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Sample records for large numerical aperture

  1. Subwavelength-thick Lenses with High Numerical Apertures and Large Efficiency Based on High Contrast Transmitarrays

    CERN Document Server

    Arbabi, Amir; Ball, Alexander J; Bagheri, Mahmood; Faraon, Andrei

    2014-01-01

    We report subwavelength-thick, polarization insensitive micro-lenses operating at telecom wavelength with focal spots as small as 0.57 wavelengths and measured focusing efficiency up to 82%. The lens design is based on high contrast transmitarrays that enable control of optical phase fronts with subwavelength spatial resolution. A rigorous method for ultra-thin lens design, and the trade-off between high efficiency and small spot size (or large numerical aperture) are discussed. The transmitarrays, composed of silicon nano-posts on glass, could be fabricated by high-throughput photo or nanoimprint lithography, thus enabling widespread adoption.

  2. Designing large, high-efficiency, high-numerical-aperture, transmissive meta-lenses for visible light

    CERN Document Server

    Byrnes, Steven J; Aieta, Francesco; Capasso, Federico

    2015-01-01

    A metasurface lens (meta-lens) is a lens that bends light with an array of nanostructures on a flat surface, rather than by refraction. Macroscopic meta-lenses (mm- to cm-scale diameter) have been quite difficult to simulate and optimize, due to the large area, the lack of periodicity, and the billions of adjustable parameters. We describe a method for designing a large-area meta-lens that allows not only prediction of the efficiency and far-field, but also optimization of the shape and position of each individual nanostructure, with a computational cost that is almost independent of the lens size. Loosely speaking, the technique consists of designing a series of metasurface beam deflectors (blazed gratings), and then gluing them together. As a test of this framework, we design some high-numerical-aperture (NA=0.94) meta-lenses for visible light, based on TiO2 nano-pillars on a glass substrate. One of our designs is predicted to focus unpolarized 580nm light with 79% predicted efficiency; another focuses 580n...

  3. High numerical aperture large-core photonic crystal fiber for a broadband infrared transmission

    Science.gov (United States)

    Pniewski, J.; Stepniewski, G.; Kasztelanic, R.; Siwicki, B.; Pierscinska, D.; Pierscinski, K.; Pysz, D.; Borzycki, K.; Stepien, R.; Bugajski, M.; Buczynski, R.

    2016-11-01

    In this paper we present a large mode area photonic crystal fiber made of the heavy metal oxide glass CS-740, dedicated for a broadband light guidance in the visible, near- and mid-infrared regions of wavelengths from 0.4 to 4.7 μm. The fiber is effectively multi-mode in the considered wavelength range. It is composed of a ring of air-holes surrounding the core, with a high linear filling factor of 0.97. The fiber was made using a standard stack-and-draw technique. Each hole has a size of approx. 2.5 × 3.0 μm and diameter of core is 80 μm. Fiber attenuation is below 3 dB/m in the 0.9-1.7 μm wavelength range, while at 4.4 μm (mid-IR) it is approx. 5 dB/cm. Bending loss at the 1.55 μm wavelength is 0.45 dB per loop of 8 mm radius. Fiber numerical aperture is 0.53 at 1.55 μm. The effective mode area of the fundamental mode is approx. 2400 μm2 in the wavelength range of 0.8-1.7 μm. We present a proof-of-concept demonstration that our large core photonic crystal fiber is able to efficiently collect light directly from a mid-IR quantum cascade laser without use of additional optics and can be used for pigtailing mid-IR sources and detectors.

  4. Single-mode large-mode-area laser fiber with ultralow numerical aperture and high beam quality.

    Science.gov (United States)

    Peng, Kun; Zhan, Huan; Ni, Li; Wang, Xiaolong; Wang, Yuying; Gao, Cong; Li, Yuwei; Wang, Jianjun; Jing, Feng; Lin, Aoxiang

    2016-12-10

    By using the chelate precursor doping technique, we report on an ytterbium-doped aluminophosphosilicate (APS) large-mode-area fiber with ultralow numerical aperture of 0.036 and effective fundamental mode area of ∼550  μm2. With a bend diameter of 600 mm, the bending loss of fundamental mode LP01 was measured to be -3  dB/m, in agreement with the corresponding simulation results, while that of higher order mode LP11 is >100  dB/m at 1080 nm. Measured in an all-fiber oscillator laser cavity, 592 W single-mode laser output was obtained at 1079.64 nm with high-beam quality M2 of 1.12. The results indicate that the chelate precursor doping technique is a competitive method for ultralow numerical aperture fiber fabrication, which is very suitable for developing single-mode seed lasers for high power laser systems.

  5. Very large aperture optics for space applications

    Science.gov (United States)

    Horwath, T. G.; Smith, J. P.; Johnson, M. T.

    1994-09-01

    A new type of space optics technology is presented which promises the realization of very large apertures (tens of meters), while packagable into lightweight, small volume containers compatible with conventional launch vehicles. This technology makes use of thin foils of circular shape which are uniformly mass loaded around the perimeter. Once unfurled and set into rapid rotation about the transversal axis, the foil is stretched into a perfectly flat plane by the centrifugal forces acting on the peripheral masses. The simplest applications of this novel technology are optically flat reflectors, using metallized foils of Mylar, Kevlar, or Kapton. Other more complex optical components can be realized by use of binary optics techniques, such as depositing holograms by selective local microscale removal of the reflective surface. Electrostatic techniques, in conjunction with an auxiliary foil, under local, distributed real-time control of the optical parameters, allow implementation of functions like beam steering and focal length adjustments. Gas pressurization allows stronger curvatures and thus smaller focal ratios for non-imaging applications. Limits on aperture are imposed primarily by manufacturing capabilities. Applications of such large optics in space are numerous. They range from military, such as space based lasers, to the civilian ones of power beaming, solar energy collection, and astronomy. This paper examines this simple and innovative concept in detail, discusses deployment and attitude control issues and presents approaches for realization.

  6. Ultrasound Beamforming Methods for Large Coherent Apertures

    Science.gov (United States)

    Bottenus, Nick

    This dissertation investigates the use of large coherent ultrasound apertures to improve diagnostic image quality for deep clinical targets. The current generation of ultrasound scanners restrict aperture size and geometry based on hardware limitations and field of view requirements at the expense of image quality. This work posits that, without these restrictions, ultrasound could be used for higher quality non-invasive imaging. To support this claim, an experimental device was constructed to acquire in vivo liver images with a synthetic aperture spanning at least 35 degrees at a radius of 10.2 cm with a scan time under one second. Using a 2.5 MHz commercial matrix array with the device, a lateral resolution of 0.45 mm at a depth of 11.6 cm was achieved, surpassing the capabilities of existing commercial systems. This work formed the basis for an in-depth investigation of the clinical promise of large aperture imaging. Ex vivo study of volumetric imaging through the human abdominal wall demonstrated the ability of large apertures to improve target detectability at depth by significantly increasing lateral resolution, even in the presence of tissue-induced aberration and reverberation. For various abdominal wall samples studied, full-width at half-maximum resolution was increased by 1.6 to 4.3 times using a 6.4 cm swept synthetic aperture compared to conventional imaging. Harmonic plane wave imaging was shown to limit the impact of reverberation clutter from the tissue layer and produce images with the highest target detectability, up to a 45.9% improvement in contrast-to-noise ratio (CNR) over fundamental imaging. This study was corroborated by simulation of a 10 cm concave matrix array imaging through an abdominal wall based on the Visible Human Project data set. The large aperture data were processed in several ways, including in their entirety as a fully populated large array as well as mimicking the swept synthetic aperture configuration. Image quality

  7. 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

  8. Interdisciplinary science with large aperture detectors

    Directory of Open Access Journals (Sweden)

    Wiencke Lawrence

    2013-06-01

    Full Text Available Large aperture detector systems to measure high energy cosmic rays also offer unique opportunities in other areas of science. Disciplines include geophysics such as seismic and volcanic activity, and atmospheric science ranging from clouds to lightning to aerosols to optical transients. This paper will discuss potential opportunities based on the ongoing experience of the Pierre Auger Observatory.

  9. Very Large Aperture Diffractive Space Telescope

    Energy Technology Data Exchange (ETDEWEB)

    Hyde, Roderick Allen

    1998-04-20

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

  10. Design of large aperture focal plane shutter

    Science.gov (United States)

    Hu, Jia-wen; Ma, Wen-li; Huang, Jin-long

    2012-09-01

    To satisfy the requirement of large telescope, a large aperture focal plane shutter with aperture size of φ200mm was researched and designed to realize, which could be started and stopped in a relative short time with precise position, and also the blades could open and close at the same time at any orientation. Timing-belts and stepper motors were adopted as the drive mechanism. Velocity and position of the stepper motors were controlled by the PWM pulse generated by DSP. Exponential curve is applied to control the velocity of the stepper motors to make the shutter start and stop in a short time. The closing/open time of shutter is 0.2s, which meets the performance requirements of large telescope properly.

  11. Experimental and numerical investigation of ADP square crystal with large aperture in the new Final Optics Assembly under the non-critical phase matching

    Science.gov (United States)

    Sun, Fuzhong; Zhang, Peng; Bai, Qingshun; Lu, Lihua; Xiang, Yong

    2016-04-01

    This paper presented a new Final Optics Assembly (FOA) of ammonium dihydrogen phosphate (ADP) square crystal with large aperture under the non-critical phase matching (NCPM), which controlled by the constant temperature water, and the temperature distribution was analyzed by simulation and experiment. Firstly, thermal analysis was carried out, as well as the temperature distribution of the cavity only heated under different velocities was analyzed. Then, the temperature distributions of ADP square crystal in the cavity were achieved using the Finite Volume Method (FVM), and this prediction was validated by the experiment results when the velocity is 0.1 m/s and 0.5 m/s. Finally, the optimal FHG conversion efficiency was obtained and the comparison of different heating methods was also highlighted.

  12. Absorption tomography of laser induced plasmas with a large aperture

    CERN Document Server

    Shabanov, Sergei V

    2010-01-01

    An emission tomography of laser-induced plasmas employed in the laser induced breakdown spectroscopy (LIBS) requires long signal integration times during which the plasma cannot be considered stationary. To reduce the integration time, it is proposed to measure a plasma absorption in parallel rays with an aperture that collects light coming from large fractions of the plasma plume at each aperture position. The needed spatial resolution is achieved by a special numerical data processing. Another advantage of the proposed procedure is that inexpensive linear CCD or non-discrete (PMT, photodiode) detectors can be used instead of costly 2-dimensional detectors.

  13. Large-aperture hybrid photo-detector

    Energy Technology Data Exchange (ETDEWEB)

    Kawai, Y. [Institute for Particle and Nuclear Studies, The Graduate University for Advanced Studies, 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Electron Tube Division, Hamamatsu Photonics K.K., 314-5 Shimokanzo, Iwata City 438-0193, Shizuoka (Japan)], E-mail: kawaiy@post.kek.jp; Nakayama, H.; Kusaka, A.; Kakuno, H.; Abe, T.; Iwasaki, M.; Aihara, H. [Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Tanaka, M. [Institute for Particle and Nuclear Studies, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Shiozawa, M. [Institute for Cosmic Ray Research, University of Tokyo, Higashi-Mozumi, Kamioka-cho, Hida City, Gifu 506-1205 (Japan); Kyushima, H.; Suyama, M. [Electron Tube Division, Hamamatsu Photonics K.K., 314-5 Shimokanzo, Iwata City 438-0193, Shizuoka (Japan)

    2007-08-21

    We have developed the first complete large-aperture (13-inch diameter) hybrid photo-detector (HPD). The withstanding voltage problem has been overcome and we were able to attain an HPD operating voltage of +20 kV. Adoption of our newly developed backside illumination avalanche diode (AD) was also critical in successfully countering the additional problem of an increase in AD leakage after the activation process. We observed single photon signal timing jitter of under 450 ps in FWHM, electron transit time of {approx}12 ns, and clear pulse height separation up to several photoelectron peaks, all greatly superior to the performance of any conventional large-aperture photomultiplier tubes (PMTs). In addition, our HPD has a much simpler structure than conventional large-aperture PMTs, which simplifies mass production and lowers manufacturing cost. We believe that these attributes position our HPD as the most suitable photo-detector for the next generation mega-ton class water-Cherenkov detector, which is expected to be more than 20x larger than the Super-Kamiokande (SK) detector.

  14. Development of large aperture composite adaptive optics

    Science.gov (United States)

    Kmetik, Viliam; Vitovec, Bohumil; Jiran, Lukas; Nemcova, Sarka; Zicha, Josef; Inneman, Adolf; Mikulickova, Lenka; Pavlica, Richard

    2015-01-01

    Large aperture composite adaptive optics for laser applications is investigated in cooperation of Institute of Plasma Physic, Department of Instrumentation and Control Engineering FME CTU and 5M Ltd. We are exploring opportunity of a large-size high-power-laser deformable-mirror production using a lightweight bimorph actuated structure with a composite core. In order to produce a sufficiently large operational free aperture we are developing new technologies for production of flexible core, bimorph actuator and deformable mirror reflector. Full simulation of a deformable-mirrors structure was prepared and validated by complex testing. A deformable mirror actuation and a response of a complicated structure are investigated for an accurate control of the adaptive optics. An original adaptive optics control system and a bimorph deformable mirror driver were developed. Tests of material samples, components and sub-assemblies were completed. A subscale 120 mm bimorph deformable mirror prototype was designed, fabricated and thoroughly tested. A large-size 300 mm composite-core bimorph deformable mirror was simulated and optimized, fabrication of a prototype is carried on. A measurement and testing facility is modified to accommodate large sizes optics.

  15. Trapped ion imaging with a high numerical aperture spherical mirror

    Energy Technology Data Exchange (ETDEWEB)

    Shu, G; Dietrich, M R; Kurz, N; Blinov, B B, E-mail: shugang@u.washington.ed [Department of Physics, University of Washington, Seattle, WA 98105-1560 (United States)

    2009-08-14

    Efficient collection and analysis of trapped ion qubit fluorescence is essential for robust qubit state detection in trapped ion quantum computing schemes. We discuss simple techniques of improving photon collection efficiency using high numerical aperture (N.A.) reflective optics. To test these techniques we placed a spherical mirror with an effective N.A. of about 0.9 inside a vacuum chamber in the vicinity of a linear Paul trap. We demonstrate stable and reliable trapping of single barium ions, in excellent agreement with our simulations of the electric field in this setup. While a large N.A. spherical mirror introduces significant spherical aberration, the ion image quality can be greatly improved by a specially designed aspheric corrector lens located outside the vacuum system. Our simulations show that the spherical mirror/corrector design is an easy and cost-effective way to achieve high photon collection rates when compared to a more sophisticated parabolic mirror setup.

  16. Towards Very Large Aperture Massive MIMO

    DEFF Research Database (Denmark)

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

    2014-01-01

    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...

  17. High numerical aperture all-dielectric metasurface micro-lenses

    NARCIS (Netherlands)

    Silvestri, F.; Gerini, G.; Pisano, E.; Galdi, V.

    2015-01-01

    In this paper, the design principles and the sensitivity analysis needed for the realization of a high numerical aperture metasurface micro-lens are presented. The metasurface micro-lens is realized defining a surface with spatially-variant dielectric resonators embedded in a dielectric bulk. The de

  18. Numerical Simulation of Transient Gauss pulse Coupling through Small Apertures

    Directory of Open Access Journals (Sweden)

    Jinshi Xiao

    2011-08-01

    Full Text Available Transient electromagnetic pulse (EMP can easily couple into equipments through small apertures in its shells. To study the coupling effects of transient Gauss pulse to a cubic cavity with openings, coupling course is simulated using sub-gridding finite difference in time domain (FDTD algorithm in this paper. A new grid partition approach is provided to simulate each kind of apertures with complex shapes. With this approach, the whole calculation space is modeled, and six kinds of aperture with different shapes are simulated. Coupling course is simulate in the whole time domain using sub-gridding FDTD approach. Selecting apertures with dimension of several millimeters to research, coupled electric field waveform, power density and coupling coefficient are calculated. The affect on coupling effects by varied incident angle and varied pulse width are also analyzed. The main conclusion includes interior resonance phenomenon, increase effect around rectangle aperture and several distributing rules of coupled electric field in the cavity. The correctness of these results is validated by comparing with other scholars’ results. These numerical results can help us to understand coupling mechanism of the transient Gauss pulse.

  19. 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.

  20. 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.

  1. 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.

    2016-11-01

    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.

  2. Foamed Antenna Support for Very Large Apertures Project

    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. Foamed Antenna Support for Very Large Apertures Project

    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,...

  4. Ultra-Lightweight Large Aperture Support Structures Project

    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...

  5. 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.

  6. Large Aperture, Scanning, L-Band SAR

    Science.gov (United States)

    Moussessian, Alina; DelCastillo, Linda; Bach, Vinh; Grando, Maurio; Quijano, Ubaldo; Smith, Phil; Zawadzki, Mark

    2011-01-01

    We have developed the first L-band membrane-based active phased array. The antenna is a 16x16 element patch array with dimensions of 2.3mx2.6m. The array uses membrane-compatible Transmit/Receive (T/R) modules for electronic beam steering. We will discuss the antenna design, the fabrication of this large array, the T/R module development, the signal distribution approach and the measured results of the array

  7. Off-axis multipass amplifier as a large aperture driver stage for fusion lasers.

    Science.gov (United States)

    Murray, J E; Downs, D C; Hunt, J T; Hermes, G L; Warren, W E

    1981-03-01

    A multipass amplifier configuration is described which has potential as a large aperture, high gain driver stage for fusion laser systems. We avoid the present limitations of large aperture switches by using an off-angle geometry that does not require an optical switch. The saturated gain characteristics of this multipass amplifier are optimized numerically. Three potential problems are investigated experimentally, self-lasing, output beam quality, and amplified spontaneous emission output. The results indicate comparable cost for comparable performance to a linear chain, with some operational advantage for the multipass driver stage.

  8. Predicting polarization performance of high-numerical aperture inspection lenses

    Science.gov (United States)

    Fahr, Stephan; Werschnik, Jan; Bening, Matthias; Uhlendorf, Kristina

    2015-09-01

    Along the course of increasing through-put and improving signal to noise ratio in optical wafer and mask inspection, demands on wave front aberrations and polarization characteristics are ever increasing. The system engineers and optical designers involved in the development of such optical systems will be responsible for specifying the quality of the optical material and the mechanical tolerances. Among optical designers it is well established how to estimate the wave front error of assembled and adjusted optical devices via sensitivity or Monte-Carlo analysis. However, when compared with the scalar problem of wave front estimation, the field of polarization control deems to pose a more complex problem due to its vectorial nature. Here we show our latest results in how to model polarization affecting aspects. In the realm of high numerical aperture (NA) inspection optics we will focus on the impact of coatings, stress induced birefringence due to non-perfect lens mounting, and finally the birefringence of the optical material. With all these tools at hand, we have a more complete understanding of the optical performance of our assembled optical systems. Moreover, we are able to coherently develop optical systems meeting demanding wave front criteria as well as high end polarization specifications.

  9. High numerical aperture multimode fibers for prime focus use

    Science.gov (United States)

    Zhang, Kaiyuan; Zheng, Jessica R.; Saunders, Will

    2016-07-01

    Modern telescopes typically have prime focus speeds too fast for direct use with standard numerical aperture (NA=0.22+/-0.02) silica-cored fibers. Specifically, the current design for the proposed Maunakea Spectroscopic Explorer (MSE) telescope is f/2, requiring fibers with NA>0.25. Micro foreoptics can be used to slow the beam, as used on the prime focus spectrograph (PFS) on Subaru, but this adds cost and complexity, and increases losses. An attractive alternative is offered by high NA pure silica-cored fibers, which can be used directly at f/2, and which are now available from multiple vendors. We present throughput and focal ratio degradation measurements on two samples of these high NA fibers. It is found that the measured attenuation losses are comparable with the best available standard NA fibers. The fibers were also tested for focal ratio degradation, and the fiber from CeramOptec was found to have acceptable FRD, representng additional collimator losses 1%. The near field performance of the high NA fiber is also investigated and these high NA fibers exhibit very good scrambling performance; we saw no evidence for significant output near-field variations for varying input beam angles or position in a 50m fiber.

  10. Development of large aperture elements for active and adaptive optics

    Directory of Open Access Journals (Sweden)

    Stranakova E.

    2013-05-01

    Full Text Available Large-aperture elements for laser active and adaptive optics are investigated in collaboration within IOP AcSci CR, FEng CTU and 5M. A bimorph deformable mirror for high-power lasers based on a lightweight structure with a composite core is currently in development. In order to realize a sufficiently large working aperture we are using new technologies for production of core, bimorph actuator and DM reflector. Detailed simulation of components and structure is validated by measurement and testing. A research of DM actuation and response of a complicated mirror structure needed for an accurate control of a deformation is performed. Testing of samples and subscale measurements are currently performed, measurement of a complete structure is in preparation.

  11. Lyot coronagraph design study for large, segmented space telescope apertures

    Science.gov (United States)

    Zimmerman, Neil T.; N'Diaye, Mamadou; St. Laurent, Kathryn E.; Soummer, Rémi; Pueyo, Laurent; Stark, Christopher C.; Sivaramakrishnan, Anand; Perrin, Marshall; Vanderbei, Robert J.; Kasdin, N. J.; Shaklan, Stuart; Carlotti, Alexis

    2016-07-01

    Recent efforts combining the optimization techniques of apodized pupil Lyot coronagraphs (APLC) and shaped pupils have demonstrated the viability of a binary-transmission mask architecture for extremely high contrast (10-10) exoplanet imaging. We are now building on those innovations to carry out a survey of Lyot coronagraph performance for large, segmented telescope apertures. These apertures are of the same kind under considera- tion for NASA's Large UV/Optical/IR (LUVOIR) observatory concept. To map the multi-dimensional design parameter space, we have developed a software toolkit to manage large sets of mask optimization programs and execute them on a computing cluster. Here we summarize a preliminary survey of 500 APLC solutions for 4 reference hexagonal telescope apertures. Several promising designs produce annular, 10-10 contrast dark zones down to inner working angle 4λ0=D over a 15% bandpass, while delivering a half-max PSF core throughput of 18%. We also report our progress on devising solutions to the challenges of Lyot stop alignment/fabrication tolerance that arise in this contrast regime.

  12. Numerical aperture characteristics of angle-ended plastic optical fiber

    Science.gov (United States)

    Gao, Cheng; Farrell, Gerard

    2003-03-01

    With the increasing information rates demanded in consumer, automotive and aeronautical applications, a low cost and high performance physical transmission medium is required. Compared with Silica Optical Fiber, Plastic Optical Fiber (POF) offers an economic solution for a range of high-capacity, short-haul applications in industrial and military environments. Recently, a new type of POF, the perfluorinated graded-index plastic optical fiber (PF GI-POF), has been introduced that has low losses and high bandwidth at the communication wavelengths 850 nm and 1300nm. POF is normally terminated perpendicular to the fiber axis. We propose an angle-ended POF, which is terminated at non-perpendicular angles to the fiber axis. The aim of the research is to investigate the numerical aperture (NA) characteristics of angle-ended POF along the major axis of the elliptical endface. A theoretical model indicates that the NA of the angle-ended POF will increase nonlinearly with tilt-angle and the acceptance cone will be deflected with the angle of the deflection increasing nonlinearly with tilt-angle. We present results for the measured NA and the measured deflection angle using the far-field radiation method. Results are presented for 13 angle-ended SI-POF tilt-angles. We also present results for theoretical value of NA and deflection angle as a function of tilt-angle. The agreement between the measured and theoretical value is good up to tilt-angles of about 15 degrees, beyond which deviation occurs.

  13. 3D Source Localization and Polarimetry using High Numerical Aperture Imaging with Rotating PSF

    CERN Document Server

    Yu, Zhixian

    2014-01-01

    Rotating-PSF imaging via spiral phase engineering can localize point sources over large focal depths in a snapshot mode. This letter presents a full vector-field analysis of the rotating-PSF imager that quantifies the PSF signature of the polarization state of the imaging light. For sufficiently high image-space numerical apertures, there can be significant wave-polarization dependent contributions to the overall PSF, which would allow one to jointly localize and sense the polarization state of light emitted by point sources in a 3D field.

  14. Thermal front propagation in variable aperture fracture-matrix system: A numerical study

    Indian Academy of Sciences (India)

    Nikhil Bagalkot; G Suresh Kumar

    2015-04-01

    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 functions have been used to capture the variation in fracture aperture. Modifications have been made to existing coupled partial differential governing equations to consider the variation of fracture aperture. Effect of temperature on the thermal and physical properties of rock have been incorporated. A fully implicit finite difference scheme has been used to discretize the coupled governing equations. Thermal convection, dispersion and conduction are the major transport processes within fracture, while conduction is the major transport process within rock matrix. The results suggest that variation of fracture aperture increases the heat transfer rate at the fracture-matrix interface. Sensitivity analysis on rock thermal conductivity and fracture aperture have been carried out. The results suggest that the heat transfer from rock matrix to fracture for the case of the parallel plate model is greatly dependent on the rock thermal conductivity (m) as compared to variable aperture model. Further, the thermal front propagation for both parallel plate model and variable aperture model is sensitive to changes in fracture aperture. The heat transfer rate at the interface is greater at smaller fracture apertures and decreases with increase in aperture.

  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. 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

  17. Large-Aperture Membrane Active Phased-Array Antennas

    Science.gov (United States)

    Karasik, Boris; McGrath, William; Leduc, Henry

    2009-01-01

    Large-aperture phased-array microwave antennas supported by membranes are being developed for use in spaceborne interferometric synthetic aperture radar systems. There may also be terrestrial uses for such antennas supported on stationary membranes, large balloons, and blimps. These antennas are expected to have areal mass densities of about 2 kg/sq m, satisfying a need for lightweight alternatives to conventional rigid phased-array antennas, which have typical areal mass densities between 8 and 15 kg/sq m. The differences in areal mass densities translate to substantial differences in total mass in contemplated applications involving aperture areas as large as 400 sq m. A membrane phased-array antenna includes patch antenna elements in a repeating pattern. All previously reported membrane antennas were passive antennas; this is the first active membrane antenna that includes transmitting/receiving (T/R) electronic circuits as integral parts. Other integral parts of the antenna include a network of radio-frequency (RF) feed lines (more specifically, a corporate feed network) and of bias and control lines, all in the form of flexible copper strip conductors on flexible polymeric membranes. Each unit cell of a prototype antenna (see Figure 1) contains a patch antenna element and a compact T/R module that is compatible with flexible membrane circuitry. There are two membrane layers separated by a 12.7-mm air gap. Each membrane layer is made from a commercially available flexible circuit material that, as supplied, comprises a 127-micron-thick polyimide dielectric layer clad on both sides with 17.5-micron-thick copper layers. The copper layers are patterned into RF, bias, and control conductors. The T/R module is located on the back side of the ground plane and is RF-coupled to the patch element via a slot. The T/R module is a hybrid multilayer module assembled and packaged independently and attached to the membrane array. At the time of reporting the information for

  18. 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.

  19. 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 x 8 m x 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.

  20. Low-stress mounting configuration design for large aperture laser transport mirror

    Science.gov (United States)

    Zhang, Zheng; Quan, Xusong; Yao, Chao; Wang, Hui

    2016-10-01

    TM1-6S1 large aperture laser transport mirror is a crucial optical unit of high power solid-state laser in the Inertial Confinement Fusion (ICF) facility. This article focuses on the low-stress and precise mounting method of large-aperture mirror. Based on the engineering practice of SG-III, the state-of-the-art and key problems of current mounting configuration are clarified firstly. Subsequently, a brand new low-stress mounting configuration with flexure supports is proposed. Opto-mechanical model of the mirror under mounting force is built up with elastic mechanics theory. Further, numerical methods and field tests are employed to verify the favorable load uniform capacity and load adjust capacity of flexure supports. With FEM, the relation between the mounting force from new configuration and the mirror surface distortion (wavefront error) is clarified. The novel mounting method of large aperture optics could be not only used on this laser transport mirror, but also on the other transmission optics and large crystals in ICF facilities.

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

    Energy Technology Data Exchange (ETDEWEB)

    Campbell, J.H.; Atherton, L.J.; DeYoreo, J.J. [and others

    1996-06-01

    Beamlet serves as a test bed for the proposed National Ignition Facility (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 the 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, the authors discuss the properties and characteristics of the large-aperture optics used on Beamlet.

  2. Cavity-excited Huygens' metasurface antennas: near-unity aperture efficiency from arbitrarily-large apertures

    CERN Document Server

    Epstein, Ariel; Eleftheriades, George V

    2015-01-01

    One of the long-standing problems in antenna engineering is the realization of highly-directive beams using low-profile devices. In this paper we provide a solution to this problem by means of Huygens' metasurfaces (HMSs), based on the equivalence principle. This principle states that a given excitation can be transformed to a desirable aperture field by inducing suitable electric and magnetic surface currents. Building on this concept, we propose and demonstrate cavity-excited HMS antennas, where the single-source cavity excitation is designed to optimize aperture illumination, while the HMS facilitates the current distribution that ensures phase purity of aperture fields. The HMS breaks the coupling between the excitation and radiation spectrum typical to standard partially-reflecting surfaces, allowing tailoring of the aperture properties to produce a desirable radiation pattern. As shown, a single semianalytical formalism can be followed to achieve control of a variety of radiation features, such as the d...

  3. NST: Thermal Modeling for a Large Aperture Solar Telescope

    Science.gov (United States)

    Coulter, Roy

    2011-05-01

    Late in the 1990s the Dutch Open Telescope demonstrated that internal seeing in open, large aperture solar telescopes can be controlled by flushing air across the primary mirror and other telescope structures exposed to sunlight. In that system natural wind provides a uniform air temperature throughout the imaging volume, while efficiently sweeping heated air away from the optics and mechanical structure. Big Bear Solar Observatory's New Solar Telescope (NST) was designed to realize that same performance in an enclosed system by using both natural wind through the dome and forced air circulation around the primary mirror to provide the uniform air temperatures required within the telescope volume. The NST is housed in a conventional, ventilated dome with a circular opening, in place of the standard dome slit, that allows sunlight to fall only on an aperture stop and the primary mirror. The primary mirror is housed deep inside a cylindrical cell with only minimal openings in the side at the level of the mirror. To date, the forced air and cooling systems designed for the NST primary mirror have not been implemented, yet the telescope regularly produces solar images indicative of the absence of mirror seeing. Computational Fluid Dynamics (CFD) analysis of the NST primary mirror system along with measurements of air flows within the dome, around the telescope structure, and internal to the mirror cell are used to explain the origin of this seemingly incongruent result. The CFD analysis is also extended to hypothetical systems of various scales. We will discuss the results of these investigations.

  4. Cavity-excited Huygens' metasurface antennas for near-unity aperture illumination efficiency from arbitrarily large apertures.

    Science.gov (United States)

    Epstein, Ariel; Wong, Joseph P S; Eleftheriades, George V

    2016-01-21

    One of the long-standing problems in antenna engineering is the realization of highly directive beams using low-profile devices. In this paper, we provide a solution to this problem by means of Huygens' metasurfaces (HMSs), based on the equivalence principle. This principle states that a given excitation can be transformed to a desirable aperture field by inducing suitable electric and (equivalent) magnetic surface currents. Building on this concept, we propose and demonstrate cavity-excited HMS antennas, where the single-source-fed cavity is designed to optimize aperture illumination, while the HMS facilitates the current distribution that ensures phase purity of aperture fields. The HMS breaks the coupling between the excitation and radiation spectra typical to standard partially reflecting surfaces, allowing tailoring of the aperture properties to produce a desirable radiation pattern, without incurring edge-taper losses. The proposed low-profile design yields near-unity aperture illumination efficiencies from arbitrarily large apertures, offering new capabilities for microwave, terahertz and optical radiators.

  5. Genetic algorithm optimization of grating coupled near-field interference lithography systems at extreme numerical apertures

    Science.gov (United States)

    Bourke, Levi; Blaikie, Richard J.

    2017-09-01

    Grating coupled near-field interference lithography has the ability to produce deep-subwavelength interference patterns. Simulations of these systems is very computationally intensive. An inverse design procedure employing a genetic algorithm is utilized here to massively reduce the computational load and allow for the design of systems capable of interfering extremely high numerical apertures. This method is used to optimize systems with an interference patterns with a half pitch of λ /40 corresponding to a numerical aperture of 20. It is also used to demonstrate interference of higher | m| diffraction orders.

  6. Measurement of focusing properties for high numerical aperture optics using an automated submicron beamprofiler

    CERN Document Server

    Chapman, J J; Streed, E W; Kielpinski, D

    2007-01-01

    The focusing properties of three aspheric lenses with numerical aperture (NA) between 0.53 and 0.68 were directly measured using an interferometrically referenced scanning knife-edge beam profiler with sub-micron resolution. The results obtained for two of the three lenses tested were in agreement with paraxial gaussian beam theory. It was also found that the highest NA aspheric lens which was designed for 830nm was not diffraction limited at 633nm. This process was automated using motorized translation stages and provides a direct method for testing the design specifications of high numerical aperture optics.

  7. Label-free single molecule imaging with numerical aperture-shaped interferometric scattering microscopy

    CERN Document Server

    Cole, Daniel; Weigel, Alexander; Kukura, P

    2016-01-01

    Our ability to optically interrogate nanoscopic objects is controlled by the difference between their extinction cross sections and the diffraction limited area to which light can be confined in the far field. We show that a partially transmissive spatial mask placed near the back focal plane of a high numerical aperture microscope objective enhances the extinction contrast of a scatterer near an interface by approximately $T^{-1/2}$, where T is the transmissivity of the mask. Numerical aperture based differentiation of background from scattered light represents a general approach to increasing extinction contrast and enables routine label free imaging down to the single molecule level.

  8. Structural-optical integrated analysis on the large aperture mirror with active mounting

    Science.gov (United States)

    Ren, Zhiyuan; Zhu, Jianqiang; Liu, Zhigang

    2016-11-01

    Deformation of the large aperture mirror caused by the external environment load seriously affects the optical performance of the optical system, and there is a limit to develop the shape quality of large aperture mirror with traditional mounting method. It is effective way to reduce the optical mirror distortion with active support method, and the structural-optical integrated method is the effective means to assess the merits of the mounting for large aperture mirror. Firstly, we proposes a new support scheme that uses specific boundary constraints on the large lens edges and imposes flexible torque to resist deformation induced by gravity to improve surface quantity of large aperture mirror. We calculate distortion of the large aperture mirror at the edges of the flexible torque respectively with the finite element method; secondly, we extract distortion value within clear aperture of the mirror with MATLAB, solve the corresponding Zernike polynomial coefficients; lastly, we obtain the peak-valley value (PV) and root mean square value (RMS) with optical-structural integrated analysis . The results for the 690x400x100mm mirror show that PV and RMS values within the clear aperture with 0.4MPa torques than the case without applying a flexible torque reduces 82.7% and 72.9% respectively. The active mounting on the edge of the large aperture mirror can greatly improve the surface quality of the large aperture mirror.

  9. BLAST: A balloon-borne, large-aperture, submillimetre telescope

    Science.gov (United States)

    Wiebe, Donald Victor

    BLAST is a balloon-borne large-aperture, submillimetre telescope, which makes large area (1--200 square degree) surveys of Galactic and extragalactic targets. Since BLAST observes in the stratosphere, it is able to make broad-band observations between 200 mum and 550 mum which are difficult or impossible to perform from the ground. BLAST has been designed to probe star formation both in the local Galaxy and in the high redshift (z = 1--4) universe. Because BLAST is flown on an unmanned stratospheric balloon platform, it has been designed to be able to operate autonomously, without needing operator intervention to perform its scientific goals. This thesis includes an overview of the design of the BLAST platform, with emphasis on the command and control systems used to operate the telescope. BLAST has been flown on two long-duration balloon flights. The first of these, from Esrange, Sweden in June of 2005, acquired ˜70 hours of primarily Galactic data. During the second flight, from Willy Field, Antarctica in December of 2006, BLAST acquired ˜225 hours of both Galactic and extragalactic data. Operational performance of the platform during these two flights is reviewed, with the goal of providing insight on how future flights can be improved. Reduction of the data acquired by these large-format bolometer arrays is a challenging procedure, and techniques developed for BLAST data reduction are reviewed. The ultimate goal of this reduction is the generation of high quality astronomical maps which can be used for subsequent portions of data analysis. This thesis treats, in detail, the iterative, maximum likelihood map maker developed for BLAST. Results of simulations performed on the map maker to characterise its ability to reconstruct astronomical signals are presented. Finally, astronomical maps produced by this map maker using real data acquired by BLAST are presented, with a discussion on non-physical map pathologies resulting from the data reduction pipeline and

  10. The Balloon-borne Large Aperture Submillimeter Telescope: BLAST

    Science.gov (United States)

    Truch, Matthew D. P.; Ade, P. A. R.; Bock, J. J.; Chapin, E. L.; Chung, J.; Devlin, M. J.; Dicker, S.; Griffin, M.; Gundersen, J. O.; Halpern, M.; Hargrave, P. C.; Hughes, D. H.; Klein, J.; MacTavish, C. J.; Marsden, G.; Martin, P. G.; Martin, T. G.; Mauskopf, P.; Netterfield, C. B.; Olmi, L.; Pascale, E.; Patanchon, G.; Rex, M.; Scott, D.; Semisch, C.; Thomas, N. E.; Tucker, C.; Tucker, G. S.; Viero, M. P.; Wiebe, D. V.

    2009-01-01

    The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) is a suborbital surveying experiment designed to study the evolutionary history and processes of star formation in local galaxies (including the Milky Way) and galaxies at cosmological distances. The BLAST continuum camera, which consists of 270 detectors distributed between three arrays, observes simultaneously in broadband (30%) spectral windows at 250, 350, and 500 microns. The optical design is based on a 2 m diameter telescope, providing a diffraction-limited resolution of 30" at 250 microns. The gondola pointing system enables raster mapping of arbitrary geometry, with a repeatable positional accuracy of 30"; postflight pointing reconstruction to manual override. On this poster, we describe the primary characteristics and measured in-flight performance of BLAST. BLAST performed a test flight in 2003 and has since made two scientifically productive long-duration balloon flights: a 100 hour flight from ESRANGE (Kiruna), Sweden to Victoria Island, northern Canada in 2005 June; and a 250 hour, circumpolar flight from McMurdo Station, Antarctica in 2006 December. The BLAST collaboration acknowledges the support of NASA through grants NAG5-12785, NAG5-13301, and NNGO-6GI11G, the Canadian Space Agency (CSA), the Science and Technology Facilities Council (STFC), Canada's Natural Sciences and Engineering Research Council (NSERC), the Canada Foundation for Innovation, the Ontario Innovation Trust, the Puerto Rico Space Grant Consortium, the Fondo Institucional para la Investigacion of the University of Puerto Rico, and the National Science Foundation Office of Polar Programs.

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

    CERN Document Server

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

    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 LAGO collaboration to share data, and computer resources through its different sites. This environment has the possibility to generate synthetic data by simulating the showers through AIRES application and to store/preserve distributed data files collected by the WCD at the LAGO sites. The present article concerns the implementation of a prototype of LAGO-DR adapting DSpace, with a hierarchical structure (i.e. country, institution, followed by collections that contain the metadata and data files), for the captured/simulate...

  12. The Balloon-borne Large Aperture Submillimeter Telescope: BLAST

    CERN Document Server

    Pascale, E; Bock, J J; Chapin, E L; Chung, J; Devlin, M J; Dicker, S; Griffin, M; Gundersen, J O; Halpern, M; Hargrave, P C; Hughes, D H; Klein, J; MacTavish, C J; Marsden, G; Martin, P G; Martin, T G; Mauskopf, P; Netterfield, C B; Olmi, L; Patanchon, G; Rex, M; Scott, D; Semisch, C; Thomas, N; Truch, M D P; Tucker, C; Tucker, G S; Viero, M P; Wiebe, D V

    2007-01-01

    The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) is a sub-orbital survey-experiment designed to study the evolutionary history and processes of star formation in local galaxies (including the Milky Way) and galaxies at cosmological distances. The BLAST continuum camera, which consists of 270 detectors distributed between 3 arrays, observes simultaneously in broad-band (30%) spectral-windows at 250, 350, and 500 micron. The optical design is based on a 2m diameter Cassegrain telescope, providing a diffraction-limited resolution of 30" at 250 micron. The gondola pointing system enables raster-like maps of arbitrary geometry, with a repeatable positional accuracy of ~30" post-flight pointing reconstruction to ~<5" rms is also achieved. The on-board telescope control software permits autonomous execution of a pre-selected set of maps, with the option of manual intervention. In this paper we describe the primary characteristics and measured in-flight performance of BLAST. Since a test-flight in ...

  13. Large- and Small-Aperture Fixed-Point Cells of Cu, Pt C, and Re C

    Science.gov (United States)

    Anhalt, Klaus; Wang, Yunfen; Yamada, Yoshiro; Hartmann, Jürgen

    2008-06-01

    Extending the application of metal (carbide) carbon eutectic fixed-point cells to radiometry, e.g., for measurements in irradiance mode, requires fixed-point cells with large apertures. In order to make large-aperture cells more readily usable in furnace systems with smaller furnace tubes commonly used for small-aperture fixed-point cells, a novel cell design was developed. For each of Cu, Pt C, and Re C fixed points, two types of fixed-point cells were manufactured, the small- and large-aperture cell. For Pt C and Re C, the large-aperture cells were filled with a hyper-eutectic metal carbon mixture; for the small cells, a hypo-eutectic mixture was used for filling. For each material, the small and large cells were compared with respect to radiometric differences. Whereas plateau shape and melting temperature are in good agreement for the small- and large-aperture Cu cells, a larger difference was observed between small- and large-aperture cells of Pt C and Re C, respectively. The origin of these observations, attributed to the temperature distribution inside the furnace, ingot contamination during manufacture, and non-uniform ingot formation for the larger cells, is discussed. The comparison of measurements by a radiation thermometer and filter radiometer of the Re C and Pt C large-aperture cells showed large differences that could be explained only by a strong radiance distribution across the cavity bottom. Further investigations are envisaged to clarify the cause.

  14. Improved design of support for large aperture space lightweight mirror

    Science.gov (United States)

    Wang, Chao; Ruan, Ping; Liu, Qimin

    2013-08-01

    In order to design a kind of rational large aperture space mirror which can adapt to the space gravity and thermal environment, by taking the choice of material, the lightweight of the mirror and the design of support into account in detail, a double-deck structure with traditional flexible hinge was designed, then the analytical mathematical model of the mirror system was established. The design adopts six supports on back. in order to avoid the constraints, mirror is connected to three middle transition pieces through six flexible hinges, and then the three transition pieces are connected to support plate through another three flexible hinges. However, the initial structure is unable to reach the expected design target and needs to be made further adjustments. By improving and optimizing the original structure, a new type of flexible hinge in the shape of the letter A is designed finally. Compared with the traditional flexible hinge structure, the new structure is simpler and has less influence on the surface figure accuracy of mirror. By using the finite element analysis method, the static and dynamic characteristics as well as the thermal characteristics of the mirror system are analyzed. Analysis results show that the maximum PV value is 37 nm and the maximum RMS value is 10.4 nm when gravity load is applied. Furthermore, the maximum PV value is 46 nm and the maximum RMS value is 10.5 nm under the load case of gravity coupled with 4℃ uniform temperature rise. The results satisfy the index of optical design. The first order natural frequency of the mirror component is 130 Hz according to the conclusion obtained by modal analytical solution, so the mirror structure has high enough fundamental frequency. And, the structural strength can meet the demand under the overload and the random vibration environment respectively. It indicates that the mirror component structure has enough dynamic, static stiffness and thermal stability, meeting the design requirements.

  15. Dynamic aperture computation for the as-built CERN Large Hadron Collider and impact of main dipoles sorting

    Science.gov (United States)

    Fartoukh, S.; Giovannozzi, M.

    2012-04-01

    During the design phase of the CERN Large Hadron Collider the dynamic aperture, i.e. the amplitude of the domain in phase space where the particle motion is stable, was used as one of the most important figures-of-merit to specify the field quality of the various types of superconducting magnets and to quantify the machine performance. The programme of magnetic measurements performed during the production and acceptance testing of the magnets generated a large amount of information, which was used to obtain a best estimate of the dynamic aperture of the actual machine. In this paper the results of massive numerical simulations based on the measured field quality of several optical configurations and beam energies, are presented and discussed. The effect of the sorting of the main dipoles on the final value of the dynamic aperture has also been studied and the results are reviewed in detail.

  16. Dynamic aperture computation for the AS-built CERN Large Hadron Collider and impact of main dipoles sorting

    CERN Document Server

    Fartoukh, S

    2012-01-01

    During the design phase of the CERN Large Hadron Collider the dynamic aperture, i.e., the amplitude of the domain in phase space where the particle motion is stable, was used as one of the most important figures-of-merit to specify the field quality of the various types of superconducting magnets and to quantify the machine performance. The programme of magnetic measurements performed during the production and acceptance testing of the magnets generated a large amount of information, which was used to obtain a best estimate of the dynamic aperture of the actual machine. In this paper the results of massive numerical simulations based on the measured field quality of several optical configurations and beam energies, are presented and discussed. The effect of the sorting of the main dipoles on the final value of the dynamic aperture has also been studied and the results are reviewed in detail.

  17. Geometric phase low-coherence interference microscopy at high numerical apertures

    Science.gov (United States)

    Roy, Maitreyee; Svahn, Peter; Sheppard, Colin J. R.

    2001-09-01

    A low-coherence Linnik interference microscope using high numerical aperture optics has been constructed. The system uses a tungsten halogen lamp and a Koehler illumination, with separate control over field and aperture stops, so that experiments can be conducted with a range of different geometric phase which is achieved by using a polarizing beam splitter, a quarter wave plate and a rotating polarizer. Image information is extracted from the visibility of the fringes, and the position of the visibility peak along the scanning axis, yielding the height of the test surface at the corresponding points.

  18. Intense THz Pulses with large ponderomotive potential generated from large aperture photoconductive antennas.

    Science.gov (United States)

    Ropagnol, X; Khorasaninejad, M; Raeiszadeh, M; Safavi-Naeini, S; Bouvier, M; Côté, C Y; Laramée, A; Reid, M; Gauthier, M A; Ozaki, T

    2016-05-30

    We report the generation of free space terahertz (THz) pulses with energy up to 8.3 ± 0.2 µJ from an encapsulated interdigitated ZnSe Large Aperture Photo-Conductive Antenna (LAPCA). An aperture of 12.2 cm2 is illuminated using a 400 nm pump laser with multi-mJ energies at 10 Hz repetition rate. The calculated THz peak electric field is 331 ± 4 kV/cm with a spectrum characterized by a median frequency of 0.28 THz. Given its relatively low frequency, this THz field will accelerate charged particles efficiently having very large ponderomotive energy of 15 ± 1 eV for electrons in vacuum. The scaling of the emission is studied with respect to the dimensions of the antenna, and it is observed that the capacitance of the LAPCA leads to a severe decrease in and distortion of the biasing voltage pulse, fundamentally limiting the maximum applied bias field and consequently the maximum energy of the radiated THz pulses. In order to demonstrate the advantages of this source in the strong field regime, an open-aperture Z-scan experiment was performed on n-doped InGaAs, which showed significant absorption bleaching.

  19. A compact, large-aperture tunable lens with adaptive spherical correction

    CERN Document Server

    Wapler, Matthias C; Wallrabe, Ulrike

    2014-01-01

    In this paper, we present the proof of concept of a very fast adaptive glass membrane lens with a large aperture/diameter ratio, spherical aberration correction and integrated actuation. The membrane is directly deformed using two piezo actuators that can tune the focal length and the conical parameter. This operating principle allows for a usable aperture of the whole membrane diameter. Together with the efficient actuation mechanism, the aperture is around 2/3 of the total system diameter - at a thickness of less than 2mm. The response time is a few milliseconds at 12mm aperture, which is fast compared to similar systems.

  20. High-numerical-aperture microlensed tip on an air-clad optical fiber.

    Science.gov (United States)

    Kato, Shinya; Chonan, Sho; Aoki, Takao

    2014-02-15

    We show that a hemispherically shaped tip on an air-clad optical fiber simultaneously works as a high-numerical-aperture lens and efficiently collects photons from an emitter placed near the beam waist into the fundamental guided mode. Numerical simulations show that the coupling efficiency reaches about 25%. We have constructed a confocal microscope with such a lensed fiber. The measurements are in good agreement with the numerical simulation. The monolithic structure with a high-photon-collection efficiency will provide a flexible substitute for a conventional lens system in various experiments such as single-atom trapping with a tightly focused optical trap.

  1. Two-phase flow properties in aperture-based fractures under normal deformation conditions: Analytical approach and numerical simulation

    Science.gov (United States)

    Ye, Zuyang; Liu, Hui-Hai; Jiang, Qinghui; Liu, Yanzhang; Cheng, Aiping

    2017-02-01

    A systematic method has been proposed to estimate the two-phase flow properties of horizontal fractures under normal deformation condition. Based on Gaussian aperture distributions and the assumption of local parallel plate model, a simple model was obtained in closed form to predict the capillary pressure-saturation relationships for both wetting and non-wetting phases. Three conceptual models were also developed to characterize the relative permeability behaviors. In order to investigate the effect of normal deformation on two-phase flow properties, the normal deformation could be represented with the maximum void space closure on the basis of penetration model. A rigorous successive random addition (SRA) method was used to generate the aperture-based fractures and a numerical approach based on invasion percolation (IP) model was employed to model capillary-dominated displacements between wetting and non-wetting phases. The proposed models were partially verified by a laboratory dataset and numerical calculations without consideration of deformation. Under large normal deformations, it was found that the macroscopic model is in better agreement with simulated observations. The simulation results demonstrated that the two-phase flow properties including the relationships between capillary pressure, relative permeability and saturation, phase interference, phase structures, residual-saturation-rated parameters and tortuosity factor, were highly sensitive to the spatial correlation of aperture distribution and normal deformation.

  2. High numerical aperture microendoscope objective for a fiber confocal reflectance microscope

    Science.gov (United States)

    Kester, Robert T.; Tkaczyk, Tomasz S.; Descour, Michael R.; Christenson, Todd; Richards-Kortum, Rebecca

    2007-03-01

    A disposable high numerical aperture microendoscope objective has been designed, fabricated, and tested for use with a fiber confocal reflectance microscope. The objective uses high precision LIGA fabricated components to integrate imaging components and hydraulic suction lines into a housing that measures only 3.85 mm in outer diameter and 14.65 mm in length. The hydraulics are used to translate tissue through the focal plane for three dimensional imaging. This device is diffraction limited for λ = 850 nm, has a numerical aperture of 1.0, a field of view of 250 µm, and a working distance of 450 µm. The objective is intended for in vivo imaging of precancerous cells.

  3. 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.

  4. Measurement of the optical fiber numeric aperture exposed to thermal and radiation aging

    Science.gov (United States)

    Vanderka, Ales; Bednarek, Lukas; Hajek, Lukas; Latal, Jan; Poboril, Radek; Zavodny, Petr; Vasinek, Vladimir

    2016-12-01

    This paper deals with the aging of optical fibers influenced by temperature and radiation. There are analyzed changes in the structure of the optical fiber, related to the propagation of light in the fiber structure. In this case for numerical aperture. For experimental measurement was used MM fiber OM1 with core diameter 62.5 μm, cladding diameter 125 μm in 2.8 mm secondary coating. Aging of the optical fiber was achieved with dry heat and radiation. For this purpose, we were using a temperature chamber with a stable temperature of 105 °C where the cables after two months. Cables were then irradiated with gamma radiation 60Co in doses of 1.5 kGy and then 60 kGy. These conditions simulated 50 years aging process of optical cables. According to European Standard EN 60793-1-43:2015 was created the automatic device for angular scan working with LabVIEW software interface. Numerical aperture was tested at a wavelength of 850 nm, with an output power 1 mW. Scanning angle was set to 50° with step 0.25°. Numerical aperture was calculated from the position where power has fallen from maximal power at e2 power. The measurement of each sample was performed 10 hours after thermal and radiation aging. The samples were subsequently tested after six months from the last irradiation. In conclusion, the results of the experiment were analyzed and compared.

  5. 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

  6. SUPERPOLISHED SI COATED SIC OPTICS FOR RAPID MANUFACTURE OF LARGE APERTURE UV AND EUV TELESCOPES Project

    Data.gov (United States)

    National Aeronautics and Space Administration — SSG/Tinsley proposes an innovative optical manufacturing process that will allow the advancement of state-of-the-art Silicon Carbide (SiC) mirrors for large aperture...

  7. The scaling relationship between telescope cost and aperture size for very large telescopes

    Science.gov (United States)

    van Belle, Gerard T.; Meinel, Aden Baker; Meinel, Marjorie Pettit

    2004-01-01

    Cost data for ground-based telescopes of the last century are analyzed for trends in the relationship between aperture size and cost. We find that for apertures built prior to 1980, costs scaled as aperture size to the 2.8 power, which is consistent with the precious finding of Meinel (1978). After 1980, 'traditional' monolithic mirror telescope costs have scaled as aperture to the 2.5 power. The large multiple mirror telescopes built or in construction during this time period (Keck, LBT, GTC) appear to deviate from this relationship with significant cost savings as a result, although it is unclear what power law such structures follow. We discuss the implications of the current cost-aperture size data on the proposed large telescope projects of the next ten to twenty years. Structures that naturally tend towards the 2.0 power in the cost-aperture relationship will be the favorable choice for future extremely large apertures; out expectation is that space-based structures will ultimately gain economic advantage over ground-based ones.

  8. Focal plane internal energy flows of singular beams in astigmatically aberrated low numerical aperture systems.

    Science.gov (United States)

    Bahl, Monika; Senthilkumaran, P

    2014-09-01

    Singular beams have circulating energy components. When such beams are focused by low numerical aperture systems suffering from astigmatic aberration, these circulating energy components get modified. The phase gradient introduced by this type of aberration splits the higher charge vortices. The dependence of the charge, the aberration coefficient, and the size of the aperture on the nature of the splitting process are reported in this paper. The transverse components of the Poynting vector fields that can be derived from the phase gradient vector field distributions are further decomposed into solenoidal and irrotational components using the Helmholtz-Hodge decomposition method. The solenoidal components relate to the orbital angular momentum of the beams, and the irrotational components are useful in the transport of intensity equations for phase retrieval.

  9. Parasitic suppression in large aperture disk lasers employing liquid edge claddings.

    Science.gov (United States)

    Guch, S

    1976-06-01

    A liquid edge cladding system for parasitic suppression in large aperture, high gain disk laser amplifiers has been developed and tested. A near-saturated aqueous solution of Znl(2) was employed for index-matching. Adequate fluorescence absorption was demonstrated using either dissolved NiCl(2) or chrome black oxide coating applied to the disk holder. Application of liquid cladding to a 20-cm aperture disk laser amplifier increased energy storage capability by approximately 20% over conventional solder glass claddings.

  10. Numerical simulation of the coupling of ultra-wide band electromagnetic pulse into landmine by aperture

    Science.gov (United States)

    Gao, Zhen-Ru; Zhao, Hui-Chang; Yang, Li; Wang, Feng-Shan

    2015-09-01

    The modern landmine’s electronic fuse is susceptible to strong interference or can even be damaged by the ultra-wide band electromagnetic pulse (UWB-EMP). The finite-difference time-domain (FDTD) method in lossy media with cylindrical coordinates is used to study the interactions of the UWB-EMP with the landmine. First, the coupling of UWB-EMP into the landmine shielding shell through an aperture is numerically simulated. Second, the coupled electromagnetic field of mine shells made of different shielding materials and with apertures of different sizes is plotted. Third, the aperture coupling laws of UWB-EMP into shells are analyzed and categorized. Such an algorithm is capable of effectively preventing ladder similar errors, and consequently improving the calculation precision, and in addition to adopting the message passing interface (MPI) parallel method to divide the total calculating range into more sub-ranges, the overall calculating efficiency is greatly increased. These calculations are surely a constructive reference for modern landmine design against electromagnetic damage. Project supported by the Postdoctoral Science Foundation of China (Grant No. 2014M552610).

  11. A study on the short-wavelength and high-numerical-aperture phase-change recording

    Institute of Scientific and Technical Information of China (English)

    刘波; 阮昊; 干福熹

    2003-01-01

    In this paper, we discuss the phase-change recording at a short-wavelength (514 nm) and a high numerical aperture (0.85). Effects of recording power and pulse width on the size of the recording marks are studied. The minimum recording mark with a length of approximately 220 nm has been observed. The capacity of about 17 GB for a single-layer disc of a 12 cm diameter can be obtained. The maximum carrier-to-noise ratio reaches 45 dB at a writing power of 13-14 mW.

  12. Three-dimensional reconstruction of far and large objects using synthetic aperture integral imaging

    Science.gov (United States)

    Piao, Yongri; Xing, Luyan; Zhang, Miao; Lee, Byung-Gook

    2017-01-01

    In this paper, we present a three-dimensional reconstruction of far and large objects in a synthetic aperture integral imaging system. In the proposed method, the far and large size objects are recorded as a set of elemental images by using an additional Plano-concave lens in the synthetic aperture integral imaging system. Due to the use of the Plano-concave lens, the reconstruction distance can be significantly reduced. This enables us to computationally reconstruct the objects in the far-field region. Experimental results are carried out, and the feasibility of the proposed method is verified.

  13. 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.

  14. Eyeglass Large Aperture, Lightweight Space Optics FY2000 - FY2002 LDRD Strategic Initiative

    Energy Technology Data Exchange (ETDEWEB)

    Hyde, R

    2003-02-10

    A series of studies by the Air Force, the National Reconnaissance Office and NASA have identified the critical role played by large optics in fulfilling many of the space related missions of these agencies. Whether it is the Next Generation Space Telescope for NASA, high resolution imaging systems for NRO, or beam weaponry for the Air Force, the diameter of the primary optic is central to achieving high resolution (imaging) or a small spot size on target (lethality). While the detailed requirements differ for each application (high resolution imaging over the visible and near-infrared for earth observation, high damage threshold but single-wavelength operation for directed energy), the challenges of a large, lightweight primary optic which is space compatible and operates with high efficiency are the same. The advantage of such large optics to national surveillance applications is that it permits these observations to be carried-out with much greater effectiveness than with smaller optics. For laser weapons, the advantage is that it permits more tightly focused beams which can be leveraged into either greater effective range, reduced laser power, and/or smaller on-target spot-sizes; weapon systems can be made either much more effective or much less expensive. This application requires only single-wavelength capability, but places an emphasis upon robust, rapidly targetable optics. The advantages of large aperture optics to astronomy are that it increases the sensitivity and resolution with which we can view the universe. This can be utilized either for general purpose astronomy, allowing us to examine greater numbers of objects in more detail and at greater range, or it can enable the direct detection and detailed examination of extra-solar planets. This application requires large apertures (for both light-gathering and resolution reasons), with broad-band spectral capability, but does not emphasize either large fields-of-view or pointing agility. Despite

  15. Automated aberration compensation in high numerical aperture systems for arbitrary laser modes (Conference Presentation)

    Science.gov (United States)

    Hering, Julian; Waller, Erik H.; von Freymann, Georg

    2017-02-01

    Since a large number of optical systems and devices are based on differently shaped focal intensity distributions (point-spread-functions, PSF), the PSF's quality is crucial for the application's performance. E.g., optical tweezers, optical potentials for trapping of ultracold atoms as well as stimulated-emission-depletion (STED) based microscopy and lithography rely on precisely controlled intensity distributions. However, especially in high numerical aperture (NA) systems, such complex laser modes are easily distorted by aberrations leading to performance losses. Although different approaches addressing phase retrieval algorithms have been recently presented[1-3], fast and automated aberration compensation for a broad variety of complex shaped PSFs in high NA systems is still missing. Here, we report on a Gerchberg-Saxton[4] based algorithm (GSA) for automated aberration correction of arbitrary PSFs, especially for high NA systems. Deviations between the desired target intensity distribution and the three-dimensionally (3D) scanned experimental focal intensity distribution are used to calculate a correction phase pattern. The target phase distribution plus the correction pattern are displayed on a phase-only spatial-light-modulator (SLM). Focused by a high NA objective, experimental 3D scans of several intensity distributions allow for characterization of the algorithms performance: aberrations are reliably identified and compensated within less than 10 iterations. References 1. B. M. Hanser, M. G. L. Gustafsson, D. A. Agard, and J. W. Sedat, "Phase-retrieved pupil functions in wide-field fluorescence microscopy," J. of Microscopy 216(1), 32-48 (2004). 2. A. Jesacher, A. Schwaighofer, S. Frhapter, C. Maurer, S. Bernet, and M. Ritsch-Marte, "Wavefront correction of spatial light modulators using an optical vortex image," Opt. Express 15(9), 5801-5808 (2007). 3. A. Jesacher and M. J. Booth, "Parallel direct laser writing in three dimensions with spatially dependent

  16. Quantification of numerical aperture-dependence of the OCT attenuation coefficient (Conference Presentation)

    Science.gov (United States)

    Peinado, Liliana M.; Bloemen, Paul R.; Almasian, Mitra; van Leeuwen, Ton G.; Faber, Dirk J.

    2016-03-01

    Despite the improvements in early cancer diagnosis, adequate diagnostic tools for early staging of bladder cancer tumors are lacking [1]. MEMS-probes based on optical coherence tomography (OCT) provide cross-sectional imaging with a high-spatial resolution at a high-imaging speed, improving visualization of cancerous tissue [2-3]. Additionally, studies show that the measurement of localized attenuation coefficient allows discrimination between healthy and cancerous tissue [4]. We have designed a new miniaturized MEMS-probe based on OCT that will optimize early diagnosis by improving functional visualization of suspicious lesions in bladder. During the optical design phase of the probe, we have studied the effect of the numerical aperture (NA) on the OCT signal attenuation. For this study, we have employed an InnerVision Santec OCT system with several numerical apertures (25mm, 40mm, 60mm, 100mm, 150mm and 200mm using achromatic lenses). The change in attenuation coefficient was studied using 15 dilutions of intralipid ranging between 6*10-5 volume% and 20 volume%. We obtained the attenuation coefficient from the OCT images at several fixed positions of the focuses using established OCT models (e.g. single scattering with known confocal point spread function (PSF) [5] and multiple scattering using the Extended Huygens Fresnel model [6]). As a result, a non-linear increase of the scattering coefficient as a function of intralipid concentration (due to dependent scattering) was obtained for all numerical apertures. For all intralipid samples, the measured attenuation coefficient decreased with a decrease in NA. Our results suggest a non-negligible influence of the NA on the measured attenuation coefficient. [1] Khochikar MV. Rationale for an early detection program for bladder cancer. Indian J Urol 2011 Apr-Jun; 27(2): 218-225. [2] Sun J and Xie H. Review Article MEMS-Based Endoscopic Optical Coherence Tomography. IJO 2011, Article ID 825629, 12 pages. doi:10

  17. Beamforming Techniques for Large-N Aperture Arrays

    CERN Document Server

    Faulkner, A J; de Vaate, J G Bij; Kant, G W; Pickard, P

    2010-01-01

    Beamforming is central to the processing function of all phased arrays and becomes particularly challenging with a large number of antenna element (e.g. >100,000). The ability to beamform efficiently with reasonable power requirements is discussed in this paper. Whilst the most appropriate beamforming technology will change over time due to semiconductor and processing developments, we present a hierarchical structure which is technology agnostic and describe both Radio-Frequency (RF) and digital hierarchical beamforming approaches. We present implementations of both RF and digital beamforming systems on two antenna array demonstrators, namely the Electronic Multi Beam Radio Astronomy ConcEpt (EMBRACE) and the dualpolarisation all-digital array (2-PAD). This paper will compare and contrast both digital and analogue implementations without considering the deep system design of these arrays.

  18. 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...

  19. Large Aperture Scanning Lidar Based on Holographic Optical Elements

    Science.gov (United States)

    Schwemmer, Geary K.; Miller, David O.; Wilkerson, Thomas D.; Andrus, Ionio; Guerra, David V.; Einaudi, Franco (Technical Monitor)

    2001-01-01

    Lidar remote sensing instruments can make a significant contribution to satisfying many of the required measurements of atmospheric and surface parameters for future spaceborne platforms, including topographic altimeters, atmospheric profiles of, wind, humidity, temperature, trace molecules, aerosols, and clouds. It is highly desirable to have wide measurement swaths for rapid coverage rather than just the narrow ribbon of data that is obtained with a nadir only observation. For most applications global coverage is required, and for wind measurements scanning or pointing is required in order to retrieve the full 3-D wind vector from multiple line-of-sight Doppler measurements. Conventional lidar receivers make up a substantial portion of the instrument's size and weight. Wide angle scanning typically requires a large scanning mirror in front of the receiver telescope, or pointing the entire telescope and aft optics assembly, Either of these methods entails the use of large bearings, motors, gearing and their associated electronics. Spaceborne instruments also need reaction wheels to counter the torque applied to the spacecraft by these motions. NASA has developed simplified conical scanning telescopes using Holographic Optical Elements (HOEs) to reduce the size, mass, angular momentum, and cost of scanning lidar systems. NASA has developed two operating lidar systems based on 40 cm diameter HOEs. The first such system, named Prototype Holographic Atmospheric Scanner for Environmental Remote Sensing (PHASERS) was a joint development between NASA Goddard Space Flight Center (GSFC) and the University of Maryland College Park. PHASERS is based on a reflection HOE for use at the doubled Nd:YAG laser wavelength of 532 nm and has recently undergone a number of design changes in a collaborative effort between GSFC and Saint Anselm College in New Hampshire. The next step was to develop IR transmission HOEs for use with the Nd:YAG fundamental in the Holographic Airborne

  20. 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. Measur

  1. 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).

  2. The role of numerical aperture in efficient estimation of spatially resolved reflectance by a Monte Carlo light propagation model

    Science.gov (United States)

    Ivančič, Matic; Naglič, Peter; Likar, Boštjan; Pernuš, Franjo; Bürmen, Miran

    2017-02-01

    For a given experimental setting, the measured spatially resolved reflectance rapidly drops with decreasing numerical aperture of the detection scheme. Consequently, for detection schemes with small numerical apertures, the computational time of MC simulations required to obtain adequate signal-to-noise ratio of the spatially resolved reflectance can become very long. We mitigate the issue by virtually increasing the numerical aperture of the detection scheme in MC simulations and devise a criterion for robust estimation of its maximum value. By using the proposed methodology, we show that the acceptance angle of a selected imaging system can be virtually increased from 3 to 11 while preserving a low relative error of the simulated spatially resolved reflectance over a wide range of tissue-like optical properties. As a result, a more than eightfold improvement in the computation time is attained.

  3. R and D status of a large-aperture hybrid avalanche photo-detector

    Energy Technology Data Exchange (ETDEWEB)

    Abe, Toshinori, E-mail: toshi@hep.phys.s.u-tokyo.ac.j [University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Aihara, Hiroaki; Iwasaki, Masako; Fujimori, Hiroki; Kasimura, Keizo; Mineo, Sogo; Uchida, Tomohisa [University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Tanaka, Manobu [Institute for Particle and Nuclear Studies, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Kawai, Yoshihiko; Kyushima, Hiroyuki; Suyama, Motohiro [Electron Tube Division, Hamamatsu Photonics K.K., 314-5 Shimokanzo, Iwata City, Shizuoka 438-0193 (Japan); Shiozawa, Masato [Kamioka Observatory, Institute for Cosmic Ray Research ICRR, University of Tokyo, Higashi-Mozumi, Kamioka-cho, Hida City, Gifu 506-1205 (Japan)

    2010-11-01

    This paper reports on the R and D status of a large-aperture Hybrid Avalanche Photo-Detector (HAPD). We have developed a 13-inch aperture HAPD and its readout system. The HAPD is a photo-detector expected to replace the photomultiplier tube (PMT) in next-generation imaging water Cherenkov detectors such as Hyper Kamiokande. We will present the recent progress made in readout system development. The readout system involves a fast sampling device. The sampling depth (number of cells) has been extended to 256 from 64 in order to measure longer waveform length. The variation in AC gain is now fixed and the input analog bandwidth improved.

  4. XUV coherent diffraction imaging in reflection geometry with low numerical aperture.

    Science.gov (United States)

    Zürch, Michael; Kern, Christian; Spielmann, Christian

    2013-09-09

    We present an experimental realization of coherent diffraction imaging in reflection geometry illuminating the sample with a laser driven high harmonic generation (HHG) based XUV source. After recording the diffraction pattern in reflection geometry, the data must be corrected before the image can be reconstructed with a hybrid-input-output (HIO) algorithm. In this paper we present a detailed investigation of sources of spoiling the reconstructed image due to the nonlinear momentum transfer, errors in estimating the angle of incidence on the sample, and distortions by placing the image off center in the computation grid. Finally we provide guidelines for the necessary parameters to realize a satisfactory reconstruction within a spatial resolution in the range of one micron for an imaging scheme with a numerical aperture NA < 0.03.

  5. Large Metasurface Aperture for Millimeter Wave Computational Imaging at the Human-Scale

    Science.gov (United States)

    Gollub, J. N.; Yurduseven, O.; Trofatter, K. P.; Arnitz, D.; F. Imani, M.; Sleasman, T.; Boyarsky, M.; Rose, A.; Pedross-Engel, A.; Odabasi, H.; Zvolensky, T.; Lipworth, G.; Brady, D.; Marks, D. L.; Reynolds, M. S.; Smith, D. R.

    2017-02-01

    We demonstrate a low-profile holographic imaging system at millimeter wavelengths based on an aperture composed of frequency-diverse metasurfaces. Utilizing measurements of spatially-diverse field patterns, diffraction-limited images of human-sized subjects are reconstructed. The system is driven by a single microwave source swept over a band of frequencies (17.5–26.5 GHz) and switched between a collection of transmit and receive metasurface panels. High fidelity image reconstruction requires a precise model for each field pattern generated by the aperture, as well as the manner in which the field scatters from objects in the scene. This constraint makes scaling of computational imaging systems inherently challenging for electrically large, coherent apertures. To meet the demanding requirements, we introduce computational methods and calibration approaches that enable rapid and accurate imaging performance.

  6. Advanced Technology Large-Aperture Space Telescope (ATLAST): Characterizing Habitable Worlds

    CERN Document Server

    Postman, M; Krist, J; Stapelfeldt, K; Brown, R; Oegerle, W; Lo, A; Clampin, M; Soummer, R; Wiseman, J; Mountain, M

    2009-01-01

    The Advanced Technology Large Aperture Space Telescope (ATLAST) is a set of mission concepts for the next generation UV-Optical-Near Infrared space telescope with an aperture size of 8 to 16 meters. ATLAST, using an internal coronagraph or an external occulter, can characterize the atmosphere and surface of an Earth-sized exoplanet in the Habitable Zone of long-lived stars at distances up to ~45 pc, including its rotation rate, climate, and habitability. ATLAST will also allow us to glean information on the nature of the dominant surface features, changes in cloud cover and climate, and, potentially, seasonal variations in surface vegetation. ATLAST will be able to visit up to 200 stars in 5 years, at least three times each, depending on the technique used for starlight suppression and the telescope aperture. More frequent visits can be made for interesting systems.

  7. Large-aperture space optical system testing based on the scanning Hartmann.

    Science.gov (United States)

    Wei, Haisong; Yan, Feng; Chen, Xindong; Zhang, Hao; Cheng, Qiang; Xue, Donglin; Zeng, Xuefeng; Zhang, Xuejun

    2017-03-10

    Based on the Hartmann testing principle, this paper proposes a novel image quality testing technology which applies to a large-aperture space optical system. Compared with the traditional testing method through a large-aperture collimator, the scanning Hartmann testing technology has great advantages due to its simple structure, low cost, and ability to perform wavefront measurement of an optical system. The basic testing principle of the scanning Hartmann testing technology, data processing method, and simulation process are presented in this paper. Certain simulation results are also given to verify the feasibility of this technology. Furthermore, a measuring system is developed to conduct a wavefront measurement experiment for a 200 mm aperture optical system. The small deviation (6.3%) of root mean square (RMS) between experimental results and interferometric results indicates that the testing system can measure low-order aberration correctly, which means that the scanning Hartmann testing technology has the ability to test the imaging quality of a large-aperture space optical system.

  8. Annular sub-aperture stitching interferometry testing for large-caliber aspheric

    Science.gov (United States)

    Wu, Pengfei; Yang, Shuming; Sun, Lin; Zhao, Pu; Jiang, Zhuangde

    2016-09-01

    An annular sub-aperture stitching interferometry testing is proposed for large-caliber aspheric lens testing, expanding the dynamic range of the interferometer, broadening the scope of the measurement, and reducing the cost of the measurement to a large extent without the use of compensating elements. The large-caliber aspheric is divided into several annular sub-apertures, and there are some overlapping areas between each two adjacent sub-apertures. When testing, the test aspheric is moved along the optical axis according to path planning so that the reference spherical shape and the test aspheric interest at points of common tangency to reduce the fringe density of the sub-aperture. However, in the process of moving the test optic, six DOF (degrees of freedom) misalignment errors will occur. According to the rigid body kinematics theory, the misalignment error separation model is established so that the misalignment factors can be calculated by the information of each overlapping regions. Then all sub-apertures are unified to the same reference with proper algorithm, and subsequently, misalignment error of the reference is removed by Zernike polynomial fitting, and the whole surface error is recovered. Simulation results are shown to demonstrate the feasibility of the method we developed. By analyzing the influence of the six DOF on the stitching result, the most important factor is obtained, and some measures are taken, that is, a measurement system combining two interferometers is designed, one of which is to measure the departures between the reference and the aspheric, and another to test the piston errors to be transmitted to the control system to improve the accuracy.

  9. Large Aperture "Photon Bucket" Optical Receiver Performance in High Background Environments

    Science.gov (United States)

    Vilnrotter, Victor A.; Hoppe, D.

    2011-01-01

    The potential development of large aperture groundbased "photon bucket" optical receivers for deep space communications, with acceptable performance even when pointing close to the sun, is receiving considerable attention. Sunlight scattered by the atmosphere becomes significant at micron wavelengths when pointing to a few degrees from the sun, even with the narrowest bandwidth optical filters. In addition, high quality optical apertures in the 10-30 meter range are costly and difficult to build with accurate surfaces to ensure narrow fields-of-view (FOV). One approach currently under consideration is to polish the aluminum reflector panels of large 34-meter microwave antennas to high reflectance, and accept the relatively large FOV generated by state-of-the-art polished aluminum panels with rms surface accuracies on the order of a few microns, corresponding to several-hundred micro-radian FOV, hence generating centimeter-diameter focused spots at the Cassegrain focus of 34-meter antennas. Assuming pulse-position modulation (PPM) and Poisson-distributed photon-counting detection, a "polished panel" photon-bucket receiver with large FOV will collect hundreds of background photons per PPM slot, along with comparable signal photons due to its large aperture. It is demonstrated that communications performance in terms of PPM symbol-error probability in high-background high-signal environments depends more strongly on signal than on background photons, implying that large increases in background energy can be compensated by a disproportionally small increase in signal energy. This surprising result suggests that large optical apertures with relatively poor surface quality may nevertheless provide acceptable performance for deep-space optical communications, potentially enabling the construction of cost-effective hybrid RF/optical receivers in the future.

  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

    2016-07-01

    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. 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.

  12. Partial feedback unstable resonator on small scale supersonic large aperture chemical laser

    Science.gov (United States)

    Wang, Hongyan; Wang, Rui; Li, Lei

    2015-05-01

    There is always a challenge on large aperture medium power laser's resonator design, stable resonator would supports significant higher order transverse modes, folded and telescope stable resonator are too complex and not preferred by engineers, unstable resonator need rather large round trip gain to compensate its high geometric out-coupling, which is difficult for this kind of laser since its gain length is limited due to the power level and large aperture. Partial feedback unstable resonator had been proposed to tackle this difficulty since the early days of laser development, however, the debates of its effect never stopped even with those distinguished optical resonator scientists such as Siegman, Anan'ev, and Weber. Recently integrated partial feedback unstable resonator design had been successfully demonstrated on a medium size chemical oxygen iodine laser. In this paper, we carry this resonator configuration on a small scale discharge driven supersonic nozzle array Hydrogen Fluoride chemical laser, a typical large aperture short gain length device. With magnification equals 4/3, we successfully get ten Watts level ring beam output.

  13. Advanced Technology Large-Aperture Space Telescope (ATLAST): A Technology Roadmap for the Next Decade

    CERN Document Server

    Postman, Marc

    2009-01-01

    The Advanced Technology Large-Aperture Space Telescope (ATLAST) is a set of mission concepts for the next generation of UVOIR space observatory with a primary aperture diameter in the 8-m to 16-m range that will allow us to perform some of the most challenging observations to answer some of our most compelling questions, including "Is there life elsewhere in the Galaxy?" We have identified two different telescope architectures, but with similar optical designs, that span the range in viable technologies. The architectures are a telescope with a monolithic primary mirror and two variations of a telescope with a large segmented primary mirror. This approach provides us with several pathways to realizing the mission, which will be narrowed to one as our technology development progresses. The concepts invoke heritage from HST and JWST design, but also take significant departures from these designs to minimize complexity, mass, or both. Our report provides details on the mission concepts, shows the extraordinary s...

  14. Eyeglass Large Aperture, Lightweight Space Optics FY2000 - FY2002 LDRD Strategic Initiative

    Energy Technology Data Exchange (ETDEWEB)

    Hyde, R

    2003-02-10

    A series of studies by the Air Force, the National Reconnaissance Office and NASA have identified the critical role played by large optics in fulfilling many of the space related missions of these agencies. Whether it is the Next Generation Space Telescope for NASA, high resolution imaging systems for NRO, or beam weaponry for the Air Force, the diameter of the primary optic is central to achieving high resolution (imaging) or a small spot size on target (lethality). While the detailed requirements differ for each application (high resolution imaging over the visible and near-infrared for earth observation, high damage threshold but single-wavelength operation for directed energy), the challenges of a large, lightweight primary optic which is space compatible and operates with high efficiency are the same. The advantage of such large optics to national surveillance applications is that it permits these observations to be carried-out with much greater effectiveness than with smaller optics. For laser weapons, the advantage is that it permits more tightly focused beams which can be leveraged into either greater effective range, reduced laser power, and/or smaller on-target spot-sizes; weapon systems can be made either much more effective or much less expensive. This application requires only single-wavelength capability, but places an emphasis upon robust, rapidly targetable optics. The advantages of large aperture optics to astronomy are that it increases the sensitivity and resolution with which we can view the universe. This can be utilized either for general purpose astronomy, allowing us to examine greater numbers of objects in more detail and at greater range, or it can enable the direct detection and detailed examination of extra-solar planets. This application requires large apertures (for both light-gathering and resolution reasons), with broad-band spectral capability, but does not emphasize either large fields-of-view or pointing agility. Despite

  15. Development of atmospheric pressure plasma processing machine tool for large aperture optics

    Science.gov (United States)

    Su, Xing; Wu, Yangong; Zhang, Peng; Xin, Qiang; Wang, Bo

    2016-10-01

    In recent years, major projects, such as National Ignition Facility and Laser Mégajoule, have generated great demands for large aperture optics with high surface accuracy and low Subsurface Damage (SSD) at the mean time. In order to remove SSD and improve surface quality, optics is fabricated by sub-aperture polishing. However, the efficiency of the sub-aperture polishing has been a bottleneck step for the optics manufacturing. Atmospheric Pressure Plasma Processing (APPP) as an alternate method offers high potential for speeding up the polishing process. This technique is based on chemical etching, hence there is no physical contact and no damage is induced. In this paper, a fast polishing machine tool is presented which is designed for fast polishing of the large aperture optics using APPP. This machine tool employs 3PRS-XY hybrid structure as its framework. There is a platform in the 3PRS parallel module to support the plasma generating system. And the large work piece is placed on the XY stage. In order to realize the complex motion trajectory for polishing the freeform optics, five axis of the tool operate simultaneously. To overcome the complexity of inverse kinematics calculation, a dedicated motion control system is also designed for speeding up the motion response. For high removal rate, the individual influence of several key processing parameters is investigated. And under specific production condition, this machine tool offers a high material over 30mm3/min for fused silica substrates. This results shows that APPP machine tool has a strong potential for fast polishing large optics without introducing SSD.

  16. Numerical Analysis of Large Diameter Butterfly Valve

    Science.gov (United States)

    Youngchul, Park; Xueguan, Song

    In this paper, a butterfly valve with the diameter of 1,800 mm was studied. Three-dimensional numerical technique by using commercial code CFX were conducted to observe the flow patterns and to measure flow coefficient, hydrodynamic torque coefficient and so on, when the large butterfly valve operated with various angles and uniform incoming velocity.

  17. High-numerical-aperture cryogenic light microscopy for increased precision of superresolution reconstructions.

    Science.gov (United States)

    Nahmani, Marc; Lanahan, Conor; DeRosier, David; Turrigiano, Gina G

    2017-04-11

    Superresolution microscopy has fundamentally altered our ability to resolve subcellular proteins, but improving on these techniques to study dense structures composed of single-molecule-sized elements has been a challenge. One possible approach to enhance superresolution precision is to use cryogenic fluorescent imaging, reported to reduce fluorescent protein bleaching rates, thereby increasing the precision of superresolution imaging. Here, we describe an approach to cryogenic photoactivated localization microscopy (cPALM) that permits the use of a room-temperature high-numerical-aperture objective lens to image frozen samples in their native state. We find that cPALM increases photon yields and show that this approach can be used to enhance the effective resolution of two photoactivatable/switchable fluorophore-labeled structures in the same frozen sample. This higher resolution, two-color extension of the cPALM technique will expand the accessibility of this approach to a range of laboratories interested in more precise reconstructions of complex subcellular targets.

  18. The effect of changing the numerical aperture in SHG microscopy of cartilage

    Science.gov (United States)

    Finnøy, Andreas; Olstad, Kristin; Lilledahl, Magnus B.

    2017-02-01

    Second harmonic generation (SHG) microscopy is a promising imaging technique for collagenous tissues due to its noninvasiveness and potential for 3D imaging. In tissues with densely packed and thin collagen fibrils, such as cartilage, the focal volume of the laser can comprise multiple fibrils, and the SHG from each of these fibrils can interact and contribute to the detected signal. Coherent amplification is achieved when the fibrils are aligned and oriented in the same direction. The effect of changing the size of the focal volume, as determined by the numerical aperture (NA), is therefore dependent on the length scale at which the fibrils are aligned. This effect on the image contrast is important to examine experimentally before SHG can be used in the clinic. In this study, we measured the SHG intensity and radiation direction as a function of the NA of the excitation and collecting objectives in different areas of the immature articular cartilage of young pigs. The results showed that varying the NA of the excitation objective had more effect on the SHG signals detected in the forward compared to the backward direction and that this effect varied considerably throughout the tissue. The results clearly demonstrated that SHG imaging differs from conventional histology, and the image contrast should only be interpreted in light of the imaging conditions.

  19. Phase-Change Media for High-Numerical-Aperture and Blue-Wavelength Recording

    Science.gov (United States)

    Borg, Herman J.; Schijndel, Mark van; Rijpers, Jan C. N.; Lankhorst, Martijn H. R.; Zhou, Guofu; Dekker, Martijn J.; Ubbens, Igolt P. D.; Kuijper, Maarten

    2001-03-01

    We have studied the feasibility of doped eutectic SbTe alloys for practical application in digital video recording (DVR) rewritable phase-change media for high-numerical-aperture (NA=0.85) and blue-wavelength (λ=405 nm) recording. Remaining issues such as thermal cross-erase in land/groove recording and the thermal stability of recorded amorphous marks have been investigated and resolved. This work has resulted in the realisation of 22.5 GB phase-change media complying with the DVR blue format. The future of doped eutectic SbTe alloys in the phase-change recording-speed race is also promising, as the crystallisation speed and archival life stability can be optimised more or less independently by tuning the Sb/Te atomic ratio and adding Ge, respectively. We have demonstrated that a user data transfer rate of 70 Mbit/s (DVR double speed) is within reach using our current phase-change composition, and are expecting to realise data rates of over 100 Mbit/s in the near future.

  20. 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.

  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, Olivier; Stark, Chris; Arenberg, Jon

    2016-07-01

    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 these missions.

  2. ATLAST-9.2m: a Large-Aperture Deployable Space Telescope

    Science.gov (United States)

    Oergerle, William; Feinberg, Lee D.; Purves, Lloyd R.; Hyde, T. Tupper; Thronson, Harley A.; Townsend, Jacqueline A.; Postman, Marc; Bolear, Matthew R.; Budinoff, Jason G.; Dean, Bruce H.; hide

    2010-01-01

    We present results of a study of a deployable version of the Advanced Technology Large-Aperture Space Telescope (ATLAST), designed to operate in a Sun-Earth L2 orbit. The primary mirror of the segmented 9.2-meter aperture has 36 hexagonal 1.315 m (flat to flat) glass mirrors. The architecture and folding of the telescope is similar to JWST, allowing it to fit into the 6.5 m fairing of a modest upgrade to the Delta-IV Heavy version of the Evolved Expendable Launch Vehicle (EELV). We discuss the overall observatory design, optical design, instruments, stray light, wavefront sensing and control, pointing and thermal control, and in-space servicing options.

  3. Detection of and compensation for blocked elements using large coherent apertures: ex vivo studies

    Science.gov (United States)

    Jakovljevic, Marko; Bottenus, Nick; Kuo, Lily; Kumar, Shalki; Dahl, Jeremy; Trahey, Gregg

    2016-04-01

    When imaging with ultrasound through the chest wall, it is not uncommon for parts of the array to get blocked by ribs, which can limit the acoustic window and significantly impede visualization of the structures of interest. With the development of large-aperture, high-element-count, 2-D arrays and their potential use in transthoracic imaging, detecting and compensating for the blocked elements is becoming increasingly important. We synthesized large coherent 2-D apertures and used them to image a point target through excised samples of canine chest wall. Blocked elements are detected based on low amplitude of their signals. As a part of compensation, blocked elements are turned off on transmit (Tx) and receive (Rx), and point-target images are created using: coherent summation of the remaining channels, compounding of intercostal apertures, and adaptive weighting of the available Tx/Rx channel-pairs to recover the desired k-space response. The adaptive compensation method also includes a phase aberration correction to ensure that the non-blocked Tx/Rx channel pairs are summed coherently. To evaluate the methods, we compare the point-spread functions (PSFs) and near-field clutter levels for the transcostal and control acquisitions. Specifically, applying k-space compensation to the sparse aperture data created from the control acquisition reduces sidelobes from -6.6 dB to -12 dB. When applied to the transcostal data in combination with phase-aberration correction, the same method reduces sidelobes only by 3 dB, likely due to significant tissue induced acoustic noise. For the transcostal acquisition, turning off blocked elements and applying uniform weighting results in maximum clutter reduction of 5 dB on average, while the PSF stays intact. Compounding reduces clutter by about 3 dB while the k-space compensation increases clutter magnitude to the non-compensated levels.

  4. Numerical solution of large Lyapunov equations

    Science.gov (United States)

    Saad, Youcef

    1989-01-01

    A few methods are proposed for solving large Lyapunov equations that arise in control problems. The common case where the right hand side is a small rank matrix is considered. For the single input case, i.e., when the equation considered is of the form AX + XA(sup T) + bb(sup T) = 0, where b is a column vector, the existence of approximate solutions of the form X = VGV(sup T) where V is N x m and G is m x m, with m small is established. The first class of methods proposed is based on the use of numerical quadrature formulas, such as Gauss-Laguerre formulas, applied to the controllability Grammian. The second is based on a projection process of Galerkin type. Numerical experiments are presented to test the effectiveness of these methods for large problems.

  5. Combining rotating-coil measurements of large-aperture accelerator magnets

    CERN Document Server

    AUTHOR|(CDS)2089510

    2016-10-05

    The rotating coil is a widely used tool to measure the magnetic field and the field errors in accelerator magnets. The coil has a length that exceeds the entire magnetic field along the longitudinal dimension of the magnet and gives therefore a two-dimensional representation of the integrated field. Having a very good precision, the rotating coil lacks in versatility. The fixed dimensions make it impractical and inapplicable in situations, when the radial coil dimension is much smaller than the aperture or when the aperture is only little covered by the coil. That being the case for rectangular apertures with large aspect ratio, where a basic measurement by the rotating coil describes the field only in a small area of the magnet. A combination of several measurements at different positions is the topic of this work. Very important for a combination is the error distribution on the measured field harmonics. To preserve the good precision of the higher-order harmonics, the combination must not rely on the main ...

  6. Relationship between the external aperture and hearing loss in large vestibular aqueduct syndrome

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Backgroud Large vestibular aqueduct syndrome (LVAS) is a major cause of hearing loss in childhood. This study aimed at measuring external aperture of enlargement of the vestibular aqueduct (EVA) and analyzing relationship between the size of external aperture and hearing loss.Methods Diagnostic criteria of LVAS were based on hearing loss and CT images. CT images of temporal bone of 100 LVAS patients were collected and 60 control subjects were reviewed retrospectively in the past 10 years. A battery of audiometric and vestibular function tests were performed. The width of the vestibular aqueduct (VA) was measured on axial CT images of the temporal bone.Results One hundred patients (65 men, 35 women) were diagnosed as having the isolated EVA. Hearing loss mostly occurred in early childhood. The diagnosis age of LVAS was 7.7 years on average. The causes of hearing loss could not be confirmed by initial consult. Typically, audiometric curve is the high-frequency down-sloping configuration. 92% of the cases had severe or profound sonsorineural hearing loss (SNHL). The mean size of the external aperture was (7.5±1.2) mm in present LVAS. Statistical analysis showed that the degree of hearing loss is unrelated to the width of VA. Conclusions LVAS is a distinct clinical entity characterized by fluctuating, progressive SNHL. The degree of hearing loss is unrelated to the size of external aperture of VA. The protective management and hearing aid have become the main therapies. The cochlear implantation might be performed if the hearing loss affected learning at school.

  7. A high numerical aperture (NA = 0.92) objective lens for imaging and addressing of cold atoms

    CERN Document Server

    Robens, Carsten; Alt, Wolfgang; Kleißler, Felix; Meschede, Dieter; Moon, Geol; Ramola, Gautam; Alberti, Andrea

    2016-01-01

    We have designed, built, and characterized a high-resolution objective lens that is compatible with an ultra-high vacuum environment. The lens system exploits the principle of the Weierstrass-sphere solid immersion lens to reach a numerical aperture (NA) of 0.92. Tailored to the requirements of optical lattice experiments, the objective lens features a relatively long working distance of 150 micrometers. Our two-lens design is remarkably insensitive to mechanical tolerances in spite of the large NA. Additionally, we demonstrate the application of a tapered optical fiber tip, as used in scanning near-field optical microscopy, to measure the point spread function of a high NA optical system. From the point spread function, we infer the wavefront aberration for the entire field of view of about 75 micrometers. Pushing the NA of an optical system to its ultimate limit enables novel applications in quantum technologies such as quantum control of atoms in optical microtraps with an unprecedented spatial resolution ...

  8. Large-aperture MOEMS Fabry-Perot interferometer for miniaturized spectral imagers

    Science.gov (United States)

    Rissanen, Anna; Langner, Andreas; Viherkanto, Kai; Mannila, Rami

    2015-02-01

    VTT's optical MEMS Fabry-Perot interferometers (FPIs) are tunable optical filters, which enable miniaturization of spectral imagers into small, mass producible hand-held sensors with versatile optical measurement capabilities. FPI technology has also created a basis for various hyperspectral imaging instruments, ranging from nanosatellites, environmental sensing and precision agriculture with UAVs to instruments for skin cancer detection. Until now, these application demonstrations have been mostly realized with piezo-actuated FPIs fabricated by non-monolithical assembly method, suitable for achieving very large optical apertures and with capacity to small-to-medium volumes; however large-volume production of MEMS manufacturing supports the potential for emerging spectral imaging applications also in large-volume applications, such as in consumer/mobile products. Previously reported optical apertures of MEMS FPIs in the visible range have been up to 2 mm in size; this paper presents the design, successful fabrication and characterization of MEMS FPIs for central wavelengths of λ = 500 nm and λ = 650 nm with optical apertures up to 4 mm in diameter. The mirror membranes of the FPI structures consist of ALD (atomic layer deposited) TiO2-Al2O3 λ/4- thin film Bragg reflectors, with the air gap formed by sacrificial polymer etching in O2 plasma. The entire fabrication process is conducted below 150 °C, which makes it possible to monolithically integrate the filter structures on other ICdevices such as detectors. The realized MEMS devices are aimed for nanosatellite space application as breadboard hyperspectral imager demonstrators.

  9. A novel hybrid surface micromachined segmented mirror for large aperture laser applications

    Institute of Scientific and Technical Information of China (English)

    Jie Li; Haiqing Chen; Hongbin Yu

    2006-01-01

    @@ A novel hybrid surface micromachined segmented mirror array is described. This device is capable of scaling to large apertures for correcting time-varying aberrations in laser applications. Each mirror is composed of bottom electrode, support part, and mirror plate, in which a T-shaped beam structure is used to support the mirror plate. It can provide mirror with vertical movement and rotation around two horizontal axes. The test results show that the maximum deflection along the vertical direction of the mirror plate is 2μm, while the rotation angles around x and y axes are ±2.3° and ±1.45°, respectively.

  10. End-to-End Assessment of a Large Aperture Segmented Ultraviolet Optical Infrared (UVOIR) Telescope Architecture

    Science.gov (United States)

    Feinberg, Lee; Bolcar, Matt; Liu, Alice; Guyon, Olivier; 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.

  11. Development of an efficient large-aperture high damage-threshold sol-gel diffraction grating.

    Energy Technology Data Exchange (ETDEWEB)

    Ashley, Carol S.; Rambo, Patrick K.; Schwarz, Jens; Dunphy, Darren Robert; Branson, Eric D.; Smith, Ian Craig; Johnson, William Arthur; Reed, Scott T.; Cook, Adam W.

    2005-03-01

    In order to develop the next generation of high peak intensity lasers, new grating technology providing higher damage thresholds and large apertures is required. The current assumption is that this technical innovation will be multilayer dielectric gratings, wherein the uppermost layer of a thin film mirror is etched to create the desired binary phase grating. A variant of this is explored with the upper grating layer being a lower density gelatin-based volume phase grating in either sol-gel or dichromated gelatin. One key benefit is the elimination of the etching step.

  12. Spacecraft Conceptual Design for the 8-Meter Advanced Technology Large Aperture Space Telescope (ATLAST)

    Science.gov (United States)

    Hopkins, Randall C.; Capizzo, Peter; Fincher, Sharon; Hornsby, Linda S.; Jones, David

    2010-01-01

    The Advanced Concepts Office at Marshall Space Flight Center completed a brief spacecraft design study for the 8-meter monolithic Advanced Technology Large Aperture Space Telescope (ATLAST-8m). This spacecraft concept provides all power, communication, telemetry, avionics, guidance and control, and thermal control for the observatory, and inserts the observatory into a halo orbit about the second Sun-Earth Lagrange point. The multidisciplinary design team created a simple spacecraft design that enables component and science instrument servicing, employs articulating solar panels for help with momentum management, and provides precise pointing control while at the same time fast slewing for the observatory.

  13. A large aperture reflective wave-plate for high-intensity short-pulse laser experiments

    CERN Document Server

    Aurand, Bastian; Zhao, Huanyu; Kuschel, Stephan; Wünsche, Martin; Jäckel, Oliver; Heyer, Martin; Wunderlich, Frank; Kaluza, Malte C; Paulus, Gerhard G; Kuehl, Thomas

    2012-01-01

    We report on a reflective wave-plate system utilizing phase-shifting mirrors (PSM) for a continuous variation of elliptical polarization without changing the beam position and direction. The scalability of multilayer optics to large apertures and the suitability for high-intensity broad-bandwidth laser beams make reflective wave-plates an ideal tool for experiments on relativistic laser-plasma interaction. Our measurements confirm the preservation of the pulse duration and spectrum when a 30-fs Ti:Sapphire laser beam passes the system.

  14. Compact large-aperture Fabry-Perot interferometer modules for gas spectroscopy at mid-IR

    Science.gov (United States)

    Kantojärvi, Uula; Varpula, Aapo; Antila, Tapani; Holmlund, Christer; Mäkynen, Jussi; Näsilä, Antti; Mannila, Rami; Rissanen, Anna; Antila, Jarkko; Disch, Rolf J.; Waldmann, Torsten A.

    2014-03-01

    VTT has developed Fabry-Pérot Interferometers (FPI) for visible and infrared wavelengths since 90's. Here we present two new platforms for mid-infrared gas spectroscopy having a large optical aperture to provide high optical throughput but still enabling miniaturized instrument size. First platform is a tunable filter that replaces a traditional filter wheel, which operates between wavelengths of 4-5 um. Second platform is for correlation spectroscopy where the interferometer provides a comb-like transmission pattern mimicking absorption of diatomic molecules at the wavelength range of 4.7-4.8 um. The Bragg mirrors have 2-4 thin layers of polysilicon and silicon oxide.

  15. Research on new-style flexure supports method for large-aperture transport mirror mounting

    Science.gov (United States)

    Quan, Xusong; Zhang, Zheng; Xiong, Zhao; Wang, Hui; Yuan, Xiaodong; Liu, Changchun

    2016-10-01

    In high-power solid-state laser facility (SG-III), focusing laser beams into the target center with precision better than 50 microns (RMS) is dependent on the stringent specifications of thousands of large-aperture transport mirror units and is a huge challenge on the surface aberration control of mirrors. The current mirror's mounting techniques with screw fastening loads has several engineering conundrums - low control precision for loads (higher scatter even +/-30%), and low assembly-rectification efficiency ( 100 screws). To improve the current screw-fastening method, a new-style flexure supports method, which has a wonderful performance on uniform control of the external loads and only uses 30 screws, is proposed to mount the mirror (size: 610mm×440mm×85mm). With theoretical modeling and FEM analysis, the impacts of mounting loads on mirror's surface aberrations are analyzed and discussed in detail, and the flexure supports system is designed. Finally, with experimental research and case studies, the proposed flexure supports method shows a powerful performance on even control precision of external loads with scatter even less than +/-10%, which is a promising mounting process to replace the threaded fasteners mounting the large-aperture optics. These improvements can lay a foundation for mounting process consistency, robustness, and assembly-rectification efficiency of large optical component.

  16. A low-cost large-aperture optical receiver for remote sensing and imaging applications

    Science.gov (United States)

    Hanes, Stephen A.

    2003-03-01

    An inexpensive large aperture (10 m class) receiver for optical wavelength imaging and remote sensing applications is discussed. The design was developed for active (laser illumination) imaging of remote objects using pupil plane measurement techniques, where relatively low optical quality collecting elements can be used. The approach is also well suited for conventional imaging at lower resolutions when light collection capability is of primary importance. The approach relies on a large aperture heliostat consisting of an array of flat mirror segments, like those used in solar collector systems, to collect light from the region of interest. The heliostat segments are tilted in a manner to concentrate the light, by making the light from all segments overlap at a common point, resulting in a region of higher intensity about the size of a segment at the heliostat "focus". A smaller secondary collector, consisting of a concave mirror located at the overlap point, further concentrates the light and forms a pupil image of the heliostat. Additional optics near the pupil image collimate the light for efficient transmission though a narrow band interference filter used to reduce sky background, and focus the light onto a PMT, or other sensor, for detection. Several design approaches for the collimating optics are discussed as well as system performance and limitations.

  17. Designs for a large-aperture telescope to map the CMB 10× faster.

    Science.gov (United States)

    Niemack, Michael D

    2016-03-01

    Current large-aperture cosmic microwave background (CMB) telescopes have nearly maximized the number of detectors that can be illuminated while maintaining diffraction-limited image quality. The polarization-sensitive detector arrays being deployed in these telescopes in the next few years will have roughly 10⁴ detectors. Increasing the mapping speed of future instruments by at least an order of magnitude is important to enable precise probes of the inflationary paradigm in the first fraction of a second after the big bang and provide strong constraints on cosmological parameters. The CMB community has begun planning a next generation "Stage IV" CMB project that will be comprised of multiple telescopes with between 10⁵-10⁶ detectors to pursue these goals. This paper introduces the new crossed Dragone telescope and receiver optics designs that increase the usable diffraction-limited field-of-view, and therefore the mapping speed, by an order of magnitude compared to the upcoming generation of large-aperture instruments. Polarization systematics and engineering considerations are presented, including a preliminary receiver model to demonstrate that these designs will enable high efficiency illumination of >10⁵ detectors in a next generation CMB telescope.

  18. Pattern transfer on large samples using a sub-aperture reactive ion beam

    Energy Technology Data Exchange (ETDEWEB)

    Miessler, Andre; Mill, Agnes; Gerlach, Juergen W.; Arnold, Thomas [Leibniz-Institut fuer Oberflaechenmodifizierung (IOM), Permoserstrasse 15, D-04318 Leipzig (Germany)

    2011-07-01

    In comparison to sole Ar ion beam sputtering Reactive Ion Beam Etching (RIBE) reveals the main advantage of increasing the selectivity for different kind of materials due to chemical contributions during the material removal. Therefore RIBE is qualified to be an excellent candidate for pattern transfer applications. The goal of the present study is to apply a sub-aperture reactive ion beam for pattern transfer on large fused silica samples. Concerning this matter, the etching behavior in the ion beam periphery plays a decisive role. Using CF{sub 4} as reactive gas, XPS measurements of the modified surface exposes impurities like Ni, Fe and Cr, which belongs to chemically eroded material of the plasma pot as well as an accumulation of carbon (up to 40 atomic percent) in the beam periphery, respectively. The substitution of CF{sub 4} by NF{sub 3} as reactive gas reveals a lot of benefits: more stable ion beam conditions in combination with a reduction of the beam size down to a diameter of 5 mm and a reduced amount of the Ni, Fe and Cr contaminations. However, a layer formation of silicon nitride handicaps the chemical contribution of the etching process. These negative side effects influence the transfer of trench structures on quartz by changing the selectivity due to altered chemical reaction of the modified resist layer. Concerning this we investigate the pattern transfer on large fused silica plates using NF{sub 3}-sub-aperture RIBE.

  19. Large aperture N31 neodymium phosphate laser glass for use in a high power laser facility

    Institute of Scientific and Technical Information of China (English)

    Lili; Hu; Shubin; Chen; Jingping; Tang; Biao; Wang; Tao; Meng; Wei; Chen; Lei; Wen; Junjiang; Hu; Shunguang; Li; Yongchun; Xu; Yasi; Jiang; Junzhou; Zhang; Zhonghong; Jiang

    2014-01-01

    Large aperture Nd:phosphate laser glass is a key optical element for an inertial confinement fusion(ICF) facility. N31,one type of neodymium doped phosphate glasses, was developed for high peak power laser facility applications in China. The composition and main properties of N31 glass are given, together with those of LHG-8, LG-770, and KGSS-0180 Nd:phosphate laser glasses, from Hoya and Schott, and from Russia. The technologies of pot melting, continuous melting, and edge cladding of large size N31 phosphate laser glass are briefly described. The small signal gain profiles of N31 glass slabs from both pot melting and continuous melting at various values of the pumping energy of the xenon lamp are presented. N31 glass is characterized by a stimulated emission cross section of 3.8 × 10-20cm2 at 1053 nm,an absorption coefficient of 0.10–0.15% cm-1at laser wavelength, small residual stress around the interface between the cladding glass and the laser glass, optical homogeneity of ~2 × 10-6in a 400 mm aperture, and laser damage threshold larger than 42 J/cm2 for a 3 ns pulse width at 1064 nm wavelength.

  20. Study on supporting force sensing and control during large aperture space mirror test

    Science.gov (United States)

    Zhang, Long; Hu, Wenqi; Zheng, Liehua; Hao, Peiming

    2016-10-01

    During the machining of large aperture lightweight space mirror, the mirror figure consistency between ground test and space mission is a problem. In order to effectively control the supporting deformation effect on test results in gravity environment, in view of a 1.2-m space mirror with back blind holes, a supporting method for optical axis horizontal test is proposed, with this method, mirror under test is positioned by three center hole surfaces and supported by six external hole surfaces. The effect of deformation caused by different supporting force value, area and position is analyzed by finite element method, the simulation results show that this supporting method can control the mirror supporting deformation within PV0.035λ rms0.005λ. The actual supporting system uses soft expansion mandrel to control the mirror position and pneumatic lever to realize the floating support. In order to ensure that the support force can evenly distribute on the contact surface, a pressure mapping system is adopted to measure the interface pressure between the mirror blind holes and the soft supporting pads for the first time. This method can meet the test requirements of rms=1/40λ mirror and provides a technical support for high precision test of large aperture space mirror with back blind holes.

  1. Development of large aperture projection scatterometry for catalyst loading evaluation in proton exchange membrane fuel cells

    Science.gov (United States)

    Stocker, Michael T.; Barnes, Bryan M.; Sohn, Martin; Stanfield, Eric; Silver, Richard M.

    2017-10-01

    Widespread commercialization of proton exchange membrane fuel cells remains curbed by various manufacturing and infrastructure challenges. One such technical barrier identified by the U. S. Department of Energy is the need for high-speed, in-line process control of platinum-based catalyst layers in the membrane electrode assembly of the fuel cell. Using multiple reflectivity-based optical methods, such as optical scatterometry and large aperture projection scatterometry, we demonstrate in-line-capable catalyst loading measurements of carbon-supported Pt nanoparticle and Pt-alloy nanostructured thin film catalyst coated membranes. Large aperture projection scatterometry is a new high-throughput approach developed at the National Institute of Standards and Technology specifically for fuel cell manufacturing metrology. Angle- and wavelength-resolved measurements of these fuel cell soft goods validate the ability of reflectivity-based measurements to produce industrially relevant sensitivities to changes in Pt and Pt-alloy loading. The successful application of these optical methods to fuel cell manufacturing metrology directly addresses the shortage of high-throughput process control approaches needed to facilitate performance improvements and manufacturing cost-reductions required to make fuel cells commercially viable.

  2. Diffractive imaging analysis of large-aperture segmented telescope based on partial Fourier transform

    Science.gov (United States)

    Dong, Bing; Qin, Shun; Hu, Xinqi

    2013-09-01

    Large-aperture segmented primary mirror will be widely used in next-generation space-based and ground-based telescopes. The effects of intersegment gaps, obstructions, position and figure errors of segments, which are all involved in the pupil plane, on the image quality metric should be analyzed using diffractive imaging theory. Traditional Fast Fourier Transform (FFT) method is very time-consuming and costs a lot of memory especially in dealing with large pupil-sampling matrix. A Partial Fourier Transform (PFT) method is first proposed to substantially speed up the computation and reduce memory usage for diffractive imaging analysis. Diffraction effects of a 6-meter segmented mirror including 18 hexagonal segments are simulated and analyzed using PFT method. The influence of intersegment gaps and position errors of segments on Strehl ratio is quantitatively analyzed by computing the Point Spread Function (PSF). By comparing simulation results with theoretical results, the correctness and feasibility of PFT method is confirmed.

  3. Numerical simulation of large fabric filter

    Directory of Open Access Journals (Sweden)

    Kovařík Petr

    2012-04-01

    Full Text Available Fabric filters are used in the wide range of industrial technologies for cleaning of incoming or exhaust gases. To achieve maximal efficiency of the discrete phase separation and long lifetime of the filter hoses, it is necessary to ensure uniform load on filter surface and to avoid impacts of heavy particles with high velocities to the filter hoses. The paper deals with numerical simulation of two phase flow field in a large fabric filter. The filter is composed of six chambers with approx. 1600 filter hoses in total. The model was simplified to one half of the filter, the filter hoses walls were substituted by porous zones. The model settings were based on experimental data, especially on the filter pressure drop. Unsteady simulations with different turbulence models were done. Flow field together with particles trajectories were analyzed. The results were compared with experimental observations.

  4. Numerical simulation of large fabric filter

    Science.gov (United States)

    Sedláček, Jan; Kovařík, Petr

    2012-04-01

    Fabric filters are used in the wide range of industrial technologies for cleaning of incoming or exhaust gases. To achieve maximal efficiency of the discrete phase separation and long lifetime of the filter hoses, it is necessary to ensure uniform load on filter surface and to avoid impacts of heavy particles with high velocities to the filter hoses. The paper deals with numerical simulation of two phase flow field in a large fabric filter. The filter is composed of six chambers with approx. 1600 filter hoses in total. The model was simplified to one half of the filter, the filter hoses walls were substituted by porous zones. The model settings were based on experimental data, especially on the filter pressure drop. Unsteady simulations with different turbulence models were done. Flow field together with particles trajectories were analyzed. The results were compared with experimental observations.

  5. A free-air ionization chamber with a large aperture diaphragm

    Energy Technology Data Exchange (ETDEWEB)

    Takata, N., E-mail: n.takata@aist.go.j [Ionizing Radiation Section, NMIJ, AIST, Tsukuba, Ibaraki 305-8568 (Japan)

    2010-07-21

    Calculations of the electric field distributions in free-air ionization chambers reveal that the distortion of the charge collection volume is small even for wide X-ray beam passage if the diaphragm and the X-ray shielding box are kept at a potential equal to half that applied to the high-voltage electrode. Applying this potential to the diaphragm and the shielding box permits a larger aperture diaphragm to be used. This will allow a wider X-ray beam to enter the chamber, thus generating a larger signal. In addition, the distance between the diaphragm and the charge collection volume can be shortened to reduce the amount of X-ray attenuation. It is also possible to calibrate a dosimeter against a free-air ionization chamber that has a diaphragm whose aperture size is equal to the size of the dosimeter in an X-ray field that is collimated to the same size. This is important since free-air ionization chambers are not sensitive to X-rays that are incident at large angles, such as those scattered by the collimator, filters and air.

  6. Signal-to-noise ratio of Singer product apertures

    Science.gov (United States)

    Shutler, Paul M. E.; Byard, Kevin

    2017-09-01

    Formulae for the signal-to-noise ratio (SNR) of Singer product apertures are derived, allowing optimal Singer product apertures to be identified, and the CPU time required to decode them is quantified. This allows a systematic comparison to be made of the performance of Singer product apertures against both conventionally wrapped Singer apertures, and also conventional product apertures such as square uniformly redundant arrays. For very large images, equivalently for images at very high resolution, the SNR of Singer product apertures is asymptotically as good as the best conventional apertures, but Singer product apertures decode faster than any conventional aperture by at least a factor of ten for image sizes up to several megapixels. These theoretical predictions are verified using numerical simulations, demonstrating that coded aperture video is for the first time a realistic possibility.

  7. Operating Water Cherenkov Detectors in high altitude sites for the Large Aperture GRB Observatory

    CERN Document Server

    Allard, D; Asorey, H; Barros, H; Bertou, X; Castillo, M; Chirinos, J M; De Castro, A; Flores, S; González, J; Berisso, M Gomez; Grajales, J; Guada, C; Day, W R Guevara; Ishitsuka, J; López, J A; Martínez, O; Melfo, A; Meza, E; Loza, P Miranda; Barbosa, E Moreno; Murrugarra, C; Núñez, L A; Ormachea, L J Otiniano; Pérez, G; Perez, Y; Ponce, E; Quispe, J; Quintero, C; Rivera, H; Rosales, M; Rovero, A C; Saavedra, O; Salazar, H; Tello, J C; Peralda, R Ticona; Varela, E; Velarde, A; Villaseñor, L; Wahl, D; Zamalloa, M A

    2009-01-01

    Water Cherenkov Detectors (WCD) are efficient detectors for detecting GRBs in the 10 GeV - 1 TeV energy range using the single particle technique, given their sensitivity to low energy secondary photons produced by high energy photons when cascading in the atmosphere. The Large Aperture GRB Observatory (LAGO) operates arrays of WCD in high altitude sites (above 4500 m a.s.l.) in Bolivia, Mexico and Venezuela, with planned extension to Peru. Details on the operation and stability of these WCD in remote sites with high background rates of particles will be detailed, and compared to simulations. Specific issues due to operation at high altitude, atmospheric effects and solar activity, as well as possible hardware enhancements will also be presented.

  8. The Balloon-borne Large Aperture Submillimetre Telescope (BLAST) and BLASTPol

    Science.gov (United States)

    Pascale, Enzo; Pascale

    2013-01-01

    Balloon observations from Antarctica have proven an effective and efficient way to address open Cosmological questions as well as problems in Galactic astronomy. The Balloon-borne Large Aperture Submillimetre Telescope (BLAST) is a sub-orbital mapping experiment which uses 270 bolometric detectors to image the sky in three wavebands centred at 250, 350 and 500 μm with a 1.8 m telescope. In the years before Herschel launched, BLAST provided data of unprecedented angular and spectral coverage in frequency bands close to the peak of dust emission in star forming regions in our Galaxy, and in galaxies at cosmological distances. More recently, BLASTPol was obtained by reconfiguring the BLAST focal plane as a submillimetric polarimeter to study the role that Galactic magnetic fields have in regulating the processes of star-formation. The first and successful BLASTPol flight from Antarctica in 2010 is followed by a second flight, currently scheduled for the end of 2012.

  9. A cryogenic rotation stage with a large clear aperture for a half-wave plate

    CERN Document Server

    Bryan, Sean; Amiri, Mandana; Benton, Steven; Bihary, Richard; Bock, James; Bond, J Richard; Chiang, H Cynthia; Contaldi, Carlo; Crill, Brendan; Dore, Olivier; Elder, Benjamin; Filippini, Jeffrey; Fraisse, Aurelien; Gambrel, Anne; Gandilo, Natalie; Gudmundsson, Jon; Hasselfield, Matthew; Halpern, Mark; Hilton, Gene; Holmes, Warren; Hristov, Viktor; Irwin, Kent; Jones, William; Kermish, Zigmund; Lawrie, Craig; MacTavish, Carrie; Mason, Peter; Megerian, Krikor; Moncelsi, Lorenzo; Montroy, Thomas; Morford, Tracy; Nagy, Johanna; Netterfield, C Barth; Rahlin, Alexandra S; Reintsema, Carl; Riley, Daniel C; Ruhl, John; Runyan, Marcus; Saliwanchik, Benjamin; Shariff, Jamil; Soler, Juan; Trangsrud, Amy; Tucker, Carole; Tucker, Rebecca; Turner, Anthony; Wen, Shyang; Wiebe, Donald; Young, Edward

    2016-01-01

    We describe the cryogenic half-wave plate rotation mechanisms built for and used in Spider, a polarization-sensitive balloon-borne telescope array that observed the Cosmic Microwave Background at 95 GHz and 150 GHz during a stratospheric balloon flight from Antarctica in January 2015. The mechanisms operate at liquid helium temperature in flight. A three-point contact design keeps the mechanical bearings relatively small but allows for a large (305 mm) diameter clear aperture. A worm gear driven by a cryogenic stepper motor allows for precise positioning and prevents undesired rotation when the motors are depowered. A custom-built optical encoder system monitors the bearing angle to an absolute accuracy of 0.1 degrees. The system performed well in Spider during its successful 16 day flight.

  10. Development of a large aperture Nb$_{3}$ Sn racetrack quadrupole magnet

    CERN Document Server

    Ferracin, Paolo; Caspi, Shlomo; Dietderich, D R; Gourlay, Stephen A; Hafalia, Aurelio R; Hannaford, C R; Lietzke, A F; Mattafirri, Sara; McInturff, A D; Nyman, M A; Sabbi, Gianluca

    2005-01-01

    The U.S. LHC Accelerator Research Program (LARP), a collaboration between BNL, FNAL, LBNL, and SLAC, has among its major objectives the development of advanced magnet technology for an LHC luminosity upgrade. The LBNL Superconducting Magnet Group supports this program with a broad effort involving design studies, Nb/sub 3/Sn conductor development, mechanical models, and basic prototypes. This paper describes the development of a large aperture Nb/sub 3/Sn racetrack quadrupole magnet using four racetrack coils from the LBNL Subscale Magnet (SM) Program. The magnet provides a gradient of 95 T/m in a 110 mm bore, with a peak field in the conductor of 11.2 T. The coils are pre-stressed by a mechanical structure based on a pre-tensioned aluminum shell, and axially supported with aluminum rods. The mechanical behavior has been monitored with strain gauges and the magnetic field has been measured. Results of the test are reported and analyzed.

  11. Large aperture discharge-pumped KrF laser for picosecond amplification

    CERN Document Server

    Yuan Xiao; LiuJingRu; Goldhar, J

    2002-01-01

    A large aperture discharge-pumped KrF laser module with simple spark gaps was developed. The laser beam cross section of 4 cm x 3 cm and the maximum laser output energy of 1.3J in 20ns were obtained at the charging voltage of 30 kV and gas mixtures of [F sub 2] : [Kr] : [Ne] = 0.1 : 2 : 97.9. The gain and absorption coefficients at different gas mixtures were measured with a frequency doubled dye laser pumped by a XeCl laser. Using this laser module as a ps amplifier, the output energy of 140 mJ in 10 ps was obtained

  12. Large Aperture Scintillometer Used Over A Homogeneous Irrigated Area, Partly Affected By Regional Advection

    Science.gov (United States)

    Hoedjes, J. C. B.; Zuurbier, R. M.; Watts, C. J.

    Scintillometer measurements were collected over an irrigated wheat field ina semi-arid region in northwest Mexico. Conditions were unstable in the morning andstable during the afternoon, while latent heat fluxes remained high throughout the day.Regional advection was observed during near-neutral conditions. Monin-Obukhovsimilarity relationships for the structure parameter of temperature were verified in both unstable and stable conditions, but were violated close to near-neutral conditions. We found that, using additional measurements of radiation, soil heat flux and windspeed, areally averages of both sensible and latent heat fluxes can be reliably predicted by large aperture scintillometer measurements, as long as the net radiation is greater than zero.

  13. A large-aperture telescope to map the CMB 10X faster

    CERN Document Server

    Niemack, Michael D

    2015-01-01

    Current large-aperture cosmic microwave background (CMB) telescopes have nearly maximized the number of detectors that can be illuminated while maintaining diffraction-limited image quality. The polarization-sensitive detector arrays being deployed in these telescopes in the next few years will have roughly $10^4$ detectors. Increasing the mapping speed of future instruments by at least an order of magnitude is important to enable precise probes of the inflationary paradigm in the first fraction of a second after the big bang and provide strong constraints on cosmological parameters. This paper introduces new crossed Dragone telescope and receiver optics designs that increase the usable diffraction-limited field-of-view, and therefore the mapping speed, by over an order of magnitude to enable high efficiency illumination of $>10^5$ detectors in a next generation CMB telescope.

  14. Energy measurement system of a large-aperture high power laser experiment platform

    Institute of Scientific and Technical Information of China (English)

    Yanwen; Xia; Yue; Liang; Sen; Li; Junpu; Zhao; Zhitao; Peng; Hongguang; Li; Hua; Liu; Zhihong; Sun; Kuixing; Zheng; Xiaofeng; Wei

    2013-01-01

    An energy measurement system in a large-aperture high power laser experiment platform is introduced. The entire measurement system includes five calorimeters, which carry out the energy measurement of the fundamental frequency before the frequency conversion unit, remaining fundamental frequency, remaining second-harmonics, third-harmonics,as well as the energy balance measurement after the frequency conversion unit. Combinational indirect calibration and direct calibration are employed to calibrate the sampling coefficients of the calorimeters. The analysis of the data showed that, regarding the energy balance coefficients, combinational calibration approach gives a higher precision, and leads to an energy balance with 1%; and regarding the energy sampling coefficients for the various wavelengths after the frequency conversion, the results from direct and combinational calibration are consistent. The uncertainties for all energy sampling coefficients are within 3%, which guarantees the reliability of the energy measurement for the laser facility.

  15. Thermal design and performance of the balloon-borne large aperture submillimeter telescope for polarimetry BLASTPol

    CERN Document Server

    Soler, J D; Angilè, F E; Benton, S J; Devlin, M J; Dober, B; Fissel, L M; Fukui, Y; Galitzki, N; Gandilo, N N; Klein, J; Korotkov, A L; Matthews, T G; Moncelsi, L; Mroczkowski, A; Netterfield, C B; Novak, G; Nutter, D; Pascale, E; Poidevin, F; Savini, G; Scott, D; Shariff, J A; Thomas, N E; Truch, M D; Tucker, C E; Tucker, G S; Ward-Thompson, D

    2014-01-01

    We present the thermal model of the Balloon-borne Large-Aperture Submillimeter Telescope for Polarimetry (BLASTPol). This instrument was successfully flown in two circumpolar flights from McMurdo, Antarctica in 2010 and 2012. During these two flights, BLASTPol obtained unprecedented information about the magnetic field in molecular clouds through the measurement of the polarized thermal emission of interstellar dust grains. The thermal design of the experiment addresses the stability and control of the payload necessary for this kind of measurement. We describe the thermal modeling of the payload including the sun-shielding strategy. We present the in-flight thermal performance of the instrument and compare the predictions of the model with the temperatures registered during the flight. We describe the difficulties of modeling the thermal behavior of the balloon-borne platform and establish landmarks that can be used in the design of future balloon-borne instruments.

  16. Terahertz Radiation from Large Aperture Bulk Semi-insulating GaAs Photoconductive Dipole Antenna

    Institute of Scientific and Technical Information of China (English)

    施卫; 贾婉丽; 侯磊; 许景周; 张希成

    2004-01-01

    We report the experimental results of a large-aperture biased semi-insulating GaAs photoconductive dipole antenna, with a gap of 3mm between two Au/Ge/Ni electrodes, triggered by 800nm Ti-sapphire laser pulses with 82 MHz repetition rate. A direct comparison is made between insulated GaAs dipole antenna with a Si3N4 layer and bare GaAs dipole antenna. Both the current in the antenna and the radiation amplitude present as linear to the exciting power when the applied voltage is fixed. The Si3N4 insulated GaAs dipole antenna can hold higher biased voltage than a normal GaAs dipole antenna; its terahertz radiation generation efficiency is significantly higher than that of a normal GaAs dipole antenna.

  17. ATLAST-9.2: A Deployable Large Aperture UVOIR Space Telescope

    Science.gov (United States)

    Oegerle, William R.; Feinberg, L.; Purves, L.; Hyde, T.; Thronson, H.; Townsend, J.; Postman, M.; Bolcar, M.; Budinoff, J.; Dean, B.; hide

    2010-01-01

    We present the results of a study of a deployable version of the Advanced Technology Large Aperture Space Telescope (ATLAST) that could be launched on an Evolved Expendable Launch Vehicle (EELV). ATLAST is a concept for a next-generation UVOIR observatory to follow HST and JWST. The observatory retains significant heritage from JWST, thereby taking advantage of technologies and engineering already developed for that mission. At the same time, we have identified several design changes to the JWST architecture, some of which are required due to the demanding wavefront error requirements at visible wavelengths. The optical telescope assembly has a segmented 9.2-meter aperture and consists of 36 hexagonal glass mirrors, each of which is I.3l5m in size (flat-to-flat). The telescope can be folded to fit in the 6.5m fairing on the planned upgrade to the Delta-IV heavy launch vehicle. Near-real time wavefront sensing and control is performed on-board the telescope using stars in the field of view to deliver diffraction limited imaging performance at 500nm wavelength. The optical design of the telescope provides an 8x20 arcmin FOV in which 4-5 instruments can be accommodated, plus fine guidance and wavefront sensors. Unlike JWST, the OTA sits at the end of a multi-gimbaled arm, allowing pitch and roll motion, and is isolated from the sunshield and spacecraft bus by an active isolation system. Our design permits servicing in order to extend the life of the observatory.

  18. ATLAST-9.2: A Deployable Large Aperture UVOIR Space Telescope

    Science.gov (United States)

    Oegerle, William R.; Feinberg, L.; Purves, L.; Hyde, T.; Thronson, H.; Townsend, J.; Postman, M.; Bolcar, M.; Budinoff, J.; Dean, B.; Clampin, M.; Ebbets, D.; Gong, Q.; Gull, T.; Howard, J.; Jones, A.; Lyon, R.; Pasquale, B.; Perrygo, C.; Smith, S.; Thompson, P.; Woodgate, B.

    2010-01-01

    We present the results of a study of a deployable version of the Advanced Technology Large Aperture Space Telescope (ATLAST) that could be launched on an Evolved Expendable Launch Vehicle (EELV). ATLAST is a concept for a next-generation UVOIR observatory to follow HST and JWST. The observatory retains significant heritage from JWST, thereby taking advantage of technologies and engineering already developed for that mission. At the same time, we have identified several design changes to the JWST architecture, some of which are required due to the demanding wavefront error requirements at visible wavelengths. The optical telescope assembly has a segmented 9.2-meter aperture and consists of 36 hexagonal glass mirrors, each of which is 1.315m in size (flat-to-flat). The telescope can be folded to fit in the 6.5m fairing on the planned upgrade to the Delta-IV heavy launch vehicle. Near-real time wavefront sensing and control is performed on-board the telescope using stars in the field of view to deliver diffraction limited imaging performance at 500nm wavelength. The optical design of the telescope provides an 8x20 arcmin FOV in which 4-5 instruments can be accommodated, plus fine guidance and wavefront sensors. Unlike JWST, the OTA sits at the end of a multi-gimbaled arm, allowing pitch and roll motion, and is isolated from the sunshield and spacecraft bus by an active isolation system. Our design permits servicing in order to extend the life of the observatory.

  19. Hybrid Electrostatic/Flextensional Mirror for Lightweight, Large-Aperture, and Cryogenic Space Telescopes

    Science.gov (United States)

    Patrick, Brian; Moore, James; Hackenberger, Wesley; Jiang, Xiaoning

    2013-01-01

    A lightweight, cryogenically capable, scalable, deformable mirror has been developed for space telescopes. This innovation makes use of polymer-based membrane mirror technology to enable large-aperture mirrors that can be easily launched and deployed. The key component of this innovation is a lightweight, large-stroke, cryogenic actuator array that combines the high degree of mirror figure control needed with a large actuator influence function. The latter aspect of the innovation allows membrane mirror figure correction with a relatively low actuator density, preserving the lightweight attributes of the system. The principal components of this technology are lightweight, low-profile, high-stroke, cryogenic-capable piezoelectric actuators based on PMN-PT (piezoelectric lead magnesium niobate-lead titanate) single-crystal configured in a flextensional actuator format; high-quality, low-thermal-expansion polymer membrane mirror materials developed by NeXolve; and electrostatic coupling between the membrane mirror and the piezoelectric actuator assembly to minimize problems such as actuator print-through.

  20. A Future Large-Aperture UVOIR Space Observatory: Key Technologies and Capabilities

    Science.gov (United States)

    Bolcar, Matthew Ryan; Stahle, Carl M.; Balasubramaniam, Kunjithapatham; Clampin, Mark; Feinberg, Lee D.; Mosier, Gary E.; Quijada, Manuel A.; Rauscher, Bernard J.; Redding, David C.; Rioux, Norman M.; hide

    2015-01-01

    We present the key technologies and capabilities that will enable a future, large-aperture ultravioletopticalinfrared (UVOIR) space observatory. These include starlight suppression systems, vibration isolation and control systems, lightweight mirror segments, detector systems, and mirror coatings. These capabilities will provide major advances over current and near-future observatories for sensitivity, angular resolution, and starlight suppression. The goals adopted in our study for the starlight suppression system are 10-10 contrast with an inner working angle of 20 milliarcsec and broad bandpass. We estimate that a vibration and isolation control system that achieves a total system vibration isolation of 140 dB for a vibration-isolated mass of 5000 kg is required to achieve the high wavefront error stability needed for exoplanet coronagraphy. Technology challenges for lightweight mirror segments include diffraction-limited optical quality and high wavefront error stability as well as low cost, low mass, and rapid fabrication. Key challenges for the detector systems include visible-blind, high quantum efficiency UV arrays, photon counting visible and NIR arrays for coronagraphic spectroscopy and starlight wavefront sensing and control, and detectors with deep full wells with low persistence and radiation tolerance to enable transit imaging and spectroscopy at all wavelengths. Finally, mirror coatings with high reflectivity ( 90), high uniformity ( 1) and low polarization ( 1) that are scalable to large diameter mirror substrates will be essential for ensuring that both high throughput UV observations and high contrast observations can be performed by the same observatory.

  1. The Advanced Technology Large-Aperture Space Telescope (ATLAST) Technology Roadmap

    Science.gov (United States)

    Stahle, Carl; Balasubramanian, K.; Bolcar, M.; Clampin, M.; Feinberg, L.; Hartman, K.; Mosier, C.; Quijada, M.; Rauscher, B.; Redding, D.; hide

    2014-01-01

    We present the key technologies and capabilities that will enable a future, large-aperture ultravioletopticalinfrared (UVOIR) space observatory. These include starlight suppression systems, vibration isolation and control systems, lightweight mirror segments, detector systems, and mirror coatings. These capabilities will provide major advances over current and near-future observatories for sensitivity, angular resolution, and starlight suppression. The goals adopted in our study for the starlight suppression system are 10-10 contrast with an inner working angle of 40 milliarcsec and broad bandpass. We estimate that a vibration and isolation control system that achieves a total system vibration isolation of 140 dB for a vibration-isolated mass of 5000 kg is required to achieve the high wavefront error stability needed for exoplanet coronagraphy. Technology challenges for lightweight mirror segments include diffraction-limited optical quality and high wavefront error stability as well as low cost, low mass, and rapid fabrication. Key challenges for the detector systems include visible-blind, high quantum efficiency UV arrays, photon counting visible and NIR arrays for coronagraphic spectroscopy and starlight wavefront sensing and control, and detectors with deep full wells with low persistence and radiation tolerance to enable transit imaging and spectroscopy at all wavelengths. Finally, mirror coatings with high reflectivity ( 90), high uniformity ( 1) and low polarization ( 1) that are scalable to large diameter mirror substrates will be essential for ensuring that both high throughput UV observations and high contrast observations can be performed by the same observatory.

  2. Large-aperture wide-bandwidth antireflection-coated silicon lenses for millimeter wavelengths

    CERN Document Server

    Datta, R; Niemack, M D; McMahon, J J; Britton, J; Wollack, E J; Beall, J; Devlin, M J; Fowler, J; Gallardo, P; Hubmayr, J; Irwin, K; Newburgh, L; Nibarger, J P; Page, L; Quijada, M A; Schmitt, B L; Staggs, S T; Thornton, R; Zhang, L

    2013-01-01

    The increasing scale of cryogenic detector arrays for sub-millimeter and millimeter wavelength astrophysics has led to the need for large aperture, high index of refraction, low loss, cryogenic refracting optics. Silicon with n = 3.4, low loss, and relatively high thermal conductivity is a nearly optimal material for these purposes, but requires an antireflection (AR) coating with broad bandwidth, low loss, low reflectance, and a matched coefficient of thermal expansion. We present an AR coating for curved silicon optics comprised of subwavelength features cut into the lens surface with a custom three axis silicon dicing saw. These features constitute a metamaterial that behaves as a simple dielectric coating. We have fabricated and coated silicon lenses as large as 33.4 cm in diameter with coatings optimized for use between 125-165 GHz. Our design reduces average reflections to a few tenths of a percent for angles of incidence up to 30 degrees with low cross-polarization. We describe the design, tolerance, m...

  3. The Balloon-borne Large-Aperture Submillimeter Telescope for Polarization: BLAST-pol

    CERN Document Server

    Marsden, G; Bock, J J; Chapin, E L; Chung, J; Devlin, M J; Dicker, S; Griffin, M; Gundersen, J O; Halpern, M; Hargrave, P C; Hughes, D H; Klein, J; MacTavish, C J; Martin, P G; Martin, T G; Matthews, T G; Mauskopf, P; Moncelsi, L; Netterfield, C B; Novak, G; Pascale, E; Olmi, L; Patanchon, G; Rex, M; Savini, G; Scott, D; Semisch, C; Thomas, N; Truch, M D P; Tucker, C; Tucker, G S; Viero, M P; Ward-Thompson, D; Wiebe, D V

    2008-01-01

    The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) is a sub-orbital experiment designed to study the process of star formation in local galaxies (including the Milky Way) and in galaxies at cosmological distances. Using a 2-m Cassegrain telescope, BLAST images the sky onto a focal plane, which consists of 270 bolometric detectors split between three arrays, observing simultaneously in 30% wide bands, centered at 250, 350, and 500 microns. The diffraction-limited optical system provides a resolution of 30" at 250 microns. The pointing system enables raster-like scans with a positional accuracy of ~30", reconstructed to better than 5" rms in post-flight analysis. BLAST had two successful flights, from the Arctic in 2005, and from Antarctica in 2006, which provided the first high-resolution and large-area (~0.8-200 deg^2) submillimeter surveys at these wavelengths. As a pathfinder for the SPIRE instrument on Herschel, BLAST shares with the ESA satellite similar focal plane technology and scientific...

  4. The balloon-borne large-aperture submillimeter telescope for polarimetry: BLAST-Pol

    CERN Document Server

    Fissel, Laura M; Angile, Francesco E; Benton, Steven J; Chapin, Edward L; Devlin, Mark J; Gandilo, Natalie N; Gundersen, Joshua O; Hargrave, Peter C; Hughes, David H; Klein, Jeffrey; Korotkov, Andrei L; Marsden, Galen; Matthews, Tristan G; Moncelsi, Lorenzo; Mroczkowski, Tony K; Netterfield, C Barth; Novak, Giles; Olmi, Luca; Pascale, Enzo; Savini, Giorgio; Scott, Douglas; Shariff, Jamil A; Soler, Juan Diego; Thomas, Nicholas E; Truch, Matthew D P; Tucker, Carole E; Tucker, Gregory S; Ward-Thompson, Derek; Wiebe, Donald V

    2010-01-01

    The Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry (BLAST-Pol) is a suborbital mapping experiment designed to study the role played by magnetic fields in the star formation process. BLAST-Pol is the reconstructed BLAST telescope, with the addition of linear polarization capability. Using a 1.8 m Cassegrain telescope, BLAST-Pol images the sky onto a focal plane that consists of 280 bolometric detectors in three arrays, observing simultaneously at 250, 350, and 500 um. The diffraction-limited optical system provides a resolution of 30'' at 250 um. The polarimeter consists of photolithographic polarizing grids mounted in front of each bolometer/detector array. A rotating 4 K achromatic half-wave plate provides additional polarization modulation. With its unprecedented mapping speed and resolution, BLAST-Pol will produce three-color polarization maps for a large number of molecular clouds. The instrument provides a much needed bridge in spatial coverage between larger-scale, coarse resolutio...

  5. The Large Aperture Gamma Ray Observatory as an Observational Alternative at High Altitude

    Science.gov (United States)

    Rosales, M.

    2011-10-01

    Although satellite observations have revealed some mysteries about the origin and location of cosmic rays at low energies, questions remain to be resolved in higher energy ranges (>1 GeV). However, the flow of particles at high energies is very low, large sensitive areas are necessary, so that the detection of secondary particles from observatories on the surface of the earth is a technically viable solution. While the Pierre Auger Observatory has such capacity given its 16000 m^2 of detectors, low height above sea level greatly reduces its detection capability. The Large Aperture Gamma Ray Observatory (LAGO) is an observational alternative that attempts to overcome this limitation. This project was started in 2005, placing water Cherenkov Detectors at high altitude. Observation sites have been selected with some basic requirements: altitude, academic and technical infrastructure, existence of a research group responsible for assembly and maintenance of the detectors and the analysis, visualization, divulgation and data storage. This paper presents the general status of the observatories of Sierra Negra-México, Chacaltaya-Bolívia, Marcapomacocha-Perú, Mérida-Venezuela and Bucaramanga-Colombia.

  6. Metrological characterization of a large aperture Fizeau for x-ray mirrors measurement

    Science.gov (United States)

    Vannoni, Maurizio; Freijo Martín, Idoia

    2015-06-01

    The European XFEL is a large facility under construction in Hamburg, Germany. It will provide a transversally fully coherent x-ray radiation with outstanding characteristics: high repetition rate (up to 2700 pulses with a 0.6 milliseconds long pulse train at 10Hz), short wavelength (down to 0.05 nm), short pulse (in the femtoseconds scale) and high average brilliance (1.61025 photons / s / mm2 / mrad2/ 0.1% bandwidth). Due to the very short wavelength and very high pulse energy, all the mirrors need to have high quality surface, to be very long, and at the same time to implement an effective cooling system. Matching these tight specifications and assessing them with high precision optical measurements is very challenging. In order to measure the mirrors and to characterize their interaction with the mechanical mounts, we equipped a Metrology Laboratory with a Large Aperture Fizeau. The system is a classical 100 mm diameter commercial Fizeau, with an additional expander providing a 300 mm diameter. Despite the commercial nature of the system, special care has been done in the polishing of the reference flats and in the expander quality. In this report, we show the preparation of the instrument, the calibration and the performance characterization, together with some preliminary results. We also describe the approach that we want to follow for the x-rays mirrors measurements. The final goal will be to characterize very long mirrors, almost 1 meter long, with nanometer accuracy.

  7. Estimation of catchment averaged sensible heat fluxes using a large aperture scintillometer

    Directory of Open Access Journals (Sweden)

    Samain Bruno

    2012-05-01

    Full Text Available Evapotranspiration rates at the catchment scale are very difficult to quantify. One possible manner to continuously observe this variable could be the estimation of sensible heat fluxes (H across large distances (in the order of kilometers using a large aperture scintillometer (LAS, and inverting these observations into evapotranspiration rates, under the assumption that the LAS observations are representative for the entire catchment. The objective of this paper is to assess whether measured sensible heat fluxes from a LAS over a long distance (9.5 km can be assumed to be valid for a 102.3 km2 heterogeneous catchment. Therefore, a fully process-based water and energy balance model with a spatial resolution of 50 m has been thoroughly calibrated and validated for the Bellebeek catchmentin Belgium. A footprint analysis has been performed. In general, the sensible heat fluxes from the LAS compared well with the modeled sensible heat fluxes within the footprint. Moreover, as the modeled Hwithin the footprint has been found to be almost equal to the modeled catchment averaged H, it can be concluded that the scintillometer measurements over a distance of 9.5 km and an effective heightof 68 m are representative for the entire catchment.

  8. Results from one-year continuous operation of a large aperture scintillometer over a heterogeneous land surface

    NARCIS (Netherlands)

    Beyrich, F.; DeBruin, H.A.R.; Meijninger, W.M.L.; Schipper, J.W.; Lohse, H.

    2002-01-01

    A large-aperture scintillometer (LAS) was operated continuously during a period of more than one year over a heterogeneous land surface in Central Europe at the transition between marine and continental climates. The LAS measurements of the refractive index structure parameter, C N2, were used to es

  9. Validation of fluxes of an extra large aperture scintillometer at Cabauw using Sky Arrow aircraft flux measurements

    NARCIS (Netherlands)

    Moene, A.F.; Meijninger, W.M.L.; Kohsiek, W.; Gioli, B.; Miglietta, F.; Bosveld, F.C.

    2006-01-01

    An extra-large aperture scintillometer (XLAS) has been operated at the Cabauw tower for several years over a path of 9.8 kilometers, at an average height of 43 meters (Kohsiek et al., 2002). This yields a long term record of the area-averaged sensible heat flux. During the RECAB summer campaign on J

  10. APERTURE: a precise extremely large reflective telescope using re-configurable elements

    Science.gov (United States)

    Ulmer, M. P.; Coverstone, V. L.; Cao, J.; Chung, Y.-W.; Corbineau, M.-C.; Case, A.; Murchison, B.; Lorenz, C.; Luo, G.; Pekosh, J.; Sepulveda, J.; Schneider, A.; Yan, X.; Ye, S.

    2016-07-01

    One of the pressing needs for the UV-Vis is a design to allow even larger mirrors than the JWST primary at an affordable cost. We report here the results of a NASA Innovative Advanced Concepts phase 1 study. Our project is called A Precise Extremely large Reflective Telescope Using Reconfigurable Elements (APERTURE). The idea is to deploy a continuous membrane-like mirror. The mirror figure will be corrected after deployment to bring it into better or equal lambda/20 deviations from the prescribed mirror shape. The basic concept is not new. What is new is to use a different approach from the classical piezoelectric-patch technology. Instead, our concept is based on a contiguous coating of a so called magnetic smart material (MSM). After deployment a magnetic write head will move on the non-reflecting side of the mirror and will generate a magnetic field that will produce a stress in the MSM that will correct the mirror deviations from the prescribed shape.

  11. Distribution-dependent total exoplanet yield for a large aperture space telescope

    Science.gov (United States)

    Morris, Evan; Schiminovich, David

    2017-01-01

    A major scientific goal for future large aperture space telescopes is the discovery and characterization of habitable earth-like planets around FGK+M stars out to 10-20 pc. Using the design and observing plan for such a mission, we calculated the total exoplanet yield of a direct imaging survey, with detections including but not limited to potential earth analogs. In light of uncertainty of exoplanet occurrence rates, we used several of the best available exoplanetary distribution functions and assumed architectures to produce a Monte Carlo simulation of nearby planetary systems and observational parameters, and assessed detectability across the sample. Our calculations show a range of yields depending on the assumed distribution functions. We also compare our predictions to those of other detection methods in order to identify areas of parameter space (e.g. radius, period) uniquely constrained by direct imaging. In general, our calculations suggest that a higher completeness can be achieved with direct imaging, which will allow for calculation of a more accurate occurrence rate in local space.

  12. Large field distributed aperture laser semiactive angle measurement system design with imaging fiber bundles.

    Science.gov (United States)

    Xu, Chunyun; Cheng, Haobo; Feng, Yunpeng; Jing, Xiaoli

    2016-09-01

    A type of laser semiactive angle measurement system is designed for target detecting and tracking. Only one detector is used to detect target location from four distributed aperture optical systems through a 4×1 imaging fiber bundle. A telecentric optical system in image space is designed to increase the efficiency of imaging fiber bundles. According to the working principle of a four-quadrant (4Q) detector, fiber diamond alignment is adopted between an optical system and a 4Q detector. The structure of the laser semiactive angle measurement system is, we believe, novel. Tolerance analysis is carried out to determine tolerance limits of manufacture and installation errors of the optical system. The performance of the proposed method is identified by computer simulations and experiments. It is demonstrated that the linear region of the system is ±12°, with measurement error of better than 0.2°. In general, this new system can be used with large field of view and high accuracy, providing an efficient, stable, and fast method for angle measurement in practical situations.

  13. A procedure for combining rotating-coil measurements of large-aperture accelerator magnets

    Energy Technology Data Exchange (ETDEWEB)

    Köster, Oliver, E-mail: oliver.koester@cern.ch; Fiscarelli, Lucio, E-mail: lucio.fiscarelli@cern.ch; Russenschuck, Stephan, E-mail: stephan.russenschuck@cern.ch

    2016-05-11

    The rotating search coil is a precise and widely used tool for measuring the magnetic field harmonics of accelerator magnets. This paper deals with combining several such multipole measurements, in order to cover magnet apertures largely exceeding the diameter of the available search coil. The method relies on the scaling laws for multipole coefficients and on the method of analytic continuation along zero-homotopic paths. By acquiring several measurements of the integrated magnetic flux density at different transverse positions within the bore of the accelerator magnet, the uncertainty on the field harmonics can be reduced at the expense of tight tolerances on the positioning. These positioning tolerances can be kept under control by mounting the rotating coil and its motor-drive unit on precision alignment stages. Therefore, the proposed technique is able to yield even more precise results for the higher-order field components than a dedicated rotating search coil of larger diameter. Moreover, the versatility of the measurement bench is enhanced by avoiding the construction of rotating search coils of different measurement radii.

  14. Origins of high-frequency scattered waves near PKKP from large aperture seismic array data

    Science.gov (United States)

    Earle, P.S.

    2002-01-01

    This article identifies the likely origin of 1-Hz scattered waves in the vicinity of PKKP by comparing measurements of slowness and onset time to ray-theoretical predictions. The measurements are obtained from slant stacks of Large Aperture Seismic Array (LASA) data from 36 earthquakes and six explosions in the range 30??-116??. Three types of scattered waves explain the main features seen in the stacks, including: P scattered to PKP near the Earth's surface (P.PKP), PKKP scattered near its core-mantle-boundary (CMB) reflection point (PK.KP), and SKKP scattered near its CMB reflection point (SK.KP). The LASA stacks image the amplitude and slowness variations of the scattered waves with time. They also show where these waves can be detected and where they are free from contaminating arrivals. SK.KP waves rise above the noise approximately 100 sec before the onset time of the main SKKP arrival near 113??. Observations of PK.KP span 30??-100??. However, at distances greater than 50?? they suffer from P.PKP contamination. At distances less than 40?? the PK.KP last for about 280 sec. This is approximately 130 sec longer than the maximum ray-theoretical prediction for waves scattered at the CMB, indicating a possible combination of near-surface scattering and contributions from the overlying mantle.

  15. Assessing inter-sensor variability and sensible heat flux derivation accuracy for a large aperture scintillometer.

    Science.gov (United States)

    Rambikur, Evan H; Chávez, José L

    2014-01-01

    The accuracy in determining sensible heat flux (H) of three Kipp and Zonen large aperture scintillometers (LAS) was evaluated with reference to an eddy covariance (EC) system over relatively flat and uniform grassland near Timpas (CO, USA). Other tests have revealed inherent variability between Kipp and Zonen LAS units and bias to overestimate H. Average H fluxes were compared between LAS units and between LAS and EC. Despite good correlation, inter-LAS biases in H were found between 6% and 13% in terms of the linear regression slope. Physical misalignment was observed to result in increased scatter and bias between H solutions of a well-aligned and poorly-aligned LAS unit. Comparison of LAS and EC H showed little bias for one LAS unit, while the other two units overestimated EC H by more than 10%. A detector alignment issue may have caused the inter-LAS variability, supported by the observation in this study of differing power requirements between LAS units. It is possible that the LAS physical misalignment may have caused edge-of-beam signal noise as well as vulnerability to signal noise from wind-induced vibrations, both having an impact on the solution of H. In addition, there were some uncertainties in the solutions of H from the LAS and EC instruments, including lack of energy balance closure with the EC unit. However, the results obtained do not show clear evidence of inherent bias for the Kipp and Zonen LAS to overestimate H as found in other studies.

  16. Tracking marine mammals and ships with small and large-aperture hydrophone arrays

    Science.gov (United States)

    Gassmann, Martin

    Techniques for passive acoustic tracking in all three spatial dimensions of marine mammals and ships were developed for long-term acoustic datasets recorded continuously over months using custom-designed arrays of underwater microphones (hydrophones) with spacing ranging from meters to kilometers. From the three-dimensional tracks, the acoustical properties of toothed whales and ships, such as sound intensity and directionality, were estimated as they are needed for the passive acoustic abundance estimation of toothed whales and for a quantitative description of the contribution of ships to the underwater soundscape. In addition, the tracks of the toothed whales reveal their underwater movements and demonstrate the potential of the developed tracking techniques to investigate their natural behavior and responses to sound generated by human activity, such as from ships or military SONAR. To track the periodically emitted echolocation sounds of toothed whales in an acoustically refractive environment in the upper ocean, a propagation-model based technique was developed for a hydrophone array consisting of one vertical and two L-shaped subarrays deployed from the floating instrument platform R/P FLIP. The technique is illustrated by tracking a group of five shallow-diving killer whales showing coordinated behavior. The challenge of tracking the highly directional echolocation sounds of deep-diving (whales, in particular Cuvier's beaked whales, was addressed by embedding volumetric small-aperture (≈ 1 m element spacing) arrays into a large-aperture (≈ 1 km element spacing) seafloor array to reduce the minimum number of required receivers from five to two. The capabilities of this technique are illustrated by tracking several groups of up to three individuals over time periods from 10 min to 33 min within an area of 20 km2 in the Southern California Bight. To track and measure the underwater radiated sound of ships, a frequency domain beamformer was implemented for

  17. 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)...

  18. BLAST-TNG: A Next Generation Balloon-borne Large Aperture Submillimeter Polarimeter

    Science.gov (United States)

    Fissel, Laura M.; Ade, Peter; Angilè, Francesco E.; Campbell Ashton, Peter; Austermann, Jason Edward; Billings, Tashalee; Che, George; Cho, Hsiao-Mei; Cunningham, Maria R.; Davis, Kristina; Devlin, Mark J.; Dicker, Simon; Dober, Bradley; Fukui, Yasuo; Galitzki, Nicholas; gao, jiansong; Gordon, Sam; Groppi, Christopher E.; Hillbrand, Seth; Hilton, Gene; Hubmayr, Hannes; Irwin, Kent; Jones, Paul; Klein, Jeffrey; li, dale; Li, Zhi-Yun; lourie, nathan; Lowe, Ian; Mani, Hamdi; Martin, Peter G.; Mauskopf, Philip; McKenney, Christopher; Nati, Federico; Novak, Giles; Pascale, Enzo; pisano, giampaolo; Pereira Santos, Fábio; Scott, Douglas; Sinclair, Adrian; Diego Diego Soler, Juan; tucker, carole; Underhill, Matthew; Vissers, Michael; Williams, Paul

    2017-01-01

    Measurements of polarized thermal dust emission can be used to map magnetic fields in the interstellar medium. Recently, BLASTPol, the Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry, has published the most detailed map ever made of a giant molecular cloud forming high-mass stars. I will present an overview of The Next Generation BLAST polarimeter (BLAST-TNG), the successor telescope to BLASTPol, which maps linearly polarized dust emission at 250, 350 and 500 μm. BLAST-TNG utilizes a 2.5-meter carbon-fiber primary mirror that illuminates focal plane arrays containing over 3,000 microwave kinetic inductance detectors. This new polarimeter has an order of magnitude increase in mapping speed and resolution compared to BLASTPol and we expect to make over 500,000 measurements of magnetic field orientation per flight. BLAST-TNG will have the sensitivity to map entire molecular cloud complexes as well as regions of diffuse high Galactic latitude dust. It also has the resolution (FWHM = 25’’ at 250 μm) necessary to trace magnetic fields in prestellar cores and dense filaments. BLAST-TNG will thus provide a crucial link between the low resolution Planck all-sky maps and the detailed but narrow field of view polarimetry capabilities of ALMA. For our first Antarctic flight in December 2017 we are putting out a call for shared-risk proposals to fill 25% of the available science time. In addition, BLAST-TNG data will be publicly released within a year of the publication of our first look papers, leaving a large legacy data set for the study of the role played by magnetic fields in the star formation process and the properties of interstellar dust.

  19. Active compensation of aperture discontinuities for WFIRST-AFTA: analytical and numerical comparison of propagation methods and preliminary results with a WFIRST-AFTA-like pupil

    Science.gov (United States)

    Mazoyer, Johan; Pueyo, Laurent; Norman, Colin; N'Diaye, Mamadou; van der Marel, Roeland P.; Soummer, Rémi

    2016-03-01

    The new frontier in the quest for the highest contrast levels in the focal plane of a coronagraph is now the correction of the large diffraction artifacts introduced at the science camera by apertures of increasing complexity. Indeed, the future generation of space- and ground-based coronagraphic instruments will be mounted on on-axis and/or segmented telescopes; the design of coronagraphic instruments for such observatories is currently a domain undergoing rapid progress. One approach consists of using two sequential deformable mirrors (DMs) to correct for aberrations introduced by secondary mirror structures and segmentation of the primary mirror. The coronagraph for the WFIRST-AFTA mission will be the first of such instruments in space with a two-DM wavefront control system. Regardless of the control algorithm for these multiple DMs, they will have to rely on quick and accurate simulation of the propagation effects introduced by the out-of-pupil surface. In the first part of this paper, we present the analytical description of the different approximations to simulate these propagation effects. In Appendix A, we prove analytically that in the special case of surfaces inducing a converging beam, the Fresnel method yields high fidelity for simulations of these effects. We provide numerical simulations showing this effect. In the second part, we use these tools in the framework of the active compensation of aperture discontinuities (ACAD) technique applied to pupil geometries similar to WFIRST-AFTA. We present these simulations in the context of the optical layout of the high-contrast imager for complex aperture telescopes, which will test ACAD on a optical bench. The results of this analysis show that using the ACAD method, an apodized pupil Lyot coronagraph, and the performance of our current DMs, we are able to obtain, in numerical simulations, a dark hole with a WFIRST-AFTA-like. Our numerical simulation shows that we can obtain contrast better than 2×10-9 in

  20. Spatial and Temporal Characterization of Femtosecond Pulses at High-Numerical Aperture Using Collinear, Background-Free, Third-Harmonic Autocorrelation

    Energy Technology Data Exchange (ETDEWEB)

    Fittinghoff, D N; der Au, J A; Squier, J A

    2004-08-09

    We show that a simple plane wave analysis can be used even under tight focusing conditions to predict the dependence of third-harmonic generation on the polarization state of the incident beam. Exploiting this fact, we then show that circularly polarized beams may be used to spatially characterize the beam focus and temporally characterize ultrashort pulses in high numerical aperture systems by experimentally demonstrating, for the first time, novel collinear, background-free, third-harmonic intensity autocorrelations in time and space in a high numerical aperture microscope. We also discuss the possibility of using third harmonic generation with circularly polarized beams for background-free collinear frequency resolved optical gating.

  1. Determining suitability of Large Aperture Scintillometer for validating remote sensing based evapotranspiration maps

    Science.gov (United States)

    Paul, G.; Gowda, P. H.; Howell, T. A.; Basu, S.; Colaizzi, P. D.; Marek, T.

    2013-12-01

    Scintillation method is a relatively new technique for measuring the sensible heat and water fluxes over land surfaces. Path integrating capabilities of scintillometer over heterogeneous landscapes make it a potential tool for comparing the energy fluxes derived from remote sensing based energy balance algorithms. For this reason, scintillometer-derived evapotranspiration (ET) fluxes are being used to evaluate remote sensing based energy balance algorithms for their ability to estimate ET fluxes. However, LAS' (Large Aperture Scintillometer) ability to derive ET fluxes is not thoroughly tested. The objective of this study was to evaluate LAS- and Surface Energy Balance System (SEBS)-derived fluxes against lysimetric data to determine LAS' suitability for validating remote sensing based evapotranspiration (ET) maps. The study was conducted during the Bushland Evapotranspiration and Agricultural Remote sensing EXperiment - 2008 (BEAREX-08) at the USDA-ARS Conservation and Production Research Laboratory (CPRL), Bushland, Texas. SEBS was coded in a GIS environment to retrieve ET fluxes from the high resolution imageries acquired using airborne multispectral sensors. The CPRL has four large weighing lysimeters (3 m long x 3 m wide x 2.4 m deep), each located in the middle of approximately 5 ha fields, arranged in a block pattern. The two lysimeter fields located on the east (NE and SE) were managed under irrigated conditions, and the other two lysimeters on the west (NW and SW) were under dryland management. Each lysimeter field was equipped with an automated weather station that provided measurements for net radiation (Rn), Ts, soil heat flux (Go), Ta, relative humidity, and wind speed. During BEAREX08, the NE and SE fields were planted to cotton on May 21, and the NW and SW dryland lysimeters fields were planted to cotton on June 5. One LAS each was deployed across two large dryland lysimeter fields (NW and SW) and two large irrigated lysimeter fields (NE and SE). The

  2. Micro-lensed single-mode optical fiber with high numerical aperture

    CERN Document Server

    Kato, Shinya; Aoki, Takao

    2013-01-01

    We show that the output mode of a single-mode optical fiber can be directly focused to a sub-wavelength waist with a finite working distance by tapering the fiber to a diameter of the order of the wavelength and terminating it with a spherically/hemispherically shaped tip. Numerical simulations show that a beam waist with a width of as small as 0.62\\lambda can be formed. We fabricate micro-lensed fibers and construct a probe-scanning confocal reflection microscope. Measurements on gold nano-particles show a spatial profile with a width of 0.29\\lambda for \\lambda = 850 nm, which is in good agreement with the numerical simulations. Due to their monolithic structures, these micro-lensed fibers will be flexible substitutes for conventional compound lenses in various experimental conditions such as cryogenic temperature and ultra-high vacuum.

  3. Assessing Inter-Sensor Variability and Sensible Heat Flux Derivation Accuracy for a Large Aperture Scintillometer

    Directory of Open Access Journals (Sweden)

    Evan H. Rambikur

    2014-01-01

    Full Text Available The accuracy in determining sensible heat flux (H of three Kipp and Zonen large aperture scintillometers (LAS was evaluated with reference to an eddy covariance (EC system over relatively flat and uniform grassland near Timpas (CO, USA. Other tests have revealed inherent variability between Kipp and Zonen LAS units and bias to overestimate H. Average H fluxes were compared between LAS units and between LAS and EC. Despite good correlation, inter-LAS biases in H were found between 6% and 13% in terms of the linear regression slope. Physical misalignment was observed to result in increased scatter and bias between H solutions of a well-aligned and poorly-aligned LAS unit. Comparison of LAS and EC H showed little bias for one LAS unit, while the other two units overestimated EC H by more than 10%. A detector alignment issue may have caused the inter-LAS variability, supported by the observation in this study of differing power requirements between LAS units. It is possible that the LAS physical misalignment may have caused edge-of-beam signal noise as well as vulnerability to signal noise from wind-induced vibrations, both having an impact on the solution of H. In addition, there were some uncertainties in the solutions of H from the LAS and EC instruments, including lack of energy balance closure with the EC unit. However, the results obtained do not show clear evidence of inherent bias for the Kipp and Zonen LAS to overestimate H as found in other studies.

  4. Thermal Analysis of the Advanced Technology Large Aperture Space Telescope (ATLAST) 8 Meter Primary Mirror

    Science.gov (United States)

    Hornsby, Linda; Stahl, H. Philip; Hopkins, Randall C.

    2010-01-01

    The Advanced Technology Large Aperture Space Telescope (ATLAST) preliminary design concept consists of an 8 meter diameter monolithic primary mirror enclosed in an insulated, optical tube with stray light baffles and a sunshade. ATLAST will be placed in orbit about the Sun-Earth L2 and will experience constant exposure to the sun. The insulation on the optical tube and sunshade serve to cold bias the telescope which helps to minimize thermal gradients. The primary mirror will be maintained at 280K with an active thermal control system. The geometric model of the primary mirror, optical tube, sun baffles, and sunshade was developed using Thermal Desktop(R) SINDA/FLUINT(R) was used for the thermal analysis and the radiation environment was analyzed using RADCAD(R). A XX node model was executed in order to characterize the static performance and thermal stability of the mirror during maneuvers. This is important because long exposure observations, such as extra-solar terrestrial planet finding and characterization, require a very stable observatory wave front. Steady state thermal analyses served to predict mirror temperatures for several different sun angles. Transient analyses were performed in order to predict thermal time constant of the primary mirror for a 20 degree slew or 30 degree roll maneuver. This paper describes the thermal model and provides details of the geometry, thermo-optical properties, and the environment which influences the thermal performance. All assumptions that were used in the analysis are also documented. Parametric analyses are summarized for design parameters including primary mirror coatings and sunshade configuration. Estimates of mirror heater power requirements are reported. The thermal model demonstrates results for the primary mirror heated from the back side and edges using a heater system with multiple independently controlled zones.

  5. Large-aperture, tapered fiber-coupled, 10-kHz particle-image velocimetry.

    Science.gov (United States)

    Hsu, Paul S; Roy, Sukesh; Jiang, Naibo; Gord, James R

    2013-02-11

    We demonstrate the design and implementation of a fiber-optic beam-delivery system using a large-aperture, tapered step-index fiber for high-speed particle-image velocimetry (PIV) in turbulent combustion flows. The tapered fiber in conjunction with a diffractive-optical-element (DOE) fiber-optic coupler significantly increases the damage threshold of the fiber, enabling fiber-optic beam delivery of sufficient nanosecond, 532-nm, laser pulse energy for high-speed PIV measurements. The fiber successfully transmits 1-kHz and 10-kHz laser pulses with energies of 5.3 mJ and 2 mJ, respectively, for more than 25 min without any indication of damage. It is experimentally demonstrated that the tapered fiber possesses the high coupling efficiency (~80%) and moderate beam quality for PIV. Additionally, the nearly uniform output-beam profile exiting the fiber is ideal for PIV applications. Comparative PIV measurements are made using a conventionally (bulk-optic) delivered light sheet, and a similar order of measurement accuracy is obtained with and without fiber coupling. Effective use of fiber-coupled, 10-kHz PIV is demonstrated for instantaneous 2D velocity-field measurements in turbulent reacting flows. Proof-of-concept measurements show significant promise for the performance of fiber-coupled, high-speed PIV using a tapered optical fiber in harsh laser-diagnostic environments such as those encountered in gas-turbine test beds and the cylinder of a combustion engine.

  6. Large-aperture $Nb_{3}Sn$ quadrupoles for $2^{nd}$ generation LHC IRs

    CERN Document Server

    Zlobin, A V; Chichili, D R; Huang Yu; Kashikhin, V V; Lamm, M J; Limon, P J; Mokhov, N V; Novitski, I; Peterson, T; Strait, J B; Yadav, S

    2002-01-01

    The 1/sup st/ generation of low-beta quadrupoles for the LHC interaction region (IR) was designed to achieve the nominal LHC luminosity of 10/sup 34/ cm/sup -2/s/sup -1/. Given that the lifetime of the 1/sup st/ generation IR quadrupoles is limited by ionizing radiation to 6-7 years, the 2/sup nd/ generation of IR quadrupoles has to be developed with the goal to achieve the ultimate luminosity up to 10/sup 35/ cm/sup -2/s/sup -1/. The IR quadrupole parameters such as nominal gradient, dynamic aperture and physical aperture, operation margins are the main factors limiting the machine performance. Conceptual designs of 90-mm aperture high-gradient quadrupoles, suitable for use in 2/sup nd/ generation high-luminosity LHC IRs with the similar optics, are presented. The issues related to the field gradient, field quality and operation margins are discussed. (5 refs).

  7. 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.

  8. Measuring parameters of large-aperture crystals used for generating optical harmonics

    Energy Technology Data Exchange (ETDEWEB)

    English, R. E. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Hibbard, R. L. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Michie, R. B. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Wegner, P. J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Auerbach, J. M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Norton, M. A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Summers, M. D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Perfect, S. A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    1999-02-23

    The purpose of this project was to develop tools for understanding the influence of crystal quality and crystal mounting on harmonic-generation efficiency at high irradiance. Measuring the homogeneity of crystals interferometrically, making detailed physics calculations of conversion efficiency, performing finite- element modeling of mounted crystals, and designing a new optical metrology tool were key elements in obtaining that understanding. For this work, we used the following frequency-tripling scheme: type I second- harmonic generation followed by type II sum-frequency mixing of the residual fundamental and the second harmonic light. The doubler was potassium dihydrogen phosphate (KDP), and the tripler was deuterated KDP (KD*P). With this scheme, near-infrared light (1053 nm) can be frequency tripled (to 351 nm) at high efficiency (theoretically >90%) for high irradiance (>3 GW/cm²). Spatial variations in the birefringence of the large crystals studied here (37 to 41 cm square by about 1 cm thick) imply that the ideal phase-matching orientation of the crystal with respect to the incident laser beam varies across the crystal. We have shown that phase-measuring interferometry can be used to measure these spatial variations. We observed transmitted wavefront differences between orthogonally polarized interferograms of {lambda}/50 to {lambda}/100, which correspond to index variations of order 10-6. On some plates that we measured, the standard deviation of angular errors is 22-23 µrad; this corresponds to a 1% reduction in efficiency. Because these conversion crystals are relatively thin, their surfaces are not flat (deviate by k2.5 urn from flat). A crystal is mounted against a precision-machined surface that supports the crystal on four edges. This mounting surface is not flat either (deviates by +2.5 µm from flat). A retaining flange presses a compliant element against the crystal. The load thus applied near the edges of the crystal surface holds

  9. Surface accuracy analysis and mathematical modeling of deployable large aperture elastic antenna reflectors

    Science.gov (United States)

    Coleman, Michael J.

    One class of deployable large aperture antenna consists of thin light-weight parabolic reflectors. A reflector of this type is a deployable structure that consists of an inflatable elastic membrane that is supported about its perimeter by a set of elastic tendons and is subjected to a constant hydrostatic pressure. A design may not hold the parabolic shape to within a desired tolerance due to an elastic deformation of the surface, particularly near the rim. We can compute the equilibrium configuration of the reflector system using an optimization-based solution procedure that calculates the total system energy and determines a configuration of minimum energy. Analysis of the equilibrium configuration reveals the behavior of the reflector shape under various loading conditions. The pressure, film strain energy, tendon strain energy, and gravitational energy are all considered in this analysis. The surface accuracy of the antenna reflector is measured by an RMS calculation while the reflector phase error component of the efficiency is determined by computing the power density at boresight. Our error computation methods are tailored for the faceted surface of our model and they are more accurate for this particular problem than the commonly applied Ruze Equation. Previous analytical work on parabolic antennas focused on axisymmetric geometries and loads. Symmetric equilibria are not assumed in our analysis. In addition, this dissertation contains two principle original findings: (1) the typical supporting tendon system tends to flatten a parabolic reflector near its edge. We find that surface accuracy can be significantly improved by fixing the edge of the inflated reflector to a rigid structure; (2) for large membranes assembled from flat sheets of thin material, we demonstrate that the surface accuracy of the resulting inflated membrane reflector can be improved by altering the cutting pattern of the flat components. Our findings demonstrate that the proper choice

  10. Internal energy flows of coma-affected singular beams in low-numerical-aperture systems.

    Science.gov (United States)

    Bahl, Monika; Singh, Brijesh Kumar; Singh, Rakesh Kumar; Senthilkumaran, P

    2015-04-01

    The circulating phase gradient component of a singular beam gets modified when focused by a low-numerical-aperature system suffering from coma aberration. The gradient due to this coma aberration splits the higher charge vortex into elementary vortices and distributes them spatially. This splitting depends on the charge and polarity of the incident singular beam as well as the sign and magnitude of the aberration coefficient. The transverse component of the Poynting vector field distribution at the focal plane is decomposed into the curl or solenoidal component and divergence or irrotational component using the Helmholtz-Hodge decomposition technique. The solenoidal component that relates to the orbital angular momentum carries the circulating energy, while the irrotational component shows the sources and sinks of the energy. Intriguing results of the study of energy flow around the edge dislocations apart from the point phase defects in the irrotational components are also presented.

  11. NPT: a large-aperture telescope for high dynamic range astronomy

    Science.gov (United States)

    Joseph, Robert D.; Kuhn, Jeff R.; Tokunaga, Alan T.; Coulter, Roy; Ftaclas, Christo; Graves, J. Elon; Hull, Charles L.; Jewitt, D.; Mickey, Donald L.; Moretto, Gilberto; Neill, Doug; Northcott, Malcolm J.; Roddier, Claude A.; Roddier, Francois J.; Siegmund, Walter A.; Owen, Tobias C.

    2000-06-01

    All existing night-time astronomical telescopes, regardless of aperture, are blind to an important part of the universe - the region around bright objects. Technology now exist to build an unobscured 6.5 m aperture telescope which will attain coronagraphic sensitivity heretofore unachieved. A working group hosted by the University of Hawaii Institute for Astronomy has developed plans for a New Planetary Telescope which will permit astronomical observations which have never before ben possible. In its narrow-field mode the off-axis optical design, combined with adaptive optics, provides superb coronagraphic capabilities, and a very low thermal IR background. These make it ideal for studies of extra-solar planets and circumstellar discs, as well as for general IR astronomy. In its wide-field mode the NPT provides a 2 degree diameter field for surveys of Kuiper Belt Objects and Near-Earth Objects, surveys central to current intellectual interests in solar system astronomy.

  12. Large scale experiments as a tool for numerical model development

    DEFF Research Database (Denmark)

    Kirkegaard, Jens; Hansen, Erik Asp; Fuchs, Jesper;

    2003-01-01

    for improvement of the reliability of physical model results. This paper demonstrates by examples that numerical modelling benefits in various ways from experimental studies (in large and small laboratory facilities). The examples range from very general hydrodynamic descriptions of wave phenomena to specific......Experimental modelling is an important tool for study of hydrodynamic phenomena. The applicability of experiments can be expanded by the use of numerical models and experiments are important for documentation of the validity of numerical tools. In other cases numerical tools can be applied...... hydrodynamic interaction with structures. The examples also show that numerical model development benefits from international co-operation and sharing of high quality results....

  13. Numerical simulation and validation of ocean waves measured by an Along-Track Interferometric Synthetic Aperture Radar

    Institute of Scientific and Technical Information of China (English)

    ZHANG Biao; HE Yijun; Paris W.VACHON

    2008-01-01

    A new nonlinear integral transform of ocean wave spectra into Along-Track Interferometric Synthetic Aperture Radar (ATI-SAR )image spectra is described.ATI-SAR phase image spectra are calculated for various sea states and radar configurations based on the nonlinear integral transform.The numerical simulations show that the slant range to velocity ratio(R/V),significant wave height to ocean wavelength ratio(Hs/λ),the baseline (2B) and incident angle(θ)affect ATI-SAR imaging.The ATI-SAR imaging theory is validated by means of Two X-band,HH-polarized ATI-SAR phase images of ocean waves and eight C-band,HH-polarized ATI-SAR phase image spectra of ocean waves.It is shown that ATI-SAR phase image spectra are in agreement with those calculated by forward mapping in situ directional wave soectra collected simultaneously with available ATI-SAR observations.ATI-SAR spectral correlation coefficients between observed and simulated are greater than 0.6 and ale not sensitive to the degree of nonlinearity.However,the ATI-SAR phase image spectral turns towards the range direction.even if the real ocean wave direction is 30°.It is also shown that the ATI-SAR imaging mechanism is significantly affected by the degree of velocity bunching nonlinearity,especially for high values of R/V and Hs/λ.

  14. Numerical Simulation of Large Diameter Cylindrical Structure Slamming

    Institute of Scientific and Technical Information of China (English)

    XU Jing; WANG De-yu

    2008-01-01

    The water entry of large diameter cylindrical structure is studied by applying numerical simulation method. The processes of different diameter cylindrical structures impacting water with various constant velocities are calculated numerically. Thereafter, analyzed are the distribution of slamming pressure on structure during slamming course and the influence of slamming velocity and cylindrical diameter on slamming process. Furthermore, presented herein is an equation being used to forecast the peak slamming force on a large diameter cylindrical structure.

  15. Near-Space TOPSAR Large-Scene Full-Aperture Imaging Scheme Based on Two-Step Processing.

    Science.gov (United States)

    Zhang, Qianghui; Wu, Junjie; Li, Wenchao; Huang, Yulin; Yang, Jianyu; Yang, Haiguang

    2016-07-27

    Free of the constraints of orbit mechanisms, weather conditions and minimum antenna area, synthetic aperture radar (SAR) equipped on near-space platform is more suitable for sustained large-scene imaging compared with the spaceborne and airborne counterparts. Terrain observation by progressive scans (TOPS), which is a novel wide-swath imaging mode and allows the beam of SAR to scan along the azimuth, can reduce the time of echo acquisition for large scene. Thus, near-space TOPS-mode SAR (NS-TOPSAR) provides a new opportunity for sustained large-scene imaging. An efficient full-aperture imaging scheme for NS-TOPSAR is proposed in this paper. In this scheme, firstly, two-step processing (TSP) is adopted to eliminate the Doppler aliasing of the echo. Then, the data is focused in two-dimensional frequency domain (FD) based on Stolt interpolation. Finally, a modified TSP (MTSP) is performed to remove the azimuth aliasing. Simulations are presented to demonstrate the validity of the proposed imaging scheme for near-space large-scene imaging application.

  16. Near-Space TOPSAR Large-Scene Full-Aperture Imaging Scheme Based on Two-Step Processing

    Directory of Open Access Journals (Sweden)

    Qianghui Zhang

    2016-07-01

    Full Text Available Free of the constraints of orbit mechanisms, weather conditions and minimum antenna area, synthetic aperture radar (SAR equipped on near-space platform is more suitable for sustained large-scene imaging compared with the spaceborne and airborne counterparts. Terrain observation by progressive scans (TOPS, which is a novel wide-swath imaging mode and allows the beam of SAR to scan along the azimuth, can reduce the time of echo acquisition for large scene. Thus, near-space TOPS-mode SAR (NS-TOPSAR provides a new opportunity for sustained large-scene imaging. An efficient full-aperture imaging scheme for NS-TOPSAR is proposed in this paper. In this scheme, firstly, two-step processing (TSP is adopted to eliminate the Doppler aliasing of the echo. Then, the data is focused in two-dimensional frequency domain (FD based on Stolt interpolation. Finally, a modified TSP (MTSP is performed to remove the azimuth aliasing. Simulations are presented to demonstrate the validity of the proposed imaging scheme for near-space large-scene imaging application.

  17. Technology Development for the Advanced Technology Large Aperture Space Telescope (ATLAST) as a Candidate Large UV-Optical-Infrared (LUVOIR) Surveyor

    Science.gov (United States)

    Bolcar, Matthew R.; Balasubramanian, Kunjithapatha; Clampin, Mark; Crooke, Julie; Feinberg, Lee; Postman, Marc; Quijada, Manuel; Rauscher, Bernard; Redding, David; Rioux, Norman; Shaklan, Stuart; Stahl, H. Philip; Stahle, Carl; Thronson, Harley

    2015-01-01

    The Advanced Technology Large Aperture Space Telescope (ATLAST) team has identified five key technologies to enable candidate architectures for the future large-aperture ultraviolet/optical/infrared (LUVOIR) space observatory envisioned by the NASA Astrophysics 30-year roadmap, Enduring Quests, Daring Visions. The science goals of ATLAST address a broad range of astrophysical questions from early galaxy and star formation to the processes that contributed to the formation of life on Earth, combining general astrophysics with direct-imaging and spectroscopy of habitable exoplanets. The key technologies are: internal coronagraphs, starshades (or external occulters), ultra-stable large-aperture telescopes, detectors, and mirror coatings. Selected technology performance goals include: 1x10?10 raw contrast at an inner working angle of 35 milli-arcseconds, wavefront error stability on the order of 10 pm RMS per wavefront control step, autonomous on-board sensing & control, and zero-read-noise single-photon detectors spanning the exoplanet science bandpass between 400 nm and 1.8 µm. Development of these technologies will provide significant advances over current and planned observatories in terms of sensitivity, angular resolution, stability, and high-contrast imaging. The science goals of ATLAST are presented and flowed down to top-level telescope and instrument performance requirements in the context of a reference architecture: a 10-meter-class, segmented aperture telescope operating at room temperature (290 K) at the sun-Earth Lagrange-2 point. For each technology area, we define best estimates of required capabilities, current state-of-the-art performance, and current Technology Readiness Level (TRL) - thus identifying the current technology gap. We report on current, planned, or recommended efforts to develop each technology to TRL 5.

  18. Developing Magnetorheological Finishing (MRF) Technology for the Manufacture of Large-Aperture Optics in Megajoule Class Laser Systems

    Energy Technology Data Exchange (ETDEWEB)

    Menapace, J A

    2010-10-27

    Over the last eight years we have been developing advanced MRF tools and techniques to manufacture meter-scale optics for use in Megajoule class laser systems. These systems call for optics having unique characteristics that can complicate their fabrication using conventional polishing methods. First, exposure to the high-power nanosecond and sub-nanosecond pulsed laser environment in the infrared (>27 J/cm{sup 2} at 1053 nm), visible (>18 J/cm{sup 2} at 527 nm), and ultraviolet (>10 J/cm{sup 2} at 351 nm) demands ultra-precise control of optical figure and finish to avoid intensity modulation and scatter that can result in damage to the optics chain or system hardware. Second, the optics must be super-polished and virtually free of surface and subsurface flaws that can limit optic lifetime through laser-induced damage initiation and growth at the flaw sites, particularly at 351 nm. Lastly, ultra-precise optics for beam conditioning are required to control laser beam quality. These optics contain customized surface topographical structures that cannot be made using traditional fabrication processes. In this review, we will present the development and implementation of large-aperture MRF tools and techniques specifically designed to meet the demanding optical performance challenges required in large-aperture high-power laser systems. In particular, we will discuss the advances made by using MRF technology to expose and remove surface and subsurface flaws in optics during final polishing to yield optics with improve laser damage resistance, the novel application of MRF deterministic polishing to imprint complex topographical information and wavefront correction patterns onto optical surfaces, and our efforts to advance the technology to manufacture large-aperture damage resistant optics.

  19. Design, Fabrication and Initial Testing of a Large Bore Single Aperture 1 m Long Superconducting Dipole Made with Phenolic Inserts

    CERN Document Server

    Boschmann, H; Kirby, G A; Lucas, J; Ostojic, R; Russenschuck, Stephan; Siemko, A; Vanenkov, I; Weterings, W

    1997-01-01

    In the framework of the LHC magnet development programme, a large bore single aperture 1-meter long superconducting dipole has been built in collaboration with HOLEC. The magnet features a single layer coil wound using the LHC main dipole outer layer cable, phenolic inserts, and a keyed two part structural iron yoke. This paper presents the magnetic and mechanical design and optimisation of the magnet. We describe the coil winding and curing, and present the construction and assembly procedures. Finally we report on the mechanical behaviour during assembly and cooling, and present the magnet training behaviour.

  20. Use of water-Cherenkov detectors to detect Gamma Ray Bursts at the Large Aperture GRB Observatory (LAGO)

    Energy Technology Data Exchange (ETDEWEB)

    Allard, D. [APC, CNRS et Universite Paris 7 (France); Allekotte, I. [Centro Atomico Bariloche, Instituto Balseiro (Argentina); Alvarez, C. [Facultad de Ciencias Fisico-Matematicas de la BUAP (Mexico); Asorey, H. [Centro Atomico Bariloche, Instituto Balseiro (Argentina); Barros, H. [Laboratorio de Fisica Nuclear, Universidad Simon Bolivar, Caracas (Venezuela, Bolivarian Republic of); Bertou, X. [Centro Atomico Bariloche, Instituto Balseiro (Argentina)], E-mail: bertou@cab.cnea.gov.ar; Burgoa, O. [Instituto de Investigaciones Fisicas, UMSA (Bolivia); Gomez Berisso, M. [Centro Atomico Bariloche, Instituto Balseiro (Argentina); Martinez, O. [Facultad de Ciencias Fisico-Matematicas de la BUAP (Mexico); Miranda Loza, P. [Instituto de Investigaciones Fisicas, UMSA (Bolivia); Murrieta, T.; Perez, G. [Facultad de Ciencias Fisico-Matematicas de la BUAP (Mexico); Rivera, H. [Instituto de Investigaciones Fisicas, UMSA (Bolivia); Rovero, A. [Instituto de Astronomia y Fisica del Espacio (Argentina); Saavedra, O. [Dipartimento di Fisica Generale and INFN, Torino (Italy); Salazar, H. [Facultad de Ciencias Fisico-Matematicas de la BUAP (Mexico); Tello, J.C. [Laboratorio de Fisica Nuclear, Universidad Simon Bolivar, Caracas (Venezuela, Bolivarian Republic of); Ticona Peralda, R.; Velarde, A. [Instituto de Investigaciones Fisicas, UMSA (Bolivia); Villasenor, L. [Facultad de Ciencias Fisico-Matematicas de la BUAP (Mexico); Instituto de Fisica y Matematicas, Universidad de Michoacan (Mexico)

    2008-09-21

    The Large Aperture GRB Observatory (LAGO) project aims at the detection of high energy photons from Gamma Ray Bursts (GRB) using the single particle technique in ground-based water-Cherenkov detectors (WCD). To reach a reasonable sensitivity, high altitude mountain sites have been selected in Mexico (Sierra Negra, 4550 m a.s.l.), Bolivia (Chacaltaya, 5300 m a.s.l.) and Venezuela (Merida, 4765 m a.s.l.). We report on detector calibration and operation at high altitude, search for bursts in 4 months of preliminary data, as well as search for signal at ground level when satellites report a burst.

  1. Active compensation of aperture discontinuities for WFIRST-AFTA: analytical and numerical comparison of propagation methods and preliminary results with an AFTA like pupil

    CERN Document Server

    Mazoyer, Johan; Norman, Colin; N'Diaye, Mamadou; van der Marel, Roeland P; Soummer, Rémi

    2015-01-01

    The new frontier in the quest for the highest contrast levels in the focal plane of a coronagraph is now the correction of the large diffractive artifacts effects introduced at the science camera by apertures of increasing complexity. The coronagraph for the WFIRST/AFTA mission will be the first of such instruments in space with a two Deformable Mirrors wavefront control system. Regardless of the control algorithm for these multi Deformable Mirrors, they will have to rely on quick and accurate simulation of the propagation effects introduced by the out-of-pupil surface. In the first part of this paper, we present the analytical description of the different approximations to simulate these propagation effects. In Annex A, we prove analytically that, in the special case of surfaces inducing a converging beam, the Fresnel method yields high fidelity for simulations of these effects. We provide numerical simulations showing this effect. In the second part, we use these tools in the framework of the Active Compens...

  2. Large-scale numerical simulations of polydisperse particle flow in a silo

    Science.gov (United States)

    Rubio-Largo, S. M.; Maza, D.; Hidalgo, R. C.

    2016-09-01

    Very recently, we have examined experimentally and numerically the micro-mechanical details of monodisperse particle flows through an orifice placed at the bottom of a silo (Rubio-Largo et al. in Phys Rev Lett 114:238002, 2015). Our findings disentangled the paradoxical ideas associated to the free-fall arch concept, which has historically served to justify the dependence of the flow rate on the outlet size. In this work, we generalize those findings examining large-scale polydisperse particle flows in silos. In the range of studied apertures, both velocity and density profiles at the aperture are self-similar, and the obtained scaling functions confirm that the relevant scale of the problem is the size of the aperture. Moreover, we find that the contact stress monotonically decreases when the particles approach the exit and vanish at the outlet. The behavior of this magnitude is practically independent of the size of the orifice. However, the total and partial kinetic stress profiles suggest that the outlet size controls the propagation of the velocity fluctuations inside the silo. Examining this magnitude, we conclusively argue that indeed there is a well-defined transition region where the particle flow changes its nature. The general trend of the partial kinetic pressure profiles and the location of the transition region results the same for all particle types. We find that the partial kinetic stress is larger for bigger particles. However, the small particles carry a higher fraction of kinetic stress respect to their concentration, which suggest that the small particles have larger velocity fluctuations than the large ones and showing lower strength of correlation with the global flow. Our outcomes explain why the free-fall arch picture has served to describe the polydisperse flow rate in the discharge of silos.

  3. Aperture optical antennas

    CERN Document Server

    Wenger, Jerome

    2014-01-01

    This contribution reviews the studies on subwavelength aperture antennas in the optical regime, paying attention to both the fundamental investigations and the applications. Section 2 reports on the enhancement of light-matter interaction using three main types of aperture antennas: single subwavelength aperture, single aperture surrounded by shallow surface corrugations, and subwavelength aperture arrays. A large fraction of nanoaperture applications is devoted to the field of biophotonics to improve molecular sensing, which are reviewed in Section 3. Lastly, the applications towards nano-optics (sources, detectors and filters) are discussed in Section 4.

  4. Flextensional Microactuators for Large-Aperture Lightweight Cryogenic Deformable Mirrors Project

    Data.gov (United States)

    National Aeronautics and Space Administration — TRS Technologies proposes large stroke and high precision single crystal flextensional piezoelectric microactuators for cryogenic optic devices such as large...

  5. Hybrid Electrostatic/Flextensional Deformable Membrane Mirror for Lightweight, Large Aperture and Cryogenic Space Telescopes Project

    Data.gov (United States)

    National Aeronautics and Space Administration — TRS Technologies proposes innovative hybrid electrostatic/flextensional membrane deformable mirror capable of large amplitude aberration correction for large...

  6. Large-aperture ground glass surface profile measurement using coherence scanning interferometry.

    Science.gov (United States)

    Bae, Eundeok; Kim, Yunseok; Park, Sanguk; Kim, Seung-Woo

    2017-01-23

    We present a coherence scanning interferometer configured to deal with rough glass surfaces exhibiting very low reflectance due to severe sub-surface light scattering. A compound light source is prepared by combining a superluminescent light-emitting diode with an ytterbium-doped fiber amplifier. The light source is attuned to offer a short temporal coherence length of 15 μm but with high spatial coherence to secure an adequate correlogram contrast by delivering strongly unbalanced optical power to the low reflectance target. In addition, the infrared spectral range of the light source is shifted close to the visible side at a 1,038 nm center wavelength, so a digital camera of multi-mega pixels available for industrial machine vision can be used to improve the correlogram contrast further with better lateral image resolutions. Experimental results obtained from a ground Zerodur mirror of 200 mm aperture size and 0.9 μm rms roughness are discussed to validate the proposed interferometer system.

  7. Distributed Bragg reflector ring oscillators: A large aperture source of high single-mode optical power

    Energy Technology Data Exchange (ETDEWEB)

    Dzurko, K.M.; Hardy, A.; Scifres, D.R.; Welch, D.F.; Waarts, R.G.; Lang, R.J. (Spectra Diode Labs., San Jose, CA (United States))

    1993-06-01

    Distributed Bragg reflector (DBR) ring oscillators are the first monolithic semiconductor lasers containing broad-area active regions which operate in a single mode to several times their threshold current. Orthogonally oriented diffraction gratings surrounding an unpatterned active region select a single spatial and temporal mode of oscillation. This paper presents both analytic and experimental verification of single mode operation for active dimensions up to 368 [times] 1000 [mu]m. Threshold current densities under 200 A/cm[sup 2] and total differential efficiencies greater than 60% have been measured. DBR ring oscillators have demonstrated over 1 W of single frequency output power, 460 mW of spatially coherent, single frequency output power, and nearly circular diffraction limited output to 4 [times] I[sub th]. The performance potential of these devices is enormous, considering that the output apertures are nearly two orders of magnitude wider than conventional single mode sources which generate up to 0.2 W of coherent output.

  8. Are Large-Aperture NbTi Magnets Compatible with 1e35?

    CERN Document Server

    Wildner, E; Laface, E; Sterbini, G

    2008-01-01

    To protect magnets in the insertion region, we have some degrees of freedom to use for optimal performance. Aperture, distance from the IP, the length of the magnets and the design of absorption systems are important parameters for the optimization. We look exclusively here at the effects of the collision debris, which give the major contribution to the heat deposition in the insertion magnets. To answer the challenging question in the title of this contribution, the approach was to use the baseline upgrade scenario for phase 1 and simply imagine higher particle fluxes from the higher luminosity (no change in optics). From this, a simple approach of magnet shielding using a liner in the cold bore tube gave us the answer: NbTi technology may be compatible with a luminosity of 1035. This gives also the interesting possibility to extract heat from this liner at a higher cryogenic temperature. However the final demonstration needs a detailed model. We have also made some parameter variations (crossing angle, TAS ...

  9. Sensitivity of Large-Aperture Scintillometer Measurements of Area-Average Heat Fluxes to Uncertainties in Topographic Heights

    CERN Document Server

    Gruber, Matthew A; Hartogensis, Oscar K

    2013-01-01

    Scintillometers measure $C_n^2$ over large areas of turbulence in the atmospheric surface layer. Turbulent fluxes of heat and momentum are inferred through coupled sets of equations derived from the Monin-Obukhov similarity hypothesis. One-dimensional sensitivity functions have been produced which relate the sensitivity of heat fluxes to uncertainties in single values of beam height over homogeneous and flat terrain. Real field sites include variable topography and heterogeneous surface properties such as roughness length. We develop here the first analysis of the sensitivity of scintillometer derived sensible heat fluxes to uncertainties in spacially distributed topographic measurements. For large-aperture scintillometers and independent $u_\\star$ measurements, sensitivity is shown to be concentrated in areas near the center of the beam and where the underlying topography is closest to the beam height. Uncertainty may be greatly reduced by focusing precise topographic measurements in these areas. The new two...

  10. Cryogenic Piezo Actuators for Lightweight, Large Aperture, Deployable Membrane Mirrors Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Single crystal piezoelectric actuators are proposed to enable large stroke, high precision, shape control for cryogenic lightweight deployable membrane mirror...

  11. Mg-doped congruent LiTaO3 crystal for large-aperture quasi-phase matching device.

    Science.gov (United States)

    Ishizuki, Hideki; Taira, Takunori

    2008-10-13

    Mg-doped congruent composition LiTaO(3) (MgLT) crystal, which can be grown by a conventional Czochralski method, has improved properties such as transparent range, thermal conductivity, and coercive field compared to conventional undoped congruent LiTaO(3). In this paper, various properties of MgLT including Mg-doping dependence are characterized, and also compared to that of undoped congruent LiTaO(3), LiNbO(3), and Mg-doped congruent LiNbO(3), as a material of high power quasi-phase matching (QPM) device. Up to 3-mm-thick periodically poled MgLT crystal is shown to demonstrate the possibility of large-aperture QPM-MgLT devices. Subsequently, optical parametric oscillation experiments by using periodically poled MgLT are demonstrated to discuss an efficient QPM condition.

  12. Design, development and performance characteristics of a large aperture disc amplifier for high power Nd: Glass laser chain

    Indian Academy of Sciences (India)

    M P Kamath; P K Tripathi; A P Kulkarni; R Chandra; A S Joshi; C P Navathe; P D Gupta

    2008-08-01

    A large aperture disc amplifier has been designed, set-up and characterized for its performance on small signal gain, spatial variation of gain, and thermal recovery time. This amplifier, consisting of three elliptical Nd: phosphate glass discs of size 214 × 114 × 20 mm mounted at Brewster angle and pumped by ten xenon filled flash lamps of 600 mm arc length, provided a small signal gain of 6 at electrical pump energy of 36 kJ (in a pulse of 450 s) using an in-house developed dual-polarity capacitor bank based power supply. It was coupled to a high power Nd: phosphate glass laser chain and a maximum output pulse energy exceeding 100 J in a 1·5 ns (FWHM) pulse has been measured. A dry nitrogen gas based cooling system was developed for cooling the glass discs with a thermal recovery time of ∼ 20 minutes.

  13. The Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry-BLASTPol: Performance and results from the 2012 Antarctic flight

    CERN Document Server

    Galitzki, N; Angilé, F E; Benton, S J; Devlin, M J; Dober, B; Fissel, L M; Fukui, Y; Gandilo, N N; Klein, J; Korotkov, A L; Matthews, T G; Moncelsi, L; Netterfield, C B; Novak, G; Nutter, D; Pascale, E; Poidevin, F; Savini, G; Scott, D; Shariff, J A; Soler, J D; Tucker, C E; Tucker, G S; Ward-Thompson, D

    2014-01-01

    The Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry (BLASTPol) is a suborbital mapping experiment, designed to study the role played by magnetic fields in the star formation process. BLASTPol observes polarized light using a total power instrument, photolithographic polarizing grids, and an achromatic half-wave plate to modulate the polarization signal. During its second flight from Antarctica in December 2012, BLASTPol made degree scale maps of linearly polarized dust emission from molecular clouds in three wavebands, centered at 250, 350, and 500 microns. The instrumental performance was an improvement over the 2010 BLASTPol flight, with decreased systematics resulting in a higher number of confirmed polarization vectors. The resultant dataset allows BLASTPol to trace magnetic fields in star-forming regions at scales ranging from cores to entire molecular cloud complexes.

  14. The study on servo-control system in the large aperture telescope

    Science.gov (United States)

    Hu, Wei; Zhenchao, Zhang; Daxing, Wang

    2008-08-01

    Large astronomical telescope or extremely enormous astronomical telescope servo tracking technique will be one of crucial technology that must be solved in researching and manufacturing. To control technique feature of large astronomical telescope or extremely enormous astronomical telescope, this paper design a sort of large astronomical telescope servo tracking control system. This system composes a principal and subordinate distributed control system, host computer sends steering instruction and receive slave computer functional mode, slave computer accomplish control algorithm and execute real-time control. Large astronomical telescope servo control use direct drive machine, and adopt DSP technology to complete direct torque control algorithm, Such design can not only increase control system performance, but also greatly reduced volume and costs of control system, which has a significant occurrence. The system design scheme can be proved reasonably by calculating and simulating. This system can be applied to large astronomical telescope.

  15. Large-scale numerical simulation of rotationally constrained convection

    Science.gov (United States)

    Sprague, Michael; Julien, Keith; Knobloch, Edgar; Werne, Joseph; Weiss, Jeffrey

    2007-11-01

    Using direct numerical simulation (DNS), we investigate solutions of an asymptotically reduced system of nonlinear PDEs for rotationally constrained convection. The reduced equations filter fast inertial waves and relax the need to resolve Ekman boundary layers, which allow exploration of a parameter range inaccessible with DNS of the full Boussinesq equations. The equations are applicable to ocean deep convection, which is characterized by small Rossby number and large Rayleigh number. Previous numerical studies of the reduced equations examined upright convection where the gravity vector was anti-parallel to the rotation vector. In addition to the columnar and geostrophic-turbulence regimes, simulations revealed a third regime where Taylor columns were shielded by sleeves of opposite-signed vorticity. We here extend our numerical simulations to examine both upright and tilted convection at high Rayleigh numbers.

  16. Study of numerical errors in direct numerical simulation and large eddy simulation

    Institute of Scientific and Technical Information of China (English)

    YANG Xiao-long; FU Song

    2008-01-01

    By comparing the energy spectrum and total kinetic energy, the effects of numerical errors (which arise from aliasing and discretization errors), subgrid-scale (SGS) models, and their interactions on direct numerical simulation (DNS) and large eddy simulation (LES) are investigated. The decaying isotropic turbulence is chosen as the test case. To simulate complex geometries, both the spectral method and Pade compact difference schemes are studied. The truncated Navier-Stokes (TNS) equation model with Pade discrete filter is adopted as the SGS model. It is found that the discretization error plays a key role in DNS. Low order difference schemes may be unsuitable. However, for LES, it is found that the SGS model can represent the effect of small scales to large scales and dump the numerical errors. Therefore, reasonable results can also be obtained with a low order discretization scheme.

  17. Large aperture cube corner interferometer with a resolution of 0.001 cm(-1).

    Science.gov (United States)

    Kauppinen, J; Horneman, V M

    1991-06-20

    The interferometer of the Fourier transform spectrometer at the University of Oulu has been modified so that the maximum instrumental resolution is better than 10(-3) cm(-1). The resolution of the previous interferometer was 4.5 x 10(-3) cm(-1). The present interferometer consists of large cube corner mirrors and a large Mylar beam splitter. Each corner mirror has been made with three flat mirrors on an adjustable supporting frame. The interferometer was already in practical use in 1985. The first spectra (H(2)O, CO(2), N(2)O, OCS) recorded on this interferometer have been presented in HANDBOOK OF INFRARED STANDARDS WITH SPECTRAL MAPS AND TRANSITION ASSIGNMENTS BETWEEN 3 AND 2600 microm, G. Guelachvili and K. Narahari Rao, Eds. (Academic, New York, 1986).

  18. Rapid growth of a large-scale(600 mm aperture) KDP crystal and its optical quality

    Institute of Scientific and Technical Information of China (English)

    Guohui; Li; Guozong; Zheng; Yingkun; Qi; Peixiu; Yin; En; Tang; Fei; Li; Jing; Xu; Taiming; Lei; Xiuqin; Lin; Min; Zhang; Junye; Lu; Jinbo; Ma; Youping; He; Yuangen; Yao

    2014-01-01

    Potassium dihydrogen phosphate(KDP) single crystals are the only nonlinear crystals currently used for electro-optic switches and frequency converters in inertial confinement fusion research, due to their large dimension and exclusive physical properties. Based on the traditional solution-growth process, large bulk KDP crystals, usually with sizes up to600 × 600 mm2 so as to make a frequency doubler for the facility requirement loading highly flux of power laser, can be grown in standard Holden-type crystallizers, without spontaneous nucleation and visible defects, one to two orders of magnitude faster than by conventional methods. Pure water and KDP raw material with a few ion impurities such as Fe,Cr, and Al(less than 0.1 ppm) were used. The rapid-growth method includes extreme conditions such as temperature range from 60 to 35℃ , overcooling up to 5℃ , growth rates exceeding 10 mm/day, and crystal size up to 600 mm. The optical parameters of KDP crystals were determined. The optical properties of crystals determined indicate that they are of favorable quality for application in the facility.

  19. Constraining cosmological ultra-large scale structure using numerical relativity

    CERN Document Server

    Braden, Jonathan; Peiris, Hiranya V; Aguirre, Anthony

    2016-01-01

    Cosmic inflation, a period of accelerated expansion in the early universe, can give rise to large amplitude ultra-large scale inhomogeneities on distance scales comparable to or larger than the observable universe. The cosmic microwave background (CMB) anisotropy on the largest angular scales is sensitive to such inhomogeneities and can be used to constrain the presence of ultra-large scale structure (ULSS). We numerically evolve nonlinear inhomogeneities present at the beginning of inflation in full General Relativity to assess the CMB quadrupole constraint on the amplitude of the initial fluctuations and the size of the observable universe relative to a length scale characterizing the ULSS. To obtain a statistically significant number of simulations, we adopt a toy model in which inhomogeneities are injected along a preferred direction. We compute the likelihood function for the CMB quadrupole including both ULSS and the standard quantum fluctuations produced during inflation. We compute the posterior given...

  20. Design of high gain OPCPA for multiterawatt and petawatt class systems on large aperture LBO crystals

    Science.gov (United States)

    Pestryakov, E. V.; Petrov, V. V.; Trunov, V. I.; Frolov, S. A.; Kirpichnikov, A. V.; Bagayev, S. N.; Kokh, A. E.

    2011-02-01

    Comparative analysis of optimal scheme of non-collinear optical chirped-pulse parametric amplification of fewcycle femtosecond pulses from Ti:Sa laser in LBO and DKDP crystals pumped by picosecond pulses up to petawatt level is presented. A flexible code, based on the extended model of parametric amplification, which takes into account the large set of effects such as saturation, phase self-modulation, influence of beam divergence, thermal effects, and amplification of spontaneous emission was realized. A way of creating nearly 1 PW system based on LBO crystals with transform-limited pulse duration about 9 fs has been demonstrated. Comparison between DKDP and LBO crystal showed that the latter is much better for OPCPA petawatt system design than DKDP.

  1. A 16-m Telescope for the Advanced Technology Large Aperture Telescope (ATLAST) Mission

    Science.gov (United States)

    Lillie, Charles F.; Dailey, D. R.; Polidan, R. S.

    2010-01-01

    Future space observatories will require increasingly large telescopes to study the earliest stars and galaxies, as well as faint nearby objects. Technologies now under development will enable telescopes much larger than the 6.5-meter diameter James Webb Space Telescope (JWST) to be developed at comparable costs. Current segmented mirror and deployable optics technology enables the 6.5 meter JWST telescope to be folded for launch in the 5-meter diameter Ariane 5 payload fairing, and deployed autonomously after reaching orbit. Late in the next decade, when the Ares V Cargo Launch Vehicle payload fairing becomes operational, even larger telescope can be placed in orbit. In this paper we present our concept for a 16-meter JWST derivative, chord-fold telescope which could be stowed in the 10-m diameter Ares V fairing, plus a description of the new technologies that enable ATLAST to be developed at an affordable price.

  2. Numerical studies towards practical large-eddy simulation

    Institute of Scientific and Technical Information of China (English)

    J. Boudet; J. Caro; L. Shao; E. Lévêque

    2007-01-01

    Large-eddy simulation developments and validations are presented for an improved simulation of turbulent internal flows. Numerical methods are proposed according to two competing criteria: numerical qualities (precision and spectral characteristics), and adaptability to complex configurations. First, methods are tested on academic test-cases, in order to abridge with fundamental studies. Consistent results are obtained using adaptable finite volume method, with higher order advection fluxes, implicit grid filtering and "low-cost" shear-improved Smagorinsky model. This analysis particularly focuses on mean flow, fluctuations, two-point correlations and spectra.Moreover, it is shown that exponential averaging is a promising tool for LES implementation in complex geometry with deterministic unsteadiness. Finally, adaptability of the method is demonstrated by application to a configuration representative of blade-tip clearance flow in a turbomachine.

  3. Lupus I Observations from the 2010 Flight of the Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry

    Science.gov (United States)

    Matthews, Tristan G.; Ade, Peter A. R.; Angilè, Francesco E.; Benton, Steven J.; Chapin, Edward L.; Chapman, Nicholas L.; Devlin, Mark J.; Fissel, Laura M.; Fukui, Yasuo; Gandilo, Natalie N.; Gundersen, Joshua O.; Hargrave, Peter C.; Klein, Jeffrey; Korotkov, Andrei L.; Moncelsi, Lorenzo; Mroczkowski, Tony K.; Netterfield, Calvin B.; Novak, Giles; Nutter, David; Olmi, Luca; Pascale, Enzo; Poidevin, Frédérick; Savini, Giorgio; Scott, Douglas; Shariff, Jamil A.; Soler, Juan Diego; Tachihara, Kengo; Thomas, Nicholas E.; Truch, Matthew D. P.; Tucker, Carole E.; Tucker, Gregory S.; Ward-Thompson, Derek

    2014-04-01

    The Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry (BLASTPol) was created by adding polarimetric capability to the BLAST experiment that was flown in 2003, 2005, and 2006. BLASTPol inherited BLAST's 1.8 m primary and its Herschel/SPIRE heritage focal plane that allows simultaneous observation at 250, 350, and 500 μm. We flew BLASTPol in 2010 and again in 2012. Both were long duration Antarctic flights. Here we present polarimetry of the nearby filamentary dark cloud Lupus I obtained during the 2010 flight. Despite limitations imposed by the effects of a damaged optical component, we were able to clearly detect submillimeter polarization on degree scales. We compare the resulting BLASTPol magnetic field map with a similar map made via optical polarimetry. (The optical data were published in 1998 by J. Rizzo and collaborators.) The two maps partially overlap and are reasonably consistent with one another. We compare these magnetic field maps to the orientations of filaments in Lupus I, and we find that the dominant filament in the cloud is approximately perpendicular to the large-scale field, while secondary filaments appear to run parallel to the magnetic fields in their vicinities. This is similar to what is observed in Serpens South via near-IR polarimetry, and consistent with what is seen in MHD simulations by F. Nakamura and Z. Li.

  4. Sensitivity of large-aperture scintillometer measurements of area-average heat fluxes to uncertainties in topographic heights

    Directory of Open Access Journals (Sweden)

    M. A. Gruber

    2014-01-01

    Full Text Available Scintillometer measurements allow for estimations of the refractive index structure parameter Cn2 over large areas in the atmospheric surface layer. Turbulent fluxes of heat and momentum are inferred through coupled sets of equations derived from the Monin–Obukhov similarity hypothesis. One-dimensional sensitivity functions have been produced that relate the sensitivity of heat fluxes to uncertainties in single values of beam height over homogeneous and flat terrain. However, real field sites include variable topography and heterogeneous surfaces. We develop here the first analysis of the sensitivity of scintillometer derived sensible heat fluxes to uncertainties in spatially distributed topographic measurements. For large-aperture scintillometers and independent friction velocity u* measurements, sensitivity is shown to be concentrated in areas near the center of the beam path and where the underlying topography is closest to the beam height. Uncertainty may be greatly reduced by focusing precise topographic measurements in these areas. A new two-dimensional variable terrain sensitivity function is developed for quantitative error analysis. This function is compared with the previous one-dimensional sensitivity function for the same measurement strategy over flat and homogeneous terrain. Additionally, a new method of solution to the set of coupled equations is produced that eliminates computational error. The results are produced using a new methodology for error analysis involving distributed parameters that may be applied in other disciplines.

  5. LUPUS I observations from the 2010 flight of the Balloon-borne large aperture submillimeter telescope for polarimetry

    Energy Technology Data Exchange (ETDEWEB)

    Matthews, Tristan G.; Chapman, Nicholas L.; Novak, Giles [Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (United States); Ade, Peter A. R.; Hargrave, Peter C.; Nutter, David [Cardiff University, School of Physics and Astronomy, Queens Buildings, The Parade, Cardiff, CF24 3AA (United Kingdom); Angilè, Francesco E.; Devlin, Mark J.; Klein, Jeffrey [Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104 (United States); Benton, Steven J.; Fissel, Laura M.; Gandilo, Natalie N.; Netterfield, Calvin B. [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street Toronto, ON M5S 3H4 (Canada); Chapin, Edward L. [XMM SOC, ESAC, Apartado 78, E-28691 Villanueva de la Cañada, Madrid (Spain); Fukui, Yasuo [Department of Physics, Nagoya University, Nagoya 464-8602 (Japan); Gundersen, Joshua O. [Department of Physics, University of Miami, 1320 Campo Sano Drive, Coral Gables, FL 33146 (United States); Korotkov, Andrei L. [Department of Physics, Brown University, 182 Hope Street, Providence, RI 02912 (United States); Moncelsi, Lorenzo; Mroczkowski, Tony K. [California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Olmi, Luca [University of Puerto Rico, Rio Piedras Campus, Physics Department, Box 23343, UPR station, San Juan (Puerto Rico); and others

    2014-04-01

    The Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry (BLASTPol) was created by adding polarimetric capability to the BLAST experiment that was flown in 2003, 2005, and 2006. BLASTPol inherited BLAST's 1.8 m primary and its Herschel/SPIRE heritage focal plane that allows simultaneous observation at 250, 350, and 500 μm. We flew BLASTPol in 2010 and again in 2012. Both were long duration Antarctic flights. Here we present polarimetry of the nearby filamentary dark cloud Lupus I obtained during the 2010 flight. Despite limitations imposed by the effects of a damaged optical component, we were able to clearly detect submillimeter polarization on degree scales. We compare the resulting BLASTPol magnetic field map with a similar map made via optical polarimetry. (The optical data were published in 1998 by J. Rizzo and collaborators.) The two maps partially overlap and are reasonably consistent with one another. We compare these magnetic field maps to the orientations of filaments in Lupus I, and we find that the dominant filament in the cloud is approximately perpendicular to the large-scale field, while secondary filaments appear to run parallel to the magnetic fields in their vicinities. This is similar to what is observed in Serpens South via near-IR polarimetry, and consistent with what is seen in MHD simulations by F. Nakamura and Z. Li.

  6. Design of axisymmetric multi-mirror grazing incidence system to increase the numerical aperture of neutron and X-ray microscopes

    Science.gov (United States)

    Aoki, Sadao; Watanabe, Norio; Asami, Hiroshi; Shimada, Akihiro

    2016-04-01

    An axisymmetric multi-mirror system for neutron and X-ray microscopes is proposed to increase their numerical aperture and collection efficiency. A Wolter type-I mirror is used as the basis of the multi-mirror system at grazing incidence. The addition of an even number of hyperboloid mirrors to the Wolter type-I mirror can satisfy both an equal optical path length and Abbe's sine condition. The numerical aperture increases in proportion to the number of mirrors. The optical parameters of the system with four tandem mirrors are calculated for neutrons and X-rays with a wavelength of 0.4 nm by assuming that the average grazing angle of incidence is 5.4 mrad and the magnification is 10. The inner diameters of the mirrors are limited to <10 mm considering the total length of the optical system. Tolerance of off-axis distance was calculated using a ray-tracing computer simulation. Ray tracing shows that a blur size <14 nm will be possible at an off-axis displacement of 10 μm.

  7. Processing method and process modeling of large aperture transparent magnesium aluminate spinel domes

    Science.gov (United States)

    Yu, Jian; McWilliams, Brandon; Kilczewski, Steven; Gilde, Gary; Lidie, Ashley; Sands, James

    2009-05-01

    Polycrystalline spinel serves as an alternative to materials such as sapphire and magnesium fluoride that are currently being used in electromagnetic window applications such as missile domes, where high strength, high hardness and high transmittance in the visible and infrared spectra are required. The cubic crystal lattice of spinel imparts an isotropy to the bulk optical property, which eliminates optical distortion due to birefringence that occurs in sapphire and other non-cubic materials. The current study is to find a reliable manufacturing process to produce large magnesium aluminate spinel domes from powder consolidation efficiently. A binder-less dry ball milling process was used to deflocculate the spinel powder to increase its fluidity in an effort to ease the shape-forming. Dry ball milling time trials were conducted at several intervals to determine the appropriate level of time required to break up both the hard and soft agglomerates associated with the virgin spinel powder. The common problems encountered in dry powder shape-forming are crack growth and delamination of the green body during cold isostatic pressing (CIPing). The cracking and the delamination are due to the buildup of stress gradients on the green body that are created by the frictional force between the powder and the die wall or mold wall. To understand the stresses during the CIPing process, a finite element analysis of stresses on the green body was conducted. The simulation was used to evaluate the effect of die tooling and process characteristics on the development of stress gradients in the green body dome. Additionally, the effect of friction between the die wall and powder was examined by the simulation. It was found that by mitigating the frictional forces, cracking and delamination on the green body could be eliminated. A stepped-pressure CIPing technique was developed to reduce stress gradient build-up during CIPing. Also, oleic acid lubricant was applied to the die wall to

  8. Integrated opto-mechanical optimization analysis of large-aperture primary mirror's support position

    Science.gov (United States)

    Ke, Ding; Bo, Qi; Jiang, Bian

    2016-10-01

    Large mirror's support position plays a very important role in optical system's wave-front error. This paper took a Φ1.2m diameter primary mirror as an example and introduced the method of integrated opto-mechanical optimization analysis, then structure's parametric model in Proe, finite element's parametric model in Patran, structure analysis in Nastran and opto-mechanical coupling analysis in Sigfit were integrated as a fully automatic process in Isight by use of command streams and result documents produced by these soft wares. After the process was established and verified, automatic gradient searches of primary mirror's optimal support position were conducted using optimizer embedded in Isight. The optimization objective is the minimum of surface error's RMS and the optimization variables are support positions. New searches can easily be conducted repeatedly after mirror's model is modified in the structure parameter document. Because of the search process is fully automatic, manpower and computing time are greatly saved. This example also provides a good reference for problems in opto-mechanical fields.

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

    Science.gov (United States)

    Vilnrotter, Victor

    2013-01-01

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

  10. Laboratory demonstration of a primary active mirror for space with the LATT: large aperture telescope technology

    Science.gov (United States)

    Briguglio, Runa; Biasi, Roberto; Gallieni, Daniele; Vettore, Christian; d'Amato, Francesco; Xompero, Marco; Arcidiacono, Carmelo; Lisi, Franco; Riccardi, Armando; Patauner, Christian; Lazzarini, Paolo; Tintori, Matteo; Duò, Fabrizio; Pucci, Mauro; Zuccaro Marchi, Alessandro; Maresi, Luca

    2016-07-01

    The LATT project is an ESA contract under TRP programme to demonstrate the scalability of the technology from ground-based adaptive mirrors to space active primary mirrors. A prototype spherical mirror based on a 40 cm diameter 1 mm thin glass shell with 19 contactless, voice-coil actuators and co-located position sensors have been manufactured and integrated into a final unit with an areal density lower than 20 kg/m2. Laboratory tests demonstrated the controllability with very low power budget and the survival of the fragile glass shell exposed to launch accelerations, thanks to an electrostatic locking mechanism; such achievements pushes the technology readiness level toward 5. With this prototype, the LATT project explored the feasibility of using an active and lightweight primary for space telescopes. The concept is attractive for large segmented telescopes, with surface active control to shape and co-phase them once in flight. In this paper we will describe the findings of the technological advances and the results of the environmental and optical tests.

  11. Determination of area averaged water vapour fluxes with large aperture and radio wave scintillometers over a heterogeneous surface - Flevoland field experiment

    NARCIS (Netherlands)

    Meijninger, W.M.L.; Green, A.E.; Hartogensis, O.K.; Kohsiek, W.; Hoedjes, J.C.B.; Zuurbier, R.M.; DeBruin, H.A.R.

    2002-01-01

    A large aperture scintillometer (LAS) and radio wave scintillometer (RWS) were installed over a heterogeneous area to test the applicability of the scintillation method. The heterogeneity in the area, which consisted of many plots, was mainly caused by differences in thermal properties of the crops;

  12. Comparison of large aperture scintillometer and eddy covariance measurements: Can thermal infrared data be used to capture footprint-induced differences?

    NARCIS (Netherlands)

    Hoedjes, J.C.B.; Chehbouni, A.; Ezzahar, J.; Escadafal, R.; Bruin, de H.A.R.

    2007-01-01

    Eddy covariance (EC) and large aperture scintillometer (LAS) measurements were collected over an irrigated olive orchard near Marrakech, Morocco. The tall, sparse vegetation in the experimental site was relatively homogeneous, but during irrigation events spatial variability in soil humidity was lar

  13. Constraining lowermost mantle structure with PcP/P amplitude ratios from large aperture arrays

    Science.gov (United States)

    Ventosa, S.; Romanowicz, B. A.

    2015-12-01

    Observations of weak short-period teleseismic body waves help to resolve lowermost mantle structure at short wavelengths, which is essential for understanding mantle dynamics and the interactions between the mantle and core. Their limited amount and uneven distribution are however major obstacles to solve for volumetric structure of the D" region, topography of the core-mantle boundary (CMB) and D" discontinuity, and the trade-offs among them. While PcP-P differential travel times provide important information, there are trade-offs between velocity structure and core-mantle boundary topography, which PcP/P amplitude ratios can help resolve, as long as lateral variations in attenuation and biases due to focusing are small or can be corrected for. Dense broadband seismic networks help to improve signal-to-noise ratio (SNR) of the target phases and signal-to-interference ratio (SIR) of other mantle phases when the slowness difference is large enough. To improve SIR and SNR of teleseismic PcP data, we have introduced the slant-stacklet transform to define coherent-guided filters able to separate and enhance signals according to their slowness, time of arrival and frequency content. We thus obtain optimal PcP/P amplitude ratios in the least-square sense using two short sliding windows to match the P signal with a candidate PcP signal. This method allows us to dramatically increase the amount of high-quality observations of short-period PcP/P amplitude ratios by allowing for smaller events and wider epicentral distance and depth ranges.We present the results of measurement of PcP/P amplitude ratios, sampling regions around the Pacific using dense arrays in North America and Japan. We observe that short-period P waves traveling through slabs are strongly affected by focusing, in agreement with the bias we have observed and corrected for due to mantle heterogeneities on PcP-P travel time differences. In Central America, this bias is by far the stronger anomaly we observe

  14. Lupus I Observations from the 2010 Flight of the Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry

    CERN Document Server

    Matthews, Tristan G; Angilè, Francesco E; Benton, Steven J; Chapin, Edward L; Chapman, Nicholas L; Devlin, Mark J; Fissel, Laura M; Fukui, Yasuo; Gandilo, Natalie N; Gundersen, Joshua O; Hargrave, Peter C; Klein, Jeffrey; Korotkov, Andrei L; Moncelsi, Lorenzo; Mroczkowski, Tony K; Netterfield, Calvin B; Novak, Giles; Nutter, David; Olmi, Luca; Pascale, Enzo; Poidevin, Frédérick; Savini, Giorgio; Scott, Douglas; Shariff, Jamil A; Soler, Juan Diego; Tachihara, Kengo; Thomas, Nicholas E; Truch, Matthew D P; Tucker, Carole E; Tucker, Gregory S; Ward-Thompson, Derek

    2013-01-01

    The Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry (BLASTPol) was created by adding polarimetric capability to the BLAST experiment that was flown in 2003, 2005, and 2006. BLASTPol inherited BLAST's 1.8 m primary and its Herschel/SPIRE heritage focal plane that allows simultaneous observation at 250, 350, and 500 {\\mu}m. We flew BLASTPol in 2010 and again in 2012. Both were long duration Antarctic flights. Here we present polarimetry of the nearby filamentary dark cloud Lupus I obtained during the 2010 flight. Despite limitations imposed by the effects of a damaged optical component, we were able to clearly detect submillimeter polarization on degree scales. We compare the resulting BLASTPol magnetic field map with a similar map made via optical polarimetry (The optical data were published in 1998 by J. Rizzo and collaborators.). The two maps partially overlap and are reasonably consistent with one another. We compare these magnetic field maps to the orientations of filaments in Lupus I,...

  15. A conceptual design for a Cassegrain-mounted high-resolution optical spectrograph for large-aperture telescopes

    Science.gov (United States)

    Froning, Cynthia S.; Osterman, Steven; Burgh, Eric; Beasley, Matthew; Scowen, Paul; Veach, Todd; Jordan, Steven; Ebbets, Dennis; Lieber, Michael; deCino, James; Castilho, Bruno Vaz; Gneiding, Clemens; César de Oliveira, Antonio

    2013-09-01

    We present a conceptual design for a high-resolution optical spectrograph appropriate for mounting at Cassegrain on a large aperture telescope. The design is based on our work for the Gemini High Resolution Optical Spectrograph (CUGHOS) project. Our design places the spectrograph at Cassegrain focus to maximize throughput and blue wavelength coverage, delivering R=40,000 resolving power over a continuous 320-1050 nm waveband with throughputs twice those of current instruments. The optical design uses a two-arm, cross-dispersed echelle format with each arm optimized to maximize efficiency. A fixed image slicer is used to minimize optics sizes. The principal challenge for the instrument design is to minimize flexure and degradation of the optical image. To ensure image stability, our opto-mechanical design combines a cost-effective, passively stable bench employing a honeycomb aluminum structure with active flexure control. The active flexure compensation consists of hexapod mounts for each focal plane with full 6-axis range of motion capability to correct for focus and beam displacement. We verified instrument performance using an integrated model that couples the optical and mechanical design to image performance. The full end-to-end modeling of the system under gravitational, thermal, and vibrational perturbations shows that deflections of the optical beam at the focal plane are active control to meet the stability requirement. The design elements and high fidelity modeling process are generally applicable to instruments requiring high stability under a varying gravity vector.

  16. Spaceborne Microwave Instrument for High Resolution Remote Sensing of the Earth's Surface Using a Large-Aperture Mesh Antenna

    Science.gov (United States)

    Njoku, E.; Wilson, W.; Yueh, S.; Freeland, R.; Helms, R.; Edelstein, W.; Sadowy, G.; Farra, D.; West, R.; Oxnevad, K.

    2001-01-01

    This report describes a two-year study of a large-aperture, lightweight, deployable mesh antenna system for radiometer and radar remote sensing of the Earth from space. The study focused specifically on an instrument to measure ocean salinity and Soil moisture. Measurements of ocean salinity and soil moisture are of critical . importance in improving knowledge and prediction of key ocean and land surface processes, but are not currently obtainable from space. A mission using this instrument would be the first demonstration of deployable mesh antenna technology for remote sensing and could lead to potential applications in other remote sensing disciplines that require high spatial resolution measurements. The study concept features a rotating 6-m-diameter deployable mesh antenna, with radiometer and radar sensors, to measure microwave emission and backscatter from the Earth's surface. The sensors operate at L and S bands, with multiple polarizations and a constant look angle, scanning across a wide swath. The study included detailed analyses of science requirements, reflector and feedhorn design and performance, microwave emissivity measurements of mesh samples, design and test of lightweight radar electronic., launch vehicle accommodations, rotational dynamics simulations, and an analysis of attitude control issues associated with the antenna and spacecraft, The goal of the study was to advance the technology readiness of the overall concept to a level appropriate for an Earth science emission.

  17. Seasonal variability of turbulent fluxes over a vegetated subtropical coastal wetland measured by large aperture scintillometry and eddy covariance

    Science.gov (United States)

    Guyot, Adrien; Gray, Michael; Riesenkamp, Michiel; Lockington, David; McGowan, Hamish

    2016-04-01

    Subtropical coastal wetlands are particularly susceptible to the impacts of climate variability: their recharge rates strongly depend on rainfall, and the occurrence of prolonged droughts or wet periods have direct consequences for wetland health and bio-diversity. There is therefore a need to close the water budget of these ecosystems and this requires the quantification of rates of evaporation/evapotranspiration. However, few studies have documented land-atmosphere exchanges over wetlands for which water level varies considerably during a typical annual cycle. Here, we present a year of turbulent flux observations over a wetland on the subtropical coast of eastern Australia. Large Aperture Scintillometry and Eddy Covariance are used to derive sensible heat fluxes. Latent heat fluxes are also derived through an energy balance for both instruments' observations and also directly through Eddy Covariance. Careful sensitivity analysis of the instrumental footprints, seasonal variations of land surface parameters such as roughness length and displacement height are examined and subsequent uncertainties in the derived turbulent fluxes are discussed. Finally we show how these observations can also help better understand hydrological processes at the catchment scale.

  18. CONSTRUCTION METHOD FOR LARGE-APERTURE DEWATERING WELL SEALING%大孔降水井封井工法

    Institute of Scientific and Technical Information of China (English)

    刘勇; 顾冠忠

    2012-01-01

    目前大压力水的降水井封闭一般由专业队伍施工,费用较高.采用大孔降水井封井工法,利用千斤顶压住地下水,用膨胀橡胶止水条填塞钢板与井管间的缝隙,再焊接钢板与导管的横缝,将地下水封在井下.该做法简便易行,经济实用.%At present, sealing of high-pressure dewatering well is usually carried out by professionals and the construction cost is high. Large -aperture dewatering well sealing method could successfully seal the groundwater in well by using jack to press down the groundwater and expansion rubber strip to fill the clearance between steel sheet and well tube before welding the cross joint between steel sheet and pipeline. This is a simple, economic, practical and feasible method.

  19. The ExaVolt Antenna: A Large-Aperture, Balloon-embedded Antenna for Ultra-high Energy Particle Detection

    CERN Document Server

    Gorham, P W; Allison, P; Liewer, K M; Miki, C; Hill, B; Varner, G S

    2011-01-01

    We describe the scientific motivation, experimental basis, design methodology, and simulated performance of the ExaVolt Antenna (EVA) mission, and planned ultra-high energy (UHE) particle observatory under development for NASA's suborbital super-pressure balloon program in Antarctica. EVA will improve over ANITA's integrated totals - the current state-of-the-art in UHE suborbital payloads - by 1-2 orders of magnitude in a single flight. The design is based on a novel application of toroidal reflector optics which utilizes a super-pressure balloon surface, along with a feed-array mounted on an inner membrane, to create an ultra-large radio antenna system with a synoptic view of the Antarctic ice sheet below it. Radio impulses arise via the Askaryan effect when UHE neutrinos interact within the ice, or via geosynchrotron emission when UHE cosmic rays interact in the atmosphere above the continent. EVA's instantaneous antenna aperture is estimated to be several hundred square meters for detection of these events...

  20. A scalable multi-chip architecture to realise large-format microshutter arrays for coded aperture applications

    Science.gov (United States)

    McNie, Mark E.; King, David O.; Smith, Gilbert W.; Stone, Steven M.; Brown, Alan G.; Gordon, Neil T.; Slinger, Christopher W.; Cannon, Kevin; Riches, Stephen; Rogers, Stanley

    2009-08-01

    Coded aperture imaging has been used for astronomical applications for several years. Typical implementations used a fixed mask pattern and are designed to operate in the X-Ray or gamma ray bands. Recently applications have emerged in the visible and infra red bands for low cost lens-less imaging systems and system studies have shown that considerable advantages in image resolution may accrue from the use of multiple different images of the same scene - requiring a reconfigurable mask. Previously we reported on the realization of a 2x2cm single chip mask in the mid-IR based on polysilicon micro-opto-electro-mechanical systems (MOEMS) technology and its integration with ASIC drive electronics using conventional wire bonding. The MOEMS architecture employs interference effects to modulate incident light - achieved by tuning a large array of asymmetric Fabry-Perot optical cavities via an applied voltage and uses a hysteretic row/column scheme for addressing. In this paper we present the latest transmission results in the mid-IR band (3-5μm) and report on progress in developing a scalable architecture based on a tiled approach using multiple 2 x 2cm MOEMS chips with associated control ASICs integrated using flip chip technology. Initial work has focused on a 2 x 2 tiled array as a stepping stone towards an 8 x 8 array.

  1. Direct Numerical Simulation of Reionization in Large Cosmological Volumes I: Numerical Methods and Tests

    CERN Document Server

    Norman, Michael L; So, Geoffrey C; Harkness, Robsert P

    2013-01-01

    We describe an extension of the {\\em Enzo} code to enable the direct numerical simulation of inhomogeneous reionization in large cosmological volumes. By direct we mean all dynamical, radiative, and chemical properties are solved self-consistently on the same mesh, as opposed to a postprocessing approach which coarse-grains the radiative transfer. We do, however, employ a simple subgrid model for star formation, which we calibrate to observations. The numerical method presented is a modification of an earlier method presented in Reynolds et al. Radiation transport is done in the grey flux-limited diffusion (FLD) approximation, which is solved by implicit time integration split off from the gas energy and ionization equations, which are solved separately. This results in a faster and more robust scheme for cosmological applications compared to the earlier method. The FLD equation is solved using the {\\em hypre} optimally scalable geometric multigrid solver from LLNL. By treating the ionizing radiation as a gri...

  2. A numerical shoreline model for shorelines with large curvature

    DEFF Research Database (Denmark)

    Kærgaard, Kasper Hauberg; Fredsøe, Jørgen

    2013-01-01

    This paper presents a new numerical model for shoreline change which can be used to model the evolution of shorelines with large curvature. The model is based on a one-line formulation in terms of coordinates which follow the shape of the shoreline, instead of the more common approach where the two...... orthogonal horizontal directions are used. The volume error in the sediment continuity equation which is thereby introduced is removed through an iterative procedure. The model treats the shoreline changes by computing the sediment transport in a 2D coastal area model, and then integrating the sediment...... transport field across the coastal profile to obtain the longshore sediment transport variation along the shoreline. The model is used to compute the evolution of a shoreline with a 90° change in shoreline orientation; due to this drastic change in orientation a migrating shoreline spit develops...

  3. Nearly diffraction-limited X-ray focusing with variable-numerical-aperture focusing optical system based on four deformable mirrors

    Science.gov (United States)

    Matsuyama, Satoshi; Nakamori, Hiroki; Goto, Takumi; Kimura, Takashi; Khakurel, Krishna P.; Kohmura, Yoshiki; Sano, Yasuhisa; Yabashi, Makina; Ishikawa, Tetsuya; Nishino, Yoshinori; Yamauchi, Kazuto

    2016-04-01

    Unlike the electrostatic and electromagnetic lenses used in electron microscopy, most X-ray focusing optical systems have fixed optical parameters with constant numerical apertures (NAs). This lack of adaptability has significantly limited application targets. In the research described herein, we developed a variable-NA X-ray focusing system based on four deformable mirrors, two sets of Kirkpatrick-Baez-type focusing mirrors, in order to control the focusing size while keeping the position of the focus unchanged. We applied a mirror deformation procedure using optical/X-ray metrology for offline/online adjustments. We performed a focusing test at a SPring-8 beamline and confirmed that the beam size varied from 108 nm to 560 nm (165 nm to 1434 nm) in the horizontal (vertical) direction by controlling the NA while maintaining diffraction-limited conditions.

  4. Analysis of line-and-space resist patterns with sub-20 nm half-pitch fabricated using high-numerical-aperture exposure tool of extreme ultraviolet lithography

    Science.gov (United States)

    Kozawa, Takahiro; Santillan, Julius Joseph; Itani, Toshiro

    2016-09-01

    The resolution of resist processes for extreme ultraviolet (EUV) lithography has been steadily improved and has reached the sub-20 nm half-pitch region. Currently, the resist materials capable of resolving 11 nm half-pitch line-and-space patterns are being developed in industrial fields. In this study, the line-and-space resist patterns with sub-20 nm half-pitches were fabricated using a high-numerical-aperture (NA) EUV exposure tool and analyzed by the Monte Carlo simulation. The scanning electron microscopy (SEM) images of resist patterns after their development were compared with the latent images calculated on the basis of the sensitization and reaction mechanisms of chemically amplified EUV resists. The approximate relationship between resist patterns and latent images was clarified for the sub-20 nm half-pitch region. For the realization of 11 nm half-pitch fabrication, the suppression of the stochastic effects in the development process is an important consideration.

  5. Nearly diffraction-limited X-ray focusing with variable-numerical-aperture focusing optical system based on four deformable mirrors.

    Science.gov (United States)

    Matsuyama, Satoshi; Nakamori, Hiroki; Goto, Takumi; Kimura, Takashi; Khakurel, Krishna P; Kohmura, Yoshiki; Sano, Yasuhisa; Yabashi, Makina; Ishikawa, Tetsuya; Nishino, Yoshinori; Yamauchi, Kazuto

    2016-04-21

    Unlike the electrostatic and electromagnetic lenses used in electron microscopy, most X-ray focusing optical systems have fixed optical parameters with constant numerical apertures (NAs). This lack of adaptability has significantly limited application targets. In the research described herein, we developed a variable-NA X-ray focusing system based on four deformable mirrors, two sets of Kirkpatrick-Baez-type focusing mirrors, in order to control the focusing size while keeping the position of the focus unchanged. We applied a mirror deformation procedure using optical/X-ray metrology for offline/online adjustments. We performed a focusing test at a SPring-8 beamline and confirmed that the beam size varied from 108 nm to 560 nm (165 nm to 1434 nm) in the horizontal (vertical) direction by controlling the NA while maintaining diffraction-limited conditions.

  6. A comparison of eddy-covariance and large aperture scintillometer measurements with respect to the energy balance closure problem

    Directory of Open Access Journals (Sweden)

    S. M. Liu

    2011-04-01

    Full Text Available We analyzed the seasonal variations of energy balance components over three different surfaces: irrigated cropland (Yingke, YK, alpine meadow (A'rou, AR, and spruce forest (Guantan, GT. The energy balance components were measured using eddy covariance (EC systems and a large aperture scintillometer (LAS in the Heihe River Basin, China, in 2008 and 2009. We also determined the source areas of the EC and LAS measurements with a footprint model for each site and discussed the differences between the sensible heat fluxes measured with EC and LAS at AR. The results show that the main EC source areas were within a radius of 250 m at all of the sites. The main source area for the LAS (with a path length of 2390 m stretched along a path line approximately 2000 m long and 700 m wide. The surface characteristics in the source areas changed with the season at each site, and there were characteristic seasonal variations in the energy balance components at all of the sites. The sensible heat flux was the main term of the energy budget during the dormant season. During the growing season, however, the latent heat flux dominated the energy budget, and an obvious "oasis effect" was observed at YK. The sensible heat fluxes measured by LAS at AR were larger than those measured by EC at the same site. This difference seems to be caused by the so-called energy imbalance phenomenon, the heterogeneity of the underlying surfaces, and the difference between the source areas of the LAS and EC measurements.

  7. Coded Aperture Imaging for Fluorescent X-rays-Biomedical Applications

    Energy Technology Data Exchange (ETDEWEB)

    Haboub, Abdel; MacDowell, Alastair; Marchesini, Stefano; Parkinson, Dilworth

    2013-06-01

    Employing a coded aperture pattern in front of a charge couple device pixilated detector (CCD) allows for imaging of fluorescent x-rays (6-25KeV) being emitted from samples irradiated with x-rays. Coded apertures encode the angular direction of x-rays and allow for a large Numerical Aperture x- ray imaging system. The algorithm to develop the self-supported coded aperture pattern of the Non Two Holes Touching (NTHT) pattern was developed. The algorithms to reconstruct the x-ray image from the encoded pattern recorded were developed by means of modeling and confirmed by experiments. Samples were irradiated by monochromatic synchrotron x-ray radiation, and fluorescent x-rays from several different test metal samples were imaged through the newly developed coded aperture imaging system. By choice of the exciting energy the different metals were speciated.

  8. 地基大口径望远镜系统结构技术综述%Overview of structure technologies of large aperture ground-based telescopes

    Institute of Scientific and Technical Information of China (English)

    张景旭

    2012-01-01

    The developing status of large aperture ground-based telescopes is reviewed in this paper.The significance of bigger apertures for telescopes and their main technological approaches are expatiated and the summary on appliance values of modern large aperture telescopes is given.Then,it introduces five kinds of modern typical large telescope systems,which represent the topmost technological level.The key structures and technologies of large telescopes about mount,telescope tubes,primary mirror supports and secondary mirror assemblies are disscussed.Finally,it summarizes the developing trends of the large aperture ground-based telescopes and points out that some of the optical systems in the telescopes have been changed from coaxial systems to off-axial systems,while they are better application prospects.%概述了地基大口径望远镜的发展状况,阐述了口径变大的意义及实现的关键技术途径。概括了当前大口径望远镜的应用价值。介绍了国外5种典型的大口径望远镜系统,它们代表了当前地基大口径望远镜发展的最高技术水平。从跟踪架、主望远镜筒、主镜支撑及次镜支撑调整几个方面论述了大口径望远镜的结构特点及关键技术。最后,总结了大口径望远镜系统的发展趋势,指出其光学系统已从同轴系统向离轴系统发展并极具应用前景。

  9. Assessment of large aperture scintillometry for large-area surface energy fluxes over an irrigated cropland in north India

    Indian Academy of Sciences (India)

    Abhishek Danodia; V K Sehgal; N R Patel; R Dhakar; J Mukherjee; S K Saha; A Senthil Kumar

    2017-07-01

    Amount of available net energy and its partitioning into sensible, latent and soil heat fluxes over an agricultural landscape are critical to improve estimation of evapotranspiration and modelling parse (ecosystem modelling, hydrological and meteorological modelling). Scintillometry is a peculiar and robust methodology to provide structure parameter of refractive index and energy balance. Scintillometer has proven for assessment of sensible and latent heat flux, which is based on the principle of Monin–Obukhov similarity theory. Scintillometer has been installed in the agricultural experimental farm of ICAR-Indian Agricultural Research Institute, New Delhi, with a spatial covering path length of 990 m of irrigated and cultivable agricultural landscape. This paper discusses the patterns of energy flux as diurnal and seasonal basis at scintillometer path which was mainly covered by maize in Kharif and wheat in Rabi season during a crop growing seasons of 2014–2015. The biophysical parameters (leaf area, soil moisture, crop height) were recorded at a temporal resolution of fortnight basis along the path length at usual sampling distance. The Bowen ratio value for both Kharif and Rabi season was 0.76 and 0.88, respectively by scintillometer. Leaf area index had a significantly positive correlation with latent heat flux ($R^{2} =0.80$) while a significantly negative correlation with sensible heat flux ($R^{2}{=}-0.79$). Soil moisture had a significant negative correlation with sensible heat flux ($R^{2}{=}-0.68$). The average evapotranspiration from crop land was 1.58 mm d−1 and total evapotranspiration was 543 mm over the 12 months study period. 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

  10. Estimating Evapotranspiration over Heterogeneously Vegetated Surfaces using Large Aperture Scintillometer, LiDAR, and Airborne Multispectral Imagery

    Science.gov (United States)

    Geli, H. M.; Neale, C. M.; Pack, R. T.; Watts, D. R.; Osterberg, J.

    2011-12-01

    Estimates of evapotranspiration (ET) over heterogeneous areas is challenging especially in water-limited sparsely vegetated environments. New techniques such as airborne full-waveform LiDAR (Light Detection and Ranging) and high resolution multispectral and thermal imagery can provide enough detail of sparse canopies to improve energy balance model estimations as well as footprint analysis of scintillometer data. The objectives of this study were to estimate ET over such areas and develop methodologies for the use of these airborne data technologies. Because of the associated heterogeneity, this study was conducted over the Cibola National wildlife refuge, southern California on an area dominated with tamarisk (salt cedar) forest (90%) interspersed with arrowweed and bare soil (10%). A set of two large aperture scintillometers (LASs) were deployed over the area to provide estimates of sensible heat flux (HLAS). The LASs were distributed over the area in a way that allowed capturing different surface spatial heterogeneity. Bowen ratio systems were used to provide hydrometeorological variables and surface energy balance fluxes (SEBF) (i.e. Rn, G, H, and LE) measurements. Scintillometer-based estimates of HLAS were improved by considering the effect of the corresponding 3D footprint and the associated displacement height (d) and the roughness length (z0) following Geli et al. (2011). The LiDAR data were acquired using the LASSI Lidar developed at Utah State University (USU). The data was used to obtain 1-m spatial resolution DEM's and vegetation canopy height to improve the HLAS estimates. The BR measurements of Rn and G were combined with LAS estimates, HLAS, to provide estimates of LELASas a residual of the energy balance equation. A thermal remote sensing model namely the two source energy balance (TSEB) of Norman et al. (1995) was applied to provide spatial estimates of SEBF. Four airborne images at 1-4 meter spatial resolution acquired using the USU airborne

  11. Development of design technique for vacuum insulation in large size multi-aperture multi-grid accelerator for nuclear fusion

    Science.gov (United States)

    Kojima, A.; Hanada, M.; Tobari, H.; Nishikiori, R.; Hiratsuka, J.; Kashiwagi, M.; Umeda, N.; Yoshida, M.; Ichikawa, M.; Watanabe, K.; Yamano, Y.; Grisham, L. R.

    2016-02-01

    Design techniques for the vacuum insulation have been developed in order to realize a reliable voltage holding capability of multi-aperture multi-grid (MAMuG) accelerators for fusion application. In this method, the nested multi-stage configuration of the MAMuG accelerator can be uniquely designed to satisfy the target voltage within given boundary conditions. The evaluation of the voltage holding capabilities of each acceleration stages was based on the previous experimental results about the area effect and the multi-aperture effect. Since the multi-grid effect was found to be the extension of the area effect by the total facing area this time, the total voltage holding capability of the multi-stage can be estimated from that per single stage by assuming the stage with the highest electric field, the total facing area, and the total apertures. By applying these consideration, the analysis on the 3-stage MAMuG accelerator for JT-60SA agreed well with the past gap-scan experiments with an accuracy of less than 10% variation, which demonstrated the high reliability to design MAMuG accelerators and also multi-stage high voltage bushings.

  12. Development of design technique for vacuum insulation in large size multi-aperture multi-grid accelerator for nuclear fusion

    Energy Technology Data Exchange (ETDEWEB)

    Kojima, A., E-mail: kojima.atsushi@jaea.go.jp; Hanada, M.; Tobari, H.; Nishikiori, R.; Hiratsuka, J.; Kashiwagi, M.; Umeda, N.; Yoshida, M.; Ichikawa, M.; Watanabe, K. [Japan Atomic Energy Agency, Naka, Ibaraki 311-0193 (Japan); Yamano, Y. [Saitama University, Saitama, Saitama-ken 338-8570 (Japan); Grisham, L. R. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)

    2016-02-15

    Design techniques for the vacuum insulation have been developed in order to realize a reliable voltage holding capability of multi-aperture multi-grid (MAMuG) accelerators for fusion application. In this method, the nested multi-stage configuration of the MAMuG accelerator can be uniquely designed to satisfy the target voltage within given boundary conditions. The evaluation of the voltage holding capabilities of each acceleration stages was based on the previous experimental results about the area effect and the multi-aperture effect. Since the multi-grid effect was found to be the extension of the area effect by the total facing area this time, the total voltage holding capability of the multi-stage can be estimated from that per single stage by assuming the stage with the highest electric field, the total facing area, and the total apertures. By applying these consideration, the analysis on the 3-stage MAMuG accelerator for JT-60SA agreed well with the past gap-scan experiments with an accuracy of less than 10% variation, which demonstrated the high reliability to design MAMuG accelerators and also multi-stage high voltage bushings.

  13. Development of design technique for vacuum insulation in large size multi-aperture multi-grid accelerator for nuclear fusion.

    Science.gov (United States)

    Kojima, A; Hanada, M; Tobari, H; Nishikiori, R; Hiratsuka, J; Kashiwagi, M; Umeda, N; Yoshida, M; Ichikawa, M; Watanabe, K; Yamano, Y; Grisham, L R

    2016-02-01

    Design techniques for the vacuum insulation have been developed in order to realize a reliable voltage holding capability of multi-aperture multi-grid (MAMuG) accelerators for fusion application. In this method, the nested multi-stage configuration of the MAMuG accelerator can be uniquely designed to satisfy the target voltage within given boundary conditions. The evaluation of the voltage holding capabilities of each acceleration stages was based on the previous experimental results about the area effect and the multi-aperture effect. Since the multi-grid effect was found to be the extension of the area effect by the total facing area this time, the total voltage holding capability of the multi-stage can be estimated from that per single stage by assuming the stage with the highest electric field, the total facing area, and the total apertures. By applying these consideration, the analysis on the 3-stage MAMuG accelerator for JT-60SA agreed well with the past gap-scan experiments with an accuracy of less than 10% variation, which demonstrated the high reliability to design MAMuG accelerators and also multi-stage high voltage bushings.

  14. APT: Aperture Photometry Tool

    Science.gov (United States)

    Laher, Russ

    2012-08-01

    Aperture Photometry Tool (APT) is software for astronomers and students interested in manually exploring the photometric qualities of astronomical images. It has a graphical user interface (GUI) which allows the image data associated with aperture photometry calculations for point and extended sources to be visualized and, therefore, more effectively analyzed. Mouse-clicking on a source in the displayed image draws a circular or elliptical aperture and sky annulus around the source and computes the source intensity and its uncertainty, along with several commonly used measures of the local sky background and its variability. The results are displayed and can be optionally saved to an aperture-photometry-table file and plotted on graphs in various ways using functions available in the software. APT is geared toward processing sources in a small number of images and is not suitable for bulk processing a large number of images, unlike other aperture photometry packages (e.g., SExtractor). However, APT does have a convenient source-list tool that enables calculations for a large number of detections in a given image. The source-list tool can be run either in automatic mode to generate an aperture photometry table quickly or in manual mode to permit inspection and adjustment of the calculation for each individual detection. APT displays a variety of useful graphs, including image histogram, and aperture slices, source scatter plot, sky scatter plot, sky histogram, radial profile, curve of growth, and aperture-photometry-table scatter plots and histograms. APT has functions for customizing calculations, including outlier rejection, pixel “picking” and “zapping,” and a selection of source and sky models. The radial-profile-interpolation source model, accessed via the radial-profile-plot panel, allows recovery of source intensity from pixels with missing data and can be especially beneficial in crowded fields.

  15. Reflecting microscope system with a 0.99 numerical aperture designed for three-dimensional fluorescence imaging of individual molecules at cryogenic temperatures

    Science.gov (United States)

    Inagawa, H.; Toratani, Y.; Motohashi, K.; Nakamura, I.; Matsushita, M.; Fujiyoshi, S.

    2015-01-01

    We have developed a cryogenic fluorescence microscope system, the core of which is a reflecting objective that consists of spherical and aspherical mirrors. The use of an aspherical mirror allows the reflecting objective to have a numerical aperture (NA) of up to 0.99, which is close to the maximum possible NA of 1.03 in superfluid helium. The performance of the system at a temperature of 1.7 K was tested by recording a three-dimensional fluorescence image of individual quantum dots using excitation wavelengths (λex) of 532 nm and 635 nm. At 1.7 K, the microscope worked with achromatic and nearly diffraction-limited performance. The 1/e2 radius (Γ) of the point spread function of the reflecting objective in the lateral (xy) direction was 0.212 ± 0.008 μm at λex = 532 nm and was less than 1.2 times the simulated value for a perfectly polished objective. The radius Γ in the axial (z) direction was 0.91 ± 0.04 μm at λex = 532 nm and was less than 1.4 times the simulated value of Γ. The chromatic aberrations between the two wavelengths were one order of magnitude smaller than Γ in each direction. PMID:26239746

  16. Reduction of large-scale numerical ground water flow models

    NARCIS (Netherlands)

    Vermeulen, P.T.M.; Heemink, A.W.; Testroet, C.B.M.

    2002-01-01

    Numerical models are often used for simulating ground water flow. Written in state space form, the dimension of these models is of the order of the number of model cells and can be very high (> million). As a result, these models are computationally very demanding, especially if many different scena

  17. Plane-polar Fresnel and far-field computations using the Fresnel-Wilcox and Jacobi-Bessel expansions. [for large aperture antennas

    Science.gov (United States)

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

    1981-01-01

    It is pointed out that the computation of the Fresnel fields for large aperture antennas is significant for many applications. The present investigation is concerned with an approach for the effective utilization of the coefficients of the Jacobi-Bessel series for the far-field to obtain an analytically continuous representation of the antenna field which is valid from the Fresnel region into the far field. Attention is given to exact formulations and closed form solutions, Fresnel and Fresnel small angle approximations, aspects of field expansion, the accuracy of the Fresnel and Fresnel small angle approximations, and the Jacobi-Bessel expansion applied to the Fresnel small angle approximation.

  18. High efficiency, high energy second-harmonic generation of Nd glass laser radiation in large aperture CsLiB sub 6 O sub 1 sub 0 crystals

    CERN Document Server

    Kiriyama, H; Yamakawa, K

    2002-01-01

    We have demonstrated the generation of a high-energy green laser pulse using large aperture CsLiB sub 6 O sub 1 sub 0 (CLBO) crystals. A pulsed energy of 25 J at 532-nm was generated using the 1064-nm incident Nd:glass laser radiation with an energy of 34 J. High conversion efficiency of 74% at intensities of only 370 MW/cm sup 2 was obtained using a two-stage crystal architecture. This result represents the highest green pulse energy ever reported using the CLBO crystals. We discuss in detail the design and performance of SHG using CLBO crystals.

  19. Optimal Numerical Schemes for Compressible Large Eddy Simulations

    Science.gov (United States)

    Edoh, Ayaboe; Karagozian, Ann; Sankaran, Venkateswaran; Merkle, Charles

    2014-11-01

    The design of optimal numerical schemes for subgrid scale (SGS) models in LES of reactive flows remains an area of continuing challenge. It has been shown that significant differences in solution can arise due to the choice of the SGS model's numerical scheme and its inherent dissipation properties, which can be exacerbated in combustion computations. This presentation considers the individual roles of artificial dissipation, filtering, secondary conservation (Kinetic Energy Preservation), and collocated versus staggered grid arrangements with respect to the dissipation and dispersion characteristics and their overall impact on the robustness and accuracy for time-dependent simulations of relevance to reacting and non-reacting LES. We utilize von Neumann stability analysis in order to quantify these effects and to determine the relative strengths and weaknesses of the different approaches. Distribution A: Approved for public release, distribution unlimited. Supported by AFOSR (PM: Dr. F. Fahroo).

  20. Numerical modeling of a large deformation thermoforming process

    Energy Technology Data Exchange (ETDEWEB)

    Schrank, M.G.

    1988-04-01

    A numerical solution, using finite element methods, is presented for the simulation of a blow-molding process used to form a thermoplastic polymer (polyethylene terephthalate). The constitutive relationship employed in the analysis is a modification of the creep power law, allowing both strain hardening and strain rate hardening of the material. Analytical results compare well with experimental data for both rate of deformation during the forming process and strain distribution in the final formed configuration. 15 figs.

  1. Numerical integration methods for large-scale biophysical simulations

    CERN Document Server

    Chignola, Roberto; Milotti, Edoardo

    2009-01-01

    Simulations of biophysical systems inevitably include steps that correspond to time integrations of ordinary differential equations. These equations are often related to enzyme action in the synthesis and destruction of molecular species, and in the regulation of transport of molecules into and out of the cell or cellular compartments. Enzyme action is almost invariably modeled with the quasi-steady-state Michaelis-Menten formula or its close relative, the Hill formula: this description leads to systems of equations that may be stiff and hard to integrate, and poses unusual computational challenges in simulations where a smooth evolution is interrupted by the discrete events that mark the cells' lives. This is the case of a numerical model (Virtual Biophysics Lab - VBL) that we are developing to simulate the growth of three-dimensional tumor cell aggregates (spheroids). The program must be robust and stable, and must be able to accept frequent changes in the underlying theoretical model: here we study the app...

  2. Large-scale numerical investigations of the antiferromagnetic Heisenberg icosidodecahedron

    Energy Technology Data Exchange (ETDEWEB)

    Ummethum, Joerg [Department of Physics, Bielefeld University, P.O. Box 100131, D-33501 Bielefeld (Germany); Schnack, Juergen, E-mail: jschnack@uni-bielefeld.de [Department of Physics, Bielefeld University, P.O. Box 100131, D-33501 Bielefeld (Germany); Laeuchli, Andreas M. [Inst. f. Theoretische Physik, Innsbruck University, Technikerstr. 25, 6020 Innsbruck (Austria)

    2013-02-15

    We present up to date investigations of the antiferromagnetic Heisenberg icosidodecahedron by means of the density matrix renormalization group method. We compare our results with modern correlator product state as well as Lanczos calculations. - Highlights: Black-Right-Pointing-Pointer Results of unprecedented accuracy for energies and correlation functions of a frustrated spin system. Black-Right-Pointing-Pointer Relevance for a large set of magnetic molecules. Black-Right-Pointing-Pointer Demonstration of accuracy of DDMRG.

  3. Research on sub-surface damage and its stress deformation in the process of large aperture and high diameter-to-thickness ratio TMT M3MP

    Science.gov (United States)

    Hu, Hai-xiang; Qi, Erhui; Cole, Glen; Hu, Hai-fei; Luo, Xiao; Zhang, Xue-jun

    2016-10-01

    Large flat mirrors play important roles in large aperture telescopes. However, they also introduce unpredictable problems. The surface errors created during manufacturing, testing, and supporting are all combined during measurement, thus making understanding difficult for diagnosis and treatment. Examining a high diameter-to-thickness ratio flat mirror, TMT M3MP, and its unexpected deformation during processing, we proposed a strain model of subsurface damage to explain the observed phenomenon. We designed a set of experiment, and checked the validity of our diagnosis. On that basis, we theoretical predicted the trend of this strain and its scale effect on Zerodur®, and checked the validity on another piece experimentally. This work guided the grinding-polishing process of M3MP, and will be used as reference for M3M processing as well.

  4. Aperture Photometry Tool

    Science.gov (United States)

    Laher, Russ R.; Gorjian, Varoujan; Rebull, Luisa M.; Masci, Frank J.; Fowler, John W.; Helou, George; Kulkarni, Shrinivas R.; Law, Nicholas M.

    2012-07-01

    Aperture Photometry Tool (APT) is software for astronomers and students interested in manually exploring the photometric qualities of astronomical images. It is a graphical user interface (GUI) designed to allow the image data associated with aperture photometry calculations for point and extended sources to be visualized and, therefore, more effectively analyzed. The finely tuned layout of the GUI, along with judicious use of color-coding and alerting, is intended to give maximal user utility and convenience. Simply mouse-clicking on a source in the displayed image will instantly draw a circular or elliptical aperture and sky annulus around the source and will compute the source intensity and its uncertainty, along with several commonly used measures of the local sky background and its variability. The results are displayed and can be optionally saved to an aperture-photometry-table file and plotted on graphs in various ways using functions available in the software. APT is geared toward processing sources in a small number of images and is not suitable for bulk processing a large number of images, unlike other aperture photometry packages (e.g., SExtractor). However, APT does have a convenient source-list tool that enables calculations for a large number of detections in a given image. The source-list tool can be run either in automatic mode to generate an aperture photometry table quickly or in manual mode to permit inspection and adjustment of the calculation for each individual detection. APT displays a variety of useful graphs with just the push of a button, including image histogram, x and y aperture slices, source scatter plot, sky scatter plot, sky histogram, radial profile, curve of growth, and aperture-photometry-table scatter plots and histograms. APT has many functions for customizing the calculations, including outlier rejection, pixel "picking" and "zapping," and a selection of source and sky models. The radial-profile-interpolation source model

  5. Numerical simulation of busbar configuration in large aluminum electrolysis cell

    Institute of Scientific and Technical Information of China (English)

    LI Mao; ZHOU Jie-ming

    2008-01-01

    Various busbar configurations were built and modeled by the custom code based on the commercial package ANSYS for the 500 kA aluminum electrolysis cell. The configuration parameters, such as side riser entry ratio, number of cathode bars connected to each riser, vertical location of side cathode busbar and short side cathode busbar, distance between rows of cells in potline, the number of neighboring cells, ratio of compensation busbar carried passing under cell and its horizontal location under cell along with large magnetohydrodynamic(MHD) computation based on the enstom evaluation function were simulated and discussed. The results show that a cell with riser entry ratio of 11:9:8:9:11 and cathode busbar located at the level of aluminum solution, 50% upstream cathode current passing under cell for magnetic field compensation, the distance between rows of 50 m is more stable.

  6. Numerical techniques for large cosmological N-body simulations

    Energy Technology Data Exchange (ETDEWEB)

    Efstathiou, G.; Davis, M.; Frenk, C.S.; White, S.D.M.

    1985-02-01

    We describe and compare techniques for carrying out large N-body simulations of the gravitational evolution of clustering in the fundamental cube of an infinite periodic universe. In particular, we consider both particle mesh (PM) codes and P/sup 3/M codes in which a higher resolution force is obtained by direct summation of contributions from neighboring particles. We discuss the mesh-induced anisotropies in the forces calculated by these schemes, and the extent to which they can model the desired 1/r/sup 2/ particle-particle interaction. We also consider how transformation of the time variable can improve the efficiency with which the equations of motion are integrated. We present tests of the accuracy with which the resulting schemes conserve energy and are able to follow individual particle trajectories. We have implemented an algorithm which allows initial conditions to be set up to model any desired spectrum of linear growing mode density fluctuations. A number of tests demonstrate the power of this algorithm and delineate the conditions under which it is effective. We carry out several test simulations using a variety of techniques in order to show how the results are affected by dynamic range limitations in the force calculations, by boundary effects, by residual artificialities in the initial conditions, and by the number of particles employed. For most purposes cosmological simulations are limited by the resolution of their force calculation rather than by the number of particles they can employ. For this reason, while PM codes are quite adequate to study the evolution of structure on large scale, P/sup 3/M methods are to be preferred, in spite of their greater cost and complexity, whenever the evolution of small-scale structure is important.

  7. Comparison of numerical schemes in large-eddy simulation of the temporal mixing layer

    NARCIS (Netherlands)

    Vreman, A.W.; Geurts, Bernardus J.; Kuerten, Johannes G.M.

    1996-01-01

    A posteriori tests of large-eddy simulations for the temporal mixing layer are performed using a variety of numerical methods in conjunction with the dynamic mixed subgrid model for the turbulent stress tensor. The results of the large-eddy simulations are compared with filtered direct numerical

  8. Numerical techniques for large cosmological N-body simulations

    Science.gov (United States)

    Efstathiou, G.; Davis, M.; White, S. D. M.; Frenk, C. S.

    1985-01-01

    Techniques for carrying out large N-body simulations of the gravitational evolution of clustering in the fundamental cube of an infinite periodic universe are described and compared. The accuracy of the forces derived from several commonly used particle mesh schemes is examined, showing how submesh resolution can be achieved by including short-range forces between particles by direct summation techniques. The time integration of the equations of motion is discussed, and the accuracy of the codes for various choices of 'time' variable and time step is tested by considering energy conservation as well as by direct analysis of particle trajectories. Methods for generating initial particle positions and velocities corresponding to a growing mode representation of a specified power spectrum of linear density fluctuations are described. The effects of force resolution are studied and different simulation schemes are compared. An algorithm is implemented for generating initial conditions by varying the number of particles, the initial amplitude of density fluctuations, and the initial peculiar velocity field.

  9. Evolving design criteria for very large aperture space-based telescopes and their influence on the need for intergrated tools in the optimization process

    Science.gov (United States)

    Arnold, William R.

    2015-09-01

    NASA's Advanced Mirror Technology Development (AMTD) program has been developing the means to design and build the future generations of space based telescopes. With the nearing completion of the James Webb Space Telescope (JWST), the astrophysics community is already starting to define the requirements for follow on observatories. The restrictions of available launch vehicles and the possibilities of planned future vehicles have fueled the competition between monolithic primaries (with better optical quality) and segmented primaries (with larger apertures, but with diffraction, costs and figure control issues). Regardless of the current shroud sizes and lift capacities, these competing architectures share the need for rapid design tools. As part of the AMTD program a number of tools have been developed and tested to speed up the design process. Starting with the Arnold Mirror Modeler (which creates Finite Element Models (FEM) for structural analysis) and now also feeds these models into thermal stability analyses. They share common file formats and interchangeable results. During the development of the program, numerous trade studies were created for 4 meter and 8 meter monolithic primaries, complete with support systems. Evaluation of these results has led to a better understanding of how the specification drives the results. This paper will show some of the early trade studies for typical specification requirements such as lowest mirror bending frequency and suspension system lowest frequency. The results use representative allowable stress values for each mirror substrate material and construction method and generic material properties. These studies lead to some interesting relationships between feasible designs and the realities of actually trying to build these mirrors. Much of the traditional specifications were developed for much smaller systems, where the mass and volume of the primary where a small portion of the overall satellite. JWST shows us that as

  10. Full-band error control and crack-free surface fabrication techniques for ultra-precision fly cutting of large-aperture KDP crystals

    Science.gov (United States)

    Zhang, F. H.; Wang, S. F.; An, C. H.; Wang, J.; Xu, Q.

    2017-06-01

    Large-aperture potassium dihydrogen phosphate (KDP) crystals are widely used in the laser path of inertial confinement fusion (ICF) systems. The most common method of manufacturing half-meter KDP crystals is ultra-precision fly cutting. When processing KDP crystals by ultra-precision fly cutting, the dynamic characteristics of the fly cutting machine and fluctuations in the fly cutting environment are translated into surface errors at different spatial frequency bands. These machining errors should be suppressed effectively to guarantee that KDP crystals meet the full-band machining accuracy specified in the evaluation index. In this study, the anisotropic machinability of KDP crystals and the causes of typical surface errors in ultra-precision fly cutting of the material are investigated. The structures of the fly cutting machine and existing processing parameters are optimized to improve the machined surface quality. The findings are theoretically and practically important in the development of high-energy laser systems in China.

  11. Development and Testing of a Power Trough System Using a Structurally-Efficient, High-Performance, Large-Aperture Concentrator with Thin Glass Reflector and Focal Point Rotation

    Energy Technology Data Exchange (ETDEWEB)

    May, E. K.; Forristall, R.

    2005-11-01

    Industrial Solar Technology has assembled a team of experts to develop a large-aperture parabolic trough for the electric power market that moves beyond cost and operating limitations of 1980's designs based on sagged glass reflectors. IST's structurally efficient space frame design will require nearly 50% less material per square meter than a Solel LS-2 concentrator and the new trough will rotate around the focal point. This feature eliminates flexhoses that increase pump power, installation and maintenance costs. IST aims to deliver a concentrator module costing less than $100 per square meter that can produce temperatures up to 400 C. The IST concentrator is ideally suited for application of front surface film reflectors and ensures that US corporations will manufacture major components, except for the high temperature receivers.

  12. Unsupervised polarimetric synthetic aperture radar classification of large-scale landslides caused by Wenchuan earthquake in hue-saturation-intensity color space

    Science.gov (United States)

    Li, Ning; Wang, Robert; Deng, Yunkai; Liu, Yabo; Li, Bochen; Wang, Chunle; Balz, Timo

    2014-01-01

    A simple and effective approach for unsupervised classification of large-scale landslides caused by the Wenchuan earthquake is developed. The data sets used were obtained by a high-resolution fully polarimetric airborne synthetic aperture radar system working at X-band. In the proposed approach, Pauli decomposition false-color RGB imagery is first transformed to the hue-saturation-intensity (HSI) color space. Then, a good combination of k-means clustering and HSI imagery in different channels is used stage-by-stage for automatic landslides extraction. Two typical case studies are presented to evaluate the feasibility of the proposed scheme. Our approach is an important contribution to the rapid assessment of landslide hazards.

  13. Science drivers and requirements for an Advanced Technology Large Aperture Space Telescope (ATLAST): Implications for technology development and synergies with other future facilities

    CERN Document Server

    Postman, Marc; Sembach, Kenneth; Giavalisco, Mauro; Traub, Wesley; Stapelfeldt, Karl; Calzetti, Daniela; Oegerle, William; Rich, R Michael; Stahl, H Phillip; Tumlinson, Jason; Mountain, Matt; Soummer, Rémi; Hyde, Tupper; 10.1117/12.857044

    2010-01-01

    The Advanced Technology Large-Aperture Space Telescope (ATLAST) is a concept for an 8-meter to 16-meter UVOIR space observatory for launch in the 2025-2030 era. ATLAST will allow astronomers to answer fundamental questions at the forefront of modern astronphysics, including "Is there life elsewhere in the Galaxy?" We present a range of science drivers that define the main performance requirements for ATLAST (8 to 16 milliarcsec angular resolution, diffraction limited imaging at 0.5 {\\mu}m wavelength, minimum collecting area of 45 square meters, high sensitivity to light wavelengths from 0.1 {\\mu}m to 2.4 {\\mu}m, high stability in wavefront sensing and control). We will also discuss the synergy between ATLAST and other anticipated future facilities (e.g., TMT, EELT, ALMA) and the priorities for technology development that will enable the construction for a cost that is comparable to current generation observatory-class space missions.

  14. Output characteristics of misaligned resonator for large-aperture thin disk laser%大口径薄片激光器失调输出特性

    Institute of Scientific and Technical Information of China (English)

    朱海涛; 冯国英; 阴明; 高翔; 杨火木; 张凯; 陈念江; 周寿桓

    2011-01-01

    The output characteristics of misaligned resonator for large-aperture thin disk laser have been studied experimentally and theoretically. A plane output coupler S1 . a concave mirror S2 and an aperture stop are arranged to define the V-shape resonator. The misalignment sensitivities of the output power are given by means of matrix optics and the misalignment diffraction integral equation. The misalignment effects of the resonator having a variable aperture stop diameter on output power and beam quality have been measured by tilt -angle measurement technique at 200 Hz pump frequency, as well as the output power relationship with the misalignments of mirror S1 and mirror S2 at 300 Hz pump frequency. The experimental results show that the output power is a quadratic function of the tilt angle, the misalignment tolerance is directly proportional to mirror diameter and the beam quality factor decreases as the tilt angle increases.%对大口径的薄片激光器的失调输出特性进行了理论和实验研究,V-型腔由平而输出耦合镜和凹面反射镜及孔径光阑组成.基于矩阵光学和失调衍射积分方程得到了激光器的功率失调曲线.实验测量了在200Hz泵浦频率下加入不同孔径光阑后谐振腔失调对输出功率的影响和谐振腔失调对光束质量的影响,以及在300Hz泵浦频率下输出功率分别与平面输出耦合镜和凹面反射镜失调的关系.实验结果表明:失调输出功率和失调角度成二次函数关系,失调容限和腔镜口径成正比,光束质量因子随失调角度的增大而变小.

  15. Functional derivatives applied to error propagation of uncertainties in topography to large-aperture scintillometer-derived heat fluxes

    NARCIS (Netherlands)

    Gruber, M.A.; Fochesatto, G.J.; Hartogensis, O.K.; Lysy, M.

    2014-01-01

    Scintillometer measurements allow for estimations of the refractive index structure parameter Cn2 over large areas in the atmospheric surface layer. Turbulent fluxes of heat and momentum are inferred through coupled sets of equations derived from the Monin–Obukhov similarity hypothesis. One-dimensio

  16. A 2x2 multi-chip reconfigurable MOEMS mask: a stepping stone to large format microshutter arrays for coded aperture applications

    Science.gov (United States)

    McNie, Mark E.; Brown, Alan G.; King, David O.; Smith, Gilbert W.; Gordon, Neil T.; Riches, Stephen; Rogers, Stanley

    2010-08-01

    Coded aperture imaging has been used for astronomical applications for several years. Typical implementations used a fixed mask pattern and are designed to operate in the X-Ray or gamma ray bands. Recently applications have emerged in the visible and infra red bands for low cost lens-less imaging systems and system studies have shown that considerable advantages in image resolution may accrue from the use of multiple different images of the same scene - requiring a reconfigurable mask. Previously reported work focused on realising a 2x2cm single chip mask in the mid-IR based on polysilicon micro-optoelectro- mechanical systems (MOEMS) technology and its integration with ASIC drive electronics using conventional wire bonding. It employs interference effects to modulate incident light - achieved by tuning a large array of asymmetric Fabry-Perot optical cavities via an applied voltage and uses a hysteretic row/column scheme for addressing. In this paper we report on the latest results in the mid-IR for the single chip reconfigurable MOEMS mask, trials in scaling up to a mask based on a 2x2 multi-chip array and report on progress towards realising a large format mask comprising 44 MOEMS chips. We also explore the potential of such large, transmissive IR spatial light modulator arrays for other applications and in the current and alternative architectures.

  17. High Numerates Count Icons and Low Numerates Process Large Areas in Pictographs: Results of an Eye-Tracking Study.

    Science.gov (United States)

    Kreuzmair, Christina; Siegrist, Michael; Keller, Carmen

    2016-08-01

    In two experiments, we investigated the influence of numeracy on individuals' information processing of pictographs depending on numeracy via an eye-tracker. In two conditions, participants from the general population were presented with a scenario depicting the risk of having cancer and were asked to indicate their perceived risk. The risk level was high (63%) in experiment 1 (N = 70) and low (6%) in experiment 2 (N = 69). In the default condition, participants were free to use their default strategy for information processing. In the guiding-toward-the-number condition, they were prompted to count icons in the pictograph by answering with an explicit number. We used eye-tracking parameters related to the distance between sequential fixations to analyze participants' strategies for processing numerical information. In the default condition, the higher the numeracy was, the shorter the distances traversed in the pictograph were, indicating that participants counted the icons. People lower in numeracy performed increased large-area processing by comparing highlighted and nonhighlighted parts of the pictograph. In the guiding-toward-the-number condition, participants used short distances regardless of their numeracy, supporting the notion that short distances represent counting. Despite the different default processing strategies, participants processed the pictograph with a similar depth and derived similar risk perceptions. The results show that pictographs are beneficial for communicating medical risk. Pictographs make the gist salient by making the part-to-whole relationship visually available, and they facilitate low numerates' non-numeric processing of numerical information. Contemporaneously, pictographs allow high numerates to numerically process and rely on the number depicted in the pictograph.

  18. 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...

  19. Large aperture Fizeau interferometer commissioning and preliminary measurements of a long x-ray mirror at European X-ray Free Electron Laser

    Science.gov (United States)

    Vannoni, M.; Freijo Martín, I.

    2016-05-01

    The European XFEL (X-ray Free Electron Laser) is a large facility under construction in Hamburg, Germany. It will provide a transversally fully coherent x-ray radiation with outstanding characteristics: high repetition rate (up to 2700 pulses with a 0.6 ms long pulse train at 10 Hz), short wavelength (down to 0.05 nm), short pulse (in the femtoseconds scale), and high average brilliance (1.6 ṡ 1025 (photons s-1 mm-2 mrad-2)/0.1% bandwidth). The beam has very high pulse energy; therefore, it has to be spread out on a relatively long mirror (about 1 m). Due to the very short wavelength, the mirrors need to have a high quality surface on their entire length, and this is considered very challenging even with the most advanced polishing methods. In order to measure the mirrors and to characterize their interaction with the mechanical mount, we equipped a metrology laboratory with a large aperture Fizeau interferometer. The system is a classical 100 mm diameter commercial Fizeau, with an additional expander providing a 300 mm diameter beam. Despite the commercial nature of the system, special care has been taken in the polishing of the reference flats and in the expander quality. We report the first commissioning of the instrument, its calibration, and performance characterization, together with some preliminary results with the measurement of a 950 mm silicon substrate. The intended application is to characterize the final XFEL mirrors with nanometer accuracy.

  20. Large aperture Fizeau interferometer commissioning and preliminary measurements of a long x-ray mirror at European X-ray Free Electron Laser.

    Science.gov (United States)

    Vannoni, M; Freijo Martín, I

    2016-05-01

    The European XFEL (X-ray Free Electron Laser) is a large facility under construction in Hamburg, Germany. It will provide a transversally fully coherent x-ray radiation with outstanding characteristics: high repetition rate (up to 2700 pulses with a 0.6 ms long pulse train at 10 Hz), short wavelength (down to 0.05 nm), short pulse (in the femtoseconds scale), and high average brilliance (1.6 ⋅ 10(25) (photons s(-1) mm(-2) mrad(-2))/0.1% bandwidth). The beam has very high pulse energy; therefore, it has to be spread out on a relatively long mirror (about 1 m). Due to the very short wavelength, the mirrors need to have a high quality surface on their entire length, and this is considered very challenging even with the most advanced polishing methods. In order to measure the mirrors and to characterize their interaction with the mechanical mount, we equipped a metrology laboratory with a large aperture Fizeau interferometer. The system is a classical 100 mm diameter commercial Fizeau, with an additional expander providing a 300 mm diameter beam. Despite the commercial nature of the system, special care has been taken in the polishing of the reference flats and in the expander quality. We report the first commissioning of the instrument, its calibration, and performance characterization, together with some preliminary results with the measurement of a 950 mm silicon substrate. The intended application is to characterize the final XFEL mirrors with nanometer accuracy.

  1. 大口径反射镜及其支撑结构设计%The design of large aperture mirror and support structure

    Institute of Scientific and Technical Information of China (English)

    张军; 张帆; 高明辉

    2012-01-01

    A kind of flexible structure applied to support the large aperture mirror is put forward for space remote sensing.With FEA method,the features such as support structure,size,the shape of the lightweight hole and weight distribution are calculated to obtain the feasible and reasonable structure.The result shows that the mirror surface figure precision can reach λ/40(λ=632.8 nm) in the structure,and can meet the needs of remote sensing precision.%提出了一种采用柔性支撑的大口径反射镜组件进行遥感器地面检测的装置。通过有限元分析对反射镜的支撑结构、形状尺寸、轻量化孔的形状、尺寸及分布位置进行计算,得到了一种合理可行的支撑结构。在该支撑结构下面形精度达到λ/40(λ=632.8nm),满足遥感器地面检测的精度要求。

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

    Science.gov (United States)

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

    2015-08-01

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

  3. Improved Large Aperture Collector Manufacturing

    Energy Technology Data Exchange (ETDEWEB)

    O' Rourke, Deven [Abengoa Solar LLC, Lakewood, CO (United States); Farr, Adrian [Abengoa Solar LLC, Lakewood, CO (United States)

    2015-12-01

    The parabolic trough is the most established CSP technology and carries a long history of design experimentation dating back to the 1970’s. This has led to relatively standardized collector architectures, a maturing global supply chain, and a fairly uniform cost reduction strategy. Abengoa has deployed more than 1,500MWe of CSP troughs across several countries and has built and tested full-scale prototypes of many R&D concepts. The latest trough R&D efforts involved efforts to internalize non-CSP industry experience including a preliminary DFMA principles review done with Boothroyd Dewhurst, a construction literature review by the Arizona State University School of Construction Management, and two more focused manufacturing engineering subcontracts done by Ricardo Inc. and the nonprofit Edison Welding Institute. The first two studies highlighted strong opportunities in lowering part count, standardizing components and fasteners, developing modular designs to support prefabrication and automation, and devising simple, error-proof manual assembly methods. These principles have delivered major new cost savings in otherwise “mature” products in analogous industries like automotive, truck trailer manufacture, metal building fabrication, and shipbuilding. For this reason, they were core in the design development of the SpaceTube® collector, and arguably key to its early successes. The latter two studies were applied specifically to the first-generation SpaceTube® design and were important in setting the direction of the present SolarMat project. These studies developed a methodology to analyze the costs of manufacture and assembly, and identify new tooling concepts for more efficient manufacture. Among the main opportunities identified in these studies were the automated mirror arm manufacturing concept and the need for a less infrastructure-intensive assembly line, both of which now form central pillars of the SolarMat project strategy. These new designs will be supported by new technology in the area of quality control inspection, in which state of the art photogrammetry and laser CMM inspection methods will be used to qualify parts and assemblies, and in which the recently-developed Absorber Reflection Method will enable in-line quality control inspection of modules produced by the new high-rate production line.

  4. OpTIIX: An ISS-Based Testbed Paving the Roadmap Toward a Next Generation Large Aperture UV/Optical Space Telescope

    Science.gov (United States)

    Carpenter, Kenneth G.; Etemad, Shar; Seery, Bernard D.; Thronson, Harley; Burdick, Gary M.; Coulter, Dan; Goullioud, Renaud; Green, Joseph J.; Liu, Fengchuan; Ess, Kim; hide

    2012-01-01

    The next generation large aperture UV/Optical space telescope will need a diameter substantially larger than even that of JWST in order to address some of the most compelling unanswered scientific quests. These quests include understanding the earliest phases of the Universe and detecting life on exo-planets by studying spectra of their atmospheres. Such 8-16 meter telescopes face severe challenges in terms of cost and complexity and are unlikely to be affordable unless a new paradigm is adopted for their design and construction. The conventional approach is to use monolithic or preassembled segmented mirrors requiring complicated and risky deployments and relying on future heavy-lift vehicles, large fairings and complex geometry. The new paradigm is to launch component modules on relatively small vehicles and then perform in-orbit robotic assembly of those modules. The Optical Testbed and Integration on ISS eXperiment (OpTIIX) is designed to demonstrate, at low cost by leveraging the infrastructure provided by ISS, telescope assembly technologies and end-to-end optical system technologies. The use of ISS as a testbed permits the concentration of resources on reducing the technical risks associated with robotically integrating the components. These include laser metrology and wavefront sensing and control (WFS&C) systems, an imaging instrument, lightweight, low-cost deformable primary mirror segments and the secondary mirror. These elements are then aligned to a diffraction-limited optical system in space. The capability to assemble the optical system and remove and replace components via the existing ISS robotic systems like the Special Purpose Dexterous Manipulator (SPDM), or by the ISS flight crew, allows for future experimentation, as well as repair.

  5. Biospark: scalable analysis of large numerical datasets from biological simulations and experiments using Hadoop and Spark.

    Science.gov (United States)

    Klein, Max; Sharma, Rati; Bohrer, Chris H; Avelis, Cameron M; Roberts, Elijah

    2017-01-15

    Data-parallel programming techniques can dramatically decrease the time needed to analyze large datasets. While these methods have provided significant improvements for sequencing-based analyses, other areas of biological informatics have not yet adopted them. Here, we introduce Biospark, a new framework for performing data-parallel analysis on large numerical datasets. Biospark builds upon the open source Hadoop and Spark projects, bringing domain-specific features for biology.

  6. Direct numerical simulation of the very large anisotropic scales in a turbulent channel

    CERN Document Server

    del Alamo, Juan C

    2013-01-01

    Over the last decades the knowledge on the small scales of turbulent wall flows has experienced a significant advance, especially in the near-wall region where the highest production of turbulent energy and the maximum turbulence intensity occur. The development of computers has played an important role in this progress, making direct numerical simulations affordable (Kim, Moin & Moser, 1987), and offering wider observational possibilities than most laboratory experiments. The large scales have received less attention, and it has not been until recently that their significance and their real size have been widely recognized, thanks in part to the experiments by Hites (1997) and Kim & Adrian (1999), and to the compilation of experimental and numerical data by Jimenez (1998). The requirements of both a very large box and a high Reynolds number has made direct numerical simulation of the VLAS unapproachable until today. The purpose of this report is to serve as a preliminary description of a newly compil...

  7. Numerical simulation of elasto-plastic electro-osmosis consolidation at large strain

    NARCIS (Netherlands)

    Yuan, J.; Hicks, M.A.

    2015-01-01

    n this paper, a numerical solution for the electro-osmosis consolidation of clay in multi-dimensional domains at large strains is presented, with the coupling of the soil mechanical behaviour, pore water transport and electrical fields being considered. In particular, the Modified Cam Clay model is

  8. Numerical simulation of elasto-plastic electro-osmosis consolidation at large strain

    NARCIS (Netherlands)

    Yuan, J.; Hicks, M.A.

    2015-01-01

    n this paper, a numerical solution for the electro-osmosis consolidation of clay in multi-dimensional domains at large strains is presented, with the coupling of the soil mechanical behaviour, pore water transport and electrical fields being considered. In particular, the Modified Cam Clay model is

  9. Application of large aperture spiral CT in radiotherapy simulation positioning%大孔径螺旋CT在放疗模拟定位中的应用研究

    Institute of Scientific and Technical Information of China (English)

    李雪南; 修霞; 李高峰

    2013-01-01

    目的:探讨大孔径16排螺旋CT在放疗模拟定位中的应用。方法:应用大孔径16排螺旋CT进行乳腺癌保乳术后根治性放疗乳腺切线野的CT模拟定位,并对CT模拟定位技术与传统X射线模拟定位技术进行比较,同时与单排螺旋CT的图像进行比较。结果:大孔径16排螺旋CT在放疗模拟定位中的应用避免了因患者体位受限而造成的误差;大孔径16排螺旋CT模拟机的定位验证误差均优于传统X射线模拟机;其图像质量优于单排螺旋CT。结论:大孔径16排螺旋CT模拟定位机的应用,使得放疗定位更加精确,计划和治疗更加准确。%Objective:To discuss application of large aperture 16 row spiral CT in radiotherapy simulation positioning. Methods: To apply CT simulation positioning with large aperture 16 row spiral CT for the breast tangential field by early breast cancer after breast conserving surgery and radical radiotherapy. Compare CT-simulation and X-ray conventional positioning technique and Compare large aperture 16 row spiral CT and single row spiral CT image. Results: The application of large aperture 16 row spiral CT avoided the error because of body limited. Large aperture 16 row spiral CT simulation position validation error is superior to X-ray positioning. Its image quality is better than that of single row spiral CT. Conclusion:The application of large aperture 16 row spiral CT make simulation positioning more accurate, planned and treatment more accurate, it can provide guarantee of accurate simulation positioning for accurate plan and treatment.

  10. Source locations of teleseismic P, SV, and SH waves observed in microseisms recorded by a large aperture seismic array in China

    Science.gov (United States)

    Liu, Qiaoxia; Koper, Keith D.; Burlacu, Relu; Ni, Sidao; Wang, Fuyun; Zou, Changqiao; Wei, Yunhao; Gal, Martin; Reading, Anya M.

    2016-09-01

    Transversely polarized seismic waves are routinely observed in ambient seismic energy across a wide range of periods, however their origin is poorly understood because the corresponding source regions are either undefined or weakly constrained, and nearly all models of microseism generation incorporate a vertically oriented single force as the excitation mechanism. To better understand the origin of transversely polarized energy in the ambient seismic wavefield we make the first systematic attempt to locate the source regions of teleseismic SH waves observed in microseismic (2.5-20 s) noise. We focus on body waves instead of surface waves because the source regions can be constrained in both azimuth and distance using conventional array techniques. To locate microseismic sources of SH waves (as well as SV and P waves) we continuously backproject the vertical, radial, and transverse components of the ambient seismic wavefield recorded by a large-aperture array deployed in China during 2013-2014. As expected, persistent P wave sources are observed in the North Atlantic, North Pacific, and Indian Oceans, mainly at periods of 2.5-10 s, in regions with the strong ocean wave interactions needed to produce secondary microseisms. SV waves are commonly observed to originate from locations indistinguishable from the P wave sources, but with smaller signal-to-noise ratios. We also observe SH waves with about half or less the signal-to-noise ratio of SV waves. SH source regions are definitively located in deep water portions of the Pacific, away from the sloping continental shelves that are thought to be important for the generation of microseismic Love waves, but nearby regions that routinely generate teleseismic P waves. The excitation mechanism for the observed SH waves may therefore be related to the interaction of P waves with small-wavelength bathymetric features, such as seamounts and basins, through some sort of scattering process.

  11. Numerical Buckling Analysis of Large Suction Caissons for Wind Turbines on Deep Water

    DEFF Research Database (Denmark)

    Madsen, Søren; Andersen, Lars Vabbersgaard; Ibsen, Lars Bo

    2013-01-01

    Using large suction caissons for offshore wind turbines is an upcoming cost-effective technology also referred to as bucket foundations. During operation, the monopod bucket foundation is loaded by a large overturning moment from the wind turbine and the wave loads. However, during installation...... the suction caisson is loaded by external pressure (internal suction) due to evacuation of water inside the bucket and vertical forces due to gravity. The risk of structural buckling during installation of large-diameter suction caissons is addressed using numerical methods. Initial imperfect geometries...

  12. Development of parallel mathematical subroutine library and large scale numerical simulation

    Energy Technology Data Exchange (ETDEWEB)

    Shimizu, Futoshi [Japan Atomic Energy Research Inst., Tokyo (Japan)

    1998-03-01

    In recent years, parallel computers, namely parallel supercomputers and workstation clusters, come into use for large scale numerical simulations in the field of computational science. At present, since the parallel programming is difficult compared to using serial computers, development of efficient program in parallel computers can be easily achieved by incorporating the parallelized numerical subroutines. In Japan Atomic Energy Research Institute (JAERI), portable mathematical subroutine library using MPI (Message Passing Interface) or PVM (Parallel Virtual Machine) is being developed for distributed memory parallel computers. In this report, we present the overview of the parallel library and its application to the parallelization for tight-binding molecular dynamics. (author)

  13. A 3-D Numerical Model for the Calculation of Water Wave Transformation in Large Area

    Institute of Scientific and Technical Information of China (English)

    孙大鹏; 李玉成; 葛岚

    2001-01-01

    Based on the integral equation transformed from three dimensional Laplace equation and by the adoption of the division manner of sub-region boundary element method, the numerical computations of the velocity potential of each sub-region are given considering the continuity conditions of potential and normal derivatives at the interface of sub-regions. Therefore, computation of wave deformation in offshore flow field is realized. The present numerical model provides a good solution for the application of boundary element method to the calculation of wave deformation in large areas.

  14. Ships as salient objects in synthetic aperture radar imaginary

    CSIR Research Space (South Africa)

    Schwegmann, Colin P

    2016-07-01

    Full Text Available The widespread access to Synthetic Aperture Radar data has created a need for more precise ship extraction, specifically in low-to-medium resolution imagery. While Synthetic Aperture Radar pixel resolution is improving for a large swaths...

  15. Numerical modeling of mixing in large stably stratified enclosures using TRACMIX++

    Science.gov (United States)

    Christensen, Jakob

    This PhD dissertation focuses on the numerical modeling of stably stratified large enclosures. In stably stratified volumes, the distribution of temperature, species concentration etc become essentially 1-D throughout most of the enclosure. When the fluid in an enclosure is stratified, wall boundary buoyant jets, forced buoyant jets (injection of fluid) and natural convection plumes become the primary sources of mixing. The time constants for the buoyant jets may be considered as much smaller than the time constant for the mixing of the stratified ambient fluid, provided the combined volume occupied by the buoyant jets is small compared to the volume of the enclosure. Therefore, fluid transport by the buoyant jets may be considered as occurring instantaneously. For this reason this work focuses on deriving a numerical method which is able to solve the 1-D vertical fluid conservation equations, as given in Peterson (1994). Starting with the Eulerian fluid conservation equations given in Peterson (1994), a set of Lagrangian fluid conservation equations were derived. Combining the Lagrangian approach with operator splitting such that the convective step and the diffusive step is separated renders a very efficient, accurate, and stable numerical method as it is shown in this text. Since the stratified flow field frequently exhibits very strong gradients or so-called fronts, the generation of these fronts has to be accurately detected and tracked by the numerical method. Flow in stably stratified large enclosure has typically been modeled in the past using 1- or 2-zone models. The present model is new in that it belongs to the K-zone models where the number of zones is arbitrarily large and depends on the complexity of the solution and the accuracy requirement set by the user. Because fronts are present in the flow field, a Lagrangian type numerical method is used. A Lagrangian method facilitates front tracking and prevents numerical diffusion from altering the shape of

  16. Numerical model for the motion of large object in fluidized bed

    Science.gov (United States)

    Tsuji, Takuya; Higashida, Kyohei; Tanaka, Toshitsugu; Osaka University Team

    2011-11-01

    The motion of large object in fluidized beds is quite complex because it is influenced by the fluid force, buoyant force in addition to the contact force from emulsion particles, other immersed objects and walls. Its behavior is expected to change depending on its shape, density and size along with the condition of fluidized bed. It is a physically interesting problem and it also has a practical importance in several engineering applications such as gasification, mixing, separation and granulation. In the present study, a numerical model which predicts the motion of large object in fluidized bed is developed. We concentrate on objects larger than surrounding emulsion particles by one order of magnitude at least. The basic concept of a proposed numerical model is presented and its performance is tested for fundamental problems such as sedimentation of single spherical object in a bubbling fluidized bed.

  17. NUMERICAL STUDY ON AIR FLOW AROUND AN OPENING WITH LARGE EDDY SIMULATION

    Institute of Scientific and Technical Information of China (English)

    Fan Hong-ming; Ren Hong-ze; Li Xian-ting; Yi Jiang

    2003-01-01

    Jet characteristics of air supply opening in a ventilating or an air-conditioning system is primarily decided by the folw state in the duct connected to the opening. It is valuable to study the opening jet characteristics and the flow state in a duct. In this study, the Large Eddy Simulation (LES) technique combined with the Tarlor-Galerkin Finite Element Method (FEM) in Computational Fluid Dynamics (CFD) was applied to the problem. The 3-D flow fields in ducts around air supply opening under typical conditions were investigated by numerical simulation as well as experimental measurements. Numerical results agree well with the available experimental data. It indicates that the LES method is available under the conditions with complicated boundaries and inner accompanied by anisotropic large-scale eddies, and it is credible to predict the jet deflection characteristics around an opening.

  18. Numerical Study of Piping Limits for Installation of Large Diameter Buckets in Layered Sand

    DEFF Research Database (Denmark)

    Ibsen, Lars Bo; Thilsted, C.L.

    2010-01-01

    The bucket foundations, often referred as ‘suction caissons’, are large cylindrical structures, typically made in steel. The bucket foundations have the potential to be the cost-effective option for offshore wind turbines, if suction assisted penetration is employed. Suction installation may cause...... formation of piping channels, which break down the hydraulic seal and prevent further installation. This paper presents a numerical study of failure limits during suction installation in respect to both homogenous and layered soil profile. A numerical flow analysis is performed to determine the hydraulic...... gradients developing in response to applied suction and the results are presented as simple closed form solutions useful for evaluation of suction thresholds against piping. These close form solutions are compared with large scale model test, performed in a natural seabed at a test site in Frederikshavn...

  19. Numerical Study of Piping Limits for Installation of Large Diameter Buckets in Layered Sand

    DEFF Research Database (Denmark)

    Ibsen, Lars Bo; Thilsted, C.L.

    2010-01-01

    The bucket foundations, often referred as ‘suction caissons’, are large cylindrical structures, typically made in steel. The bucket foundations have the potential to be the cost-effective option for offshore wind turbines, if suction assisted penetration is employed. Suction installation may cause...... formation of piping channels, which break down the hydraulic seal and prevent further installation. This paper presents a numerical study of failure limits during suction installation in respect to both homogenous and layered soil profile. A numerical flow analysis is performed to determine the hydraulic...... gradients developing in response to applied suction and the results are presented as simple closed form solutions useful for evaluation of suction thresholds against piping. These close form solutions are compared with large scale model test, performed in a natural seabed at a test site in Frederikshavn...

  20. Apodized vortex coronagraph designs for segmented aperture telescopes

    CERN Document Server

    Ruane, Garreth; Mawet, Dimitri; Pueyo, Laurent; Shaklan, Stuart

    2016-01-01

    Current state-of-the-art high contrast imaging instruments take advantage of a number of elegant coronagraph designs to suppress starlight and image nearby faint objects, such as exoplanets and circumstellar disks. The ideal performance and complexity of the optical systems depends strongly on the shape of the telescope aperture. Unfortunately, large primary mirrors tend to be segmented and have various obstructions, which limit the performance of most conventional coronagraph designs. We present a new family of vortex coronagraphs with numerically-optimized gray-scale apodizers that provide the sensitivity needed to directly image faint exoplanets with large, segmented aperture telescopes, including the Thirty Meter Telescope (TMT) as well as potential next-generation space telescopes.

  1. New Aperture Partitioning Element

    Science.gov (United States)

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

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

  2. An analysis on the influence of spatial scales on sensible heat fluxes in the north Tibetan Plateau based on Eddy covariance and large aperture scintillometer data

    Science.gov (United States)

    Sun, Genhou; Hu, Zeyong; Sun, Fanglin; Wang, Jiemin; Xie, Zhipeng; Lin, Yun; Huang, Fangfang

    2017-08-01

    The influence of spatial scales on surface fluxes is an interesting but not fully investigated question. This paper presents an analysis on the influence of spatial scales on surface fluxes in the north Tibetan Plateau based on eddy covariance (EC) and large aperture scintillometer (LAS) data at site Nagqu/BJ, combined with the land surface temperature (LST) and normalized difference vegetation index (NDVI) of moderate-resolution imaging spectroradiometer (MODIS). The analysis shows that sensible heat fluxes calculated with LAS data (H_LAS) agree reasonably well with sensible heat fluxes calculated with EC data (H_EC) in the rain and dry seasons. The difference in their footprints due to the wind direction is an important reason for the differences in H_EC and H_LAS. The H_LAS are statistically more consistent with H_EC when their footprints overlap than when their footprints do not. A detailed analysis on H_EC and H_LAS changes with net radiation and wind direction in rain and dry season indicates that the spatial heterogeneity in net radiation created by clouds contributes greatly to the differences in H_EC and H_LAS in short-term variations. A significant relationship between the difference in footprint-weighted averages of LST and difference in H_EC and H_LAS suggests that the spatial heterogeneity in LST at two spatial scales is a reason for the differences in H_EC and H_LAS and that LST has a positive correlation with the differences in H_EC and H_LAS. A significant relationship between the footprint-weighted averages of NDVI and the ratio of sensible heat fluxes at two spatial scales to net radiation (H/Rn) in the rain season supports the analysis that the spatial heterogeneity in canopy at two spatial scales is another reason for differences in H_EC and H_LAS and that canopy has a negative correlation with (H/Rn). An analysis on the influence of the difference in aerodynamic roughness lengths at two spatial scales on sensible heat fluxes shows that the

  3. An analysis on the influence of spatial scales on sensible heat fluxes in the north Tibetan Plateau based on Eddy covariance and large aperture scintillometer data

    Science.gov (United States)

    Sun, Genhou; Hu, Zeyong; Sun, Fanglin; Wang, Jiemin; Xie, Zhipeng; Lin, Yun; Huang, Fangfang

    2016-05-01

    The influence of spatial scales on surface fluxes is an interesting but not fully investigated question. This paper presents an analysis on the influence of spatial scales on surface fluxes in the north Tibetan Plateau based on eddy covariance (EC) and large aperture scintillometer (LAS) data at site Nagqu/BJ, combined with the land surface temperature (LST) and normalized difference vegetation index (NDVI) of moderate-resolution imaging spectroradiometer (MODIS). The analysis shows that sensible heat fluxes calculated with LAS data (H_LAS) agree reasonably well with sensible heat fluxes calculated with EC data (H_EC) in the rain and dry seasons. The difference in their footprints due to the wind direction is an important reason for the differences in H_EC and H_LAS. The H_LAS are statistically more consistent with H_EC when their footprints overlap than when their footprints do not. A detailed analysis on H_EC and H_LAS changes with net radiation and wind direction in rain and dry season indicates that the spatial heterogeneity in net radiation created by clouds contributes greatly to the differences in H_EC and H_LAS in short-term variations. A significant relationship between the difference in footprint-weighted averages of LST and difference in H_EC and H_LAS suggests that the spatial heterogeneity in LST at two spatial scales is a reason for the differences in H_EC and H_LAS and that LST has a positive correlation with the differences in H_EC and H_LAS. A significant relationship between the footprint-weighted averages of NDVI and the ratio of sensible heat fluxes at two spatial scales to net radiation (H/Rn) in the rain season supports the analysis that the spatial heterogeneity in canopy at two spatial scales is another reason for differences in H_EC and H_LAS and that canopy has a negative correlation with (H/Rn). An analysis on the influence of the difference in aerodynamic roughness lengths at two spatial scales on sensible heat fluxes shows that the

  4. Formulation of and numerical studies with the Dutch Atmospheric Large-Eddy Simulation (DALES

    Directory of Open Access Journals (Sweden)

    T. Heus

    2010-02-01

    Full Text Available The current version of the Dutch Atmospheric Large-Eddy Simulation (DALES model is presented. DALES is a large-eddy simulation model designed for process studies of the atmospheric boundary layer, including convective and stable boundary layers as well as cloudy boundary layers. In addition, DALES can be used for studies of more specific cases, such as flow over sloping or heterogeneous terrain, and dispersion of inert and chemically active species. This paper contains an extensive description of the physical and numerical formulation of the code, and gives an overview of its applications and accomplishments in recent years.

  5. Large scale 2D numerical modelling of reservoirs sedimentation and flushing operations

    OpenAIRE

    Dewals, Benjamin; Erpicum, Sébastien; Archambeau, Pierre; Detrembleur, Sylvain; Fraikin, Catherine; Pirotton, Michel

    2004-01-01

    The quasi-3D flow solver WOLF has been developed at the University of Liege for almost a decade. It has been used to carry out the simulation of silting processes in large reservoirs and to predict the efficiency of flushing operations. Besides briefly depicting the mathematical and numerical model, the present paper demonstrates its applicability on the case of a large hydropower project in India. The silting process of the reservoir has been simulated by means of the quasi-3D flow model wit...

  6. 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....... The method is investigated using simulations and through measurements using both phased array and convex array transducers. The images all show an improved contrast compared to images without compounding, and by construction, imaging using an improved frame rate is possible. Using a phased array transducer...... 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...

  7. In vivo experiments and numerical investigations on nanocryosurgical freezing of target tissues with large blood vessels.

    Science.gov (United States)

    Sun, Zi-Qiao; Yang, Yang; Liu, Jing

    2012-02-01

    This study presented the first in vivo animal experiments of using nano-cryosurgical modality to completely freezing tumor tissues embedded with large blood vessels, which is a tough issue to tackle otherwise. Three-dimensional theoretical simulations were also performed on the complex freezing problems by considering flow and heat transfer of blood flow in large vessels. According to the experimental measurements and numerical predictions, injecting the nanoparticles with high thermal conductivity into the freezing target can significantly reduce the heating effect of blood vessel, shorten the freezing time, and enlarge the freezing range. Most importantly, the introduction of nanoparticles successfully overcomes the classical challenges in completely ablating the tumor region with large blood vessel and enhancing the freezing efficacy of cryosurgery. This investigation consolidates the practical and theoretical foundation for nano-cryosurgery which suggests a highly efficient freezing strategy for treating late stage tumor.

  8. FULLY RESOLVED NUMERICAL SIMULATION OF TURBULENT PIPE FLOWS LADEN WITH LARGE NEUTRALLY- BUOYANT PARTICLES

    Institute of Scientific and Technical Information of China (English)

    WU Teng-hu; SHAO Xue-ming; YU Zhao-sheng

    2011-01-01

    In this article, we employ a fully-resolved numerical simulation method (the fictitious domain method) to investigate the effects of large neutrally-buoyant particles on the turbulent flow in a pipe at low Reynolds number and non-dilute regimes. The tube Reynolds number is fixed to be 4 900, the particle-pipe diameter ratio is 0.1, and the particle volume fraction ranges from 0.33% to 10%. Our results indicate that the presence of large particles decreases the maximum root-of-mean-square (rms) of the streamwise velocity fluctuation near the wall by weakening the intensity of large-scale streamwise vortices, although in the region very close to the wall the particles increase the rms of streamwise velocity fluctuation. On the other hand, the particles induce small-scale vortices in the near-wall region, resulting in the enhancement of the rms of radial and circumferential velocity fluctuations there.

  9. 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.

  10. Numerical errors in the computation of subfilter scalar variance in large eddy simulations

    Science.gov (United States)

    Kaul, C. M.; Raman, V.; Balarac, G.; Pitsch, H.

    2009-05-01

    Subfilter scalar variance is a key quantity for scalar mixing at the small scales of a turbulent flow and thus plays a crucial role in large eddy simulation of combustion. While prior studies have mainly focused on the physical aspects of modeling subfilter variance, the current work discusses variance models in conjunction with the numerical errors due to their implementation using finite-difference methods. A priori tests on data from direct numerical simulation of homogeneous turbulence are performed to evaluate the numerical implications of specific model forms. Like other subfilter quantities, such as kinetic energy, subfilter variance can be modeled according to one of two general methodologies. In the first of these, an algebraic equation relating the variance to gradients of the filtered scalar field is coupled with a dynamic procedure for coefficient estimation. Although finite-difference methods substantially underpredict the gradient of the filtered scalar field, the dynamic method is shown to mitigate this error through overestimation of the model coefficient. The second group of models utilizes a transport equation for the subfilter variance itself or for the second moment of the scalar. Here, it is shown that the model formulation based on the variance transport equation is consistently biased toward underprediction of the subfilter variance. The numerical issues in the variance transport equation stem from discrete approximations to chain-rule manipulations used to derive convection, diffusion, and production terms associated with the square of the filtered scalar. These approximations can be avoided by solving the equation for the second moment of the scalar, suggesting that model's numerical superiority.

  11. LAS在西北半干旱地区的观测分析%Large Aperture Scintillometers(LAS)Observation in Semi-arid Regions of Northwestern China

    Institute of Scientific and Technical Information of China (English)

    黄山; 张文煜; 左洪超; 刘欣; 史永义

    2011-01-01

    In this paper, sensible heat flux in semi-arid region of northwestern China were calculated and analyzed by use of the observation data of Large Aperture Scintillometers (LAS) recorded per 30 minutes, the temperature, pressure data, and the observation data by Eddy Covariance System at Lanzhou University Semi-arid Climate and Environment Observatory during summer and winter of 2007.The values of the sensible heat flux in summer were bigger than that in winter, and there was a lag of peak value on diurnal variation curve in winter; at the similar weather conditions, the fluctuation of sensible flux in summer was bigger than that in winter.Weather condition had a great impact on the observations of LAS, the values of the sensible heat flux in sunny days were higher than that in cloudy days at the same season.Compared with sensible heat flux observed by Eddy Covariance System, the sensible heat flux measured by LAS was a little larger, but the values by the two methods showed a good agreement, and the correlation coefficient in summer was 0.95, and it was 0.98 in winter.%利用兰州大学半干旱气候与环境观测站2007年夏冬两季LAS观测数据.结合观测站气温、气压及同期的涡动相关仪30 min时间间隔的观测数据,计算分析了西北半干旱地区显热通量的变化特征,并将LAS所测结果与涡动相关仪的测量结果进行了对比分析.结果表明,在西北半干旱地区.夏季的显热通量值整体大于冬季,冬季显热通量的日变化峰值较夏季有明显的滞后性;在类似的天气状况下,夏季测得显热通量的波动要大于冬季;天气状况对LAS的观测结果有着很大的影响,在同一季节晴天显热通量较大,阴天较小;LAS测得显热通量H的值较涡动相关所得H值略微偏大.但LAS与涡动相关仪测得的显热通量有很好的符合性,复季相关系数为0.95,冬季相关系数为0.98.

  12. Numerical

    Directory of Open Access Journals (Sweden)

    M. Boumaza

    2015-07-01

    Full Text Available Transient convection heat transfer is of fundamental interest in many industrial and environmental situations, as well as in electronic devices and security of energy systems. Transient fluid flow problems are among the more difficult to analyze and yet are very often encountered in modern day technology. The main objective of this research project is to carry out a theoretical and numerical analysis of transient convective heat transfer in vertical flows, when the thermal field is due to different kinds of variation, in time and space of some boundary conditions, such as wall temperature or wall heat flux. This is achieved by the development of a mathematical model and its resolution by suitable numerical methods, as well as performing various sensitivity analyses. These objectives are achieved through a theoretical investigation of the effects of wall and fluid axial conduction, physical properties and heat capacity of the pipe wall on the transient downward mixed convection in a circular duct experiencing a sudden change in the applied heat flux on the outside surface of a central zone.

  13. An improved technique for obtaining well-spread metaphases from plants with numerous large chromosomes.

    Science.gov (United States)

    Rodríguez-Domínguez, J M; Ríos-Lara, L L; Tapia-Campos, E; Barba-Gonzalez, R

    2017-01-01

    Preparations that contain well-spread metaphase chromosomes are critical for plant cytogenetic analyses including chromosome counts, banding procedures, in situ hybridization, karyotyping and construction of ideograms. Chromosome spreading is difficult for plants with large and numerous chromosomes. We report here a technique for obtaining cytoplasm-free, well-spread metaphases from two Amaryllidaceae species: Sprekelia formosissima (2n = 120) and Hymenocallis howardii (2n = 96). The technique has three main steps: 1) pretreatment to cause chromosome condensation, 2) dripping onto tilted slides coated with a thin layer of pure acetic acid and 3) application of steam and acetic acid to produce cytoplasmic hydrolysis, which spreads the chromosomes.

  14. 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...

  15. Large-scale dynamo growth rates from numerical simulations and implications for mean-field theories.

    Science.gov (United States)

    Park, Kiwan; Blackman, Eric G; Subramanian, Kandaswamy

    2013-05-01

    Understanding large-scale magnetic field growth in turbulent plasmas in the magnetohydrodynamic limit is a goal of magnetic dynamo theory. In particular, assessing how well large-scale helical field growth and saturation in simulations match those predicted by existing theories is important for progress. Using numerical simulations of isotropically forced turbulence without large-scale shear with its implications, we focus on several additional aspects of this comparison: (1) Leading mean-field dynamo theories which break the field into large and small scales predict that large-scale helical field growth rates are determined by the difference between kinetic helicity and current helicity with no dependence on the nonhelical energy in small-scale magnetic fields. Our simulations show that the growth rate of the large-scale field from fully helical forcing is indeed unaffected by the presence or absence of small-scale magnetic fields amplified in a precursor nonhelical dynamo. However, because the precursor nonhelical dynamo in our simulations produced fields that were strongly subequipartition with respect to the kinetic energy, we cannot yet rule out the potential influence of stronger nonhelical small-scale fields. (2) We have identified two features in our simulations which cannot be explained by the most minimalist versions of two-scale mean-field theory: (i) fully helical small-scale forcing produces significant nonhelical large-scale magnetic energy and (ii) the saturation of the large-scale field growth is time delayed with respect to what minimalist theory predicts. We comment on desirable generalizations to the theory in this context and future desired work.

  16. Numerical investigation on super-cooled large droplet icing of fan rotor blade in jet engine

    Science.gov (United States)

    Isobe, Keisuke; Suzuki, Masaya; Yamamoto, Makoto

    2014-10-01

    Icing (or ice accretion) is a phenomenon in which super-cooled water droplets impinge and accrete on a body. It is well known that ice accretion on blades and vanes leads to performance degradation and has caused severe accidents. Although various anti-icing and deicing systems have been developed, such accidents still occur. Therefore, it is important to clarify the phenomenon of ice accretion on an aircraft and in a jet engine. However, flight tests for ice accretion are very expensive, and in the wind tunnel it is difficult to reproduce all climate conditions where ice accretion can occur. Therefore, it is expected that computational fluid dynamics (CFD), which can estimate ice accretion in various climate conditions, will be a useful way to predict and understand the ice accretion phenomenon. On the other hand, although the icing caused by super-cooled large droplets (SLD) is very dangerous, the numerical method has not been established yet. This is why SLD icing is characterized by splash and bounce phenomena of droplets and they are very complex in nature. In the present study, we develop an ice accretion code considering the splash and bounce phenomena to predict SLD icing, and the code is applied to a fan rotor blade. The numerical results with and without the SLD icing model are compared. Through this study, the influence of the SLD icing model is numerically clarified.

  17. Numerical Analysis of a Large Floating Wave Energy Converter with Adjustable Structural Geometry

    DEFF Research Database (Denmark)

    Ferri, Francesco; Pecher, Arthur Francois Serge; Kofoed, Jens Peter

    2015-01-01

    The current cost of energy (CoE) from wave energy converters (WECs) is still significantly higher than other renewable energy resources, thus the sector has not yet reached a competitive level. WECs have a relative small turnover compared to the high capital cost, which to a large extent is driven...... by the structural loads in extreme conditions. TheWeptos is a large floating WEC, with multiple absorbers, which has proven to be a serious candidate for the renewable energy market, due to both relevant power performance and reduced cost if compared with other WECs. The scope of this article is to compare two...... different configurations of the Weptos machine, using the cost of energy (CoE) as a base of comparison. The numerical results are obtained via a multi-body analysis carried out in frequency domain....

  18. Numerical Simulation of Wave Scour Around A Large-Scale Circular Cylinder

    Institute of Scientific and Technical Information of China (English)

    赵明; 滕斌; 柳淑学

    2002-01-01

    A numerical model is developed for estimation of local scour around a large circular cylinder under wave action. The model includes wave diffraction around structures, bed shear stress calculation inside the wave boundary layer and topographical change model. The wave model is based on the improved Boussinesq equations for varying depth. The wave boundary layer is calculated by solving the integrated momentum equation over the boundary layer. The bed shear stress due to streaming, an important factor affecting the sediment transport around a large-scale cylinder, is calculated. The Lagrangian drift velocity is included in calculation of the suspended sediment transport rates. The model is implemented by a finite element method and the results from the present model, which agree well with experimental data, are compared with those from other methods.

  19. Exploiting multi-scale parallelism for large scale numerical modelling of laser wakefield accelerators

    CERN Document Server

    Fonseca, Ricardo A; Fiúza, Frederico; Davidson, Asher; Tsung, Frank S; Mori, Warren B; Silva, Luís O

    2013-01-01

    A new generation of laser wakefield accelerators, supported by the extreme accelerating fields generated in the interaction of PW-Class lasers and underdense targets, promises the production of high quality electron beams in short distances for multiple applications. Achieving this goal will rely heavily on numerical modeling for further understanding of the underlying physics and identification of optimal regimes, but large scale modeling of these scenarios is computationally heavy and requires efficient use of state-of-the-art Petascale supercomputing systems. We discuss the main difficulties involved in running these simulations and the new developments implemented in the OSIRIS framework to address these issues, ranging from multi-dimensional dynamic load balancing and hybrid distributed / shared memory parallelism to the vectorization of the PIC algorithm. We present the results of the OASCR Joule Metric program on the issue of large scale modeling of LWFA, demonstrating speedups of over 1 order of magni...

  20. A Numerical Method of Large-Scale Concrete Displacing Boom Dynamic and Experimental Validation

    Directory of Open Access Journals (Sweden)

    Wu Ren

    2014-01-01

    Full Text Available Concrete displacing boom is large-scale motion manipulator. During the long distance pouring the postures needs to frequently change. This makes the real-time dynamic analysis and health monitoring difficult. Virtual spring-damper method is adopted to establish the equivalent hydraulic actuator model. Besides boom cylinder joint clearance is taken into account. Then transfer matrix method is used to build the multibody concrete placing boom model by dividing the system into two substructures. Next typical working conditions displacements and accelerations during the pouring process are studied. The results of the numerical method are correct and feasible compared with Recurdyn software and the experimental ones. So it provides reference to the real-time monitoring and structure design for such light weight large scale motion manipulators.

  1. A Numerical Methodology for Aerodynamic Shape Optimization in Turbulent Flow Enabling Large Geometric Variation

    Science.gov (United States)

    Osusky, Lana Maria

    The increase in the availability and power of computational resources over the last fifteen years has contributed to the development of many different types of numerical optimization methods and created a large area of research focussed on numerical aerodynamic shape optimization and, more recently, high-fidelity multidisciplinary optimization. Numerical optimization provides dramatic savings when designing new aerodynamic configurations, as it allows the designer to focus more on the development of a well-posed design problem rather than on performing an exhaustive search of the design space via the traditional cut-and-try approach, which is expensive and time-consuming. It also reduces the dependence on the designer's experience and intuition, which can potentially lead to more optimal designs. Numerical optimization methods are particularly attractive when designing novel, unconventional aircraft for which the designer has no pre-existing studies or experiences from which to draw; these methods have the potential to discover new designs that might never have been arrived at without optimization. This work presents an extension of an efficient gradient-based numerical aerodynamic shape optimization algorithm to enable optimization in turbulent flow. The algorithm includes an integrated geometry parameterization and mesh movement scheme, an efficient parallel Newton-Krylov-Schur algorithm for solving the Reynolds-Averaged Navier-Stokes (RANS) equations, which are fully coupled with the one-equation Spalart-Allmaras turbulence model, and a discrete-adjoint gradient evaluation. In order to develop an efficient methodology for optimization in turbulent flows, the viscous and turbulent terms in the ii governing equations were linearized by hand. Additionally, a set of mesh refinement tools was introduced in order to obtain both an acceptable control volume mesh and a sufficiently refined computational mesh from an initial coarse mesh. A series of drag minimization

  2. Towards Laser-Guide-Stars for Multi-Aperture Interferometry: an application to the Hypertelescope

    CERN Document Server

    Nuñez, Paul D; Riaud, Pierre

    2014-01-01

    Optical interferometry has been successful at achieving milliarcsecond resolution on bright stars. Imaging performance can improve greatly by increasing the number of baselines, which has motivated proposals to build large (~ 100 m) optical interferometers with tens to hundreds of telescopes. It is also desirable to adaptively correct atmospheric turbulence to obtain direct phased images of astrophysical sources. When a natural guide star is not available, we investigate the feasibility of using a modified laser-guide-star technique that is suitable for large diluted apertures. The method consists of using sub-sets of apertures to create an array of artificial stars in the sodium layer and collecting back-scattered light with the same sub-apertures. We present some numerical and laboratory simulations that quantify the requirements and sensitivity of the technique.

  3. Experimental and Numerical Analysis of Damage in Woven GFRP Composites Under Large-deflection Bending

    Science.gov (United States)

    Ullah, Himayat; Harland, Andy R.; Silberschmidt, Vadim V.

    2012-10-01

    Textile-reinforced composites such as glass fibre-reinforced polymer (GFRP) used in sports products can be exposed to different in-service conditions such as large bending deformation and multiple impacts. Such loading conditions cause high local stresses and strains, which result in multiple modes of damage and fracture in composite laminates due to their inherent heterogeneity and non-trivial microstructure. In this paper, various damage modes in GFRP laminates are studied using experimental material characterisation, non-destructive micro-structural damage evaluation and numerical simulations. Experimental tests are carried out to characterise the behaviour of these materials under large-deflection bending. To obtain in-plane shear properties of laminates, tensile tests are performed using a full-field strain-measurement digital image correlation technique. X-ray micro computed tomography (Micro CT) is used to investigate internal material damage modes - delamination and cracking. Two-dimensional finite element (FE) models are implemented in the commercial code Abaqus to study the deformation behaviour and damage in GFRP. In these models, multiple layers of bilinear cohesive-zone elements are employed to study the onset and progression of inter-ply delamination and intra-ply fabric fracture of composite laminate, based on the X-ray Micro CT study. The developed numerical models are capable to simulate these features with their mechanisms as well as subsequent mode coupling observed in tests and Micro CT scanning. The obtained results of simulations are in agreement with experimental data.

  4. Role of the aperture in Z-scan experiments:A parametric study

    Institute of Scientific and Technical Information of China (English)

    M. R. Rashidian Vaziri

    2015-01-01

    In close-aperture Z-scan experiments, a small aperture is conventionally located in the far-field thereby enabling the detection of slight changes in the laser beam profile due to the Kerr-lensing effect. In this work, by numerically solving the Fresnel–Kirchhoff diffraction integrals, the amount of transmitted power through apertures has been evaluated and a parametric study on the role of the various parameters that can infl uence this transmitted power has been done. In order to perform a comprehensive analysis, we have used a nonlinear phase shift optimized for nonlocal nonlinear media in our calculations. Our results show that apertures will result in the formation of symmetrical fl uctuations on the wings of Z-scan transmittance curves. It is further shown that the appearance of these fl uctuations can be ascribed to the natural diffraction of the Gaussian beam as it propagates up to the aperture plane. Our calculations reveal that the nonlocal parameter variations can shift the position of fl uctuations along the optical axis, whereas their magnitude depends on the largeness of the induced nonlinear phase shift. It is concluded that since the mentioned fl uctuations are produced by the natural diffraction of the Gaussian beam itself, one must take care not to mistakenly interpret them as noise and should not expect to eliminate them from experimental Z-scan transmittance curves by using apertures with different sizes.

  5. Resonant Effects in Nanoscale Bowtie Apertures

    Science.gov (United States)

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

    2016-01-01

    Nanoscale bowtie aperture antennas can be used to focus light well below the diffraction limit with extremely high transmission efficiencies. This paper studies the spectral dependence of the transmission through nanoscale bowtie apertures defined in a silver film. A realistic bowtie aperture is numerically modeled using the Finite Difference Time Domain (FDTD) method. Results show that the transmission spectrum is dominated by Fabry-Pérot (F-P) waveguide modes and plasmonic modes. The F-P resonance is sensitive to the thickness of the film and the plasmonic resonant mode is closely related to the gap distance of the bowtie aperture. Both characteristics significantly affect the transmission spectrum. To verify these numerical results, bowtie apertures are FIB milled in a silver film. Experimental transmission measurements agree with simulation data. Based on this result, nanoscale bowtie apertures can be optimized to realize deep sub-wavelength confinement with high transmission efficiency with applications to nanolithography, data storage, and bio-chemical sensing. PMID:27250995

  6. 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

  7. Numerical Investigation on Fluid Flow in a 90-Degree Curved Pipe with Large Curvature Ratio

    Directory of Open Access Journals (Sweden)

    Yan Wang

    2015-01-01

    Full Text Available In order to understand the mechanism of fluid flows in curved pipes, a large number of theoretical and experimental researches have been performed. As a critical parameter of curved pipe, the curvature ratio δ has received much attention, but most of the values of δ are very small (δ<0.1 or relatively small (δ≤0.5. As a preliminary study and simulation this research studied the fluid flow in a 90-degree curved pipe of large curvature ratio. The Detached Eddy Simulation (DES turbulence model was employed to investigate the fluid flows at the Reynolds number range from 5000 to 20000. After validation of the numerical strategy, the pressure and velocity distribution, pressure drop, fluid flow, and secondary flow along the curved pipe were illustrated. The results show that the fluid flow in a curved pipe with large curvature ratio seems to be unlike that in a curved pipe with small curvature ratio. Large curvature ratio makes the internal flow more complicated; thus, the flow patterns, the separation region, and the oscillatory flow are different.

  8. Revisiting Numerical Errors in Direct and Large Eddy Simulations of Turbulence: Physical and Spectral Spaces Analysis

    Science.gov (United States)

    Fedioun, Ivan; Lardjane, Nicolas; Gökalp, Iskender

    2001-12-01

    Some recent studies on the effects of truncation and aliasing errors on the large eddy simulation (LES) of turbulent flows via the concept of modified wave number are revisited. It is shown that all the results obtained for nonlinear partial differential equations projected and advanced in time in spectral space are not straightforwardly applicable to physical space calculations due to the nonequivalence by Fourier transform of spectral aliasing errors and numerical errors on a set of grid points in physical space. The consequences of spectral static aliasing errors on a set of grid points are analyzed in one dimension of space for quadratic products and their derivatives. The dynamical process that results through time stepping is illustrated on the Burgers equation. A method based on midpoint interpolation is proposed to remove in physical space the static grid point errors involved in divergence forms. It is compared to the sharp filtering technique on finer grids suggested by previous authors. Global performances resulting from combination of static aliasing errors and truncation errors are then discussed for all classical forms of the convective terms in Navier-Stokes equations. Some analytical results previously obtained on the relative magnitude of subgrid scale terms and numerical errors are confirmed with 3D realistic random fields. The physical space dynamical behavior and the stability of typical associations of numerical schemes and forms of nonlinear terms are finally evaluated on the LES of self-decaying homogeneous isotropic turbulence. It is shown that the convective form (if conservative properties are not strictly required) associated with highly resolving compact finite difference schemes provides the best compromise, which is nearly equivalent to dealiased pseudo-spectral calculations.

  9. Efficient numerical methods for the large-scale, parallel solution of elastoplastic contact problems

    KAUST Repository

    Frohne, Jörg

    2015-08-06

    © 2016 John Wiley & Sons, Ltd. Quasi-static elastoplastic contact problems are ubiquitous in many industrial processes and other contexts, and their numerical simulation is consequently of great interest in accurately describing and optimizing production processes. The key component in these simulations is the solution of a single load step of a time iteration. From a mathematical perspective, the problems to be solved in each time step are characterized by the difficulties of variational inequalities for both the plastic behavior and the contact problem. Computationally, they also often lead to very large problems. In this paper, we present and evaluate a complete set of methods that are (1) designed to work well together and (2) allow for the efficient solution of such problems. In particular, we use adaptive finite element meshes with linear and quadratic elements, a Newton linearization of the plasticity, active set methods for the contact problem, and multigrid-preconditioned linear solvers. Through a sequence of numerical experiments, we show the performance of these methods. This includes highly accurate solutions of a three-dimensional benchmark problem and scaling our methods in parallel to 1024 cores and more than a billion unknowns.

  10. Numerical Simulation of Local Scour Around A Large Circular Cylinder Under Wave Action

    Institute of Scientific and Technical Information of China (English)

    赵明; 滕斌

    2001-01-01

    A horizontal two-dimensional numerical model is developed for estimation of sediment transport and sea bed change around a large circular cylinder under wave action. The wave model is based on an elliptic mild slope equation.The wave-induced current by the gradient of radiation stress is considered and a depth integrated shallow water equation is applied to the calculation of the current. The mass transport velocity and the bed shear stress due to streaming are considered, which are important factors affecting the sediment transport around a structure due to waves, especially in reflective areas. Wave-current interaction is taken into account in the model for computing the bed shear stress. The model is implemented by a finite element method. The results of this model are compared with those from other methods and agree well with experimental data.

  11. Numerical Investigation of Developing Turbulent Flow in a Helical Square Duct with Large Curvature

    Institute of Scientific and Technical Information of China (English)

    Gao Hui; Guo Liejin

    2001-01-01

    A fully elliptic numerical study has been carried out to investigate the three-dimensional turbulent developing flow in a helical square duct with large curvature. A two-layer zonal model is proposed and used, in which the whole region is divided into a viscosity-affected near wall layer and a fully turbulent region. A DSM closure is applied in the former, and a one-equation model is solved in the latter. The results presented in this paper cover a Reynolds number range of (1 ~ 10) x 104. The development of flow is found to be dominated by radial pressure gradient and Dean-type secondary motion. The distribution of Reynolds stresses in fully developed flow exhibit a complex pattern of turbulence anisotropy. The development of peripherally averaged friction factor and the distribution of local friction factor in fully developed flow are given and discussed.

  12. Numerical simulation of infiltration laws of grouts in random aperture based on multi-fractional Brownian motion%基于MBM随机隙宽单裂隙浆液渗透规律的模拟研究

    Institute of Scientific and Technical Information of China (English)

    罗平平; 王兰甫; 范波; 张芳

    2012-01-01

    In order to study the influence of aperture distribution on the infiltration in a single fracture, based on the fractal theory of multi-fractional Brownian motion(MBM), four groups of fracture surfaces at different regularization dimensions are constructed, all of which more realistically reflect the asymptotic self-similarity of aperture distribution of natural fracture surface. From the numerical simulation of grouting in a single random aperture fracture, it is indicated that pressure contours show twists and turns spreading over time, which reflects the distinct non-uniform characteristics. The distribution of closed area has a tendency that is from dot-like scatter to focused plane with the regularization dimensions tending to reduce, and its spatial location has obvious influence on the pressure and grouting time. As the development of percolation, there appears a tendency that the node pressure is from monotonically rapid increase to stepwise stability, and the more the node approaching the percolation border, the shorter the grouting time used in the case of reaching the steady pressure. Moreover, there is a power relationship between the node pressure and the grouting time. In view of this rule, empirical equations with different parameters are also obtained by fitting curves.%为了研究单裂隙面隙宽分布对浆液渗透的影响,基于多重分数布朗运动(MBM)分形理论构建出4种不同规则维数下的随机隙宽单裂隙几何模型,从而较真实的反应了天然裂隙面隙宽分布的局部渐进自相似性。通过注浆数值模拟研究发现,压力等值线随时间延续呈现曲折扩散形式,反映了其非均匀渗透特征。裂隙面闭合区分布形态随规则维数降低由点状散布趋向面状集中,其空间位置对浆液后期渗透压力和全程注浆时间影响很大;并且随着浆液入渗发展,节点压力由前期的较快单调增长到后期逐步趋于稳定,越靠近入渗边界的节点

  13. Broadband synthetic aperture geoacoustic inversion.

    Science.gov (United States)

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

    2013-07-01

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

  14. Numerical investigation of high pressure and high Reynolds diffusion flame using Large Eddy Simulation

    Science.gov (United States)

    Nichkoohi, Ali Lohrasbi; Tousi, Abolghasem Mesgarpour

    2014-10-01

    Today, with nonstop improvement in computational power, Large-Eddy Simulation (LES) is a high demanding research tool for predicting engineering flows. Such flows on high pressure condition like diesel engines is extensively employed in ground and marine transportation, oblige the designer to control and predict toxic pollutants, while maintaining or improving their high thermal efficiency. This becomes one of the main challenging issues in decades. In the present work, numerical investigation of diffusion flame dynamics is performed in the near-field of high-Reynolds jet flow on high pressure condition encountered in diesel engine applications. This work discusses the implementation of Partially Stirred Reactor (PaSR) combustion model by the approaches of large eddy simulation (LES). The simulation results show that LES, in comparison with Reynolds-Averaged Navier-Stokes (RANS) simulation predicts and captures transient phenomena very well. These phenomena such as unsteadiness and curvature are inherent in the near-field of high Reynolds diffusion flame. The outcomes of this research are compared and validated by other researchers' results. Detailed comparisons of the statistics show good agreement with the corresponding experiments.

  15. Morphotectonic evolution of passive margins undergoing active surface processes: large-scale experiments using numerical models.

    Science.gov (United States)

    Beucher, Romain; Huismans, Ritske S.

    2016-04-01

    Extension of the continental lithosphere can lead to the formation of a wide range of rifted margins styles with contrasting tectonic and geomorphological characteristics. It is now understood that many of these characteristics depend on the manner extension is distributed depending on (among others factors) rheology, structural inheritance, thermal structure and surface processes. The relative importance and the possible interactions of these controlling factors is still largely unknown. Here we investigate the feedbacks between tectonics and the transfers of material at the surface resulting from erosion, transport, and sedimentation. We use large-scale (1200 x 600 km) and high-resolution (~1km) numerical experiments coupling a 2D upper-mantle-scale thermo-mechanical model with a plan-form 2D surface processes model (SPM). We test the sensitivity of the coupled models to varying crust-lithosphere rheology and erosional efficiency ranging from no-erosion to very efficient erosion. We discuss how fast, when and how the topography of the continents evolves and how it can be compared to actual passive margins escarpment morphologies. We show that although tectonics is the main factor controlling the rift geometry, transfers of masses at the surface affect the timing of faulting and the initiation of sea-floor spreading. We discuss how such models may help to understand the evolution of high-elevated passive margins around the world.

  16. On the generation and evolution of numerically simulated large-amplitude internal gravity wave packets

    Science.gov (United States)

    Abdilghanie, Ammar M.; Diamessis, Peter J.

    2012-01-01

    Numerical simulations of internal gravity wave (IGW) dynamics typically rely on wave velocity and density fields which are either generated through forcing terms in the governing equations or are explicitly introduced as initial conditions. Both approaches are based on the associated solution to the inviscid linear internal wave equations and, thus, assume weak-amplitude, space-filling waves. Using spectral multidomain-based numerical simulations of the two-dimensional Navier-Stokes equations and focusing on the forcing-driven approach, this study examines the generation and subsequent evolution of large-amplitude IGW packets which are strongly localized in the vertical in a linearly stratified fluid. When the vertical envelope of the forcing terms varies relatively rapid when compared to the vertical wavelength, the associated large vertical gradients in the Reynolds stress field drive a nonpropagating negative horizontal mean flow component in the source region. The highly nonlinear interaction of this mean current with the propagating IGW packet leads to amplification of the wave, a significant distortion of its rear flank, and a substantial decay of its amplitude. Scaling arguments show that the mean flow is enhanced with a stronger degree of localization of the forcing, larger degree of hydrostaticity, and increasing wave packet steepness. Horizontal localization results in a pronounced reduction in mean flow strength mainly on account of the reduced vertical gradient of the wave Reynolds stress. Finally, two techniques are proposed toward the efficient containment of the mean flow at minimal computational cost. The findings of this study are of particular value in overcoming challenges in the design of robust computational process studies of IGW packet (or continuously forced wave train) interactions with a sloping boundary, critical layer, or caustic, where large wave amplitudes are required for any instabilities to develop. In addition, the detailed

  17. 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.

  18. Finding Large Aperture Fractures in Geothermal Resource Areas Using a Three-Component Long-Offset Surface Seismic Survey, PSInSAR and Kinematic Structural Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Teplow, William J. [US Geothermal, Inc., Boise, ID (United States); Warren, Ian [US Geothermal, Inc., Boise, ID (United States)

    2015-08-12

    The DOE cost-share program applied innovative and cutting edge seismic surveying and processing, permanent scatter interferometry-synthetic aperture radar (PSInSAR) and structural kinematics to the exploration problem of locating and mapping largeaperture fractures (LAFs) for the purpose of targeting geothermal production wells. The San Emidio geothermal resource area, which is under lease to USG, contains production wells that have encountered and currently produce from LAFs in the southern half of the resource area (Figure 2). The USG lease block, incorporating the northern extension of the San Emidio geothermal resource, extends 3 miles north of the operating wellfield. The northern lease block was known to contain shallow thermal waters but was previously unexplored by deep drilling. Results of the Phase 1 exploration program are described in detail in the Phase 1 Final Report (Teplow et al., 2011). The DOE cost shared program was completed as planned on September 30, 2014. This report summarizes results from all of Phase 1 and 2 activities.

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

    Science.gov (United States)

    Rahmat-Samii, Yahya

    1987-01-01

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

  20. Fractional Fourier transform of apertured paraboloid refracting system

    Institute of Scientific and Technical Information of China (English)

    Jiannong Chen; Jinliang Yan; Defa Wang; Yongjiang Yu

    2007-01-01

    The limitation of paraxial condition of paraboloid refracting system in performing fractional Fourier transform acts like an aperture, which makes the system different from ideal systems. With aperture expanded as the sum of finite complex Gaussian terms, a more practical approximate analytical solution of fractional Fourier transform of Gaussian beam in an apertured paraboloid refracting system is obtained and also numerical investigation is presented. Complicated and practical fractional Fourier transform systems can be constructed by cascading several apertured paraboloid refracting systems which are the simplest and the most basic units for performing more precise transform.

  1. Investigation of standing-wave formation in a human skull for a clinical prototype of a large-aperture, transcranial MR-guided focused ultrasound (MRgFUS) phased array: an experimental and simulation study.

    Science.gov (United States)

    Song, Junho; Pulkkinen, Aki; Huang, Yuexi; Hynynen, Kullervo

    2012-02-01

    Standing-wave formation in an ex vivo human skull was investigated using a clinical prototype of a 30-cm diameter with 15-cm radius of curvature, low-frequency (230 kHz), hemispherical transcranial magnetic resonance-guided focused ultrasound phased array. Experimental and simulation studies were conducted with changing aperture size and f -number configurations of the phased array and qualitatively and quantitatively examined the acoustic pressure variation at the focus due to standing waves. The results demonstrated that the nodes and antinodes of standing wave produced by the small-aperture array were clearly seen at approximately every 3 mm. The effect of the standing wave became more pronounced as the focus was moved closer to skull base. However, a sharp focus was seen for the full array, and there was no such standing-wave pattern in the acoustic plane or near the skull base. This study showed that the fluctuation pressure amplitude would be greatly reduced by using a large-scale, hemispherical phased array with a low f-number.

  2. Numerical simulation of sloshing with large deforming free surface by MPS-LES method

    Science.gov (United States)

    Pan, Xu-jie; Zhang, Huai-xin; Sun, Xue-yao

    2012-12-01

    the large impact pressure accurately on rolling tank wall but also can generate all physical phenomena successfully. The good agreement between numerical and experimental results proves that the modified MPS-LES method is a good CFD methodology in free surface flow simulations.

  3. Numerical Simulation of Sloshing with Large Deforming Free Surface by MPS-LES Method

    Institute of Scientific and Technical Information of China (English)

    PAN Xu-jie; ZHANG Huai-xin; SUN Xue-yao

    2012-01-01

    Moving particle semi-implicit (MPS) method is a fully Lagrangian particle method which can easily solve problems with violent free surface.Although it has demonstrated its advantage in ocean engineering applications,it still has some defects to be improved.In this paper,MPS method is extended to the large eddy simulation (LES) by coupling with a sub-particle-scale (SPS) turbulence model.The SPS turbulence model turns into the Reynolds stress terms in the filtered momentum equation,and the Smagorinsky model is introduced to describe the Reynolds stress terms.Although MPS method has the advantage in the simulation of the free surface flow,a lot of non-free surface particles are treated as free surface particles in the original MPS model.In this paper,we use a new free surface tracing method and the key point is “neighbor particle”.In this new method,the zone around each particle is divided into eight parts,and the particle will be treated as a free surface particle as long as there are no “neighbor particles” in any two parts of the zone.As the number density parameter judging method has a high efficiency for the free surface particles tracing,we combine it with the neighbor detected method.First,we select out the particles which may be mistreated with high probabilities by using the number density parameter judging method.And then we deal with these particles with the neighbor detected method.By doing this,the new mixed free surface tracing method can reduce the mistreatment problem efficiently.The serious pressure fluctuation is an obvious defect in MPS method,and therefore an area-time average technique is used in this paper to remove the pressure fluctuation with a quite good result.With these improvements,the modified MPS-LES method is applied to simulate liquid sloshing problems with large deforming free surface.Results show that the modified MPS-LES method can simulate the large deforming free surface easily.It can not only capture the large impact

  4. Asynchronous rotation scan for synthetic aperture interferometric radiometer

    Institute of Scientific and Technical Information of China (English)

    WU Ji; ZHANG Cheng; LIU Hao; SUN WeiYing

    2009-01-01

    Synthetic aperture interferometric technique has wide applications in optics, radio astronomy and mi-crowave remote sensing areas. With the increasing demands of high resolution imaging observation, a new time-sharing sampling scheme of asynchronous rotation scan is proposed to meet the technical challenge of achieving a large equivalent aperture and overcome the operating barriers of space borne application. This configuration is basically composed by two asynchronously and concentrically ro-tating antenna groups, whose revolving radii and speeds are different. The synthetic aperture system with asynchronous rotation scanning scheme can effectively solve the trade-off problem of system complexity, and greatly simplify the system hardware at the cost of sacrificing a certain time resolution. The basic rules and design methods of asynchronous rotation scan are investigated The Gridding method is introduced to inverse the spiral sampling data for image reconstruction. The potential ap-plications of geostationary orbit (GEO) earth observation and solar polar orbit (SPO) plasma cloud observation are explored with numerical simulations to validate the significance and feasibility of this new imaging configuration.

  5. Asynchronous rotation scan for synthetic aperture interferometric radiometer

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Synthetic aperture interferometric technique has wide applications in optics,radio astronomy and mi-crowave remote sensing areas.With the increasing demands of high resolution imaging observation,a new time-sharing sampling scheme of asynchronous rotation scan is proposed to meet the technical challenge of achieving a large equivalent aperture and overcome the operating barriers of space borne application.This configuration is basically composed by two asynchronously and concentrically ro-tating antenna groups,whose revolving radii and speeds are different.The synthetic aperture system with asynchronous rotation scanning scheme can effectively solve the trade-off problem of system complexity,and greatly simplify the system hardware at the cost of sacrificing a certain time resolution.The basic rules and design methods of asynchronous rotation scan are investigated The Gridding method is introduced to inverse the spiral sampling data for image reconstruction.The potential ap-plications of geostationary orbit(GEO)earth observation and solar polar orbit(SPO)plasma cloud observation are explored with numerical simulations to validate the significance and feasibility of this new imaging configuration.

  6. Optimal Numerical Schemes for Time Accurate Compressible Large Eddy Simulations: Comparison of Artificial Dissipation and Filtering Schemes

    Science.gov (United States)

    2014-11-01

    for Time Accurate Compressible Large Eddy Simulations : Comparison of Artificial Dissipation and Filtering Schemes 5b. GRANT NUMBER 5c. PROGRAM...Optimal Numerical Schemes for Time Accurate Compressible Large Eddy Simulations : Comparison of Artificial Dissipation and Filtering Schemes 67th

  7. Parallel optical nanolithography using nanoscale bowtie apertures

    Science.gov (United States)

    Uppuluri, Sreemanth M. V.

    needed to bring an array of bowtie apertures into intimate contact with the photoresist surface we present an optical interference based alignment system that aligns the mask and photoresist surfaces to within 0.1 mrad of parallelism. In this work we show that bowtie apertures can be used to produce patterns in the photoresist of dimensions in the order of 85-90 nm. We also demonstrate parallel optical nanolithography using an array of bowtie apertures that opens up the possibility of using arrays of bowtie apertures to produce a large number of nanoscale light spots for parallel nano-manufacturing.

  8. Numerical analysis of blood flow through an elliptic stenosis using large eddy simulation.

    Science.gov (United States)

    Jabir, E; Lal, S Anil

    2016-08-01

    The presence of a stenosis caused by the abnormal narrowing of the lumen in the artery tree can cause significant variations in flow parameters of blood. The original flow, which is believed to be laminar in most situations, may turn out to turbulent by the geometric perturbation created by the stenosis. Flow may evolve to fully turbulent or it may relaminarise back according to the intensity of the perturbation. This article reports the numerical simulation of flow through an eccentrically located asymmetric stenosis having elliptical cross section using computational fluid dynamics. Large eddy simulation technique using dynamic Smagorinsky sub-grid scale model is applied to capture the turbulent features of flow. Analysis is carried out for two situations: steady inflow as ideal condition and pulsatile inflow corresponding to the actual physiological condition in common carotid artery. The spatially varying pulsatile inflow waveforms are mathematically derived from instantaneous mass flow measurements available in the literature. Carreau viscosity model is used to estimate the effect of non-Newtonian nature of blood. The present simulations for steady and pulsatile conditions show that post-stenotic flow field undergoes transition to turbulence in all cases. The characteristics of mean and turbulent flow fields have been presented and discussed in detail.

  9. Supersonic Virtual Valve Design for Numerical Simulation of a Large-Bore Natural Gas Engine

    Energy Technology Data Exchange (ETDEWEB)

    Kim, G.-H.; Kirkpatrick, A.; Mitchell, C.

    2007-10-01

    In many applications of supersonic injection devices, three-dimensional computation that can model a complex supersonic jet has become critical. However, in spite of its increasing necessity, it is computationally costly to capture the details of supersonic structures in intricate three-dimensional geometries with moving boundaries. In large-bore stationary natural gas fueled engine research, one of the most promising mixing enhancement technologies currently used for natural gas engines is high-pressure fuel injection. Consequently, this creates considerable interest in three-dimensional computational simulations that can examine the entire injection and mixing process in engines using high-pressure injection and can determine the impact of injector design on engine performance. However, the cost of three-dimensional engine simulations-including a moving piston and the kinetics of combustion and pollutant production quickly becomes considerable in terms of simulation time requirements. One limiting factor is the modeling of the small length scales of the poppet valve flow. Such length scales can be three orders of magnitude smaller than cylinder length scales. The objective of this paper is to describe the development of a methodology for the design of a simple geometry supersonic virtual valve that can be substituted in three-dimensional numerical models for the complex shrouded poppet valve injection system actually installed in the engine to be simulated.

  10. Hydrodynamical numerical simulation of wind production from black hole hot accretion flows at very large radii

    CERN Document Server

    Bu, De-Fu; Gan, Zhao-Ming; Yang, Xiao-hong

    2015-01-01

    In previous works, it has been shown that strong winds exist in hot accretion flows around black holes. Those works focus only on the region close to the black hole thus it is unknown whether or where the wind production stops at large radii. In this paper, we investigate this problem based on hydrodynamical numerical simulations. For this aim, we have taken into account the gravity of both the central black hole and the nuclear star clusters. When calculating the latter, we assume that the velocity dispersion of stars is a constant and the gravitational potential of the nuclear star cluster $\\propto \\sigma^2 \\ln (r)$, where $\\sigma$ is the velocity dispersion of stars and $r$ is the distance from the center of the galaxy. Different from previous works, we focus on the region where the gravitational potential is dominated by the star cluster. We find that, same as the accretion flow at small radii, the mass inflow rate decreases inward and the flow is convectively unstable. However, trajectory analysis has sh...

  11. What can large-scale magnetohydrodynamic numerical experiments tell us about coronal heating?

    Science.gov (United States)

    Peter, H

    2015-05-28

    The upper atmosphere of the Sun is governed by the complex structure of the magnetic field. This controls the heating of the coronal plasma to over a million kelvin. Numerical experiments in the form of three-dimensional magnetohydrodynamic simulations are used to investigate the intimate interaction between magnetic field and plasma. These models allow one to synthesize the coronal emission just as it would be observed by real solar instrumentation. Large-scale models encompassing a whole active region form evolving coronal loops with properties similar to those seen in extreme ultraviolet light from the Sun, and reproduce a number of average observed quantities. This suggests that the spatial and temporal distributions of the heating as well as the energy distribution of individual heat deposition events in the model are a good representation of the real Sun. This provides evidence that the braiding of fieldlines through magneto-convective motions in the photosphere is a good concept to heat the upper atmosphere of the Sun.

  12. 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....

  13. Method of off-loading supporting for large aperture light weighted reflect mirror at optical axis horizontal situation%大口径轻质反射镜光轴水平卸载支撑方法

    Institute of Scientific and Technical Information of China (English)

    周于鸣; 赵野; 王海超; 闻广泉

    2013-01-01

      大口径轻质反射镜的重力环境下高精度检测是目前的一个难点,由于其轻量化程度高,绝对刚度低,在重力环境下,支撑形式的不同对光学检测结果影响巨大。提出了一种以提供提拉牵引力的方法实现光轴水平支撑测试的解决方案,通过一系列的滑轮组的自适应调整,获得预定义的力学支撑,实现轻质反射镜光轴水平状态重力环境下的高精度面形测试。有限元力学分析结果表明,依据本方法开展的光轴水平状态检测,能够有效减少重力引起的光轴竖直和光轴水平两种状态下的面形变化RMS值差异,其差异值小于0.003(=632.8 nm)。文中所提出的方法具有良好的可实施性,它可推广应用到其他大口径轻质反射镜的检测支撑的设计中,为此类大口径相机的研制提供技术基础。%  The precise testing of large aperture light weighted reflecting mirror in gravity environment is a difficult problem at present. In view of the high rate of light weighting and the absolute low stiffness, in this situation, different forms of support have huge impacts on optical test results in gravity environment. In this paper, a solution was suggested that pre-defining of supporting force was achieved through a series of pulley blocks self-adapting to solve large aperture mirror testing in gravity environment. The result of mechanics model analysis shows that the testing of optical axis horizontal can reduce the Rams variation of surface shape effectively, which is caused by gravity in vertical and horizontal state, and the variation less than 0.003 ( =632.8 nm). The method can be extended and applied to the design of testing supporting for other large aperture light weighted reflect mirror, and provid; technology foundation for large aperture mirror.

  14. Confocal coded aperture imaging

    Energy Technology Data Exchange (ETDEWEB)

    Tobin, Jr., Kenneth William (Harriman, TN); Thomas, Jr., Clarence E. (Knoxville, TN)

    2001-01-01

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

  15. Numerical investigations of submerged vortices in a model pump sump by using Large Eddy Simulation

    Science.gov (United States)

    Yamade, Y.; Kato, C.; Nagahara, T.; Matsui, Jun

    2016-11-01

    Submerged vortices in a model pump sump and their flow structures were investigated numerically. The model pump sump is composed of a 2,500 mm-long water channel with rectangular cross section of 150 mm (channel width) by 100 mm (water height) and a vertical suction pipe with 100 mm diameter installed at its downstream end. At the upstream end of the channel, a uniform velocity of 0.37 m/s is given. In order to capture appearances and disappearances of submerged vortices in the pump sump, large eddy simulations (LES) are performed. The computational grids for the LES are composed of 2 billion hexahedral elements with 0.255 mm resolution. These grids can resolve the streamwise vortices in the approaching turbulent boundary layers that develops on the channel walls. However, it is not sufficiently fine to capture the vortex cores of the submerged vortices. The LES succeeded to capture appearances of the submerged vortices. By performing LES with several different sets of the wall boundary conditions, we have clearly identified, to the best of our knowledge for the first time, the origin of the submerged vortices. Computations that used a simplified computational model, where the computational domain was localized to the region close to the vortex core, were also performed to predict correctly the vortex core and to investigate dynamics of the vortices. The grid resolution in the simplified computational model was 0.03 mm. We successfully computed the size of vortex core in the simplified computational model. For this model, we also investigated the conditions under which a vortex appears by changing inlet tangential velocity.

  16. Enhanced transmission of transverse electric waves through periodic arrays of structured subwavelength apertures

    DEFF Research Database (Denmark)

    Xiao, Sanshui; Peng, Liang; Mortensen, Asger

    2010-01-01

    Transmission through sub-wavelength apertures in perfect metals is expected to be strongly suppressed. However, by structural engineering of the apertures, we numerically demonstrate that the transmission of transverse electric waves through periodic arrays of subwavelength apertures in a thin...

  17. Experimental and Numerical Analysis of Hull Girder Vibrations and Bow Impact of a Large Ship Sailing in Waves

    Directory of Open Access Journals (Sweden)

    Jialong Jiao

    2015-01-01

    Full Text Available It is of great importance to evaluate the hull structural vibrations response of large ships in extreme seas. Studies of hydroelastic response of an ultra large ship have been conducted with comparative verification between experimental and numerical methods in order to estimate the wave loads response considering hull vibration and water impact. A segmented self-propelling model with steel backbone system was elaborately designed and the experiments were performed in a tank. Time domain numerical simulations of the ship were carried out by using three-dimensional nonlinear hydroelasticity theory. The results from the computational analyses have been correlated with those from model tests.

  18. Numerical analysis and simulation of Czochralski growth processes for large diameter silicon crystals

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Numerical analysis and simulation have been an effective means to develop the advanced growth technology and to control the defects type, size and density for silicon crystals of 300 mm and beyond In the present paper, numerical analysis of the melt flow in the Czochralski (CZ) crystal growth configuration, the three dimensional (3D) modeling, the simulation of melt flow under the magnetic field, the inverse modeling and the time-dependent simulation are reviewed. Finally, comparison of numerical analysis with experimental measurements is discussed.

  19. Synthetic Aperture Radar Interferometry

    Science.gov (United States)

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

    1998-01-01

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

  20. Variable optofluidic slit aperture

    Institute of Scientific and Technical Information of China (English)

    Stefan Schuhladen; Kaustubh Banerjee; Moritz Stürmer; Philipp Müller; Ulrike Wallrabe; Hans Zappe

    2016-01-01

    The shape of liquid interfaces can be precisely controlled using electrowetting,an actuation mechanism which has been widely used for tunable optofluidic micro-optical components such as lenses or irises.We have expanded the considerable flexibility inherent in electrowetting actuation to realize a variable optofluidic slit,a tunable and reconfigurable two-dimensional aperture with no mechanically moving parts.This optofluidic slit is formed by precisely controlled movement of the liquid interfaces of two highly opaque ink droplets.The 1.5 mm long slit aperture,with controllably variable discrete widths down to 45 μm,may be scanned across a length of 1.5 mm with switching times between adjacent slit positions of less than 120 ms.In addition,for a fixed slit aperture position,the width may be tuned to a minimum of 3 μm with high uniformity and linearity over the entire slit length.This compact,purely fluidic device offers an electrically controlled aperture tuning range not achievable with extant mechanical alternatives of a similar size.

  1. Influence of initial heterogeneities and recharge limitations on the evolution of aperture distributions in carbonate aquifers

    Directory of Open Access Journals (Sweden)

    B. Hubinger

    2011-12-01

    Full Text Available Karst aquifers evolve where the dissolution of soluble rocks causes the enlargement of discrete pathways along fractures or bedding planes, thus creating highly conductive solution conduits. To identify general interrelations between hydrogeological conditions and the properties of the evolving conduit systems the aperture-size frequency distributions resulting from generic models of conduit evolution are analysed. For this purpose, a process-based numerical model coupling flow and rock dissolution is employed. Initial protoconduits are represented by tubes with log-normally distributed aperture sizes with a mean μ0 = 0.5 mm for the logarithm of the diameters. Apertures are spatially uncorrelated and widen up to the metre range due to dissolution by chemically aggressive waters. Several examples of conduit development are examined focussing on influences of the initial heterogeneity and the available amount of recharge. If the available recharge is sufficiently high the evolving conduits compete for flow and those with large apertures and high hydraulic gradients attract more and more water. As a consequence, the positive feedback between increasing flow and dissolution causes the breakthrough of a conduit pathway connecting the recharge and discharge sides of the modelling domain. Under these competitive flow conditions dynamically stable bimodal aperture distributions are found to evolve, i.e. a certain percentage of tubes continues to be enlarged while the remaining tubes stay small-sized. The percentage of strongly widened tubes is found to be independent of the breakthrough time and decreases with increasing heterogeneity of the initial apertures and decreasing amount of available water. If the competition for flow is suppressed because the availability of water is strongly limited breakthrough of a conduit pathway is inhibited and the conduit pathways widen very slowly. The resulting aperture distributions are found to be

  2. IMPROVED SYNTHETIC APERTURE SONAR MOTION COMPENSATION COMBINED DPCA WITH SUB-APERTURE IMAGE CORRELATION

    Institute of Scientific and Technical Information of China (English)

    Liu Wei; Zhang Chunhua; Liu Jiyuan

    2009-01-01

    Estimation precision of Displaced Phase Center Algorithm (DPCA) is affected by the number of displaced phase center pairs, the bandwidth of transmitting signal and many other factors. Detailed analysis is made on DPCA's estimation precision. Analysis results show that the directional vector estimation precision of DPCA is low, which will produce accumulating errors when phase centers' track is estimated. Because of this reason, DPCA suffers from accumulating errors seriously. To overcome this problem, a method combining DPCA with Sub Aperture Image Correlation (SAIC) is presented. Large synthetic aperture is divided into sub-apertures. Micro errors in sub-aperture are estimated by DPCA and compensated to raw echo data. Bulk errors between sub-apertures are estimated by SAIC and compensated directly to sub-aperture images. After that, sub-aperture images are directly used to generate ultimate SAS image. The method is applied to the lake-trial dataset of a 20 kHz SAS prototype system. Results show the method can successfully remove the accumulating error and produce a better SAS image.

  3. Fast numerical method for electromagnetic scattering from an object above a large-scale layered rough surface at large incident angle: vertical polarization.

    Science.gov (United States)

    Wang, A-Q; Guo, L-X; Chai, C

    2011-02-01

    A fast numerical method has been proposed in this paper for calculating the electromagnetic scattering from a perfectly electric conducting object above a two-layered dielectric rough surface. The focus in this study is large incidence. The parallel fast multipole method is combined with the method of moments for fast implementation of the scattering from this composite model. The biconjugate gradient method is adopted to solve the unsymmetrical matrix equation and parallelized. The simulating time and parallel speedup ratio with different processors are provided. Several numerical results are shown and analyzed to discuss the influences of the parameters of the rough surface, the object, and the intermediate medium on the bistatic scattering.

  4. Large Eddy Simulations (LES) and Direct Numerical Simulations (DNS) for the computational analyses of high speed reacting flows

    Science.gov (United States)

    Givi, Peyman; Madnia, Cyrus K.; Steinberger, C. J.; Frankel, S. H.

    1992-01-01

    The principal objective is to extend the boundaries within which large eddy simulations (LES) and direct numerical simulations (DNS) can be applied in computational analyses of high speed reacting flows. A summary of work accomplished during the last six months is presented.

  5. Numerical modeling of the spring thermal bar and pollutant transport in a large lake

    Science.gov (United States)

    Tsydenov, Bair O.; Kay, Anthony; Starchenko, Alexander V.

    2016-08-01

    The spring riverine thermal bar phenomenon is investigated numerically on an example of Lake Baikal, and the spread of pollutants coming from the Selenga River is forecast using the 2.5 D non-hydrostatic model in the Boussinesq approximation. This hydrodynamic model takes into account the diurnal variability of the heat fluxes on the lake surface and the effects of wind and the Earth's rotation. The results of numerical modeling show that the variability of the total heat flux over 24 h plays a significant role in the variation of the thermal bar movement rate that contributes to the rapid mixing of impurities entering with river water.

  6. Numerical Modeling of Thermal Pollution of Large Water Bodies from Thermal and Nuclear Power Plants

    Science.gov (United States)

    Lyubimova, Tatyana; Lepikhin, Anatoly; Lyakhin, Yury; Parshakova, Yanina; Tiunov, Alexey

    2016-04-01

    Currently, the major manufacturers of electrical energy are the thermal and nuclear power plants including the cooling ponds in the processing chains. For a wide range of both environmental and technological problems, the evaluation of the temperature fields in the cooling ponds at certain critical values of hydrological and meteorological parameters is important. The present paper deals with the evaluation of the thermal effect of one of the largest thermal power plant in Europe - Perm GRES - to its cooling pond which is the Kama Reservoir. Since the area of the possible impact is rather large and the reservoir itself is characterized by a very complex morphometry, numerical modeling of thermal spot propagation in the Kama River due to the discharge of warm water by Perm GRES for the entire area in the 3D-formulation with the desired detail setting morphometric characteristics of the water body meets very serious difficulties. Because of that, to solve the problem, a combined scheme of calculations based on the combination of hydrodynamic models in 2D and 3D formulations was used. At the first stage of the combined scheme implementation, 2D hydrodynamical model was developed for all possible area, using software SMS v.11.1. The boundary and initial conditions for this model were formulated on the basis of calculations made using 1D hydrodynamical model developed and applied for the entire Kama Reservoir. Application of 2D hydrodynamical model for solving the problem under consideration was needed to obtain the necessary information for setting the boundary conditions for the 3D model. Software package ANSYS Fluent v.6.3 was used for the realization of 3D model. 3D modeling was performed for different wind speeds and directions and quantitative characteristics of the discharge of warm water. To verify the models, the data of the detailed field measurements in the zones of thermal pollution of the Kama reservoir due to impact of the Perm GRES were used. A

  7. 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...... resolutions; 2) the lack of capability in detecting flow other than the one along the direction of the beam. Addressing these technical limitations would translate in the clinic as a gain in valuable clinical information and a removal of operator-dependant sources of error, which would improve the diagnosis....... The main contribution of this work was the development of an angle estimator which features high accuracy and low standard deviation over the full 360◦ range. The estimator demonstrated its capability of operating at high frame rates (> 1000 Hz), and simultaneously detecting a large range of flow...

  8. 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.)

  9. Aperture effects in squid jet propulsion.

    Science.gov (United States)

    Staaf, Danna J; Gilly, William F; Denny, Mark W

    2014-05-01

    Squid are the largest jet propellers in nature as adults, but as paralarvae they are some of the smallest, faced with the inherent inefficiency of jet propulsion at a low Reynolds number. In this study we describe the behavior and kinematics of locomotion in 1 mm paralarvae of Dosidicus gigas, the smallest squid yet studied. They swim with hop-and-sink behavior and can engage in fast jets by reducing the size of the mantle aperture during the contraction phase of a jetting cycle. We go on to explore the general effects of a variable mantle and funnel aperture in a theoretical model of jet propulsion scaled from the smallest (1 mm mantle length) to the largest (3 m) squid. Aperture reduction during mantle contraction increases propulsive efficiency at all squid sizes, although 1 mm squid still suffer from low efficiency (20%) because of a limited speed of contraction. Efficiency increases to a peak of 40% for 1 cm squid, then slowly declines. Squid larger than 6 cm must either reduce contraction speed or increase aperture size to maintain stress within maximal muscle tolerance. Ecological pressure to maintain maximum velocity may lead them to increase aperture size, which reduces efficiency. This effect might be ameliorated by nonaxial flow during the refill phase of the cycle. Our model's predictions highlight areas for future empirical work, and emphasize the existence of complex behavioral options for maximizing efficiency at both very small and large sizes.

  10. Experimental investigation and numerical simulation of large-sized aluminum tube extrusion forming

    Institute of Scientific and Technical Information of China (English)

    吕亚臣; 骆俊廷; 马春荣; 徐岩

    2008-01-01

    Large-sized aluminum tube has big section effect, aspect ratio and thin thickness, so that the extrusion technology is complex and the large specific pressure is generated in extrusion cavity. The temperature variation and velocity effect is difficult to control. The extrusion forming of large-sized aluminum tube was researched and simulated. Three-dimensional thermo-mechanical coupled finite element model was constructed and appropriate boundary conditions were given out. The results show that large-sized aluminum tube can be formed by isothermal extrusion through controlling the extrusion velocity and founding the relationship between extrusion velocity and extrusion temperature.

  11. The slant-stacklet transform and its application to teleseismic PcP-P data recorded at large aperture seismic array

    Science.gov (United States)

    Ventosa, S.; Romanowicz, B. A.

    2015-12-01

    In most high-resolution studies of the Earth's Deep Interior, the limited amount and uneven distribution of high-quality observations of short-period teleseismic body waves are major obstacles. Dense broadband seismic networks help to overcome major challenges of low signal-to-noise ratio (SNR) of the target phases and of signal-to-interference ratio (SIR) of other (often stronger) mantle phases when the slowness difference is large enough. Intuitive delay-and-sum (i.e. slant-stack) approaches are routinely applied to combine data of many spatially close stations to improve data quality. Alternative methods developed in the context of image processing, such as Radon transform-based methods, have proven useful in exploration seismology to facilitate enhancement and separation of signals according to their slowness and time of arrival. In this spirit, we have introduced the slant-stacklet transform to define coherency-guided filters able to exploit signals that would have been otherwise rejected because of low SNR or SIR. As an illustration, this method allows us to dramatically increase the amount of high-quality PcP observations using dense arrays in North America and Japan, sampling Central America, the western Pacific and Alaska/western Canada with unprecedented resolution and accuracy. After mantle corrections, the main signal left in these regions is relatively long wavelength in these regions of fast velocities around the Pacific, except at the western border of the Pacific large-low shear-velocity province (LLSVP) where we observe a rapid reduction of Vp velocity over a distance of about 10˚. This is just one step to further increase lowermost mantle imaging using P waves, much more information from PcP and other complementary signals (e.g. PdP) around the globe are needed to resolve volumetric structure, topography of the core-mantle boundary and D" discontinuity, and the trade-offs between them, in order to improve our understanding of the interaction

  12. Advanced Multiple Aperture Seeing Profiler

    Science.gov (United States)

    Ren, Deqing; Zhao, Gang

    2016-10-01

    Measurements of the seeing profile of the atmospheric turbulence as a function of altitude are crucial for solar astronomical site characterization, as well as the optimized design and performance estimation of solar Multi-Conjugate Adaptive Optics (MCAO). Knowledge of the seeing distribution, up to 30 km, with a potential new solar observation site, is required for future solar MCAO developments. Current optical seeing profile measurement techniques are limited by the need to use a large facility solar telescope for such seeing profile measurements, which is a serious limitation on characterizing a site's seeing conditions in terms of the seeing profile. Based on our previous work, we propose a compact solar seeing profiler called the Advanced Multiple Aperture Seeing Profile (A-MASP). A-MASP consists of two small telescopes, each with a 100 mm aperture. The two small telescopes can be installed on a commercial computerized tripod to track solar granule structures for seeing profile measurement. A-MASP is extreme simple and portable, which makes it an ideal system to bring to a potential new site for seeing profile measurements.

  13. The physics of light transmission through subwavelength apertures and aperture arrays

    Science.gov (United States)

    Weiner, J.

    2009-06-01

    The passage of light through apertures much smaller than the wavelength of the light has proved to be a surprisingly subtle phenomenon. This report describes how modern developments in nanofabrication, coherent light sources and numerical vector field simulations have led to the upending of early predictions from scalar diffraction theory and classical electrodynamics. Optical response of real materials to incident coherent radiation at petahertz frequencies leads to unexpected consequences for transmission and extinction of light through subwavelength aperture arrays. This paper is a report on progress in our understanding of this phenomenon over the past decade.

  14. Design of lightweight large aperture mirrors and supporting structures%大口径反射镜轻量化及其支撑结构设计

    Institute of Scientific and Technical Information of China (English)

    李畅; 何欣

    2015-01-01

    为了满足大口径(800mm ×400mm)矩形轮廓反射镜的结构稳定性设计要求,采用背部3点支撑方式,基于Bipod原理,为某超宽覆盖空间的相机主镜设计了一种新型柔性支撑结构。分析了反射镜各结构参量对其质量和刚度的影响,选取其中影响较大的参量作为设计变量,对镜体轻量化结构进行了优化设计,并进行了有限元分析。结果表明,优化设计后的反射镜组件具有较好的力学适应性、温度适应性和动态刚度。振动试验结果与有限元分析结果相符,证明了其准确性。%In order to satisfy the structure stability of a large rectangle mirror (800mm ×400mm), a novel flexible supporting structure of space camera primary mirror with super wide coverage was designed by Bipod principle in which three supporting points were adopted in backside of the mirror .The influence of the structure parameters on the mass and stiffness of the mirror was analyzed .The parameters which had significant effect were chosen as the design variables and the optimization design of mirror lightweight structure was carried out .The finite element analysis was conducted .The results indicate that the mirror structure has better mechanical adaptability , thermal adaptability and dynamical stiffness .The results of finite element analysis are consistent with the results of vibration test .

  15. Numerical experiments with assimilation of the mean and unresolved meteorological conditions into large-eddy simulation model

    CERN Document Server

    Esau, Igor

    2010-01-01

    Micrometeorology, city comfort, land use management and air quality monitoring increasingly become important environmental issues. To serve the needs, meteorology needs to achieve a serious advance in representation and forecast on micro-scales (meters to 100 km) called meteorological terra incognita. There is a suitable numerical tool, namely, the large-eddy simulation modelling (LES) to support the development. However, at present, the LES is of limited utility for applications. The study addresses two problems. First, the data assimilation problem on micro-scales is investigated as a possibility to recover the turbulent fields consistent with the mean meteorological profiles. Second, the methods to incorporate of the unresolved surface structures are investigated in a priopi numerical experiments. The numerical experiments demonstrated that the simplest nudging or Newtonian relaxation technique for the data assimilation is applicable on the turbulence scales. It is also shown that the filtering property of...

  16. On Estimation of Fracture Aperture with Ground Penetrating Radar

    Science.gov (United States)

    Linde, N.; Shakas, A.

    2016-12-01

    Ground penetrating radar (GPR) is an excellent tool for fracture imaging, but GPR-assisted estimation of fracture aperture is a largely unresolved challenge. The main reason for this is that traditional modeling techniques face severe limitations in fractured rock environments. For example, finite-difference time-domain (FDTD) formulations of Maxwell's equations are poorly adapted to deal with fractures of arbitrary orientations and apertures that are three-five orders of magnitude smaller than the modeling domain. An alternative is to use analytical solutions for thin-bed responses, but they are based on strong assumptions that often do not apply in practise. We have recently developed an efficient modeling approach to simulate GPR propagation and reflection in fractured rock. Here, we first use this modeling formulation to examine the ability of the thin-bed solution to infer the aperture of a homogeneous fracture. We then consider a suite of synthetic examples with heterogeneous fracture aperture fields of varying fractal (Hurst) exponents and spatial correlation lengths. We then use a global optimization algorithm to infer a mean (effective) fracture aperture in each case using the noise-contaminated synthetic data. The thin-bed solution leads to biased aperture estimates even if the fracture has a constant aperture and all other modeling parameters are known. With our modeling approach, we find that appropriate mean apertures are estimated in the homogeneous case, and when the correlation length of the aperture distribution is of similar scale (or larger) than the dominant GPR wavelength.

  17. Safety Analysis in Large Volume Vacuum Systems Like Tokamak: Experiments and Numerical Simulation to Analyze Vacuum Ruptures Consequences

    Directory of Open Access Journals (Sweden)

    A. Malizia

    2014-01-01

    Full Text Available The large volume vacuum systems are used in many industrial operations and research laboratories. Accidents in these systems should have a relevant economical and safety impact. A loss of vacuum accident (LOVA due to a failure of the main vacuum vessel can result in a fast pressurization of the vessel and consequent mobilization dispersion of hazardous internal material through the braches. It is clear that the influence of flow fields, consequence of accidents like LOVA, on dust resuspension is a key safety issue. In order to develop this analysis an experimental facility is been developed: STARDUST. This last facility has been used to improve the knowledge about LOVA to replicate a condition more similar to appropriate operative condition like to kamaks. By the experimental data the boundary conditions have been extrapolated to give the proper input for the 2D thermofluid-dynamics numerical simulations, developed by the commercial CFD numerical code. The benchmark of numerical simulation results with the experimental ones has been used to validate and tune the 2D thermofluid-dynamics numerical model that has been developed by the authors to replicate the LOVA conditions inside STARDUST. In present work, the facility, materials, numerical model, and relevant results will be presented.

  18. Numerical Modelling of Large-Diameter Steel Piles at Horns Rev

    DEFF Research Database (Denmark)

    Augustesen, Anders Hust; Brødbæk, K. T.; Møller, M.;

    2009-01-01

    Today large-diameter monopiles are the most common foundation type used for large offshore wind farms. This paper aims to investigate the behaviour of monopiles under monotonic loading taking the interaction between the pile and the subsoil into account. Focus is paid to a monopile used as founda......Today large-diameter monopiles are the most common foundation type used for large offshore wind farms. This paper aims to investigate the behaviour of monopiles under monotonic loading taking the interaction between the pile and the subsoil into account. Focus is paid to a monopile used...... as foundation for a wind turbine at Horns Rev located in the Danish sector of the North Sea. The outer diameter of the pile is 4 m and the subsoil at the location consists primarily of sand. The behaviour of the pile is investigated under realistic loading conditions by means of a traditional Winkler...

  19. A numerical study of the large-period limit of a Zakharov-Shabat eigenvalue problem with periodic potentials

    Science.gov (United States)

    Olivier, C. P.; Herbst, B. M.; Molchan, M. A.

    2012-06-01

    Deconinck and Kutz (2006 J. Comput. Phys. 219 296-321) developed an efficient algorithm for solving the Zakharov-Shabat eigenvalue problem with periodic potentials numerically. It is natural to use the same algorithm for solving the problem for non-periodic potential (decaying potentials defined over the whole real line) using large periods. In this paper, we propose the use of a specific value of the Floquet exponent. Our numerical results indicate that it can produce accurate results long before the period becomes large enough for the analytical convergence results of Gardner (1997 J. Reine Angew. Math. 491 149-81) to be valid. We also illustrate the rather complicated path to convergence of some nonlinear Schrödinger potentials.

  20. Experimental and numerical modelling of ductile crack propagation in large-scale shell structures

    DEFF Research Database (Denmark)

    Simonsen, Bo Cerup; Törnquist, R.

    2004-01-01

    for steel and aluminium plates, mainly as curves showing the critical element deformation versus the shell element size. These derived crack propagation criteria are then validated against a separate set of experiments considering centre crack specimens (CCS) which have a different crack-tip constraint...... is in general good and it is believed that the presented results and experimental-numerical calibration procedure can be of use in practical finite-element simulations of collision and grounding events with the use of shell elements. As discussed, the paper provides a clean framework for further development...

  1. The micro-vibration analysis for the large aperture grating tiling device%大口径光栅拼接装置的微振动响应分析

    Institute of Scientific and Technical Information of China (English)

    周忆; 廖云飞; 刘有海; 罗跃飞; 王逍; 周海

    2012-01-01

    A new grating tiling device with 2×2 gratings is developed to obtain a large aperture grating.For the stability of the device impacted by the HVAC vibration,a dynamic finite element analysis model is established.The random vibration response of the model under the measured power spectral density as stimulus has been carried out by the ANSYS software,and the data has been compared to the experimental data.The results show that the device can meet the stability requirements in the work environment.%针对2×2大口径光栅拼接装置在暖通空调振动影响下的稳定性问题,建立了有限元动力分析模型。以实测的震动功率谱密度为激励,运用ANSYS软件对其随机振动响应进行分析计算,并与实测结果进行了比较。结果表明,该装置在工作环境中满足稳定性要求。

  2. Numerical studies of large-amplitude internal waves shoaling and breaking at shelf slopes

    Science.gov (United States)

    Thiem, Øyvind; Berntsen, Jarle

    2009-12-01

    Hydro carbon fields beyond the shelf break are presently being explored and developed, which has increased the scientific focus in this area. Measurements from the slopes reveal large variability in temperature and velocity, and some of the observed events are due to interactions between large-amplitude oscillations of the thermocline and the topography. The present study focuses on the strong currents that are generated near the seabed during shoaling and breaking of internal waves along shelf slopes. The parameter regime used is similar to the one for the Nordic Seas. The results show that, during shoaling of large internal waves along (gentle) slopes, the energy is transferred towards smaller scales and strong velocities (over 1 m s - 1) can be generated. To resolve all scales involved is still not feasible, and therefore, the model results are sensitive to the grid size and the subgrid scale closure.

  3. HPF: a data parallel programming interface for large-scale numerical simulations

    Energy Technology Data Exchange (ETDEWEB)

    Seo, Yoshiki; Suehiro, Kenji; Murai, Hitoshi [NEC Corp., Tokyo (Japan)

    1998-03-01

    HPF (High Performance Fortran) is a data parallel language designed for programming on distributed memory parallel systems. The first draft of HPF1.0 was defined in 1993 as a de facto standard language. Recently, relatively reliable HPF compilers have become available on several distributed memory parallel systems. Many projects to parallelize real world programs have started mainly in the U.S. and Europe, and the weak and strong points in the current HPF have been made clear. In this paper, major data transfer patterns required to parallelize numerical simulations, such as SHIFT, matrix transposition, reduction, GATHER/SCATTER and irregular communication, and the programming methods to implement them with HPF are described. The problems in the current HPF interface for developing efficient parallel programs and recent activities to deal with them is presented as well. (author)

  4. Numerical analysis of jet impingement heat transfer at high jet Reynolds number and large temperature difference

    DEFF Research Database (Denmark)

    Jensen, Michael Vincent; Walther, Jens Honore

    2013-01-01

    was investigated at a jet Reynolds number of 1.66 × 105 and a temperature difference between jet inlet and wall of 1600 K. The focus was on the convective heat transfer contribution as thermal radiation was not included in the investigation. A considerable influence of the turbulence intensity at the jet inlet......Jet impingement heat transfer from a round gas jet to a flat wall was investigated numerically for a ratio of 2 between the jet inlet to wall distance and the jet inlet diameter. The influence of turbulence intensity at the jet inlet and choice of turbulence model on the wall heat transfer...... was observed in the stagnation region, where the wall heat flux increased by a factor of almost 3 when increasing the turbulence intensity from 1.5% to 10%. The choice of turbulence model also influenced the heat transfer predictions significantly, especially in the stagnation region, where differences of up...

  5. A multirate numerical scheme for large-scale vehicle traffic simulation

    CERN Document Server

    Kurtc, Valentina

    2016-01-01

    Nowadays the city-wide traffic contains hundreds of thousands of vehicles with different scenarios of their behavior. If a microscopic approach is used it leads to solving tremendous systems of ordinary differential equations whose components have a wide range of variation rates. The given paper has introduced a multirate numerical scheme with a self-adjusting time stepping strategy. Instead of using a single step size for the whole system we have determined the step size for each component by estimating its own local variation. We also performed the stability analysis for the developed scheme. The presented multirate scheme provides a significant speed-up in processor times compared to the corresponding single-rate one. The use of multiple time steps admits parallel computing.

  6. Mathematical Models and Numerical Simulations for the Blood Flow in Large Vessels

    Directory of Open Access Journals (Sweden)

    Titus PETRILA

    2012-12-01

    Full Text Available We are proposing a non-Newtonian, Cross type rheological model for the blood flow, under the conditions of an unsteady flow regime connected with the rhythmic pumping of the blood by the heart. We admit the incompressibility and homogeneity of the blood while its flow is laminar and the exterior body forces are neglected. We take also into account the viscoelastic behavior of the vessel walls. The mathematical equations and the appropriate boundary conditions are considered in cylindrical (axisymmetric coordinates. Numerical experiments in case of stenosed artery and in artery with aneurysm (using COMSOL Multiphysics 3.3 are made. The variation of the wall shear stress, which is believed to have a special importance in the rupture of aneurysms, is calculated using both a Newtonian and a non-Newtonian model.

  7. Numerical investigation of cavitation flow inside spool valve with large pressure drop

    Science.gov (United States)

    Deng, Jian; Pan, Dingyi; Xie, Fangfang; Shao, Xueming

    2015-12-01

    Spool valves play an important role in fluid power system. Cavitation phenomena happen frequently inside the spool valves, which cause structure damages, noise and lower down hydrodynamic performance. A numerical tools incorporating the cavitation model, are developed to predict the flow structure and cavitation pattern in the spool valve. Two major flow states in the spool valve chamber, i.e. flow-in and flow-out, are studies. The pressure distributions along the spool wall are first investigated, and the results agree well with the experimental data. For the flow-in cases, the local pressure at the throttling area drops much deeper than the pressure in flow-out cases. Meanwhile, the bubbles are more stable in flow-in cases than those in flow-out cases, which are ruptured and shed into the downstream.

  8. Numerical Simulations of the Aeroelastic Behavior of Large Horizontal-Axis Wind Turbines: The Drivetrain Case

    DEFF Research Database (Denmark)

    Gebhardt, Cristian; Veluri, Badrinath; Preidikman, Sergio

    2010-01-01

    In this work an aeroelastic model that describes the interaction between aerodynamics and drivetrain dynamics of a large horizontal–axis wind turbine is presented. Traditional designs for wind turbines are based on the output of specific aeroelastic simulation codes. The output of these codes giv...

  9. Numerics-Characteristics-Asymptotics: A Case Study from Large Scale Ocean Circulation

    Science.gov (United States)

    Hodnett, P. F.; Courtney, C.

    2007-01-01

    This paper uses a partial differential equation which occurs in a reduced model of large scale circulation in an ocean basin as an educational vehicle through which to demonstrate the usefulness of a set of mathematical techniques in analysing the equation. A parameter occurring in the equation does in reality vary from very small through…

  10. Numerical Simulations of the Aeroelastic Behavior of Large Horizontal-Axis Wind Turbines: The Drivetrain Case

    DEFF Research Database (Denmark)

    Gebhardt, Cristian; Veluri, Badrinath; Preidikman, Sergio

    2010-01-01

    In this work an aeroelastic model that describes the interaction between aerodynamics and drivetrain dynamics of a large horizontal–axis wind turbine is presented. Traditional designs for wind turbines are based on the output of specific aeroelastic simulation codes. The output of these codes giv...

  11. Experimental and numerical friction characterization for large-scale forming simulations

    NARCIS (Netherlands)

    Hol, J.; Meinders, Vincent T.; van den Boogaard, Antonius H.; Hora, P.

    2013-01-01

    A new trend in forming simulation technology is the development of friction models applicable to large scale forming simulations. In this respect, the optimization of forming processes and the success of newly developed friction models requires a complete understanding of the tribological behavior

  12. Numerical Analysis of a Large Floating Wave Energy Converter with Adjustable Structural Geometry

    DEFF Research Database (Denmark)

    Ferri, Francesco; Pecher, Arthur Francois Serge; Kofoed, Jens Peter

    2015-01-01

    The current cost of energy (CoE) from wave energy converters (WECs) is still significantly higher than other renewable energy resources, thus the sector has not yet reached a competitive level. WECs have a relative small turnover compared to the high capital cost, which to a large extent is drive...

  13. Adaptive Techniques for Large Space Apertures.

    Science.gov (United States)

    1980-03-01

    frequencies (A20 criterion very small). The penality occurs in requiring long focal length optics to match the ob- ject (target) displacement to the...GP Anitern, 200l de or,~,’rn, receiner/ proceso 1"’ - requires enternal !titude deter- minationr such as a star tracker Increased mechanizatio’ Sensor

  14. 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...... harmonic techniques have been made, but none of these methods have so far been applicable for in-vivo imaging. The basis of this project is a synthetic aperture technique known as synthetic aperture sequential beamforming (SASB). The technique utilizes a two step beamforming approach to drastically reduce...

  15. PREDICTIONS OF WAVE INDUCED SHIP MOTIONS AND LOADS BY LARGE-SCALE MODEL MEASUREMENT AT SEA AND NUMERICAL ANALYSIS

    Directory of Open Access Journals (Sweden)

    Jialong Jiao

    2016-06-01

    Full Text Available In order to accurately predict wave induced motion and load responses of ships, a new experimental methodology is proposed. The new method includes conducting tests with large-scale models under natural environment conditions. The testing technique for large-scale model measurement proposed is quite applicable and general to a wide range of standard hydrodynamics experiments in naval architecture. In this study, a large-scale segmented self-propelling model allowed for investigating seakeeping performance and wave load behaviour as well as the testing systems were designed and experiments performed. A 2-hour voyage trial of the large-scale model aimed to perform a series of simulation exercises was carried out at Huludao harbour in October 2014. During the voyage, onboard systems, operated by crew, were used to measure and record the sea waves and the model responses. The post-voyage analysis of the measurements, both of the sea waves and the model’s responses, were made to predict the ship’s motion and load responses of short-term under the corresponding sea state. Furthermore, numerical analysis of short-term prediction was made by an in-house code and the result was compared with the experiment data. The long-term extreme prediction of motions and loads was also carried out based on the numerical results of short-term prediction.

  16. Numerical Solution of Membrane Forces for A Free-Free Floating Plate with Large Deflection

    Institute of Scientific and Technical Information of China (English)

    陈徐均; 崔维成; 宋皓; 汤雪峰

    2003-01-01

    Considering that the thickness of a pontoon-type very large floating structure (VLFS) is very small in comparison with the length and width, VLFS can be modeled as a thin plate. In theory, the displacements and the membrane forces of a plate with large deflection are all the functions of the second-order differentials of the Ariy stress function. With these characteristics considered, the Ariy stress function of a floating free-free plate is calculated by setting the virtual values of three of the corner points. The finite difference method is chosen to solve the problem. When the Ariy stress function of the plate is obtained, the membrane forces can easily be calculated. Comparisons between the forces induced by the membrane forces and by the fluid are considered. It is shown that the membrane forces can not be neglected in many cases.

  17. Optimum synthetic-aperture imaging of extended astronomical objects

    NARCIS (Netherlands)

    Van der Avoort, C.; Pereira, S.F.; Braat, J.J.M.; Den Herder, J.W.

    2007-01-01

    In optical aperture-synthesis imaging of stellar objects, different beam combination strategies are used and proposed. Coaxial Michelson interferometers are very common and a homothetic multiaxial interferometer is recently realized in the Large Binocular Telescope. Laboratory experiments have demon

  18. Large scale Direct Numerical Simulation of premixed turbulent jet flames at high Reynolds number

    Science.gov (United States)

    Attili, Antonio; Luca, Stefano; Lo Schiavo, Ermanno; Bisetti, Fabrizio; Creta, Francesco

    2016-11-01

    A set of direct numerical simulations of turbulent premixed jet flames at different Reynolds and Karlovitz numbers is presented. The simulations feature finite rate chemistry with 16 species and 73 reactions and up to 22 Billion grid points. The jet consists of a methane/air mixture with equivalence ratio ϕ = 0 . 7 and temperature varying between 500 and 800 K. The temperature and species concentrations in the coflow correspond to the equilibrium state of the burnt mixture. All the simulations are performed at 4 atm. The flame length, normalized by the jet width, decreases significantly as the Reynolds number increases. This is consistent with an increase of the turbulent flame speed due to the increased integral scale of turbulence. This behavior is typical of flames in the thin-reaction zone regime, which are affected by turbulent transport in the preheat layer. Fractal dimension and topology of the flame surface, statistics of temperature gradients, and flame structure are investigated and the dependence of these quantities on the Reynolds number is assessed.

  19. Numerical research of a super-large cooling tower subjected to accidental loads

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yi; Lin, Feng [Department of Building Engineering, Tongji University, Shanghai 200092 (China); Gu, Xianglin, E-mail: gxl@tongji.edu.cn [Department of Building Engineering, Tongji University, Shanghai 200092 (China); Lu, Xiaoqin [Guangdong Electric Power Design Institute, Guangzhou 510660 (China)

    2014-04-01

    With the continued development of nuclear power plants, more and more super-large cooling towers are to be built in China and around the world. For the safe operation of nuclear power plants, research work has been done on the causes of collapse of cooling towers, collapse modes and the secondary disasters caused by the collapse of cooling towers. However, the collapse modes and the ground vibration induced by the collapse of cooling towers subjected to the accidental loads have not been fully understood. This paper has been focused on the modes and mechanisms behavior of the collapse of cooling towers subjected to accidental loads. Meanwhile, prediction of the ground vibration due to the collapse of the cooling towers has also been completed in a parallel project. Using dynamic finite element program LS-DYNA, a 3D finite element model for a super-large cooling tower was developed and the nonlinear material models were incorporated. In this paper, four types of accidental loads were considered to trigger the collapse or local failure of the tower, including vehicle collision, airplane impact, local explosion and missile attack. It was found that vehicle collision, missile attack and small TNT equivalent explosives (2 kg, 20 kg, 200 kg) might result in local failure of the cooling tower, however, the tower can still keep stable. On the other hand, large TNT equivalent explosives (2000 kg, 4500 kg) could cause severe damages in the inclined columns of the cooling tower, and lead to progressive collapse of the entire cooling tower. The two kinds of TNT equivalent explosives caused the same collapse mode while the collapsing duration was different. The airplane impacted at the throat of the cooling tower caused the local failure of shell structure of the tower, and then the progressive collapse of the cooling tower happened due to the gravitational action. The resulting collapse mode was different from that triggered by the local explosion.

  20. Numerical modelling of odour dispersion around a cubical obstacle using large eddy simulation.

    Science.gov (United States)

    Dourado, Harerton Oliveira; Santos, Jane Meri; Reis, Neyval C; Mavroidis, Ilias

    2012-01-01

    In the present work two different large eddy simulation (LES) approaches, namely the Dynamic Smagorinsky model and the Wale model, are used to simulate the air flow and pollutant dispersion around a cubical obstacle. Results are compared with wind tunnel data (WT) and with results from the Smagorinsky LES model. Overall agreement was good between the different LES approaches and the WT results, both for the mean and fluctuating flow and concentration patterns. LES models can provide good estimates of concentration fluctuation intensity and enable the calculation of the intermittency factor. The model results indicate that LES is a viable tool for odour impact assessment.

  1. Numerical and analytical approaches to an advection-diffusion problem at small Reynolds number and large P\\'eclet number

    CERN Document Server

    Fuller, Nathaniel J

    2016-01-01

    Obtaining a detailed understanding of the physical interactions between a cell and its environment often requires information about the flow of fluid surrounding the cell. Cells must be able to effectively absorb and discard material in order to survive. Strategies for nutrient acquisition and toxin disposal, which have been evolutionarily selected for their efficacy, should reflect knowledge of the physics underlying this mass transport problem. Motivated by these considerations, in this paper we consider a two-dimensional advection-diffusion problem at small Reynolds number and large P\\'eclet number. We discuss the problem of mass transport for a circular cell in a uniform far-field flow. We approach the problem numerically, and also analytically through a rescaling of the concentration boundary layer. A biophysically motivated first-passage problem for the absorption of material by the cell demonstrates quantitative agreement between the numerical and analytical approaches.

  2. Flame Reconstruction Using Synthetic Aperture Imaging

    CERN Document Server

    Murray, Preston; Tree, Dale; Truscott, Tadd

    2011-01-01

    Flames can be formed by burning methane (CH4). When oxygen is scarce, carbon particles nucleate into solid particles called soot. These particles emit photons, making the flame yellow. Later, methane is pre-mixed with air forming a blue flame; burning more efficiently, providing less soot and light. Imaging flames and knowing their temperature are vital to maximizing efficiency and validating numerical models. Most temperature probes disrupt the flame and create differences leading to an inaccurate measurement of the flame temperature. We seek to image the flame in three dimensions using synthetic aperture imaging. This technique has already successfully measured velocity fields of a vortex ring [1]. Synthetic aperture imaging is a technique that views one scene from multiple cameras set at different angles, allowing some cameras to view objects that are obscured by others. As the resulting images are overlapped different depths of the scene come into and out of focus, known as focal planes, similar to tomogr...

  3. Cross-flow turbines: progress report on physical and numerical model studies at large laboratory scale

    Science.gov (United States)

    Wosnik, Martin; Bachant, Peter

    2016-11-01

    Cross-flow turbines show potential in marine hydrokinetic (MHK) applications. A research focus is on accurately predicting device performance and wake evolution to improve turbine array layouts for maximizing overall power output, i.e., minimizing wake interference, or taking advantage of constructive wake interaction. Experiments were carried with large laboratory-scale cross-flow turbines D O (1 m) using a turbine test bed in a large cross-section tow tank, designed to achieve sufficiently high Reynolds numbers for the results to be Reynolds number independent with respect to turbine performance and wake statistics, such that they can be reliably extrapolated to full scale and used for model validation. Several turbines of varying solidity were employed, including the UNH Reference Vertical Axis Turbine (RVAT) and a 1:6 scale model of the DOE-Sandia Reference Model 2 (RM2) turbine. To improve parameterization in array simulations, an actuator line model (ALM) was developed to provide a computationally feasible method for simulating full turbine arrays inside Navier-Stokes models. Results are presented for the simulation of performance and wake dynamics of cross-flow turbines and compared with experiments and body-fitted mesh, blade-resolving CFD. Supported by NSF-CBET Grant 1150797, Sandia National Laboratories.

  4. The Large Scale Bias of Dark Matter Halos: Numerical Calibration and Model Tests

    CERN Document Server

    Tinker, Jeremy L; Kravtsov, Andrey V; Klypin, Anatoly; Warren, Michael S; Yepes, Gustavo; Gottlober, Stefan

    2010-01-01

    We measure the clustering of dark matter halos in a large set of collisionless cosmological simulations of the flat LCDM cosmology. Halos are identified using the spherical overdensity algorithm, which finds the mass around isolated peaks in the density field such that the mean density is Delta times the background. We calibrate fitting functions for the large scale bias that are adaptable to any value of Delta we examine. We find a ~6% scatter about our best fit bias relation. Our fitting functions couple to the halo mass functions of Tinker et. al. (2008) such that bias of all dark matter is normalized to unity. We demonstrate that the bias of massive, rare halos is higher than that predicted in the modified ellipsoidal collapse model of Sheth, Mo, & Tormen (2001), and approaches the predictions of the spherical collapse model for the rarest halos. Halo bias results based on friends-of-friends halos identified with linking length 0.2 are systematically lower than for halos with the canonical Delta=200 o...

  5. Large fluctuations of the macroscopic current in diffusive systems: A numerical test of the additivity principle

    Science.gov (United States)

    Hurtado, Pablo I.; Garrido, Pedro L.

    2010-04-01

    Most systems, when pushed out of equilibrium, respond by building up currents of locally conserved observables. Understanding how microscopic dynamics determines the averages and fluctuations of these currents is one of the main open problems in nonequilibrium statistical physics. The additivity principle is a theoretical proposal that allows to compute the current distribution in many one-dimensional nonequilibrium systems. Using simulations, we validate this conjecture in a simple and general model of energy transport, both in the presence of a temperature gradient and in canonical equilibrium. In particular, we show that the current distribution displays a Gaussian regime for small current fluctuations, as prescribed by the central limit theorem, and non-Gaussian (exponential) tails for large current deviations, obeying in all cases the Gallavotti-Cohen fluctuation theorem. In order to facilitate a given current fluctuation, the system adopts a well-defined temperature profile different from that of the steady state and in accordance with the additivity hypothesis predictions. System statistics during a large current fluctuation is independent of the sign of the current, which implies that the optimal profile (as well as higher-order profiles and spatial correlations) are invariant upon current inversion. We also demonstrate that finite-time joint fluctuations of the current and the profile are well described by the additivity functional. These results suggest the additivity hypothesis as a general and powerful tool to compute current distributions in many nonequilibrium systems.

  6. Numerical simulations of the aerodynamic behavior of large horizontal-axis wind turbines

    Energy Technology Data Exchange (ETDEWEB)

    Gebhardt, C.G. [Departamento de Estructuras, Facultad de Ciencias Exactas Fisicas y Naturales, Universidad Nacional de Cordoba, Av. Velez Sarsfield N 1611, CP 5000, Cordoba (Argentina); Consejo Nacional de Investigaciones Cientificas y Tecnicas, Avenida Rivadavia 1917, CP C1033AAJ, Ciudad de Buenos Aires (Argentina); Preidikman, S. [Departamento de Estructuras, Facultad de Ciencias Exactas Fisicas y Naturales, Universidad Nacional de Cordoba, Av. Velez Sarsfield N 1611, CP 5000, Cordoba (Argentina); Departamento de Mecanica, Facultad de Ingenieria, Universidad Nacional de Rio, Cuarto, Ruta Nacional 36, Km 601, CP 5800, Rio Cuarto (Argentina); Consejo Nacional de Investigaciones Cientificas y Tecnicas, Avenida Rivadavia 1917, CP C1033AAJ, Ciudad de Buenos Aires (Argentina); Massa, J.C. [Departamento de Estructuras, Facultad de Ciencias Exactas Fisicas y Naturales, Universidad Nacional de Cordoba, Av. Velez Sarsfield N 1611, CP 5000, Cordoba (Argentina); Departamento de Mecanica, Facultad de Ingenieria, Universidad Nacional de Rio, Cuarto, Ruta Nacional 36, Km 601, CP 5800, Rio Cuarto (Argentina)

    2010-06-15

    In the present work, the non-linear and unsteady aerodynamic behavior of large horizontal-axis wind turbines is analyzed. The flowfield around the wind turbine is simulated with the general non-linear unsteady vortex-lattice method, widely used in aerodynamics. By using this technique, it is possible to compute the aerodynamic loads and their evolution in the time domain. The results presented in this paper help to understand how the existence of the land-surface boundary layer and the presence of the turbine support tower, affect its aerodynamic efficiency. The capability to capture these phenomena is a novel aspect of the computational tool developed in the present effort. (author)

  7. Numerical modeling of in-vessel melt water interaction in large scale PWR`s

    Energy Technology Data Exchange (ETDEWEB)

    Kolev, N.I. [Siemens AG, KWU NA-M, Erlangen (Germany)

    1998-01-01

    This paper presents a comparison between IVA4 simulations and FARO L14, L20 experiments. Both experiments were performed with the same geometry but under different initial pressures, 51 and 20 bar respectively. A pretest prediction for test L21 which is intended to be performed under an initial pressure of 5 bar is also presented. The strong effect of the volume expansion of the evaporating water at low pressure is demonstrated. An in-vessel simulation for a 1500 MW el. PWR is presented. The insight gained from this study is: that at no time are conditions for the feared large scale melt-water intermixing at low pressure in force, with this due to the limiting effect of the expansion process which accelerates the melt and the water into all available flow paths. (author)

  8. Enhanced terahertz transmission through a periodic array of tapered rectangular apertures

    CERN Document Server

    Devi, Koijam Monika; Kumar, Gagan

    2016-01-01

    We numerically analyse extraordinary terahertz transmission properties of an array of rectangular shaped apertures perforated periodically on a thin metal film. The apertures are tapered at different angles to achieve higher field concentration at the tapered end. The periodic sub-wavelength scale apertures ensure plasmonic behaviour giving rise to the enhanced transmission of a specific frequency mode decided by the periodicity. We compare results of transmission with the rectangular shaped apertures of same parameters and observe a significant increase in the transmission for the tapered case. We have compared results of our numerical simulations with theory and have found them consistent.

  9. Synthetic Aperture Ultrasound Imaging

    DEFF Research Database (Denmark)

    Jensen, Jørgen Arendt; Nikolov, Svetoslav; Gammelmark, Kim Løkke

    2006-01-01

    The paper describes the use of synthetic aperture (SA) imaging in medical ultrasound. SA imaging is a radical break with today's commercial systems, where the image is acquired sequentially one image line at a time. This puts a strict limit on the frame rate and the possibility of acquiring...... a sufficient amount of data for high precision flow estimation. These constrictions can be lifted by employing SA imaging. Here data is acquired simultaneously from all directions over a number of emissions, and the full image can be reconstructed from this data. The talk will demonstrate the many benefits...... of SA imaging. Due to the complete data set, it is possible to have both dynamic transmit and receive focusing to improve contrast and resolution. It is also possible to improve penetration depth by employing codes during ultrasound transmission. Data sets for vector flow imaging can be acquired using...

  10. 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,...

  11. 高压线电磁场强度对大孔径闪烁仪观测的影响%Effect of high voltage wire electromagnetic field intensity on Large Aperture Scintillometer (LAS) observation

    Institute of Scientific and Technical Information of China (English)

    杨凡; 张玉翠; 齐永青; 胡文清; Bridget R.Scanlon; 沈彦俊

    2011-01-01

    大孔径闪烁仪(Large Aperture Scintillometer,LAS)是测量水平距离上250~4 500 m地表能量平衡和水热通量的仪器.在其红外波传输的过程中会受到环境因素以及下垫面属性的影响.鉴于外界条件的复杂性,还会受到树木的阻挡以及高压线电磁场辐射等因素的影响.本文通过分析2009年8月~2010年3月在中国科学院栾城农业生态系统试验站开展LAS观测过程中的影响因素,研究了高压输电线电磁场对LAS观测的影响.结果表明,当LAS红外光路径距高压线过近时对测定的感热通量HLAS影响较大,导致计算结果与实际不符.通过计算提出了避免高压输电线电磁场干扰LAS观测信号的安全安装距离应是保证高压输电线电磁场强度小于4.05 μT的距离.结果可为开展同类观测试验提供参考.%Large Aperture Scintillometer was widely used to measure horizontal distance (250~4 500 m) surface energy balance and fluxes of water and heat. In transmitting infrared waves, several environmental factors and land surface properties affect LAS signal.Further given the complexity of external conditions, high trees and electromagnetic fields of high voltage wires in the path of LAS light also blur receiver signal detection. Through experimentation at Luancheng Agro-Ecosystem Experimental Station of Chinese Academy of Sciences in August 2009 through March 2010, this paper, analyzed the effects of electromagnetic fields of high voltage wires on LAS observation. The result indicated when the space between the path of LAS infrared waves and high voltage wire was too narrow, measured sensitive heat flux (HLAs) was greatly affected, causing the difference between the calculations and the practice.Following detailed analysis of the experimental data, the paper suggested safe distance, in which electromagnetic field intensity should be less than 4.05 μT, from high voltage wires during LAS installation in densely populated areas. The

  12. Observation Study in Desert Homogeneous of Arid Region in Northwestern of China Using Large Aperture Scintillometers%LAS在西北干旱区荒漠均匀下垫面的观测研究

    Institute of Scientific and Technical Information of China (English)

    陈继伟; 左洪超; 王介民; 王树金; 陈伯龙; 庄少伟

    2013-01-01

    Using the experimental data that came from the instrument parallel comparison in Gulang Heterogeneous Underlying Surface Layer Experiment, the consistency of friction velocity and sensible heat flux observed by four sets of EC (Eddy Covariance System) which equidistantly lay on light path line of LAS (Large Aperture Scintillometer) was analyzed at first, and then the difference among the calculated regional sensible heat fluxs observed by LAS based on universal stability functions established by four different kinds of underlying surface employing the mean value of observation friction velocity from four sets of EC was analyzed, finally a further comparison between the two observations of LAS and EC was made. The results show that, friction velocity and sensible heat flux observed by four sets of EC have a good trend of consistency; the difference of friction velocity is less than 10% , and the difference of sensible heat flux is about 10%. The regional sensible heat flux of LAS calculated by four kinds of universal stability functions in the daytime and nighttime have identical changing trend with the average observed by EC, the calculated value is usually bigger than normal, the calculated value of TAG universal stability function is closer to the average value observed by EC. Except for the main reason that universal stability functions from experiments of different underlying surface have some differences, the sensible heat flux observed by Kipp&Zonen LAS is systemic higher can not be ignored too.%利用“古浪非均匀近地层观测试验”的仪器平行对比观测部分试验数据,首先分析荒漠均匀下垫面大孔径闪烁仪(Large Aperture Scintillometer,LAS)光径线上等间距架设的4台涡动相关仪(Eddy Covariance System,EC)观测的摩擦速度和感热通量的一致性.然后,基于4种不同下垫面建立稳定度普适函数分析,利用4台EC观测摩擦速度平均值,计算了LAS观测区域的感热通量,进而比较了LAS

  13. Numerical Model of Turbulence, Sediment Transport, and Sediment Cover in a Large Canyon-Bound River

    Science.gov (United States)

    Alvarez, L. V.; Schmeeckle, M. W.

    2013-12-01

    The Colorado River in Grand Canyon is confined by bedrock and coarse-grained sediments. Finer grain sizes are supply limited, and sandbars primarily occur in lateral separation eddies downstream of coarse-grained tributary debris fans. These sandbars are important resources for native fish, recreational boaters, and as a source of aeolian transport preventing the erosion of archaeological resources by gully extension. Relatively accurate prediction of deposition and, especially, erosion of these sandbar beaches has proven difficult using two- and three-dimensional, time-averaged morphodynamic models. We present a parallelized, three-dimensional, turbulence-resolving model using the Detached-Eddy Simulation (DES) technique. DES is a hybrid large eddy simulation (LES) and Reynolds-averaged Navier Stokes (RANS). RANS is applied to the near-bed grid cells, where grid resolution is not sufficient to fully resolve wall turbulence. LES is applied further from the bed and banks. We utilize the Spalart-Allmaras one equation turbulence closure with a rough wall extension. The model resolves large-scale turbulence using DES and simultaneously integrates the suspended sediment advection-diffusion equation. The Smith and McLean suspended sediment boundary condition is used to calculate the upward and downward settling of sediment fluxes in the grid cells attached to the bed. The model calculates the entrainment of five grain sizes at every time step using a mixing layer model. Where the mixing layer depth becomes zero, the net entrainment is zero or negative. As such, the model is able to predict the exposure and burial of bedrock and coarse-grained surfaces by fine-grained sediments. A separate program was written to automatically construct the computational domain between the water surface and a triangulated surface of a digital elevation model of the given river reach. Model results compare favorably with ADCP measurements of flow taken on the Colorado River in Grand Canyon

  14. Numerical Simulation of Condensation of Sulfuric Acid and Water in a Large Two-stroke Marine Diesel Engine

    DEFF Research Database (Denmark)

    Walther, Jens Honore; Karvounis, Nikolas; Pang, Kar Mun

    2016-01-01

    We present results from computational fluid dynamics simulations of the condensation of sulfuric acid (H2SO4) and water (H2O) in a large two-stroke marine diesel engine. The model uses a reduced n-heptane skeletal chemical mechanism coupled with a sulfur subsetto simulate the combustion process...... and the formation of SOx and H2SO4. Condensation is modeled using a fluid film model coupled with the Eulerian in-cylindergas phase. The fluid film condensation model is validated against both experimental and numerical results. The engine simulations reveal that the fluid film has a significant effect...

  15. Analysis of Seismic Response to the Large Aperture All-movable Telescope Structure%超大口径全可动望远镜结构地震响应分析

    Institute of Scientific and Technical Information of China (English)

    刘岩; 钱宏亮; 范峰

    2016-01-01

    为掌握超大口径全可动射电望远镜结构抗震性能特性,以待建的110 m全可动射电望远镜为研究平台,以三水准原则为控制目标,运用时程分析法对望远镜结构在小震和大震作用下的受力性能进行分析,给出了结构在多遇地震作用下、多遇地震与静力组合工况下以及罕遇地震作用下的关键力学响应指标,评估了结构在地震作用下的安全性能。%In order to understand the aseismic ability of large aperture all-movable radio telescope structures ,the pro-posed 110 m fully-steerable radio telescope to was used as an example .Based on the three levels in earthquake fortifica-tion as control condition ,the mechanical properties of the telescope structure was analyzed under situations of frequent and rare earthquakes by using time-history method .The mechanical responsive targets which are crucial to the structure under activities of frequent earthquakes ,frequent earthquakes combined with static unitized load mode and rare earth-quakes were calculated .The safety properties of the telescope structure were also evaluated under different kinds of earth-quakes .

  16. Optimization Design of Long Focal Distance and Large Aperture Infrared Optical System%长焦距大口径红外光学系统的优化设计

    Institute of Scientific and Technical Information of China (English)

    付学志; 王日胜; 胡兵; 李岩

    2015-01-01

    针对某长焦距大口径光电设备的特殊要求,基于卡塞格林光学折反系统达到了较好的红外成像质量和紧凑的结构尺寸。首先通过计算对红外光学系统进行了初步焦距分配;然后对卡塞格林反射组件和红外组件进行了分段优化设计,特别是为克服温度变化对焦距和像质的影响,在后组设计三片透镜作为调焦组,保证了成像质量;最后,为了消除杂光的影响,分别对轴上、轴外光线进行追迹并设计了主、次镜遮光罩。设计结果分析表明主要指标均满足设计要求。%According to the special requirements of a large aperture and long focal length optical equipment, better quality of infrared imaging and compact structure was achieved based on Cassegrain optical catadioptric system. Firstly, focal length assignment was calculated. Then, Cassegrain reflect component and infrared component was optimized respectively. Specially, in order to overcome the impact of temperature’s change on focal length and image quality, designed three lenses as focus group. Lastly, the main and subordinate lens’s hoods were designed to eliminate the influence of stray light. The design results show that the main indexes meet the design requirements.

  17. Current status and development tendency of image stabilization system of large aperture space telescope%空间大口径望远镜稳像系统发展现状及趋势

    Institute of Scientific and Technical Information of China (English)

    曹小涛; 孙天宇; 赵运隆; 王栋; 郭权锋

    2014-01-01

    介绍了目前国际上已发射及正在论证的大型空间望远镜的稳像控制系统,主要包括自由飞行模式的HUBBLE、JWST、ATLAST-8m和ATLAST-9.2m,载体搭载模式的SOFIA和OPTIIX。详细论述了这些空间望远镜稳像系统的组成、工作原理、主要元件、性能指标和控制算法,并对基于磁悬浮技术的无扰动载荷设计概念和机械臂直接驱动空间相机的设计思想进行了介绍。分析表明,基于机械臂和磁悬浮技术的精密稳像及主动振动抑制系统是未来的发展趋势。%In this paper , the image stabilization system of large aperture space telescope on orbit or being de-signed is introduced, including HUBBLE, JWST, ATLAST-8m and ATLAST-16m in free flying mode, and SOFIA, OPTIIX in space-borne mode .The composition , working principle , major component , performance requirements and control algorithm of image stabilization system are discussed in detail .Then, the disturb-ance-free payload design concept based on the magnetically suspend technology and design idea of space tele -scope directly driven by the manipulator are introduced .Analysis results indicate that the precise image stabi-lization and active vibration isolation system based on the magnetically suspend and manipulator technology is the future development tendency .

  18. Typhoon Winnie (1997) with a Very Large Eye: High Resolution Numerical Simulation

    Institute of Scientific and Technical Information of China (English)

    ZHANG Qinghong; GUO Chunrui

    2007-01-01

    Typhoon Winnie (1997) was one of the hurricanes that had extremely large eyewall ever recorded with a diameter of eyewall reaching 370 km. Using the Penn State University/National Center for Atmospheric Research mesoscale model MM5 with 3-kmn grid horizontal spacing on the finest nested mesh, Winnie was successfully simulated in terms of track, intensity, eye and concentric eyewalls. The dynamic and thermal structures of concentric eyewalls were studied based on the model output. It was found that the concentric eyewalls and their surrounding wind fields were asymmetric in observation as well as in simulation. Winnie's outer eyewall was associated with a maximum wind ring, a warm moist ring, and a high vorticity ring. The inner eyewall was associated with a secondary maximum wind ring and a warm moist ring. Upward motion dominated the whole layer of inner eyewall and the area above 2-km altitude of the outer eyewall. Downward motion was found inside the eye and the moat. Radial inflow happened in the boundary layer of the outer eyewall and the moat, but radial outflow dominated the middle and upper levels of the outer eyewall.

  19. Penumbral imaging and numerical evaluation of large area source neutron imaging system

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The fusion neutron penumbral imaging system Monte Carlo model was established. The transfer functions of the two discrete units in the neutron source were obtained in two situations:Imaging in geometrical near-optical and real situation. The spatial resolutions of the imaging system in two situations were evaluated and compared. The penumbral images of four units in the source were obtained by means of 2-dimensional (2D) convolution and Monte Carlo simulation. The penumbral images were reconstructed with the same method of filter. The same results were confirmed. The encoding essence of penumbral imaging was revealed. With MCNP(Monte Carlo N-particle) simulation,the neutron penumbral images of the large area source (200 μm×200 μm) on scintillation fiber array were obtained. The improved Wiener filter method was used to reconstruct the penumbral image and the source image was obtained. The results agree with the preset neutron source image. The feasibility of the neutron imaging system was verified.

  20. Penumbral imaging and numerical evaluation of large area source neutron imaging system

    Institute of Scientific and Technical Information of China (English)

    WU YueLei; HU HuaSi; ZHANG BoPing; LI LinBo; CHEN Da; SHAN Qing; ZHU Jie

    2009-01-01

    The fusion neutron penumbral imaging system Monte Carlo model was established. The transfer func-tions of the two discrete units in the neutron source were obtained in two situations: Imaging in geo-metrical near-optical and real situation. The spatial resolutions of the imaging system in two situations were evaluated and compared. The penumbral images of four units in the source were obtained by means of 2-dimensional (2D) convolution and Monte Carlo simulation. The penumbral images were reconstructed with the same method of filter. The same results were confirmed. The encoding essence of penumbral imaging was revealed. With MCNP(Monte Carlo N-particle) simulation, the neutron pen-umbral images of the large area source (200 μm×200 μm) on scintillation fiber array were obtained. The improved Wiener filter method was used to reconstruct the penumbral image and the source image was obtained. The results agree with the preset neutron source image. The feasibility of the neutron imaging system was verified.

  1. Holographically Correcting Synthetic Aperture Aberrations.

    Science.gov (United States)

    1987-12-01

    Malacara (20:105-148). The synthetic aperture was aligned in accordance with the synthetic-aperture alignment technique of Gill (8:61-64). The...1987. 20. Malacara , Daniel, ed. Optical Shop Testing. New York: John Wiley & Sons, 1978. 21. Marciniak, Capt Michael. Tutorial Presentation of mV

  2. Numerical simulation and experimental validation of a large-area capacitive strain sensor for fatigue crack monitoring

    Science.gov (United States)

    Kong, Xiangxiong; Li, Jian; Bennett, Caroline; Collins, William; Laflamme, Simon

    2016-12-01

    A large-area electronics in the form of a soft elastomeric capacitor (SEC) has shown great promise as a strain sensor for fatigue crack monitoring in steel structures. The SEC sensors are inexpensive, easy to fabricate, highly stretchable, and mechanically robust. It is a highly scalable technology, capable of monitoring deformations on mesoscale systems. Preliminary experiments verified the SEC sensor’s capability in detecting, localizing, and monitoring crack growth in a compact specimen. Here, a numerical simulation method is proposed to simulate accurately the sensor’s performance under fatigue cracks. Such a method would provide a direct link between the SEC’s signal and fatigue crack geometry, extending the SEC’s capability to dense network applications on mesoscale structural components. The proposed numerical procedure consists of two parts: (1) a finite element (FE) analysis for the target structure to simulate crack growth based on an element deletion method; (2) an algorithm to compute the sensor’s capacitance response using the FE analysis results. The proposed simulation method is validated based on test data from a compact specimen. Results from the numerical simulation show good agreement with the SEC’s response from the laboratory tests as a function of the crack size. Using these findings, a parametric study is performed to investigate how the SEC would perform under different geometries. Results from the parametric study can be used to optimize the design of a dense sensor network of SECs for fatigue crack detection and localization.

  3. Numerical study of large-N phase transition of smeared Wilson loops in 4D pure YM theory

    CERN Document Server

    Lohmayer, Robert

    2011-01-01

    In Euclidean four-dimensional SU(N) pure gauge theory, eigenvalue distributions of Wilson loop parallel transport matrices around closed spacetime curves show non-analytic behavior (a 'large-N phase transition') at a critical size of the curve. We focus mainly on an observable composed of traces of the Wilson loop operator in all totally antisymmetric representations, which is regularized with the help of smearing. By studying sequences of square Wilson loops on a hypercubic lattice with standard Wilson action, it is shown that this observable has a nontrivial continuum limit as a function of the physical size of the loop. We furthermore present (preliminary) numerical results confirming that, for large N, the N dependence in the critical regime is governed by the universal exponents 1/2 and 3/4 as expected (Burgers universality).

  4. Effects of process parameters on numerical control bending process for large diameter thin-walled aluminum alloy tubes

    Institute of Scientific and Technical Information of China (English)

    LI Cheng; YANG He; ZHAN Mei; XU Xu-dong; LI Guang-jun

    2009-01-01

    Numerical control(NC) bending experiments with different process parameters were carried out for 5052O aluminum alloy tubes with outer diameter of 70 mm, wall thickness of 1.5 mm, and centerline bending radius of 105 mm. And the effects of process parameters on tube wall thinning and cross section distortion were investigated. Meanwhile, acceptable bending of the 5052O aluminum tubes was accomplished based on the above experiments. The results show that the effects of process parameters on bending process for large diameter thin-walled aluminum alloy tubes are similar to those for small diameter thin-walled tubes, but the forming quality of the large diameter thin-walled aluminum alloy tubes is much more sensitive to the process parameters and thus it is more difficult to form.

  5. Sparse synthetic aperture radar imaging with optimized azimuthal aperture

    Institute of Scientific and Technical Information of China (English)

    ZENG Cao; WANG MinHang; LIAO GuiSheng; ZHU ShengQi

    2012-01-01

    To counter the problem of acquiring and processing huge amounts of data for synthetic aperture radar (SAR) using traditional sampling techniques,a method for sparse SAR imaging with an optimized azimuthal aperture is presented.The equivalence of an azimuthal match filter and synthetic array beamforming is shown so that optimization of the azimuthal sparse aperture can be converted to optimization of synthetic array beamforming.The azimuthal sparse aperture,which is composed of a middle aperture and symmetrical bilateral apertures,can be obtained by optimization algorithms (density weighting and simulated annealing algorithms,respectively).Furthermore,sparse imaging of spectrum analysis SAR based on the optimized sparse aperture is achieved by padding zeros at null samplings and using a non-uniform Taylor window. Compared with traditional sampling,this method has the advantages of reducing the amount of sampling and alleviating the computational burden with acceptable image quality.Unlike periodic sparse sampling,the proposed method exhibits no image ghosts.The results obtained from airborne measurements demonstrate the effectiveness and superiority of the proposed method.

  6. Numerical modeling of the deformations associated with large subduction earthquakes through the seismic cycle

    Science.gov (United States)

    Fleitout, L.; Trubienko, O.; Garaud, J.; Vigny, C.; Cailletaud, G.; Simons, W. J.; Satirapod, C.; Shestakov, N.

    2012-12-01

    A 3D finite element code (Zebulon-Zset) is used to model deformations through the seismic cycle in the areas surrounding the last three large subduction earthquakes: Sumatra, Japan and Chile. The mesh featuring a broad spherical shell portion with a viscoelastic asthenosphere is refined close to the subduction zones. The model is constrained by 6 years of postseismic data in Sumatra area and over a year of data for Japan and Chile plus preseismic data in the three areas. The coseismic displacements on the subduction plane are inverted from the coseismic displacements using the finite element program and provide the initial stresses. The predicted horizontal postseismic displacements depend upon the thicknesses of the elastic plate and of the low viscosity asthenosphere. Non-dimensionalized by the coseismic displacements, they present an almost uniform value between 500km and 1500km from the trench for elastic plates 80km thick. The time evolution of the velocities is function of the creep law (Maxwell, Burger or power-law creep). Moreover, the forward models predict a sizable far-field subsidence, also with a spatial distribution which varies with the geometry of the asthenosphere and lithosphere. Slip on the subduction interface does not induce such a subsidence. The observed horizontal velocities, divided by the coseismic displacement, present a similar pattern as function of time and distance from trench for the three areas, indicative of similar lithospheric and asthenospheric thicknesses and asthenospheric viscosity. This pattern cannot be fitted with power-law creep in the asthenosphere but indicates a lithosphere 60 to 90km thick and an asthenosphere of thickness of the order of 100km with a burger rheology represented by a Kelvin-Voigt element with a viscosity of 3.1018Pas and μKelvin=μelastic/3. A second Kelvin-Voigt element with very limited amplitude may explain some characteristics of the short time-scale signal. The postseismic subsidence is

  7. Focusing properties of Gaussian Schell-model beams by an astigmatic aperture lens

    Institute of Scientific and Technical Information of China (English)

    Pan Liu-Zhan; Ding Chao-Liang

    2007-01-01

    This paper studies the focusing properties of Gaussian Schell-model (GSM) beams by an astigmatic aperture lens.It is shown that the axial irradiance distribution, the maximum axial irradiance and its position of focused GSM beams by an astigmatic aperture lens depend upon the astigmatism of the lens, the coherence of partially coherent light, the truncation parameter of the aperture and Fresnel number. The numerical calculation results are given to illustrate how these parameters affect the focusing property.

  8. Cavity Quantum Electrodynamics in a wide aperture spherical resonator. Part II Vacuum-field atom trapping

    CERN Document Server

    Daul, J M; Daul, Jean-Marc; Grangier, Philippe

    2003-01-01

    We consider the situation where a two-level atom is placed in the vicinity of the center of a spherical cavity with a large numerical aperture. The vacuum field at the center of the cavity is actually equivalent to the one obtained in a microcavity, and both the dissipative and the reactive parts of the atom's spontaneous emission are significantly modified. Using an explicit calculation of the spatial dependence of the radiative relaxation rate and of the associated level shift, we show that for a weakly excitating light field, the atom can be attracted to the center of the cavity by vacuum-induced light shifts.

  9. Finite-Element Simulations of Light Propagation through Circular Subwavelength Apertures

    CERN Document Server

    Burger, S; Zschiedrich, L; Schmidt, F; 10.1117/12.822828

    2009-01-01

    Light transmission through circular subwavelength apertures in metallic films with surrounding nanostructures is investigated numerically. Numerical results are obtained with a frequency-domain finite-element method. Convergence of the obtained observables to very low levels of numerical error is demonstrated. Very good agreement to experimental results from the literature is reached, and the utility of the method is demonstrated in the investigation of the influence of geometrical parameters on enhanced transmission through the apertures.

  10. Model reduction for the dynamics and control of large structural systems via neutral network processing direct numerical optimization

    Science.gov (United States)

    Becus, Georges A.; Chan, Alistair K.

    1993-01-01

    Three neural network processing approaches in a direct numerical optimization model reduction scheme are proposed and investigated. Large structural systems, such as large space structures, offer new challenges to both structural dynamicists and control engineers. One such challenge is that of dimensionality. Indeed these distributed parameter systems can be modeled either by infinite dimensional mathematical models (typically partial differential equations) or by high dimensional discrete models (typically finite element models) often exhibiting thousands of vibrational modes usually closely spaced and with little, if any, damping. Clearly, some form of model reduction is in order, especially for the control engineer who can actively control but a few of the modes using system identification based on a limited number of sensors. Inasmuch as the amount of 'control spillover' (in which the control inputs excite the neglected dynamics) and/or 'observation spillover' (where neglected dynamics affect system identification) is to a large extent determined by the choice of particular reduced model (RM), the way in which this model reduction is carried out is often critical.

  11. Conceptual Numerical Modeling of Large-Scale Footwall Behavior at the Kiirunavaara Mine, and Implications for Deformation Monitoring

    Science.gov (United States)

    Svartsjaern, M.; Saiang, D.; Nordlund, E.; Eitzenberger, A.

    2016-03-01

    Over the last 30 years, the Kiirunavaara mine has experienced a slow but progressive fracturing and movement in the footwall rock mass, which is directly related to the sublevel caving (SLC) method utilized by Luossavaara-Kiirunavaara Aktiebolag (LKAB). As part of an ongoing work, this paper focuses on describing and explaining a likely evolution path of large-scale fracturing in the Kiirunavaara footwall. The trace of this fracturing was based on a series of damage mapping campaigns carried out over the last 2 years, accompanied by numerical modeling. Data collected from the damage mapping between mine levels 320 and 907 m was used to create a 3D surface representing a conceptual boundary for the extent of the damaged volume. The extent boundary surface was used as the basis for calibrating conceptual numerical models created in UDEC. The mapping data, in combination with the numerical models, indicated a plausible evolution path of the footwall fracturing that was subsequently described. Between levels 320 and 740 m, the extent of fracturing into the footwall appears to be controlled by natural pre-existing discontinuities, while below 740 m, there are indications of a curved shear or step-path failure. The step-path is hypothesized to be activated by rock mass heave into the SLC zone above the current extraction level. Above the 320 m level, the fracturing seems to intersect a subvertical structure that daylights in the old open pit slope. Identification of these probable damage mechanisms was an important step in order to determine the requirements for a monitoring system for tracking footwall damage. This paper describes the background work for the design of the system currently being installed.

  12. Fracture-aperture alteration induced by calcite precipitation

    Science.gov (United States)

    Jones, T.; Detwiler, R. L.

    2013-12-01

    Mineral precipitation significantly alters the transport properties of fractured rock. Chemical solubility gradients that favor precipitation induce mineral growth, which decreases the local aperture and alters preferential flow paths. Understanding the resulting development of spatial heterogeneities is necessary to predict the evolution of transport properties in the subsurface. We present experimental results that quantify the relationship between mineral precipitation and aperture alteration in a transparent analog fracture, 7.62cm x 7.62cm, with a uniform aperture of ~200 μm. Prior to flow experiments, a pump circulated a super-saturated calcite solution over the bottom glass, coating the glass surface with calcite. This method of seeding resulted in clusters of calcite crystals with large reactive surface area and provided micro-scale variability in the aperture field. A continuous flow syringe pump injected a reactive fluid into the fracture at 0.5 ml/min. The fluid was a mixture of sodium bicarbonate (NaHCO3, 0.02M) and calcium chloride (CaCl2 0.0004M) with a saturation index, Ω, of 8.51 with respect to calcite. A strobed LED panel backlit the fracture and a high-resolution CCD camera monitored changes in transmitted light intensity. Light transmission techniques provided a quantitative measurement of fracture aperture over the flow field. Results from these preliminary experiments showed growth near the inlet of the fracture, with decreasing precipitation rates in the flow direction. Over a period of two weeks, the fracture aperture decreased by 17% within the first 4mm of the inlet. Newly precipitated calcite bridged individual crystal clusters and smoothed the reacting surface. This observation is an interesting contradiction to the expectation of surface roughening induced by mineral growth. Additionally, the aperture decreased uniformly across the width of the fracture due to the initial aperture distribution. Future experiments of precipitation

  13. Numerical Analyses of Bearing Capacity of Deep-Embedded Large-Diameter Cylindrical Structure on Soft Ground Against Lateral Loads

    Institute of Scientific and Technical Information of China (English)

    LUAN Mao-tian; FAN Qing-lai

    2006-01-01

    Presented in this paper is a three-dimensional plastic limit analysis method of bearing capacity of the deeply-embedded large-diameter cylindrical structure in the cross-anisotropic soft ground. The most likely failure mechanism is assumed to be of a composite rupture surface which is composed of an individual wedge in the passive zone or two wedges in both active and passive zones near the mudline, depending on the separation or bonding state at the interface between the cylindrical structure and neighboring soils in the active wedge, and a truncated spherical slip surface at the base of the cylinder when the structure tends to overturn around a point located on the symmetry axis of the structure. The cylindrical structure and soil interaction system under consideration is also numerically analyzed by the finite element method by virtue of the general-purpose FEM software ABAQUS, in which the soil is assumed to obey tie Hill's criterion of yield. Both the failure mechanism assumed and the plastic limit analysis predictions are validated by numerical computations based on FEM. For the K0-consolidated ground of clays typically with anisotropic undrained strength property, it is indicated through a parametric study that limit analysis without consideration of anisotropy of soil overestimates the lateral ultimate bearing capacity of a deeply-embedded cylindrical structure in soft ground in a certain condition.

  14. Numerical computation of arbitrary order transfer maps and reconstructive correction of aberrations in the large acceptance spectrometer MAGNEX

    CERN Document Server

    Shchepunov, V A; Cappuzzello, F; Foti, A; Lazzaro, A; Melita, A L; Nociforo, C; Winfield, J S

    2003-01-01

    The large angular (approx 50 msr) and momentum (approx 20%) acceptance spectrometer MAGNEX is under construction at the South National Laboratories INFN. In the spectrometer, positions of ions in two planes near the focal plane and their vertical positions near the target are measured. The energy resolution of about 1000 is achieved due to the use of the reconstruction of trajectories and reconstructive correction of aberrations. Main features of the spectrometer ion optics are considered. A numerical method of calculation of an arbitrary order transfer map is proposed. In this method, a transfer map is calculated using, as input, initial and final coordinates of a set of rays in an ion-optical system. The rays start at the nods of a regular multi-dimensional mesh in the particle phase space. Rays of the set are chosen automatically according to the order and dimension of the map to be calculated. Final coordinates of the rays are calculated with a regular numerical integration. The proposed is, in fact, a ge...

  15. Airy-like pulses in models of large molecular chains, and conservative numerical methods for quasi-linear Hamiltonian systems

    CERN Document Server

    LeMesurier, Brenton

    2013-01-01

    The phenomenon of coherent energetic pulse propagation in macromolecular chains such as $\\alpha$-helix protein is studied using the Davydov-Scott model, with both numerical studies using a new unconditionally stable fourth order accurate energy-momentum conserving time discretization, and with analysis based on ideas of center manifold theory. It is shown that for physically natural impulsive initial data, the coherent traveling pulses seen have a form related to the Airy function, but with rapid variation of phase along the chain. This can be explained in terms of a new continuum limit approximation by the third derivative nonlinear Schr\\"odinger equation, which differs from the previous continuum limit approximations related to the standard NLS equation. A theorem is given describing the construction of such conservative time discretizations for a large class of Hamiltonian systems.

  16. On numerical solutions to the QCD ’t Hooft equation in the limit of large quark mass

    Energy Technology Data Exchange (ETDEWEB)

    Zubov, Roman; Prokhvatilov, Evgeni [Saint Petersburg State University, Saint Petersburg, Russia e-mail: roman.zubov@hep.phys.spbu.ru, evgeni.prokhvat@pobox.spbu.ru (Russian Federation)

    2016-01-22

    First we give a short informal introduction to the theory behind the ’t Hooft equation. Then we consider numerical solutions to this equation in the limit of large fermion masses. It turns out that the spectrum of eigenvalues coincides with that of the Airy differential equation. Moreover when we take the Fourier transform of eigenfunctions, they look like the corresponding Airy functions with appropriate symmetry. It is known that these functions correspond to solutions of a one dimensional Schrodinger equation for a particle in a triangular potential well. So we find the analogy between this problem and the ’t Hooft equation. We also present a simple intuition behind these results.

  17. A numerical approach for simulating fluid structure interaction of flexible thin shells undergoing arbitrarily large deformations in complex domains

    Energy Technology Data Exchange (ETDEWEB)

    Gilmanov, Anvar, E-mail: agilmano@umn.edu [Saint Anthony Falls Laboratory, University of Minnesota, Minneapolis, MN 55414 (United States); Le, Trung Bao, E-mail: lebao002@umn.edu [Saint Anthony Falls Laboratory, University of Minnesota, Minneapolis, MN 55414 (United States); Sotiropoulos, Fotis, E-mail: fotis@umn.edu [Saint Anthony Falls Laboratory, University of Minnesota, Minneapolis, MN 55414 (United States); Department of Civil, Environmental and Geo-Engineering, University of Minnesota, Minneapolis, MN 55414 (United States)

    2015-11-01

    We present a new numerical methodology for simulating fluid–structure interaction (FSI) problems involving thin flexible bodies in an incompressible fluid. The FSI algorithm uses the Dirichlet–Neumann partitioning technique. The curvilinear immersed boundary method (CURVIB) is coupled with a rotation-free finite element (FE) model for thin shells enabling the efficient simulation of FSI problems with arbitrarily large deformation. Turbulent flow problems are handled using large-eddy simulation with the dynamic Smagorinsky model in conjunction with a wall model to reconstruct boundary conditions near immersed boundaries. The CURVIB and FE solvers are coupled together on the flexible solid–fluid interfaces where the structural nodal positions, displacements, velocities and loads are calculated and exchanged between the two solvers. Loose and strong coupling FSI schemes are employed enhanced by the Aitken acceleration technique to ensure robust coupling and fast convergence especially for low mass ratio problems. The coupled CURVIB-FE-FSI method is validated by applying it to simulate two FSI problems involving thin flexible structures: 1) vortex-induced vibrations of a cantilever mounted in the wake of a square cylinder at different mass ratios and at low Reynolds number; and 2) the more challenging high Reynolds number problem involving the oscillation of an inverted elastic flag. For both cases the computed results are in excellent agreement with previous numerical simulations and/or experiential measurements. Grid convergence tests/studies are carried out for both the cantilever and inverted flag problems, which show that the CURVIB-FE-FSI method provides their convergence. Finally, the capability of the new methodology in simulations of complex cardiovascular flows is demonstrated by applying it to simulate the FSI of a tri-leaflet, prosthetic heart valve in an anatomic aorta and under physiologic pulsatile conditions.

  18. A numerical approach for simulating fluid structure interaction of flexible thin shells undergoing arbitrarily large deformations in complex domains

    Science.gov (United States)

    Gilmanov, Anvar; Le, Trung Bao; Sotiropoulos, Fotis

    2015-11-01

    We present a new numerical methodology for simulating fluid-structure interaction (FSI) problems involving thin flexible bodies in an incompressible fluid. The FSI algorithm uses the Dirichlet-Neumann partitioning technique. The curvilinear immersed boundary method (CURVIB) is coupled with a rotation-free finite element (FE) model for thin shells enabling the efficient simulation of FSI problems with arbitrarily large deformation. Turbulent flow problems are handled using large-eddy simulation with the dynamic Smagorinsky model in conjunction with a wall model to reconstruct boundary conditions near immersed boundaries. The CURVIB and FE solvers are coupled together on the flexible solid-fluid interfaces where the structural nodal positions, displacements, velocities and loads are calculated and exchanged between the two solvers. Loose and strong coupling FSI schemes are employed enhanced by the Aitken acceleration technique to ensure robust coupling and fast convergence especially for low mass ratio problems. The coupled CURVIB-FE-FSI method is validated by applying it to simulate two FSI problems involving thin flexible structures: 1) vortex-induced vibrations of a cantilever mounted in the wake of a square cylinder at different mass ratios and at low Reynolds number; and 2) the more challenging high Reynolds number problem involving the oscillation of an inverted elastic flag. For both cases the computed results are in excellent agreement with previous numerical simulations and/or experiential measurements. Grid convergence tests/studies are carried out for both the cantilever and inverted flag problems, which show that the CURVIB-FE-FSI method provides their convergence. Finally, the capability of the new methodology in simulations of complex cardiovascular flows is demonstrated by applying it to simulate the FSI of a tri-leaflet, prosthetic heart valve in an anatomic aorta and under physiologic pulsatile conditions.

  19. Comparison Study of Flow in A Compound Channel: Experimental and Numerical Method Using Large Eddy Simulation SDS-2DH Model

    Directory of Open Access Journals (Sweden)

    Eka Oktariyanto Nugroho

    2007-11-01

    Full Text Available Flow modeling in a compound channel is a complex matter. Indeed, due to the smaller velocities in the floodplains than in the main channel, shear layers develop at the interfaces between two stage channels, and the channel conveyance is affected by a momentum transfer corresponding to this shear layer. Since a compound channel is characterized by a deep main channel flanked by relatively shallow flood plains, the interaction between the faster fluid velocities in the main channel and the slower moving flow on the floodplains causes shear stresses at their interface which significantly distort flow and boundary shear stress patterns. The distortion implies that flow field in rivers is highly non homogeneous turbulent, which lateral transport of fluid momentum and suspended sediment are influenced by the characteristics of flow in rivers. The nature of mechanism of lateral transport needs to be understood for the design of river engineering schemes that rely upon realistic flow. Furthermore, the flows in river are also almost turbulent. This means that the fluid motion is highly random, unsteady, and three-dimensional. Due to these complexities, the flow can not be properly predicted by using approximate analytical solutions to the governing equations of motion. With the complexity of the problems, the solution of turbulent is simplified with mathematics equation. The momentum transfer due to turbulent exchanges is then studied experimentally and numerically. Experimental data is obtained by using Electro Magnetic Velocimetry and Wave Height Gauge. The Large Eddy Simulation Sub Depth Scale (LES SDS-2 Dimensional Horizontal (2DH Model is used to solve the turbulent problem. Successive Over Relaxation (SOR method is employed to solve the numerical computation based ob finite difference discretization. The model has been applied to the compound channel with smooth roughness. Some organized large eddies were found in the boundary between main channel

  20. Investigation of standing wave formation in a human skull for a clinical prototype of a large-aperture, transcranial MR-guided Focused Ultrasound (MRgFUS) phased array: An experimental and simulation study

    OpenAIRE

    Song, Junho; Pulkkinen, Aki; Huang, Yuexi; Hynynen, Kullervo

    2011-01-01

    Standing wave formation in an ex vivo human skull was investigated using a clinical prototype of a 30 cm diameter with 15 cm radius of curvature, low frequency (230 kHz), hemispherical transcranial Magnetic Resonance guided Focused Ultrasound (MRgFUS) phased-array. Experimental and simulation studies were conducted with changing aperture size and f-number configurations of the phased array, and qualitatively and quantitatively examined the acoustic pressure variation at the focus due to stand...

  1. 高能拍瓦激光系统中大口径离轴抛物面聚焦特性研究%Study on Focusing Characteristic of Large Aperture Off-Axis Paraboloidal Mirror in the High-Energy Petawatt Laser System

    Institute of Scientific and Technical Information of China (English)

    岳峰; 朱健强; 赵东峰

    2012-01-01

    为进行快点火实验,需对高能拍瓦激光聚焦系统中的核心元件即大口径离轴抛物面,进行深入量化研究,以便对其结构选型和精密调整提供准确的理论依据.利用基于严格的矢量衍射理论的数值计算方法,并结合像差分析得到了大孔径、大离轴量的抛物面镜(OAP)的物理光学成像特性.首先用理想平行光入射,得出OAP的三维平动公差与其焦深密切相关,OAP绕旋转刘称轴的转动可归结为平动问题,其公差与焦深也有简单关系;入射光轴失准时,像散占主导作用,并可由一结构因子来定性描述其对像斑的影响.其次当入射光有一定的发散角时,除引起最佳像面位置变化外,还会由于OAP不对称性而引起的彗差使得像斑的峰值光强大大降低,并论述了OAP的结构参数对此的影响.%To realize the fast ignition experiments,deep and quantitative research needs to be taken on the large aperture off-axis paraboloidal mirror (OAP) which is the core component in the high-energy petawatt laser focusing system,in order to provide an accurate basic theory for the OAP structure model selection and precision adjustments. This paper uses a numerical calculation method based on the rigorous vector diffraction theory combining with wavefront aberration analysis,by which the physical optical imaging characteristics of a large aperture and far off-axis OAP are obtained. First,using parallel light incidence,a conclusion can be obtained that the tolerances of OAP translation and revolving around its symmetric axis are closely related with its focal depth. When the optical axis misalignment occurs,astigmatism will play a leading role in the influence on the optical spot which can be described qualitatively by a structural factor. Then,when the incident light has a divergence angle,the best image plane location will change and coma is produced to decrease the power density of the optical spot owing to the asymmetry of

  2. Radiation calibration and error analysis for a large-aperture infrared opto-electric system%大口径红外光电系统辐射定标及误差分析

    Institute of Scientific and Technical Information of China (English)

    杨词银; 曹立华

    2011-01-01

    为了实现对大口径红外光电系统的辐射定标,建立了基于大面源黑体的辐射定标系统以及基于红外单色照明光管的光谱定标系统.利用腔型黑体、连续可变滤光片CVF和平行光管组成红外单色照明光管,对红外系统进行光谱定标,确定系统归一化相对光谱响应函数.利用大面源黑体覆盖红外系统入瞳和视场,对红外系统进行辐射定标,确定系统绝对辐射亮度响应度α.对α的误差源进行了分析计算:α的不确定度主要来自于红外系统输出数码值、大面源黑体辐射、光谱定标和背景辐射的不确定度,经测量和计算分别为0.4%、4.9%、2.5%、1.9%.计算结果表明,响应度α的不确定度为6.1%,满足红外系统10%定标精度的要求.%To perform radation calibration on infrared opto-electric system with a large-aperture, a radiation calibration system based on extended area blackbody and a spectral calibration system based on infrared monochroic collimator were established. The infrared monochroic collimator was composed of a cavity blackbody, a circular variable filter (CVF) and a collimator. It was used to calibrate the infrared opto-electric system spectrally in order to determine its normalized relative spectral response function. A large extended area blackbody, which covered the input pupil and the view field of the infrared opto-electric system, was used to perform radiation calibration on the infrared system in order to determine its absolute radiance responsivity. Analysis on error sources of the radiance responsivity was performed, and the uncertainty of the responsivity came from uncertainties for the output value of the infrared opto-electric system, radiation emitting from the extended area blackbody, the spectral calibration and the background radiation, which were 0.4% 、4.9% ,2.5% 、 1.9% respectively after measuring and calculating. The calculation results show that the uncertainty of the

  3. Mathematical Problems in Synthetic Aperture Radar

    CERN Document Server

    Klein, Jens

    2010-01-01

    This thesis is concerned with problems related to Synthetic Aperture Radar (SAR). The thesis is structured as follows: The first chapter explains what SAR is, and the physical and mathematical background is illuminated. The following chapter points out a problem with a divergent integral in a common approach and proposes an improvement. Numerical comparisons are shown that indicate that the improvements allow for a superior image quality. Thereafter the problem of limited data is analyzed. In a realistic SAR-measurement the data gathered from the electromagnetic waves reflected from the surface can only be collected from a limited area. However the reconstruction formula requires data from an infinite distance. The chapter gives an analysis of the artifacts which can obscure the reconstructed images due to this problem. Additionally, some numerical examples are shown that point to the severity of the problem. In chapter 4 the fact that data is available only from a limited area is used to propose a new invers...

  4. Study of coherent structures of turbulence with large wall-normal gradients in thermophysical properties using direct numerical simulation

    Science.gov (United States)

    Reinink, Shawn K.; Yaras, Metin I.

    2015-06-01

    Forced-convection heat transfer in a heated working fluid at a thermodynamic state near its pseudocritical point is poorly predicted by correlations calibrated with data at subcritical temperatures and pressures. This is suggested to be primarily due to the influence of large wall-normal thermophysical property gradients that develop in proximity of the pseudocritical point on the concentration of coherent turbulence structures near the wall. The physical mechanisms dominating this influence remain poorly understood. In the present study, direct numerical simulation is used to study the development of coherent vortical structures within a turbulent spot under the influence of large wall-normal property gradients. A turbulent spot rather than a fully turbulent boundary layer is used for the study, for the coherent structures of turbulence in a spot tend to be in a more organized state which may allow for more effective identification of cause-and-effect relationships. Large wall-normal gradients in thermophysical properties are created by heating the working fluid which is near the pseudocritical thermodynamic state. It is found that during improved heat transfer, wall-normal gradients in density accelerate the growth of the Kelvin-Helmholtz instability mechanism in the shear layer enveloping low-speed streaks, causing it to roll up into hairpin vortices at a faster rate. It is suggested that this occurs by the baroclinic vorticity generation mechanism which accelerates the streamwise grouping of vorticity during shear layer roll-up. The increased roll-up frequency leads to reduced streamwise spacing between hairpin vortices in wave packets. The density gradients also promote the sinuous instability mode in low-speed streaks. The resulting oscillations in the streaks in the streamwise-spanwise plane lead to locally reduced spanwise spacing between hairpin vortices forming over adjacent low-speed streaks. The reduction in streamwise and spanwise spacing between

  5. Numerical laser beam propagation using a Large Eddy Simulation refractive index field representing a jet engine exhaust

    Science.gov (United States)

    Sjöqvist, Lars; Henriksson, Markus; Fedina, Ekaterina; Fureby, Christer

    2010-10-01

    The exhaust from jet engines introduces extreme turbulence levels in local environments around aircrafts. This may degrade the performance of electro-optical missile warning and laser-based DIRCM systems used to protect aircrafts against heat-seeking missiles. Full scale trials using real engines are expensive and difficult to perform motivating numerical simulations of the turbulence properties within the jet engine exhaust. Large Eddy Simulations (LES) is a computational fluid dynamics method that can be used to calculate spatial and temporal refractive index dynamics of the turbulent flow in the engine exhaust. From LES simulations the instantaneous refractive index in each grid point can be derived and interpolated to phase screens for numerical laser beam propagation or used to estimate aberration effects from optical path differences. The high computation load of LES limits the available data in terms of the computational volume and number of time steps. In addition the phase screen method used in laser beam propagation may also be too slow. For this reason extraction of statistical parameters from the turbulence field and statistical beam propagation methods are studied. The temporal variation of the refractive index is used to define a spatially varying structure constant. Ray-tracing through the mean refractive index field provides integrated static aberrations and the path integrated structure constant. These parameters can be used in classical statistical parameterised models describing propagation through turbulence. One disadvantage of using the structure constant description is that the temporal information is lost. Methods for studying the variation of optical aberrations based on models of Zernike coefficients are discussed. The results of the propagation calculations using the different methods are compared to each other and to available experimental data. Advantages and disadvantages of the different methods are briefly discussed.

  6. Fabrication of bowtie aperture antennas for producing sub-20 nm optical spots.

    Science.gov (United States)

    Chen, Yang; Chen, Jianfeng; Xu, Xianfan; Chu, Jiaru

    2015-04-01

    Bowtie aperture antennas are known to generate sub-diffraction limited optical spots in the visible and near-infrared frequencies, which can be applied to many areas. Regular bowtie apertures fabricated by FIB suffer from tapered sidewall and rounded corner, which degrade its optical enhancement and localization. In this work, a new fabrication method is demonstrated to manufacture bowtie aperture antennas which can produce optical spots with lateral size smaller than 20 nm. We also employ numerical simulations to compute the near-field distribution on the surface of the bowtie aperture with topography extracted from the fabrication antennas. The near-field distribution measured by s-NSOM agrees well with the simulation and confirms the improved near-field localization of our bowtie aperture. This new fabrication method can be applied to other types of ridged apertures, which promises wide applications of deep sub-diffraction limited optical spots in many areas.

  7. Numerical Simulation of Condensation of Sulfuric Acid and Water in a Large Two-stroke Marine Diesel Engine

    Science.gov (United States)

    Walther, J. H.; Karvounis, N.; Pang, K. M.

    2016-11-01

    We present results from computational fluid dynamics simulations of the condensation of sulfuric acid (H2SO 4) and water (H2 O) in a large two-stroke marine diesel engine. The model uses a reduced n-heptane skeletal chemical mechanism coupled with a sulfur subset to simulate the combustion process and the formation of SOx and H2SO 4 . Condensation is modeled using a fluid film model coupled with the Eulerian in-cylinder gas phase. The fluid film condensation model is validated against both experimental and numerical results. The engine simulations reveal that the fluid film has a significant effect on the sulfuric acid gas phase. A linear correlation is found between the fuel sulfur content and the sulfuric acid condensation rate. The initial in-cylinder water content is found not to affect the sulfuric acid condensation but it has a high impact on water condensation. The scavenging pressure level shows an inverse correlation between pressure and condensation rate due to change in the flame propagation speed. Finally, increasing the cylinder liner temperature significantly decreases water condensation but has a negligible influence on the condensation of sulfuric acid.

  8. Numerical study on flow-induced noise for a steam stop-valve using large eddy simulation

    Science.gov (United States)

    Liu, Jiming; Zhang, Tao; Zhang, Yong'ou

    2013-09-01

    The noise induced by the fluctuant saturated steam flow under 250 °C in a stop-valve was numerically studied. The simulation was carried out using computational fluid dynamics (CFD) and ACTRAN. The acoustic field was investigated with Lighthill's acoustic analogy based on the properties of the flow field obtained using a large-eddy simulation that employs the LES-WALE dynamic model as the sub-grid-scale model. Firstly, the validation of mesh was well conducted, illustrating that two million elements were sufficient in this situation. Secondly, the treatment of the steam was deliberated, and conclusions indicate that when predicting the flow-induced noise of the stop-valve, the steam can be treated as incompressible gas at a low inlet velocity. Thirdly, the flow-induced noises under different inlet velocities were compared. The findings reveal it has remarkable influence on the flow-induced noises. Lastly, whether or not the heat preservation of the wall has influence on the noise was taken into account. The results show that heat preservation of the wall had little influence.

  9. Multi-aperture digital coherent combining for free-space optical communication receivers.

    Science.gov (United States)

    Geisler, David J; Yarnall, Timothy M; Stevens, Mark L; Schieler, Curt M; Robinson, Bryan S; Hamilton, Scott A

    2016-06-13

    Space-to-ground optical communication systems can benefit from reducing the size, weight, and power profiles of space terminals. One way of reducing the required power-aperture product on a space platform is to implement effective, but costly, single-aperture ground terminals with large collection areas. In contrast, we present a ground terminal receiver architecture in which many small less-expensive apertures are efficiently combined to create a large effective aperture while maintaining excellent receiver sensitivity. This is accomplished via coherent detection behind each aperture followed by digitization. The digitized signals are then combined in a digital signal processing chain. Experimental results demonstrate lossless coherent combining of four lasercom signals, at power levels below 0.1 photons/bit/aperture.

  10. Fast-neutron, coded-aperture imager

    Energy Technology Data Exchange (ETDEWEB)

    Woolf, Richard S., E-mail: richard.woolf@nrl.navy.mil; Phlips, Bernard F., E-mail: bernard.phlips@nrl.navy.mil; Hutcheson, Anthony L., E-mail: anthony.hutcheson@nrl.navy.mil; Wulf, Eric A., E-mail: eric.wulf@nrl.navy.mil

    2015-06-01

    This work discusses a large-scale, coded-aperture imager for fast neutrons, building off a proof-of concept instrument developed at the U.S. Naval Research Laboratory (NRL). The Space Science Division at the NRL has a heritage of developing large-scale, mobile systems, using coded-aperture imaging, for long-range γ-ray detection and localization. The fast-neutron, coded-aperture imaging instrument, designed for a mobile unit (20 ft. ISO container), consists of a 32-element array of 15 cm×15 cm×15 cm liquid scintillation detectors (EJ-309) mounted behind a 12×12 pseudorandom coded aperture. The elements of the aperture are composed of 15 cm×15 cm×10 cm blocks of high-density polyethylene (HDPE). The arrangement of the aperture elements produces a shadow pattern on the detector array behind the mask. By measuring of the number of neutron counts per masked and unmasked detector, and with knowledge of the mask pattern, a source image can be deconvolved to obtain a 2-d location. The number of neutrons per detector was obtained by processing the fast signal from each PMT in flash digitizing electronics. Digital pulse shape discrimination (PSD) was performed to filter out the fast-neutron signal from the γ background. The prototype instrument was tested at an indoor facility at the NRL with a 1.8-μCi and 13-μCi 252Cf neutron/γ source at three standoff distances of 9, 15 and 26 m (maximum allowed in the facility) over a 15-min integration time. The imaging and detection capabilities of the instrument were tested by moving the source in half- and one-pixel increments across the image plane. We show a representative sample of the results obtained at one-pixel increments for a standoff distance of 9 m. The 1.8-μCi source was not detected at the 26-m standoff. In order to increase the sensitivity of the instrument, we reduced the fastneutron background by shielding the top, sides and back of the detector array with 10-cm-thick HDPE. This shielding configuration led

  11. Coronagraph-Integrated Wavefront Sensing with a Sparse Aperture Mask

    CERN Document Server

    Subedi, Hari; Kasdin, N Jeremy; Cavanagh, Kathleen; Riggs, A J Eldorado

    2015-01-01

    Stellar coronagraph performance is highly sensitive to optical aberrations. In order to effectively suppress starlight for exoplanet imaging applications, low-order wavefront aberrations entering a coronagraph such as tip-tilt, defocus and coma must be determined and compensated. Previous authors have established the utility of pupil-plane masks (both non-redundant/sparse-aperture and generally asymmetric aperture masks) for wavefront sensing. Here we show how a sparse aperture mask (SAM) can be integrated with a coronagraph to measure low-order, differential phase aberrations. Starlight rejected by the coronagraph's focal plane stop is collimated to a relay pupil, where the mask forms an interference fringe pattern on a subsequent detector. Our numerical Fourier propagation models show that the information encoded in the fringe intensity distortions is sufficient to accurately discriminate and estimate Zernike phase modes extending from tip-tilt up to radial degree $n=5$, with amplitude up to $\\lambda/20$ RM...

  12. Sequential Beamforming Synthetic Aperture Imaging

    DEFF Research Database (Denmark)

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

    2013-01-01

    Synthetic aperture sequential beamforming (SASB) is a novel technique which allows to implement synthetic aperture beamforming on a system with a restricted complexity, and without storing RF-data. The objective is to improve lateral resolution and obtain a more depth independent resolution...... and a range independent lateral resolution is obtained. The SASB method has been investigated using simulations in Field II and by off-line processing of data acquired with a commercial scanner. The lateral resolution increases with a decreasing F#. Grating lobes appear if F# 6 2 for a linear array with k-pitch...

  13. Casimir-Polder repulsion near edges: wedge apex and a screen with an aperture

    CERN Document Server

    Milton, Kimball A; Parashar, Prachi; Pourtolami, Nima; Brevik, Iver; Ellingsen, Simen A

    2011-01-01

    Although repulsive effects have been predicted for quantum vacuum forces between bodies with nontrivial electromagnetic properties, such as between a perfect electric conductor and a perfect magnetic conductor, realistic repulsion seems difficult to achieve. Repulsion is possible if the medium between the bodies has a permittivity in value intermediate to those of the two bodies, but this may not be a useful configuration. Here, inspired by recent numerical work, we initiate analytic calculations of the Casimir-Polder interaction between an atom with anisotropic polarizability and a plate with an aperture. In particular, for a semi-infinite plate, and, more generally, for a wedge, the problem is exactly solvable, and for sufficiently large anisotropy, Casimir-Polder repulsion is indeed possible, in agreement with the previous numerical studies. In order to achieve repulsion, what is needed is a sufficiently sharp edge (not so very sharp, in fact) so that the directions of polarizability of the conductor and t...

  14. Large and meso scale eddy structures forced by a river flow in the west Mediterranean under rotating conditions: Numerical and laboratory experiments.

    Science.gov (United States)

    Carrillo, J.; Redondo, J.; Fraunie, P.; Durand, N.

    2003-04-01

    This work presents the results of two laboratory and numerical experiments. The characteristic induced structures by stationer typical conditions from spring, summer, fall and winter. Laboratory experiences were developed on a five meters turntable (SINTEF facilities) obeys the Froude-Rossby similarities. While, the meso-escale numerical model was developed in the LSEET laboratory. This work evidences complementary results from the vortex sort characteristic by radius from both experimental and model methods. Additionally numerical model has a better representation from the conditions in the first 15km and the laboratory model represent the resolution between the large and the meso scale boundary.

  15. Detailed characteristics of drop-laden mixing layers: Large eddy simulation predictions compared to direct numerical simulation

    Science.gov (United States)

    Okong'o, Nora; Leboissetier, Anthony; Bellan, Josette

    2008-10-01

    Results are compared from direct numerical simulation (DNS) and large eddy simulation (LES) of a temporal mixing layer laden with evaporating drops to assess the ability of LES to reproduce detailed characteristics of DNS. The LES used computational drops, each of which represented eight physical drops, and a reduced flow field resolution using a grid spacing four times larger than that of the DNS. The LES also used models for the filtered source terms, which express the coupling of the drops with the flow, and for the unresolved subgrid-scale (SGS) fluxes of species mass, momentum, and enthalpy. The LESs were conducted using one of three different SGS-flux models: dynamic-coefficient gradient (GRD), dynamic-coefficient Smagorinsky (SMD), and constant-coefficient scale similarity (SSC). The comparison of the LES with the filtered-and-coarsened (FC) DNS considered detailed aspects of the flow that are of interest in ignition or full combustion. All LESs captured the largest-scale vortex, the global amount of vapor emanating from the drops, and the overall size distribution of the drops. All LESs tended to underpredict the global amount of irreversible entropy production (dissipation). The SMD model was found unable to capture either the global or local vorticity variation and had minimal small-scale activity in dynamic and thermodynamic variables compared to the FC-DNS. The SMD model was also deficient in predicting the spatial distribution of drops and of the dissipation. In contrast, the GRD and SSC models did mimic the small-scale activity of the FC-DNS and the spatial distribution of drops and of the dissipation. Therefore, the GRD and SSC models are recommended, while the SMD model seems inappropriate for combustion or other problems where the local activity must be predicted.

  16. Optimizing Synthetic Aperture Compound Imaging

    DEFF Research Database (Denmark)

    Hansen, Jens Munk; Jensen, Jørgen Arendt

    2012-01-01

    Spatial compound images are constructed from synthetic aperture data acquired using a linear phased-array transducer. Compound images of wires, tissue, and cysts are created using a method, which allows both transmit and receive compounding without any loss in temporal resolution. Similarly to co...

  17. 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...

  18. 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.  

  19. Synthetic Aperture Radar - Hardware Development

    Directory of Open Access Journals (Sweden)

    V. Rosner

    2009-06-01

    Full Text Available Experimental real and synthetic aperture radar are developed from the base-band digital unit to the analogue RF parts, based on solid state units, using pulse compression for radar imaging. Proper QPSK code is found for matched filter.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  1. The Configurable Aperture Space Telescope (CAST)

    Science.gov (United States)

    Ennico, Kimberly; Bendek, Eduardo A.; Lynch, Dana H.; Vassigh, Kenny K.; Young, Zion

    2016-07-01

    The Configurable Aperture Space Telescope, CAST, is a concept that provides access to a UV/visible-infrared wavelength sub-arcsecond imaging platform from space, something that will be in high demand after the retirement of the astronomy workhorse, the 2.4 meter diameter Hubble Space Telescope. CAST allows building large aperture telescopes based on small, compatible and low-cost segments mounted on autonomous cube-sized satellites. The concept merges existing technology (segmented telescope architecture) with emerging technology (smartly interconnected modular spacecraft, active optics, deployable structures). Requiring identical mirror segments, CAST's optical design is a spherical primary and secondary mirror telescope with modular multi-mirror correctors placed at the system focal plane. The design enables wide fields of view, up to as much as three degrees, while maintaining aperture growth and image performance requirements. We present a point design for the CAST concept based on a 0.6 meter diameter (3 x 3 segments) growing to a 2.6 meter diameter (13 x 13 segments) primary, with a fixed Rp=13,000 and Rs=8,750 mm curvature, f/22.4 and f/5.6, respectively. Its diffraction limited design uses a two arcminute field of view corrector with a 7.4 arcsec/mm platescale, and can support a range of platescales as fine as 0.01 arcsec/mm. Our paper summarizes CAST, presents a strawman optical design and requirements for the underlying modular spacecraft, highlights design flexibilities, and illustrates applications enabled by this new method in building space observatories.

  2. Coherence Studies for Synthetic Aperture Sonar

    Science.gov (United States)

    2014-09-30

    TITLE AND SUBTITLE Coherence Studies for Synthetic Aperture Sonar 5a. CONTRACT NUMBER 5b. GRANT NUMBER N00014-13-1-0020 5c. PROGRAM...systematic look at, coherence. 15. SUBJECT TERMS Synthetic; Aperture Sonar , Coherence, Seafloor Scatter, Propagation Variability 16. SECURITY...reconstruction of the document. Coherence Studies for Synthetic Aperture Sonar Anthony P. Lyons The Pennsylvania State University Applied Research

  3. Cavity Quantum Electrodynamics in a wide aperture spherical resonator. Part I Cavity-induced damping and level shifts

    CERN Document Server

    Daul, J M; Daul, Jean-Marc; Grangier, Philippe

    2003-01-01

    We calculate explicitly the space dependence of the radiative relaxation rates and associated level shifts for a dipole placed in the vicinity of the center of a spherical cavity with a large numerical aperture and a relatively low finesse. In particular, we give simple and useful analytic formulas for these quantities, that can be used with arbitrary mirrors transmissions. The vacuum field in the vicinity of the center of the cavity is actually equivalent to the one obtained in a microcavity, and this scheme allows one to predict significant cavity QED effects

  4. Optimization of dynamic aperture for hadron lattices in eRHIC

    Energy Technology Data Exchange (ETDEWEB)

    Jing, Yichao [Brookhaven National Lab. (BNL), Upton, NY (United States); Litvinenko, Vladimir [Brookhaven National Lab. (BNL), Upton, NY (United States); Trbojevic, Dejan [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2015-05-03

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

  5. Numerical Simulation of Thermal Striping Phenomena in a T-Junction Piping System Using Large Eddy Simulation

    Science.gov (United States)

    Tanaka, Masa-Aki; Ohshima, Hiroyuki; Monji, Hideaki

    At the Japan Atomic Energy Agency (JAEA), the simulation code “MUGTHES (MUlti Geometry simulation code for THErmal-hydraulic and Structure heat conduction analysis in boundary fitted coordinate)” has been developed to evaluate thermal striping phenomena that are caused by the turbulence mixing of fluids at different temperatures. In this paper, numerical schemes for thermal-hydraulic simulation employed in MUGTHES are described, including the LES model. A simple method to limit numerical oscillation is adopted in energy equation solutions. A new iterative method to solve the Poisson equation in the BFC system is developed for effective transient calculations. This method is based on the BiCGSTAB method and the SOR technique. As the code validation of MUGTHES, a numerical simulation in a T-junction piping system with the LES approach was conducted. Numerical results related to velocity and fluid temperature distributions were compared with existing water experimental data and the applicability of numerical schemes with the LES model in MUGTHES to the thermal striping phenomenon was confirmed.

  6. Crosswind from a Single Aperture Scintillometer using Spectral Techniques

    NARCIS (Netherlands)

    Dinther, van D.; Hartogensis, O.K.; Moene, A.F.

    2013-01-01

    In this study, spectral techniques to obtain the crosswind from a single large aperture scintillometer (SLAS) time series are investigated. The crosswind is defined as the wind component perpendicular to a path. A scintillometer obtains a path-averaged estimate of the crosswind. For certain applicat

  7. Hydraulic transmissivity and heat exchange efficiency of open fractures: a model based on lowpass filtered apertures

    CERN Document Server

    Neuville, Amélie; Schmittbuhl, Jean; 10.1111/j.1365-246X.2011.05126.x

    2011-01-01

    Natural open joints in rocks commonly present multi-scale self-affine apertures. This geometrical complexity affects fluid transport and heat exchange between the flow- ing fluid and the surrounding rock. In particular, long range correlations of self-affine apertures induce strong channeling of the flow which influences both mass and heat advection. A key question is to find a geometrical model of the complex aperture that describes at best the macroscopic properties (hydraulic conductivity, heat exchange) with the smallest number of parameters. Solving numerically the Stokes and heat equa- tions with a lubrication approximation, we show that a low pass filtering of the aperture geometry provides efficient estimates of the effective hydraulic and thermal properties (apertures). A detailed study of the influence of the bandwidth of the lowpass filtering on these transport properties is also performed. For instance, keeping the information of amplitude only of the largest Fourier length scales allows us to rea...

  8. A Discussion of Taylor Weighting for Continuous Apertures

    Science.gov (United States)

    2016-06-07

    111111111111 Wlllllll 85111!11!4 11!12i!N A DISCUSSION OF TAYLOR WEIGHTING FOR CONTINUOUS APERTURES Date: 4 January 1985 Prepared by: ~ /. UJ Roy L...COVERED 04-01-1985 to 04-01-1985 4. TITLE AND SUBTITLE A Discussion of Taylor Weighting for Continuous Apertures 5a. CONTRACT NUMBER 5b. GRANT...derived. It is pointed out that the Taylor weighting function can be negative for large n^_, a fact that does not seem to be well known. In addition

  9. ESTAR - A synthetic aperture microwave radiometer for measuring soil moisture

    Science.gov (United States)

    Le Vine, D. M.; Griffis, A.; Swift, C. T.; Jackson, T. J.

    1992-01-01

    The measurement of soil moisture from space requires putting relatively large microwave antennas in orbit. Aperture synthesis, an interferometric technique for reducing the antenna aperture needed in space, offers the potential for a practical means of meeting these requirements. An aircraft prototype, electronically steered thinned array L-band radiometer (ESTAR), has been built to develop this concept and to demonstrate its suitability for the measurement of soil moisture. Recent flights over the Walnut Gulch Watershed in Arizona show good agreement with ground truth and with measurements with the Pushbroom Microwave Radiometer (PBMR).

  10. 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 cornealpatch, 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

  11. Synthesis of offset dual reflector antennas transforming a given feed illumination pattern into a specified aperture distribution

    Science.gov (United States)

    Mittra, R.; Galindo-Israel, V.; Hyjazie, F.

    1982-01-01

    The problem of transforming a given primary feed pattern into a desired aperture field distribution through two reflections by an offset dual reflector system is investigated using the concepts of geometrical optics. A numerically rigorous solution for the reflector surfaces is developed which realizes an exact aperture phase distribution and an aperture amplitude distribution that is accurate to within an arbitrarily small numerical tolerance. However, this procedure does not always yield a smooth solution, i.e., the reflector surfaces thus realized may not be continuous or their slopes may vary too rapidly. In the event of nonexistence of a numerically rigorous smooth solution, an approximate solution that enforces the smoothness of the reflector surfaces can be obtained. In the approximate solution, only the requirement for the aperture amplitude distribution is relaxed, and the condition on the aperture phase distribution is continued to be satisfied exactly.

  12. 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).

  13. Motion compensated beamforming in synthetic aperture vector flow imaging

    DEFF Research Database (Denmark)

    Oddershede, Niels; Jensen, Jørgen Arendt

    2006-01-01

    . Here the SNR is -10 dB compared to the stationary scatterer. A 2D motion compensation method for synthetic aperture vector flow imaging is proposed, where the former vector velocity estimate is used for compensating the beamforming of new data. This method is tested on data from an experimental flow......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......) 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...

  14. Lensless image scanner using multilayered aperture array for noncontact imaging

    Science.gov (United States)

    Kawano, Hiroyuki

    2016-10-01

    We propose a new imaging system of a simple structure that uses a set of layered aperture arrays above a linear image sensor instead of an imaging lens. The image scanner transfers the image information by detecting the scattering rays from the object directly without any collecting power, as if it were an optical stamp. Since the aperture arrays shield the stray rays propagating obliquely, the image information can be read with high resolution even if the object floats within a few millimeters. The aperture arrays with staggered alignment in two lines widen the space with the adjacent pixel without decimating information. We manufactured a prototype model of 300-dpi resolution, whose height is as little as 5 mm. The experimental result shows that ghost images can be restricted sufficiently, and our scanner can clearly read an object within a space of <3.5 mm, meaning that it has a large depth of field of 3.5 mm.

  15. Optimum synthetic-aperture imaging of extended astronomical objects.

    Science.gov (United States)

    van der Avoort, Casper; Pereira, Silvania F; Braat, Joseph J M; den Herder, Jan-Willem

    2007-04-01

    In optical aperture-synthesis imaging of stellar objects, different beam combination strategies are used and proposed. Coaxial Michelson interferometers are very common and a homothetic multiaxial interferometer is recently realized in the Large Binocular Telescope. Laboratory experiments have demonstrated the working principles of two new approaches: densified pupil imaging and wide field-of-view (FOV) coaxial imaging using a staircase-shaped mirror. We develop a common mathematical formulation for direct comparison of the resolution and noise sensitivity of these four telescope configurations for combining beams from multiple apertures for interferometric synthetic aperture, wide-FOV imaging. Singular value decomposition techniques are used to compare the techniques and observe their distinct signal-to-noise ratio behaviors. We conclude that for a certain chosen stellar object, clear differences in performance of the imagers are identifiable.

  16. The SKA New Instrumentation: Aperture Arrays

    Science.gov (United States)

    van Ardenne, A.; Faulkner, A. J.; de Vaate, J. G. bij

    The radio frequency window of the Square Kilometre Array is planned to cover the wavelength regime from cm up to a few meters. For this range to be optimally covered, different antenna concepts are considered enabling many science cases. At the lowest frequency range, up to a few GHz, it is expected that multi-beam techniques will be used, increasing the effective field-of-view to a level that allows very efficient detailed and sensitive exploration of the complete sky. Although sparse narrow band phased arrays are as old as radio astronomy, multi-octave sparse and dense arrays now being considered for the SKA, requiring new low noise design, signal processing and calibration techniques. These new array techniques have already been successfully introduced as phased array feeds upgrading existing reflecting telescopes and for new telescopes to enhance the aperture efficiency as well as greatly increasing their field-of-view (van Ardenne et al., Proc IEEE 97(8):2009) by [1]. Aperture arrays use phased arrays without any additional reflectors; the phased array elements are small enough to see most of the sky intrinsically offering a large field of view.

  17. Alternative synthetic aperture radar (SAR) modalities using a 1D dynamic metasurface antenna

    Science.gov (United States)

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

    2017-05-01

    Synthetic aperture radar (SAR) systems conventionally rely on mechanically-actuated reflector dishes or large phased arrays for generating steerable directive beams. While these systems have yielded high-resolution images, the hardware suffers from considerable weight, high cost, substantial power consumption, and moving parts. Since these disadvantages are particularly relevant in airborne and spaceborne systems, a flat, lightweight, and low-cost solution is a sought-after goal. Dynamic metasurface antennas have emerged as a recent technology for generating waveforms with desired characteristics. Metasurface antennas consist of an electrically-large waveguide loaded with numerous subwavelength radiators which selectively leak energy from a guided wave into free space to form various radiation patterns. By tuning each radiating element, we can modulate the aperture's overall radiation pattern to generate steered directive beams, without moving parts or phase shifters. Furthermore, by using established manufacturing methods, these apertures can be made to be lightweight, low-cost, and planar, while maintaining high performance. In addition to their hardware benefits, dynamic metasurfaces can leverage their dexterity and high switching speeds to enable alternative SAR modalities for improved performance. In this work, we briefly discuss how dynamic metasurfaces can conduct existing SAR modalities with similar performance as conventional systems from a significantly simpler hardware platform. We will also describe two additional modalities which may achieve improved performance as compared to traditional modalities. These modalities, enhanced resolution stripmap and diverse pattern stripmap, offer the ability to circumvent the trade-off between resolution and region-of-interest size that exists within stripmap and spotlight. Imaging results with a simulated dynamic metasurface verify the benefits of these modalities and a discussion of implementation considerations

  18. 集中负载对大口径天线反射面精度的影响%Impact of Concentrate Load on Accuracy of Large Aperture Reflector Antenna

    Institute of Scientific and Technical Information of China (English)

    张萍

    2014-01-01

    本文详细介绍了集中负载对天线反射面精度的影响,建立了66 m天线结构有限元模型,依据模型分析结果,对集中负载引起的天线主面误差进行了分析和数值计算;引入保型设计概念,对集中负载的承载点进行了优化设计,提出了对集中载荷作用分散化、变形均匀化的处理方式。该方法在66米天线上的成功应用,证明了其可以有效的提高天线反射面精度,保障了探月二期任务的圆满完成。该方法对大口径、高精度反射面天线的研制有重要的指导意义。%Impact of concentrate load on accuracy of reflector antenna is analyzed in detail;finite element model of the 66 m-diameter antenna structure is constructed; main reflector error caused by concentrate load is analyzed based on the model analyzing result and numerical computation is conducted. Through introducing flexible design concept, bearing points of concentrate load are designed and optimized. Dispersion and uniform deformation pro-cessing approach is proposed to deal with concentrate load. Successful application of this method in the 66m-di-ameter antenna proves that this method can effectively improve the accuracy of antenna reflector, which gave great support for successful of the Lunar Exploration Phase II Program. The method provides an important guideline for development of large-diameter and high-precision reflector antenna.

  19. Aperture

    OpenAIRE

    Tenace, Stephen M

    1991-01-01

    In the beginning God created the world. Waste and void, waste and void. And darkness was upon the face of the deep. And when there were men, in their various ways, they struggled in torment towards God. Blindly and vainly, for man is a vain thing, and man without God is a seed upon the wind: driven this way and that, and finding no place of lodgment and germination. They followed the light and the shadow, and the light led them forward to light and the ...

  20. High contrast imaging with an arbitrary aperture: active correction of aperture discontinuities: fundamental limits and practical trades offs

    Science.gov (United States)

    Pueyo, Laurent; Norman, Colin Arthur; Soummer, Remi; Perrin, Marshall D.; N'Diaye, Mamadou; Choquet, Elodie

    2015-01-01

    In a recent paper we discussed a new method to achieve high-contrast images using segmented and/or on-axis telescopes. Our approach, named Active Compensation of Aperture Discontinuities (ACAD) relies on 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 particular we showed that broadband high contrast solutions can be achieved using realistic surface deformations that are accessible using existing technologies for a variety of telescope pupil geometries. In this paper we first focus on the fundamental limits and practical trade-offs associated with ACAD. In a first part we will study the fundamental limits and practical tradeoffs associated with ACAD, regardless of the downstream coronagraphic architecture. The mathematical techniques to finding ACAD DM shapes require to solve a complex differential equation. We will first discuss the scaling laws underlying this non-linear solution and their impact of DM placement and geometry wishing the optical design of an instrument. We will then consider the sensitivity to low order aberrations: in principle an ACAD solution that comprises large strokes will be more sensitive to these aberrations than one with smaller strokes. As a consequence, we will quantify this sensitive both using analytical models and numerical simulations. We will present diffractive end to end simulations and quantify the ultimate contrast and bandwidth achievable with ACAD, which can be reached by superposing using a classical linear wavefront control algorithms on top of the Monge Ampere solution. Finally, recent work has shown that coronagraph designs can also accommodate for secondary support structures and/or segments gaps, at a

  1. One dimensional focusing with high numerical aperture multilayer Laue lens

    Energy Technology Data Exchange (ETDEWEB)

    Bajt, Saša, E-mail: sasa.bajt@desy.de; Prasciolu, Mauro [Photon Science, DESY, Notkestrasse 85, 22607 Hamburg (Germany); Morgan, Andrew J. [Center for Free-Electron Laser Science, DESY, Notkestrasse 85, 22607 Hamburg (Germany); Chapman, Henry N. [Center for Free-Electron Laser Science, DESY, Notkestrasse 85, 22607 Hamburg (Germany); Dept. of Physics, University of Hamburg, Luruper Chaussee 149, 22607 Hamburg (Germany); Centre for Ultrafast Imaging, Luruper Chaussee 149, 22607 Hamburg (Germany); Krzywinski, Jacek [SLAC, 2575 Sand Hill Rd., Menlo Park, CA 94025 (United States); Andrejczuk, Andrzej [Faculty of Physics, University of Bialystok, K. Ciolkowskiego 1L, 15-245, Bialystok (Poland)

    2016-01-28

    Multilayer Laue lenses (MLLs) capitalize on the developments in multilayer deposition technologies for fabricating reflective coatings, specifically undertaken for EUV lithography, where layer thicknesses of several nanometers can be achieved. MLLs are deposited layer by layer, with their thicknesses following the zone plate law, and then pieces are sliced and extracted for use in focusing. Rays are reflected in the Laue geometry. The efficiency of a MLL can be very high, and is maximized by making the slice equal to about a half Pendellosung period so that most energy is transferred from the undiffracted to the diffracted beam, and by ensuring that the Bragg condition is met at each point in the zone plate. This latter condition requires that the layers are tilted to the beam by an amount that varies with layer position; e.g. for focusing a collimated beam, the layers should be normal to a cylinder of radius of twice the focal length. We have fabricated such tilted-zone MLLs and find that they exhibit improved efficiency across their entire pupil as compared with parallel-zone MLLs. This leads to a higher effective NA of the optic and hence higher resolution.

  2. Theoretical and numerical study of free shear flows with large density ratio; Etude theorique et numerique des ecoulements cisailles libres a masse volumique fortement variable

    Energy Technology Data Exchange (ETDEWEB)

    Lardjane, N.

    2002-05-15

    The subject of this work concerns the application of large-eddy simulation to the mixing of two fluids with different thermodynamical properties. Numerical errors in the discretization of Navier-Stokes equations and their interaction with sub-grid models are investigated on a self decaying isotropic homogeneous turbulence. A high resolution numerical code is then developed for the simulation of binary mixing layers. Reduction of early acoustic waves amplitude is achieved by use of a temporal self-similar initial condition. The relative magnitude of sub-grid terms arising from filtered equations is investigated on explicit filtering of direct numerical simulation results of temporal N{sub 2}/O{sub 2} and H{sub 2}/O{sub 2} mixing layers. Implicit closure (MILES) is then evoked on the basis of WENO schemes. (author)

  3. A Circular aperture-array structure optical system for digital sun sensor

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Based on the first type of Rayleigh Sommerfeld diffraction formula, an imaging model of circular aperture-array structure digital sun sensor optical system is developed. Then a 6×6 circular aperture-array structure optical system is designed. The results of numerical simulation show that the optical system is designed well and is conformed to the requirements of miniaturization and high accuracy of sun sensor.

  4. Light-Regulated Stomatal Aperture in Arabidopsis

    Institute of Scientific and Technical Information of China (English)

    Chen Chen; Yu-Guo Xiao; Xin Li; Min Ni

    2012-01-01

    The stomatal pores of plant leaves,situated in the epidermis and surrounded by a pair of guard cells,allow CO2 uptake for photosynthesis and water loss through transpiration.Blue light is one of the dominant environmental signals that control stomatal movements in leaves of plants in a natural environment.This blue light response is mediated by blue/UV A light-absorbing phototropins (phots) and cryptochromes (crys).Red/far-red light-absorbing phytochromes (phys) also play a role in the control of stomatal aperture.The signaling components that link the perception of light signals to the stomatal opening response are largely unknown.This review discusses a few newly discovered nuclear genes,their function with respect to the phot-,cry-,and phy-mediated signal transduction cascades,and possible involvement of circadian clock.

  5. Aperture scanning Fourier ptychographic microscopy

    Science.gov (United States)

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

    2016-01-01

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

  6. Terahertz wide aperture reflection tomography

    Science.gov (United States)

    Pearce, Jeremy; Choi, Hyeokho; Mittleman, Daniel M.; White, Jeff; Zimdars, David

    2005-07-01

    We describe a powerful imaging modality for terahertz (THz) radiation, THz wide aperture reflection tomography (WART). Edge maps of an object's cross section are reconstructed from a series of time-domain reflection measurements at different viewing angles. Each measurement corresponds to a parallel line projection of the object's cross section. The filtered backprojection algorithm is applied to recover the image from the projection data. To our knowledge, this is the first demonstration of a reflection computed tomography technique using electromagnetic waves. We demonstrate the capabilities of THz WART by imaging the cross sections of two test objects.

  7. 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...

  8. Space noise synthetic aperture radar

    Science.gov (United States)

    Kulpa, Krzysztof S.

    2006-03-01

    The paper presents limitations of space borne synthetic aperture radars, caused by range and Doppler velocity ambiguities, and the concept of usage of the noise radar technology for creation of high-resolution space SAR images. The noise SAR is free from limitation caused by the periodicity of pulse waveform ambiguity function, and therefore this technology can be used in the future space missions. The basic concept of noise SAR image formation is also presented. The image formation algorithm has been verified using the simulated data produced by Raw Radar Data Simulator.

  9. Large-scale thermal convection of viscous fluids in a faulted system: 3D test case for numerical codes

    Science.gov (United States)

    Magri, Fabien; Cacace, Mauro; Fischer, Thomas; Kolditz, Olaf; Wang, Wenqing; Watanabe, Norihiro

    2017-04-01

    In contrast to simple homogeneous 1D and 2D systems, no appropriate analytical solutions exist to test onset of thermal convection against numerical models of complex 3D systems that account for variable fluid density and viscosity as well as permeability heterogeneity (e.g. presence of faults). Owing to the importance of thermal convection for the transport of energy and minerals, the development of a benchmark test for density/viscosity driven flow is crucial to ensure that the applied numerical models accurately simulate the physical processes at hands. The presented study proposes a 3D test case for the simulation of thermal convection in a faulted system that accounts for temperature dependent fluid density and viscosity. The linear stability analysis recently developed by Malkovsky and Magri (2016) is used to estimate the critical Rayleigh number above which thermal convection of viscous fluids is triggered. The numerical simulations are carried out using the finite element technique. OpenGeoSys (Kolditz et al., 2012) and Moose (Gaston et al., 2009) results are compared to those obtained using the commercial software FEFLOW (Diersch, 2014) to test the ability of widely applied codes in matching both the critical Rayleigh number and the dynamical features of convective processes. The methodology and Rayleigh expressions given in this study can be applied to any numerical model that deals with 3D geothermal processes in faulted basins as by example the Tiberas Basin (Magri et al., 2016). References Kolditz, O., Bauer, S., Bilke, L., Böttcher, N., Delfs, J. O., Fischer, T., U. J. Görke, T. Kalbacher, G. Kosakowski, McDermott, C. I., Park, C. H., Radu, F., Rink, K., Shao, H., Shao, H.B., Sun, F., Sun, Y., Sun, A., Singh, K., Taron, J., Walther, M., Wang,W., Watanabe, N., Wu, Y., Xie, M., Xu, W., Zehner, B., 2012. OpenGeoSys: an open-source initiative for numerical simulation of thermo-hydro-mechanical/chemical (THM/C) processes in porous media. Environmental

  10. 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.

  11. Large-scale numerical simulations of star formation put to the test: Comparing synthetic images and actual observations for statistical samples of protostars

    CERN Document Server

    Frimann, Søren; Haugbølle, Troels

    2015-01-01

    (abridged) Context: Both observations and simulations of embedded protostars have progressed rapidly in recent years. Bringing them together is an important step in advancing our knowledge about the earliest phases of star formation. Aims: To compare synthetic continuum images and SEDs, created from large-scale numerical simulations, to observational studies - thereby aiding both in the interpretation of observations and test the fidelity of the simulations. Methods: The radiative transfer code RADMC-3D is used to create synthetic continuum images and SEDs of protostellar systems in a large numerical simulation of a molecular cloud. More than 13000 unique radiative transfer models are produced of a variety of different protostellar systems. Results: Over the course of 0.76 Myr more than 500 protostars are formed in the simulation - primarily within two sub-clusters. Synthetic SEDs are used to calculate evolutionary tracers Tbol and Lsmm/Lbol. It is shown that, while the observed distributions of tracers are w...

  12. Coupling a Mesoscale Numerical Weather Prediction Model with Large-Eddy Simulation for Realistic Wind Plant Aerodynamics Simulations (Poster)

    Energy Technology Data Exchange (ETDEWEB)

    Draxl, C.; Churchfield, M.; Mirocha, J.; Lee, S.; Lundquist, J.; Michalakes, J.; Moriarty, P.; Purkayastha, A.; Sprague, M.; Vanderwende, B.

    2014-06-01

    Wind plant aerodynamics are influenced by a combination of microscale and mesoscale phenomena. Incorporating mesoscale atmospheric forcing (e.g., diurnal cycles and frontal passages) into wind plant simulations can lead to a more accurate representation of microscale flows, aerodynamics, and wind turbine/plant performance. Our goal is to couple a numerical weather prediction model that can represent mesoscale flow [specifically the Weather Research and Forecasting model] with a microscale LES model (OpenFOAM) that can predict microscale turbulence and wake losses.

  13. Mussel farming as a large-scale bioengineering tool: a numerical modelling case study in Rødsand lagoon, Denmark

    DEFF Research Database (Denmark)

    Forsberg, Pernille Louise; Ernstsen, Verner Brandbyge; Lumborg, Ulrik

    mussels as a bioengineering measure in a numerical sediment transport model and investigated how the implementation of an exterior mussel farm affect the sediment dynamics within Rødsand lagoon. On the basis of 2D modelling (MIKE21 by DHI) and field measurements, the flow and sediment dynamics to and from....... Apart from bioengineering purposes, the mussel module extension can be utilized to improve and develop sediment transport models where known natural patches of mussels are present. Acknowledgements This study is part of the research project “SEDILINK – Flow circulation and sediment dynamics...

  14. Aperture Effects on Spectroscopic Galaxy Activity Classification

    CERN Document Server

    Maragkoudakis, A; Ashby, M L N; Willner, S P

    2014-01-01

    Activity classification of galaxies based on long-slit and fiber spectroscopy can be strongly influenced by aperture effects. Here we investigate how activity classification for 14 nearby galaxies depends on the proportion of the host galaxy's light that is included in the aperture. We use both observed long-slit spectra and simulated elliptical-aperture spectra of different sizes. The degree of change varies with galaxy morphology and nuclear activity type. Starlight removal techniques can mitigate but not remove the effect of host galaxy contamination in the nuclear aperture. Galaxies with extra-nuclear star formation can show higher [O III] {\\lambda}5007/H{\\beta} ratios with increasing aperture, in contrast to the naive expectation that integrated light will only dilute the nuclear emission lines. We calculate the mean dispersion for the diagnostic line ratios used in the standard BPT diagrams with respect to the central aperture of spectral extraction to obtain an estimate of the uncertainties resulting f...

  15. An extended numerical calibration method for an electrochemical probe in thin wavy flow with large amplitude waves

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Ki Yong; No, Hee Cheon [Korea Advanced Institute of Science and Technology, Taejon (Korea, Republic of)

    1998-12-31

    The calibrating method for an electrochemical probe, neglecting the effect of the normal velocity on the mass transport, can cause large errors when applied to the measurement of wall shear rates in thin wavy flow with large amplitude waves. An extended calibrating method is developed to consider the contributions of the normal velocity. The inclusion of the turbulence-induced normal velocity term is found to have a negligible effect on the mass transfer coefficient. The contribution of the wave-induced normal velocity can be classified on the dimensionless parameter, V. If V is above a critical value of V, V{sub crit}, the effects of the wave-induced normal velocity become larger with an increase in V. While its effects negligible for inversely. The present inverse method can predict the unknown shear rate more accurately in thin wavy flow with large amplitude waves than the previous method. 18 refs., 8 figs. (Author)

  16. 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.

  17. Advanced Optics Experiments Using Nonuniform Aperture Functions

    CERN Document Server

    Wood, Lowell T

    2012-01-01

    A method to create instructive, nonuniform aperture functions using spatial frequency filtering is described. The diffraction from a single slit in the Fresnel limit and the interference from a double slit in the Fraunhofer limit are spatially filtered to create electric field distributions across an aperture to produce apodization, inverse apodization or super-resolution, and apertures with phase shifts across their widths. The diffraction effects from these aperture functions are measured and calculated. The excellent agreement between the experimental results and the calculated results makes the experiment ideal for use in an advanced undergraduate or graduate optics laboratory to illustrate experimentally several effects in Fourier optics.

  18. A new look on the stabilization of inverted pendulum with parametric excitation and large random frequencies: Analytical and numerical approaches

    Science.gov (United States)

    da Silva, Roberto; Prado, Sandra D.; Fernandes, Henrique A.

    2017-10-01

    In this paper we explore the stability of an inverted pendulum with generalized parametric excitation described by a superposition of N sines with different frequencies and phases. We show that when the amplitude is scaled with the frequency we obtain the stabilization of the real inverted pendulum, i.e., with values of g according to planet Earth (g ≈ 9.8 m/s2) for high frequencies. By randomly sorting the frequencies, we obtain a critical amplitude in light of perturbative theory in classical mechanics which is numerically tested by exploring its validity regime in many alternatives. We also analyse the effects when different values of N as well as the pendulum size l are taken into account.

  19. Flat light guides with prismatic elements coupled with a mini aperture fluorescent lamp

    Science.gov (United States)

    Zaremba, Krzysztof

    2005-09-01

    Flat light guides are modern solution enabling production of luminaries characterised by large area and low height. The amount of the luminous flux, which might penetrate the side-lit flat light waveguide with a predefined thickness depends on the light source's luminance. Special fluorescent lamps equipped with an internal reflector layer were designed for this kind of illumination systems. Such lamps are typically characterised by small aperture along the spine of the lamp. The aperture technology boosts the luminance value within the lamp's aperture to levels even 4 to 5 times higher than the average luminance of a standard fluorescent lamp. The presented article contains a detailed analysis of the impact of the aperture angle size on the coupling efficiency. It was also shown that application of a mini aperture fluorescent lamp influences changes in the luminous intensity curves of prismatic elements, which are most commonly used to direct the luminous flux.

  20. Adaptive Matching of the Scanning Aperture of the Environment Parameter

    Science.gov (United States)

    Choni, Yu. I.; Yunusov, N. N.

    2016-04-01

    We analyze a matching system for the scanning aperture antenna radiating through a layer with unpredictably changing parameters. Improved matching has been achieved by adaptive motion of a dielectric plate in the gap between the aperture and the radome. The system is described within the framework of an infinite layered structure. The validity of the model has been confirmed by numerical simulation using CST Microwave Studio software and by an experiment. It is shown that the reflection coefficient at the input of some types of a matching device, which is due to the deviation of the load impedance from the nominal value, is determined by a compact and versatile formula. The potential efficiency of the proposed matching system is shown by a specific example, and its dependence on the choice of the starting position of the dielectric plate is demonstrated.

  1. Large-mode-area leaky optical fibre fabricated by MCVD

    OpenAIRE

    Dussardier, Bernard; Trzesien, Stanislaw; Ude, Michèle; Rastogi, Vipul; Kumar, Ajeet; Monnom, Gérard

    2008-01-01

    International audience; A large mode area single-mode optical fibre based on leaky mode filtering was prepared by MCVD. The cladding structure discriminates the fundamental mode from the higher order ones. A preliminary version has 25-µm core diameter and 0.11 numerical aperture. A Gaussian-like mode with 22-µm MFD is observed after 3-m propagation, in agreement with modeling.

  2. Theoretical analysis and numerical simulation on behaviour properties of large span cable-supported structures under fire conditions

    Institute of Scientific and Technical Information of China (English)

    BAI Yin; SHI YongJiu; WANG YuanQing

    2009-01-01

    Large span cable-supported structures have been developed rapidly in China,and they always adopt high-strength steel cables as structural members.However,the modulus of elasticity and yield strength of steel material will decrease seriously under fire conditions while fire protection is unlikely to be provided for steel cable.Several typical large span cable-supported structures such as cable truss,beam string structure and prestressed cable net are studied on their structural behaviour in this paper.Theoretical formulae are derived in terms of geometrical and material nonlinearity with high temperature effect.Finite element models are also established to simulate the structural performance under fire conditions.The calculation formulae for fire-resisting design are suggested for these three types of structures,while displacement and prestressed force variation rules are also given.

  3. Theoretical analysis and numerical simulation on behaviour properties of large span cable-supported structures under fire conditions

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Large span cable-supported structures have been developed rapidly in China, and they always adopt high-strength steel cables as structural members. However, the modulus of elasticity and yield strength of steel material will decrease seriously under fire conditions while fire protection is unlikely to be provided for steel cable. Several typical large span cable-supported structures such as cable truss, beam string structure and prestressed cable net are studied on their structural behaviour in this paper. Theoretical formulae are derived in terms of geometrical and material nonlinearity with high temperature effect. Finite element models are also established to simulate the structural performance under fire conditions. The calculation formulae for fire-resisting design are suggested for these three types of structures, while displacement and prestressed force variation rules are also given.

  4. A novel approach to correct the coded aperture misalignment for fast neutron imaging

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, F. N.; Hu, H. S., E-mail: huasi-hu@mail.xjtu.edu.cn; Wang, D. M.; Jia, J. [School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an 710049 (China); Zhang, T. K. [Laser Fusion Research Center, CAEP, Mianyang, 621900 Sichuan (China); Jia, Q. G. [Institute of Applied Physics and Computational Mathematics, Beijing 100094 (China)

    2015-12-15

    Aperture alignment is crucial for the diagnosis of neutron imaging because it has significant impact on the coding imaging and the understanding of the neutron source. In our previous studies on the neutron imaging system with coded aperture for large field of view, “residual watermark,” certain extra information that overlies reconstructed image and has nothing to do with the source is discovered if the peak normalization is employed in genetic algorithms (GA) to reconstruct the source image. Some studies on basic properties of residual watermark indicate that the residual watermark can characterize coded aperture and can thus be used to determine the location of coded aperture relative to the system axis. In this paper, we have further analyzed the essential conditions for the existence of residual watermark and the requirements of the reconstruction algorithm for the emergence of residual watermark. A gamma coded imaging experiment has been performed to verify the existence of residual watermark. Based on the residual watermark, a correction method for the aperture misalignment has been studied. A multiple linear regression model of the position of coded aperture axis, the position of residual watermark center, and the gray barycenter of neutron source with twenty training samples has been set up. Using the regression model and verification samples, we have found the position of the coded aperture axis relative to the system axis with an accuracy of approximately 20 μm. Conclusively, a novel approach has been established to correct the coded aperture misalignment for fast neutron coded imaging.

  5. Numerical response analysis of a large mat-type floating structure in regular waves; Matogata choogata futai kozobutsu no haro oto kaiseki

    Energy Technology Data Exchange (ETDEWEB)

    Yasuzawa, Y.; Kagawa, K.; Kitabayashi, K. [Kyushu University, Fukuoka (Japan); Kawano, D. [Mitsubishi Heavy Industries, Ltd., Tokyo (Japan)

    1997-08-01

    The theory and formulation for the numerical response analysis of a large floating structure in regular waves were given. This paper also reports the comparison between the experiment in the Shipping Research Institute in the Minitry of Transport and the result calculated using numerical analytic codes in this study. The effect of the bending rigidity of a floating structure and the wave direction on the dynamic response of a structure was examined by numerical calculation. When the ratio of structure length and incident wavelength (L/{lambda}) is lower, the response amplitude on the transmission side becomes higher in a wave-based response. The hydrodynamic elasticity exerts a dominant influence when L/{lambda} becomes higher. For incident oblique waves, the maximum response does not necessarily appear on the incidence side. Moreover, the response distribution is also complicated. For example, the portion where any flexible amplitude hardly appears exists. A long structure response can be predicted from a short structure response to some degree. They differ in response properties when the ridigity based on the similarity rule largely differs, irrespective of the same L/{lambda}. For higher L/{lambda}, the wave response can be easily predicted when the diffrection force is replaced by the concentrated exciting force on the incidence side. 13 refs., 14 figs., 3 tabs.

  6. Numerical Simulation of Hot Accretion Flows (I): A Large Radial Dynamical Range and the Density Profile of Accretion Flow

    CERN Document Server

    Yuan, Feng; Bu, Defu

    2012-01-01

    Numerical simulations of hot accretion flow have shown that the mass accretion rate decreases with decreasing radius; consequently the density profile of accretion flow becomes flatter compared to the case of a constant accretion rate. This result has important theoretical and observational implications. However, because of technical difficulties, the radial dynamic range in almost all previous simulations usually spans at most two orders of magnitude. This small dynamical range, combined with the effects of boundary conditions, makes the simulation results suspectable. Especially, the radial profiles of density and accretion rate may not be precise enough to be used to compare with observations. In this paper we present a "two-zone" approach to expand the radial dynamical range from two to four orders of magnitude. We confirm previous results and find that from $r_s$ to $ 10^4r_s$ the radial profiles of accretion rate and density can be well described by $\\dot{M}(r)\\propto r^s$ and $\\rho\\propto r^{-p}$. The ...

  7. Data Collection via Synthetic Aperture Radiometry towards Global System

    Directory of Open Access Journals (Sweden)

    Ali. A. J.Al-Sabbagh

    2015-10-01

    Full Text Available Nowadays it is widely accepted that remote sensing is an efficient way of large data management philosophy. In this paper, we present a future view of the big data collection by synthetic aperture radiometry as a passive microwave remote sensing towards building a global monitoring system. Since the collected data may not have any value, it is mandatory to analyses these data in order to get valuable and beneficial information with respect to their base data. The collected data by synthetic aperture radiometry is one of the high resolution earth observation, these data will be an intensive problems, Meanwhile, Synthetic Aperture Radar able to work in several bands, X, C, S, L and P-band. The important role of synthetic aperture radiometry is how to collect data from areas with inadequate network infrastructures where the ground network facilities were destroyed. The future concern is to establish a new global data management system, which is supported by the groups of international teams working to develop technology based on international regulations. There is no doubt that the existing techniques are so limited to solve big data problems totally. There is a lot of work towards improving 2- D and 3-D SAR to get better resolution.

  8. An analysis of beamed wireless power transfer in the Fresnel zone using a dynamic, metasurface aperture

    Science.gov (United States)

    Smith, David R.; Gowda, Vinay R.; Yurduseven, Okan; Larouche, Stéphane; Lipworth, Guy; Urzhumov, Yaroslav; Reynolds, Matthew S.

    2017-01-01

    Wireless power transfer (WPT) has been an active topic of research, with a number of WPT schemes implemented in the near-field (coupling) and far-field (radiation) regimes. Here, we consider a beamed WPT scheme based on a dynamically reconfigurable source aperture transferring power to receiving devices within the Fresnel region. In this context, the dynamic aperture resembles a reconfigurable lens capable of focusing power to a well-defined spot, whose dimension can be related to a point spread function. The necessary amplitude and phase distribution of the field imposed over the aperture can be determined in a holographic sense, by interfering a hypothetical point source located at the receiver location with a plane wave at the aperture location. While conventional technologies, such as phased arrays, can achieve the required control over phase and amplitude, they typically do so at a high cost; alternatively, metasurface apertures can achieve dynamic focusing with potentially lower cost. We present an initial tradeoff analysis of the Fresnel region WPT concept assuming a metasurface aperture, relating the key parameters such as spot size, aperture size, wavelength, and focal distance, as well as reviewing system considerations such as the availability of sources and power transfer efficiency. We find that approximate design formulas derived from the Gaussian optics approximation provide useful estimates of system performance, including transfer efficiency and coverage volume. The accuracy of these formulas is confirmed through numerical studies.

  9. Numerical simulation of strain localization and damage evolution in large plastic deformation using mixed finite element method

    Institute of Scientific and Technical Information of China (English)

    Zhanghua Chen; Jiajian Jin; Jiumei Xiao

    2004-01-01

    An investigation of computer simulation is presented to analyze the effects of strain localization and damage evolution in large plastic deformation. The simulation is carried out by using an elastic-plastic-damage coupling finite element program that is developed based on the concept of mixed interpolation of displacement/pressure. This program has been incorporated into a damage mechanics model as well as the corresponding damage criterion. To illustrate the performance of the proposed approach, a typical strain localization problem has been simulated. The results show that the proposed approach is of good capability to capture strain localization and predict the damage evolution.

  10. High-aperture cryogenic light microscopy

    Science.gov (United States)

    LE GROS, M.A.; McDERMOTT, G.; UCHIDA, M.; KNOECHEL, C.G.; LARABELL, C.A.

    2012-01-01

    Summary We report here the development of instruments and protocols for carrying out high numerical aperture immersion light microscopy on cryogenic specimens. Imaging by this modality greatly increases the lifetimes of fluorescence probes, including those commonly used for protein localization studies, while retaining the ability to image the specimen with high fidelity and spatial resolution. The novel use of a cryogenic immersion fluid also minimizes the refractive index mismatch between the sample and lens, leading to a more efficient coupling of the light from the sample to the image forming system. This enhancement is applicable to both fluorescence and transmitted light microscopy techniques. The design concepts used for the cryogenic microscope can be applied to virtually any existing light-based microscopy technique. This prospect is particularly exciting in the context of ‘super-resolution’ techniques, where enhanced fluorescence lifetime probes are especially useful. Thus, using this new modality it is now possible to observe dynamic events in a live cell, and then rapidly vitrify the specimen at a specific time point prior to carrying out high-resolution imaging. The techniques described can be used in conjunction with other imaging modalities in correlated studies. We have also developed instrumentation to perform cryo-light imaging together with soft X-ray tomography on the same cryo-fixed specimen as a means of carrying out high content, quantifiable correlated imaging analyses. These methods are equally applicable to correlated light and electron microscopy of frozen biological objects. PMID:19566622

  11. Multistatic synthetic aperture radar image formation.

    Science.gov (United States)

    Krishnan, V; Swoboda, J; Yarman, C E; Yazici, B

    2010-05-01

    In this paper, we consider a multistatic synthetic aperture radar (SAR) imaging scenario where a swarm of airborne antennas, some of which are transmitting, receiving or both, are traversing arbitrary flight trajectories and transmitting arbitrary waveforms without any form of multiplexing. The received signal at each receiving antenna may be interfered by the scattered signal due to multiple transmitters and additive thermal noise at the receiver. In this scenario, standard bistatic SAR image reconstruction algorithms result in artifacts in reconstructed images due to these interferences. In this paper, we use microlocal analysis in a statistical setting to develop a filtered-backprojection (FBP) type analytic image formation method that suppresses artifacts due to interference while preserving the location and orientation of edges of the scene in the reconstructed image. Our FBP-type algorithm exploits the second-order statistics of the target and noise to suppress the artifacts due to interference in a mean-square sense. We present numerical simulations to demonstrate the performance of our multistatic SAR image formation algorithm with the FBP-type bistatic SAR image reconstruction algorithm. While we mainly focus on radar applications, our image formation method is also applicable to other problems arising in fields such as acoustic, geophysical and medical imaging.

  12. NSLS-II Control of Dynamic Aperture

    Energy Technology Data Exchange (ETDEWEB)

    Bengtsson,J.

    2008-10-31

    We have outlined how, by an intuitive approach, the on- and off-momentum dynamic aperture for a synchrotron light source can be estimated from a nonlinear system of algebraic equations for the sextupole/multipole strengths. The approach has only two free parameters: the relative weight for resonance vs. tune shift terms and the tune footprint for stable trajectories in a modern third generation synchrotron light source. In other words, we have established a control theory approach for the medium term (10{sup 3} turns) stability for a dynamic system described by a nonlinear system of ordinary differential equations. Equipped with a predictive, quantitative model for stability, we have then evaluated how to improve the control of the dynamics by analyzing and modifying the properties of the corresponding algebraic system. In particular, by changing the number- and characteristics of the parameters, i.e., we have not evaluated how the underlying (linear) optics could be improved. We have also validated our conjectures by numerical simulations with a realistic model. Presumably, our conclusions, summarized in Section 1.0, are a direct result of the presented analysis and observations.

  13. Fast Parametric Beamformer for Synthetic Aperture Imaging

    DEFF Research Database (Denmark)

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

    2008-01-01

    . 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...

  14. 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...

  15. Momentum aperture of the advanced light source

    Science.gov (United States)

    Decking, W.; Robin, D.

    1999-04-01

    This paper shows measurements of the momentum aperture of the Advanced Light Source (ALS) based on Touschek lifetime measurements. The measured data is compared with tracking simulations and a simple model for the apertures will help to explain the observed effects.

  16. Numerical Investigation of Wall Cooling and Suction Effects on Supersonic Flat-Plate Boundary Layer Transition Using Large Eddy Simulation

    Directory of Open Access Journals (Sweden)

    Suozhu Wang

    2015-02-01

    Full Text Available Reducing friction resistance and aerodynamic heating has important engineering significance to improve the performances of super/hypersonic aircraft, so the purpose of transition control and turbulent drag reduction becomes one of the cutting edges in turbulence research. In order to investigate the influences of wall cooling and suction on the transition process and fully developed turbulence, the large eddy simulation of spatially evolving supersonic boundary layer transition over a flat-plate with freestream Mach number 4.5 at different wall temperature and suction intensity is performed in the present work. It is found that the wall cooling and suction are capable of changing the mean velocity profile within the boundary layer and improving the stability of the flow field, thus delaying the onset of the spatial transition process. The transition control will become more effective as the wall temperature decreases, while there is an optimal wall suction intensity under the given conditions. Moreover, the development of large-scale coherent structures can be suppressed effectively via wall cooling, but wall suction has no influence.

  17. Divided-aperture differential confocal fast-imaging microscopy

    Science.gov (United States)

    Wang, Yun; Qiu, Lirong; Zhao, Xiangye; Zhao, Weiqian

    2017-03-01

    A new method, laser divided-aperture differential confocal microscopy (DDCM), is proposed to achieve high-resolution 3D imaging of microstructures of large-scale sample surfaces. This method uses a divided-aperture confocal structure to significantly improve the axial resolution of confocal microscopy and keep a long working distance simultaneously; uses two radically offset point detectors to achieve differential detection to further improve the axial response sensitivity and realize fast imaging of a large-scale sample surface with a big axial scan-step interval. Theoretical analyses and experimental results show that the DDCM can reach an axial resolution of 5 nm with a 3.1 mm working distance with a 3 times imaging speed of a confocal system with the same resolution.

  18. Measuring and optimizing the momentum aperture in a particle accelerator

    Science.gov (United States)

    Steier, C.; Robin, D.; Nadolski, L.; Decking, W.; Wu, Y.; Laskar, J.

    2002-05-01

    Particle motion in storage rings is confined by various aperture limits, the size of which restricts the performance of the ring in terms of injection efficiency, lifetime, etc. Intrabeam scattering makes particles sweep a large portion of the phase space, where their motion may eventually be resonantly or chaotically excited to large amplitudes leading to collision with the vacuum chamber. We report here the studies performed at the Advanced Light Source (ALS) on the on- and off-momentum particle motion that provides a good understanding of these limitations. Using off-momentum simulations and experiments together with frequency map analysis, we could precisely correlate beam loss areas with resonance locations. The very good agreement between simulations and experiments allowed us to provide guidance for avoiding these dangerous areas. This analysis results in predictive improvements of the momentum aperture, which actually led to a lifetime increase of 25% at the ALS for very high bunch charge.

  19. A pump driving liquid cooling circuit method for the aperture of an infrared cold optical system

    Science.gov (United States)

    Xie, RongJian

    2017-06-01

    To enhance the optical recognition and wavelength filtering of an infrared cold optical system, some lens need to be maintained within a certain temperature range, which requires specific thermal management of the aperture. A 250K liquid cooling circuit designed for this purpose is introduced, and the experimental results established and operated in a vacuum environmental simulation chamber is carried out and analyzed. A practical cooling power source of radiation cooling equipment is adopted and the sun exposure heat load is imitated by array of planar membrane heaters attached on the specific designed structure of the aperture. Controlling the aperture temperature and improving the optical system performance are proved effective. Numerical optimization of the cooling circuit and simulation of the aperture are performed , and the factors affect the optical system performance in the mean time are also investigated.

  20. Numerical analysis of the scavenge flow and convective heat transfer in large two-stroke marine diesel engines

    DEFF Research Database (Denmark)

    Sigurdsson, Eythor; Ingvorsen, Kristian Mark; Jensen, Michael Vincent

    2014-01-01

    A novel computational fluid dynamics (CFD) model is presented for the study of the scavenging processand convective heat transfer in a large two-stroke low-speed uniflow-scavenged marine diesel engine.The engine is modeled using a fully resolved 12 sector, corresponding to one scavenge port...... an effective scavenging and a low convective heat loss in agreement with experimental data forlarge marine diesel engines.© 2014 Elsevier Ltd. All rights reserved......., with cyclicboundaries in the tangential direction. The CFD model is strongly coupled to experiments and effectivelyprovides a high order ‘‘interpolation’’ of the engine processes through the solution of the Reynolds-AveragedNavier–Stokes (RANS) equations subject to boundary conditions obtained through experiments...