can manufacture large and complex SiC assemblies. The key technologies of fabricating and testing SiC brazing flat mirror especially for large aperture were studied. The SiC brazing flat mirror was ground by smart ultrasonic-milling machine, and then it was lapped by the lapping smart robot and measured by Coordinate Measuring Machine (CMM). After the PV of the surface below 4um, we did classic coarse polishing to the surface and studied the shape of the polishing tool which directly effects removal amount distribution. Finally, it was figured by the polishing smart robot and measured by Fizeau interferometer. We also studied the influence of machining path and removal functions of smart robots on the manufacturing results and discussed the use of abrasive in this process. At last, an example for fabricating and measuring a similar SiC brazing flat mirror with the aperture of 600 mm made by Shanghai Institute of Ceramics was given. The mirror blank consists of 6 SiC sectors and the surface was finally processed to a result of the Peak-to-Valley (PV) 150nm and Root Mean Square (RMS) 12nm.

  6. Frequency-domain synthetic aperture focusing for helical ultrasonic imaging

    Science.gov (United States)

    Jin, H.; Chen, J.; Wu, E.; Yang, K.

    2017-04-01

    The synthetic aperture focusing technique (SAFT) is widely used to provide significant improvement in the lateral resolution of ultrasonic images. Frequency-domain SAFT has shown higher accuracy and greater efficiency than time-domain SAFT. However, frequency-domain SAFT should be helix-based for ultrasonic scanning of cylindrical structures such as pipes and axletrees. In this study, a frequency-domain SAFT is proposed for 3D helical ultrasonic imaging applications. This technique adjusts the phase spectra of the images to complete the synthetic aperture focusing process. The focused image is precise because the proposed algorithm is established on the basis of the wave equation in a helical coordinate system. In addition, the algorithm can efficiently separate out point scatterers and present volume scatterers. The experimental results show that the proposed algorithm yields lower side lobes and enhances the angular resolution of the ultrasonic image to approximately 1°- 1.5°, which is much better than the performance of time-domain SAFT. The maximum deviations are only 0.6 mm, 0.5°, and 0.4 mm along the r-axes, θ-axes, and z-axes, respectively, which are appropriate for normal ultrasonic nondestructive testing.

  7. Aperture-based antihydrogen gravity experiment: Parallel plate geometry

    Directory of Open Access Journals (Sweden)

    J. R. Rocha

    2013-10-01

    Full Text Available An analytical model and a Monte Carlo simulation are presented of an experiment that could be used to determine the direction of the acceleration of antihydrogen due to gravity. The experiment would rely on methods developed by existing antihydrogen research collaborations. The configuration consists of two circular, parallel plates that have an axis of symmetry directed away from the center of the earth. The plates are separated by a small vertical distance, and include one or more pairs of circular barriers that protrude from the upper and lower plates, thereby forming an aperture between the plates. Antihydrogen annihilations that occur just beyond each barrier, within a “shadow” region, are asymmetric on the upper plate relative to the lower plate. The probability for such annihilations is determined for a point, line and spheroidal source of antihydrogen. The production of 100,000 antiatoms is predicted to be necessary for the aperture-based experiment to indicate the direction of free fall acceleration of antimatter, provided that antihydrogen is produced within a sufficiently small antiproton plasma at a temperature of 4 K.

  8. Direct aperture deformation: An interfraction image guidance strategy

    International Nuclear Information System (INIS)

    Feng Yuanming; Castro-Pareja, Carlos; Shekhar, Raj; Yu, Cedric

    2006-01-01

    A new scheme, called direct aperture deformation (DAD), for online correction of interfraction geometric uncertainties under volumetric imaging guidance is presented. Using deformable image registration, the three-dimensional geometric transformation matrix can be derived that associates the planning image set and the images acquired on the day of treatment. Rather than replanning or moving the patient, we use the deformation matrix to morph the treatment apertures as a potential online correction method. A proof-of-principle study using an intensity-modulated radiation therapy plan for a prostate cancer patient was conducted. The method, procedure, and algorithm of DAD are described. The dose-volume histograms from the original plan, reoptimized plan, and rigid-body translation plan are compared with the ones from the DAD plan. The study showed the feasibility of the DAD as a general method for both target dislocation and deformation. As compared with using couch translation to move the patient, DAD is capable of correcting both target dislocation and deformations. As compared with reoptimization, online correction using the DAD scheme could be completed within a few minutes rather than tens of minutes and the speed gain would be at a very small cost of plan quality

  9. Deterministic direct aperture optimization using multiphase piecewise constant segmentation.

    Science.gov (United States)

    Nguyen, Dan; O'Connor, Daniel; Ruan, Dan; Sheng, Ke

    2017-11-01

    Direct aperture optimization (DAO) attempts to incorporate machine constraints in the inverse optimization to eliminate the post-processing steps in fluence map optimization (FMO) that degrade plan quality. Current commercial DAO methods utilize a stochastic or greedy approach to search a small aperture solution space. In this study, we propose a novel deterministic direct aperture optimization that integrates the segmentation of fluence map in the optimization problem using the multiphase piecewise constant Mumford-Shah formulation. The Mumford-Shah based direct aperture optimization problem was formulated to include an L2-norm dose fidelity term to penalize differences between the projected dose and the prescribed dose, an anisotropic total variation term to promote piecewise continuity in the fluence maps, and the multiphase piecewise constant Mumford-Shah function to partition the fluence into pairwise discrete segments. A proximal-class, first-order primal-dual solver was implemented to solve the large scale optimization problem, and an alternating module strategy was implemented to update fluence and delivery segments. Three patients of varying complexity-one glioblastoma multiforme (GBM) patient, one lung (LNG) patient, and one bilateral head and neck (H&N) patient with 3 PTVs-were selected to test the new DAO method. For each patient, 20 non-coplanar beams were first selected using column generation, followed by the Mumford-Shah based DAO (DAO MS ). For comparison, a popular and successful approach to DAO known as simulated annealing-a stochastic approach-was replicated. The simulated annealing DAO (DAO SA ) plans were then created using the same beam angles and maximum number of segments per beam. PTV coverage, PTV homogeneity D95D5, and OAR sparing were assessed for each plan. In addition, high dose spillage, defined as the 50% isodose volume divided by the tumor volume, as well as conformity, defined as the van't Riet conformation number, were evaluated

  10. Translation symmetry of the Fraunhofer diffraction pattern from a polygonal aperture

    International Nuclear Information System (INIS)

    Vinogradov, I.R.; Tarlykov, V.A.

    1995-01-01

    The problem of observing the translation symmetry in the Fraunhofer diffraction pattern is treated. The objective of this study is to show that translation symmetry can be observed in the Fraunhofer diffraction pattern if the diffraction aperture can be represented in the form of a set of parallelogram apertures. It is shown that the diffraction field produced by such an aperture can be represented as a system of point sources modulated with an amplitude factor. 10 refs., 2 figs

  11. The Effect of Vibration Characteristics on the Atomization Rate in a Micro-Tapered Aperture Atomizer

    OpenAIRE

    Qiufeng Yan; Jianhui Zhang; Jun Huang; Ying Wang

    2018-01-01

    Because little is known about the atomization theory of a micro-tapered aperture atomizer, we investigated the vibration characteristics of this type of atomizer. The atomization mechanism of a micro-tapered aperture atomizer was described, and the atomization rate equation was deduced. As observed via microscopy, the angle of the micro-tapered aperture changes with the applied voltage, which proved the existence of a dynamic cone angle. The forward and reverse atomization rates were measured...

  12. 11 T Twin-Aperture Nb$_3$Sn Dipole Development for LHC Upgrades

    CERN Document Server

    Zlobin, A V; Apollinari, G; Auchmann, B; Barzi, E; Izquierdo Bermudez, S; Bossert, R; Buehler, M; Chlachidze, G; DiMarco, J; Karppinen, M; Nobrega, F; Novitski, I; Rossi, L; Smekens, D; Tartaglia, M; Turrioni, D; Velev, Genadi

    2015-01-01

    FNAL and CERN are developing a twin-aperture 11 T Nb3Sn dipole suitable for installation in the LHC. This paper describes the design and parameters of the 11 T dipole developed at FNAL for the LHC upgrades in both single-aperture and twin-aperture configurations, and presents details of the constructed dipole models. Results of studies of magnet quench performance, quench protection and magnetic measurements performed using short 1 m long coils in the dipole mirror and single-aperture configurations are reported and discussed.

  13. Broadband light funneling in ultrasubwavelength channels having periodic connected unfilled apertures

    Science.gov (United States)

    Subramania, Ganapathi Subramanian; Brener, Igal; Foteinopoulou, Stavroula

    2017-08-01

    A structure for broadband light funneling comprises a two-dimensional periodic array of connected ultrasubwavelength apertures, each aperture comprising a large sub-aperture that aids in the coupling of the incoming incident light and a small sub-aperture that funnels a significant fraction of the incident light power. The structure possesses all the capabilities of prior extraordinary optical transmission platforms, yet operates nonresonantly on a distinctly different mechanism. The structure demonstrates efficient ultrabroadband funneling of optical power confined in an area as small as .about.(.lamda./500).sup.2, where optical fields are enhanced, thus exhibiting functional possibilities beyond resonant platforms.

  14. An Efficient Hybrid MoM/FEM Method for Analyzing the Enclosures With Apertures

    Directory of Open Access Journals (Sweden)

    SİBEL YENİKAYA

    2011-03-01

    Full Text Available In this paper a hybrid formulation is presented which combines edge-based vector finite method (FEM and Method of Moments (MoM in frequency domain to predict electromagnetic field distribution inside an enclosure with aperture. While MoM is used for solving the surface integrals related with the aperture field components via equivalent surface currents, FEM is used for solving electromagnetic fields inside of the enclosure. Numerical results for shielding effectiveness and electrical energy of enclosure with aperture are calculated by the hybrid method and they are presented and validated with the existing literature. Then the method is applied to different enclosures with different aperture sizes.

  15. Quench Performance of the First Twin-aperture 11 T Dipole for LHC upgrades

    CERN Document Server

    Zlobin, A V; Apollinari, G; Barzi, E; Chlachidze, G; Nobrega, A; Novitski, I; Stoynev, S; Turrioni, D; Auchmann, B; Izquierdo Bermudez, S; Karppinen, M; Rossi, L; Savary, F; Smekens, D

    2015-01-01

    FNAL and CERN are developing a twin-aperture 11 T $Nb_{3}Sn$ dipole suitable for installation in the LHC. A single-aperture 2-m long dipole demonstrator and two 1-m long dipole models have been fabricated and tested at FNAL in 2012-2014. The two 1 m long collared coils were then assembled into the first twin-aperture $Nb_{3}Sn$ demonstrator dipole and tested. Test results of this twin-aperture $Nb_{3}Sn$ dipole model are reported and discussed.

  16. AlGaN/GaN current aperture vertical electron transistors with regrown channels

    OpenAIRE

    Ben-Yaacov, I; Seck, Y K; Mishra, U K; DenBaars, S P

    2004-01-01

    AlGaN/GaN current aperture vertical electron transistors with regrown aperture and source regions have been fabricated and tested. A 2 mum thick GaN:Si drain region followed by a 0.4 mum GaN:Mg current-blocking layer were grown by metalorganic chemical vapor deposition on a c-plane sapphire substrate. Channel apertures were etched, and a maskless regrowth was performed to grow unintentionally doped GaN inside the aperture as well as above the insulating layer, and to add an AlGaN cap layer. C...

  17. Effect Study of Aperture Distribution on the Capillary Pressure-Saturation Relation for the Single Fracture

    Directory of Open Access Journals (Sweden)

    Yuan Wang

    2017-01-01

    Full Text Available A systematic numerical method was presented to investigate the effect of aperture distribution on the relation of capillary pressure versus fluid saturation (P-S relation for a single fracture. The fracture was conceptualized as a two-dimensional lattice-grid model and its aperture field was described by a probability distribution. Based on the invasion percolation theory, a program was developed to simulate the quasi-static displacement. The simulation was verified validly by comparisons of the experimental results. The effects of the statistical parameters were further quantified. The results show that the largest local aperture on the fracture boundary determines the AEV. The larger mean decreases the variation coefficient, which causes the more uniform aperture field, smoother air invasion front, and steeper capillary pressure-saturation curve (CPSC. The larger standard deviation increases not only the range but also the contrast degree of the apertures, thus providing a nondeterministic rule in the P-S relation. The larger correlation length causes a more homogeneous aperture field and a dual connectivity of the fracture. The increase of the difference and contrast degree between the small and large apertures results in dual-aperture fields. The dual-aperture field and dual connectivity of the fracture both contribute to the bimodal characteristic of the CPSC.

  18. On-axis parallel ion speeds near mechanical and magnetic apertures in a helicon plasma device

    International Nuclear Information System (INIS)

    Sun Xuan; Cohen, S.A.; Scime, Earl E.; Miah, Mahmood

    2005-01-01

    Using laser-induced fluorescence, measurements of parallel ion velocities were made along the axis of a helicon-generated Ar plasma column whose radius was modified by spatially separated mechanical and magnetic apertures. Ion acceleration to supersonic speeds was observed 0.1-5 cm downstream of both aperture types, simultaneously generating two steady-state double layers (DLs) when both apertures were in place. The DL downstream of the mechanical aperture plate had a larger potential drop, Δφ DL =6-9 kT e , compared to the DL downstream of the magnetic aperture, Δφ DL ∼3 kT e . In the presheath region upstream of the mechanical aperture, the convective ion speed increased over a collisional distance; from stagnant at 4 cm from the aperture to the 1.4 times the sound speed at the aperture. The dependence of the free- and trapped-ion-velocity-distribution functions on the magnetic-field strength and mechanical-aperture electrical bias are also presented

  19. Use of Synthetic Aperture Radar in Cold Climate Flood Response

    Science.gov (United States)

    Yarbrough, L. D.

    2009-12-01

    The purpose of this study was to investigate the usefulness of Synthetic Aperture Radar (SAR) satellite images during a cold climate disaster response event. There were 15 European Space Agency (ESA) Advanced Synthetic Aperture Radar ASAR scenes, five Japan Aerospace Exploration Agency (JAXA) Phased Array type L-band Synthetic Aperture Radar (PALSAR) scenes, one RADARSAT2 scene, and numerous optical sensor data. These data were primarily used to indentify floodwater inundation polygons and flow vectors. However, in cold climate flooding, there are complicating factors such as frazil ice, ice jams, and snow-covered, frozen flood waters that are not present during warmer flooding events. The imagery was obtained through the International Charter "Space and Major Disasters.” The Charter aims at providing a unified system of space data acquisition and delivery to those affected by natural or man-made disasters through Authorized Users. Each member agency has committed resources to support the provisions of the Charter, and thus is helping to mitigate the effects of disasters on human life and property. On 25 March 2009, the Charter was activated in response to the flooding along the Red River of the North in the states of North Dakota and Minnesota of the United States. The delivery time of a single SAR scene from a Charter participant was less than 12 hours from the time of acquisition. This expedited service allowed additional time for creating image-based derivations, field checking and delivery to a decision maker or emergency responder. SAR-derived data sets include identification of river ice and saturated ground conditions. This data could be provided to experts in river ice engineering for use in the development of plans to reduce ice jamming, its effect on water levels and additional stresses on river infrastructure. During disaster response applications, SAR data was found to very useful in indentifying open water and the front of ice jams. Using a river

  20. Wideband Low Side Lobe Aperture Coupled Patch Phased Array Antennas

    Science.gov (United States)

    Poduval, Dhruva

    Low profile printed antenna arrays with wide bandwidth, high gain, and low Side Lobe Level (SLL) are in great demand for current and future commercial and military communication systems and radar. Aperture coupled patch antennas have been proposed to obtain wide impedance bandwidths in the past. Aperture coupling is preferred particularly for phased arrays because of their advantage of integration to other active devices and circuits, e.g. phase shifters, power amplifiers, low noise amplifiers, mixers etc. However, when designing such arrays, the interplay between array performance characteristics, such as gain, side lobe level, back lobe level, mutual coupling etc. must be understood and optimized under multiple design constraints, e.g. substrate material properties and thicknesses, element to element spacing, and feed lines and their orientation and arrangements with respect to the antenna elements. The focus of this thesis is to investigate, design, and develop an aperture coupled patch array with wide operating bandwidth (30%), high gain (17.5 dBi), low side lobe level (20 dB), and high Forward to Backward (F/B) ratio (21.8 dB). The target frequency range is 2.4 to 3 GHz given its wide application in WLAN, LTE (Long Term Evolution) and other communication systems. Notwithstanding that the design concept can very well be adapted at other frequencies. Specifically, a 16 element, 4 by 4 planar microstrip patch array is designed using HFSS and experimentally developed and tested. Starting from mutual coupling minimization a corporate feeding scheme is designed to achieve the needed performance. To reduce the SLL the corporate feeding network is redesigned to obtain a specific amplitude taper. Studies are conducted to determine the optimum location for a metallic reflector under the feed line to improve the F/B. An experimental prototype of the antenna was built and tested validating and demonstrating the performance levels expected from simulation predictions

  1. Simultaneous beam sampling and aperture shape optimization for SPORT

    International Nuclear Information System (INIS)

    Zarepisheh, Masoud; Li, Ruijiang; Xing, Lei; Ye, Yinyu

    2015-01-01

    Purpose: Station parameter optimized radiation therapy (SPORT) was recently proposed to fully utilize the technical capability of emerging digital linear accelerators, in which the station parameters of a delivery system, such as aperture shape and weight, couch position/angle, gantry/collimator angle, can be optimized simultaneously. SPORT promises to deliver remarkable radiation dose distributions in an efficient manner, yet there exists no optimization algorithm for its implementation. The purpose of this work is to develop an algorithm to simultaneously optimize the beam sampling and aperture shapes. Methods: The authors build a mathematical model with the fundamental station point parameters as the decision variables. To solve the resulting large-scale optimization problem, the authors devise an effective algorithm by integrating three advanced optimization techniques: column generation, subgradient method, and pattern search. Column generation adds the most beneficial stations sequentially until the plan quality improvement saturates and provides a good starting point for the subsequent optimization. It also adds the new stations during the algorithm if beneficial. For each update resulted from column generation, the subgradient method improves the selected stations locally by reshaping the apertures and updating the beam angles toward a descent subgradient direction. The algorithm continues to improve the selected stations locally and globally by a pattern search algorithm to explore the part of search space not reachable by the subgradient method. By combining these three techniques together, all plausible combinations of station parameters are searched efficiently to yield the optimal solution. Results: A SPORT optimization framework with seamlessly integration of three complementary algorithms, column generation, subgradient method, and pattern search, was established. The proposed technique was applied to two previously treated clinical cases: a head and

  2. Direct aperture optimization: A turnkey solution for step-and-shoot IMRT

    International Nuclear Information System (INIS)

    Shepard, D.M.; Earl, M.A.; Li, X.A.; Naqvi, S.; Yu, C.

    2002-01-01

    IMRT treatment plans for step-and-shoot delivery have traditionally been produced through the optimization of intensity distributions (or maps) for each beam angle. The optimization step is followed by the application of a leaf-sequencing algorithm that translates each intensity map into a set of deliverable aperture shapes. In this article, we introduce an automated planning system in which we bypass the traditional intensity optimization, and instead directly optimize the shapes and the weights of the apertures. We call this approach 'direct aperture optimization'. This technique allows the user to specify the maximum number of apertures per beam direction, and hence provides significant control over the complexity of the treatment delivery. This is possible because the machine dependent delivery constraints imposed by the MLC are enforced within the aperture optimization algorithm rather than in a separate leaf-sequencing step. The leaf settings and the aperture intensities are optimized simultaneously using a simulated annealing algorithm. We have tested direct aperture optimization on a variety of patient cases using the EGS4/BEAM Monte Carlo package for our dose calculation engine. The results demonstrate that direct aperture optimization can produce highly conformal step-and-shoot treatment plans using only three to five apertures per beam direction. As compared with traditional optimization strategies, our studies demonstrate that direct aperture optimization can result in a significant reduction in both the number of beam segments and the number of monitor units. Direct aperture optimization therefore produces highly efficient treatment deliveries that maintain the full dosimetric benefits of IMRT

  3. Statistical analysis for coded aperture γ-ray telescope

    International Nuclear Information System (INIS)

    Ducros, G.; Ducros, R.

    1984-01-01

    We have developed a statistical analysis of the image recorded by a position sensitive detector associated with a coded mask for the French gamma ray satellite SIGMA, in the energy range (20-2 000 keV). The aperture of the telescope is not limited to the size of the mask. In the first part, we described the principle of the image analysis based on the least squares method with a fit function generated and tested term after term. The statistical test is performed on the F distribution followed by the relative improvement of chi 2 when the fit function has an additional term. The second part deals with digital processing aspects: the adjustment of the method to reduce computation time, and the analysis results of two simulated images. (orig.)

  4. Photometric Reverberation Mapping with a Small Aperture Telescope

    Science.gov (United States)

    Hood, Carol E.; Rivera, Noah I.; Thackeray-Lacko, Beverly; Powers, Randy M.; Stuckey, Harrison; Watson, Rene; Hood, Michael A.

    2015-01-01

    We present photometric observations of a sample of bright, broad-line AGN in order to monitor variability and verify their black hole masses using the photometric reverberation mapping technique. Observations were taken, primarily remotely, using the 20-inch telescope at the Murillo Family Observatory, a campus-based observatory located on the outskirts of the Southern California metro area, in both monitored and automated mode nightly in BVRI over a period of 2-5 months. We will show the viability of such a technique for small-aperture telescopes in bright-sky locations and discuss the possibilities of extending this program in the future. We also note that undergraduate students (both from 4-year and community colleges) have been and will continue to be instrumental in the success of similar research programs at CSUSB.

  5. INTERFEROMETRIC SYNTHETIC APERTURE RADAR (INSAR TECHNOLOGY AND GEOMORPHOLOGY INTERPRETATION

    Directory of Open Access Journals (Sweden)

    M. Maghsoudi

    2013-09-01

    Full Text Available Geomorphology is briefly the study of landforms and their formative processes on the surface of the planet earth as human habitat. The landforms evolution and the formative processes can best be studied by technologies with main application in study of elevation. Interferometric Synthetic Aperture Radar (InSAR is the appropriate technology for this application. With phase differences calculations in radar waves, the results of this technology can extensively be interpreted for geomorphologic researches. The purpose of the study is to review the geomorphologic studies using InSAR and also the technical studies about InSAR with geomorphologic interpretations. This study states that the InSAR technology can be recommended to be employed as a fundamental for geomorphology researches.

  6. Low-redundancy linear arrays in mirrored interferometric aperture synthesis.

    Science.gov (United States)

    Zhu, Dong; Hu, Fei; Wu, Liang; Li, Jun; Lang, Liang

    2016-01-15

    Mirrored interferometric aperture synthesis (MIAS) is a novel interferometry that can improve spatial resolution compared with that of conventional IAS. In one-dimensional (1-D) MIAS, antenna array with low redundancy has the potential to achieve a high spatial resolution. This Letter presents a technique for the direct construction of low-redundancy linear arrays (LRLAs) in MIAS and derives two regular analytical patterns that can yield various LRLAs in short computation time. Moreover, for a better estimation of the observed scene, a bi-measurement method is proposed to handle the rank defect associated with the transmatrix of those LRLAs. The results of imaging simulation demonstrate the effectiveness of the proposed method.

  7. Geometrical Aberration Suppression for Large Aperture Sub-THz Lenses

    Science.gov (United States)

    Rachon, M.; Liebert, K.; Siemion, A.; Bomba, J.; Sobczyk, A.; Knap, W.; Coquillat, D.; Suszek, J.; Sypek, M.

    2017-03-01

    Advanced THz setups require high performance optical elements with large numerical apertures and small focal lengths. This is due to the high absorption of humid air and relatively low efficiency of commercially available detectors. Here, we propose a new type of double-sided sub-THz diffractive optical element with suppressed geometrical aberration for narrowband applications (0.3 THz). One side of the element is designed as thin structure in non-paraxial approach which is the exact method, but only for ideally flat elements. The second side will compensate phase distribution differences between ideal thin structure and real volume one. The computer-aided optimization algorithm is performed to design an additional phase distribution of correcting layer assuming volume designing of the first side of the element. The experimental evaluation of the proposed diffractive component created by 3D printing technique shows almost two times larger performance in comparison with uncorrected basic diffractive lens.

  8. Design studies of a depth encoding large aperture PET camera

    International Nuclear Information System (INIS)

    Moisan, C.; Rogers, J.G.; Buckley, K.R.; Ruth, T.J.; Stazyk, M.W.; Tsang, G.

    1994-10-01

    The feasibility of a wholebody PET tomograph with the capacity to correct for the parallax error induced by the Depth-Of-Interaction of γ-rays is assessed through simulation. The experimental energy, depth, and transverse position resolutions of BGO block detector candidates are the main inputs to a simulation that predicts the point source resolution of the Depth Encoding Large Aperture Camera (DELAC). The results indicate that a measured depth resolution of 7 mm (FWHM) is sufficient to correct a substantial part of the parallax error for a point source at the edge of the Field-Of-View. A search for the block specifications and camera ring radius that would optimize the spatial resolution and its uniformity across the Field-Of-View is also presented. (author). 10 refs., 1 tab., 5 figs

  9. Seamless Synthetic Aperture Radar Archive for Interferometry Analysis

    Science.gov (United States)

    Baker, S.; Baru, C.; Bryson, G.; Buechler, B.; Crosby, C.; Fielding, E.; Meertens, C.; Nicoll, J.; Youn, C.

    2014-11-01

    The NASA Advancing Collaborative Connections for Earth System Science (ACCESS) seamless synthetic aperture radar (SAR) archive (SSARA) project is a collaboration between UNAVCO, the Alaska Satellite Facility (ASF), the Jet Propulsion Laboratory (JPL), and OpenTopography at the San Diego Supercomputer Center (SDSC) to design and implement a seamless distributed access system for SAR data and derived interferometric SAR (InSAR) data products. A unified application programming interface (API) has been created to search the SAR archives at ASF and UNAVCO, 30 and 90-m SRTM DEM data available through OpenTopography, and tropospheric data from the NASA OSCAR project at JPL. The federated query service provides users a single access point to search for SAR granules, InSAR pairs, and corresponding DEM and tropospheric data products from the four archives, as well as the ability to search and download pre-processed InSAR products from ASF and UNAVCO.

  10. Real-time synthetic aperture imaging: opportunities and challenges

    DEFF Research Database (Denmark)

    Nikolov, Svetoslav; Tomov, Borislav Gueorguiev; Jensen, Jørgen Arendt

    2006-01-01

    the development and implementation of the signal processing stages employed in SA imaging: compression of received data acquired using codes, and beamforming. The goal was to implement the system using commercially available field programmable gate arrays. The compression filter operates on frequency modulated......Synthetic aperture (SA) ultrasound imaging has not been introduced in commercial scanners mainly due to the computational cost associated with the hardware implementation of this imaging modality. SA imaging redefines the term beamformed line. Since the acquired information comes from all points...... in 3D. This parametric description makes it possible to quickly change the image geometry during scanning, thus enabling adaptive imaging and precise flow estimation. The paper addresses problems such as large bandwidth and computational load and gives the solutions that have been adopted...

  11. Segmented Aperture Interferometric Nulling Testbed (SAINT) II: component systems update

    Science.gov (United States)

    Hicks, Brian A.; Bolcar, Matthew R.; Helmbrecht, Michael A.; Petrone, Peter; Burke, Elliot; Corsetti, James; Dillon, Thomas; Lea, Andrew; Pellicori, Samuel; Sheets, Teresa; Shiri, Ron; Agolli, Jack; DeVries, John; Eberhardt, Andrew; McCabe, Tyler

    2017-09-01

    This work presents updates to the coronagraph and telescope components of the Segmented Aperture Interferometric Nulling Testbed (SAINT). The project pairs an actively-controlled macro-scale segmented mirror with the Visible Nulling Coronagraph (VNC) towards demonstrating capabilities for the future space observatories needed to directly detect and characterize a significant sample of Earth-sized worlds around nearby stars in the quest for identifying those which may be habitable and possibly harbor life. Efforts to improve the VNC wavefront control optics and mechanisms towards repeating narrowband results are described. A narrative is provided for the design of new optical components aimed at enabling broadband performance. Initial work with the hardware and software interface for controlling the segmented telescope mirror is also presented.

  12. Performance limits for maritime Inverse Synthetic Aperture Radar (ISAR)

    Energy Technology Data Exchange (ETDEWEB)

    Doerry, Armin Walter [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2013-11-01

    The performance of an Inverse Synthetic Aperture Radar (ISAR) system depends on a variety of factors, many which are interdependent in some manner. In this report we specifically examine ISAR as applied to maritime targets (e.g. ships). It is often difficult to get your arms around the problem of ascertaining achievable performance limits, and yet those limits exist and are dictated by physics. This report identifies and explores those limits, and how they depend on hardware system parameters and environmental conditions. Ultimately, this leads to a characterization of parameters that offer optimum performance for the overall ISAR system. While the information herein is not new to the literature, its collection into a single report hopes to offer some value in reducing the seek time.

  13. Large-aperture, high-damage-threshold optics for beamlet

    International Nuclear Information System (INIS)

    Campbell, J.H.; Atherton, L.J.; DeYoreo, J.J.; Kozlowski, M.R.; Maney, R.T.; Montesanti, R.C.; Sheehan, L.M.; Barker, C.E.

    1995-01-01

    Beamlet serves as a test bed for the proposed NIF laser design and components. Therefore, its optics are similar in size and quality to those proposed for the NIF. In general, the optics in the main laser cavity and transport section of Beamlet are larger and have higher damage thresholds than the optics manufactured for any of our previous laser systems. In addition, the quality of the Beamlet optical materials is higher, leading to better wavefront quality, higher optical transmission, and lower-intensity modulation of the output laser beam than, for example, that typically achieved on Nova. In this article, we discuss the properties and characteristics of the large-aperture optics used on Beamlet

  14. Convolution backprojection image reconstruction for spotlight mode synthetic aperture radar.

    Science.gov (United States)

    Desai, M D; Jenkins, W K

    1992-01-01

    Convolution backprojection (CBP) image reconstruction has been proposed as a means of producing high-resolution synthetic-aperture radar (SAR) images by processing data directly in the polar recording format which is the conventional recording format for spotlight mode SAR. The CBP algorithm filters each projection as it is recorded and then backprojects the ensemble of filtered projections to create the final image in a pixel-by-pixel format. CBP reconstruction produces high-quality images by handling the recorded data directly in polar format. The CBP algorithm requires only 1-D interpolation along the filtered projections to determine the precise values that must be contributed to the backprojection summation from each projection. The algorithm is thus able to produce higher quality images by eliminating the inaccuracies of 2-D interpolation, as well as using all the data recorded in the spectral domain annular sector more effectively. The computational complexity of the CBP algorithm is O(N (3)).

  15. The Signal Processing Firmware for the Low Frequency Aperture Array

    Science.gov (United States)

    Comoretto, Gianni; Chiello, Riccardo; Roberts, Matt; Halsall, Rob; Adami, Kristian Zarb; Alderighi, Monica; Aminaei, Amin; Baker, Jeremy; Belli, Carolina; Chiarucci, Simone; D'Angelo, Sergio; De Marco, Andrea; Mura, Gabriele Dalle; Magro, Alessio; Mattana, Andrea; Monari, Jader; Naldi, Giovanni; Pastore, Sandro; Perini, Federico; Poloni, Marco; Pupillo, Giuseppe; Rusticelli, Simone; Schiaffino, Marco; Schillirò, Francesco; Zaccaro, Emanuele

    The signal processing firmware that has been developed for the Low Frequency Aperture Array component of the Square Kilometre Array (SKA) is described. The firmware is implemented on a dual FPGA board, that is capable of processing the streams from 16 dual polarization antennas. Data processing includes channelization of the sampled data for each antenna, correction for instrumental response and for geometric delays and formation of one or more beams by combining the aligned streams. The channelizer uses an oversampling polyphase filterbank architecture, allowing a frequency continuous processing of the input signal without discontinuities between spectral channels. Each board processes the streams from 16 antennas, as part of larger beamforming system, linked by standard Ethernet interconnections. These are envisaged to be 8192 of these signal processing platforms in the first phase of the SKA so particular attention has been devoted to ensure the design is low cost and low power.

  16. Design of large aperture, low mass vacuum windows

    International Nuclear Information System (INIS)

    Leonhardt, W.J.; Mapes, M.

    1993-01-01

    Large vacuum vessels are employed downstream of fixed targets in High Energy Physics experiments to provide a long path for particles to traverse without interacting with air molecules. These vessels generally have a large aperture opening known as a vacuum window which employs a thin membrane to preserve the vacuum environment yet allows the particles to pass through with a minimal effect on them. Several large windows have been built using a composite of Kevlar/Mylar including circular windows to a diameter of 96.5 cm and rectangular windows up to 193 cm x 86 cm. This paper describes the design, fabrication, testing and operating experience with these windows and relates the actual performance to theoretical predictions

  17. Support subspaces method for synthetic aperture radar automatic target recognition

    Directory of Open Access Journals (Sweden)

    Vladimir Fursov

    2016-09-01

    Full Text Available This article offers a new object recognition approach that gives high quality using synthetic aperture radar images. The approach includes image preprocessing, clustering and recognition stages. At the image preprocessing stage, we compute the mass centre of object images for better image matching. A conjugation index of a recognition vector is used as a distance function at clustering and recognition stages. We suggest a construction of the so-called support subspaces, which provide high recognition quality with a significant dimension reduction. The results of the experiments demonstrate that the proposed method provides higher recognition quality (97.8% than such methods as support vector machine (95.9%, deep learning based on multilayer auto-encoder (96.6% and adaptive boosting (96.1%. The proposed method is stable for objects processed from different angles.

  18. Dynamical Aperture Control in Accelerator Lattices With Multipole Potentials

    CERN Document Server

    Morozov, I

    2017-01-01

    We develop tools for symbolic representation of a non-linear accelerator model and analytical methods for description of non-linear dynamics. Information relevant to the dynamic aperture (DA) is then obtained from this model and can be used for indirect DA control or as a complement to direct numerical optimization. We apply two analytical methods and use multipole magnets to satisfy derived analytical constraints. The accelerator model is represented as a product of unperturbed and perturbed exponential operators with the exponent of the perturbed operator given as a power series in the perturbation parameter. Normal forms can be applied to this representation and the lattice parameters are used to control the normal form Hamiltonian and normal form transformation. Hamiltonian control is used to compute a control term or controlled operator. Lattice parameters are then fitted to satisfy the imposed control constraints. Theoretical results, as well as illustrative examples, are presented.

  19. Hybrid coded aperture and Compton imaging using an active mask

    International Nuclear Information System (INIS)

    Schultz, L.J.; Wallace, M.S.; Galassi, M.C.; Hoover, A.S.; Mocko, M.; Palmer, D.M.; Tornga, S.R.; Kippen, R.M.; Hynes, M.V.; Toolin, M.J.; Harris, B.; McElroy, J.E.; Wakeford, D.; Lanza, R.C.; Horn, B.K.P.; Wehe, D.K.

    2009-01-01

    The trimodal imager (TMI) images gamma-ray sources from a mobile platform using both coded aperture (CA) and Compton imaging (CI) modalities. In this paper we will discuss development and performance of image reconstruction algorithms for the TMI. In order to develop algorithms in parallel with detector hardware we are using a GEANT4 [J. Allison, K. Amako, J. Apostolakis, H. Araujo, P.A. Dubois, M. Asai, G. Barrand, R. Capra, S. Chauvie, R. Chytracek, G. Cirrone, G. Cooperman, G. Cosmo, G. Cuttone, G. Daquino, et al., IEEE Trans. Nucl. Sci. NS-53 (1) (2006) 270] based simulation package to produce realistic data sets for code development. The simulation code incorporates detailed detector modeling, contributions from natural background radiation, and validation of simulation results against measured data. Maximum likelihood algorithms for both imaging methods are discussed, as well as a hybrid imaging algorithm wherein CA and CI information is fused to generate a higher fidelity reconstruction.

  20. Aperture Synthesis Methods and Applications to Optical Astronomy

    CERN Document Server

    Saha, Swapan Kumar

    2011-01-01

    Over the years long baseline optical interferometry has slowly gained in importance and today it is a powerful tool. This timely book sets out to highlight the basic principles of long baseline optical interferometry. The book addresses the fundamentals of stellar interferometry with emphasis on aperture synthesis using an array of telescopes particularly at optical/IR wavelengths. It discusses the fundamentals of electromagnetic fields, wave optics, interference, diffraction, and imaging at length. There is a chapter dedicated to radio and intensity interferometry corroborating with basic mathematical steps. The basic principle of optical interferometry and its requirements, its limitations and the technical challenges it poses, are also covered in depth. Assisted by illustrations and footnotes, the book examines the basic tricks of the trade, current trends and methods, and it points to the potential of true interferometry both from the ground and space.

  1. Signal based motion compensation for synthetic aperture radar

    Energy Technology Data Exchange (ETDEWEB)

    John Kirk

    1999-06-07

    The purpose of the Signal Based Motion Compensation (SBMC) for Synthetic Aperture Radar (SAR) effort is to develop a method to measure and compensate for both down range and cross range motion of the radar in order to provide high quality focused SAR imagery in the absence of precision measurements of the platform motion. Currently SAR systems require very precise navigation sensors for motion compensation. These sensors are very expensive and are often supplied in pairs for reliability. In the case of GPS they can be jammed, further degrading performance. This makes for a potentially very expensive and possibly vulnerable SAR system. SBMC can eliminate or reduce the need for these expensive navigation sensors thus reducing the cost of budget minded SAR systems. The results on this program demonstrated the capability of the SBMC approach.

  2. One-dimensional rainbow thermometry system by using slit apertures.

    Science.gov (United States)

    Wu, Xuecheng; Jiang, Haoyu; Wu, Yingchun; Song, Jin; Gréhan, Gérard; Saengkaew, Sawitree; Chen, Linghong; Gao, Xiang; Cen, Kefa

    2014-02-01

    A new rainbow thermometry system by using slit apertures and a laser light sheet, called a one-dimensional rainbow thermometry (ORT) system, has been developed as an extension of global rainbow thermometry (GRT). This system is capable of one-dimensional or line measurements of the size and refractive index of droplets in the spray space, while the conventional GRT system is normally considered a typical "single-point" or "small volume" measurement method. The performance of this new system was tested and verified with both water and ethanol spray. The results show the feasibility and potential of ORT in simultaneous and one-dimensional measurement of the size and refractive index of liquid droplets, especially in the research field of spray evaporation and combustion.

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

    Science.gov (United States)

    Xi, Jinxiang; Yan, Hong; Dong, Haibo

    2008-11-01

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

  4. In Vivo Real Time Volumetric Synthetic Aperture Ultrasound Imaging

    DEFF Research Database (Denmark)

    Bouzari, Hamed; Rasmussen, Morten Fischer; Brandt, Andreas Hjelm

    2015-01-01

    Synthetic aperture (SA) imaging can be used to achieve real-time volumetric ultrasound imaging using 2-D array transducers. The sensitivity of SA imaging is improved by maximizing the acoustic output, but one must consider the limitations of an ultrasound system, both technical and biological......-average intensity for parallel beamforming (PB) are 0.83 and 377.5mW/cm2, and for SA are 0.48 and 329.5mW/cm2. A human kidney was volumetrically imaged with SA and PB techniques simultaneously. Two radiologists for evaluation of the volumetric SA were consulted by means of a questionnaire on the level of details...

  5. Bridgman growth of large-aperture yttrium calcium oxyborate crystal

    International Nuclear Information System (INIS)

    Wu, Anhua; Jiang, Linwen; Qian, Guoxing; Zheng, Yanqing; Xu, Jun; Shi, Erwei

    2012-01-01

    Highlights: ► YCOB is a novel non-linear optical crystal possessing good thermal, mechanical and nonlinear optical properties. ► Large size crystal growth is key technology question for YCOB crystal. ► YCOB crystals 3 in. in diameter were grown with modified vertical Bridgman method. ► It is a more effective growth method to obtain large size and high quality YCOB crystal. -- Abstract: Large-aperture yttrium calcium oxyborate YCa 4 O(BO 3 ) 3 (YCOB) crystals with 3 in. in diameter were grown with modified vertical Bridgman method, and the large crystal plate (63 mm × 68 mm × 20 mm) was harvested for high-average power frequency conversion system. The crack, facet growth and spiral growth can be effectively controlled in the as-grown crystal, and Bridgman method displays more effective in obtain large size and high quality YCOB crystal plate than Czochralski technique.

  6. Factors affecting the performance of large-aperture microphone arrays

    Science.gov (United States)

    Silverman, Harvey F.; Patterson, William R.; Sachar, Joshua

    2002-05-01

    Large arrays of microphones have been proposed and studied as a possible means of acquiring data in offices, conference rooms, and auditoria without requiring close-talking microphones. When such an array essentially surrounds all possible sources, it is said to have a large aperture. Large-aperture arrays have attractive properties of spatial resolution and signal-to-noise enhancement. This paper presents a careful comparison of theoretical and measured performance for an array of 256 microphones using simple delay-and-sum beamforming. This is the largest currently functional, all digital-signal-processing array that we know of. The array is wall-mounted in the moderately adverse environment of a general-purpose laboratory (8 m×8 m×3 m). The room has a T60 reverberation time of 550 ms. Reverberation effects in this room severely impact the array's performance. However, the width of the main lobe remains comparable to that of a simplified prediction. Broadband spatial resolution shows a single central peak with 10 dB gain about 0.4 m in diameter at the -3 dB level. Away from that peak, the response is approximately flat over most of the room. Optimal weighting for signal-to-noise enhancement degrades the spatial resolution minimally. Experimentally, we verify that signal-to-noise gain is less than proportional to the square root of the number of microphones probably due to the partial correlation of the noise between channels, to variation of signal intensity with polar angle about the source, and to imperfect correlation of the signal over the array caused by reverberations. We show measurements of the relative importance of each effect in our environment.

  7. Analysis of the Systematic Errors Found in the Kipp & Zonen Large-Aperture Scintillometer

    NARCIS (Netherlands)

    Kesteren, van A.J.H.; Hartogensis, O.K.

    2011-01-01

    Studies have shown a systematic error in the Kipp & Zonen large-aperture scintillometer (K&ZLAS) measurements of the sensible heat flux, H. We improved on these studies and compared four K&ZLASs with a Wageningen large-aperture scintillometer at the Chilbolton Observatory. The

  8. The influence of target object shape on maximum grip aperture in human grasping movements

    NARCIS (Netherlands)

    Verheij, R.; Brenner, E.; Smeets, J.B.J.

    2014-01-01

    The shape of a target object could influence maximum grip aperture in human grasping movements in several different ways. Maximum grip aperture could be influenced by the required precision of digit placement, by the aim to avoid colliding with the wrong parts of the target objects, by the mass of

  9. Increasing the sensitivity of controlled-source electromagnetics with synthetic aperture

    NARCIS (Netherlands)

    Fan, Y.; Snieder, R.; Slob, E.C.; Hunziker, J.W.; Singer, J.; Sheiman, J.; Rosenquist, M.

    2012-01-01

    Controlled-source electromagnetics (CSEM) has been used as a derisking tool in the hydrocarbon exploration industry. We apply the concept of synthetic aperture to the lowfrequency electromagnetic field in CSEM. Synthetic aperture sources have been used in radar imaging for many years. Using the

  10. An examination of the number of required apertures for step-and-shoot IMRT

    International Nuclear Information System (INIS)

    Jiang, Z; Earl, M A; Zhang, G W; Yu, C X; Shepard, D M

    2005-01-01

    We have examined the degree to which step-and-shoot IMRT treatment plans can be simplified (using a small number of apertures) without sacrificing the dosimetric quality of the plans. A key element of this study was the use of direct aperture optimization (DAO), an inverse planning technique where all of the multi-leaf collimator constraints are incorporated into the optimization. For seven cases (1 phantom, 1 prostate, 3 head-and-neck and 2 lung), DAO was used to perform a series of optimizations where the number of apertures per beam direction varied from 1 to 15. In this work, we attempt to provide general guidelines for how many apertures per beam direction are sufficient for various clinical cases using DAO. Analysis of the optimized treatment plans reveals that for most cases, only modest improvements in the objective function and the corresponding DVHs are seen beyond 5 apertures per beam direction. However, for more complex cases, some dosimetric gain can be achieved by increasing the number of apertures per beam direction beyond 5. Even in these cases, however, only modest improvements are observed beyond 9 apertures per beam direction. In our clinical experience, 38 out of the first 40 patients treated using IMRT plans produced using DAO were treated with 9 or fewer apertures per beam direction. The results indicate that many step-and-shoot IMRT treatment plans delivered today are more complex than necessary and can be simplified without sacrificing plan quality

  11. Spaceborne L-band Radiometers: Push-broom or Synthetic Aperture?

    DEFF Research Database (Denmark)

    Skou, Niels

    2004-01-01

    L-band radiometers can measure ocean salinity and soil moisture from space. A synthetic aperture radiometer system, SMOS, is under development by ESA for launch in 2007. A real aperture push-broom system, Aquarius, has been approved by NASA for launch in 2008. Pros et cons of the two fundamentally...

  12. The implementation of temporal synthetic aperture imaging for ultrafast optical processing

    Science.gov (United States)

    Zhao, Xiaoxiang; Xiao, Shaoqiu; Gong, Cheng; Yi, Tao; Liu, Shenye

    2017-12-01

    A new technique of temporal imaging, called temporal synthetic aperture imaging (TSAI), is proposed to achieve higher time resolution of the imaging system for ultrafast optical processing. The proposed technique combines several of independent small-aperture systems together to get a higher time resolution and better image quality as a large-aperture system. It can solve the problem that an oversized aperture time lens is difficult to achieve in practice. In this paper, after analyzing the filtering effect, a novel implementation method of TSAI is presented. In order to verify the correctness, we demonstrate a decuple magnification of a signal with two 1ps width pulse separated 2ps, using a synthetic aperture by the system simulation.

  13. First Beam Based Aperture Measurements in the Arcs of the CERN Large Hadron Collider

    CERN Document Server

    Redaelli, S; Calaga, R; Dehning, B; Giovannozzi, M; Roncarolo, F; Tomás, R

    2010-01-01

    The LHC injection tests performed in August and early September 2008 in preparation for the circulating beam operation provided the first opportunity to measure with beam the mechanical aperture in two LHC sectors (2-3 and 7- 8). The aperture was probed by exciting free oscillations and local orbit bumps of the injected beam trajectories. Intensities of a few 109 protons were used to remain safely below the quench limit of superconductingmagnets in case of beam losses. The methods used to measure the mechanical aperture, the available on-line tools, and beam measurements for both sectors are presented. Detailed comparisons with the expected results from the as-built aperture models are also presented. It is shown that the measurements results are in good agreement with the LHC design aperture.

  14. Acoustic Source Localization via Subspace Based Method Using Small Aperture MEMS Arrays

    Directory of Open Access Journals (Sweden)

    Xin Zhang

    2014-01-01

    Full Text Available Small aperture microphone arrays provide many advantages for portable devices and hearing aid equipment. In this paper, a subspace based localization method is proposed for acoustic source using small aperture arrays. The effects of array aperture on localization are analyzed by using array response (array manifold. Besides array aperture, the frequency of acoustic source and the variance of signal power are simulated to demonstrate how to optimize localization performance, which is carried out by introducing frequency error with the proposed method. The proposed method for 5 mm array aperture is validated by simulations and experiments with MEMS microphone arrays. Different types of acoustic sources can be localized with the highest precision of 6 degrees even in the presence of wind noise and other noises. Furthermore, the proposed method reduces the computational complexity compared with other methods.

  15. Aperture-Tolerant, Chemical-Based Methods to Reduce Channeling

    Energy Technology Data Exchange (ETDEWEB)

    Randall S. Seright

    2007-09-30

    This final technical progress report describes work performed from October 1, 2004, through May 16, 2007, for the project, 'Aperture-Tolerant, Chemical-Based Methods to Reduce Channeling'. We explored the potential of pore-filling gels for reducing excess water production from both fractured and unfractured production wells. Several gel formulations were identified that met the requirements--i.e., providing water residual resistance factors greater than 2,000 and ultimate oil residual resistance factors (F{sub rro}) of 2 or less. Significant oil throughput was required to achieve low F{sub rro} values, suggesting that gelant penetration into porous rock must be small (a few feet or less) for existing pore-filling gels to provide effective disproportionate permeability reduction. Compared with adsorbed polymers and weak gels, strong pore-filling gels can provide greater reliability and behavior that is insensitive to the initial rock permeability. Guidance is provided on where relative-permeability-modification/disproportionate-permeability-reduction treatments can be successfully applied for use in either oil or gas production wells. When properly designed and executed, these treatments can be successfully applied to a limited range of oilfield excessive-water-production problems. We examined whether gel rheology can explain behavior during extrusion through fractures. The rheology behavior of the gels tested showed a strong parallel to the results obtained from previous gel extrusion experiments. However, for a given aperture (fracture width or plate-plate separation), the pressure gradients measured during the gel extrusion experiments were much higher than anticipated from rheology measurements. Extensive experiments established that wall slip and first normal stress difference were not responsible for the pressure gradient discrepancy. To explain the discrepancy, we noted that the aperture for gel flow (for mobile gel wormholing through concentrated

  16. Method of moments analysis of an aperture in a thick ground plane

    Science.gov (United States)

    Olcen, Ahmet Burak

    The problem of electromagnetic scattering from and transmission through an arbitrarily shaped aperture is considered. The aperture is in a thick infinite perfectly conducting ground plane. The conducting walls of the cavity inside the ground plane are of arbitrary shape. The apertures at both ends of the cavity are also of arbitrary shape. The structure is illuminated by an incident plane electromagnetic wave. The Green's function for this complicated problem is almost impossible to determine. Therefore the surface equivalence principle is used to reduce this complex problem into three simpler ones. Each such problem consists of equivalent surface currents radiating in unbounded media. Therefore the free space Green's function is used for each problem. An equivalent surface magnetic current placed on the top aperture produces the scattered field in the region where the impressed sources are. The total field inside the cavity is produced by two surface equivalent magnetic currents on the apertures and an equivalent surface electric current residing on the walls of the cavity as well as on both apertures. The transmitted field on the opposite side of the impressed sources is computed by an equivalent surface magnetic current residing on the bottom aperture. Enforcing the boundary conditions on the tangential components of electric and magnetic fields on both apertures and on the tangential components of electric field on the cavity walls results in a set of three coupled integral equations for the equivalent surface currents. Whenever possible, image theory is used to simplify the equations. These equations are numerically solved using the method of moments. The surfaces are approximated by planar triangular patches. RWG functions are used for expansion functions. An approximate Galerkin method is used for testing. The method is applicable for the general case where all three regions have different material parameters. Results are computed for the case where all

  17. Analysis and Optimization of Medical Ultrasound Imaging Using the Effective Aperture Approach

    Directory of Open Access Journals (Sweden)

    Vera Behar

    2005-12-01

    Full Text Available An effective aperture approach is used as a tool for analysis and parameter optimization of mostly known ultrasound imaging systems - phased array systems, compounding systems and synthetic aperture imaging systems. Both characteristics of an imaging system , the effective aperture function and the corresponding two-way radiation pattern, provide information about two the most important parameters of images produced by an ultrasound system - lateral resolution and contrast. Therefore, in the design, optimization of the effective aperture function leads to optimal choice of such parameters of an imaging systems that influence on lateral resolution and contrast of images produced by this imaging system. The numerical results show that Hamming apodization gives the best compromise between the contrast of images and the lateral resolution produced by a conventional phased array imaging system. In compound imaging, the number of transducers and its spatial separation should be chosen in result of optimization of the effective aperture function of a system. It is shown that the effective aperture approach can be also used for optimization of a sparse synthetic transmit aperture (STA imaging system. A new two-stage algorithm is proposed for optimization of both the positions of the transmit elements and the weights of the receive elements. The proposed system employs a 64- element array with only four active elements used during transmit.

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

    Energy Technology Data Exchange (ETDEWEB)

    Adam B. Sefkow and Samuel A. Cohen

    2009-04-09

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

  19. Constraints on flow regimes in wide-aperture fractures

    Energy Technology Data Exchange (ETDEWEB)

    Ghezzehei, Teamrat A.

    2004-02-28

    In recent years, significant advances have been made in our understanding of the complex flow processes in individual fractures, aided by flow visualization experiments and conceptual modeling efforts. These advances have led to the recognition of several flow regimes in individual fractures subjected to different initial and boundary conditions. Of these, the most important regimes are film flow, rivulet flow, and sliding of droplets. The existence of such significantly dissimilar flow regimes has been a major hindrance in the development of self-consistent conceptual models of flow for single fractures that encompass all the flow regimes. The objective of this study is to delineate the existence of the different flow regimes in individual fractures. For steady-state flow conditions, we developed physical constraints on the different flow regimes that satisfy minimum energy configurations, which enabled us to segregate the wide range of fracture transmissivity (volumetric flow rate per fracture width) into several flow regimes. These are, in increasing order of flow rate, flow of adsorbed films, flow of sliding drops, rivulet flow, stable film flow, and unstable (turbulent) film flow. The scope of this study is limited to wide-aperture fractures with the flow on the opposing sides of fracture being independent.

  20. Synthetic aperture radar imaging simulator for pulse envelope evaluation

    Science.gov (United States)

    Balster, Eric J.; Scarpino, Frank A.; Kordik, Andrew M.; Hill, Kerry L.

    2017-10-01

    A simulator for spotlight synthetic aperture radar (SAR) image formation is presented. The simulator produces radar returns from a virtual radar positioned at an arbitrary distance and altitude. The radar returns are produced from a source image, where the return is a weighted summation of linear frequency-modulated (LFM) pulse signals delayed by the distance of each pixel in the image to the radar. The imagery is resampled into polar format to ensure consistent range profiles to the position of the radar. The SAR simulator provides a capability enabling the objective analysis of formed SAR imagery, comparing it to an original source image. This capability allows for analysis of various SAR signal processing techniques previously determined by impulse response function (IPF) analysis. The results suggest that IPF analysis provides results that may not be directly related to formed SAR image quality. Instead, the SAR simulator uses image quality metrics, such as peak signal-to-noise ratio (PSNR) and structured similarity index (SSIM), for formed SAR image quality analysis. To showcase the capability of the SAR simulator, it is used to investigate the performance of various envelopes applied to LFM pulses. A power-raised cosine window with a power p=0.35 and roll-off factor of β=0.15 is shown to maximize the quality of the formed SAR images by improving PSNR by 0.84 dB and SSIM by 0.06 from images formed utilizing a rectangular pulse, on average.

  1. Event Localization in Bulk Scintillator Crystals Using Coded Apertures

    Energy Technology Data Exchange (ETDEWEB)

    Ziock, Klaus-Peter [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Tennessee, Knoxville, TN (United States). Dept. of Physics and Astronomy; Braverman, Joshua B. [Univ. of Tennessee, Knoxville, TN (United States). Dept. of Physics and Astronomy; Fabris, Lorenzo [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Harrison, Mark J. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Hornback, Donald Eric [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Newby, Jason [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2015-06-01

    The localization of radiation interactions in bulk scintillators is generally limited by the size of the light distribution at the readout surface of the crystal/light-pipe system. By finding the centroid of the light spot, which is typically of order centimeters across, practical single-event localization is limited to ~2 mm/cm of crystal thickness. Similar resolution can also be achieved for the depth of interaction by measuring the size of the light spot. Through the use of near-field coded-aperture techniques applied to the scintillation light, light transport simulations show that for 3-cm-thick crystals, more than a five-fold improvement (millimeter spatial resolution) can be achieved both laterally and in event depth. At the core of the technique is the requirement to resolve the shadow from an optical mask placed in the scintillation light path between the crystal and the readout. In this paper, experimental results are presented that demonstrate the overall concept using a 1D shadow mask, a thin-scintillator crystal and a light pipe of varying thickness to emulate a 2.2-cm-thick crystal. Spatial resolutions of ~ 1 mm in both depth and transverse to the readout face are obtained over most of the crystal depth.

  2. Relative error-constrained compression for synthetic aperture radar data

    Science.gov (United States)

    Aiazzi, Bruno; Alparone, Luciano; Baronti, Stefano

    2001-12-01

    Near-lossless compression, i.e., yielding strictly bounded reconstruction error, is extended to preserve the radiometric resolution of data produced by coherent imaging systems, like Synthetic Aperture Radar (SAR). First a causal spatial DPCM based on a fuzzy matching-pursuit (FMP) prediction is adjusted to yield a relative-error bounded compression by applying a logarithmic quantization to the ratio of original to predicted pixel values. Then, a noncausal DPCM is achieved based on the Rational Laplacian Pyramid (RLP), recently introduced by the authors for despeckling. The baseband icon of the RLP is (causally) DPCM encoded, the intermediate layers are uniformly quantized, and the bottom layer is logarithmically quantized. As a consequence, the relative error, i.e., pixel ratio of original to decoded image, can be strictly bounded around unity by the quantization step size of the bottom layer of the RLP. Experimental results reported on true SAR data from NASA/JPL AIRSAR show that virtually lossless images can be achieved with compression ratios larger than three.

  3. Smoothing-Based Relative Navigation and Coded Aperture Imaging

    Science.gov (United States)

    Saenz-Otero, Alvar; Liebe, Carl Christian; Hunter, Roger C.; Baker, Christopher

    2017-01-01

    This project will develop an efficient smoothing software for incremental estimation of the relative poses and velocities between multiple, small spacecraft in a formation, and a small, long range depth sensor based on coded aperture imaging that is capable of identifying other spacecraft in the formation. The smoothing algorithm will obtain the maximum a posteriori estimate of the relative poses between the spacecraft by using all available sensor information in the spacecraft formation.This algorithm will be portable between different satellite platforms that possess different sensor suites and computational capabilities, and will be adaptable in the case that one or more satellites in the formation become inoperable. It will obtain a solution that will approach an exact solution, as opposed to one with linearization approximation that is typical of filtering algorithms. Thus, the algorithms developed and demonstrated as part of this program will enhance the applicability of small spacecraft to multi-platform operations, such as precisely aligned constellations and fractionated satellite systems.

  4. photPARTY: Python automated square-aperture photometry

    Science.gov (United States)

    Symons, Teresa A.; Anthony-Twarog, Barbara J.

    2017-01-01

    As CCD’s have drastically increased the amount of information recorded per frame, so too have they increased the time and effort needed to sift through the data. For observations of a single star, information from millions of pixels needs to be distilled into one number: the magnitude. Various computer systems have been used to streamline this process over the years. The CCDPhot photometer, in use at the Kitt Peak 0.9-m telescope in the 1990’s, allowed for user settings and provided real time magnitudes during observation of single stars. It is this level of speed and convenience that inspired the development of the Python-based software analysis system photPARTY, which can quickly and efficiently produce magnitudes for a set of single-star or un-crowded field CCD frames. Seeking to remove the need for manual interaction after initial settings for a group of images, photPARTY automatically locates stars, subtracts the background, and performs square-aperture photometry. Rather than being a package of available functions, it is essentially a self-contained, one-click analysis system, with the capability to process several hundred frames in just a couple of minutes. Results of comparisons against present systems such as IRAF will be presented. The support of the National Science Foundation through grant AST-1211621 is gratefully acknowledged.

  5. Supports with apertures for fuel assemblies in a nuclear reactor

    International Nuclear Information System (INIS)

    Jabsen, F.S.

    1977-01-01

    This invention concerns couplings for nuclear reactor fuel rod bundle and, inter alia, for holders fitted with apertures which uncover the ends of the fuel rods for inspection, and a similar operation. The difficulties arising from the use of slid cast holders of control rods and burnable poison rods, which have marked previous designs, are overcome to a large extent through the use of the invention. Under this invention a network of interpenetrating plates is provided to hold a guide tube arrangement for the control rods or the burnable poison rods. This network forms an open cellular structure that uncovers the ends of the fuel rods, for easy routine inspection. This structure is less costly and yet has the strength of the previous solid cast holders. It avoids problems of quality guaranty encountered in the fabrication of cast metal products having a complicated shape. It allows for the re-arrangement of the partially burnt up rods inside a reactor core, without requiring any structural changes in the fuel rod bundle. It also makes it possible to overcome a want of thermal efficiency that was a hindrance in the past [fr

  6. Feasibility of Using Synthetic Aperture Radar to Aid UAV Navigation

    Directory of Open Access Journals (Sweden)

    Davide O. Nitti

    2015-07-01

    Full Text Available This study explores the potential of Synthetic Aperture Radar (SAR to aid Unmanned Aerial Vehicle (UAV navigation when Inertial Navigation System (INS measurements are not accurate enough to eliminate drifts from a planned trajectory. This problem can affect medium-altitude long-endurance (MALE UAV class, which permits heavy and wide payloads (as required by SAR and flights for thousands of kilometres accumulating large drifts. The basic idea is to infer position and attitude of an aerial platform by inspecting both amplitude and phase of SAR images acquired onboard. For the amplitude-based approach, the system navigation corrections are obtained by matching the actual coordinates of ground landmarks with those automatically extracted from the SAR image. When the use of SAR amplitude is unfeasible, the phase content can be exploited through SAR interferometry by using a reference Digital Terrain Model (DTM. A feasibility analysis was carried out to derive system requirements by exploring both radiometric and geometric parameters of the acquisition setting. We showed that MALE UAV, specific commercial navigation sensors and SAR systems, typical landmark position accuracy and classes, and available DTMs lead to estimated UAV coordinates with errors bounded within ±12 m, thus making feasible the proposed SAR-based backup system.

  7. Feasibility of Using Synthetic Aperture Radar to Aid UAV Navigation.

    Science.gov (United States)

    Nitti, Davide O; Bovenga, Fabio; Chiaradia, Maria T; Greco, Mario; Pinelli, Gianpaolo

    2015-07-28

    This study explores the potential of Synthetic Aperture Radar (SAR) to aid Unmanned Aerial Vehicle (UAV) navigation when Inertial Navigation System (INS) measurements are not accurate enough to eliminate drifts from a planned trajectory. This problem can affect medium-altitude long-endurance (MALE) UAV class, which permits heavy and wide payloads (as required by SAR) and flights for thousands of kilometres accumulating large drifts. The basic idea is to infer position and attitude of an aerial platform by inspecting both amplitude and phase of SAR images acquired onboard. For the amplitude-based approach, the system navigation corrections are obtained by matching the actual coordinates of ground landmarks with those automatically extracted from the SAR image. When the use of SAR amplitude is unfeasible, the phase content can be exploited through SAR interferometry by using a reference Digital Terrain Model (DTM). A feasibility analysis was carried out to derive system requirements by exploring both radiometric and geometric parameters of the acquisition setting. We showed that MALE UAV, specific commercial navigation sensors and SAR systems, typical landmark position accuracy and classes, and available DTMs lead to estimated UAV coordinates with errors bounded within ±12 m, thus making feasible the proposed SAR-based backup system.

  8. Experiment in Onboard Synthetic Aperture Radar Data Processing

    Science.gov (United States)

    Holland, Matthew

    2011-01-01

    Single event upsets (SEUs) are a threat to any computing system running on hardware that has not been physically radiation hardened. In addition to mandating the use of performance-limited, hardened heritage equipment, prior techniques for dealing with the SEU problem often involved hardware-based error detection and correction (EDAC). With limited computing resources, software- based EDAC, or any more elaborate recovery methods, were often not feasible. Synthetic aperture radars (SARs), when operated in the space environment, are interesting due to their relevance to NASAs objectives, but problematic in the sense of producing prodigious amounts of raw data. Prior implementations of the SAR data processing algorithm have been too slow, too computationally intensive, and require too much application memory for onboard execution to be a realistic option when using the type of heritage processing technology described above. This standard C-language implementation of SAR data processing is distributed over many cores of a Tilera Multicore Processor, and employs novel Radiation Hardening by Software (RHBS) techniques designed to protect the component processes (one per core) and their shared application memory from the sort of SEUs expected in the space environment. The source code includes calls to Tilera APIs, and a specialized Tilera compiler is required to produce a Tilera executable. The compiled application reads input data describing the position and orientation of a radar platform, as well as its radar-burst data, over time and writes out processed data in a form that is useful for analysis of the radar observations.

  9. Full aperture backscatter diagnostic for the NIF laser facility (abstract)

    International Nuclear Information System (INIS)

    Sewall, Noel; Lewis, Izzy; Kirkwood, Robert; Moody, John; Celeste, John

    2001-01-01

    The current schemes for achieving ignition on the National Ignition Facility require efficient coupling of energy from 192 laser beams to the deuterium--tritium fuel capsule. Each laser beam must propagate through a long scalelength plasma region before being converted to x rays (indirect drive) or being absorbed on the capsule (direct drive). Laser-plasma instabilities such as stimulated Brillouin and stimulated Raman scattering (SBS and SRS) will scatter a fraction of the incident laser energy out of the target leading to an overall reduction in the coupling efficiency. It is important to measure the character of this scattered light in order to understand it and to develop methods for reducing it to acceptable levels. We are designing a system called the full aperature backscatter diagnostic with the capability to measure the time-dependent amplitude and spectral content of the light which is backscattered through the incident beam focusing optic. The backscattered light will be collected over about 85% of the full beam aperture and separated into the SBS wavelength band (348--354 nm) and the SRS wavelength band (400--700 nm). Spectrometers coupled to streak cameras will provide time-resolved spectra for both scattered light components. The scattered light amplitude will be measured with fast and slow diodes. The entire system will be routinely calibrated. Analysis of the data will provide important information for reducing scattered power, achieving power balance, and finally achieving ignition

  10. Mask design and fabrication in coded aperture imaging

    International Nuclear Information System (INIS)

    Shutler, Paul M.E.; Springham, Stuart V.; Talebitaher, Alireza

    2013-01-01

    We introduce the new concept of a row-spaced mask, where a number of blank rows are interposed between every pair of adjacent rows of holes of a conventional cyclic difference set based coded mask. At the cost of a small loss in signal-to-noise ratio, this can substantially reduce the number of holes required to image extended sources, at the same time increasing mask strength uniformly across the aperture, as well as making the mask automatically self-supporting. We also show that the Finger and Prince construction can be used to wrap any cyclic difference set onto a two-dimensional mask, regardless of the number of its pixels. We use this construction to validate by means of numerical simulations not only the performance of row-spaced masks, but also the pixel padding technique introduced by in ’t Zand. Finally, we provide a computer program CDSGEN.EXE which, on a fast modern computer and for any Singer set of practical size and open fraction, generates the corresponding pattern of holes in seconds

  11. Design considerations for a large aperture high field superconducting dipole

    Energy Technology Data Exchange (ETDEWEB)

    Harfoush, F.; Ankenbrandt, C.; Harrison, M.; Kerby, J.; Koepke, K.; Mantsch, P.; Nicol, T.; Riddiford, A.; Theilacker, J.

    1989-03-01

    The final phase of the Fermilab upgrade proposal calls for a new ring of superconducting magnets to be placed in the existing Main Accelerator tunnel. The goal of this design study is to specify a high field dipole (HFD) that is capable of supporting fixed target operation (ramping, resonant extraction) at a field of 6.6T (1.5 Tev) and colliding beam physics at 8.0T (1.8 Tev). The magnetic field quality at high field is set by the large amplitude orbits associated with resonant extraction. The field quality must therefore be at least as good as the existing Tevatron magnets which fulfill these criteria. The high fields and large aperture of this magnet result in large forces on the coil and collar assemblies. Therefore, the cold mass design must be able to sustain these forces while providing sufficient cooling to the coils during 4.2 K fixed target operation, and a minimum heat load during 1.8 K collider operation. The design work is still in progress but a cosine-theta, cold-iron dipole with a 70mm inner diameter coil has been tentatively adopted. This report presents details on the conductor and cable parameters, coil cross-section, projected manufacturing tolerances, iron yoke design, and cold mass assembly. 4 refs., 5 figs., 1 tab.

  12. Design considerations for a large aperture high field superconducting dipole

    International Nuclear Information System (INIS)

    Harfoush, F.; Ankenbrandt, C.; Harrison, M.; Kerby, J.; Koepke, K.; Mantsch, P.; Nicol, T.; Riddiford, A.; Theilacker, J.

    1989-03-01

    The final phase of the Fermilab upgrade proposal calls for a new ring of superconducting magnets to be placed in the existing Main Accelerator tunnel. The goal of this design study is to specify a high field dipole (HFD) that is capable of supporting fixed target operation (ramping, resonant extraction) at a field of 6.6T (1.5 Tev) and colliding beam physics at 8.0T (1.8 Tev). The magnetic field quality at high field is set by the large amplitude orbits associated with resonant extraction. The field quality must therefore be at least as good as the existing Tevatron magnets which fulfill these criteria. The high fields and large aperture of this magnet result in large forces on the coil and collar assemblies. Therefore, the cold mass design must be able to sustain these forces while providing sufficient cooling to the coils during 4.2 K fixed target operation, and a minimum heat load during 1.8 K collider operation. The design work is still in progress but a cosine-theta, cold-iron dipole with a 70mm inner diameter coil has been tentatively adopted. This report presents details on the conductor and cable parameters, coil cross-section, projected manufacturing tolerances, iron yoke design, and cold mass assembly. 4 refs., 5 figs., 1 tab

  13. Investigation of the feasability for 3D synthetic aperture imaging

    DEFF Research Database (Denmark)

    Nikolov, Svetoslav; Jensen, Jørgen Arendt

    2003-01-01

    This paper investigates the feasibility of implementing real-time synthetic aperture 3D imaging on the experimental system developed at the Center for Fast Ultrasound Imaging using a 2D transducer array. The target array is a fully populated 32 × 32 3 MHz array with a half wavelength pitch...... with an elliptic footprint. The results of simulations show that the angular resolution at -6dB is 2.7 degrees, and is determined by the distance between the outer-most transmit elements. The peak gratinglobe levels are −23.5, −25, 27.2, −44.5 dB below the main peak for 64, 100, 144, and 169 transmit events...... experimental array made by Vermon with a center frequency of 2.93 MHz, fractional bandwidth of 58 %, and a pitch of 300 µm. The simulations show, that using all of the 128 elements a spherical wave within ±50 degrees sector can be created. The level of the edge waves is reduced by applying apodization...

  14. Quantitative emission tomography by coded aperture imaging in nuclear medicine

    International Nuclear Information System (INIS)

    Guilhem, J.B.

    1982-06-01

    The coded aperture imaging is applied to nuclear medicine, since ten years. However no satisfactory clinical results have been obtained thus for. The reason is that digital reconstruction methods which have been implemented, in particular the method which use deconvolution filtering are not appropriate for quantification. Indeed these methods which all based on the assumption of shift invariance of the coding procedure, which is contradictory to the geometrical recording conditions giving the best depth resolution, do not take into account gamma rays attenuation by tissues and in most cases give tomograms with artefacts from blurred structures. A method is proposed which has not these limitations and considers the reconstruction problem as the ill-conditioned problem of solving a Fredholm integral equation. The main advantage of this method lies in fact that the transmission kernel of the integral equation is obtained experimentally, and the approximate solution of this equation, close enough to the original 3-D radioactive object, can be obtained in spite of the ill-conditioned nature of the problem, by use of singular values decomposition (S. V. D.) of the kernel [fr

  15. Three-dimensional subsurface imaging synthetic aperture radar

    International Nuclear Information System (INIS)

    Moussally, G.J.

    1995-01-01

    The objective of this applied research and development project is to develop a system known as '3-D SISAR'. This system consists of a ground penetrating radar with software algorithms designed for the detection, location, and identification of buried objects in the underground hazardous waste environments found at DOE storage sites. Three-dimensional maps of the object locations will be produced which can assist the development of remediation strategies and the characterization of the digface during remediation operations. It is expected that the 3-D SISAR will also prove useful for monitoring hydrocarbon based contaminant migration after remediation. The underground imaging technique being developed under this contract utilizes a spotlight mode Synthetic Aperture Radar (SAR) approach which, due to its inherent stand-off capability, will permit the rapid survey of a site and achieve a high degree of productivity over large areas. When deployed from an airborne platform, the stand-off techniques is also seen as a way to overcome practical survey limitations encountered at vegetated sites

  16. Error analysis of large aperture static interference imaging spectrometer

    Science.gov (United States)

    Li, Fan; Zhang, Guo

    2015-12-01

    Large Aperture Static Interference Imaging Spectrometer is a new type of spectrometer with light structure, high spectral linearity, high luminous flux and wide spectral range, etc ,which overcomes the contradiction between high flux and high stability so that enables important values in science studies and applications. However, there're different error laws in imaging process of LASIS due to its different imaging style from traditional imaging spectrometers, correspondingly, its data processing is complicated. In order to improve accuracy of spectrum detection and serve for quantitative analysis and monitoring of topographical surface feature, the error law of LASIS imaging is supposed to be learned. In this paper, the LASIS errors are classified as interferogram error, radiometric correction error and spectral inversion error, and each type of error is analyzed and studied. Finally, a case study of Yaogan-14 is proposed, in which the interferogram error of LASIS by time and space combined modulation is mainly experimented and analyzed, as well as the errors from process of radiometric correction and spectral inversion.

  17. Synthetic Aperture Focusing Technique 3D-CAD-SAFT

    International Nuclear Information System (INIS)

    Schmitz, V.; Kroening, M.; Chakhlov, S.; Fischer, W.

    2000-01-01

    Till the 80's ultrasonic holography has been used as an analyzing technique, a procedure which has been replaced by the Synthetic Aperture Focusing Technique 'SAFT'. This technique has been applied on metallic components in different power plants, mostly on pipe systems on pressure vessels or on specimen made of composite or concrete material. SAFT exists in different versions, either in 2D or 3D, for plane or arbitrarily shaped surfaces, for pulse echo or pitch- and catch arrangements. The defect sizes ranged from 100 μm in turbine shafts till fractures of meters in research pressure vessels. The paper covers the latest results of the SAFT-reconstruction technique under Windows NT which has been guided by the experience obtained in the field. It contributes to the currently discussed question of the possible benefit using TOFD-techniques versus pulse echo techniques; the target has been a fatigue crack in a pipe segment which was investigated by different insonification angles, wave modes and probe arrangements. The results are evaluated with respect to signal-to-noise ratio improvement; problems of TOFD are demonstrated using an animation procedure which allows to walk through the weld in three orthogonal directions. A special example will be shown from a bore hole inspection of water power station valves where the reconstruction procedure follows the radial axial insonification planes. The multi-line SAFT images can be cut according to the situation of the crack position and orientation

  18. SU-E-J-20: Adaptive Aperture Morphing for Online Correction for Prostate Cancer Radiotherapy

    International Nuclear Information System (INIS)

    Sandhu, R; Qin, A; Yan, D

    2014-01-01

    Purpose: Online adaptive aperture morphing is desirable over translational couch shifts to accommodate not only the target position variation but also anatomic changes (rotation, deformation, and relation of target to organ-atrisks). We proposed quick and reliable method for adapting segment aperture leaves for IMRT treatment of prostate. Methods: The proposed method consists of following steps: (1) delineate the contours of prostate, SV, bladder and rectum on kV-CBCT; (2) determine prostate displacement from the rigid body registration of the contoured prostate manifested on the reference CT and the CBCT; (3) adapt the MLC segment apertures obtained from the pre-treatment IMRT planning to accommodate the shifts as well as anatomic changes. The MLC aperture adaptive algorithm involves two steps; first move the whole aperture according to prostate translational/rotational shifts, and secondly fine-tune the aperture shape to maintain the spatial relationship between the planning target contour and the MLC aperture to the daily target contour. Feasibility of this method was evaluated retrospectively on a seven-field IMRT treatment of prostate cancer patient by comparing dose volume histograms of the original plan and the aperture-adjusted plan, with/without additional segments weight optimization (SWO), on two daily treatment CBCTs selected with relative large motion and rotation. Results: For first daily treatment, the prostate rotation was significant (12degree around lateral-axis). With apertureadjusted plan, the D95 to the target was improved 25% and rectum dose (D30, D40) was reduced 20% relative to original plan on daily volumes. For second treatment-fraction, (lateral shift = 6.7mm), after adjustment target D95 improved by 3% and bladder dose (D30, maximum dose) was reduced by 1%. For both cases, extra SWO did not provide significant improvement. Conclusion: The proposed method of adapting segment apertures is promising in treatment position correction

  19. SU-E-J-20: Adaptive Aperture Morphing for Online Correction for Prostate Cancer Radiotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Sandhu, R; Qin, A; Yan, D [William Beaumont Hospital, Royal Oak, MI (United States)

    2014-06-01

    Purpose: Online adaptive aperture morphing is desirable over translational couch shifts to accommodate not only the target position variation but also anatomic changes (rotation, deformation, and relation of target to organ-atrisks). We proposed quick and reliable method for adapting segment aperture leaves for IMRT treatment of prostate. Methods: The proposed method consists of following steps: (1) delineate the contours of prostate, SV, bladder and rectum on kV-CBCT; (2) determine prostate displacement from the rigid body registration of the contoured prostate manifested on the reference CT and the CBCT; (3) adapt the MLC segment apertures obtained from the pre-treatment IMRT planning to accommodate the shifts as well as anatomic changes. The MLC aperture adaptive algorithm involves two steps; first move the whole aperture according to prostate translational/rotational shifts, and secondly fine-tune the aperture shape to maintain the spatial relationship between the planning target contour and the MLC aperture to the daily target contour. Feasibility of this method was evaluated retrospectively on a seven-field IMRT treatment of prostate cancer patient by comparing dose volume histograms of the original plan and the aperture-adjusted plan, with/without additional segments weight optimization (SWO), on two daily treatment CBCTs selected with relative large motion and rotation. Results: For first daily treatment, the prostate rotation was significant (12degree around lateral-axis). With apertureadjusted plan, the D95 to the target was improved 25% and rectum dose (D30, D40) was reduced 20% relative to original plan on daily volumes. For second treatment-fraction, (lateral shift = 6.7mm), after adjustment target D95 improved by 3% and bladder dose (D30, maximum dose) was reduced by 1%. For both cases, extra SWO did not provide significant improvement. Conclusion: The proposed method of adapting segment apertures is promising in treatment position correction

  20. Coded diffraction system in X-ray crystallography using a boolean phase coded aperture approximation

    Science.gov (United States)

    Pinilla, Samuel; Poveda, Juan; Arguello, Henry

    2018-03-01

    Phase retrieval is a problem present in many applications such as optics, astronomical imaging, computational biology and X-ray crystallography. Recent work has shown that the phase can be better recovered when the acquisition architecture includes a coded aperture, which modulates the signal before diffraction, such that the underlying signal is recovered from coded diffraction patterns. Moreover, this type of modulation effect, before the diffraction operation, can be obtained using a phase coded aperture, just after the sample under study. However, a practical implementation of a phase coded aperture in an X-ray application is not feasible, because it is computationally modeled as a matrix with complex entries which requires changing the phase of the diffracted beams. In fact, changing the phase implies finding a material that allows to deviate the direction of an X-ray beam, which can considerably increase the implementation costs. Hence, this paper describes a low cost coded X-ray diffraction system based on block-unblock coded apertures that enables phase reconstruction. The proposed system approximates the phase coded aperture with a block-unblock coded aperture by using the detour-phase method. Moreover, the SAXS/WAXS X-ray crystallography software was used to simulate the diffraction patterns of a real crystal structure called Rhombic Dodecahedron. Additionally, several simulations were carried out to analyze the performance of block-unblock approximations in recovering the phase, using the simulated diffraction patterns. Furthermore, the quality of the reconstructions was measured in terms of the Peak Signal to Noise Ratio (PSNR). Results show that the performance of the block-unblock phase coded apertures approximation decreases at most 12.5% compared with the phase coded apertures. Moreover, the quality of the reconstructions using the boolean approximations is up to 2.5 dB of PSNR less with respect to the phase coded aperture reconstructions.

  1. Active Correction of Aperture Discontinuities-Optimized Stroke Minimization. I. A New Adaptive Interaction Matrix Algorithm

    Science.gov (United States)

    Mazoyer, J.; Pueyo, L.; N'Diaye, M.; Fogarty, K.; Zimmerman, N.; Leboulleux, L.; St. Laurent, K. E.; Soummer, R.; Shaklan, S.; Norman, C.

    2018-01-01

    Future searches for bio-markers on habitable exoplanets will rely on telescope instruments that achieve extremely high contrast at small planet-to-star angular separations. Coronagraphy is a promising starlight suppression technique, providing excellent contrast and throughput for off-axis sources on clear apertures. However, the complexity of space- and ground-based telescope apertures goes on increasing over time, owing to the combination of primary mirror segmentation, the secondary mirror, and its support structures. These discontinuities in the telescope aperture limit the coronagraph performance. In this paper, we present ACAD-OSM, a novel active method to correct for the diffractive effects of aperture discontinuities in the final image plane of a coronagraph. Active methods use one or several deformable mirrors that are controlled with an interaction matrix to correct for the aberrations in the pupil. However, they are often limited by the amount of aberrations introduced by aperture discontinuities. This algorithm relies on the recalibration of the interaction matrix during the correction process to overcome this limitation. We first describe the ACAD-OSM technique and compare it to the previous active methods for the correction of aperture discontinuities. We then show its performance in terms of contrast and off-axis throughput for static aperture discontinuities (segmentation, struts) and for some aberrations evolving over the life of the instrument (residual phase aberrations, artifacts in the aperture, misalignments in the coronagraph design). This technique can now obtain the Earth-like planet detection threshold of {10}10 contrast on any given aperture over at least a 10% spectral bandwidth, with several coronagraph designs.

  2. Assessing the validity of the channel model of fracture aperture under field conditions

    Science.gov (United States)

    Shapiro, Allen M.; Nicholas, James R.

    1989-01-01

    In recent investigations of fluid and solute movement in discrete fractures, spatial heterogeneity of the fracture aperture has been conceptualized as a series of noninterconnecting constant aperture flow paths, or channels. Two methods of estimating the distribution of the aperture sizes are presented using information from a single-hole pumping test and a radially converging tracer test. The first method uses the transmissivity of the fracture and mean arrival time of the tracer, while the second method uses the mean and variance of the solute arrival time. If the fracture can be conceptualized as a series of nonintersecting flow paths of constant aperture, the two methods should yield identical estimates for the parameters of the distribution. The validity of the channel model can be assessed by comparing the parameters of the distribution that are estimated by the two methods. This technique was demonstrated using hydraulic and tracer tests conducted in a discrete, areally extensive, horizontal fracture in the Silurian dolomite in the northeastern Illinois. A lognormal and a truncated gamma distribution were used to describe the distribution of constant aperture flow paths. The lognormal distribution could not reproduce the abrupt rising limb and maximum rate of mass arrival that characterized the tracer tests. The gamma distribution more accurately predicted the shape of the breakthrough curves; however, the two methods of estimating the parameters of the distribution provided significantly different estimates of the variances of the aperture sizes. The mean aperture as estimated by the two methods was similar. The difference in the variance of the aperture as estimated by the two methods indicates that alternative conceptual models of aperture heterogeneity are required to more accurately describe both fluid and solute movement in this field situation.

  3. Design and analysis of high-numerical-aperture beam shaping systems; Design und Analyse von Strahlformungssystemen hoher numerischer Apertur

    Energy Technology Data Exchange (ETDEWEB)

    Schweitzer, Hagen

    2009-11-24

    The generation of light tailored to measure stands today in the center of many innovative applications. A possibility of the flexible manipulation of light is the laser-beam shaping.Aim is thereby to transform the intensity profile of a laser beam to a wanted profile. The main topic of this thesis is the modeling and propagation of laser light in paraxial and non-paraxial beam-shaping systems as well as the optimization of these systems by means of a generalized projection algorithm. This algorithm is applied for the optimization by means of aspherical formula or polynomials point-by-point parametrized beam shaping surfaces. It is shown that during the optimization a regardment of diffraction, interference, and abberations is possible. The latter can not only be regarded, but directly used for the beam shaping. Finally it is shown that the aberrations of spherical catalogue lenses are already sufficient for some beam-shaping applications. The efficiency of the developed optimization algorithms is demonstrated both on paraxial and on non-paraxial beam-shaping examples with a numerical aperture of up to 0.62. Finally in the present thesis concepts for the achromatization and for the wave-length multiplexing are introduced, which are based on the application of diverse surfaces and materials with different dispersion. While the achromatization aims to make the optical function of a beam-shaping system wave-length independent, the wavelength multiplexing tries directly to realize different optical functions for diverse design wavelengths. [German] Die Erzeugung massgeschneiderten Lichts steht heute im Mittelpunkt vieler innovativer Anwendungen. Eine Moeglichkeit der flexiblen Manipulation von Licht ist die Laserstrahlformung. Ziel ist es dabei, das Intensitaetsprofil eines Laserstrahls in ein gewuenschtes Profil umzuformen. Schwerpunkt dieser Arbeit ist die Modellierung und Ausbreitung von Laserlicht in paraxialen und nicht-paraxialen Strahlformungssystemen sowie die

  4. Confocal pattern period in multiple-aperture confocal imaging systems with coherent illumination.

    Science.gov (United States)

    Liang, M; Stehr, R L; Krause, A W

    1997-06-01

    We have built a programmable multiple-aperture confocal imaging system that uses a spatial light modulator (a Texas Instruments digital micromirror device). Excellent axial resolution and confocal imaging quality have been experimentally demonstrated with this system, even when the distance between adjacent ON pixels is four times the size of the pixel aperture. By contrast, typical pinhole-based systems (e.g., a Nipkow disk) employ an adjacent aperture distance-to-size ratio of 10x . We have achieved improvement over such systems by 6.25x in both light-utilization efficiency and confocal image rate without adding more components and extra processing time.

  5. Parameter scans and accuracy estimates of the dynamical aperture of the CERN LHC

    CERN Document Server

    Giovannozzi, Massimo

    2006-01-01

    Techniques to make use of large distributed computing facilities allow for denser parameter scans of the dynamic aperture, i.e., the domain in phase space where bounded single-particle motion prevails. Moreover, one can also increase the number of 'seeds' each of which represents a possible realization of multipolar components around the machine. In this paper the dependence of the dynamic aperture on the step size of the grid of initial conditions and on the number of seeds is studied. Estimates on the accuracy of the dynamic aperture are derived and the definition of an improved protocol for numerical simulations is presented.

  6. Forward scattering from square cylinders in the resonance region with application to aperture blockage

    DEFF Research Database (Denmark)

    Rusch, W.; Appel-Hansen, Jørgen; Klein, C

    1976-01-01

    The relationship between the induced field ratio (IFR) of a cylinder and aperture blocking of a constant-phase aperture by cylindrical struts is discussed. An analytical technique is presented whereby the IFR of rectangular cylinders can be calculated using the method-of-moments with internal...... constraint points. An experimental technique using a forward-scattering range is used to measure the IFR's of square and circular cylinders in an anechoic chamber. These experimental results are compared with the theory, and their implications on aperture blocking losses and boresight cross polarization...

  7. Aperture Photometry Tool Versus SExtractor for Noncrowded Fields

    Science.gov (United States)

    Laher, Russ R.; Rebull, Luisa M.; Gorjian, Varoujan; Masci, Frank J.; Fowler, John W.; Grillmair, Carl; Surace, Jason; Mattingly, Sean; Jackson, Ed; Hacopeans, Eugean; Hamam, Nouhad; Groom, Steve; Teplitz, Harry; Mi, Wei; Helou, George; van Eyken, Julian C.; Law, Nicholas M.; Dekany, Richard G.; Rahmer, Gustavo; Hale, David; Smith, Roger; Quimby, Robert M.; Ofek, Eran O.; Kasliwal, Mansi M.; Zolkower, Jeff; Velur, Viswa; Walters, Richard; Henning, John; Bui, Khahn; McKenna, Dan; Kulkarni, Shrinivas R.

    2012-07-01

    Outputs from new software program Aperture Photometry Tool (APT) are compared with similar outputs from SExtractor for sources extracted from R-band optical images acquired by the Palomar Transient Factory (PTF), infrared mosaics constructed from Spitzer Space Telescope images, and a processed visible/near-infrared image from the Hubble Legacy Archive (HLA). Two large samples from the PTF images are studied, each containing around 3 × 103 sources from noncrowded fields. The median values of source-intensity relative percentage differences between the two software programs, computed separately for two PTF samples, are +0.13% and +0.17%, with corresponding statistical dispersions of 1.43% and 1.84%, respectively. For the Spitzer mosaics, a similar large sample of extracted sources for each of channels 1-4 of Spitzer’s Infrared Array Camera (IRAC) are analyzed with two different sky annulus sizes, and we find that the median and modal values of source-intensity relative percentage differences between the two software programs are between -0.5% and +2.0%, and the corresponding statistical dispersions range from 1.4 to 6.7%, depending on the Spitzer IRAC channel and sky annulus. The results for the HLA image are mixed, as might be expected for a moderately crowded field. The comparisons for the three different kinds of images show that there is generally excellent agreement between APT and SExtractor. Differences in source-intensity uncertainty estimates for the PTF images amount to less than 3% for the PTF sources, and these are potentially caused by SExtractor’s omission of the sky background uncertainty term in the formula for source-intensity uncertainty, as well as differing methods of sky background estimation.

  8. Multipinhole collimator with 20 apertures for a brain SPECT application

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Tzu-Cheng; Ellin, Justin R.; Shrestha, Uttam; Seo, Youngho, E-mail: youngho.seo@ucsf.edu [Physics Research Laboratory, Department of Radiology and Biomedical Imaging, University of California, San Francisco, California 94107 (United States); Huang, Qiu [School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200030 (China); Gullberg, Grant T. [Department of Radiotracer Development and Imaging Technology, Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94702 (United States)

    2014-11-01

    Purpose: Several new technologies for single photon emission computed tomography (SPECT) instrumentation with parallel-hole collimation have been proposed to improve detector sensitivity and signal collection efficiency. Benefits from improved signal efficiency include shorter acquisition times and lower dose requirements. In this paper, the authors show a possibility of over an order of magnitude enhancement in photon detection efficiency (from 7.6 × 10{sup −5} to 1.6 × 10{sup −3}) for dopamine transporter (DaT) imaging of the striatum over the conventional SPECT parallel-hole collimators by use of custom-designed 20 multipinhole (20-MPH) collimators with apertures of 0.75 cm diameter. Methods: Quantifying specific binding ratio (SBR) of {sup 123}I-ioflupane or {sup 123}I-iometopane’s signal at the striatal region is a common brain imaging method to confirm the diagnosis of the Parkinson’s disease. The authors performed imaging of a striatal phantom filled with aqueous solution of I-123 and compared camera recovery ratios of SBR acquired between low-energy high-resolution (LEHR) parallel-hole collimators and 20-MPH collimators. Results: With only two-thirds of total acquisition time (20 min against 30 min), a comparable camera recovery ratio of SBR was achieved using 20-MPH collimators in comparison to that from the LEHR collimator study. Conclusions: Their systematic analyses showed that the 20-MPH collimator could be a promising alternative for the DaT SPECT imaging for brain over the traditional LEHR collimator, which could give both shorter scan time and improved diagnostic accuracy.

  9. Three-dimensional synthetic aperture particle image velocimetry

    Science.gov (United States)

    Belden, Jesse; Truscott, Tadd T.; Axiak, Michael C.; Techet, Alexandra H.

    2010-12-01

    We present a new method for resolving three-dimensional (3D) fluid velocity fields using a technique called synthetic aperture particle image velocimetry (SAPIV). By fusing methods from the imaging community pertaining to light field imaging with concepts that drive experimental fluid mechanics, SAPIV overcomes many of the inherent challenges of 3D particle image velocimetry (3D PIV). This method offers the ability to digitally refocus a 3D flow field at arbitrary focal planes throughout a volume. The viewable out-of-plane dimension (Z) can be on the same order as the viewable in-plane dimensions (X-Y), and these dimensions can be scaled from tens to hundreds of millimeters. Furthermore, the digital refocusing provides the ability to 'see-through' partial occlusions, enabling measurements in densely seeded volumes. The advantages are achieved using a camera array (typically at least five cameras) to image the seeded fluid volume. The theoretical limits on refocused plane spacing and viewable depth are derived and explored as a function of camera optics and spacing of the array. A geometric optics model and simulated PIV images are used to investigate system performance for various camera layouts, measurement volume sizes and seeding density; performance is quantified by the ability to reconstruct the 3D intensity field, and resolve 3D vector fields in densely seeded simulated flows. SAPIV shows the ability to reconstruct fields with high seeding density and large volume size. Finally, results from an experimental implementation of SAPIV using a low cost eight-camera array to study a vortex ring in a 65 × 40 × 32 mm3 volume are presented. The 3D PIV results are compared with 2D PIV data to demonstrate the capability of the 3D SAPIV technique.

  10. Spaceborne synthetic aperture radar signal processing using FPGAs

    Science.gov (United States)

    Sugimoto, Yohei; Ozawa, Satoru; Inaba, Noriyasu

    2017-10-01

    Synthetic Aperture Radar (SAR) imagery requires image reproduction through successive signal processing of received data before browsing images and extracting information. The received signal data records of the ALOS-2/PALSAR-2 are stored in the onboard mission data storage and transmitted to the ground. In order to compensate the storage usage and the capacity of transmission data through the mission date communication networks, the operation duty of the PALSAR-2 is limited. This balance strongly relies on the network availability. The observation operations of the present spaceborne SAR systems are rigorously planned by simulating the mission data balance, given conflicting user demands. This problem should be solved such that we do not have to compromise the operations and the potential of the next-generation spaceborne SAR systems. One of the solutions is to compress the SAR data through onboard image reproduction and information extraction from the reproduced images. This is also beneficial for fast delivery of information products and event-driven observations by constellation. The Emergence Studio (Sōhatsu kōbō in Japanese) with Japan Aerospace Exploration Agency is developing evaluation models of FPGA-based signal processing system for onboard SAR image reproduction. The model, namely, "Fast L1 Processor (FLIP)" developed in 2016 can reproduce a 10m-resolution single look complex image (Level 1.1) from ALOS/PALSAR raw signal data (Level 1.0). The processing speed of the FLIP at 200 MHz results in twice faster than CPU-based computing at 3.7 GHz. The image processed by the FLIP is no way inferior to the image processed with 32-bit computing in MATLAB.

  11. Full aperture imaging with stereoscopic properties in nuclear medicine

    International Nuclear Information System (INIS)

    Strocovsky, Sergio G.; Otero, D.

    2011-01-01

    The imaging techniques based on gamma camera (CG) and used in nuclear medicine have low spatial resolution and low sensitivity due to the use of the collimator. However, this element is essential for the formation of images in CG. The aim of this work is to show the principles of a new technique to overcome the limitations of existing techniques based on CG. Here, we present a Full Aperture Imaging (FAI) technique which is based on the edge-encoding of gamma radiation and differential detection. It takes advantage of the fact that gamma radiation is spatially incoherent. The mathematical principles and the method of images reconstruction with the new proposed technique are explained in detail. The FAI technique is tested by means of Monte Carlo simulations with filiform and spherical sources. The results show that FAI technique has greater sensitivity (>100 times) and greater spatial resolution (>2.6 times) than that of GC with LEHR collimator, in both cases, with and without attenuating material and long and short-distance configurations. The FAI decoding algorithm reconstructs simultaneously four different projections which are located in separate image fields on the detector plane, while GC produces only one projection per acquisition. Simulations have allowed comparison of both techniques under ideal identical conditions. Our results show it is possible to apply an extremely simple encoded imaging technique, and get three-dimensional radioactivity information for simplistic geometry sources. The results are promising enough to evaluate the possibility of future research with more complex sources typical of nuclear medicine imaging. (author)

  12. Subsidence feature discrimination using deep convolutional neral networks in synthetic aperture radar imagery

    CSIR Research Space (South Africa)

    Schwegmann, Colin P

    2017-07-01

    Full Text Available Effective detection and discrimination of surface deformation features in Synthetic Aperture Radar imagery is one of the most important applications of the data. Areas that undergo surface deformation can pose health and safety risks which...

  13. Beam loss due to the aperture limitation resulting from intrabeam scattering

    International Nuclear Information System (INIS)

    Lee, S.Y.

    1984-01-01

    Diffusion equation is used to evaluate the beam loss in the presence of aperture limitation resulting from the intrabeam scattering. We discuss the effect of different boundary conditions. Satisfactory beam intensity can be maintained within the proposed RHIC operation time

  14. Enabling Larger Deployable Ka-Band Antenna Apertures with Novel Rib, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The significance and relevance of the proposed innovation is to design and develop a novel rib that will enable larger aperture parabolic reflectors and antennas....

  15. High numerical aperture imaging by using multimode fibers with micro-fabricated optics

    KAUST Repository

    Bianchi, Silvio

    2014-01-01

    Controlling light propagation into multimode optical fibers through spatial light modulators provides highly miniaturized endoscopes and optical micromanipulation probes. We increase the numerical aperture up to nearly 1 by micro-optics fabricated on the fiber-end.

  16. Forensic Facial Reconstruction: Relationship Between the Alar Cartilage and Piriform Aperture.

    Science.gov (United States)

    Strapasson, Raíssa Ananda Paim; Herrera, Lara Maria; Melani, Rodolfo Francisco Haltenhoff

    2017-11-01

    During forensic facial reconstruction, facial features may be predicted based on the parameters of the skull. This study evaluated the relationships between alar cartilage and piriform aperture and nose morphology and facial typology. Ninety-six cone beam computed tomography images of Brazilian subjects (49 males and 47 females) were used in this study. OsiriX software was used to perform the following measurements: nasal width, distance between alar base insertion points, lower width of the piriform aperture, and upper width of the piriform aperture. Nasal width was associated with the lower width of the piriform aperture, sex, skeletal vertical pattern of the face, and age. The current study contributes to the improvement of forensic facial guides by identifying the relationships between the alar cartilages and characteristics of the biological profile of members of a population that has been little studied thus far. © 2017 American Academy of Forensic Sciences.

  17. Developing Kinetic Inductance Detectors for the Balloon‐borne Large Aperture Submillimeter Telescope (BLAST)

    Data.gov (United States)

    National Aeronautics and Space Administration — As an NSTRF fellow, I will use the new Polarized Balloon-borne Large Aperture Submillimeter Telescope (Super BLASTPol) to make groundbreaking measurements of...

  18. Synthetic Aperture Ladar (SAL): Fundamental Theory, Design Equations for a Satellite System, and Laboratory Demonstration

    National Research Council Canada - National Science Library

    Lucke, Robert

    2002-01-01

    .... Design equations are presented to allow quick assessment of the hardware parameters required for a notional system, most notably optical aperture sizes and the laser's power, chirp, and pulse rate capabilities...

  19. Flexible T/R Modules for Large-Aperture, Space-Based SAR Project

    Data.gov (United States)

    National Aeronautics and Space Administration — SI2 Technologies, Inc (SI2) proposes to develop membrane compatible transmit/receive (T/R) modules for flexible, space-deployable synthetic aperture radar (SAR)...

  20. Method and apparatus for shadow aperture backscatter radiography (SABR) system and protocol

    Science.gov (United States)

    Shedlock, Daniel (Inventor); Jacobs, Alan M. (Inventor); Jacobs, Sharon Auerback (Inventor); Dugan, Edward (Inventor)

    2010-01-01

    A shadow aperture backscatter radiography (SABR) system includes at least one penetrating radiation source for providing a penetrating radiation field, and at least one partially transmissive radiation detector, wherein the partially transmissive radiation detector is interposed between an object region to be interrogated and the radiation source. The partially transmissive radiation detector transmits a portion of the illumination radiation field. A shadow aperture having a plurality of radiation attenuating regions having apertures therebetween is disposed between the radiation source and the detector. The apertures provide illumination regions for the illumination radiation field to reach the object region, wherein backscattered radiation from the object is detected and generates an image by the detector in regions of the detector that are shadowed by the radiation attenuation regions.

  1. Investigations of a high current linear aperture radial multichannel pseudospark switch

    Science.gov (United States)

    Lamba, R. P.; Pathania, V.; Meena, B. L.; Rahaman, H.; Pal, U. N.; Prakash, Ram

    2015-10-01

    In this paper, a high current linear aperture radial multichannel Pseudospark switch (LARM-PSS) is reported which has been analyzed for its high current characteristics. In order to enhance hold-off voltage and support hollow cathode effect for the ignition of the discharge in this configuration, the field penetration analysis through circular and linear apertures of the electrodes has been carried out. The linear apertures in the electrodes increase the current handling capacity than that of circular aperture electrodes without significant compromise of the hold-off capacity. The developed LARM-PSS switch is capable to hold voltage up to 25 kV at gas pressure between 10 and 50 Pa for hydrogen. The switch has been operated using a 800 nF capacitor bank and conducted an effective charge up to 1.5 C with peak switch current ˜20 kA at applied voltage 19 kV.

  2. The propagation of hypergeometric beams through an annular apertured paraxial ABCD optical system

    International Nuclear Information System (INIS)

    Tang, Bin; Jiang, Chun; Zhu, Haibin; Zhou, Xin; Wang, Shuai

    2014-01-01

    By means of expanding the hard aperture function into a finite sum of complex Gaussian functions and based on the generalized Huygens–Fresnel diffraction integral, a novel approximate analytical expression of hypergeometric (HyG) beams passing through a paraxial ABCD optical system with an annular aperture is derived. The results could be reduced to the case of a circular aperture or a circular black screen. Some numerical simulations are also performed and illustrated for the propagation characteristics and focusing properties of a HyG beam through a paraxial ABCD optical system with an annular aperture. The results obtained from the approximate analytical formula provide more efficiency than the usual way of using diffraction integral formula directly. (paper)

  3. Quench Performance and Field Quality of FNAL Twin-Aperture 11 T Nb3Sn Dipole Model for LHC Upgrades

    CERN Document Server

    Stoynev, S; Apollinari, G; Auchmann, B; Barzi, E; Izquierdo Bermudez, S; Bossert, R; Chlachidze, G; DiMarco, J; Karppinen, M; Nobrega, F; Novitski, I; Rossi, F; Savary, F; Smekens, D; Strauss, T; Turrioni, D; Velev, G; Zlobin, A V

    2016-01-01

    A 2 m long single-aperture dipole demonstrator and two 1 m long single-aperture models based on Nb3Sn superconductor have been built and tested at FNAL. The two 1 m long collared coils were then assembled in a twin-aperture Nb3Sn dipole demonstrator compatible with the LHC main dipole and tested in two thermal cycles. This paper summarizes the quench performance of the FNAL twin-aperture Nb3Sn 11 T dipole in the temperature range of 1.9-4.5 K. The results of magnetic measurements for one of the two apertures are also presented. Test results are compared to the performance of coils in a single-aperture configuration. A summary of quench propagation studies in both apertures is given.

  4. Vibrating mirror system suitable for q-switching large-aperture lasers

    Energy Technology Data Exchange (ETDEWEB)

    Beckwith, P.J.

    1977-11-01

    Resonant vibrating mirrors provide a convenient means of Q-switching a laser, but large-aperture versions require careful design if the drive power is not to become excessive. This report outlines the design principles involved in the optimisation of moving-iron galvanometer drivers, and describes a prototype device with an aperture of 40 mm x 80 mm which is capable of beam deflections of + or - 40 mrad at 800 Hz. Some suggestions are made concerning more refined designs.

  5. Field Quality Measurements in the FNAL Twin-Aperture 11 T Dipole for LHC Upgrades

    CERN Document Server

    Strauss, T; Barzi, E; Chlachidze, G; Di Marco, J; Nobrega, F; Novitski, I; Stoynev, S; Turrioni, D; Velev, G; Zlobin, A V; Auchmann, B; Izquierdo Bermudez, S; Karppinen, M; Rossi, L; Savary, F; Smekens, D

    2017-01-01

    FNAL and CERN are developing an 11 T Nb3Sn dipole suitable for installation in the LHC to provide room for additional collimators. Two 1 m long collared coils previously tested at FNAL in single-aperture dipole configuration were assembled into the twin-aperture configuration and tested including magnet quench performance and field quality. The results of magnetic measurements are reported and discussed in this paper.

  6. Effects of surface-mapping corrections and synthetic-aperture focusing techniques on ultrasonic imaging

    International Nuclear Information System (INIS)

    Barna, B.A.; Johnson, J.A.

    1981-01-01

    Improvements in ultrasonic imaging that can be obtained using algorithms that map the surface of targets are evaluated. This information is incorporated in the application of synthetic-aperture focusing techniques which also have the potential to improve image resolution. Images obtained using directed-beam (flat) transducers and the focused transducers normally used for synthetic-aperture processing are quantitatively compared by using no processing, synthetic-aperture processing with no corrections for surface variations, and synthetic-aperture processing with surface mapping. The unprocessed images have relatively poor lateral resolutions because echoes from two adjacent reflectors show interference effects which prevent their identification even if the spacing is larger than the single-hole resolution. The synthetic-aperture-processed images show at least a twofold improvement in lateral resolution and greatly reduced interference effects in multiple-hole images compared to directed-beam images. Perhaps more importantly, in images of test blocks with substantial surface variations portions of the image are displaced from their actual positions by several wavelengths. To correct for this effect an algorithm has been developed for calculating the surface variations. The corrected images produced using this algorithm are accurate within the experimental error. In addition, the same algorithm, when applied to the directed-beam data, produced images that are not only accurately positioned, but that also have a resolution comparable to conventional synthetic-aperture-processed images obtained from focused-transducer data. This suggests that using synthetic-aperture processing on the type of data normally collected during directed-beam ultrasonic inspections would eliminate the need to rescan for synthetic-aperture enhancement

  7. Field Quality Measurements in the FNAL Twin-Aperture 11 T Dipole for LHC Upgrades

    Energy Technology Data Exchange (ETDEWEB)

    Strauss, T. [Fermilab; Apollinari, G. [Fermilab; Apollinari, G. [Fermilab; Barzi, E. [Fermilab; Chlachidze, G. [Fermilab; Di Marco, J. [Fermilab; Nobrega, F. [Fermilab; Novitski, I. [Fermilab; Stoynev, S. [Fermilab; Turrioni, D. [Fermilab; Velev, G. [Fermilab; Zlobin, A. V. [Fermilab; Auchmann, B. [CERN; Izquierdo Bermudez, S, [CERN; Karppinen, M. [CERN; Rossi, L. [CERN; Savary, F. [CERN; Smekens, D. [CERN

    2016-11-08

    FNAL and CERN are developing an 11 T Nb3Sn dipole suitable for installation in the LHC to provide room for additional collimators. Two 1 m long collared coils previously tested at FNAL in single-aperture dipole configuration were assembled into the twin-aperture configuration and tested including magnet quench performance and field quality. The results of magnetic measurements are reported and discussed in this paper.

  8. Process and device for closing the apertures of a nuclear reactor core baffle formers

    International Nuclear Information System (INIS)

    Chevereau, G.

    1990-01-01

    The blades of at least two sets of blades along a shaft have bearing pads on the apertures of the formers with a length superior at the apertures radius. This device produces a transversal stagger of the shaft in two different directions in two zones of the shaft. It is possible to put in place and fix the closing device by an axial thrust [fr

  9. Resonance of Superconducting Microstrip Antenna with Aperture in the Ground Plane

    Directory of Open Access Journals (Sweden)

    S. Benkouda

    2013-08-01

    Full Text Available This paper presents a rigorous full-wave analysis of a high Tc superconducting rectangular microstrip antenna with a rectangular aperture in the ground plane. To include the effect of the superconductivity of the microstrip patch in the full-wave analysis, a complex surface impedance is considered. The proposed approach is validated by comparing the computed results with previously published data. Results showing the effect of the aperture on the resonance of the superconducting microstrip antenna are given.

  10. Study of Zernike polynomials of an elliptical aperture obscured with an elliptical obscuration.

    Science.gov (United States)

    Hasan, Sundus Y; Shaker, Ali S

    2012-12-10

    In this research, Zernike polynomials for a unit annular elliptical aperture (ellipse inscribed by a unit circle of unit radius obscured by elliptical obscuration) have been studied in Cartesian coordinates and in polar coordinates. These polynomials have been shown to form a complete basis orthogonal on a unit annular ellipse aperture, and they represent balanced classical aberrations just as Zernike circular polynomials in a unit circle.

  11. Implementation of Tissue Harmonic Synthetic Aperture Imaging on a Commercial Ultrasound System

    DEFF Research Database (Denmark)

    Rasmussen, Joachim; Hemmsen, Martin Christian; Madsen, Signe Sloth

    2012-01-01

    This paper presents an imaging technique for synthetic aperture (SAI) tissue harmonic imaging (THI) on a commercial ultrasound system. Synthetic aperture sequential beamforming (SASB) is combined with a pulse inversion (PI) technique on a commercial BK 2202 UltraView system. An interleaved scan...... implementation of SASB-THI was achieved on a commercial system, which can be used for future pre-clinical trials....

  12. Electromagnetic pulse coupling through an aperture into a two-parallel-plate region

    Science.gov (United States)

    Rahmat-Samii, Y.

    1978-01-01

    Analysis of electromagnetic-pulse (EMP) penetration via apertures into cavities is an important study in designing hardened systems. In this paper, an integral equation procedure is developed for determining the frequency and consequently the time behavior of the field inside a two-parallel-plate region excited through an aperture by an EMP. Some discussion of the numerical results is also included in the paper for completeness.

  13. Deliverable navigation for multicriteria IMRT treatment planning by combining shared and individual apertures

    International Nuclear Information System (INIS)

    Fredriksson, Albin; Bokrantz, Rasmus

    2013-01-01

    We consider the problem of deliverable Pareto surface navigation for step-and-shoot intensity-modulated radiation therapy. This problem amounts to calculation of a collection of treatment plans with the property that convex combinations of plans are directly deliverable. Previous methods for deliverable navigation impose restrictions on the number of apertures of the individual plans, or require that all treatment plans have identical apertures. We introduce simultaneous direct step-and-shoot optimization of multiple plans subject to constraints that some of the apertures must be identical across all plans. This method generalizes previous methods for deliverable navigation to allow for treatment plans with some apertures from a collective pool and some apertures that are individual. The method can also be used as a post-processing step to previous methods for deliverable navigation in order to improve upon their plans. By applying the method to subsets of plans in the collection representing the Pareto set, we show how it can enable convergence toward the unrestricted (non-navigable) Pareto set where all apertures are individual. (paper)

  14. Grating-flanked plasmonic coaxial apertures for efficient fiber optical tweezers.

    Science.gov (United States)

    Saleh, Amr A E; Sheikhoelislami, Sassan; Gastelum, Steven; Dionne, Jennifer A

    2016-09-05

    Subwavelength plasmonic apertures have been foundational for direct optical manipulation of nanoscale specimens including sub-100 nm polymeric beads, metallic nanoparticles and proteins. While most plasmonic traps result in two-dimensional localization, three-dimensional manipulation has been demonstrated by integrating a plasmonic aperture on an optical fiber tip. However, such 3D traps are usually inefficient since the optical mode of the fiber and the subwavelength aperture only weakly couple. In this paper we design more efficient optical-fiber-based plasmonic tweezers combining a coaxial plasmonic aperture with a plasmonic grating coupler at the fiber tip facet. Using full-field finite difference time domain analysis, we optimize the grating design for both gold and silver fiber-based coaxial tweezers such that the optical transmission through the apertures is maximized. With the optimized grating, we show that the maximum transmission efficiency increases from 2.5% to 19.6% and from 1.48% to 16.7% for the gold and silver structures respectively. To evaluate their performance as optical tweezers, we calculate the optical forces and the corresponding trapping potential on dielectric particles interacting with the apertures. We demonstrate that the enahncement in the transmission translates into an equivalent increase in the optical forces. Consequently, the optical power required to achieve stable optical trapping is significantly reduced allowing for efficient localization and 3D manipulation of sub-30 nm dielectric particles.

  15. Research on primary mirror lateral support structure of large-aperture telescope

    Science.gov (United States)

    Wang, Yang

    2010-05-01

    The primary mirror of large-aperture telescope is an important component of telescope system. The surface figure error of the primary mirror is a critical factor affecting the imaging quality of telescope system. With the augment of primary mirror aperture, the surface figure error of the primary mirror is affected by many factors, such as gravity, thermal deformation and so on. The factors that influence the surface figure error of the primary mirror are considered and analyzed roundly according to technical requirements of optical system. So the feasible project is researched on the lateral support structure of large-aperture telescope primary mirror. The primary mirror support system of large-aperture telescope is composed of axial support and lateral support. In traditional telescope, the contribution of lateral support to surface distortion is less than axial support. With increase of diameter to thickness ratio, lateral support is becoming more complicated and important than before. Lateral support is a key technology the same as axial support for the large-aperture telescope primary mirror. With the foundation of analysis, comparison and conclusion of related literature and monograph, according to primary mirror supporting principle of the large-aperture telescope. Lateral support methods, the influence of the primary mirror surface figure error due to primary mirror lateral support and lateral support structure of primary mirror are analyzed.

  16. The Balloon-borne Large Aperture Telescope for Polarization - BLASTPol

    Science.gov (United States)

    Devlin, Mark

    We are proposing a comprehensive program to study the link between Galactic magnetic fields and star formation. After decades of study, the physical processes regulating star formation still remain poorly understood. Large-scale observations of star forming regions provide counts of the number of dense clouds each of which will eventually evolve into tens to hundreds of stars. However, when simple models of gravitational collapse are applied to the clouds they yield a Galactic star formation rate (SFR) which is many times what is actually observed. Some process or combination of processes must be slowing the collapse of the clouds. The two prevailing theories involve turbulence which prevents the effective dissipation of energy and Galactic magnetic fields which are captured and squeezed by the collapsing cloud provide a mechanism for mechanical support. Understanding these effects fits very well the SMD 2010 Science Plan's Cosmic Origins program. The Balloon-borne Large Aperture Telescope - BLAST was originally designed to conduct confusion-limited and wide-area extragalactic and Galactic surveys at submillimeter wavelengths from a long-duration balloon (LDB) platform. These wavelengths are impossible or very difficult to observe from even the best groundbased telescope sites. After a series of successful flights (Ft. Sumner 2003, Sweden 2005, and Antarctica 2006) resulting in over 25 publications, BLAST was converted to BLASTPol. The combination of a polarizing grid in front of each of the 266 feed horns at 250, 350 and 500 micron with a stepped Half Wave Plate (HWP) provided a quick and inexpensive way to make initial measurements of polarized dust emission in star forming regions. By mapping polarization from dust grains aligned with respect to their local magnetic field, the field orientation (projected on the sky) can be traced. The development of the Next Generation BLASTPol instrument is now complete. It has increased spatial resolution (22 arcseconds at

  17. Improving land vehicle situational awareness using a distributed aperture system

    Science.gov (United States)

    Fortin, Jean; Bias, Jason; Wells, Ashley; Riddle, Larry; van der Wal, Gooitzen; Piacentino, Mike; Mandelbaum, Robert

    2005-05-01

    U.S. Army Research, Development, and Engineering Command (RDECOM) Communications Electronics Research, Development and Engineering Center (CERDEC) Night Vision and Electronic Sensors Directorate (NVESD) has performed early work to develop a Distributed Aperture System (DAS). The DAS aims at improving the situational awareness of armored fighting vehicle crews under closed-hatch conditions. The concept is based on a plurality of sensors configured to create a day and night dome of surveillance coupled with heads up displays slaved to the operator's head to give a "glass turret" feel. State-of-the-art image processing is used to produce multiple seamless hemispherical views simultaneously available to the vehicle commander, crew members and dismounting infantry. On-the-move automatic cueing of multiple moving/pop-up low silhouette threats is also done with the possibility to save/revisit/share past events. As a first step in this development program, a contract was awarded to United Defense to further develop the Eagle VisionTM system. The second-generation prototype features two camera heads, each comprising four high-resolution (2048x1536) color sensors, and each covering a field of view of 270°hx150°v. High-bandwidth digital links interface the camera heads with a field programmable gate array (FPGA) based custom processor developed by Sarnoff Corporation. The processor computes the hemispherical stitch and warp functions required for real-time, low latency, immersive viewing (360°hx120°v, 30° down) and generates up to six simultaneous extended graphics array (XGA) video outputs for independent display either on a helmet-mounted display (with associated head tracking device) or a flat panel display (and joystick). The prototype is currently in its last stage of development and will be integrated on a vehicle for user evaluation and testing. Near-term improvements include the replacement of the color camera heads with a pixel-level fused combination of

  18. Direct aperture optimization for online adaptive radiation therapy

    International Nuclear Information System (INIS)

    Mestrovic, Ante; Milette, Marie-Pierre; Nichol, Alan; Clark, Brenda G.; Otto, Karl

    2007-01-01

    This paper is the first investigation of using direct aperture optimization (DAO) for online adaptive radiation therapy (ART). A geometrical model representing the anatomy of a typical prostate case was created. To simulate interfractional deformations, four different anatomical deformations were created by systematically deforming the original anatomy by various amounts (0.25, 0.50, 0.75, and 1.00 cm). We describe a series of techniques where the original treatment plan was adapted in order to correct for the deterioration of dose distribution quality caused by the anatomical deformations. We found that the average time needed to adapt the original plan to arrive at a clinically acceptable plan is roughly half of the time needed for a complete plan regeneration, for all four anatomical deformations. Furthermore, through modification of the DAO algorithm the optimization search space was reduced and the plan adaptation was significantly accelerated. For the first anatomical deformation (0.25 cm), the plan adaptation was six times more efficient than the complete plan regeneration. For the 0.50 and 0.75 cm deformations, the optimization efficiency was increased by a factor of roughly 3 compared to the complete plan regeneration. However, for the anatomical deformation of 1.00 cm, the reduction of the optimization search space during plan adaptation did not result in any efficiency improvement over the original (nonmodified) plan adaptation. The anatomical deformation of 1.00 cm demonstrates the limit of this approach. We propose an innovative approach to online ART in which the plan adaptation and radiation delivery are merged together and performed concurrently--adaptive radiation delivery (ARD). A fundamental advantage of ARD is the fact that radiation delivery can start almost immediately after image acquisition and evaluation. Most of the original plan adaptation is done during the radiation delivery, so the time spent adapting the original plan does not

  19. Coupled Effects of non-Newtonian Rheology and Aperture Variability on Flow in a Single Fracture

    Science.gov (United States)

    Di Federico, V.; Felisa, G.; Lauriola, I.; Longo, S.

    2017-12-01

    Modeling of non-Newtonian flow in fractured media is essential in hydraulic fracturing and drilling operations, EOR, environmental remediation, and to understand magma intrusions. An important step in the modeling effort is a detailed understanding of flow in a single fracture, as the fracture aperture is spatially variable. A large bibliography exists on Newtonian and non-Newtonian flow in variable aperture fractures. Ultimately, stochastic or deterministic modeling leads to the flowrate under a given pressure gradient as a function of the parameters describing the aperture variability and the fluid rheology. Typically, analytical or numerical studies are performed adopting a power-law (Oswald-de Waele) model. Yet the power-law model, routinely used e.g. for hydro-fracturing modeling, does not characterize real fluids at low and high shear rates. A more appropriate rheological model is provided by e.g. the four-parameter Carreau constitutive equation, which is in turn approximated by the more tractable truncated power-law model. Moreover, fluids of interest may exhibit yield stress, which requires the Bingham or Herschel-Bulkely model. This study employs different rheological models in the context of flow in variable aperture fractures, with the aim of understanding the coupled effect of rheology and aperture spatial variability with a simplified model. The aperture variation, modeled within a stochastic or deterministic framework, is taken to be one-dimensional and i) perpendicular; ii) parallel to the flow direction; for stochastic modeling, the influence of different distribution functions is examined. Results for the different rheological models are compared with those obtained for the pure power-law. The adoption of the latter model leads to overestimation of the flowrate, more so for large aperture variability. The presence of yield stress also induces significant changes in the resulting flowrate for assigned external pressure gradient.

  20. THE TIBIAL APERTURE SURFACE ANALYSIS IN ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION PROCESS.

    Science.gov (United States)

    Milojević, Zoran; Tabaković, Slobodan; Vićević, Marija; Obradović, Mirko; Vranjes, Miodrag; Milankov, Miroslav Z

    2016-01-01

    The tibial tunnel aperture in the anterior cruciate ligament reconstruction is usually analyzed as an ellipse, generated as an intersection between a tibial plateau and a tibial bone tunnel. The aim of this study is to show that the tibial tunnel aperture, which utilizes 3D tibial surface bone model, differs significantly from common computations which present the tibial tunnel anterior cruciate ligament aperture surface as an ellipse. An interactive program system was developed for the tibial tunnel aperture analysis which included the real tibia 3D surface bone model generated from a series of computed tomography images of ten male patients, their mean age being 25 years. In aperture calculation, the transverse drill angle of 10 degrees was used, whereas sagittal drill angles of 40 degrees, 50 degrees and 60 degrees were used with the drill-bit diameter set to 10 mm. The real 3D and 2D tibial tunnel aperture surface projection was calculated and compared with an ellipse. According to the calculations, generated 3D aperture surfaces were different for every patient even though the same drill parameters were used. For the sagittal drill angles of 40 degrees, 50 degrees and 60 degrees, the mean difference between the projected 3D and 2D area on the tibial plateau was 19.6 +/- 5.4%, 21.1 +/- 8.0% and 21.3 +/- 9.6%, respectively. The difference between the projected 3D area on the tibial plateau and ellipse surface was 54.8 +/- 16.3%, 39.6 +/- 10.4% and 25.0 +/- 8.0% for sagittal drill angles of 40 degrees, 50 degrees and 60 degrees, respectively. The tibial tunnel aperture surface area differs significantly from the ellipse surface area, which is commonly used in the anterior cruciate ligament reconstruction analysis. Inclusion of the 3D shape of the tibial attachment site in the preoperative anterior cruciate ligament reconstruction planning process can lead to a more precise individual anatomic anterior cruciate ligament reconstruction on the tibial bone. Both

  1. An exact approach to direct aperture optimization in IMRT treatment planning

    International Nuclear Information System (INIS)

    Men Chunhua; Romeijn, H Edwin; Taskin, Z Caner; Dempsey, James F

    2007-01-01

    We consider the problem of intensity-modulated radiation therapy (IMRT) treatment planning using direct aperture optimization. While this problem has been relatively well studied in recent years, most approaches employ a heuristic approach to the generation of apertures. In contrast, we use an exact approach that explicitly formulates the fluence map optimization (FMO) problem as a convex optimization problem in terms of all multileaf collimator (MLC) deliverable apertures and their associated intensities. However, the number of deliverable apertures, and therefore the number of decision variables and constraints in the new problem formulation, is typically enormous. To overcome this, we use an iterative approach that employs a subproblem whose optimal solution either provides a suitable aperture to add to a given pool of allowable apertures or concludes that the current solution is optimal. We are able to handle standard consecutiveness, interdigitation and connectedness constraints that may be imposed by the particular MLC system used, as well as jaws-only delivery. Our approach has the additional advantage that it can explicitly account for transmission of dose through the part of an aperture that is blocked by the MLC system, yielding a more precise assessment of the treatment plan than what is possible using a traditional beamlet-based FMO problem. Finally, we develop and test two stopping rules that can be used to identify treatment plans of high clinical quality that are deliverable very efficiently. Tests on clinical head-and-neck cancer cases showed the efficacy of our approach, yielding treatment plans comparable in quality to plans obtained by the traditional method with a reduction of more than 75% in the number of apertures and a reduction of more than 50% in beam-on time, with only a modest increase in computational effort. The results also show that delivery efficiency is very insensitive to the addition of traditional MLC constraints; however, jaws

  2. Effects of Aperture Size on Q factor and Shielding Effectiveness of a Cubic Resonator

    Science.gov (United States)

    Parr, Stefan; Chromy, Stephan; Dickmann, Stefan; Schaarschmidt, Martin

    2017-09-01

    The EMC properties of a cubic metallic shield are highly affected by its resonances. At the resonant frequencies, the shielding effectiveness (SE) collapses, which results in high field strengths inside the cavity. This can cause failure or even breakdown of electronic devices inside the shield. The resonant behaviour is mainly determined by the quality or Q factor of the shield. In this paper, the effects of the aperture size on the Q factor and the SE of an electrically large, cubic shield are analysed. At first, a method is developed in order to determine the Q factor based on the resonance behaviour of the shield in time domain. Only the first resonance of the shield is considered therefore. The results are evaluated for different aperture diameters and compared with theory for the Q factor. The dominant coupling mechanism of electromagnetic energy into the shield is thus identified. Then the effect of aperture size on the SE is analysed. The excitation of resonances is very probable if the interfering signal is an ultrawideband (UWB) pulse, which constitutes a typical intentional electromagnetic interference (IEMI) scenario. Therefore, the relation between aperture size and SE is analysed using the theory of the transient SE for a broadband signal with a constant spectral density distribution. The results show, that a worst case aperture size exists, where the SE has its minimum.

  3. Comparison of binocular through-focus visual acuity with monovision and a small aperture inlay

    Science.gov (United States)

    Schwarz, Christina; Manzanera, Silvestre; Prieto, Pedro M.; Fernández, Enrique J.; Artal, Pablo

    2014-01-01

    Corneal small aperture inlays provide extended depth of focus as a solution to presbyopia. As this procedure is becoming more popular, it is interesting to compare its performance with traditional approaches, such as monovision. Here, binocular visual acuity was measured as a function of object vergence in three subjects by using a binocular adaptive optics vision analyzer. Visual acuity was measured at two luminance levels (photopic and mesopic) under several optical conditions: 1) natural vision (4 mm pupils, best corrected distance vision), 2) pure-defocus monovision ( + 1.25 D add in the nondominant eye), 3) small aperture monovision (1.6 mm pupil in the nondominant eye), and 4) combined small aperture and defocus monovision (1.6 mm pupil and a + 0.75 D add in the nondominant eye). Visual simulations of a small aperture corneal inlay suggest that the device extends DOF as effectively as traditional monovision in photopic light, in both cases at the cost of binocular summation. However, individual factors, such as aperture centration or sensitivity to mesopic conditions should be considered to assure adequate visual outcomes. PMID:25360355

  4. The Effect of Vibration Characteristics on the Atomization Rate in a Micro-Tapered Aperture Atomizer.

    Science.gov (United States)

    Yan, Qiufeng; Zhang, Jianhui; Huang, Jun; Wang, Ying

    2018-03-21

    Because little is known about the atomization theory of a micro-tapered aperture atomizer, we investigated the vibration characteristics of this type of atomizer. The atomization mechanism of a micro-tapered aperture atomizer was described, and the atomization rate equation was deduced. As observed via microscopy, the angle of the micro-tapered aperture changes with the applied voltage, which proved the existence of a dynamic cone angle. The forward and reverse atomization rates were measured at various voltages, and the influence of the micro-tapered aperture and its variation on the atomization rate was characterized. The resonance frequency of the piezoelectric vibrator was obtained using a laser vibrometer, and the atomization rates were measured at each resonance frequency. From experiments, we found that the atomization rates at the first five resonance frequencies increased as the working frequency increased. At the fifth resonance frequency (121.1 kHz), the atomization rate was maximized (0.561 mL/min), and at the sixth resonance frequency (148.3 kHz), the atomization rate decreased significantly (0.198 mL/min). The experimental results show that the vibration characteristics of the piezoelectric vibrator have a relatively strong impact on the atomization rate. This research is expected to contribute to the manufacture of micro-tapered aperture atomizers.

  5. The Effect of Vibration Characteristics on the Atomization Rate in a Micro-Tapered Aperture Atomizer

    Directory of Open Access Journals (Sweden)

    Qiufeng Yan

    2018-03-01

    Full Text Available Because little is known about the atomization theory of a micro-tapered aperture atomizer, we investigated the vibration characteristics of this type of atomizer. The atomization mechanism of a micro-tapered aperture atomizer was described, and the atomization rate equation was deduced. As observed via microscopy, the angle of the micro-tapered aperture changes with the applied voltage, which proved the existence of a dynamic cone angle. The forward and reverse atomization rates were measured at various voltages, and the influence of the micro-tapered aperture and its variation on the atomization rate was characterized. The resonance frequency of the piezoelectric vibrator was obtained using a laser vibrometer, and the atomization rates were measured at each resonance frequency. From experiments, we found that the atomization rates at the first five resonance frequencies increased as the working frequency increased. At the fifth resonance frequency (121.1 kHz, the atomization rate was maximized (0.561 mL/min, and at the sixth resonance frequency (148.3 kHz, the atomization rate decreased significantly (0.198 mL/min. The experimental results show that the vibration characteristics of the piezoelectric vibrator have a relatively strong impact on the atomization rate. This research is expected to contribute to the manufacture of micro-tapered aperture atomizers.

  6. Hydrocephalus secondary to obstruction of the lateral apertures in two dogs.

    Science.gov (United States)

    Kent, M; Glass, E N; Haley, A C; Shaikh, L S; Sequel, M; Blas-Machado, U; Bishop, T M; Holmes, S P; Platt, S R

    2016-11-01

    Traditionally, hydrocephalus is divided into communicating or non-communicating (obstructive) based on the identification of a blockage of cerebrospinal fluid (CSF) flow through the ventricular system. Hydrocephalus ex vacuo refers to ventricular enlargement as a consequence of neuroparenchymal loss. Hydrocephalus related to obstruction of the lateral apertures of the fourth ventricles has rarely been described. The clinicopathologic findings in two dogs with hydrocephalus secondary to obstruction of the lateral apertures of the fourth ventricle are reported. Signs were associated with a caudal cervical spinal cord lesion in one dog and a caudal brain stem lesion in the other dog. Magnetic resonance imaging (MRI) disclosed dilation of the ventricular system, including the lateral recesses of the fourth ventricle. In one dog, postmortem ventriculography confirmed obstruction of the lateral apertures. Microscopic changes were identified in the choroid plexus in both dogs, yet a definitive cause of the obstructions was not identified. The MRI findings in both dogs are similar to membranous occlusion of the lateral and median apertures in human patients. MRI detection of dilation of the entire ventricular system in the absence of an identifiable cause should prompt consideration of an obstruction of the lateral apertures. In future cases, therapeutic interventions aimed at re-establishing CSF flow or ventriculoperitoneal catheterisation should be considered. © 2016 Australian Veterinary Association.

  7. Electrically Pumped III-N Microcavity Light Emitters Incorporating an Oxide Confinement Aperture

    Science.gov (United States)

    Lai, Ying-Yu; Chang, Tsu-Chi; Li, Ya-Chen; Lu, Tien-Chang; Wang, Shing-Chung

    2017-01-01

    In this work, we report on electrically pumped III-N microcavity (MC) light emitters incorporating oxide confinement apertures. The utilized SiO2 aperture can provide a planar ITO design with a higher index contrast ( 1) over other previously reported approaches. The fabricated MC light emitter with a 15-μm-aperture shows a turn-on voltage of 3.3 V, which is comparable to conventional light emitting diodes (LEDs), showing a good electrical property of the proposed structure. A uniform light output profile within the emission aperture suggesting the good capability of current spreading and current confinement of ITO and SiO2 aperture, respectively. Although the quality factor ( Q) of fabricated MC is not high enough to achieve lasing action ( 500), a superlinear emission can still be reached under a high current injection density (2.83 kA/cm2) at 77 K through the exciton-exciton scattering, indicating the high potential of this structure for realizing excitonic vertical-cavity surface-emitting laser (VCSEL) action or even polariton laser after fabrication optimization.

  8. Focusing optical waves with a rotationally symmetric sharp-edge aperture

    Science.gov (United States)

    Hu, Yanwen; Fu, Shenhe; Li, Zhen; Yin, Hao; Zhou, Jianying; Chen, Zhenqiang

    2018-04-01

    While there has been various kinds of patterned structures proposed for wave focusing, these patterned structures usually involve complicated lithographic techniques since the element size of the patterned structures should be precisely controlled in microscale or even nanoscale. Here we propose a new and straightforward method for focusing an optical plane wave in free space with a rotationally symmetric sharp-edge aperture. The focusing phenomenon of wave is realized by superposition of a portion of the higher-order symmetric plane waves generated from the sharp edges of the apertures, in contrast to previously focusing techniques which usually depend on a curved phase. We demonstrate both experimentally and theoretically the focusing effect with a series of apertures having different rotational symmetry, and find that the intensity of the hotspots could be controlled by the symmetric strength of the sharp-edge apertures. The presented results would advance the conventional wisdom that light would diffract in all directions and become expanding when it propagates through an aperture. The proposed method is easy to be processed, and might open potential applications in interferometry, image, and superresolution.

  9. Coded aperture optimization in compressive X-ray tomography: a gradient descent approach.

    Science.gov (United States)

    Cuadros, Angela P; Arce, Gonzalo R

    2017-10-02

    Coded aperture X-ray computed tomography (CT) has the potential to revolutionize X-ray tomography systems in medical imaging and air and rail transit security - both areas of global importance. It allows either a reduced set of measurements in X-ray CT without degradation in image reconstruction, or measure multiplexed X-rays to simplify the sensing geometry. Measurement reduction is of particular interest in medical imaging to reduce radiation, and airport security often imposes practical constraints leading to limited angle geometries. Coded aperture compressive X-ray CT places a coded aperture pattern in front of the X-ray source in order to obtain patterned projections onto a detector. Compressive sensing (CS) reconstruction algorithms are then used to recover the image. To date, the coded illumination patterns used in conventional CT systems have been random. This paper addresses the code optimization problem for general tomography imaging based on the point spread function (PSF) of the system, which is used as a measure of the sensing matrix quality which connects to the restricted isometry property (RIP) and coherence of the sensing matrix. The methods presented are general, simple to use, and can be easily extended to other imaging systems. Simulations are presented where the peak signal to noise ratios (PSNR) of the reconstructed images using optimized coded apertures exhibit significant gain over those attained by random coded apertures. Additionally, results using real X-ray tomography projections are presented.

  10. Effects of Aperture Size on Q factor and Shielding Effectiveness of a Cubic Resonator

    Directory of Open Access Journals (Sweden)

    S. Parr

    2017-09-01

    Full Text Available The EMC properties of a cubic metallic shield are highly affected by its resonances. At the resonant frequencies, the shielding effectiveness (SE collapses, which results in high field strengths inside the cavity. This can cause failure or even breakdown of electronic devices inside the shield. The resonant behaviour is mainly determined by the quality or Q factor of the shield. In this paper, the effects of the aperture size on the Q factor and the SE of an electrically large, cubic shield are analysed. At first, a method is developed in order to determine the Q factor based on the resonance behaviour of the shield in time domain. Only the first resonance of the shield is considered therefore. The results are evaluated for different aperture diameters and compared with theory for the Q factor. The dominant coupling mechanism of electromagnetic energy into the shield is thus identified. Then the effect of aperture size on the SE is analysed. The excitation of resonances is very probable if the interfering signal is an ultrawideband (UWB pulse, which constitutes a typical intentional electromagnetic interference (IEMI scenario. Therefore, the relation between aperture size and SE is analysed using the theory of the transient SE for a broadband signal with a constant spectral density distribution. The results show, that a worst case aperture size exists, where the SE has its minimum.

  11. Pinholes Meet Fabry-Pérot: Perfect and Imperfect Transmission of Waves through Small Apertures

    Directory of Open Access Journals (Sweden)

    R. Merlin

    2012-09-01

    Full Text Available Waves, of wavelength λ, transmit poorly through apertures of dimensions ℓ≪λ. Here it is shown that coupling of a subwavelength aperture to an electromagnetic oscillator makes it possible for a focused, diffraction-limited beam that impinges on the aperture to undergo perfect transmission. Ignoring nonradiative losses, and for apertures with closed boundaries in a metallic screen, the transmitted power at the oscillator’s natural frequency is enhanced by a factor of (λ/ℓ^{6} compared with the nonresonant case. As a nontrivial extension to apertures with open boundaries, an analytically solvable problem is introduced and analyzed, which involves a pair of arbitrarily small slits in a two-dimensional waveguide. The system displays perfect transmission at a frequency corresponding to that of a quasilocalized, cavitylike mode bound to the slits, the frequency of which is below that of the cutoff mode of the continuum. In contrast, and remarkably, the Fabry-Pérot-like resonance with the extended cutoff mode leads to imperfect transmission, comparable to that of an individual, nonresonated slit. An explanation of this single-slit-like behavior is presented, which also applies to the closely related phenomenon of light funneling concerning transmission through subwavelength channels [see F. Pardo et al., Light Funneling Mechanism Explained by Magnetoelectric Interference, Phys. Rev. Lett. 107, 093902 (2011PRLTAO0031-900710.1103/PhysRevLett.107.093902, and references therein].

  12. SU-E-T-344: Dynamic Electron Beam Therapy Using Multiple Apertures in a Single Cut-Out

    International Nuclear Information System (INIS)

    Rodrigues, A; Yin, F; Wu, Q

    2015-01-01

    Purpose: Few leaf electron collimators (FLEC) or electron MLCs (eMLC) are highly desirable for dynamic electron beam therapies as they produce multiple apertures within a single delivery to achieve conformal dose distributions. However, their clinical implementation has been challenging. Alternatively, multiple small apertures in a single cut-out with variable jaw sizes could be utilized in a single dynamic delivery. In this study, we investigate dosimetric characteristics of such arrangement. Methods: Monte Carlo (EGSnrc/BEAMnrc/DOSXYnrc) simulations utilized validated Varian TrueBeam phase spaces. Investigated quantities included: Energy (6 MeV), jaw size (1×1 to 22×22 cm 2 ; centered to aperture), applicator/cut-out (15×15 cm 2 ), aperture (1×1, 2×2, 3×3, 4×4 cm 2 ), and aperture placement (on/off central axis). Three configurations were assessed: (1) single aperture on-axis, (2) single aperture off-axis, and (3) multiple apertures. Reference was configuration (1) with standard jaw size. Aperture placement and jaw size were optimized to maintain reference dosimetry and minimize leakage through unused apertures to <5%. Comparison metrics included depth dose and orthogonal profiles. Results: Configuration (1) and (2): Jaw openings were reduced to 10×10 cm 2 without affecting dosimetry (gamma 2%/1mm) regardless of on- or off-axis placement. For smaller jaw sizes, reduced surface (<2%, 5% for 1×1 cm 2 aperture) and increased Bremsstrahlung (<2%, 10% for 1×1 cm 2 aperture) dose was observed. Configuration (3): Optimal aperture placement was in the corners (order: 1×1, 4×4, 2×2, 3×3 cm 2 ) and jaw sizes were 4×4, 4×4, 7×7, and 5×5 cm 2 (apertures: 1×1, 2×2, 3×3, 4×4 cm 2 ). Asymmetric leakage was found from upper and lower jaws. Leakage was generally within 5% with a maximum of 10% observed for the 1×1 cm 2 aperture irradiation. Conclusion: Multiple apertures in a single cut-out with variable jaw size can be used in a single dynamic delivery

  13. Exo-planet Direct Imaging with On-Axis and/or Segmented Apertures in Space: Adaptive Compensation of Aperture Discontinuities

    Science.gov (United States)

    Soummer, Remi

    Capitalizing on a recent breakthrough in wavefront control theory for obscured apertures made by our group, we propose to demonstrate a method to achieve high contrast exoplanet imaging with on-axis obscured apertures. Our new algorithm, which we named Adaptive Compensation of Aperture Discontinuities (ACAD), provides the ability to compensate for aperture discontinuities (segment gaps and/or secondary mirror supports) by controlling deformable mirrors in a nonlinear wavefront control regime not utilized before but conceptually similar to the beam reshaping used in PIAA coronagraphy. We propose here an in-air demonstration at 1E- 7 contrast, enabled by adding a second deformable mirror to our current test-bed. This expansion of the scope of our current efforts in exoplanet imaging technologies will enabling us to demonstrate an integrated solution for wavefront control and starlight suppression on complex aperture geometries. It is directly applicable at scales from moderate-cost exoplanet probe missions to the 2.4 m AFTA telescopes to future flagship UVOIR observatories with apertures potentially 16-20 m. Searching for nearby habitable worlds with direct imaging is one of the top scientific priorities established by the Astro2010 Decadal Survey. Achieving this ambitious goal will require 1e-10 contrast on a telescope large enough to provide angular resolution and sensitivity to planets around a significant sample of nearby stars. Such a mission must of course also be realized at an achievable cost. Lightweight segmented mirror technology allows larger diameter optics to fit in any given launch vehicle as compared to monolithic mirrors, and lowers total life-cycle costs from construction through integration & test, making it a compelling option for future large space telescopes. At smaller scales, on-axis designs with secondary obscurations and supports are less challenging to fabricate and thus more affordable than the off-axis unobscured primary mirror designs

  14. Study on 3D gamma-ray imaging for medical diagnosis with coded aperture

    International Nuclear Information System (INIS)

    Horiki, Kazunari; Shimazoe, Kenji; Ohno, Masashi; Takahashi, Hiroyuki; Kobashi, Keiji; Moro, Eiji

    2014-01-01

    The conventional methods for medical imaging have several disadvantages such as restriction on the energy and detection efficiency. Coded aperture imaging can be used for medical imagings without restriction on the energy, which makes it possible to use multiple tracers in diagnosis. The detection efficiency of Coded aperture imaging is ten times better than that of the pinhole collimator. First, simulations of the coded aperture imaging have been done to confirm M-array's effectiveness. Second, two experiments have been done with low-energy gamma-ray (122 keV( 57 Co)) and with high-energy gamma-ray (662 keV( 137 Cs)). In both cases reconstructed image was successfully acquired. The measured spatial resolution in the experiment using 57 Co is 4.3 mm (FWHM). (author)

  15. Effect of SO/sub 2/ on stomatal aperture and sulfur uptake of woody angiosperm seedlings

    Energy Technology Data Exchange (ETDEWEB)

    Noland, T.L.; Kozlowski, T.T.

    1979-01-01

    Effects of SO/sub 2/ pollution on stomatal aperture and sulfur uptake varied with SO/sub 2/ dosage and plant species. Fumigation of Ulmus americana L. seedlings with 1 ppm SO/sub 2/ for 8 h inhibited stomatal closure and fumigation with 2 ppm SO/sub 2/ for 12 h induced stomatal closure. Sulfur uptake of fumigated Ulmus americana seedlings depended on stomatal aperture and was much higher in the light than in the dark. Fumigation of water-stressed Ginkgo biloba L. seedlings with 2 ppm SO/sub 2/ for 6.5 h tended to prevent stomatal closure. However, the effects of SO/sub 2/ on stomatal aperture were modulated and often overridden by environmental stresses such as low light intensity and drought.

  16. Sub-aperture switching based ptychographic iterative engine (sasPIE) method for quantitative imaging

    Science.gov (United States)

    Sun, Aihui; Kong, Yan; Jiang, Zhilong; Yu, Wei; Liu, Fei; Xue, Liang; Wang, Shouyu; Liu, Cheng

    2018-03-01

    Though ptychographic iterative engine (PIE) has been widely adopted in the quantitative micro-imaging with various illuminations as visible light, X-ray and electron beam, the mechanical inaccuracy in the raster scanning of the sample relative to the illumination always degrades the reconstruction quality seriously and makes the resolution reached much lower than that determined by the numerical aperture of the optical system. To overcome this disadvantage, the sub-aperture switching based PIE method is proposed: the mechanical scanning in the common PIE is replaced by the sub-aperture switching, and the reconstruction error related to the positioning inaccuracy is completely avoided. The proposed technique remarkably improves the reconstruction quality, reduces the complexity of the experimental setup and fundamentally accelerates the data acquisition and reconstruction.

  17. Field quality in the twin aperture D2 dipoles for LHC under asymmetric excitation

    CERN Document Server

    Jain, A; Willen, E

    1999-01-01

    Twin aperture D2 magnets are one of the several types of dipoles to be built by BNL for the interaction regions of LHC. To minimize the number of dipole correctors required in the interaction regions, D2 will also be used as part of the steering system. Consequently, the operating fields in the two apertures may differ by up to ~10at 7 TeV operation and ~33at injection in order to compensate for the strengths of the correctors that would otherwise be required. Such asymmetric excitation of the two apertures may induce undesirable field harmonics. The saturation behavior of various harmonics is studied using POISSON and OPERA-2D. It is shown that the changes in harmonics resulting from the anticipated asymmetry are within tolerable limits. (2 refs).

  18. Hypothetical way of pollen aperture patterning. 2. Formation of polycolpate patterns and pseudoaperture geometry.

    Science.gov (United States)

    Pozhidaev

    2000-05-01

    Deviant forms of polycolpate pollen, differing from the typical pattern in the number and arrangement of apertures, are found to be similar in distantly related dicotyledon taxa. The range of variation of common and deviant aperture patterns may be arranged as a continuous series, which may be described as a gradual and geometrically regular transformation of the deviant form with a meridional circular colpus to one of the common polycolpate conditions. Similar series have been observed in the taxa with colporate and pseudocolpate pollen. All possible spatial isomers and their mirror symmetrical variants of the deviant polycolpate and polypseudocolpate pollen have been predicted in terms of the suggested regularities of aperture multiplication. Some of them have been identified in the samples studied.

  19. Early development in synthetic aperture lidar sensing and processing for on-demand high resolution imaging

    Science.gov (United States)

    Bergeron, Alain; Turbide, Simon; Terroux, Marc; Marchese, Linda; Harnisch, Bernd

    2017-11-01

    The quest for real-time high resolution is of prime importance for surveillance applications specially in disaster management and rescue mission. Synthetic aperture radar provides meter-range resolution images in all weather conditions. Often installed on satellites the revisit time can be too long to support real-time operations on the ground. Synthetic aperture lidar can be lightweight and offers centimeter-range resolution. Onboard airplane or unmanned air vehicle this technology would allow for timelier reconnaissance. INO has developed a synthetic aperture radar table prototype and further used a real-time optronic processor to fulfill image generation on-demand. The early positive results using both technologies are presented in this paper.

  20. Exponentiated Weibull distribution family under aperture averaging for Gaussian beam waves.

    Science.gov (United States)

    Barrios, Ricardo; Dios, Federico

    2012-06-04

    Nowadays, the search for a distribution capable of modeling the probability density function (PDF) of irradiance data under all conditions of atmospheric turbulence in the presence of aperture averaging still continues. Here, a family of PDFs alternative to the widely accepted Log-Normal and Gamma-Gamma distributions is proposed to model the PDF of the received optical power in free-space optical communications, namely, the Weibull and the exponentiated Weibull (EW) distribution. Particularly, it is shown how the proposed EW distribution offers an excellent fit to simulation and experimental data under all aperture averaging conditions, under weak and moderate turbulence conditions, as well as for point-like apertures. Another very attractive property of these distributions is the simple closed form expression of their respective PDF and cumulative distribution function.

  1. Aperture averaging in a free-space laser communication system with a phase diffuser

    Science.gov (United States)

    Ricklin, Jennifer C.; Davidson, Frederic M.

    2002-12-01

    The effects of aperture averagign in a free-space laser communication system with a phase diffuser placed in front of the transmitting aperture are studied. The partially coherent beam created by the use of a phase diffuser is modeled as a Gaussian Schell beam. To evaluate aperture averaging, an analytic expression is used for the spatial covariance of irradiance fluctuations that is valid for Gaussian beams of any degree of coherence, subject to the restriction that the atmospheic turbulence-corrupted laser beam can be described as a Gaussian stochastic process. In the weak fluctuation regime this analytic expression is found to compare reasonably well with published data. It is shown that when a partially coherent source beam is used irradiance fluctuations can be significantly reduced in the weak fluctuation regime.

  2. Determination of Electron Optical Properties for Aperture Zoom Lenses Using an Artificial Neural Network Method.

    Science.gov (United States)

    Isik, Nimet

    2016-04-01

    Multi-element electrostatic aperture lens systems are widely used to control electron or charged particle beams in many scientific instruments. By means of applied voltages, these lens systems can be operated for different purposes. In this context, numerous methods have been performed to calculate focal properties of these lenses. In this study, an artificial neural network (ANN) classification method is utilized to determine the focused/unfocused charged particle beam in the image point as a function of lens voltages for multi-element electrostatic aperture lenses. A data set for training and testing of ANN is taken from the SIMION 8.1 simulation program, which is a well known and proven accuracy program in charged particle optics. Mean squared error results of this study indicate that the ANN classification method provides notable performance characteristics for electrostatic aperture zoom lenses.

  3. In vivo visualization of robotically implemented synthetic tracked aperture ultrasound (STRATUS) imaging system using curvilinear array

    Science.gov (United States)

    Zhang, Haichong K.; Aalamifar, Fereshteh; Boctor, Emad M.

    2016-04-01

    Synthetic aperture for ultrasound is a technique utilizing a wide aperture in both transmit and receive to enhance the ultrasound image quality. The limitation of synthetic aperture is the maximum available aperture size limit determined by the physical size of ultrasound probe. We propose Synthetic-Tracked Aperture Ultrasound (STRATUS) imaging system to overcome the limitation by extending the beamforming aperture size through ultrasound probe tracking. With a setup involving a robotic arm, the ultrasound probe is moved using the robotic arm, while the positions on a scanning trajectory are tracked in real-time. Data from each pose are synthesized to construct a high resolution image. In previous studies, we have demonstrated the feasibility through phantom experiments. However, various additional factors such as real-time data collection or motion artifacts should be taken into account when the in vivo target becomes the subject. In this work, we build a robot-based STRATUS imaging system with continuous data collection capability considering the practical implementation. A curvilinear array is used instead of a linear array to benefit from its wider capture angle. We scanned human forearms under two scenarios: one submerged the arm in the water tank under 10 cm depth, and the other directly scanned the arm from the surface. The image contrast improved 5.51 dB, and 9.96 dB for the underwater scan and the direct scan, respectively. The result indicates the practical feasibility of STRATUS imaging system, and the technique can be potentially applied to the wide range of human body.

  4. Precise Aperture-Dependent Motion Compensation with Frequency Domain Fast Back-Projection Algorithm

    Directory of Open Access Journals (Sweden)

    Man Zhang

    2017-10-01

    Full Text Available Precise azimuth-variant motion compensation (MOCO is an essential and difficult task for high-resolution synthetic aperture radar (SAR imagery. In conventional post-filtering approaches, residual azimuth-variant motion errors are generally compensated through a set of spatial post-filters, where the coarse-focused image is segmented into overlapped blocks concerning the azimuth-dependent residual errors. However, image domain post-filtering approaches, such as precise topography- and aperture-dependent motion compensation algorithm (PTA, have difficulty of robustness in declining, when strong motion errors are involved in the coarse-focused image. In this case, in order to capture the complete motion blurring function within each image block, both the block size and the overlapped part need necessary extension leading to degeneration of efficiency and robustness inevitably. Herein, a frequency domain fast back-projection algorithm (FDFBPA is introduced to deal with strong azimuth-variant motion errors. FDFBPA disposes of the azimuth-variant motion errors based on a precise azimuth spectrum expression in the azimuth wavenumber domain. First, a wavenumber domain sub-aperture processing strategy is introduced to accelerate computation. After that, the azimuth wavenumber spectrum is partitioned into a set of wavenumber blocks, and each block is formed into a sub-aperture coarse resolution image via the back-projection integral. Then, the sub-aperture images are straightforwardly fused together in azimuth wavenumber domain to obtain a full resolution image. Moreover, chirp-Z transform (CZT is also introduced to implement the sub-aperture back-projection integral, increasing the efficiency of the algorithm. By disusing the image domain post-filtering strategy, robustness of the proposed algorithm is improved. Both simulation and real-measured data experiments demonstrate the effectiveness and superiority of the proposal.

  5. Prospective multicenter trial of a small-aperture intraocular lens in cataract surgery.

    Science.gov (United States)

    Dick, H Burkhard; Piovella, Matteo; Vukich, John; Vilupuru, Srividhya; Lin, Ling

    2017-07-01

    To evaluate the clinical acceptability of monocular implantation of the small-aperture (IC-8) intraocular lens (IOL) in 1 eye and an aspheric monofocal IOL in the fellow eye of bilateral cataract patients over 6 months postoperatively. Twelve clinics in Austria, Belgium, Germany, Italy, Spain, and Norway. Prospective case series. The visual acuity, depth of focus, contrast sensitivity, patient satisfaction, visual symptoms, and adverse events were assessed in patients who had bilateral cataract surgery followed by implantation of the small-aperture IOL in 1 eye and an aspheric monofocal IOL in the fellow eye. Uncorrected distance (UDVA), intermediate (UIVA), and near (UNVA) visual acuities were reported in Snellen notation. The study comprised 105 patients. At 6 months, the UDVA, UIVA, and UNVA in eyes with the small-aperture IOL were 20/23, 20/24, and 20/30, respectively. Ninety-nine percent, 95%, and 79% of patients achieved 20/32 or better binocular UDVA, UIVA, and UNVA, respectively. Ninety-three patients (95.9%) reported they would have the procedure again versus 4 patients (4.1%) who reported they would not have the procedure again. In eyes with the small-aperture IOL, the target-corrected defocus curve measured with 0.75 diopter (D) of myopia extended the range of functional near vision by an additional diopter without loss of distance vision compared with the distance-corrected defocus curves. The mean UIVA and UNVA remained at 20/25 and 20/32, respectively, for up to 1.5 D of residual astigmatism in eyes with the small-aperture IOL. The small-aperture IOL showed excellent visual performance, safety, patient satisfaction, and tolerance to residual astigmatism 6 months after implantation. Copyright © 2017 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  6. Single-well tracer push-pull test sensitivity w. r. to fracture aperture and spacing

    Science.gov (United States)

    Ghergut, I.; Behrens, H.; Karmakar, S.; Sauter, M.

    2012-04-01

    Dealing with a parallel-fracture system of infinite lateral extension, four characteristic regimes of tracer signal sensitivity w. r. to fracture aperture and w. r. to fracture spacing s (whose reciprocal defines fracture density, or the fluid-rock interface area per volume) can be identified during the pull phase of a single-well push-pull test, also depending upon the ratio between push-phase duration Tpush and a characteristic time scale Ts (defined by s2 / D = Ts , with D denoting the tracer's effective diffusion coefficient): early-time regime: tracer signals are sensitive w. r. to fracture aperture, but insensitive w. r. to fracture spacing; sensitivity w. r. to fracture aperture first increases, then decreases with Tpush / Ts (thus there will be an optimum in terms of to Tpush / Ts , at early pull times); mid-time regime: tracer signals are sensitive w. r. to fracture spacing, but insensitive w. r. to fracture aperture; sensitivity w. r. to fracture spacing increases with Tpush / Ts ; late-time regime: with increasing pull duration, tracer signals become increasingly insensitive w. r. to fracture spacing, while regaining sensitivity w. r. to fracture aperture; 'very late'-time regime: sensitivity w. r. to fracture aperture becomes independent upon Tpush / Ts . From these different regimes, some recommendations can be derived regarding the design and dimensioning of dual-tracer single-well push-pull tests for the specific purposes of geothermal reservoir characterization, using conservative solutes and heat as tracers. Acknowledgement: This study is funded by MWK Niedersachsen (Lower-Saxony's Science and Culture Ministry) and by Baker Hughes (Celle) within task unit 'G6' of the Collaborative Research Project 'gebo' (Geothermal Energy and High-Performance Drilling).

  7. Study on fine annealing process of the large-aperture K9 glasses

    Science.gov (United States)

    Gang, Wang; Bin, Liu Yi; Zheng, Li Li; Hui, Zhang; Lei, Xie; Min, Qiu Fu; Ping, Ma; Yao, Yan Ding

    2016-10-01

    Study on fine annealing process of the large-aperture K9 glasses was carried out in the report. The process parameters of glass placed way, fan speed and design of the cavity for keeping temperature uniformity were attained. By the fine annealing experiment, the stress distribution was improved evidently. The stress changed from Irregular distribution to consistency symmetric distribution and the stress max was reduced. The surface profile accuracy of the large-aperture K9 glasses was controlled steadily during CNC polishing.

  8. Broad-aperture polarized proton target with arbitrary orientation of polarization vector

    International Nuclear Information System (INIS)

    Belyaev, A.A.; Get'man, V.A.; Derkach, A.Ya.; Karnaukhov, I.M.; Lukhanin, A.A.; Razumnyj, A.A.; Sorokin, P.V.; Sporov, E.A.; Telegin, Yu.N.; Trotsenko, V.I.

    1985-01-01

    Polarized proton target with the Helmholtz broad-aperture superconducting magnetic system is described. Axial aperture α=95 deg, inter-coil access angle β=23 deg. The structure of the target allows various versions of the installation what make sure an arbitrary orientation of polarization vector. The 0.1 W cold output 3 He evaporation cryostat was used to obtain the work temperature 0.5 K allowing quick transformation to a 3 He- 4 He dilution refrigerator. Results of the study are given on the dynamical proton polarization in 1,2-propylenglycol with various stable Cr 5 complexes

  9. Preliminary Experimental Verification of Synthetic Aperture Flow Imaging Using a Dual Stage Beamformer Approach

    DEFF Research Database (Denmark)

    Li, Ye; Jensen, Jørgen Arendt

    2011-01-01

    A dual stage beamformer method for synthetic aperture flow imaging has been developed. The motivation is to increase the frame rate and still maintain a beamforming quality sufficient for flow estimation that is possible to implement in a commercial scanner. With the new method high resolution...... images can be obtained continuously, which will highly increase the frame rate. The flow velocity is estimated by using a time-domain cross-correlation technique. The approach is investigated through experiments with the SARUS scanner (Synthetic Aperture Real-time Ultrasound System). A flow rig generates...

  10. Directional synthetic aperture flow imaging using a dual stage beamformer approach

    DEFF Research Database (Denmark)

    Li, Ye; Jensen, Jørgen Arendt

    2011-01-01

    A new method for directional synthetic aperture flow imaging using a dual stage beamformer approach is presented. The velocity estimation is angle independent and the amount of calculations is reduced compared to full synthetic aperture, but still maintains all the advantages at the same time.......3% and bias of 6.4% at 65 were achieved in the simulations, and 4.3% and 4.2% for the experimental measurements. A color flow map image was made in 48 emissions corresponding to a frame rate of 83 frames/s....

  11. Experimental Observations from the LHC Dynamic Aperture Machine Development Study in 2012

    CERN Document Server

    Cave, SC; Giovannozzi, M; Ludwig, M; Macpherson, A; Redaelli, S; Roncarolo, F; Camillocci, MS; Delsolaro, WV

    2013-01-01

    In view of improving the understanding of the behaviour of the dynamic aperture and to benchmark the numerical simulations performed so far, two experimental sessions have been scheduled at the LHC. The observations of the first sessions have been reported elsewhere, while in this paper the latest observations in terms of beam currents, local losses and beam sizes will be described. The octupolar spool pieces have been used to artificially reduce the dynamic aperture and then induced slow beam losses. Alternating signs have been used in order to probe different configurations. Finally, scans over the strength of the decapolar spool pieces have been performed too.

  12. Oxide-apertured microcavity single-photon-emitting diodes-simultaneous confinement of current and light

    International Nuclear Information System (INIS)

    Ellis, David J P; Bennett, Anthony J; Dewhurst, Samuel J; Shields, Andrew J; Atkinson, Paola; Nicoll, Christine A; Ritchie, David A

    2008-01-01

    We report on the development of a generation of microcavity single-photon sources in which an aluminium oxide aperture provides simultaneous confinement of the injected current and the optical mode. The aperture is formed by the wet oxidation of an aluminium-rich AlGaAs layer. This approach allows a high quality cavity to be successfully integrated into an electrical device, from which enhanced photon emission is observed through the Purcell effect. The resulting source demonstrated an improved photon collection efficiency and was shown to operate at repetition rates in excess of 0.5 GHz.

  13. Walking through apertures: do you know what you are doing during body-scaled action?

    Science.gov (United States)

    Keizer, Anouk; De Bruijn, Suzanne E M; Smeets, Monique A M; Dijkerman, H Chris; Postma, Albert

    2013-01-01

    We investigated whether body-scaled action is influenced by awareness of task performance. Participants walked through apertures varying in size. Awareness of performing the action was manipulated by asking half of the participants to concurrently perform a haptic memory task. Distracted participants showed a smaller maximum amount of shoulder rotation at A/S(crit). Walking through apertures thus seems a rather automatic/uniform process regarding action planning, but being distracted from performing the action appears to influence how the action is performed, and may increase its efficiency.

  14. A singularity extraction technique for computation of antenna aperture fields from singular plane wave spectra

    DEFF Research Database (Denmark)

    Cappellin, Cecilia; Breinbjerg, Olav; Frandsen, Aksel

    2008-01-01

    An effective technique for extracting the singularity of plane wave spectra in the computation of antenna aperture fields is proposed. The singular spectrum is first factorized into a product of a finite function and a singular function. The finite function is inverse Fourier transformed...... numerically using the Inverse Fast Fourier Transform, while the singular function is inverse Fourier transformed analytically, using the Weyl-identity, and the two resulting spatial functions are then convolved to produce the antenna aperture field. This article formulates the theory of the singularity...

  15. Optimization for imaging through scattering media for confocal microscopes with divided elliptical apertures.

    Science.gov (United States)

    Tang, Hengjie; Wu, Chenxue; Gong, Wei; Zheng, Yao; Zhu, Xinpei; Wang, Jiahao; Si, Ke

    2017-12-29

    We develop a confocal system equipped with optimal elliptical apertures to improve axial point spread function and signal-to-background ratio (SBR) for different detector sizes. By adjusting the parameters of the elliptical apertures, the axial half width at half-maximum can be reduced to 4.986 (described in optical coordinates) and SBR can be improved to 0.176. We evaluate this system with the 1951 USAF resolution test chart and the primary cultured neuron from SD rat stained by Map-2, and observe better imaging performance, which indicates the potential applications in biological science. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Fringe fields modeling for the high luminosity LHC large aperture quadrupoles

    CERN Document Server

    Dalena, B; Payet, J; Chancé, A; Brett, D R; Appleby, R B; De Maria, R; Giovannozzi, M

    2014-01-01

    The HL-LHC Upgrade project relies on large aperture magnets (mainly the inner Triplet and the separation dipole D1). The beam is much more sensitive to non-linear perturbations in this region, such as those induced by the fringe fields of the low-beta quadrupoles. Different tracking models are compared in order to provide a numerical estimate of the impact of fringe fields for the actual design of the inner triplet quadrupoles. The implementation of the fringe fields in SixTrack, to be used for dynamic apertures studies, is also discussed.

  17. Volumetric Synthetic Aperture Imaging with a Piezoelectric 2-D Row-Column Probe

    DEFF Research Database (Denmark)

    Bouzari, Hamed; Engholm, Mathias; Christiansen, Thomas Lehrmann

    2016-01-01

    The synthetic aperture (SA) technique can be used for achieving real-time volumetric ultrasound imaging using 2-D row-column addressed transducers. This paper investigates SA volumetric imaging performance of an in-house prototyped 3 MHz λ/2-pitch 62+62 element piezoelectric 2-D row-column addres......The synthetic aperture (SA) technique can be used for achieving real-time volumetric ultrasound imaging using 2-D row-column addressed transducers. This paper investigates SA volumetric imaging performance of an in-house prototyped 3 MHz λ/2-pitch 62+62 element piezoelectric 2-D row...

  18. Saturated excitation of Fluorescence to quantify excitation enhancement in aperture antennas

    KAUST Repository

    Aouani, Heykel

    2012-07-23

    Fluorescence spectroscopy is widely used to probe the electromagnetic intensity amplification on optical antennas, yet measuring the excitation intensity amplification is a challenge, as the detected fluorescence signal is an intricate combination of excitation and emission. Here, we describe a novel approach to quantify the electromagnetic amplification in aperture antennas by taking advantage of the intrinsic non linear properties of the fluorescence process. Experimental measurements of the fundamental f and second harmonic 2f amplitudes of the fluorescence signal upon excitation modulation are used to quantify the electromagnetic intensity amplification with plasmonic aperture antennas. © 2012 Optical Society of America.

  19. Testing of the large bore single aperture 1-meter superconducting dipoles made with phenolic inserts

    CERN Document Server

    Boschmann, H; Dubbeldam, R L; Kirby, G A; Lucas, J; Ostojic, R; Russenschuck, Stephan; Siemko, A; Taylor, T M; Vanenkov, I; Weterings, W

    1998-01-01

    Two identical single aperture 1-metre superconducting dipoles have been built in collaboration with HMA Power Systems and tested at CERN. The 87.8 mm aperture magnets feature a single layer coil wound using LHC main dipole outer layer cable, phenolic spacer type collars, and a keyed two part structural iron yoke. The magnets are designed as models of the D1 separation dipole in the LHC experimental insertions, whose nominal field is 4.5 T at 4.5 K. In this report we present the test results of the two magnets at 4.3 K and 1.9 K.

  20. Proposal of a relationship between dynamic aperture adn intensity evolution in a storage ring

    CERN Document Server

    Giovannozzi, M

    2010-01-01

    A scaling law for the time-dependence of the dynamic aperture, i.e., the region of phase space where stable motion occurs, was proposed in previous papers, about ten years ago. The use of fundamental theorems of the theory of dynamical systems allowed showing that the dynamic aperture has a logarithmic dependence on time. In this paper this result, proved by mean of numerical simulations, is used as a basis for deriving a scaling law for the intensity evolution in a storage ring. The proposed scaling law is also tested against experimental data showing a remarkable agreement.

  1. Polarization measurement and vertical aperture optimization for obtaining circularly polarized bend-magnet radiation

    Energy Technology Data Exchange (ETDEWEB)

    Kortright, J.B.; Rice, M.; Hussain, Z. [Lawrence Berkeley National Lab., CA (United States)] [and others

    1997-04-01

    Growing interest in utilizing circular polarization prompted the design of bend-magnet beamline 9.3.2 at the Advanced Light Source, covering the 30-1500 eV spectral region, to include vertical aperturing capabilities for optimizing the collection of circular polarization above and below the orbit plane. After commissioning and early use of the beamline, a multilayer polarimeter was used to characterize the polarization state of the beam as a function of vertical aperture position. This report partially summarizes the polarimetry measurements and compares results with theoretical calculations intended to simulate experimental conditions.

  2. Synthetic Aperture Sequential Beamforming and other Beamforming Techniques in Ultrasound Imaging

    DEFF Research Database (Denmark)

    Kortbek, Jacob

    deviation below 5±. The two synthetic aperture imaging techniques described in this thesis are both candidates for a realistic implementation in a commercial scanner. In one technique synthetic aperture focusing (SAF) is applied to 2-dimensional imaging with a single rotating mechanically focused concave...... element. Emission and reception are done while the transducer element continuously rotates and the received RF signals are stored. The geometrical focal point can be considered as a point source emitting a spherical wave in a limited angular region. For each image point in a high resolution image line...

  3. A compact, high numerical aperture imaging Fourier transform spectrometer and its application

    Science.gov (United States)

    Alcock, R. D.; Coupland, J. M.

    2006-11-01

    This paper describes a compact imaging Fourier transform spectrometer with high numerical aperture. In comparison with other optical arrangements in which extended interferometer paths are required for the inclusion of dispersion compensation optics, this technique utilizes a rudimentary cubic beam splitter based Michelson interferometer with minimal optical path so that the numerical aperture of the system is maximized. Mathematical modelling is presented showing that the fringe distortions caused by the dispersion in the cubic beam splitter can be entirely removed without any loss of the spectral information. An illustration of the power of the technique is given classifying between different plant foliage performed using a Fisher discriminant function based optimal linear filtering.

  4. Investigation of novel fractal shape of the nano-aperture as a metasurface for bio sensing application

    Energy Technology Data Exchange (ETDEWEB)

    Heydari, Samaneh [Sama Technical and Vocational Training College, Islamic Azad University, Isfahan Branch, Khorasgan (Iran, Islamic Republic of); Rastan, Iman; Parvin, Amin [Faculty of Eng., Science and Research Branch, Islamic Azad University, Shiraz (Iran, Islamic Republic of); Pirooj, Azadeh [Faculty of Eng., Science and Research Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of); Zarrabi, Ferdows B., E-mail: ferdows.zarrabi@yahoo.com [Young Researchers and Elite Club, Babol Branch, Islamic Azad University, Babol (Iran, Islamic Republic of)

    2017-01-23

    Recently, nano-aperture is noticed due to its good transmission in the optical regime. Also, the nano-apertures are developed at the metasurface design for circular polarization; for this aim, various shapes of the nano-aperture are suggested. To reach this objective, we have developed a novel Jerusalem cross fractal shape for a mid-infrared application. We have simulated various formations of the nano-fractal Jerusalem cross based on a simple cross to show the effect of nano-aperture shape on electrical field enhancement in the near-field which is important in spectroscopy and optical imaging. In addition, we have used a single layer graphene over the aperture as a coat for making reconfigurable characteristic also creating a membrane for placement of nano-particle over the aperture. Implementation of the graphene is an amendment to the transfer of the nano-apertures. The biological materials with a thickness of 80 nm have been placed over the graphene layer and the Figures of Merits (FOM) have been obtained. Additionally, the prototype of nano-antenna is independent from incident wave polarization. The Finite Difference Time Domain (FDTD) calculations have been implemented in the simulation and modeling the nano-apertures. - Highlights: • Nano-apertures are developed at the metasurface design for circular polarization. • We have developed a novel Jerusalem cross fractal shape for a mid-infrared application. • Effect of nano-aperture shape on near-field enhancement is noticed which is important in spectroscopy and optical imaging. • Single layer graphene over the aperture as a coat for making reconfigurable characteristic.

  5. A High-Resolution, Reproducible Technique for Measuring Fracture Aperture in Centimeter-Scale Rock Cores

    Science.gov (United States)

    Ameli, P.; Detwiler, R. L.; Elkhoury, J. E.

    2011-12-01

    Mechanical and chemical processes can alter fracture surfaces and their corresponding aperture. Understanding the relationship between physicochemical processes and the alteration of fracture apertures is fundamental to quantifying the evolution of transport properties in the subsurface. Therefore, relevant experiments that quantify these processes require the ability to measure fracture surfaces and reconstruct fracture aperture fields at high resolutions before and after experiments. Furthermore, to meaningfully compare measured aperture fields before and after experiments, it is critical that the measurements are reproducible to ensure that differences in fracture apertures are due to physical changes and not data acquisition or reconstruction errors. Energy transmission techniques can provide direct, non-destructive measurement of fracture apertures. However, while X-ray CT is capable of μm-scale resolution, at those resolutions, it is limited to millimeter-scale cores. Alternatively, light absorbance techniques are limited to transparent analogs or casts of real rocks. Modern surface-profilometry instruments provide the ability to measure surface topography at high resolution, but it is difficult to reconstruct fracture apertures from the measured surfaces. We present a rigorous approach for using high-resolution measurements of surface topography to reproducibly reconstruct fracture aperture fields. An optical profilometer (NANOVEA ST400) provides surface topography measurements averaged over a spot size of 8 μm with spatial accuracy of ±0.1 μm and elevation accuracy of ±0.9 μm. Numerically mating the measured surfaces requires accurate, reproducible alignment of the two fracture halves in three-dimensional space. To facilitate alignment and provide a means for checking the alignment of scanned surfaces, we fabricated a jig for securing the halves of the core to the profilometer stage. The jig consists of two mated blocks of precision-milled steel that

  6. Modeling Flow in Naturally Fractured Reservoirs : Effect of Fracture Aperture Distribution on Critical Sub-Network for Flow

    NARCIS (Netherlands)

    Gong, J.; Rossen, W.R.

    2014-01-01

    Fracture network connectivity and aperture (or conductivity) distribution are two crucial features controlling the flow behavior of fractured formations. The effect of connectivity on flow properties is well documented. We focus here on the influence of fracture aperture distribution. We model a

  7. Formation and function of a new pollen aperture pattern in angiosperms: The proximal sulcus of Tillandsia leiboldiana (Bromeliaceae).

    Science.gov (United States)

    Albert, Béatrice; Matamoro-Vidal, Alexis; Raquin, Christian; Nadot, Sophie

    2010-02-01

    Pollen grains are generally surrounded by an extremely resistant wall interrupted in places by apertures that play a key role in reproduction; pollen tube growth is initiated at these sites. The shift from a proximal to distal aperture location is a striking innovation in seed plant reproduction. Reversals to proximal aperture position have only very rarely been described in angiosperms. The genus Tillandsia belongs to the Bromeliaceae family, and its aperture pattern has been described as distal monosulcate, the most widespread aperture patterns recorded in monocots and basal angiosperms. Here we report developmental and functional elements to demonstrate that the sulcate aperture in Tillandsia leiboldiana is not distal as previously described but proximal. Postmeitotic tetrad observation indicates unambiguously the proximal position of the sulcus, and in vitro germination of pollen grains confirms that the aperture is functional. This is the first report of a sulcate proximal aperture with proximal germination. The observation of microsporogenesis reveals specific features in the patterns of callose thickenings in postmeiotic tetrads.

  8. An atlas of November 1978 synthetic aperture radar digitized imagery for oil spill studies

    Science.gov (United States)

    Maurer, H. E.; Oderman, W.; Crosswell, W. F.

    1982-01-01

    A data set is described which consists of digitized synthetic aperture radar (SAR) imagery plus correlative data and some preliminary analysis results. This data set should be of value to experimenters who are interested in the SAR instrument and its application to the detection and monitoring of oil on water and other distributed targets.

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

    Science.gov (United States)

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

    2015-07-01

    Reliable and valid population specific standards are necessary to accurately develop a biological profile, which includes an estimation of peer-reported social identification (Hefner, 2009). During the last 300 years, colonialism, slavery and apartheid created geographic, physical and social divisions of population groups in South Africa. The purpose of this study was to evaluate variation in nasal bone and aperture shape in a modern population of black, white, and coloured South Africans using standard craniometric variables and geometric morphometrics, namely general Procrustes and elliptical Fourier analyses. Fourteen standard landmarks were digitally recorded or computationally derived from 310 crania using a 3D coordinate digitizer for discriminant function, principal components and generalized Procrustes analyses. For elliptical Fourier analysis, outlines of the nasal aperture were generated from standardized photographs. All classification accuracies were better than chance; the lowest accuracies were for coloured and the highest accuracies were for white South Africans. Most difficulties arose in distinguishing coloured and black South African groups from each other. Generally, misclassifications were noted between the sexes within each group rather than among groups, which suggests that sex has less influence on nasal bone and aperture shape than ancestry. Quantifiable variation in shape of the nasal aperture region between white and non-white South African groups was observed. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  10. Modified Range-Doppler Processing for FM-CW Synthetic Aperture Radar

    NARCIS (Netherlands)

    Wit, J.J.M. de; Meta, A.; Hoogeboom, P.

    2006-01-01

    The combination of compact frequency-modulated continuous-wave (FM-CW) technology and high-resolution synthetic aperture radar (SAR) processing techniques should pave the way for the development of a lightweight, cost-effective, high-resolution, airborne imaging radar. Regarding FM-CW SAR signal

  11. Energy control of neutral oxygen particles passing through an aperture electrode

    Science.gov (United States)

    Ohno, Takeo; Nakayama, Daiki; Okada, Takeru; Samukawa, Seiji

    2018-03-01

    The kinetic energy of neutralized oxygen particles passing through an aperture electrode was measured by a quadrupole mass spectrometer. The peak energy position was controlled by changing the plasma source power, acceleration bias power, and gas pressure in the vacuum chamber.

  12. Nonpolar III-nitride vertical-cavity surface-emitting lasers incorporating an ion implanted aperture

    KAUST Repository

    Leonard, J. T.

    2015-07-06

    © 2015 AIP Publishing LLC. We report on our recent progress in improving the performance of nonpolar III-nitride vertical-cavity surface-emitting lasers (VCSELs) by using an Al ion implanted aperture and employing a multi-layer electron-beam evaporated ITO intracavity contact. The use of an ion implanted aperture improves the lateral confinement over SiNx apertures by enabling a planar ITO design, while the multi-layer ITO contact minimizes scattering losses due to its epitaxially smooth morphology. The reported VCSEL has 10 QWs, with a 3nm quantum well width, 1nm barriers, a 5nm electron-blocking layer, and a 6.95- λ total cavity thickness. These advances yield a single longitudinal mode 406nm nonpolar VCSEL with a low threshold current density (∼16kA/cm2), a peak output power of ∼12μW, and a 100% polarization ratio. The lasing in the current aperture is observed to be spatially non-uniform, which is likely a result of filamentation caused by non-uniform current spreading, lateral optical confinement, contact resistance, and absorption loss.

  13. Design of a Large Single-Aperture Dipole Magnet for HL-LHC Upgrade

    CERN Document Server

    Qingjin, Xu; Iio, Masami; Ogitsu, Toru; Sasaki, Kenichi; Yamamoto, Akira; Todesco, Ezio

    2013-01-01

    An upgrade of the low-beta insertion system for the ATLAS and Compact Muon Solenoid experiments is proposed in the high luminosity Large Hadron Collider upgrade project. It includes final beam focusing quadrupoles, beam separation and recombination dipoles, and larger aperture matching section quadrupoles. KEK is in charge of the conceptual design of the large aperture separation dipole D1. The latest design parameters are a main field of ~ 5 T at 1.9 K with Nb-Ti superconducting technology, a coil aperture of 160 mm, and a cos-theta one-layer coil with Large Hadron Collider dipole cable. Because the new D1 is expected to be operated in a very high radiation environment, radiation resistance and a cooling scheme are being carefully considered. The collaring-yoke structure is adopted to provide the mechanical support for the single-layer Nb-Ti coil. We summarize the design study of this magnet, including i) the very large iron saturation effect on field quality due to the large aperture and limited size of the...

  14. Numerical simulation of microwave pulse coupling into the rectangular cavity with aperture arrays

    International Nuclear Information System (INIS)

    Li Rui; Yang Yiming; Qian Baoliang

    2008-01-01

    In this paper, the finite-difference time-domain (FDTD) algorithm is employed to simulate microwave pulse coupling into the rectangular cavity with aperture arrays. In the case in which the long-side of the slot in aperture arrays is perpendicular to the incident electrical field, and the electrical distribution of each center of slot in the aperture arrays in the process of microwave pulse coupling into the rectangular cavity with aperture arrays is analyzed in detail. We find that the effect of field enhancement of the slot in the middle of all the slots which distribute in the direction parallel to the incident electrical field is minimum and increases in turn from the middle to both sides symmetrically. We also find that the effect of field enhancement of the slot in the middle of all the slots which distribute in the direction perpendicular to the incident electrical field is maximum and decreases in turn from the middle to both sides symmetrically. In the same time, we investigate the factors that influence the effect of field enhancement of the center of each slot and the coupling electrical distribution in the cavity, including the number of slots and the spacing between slots. (authors)

  15. Retrieval of Wind Speed Using an L-band Synthetic Aperture Radar

    DEFF Research Database (Denmark)

    Monaldo, Frank M.; Thompson, Donald R.; Badger, Merete

    2007-01-01

    usefulness over the ocean. Most recent wind retrievals from spaceborne SARs have been at C-band for ERS-1/2, Radarsat, and Envisat. With the launch of the sophisticated multi- polarization Phased Array L-band Synthetic Aperture Radar (PALSAR) on the Advanced Land Observing Satellite (ALOS), we renew...

  16. Integrating polarimetric synthetic aperture radar and imaging spectrometry for wildland fuel mapping in southern California

    Science.gov (United States)

    P.E. Dennison; D.A. Roberts; J. Regelbrugge; S.L. Ustin

    2000-01-01

    Polarimetric synthetic aperture radar (SAR) and imaging spectrometry exemplify advanced technologies for mapping wildland fuels in chaparral ecosystems. In this study, we explore the potential of integrating polarimetric SAR and imaging spectrometry for mapping wildland fuels. P-band SAR and ratios containing P-band polarizations are sensitive to variations in stand...

  17. Collarless, close-in, shaped iron aperture designs for the SSC [Superconducting Super Collider] dipole

    International Nuclear Information System (INIS)

    Gupta, R.C.; Morgan, G.H.

    1989-01-01

    The nominal-design SSC (Superconducting Super Collider) dipole encloses the coil in an iron yoke having a circular aperture. The radial gap between the coil and the iron is about 15 mm to provide space for a strong annular collar around the coil, and also to reduce the effects of iron saturation on central field harmonics. The 15 mm gap also reduces the desirable dipole field contributed by the iron. The present paper gives a coil and aperture configuration in which the gap is reduced to 5 mm at the midplane, in which the aperture is shaped to reduce the unwanted effects of iron saturation. The transfer function is increased about 5% at 6.6 Tesla and the unwanted harmonics are within SSC tolerances at all field levels. These designs would require that the yoke and containment vessel absorb the stresses due to assembly and magnetic forces. A short magnet is being built with a close-in shaped iron aperture and existing coil geometry to assess the benefits of this concept. 7 refs., 3 figs., 6 tabs

  18. Offshore wind resource mapping for Europe by Synthetic Aperture Radar (SAR) satellite data

    DEFF Research Database (Denmark)

    Hasager, Charlotte Bay; Badger, Merete

    2015-01-01

    of satellite remote sensing observations and atmospheric modelling. The satellite data include Synthetic Aperture Radar (SAR) from the European Space Agency from Envisat and the Copernicus mission Sentinel-1. SAR has the advantage of high spatial resolution such that we can cover near-coastal areas where many...

  19. Position measurement of the direct drive motor of Large Aperture Telescope

    Science.gov (United States)

    Li, Ying; Wang, Daxing

    2010-07-01

    Along with the development of space and astronomy science, production of large aperture telescope and super large aperture telescope will definitely become the trend. It's one of methods to solve precise drive of large aperture telescope using direct drive technology unified designed of electricity and magnetism structure. A direct drive precise rotary table with diameter of 2.5 meters researched and produced by us is a typical mechanical & electrical integration design. This paper mainly introduces position measurement control system of direct drive motor. In design of this motor, position measurement control system requires having high resolution, and precisely aligning the position of rotor shaft and making measurement, meanwhile transferring position information to position reversing information corresponding to needed motor pole number. This system has chosen high precision metal band coder and absolute type coder, processing information of coders, and has sent 32-bit RISC CPU making software processing, and gained high resolution composite coder. The paper gives relevant laboratory test results at the end, indicating the position measurement can apply to large aperture telescope control system. This project is subsidized by Chinese National Natural Science Funds (10833004).

  20. Influence of stomatic aperture on photosynthetic activity of bean-seedlings leaves

    International Nuclear Information System (INIS)

    Suarez Moya, J.; Fernandez Gonzalez, J.

    1984-01-01

    The present paper contains the data of photosynthetic activity and stomatic aperture of bean-seedlings Ieaves, and the relations obtained with both results. It has been observed that the product of photosynthetic activity by the resistance; to transpiration measured by a promoter ia a constant, between some limits. (Author) 45 refs

  1. Implementasi Augmented Reality Untuk Pengenalan Komponen Very Small Aperture Terminal (Vsat) Berbasis Android

    OpenAIRE

    Juanda, Irfan

    2016-01-01

    141421066 Augmented reality adalah penggabungan objek digital untuk pengguna dalam lingkungan secara waktu nyata. Augmented Reality dapat digunakan sebagai media pembelajaran interaktif dan inovatif. Salah satu diantaranya adalah untuk memperkenalkan komponen dari Very Small Aperture Terminal (VSAT). Dengan memanfaatkan Augmented Reality, komponen VSAT dapat dilihat dalam bentuk objek 3D menggunakan smartphone android, tujuannya adalah membantu pengguna dalam belajar mengenal komponen VSAT...

  2. Enhanced performance of a wide-aperture copper vapour laser with ...

    Indian Academy of Sciences (India)

    E-mail: bsingh@rrcat.gov.in. Abstract. A wide-aperture ... based on longitudinal step profiling of the thermal insulation density around the. CVL discharge tube. Such design changes have been discussed elsewhere in detail. [11]. The main objective of using the step profiling was to reduce end thermal losses particularly in ...

  3. Path-average rainfall estimation from optical extinction measurements using a large-aperture scintillometer

    NARCIS (Netherlands)

    Uijlenhoet, R.; Cohard, J.M.; Gosset, M.

    2011-01-01

    The potential of a near-infrared large-aperture boundary layer scintillometer as path-average rain gauge is investigated. The instrument was installed over a 2.4-km path in Benin as part of the African Monsoon Multidisciplinary Analysis (AMMA) Enhanced Observation Period during 2006 and 2007.

  4. Test results of BNL built 40-mm aperture, 17-m-long SSC collider dipole magnets

    Energy Technology Data Exchange (ETDEWEB)

    Kuzminski, J.; Bush, T.; Coombes, R.; Devred, A.; DiMarco, J.; Goodzeit, C.; Puglisi, M.; Radusewicz, P.; Sanger, P.; Schermer, R.; Tompkins, J.C.; Wolf, Z.; Yu, Y.; Zheng, H. (Superconducting Super Collider Lab., Dallas, TX (United States)); Ogitsu, T. (Superconducting Super Collider Lab., Dallas, TX (United States) National Lab. for High Energy Physics, Tsukuba, Ibaraki (Japan)); Anerella, M.; Cottingham, J.

    1991-06-01

    Eleven 17 m long, 40 mm aperture SSC R D superconducting collider dipole magnets, built at BNL, have been extensively tested at BNL and Fermilab during 1990--91. Quench performance of these magnets and details of their mechanical behavior are presented. 7 refs., 5 figs.

  5. A Nb-Ti 90 mm Double-Aperture Quadrupole for the High Luminosity LHC Upgrade

    CERN Document Server

    Segreti, M; Todesco, E

    2015-01-01

    The luminosity upgrade of the LHC requires replacing the magnets around the ATLAS and CMS experiments with larger aperture dipoles, quadrupoles and correctors. The goal is to have a magnetic lattice that can allow to halve the beam size in the collision points with respect to present baseline. Within the framework of HiLumi LHC, CEA-Saclay studied the replacement of the 70-mm double aperture quadrupole Q4, with a 90-mm magnet based on Nb-Ti technology. The main challenges are due to the distance between the beams of 194 mm, giving a non-negligible magnetic coupling between the two apertures. The coil chosen to be the baseline is a single layer with 15-mm-width cable of the LHC MQ quadrupole. The mechanical structure is based on stainless steel collars to withstand the Lorentz forces. The iron yoke has a magnetic function, and guarantees the alignment of the two apertures. Electromagnetic and mechanical aspects and effects of unbalanced regimes on the field quality have been analyzed. A 3-D design of the coil ...

  6. Apertures with Laval Nozzle and Circular Orifice in Secondary Electron Detector for Environmental Scanning Electron Microscope

    Czech Academy of Sciences Publication Activity Database

    Vyroubal, P.; Maxa, J.; Neděla, Vilém; Jirák, Josef; Hladká, K.

    2013-01-01

    Roč. 8, č. 1 (2013), s. 59-69 ISSN 1802-2308 R&D Projects: GA ČR GAP102/10/1410 Institutional support: RVO:68081731 Keywords : Aperture * Laval nozzle * circular orifice * pressure * detector * Mach number * flow * trajectory of secondary electrons Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering

  7. Scattering of Electromagnetic Radiation by Apertures: II. Oblique Incidence on the Slotted Plane for Parallel Polarization,

    Science.gov (United States)

    The report is the second in a series of investigations into the diffraction of electromagnetic radiation by apertures in conducting screens. Herein...is presented a technique for obtaining the fields everywhere for plane electromagnetic radiation incident obliquely on a slotted conducting plane. The

  8. Optical aperture synthesis : A comparison of techniques for wide-field interferometric imaging

    NARCIS (Netherlands)

    Van der Avoort, C.

    2006-01-01

    The research described in this thesis provides onsets for research in several areas of interest related to aperture synthesis and guidelines concerning the design of synthetic telescopes for imaging. As such, this research contributes to the improvement of instrumentation for observational

  9. Design of a Small, Low Cost, P-Band Airborne Polarimetric Synthetic Aperture Radar

    NARCIS (Netherlands)

    Figueras i Ventura, J.; Hoogeboom, P.

    2004-01-01

    A preliminary study of the design of a small, low cost, P-band airborne, polarimetric Synthetic Aperture Radar desired by the Wageningen University and the Borneo Orangutan Survival Foundation (BOS) to carry out forest biomass monitoring in Indonesia is presented. The requirements of the application

  10. Photoacoustic imaging of blood vessels with a double-ring sensor featuring a narrow angular aperture

    NARCIS (Netherlands)

    Kolkman, R.G.M.; Hondebrink, Erwin; Steenbergen, Wiendelt; van Leeuwen, Ton; de Mul, F.F.M.

    2004-01-01

    A photoacoustic double-ring sensor, featuring a narrow angular aperture, is developed for laser-induced photoacoustic imaging of blood vessels. An integrated optical fiber enables reflection-mode detection of ultrasonic waves. By using the cross-correlation between the signals detected by the two

  11. Displaced-beam small aperture scintillometer test: CASES-99 stable boundary layer experiment

    NARCIS (Netherlands)

    Hartogensis, O.K.; DeBruin, H.A.R.

    2002-01-01

    In this study we investigated the performance of a displaced-beam small aperture scintillometer (DBSAS) - operated over a path length of 112 m - under stable conditions using data gathered during the CASES-99 experiment in Kansas, USA. The DBSAS has the advantage over the eddy covariance method that

  12. AMBER: An X-band FMCW digital beam forming synthetic aperture radar for a tactical UAV

    NARCIS (Netherlands)

    Graaf, M.W. van der; Otten, M.P.G.; Huizing, A.G.; Tan, R.G.; Caro Cuenca, M.; Ruizenaar, M.G.A.

    2013-01-01

    An X-band Digital Array Synthetic Aperture Radar for a Short Range Tactical UAV is presented. This system is demonstrated on a manned helicopter and motor glider. The Frequency Modulated Continuous Wave radar principle in combination with digital beam forming over 24 receive channels is used to meet

  13. Basics of Polar-Format algorithm for processing Synthetic Aperture Radar images.

    Energy Technology Data Exchange (ETDEWEB)

    Doerry, Armin Walter

    2012-05-01

    The purpose of this report is to provide a background to Synthetic Aperture Radar (SAR) image formation using the Polar Format (PFA) processing algorithm. This is meant to be an aid to those tasked to implement real-time image formation using the Polar Format processing algorithm.

  14. Wavefront curvature limitations and compensation to polar format processing for synthetic aperture radar images.

    Energy Technology Data Exchange (ETDEWEB)

    Doerry, Armin Walter

    2006-01-01

    Limitations on focused scene size for the Polar Format Algorithm (PFA) for Synthetic Aperture Radar (SAR) image formation are derived. A post processing filtering technique for compensating the spatially variant blurring in the image is examined. Modifications to this technique to enhance its robustness are proposed.

  15. PMAS: The Potsdam Multi-Aperture Spectrophotometer. II. The Wide Integral Field Unit PPak

    NARCIS (Netherlands)

    Kelz, Andreas; Verheijen, Marc A. W.; Roth, Martin M.; Bauer, Svend M.; Becker, Thomas; Paschke, Jens; Popow, Emil; Sánchez, Sebastian F.; Laux, Uwe

    2006-01-01

    PPak is a new fiber-based integral field unit (IFU) developed at the Astrophysical Institute of Potsdam and implemented as a module into the existing Potsdam Multi-Aperture Spectrophotometer (PMAS) spectrograph. The purpose of PPak is to provide an extended field of view with a large

  16. Detection optimization using linear systems analysis of a coded aperture laser sensor system

    Energy Technology Data Exchange (ETDEWEB)

    Gentry, S.M. [Sandia National Labs., Albuquerque, NM (United States). Optoelectronic Design Dept.

    1994-09-01

    Minimum detectable irradiance levels for a diffraction grating based laser sensor were calculated to be governed by clutter noise resulting from reflected earth albedo. Features on the earth surface caused pseudo-imaging effects on the sensor`s detector arras that resulted in the limiting noise in the detection domain. It was theorized that a custom aperture transmission function existed that would optimize the detection of laser sources against this clutter background. Amplitude and phase aperture functions were investigated. Compared to the diffraction grating technique, a classical Young`s double-slit aperture technique was investigated as a possible optimized solution but was not shown to produce a system that had better clutter-noise limited minimum detectable irradiance. Even though the double-slit concept was not found to have a detection advantage over the slit-grating concept, one interesting concept grew out of the double-slit design that deserved mention in this report, namely the Barker-coded double-slit. This diffractive aperture design possessed properties that significantly improved the wavelength accuracy of the double-slit design. While a concept was not found to beat the slit-grating concept, the methodology used for the analysis and optimization is an example of the application of optoelectronic system-level linear analysis. The techniques outlined here can be used as a template for analysis of a wide range of optoelectronic systems where the entire system, both optical and electronic, contribute to the detection of complex spatial and temporal signals.

  17. Radiation of a charge in presence of a dielectric object: aperture method

    Science.gov (United States)

    Tyukhtin, A. V.; Vorobev, V. V.; Belonogaya, E. S.; Galyamin, S. N.

    2018-02-01

    We develop an original method for calculation of radiation from a charge moving in the presence of a dielectric object. The method can be applied to objects which are larger than the wavelengths under consideration. First, the field of a charge in an infinite medium (without external boundaries) is calculated. Further the field at the external boundary of the object ("the aperture") is found using the Snell's and Fresnel's laws. At final step of this technique, we calculate the field outside the target using Stratton-Chu formulae ("aperture integrals"). Contrary to the ray-optic technique, this method is valid for the observation point with arbitrary wave parameter (including Fraunhofer area) as well as in neighborhoods of focuses and caustics. We apply the method developed to the cone with vacuum channel where the charge moves (axially symmetrical problem). As well, this problem is simulated using COMSOL Multiphysics. Comparing results of both techniques one can conclude that the aperture method can be applied even for relatively small objects which have the size of several wavelengths. It is important as well that the accuracy of calculations increases with an increase in the distance from the aperture.

  18. Study on coding strategies for radar coded-aperture imaging in terahertz band

    Science.gov (United States)

    Chen, Shuo; Luo, Chenggao; Deng, Bin; Qin, Yuliang; Wang, Hongqiang

    2017-09-01

    Motivated by the principle of coded-aperture imaging and microwave radar coincidence imaging (RCI), terahertz radar coded-aperture imaging (RCAI) is proposed to obtain high-resolution, forward-looking, and staring imaging. The terahertz RCAI method resolves target scatterers using the correlation processing of the modulated echoes and the reference signal matrix. This process is similar to the basic principle of RCI. To investigate the coding strategies of terahertz RCAI, this study derives three signal models describing operation with the coded aperture placed separately in the transmitting terminal and the receiving terminal and in both of them simultaneously. Furthermore, coding strategies are categorized according to coded-aperture placement and encoded signal, including amplitude modulation and phase modulation. In addition, qualitative and quantitative analysis methods are introduced to describe the resolving ability of terahertz RCAI. Numerical simulations are performed to analyze and compare the performance on different coding strategies. These analyses can provide constructive guidelines for the design of terahertz RCAI systems.

  19. Preliminary In-Vivo Evaluation of Convex Array Synthetic Aperture Imaging

    DEFF Research Database (Denmark)

    Pedersen, Morten Høgholm; Gammelmark, Kim; Jensen, Jørgen Arendt

    2004-01-01

    Synthetic transmit aperture (STA) imaging has previously been investigated and compared to traditional imaging techniques in simulations and phantom studies. However, a full in-vivo study evaluating its clinical potential has yet to be conducted. This paper presents a preliminary in-vivo study of...

  20. Analysis of aperture antenna attached to cutoff cavity for ICRF plasma heating

    International Nuclear Information System (INIS)

    Sawaya, K.; Adachi, S.

    1986-01-01

    Basic characteristics of an aperture antenna attached to a cutoff cavity for ICRF plasma heating are investigated. The analysis is performed for antennas radiating into semi-infinite free space rather than a magnetoplasma. Good agreement between theory and experiment is observed, indicating the validity of the analysis

  1. Measurement of nonlinear refractive index in open-aperture Z-scan ...

    Indian Academy of Sciences (India)

    Abstract. We present an experimental study on measurement of nonlinear refractive index (n2) of organic liquids when the thermo-optic effects manifest into large nonlinear phase shifts ( φ0) in an open-aperture Z-scan configuration. Although we do not obtain the familiar peak–valley nor- malized transmittance curve as in ...

  2. Test results of BNL built 40-mm aperture, 17-m-long SSC collider dipole magnets

    International Nuclear Information System (INIS)

    Kuzminski, J.; Bush, T.; Coombes, R.; Devred, A.; DiMarco, J.; Goodzeit, C.; Puglisi, M.; Radusewicz, P.; Sanger, P.; Schermer, R.

    1992-01-01

    Eleven 17 m long, 40 mm aperture SSC R and D superconducting collider dipole magnets, built at BNL, have been extensively tested at BNL and Fermilab during 1990-91. In this paper quench performance of these magnets and details of their mechanical behavior are presented

  3. Test results of BNL built 40-mm aperture, 17-m-long SSC collider dipole magnets

    International Nuclear Information System (INIS)

    Kuzminski, J.; Bush, T.; Coombes, R.; Devred, A.; DiMarco, J.; Goodzeit, C.; Puglisi, M.; Radusewicz, P.; Sanger, P.; Schermer, R.; Tompkins, J.C.; Wolf, Z.; Yu, Y.; Zheng, H.; Ogitsu, T.; Anerella, M.; Cottingham, J.; Ganetis, G.; Garber, M.; Gosh, A.; Greene, A.; Gupta, R.; Herrera, J.; Kahn, S.; Kelly, E.; Morgan, G.; Muratore, J.; Prodell, A.; Rehak, M.; Rohrer, E.P.; Sampson, W.; Shutt, R.; Thompson, P.; Wanderer, P.; Willen, E.; Bleadon, M.; Hanft, R.; Kuchnir, M.; Mantsch, P.; Mazur, P.O.; Orris, D.; Peterson, T.; Strait, J.; Royet, J.; Scanlan, R.; Taylor, C.

    1991-06-01

    Eleven 17 m long, 40 mm aperture SSC R ampersand D superconducting collider dipole magnets, built at BNL, have been extensively tested at BNL and Fermilab during 1990--91. Quench performance of these magnets and details of their mechanical behavior are presented. 7 refs., 5 figs

  4. Daris, a low-frequency distributed aperture array for radio astronomy in space

    NARCIS (Netherlands)

    Boonstra, A.J.; Saks, N.; Bentum, Marinus Jan; van 't Klooster, K.; Falcke, H.

    2010-01-01

    DARIS (Distributed Aperture Array for Radio Astronomy in Space) is a radio astronomy space mission concept aimed at observing the low-frequency radio sky in the range 1-10 MHz. Because of the Earth's ionospheric disturbances and opaqueness, this frequency range can only be observed from space. The

  5. An Anomaly Detector Based on Multi-aperture Mapping for Hyperspectral Data

    Directory of Open Access Journals (Sweden)

    LI Min

    2016-10-01

    Full Text Available Considering the correlationship of spectral content between anomaly and clutter background, inaccurate selection of background pixels induced estimation error of background model. In order to solve the above problems, a multi-aperture mapping based anomaly detector was proposed in this paper. Firstly, differing from background model which focused on feature extraction of background, multi-aperture mapping of hyperspectral data characterized the feature of whole hyperspectral data. According to constructed basis set of multi-aperture mapping, anomaly salience index of every test pixel was proposed to measure the relative statistic difference. Secondly, in order to analysis the moderate salience anomaly precisely, membership value was constructed to identify anomaly salience of test pixels continuously based on fuzzy logical theory. At same time, weighted iterative estimation of multi-aperture mapping was expected to converge adaptively with membership value as weight. Thirdly, classical defuzzification was proposed to fuse different detection results. Hyperspectral data was used in the experiments, and the robustness and sensitivity to anomaly with lower silence of proposed detector were tested.

  6. Measurement of nonlinear refractive index in open-aperture Z-scan ...

    Indian Academy of Sciences (India)

    We present an experimental study on measurement of nonlinear refractive index (2) of organic liquids when the thermo-optic effects manifest into large nonlinear phase shifts (0) in an open-aperture ... School of Physical Sciences, National Institute of Science Education and Research, Bhubaneswar 751 005, India ...

  7. Quench performance of 50-mm aperture, 15-m-long SSC dipole magnets built at Fermilab

    International Nuclear Information System (INIS)

    Kuzminski, J.; Bush, T.; Coombes, R.

    1992-07-01

    The quench performance, ramp rate dependence, and mechanical behavior of ten full-length, 50-mm-aperture, SSC dipole magnets built at Fermilab are discussed. Cold testing of these magnets shows that the quench plateau established at 4.35 K exceeds the design value by more than 10%, virtually without training

  8. Archaeological use of Synthetic Aperture Sonar on deepwater wreck sites in Skagerrak

    DEFF Research Database (Denmark)

    Maarleveld, Thijs J.; Ødegård, Øyvind; Hansen, Roy E.

    2018-01-01

    Marine archaeological surveying in deep waters has so far been challenging, mainly due to operational and technological constraints. The standard tool has been Side Scan Sonar (SSS) towed behind a surface vessel. Synthetic Aperture Sonar (SAS) technology is not subject to the traditional range...

  9. Performance Evaluation of a Synthetic Aperture Real-Time Ultrasound System

    DEFF Research Database (Denmark)

    Stuart, Matthias Bo; Tomov, Borislav Gueorguiev; Jensen, Jørgen Arendt

    2011-01-01

    This paper evaluates the signal-to-noise ratio, the time stability, and the phase difference of the sampling in the experimental ultrasound scanner SARUS: A synthetic aperture, real-time ultrasound system. SARUS has 1024 independent transmit and receive channels and is capable of handling 2D probes...

  10. A concept of a wide aperture klystron with RF absorbing drift tubes for linear collider

    International Nuclear Information System (INIS)

    Dolbilov, G.V.; Azorskij, N.I.; Fateev, A.A.

    1997-01-01

    This paper is devoted to a problem of optimal design of the electrodynamic structure of the X-band klystron for a linear collider. It is shown that optimal design should provide large aperture and a high power gain, about 80 dB. The most severe problem arising here is that of parasitic self-excitation of the klystron, which becomes more complicated at increasing aperture and power gain. Our investigations have shown that traditional methods for suppressing the self-excitation become ineffective at desired technical parameters of the klystron. A novel concept of a wide aperture klystron with distributed suppression of parasitic oscillations is presented. Results of experimental study of the wide-aperture relativistic klystron for VLEPP are presented. Investigations have been performed using the driving beam of the JINR LIA-3000 induction accelerator (E=1 MeV, I=250 A, τ=250 ns). To suppress self-excitation parasitic modes we have used technique of RF absorbing drift tubes. As a result, we have obtained design output parameters of the klystron and achieved level of 100 MW output power

  11. Control of aperture closure initiation during trunk-assisted reach-to-grasp movements.

    Science.gov (United States)

    Rand, Miya K; Van Gemmert, Arend W A; Hossain, Abul B M I; Shimansky, Yury P; Stelmach, George E

    2012-06-01

    The present study investigated how the involvement and direction of trunk movement during reach-to-grasp movements affect the coordination between the transport and grasping components. Seated young adults made prehensile movements in which the involvement of the trunk was varied; the trunk was not involved, moved forward (flexion), or moved backward (extension) in the sagittal plane during the reach to the object. Each of the trunk movements was combined with an extension or flexion motion of the arm during the reach. Regarding the relationship between the trunk and arm motion for arm transport, the onset of wrist motion relative to that of the trunk was delayed to a greater extent for the trunk extension than for the trunk flexion. The variability of the time period from the peak of wrist velocity to the peak of trunk velocity was also significantly greater for trunk extension compared to trunk flexion. These findings indicate that trunk flexion was better integrated into the control of wrist transport than trunk extension. In terms of the temporal relationship between wrist transport and grip aperture, the relationship between the time of peak wrist velocity and the time of peak grip aperture did not change or become less steady across conditions. Therefore, the stability of temporal coordination between wrist transport and grip aperture was maintained despite the variation of the pattern of intersegmental coordination between the arm and the trunk during arm transport. The transport-aperture coordination was further assessed in terms of the control law according to which the initiation of aperture closure during the reach occurs when the hand crosses a hand-to-target distance threshold for grasp initiation, which is a function of peak aperture, wrist velocity and acceleration, trunk velocity and acceleration, and trunk-to-target distance at the time of aperture closure initiation. The participants increased the hand-to-target distance threshold for grasp

  12. Experimental observations of deformation caused by mineral dissolution in variable-aperture fractures

    Science.gov (United States)

    Detwiler, Russell L.

    2008-08-01

    Problems such as CO2 sequestration, petroleum production and nuclear waste isolation involve the potential for rock-water reactions. Mineral alteration resulting from reactive fluid flow can lead to significant changes to fracture transport properties. At depth, these processes are further influenced by stresses in the host rock. To quantitatively explore these coupled processes, we built a new experimental apparatus designed to directly measure changes in fracture aperture in analog fractures subjected to the combined influence of a reactive fluid and an applied normal stress. Light transmission techniques provided direct measurements of the changing fracture aperture at high spatial resolution during two experiments in identical fractures with an initial mean fracture aperture of 95 μm. The two experiments were carried out at values of the dimensionless Damkohler number (Da = reaction rate/advection rate) that differed by a factor of 2. The high-Da experiment resulted in the formation of a large-scale dissolution channel in the middle of the fracture and regions with little dissolution and slow closure of the fracture surfaces. By contrast, the low-Da experiment exhibited relatively uniform dissolution across the width of the fracture, with locally enhanced dissolution in small aperture regions. This resulted in increased stresses in contacting asperities and eventual damage of the asperities accompanied by large (up to 50 μm), instantaneous displacements of the surfaces and corresponding reductions in fracture aperture. The results demonstrate the importance of the spatial variability of dissolution rates, which are controlled by both local reaction kinetics and hydrodynamics, in fractures deforming because of combined dissolution and mechanical stress.

  13. Translating bed total body irradiation lung shielding and dose optimization using asymmetric MLC apertures

    Science.gov (United States)

    Ahmed, Shahbaz; Brown, Derek; Ahmed, Saad B. S.; Kakakhel, Muhammad B.; Muhammad, Wazir

    2016-01-01

    A revised translating bed total body irradiation (TBI) technique is developed for shielding organs at risk (lungs) to tolerance dose limits, and optimizing dose distribution in three dimensions (3D) using an asymmetrically‐adjusted, dynamic multileaf collimator. We present a dosimetric comparison of this technique with a previously developed symmetric MLC‐based TBI technique. An anthropomorphic RANDO phantom is CT scanned with 3 mm slice thickness. Radiological depths (RD) are calculated on individual CT slices along the divergent ray lines. Asymmetric MLC apertures are defined every 9 mm over the phantom length in the craniocaudal direction. Individual asymmetric MLC leaf positions are optimized based on RD values of all slices for uniform dose distributions. Dose calculations are performed in the Eclipse treatment planning system over these optimized MLC apertures. Dose uniformity along midline of the RANDO phantom is within the confidence limit (CL) of 2.1% (with a confidence probability p=0.065). The issue of over‐ and underdose at the interfaces that is observed when symmetric MLC apertures are used is reduced from more than ±4% to less than ±1.5% with asymmetric MLC apertures. Lungs are shielded by 20%, 30%, and 40% of the prescribed dose by adjusting the MLC apertures. Dose‐volume histogram analysis confirms that the revised technique provides effective lung shielding, as well as a homogeneous dose coverage to the whole body. The asymmetric technique also reduces hot and cold spots at lung‐tissue interfaces compared to previous symmetric MLC‐based TBI technique. MLC‐based shielding of OARs eliminates the need to fabricate and setup cumbersome patient‐specific physical blocks. PACS number(s): 87.55.‐x, 87.55.de, 87.55.D‐ PMID:27074477

  14. Drusen detection by confocal aperture-modulated infrared scanning laser ophthalmoscopy.

    Science.gov (United States)

    Diniz, Bruno; Ribeiro, Ramiro M; Rodger, Damien C; Maia, Mauricio; Sadda, Srinivas

    2013-03-01

    To evaluate the efficiency of drusen detection by scanning laser ophthalmoscopy (SLO) using various infrared confocal apertures and differential contrast (DC) strategies. 11 eyes with non-neovascular age-related macular degeneration (AMD) underwent infrared imaging with a Nidek F-10 confocal SLO using multiple confocal apertures: central, ring, aperture on the right side (AR) and left side (AL), with and without use of the DC. A conventional colour fundus photograph was also obtained. Images were exported into a certified grading tool and all visible drusen were manually outlined by two graders. For each image type, the number of drusen and total drusen area were calculated, and the measurements obtained by the two graders were averaged. Intergrader reliability was evaluated, and paired t tests compared measurements between the various aperture/DC modes and the colour image. Agreement between graders was high (r=0.93-0.98). Drusen number values obtained with the AR (121.0, p=0.01) mode were higher than for the colour photographs (69.1). Area measurements were also significantly higher in the AR (1.93 mm(2); p=0.04) and AL modes (1.41 mm(2); p=0.03) when compared with the colour photographs (1.24 mm(2)). The addition of the DC did not seem to improve drusen detection compared with the unmodified infrared images. In this pilot study, drusen number and area grades were significantly higher using the AR and AL in which the laterally scattered light is captured (retromode). Use of the lateral confocal aperture may highlight subclinical drusen and aid in monitoring disease progression and response to emerging non-neovascular AMD therapies.

  15. Edge detection for optical synthetic aperture based on deep neural network

    Science.gov (United States)

    Tan, Wenjie; Hui, Mei; Liu, Ming; Kong, Lingqin; Dong, Liquan; Zhao, Yuejin

    2017-09-01

    Synthetic aperture optics systems can meet the demands of the next-generation space telescopes being lighter, larger and foldable. However, the boundaries of segmented aperture systems are much more complex than that of the whole aperture. More edge regions mean more imaging edge pixels, which are often mixed and discretized. In order to achieve high-resolution imaging, it is necessary to identify the gaps between the sub-apertures and the edges of the projected fringes. In this work, we introduced the algorithm of Deep Neural Network into the edge detection of optical synthetic aperture imaging. According to the detection needs, we constructed image sets by experiments and simulations. Based on MatConvNet, a toolbox of MATLAB, we ran the neural network, trained it on training image set and tested its performance on validation set. The training was stopped when the test error on validation set stopped declining. As an input image is given, each intra-neighbor area around the pixel is taken into the network, and scanned pixel by pixel with the trained multi-hidden layers. The network outputs make a judgment on whether the center of the input block is on edge of fringes. We experimented with various pre-processing and post-processing techniques to reveal their influence on edge detection performance. Compared with the traditional algorithms or their improvements, our method makes decision on a much larger intra-neighbor, and is more global and comprehensive. Experiments on more than 2,000 images are also given to prove that our method outperforms classical algorithms in optical images-based edge detection.

  16. Small-aperture monovision and the Pulfrich experience: absence of neural adaptation effects.

    Directory of Open Access Journals (Sweden)

    Sotiris Plainis

    Full Text Available PURPOSE: To explore whether adaptation reduces the interocular visual latency differences and the induced Pulfrich effect caused by the anisocoria implicit in small-aperture monovision. METHODS: Anisocoric vision was simulated in two adults by wearing in the non-dominant eye for 7 successive days, while awake, an opaque soft contact lens (CL with a small, central, circular aperture. This was repeated with aperture diameters of 1.5 and 2.5 mm. Each day, monocular and binocular pattern-reversal Visual Evoked Potentials (VEP were recorded. Additionally, the Pulfrich effect was measured: the task of the subject was to state whether a a 2-deg spot appeared in front or behind the plane of a central cross when moved left-to-right or right-to-left on a display screen. The retinal illuminance of the dominant eye was varied using neutral density (ND filters to establish the ND value which eliminated the Pulfrich effect for each lens. All experiments were performed at luminance levels of 5 and 30 cd/m(2. RESULTS: Interocular differences in monocular VEP latency (at 30 cd/m(2 rose to about 12-15 ms and 20-25 ms when the CL aperture was 2.5 and 1.5 mm, respectively. The effect was more pronounced at 5 cd/m(2 (i.e. with larger natural pupils. A strong Pulfrich effect was observed under all conditions, with the effect being less striking for the 2.5 mm aperture. No neural adaptation appeared to occur: neither the interocular differences in VEP latency nor the ND value required to null the Pulfrich effect reduced over each 7-day period of anisocoric vision. CONCLUSIONS: Small-aperture monovision produced marked interocular differences in visual latency and a Pulfrich experience. These were not reduced by adaptation, perhaps because the natural pupil diameter of the dominant eye was continually changing throughout the day due to varying illumination and other factors, making adaptation difficult.

  17. Investigation into a suitable scintillator and coded-aperture material for a mixed-field radiation imaging system

    Science.gov (United States)

    Cieślak, M. J.; Gamage, K. A. A.; Glover, R.

    2017-12-01

    Monte-Carlo modelling (MCNPX) methods have been employed to conduct an investigation into a suitable scintillator and coded-aperture material for a scintillator based mixed-field radiation imaging system. Single stilbene crystal, pure and 6Li-loaded plastic scintillators were simulated and their neutron/gamma detection performance compared when exposed to the spontaneous fission spectrum produced by 252Cf. The most suitable candidate was then incorporated into a scintillator based mixed-field coded-aperture imaging system. Coded-aperture models made of three W and 113Cd compositions were tested in different neutron/gamma environments with a square W collimator modelled around the aperture. Each simulation involved recording the interactions of neutron events in organic solid scintillator, whose neutron/gamma detection performance was assessed prior to the coded-aperture material investigation. Three coded-aperture material compositions have been tested with the simulated 252Cf spontaneous fission as well as 241AmBe neutron sources. Results generally claim very good detection sensitivity and spatial resolution for the radioactive sources located in the centre of the aperture.

  18. Manipulation of surface plasmon resonance of a graphene-based Au aperture antenna in visible and near-infrared regions

    Science.gov (United States)

    Wan, Yuan; An, Yashuai; Tao, Zhi; Deng, Luogen

    2018-03-01

    Behaviors of surface plasmon resonance (SPR) of a graphene-based Au aperture antenna are investigated in visible and near-infrared (vis-NIR) regions. Compared with the SPR wavelength of a traditional Au aperture antenna, the SPR wavelength of the graphene-based Au aperture antenna shows a remarkable blue shift due to the redistribution of the electric field in the proposed structure. The electric field of the graphene-based Au aperture antenna is highly localized on the surface of the graphene in the aperture and redistributed to be a standing wave. Moreover, the SPR of a graphene-based Au aperture antenna is sensitive to the thickness and the refractive index of the dielectric layer, the graphene Fermi energy, the refractive index of the environment and the polarization direction of the incident light. Finally, we find the wavelength, intensity and phase of the reflected light of the graphene-based Au aperture antenna array can be actively modulated by varying the graphene Fermi energy. The proposed structure provides a promising platform for realizing a tunable optical filter, a highly sensitive refractive index sensor, and other actively tunable optical and optoelectronic devices.

  19. The influence of tetrad shape and intersporal callose wall formation on pollen aperture pattern ontogeny in two eudicot species.

    Science.gov (United States)

    Albert, Béatrice; Nadot, Sophie; Dreyer, Leanne; Ressayre, Adrienne

    2010-10-01

    In flowering plants, microsporogenesis is accompanied by various types of cytoplasmic partitioning (cytokinesis). Patterns of male cytokinesis are suspected to play a role in the diversity of aperture patterns found in pollen grains of angiosperms. The relationships between intersporal wall formation, tetrad shape and pollen aperture pattern ontogeny are studied. A comparative analysis of meiosis and aperture distribution was performed within tetrads in two triporate eudicot species with contrasting aperture arrangements within their tetrads [Epilobium roseum (Onagraceae) and Paranomus reflexus (Proteaceae)]. Intersporal wall formation is a two-step process in both species. Cytokinesis is first achieved by the formation of naked centripetal cell plates. These naked cell plates are then covered by additional thick, localized callose deposits that differ in location between the two species. Apertures are finally formed in areas in which additional callose is deposited on the cell plates. The recorded variation in tetrad shape is correlated with variations in aperture pattern, demonstrating the role of cell partitioning in aperture pattern ontogeny.

  20. Atom probe tomographic assessment of the distribution of germanium atoms implanted in a silicon matrix through nano-apertures

    Science.gov (United States)

    Tu, Y.; Han, B.; Shimizu, Y.; Inoue, K.; Fukui, Y.; Yano, M.; Tanii, T.; Shinada, T.; Nagai, Y.

    2017-09-01

    Ion implantation through nanometer-scale apertures (nano-apertures) is a promising method to precisely position ions in silicon matrices, which is a requirement for next generation electronic and quantum computing devices. This paper reports the application of atom probe tomography (APT) to investigate the three-dimensional distribution of germanium atoms in silicon after implantation through nano-aperture of 10 nm in diameter, for evaluation of the amount and spatial distribution of implanted dopants. The experimental results obtained by APT are consistent with a simple simulation with consideration of several effects during lithography and ion implantation, such as channeling and resist flow.

  1. Rule of Thumb Proposing the Size of Aperture Expected to be Sufficient to Resolve Double Stars with Given Parameters

    Science.gov (United States)

    Knapp, Wilfried

    2018-01-01

    Visual observation of double stars is an anachronistic passion especially attractive for amateurs looking for sky objects suitable for visual observation even in light polluted areas. Session planning then requires a basic idea which objects might be suitable for a given equipment—this question is a long term issue for visual double star observers and obviously not easy to answer, especially for unequal bright components. Based on a reasonably large database with limited aperture observations (done with variable aperture equipment iris diaphragm or aperture masks) a heuristic approach is used to derive a statistically well founded Rule of Thumb formula.

  2. A Large Aperture Superconducting Dipole for Beta Beams to Minimize Heat Deposition in the Coil

    CERN Document Server

    Wildner, E

    The aim of beta beams in a decay ring is to produce highly energetic pure electron neutrino and anti-neutrino beams coming from b-decay of 18Ne10+ and 6He2+ ion beams. The decay products, having different magnetic rigidities than the ion beam, are deviated inside the dipole. The aperture and the length of the magnet have to be optimized to avoid that the decay products hit the coil. The decay products are intercepted by absorber blocks inside the beam pipe between the dipoles to protect the following dipole. A first design of a 6T arc dipole using a cosine theta layout of the coil with an aperture of 80 mm fulfils the optics requirements. Heat deposition in the coil has been calculated using different absorber materials to find a solution to efficiently protect the coil. Aspects of impedance minimization for the case of having the absorbers inside the beam pipe have also been addressed.

  3. A Large Aperture Superconducting Dipole for Beta Beams to Minimize Heat Deposition in the Coil

    CERN Document Server

    Wildner, E

    2007-01-01

    The aim of beta beams in a decay ring is to produce highly energetic pure electron neutrino and anti-neutrino beams coming from b-decay of 18Ne10+ and 6He2+ ion beams. The decay products, having different magnetic rigidities than the main ion beam, are deviated inside the dipole. The aperture and the length of the magnet have to be optimized to avoid that the decay products hit the coil. The decay products are intercepted by absorber blocks inside the beam pipe between the dipoles to protect the following dipole. A first design of a 6T arc dipole using a cosine theta layout of the coil with an aperture of 80 mm fulfils the optics requirements. Heat deposition in the coil has been calculated using different absorber materials to find a solution to efficiently protect the coil. Aspects of impedance minimization for the case of having the absorbers inside the beam pipe have also been addressed.

  4. High resolution earth observation from geostationary orbit by optical aperture synthesys

    Science.gov (United States)

    Mesrine, M.; Thomas, E.; Garin, S.; Blanc, P.; Alis, C.; Cassaing, F.; Laubier, D.

    2017-11-01

    In this paper, we describe Optical Aperture Synthesis (OAS) imaging instrument concepts studied by Alcatel Alenia Space under a CNES R&T contract in term of technical feasibility. First, the methodology to select the aperture configuration is proposed, based on the definition and quantification of image quality criteria adapted to an OAS instrument for direct imaging of extended objects. The following section presents, for each interferometer type (Michelson and Fizeau), the corresponding optical configurations compatible with a large field of view from GEO orbit. These optical concepts take into account the constraints imposed by the foreseen resolution and the implementation of the co-phasing functions. The fourth section is dedicated to the analysis of the co-phasing methodologies, from the configuration deployment to the fine stabilization during observation. Finally, we present a trade-off analysis allowing to select the concept wrt mission specification and constraints related to instrument accommodation under launcher shroud and in-orbit deployment.

  5. Fresnel zone plate with apodized aperture for hard X-ray Gaussian beam optics.

    Science.gov (United States)

    Takeuchi, Akihisa; Uesugi, Kentaro; Suzuki, Yoshio; Itabashi, Seiichi; Oda, Masatoshi

    2017-05-01

    Fresnel zone plates with apodized apertures [apodization FZPs (A-FZPs)] have been developed to realise Gaussian beam optics in the hard X-ray region. The designed zone depth of A-FZPs gradually decreases from the center to peripheral regions. Such a zone structure forms a Gaussian-like smooth-shouldered aperture function which optically behaves as an apodization filter and produces a Gaussian-like focusing spot profile. Optical properties of two types of A-FZP, i.e. a circular type and a one-dimensional type, have been evaluated by using a microbeam knife-edge scan test, and have been carefully compared with those of normal FZP optics. Advantages of using A-FZPs are introduced.

  6. Polarization independent high transmission large numerical aperture laser beam focusing and deflection by dielectric Huygens' metasurfaces

    Science.gov (United States)

    Özdemir, Aytekin; Hayran, Zeki; Takashima, Yuzuru; Kurt, Hamza

    2017-10-01

    In this letter, we propose all-dielectric Huygens' metasurface structures to construct high numerical aperture flat lenses and beam deflecting devices. The designed metasurface consists of two-dimensional array of all-dielectric nanodisk resonators with spatially varying radii, thereby introducing judiciously designed phase shift to the propagating light. Owing to the overlap of Mie-type magnetic and electric resonances, high transmission was achieved with rigorous design analysis. The designed flat lenses have numerical aperture value of 0.85 and transmission values around 80%. It also offers easy fabrication and compatibility with available semiconductor technology. This spectrally and physically scalable, versatile design could implement efficient wavefront manipulation or beam shaping for high power laser beams, as well as various optical microscopy applications without requiring plasmonic structures that are susceptible to ohmic loss of metals and sensitive to the polarization of light.

  7. An algorithm for 3D target scatterer feature estimation from sparse SAR apertures

    Science.gov (United States)

    Jackson, Julie Ann; Moses, Randolph L.

    2009-05-01

    We present an algorithm for extracting 3D canonical scattering features from complex targets observed over sparse 3D SAR apertures. The algorithm begins with complex phase history data and ends with a set of geometrical features describing the scene. The algorithm provides a pragmatic approach to initialization of a nonlinear feature estimation scheme, using regularization methods to deconvolve the point spread function and obtain sparse 3D images. Regions of high energy are detected in the sparse images, providing location initializations for scattering center estimates. A single canonical scattering feature, corresponding to a geometric shape primitive, is fit to each region via nonlinear optimization of fit error between the regularized data and parametric canonical scattering models. Results of the algorithm are presented using 3D scattering prediction data of a simple scene for both a densely-sampled and a sparsely-sampled SAR measurement aperture.

  8. Raw Data-Based Motion Compensation for High-Resolution Sliding Spotlight Synthetic Aperture Radar.

    Science.gov (United States)

    Li, Ning; Niu, Shilin; Guo, Zhengwei; Liu, Yabo; Chen, Jiaqi

    2018-03-12

    For accurate motion compensation (MOCO) in airborne synthetic aperture radar (SAR) imaging, a high-precision inertial navigation system (INS) is required. However, an INS is not always precise enough or is sometimes not even included in airborne SAR systems. In this paper, a new, raw, data-based range-invariant motion compensation approach, which can effectively extract the displacements in the line-of-sight (LOS) direction, is proposed for high-resolution sliding spotlight SAR mode. In this approach, the sub-aperture radial accelerations of the airborne platform are estimated via a well-developed weighted total least square (WTLS) method considering the time-varying beam direction. The effectiveness of the proposed approach is validated by two airborne sliding spotlight C band SAR raw datasets containing different types of terrain, with a high spatial resolution of about 0.15 m in azimuth.

  9. Fractal apertures in waveguides, conducting screens and cavities analysis and design

    CERN Document Server

    Ghosh, Basudeb; Kartikeyan, M V

    2014-01-01

    This book deals with the design and analysis of fractal apertures in waveguides, conducting screens and cavities using numerical electromagnetics and field-solvers. The aim is to obtain design solutions with improved accuracy for a wide range of applications. To achieve this goal, a few diverse problems are considered. The book is organized with adequate space dedicated for the design and analysis of fractal apertures in waveguides, conducting screens, and cavities, microwave/millimeter wave applications followed by detailed case-study problems to infuse better insight and understanding of the subject. Finally, summaries and suggestions are given for future work. Fractal geometries were widely used in electromagnetics, specifically for antennas and frequency selective surfaces (FSS). The self-similarity of fractal geometry gives rise to a multiband response, whereas the  space-filling nature of the fractal geometries makes it an efficient element in antenna and FSS unit cell miniaturization. Until now, no e...

  10. Initial Technology Assessment for the Large-Aperture UV-Optical-Infrared (LUVOIR) Mission Concept Study

    Science.gov (United States)

    Bolcar, Matthew R.; Feinberg, Lee; France, Kevin; Rauscher, Bernard J.; Redding, David; Schiminovich, David

    2016-01-01

    The NASA Astrophysics Division's 30-Year Roadmap prioritized a future large-aperture space telescope operating in the ultra-violet/optical/infrared wavelength regime. The Association of Universities for Research in Astronomy envisioned a similar observatory, the High Definition Space Telescope. And a multi-institution group also studied the Advanced Technology Large Aperture Space Telescope. In all three cases, a broad science case is outlined, combining general astrophysics with the search for biosignatures via direct-imaging and spectroscopic characterization of habitable exoplanets. We present an initial technology assessment that enables such an observatory that is currently being studied for the 2020 Decadal Survey by the Large UV/Optical/Infrared (LUVOIR) surveyor Science and Technology Definition Team. We present here the technology prioritization for the 2016 technology cycle and define the required technology capabilities and current state-of-the-art performance. Current, planned, and recommended technology development efforts are also reported.

  11. Measuring the aperture and locating beam obstructions in the Fermilab accelerator

    International Nuclear Information System (INIS)

    Gannon, J.C.; Schmidt, C.W.

    1977-01-01

    A method which uses the coasting beam at the injection energy to scan the aperture in a large accelerator such as the Main Accelerator at Fermilab is described. This scanning procedure serves two purposes. It provides a record of the aperture size around the entire accelerator which can be used for future reference and comparison. And it is highly useful in locating beam obstructions which may be caused by a collapsed vacuum chamber or some small object in the chamber to within a few meters. A high degree of accuracy has been achieved in finding and removing even very small obstructions. This method uses several computer programs, the main accelerator correction dipoles and beam position detectors, and some simple calculations

  12. A versatile calibration procedure for portable coded aperture gamma cameras and RGB-D sensors

    Science.gov (United States)

    Paradiso, V.; Crivellaro, A.; Amgarou, K.; de Lanaute, N. Blanc; Fua, P.; Liénard, E.

    2018-04-01

    The present paper proposes a versatile procedure for the geometrical calibration of coded aperture gamma cameras and RGB-D depth sensors, using only one radioactive point source and a simple experimental set-up. Calibration data is then used for accurately aligning radiation images retrieved by means of the γ-camera with the respective depth images computed with the RGB-D sensor. The system resulting from such a combination is thus able to retrieve, automatically, the distance of radioactive hotspots by means of pixel-wise mapping between gamma and depth images. This procedure is of great interest for a wide number of applications, ranging from precise automatic estimation of the shape and distance of radioactive objects to Augmented Reality systems. Incidentally, the corresponding results validated the choice of a perspective design model for a coded aperture γ-camera.

  13. Transmission properties of terahertz waves through asymmetric rectangular aperture arrays on carbon nanotube films

    Directory of Open Access Journals (Sweden)

    Yue Wang

    2016-04-01

    Full Text Available Transmission spectra of terahertz waves through a two-dimensional array of asymmetric rectangular apertures on super-aligned multi-walled carbon nanotube films were obtained experimentally. In this way, the anisotropic transmission phenomena of carbon nanotube films were observed. For a terahertz wave polarization parallel to the orientation of the carbon nanotubes and along the aperture short axis, sharp resonances were observed and the resonance frequencies coincided well with the surface plasmon polariton theory. In addition, the minima of the transmission spectra were in agreement with the location predicted by the theory of Wood’s anomalies. Furthermore, it was found that the resonance profiles through the carbon nanotube films could be well described by the Fano model.

  14. Improved Beamforming for Lateral Oscillations in Elastography Using Synthetic Aperture Imaging

    DEFF Research Database (Denmark)

    Liebgott, Hervé; Basarab, Adrian; Loizeau, Damien

    2007-01-01

    displacement estimation using images with lateral oscillations, it is necessary to reduce both the wavelength of the lateral oscillations and the width of the point spread function (PSF). This is reached in this work, by doing emit and receive beamforming using synthetic aperture data. We show......In this paper we present a beamforming technique based on synthetic aperture imaging that enables to improve the radio-frequency (RF) ultrasound images with lateral oscillations for lateral displacement estimation. As described in previous work, in order to increase the accuracy of the lateral...... that the wavelength of the lateral oscillations can be reduced by a factor 2, and the width of the PSF can be reduced by a factor radic2. We have used the images obtained by this beamforming technique for lateral displacement estimation in the field of elastography. We show that with this new approach it is possible...

  15. Aperture averaging and BER for Gaussian beam in underwater oceanic turbulence

    Science.gov (United States)

    Gökçe, Muhsin Caner; Baykal, Yahya

    2018-03-01

    In an underwater wireless optical communication (UWOC) link, power fluctuations over finite-sized collecting lens are investigated for a horizontally propagating Gaussian beam wave. The power scintillation index, also known as the irradiance flux variance, for the received irradiance is evaluated in weak oceanic turbulence by using the Rytov method. This lets us further quantify the associated performance indicators, namely, the aperture averaging factor and the average bit-error rate (). The effects on the UWOC link performance of the oceanic turbulence parameters, i.e., the rate of dissipation of kinetic energy per unit mass of fluid, the rate of dissipation of mean-squared temperature, Kolmogorov microscale, the ratio of temperature to salinity contributions to the refractive index spectrum as well as system parameters, i.e., the receiver aperture diameter, Gaussian source size, laser wavelength and the link distance are investigated.

  16. An ultra-lightweight, large aperture, deployable telescope for advanced lidar applications

    Science.gov (United States)

    Mazzinghi, P.; Bratina, V.; Ferruzzi, D.; Gambicorti, L.; Simonetti, F.; Zuccaro Marchi, A.; Salinari, P.; Lisi, F.; Olivier, M.; Bursi, A.; Pereira do Carmo, J.

    2017-11-01

    This work presents a new technological concept for large aperture, lightweight, telescopes using thin deployable active mirrors, currently under a feasibility study for spaceborne Lidars. The study is mainly addressed to a DIAL (Differential Absorption Lidar) at 935.5 nm for the measurement of water vapour profile in atmosphere, to be part of a typical small ESA Earth Observation satellite to be launched with ROCKOT vehicle. A detailed telescope optical design will be presented, including the results of angular and spatial resolution, effective optical aperture and radiometric transmission, optical alignment tolerances, stray-light and baffling. Also the results of a complete thermo-mechanical model will be shown, discussing temporal and thermal stability, deployment technology and performances, overall mass budget, technological and operational risk and system complexity.

  17. Research on large-aperture primary mirror supporting way of vehicle-mounted laser communication system

    Science.gov (United States)

    Meng, Lixin; Meng, Lingchen; Zhang, Yiqun; Zhang, Lizhong; Liu, Ming; Li, Xiaoming

    2018-01-01

    In the satellite to earth laser communication link, large-aperture ground laser communication terminals usually are used in order to realize the requirement of high rate and long distance communication and restrain the power fluctuation by atmospheric scintillation. With the increasing of the laser communication terminal caliber, the primary mirror weight should also be increased, and selfweight, thermal deformation and environment will affect the surface accuracy of the primary mirror surface. A high precision vehicular laser communication telescope unit with an effective aperture of 600mm was considered in this paper. The primary mirror is positioned with center hole, which back is supported by 9 floats and the side is supported by a mercury band. The secondary mirror adopts a spherical adjusting mechanism. Through simulation analysis, the system wave difference is better than λ/20 when the primary mirror is in different dip angle, which meets the requirements of laser communication.

  18. Measurement of the area of muscle distribution in inferior pelvic aperture in children with imperforate anus

    International Nuclear Information System (INIS)

    Yamamoto, Yasuo; Fujino, Toshio; Nakamura, Shiro

    1989-01-01

    The development of anal sphincter muscles is the most important prognostic factor in children with imperforate anus. In order to evaluate the develoment of anal sphincter muscles, CT examinations was carried out and the area of muscle distribution in inferior pelvic aperture was calculated with micro-computer. Our results are as follows: 1. In the low type anomalies which blind pouch was below I line, muscle distribution was as wide as in the normal cases. 2. Whereas, in the high type anomalies which blind pouch was on M line, muscle distribution was narrower. Furthermore, in the case which blind pouch was on P-C line, muscle distribution was extremely limited. 3. A ratio of the area of muscle distribution to that of inferior pelvic aperture may be a valuable index for evaluating the development of anal sphincter muscles. (author)

  19. Focusing and imaging with increased numerical apertures through multimode fibers with micro-fabricated optics

    KAUST Repository

    Bianchi, Silvio

    2013-01-01

    The use of individual multimode optical fibers in endoscopy applications has the potential to provide highly miniaturized and noninvasive probes for microscopy and optical micromanipulation. A few different strategies have been proposed recently, but they all suffer from intrinsically low resolution related to the low numerical aperture of multimode fibers. Here, we show that two-photon polymerization allows for direct fabrication of micro-optics components on the fiber end, resulting in an increase of the numerical aperture to a value that is close to 1. Coupling light into the fiber through a spatial light modulator, we were able to optically scan a submicrometer spot (300 nm FWHM) over an extended region, facing the opposite fiber end. Fluorescence imaging with improved resolution is also demonstrated. © 2013 Optical Society of America.

  20. Processing Sliding Mosaic Mode Data with Modified Full-Aperture Imaging Algorithm Integrating Scalloping Correction

    Directory of Open Access Journals (Sweden)

    Zhao Tuan

    2016-10-01

    Full Text Available In this study, we present a modified full-aperture imaging algorithm that includes scalloping correction and spike suppression for sliding-Mosaic-mode Synthetic Aperture Radar (SAR. It is innovational to correct the azimuth beam-pattern weighting altered by radar antenna rotation in the azimuth during the deramping preprocessing operation. The main idea of spike suppression is to substitute zeros between bursts with linear-predicted data extrapolated from adjacent bursts to suppress spikes caused by multiburst processing. We also integrate scalloping correction for the sliding mode into this algorithm. Finally, experiments are performed using the C-band airborne SAR system with a maximum bandwidth of 200 MHz to validate the effectiveness of this approach.

  1. End-to-End Assessment of a Large Aperture Segmented Ultraviolet Optical Infrared (UVOIR) Telescope Architecture

    Science.gov (United States)

    Feinberg, Lee; Rioux, Norman; Bolcar, Matthew; Liu, Alice; Guyon, Oliver; Stark, Chris; Arenberg, Jon

    2016-01-01

    Key challenges of a future large aperture, segmented Ultraviolet Optical Infrared (UVOIR) Telescope capable of performing a spectroscopic survey of hundreds of Exoplanets will be sufficient stability to achieve 10^-10 contrast measurements and sufficient throughput and sensitivity for high yield Exo-Earth spectroscopic detection. Our team has collectively assessed an optimized end to end architecture including a high throughput coronagraph capable of working with a segmented telescope, a cost-effective and heritage based stable segmented telescope, a control architecture that minimizes the amount of new technologies, and an Exo-Earth yield assessment to evaluate potential performance. These efforts are combined through integrated modeling, coronagraph evaluations, and Exo-Earth yield calculations to assess the potential performance of the selected architecture. In addition, we discusses the scalability of this architecture to larger apertures and the technological tall poles to enabling it.

  2. Use of an elliptical aperture to control saturation in closely coupled, cold iron superconducting dipole

    International Nuclear Information System (INIS)

    Morgan, G.

    1985-01-01

    The high fields permitted by superconducting windings result in saturation of closely-coupled iron in dipole and quadrupole beam transport magnets. Coupland suggested using a triangular cutout at the poles to reduce the change in the sextupole (b 2 ) term due to saturation. The use of an elliptical aperture in a close-coupled dipole for the Relativistic Heavy Ion Collider (RHIC) has been studied using the BNL computer program MDP (a version of GFUN). The ellipse aspect ratio was varied while holding the horizontal (minor) radius constant. The proper aspect ratio gives no shift in b 2 due to saturation, and a reduction in the b 4 shift. A modification of the ellipse also reduces b 4 . The elliptical aperture introduces a large b 2 term at low field which must be compensated for by the coil design. A practical coil design which does this for the RHIC magnet is presented

  3. Optical system design with common aperture for mid-infrared and laser composite guidance

    Science.gov (United States)

    Zhang, Xuanzhi; Yang, Zijian; Sun, Ting; Yang, Huamei; Han, Kunye; Hu, Bo

    2017-02-01

    When the field of operation of precision strike missiles is more and more complicated, autonomous seekers will soon encounter serious difficulties, especially with regard to low signature targets and complex scenarios. So the dual-mode sensors combining an imaging sensor with a semi-active laser seeker are conceived to overcome these specific problems. Here the sensors composed a dual field of view mid-infrared thermal imaging camera and a laser range finder have the common optical aperture which produced the minization of seeker construction. The common aperture optical systems for mid-infrared and laser dual-mode guildance have been developed, which could meet the passive middle infrared high-resolution imaging and the active laser high-precision indication and ranging. The optical system had good image quality, and fulfilled the performance requirement of seeker system. The design and expected performance of such a dual-mode optical system will be discussed.

  4. Shifted knife-edge aperture digital in-line holography for fluid velocimetry.

    Science.gov (United States)

    Palero, Virginia; Lobera, Julia; Andrés, Nieves; Arroyo, M Pilar

    2014-06-01

    We describe a digital holography technique that, with the simplicity of an in-line configuration, produces holograms where the real and virtual images are completely separated, as in an off-axis configuration. An in-line setup, in which the object is imaged near the sensor, is modified by placing a shifted knife-edge aperture that blocks half the frequency spectrum at the focal plane of the imaging lens. This simple modification of the in-line holographic configuration allows discriminating the virtual and real images. As a fluid velocimetry technique, the use of this aperture removes the minimum defocusing distance requisite and reduces the out-of-plane velocity measurement errors of classical in-line holography. Results with different test objects are shown.

  5. Rancang Bangun Band Pass Filter Frekuensi 1.27 GHz untuk Teknologi Synthetic Aperture Radar

    Directory of Open Access Journals (Sweden)

    RIFAN FITRIANTO

    2017-07-01

    Full Text Available ABSTRAKSynthetic Apertur Radar (SAR adalah teknologi radar yang digunakan untuk pengambilan gambar suatu objek dalam bentuk 2 atau 3 dimensi (penginderaan jarak jauh. Sistem tersebut  bekerja pada rentang frekuensi 1.265 sampai dengan 1.275 GHZ dengan frekuensi tengahnya 1.27 GHz. Agar sistem SAR ini dapat bekerja dengan optimal, dibutuhkan suatu perangkat filter yang dapat meloloskan frekuensi yang diinginkan. Sebelumnya sudah ada penelitian yang membuat perangkat ini di band frekuensi yang sama namun menggunakan bahan duroid 5880 dan resonator berbentuk kotak. Bandpass filter Pada penelitian ini dirancang dengan menggunakan metode Hairpin line dan bahan epoxy FR4. Hasil pengukuran menunjukkan nilai Return Loss masih cukup besar yaitu -9.33 dB dan nilai Insertion Loss minimal sebesar -13.51 dB.Kata kunci: Syntethic Aperture Radar, Band Pass Filter, Hairpin-lineABSTRACTSynthetic Aperture Radar (SAR is a radar technology that used for taking an object in the form of 2 or 3 dimensions (remote sensing. It works in the frequency range 1.265 to 1.275 GHZ with a middle frequency of 1.27 GHz. SAR system can work optimally if it support a filter device that can pass the desired frequency. Previously there has been research that makes this device in the same frequency band but using 5885 duroid material and square resonator. Bandpass filter In this study designed using Hairpin line method and FR4 epoxy material. The measurement results of Return Loss values are still quite large  arround -9.33 dB and Insertion Loss minimum at -13.51 dB.Keywords: Syntethic Aperture Radar, Band Pass Filter, Hairpin line

  6. Performance results for Beamlet: A large aperture multipass Nd glass laser

    International Nuclear Information System (INIS)

    Campbell, J.H.; Barker, C.E.; VanWonterghem, B.M.; Speck, D.R.; Behrendt, W.C.; Murray, J.R.; Caird, J.A.; Decker, D.E.; Smith, I.C.

    1995-01-01

    The Beamlet laser is a large aperture, flashlamp pumped Nd: glass laser that is a scientific prototype of an advanced Inertial Fusion laser. Beamlet has achieved third harmonic, conversion efficiency of near 80% with its nominal 35cm x 35cm square beam at mean 3ω fluences in excess of 8 J/cm 2 (3-ns). Beamlet uses an adaptive optics system to correct for aberrations and achieve less than 2 x diffraction limited far field spot size

  7. Quantitative wake analysis of a freely swimming fish using 3D synthetic aperture PIV

    OpenAIRE

    Mendelson, Leah Rose; Techet, Alexandra H.

    2015-01-01

    Synthetic aperture PIV (SAPIV) is used to quantitatively analyze the wake behind a giant danio (Danio aequipinnatus) swimming freely in a seeded quiescent tank. The experiment is designed with minimal constraints on animal behavior to ensure that natural swimming occurs. The fish exhibits forward swimming and turning behaviors at speeds between 0.9 and 1.5 body lengths/second. Results show clearly isolated and linked vortex rings in the wake structure, as well as the thrust jet coming off of ...

  8. Efficient electromagnetic analysis of line-fed aperture antennas in thick conducting screens

    OpenAIRE

    Stevanovic, I.; Mosig, J. R.

    2004-01-01

    This paper presents a numerical and experimental verification of an approximate but efficient integral equation technique for the scattering by apertures in conducting planes with finite thicknesses. The approach is based on a perturbation method and modified Green's functions that take into account the finite metallization thickness. The computational effort and time needed for solving the problem are the same as in zero-thickness case. When compared to full-wave cavity treatment of thick ap...

  9. Study of a 5-Tesla large aperture coil for the CLIC detector

    CERN Document Server

    Cure, B

    2011-01-01

    The present design of a CLIC detector foresees a large solenoid magnet with a 6 m aperture and a magnetic induction of 5 T at the interaction point. This can be achieved by a thin superconducting coil. This report gives the typical main parameters of such a coil and presents the feasibility based on and compared with the CMS and Atlas solenoid coil designs, indicating the limits on the conductor and the identified R&D prospects.

  10. GPR thin - layer AVO analysis for fracture aperture and fill characterization

    Science.gov (United States)

    Kana, A. A.; West, L. J.; Clark, R.

    2011-12-01

    The ability of fractures to reflect radar waves and the dependence of this reflectivity on fracture properties (aperture and fill) makes the GPR method a promising tool for rock fracture characterization. Successful characterisation requires quantification of the reflectivity (reflection coefficient (R)) of individual fractures. The AVO method applied to fractures involves measuring the reflection amplitude variation with offset (incidence angle). Measuring the full AVO response using CMP (Common Mid Point) surveys enables estimation of fracture aperture and fill permittivity which has proved difficult to achieve with normal-incidence data such as that typically collected in Common Offset (CO) profiling. We carried out analysis of CMP data acquired over a bedding plane fracture in Carboniferous Limestone in Yorkshire, United Kingdom. The reflection amplitude measured in the field is related to the reflection coefficient but however, is also influenced by other factors including the source amplitude, antenna coupling with the ground surface, transmission losses from overlying interfaces, source and receiver radiation patterns, and attenuation. Raw amplitudes were corrected for spreading and antenna radiation/receiver patterns; offsets were further converted to incidence angles to obtain a diagnostic AVA curve. The antenna patterns were measured through transillumination surveys across limestone boulders and through numerical modelling using the GprMax 3D modelling code. Being a low loss formation, conductive attenuation was considered insignificant over the ray-path length. Because of the difficulty in characterizing the source pulse strength, both theoretical and measured amplitudes were normalized. Fracture properties are then obtained by comparing the normalised field derived AVA curve with normalized theoretical reflection coefficient curves for thin fractures with various apertures and fills. Resulting aperture and fill permittivity were consistent with field

  11. Means to achieve wide swath widths in synthetic aperture satellite borne radars

    Science.gov (United States)

    Cutrona, L. J.

    1978-01-01

    The radar range equation including processing gains for pulse compression and synthetic aperture generation was the starting point. System geometry considerations were introduced. For simplicity, flat earth geometry was used, although it was realized that this was not a good model for satellite-borne radars. Next, the constraints were introduced. These included those needed to avoid ambiguities in both range and azimuth, those needed to acheive the desired resolution, and those needed to achieve the desired swath width.

  12. Enhanced performance of a wide-aperture copper vapour laser with ...

    Indian Academy of Sciences (India)

    A wide-aperture copper vapour laser was demonstrated at ∼ 10 kHz rep-rate with hydrogen additive in its buffer gas. Maximum power in excess of ∼ 50 W (at 10 kHz) was achieved by adding 1.96% hydrogen to the neon buffer gas at 20 mbar total gas pressure. This increase in output power was about 70% as compared ...

  13. Improvements of axial resolution in confocal microscopy with fan-shaped apertures.

    Science.gov (United States)

    Ma, Ye; Kuang, Cuifang; Gong, Wei; Xue, Li; Zheng, Yao; Wang, Yifan; Si, Ke; Liu, Xu

    2015-02-20

    Based on diffraction theory, this paper theoretically demonstrates improvements in axial resolution in confocal microscopy with fan-shaped apertures. It provides the optimal geometric parameters of the fan-shaped pupils to give the maximum axial resolution for a given pinhole size. To fully understand the overall performance, the signal-to-background ratio and the signal level with regard to the geometric parameters are discussed.

  14. Switched Antenna Array Tile for Real-Time Microwave Imaging Aperture

    Science.gov (United States)

    2016-06-26

    way switch. Control of the switched elements is accomplished through the use of a CPLD ( Complex Programmable Logic Device), which is depicted in 3. The...acquisition speed. The arrays use the slot antenna element depicted in Fig. 4. The element is integrated within the array’s aluminum SP4T Switch LNA Fig. 2...pattern in both E- and H- planes . III. IMAGING RESULTS To assess the imaging capability of a fully electronic tiled aperture of the array depicted in

  15. Research on Synthetic Aperture Radar Processing for the Spaceborne Sliding Spotlight Mode

    OpenAIRE

    Shijian Shen; Xin Nie; Xinggan Zhang

    2018-01-01

    Gaofen-3 (GF-3) is China’ first C-band multi-polarization synthetic aperture radar (SAR) satellite, which also provides the sliding spotlight mode for the first time. Sliding-spotlight mode is a novel mode to realize imaging with not only high resolution, but also wide swath. Several key technologies for sliding spotlight mode in spaceborne SAR with high resolution are investigated in this paper, mainly including the imaging parameters, the methods of velocity estimation and ambiguity elimina...

  16. Dynamic aperture of NR-2000 in the work regime with a small radiation emittance

    International Nuclear Information System (INIS)

    Zelinskij, A.Yu.; Karnaukhov, I.M.; Kononenko, S.G.; Tarasenko, A.S.

    1991-01-01

    NR-2000 is an electron storage ring installation with 6-pole magnets compensating its chromatism. The results of NR-2000 dynamic aperture numerical modelling in 6-dimension space are given. Perturbation of the equilibrium orbit and that of magnetic field up to the third order of magnitude were taken into consideration. Calculations were made according to DeCA programme. 7 refs.; 5 figs. (author)

  17. Automated interferometric synthetic aperture microscopy and computational adaptive optics for improved optical coherence tomography

    OpenAIRE

    Xu, Yang; Liu, Yuan-Zhi; Boppart, Stephen A.; Carney, P. Scott

    2016-01-01

    In this paper, we introduce an algorithm framework for the automation of interferometric synthetic aperture microscopy (ISAM). Under this framework, common processing steps such as dispersion correction, Fourier domain resampling, and computational adaptive optics aberration correction are carried out as metrics-assisted parameter search problems. We further present the results of this algorithm applied to phantom and biological tissue samples and compare with manually adjusted results. With ...

  18. An Engineering Design Reference Mission for a Future Large-Aperture UVOIR Space Observatory

    Science.gov (United States)

    Thronson, Harley A.; Bolcar, Matthew R.; Clampin, Mark; Crooke, Julie A.; Redding, David; Rioux, Norman; Stahl, H. Philip

    2016-01-01

    From the 2010 NRC Decadal Survey and the NASA Thirty-Year Roadmap, Enduring Quests, Daring Visions, to the recent AURA report, From Cosmic Birth to Living Earths, multiple community assessments have recommended development of a large-aperture UVOIR space observatory capable of achieving a broad range of compelling scientific goals. Of these priority science goals, the most technically challenging is the search for spectroscopic biomarkers in the atmospheres of exoplanets in the solar neighborhood. Here we present an engineering design reference mission (EDRM) for the Advanced Technology Large-Aperture Space Telescope (ATLAST), which was conceived from the start as capable of breakthrough science paired with an emphasis on cost control and cost effectiveness. An EDRM allows the engineering design trade space to be explored in depth to determine what are the most demanding requirements and where there are opportunities for margin against requirements. Our joint NASA GSFC/JPL/MSFC/STScI study team has used community-provided science goals to derive mission needs, requirements, and candidate mission architectures for a future large-aperture, non-cryogenic UVOIR space observatory. The ATLAST observatory is designed to operate at a Sun-Earth L2 orbit, which provides a stable thermal environment and excellent field of regard. Our reference designs have emphasized a serviceable 36-segment 9.2 m aperture telescope that stows within a five-meter diameter launch vehicle fairing. As part of our cost-management effort, this particular reference mission builds upon the engineering design for JWST. Moreover, it is scalable to a variety of launch vehicle fairings. Performance needs developed under the study are traceable to a variety of additional reference designs, including options for a monolithic primary mirror.

  19. Magnetic field measurements of full length 50 mm aperture SSC dipole magnets at Fermilab

    International Nuclear Information System (INIS)

    Strait, J.; Bossert, R.; Carson, J.; Delchamps, S.W.; Gourlay, S.; Hanft, R.; Koska, W.; Kuchnir, M.; Lamm, M.J.; Mazur, P.O.; Mokhtarani, A.; Orris, D.; Ozelis, J.; Wake, M.; Devred, A.; DiMarco, J.; Kuzminski, J.; Puglisi, M.; Tompkins, J.C.; Yu, Y.; Zhao, Y.; Zheng, H.; Ogitsu, T.

    1992-09-01

    Thirteen 16 m long, 50 mm aperture SSC dipole magnets, designed jointly by Fermilab, Brookhaven National Laboratory, Lawrence Berkeley Laboratory and the SSC Laboratory, have been built at Fermilab. The first nine magnets have been fully tested to date. The allowed harmonics are systematically shifted from zero by amounts larger than the specification. The unallowed harmonics, with the exception of the skew sextupole, are consistent with zero. The magnet-to-magnet RMS variation of all harmonics is much smaller than the specification

  20. Synthetic aperture radar images of ocean waves, theories of imaging physics and experimental tests

    Science.gov (United States)

    Vesecky, J. F.; Durden, S. L.; Smith, M. P.; Napolitano, D. A.

    1984-01-01

    The physical mechanism for the synthetic Aperture Radar (SAR) imaging of ocean waves is investigated through the use of analytical models. The models are tested by comparison with data sets from the SEASAT mission and airborne SAR's. Dominant ocean wavelengths from SAR estimates are biased towards longer wavelengths. The quasispecular scattering mechanism agrees with experimental data. The Doppler shift for ship wakes is that of the mean sea surface.