WorldWideScience

Sample records for inch-diameter circular aperture

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

    Directory of Open Access Journals (Sweden)

    Costa Pedro Bastos

    2016-01-01

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

  2. Seismic fragility test of a 6-inch diameter pipe system

    International Nuclear Information System (INIS)

    Chen, W.P.; Onesto, A.T.; DeVita, V.

    1987-02-01

    This report contains the test results and assessments of seismic fragility tests performed on a 6-inch diameter piping system. The test was funded by the US Nuclear Regulatory Commission (NRC) and conducted by ETEC. The objective of the test was to investigate the ability of a representative nuclear piping system to withstand high level dynamic seismic and other loadings. Levels of loadings achieved during seismic testing were 20 to 30 times larger than normal elastic design evaluations to ASME Level D limits would permit. Based on failure data obtained during seismic and other dynamic testing, it was concluded that nuclear piping systems are inherently able to withstand much larger dynamic seismic loadings than permitted by current design practice criteria or predicted by the probabilistic risk assessment (PRA) methods and several proposed nonlinear methods of failure analysis

  3. Analytical estimation of the dynamic apertures of circular accelerators

    International Nuclear Information System (INIS)

    Gao, J.

    2000-02-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Nielsen, S.A.

    1998-08-01

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

  5. Interim results: fines recycle testing using the 4-inch diameter primary graphite burner

    International Nuclear Information System (INIS)

    Palmer, W.B.

    1975-05-01

    The results of twenty-two HTGR primary burner runs in which graphite fines were recycled pneumatically to the 4-inch diameter pilot-plant primary fluidized-bed burner are described. The result of the tests showed that zero fines accumulation can easily be achieved while operating at plant equivalent burn rates. (U.S.)

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

    Science.gov (United States)

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

    2014-11-01

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

  7. Stand Development 25 Years after a 9.0-inch Diameter-Limit First Cutting In Appalachian Hardwoods

    Science.gov (United States)

    H. Clay Smith; N. I. Lamson

    1977-01-01

    This report is a case history of stand development 25 years after a 9.0-inch diameter-limit cutting in a primarily second growth 40- to 45-year-old Appalachian hardwood stand. Some old residual trees from the early 1900 logging era were scattered throughout the stand. In 1950, a 9.0-inch diameter-limit cutting removed 8,650 board feet per acre and reduced the basal...

  8. Fabrication of 0.5-inch diameter FBR mixed oxide fuel pellets

    International Nuclear Information System (INIS)

    Rasmussen, D.E.; Benecke, M.W.; McCord, R.B.

    1979-01-01

    Large diameter (0.535 inch) mixed oxide fuel pellets for Fast Breeder Reactor application were successfully fabricated by the cold-press-and-sinter technique. Enriched UO 2 , PuO 2 -UO 2 , and PuO 2 -ThO 2 compositions were fabricated into nominally 90% theoretical density pellets for the UO 2 and PuO 2 -UO 2 compositions, and 88% and 93% T.D. for the PuO 2 -ThO 2 compositions. Some processing adjustments were required to achieve satisfactory pellet quality and density. Furnace heating rate was reduced from 200 to 50 0 C/h for the organic binder burnout cycle for the large, 0.535-inch diameter pellets to eliminate pellet cracking during sintering. Additional preslugging steps and die wall lubrication during pressing were used to eliminate pressing cracks in the PuO 2 -ThO 2 pellets

  9. Polarization measurement and vertical aperture optimization for obtaining circularly polarized bend-magnet radiation

    Energy Technology Data Exchange (ETDEWEB)

    Kortright, J.B.; Rice, M.; Hussain, Z. [Lawrence Berkeley National Lab., CA (United States)] [and others

    1997-04-01

    Growing interest in utilizing circular polarization prompted the design of bend-magnet beamline 9.3.2 at the Advanced Light Source, covering the 30-1500 eV spectral region, to include vertical aperturing capabilities for optimizing the collection of circular polarization above and below the orbit plane. After commissioning and early use of the beamline, a multilayer polarimeter was used to characterize the polarization state of the beam as a function of vertical aperture position. This report partially summarizes the polarimetry measurements and compares results with theoretical calculations intended to simulate experimental conditions.

  10. Apertures with Laval Nozzle and Circular Orifice in Secondary Electron Detector for Environmental Scanning Electron Microscope

    Czech Academy of Sciences Publication Activity Database

    Vyroubal, P.; Maxa, J.; Neděla, Vilém; Jirák, Josef; Hladká, K.

    2013-01-01

    Roč. 8, č. 1 (2013), s. 59-69 ISSN 1802-2308 R&D Projects: GA ČR GAP102/10/1410 Institutional support: RVO:68081731 Keywords : Aperture * Laval nozzle * circular orifice * pressure * detector * Mach number * flow * trajectory of secondary electrons Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering

  11. GOTCHA experience report: three-dimensional SAR imaging with complete circular apertures

    Science.gov (United States)

    Ertin, Emre; Austin, Christian D.; Sharma, Samir; Moses, Randolph L.; Potter, Lee C.

    2007-04-01

    We study circular synthetic aperture radar (CSAR) systems collecting radar backscatter measurements over a complete circular aperture of 360 degrees. This study is motivated by the GOTCHA CSAR data collection experiment conducted by the Air Force Research Laboratory (AFRL). Circular SAR provides wide-angle information about the anisotropic reflectivity of the scattering centers in the scene, and also provides three dimensional information about the location of the scattering centers due to a non planar collection geometry. Three dimensional imaging results with single pass circular SAR data reveals that the 3D resolution of the system is poor due to the limited persistence of the reflectors in the scene. We present results on polarimetric processing of CSAR data and illustrate reasoning of three dimensional shape from multi-view layover using prior information about target scattering mechanisms. Next, we discuss processing of multipass (CSAR) data and present volumetric imaging results with IFSAR and three dimensional backprojection techniques on the GOTCHA data set. We observe that the volumetric imaging with GOTCHA data is degraded by aliasing and high sidelobes due to nonlinear flightpaths and sparse and unequal sampling in elevation. We conclude with a model based technique that resolves target features and enhances the volumetric imagery by extrapolating the phase history data using the estimated model.

  12. Increasing circular synthetic aperture sonar resolution via adapted wave atoms deconvolution.

    Science.gov (United States)

    Pailhas, Yan; Petillot, Yvan; Mulgrew, Bernard

    2017-04-01

    Circular Synthetic Aperture Sonar (CSAS) processing computes coherently Synthetic Aperture Sonar (SAS) data acquired along a circular trajectory. This approach has a number of advantages, in particular it maximises the aperture length of a SAS system, producing very high resolution sonar images. CSAS image reconstruction using back-projection algorithms, however, introduces a dissymmetry in the impulse response, as the imaged point moves away from the centre of the acquisition circle. This paper proposes a sampling scheme for the CSAS image reconstruction which allows every point, within the full field of view of the system, to be considered as the centre of a virtual CSAS acquisition scheme. As a direct consequence of using the proposed resampling scheme, the point spread function (PSF) is uniform for the full CSAS image. Closed form solutions for the CSAS PSF are derived analytically, both in the image and the Fourier domain. The thorough knowledge of the PSF leads naturally to the proposed adapted atom waves basis for CSAS image decomposition. The atom wave deconvolution is successfully applied to simulated data, increasing the image resolution by reducing the PSF energy leakage.

  13. Sound scattering and transmission through a circular cylindrical aperture revisited using the radial polynomials.

    Science.gov (United States)

    Rdzanek, Wojciech P

    2018-03-01

    The problem of sound scattering and transmission through a circular cylindrical aperture in a flat thick rigid wall has been revisited rigorously using the radial polynomials. The acoustic power transmission and back scattering coefficients have been presented in the form of highly convergent hypergeometric series described earlier in the literature for vibrating circular pistons and plates based on the crucial property of the polynomials in terms of the Hankel transform. The problem is solved by using the continuity conditions at both aperture outlets. The complex integrals necessary to satisfy the continuity conditions are expressed as the exact formulas, which makes the final results for the acoustic power coefficients much more accurate than in the case of numerical integration. A significant improvement has also been reached in numerical efficiency. On average, the calculations are 500 times more efficient compared to numerical integration with no accuracy loss. Additionally, the acoustic pressure on the aperture outlets has been presented exactly in the form of a highly convergent hypergeometric series as well as using the modal impedance coefficients.

  14. 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

  15. 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...

  16. Vertical Force-deflection Characteristics of a Pair of 56-inch-diameter Aircraft Tires from Static and Drop Tests with and Without Prerotation

    Science.gov (United States)

    Smiley, Robert F; Horne, Walter B

    1957-01-01

    The vertical force-deflection characteristics were experimentally determined for a pair of 56-inch-diameter tires under static and drop-test conditions with and without prerotation. For increasing force, the tires were found to be least stiff for static tests, almost the same as for the static case for prerotation drop tests as long as the tires remain rotating, and appreciably stiffer for drop tests without prerotation.

  17. Polarization-dependent atomic dipole traps behind a circular aperture for neutral-atom quantum computing

    International Nuclear Information System (INIS)

    Gillen-Christandl, Katharina; Copsey, Bert D.

    2011-01-01

    The neutral-atom quantum computing community has successfully implemented almost all necessary steps for constructing a neutral-atom quantum computer. We present computational results of a study aimed at solving the remaining problem of creating a quantum memory with individually addressable sites for quantum computing. The basis of this quantum memory is the diffraction pattern formed by laser light incident on a circular aperture. Very close to the aperture, the diffraction pattern has localized bright and dark spots that can serve as red-detuned or blue-detuned atomic dipole traps. These traps are suitable for quantum computing even for moderate laser powers. In particular, for moderate laser intensities (∼100 W/cm 2 ) and comparatively small detunings (∼1000-10 000 linewidths), trap depths of ∼1 mK and trap frequencies of several to tens of kilohertz are achieved. Our results indicate that these dipole traps can be moved by tilting the incident laser beams without significantly changing the trap properties. We also explored the polarization dependence of these dipole traps. We developed a code that calculates the trapping potential energy for any magnetic substate of any hyperfine ground state of any alkali-metal atom for any laser detuning much smaller than the fine-structure splitting for any given electric field distribution. We describe details of our calculations and include a summary of different notations and conventions for the reduced matrix element and how to convert it to SI units. We applied this code to these traps and found a method for bringing two traps together and apart controllably without expelling the atoms from the trap and without significant tunneling probability between the traps. This approach can be scaled up to a two-dimensional array of many pinholes, forming a quantum memory with single-site addressability, in which pairs of atoms can be brought together and apart for two-qubit gates for quantum computing.

  18. Far-field divergence of a vectorial plane wave diffracted by a circular aperture from the vectorial structure

    International Nuclear Information System (INIS)

    Zhou Guo-Quan

    2011-01-01

    Based on the vectorial structure of an electromagnetic wave, the analytical and concise expressions for the TE and TM terms of a vectorial plane wave diffracted by a circular aperture are derived in the far-field. The expressions of the energy flux distributions of the TE term, the TM term and the diffracted plane wave are also presented. The ratios of the power of the TE and TM terms to that of the diffracted plane wave are examined in the far-field. In addition, the far-field divergence angles of the TE term, the TM term and the diffracted plane wave, which are related to the energy flux distribution, are investigated. The different energy flux distributions of the TE and TM terms result in the discrepancy of their divergence angles. The influences of the linearly polarized angle and the radius of the circular aperture on the far-field divergence angles of the TE term, the TM term and the diffracted plane wave are discussed in detail. This research may promote the recognition of the optical propagation through a circular aperture. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  19. Experimental and numerical approach on fracture behaviour of four inches diameter carbon-manganese cracked welded pipes in four point bending

    International Nuclear Information System (INIS)

    Semete, P.; Faidy, C.; Lautier, J.L.

    2001-01-01

    EDF has conducted a research programme to demonstrate the fracture resistance of carbon-manganese welded pipes. The main task of this programme consisted of testing three four inches diameter (114.3 mm O.D.) thin welded pipes (8.56 mm thick) which are representative of those of the sites. The three pipes were loaded under four point bending at a quasi-static rate at -20 C till their maximum bending moment was reached. This paper presents the experimental results, finite element calculations and their comparison with the simplified fracture assessment method of the RSE-M Code. (author)

  20. Ductile fracture behavior of 6-inch diameter type 304 stainless steel and STS 42 carbon steel piping containing a through-wall or part-through crack

    International Nuclear Information System (INIS)

    Shibata, Katsuyuki; Ohba, Toshihiro; Kawamura, Takaichi; Miyazono, Shohachiro; Kaneko, Tadashi; Yokoyama, Norio.

    1986-05-01

    The double ended guillotine break philosophy in the design base accident of the nuclear power plant is considered to be overly conservative from the view point of piping design. Through the past experiences and developments of the fabrication, inspection, and operation of nuclear power plants, it has been recognized that the Leak-Before-Break (LBB) concept can be justified in the LWR pressure boundary pipings. In order to verify the LBB concept, extensive experimental and theoretical works are being conducted in many countries. Furthermore, a revised piping design standard, in which LBB concept is introduced, is under preparation in Japan, U.S.A., and European countries. At JAERI, a research program to investigate the unstable ductile fracture behavior of LWR piping under bending load has been carried out as a part of the LBB verification researches since 1983. This report summarizes the result of the ductile fracture tests conducted at room temperature in 1983 and 84. The 6-inch diameter pipes of type 304 stainless steel and STS 42 carbon steel pipe with a through-wall or part-through crack were tested under bending load with low or high compliance condition at room temperature. Pipe fracture data were obtained from the test as regards to load- displacement curve, crack extension, net section stress, J-resistance curve, and so on. Besides, the influence of the compliance on the fracture behavior was examined. Discussions are performed on the ductile pipe fracture criterion, flaw evaluation criterion, and LBB evaluation method. (author)

  1. Efficient twin aperture magnets for the future circular $e^+/e^- $ collider

    CERN Document Server

    AUTHOR|(CDS)2078698

    2016-01-01

    We report preliminary designs for the arc dipoles and quadrupoles of the FCC-ee double-ring collider. After recalling cross sections and parameters of warm magnets used in previous large accelerators, we focus on twin aperture layouts, with a magnetic coupling between the gaps, which minimizes construction cost and reduces the electrical power required for operation. We also indicate how the designs presented may be further optimized so as to optimally address any further constraints related to beam physics, vacuum system, and electric power consumption.

  2. A rail system for circular synthetic aperture sonar imaging and acoustic target strength measurements: design/operation/preliminary results.

    Science.gov (United States)

    Kennedy, J L; Marston, T M; Lee, K; Lopes, J L; Lim, R

    2014-01-01

    A 22 m diameter circular rail, outfitted with a mobile sonar tower trolley, was designed, fabricated, instrumented with underwater acoustic transducers, and assembled on a 1.5 m thick sand layer at the bottom of a large freshwater pool to carry out sonar design and target scattering response studies. The mobile sonar tower translates along the rail via a drive motor controlled by customized LabVIEW software. The rail system is modular and assembly consists of separately deploying eight circular arc sections, measuring a nominal center radius of 11 m and 8.64 m arc length each, and having divers connect them together in the underwater environment. The system enables full scale measurements on targets of interest with 0.1° angular resolution over a complete 360° aperture, without disrupting target setup, and affording a level of control over target environment conditions and noise sources unachievable in standard field measurements. In recent use, the mobile cart carrying an instrumented sonar tower was translated along the rail in 720 equal position increments and acoustic backscatter data were acquired at each position. In addition, this system can accommodate both broadband monostatic and bistatic scattering measurements on targets of interest, allowing capture of target signature phenomena under diverse configurations to address current scientific and technical issues encountered in mine countermeasure and unexploded ordnance applications. In the work discussed here, the circular rail apparatus is used for acoustic backscatter testing, but this system also has the capacity to facilitate the acquisition of magnetic and optical sensor data from targets of interest. A brief description of the system design and operation will be presented along with preliminary processed results for data acquired from acoustic measurements conducted at the Naval Surface Warfare Center, Panama City Division Test Pond Facility. [Work Supported by the U.S. Office of Naval Research and

  3. CIRCULARLY POLARIZED SLOTTED APERTURE ANTENNA WITH COPLANAR WAVEGUIDE FED FOR BROADBAND APPLICATIONS

    Directory of Open Access Journals (Sweden)

    B. T. P. MADHAV

    2016-02-01

    Full Text Available Coplanar waveguide fed circularly polarized microstrip patch antenna performance evaluation is presented in this paper. The broadband characteristics are attained by placing open end slot at the lower side of the antenna. The proposed design has the return loss of less than -10dB and VSWR<2 in the desired band of operation. A gain of 3dB to 4dB is attained in the desired band with good radiation characteristics and a suitable axial ratio of less than 3 dB is attained in the prescribed band of operation. Proposed antenna is fabricated on the FR4 substrate with dielectric constant of 4.4. Parametric analysis with change in substrate permittivity also performed and the optimized dimensions are presented in this work.

  4. Approximate analytical method to evaluate diffraction crosstalk in free-space optical interconnects systems that use circular microlenses with finite uniform apertures

    Science.gov (United States)

    Al-Ababneh, Nedal

    2014-07-01

    We propose an accurate analytical model to calculate the optical crosstalk of a first-order free space optical interconnects system that uses microlenses with circular apertures. The proposed model is derived by evaluating the resulted finite integral in terms of an infinite series of Bessel functions. Compared to the model that uses complex Gaussian functions to expand the aperture function, it is shown that the proposed model is superior in estimating the crosstalk and provides more accurate results. Moreover, it is shown that the proposed model gives results close to that of the numerical model with superior computational efficiency.

  5. Propagation of Single-Mode Fibre Laser Beams through an Optical ABCD System with Circular Aperture at the Fibre Output End

    International Nuclear Information System (INIS)

    Kai-Liang, Duan; Jian-Feng, Li; Wei, Zhao; Yi-Shan, Wang

    2008-01-01

    Based on the expansion expression of the fundamental mode of a single-mode fibre in terms of Laguerre–Gauss modes, the propagation of a beam of a weakly guiding fibre laser through an optical ABCD system with a circular aperture at the fibre end is studied. The results show that there is much difference between the propagation of the laser beam described by the expansion expression and by the Gaussian mode approximation. The depth of focus of the laser beam is longer than that of the Gaussian modes

  6. Test Report for MSFC Test No. 83-2: Pressure scaled water impact test of a 12.5 inch diameter model of the Space Shuttle solid rocket booster filament wound case and external TVC PCD

    Science.gov (United States)

    1983-01-01

    Water impact tests using a 12.5 inch diameter model representing a 8.56 percent scale of the Space Shuttle Solid Rocket Booster configuration were conducted. The two primary objectives of this SRB scale model water impact test program were: 1. Obtain cavity collapse applied pressure distributions for the 8.56 percent rigid body scale model FWC pressure magnitudes as a function of full-scale initial impact conditions at vertical velocities from 65 to 85 ft/sec, horizontal velocities from 0 to 45 ft/sec, and angles from -10 to +10 degrees. 2. Obtain rigid body applied pressures on the TVC pod and aft skirt internal stiffener rings at initial impact and cavity collapse loading events. In addition, nozzle loads were measured. Full scale vertical velocities of 65 to 85 ft/sec, horizontal velocities of 0 to 45 ft/sec, and impact angles from -10 to +10 degrees simulated.

  7. Antennas on circular cylinders

    DEFF Research Database (Denmark)

    Knudsen, H. L.

    1959-01-01

    On the basis of the results obtained by Silver and Saunders [4] for the field radiated from an arbitrary slot in a perfectly conducting circular cylinder, expressions have been derived for the field radiated by a narrow helical slot, with an arbitrary aperture field distribution, in a circular...... antenna in a circular cylinder. By a procedure similar to the one used by Silver and Saunders, expressions have been derived for the field radiated from an arbitrary surface current distribution on a cylinder surface coaxial with a perfectly conducting cylinder. The cases where the space between the two...

  8. Nanolithography using nanoscale ridge apertures

    Science.gov (United States)

    Wang, Liang

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

  9. Administrative Circulars

    CERN Multimedia

    Département des Ressources humaines

    2004-01-01

    Administrative Circular N° 2 (Rev. 2) - May 2004 Guidelines and procedures concerning recruitment and probation period of staff members This circular has been revised. It cancels and replaces Administrative Circular N° 2 (Rev. 1) - March 2000. Administrative Circular N° 9 (Rev. 3) - May 2004 Staff members contracts This circular has been revised. It cancels and replaces Administrative Circular N° 9 (Rev. 2) - March 2000. Administrative Circular N° 26 (Rev. 4) - May 2004 Procedure governing the career evolution of staff members This circular has also been revised. It Administrative Circulars Administrative Circular N° 26 (Rev. 3) - December 2001 and brings up to date the French version (Rev. 4) published on the HR Department Web site in January 2004. Operational Circular N° 7 - May 2004 Work from home This circular has been drawn up. Operational Circular N° 8 - May 2004 Dealing with alcohol-related problems...

  10. Revolutionary Astrophysics using an Incoherent Synthetic Optical Aperture

    Science.gov (United States)

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

    2018-01-01

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

  11. Apodised aperture assembly for high power lasers

    International Nuclear Information System (INIS)

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

    1975-01-01

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

  12. Information Circulars

    International Nuclear Information System (INIS)

    1969-01-01

    Information circulars are published from time to time under the symbol INFCIRC/. . . . for the purpose of bringing matters of general interest to the attention of all Members of the Agency. A list of the circulars which were of current interest on 15 January 1969 is given below, followed by an index to their subject matter. Other circulars can be traced by reference to earlier issues of the present document.

  13. Information Circulars

    International Nuclear Information System (INIS)

    1965-01-01

    Information circulars are published from time to time under the symbol INFCIRC/. for the purpose of bringing matters of general interest to the attention of all Members of the Agency. A list of the circulars that were current on 31 December 1964 is given, followed by an index to their subject matter.

  14. Information circulars

    International Nuclear Information System (INIS)

    1997-02-01

    The document summarizes the Information Circulars published by the IAEA for the purpose of bringing matters of general interest to the attention of all Member States. This revision contains INFCIRCs published up to February 1997, grouped by field of activity. A complete list of information circulars in numerical order is given in an annex

  15. Information circulars

    International Nuclear Information System (INIS)

    1992-08-01

    The document summarizes the Information Circulars published by the IAEA for the purpose of bringing matters of general interest to the attention of all Members of the Agency. This revision contains INFCIRCs published up to mid-August 1992. A complete numerical lift of Information Circulars with their titles is reproduced in an Annex

  16. Information circulars

    International Nuclear Information System (INIS)

    1999-06-01

    The document summarizes the Information Circulars published by the IAEA for the purpose of bringing matters of general interest to the attention of all Member States. This revision contains INFCIRCs published up to the end of May 1999, grouped by field of activity. A complete list of information circulars in numerical order is given in an annex

  17. Information circulars

    International Nuclear Information System (INIS)

    1994-08-01

    Information circulars are published from time to time under the symbol INFCIRC/... for the purpose of bringing matters of general interest to the attention of all Members of the Agency. The present revision contains INFCIRCs published up to mid-August 1994. A complete numerical list of information circulars is reproduced with their titles in the Annex

  18. Information Circulars

    International Nuclear Information System (INIS)

    1966-01-01

    Information circulars are published from time to time under the symbol INFCIRC/. . . . for the purpose of bringing matters of general interest to the attention of all Members of the Agency. A list of the circulars that were current or on the press on 15 May 1966 is given, followed by an index to their subject matter.

  19. Information circulars

    International Nuclear Information System (INIS)

    2002-05-01

    Information circulars are published from time to time under the symbol INFCIRC/... for the purpose of bringing matters of general interest to the attention of all Members of the Agency. The present revision contains INFCIRCs published up to the end of April 2002. A complete numerical list of information circulars is reproduced with their titles in the Annex

  20. Information Circulars

    International Nuclear Information System (INIS)

    1973-01-01

    Information circulars are published from time to time under the symbol INFCIRC/.. for the purpose of bringing matters of general interest to the attention of all Members of the Agency. A subject index to the circulars is presented overleaf. It covers all those published in the last five years (that is, since the beginning of 1968 and ending with INFCIRC/192), as well as others which, for one reason or another, are still considered to be of current rather than merely historical interest. Such circulars can be traced by reference to the indexes that were included in earlier revisions of the present document.

  1. Circular Updates

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Circular Updates are periodic sequentially numbered instructions to debriefing staff and observers informing them of changes or additions to scientific and specimen...

  2. Information circulars

    International Nuclear Information System (INIS)

    1987-06-01

    The document summarizes the information circulars published by the IAEA for the purpose of bringing matters of general interest to the attention of all Members of the Agency. In the main body of the document only those documents which are regarded as likely to be of current interest are listed. A complete numerical list of information circulars with their titles is reproduced in the Annex

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

    International Nuclear Information System (INIS)

    Cai Yangjian; Ge Di

    2006-01-01

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

  4. Operational Circulars

    CERN Multimedia

    2003-01-01

    Operational Circular N° 4 - April 2003 Conditions for use by members of the CERN personnel of vehicles belonging to or rented by CERN - This circular has been drawn up. Operational Circular N° 5 - October 2000 Use of CERN computing facilities - Further details on the personal use of CERN computing facilities Operational Circular N° 5 and its Subsidiary Rules http://cern.ch/ComputingRules defines the rules for the use of CERN computing facilities. One of the basic principles governing such use is that it must come within the professional duties of the user concerned, as defined by the user's divisional hierarchy. However, personal use of the computing facilities is tolerated or allowed provided : a) It is in compliance with Operational Circular N° 5 and not detrimental to official duties, including those of other users; b) the frequency and duration is limited and there is a negligible use of CERN resources; c) it does not constitute a political, commercial and/or profit-making activity; d) it is not...

  5. Information circulars

    International Nuclear Information System (INIS)

    1989-04-01

    The document summarizes the Information Circulars published by the IAEA under the symbol INFCIRC/ for the purpose of bringing matters of general interest to the attention of all Members of the Agency. A complete list of INFCIRCs in numerical order with their titles is given in the Annex

  6. Circular RNAs

    DEFF Research Database (Denmark)

    Han, Yi-Neng; Xia, Shengqiang; Zhang, Yuan-Yuan

    2017-01-01

    Circular RNAs (circRNAs) are a novel type of universal and diverse endogenous noncoding RNAs (ncRNAs) and they form a covalently closed continuous loop without 5' or 3' tails unlike linear RNAs. Most circRNAs are presented with characteristics of abundance, stability, conservatism, and often exhi...... and expression regulators, RBP sponges in cancer as well as current research methods of circRNAs, providing evidence for the significance of circRNAs in cancer diagnosis and clinical treatment....

  7. Quantum synthetic aperture radar

    Science.gov (United States)

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

    2017-05-01

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

  8. 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

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

    Science.gov (United States)

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

    2014-07-01

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

  10. 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.

  11. Hydraulic study of drilling fluid flow in circular and annular tubes

    Energy Technology Data Exchange (ETDEWEB)

    Scheid, C.M.; Calcada, L.A.; Braga, E.R.; Paraiso, E.C.H. [Universidade Federal Rural do Rio de Janeiro (PPGEQ/UFRRJ), Seropedica, RJ (Brazil). Programa de Pos-Graduacao em Engenharia Quimica. Dept. de Engenharia Qumica], E-mail: calcada@ufrrj.br; Martins, A. L. [Petroleo Brasileiro S.A. (CENPES/PETROBRAS), Rio de Janeiro, RJ (Brazil). Centro de Pesquisas

    2011-10-15

    This study investigates the drilling fluid flow behavior of two water-based drilling fluids in circular and annular tubes. The study has four main objectives: 1) to evaluate correlations between the Power Law and the Casson rheological models, 2) to characterize the flow behavior, 3) to evaluate five hydraulic-diameter equations, and 4) to evaluate the correlations of five turbulent flow-friction factors. The experimental fluid flow loop consisted of one positive displacement pump of 25 HP connected to a 500-liter tank agitated by a 3-HP mixer. The fluids passed through six meters long tubes, arranged in three horizontal rows with independent inlets and outlets. The circular tubes had a 1 inch diameter and were configured as two concentric annular tubes. Annular Tube I had an outer diameter of 1 1/4 inch and an inner diameter of 1/2 inch. Annular Tube II had an outer diameter of 2 inches and an inner diameter of 3/4 inch. The results show that, for the fluids in exam, correlations proposed in the literature were inaccurate as far as predicting hydraulic diameter, estimating pressure drop, and defining the flow regime. In general, the performance of those correlations depended on the fluid properties and on the system's geometry. Finally, literature parameters for some of the correlations were estimated for the two drilling fluids studied. These estimations improved the predictive capacity of calculating the friction factor for real drilling fluids applications for both circular and annular tubes. (author)

  12. Test report on experimental stress analysis of a 24 inch diameter tee (ORNL T-13)

    International Nuclear Information System (INIS)

    Henley, D.R.

    1975-03-01

    The experimental stress analysis and low cycle fatigue test of one 24 in. x 24 in. x 10 in. schedule 160 carbon steel, ANSI B16.9 tee performed by Combustion Engineering, Inc. are described. The tee was instrumented with 230 rectangular strain gage rosettes. Elastic data was obtained for 12 loading conditions consisting of internal pressure and orthogonal pure moments and orthogonal direct forces applied individually to the free branch and run ends of the tee. One of the run ends of the tee was ''built in'' throughout the test. All loads were applied through pipe extensions welded to the tee. The tee was tested to failure in a low cycle pressure fatigue test with a cyclic internal pressure between 100 psi and 7000 psi. A through-the-wall fatigue crack occurred at 15,084 cycles. Significant test results are summarized and compared with design values tabulated in the ASME Boiler and Pressure Vessel Code, Section III, 1971. (U.S.)

  13. Project W320 52-inch diameter equipment container load test: Test report

    International Nuclear Information System (INIS)

    Bellomy, J.R.

    1995-01-01

    This test report summarizes testing activities and documents the results of the load tests performed on-site and off-site to structural qualify the 52-inch equipment containers designed and fabricated under Project W-320

  14. Synthetic Aperture Sequential Beamforming

    DEFF Research Database (Denmark)

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

    2008-01-01

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

  15. Optical synthetic aperture radar

    Science.gov (United States)

    Ilovitsh, Asaf; Zach, Shlomo; Zalevsky, Zeev

    2013-06-01

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

  16. Analytical formula for a circular flattened Gaussian beam propagating through a misaligned paraxial ABCD optical system

    International Nuclear Information System (INIS)

    Hu Li; Cai Yangjian

    2006-01-01

    Based on the generalized diffraction integral formula for treating the propagation of a laser beam through a misaligned paraxial ABCD optical system in the cylindrical coordinate system, analytical formula for a circular flattened Gaussian beam propagating through such optical system is derived. Furthermore, an approximate analytical formula is derived for a circular flattened Gaussian beam propagating through an apertured misaligned ABCD optical system by expanding the hard aperture function as a finite sum of complex Gaussian functions. Numerical examples are given

  17. Survey of coded aperture imaging

    International Nuclear Information System (INIS)

    Barrett, H.H.

    1975-01-01

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

  18. Congenital pyriform aperture stenosis

    International Nuclear Information System (INIS)

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

    2007-01-01

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

  19. Aperture center energy showcase

    Energy Technology Data Exchange (ETDEWEB)

    Torres, J. J.

    2012-03-01

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

  20. Black silicon integrated aperture

    Science.gov (United States)

    Liu, Tianbo; Dickensheets, David L.

    2017-10-01

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

  1. 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.)

  2. Integrated electrochromic aperture diaphragm

    Science.gov (United States)

    Deutschmann, T.; Oesterschulze, E.

    2014-05-01

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

  3. Charged Particle Optics in Circular Higgs Factory

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Yunhai [SLAC National Accelerator Lab., Menlo Park, CA (United States)

    2015-02-26

    Similar to a super B-factory, a circular Higgs factory will require strong focusing systems near the interaction points and a low-emittance lattice in arcs to achieve a factory luminosity. At electron beam energy of 120 GeV, beamstrahlung effects during the collision pose an additional challenge to the collider design. In particular, a large momentum acceptance at 2 percent level is necessary to retain an adequate beam lifetime. This turns out to be the most challenging aspect in the design of circular Higgs factory. In this paper, an example will be provided to illustrate the beam dynamics in circular Higgs factory, emphasizing on the chromatic optics. Basic optical modules and advanced analysis will be presented. Most important, we will show that 2% momentum aperture is achievable

  4. Novel large aperture EBCCD

    Science.gov (United States)

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

    2011-02-01

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

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

    Science.gov (United States)

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

    2015-10-01

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

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

    International Nuclear Information System (INIS)

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

    2014-01-01

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

  7. Circular polarisation in AGN

    NARCIS (Netherlands)

    Macquart, JP

    2002-01-01

    We discuss the constraints that recent observations place on circular polarisation in AGN. In many sources the circular polarisation is variable on short timescales, indicating that it originates in compact regions of the sources. The best prospects for gleaning further information about circular

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

    Science.gov (United States)

    Hasan, Sundus Y; Shaker, Ali S

    2012-12-10

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

  9. Administrative Circulars Rev.

    CERN Multimedia

    2003-01-01

    Administrative Circular N° 19 (Rev. 3) - April 2003 Subsistence indemnity - Other expenses necessarily incurred in the course of duty travelAdministrative Circular N° 25 (Rev. 2) - April 2003 Shift work - Special provisions for the Fire and Rescue Service - These circulars have been revised. Human Resources Division Tel. 74128Copies of these circulars are available in the Divisional Secretariats. In addition, administrative and operational circulars, as well as the lists of those in force, are available for consultation on the Web at: http://humanresources.web.cern.ch/humanresources/internal/admin_services/admincirc/listadmincirc.asp

  10. Rotatable Aperture Coronagraph for Exoplanetary Studies (RACES)

    Science.gov (United States)

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

    2018-01-01

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

  11. Aperture referral in dioptric systems with stigmatic elements

    Directory of Open Access Journals (Sweden)

    W. F. Harris

    2012-12-01

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

  12. Circular SAR Optimization Imaging Method of Buildings

    Directory of Open Access Journals (Sweden)

    Wang Jian-feng

    2015-12-01

    Full Text Available The Circular Synthetic Aperture Radar (CSAR can obtain the entire scattering properties of targets because of its great ability of 360° observation. In this study, an optimal orientation of the CSAR imaging algorithm of buildings is proposed by applying a combination of coherent and incoherent processing techniques. FEKO software is used to construct the electromagnetic scattering modes and simulate the radar echo. The FEKO imaging results are compared with the isotropic scattering results. On comparison, the optimal azimuth coherent accumulation angle of CSAR imaging of buildings is obtained. Practically, the scattering directions of buildings are unknown; therefore, we divide the 360° echo of CSAR into many overlapped and few angle echoes corresponding to the sub-aperture and then perform an imaging procedure on each sub-aperture. Sub-aperture imaging results are applied to obtain the all-around image using incoherent fusion techniques. The polarimetry decomposition method is used to decompose the all-around image and further retrieve the edge information of buildings successfully. The proposed method is validated with P-band airborne CSAR data from Sichuan, China.

  13. Diagnostic for dynamic aperture

    Energy Technology Data Exchange (ETDEWEB)

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

    1985-04-01

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

  14. Synthetic Aperture Compound Imaging

    DEFF Research Database (Denmark)

    Hansen, Jens Munk

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

  15. 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,...

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

    DEFF Research Database (Denmark)

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

    1976-01-01

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

  17. Publication of administrative circular

    CERN Multimedia

    HR Department

    2009-01-01

    ADMINISTRATIVE CIRCULAR NO. 23 (REV. 2) – SPECIAL WORKING HOURS Administrative Circular No. 23 (Rev. 2) entitled "Special working hours", approved following discussion in the Standing Concertation Committee on 9 December 2008, will be available on the intranet site of the Human Resources Department as from 19 December 2008: http://cern.ch/hr-docs/admincirc/admincirc.asp It cancels and replaces Administrative Circular No. 23 (Rev. 1) entitled "Stand-by duty" of April 1988. A "Frequently Asked Questions" information document on special working hours will also be available on this site. Paper copies of this circular will shortly be available in Departmental Secretariats. Human Resources Department Tel. 78003

  18. PUBLICATION OF ADMINISTRATIVE CIRCULAR

    CERN Multimedia

    HR Department

    2008-01-01

    ADMINISTRATIVE CIRCULAR NO. 23 (REV. 2) – SPECIAL WORKING HOURS Administrative Circular No. 23 (Rev. 2) entitled "Special working hours", approved following discussion in the Standing Concertation Committee meeting of 9 December 2008, will be available on the intranet site of the Human Resources Department as from 19 December 2008: http://cern.ch/hr-docs/admincirc/admincirc.asp It cancels and replaces Administrative Circular No. 23 (Rev. 1) entitled "Stand-by duty" of April 1988. A "Frequently Asked Questions" information document on special working hours will also be available on this site. Paper copies of this circular will shortly be available in departmental secretariats. Human Resources Department Tel. 78003

  19. Coded aperture tomography revisited

    International Nuclear Information System (INIS)

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

    1983-01-01

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

  20. Bistatic synthetic aperture radar

    Science.gov (United States)

    Yates, Gillian

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

  1. Towards Circular Economy

    DEFF Research Database (Denmark)

    Guldmann, Eva

    The present report concerns the practical process of developing initiatives based on the circular economy in eight Danish companies. The report outlines how the process of integrating the circular economy was approached in each of the participating companies during 2014 and 2015 and what came out...

  2. Towards Circular Business Models

    DEFF Research Database (Denmark)

    Guldmann, Eva; Remmen, Arne

    The present report concerns the practical process of developing initiatives based on the circular economy in eight Danish companies. The report outlines how the process of integrating the circular economy was approached in each of the participating companies during 2014 and 2015 and what came out...

  3. The generalized circular model

    NARCIS (Netherlands)

    Webers, H.M.

    1995-01-01

    In this paper we present a generalization of the circular model. In this model there are two concentric circular markets, which enables us to study two types of markets simultaneously. There are switching costs involved for moving from one circle to the other circle, which can also be thought of as

  4. Circularity and Lambda Abstraction

    DEFF Research Database (Denmark)

    Danvy, Olivier; Thiemann, Peter; Zerny, Ian

    2013-01-01

    unknowns from what is done to them, which we lambda-abstract with functions. The circular unknowns then become dead variables, which we eliminate. The result is a strict circu- lar program a la Pettorossi. This transformation is reversible: given a strict circular program a la Pettorossi, we introduce...

  5. Tissue Harmonic Synthetic Aperture Imaging

    DEFF Research Database (Denmark)

    Rasmussen, Joachim

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

  6. Compounding in synthetic aperture imaging

    DEFF Research Database (Denmark)

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

    2012-01-01

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

  7. Large aperture optical switching devices

    International Nuclear Information System (INIS)

    Goldhar, J.; Henesian, M.A.

    1983-01-01

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

  8. Building a Circular Future

    DEFF Research Database (Denmark)

    Merrild, Heidi

    2016-01-01

    Natural resources are scarce and construction accounts for 40 percent of the material and energy consumption in Europe. This means that a switch to a circular future is necessary. ’Building a Circular Future’ maps out where we are, where we are going, and what is needed for this conversion to take...... of the circular strategies is not only in the future. Increased flexibility, optimized operation and maintenance, as well as a healthier building, is low-hanging fruit that can be harvested today. The project’s principles can be implemented in industrialized construction in a large scale today. That is proven...... by the three 1:1 prototypes of building elements, which are designed for maximum reuse and circular economy, that has been developed as a result of the project. Several built projects and commercially available products support this assertion. CIRCULAR PRINCIPLES The focus throughout the book is how to build...

  9. Circular differential microscopy

    International Nuclear Information System (INIS)

    Maestre, M.F.; Bustamante, C.; Keller, D.

    1985-01-01

    The authors describe the historical development of the theory of differential imaging and the invention of the circular differential imaging microscope. The technique is shown to be a logical extension of the research on the interaction of circularly polarized light with stuctures whose dimensions are arbitrary with respect to the wavelength of light. Shown is the circular dichroism spectra in arbitrary units of E. cirrhosa sperm heads, measured by techniques with different collection angles of scattered light. Also presented is a scanning electron micrograph of a freexe-dried sperm head from E. cirrhosa. It was shown that circular differential scattering is specially sensitive to the dimensions of the structure close to the wavelength of the incident light, and application of circular intensity differential scattering theory to images extend these results

  10. Phase Radiation Characteristics of an Open-Ended Circular Waveguide

    DEFF Research Database (Denmark)

    Shishkova, A.V.; Pivnenko, Sergiy; Kim, O.S.

    2002-01-01

    Analytic expressions for phase radiation characteristics of a semi-infinite open-ended circular waveguide regardless of its aperture size and operating frequency have been obtained making use of the rigorous Weinstein's theory. The analysis of phase radiation patterns has been carried out...... for the dominant mode (TE11) as well as for the high order modes TM01 and TE01, both for a single and multimode propagation. The measurement of radiation characteristics of an open-ended circular waveguide has been carried out at the DTU-ESA Spherical Near-Field Antenna Test Facility. It is shown...

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

    Science.gov (United States)

    Olcen, Ahmet Burak

    these parameters are the same. The method is applicable for arbitrary sized apertures and cavities. However due to limited computing resources, only problems in the resonance region, where dimensions are comparable to wavelength, are considered here. Computed results are given for the case of two square apertures connected by a square prism, two cross apertures connected by a square prism cavity, two circular apertures connected by a cylindrical cavity, and finally two circular apertures connected by a conical cavity. Our computed results are compared with results in the literature obtained by using other methods. Very good agreement is observed.

  12. Administrative & Operational Circulars - Reminder

    CERN Document Server

    HR Department

    2011-01-01

    All Administrative and Operational Circulars are available on the intranet site of the Human Resources Department at the following address: http://cern.ch/hr-docs/admincirc/admincirc.asp Department Head Office  

  13. The Circular Camera Movement

    DEFF Research Database (Denmark)

    Hansen, Lennard Højbjerg

    2014-01-01

    It has been an accepted precept in film theory that specific stylistic features do not express specific content. Nevertheless, it is possible to find many examples in the history of film in which stylistic features do express specific content: for instance, the circular camera movement is used re...... such as the circular camera movement. Keywords: embodied perception, embodied style, explicit narration, interpretation, style pattern, television style...

  14. Investigation of novel fractal shape of the nano-aperture as a metasurface for bio sensing application

    Energy Technology Data Exchange (ETDEWEB)

    Heydari, Samaneh [Sama Technical and Vocational Training College, Islamic Azad University, Isfahan Branch, Khorasgan (Iran, Islamic Republic of); Rastan, Iman; Parvin, Amin [Faculty of Eng., Science and Research Branch, Islamic Azad University, Shiraz (Iran, Islamic Republic of); Pirooj, Azadeh [Faculty of Eng., Science and Research Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of); Zarrabi, Ferdows B., E-mail: ferdows.zarrabi@yahoo.com [Young Researchers and Elite Club, Babol Branch, Islamic Azad University, Babol (Iran, Islamic Republic of)

    2017-01-23

    Recently, nano-aperture is noticed due to its good transmission in the optical regime. Also, the nano-apertures are developed at the metasurface design for circular polarization; for this aim, various shapes of the nano-aperture are suggested. To reach this objective, we have developed a novel Jerusalem cross fractal shape for a mid-infrared application. We have simulated various formations of the nano-fractal Jerusalem cross based on a simple cross to show the effect of nano-aperture shape on electrical field enhancement in the near-field which is important in spectroscopy and optical imaging. In addition, we have used a single layer graphene over the aperture as a coat for making reconfigurable characteristic also creating a membrane for placement of nano-particle over the aperture. Implementation of the graphene is an amendment to the transfer of the nano-apertures. The biological materials with a thickness of 80 nm have been placed over the graphene layer and the Figures of Merits (FOM) have been obtained. Additionally, the prototype of nano-antenna is independent from incident wave polarization. The Finite Difference Time Domain (FDTD) calculations have been implemented in the simulation and modeling the nano-apertures. - Highlights: • Nano-apertures are developed at the metasurface design for circular polarization. • We have developed a novel Jerusalem cross fractal shape for a mid-infrared application. • Effect of nano-aperture shape on near-field enhancement is noticed which is important in spectroscopy and optical imaging. • Single layer graphene over the aperture as a coat for making reconfigurable characteristic.

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

    Science.gov (United States)

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

    2018-04-01

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

  16. Future of synthetic aperture radar

    Science.gov (United States)

    Barath, F. T.

    1978-01-01

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

  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. Aperture-based antihydrogen gravity experiment: Parallel plate geometry

    Directory of Open Access Journals (Sweden)

    J. R. Rocha

    2013-10-01

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

  20. Pressure scaled water impact test of a 12.5 inch diameter model of the Space Shuttle solid rocket booster

    Science.gov (United States)

    1982-01-01

    A total of 59 tail first drops were made. Model entry conditions simulated full scale vertical velocities of approximately 75 to 110 ft/sec with horizontal velocities up to 45 ft/sec and impact angles to + or - 10 deg. These tests were conducted at scaled atmospheric pressures (1.26 psia or 65 mm.Hg). The model, test program, test facility, test equipment, instrumentation system, data reduction procedures, and test results are described.

  1. The effects of Earth's magnetic field on 3-inch diameter photomultipliers used in KM3NeT neutrino telescope

    Science.gov (United States)

    Giordano, V.; Aiello, S.; Leonora, E.; Randazzo, N.

    2016-04-01

    The KM3NeT neutrino telescope will be the largest underwater neutrino telescope and will be located in the abyss of the Mediterranean Sea. In neutrino telescopes the key element of the detector is the optical module and for KM3NeT it consists of 31 PMTs stored inside a transparent pressure-resistant glass sphere of 17-inch that serves as mechanical protection while ensuring good light transmission. Since the PMTs installed into an underwater neutrino telescope can change their orientation because of movements of the detector structure due to sea currents, the influence of Earth's magnetic field has been investigated. Magnetic shielding by means of a mu-metal cage is used to reduce magnetic effects and to make the response of the PMT sufficiently orientation independent. In order to quantify the effect on magnetic field, we compared measurements on variation of gain, transit time spread and detection efficiency for a 3-inch PMT in shielded and unshielded condition at 3 PMT inclinations. Data shows that variations are sufficiently low especially for timing properties.

  2. A conceptual design of circular Higgs factory

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Yunhai

    2016-11-30

    Similar to a super B-factory, a circular Higgs factory (CHF) will require strong focusing systems near the interaction points and a low-emittance lattice in the arcs to achieve a factory luminosity. At electron beam energy of 125 GeV, beamstrahlung effects during the collision pose an additional challenge to the collider design. In particular, a large momentum acceptance at the 2% level is necessary to retain an adequate beam lifetime. This turns out to be the most challenging aspect in the design of a CHF. In this paper, an example will be provided to illustrate the beam dynamics in a CHF, emphasizing the chromatic optics. Basic optical modules and advanced analysis will be presented. Most importantly, we will show that 2% momentum aperture is achievable.

  3. Transposable elements and circular DNAs

    KAUST Repository

    Mourier, Tobias

    2016-09-26

    Circular DNAs are extra-chromosomal fragments that become circularized by genomic recombination events. We have recently shown that yeast LTR elements generate circular DNAs through recombination events between their flanking long terminal repeats (LTRs). Similarly, circular DNAs can be generated by recombination between LTRs residing at different genomic loci, in which case the circular DNA will contain the intervening sequence. In yeast, this can result in gene copy number variations when circles contain genes and origins of replication. Here, I speculate on the potential and implications of circular DNAs generated through recombination between human transposable elements.

  4. Aperture measurements with AC dipole

    CERN Document Server

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

    2018-01-01

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

  5. Kappa Coefficients for Circular Classifications

    NARCIS (Netherlands)

    Warrens, Matthijs J.; Pratiwi, Bunga C.

    2016-01-01

    Circular classifications are classification scales with categories that exhibit a certain periodicity. Since linear scales have endpoints, the standard weighted kappas used for linear scales are not appropriate for analyzing agreement between two circular classifications. A family of kappa

  6. Circular fringe projection profilometry.

    Science.gov (United States)

    Zhao, Hong; Zhang, Chunwei; Zhou, Changquan; Jiang, Kejian; Fang, Meiqi

    2016-11-01

    In this Letter, a novel three-dimensional (3D) measurement method, called the circular fringe projection profilometry (CFPP), is proposed. Similar to the conventional fringe projection profilometry, CFPP also requires fringe pattern projection and capture, phase demodulation, and phase unwrapping. However, it works with a totally different mechanism. CFPP recovers the height of a point by calculating its distance to the optical center of a projector along the optical axis. This distance is calculated with the aid of the divergence angle of a projected light ray and the distance between the measured point and the optical axis. The distance between the measured point and the optical axis is detected by a camera with telecentric lenses, while the divergence angle can be calculated from the phase of a captured circular fringe pattern. The validity of CFPP is confirmed by a set of experiments.

  7. ADMINISTRATIVE CIRCULAR N° 12

    CERN Multimedia

    Human Resources Division

    2002-01-01

    Following a recommendation by the Standing Concertation Committee, the Director-General has approved the amounts used for the reimbursements mentioned in Administrative Circular N° 12 as follows : The figures, effective from 1 September 2002, are : § 8a : 16 Swiss francs (unchanged) § 9a : 640 Swiss francs (previously 622.- Swiss francs) § 9b : 32 Swiss francs (unchanged) Human Resources Division Tel. 72862

  8. Administrative Circular N° 12

    CERN Document Server

    2003-01-01

    Following a recommendation by the Standing Concertation Committee, the Director-General has approved the amounts used for the reimbursements mentioned in Administrative Circular N° 12 as follows : The figures, effective from 1 September 2003, are : § 8a : 16.50 Swiss francs (previously 16.- Swiss francs) § 9a : 663 Swiss francs (previously 640.- Swiss francs) § 9b : 33 Swiss francs (previously 32.- Swiss francs) Human Resources Division Tel. 72862/74474

  9. ADMINISTRATIVE CIRCULAR N° 12

    CERN Document Server

    HR Division

    2001-01-01

    Following a recommendation by the Standing Concertation Committee, the Director-General has approved an adjustment of the amounts used for the reimbursements mentioned in Administrative Circular N° 12. The new figures, effective from 1 September 2001, are : § 8a : 16 Swiss francs (previously 15.50 Swiss francs) § 9a : 622 Swiss francs (previously 609.- Swiss francs) § 9b : 32 Swiss francs (previously 31.- Swiss francs)

  10. ADMINISTRATIVE CIRCULAR NR 12

    CERN Document Server

    Division HR; HR Division; Tel. 72862

    2000-01-01

    Following a recommendation by the Standing Concertation Committee, the Director-General has approved an adjustment of the amounts used for the reimbursements mentioned in Administrative Circular N° 12. The new figures, effective from 1 September 2000, are : § 8a : 15.50 Swiss francs (previously 15.- Swiss francs) § 9a : 609 Swiss francs (previously 591.- Swiss francs) § 9b : 31 Swiss francs (previously 30.- Swiss francs)

  11. Circular arc structures

    KAUST Repository

    Bo, Pengbo

    2011-07-01

    The most important guiding principle in computational methods for freeform architecture is the balance between cost efficiency on the one hand, and adherence to the design intent on the other. Key issues are the simplicity of supporting and connecting elements as well as repetition of costly parts. This paper proposes so-called circular arc structures as a means to faithfully realize freeform designs without giving up smooth appearance. In contrast to non-smooth meshes with straight edges where geometric complexity is concentrated in the nodes, we stay with smooth surfaces and rather distribute complexity in a uniform way by allowing edges in the shape of circular arcs. We are able to achieve the simplest possible shape of nodes without interfering with known panel optimization algorithms. We study remarkable special cases of circular arc structures which possess simple supporting elements or repetitive edges, we present the first global approximation method for principal patches, and we show an extension to volumetric structures for truly threedimensional designs. © 2011 ACM.

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

    Science.gov (United States)

    Pozhidaev

    2000-05-01

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

  13. Slit aperture technique for mammography

    International Nuclear Information System (INIS)

    Friedrich, M.

    1984-01-01

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

  14. Synthetic Aperture Vector Flow Imaging

    DEFF Research Database (Denmark)

    Villagómez Hoyos, Carlos Armando

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

  15. 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...

  16. Aperture averaging in strong oceanic turbulence

    Science.gov (United States)

    Gökçe, Muhsin Caner; Baykal, Yahya

    2018-04-01

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

  17. 5cm aperture dipole studies

    International Nuclear Information System (INIS)

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

    1986-01-01

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

  18. Circular RNAs in cancer

    DEFF Research Database (Denmark)

    Kristensen, L S; Hansen, T B; Venø, M T

    2018-01-01

    Circular RNA (circRNA) is a novel member of the noncoding cancer genome with distinct properties and diverse cellular functions, which is being explored at a steadily increasing pace. The list of endogenous circRNAs involved in cancer continues to grow; however, the functional relevance of the vast...... for circRNA cancer research and current caveats, which must be addressed to facilitate the translation of basic circRNA research into clinical use.Oncogene advance online publication, 9 October 2017; doi:10.1038/onc.2017.361....

  19. Circularly polarized antennas

    CERN Document Server

    Gao, Steven; Zhu, Fuguo

    2013-01-01

    This book presents a comprehensive insight into the design techniques for different types of CP antenna elements and arrays In this book, the authors address a broad range of topics on circularly polarized (CP) antennas. Firstly, it introduces to the reader basic principles, design techniques and characteristics of various types of CP antennas, such as CP patch antennas, CP helix antennas, quadrifilar helix antennas (QHA), printed quadrifilar helix antennas (PQHA), spiral antenna, CP slot antennas, CP dielectric resonator antennas, loop antennas, crossed dipoles, monopoles and CP horns. Adva

  20. 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.

  1. Design of large aperture, low mass vacuum windows

    International Nuclear Information System (INIS)

    Leonhardt, W.J.; Mapes, M.

    1993-01-01

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

  2. Modeling of circular-grating surface-emitting lasers

    Science.gov (United States)

    Shams-Zadeh-Amiri, Ali M.

    Grating-coupled surface-emitting lasers became an area of growing interest due to their salient features. Emission from a broad area normal to the wafer surface, makes them very well suited in high power applications and two- dimensional laser arrays. These new possibilities have caused an interest in different geometries to fully develop their potential. Among them, circular-grating lasers have the additional advantage of producing a narrow beam with a circular cross section. This special feature makes them ideal for coupling to optical fibers. All existing theoretical models dealing with circular- grating lasers only consider first-order gratings, or second-order gratings, neglecting surface emission. In this thesis, the emphasis is to develop accurate models describing the laser performance by considering the radiation field. Toward this aim, and due to the importance of the radiation modes in surface-emitting structures, a theoretical study of these modes in multilayer planar structures has been done in a rigorous and systematic fashion. Problems like orthogonality of the radiation modes have been treated very accurately. We have considered the inner product of radiation modes using the distribution theory. Orthogonality of degenerate radiation modes is an important issue. We have examined its validity using the transfer matrix method. It has been shown that orthogonality of degenerate radiation modes in a very special case leads to the Brewster theorem. In addition, simple analytical formulas for the normalization of radiation modes have been derived. We have shown that radiation modes can be handled in a much easier way than has been thought before. A closed-form spectral dyadic Green's function formulation of multilayer planar structures has been developed. In this formulation, both rectangular and cylindrical structures can be treated within the same mathematical framework. The Hankel transform of some auxiliary functions defined on a circular aperture has

  3. Synthetic aperture interferometry: error analysis

    Energy Technology Data Exchange (ETDEWEB)

    Biswas, Amiya; Coupland, Jeremy

    2010-07-10

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

  4. Synthetic aperture interferometry: error analysis

    International Nuclear Information System (INIS)

    Biswas, Amiya; Coupland, Jeremy

    2010-01-01

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

  5. Circular Migration and Human Development

    OpenAIRE

    Newland, Kathleen

    2009-01-01

    This paper explores the human development implications of circular migration — both where it occurs naturally and where governments work to create it. The paper discusses various conceptions and definitions of circular migration, and concludes that circular migration is not intrinsically positive or negative in relation to human development; its impact depends upon the circumstances in which it occurs, the constraints that surround it and—above all—the degree of choice that ind...

  6. Synthetic aperture radar: principles and applications

    International Nuclear Information System (INIS)

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

    2003-01-01

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

  7. INTERNATIONAL UNION OF OPERATING ENGINEERS NATIONAL HAZMAT PROGRAM - MILWAUKEE WORM DRIVE CIRCULAR SAW OENHP NUMBER: 2001-02, VERSION A

    International Nuclear Information System (INIS)

    2002-01-01

    Florida International University's (FIU) Hemispheric Center for Environmental Technology (HCET) evaluated five saws for their effectiveness in cutting specially prepared fiberglass-reinforced plywood crates. These crates were built as surrogates for crates that presently hold radioactively contaminated glove boxes at the Department of Energy's (DOE) Los Alamos facility. The Milwaukee worm drive circular saw was assessed on August 14, 2001. During the FIU test of efficacy, a team from the Operating Engineers National Hazmat Program (OENHP) evaluated the occupational safety and health issues associated with this technology. The Milwaukee worm drive circular saw is a hand-held tool with a 7 1/4-inch diameter circular blade for cutting wood. The saw contains a fixed upper and a retractable lower blade guard to prevent access to the blade during use. The unit is operated with an on/off guarded trigger switch; and is supported with a handgrip mounted on top of the saw. An adjustable lever sets the depth of cut. The retractable blade guard permits blind or plunge cuts and protects from blade access during shutdown and blade coast. Kickback, the sudden reaction to a pinched blade, is possible when using this saw and could cause the saw to lift up and out of the work piece toward the operator. Proper work position and firm control of the saw minimizes the potential for a sprain or strain. Care needs to be exercised to support the work piece properly and to not force the tool. Personal noise sampling indicated that one worker was near the Occupational Safety and Health Administration's (OSHA) Action Level of 85 decibels (dBA) while the other was at the Action Level with time-weighted averages (TWA's) of 82.7 and 84.6 dBA, respectively. These data are not entirely representative as they were gathered during a simulation and not at the actual worksite. Additional sampling should be conducted on-site, but the workers should wear hearing protection until it is determined that it

  8. Operational circular No. 1 (Rev. 1) – Operational circulars

    CERN Multimedia

    HR Department

    2011-01-01

    Operational Circular No. 1 (Rev. 1) is applicable to members of the personnel and other persons concerned. Operational Circular No. 1 (Rev. 1) entitled "Operational circulars", approved following discussion at the Standing Concertation Committee meeting on 4 May 2011, is available on the intranet site of the Human Resources Department: https://hr-docs.web.cern.ch/hr-docs/opcirc/opcirc.asp It cancels and replaces Operational Circular No. 1 entitled "Operational Circulars” of December 1996. This new version clarifies, in particular, that operational circulars do not necessarily arise from the Staff Rules and Regulations, and the functional titles have been updated to bring them into line with the current CERN organigram. Department Head Office  

  9. Circular defects detection in welded joints using circular hough transform

    International Nuclear Information System (INIS)

    Hafizal Yazid; Mohd Harun; Shukri Mohd; Abdul Aziz Mohamed; Shaharudin Sayuti; Muhamad Daud

    2007-01-01

    Conventional radiography is one of the common non-destructive testing which employs manual image interpretation. The interpretation is very subjective and depends much on the inspector experience and working conditions. It is therefore useful to have pattern recognition system in order to assist human interpreter in evaluating the quality of the radiograph sample, especially radiographic image of welded joint. This paper describes a system to detect circular discontinuities that is present in the joints. The system utilizes together 2 different algorithms, which is separability filter to identify the best object candidate and Circular Hough Transform to detect the present of circular shape. The result of the experiment shows a promising output in recognition of circular discontinuities in a radiographic image. This is based on 81.82-100% of radiography film with successful circular detection by using template movement of 10 pixels. (author)

  10. Walking through Apertures in Individuals with Stroke.

    Directory of Open Access Journals (Sweden)

    Daisuke Muroi

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

  11. Fast Parametric Beamformer for Synthetic Aperture Imaging

    DEFF Research Database (Denmark)

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

    2008-01-01

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

  12. Future Circular Colliders

    CERN Document Server

    AUTHOR|(CDS)2108454; Zimmermann, Frank

    2015-01-01

    In response to a request from the 2013 Update of the European Strategy for Particle Physics, the global Future Circular Collider (FCC) study is preparing the foundation for a next-generation large-scale accelerator infrastructure in the heart of Europe. The FCC study focuses on the design of a 100-TeV hadron collider (FCC-hh), to be accommodated in a new ∼100 km tunnel near Geneva. It also includes the design of a high-luminosity electron-positron collider (FCC-ee), which could be installed in the same tunnel as a potential intermediate step, and a lepton-hadron collider option (FCC-he). The scope of the FCC study comprises accelerators, technology, infrastructure, detector, physics, concepts for worldwide data services, international governance models, and implementation scenarios. Among the FCC core technologies figure 16-T dipole magnets, based on Nb3Sn superconductor, for the FCC-hh hadron collider, and a highly efficient superconducting radiofrequency system for the FCC-ee lepton collider. The internat...

  13. Future Circular Colliders

    CERN Document Server

    AUTHOR|(CDS)2108454; Zimmermann, Frank

    2016-01-01

    In response to a request from the 2013 Update of the European Strategy for Particle Physics, the global Future Circular Collider (FCC) study is preparing the foundation for a next-generation large-scale accelerator infrastructure in the heart of Europe. The FCC study focuses on the design of a 100-TeV hadron collider (FCC-hh), to be accommodated in a new ∼100 km tunnel near Geneva. It also includes the design of a high-luminosity electron-positron collider (FCC-ee), which could be installed in the same tunnel as a potential intermediate step, and a lepton-hadron collider option (FCC-he). The scope of the FCC study comprises accelerators, technology, infrastructure, detectors, physics, concepts for worldwide data services, international governance models, and implementation scenarios. Among the FCC core technologies figure 16-T dipole magnets, based on Nb3Sn superconductor, for the FCC-hh hadron collider, and a highly efficient superconducting radiofrequency system for the FCC-ee lepton collider. The interna...

  14. Towards Future Circular Colliders

    CERN Document Server

    AUTHOR|(CDS)2108454; Zimmermann, Frank

    2016-01-01

    The Large Hadron Collider (LHC) at CERN presently provides proton-proton collisions at a centre-of-mass (c.m.) energy of 13 TeV. The LHC design was started more than 30 years ago, and its physics programme will extend through the second half of the 2030’s. The global Future Circular Collider (FCC) study is now preparing for a post-LHC project. The FCC study focuses on the design of a 100-TeV hadron collider (FCC-hh) in a new ∼100 km tunnel. It also includes the design of a high-luminosity electron-positron collider (FCC-ee) as a potential intermediate step, and a lepton-hadron collider option (FCC-he). The scope of the FCC study comprises accelerators, technology, infrastructure, detectors, physics, concepts for worldwide data services, international governance models, and implementation scenarios. Among the FCC core technologies figure 16-T dipole magnets, based on $Nb_3Sn$ superconductor, for the FCC-hh hadron collider, and a highly efficient superconducting radiofrequency system for the FCC-ee lepton c...

  15. Three-dimensional Reconstruction Method Study Based on Interferometric Circular SAR

    Directory of Open Access Journals (Sweden)

    Hou Liying

    2016-10-01

    Full Text Available Circular Synthetic Aperture Radar (CSAR can acquire targets’ scattering information in all directions by a 360° observation, but a single-track CSAR cannot efficiently obtain height scattering information for a strong directive scatter. In this study, we examine the typical target of the three-dimensional circular SAR interferometry theoryand validate the theory in a darkroom experiment. We present a 3D reconstruction of the actual tank metal model of interferometric CSAR for the first time, verify the validity of the method, and demonstrate the important potential applications of combining 3D reconstruction with omnidirectional observation.

  16. ULYSSES JUPITER HISCALE COMPOSITION APERTURE ION COUNTS

    Data.gov (United States)

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

  17. Beam Combination for Sparse Aperture Telescopes Project

    Data.gov (United States)

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

  18. Digitalizing the Circular Economy

    Science.gov (United States)

    Reuter, Markus A.

    2016-12-01

    Metallurgy is a key enabler of a circular economy (CE), its digitalization is the metallurgical Internet of Things (m-IoT). In short: Metallurgy is at the heart of a CE, as metals all have strong intrinsic recycling potentials. Process metallurgy, as a key enabler for a CE, will help much to deliver its goals. The first-principles models of process engineering help quantify the resource efficiency (RE) of the CE system, connecting all stakeholders via digitalization. This provides well-argued and first-principles environmental information to empower a tax paying consumer society, policy, legislators, and environmentalists. It provides the details of capital expenditure and operational expenditure estimates. Through this path, the opportunities and limits of a CE, recycling, and its technology can be estimated. The true boundaries of sustainability can be determined in addition to the techno-economic evaluation of RE. The integration of metallurgical reactor technology and systems digitally, not only on one site but linking different sites globally via hardware, is the basis for describing CE systems as dynamic feedback control loops, i.e., the m-IoT. It is the linkage of the global carrier metallurgical processing system infrastructure that maximizes the recovery of all minor and technology elements in its associated refining metallurgical infrastructure. This will be illustrated through the following: (1) System optimization models for multimetal metallurgical processing. These map large-scale m-IoT systems linked to computer-aided design tools of the original equipment manufacturers and then establish a recycling index through the quantification of RE. (2) Reactor optimization and industrial system solutions to realize the "CE (within a) Corporation—CEC," realizing the CE of society. (3) Real-time measurement of ore and scrap properties in intelligent plant structures, linked to the modeling, simulation, and optimization of industrial extractive process

  19. 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...

  20. Realistic Approach for Beam Dynamics Simulation with Synchrotron Radiation in High Energy Circular Lepton Colliders

    CERN Document Server

    Glukhov, S A

    2017-01-01

    In extremely high energy circular lepton colliders, correct consideration of synchrotron radiation is important for beam dynamics simulation. We developed a fast precise effective method to track particles in a realistic lattice when the radiation effects are distributed along the orbit. In the present paper we study an effect of decreasing dynamic aperture due to radiation from quadrupole lenses in the FCC-ee lepton collider.

  1. Collarless, close-in, shaped iron aperture designs for the SSC [Superconducting Super Collider] dipole

    International Nuclear Information System (INIS)

    Gupta, R.C.; Morgan, G.H.

    1989-01-01

    The nominal-design SSC (Superconducting Super Collider) dipole encloses the coil in an iron yoke having a circular aperture. The radial gap between the coil and the iron is about 15 mm to provide space for a strong annular collar around the coil, and also to reduce the effects of iron saturation on central field harmonics. The 15 mm gap also reduces the desirable dipole field contributed by the iron. The present paper gives a coil and aperture configuration in which the gap is reduced to 5 mm at the midplane, in which the aperture is shaped to reduce the unwanted effects of iron saturation. The transfer function is increased about 5% at 6.6 Tesla and the unwanted harmonics are within SSC tolerances at all field levels. These designs would require that the yoke and containment vessel absorb the stresses due to assembly and magnetic forces. A short magnet is being built with a close-in shaped iron aperture and existing coil geometry to assess the benefits of this concept. 7 refs., 3 figs., 6 tabs

  2. Fresnel zone plate with apodized aperture for hard X-ray Gaussian beam optics.

    Science.gov (United States)

    Takeuchi, Akihisa; Uesugi, Kentaro; Suzuki, Yoshio; Itabashi, Seiichi; Oda, Masatoshi

    2017-05-01

    Fresnel zone plates with apodized apertures [apodization FZPs (A-FZPs)] have been developed to realise Gaussian beam optics in the hard X-ray region. The designed zone depth of A-FZPs gradually decreases from the center to peripheral regions. Such a zone structure forms a Gaussian-like smooth-shouldered aperture function which optically behaves as an apodization filter and produces a Gaussian-like focusing spot profile. Optical properties of two types of A-FZP, i.e. a circular type and a one-dimensional type, have been evaluated by using a microbeam knife-edge scan test, and have been carefully compared with those of normal FZP optics. Advantages of using A-FZPs are introduced.

  3. Non linear field correction effects on the dynamic aperture of the FCC-hh

    CERN Document Server

    AUTHOR|(INSPIRE)INSPIRE-00361058; Seryi, Andrei; Maclean, Ewen Hamish; Martin, Roman; Tomas Garcia, Rogelio

    2017-01-01

    The Future Circular Collider (FCC) design study aims to develop the designs of possible circular colliders in the post LHC era. In particular the FCC-hh will aim to produce proton-proton collisions at a center of mass energy of 100 TeV. Given the large beta functions and integrated length of the quadrupoles of the final focus triplet the effect of systematic and random non linear errors in the magnets are expected to have a severe impact on the stability of the beam. Following the experience on the HL-LHC this work explores the implementation of non-linear correctors to minimize the resonance driving terms arising from the errors of the triplet. Dynamic aperture studies are then performed to study the impact of this correction.

  4. Large-aperture subwavelength grating couplers.

    Science.gov (United States)

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

    2016-04-10

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

  5. Steady and perturbed motion of a point vortex along a boundary with a circular cavity

    International Nuclear Information System (INIS)

    Ryzhov, E.A.; Koshel, K.V.

    2016-01-01

    The dynamics of a point vortex moving along a straight boundary with a circular cavity subjected to a background flow is investigated. Given the constant background flow, this configuration produces regular phase portraits of the vortex motion. These phase portraits are discriminated depending on the cavity's circular shape, and then the transition to chaos of the vortex motion is investigated given an oscillating perturbation superimposed on the background flow. Based on the steady-state vortex rotation, the forcing parameters that lead to effective destabilization of vortex trajectories are distinguished. We show that, provided the cavity aperture is relatively narrow, the periodic forcing superimposed on the background flow destabilizes the vortex trajectories very slightly. On the other hand, if the cavity aperture is relatively wide, the forcing can significantly destabilize vortex trajectories causing the majority of the trajectories, which would be closed without the forcing, to move towards infinity. - Highlights: • The dynamics of a point vortex moving along a straight boundary with a circular cavity is addressed. • Three phase portrait structures depending on the cavity's circular shape are singled out. • Forcing parameters that lead to effective destabilization of vortex trajectories are found.

  6. Synthetic aperture tissue and flow ultrasound imaging

    DEFF Research Database (Denmark)

    Nikolov, Svetoslav

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

  7. Solar energy apparatus with apertured shield

    Science.gov (United States)

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

    1989-01-01

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

  8. Ecodesign for a Circular Economy

    DEFF Research Database (Denmark)

    Bundgaard, Anja Marie

    The Earth is a closed system and with the exception of energy, the resources available to us are finite, but our consumption and productions systems are typically linear systems where resources are extracted, used and wasted. The circular economy is proposed as an alternative and is defined...... as a consumption and production system based on closed loops that minimise resources, energy flows and environmental degradation. In this PhD thesis, I have examined how ecodesign can close the material loops in the circular economy for electrical and electronic equipment. The study examines how to improve...... be necessary to develop both product and company specific guidelines. The analysis revealed that activities or product attributes of importance to a circular economy are not solely driven by ecodesign....

  9. Multi-antenna synthetic aperture radar

    CERN Document Server

    Wang, Wen-Qin

    2013-01-01

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

  10. High frame rate synthetic aperture duplex imaging

    DEFF Research Database (Denmark)

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

    2013-01-01

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

  11. Synthetic aperture radar capabilities in development

    Energy Technology Data Exchange (ETDEWEB)

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

    1994-11-15

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

  12. Synthetic Aperture Ladar Imaging and Atmospheric Turbulence

    Science.gov (United States)

    2016-06-09

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

  13. Logistic regression for circular data

    Science.gov (United States)

    Al-Daffaie, Kadhem; Khan, Shahjahan

    2017-05-01

    This paper considers the relationship between a binary response and a circular predictor. It develops the logistic regression model by employing the linear-circular regression approach. The maximum likelihood method is used to estimate the parameters. The Newton-Raphson numerical method is used to find the estimated values of the parameters. A data set from weather records of Toowoomba city is analysed by the proposed methods. Moreover, a simulation study is considered. The R software is used for all computations and simulations.

  14. Circular coloring and Mycielski construction

    OpenAIRE

    Alishahi, Meysam; Hajiabolhassan, Hossein

    2010-01-01

    In this paper, we investigate circular chromatic number of Mycielski construction of graphs. It was shown in \\cite{MR2279672} that $t^{{\\rm th}}$ Mycielskian of the Kneser graph $KG(m,n)$ has the same circular chromatic number and chromatic number provided that $m+t$ is an even integer. We prove that if $m$ is large enough, then $\\chi(M^t(KG(m,n)))=\\chi_c(M^t(KG(m,n)))$ where $M^t$ is $t^{{\\rm th}}$ Mycielskian. Also, we consider the generalized Kneser graph $KG(m,n,s)$ and show that there ex...

  15. Circular mats under arbitrary loading

    International Nuclear Information System (INIS)

    Banerjee, A.; Jankov, Z.D.

    1975-01-01

    The analysis of mats as in nuclear power plants may become difficult when the large number of features are intended to be accounted for. Circular mats and arbitrary loadings are only a few of these that are considered. If the subgrade reaction can be represented as the function of subgrade displacement as given by Winkler's, Boussinesq's, or two elastic characteristic approaches, the general numerical method is then possible. Boussinesq's approach was treated in more detail when applied on circular mat with arbitrary loadings. Full polar grid formation that must be used when liftoff occurs is compared to harmonic formulation. The possibility of taking into account the superstructure restraint is indicated

  16. 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.

  17. Best Practice Examples of Circular Business Models

    DEFF Research Database (Denmark)

    Guldmann, Eva

    Best practice examples of circular business models are presented in this report. The purpose is to inform and inspire interested readers, in particular companies that aspire to examine the potentials of the circular economy. Circular business models in two different sectors are examined, namely...... the textile and clothing sector as well as the durable goods sector. In order to appreciate the notion of circular business models, the basics of the circular economy are outlined along with three frameworks for categorizing the various types of circular business models. The frameworks take point of departure......, and to look for circular business opportunities in this flow of goods and value, is key in a circular economy. Establishing new or closer collaboration with stakeholders within or beyond the traditional supply chain is another important skill in creating circular business models. Many of the examined...

  18. Optimization of Synthetic Aperture Image Quality

    DEFF Research Database (Denmark)

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

    2016-01-01

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

  19. Diffraction contrast imaging using virtual apertures

    International Nuclear Information System (INIS)

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

    2015-01-01

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

  20. Automated Change Detection for Synthetic Aperture Sonar

    Science.gov (United States)

    2014-01-01

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

  1. 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....

  2. Dynamic Aperture Studies for SPEAR 3

    International Nuclear Information System (INIS)

    Nosochkov, Yuri

    1999-01-01

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

  3. MD2725: 16L2 aperture measurement

    CERN Document Server

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

    2018-01-01

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

  4. Wind energy applications of synthetic aperture radar

    DEFF Research Database (Denmark)

    Badger, Merete

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

  5. Optical trapping at low numerical aperture

    NARCIS (Netherlands)

    Stallinga, S.

    2011-01-01

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

  6. 140 CIRCULAR INTERACTION BETWEEN LINGUISTIC ...

    African Journals Online (AJOL)

    economy. Although a country or administrative district should have one or more official languages for obvious reasons, Nelde (1991) proposes that the ... circular interaction between linguistic departments and language departments. Finding an answer to' Plato's abovementioned problem entails that as many languages as ...

  7. Circular polarization observed in bioluminescence

    NARCIS (Netherlands)

    Wijnberg, Hans; Meijer, E.W.; Hummelen, J.C.; Dekkers, H.P.J.M.; Schippers, P.H.; Carlson, A.D.

    1980-01-01

    While investigating circular polarization in luminescence, and having found it in chemiluminescence, we have studied bioluminescence because it is such a widespread and dramatic natural phenomenon. We report here that left and right lanterns of live larvae of the fireflies, Photuris lucicrescens and

  8. Inverting the Circular Radon Transform

    National Research Council Canada - National Science Library

    Redding, Nicholas

    2001-01-01

    ...) can be viewed as the inversion of the circular Radon transform. The advantage of viewing image formation in this way is that it could be used in situations where more standard methods could fail such as high squint and ultra-wideband SAR...

  9. High intensity circular proton accelerators

    International Nuclear Information System (INIS)

    Craddock, M.K.

    1987-12-01

    Circular machines suitable for the acceleration of high intensity proton beams include cyclotrons, FFAG accelerators, and strong-focusing synchrotrons. This paper discusses considerations affecting the design of such machines for high intensity, especially space charge effects and the role of beam brightness in multistage accelerators. Current plans for building a new generation of high intensity 'kaon factories' are reviewed. 47 refs

  10. Fractal characteristics of fracture roughness and aperture data

    International Nuclear Information System (INIS)

    Kumar, S.; Boernge, J.

    1991-05-01

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

  11. 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.

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

    Data.gov (United States)

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

  13. Circular Business: Collaborate and Circulate : a bookreview

    NARCIS (Netherlands)

    Timmermans, Ratna W.; Witjes, S.|info:eu-repo/dai/nl/381088200

    2016-01-01

    With their book, “Circular Business: Collaborate and Circulate”, Circular Collaboration, Amersfoort, ISBN: 978-90-824902-0-6, €35, Kraaijenhagen et al. (2016) give companies practical guidance on their contribution to the development of a more circular economy by presenting a practical 10-step

  14. Capacitance of circular patch resonator

    International Nuclear Information System (INIS)

    Miano, G.; Verolino, L.; Naples Univ.; Panariello, G.; Vaccaro, V.G.; Naples Univ.

    1995-11-01

    In this paper the capacitance of the circular microstrip patch resonator is computed. It is shown that the electrostatic problem can be formulated as a system of dual integral equations, and the most interesting techniques of solutions of these systems are reviewed. Some useful approximated formulas for the capacitance are derived and plots of the capacitance are finally given in a wide range of dielectric constants

  15. Colours in a Circular Economy

    OpenAIRE

    Niinimäki, Kirsi; Smirnova, Eugenia; Ilen, Elina; Sixta, Herbert; Hummel, Michael

    2017-01-01

    | openaire: EC/H2020/646226/EU//Trash-2-Cash This paper reports on preliminary results on the recycling of coloured cellulose-based textiles using a novel dry-jet wet spinning denoted as the Ioncell-F process. The practical possibility of colour circulation is useful knowledge for colour designers in the industry. The findings can help define further parameters for circular economy products

  16. Coded aperture imaging using imperfect detector systems

    International Nuclear Information System (INIS)

    Byard, K.; Ramsden, D.

    1994-01-01

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

  17. Miniature synthetic-aperture radar system

    Science.gov (United States)

    Stockton, Wayne; Stromfors, Richard D.

    1990-11-01

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

  18. Dynamic Aperture Studies for SPEAR 3

    International Nuclear Information System (INIS)

    Corbett, William

    1998-01-01

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

  19. Dynamic aperture studies for SPEAR 3

    International Nuclear Information System (INIS)

    Nosochkov, Y.; Corbett, J.

    1999-01-01

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

  20. IR aperture measurement at β*=40 cm

    CERN Document Server

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

    2015-01-01

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

  1. Circular on planned parenthood, 1987.

    Science.gov (United States)

    1987-01-01

    In 1987 fourteen units of the Government of Henan issued a Circular stating that: "Planned parenthood must be publicized deep into the grass roots and among the people, and importance must be attached to results." The Circular stresses: "In the propaganda drive, it is necessary to successfully grasp three key links: 1. It is necessary to disseminate intensively the important directive on population problems that is contained in the report of the 13th CPC National Congress and the seriousness of the population situation of our country and province so that the cadres and the masses can understand the relationship between population control and the achievement of the strategic target of the three big steps, understand the reason for carrying out planned parenthood, understand that the one-child policy is still advocated, and conscientiously carry out planned parenthood. 2. It is essential to succeed in propagating knowledge of contraception, sterilization, childbirth, and child care and in conducting ideological education for those who undergo operations and for their family members. 3. It is imperative to visit those who have undergone operations and to help them solve practically their difficulties in making a living." The Circular concludes by demanding that under the unified leadership of party committees and governments at all levels, the propaganda drive be carried out by relying on the efforts of all of society. In conjunction with their own work, departments, including the propaganda, education, public health, and cultural departments, must carry out propaganda and education for planned parenthood. full text

  2. Multi-circular flux motor

    Energy Technology Data Exchange (ETDEWEB)

    El-Kharashi, Eyhab Aly, E-mail: EyhabElkharahi@hotmail.com [Faculty of Engineering, Electrical Power and Machines Department, Ain Shams University, 1 El-Sarayat Street, Abdou Basha Square, Abbassia 11517, Cairo (Egypt)

    2011-11-15

    Highlights: {yields} The paper uses the multi-circular rotor in the switched reluctance motor to increase its output torque and its efficiency. {yields} Finite element is used to model the new SRM accurately. {yields} The Matlab/Simulink is used to dynamically model the new SRM. {yields} The paper compares the torque capability of the multi-circular rotor SRM. {yields} The new SRM produces approximately double the torque of its equivalent conventional SRM. - Abstract: The paper introduces a new type of electrical machines which has significantly high output torque. The toothed-rotor in the conventional electrical machine is replaced by a multi-circular rotor to increase the saliency and to shorten the flux loops consequently the output torque increases. The paper presents the design steps of this new type of electrical machine and also examines its performance. In addition, the paper compares the percentage increase in output torque from the proposed new electric machine to its equivalent conventional motor. Then the paper proceeds to discuss the relation between the switching on angle and the maximum speed, the torque ripples, and the efficiency.

  3. Integrated Optical Synthetic Aperture Radar Processor.

    Science.gov (United States)

    1987-09-01

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

  4. Synthetic aperture ladar concept for infrastructure monitoring

    Science.gov (United States)

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

    2014-10-01

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

  5. 47 CFR 25.134 - Licensing provisions of Very Small Aperture Terminal (VSAT) and C-band Small Aperture Terminal...

    Science.gov (United States)

    2010-10-01

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

  6. Coded-aperture imaging in nuclear medicine

    Science.gov (United States)

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

    1989-11-01

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

  7. Synthetic aperture radar processing with tiered subapertures

    Science.gov (United States)

    Doerry, A. W.

    1994-06-01

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

  8. Towards Very Large Aperture Massive MIMO

    DEFF Research Database (Denmark)

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

    2014-01-01

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

  9. Coded-aperture imaging in nuclear medicine

    Science.gov (United States)

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

    1989-01-01

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

  10. A New Dual Circularly Polarized Feed Employing a Dielectric Cylinder-Loaded Circular Waveguide Open End Fed by Crossed Dipoles

    Directory of Open Access Journals (Sweden)

    Jae-Hoon Bang

    2016-01-01

    Full Text Available This paper presents a new dual circularly polarized feed that provides good axial ratio over wide angles and low cross-polarized radiation in backward direction. A circular waveguide open end is fed with two orthogonally polarized waves in phase quadrature by a pair of printed crossed dipoles and a compact connectorized quadrature hybrid coupler. The waveguide aperture is loaded with a dielectric cylinder to reduce the cross-polarization beyond 90 degrees off the boresight. The fabricated feed has, at 5.5 GHz, 6.33-dBic copolarized gain, 3-dB beamwidth of 106°, 10-dB beamwidth of 195°, 3-dB axial ratio beamwidth of 215°, maximum cross-polarized gain of −21.4 dBic, and 27-dB port isolation. The reflection coefficient of the feed is less than −10 dB at 4.99–6.09 GHz.

  11. Technical Progress in Research of Multibeam Synthetic Aperture Sonar

    Directory of Open Access Journals (Sweden)

    LI Haisen

    2017-10-01

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

  12. Filled aperture concepts for the Terrestrial Planet Finder

    Science.gov (United States)

    Ridgway, Stephen T.

    2003-02-01

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

  13. Small-aperture monovision and the Pulfrich experience: absence of neural adaptation effects.

    Directory of Open Access Journals (Sweden)

    Sotiris Plainis

    Full Text Available PURPOSE: To explore whether adaptation reduces the interocular visual latency differences and the induced Pulfrich effect caused by the anisocoria implicit in small-aperture monovision. METHODS: Anisocoric vision was simulated in two adults by wearing in the non-dominant eye for 7 successive days, while awake, an opaque soft contact lens (CL with a small, central, circular aperture. This was repeated with aperture diameters of 1.5 and 2.5 mm. Each day, monocular and binocular pattern-reversal Visual Evoked Potentials (VEP were recorded. Additionally, the Pulfrich effect was measured: the task of the subject was to state whether a a 2-deg spot appeared in front or behind the plane of a central cross when moved left-to-right or right-to-left on a display screen. The retinal illuminance of the dominant eye was varied using neutral density (ND filters to establish the ND value which eliminated the Pulfrich effect for each lens. All experiments were performed at luminance levels of 5 and 30 cd/m(2. RESULTS: Interocular differences in monocular VEP latency (at 30 cd/m(2 rose to about 12-15 ms and 20-25 ms when the CL aperture was 2.5 and 1.5 mm, respectively. The effect was more pronounced at 5 cd/m(2 (i.e. with larger natural pupils. A strong Pulfrich effect was observed under all conditions, with the effect being less striking for the 2.5 mm aperture. No neural adaptation appeared to occur: neither the interocular differences in VEP latency nor the ND value required to null the Pulfrich effect reduced over each 7-day period of anisocoric vision. CONCLUSIONS: Small-aperture monovision produced marked interocular differences in visual latency and a Pulfrich experience. These were not reduced by adaptation, perhaps because the natural pupil diameter of the dominant eye was continually changing throughout the day due to varying illumination and other factors, making adaptation difficult.

  14. Replacement of 13 valves by using an isolation plug in the 20 inches diameter main offshore gas pipeline at Cantarell oil field, Campeche Bay, Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Carvahal Reyes, Jorge Omar; Ulloa Ochoa, Carlos Manuel [PEMEX, Exploracion y Produccion, MX (Mexico)

    2009-12-19

    In 2002 we changed 13 valves on deck of one gas production platform called Nohoch-A-Enlace at Cantarell Offshore Oil Field. The 20'' diameter gas pipeline and 200 km of length, transport and deliver gas for others production platforms in the Gas Lift System, So 2 millions of oil barrels per day depends of the operation of this gas pipeline but there was 13 valves on pig traps to be changed after 20 years of service to high pressure (64 to 63 kg/cm{sup 2}). We could not stop the operation of this pipeline and some little gas leaks were eliminated in some parts of the valves. This pipeline has two risers so the gas can be injected by two sides of the ring of 20 Km. So we found the proper technology in order to isolate one riser nad change 8 valves and the isolate the other and change the 5, and the gas lift system never stop during the plug and maintenance operations on platform. In the first isolation plug operation this tool run 20 mts inside the riser and was actionated and resists 65 Kg/cm{sup 2} of gas pressure during 44 hours so we changed 8 valves: 2 of 20'', 2 of 10'', 3 of 4'' and 1 of 8'' diameter. In the second isolation the plug run 30 mts inside the second risers and resist 64 Kg/cm{sup 2} of gas during 46 hours and we changed 5 valves of 20'' diameter. In the paper I will describe all the details of this successful operations and procedures. Also the aspects of Health, Security and Environment that we prepared one year before this operations at platform. Pemex save almost 2.5 millions of dollars because the gas lift system never stop and all valves were changed and now we can run cleaning and inspection tools inside the full ring. We used the first isolation plug in Latin America and we want to share this experience to all the pipeline operators in the world as a good practice in pipeline maintenance using plugging technology in the main and large pipelines of high pressure. (author)

  15. Blow-Out Velocities of Solutions of Hydrocarbons and Boron Hydride - Hydrocarbon Reaction Products in a 1 7/8-Inch-Diameter Combustor

    Science.gov (United States)

    Morris, James F.; Lord, Albert M.

    1957-01-01

    Blow-out velocities were determined for JP-4 solutions containing: (1) 10 % ethylene - decaborane reaction product, (2) 10% and 20% acetylene - diborane reaction product, and (3) 5.5%, 15.7%, and 30.7% methylacetylene - diborane reaction product. These were compared with blow-out velocities for JP-4, propylene oxide, and neohexane and previously reported data for JP-4 solutions of pentaborane. For those reaction products investigated, the blow-out velocities at a fixed equivalence ratio were higher for those materials containing higher boron concentrations; that is, blow-out velocity increased in the following order: (1) methylacetylene - diborane, (2) acetylene - diborane, and (3) ethylene - decaborane reaction products.

  16. Fast parametric beamformer for synthetic aperture imaging.

    Science.gov (United States)

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

    2008-08-01

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

  17. Optimization of Spatiotemporal Apertures in Channel Sounding

    DEFF Research Database (Denmark)

    Pedersen, Troels; Pedersen, Claus; Yin, Xuefeng

    2008-01-01

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

  18. Tissue Harmonic Synthetic Aperture Ultrasound Imaging

    DEFF Research Database (Denmark)

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

    2014-01-01

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

  19. VELO aperture considerations for the LHCb Upgrade

    CERN Document Server

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

    2012-01-01

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

  20. Synthetic aperture radar autofocus via semidefinite relaxation.

    Science.gov (United States)

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

    2013-06-01

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

  1. Attenuation in Superconducting Circular Waveguides

    Directory of Open Access Journals (Sweden)

    K. H. Yeap

    2016-09-01

    Full Text Available We present an analysis on wave propagation in superconducting circular waveguides. In order to account for the presence of quasiparticles in the intragap states of a superconductor, we employ the characteristic equation derived from the extended Mattis-Bardeen theory to compute the values of the complex conductivity. To calculate the attenuation in a circular waveguide, the tangential fields at the boundary of the wall are first matched with the electrical properties (which includes the complex conductivity of the wall material. The matching of fields with the electrical properties results in a set of transcendental equations which is able to accurately describe the propagation constant of the fields. Our results show that although the attenuation in the superconducting waveguide above cutoff (but below the gap frequency is finite, it is considerably lower than that in a normal waveguide. Above the gap frequency, however, the attenuation in the superconducting waveguide increases sharply. The attenuation eventually surpasses that in a normal waveguide. As frequency increases above the gap frequency, Cooper pairs break into quasiparticles. Hence, we attribute the sharp rise in attenuation to the increase in random collision of the quasiparticles with the lattice structure.

  2. High-flux normal incidence monochromator for circularly polarized synchrotron radiation

    International Nuclear Information System (INIS)

    Schaefers, F.; Peatman, W.; Eyers, A.; Heckenkamp, C.; Schoenhense, G.; Heinzmann, U.

    1986-01-01

    A 6.5-m normal incidence monochromator installed at the storage ring BESSY, which is optimized for a high throughput of circularly polarized off-plane radiation at moderate resolution is described. The monochromator employs two exit slits and is specially designed and used for low-signal experiments such as spin- and angle-resolved photoelectron spectroscopy on solids, adsorbates, free atoms, and molecules. The Monk--Gillieson mounting (plane grating in a convergent light beam) allows for large apertures with relatively little astigmatism. With two gratings, a flux of more than 10 11 photons s -1 bandwidth -1 (0.2--0.5 nm) with a circular polarization of more than 90% in the wavelength range from 35 to 675 nm is achieved

  3. Measurements of pore-scale flow through apertures

    Energy Technology Data Exchange (ETDEWEB)

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

    2017-09-01

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

  4. Coded aperture optimization using Monte Carlo simulations

    International Nuclear Information System (INIS)

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

    2010-01-01

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

  5. Optical Ground Terminals Using Multi Aperture Digital Coherent Combining

    Science.gov (United States)

    2017-10-01

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

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

    Science.gov (United States)

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

    2010-12-14

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

  7. Extended Aperture Photometry of K2 RR Lyrae stars

    Science.gov (United States)

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

    2017-10-01

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

  8. Extended Aperture Photometry of K2 RR Lyrae stars

    Directory of Open Access Journals (Sweden)

    Plachy Emese

    2017-01-01

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

  9. Enhanced Spectral Modeling of Sparse Aperture Imaging Systems

    National Research Council Canada - National Science Library

    Introne, Robert

    2005-01-01

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

  10. Circular economy and nuclear energy

    International Nuclear Information System (INIS)

    2016-01-01

    Circular economy means no production of waste through re-using and recycling. As other industries, nuclear industry has committed itself to a policy of sustainability and resource preservation. EDF has developed a 5 point strategy: 1) the closure of the fuel cycle through recycling, 2) operating nuclear power plants beyond 40 years, 3) reducing the volume of waste, 4) diminishing the consumption of energy through the implementation of new processes (for instance the enrichment through centrifugation uses 50 times less power than gaseous diffusion enrichment) and 5) making evolve the prevailing doctrine concerning the management of very low level radioactive waste: making possible the re-use of slightly contaminated steel scrap or concrete instead of storing them in dedicated disposal centers. (A.C.)

  11. Collision Technologies for Circular Colliders

    Science.gov (United States)

    Levichev, Eugene

    2015-02-01

    For several decades already, particle colliders have been essential tools for particle physics. From the very beginning, such accelerators have been among the most complicated scientific instruments ever built, including a number of innovative technological developments. Examples are ultrahigh vacuum systems, magnets with a very high magnetic field, and equipment for sub-ns synchronization and sub-mm precision alignment of equipment inside multi-km underground tunnels. Some key technologies are related to the focusing of the beam down to a scale of sub-μm at the collision point to obtain high luminosity. This review provides an overview of collision concepts and technologies for circular particle colliders, starting from the first ideas. In particular, it discusses such novel schemes and related technologies as crab waist collision and round beam collision.

  12. Some properties of circular proteins

    International Nuclear Information System (INIS)

    Prosselkov, P.; John, P.; Dixon, N.E.; Liepinsh, E.; Williams, N.K.; University of Sydney, NSW; Matthews, J.M.; Otting, G.; Karolinska Institutet, Stockholm,

    2002-01-01

    Full text: Protein backbone cyclization can be achieved by use of a circularly-permuted split mini-intein. We have used the small N-terminal domain of the E coli DnaB helicase (DnaB-N, residues 24-136) as a model protein for cyclization because its structure has been determined both by NMR spectroscopy and X-ray crystallography, and its ends are close together. Joining of the ends of DnaB-N' via a 9-amino acid linker occurs efficiently in vivo, and the circular (cz-) protein is stabilized in comparison to the linear (Hn-) protein against thermal denaturation (ΔΔG ∼2 kcal/mol). DnaB-N exists as a dimer in the crystalline state and in solution at high concentrations. To produce linear and cyclized versions that could not dimerize, Phe102 (at the dimer interface) was changed to Glu. NMR spectra showed that the F102E mutants remained monomeric at high concentrations but otherwise had essentially the same structures as the wild-type domains. Individual rate constants for proton exchange at the amide groups in lin- and cz-DnaB-N were determined at 10 C. Although they varied as expected depending on exposure to solvent, the ratios of rates between corresponding amides in the two proteins were constant. In the same buffer, lin- and cz-DnaB-N both unfolded reversibly, with transition temperatures of 37.9 and 48.5 deg C, respectively. Correlation of the (constant) ratio of amide exchange rates with measured thermodynamic parameters suggests that amide exchange in DnaB-N occurs predominantly in a globally unfolded state. Similar studies with other proteins are underway

  13. Culture as a Caveat Towards Circular Economy

    DEFF Research Database (Denmark)

    Guerrieri, Valeria

    2015-01-01

    Circular economy represents an economic and political challenge, as well as a cultural one, requiring a massive transformation on all levels of society. But why is cultural change so important to understanding today’s economy and how can the circular model be considered a truly cross...

  14. A Random Walk on a Circular Path

    Science.gov (United States)

    Ching, W.-K.; Lee, M. S.

    2005-01-01

    This short note introduces an interesting random walk on a circular path with cards of numbers. By using high school probability theory, it is proved that under some assumptions on the number of cards, the probability that a walker will return to a fixed position will tend to one as the length of the circular path tends to infinity.

  15. Nanofocusing in circular sector-like nanoantennas

    DEFF Research Database (Denmark)

    Zenin, Volodymyr; Pors, Anders Lambertus; Han, Zhanghua

    2014-01-01

    a concentric circular line of phase contrast, demonstrating resonant excitation of a standing wave of counter-propagating surface plasmons, travelling between a tip and opposite circular edge of the antenna. Transmission spectra obtained in the range 900 - 2100 nm are in good agreement with numerical...

  16. 76 FR 60590 - Environmental Justice; Proposed Circular

    Science.gov (United States)

    2011-09-29

    ... recipients of FTA funds on how to fully engage environmental justice populations in the public transportation... Federal Transit Administration Environmental Justice; Proposed Circular AGENCY: Federal Transit... guidance in the form of a Circular on incorporating environmental justice principles into plans, projects...

  17. Defocus morphing in real aperture images.

    Science.gov (United States)

    Chaudhuri, Subhasis

    2005-11-01

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

  18. Terahertz Imaging Systems With Aperture Synthesis Techniques

    DEFF Research Database (Denmark)

    Krozer, Viktor; Löffler, Torsten; Dall, Jørgen

    2010-01-01

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

  19. INTERNATIONAL UNION OF OPERATING ENGINEERS NATIONAL HAZMAT PROGRAM - EVOLUTION 180 CIRCULAR SAW OENHP: 2001-03, VERSION A; TOPICAL

    International Nuclear Information System (INIS)

    Unknown

    2002-01-01

    Florida International University's (FIU) Hemispheric Center for Environmental Technology (HCET) evaluated five saws for their effectiveness in cutting specially prepared fiberglass-reinforced plywood crates. These crates were built as surrogates for crates that presently hold radioactively contaminated gloveboxes at the Department of Energy's (DOE) Los Alamos facility. The Evolution 180 circular saw was assessed on August 14, 2001. During the FIU test of efficacy, a team from the Operating Engineers National Hazmat Program (OENHP) evaluated the occupational safety and health issues associated with this technology. The Evolution 180 is a portable, metal cutting circular saw with a 7-inch diameter blade. The blade is contained within the main housing and has a retractable lower blade guard to prevent operator access to the blade during operation and shutdown. The saw is equipped with a chip collector. The maximum cutting thickness for metal is one-quarter inch and can cut steel tubing and pipe 2 inches in diameter. The unit is operated with an on/off guarded trigger switch and is supported with the hand guide mounted to the side of the saw. An adjustable lever sets the depth of the cut. The machine's circuitry will automatically shut the saw motor off if excessive overload is detected during operation. The one-half hour demonstration involved vertical and horizontal cuts and blade changes. During this process, operators experienced binding of the saw. This caused the blade to become hot, causing the sawdust collected in the chip collector to smoke. Care should be exercised to use the appropriate blade for the application, operator training, and personal protective equipment (PPE). Personal noise sampling indicated that neither worker was over the Occupational Safety and Health Administration's (OSHA) Action Level of 85 decibels (dBA) with time-weighted averages (TWA's) of 69.1 and 68.8 dBA. The personal noise sample taken during the special demonstration with the

  20. Large aperture nanocomposite deformable mirror technology

    Science.gov (United States)

    Chen, Peter C.; Hale, Richard D.

    2007-12-01

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

  1. Common aperture multispectral spotter camera: Spectro XR

    Science.gov (United States)

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

    2017-10-01

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

  2. Low-Gain Circularly Polarized Antenna with Torus-Shaped Pattern

    Science.gov (United States)

    Amaro, Luis R.; Kruid, Ronald C.; Vacchione, Joseph D.; Prata, Aluizio

    2012-01-01

    The Juno mission to Jupiter requires an antenna with a torus-shaped antenna pattern with approximately 6 dBic gain and circular polarization over the Deep Space Network (DSN) 7-GHz transmit frequency and the 8-GHz receive frequency. Given the large distances that accumulate en-route to Jupiter and the limited power afforded by the solar-powered vehicle, this toroidal low-gain antenna requires as much gain as possible while maintaining a beam width that could facilitate a +/-10deg edge of coverage. The natural antenna that produces a toroidal antenna pattern is the dipole, but the limited approx. = 2.2 dB peak gain would be insufficient. Here a shaped variation of the standard bicone antenna is proposed that could achieve the required gains and bandwidths while maintaining a size that was not excessive. The final geometry that was settled on consisted of a corrugated, shaped bicone, which is fed by a WR112 waveguide-to-coaxial- waveguide transition. This toroidal low-gain antenna (TLGA) geometry produced the requisite gain, moderate sidelobes, and the torus-shaped antenna pattern while maintaining a very good match over the entire required frequency range. Its "horn" geometry is also low-loss and capable of handling higher powers with large margins against multipactor breakdown. The final requirement for the antenna was to link with the DSN with circular polarization. A four-layer meander-line array polarizer was implemented; an approach that was fairly well suited to the TLGA geometry. The principal development of this work was to adapt the standard linear bicone such that its aperture could be increased in order to increase the available gain of the antenna. As one increases the aperture of a standard bicone, the phase variation across the aperture begins to increase, so the larger the aperture becomes, the greater the phase variation. In order to maximize the gain from any aperture antenna, the phase should be kept as uniform as possible. Thus, as the standard

  3. Second harmonic imaging using synthetic aperture sequential beamforming

    DEFF Research Database (Denmark)

    Du, Yigang; Rasmussen, Joachim; Jensen, Henrik

    2011-01-01

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

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

    Science.gov (United States)

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

    2011-10-26

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

  5. Shadow Enhancement in Synthetic Aperture Sonar Using Fixed Focusing

    NARCIS (Netherlands)

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

    2009-01-01

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

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

    Indian Academy of Sciences (India)

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

  7. Reconfigurable metasurface aperture for security screening and microwave imaging

    Science.gov (United States)

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

    2017-05-01

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

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

    Indian Academy of Sciences (India)

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

  9. Microfabricated high-bandpass foucault aperture for electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Glaeser, Robert; Cambie, Rossana; Jin, Jian

    2014-08-26

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

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

    Science.gov (United States)

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

    2013-03-01

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

  11. FUTURE CIRCULAR COLLIDER LOGISTICS STUDY

    CERN Document Server

    Beißert, Ulrike; Kuhlmann, Gerd; Nettsträter, Andreas; Prasse, Christian; Wohlfahrt, Andreas

    2018-01-01

    The Large Hadron Collider (LHC) at the European Organization for Nuclear Research CERN in Geneva is the largest and most powerful collider in the world. CERN and its research and experimental infrastructure is not only a focus for the science community but is also very much in the public eye. With the Future Circular Collider (FCC) Study, CERN has begun to examine the feasibility of a new underground accelerator ring with a length of approximately 100 kilometres. Logistics is of great importance for the construction, assembly and operation of the FCC. During the planning, construction and assembly of the LHC, logistics proved to be one of the key factors. As the FCC is even larger than the LHC, logistics will also become more and more significant. This report therefore shows new concepts, methods and analytics for logistics, supply chain and transport concepts as part of the FCC study. This report deals with three different logistics aspects for the planning and construction phase of FCC: 1. A discussion of d...

  12. Dual circularly polarized broadside beam antenna based on metasurfaces

    Science.gov (United States)

    Tellechea, A.; Caminita, F.; Martini, E.; Ederra, I.; Teniente, J.; Iriarte, J. C.; Gonzalo, R.; Maci, S.

    2018-02-01

    Design details of a Ku band metasurface (MTS) antenna with dual circularly polarized (CP) broadside radiation is shown in this work. By means of the surface impedance tensor modulation, synchronized propagation of two transversal magnetic (TM) and transverse electric (TE) surface waves (SWs) is ensured in the structure, which contribute to the radiation in broadside direction by the generation of a CP leaky wave. The structure is implemented by elliptical subwavelength metallic elements with a cross-shaped aperture in the center, printed on top of a thin substrate with high permittivity (AD1000 with a thickness of λ0/17). For the experimental validation, the MTS prototype has been excited employing an orthomode transducer composed by a metallic stepped septum inside an air-filled waveguide. Two orthogonal TE11 modes excited with ±90° phase shift in the feed couple with the TM and TE SWs supported by the MTS and generate RHCP or LHCP broadside beam. Experimental results are compared with the simulation predictions. Finally, conclusions are drawn.

  13. A Method for Synthetic Aperture Compounding

    DEFF Research Database (Denmark)

    Hansen, Jens Munk; Jensen, Jørgen Arendt

    2010-01-01

    and the effect is quantized by speckle statistics and by computing contrast-to-noise ratios (CNR) from the resulting images. The method is validated using Field II simulations for a 7 MHz, =2-pitch transducer with 192 elements with 64 elements active for each scan line. Circular regions (cysts) with a diameter...... of 5 mm and scattering levels ranging from -3 to -12 dB relative to the background are imaged at 2 depths. Compound images composed of 1-5 images with an angular separation of 2 degrees are constructed and for the cysts at -3, -6, -9, and -12 dB, a CNR of -0.43, -1.11, -1.44, and -1.91 dB are obtained...

  14. X-ray lenses with large aperture

    International Nuclear Information System (INIS)

    Simon, Markus

    2010-01-01

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

  15. Beamline 9.3.2 - a high-resolution, bend-magnet beamline with circular polarization capability

    Energy Technology Data Exchange (ETDEWEB)

    Moler, E.J.; Hussain, Z.; Howells, M.R. [Lawrence Berkeley National Lab., CA (United States)] [and others

    1997-04-01

    Beamline 9.3.2 is a high resolution, SGM beamline on an ALS bending magnet with access to photon energies from 30-1500 eV. Features include circular polarization capability, a rotating chamber platform that allows switching between experiments without breaking vacuum, an active feedback system that keeps the beam centered on the entrance slit of the monochromator, and a bendable refocusing mirror. The beamline optics consist of horizontally and vertically focussing mirrors, a Spherical Grating Monochromator (SGM) with movable entrance and exit slits, and a bendable refocussing mirror. In addition, a movable aperature has been installed just upstream of the vertically focussing mirror which can select the x-rays above or below the plane of the synchrotron storage ring, allowing the user to select circularly or linearly polarized light. Circularly polarized x-rays are used to study the magnetic properties of materials. Beamline 9.3.2 can supply left and right circularly polarized x-rays by a computer controlled aperture which may be placed above or below the plane of the synchrotron storage ring. The degree of linear and circular polarization has been measured and calibrated.

  16. Motion measurement for synthetic aperture radar

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-01-01

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

  17. Parametric Beamformer for Synthetic Aperture Ultrasound Imaging

    DEFF Research Database (Denmark)

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

    2006-01-01

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

  18. Adaptive synthetic aperture radar image enhancement

    Science.gov (United States)

    Cheng, Hua; Tian, Jinwen

    2009-10-01

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

  19. Deep Learning for Passive Synthetic Aperture Radar

    Science.gov (United States)

    Yonel, Bariscan; Mason, Eric; Yazici, Birsen

    2018-02-01

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

  20. Circular dichroism spectroscopy of fluorescent proteins

    NARCIS (Netherlands)

    Visser, N.V.; Hink, M.A.; Borst, J.W.; Krogt, van der G.N.M.; Visser, A.J.W.G.

    2002-01-01

    Circular dichroism (CD) spectra have been obtained from several variants of green fluorescent protein: blue fluorescent protein (BFP), enhanced cyan fluorescent protein (CFP), enhanced green fluorescent protein (GFP), enhanced yellow fluorescent protein (YFP), all from Aequorea victoria, and the red

  1. 17 CFR 230.253 - Offering circular.

    Science.gov (United States)

    2010-04-01

    .... Repetition of information should be avoided; cross-referencing of information within the document is... COMPLETENESS OF ANY OFFERING CIRCULAR OR OTHER SELLING LITERATURE. THESE SECURITIES ARE OFFERED PURSUANT TO AN...

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

    DEFF Research Database (Denmark)

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

    2007-01-01

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

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

    CERN Document Server

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

    2017-01-01

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

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

    International Nuclear Information System (INIS)

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

    1990-01-01

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

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

    Science.gov (United States)

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

    2004-01-01

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

  6. Dynamic Aperture Measurements at the Advanced Light Source

    International Nuclear Information System (INIS)

    Decking, W.; Robin, D.

    1999-01-01

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

  7. 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.

  8. A Conceptual Framework for Circular Design

    Directory of Open Access Journals (Sweden)

    Mariale Moreno

    2016-09-01

    Full Text Available Design has been recognised in the literature as a catalyst to move away from the traditional model of take-make-dispose to achieve a more restorative, regenerative and circular economy. As such, for a circular economy to thrive, products need to be designed for closed loops, as well as be adapted to generate revenues. This should not only be at the point of purchase, but also during use, and be supported by low-cost return chains and reprocessing structures, as well as effective policy and regulation. To date, most academic and grey literature on the circular economy has focused primarily on the development of new business models, with some of the latter studies addressing design strategies for a circular economy, specifically in the area of resource cycles and design for product life extension. However, these studies primarily consider a limited spectrum of the technical and biological cycles where materials are recovered and restored and nutrients (e.g., materials, energy, water are regenerated. This provides little guidance or clarity for designers wishing to design for new circular business models in practice. As such, this paper aims to address this gap by systematically analysing previous literature on Design for Sustainability (DfX (e.g., design for resource conservation, design for slowing resource loops and whole systems design and links these approaches to the current literature on circular business models. A conceptual framework is developed for circular economy design strategies. From this conceptual framework, recommendations are made to enable designers to fully consider the holistic implications for design within a circular economy.

  9. Unleashing the Power of the Circular Economy

    Energy Technology Data Exchange (ETDEWEB)

    Kok, L.; Wurpel, G.; Ten Wolde, A. [IMSA Amsterdam, Amsterdam (Netherlands)

    2013-04-15

    The concept of circular economy is an economic and industrial system that focuses on the reusability of products and raw materials, reduces value destruction in the overall system and aims at value creation within each tier of the system. This report for Circle Economy (CE) outlines the general direction and concrete steps that must be taken to accomplish a breakthrough to a circular economy. It also provides a knowledge base behind the concept, connecting it to sustainability.

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

    International Nuclear Information System (INIS)

    Pueyo, Laurent; Norman, Colin

    2013-01-01

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

  11. Fast algorithms for approximate circular string matching.

    Science.gov (United States)

    Barton, Carl; Iliopoulos, Costas S; Pissis, Solon P

    2014-03-22

    Circular string matching is a problem which naturally arises in many biological contexts. It consists in finding all occurrences of the rotations of a pattern of length m in a text of length n. There exist optimal average-case algorithms for exact circular string matching. Approximate circular string matching is a rather undeveloped area. In this article, we present a suboptimal average-case algorithm for exact circular string matching requiring time O(n). Based on our solution for the exact case, we present two fast average-case algorithms for approximate circular string matching with k-mismatches, under the Hamming distance model, requiring time O(n) for moderate values of k, that is k=O(m/logm). We show how the same results can be easily obtained under the edit distance model. The presented algorithms are also implemented as library functions. Experimental results demonstrate that the functions provided in this library accelerate the computations by more than three orders of magnitude compared to a naïve approach. We present two fast average-case algorithms for approximate circular string matching with k-mismatches; and show that they also perform very well in practice. The importance of our contribution is underlined by the fact that the provided functions may be seamlessly integrated into any biological pipeline. The source code of the library is freely available at http://www.inf.kcl.ac.uk/research/projects/asmf/.

  12. Exciton circular dichroism in channelrhodopsin.

    Science.gov (United States)

    Pescitelli, Gennaro; Kato, Hideaki E; Oishi, Satomi; Ito, Jumpei; Maturana, Andrés Daniel; Nureki, Osamu; Woody, Robert W

    2014-10-16

    Channelrhodopsins (ChRs) are of great interest currently because of their important applications in optogenetics, the photostimulation of neurons. The absorption and circular dichroism (CD) spectra of C1C2, a chimera of ChR1 and ChR2 of Chlamydomonas reinhardtii, have been studied experimentally and theoretically. The visible absorption spectrum of C1C2 shows vibronic fine structure in the 470 nm band, consistent with the relatively nonpolar binding site. The CD spectrum has a negative band at 492 nm (Δε(max) = -6.17 M(-1) cm(-1)) and a positive band at 434 nm (Δε(max) = +6.65 M(-1) cm(-1)), indicating exciton coupling within the C1C2 dimer. Time-dependent density functional theory (TDDFT) calculations are reported for three models of the C1C2 chromophore: (1) the isolated protonated retinal Schiff base (retPSB); (2) an ion pair, including the retPSB chromophore, two carboxylate side chains (Asp 292, Glu 162), modeled by acetate, and a water molecule; and (3) a hybrid quantum mechanical/molecular mechanical (QM/MM) model depicting the binding pocket, in which the QM part consists of the same ion pair as that in (2) and the MM part consists of the protein residues surrounding the ion pair within 10 Å. For each of these models, the CD of both the monomer and the dimer was calculated with TDDFT. For the dimer, DeVoe polarizability theory and exciton calculations were also performed. The exciton calculations were supplemented by calculations of the coupling of the retinal transition with aromatic and peptide group transitions. For the dimer, all three methods and three models give a long-wavelength C2-axis-polarized band, negative in CD, and a short-wavelength band polarized perpendicular to the C2 axis with positive CD, differing in wavelength by 1-5 nm. Only the retPSB model gives an exciton couplet that agrees qualitatively with experiment. The other two models give a predominantly or solely positive band. We further analyze an N-terminal truncated mutant

  13. NEAR-INFRARED IMAGING POLARIMETRY OF GGD 27: CIRCULAR POLARIZATION AND MAGNETIC FIELD STRUCTURES

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, Jungmi; Tamura, Motohide [Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Hough, James H. [University of Hertfordshire, Hatfield, Herts AL10 9AB (United Kingdom); Nagata, Tetsuya [Kyoto University, Sakyo-ku, Kyoto 606-8502 (Japan); Kusakabe, Nobuhiko [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Saito, Hiro, E-mail: jungmi.kwon@astron.s.u-tokyo.ac.jp [Department of Astronomy and Earth Sciences, Tokyo Gakugei University, Koganei, Tokyo 184-8501 (Japan)

    2016-06-20

    Near-infrared imaging polarimetry in the J , H , and K{sub s} bands was carried out for GGD 27 in the dark cloud Lynds 291. Details of an infrared reflection nebula associated with the optical nebulosity GGD 27 and the infrared nebula GGD 27 IRS are presented. Aperture photometry of 1263 point-like sources, detected in all three bands, was used to classify them based on a color–color diagram, and the linear polarization of several hundred sources was determined, with the latter used to map the magnetic field structure around GGD 27. This field, around GGD 27 IRS, appears to be associated with the extended CO outflow of IRAS 18162–2048; however, there are partly distorted or bent components in the field. The Chandrasekhar–Fermi method gives an estimate of the magnetic field strength as ∼90 μ G. A region associated with GGD 27 IRS is discovered to have a circular polarization in the range of ∼2%–11% in the K{sub s} band. The circular polarization has an asymmetric positive/negative pattern and extends out to ∼ 120″ or 1.0 pc. The circular and linear polarization patterns are explained as resulting from a combination of dense inner and fainter outer lobes, suggesting episodic outflow.

  14. Morphometric analysis of septal aperture of humerus

    Directory of Open Access Journals (Sweden)

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

    2014-04-01

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

  15. The LASS [Larger Aperture Superconducting Solenoid] spectrometer

    International Nuclear Information System (INIS)

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

    1986-04-01

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

  16. The LASS (Larger Aperture Superconducting Solenoid) spectrometer

    Energy Technology Data Exchange (ETDEWEB)

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

    1986-04-01

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

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

    CSIR Research Space (South Africa)

    Schwegmann, Colin P

    2017-05-01

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

  18. Ships as salient objects in synthetic aperture radar imaginary

    CSIR Research Space (South Africa)

    Schwegmann, Colin P

    2016-07-01

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

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

    Data.gov (United States)

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

  20. CLPX-Satellite: Radarsat Synthetic Aperture Radar Imagery

    Data.gov (United States)

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

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

    Data.gov (United States)

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

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

    National Research Council Canada - National Science Library

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

    2005-01-01

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

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

    National Research Council Canada - National Science Library

    Li, Tianfang

    2006-01-01

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

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

    Data.gov (United States)

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

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

    Data.gov (United States)

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

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

    Data.gov (United States)

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Outlaw, W. H.

    2000-09-15

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

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

    Directory of Open Access Journals (Sweden)

    Hou Yunshan

    2010-01-01

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

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

    Science.gov (United States)

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

    2010-12-01

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

  10. Beam Combination for Sparse Aperture Telescopes, Phase I

    Data.gov (United States)

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

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

    Science.gov (United States)

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

    2013-05-01

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

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

    International Nuclear Information System (INIS)

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

    2013-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-11-01

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

  14. Cygnus X-1: Discovery of variable circular polarization

    International Nuclear Information System (INIS)

    Michalsky, J.J.; Swedlund, J.B.; Stokes, R.A.

    1975-01-01

    HDE 226868, the optical counterpart of Cyg X-1, has been observed for circular polarization during 1974. Observations in five colors suggest that circular polarization results from an interstellar effect. Measurements of the blue polarization reveal circular polarization variations synchronous with the 5)./sub /6 orbital period. The circular polarization variation appears to be similar to the blue intensity variation

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

    Directory of Open Access Journals (Sweden)

    Hamed Lamei Ramandi

    2016-11-01

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

  16. Bright circularly polarized soft X-ray high harmonics for X-ray magnetic circular dichroism.

    Science.gov (United States)

    Fan, Tingting; Grychtol, Patrik; Knut, Ronny; Hernández-García, Carlos; Hickstein, Daniel D; Zusin, Dmitriy; Gentry, Christian; Dollar, Franklin J; Mancuso, Christopher A; Hogle, Craig W; Kfir, Ofer; Legut, Dominik; Carva, Karel; Ellis, Jennifer L; Dorney, Kevin M; Chen, Cong; Shpyrko, Oleg G; Fullerton, Eric E; Cohen, Oren; Oppeneer, Peter M; Milošević, Dejan B; Becker, Andreas; Jaroń-Becker, Agnieszka A; Popmintchev, Tenio; Murnane, Margaret M; Kapteyn, Henry C

    2015-11-17

    We demonstrate, to our knowledge, the first bright circularly polarized high-harmonic beams in the soft X-ray region of the electromagnetic spectrum, and use them to implement X-ray magnetic circular dichroism measurements in a tabletop-scale setup. Using counterrotating circularly polarized laser fields at 1.3 and 0.79 µm, we generate circularly polarized harmonics with photon energies exceeding 160 eV. The harmonic spectra emerge as a sequence of closely spaced pairs of left and right circularly polarized peaks, with energies determined by conservation of energy and spin angular momentum. We explain the single-atom and macroscopic physics by identifying the dominant electron quantum trajectories and optimal phase-matching conditions. The first advanced phase-matched propagation simulations for circularly polarized harmonics reveal the influence of the finite phase-matching temporal window on the spectrum, as well as the unique polarization-shaped attosecond pulse train. Finally, we use, to our knowledge, the first tabletop X-ray magnetic circular dichroism measurements at the N4,5 absorption edges of Gd to validate the high degree of circularity, brightness, and stability of this light source. These results demonstrate the feasibility of manipulating the polarization, spectrum, and temporal shape of high harmonics in the soft X-ray region by manipulating the driving laser waveform.

  17. Programmable Aperture with MEMS Microshutter Arrays

    Science.gov (United States)

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

    2011-01-01

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

  18. Wind energy applications of synthetic aperture radar

    Energy Technology Data Exchange (ETDEWEB)

    Bruun Christiansen, M.

    2006-11-15

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

  19. Feature-enhanced synthetic aperture radar imaging

    Science.gov (United States)

    Cetin, Mujdat

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

  20. Environmental issues elimination through circular economy

    Science.gov (United States)

    Špirková, M.; Pokorná, E.; Šujanová, J.; Samáková, J.

    2016-04-01

    Environmental efforts of European Union are currently going towards circular economy. Tools like Extended Producer Responsibility and Eco-design were established. The circular economy deals with resources availability issue on one hand and waste management on the other hand. There are few pioneering companies all over the world with some kind of circular economy practice. Generally the concept is not very wide-spread. The paper aims to evaluate possibility of transition towards circular economy in Slovak industrial companies. They need to have an active approach to material treatment of their products after usage stage. Innovation is another important pre-condition for the transition. Main problem of current cradle to grave system is landfilling of valuable materials after one cycle of usage. Their potential value for next manufacturing cycles is lost. Companies may do not see connection between waste management and material resource prices and volatility of supplies. Municipalities are responsible for municipal waste collection and treatment in Slovakia. The circular economy operates by cradle to cradle principle. Company manages material flow until the material comes back to the beginning of manufacturing process by itself or by another partners. Stable material supplies with quite low costs are provided this way. It is necessary to deal with environmental problems in phase of product design. Questionnaire survey results show on one hand low involvement of industrial companies in waste management area, however on the other hand they are open to environmental innovations in future.

  1. Environmental issues elimination through circular economy

    International Nuclear Information System (INIS)

    Špirková, M.; Pokorná, E.; Šujanová, J.; Samáková, J.

    2016-01-01

    Environmental efforts of European Union are currently going towards circular economy. Tools like Extended Producer Responsibility and Eco-design were established. The circular economy deals with resources availability issue on one hand and waste management on the other hand. There are few pioneering companies all over the world with some kind of circular economy practice. Generally the concept is not very wide-spread. The paper aims to evaluate possibility of transition towards circular economy in Slovak industrial companies. They need to have an active approach to material treatment of their products after usage stage. Innovation is another important pre-condition for the transition. Main problem of current cradle to grave system is landfilling of valuable materials after one cycle of usage. Their potential value for next manufacturing cycles is lost. Companies may do not see connection between waste management and material resource prices and volatility of supplies. Municipalities are responsible for municipal waste collection and treatment in Slovakia. The circular economy operates by cradle to cradle principle. Company manages material flow until the material comes back to the beginning of manufacturing process by itself or by another partners. Stable material supplies with quite low costs are provided this way. It is necessary to deal with environmental problems in phase of product design. Questionnaire survey results show on one hand low involvement of industrial companies in waste management area, however on the other hand they are open to environmental innovations in future.

  2. Environmental issues elimination through circular economy

    Energy Technology Data Exchange (ETDEWEB)

    Špirková, M., E-mail: marta.spirkova@stuba.sk; Pokorná, E.; Šujanová, J.; Samáková, J. [Paulínska 16, 917 24 Trnava, Slovakia, Slovak University of Technology in Bratislava, Faculty of Materials Science and Technology in Trnava (Slovakia)

    2016-04-21

    Environmental efforts of European Union are currently going towards circular economy. Tools like Extended Producer Responsibility and Eco-design were established. The circular economy deals with resources availability issue on one hand and waste management on the other hand. There are few pioneering companies all over the world with some kind of circular economy practice. Generally the concept is not very wide-spread. The paper aims to evaluate possibility of transition towards circular economy in Slovak industrial companies. They need to have an active approach to material treatment of their products after usage stage. Innovation is another important pre-condition for the transition. Main problem of current cradle to grave system is landfilling of valuable materials after one cycle of usage. Their potential value for next manufacturing cycles is lost. Companies may do not see connection between waste management and material resource prices and volatility of supplies. Municipalities are responsible for municipal waste collection and treatment in Slovakia. The circular economy operates by cradle to cradle principle. Company manages material flow until the material comes back to the beginning of manufacturing process by itself or by another partners. Stable material supplies with quite low costs are provided this way. It is necessary to deal with environmental problems in phase of product design. Questionnaire survey results show on one hand low involvement of industrial companies in waste management area, however on the other hand they are open to environmental innovations in future.

  3. 3D-printed coded apertures for x-ray backscatter radiography

    Science.gov (United States)

    Muñoz, André A. M.; Vella, Anna; Healy, Matthew J. F.; Lane, David W.; Jupp, Ian; Lockley, David

    2017-09-01

    Many different mask patterns can be used for X-ray backscatter imaging using coded apertures, which can find application in the medical, industrial and security sectors. While some of these patterns may be considered to have a self-supporting structure, this is not the case for some of the most frequently used patterns such as uniformly redundant arrays or any pattern with a high open fraction. This makes mask construction difficult and usually requires a compromise in its design by drilling holes or adopting a no two holes touching version of the original pattern. In this study, this compromise was avoided by 3D printing a support structure that was then filled with a radiopaque material to create the completed mask. The coded masks were manufactured using two different methods, hot cast and cold cast. Hot casting involved casting a bismuth alloy at 80°C into the 3D printed acrylonitrile butadiene styrene mould which produced an absorber with density of 8.6 g cm-3. Cold casting was undertaken at room temperature, when a tungsten/epoxy composite was cast into a 3D printed polylactic acid mould. The cold cast procedure offered a greater density of around 9.6 to 10 g cm-3 and consequently greater X-ray attenuation. It was also found to be much easier to manufacture and more cost effective. A critical review of the manufacturing procedure is presented along with some typical images. In both cases the 3D printing process allowed square apertures to be created avoiding their approximation by circular holes when conventional drilling is used.

  4. Experimental evidence for circular inference in schizophrenia

    Science.gov (United States)

    Jardri, Renaud; Duverne, Sandrine; Litvinova, Alexandra S.; Denève, Sophie

    2017-01-01

    Schizophrenia (SCZ) is a complex mental disorder that may result in some combination of hallucinations, delusions and disorganized thinking. Here SCZ patients and healthy controls (CTLs) report their level of confidence on a forced-choice task that manipulated the strength of sensory evidence and prior information. Neither group's responses can be explained by simple Bayesian inference. Rather, individual responses are best captured by a model with different degrees of circular inference. Circular inference refers to a corruption of sensory data by prior information and vice versa, leading us to `see what we expect' (through descending loops), to `expect what we see' (through ascending loops) or both. Ascending loops are stronger for SCZ than CTLs and correlate with the severity of positive symptoms. Descending loops correlate with the severity of negative symptoms. Both loops correlate with disorganized symptoms. The findings suggest that circular inference might mediate the clinical manifestations of SCZ.

  5. Optics modules for circular accelerator design

    International Nuclear Information System (INIS)

    Brown, K.L.; Servranckx, R.V.

    1986-05-01

    The first-order differential equations of motion for a single particle in a closed circular machine are solved, introducing the concepts of phase shift, beta functions, and the Courant-Snyder invariant. The transfer matrix between two points in the machine is derived as a function of the phase shift and the parameters contained in the Courant-Snyder invariant. Typical optical modules used in circular machine designs are introduced and related to their characteristic transfer matrix elements, the phase shift through them, and the Courant-Snyder-Twiss parameters. The systematics of some elementary phase ellipse matching problems between optical modules are discussed. Second-order optical modules are discussed, including how they are used to provide the momentum bandwidth needed for the design of a typical circular machine

  6. Product design in the circular economy

    DEFF Research Database (Denmark)

    Atlason, Reynir Smari; Giacalone, Davide; Parajuly, Keshav

    2017-01-01

    . Such strategies may also assist societies in the transition to a more circular economy. However, at the end of a product's useful life, it is uncertain whether the end users will handle the product according to the original intention of the product developers. Situated within this context, this research...... of according to a favorable EoL scenarios, but may not have any prior expectations at point of purchase. Reuse potential emerged as the most attractive EoL scenario, suggesting that users' preferences are largely aligned with the concept of circular economy. Interestingly, women were found to prefer all Eo...

  7. Forced vibrations of rotating circular cylindrical shells

    International Nuclear Information System (INIS)

    Igawa, Hirotaka; Maruyama, Yoshiyuki; Endo, Mitsuru

    1995-01-01

    Forced vibrations of rotating circular cylindrical shells are investigated. Basic equations, including the effect of initial stress due to rotation, are formulated by the finite-element method. The characteristic relations for finite elements are derived from the energy principle by considering the finite strain. The equations of motion can be separated into quasi-static and dynamic ones, i.e., the equations in the steady rotating state and those in the vibration state. Radial concentrated impulses are considered as the external dynamic force. The transient responses of circular cylindrical shells are numerically calculated under various boundary conditions and rotating speeds. (author)

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

    Science.gov (United States)

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

    2011-09-01

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

  9. Code aperture optimization for spectrally agile compressive imaging.

    Science.gov (United States)

    Arguello, Henry; Arce, Gonzalo R

    2011-11-01

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

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

    Science.gov (United States)

    Cauble, Galen D.; Wayne, David T.

    2017-09-01

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

  11. A New Method of Designing Circularly Symmetric Shaped Dual Reflector Antennas Using Distorted Conics

    Directory of Open Access Journals (Sweden)

    Mohammad Asif Zaman

    2014-01-01

    Full Text Available A new method of designing circularly symmetric shaped dual reflector antennas using distorted conics is presented. The surface of the shaped subreflector is expressed using a new set of equations employing differential geometry. The proposed equations require only a small number of parameters to accurately describe practical shaped subreflector surfaces. A geometrical optics (GO based method is used to synthesize the shaped main reflector surface corresponding to the shaped subreflector. Using the proposed method, a shaped Cassegrain dual reflector system is designed. The field scattered from the subreflector is calculated using uniform geometrical theory of diffraction (UTD. Finally, a numerical example is provided showing how a shaped subreflector produces more uniform illumination over the main reflector aperture compared to an unshaped subreflector.

  12. Analytical approach to chromatic correction in the final focus system of circular colliders

    Directory of Open Access Journals (Sweden)

    Yunhai Cai

    2016-11-01

    Full Text Available A conventional final focus system in particle accelerators is systematically analyzed. We find simple relations between the parameters of two focus modules in the final telescope. Using the relations, we derive the chromatic Courant-Snyder parameters for the telescope. The parameters are scaled approximately according to (L^{*}/β_{y}^{*}δ, where L^{*} is the distance from the interaction point to the first quadrupole, β_{y}^{*} the vertical beta function at the interaction point, and δ the relative momentum deviation. Most importantly, we show how to compensate its chromaticity order by order in δ by a traditional correction module flanked by an asymmetric pair of harmonic multipoles. The method enables a circular Higgs collider with 2% momentum aperture and illuminates a path forward to 4% in the future.

  13. Computation Reduction Oriented Circular Scanning SAR Raw Data Simulation on Multi-GPUs

    Directory of Open Access Journals (Sweden)

    Hu Chen

    2016-08-01

    Full Text Available As a special working mode, the circular scanning Synthetic Aperture Radar (SAR is widely used in the earth observation. With the increase of resolution and swath width, the simulation data has a massive increase, which boosts the new requirements of efficiency. Through analyzing the redundancy in the raw data simulation based on Graphics Processing Unit (GPU, a fast simulation method considering reduction of redundant computation is realized by the multi-GPUs and Message Passing Interface (MPI. The results show that the efficiency of 4-GPUs increases 2 times through the redundant reduction, and the hardware cost decreases by 50%, thus the overall speedup achieves 350 times than the traditional CPU simulation.

  14. Beam Dynamics and Beam Losses - Circular Machines

    CERN Document Server

    Kain, V

    2016-01-01

    A basic introduction to transverse and longitudinal beam dynamics as well as the most relevant beam loss mechanisms in circular machines will be presented in this lecture. This lecture is intended for physicists and engineers with little or no knowledge of this subject.

  15. Time can't be circular

    CERN Multimedia

    2003-01-01

    "Delivering the Albert Einstein lecture at the Centre for Philosophy and Foundations of Science on Tuesday, Nobel Laureate Professor Gerard Hooft said that any notion of time can not be circular or have loops or multi dimensionality" (1/2 page).

  16. Home Sewage Disposal. Special Circular 212.

    Science.gov (United States)

    Wooding, N. Henry

    This circular provides current information for homeowners who must repair or replace existing on-lot sewage disposal systems. Site requirements, characteristics and preparation are outlined for a variety of alternatives such as elevated sand mounds, sand-lined beds and trenches, and oversized absorption area. Diagrams indicating construction…

  17. 78 FR 14620 - Joint Development: Proposed Circular

    Science.gov (United States)

    2013-03-06

    ... the most common crosscutting requirements. This circular incorporates provisions of the Moving Ahead... eligibility criteria, crosscutting requirements, and restrictions on the use of real property acquired with... continuing control of real property in the context of a joint development project. E. Chapter V--Crosscutting...

  18. Breaking the Barriers to the Circular Economy

    NARCIS (Netherlands)

    Kirchherr, J.W.|info:eu-repo/dai/nl/411261487; Hekkert, M.P.|info:eu-repo/dai/nl/143777629; Bour, Ruben; Huijbrechtse-Truijens, Anne; Kostense-Smit, Erica; Muller, Jennifer

    2017-01-01

    The Copernicus Institute of Sustainable Development, Utrecht University, the Netherlands and Deloitte have jointly carried out research on barriers to the Circular Economy (CE) in the European Union. For this research, a survey with 153 businesses, 55 government officials and expert interviews with

  19. Institutional incentives in circular economy transition

    NARCIS (Netherlands)

    Fischer, Aglaia; Pascucci, Stefano

    2017-01-01

    The aim of this paper is to gain insight into how requirements for transitioning to circular economy creates new organizational forms in inter-firm collaborations, and ultimately how they stimulate the emergence of new institutions enhancing sustainability. Two strands of literature, one on

  20. Falling aprons at circular piers under currents

    NARCIS (Netherlands)

    De Sonneville, B.; Van Velzen, G.; Verheij, H.J.; Dorst, K.

    2012-01-01

    Traditional guidelines on rock protection at circular piers predominantly focus on preventing shear failure (by choosing a sufficiently large rock size), winnowing failure (by designing an appropriate filter) and edge failure (by selecting a sufficient extent). In particular areas (e.g. in an

  1. Solid angle subtended by two circular discs

    International Nuclear Information System (INIS)

    Gilly, Louis.

    1978-09-01

    Methods of calculation of solid angles, subtended by two circular discs are analysed. Calculus are methodically classified as follow: series development Legendre polynomes, defined integral, elliptic integrals, Bessel integrals, multiple integrals, Monte Carlo method, electrostatic analogy. Applications in Nuclear Physics are added as examples. List of numeric tables completes bibliography [fr

  2. Statistical investigation of hydraulic driven circular interpolation ...

    Indian Academy of Sciences (India)

    2Mechanical Education Department, Gazi University, 06500 Ankara, Turkey. 3Electrical and Electronics Engineering .... PLC (Programmable Logic Controller) set. An incremental type linear encoder with ... realize the CNC basic motions such as linear (G01) and circular interpolation (G02, G03). 2.1 CNC system. The control ...

  3. Transition from Poisson to circular unitary ensemble

    Indian Academy of Sciences (India)

    ensemble (SE). These are defined by invariance of the ensemble measure under the orthogonal, unitary and symplectic transformations respectively and are related to the time reversal and rotational symmetries of the system. Gaussian ensembles. (GE) of Hermitian matrices and circular ensembles (CE) of unitary matrices ...

  4. 76 FR 60593 - Title VI; Proposed Circular

    Science.gov (United States)

    2011-09-29

    ... recommends. In addition, we propose changing the format to make this Circular consistent with the style of... cross-referencing information related to Title VI that FTA and FHWA jointly assess and evaluate during... Title VI reporting requirements for each of these roles. We also propose cross-referencing information...

  5. the mathematics of ghanaian circular musical drumheads

    African Journals Online (AJOL)

    User

    The mathematics of percussion drums and other musical instruments has been delved into by lots of researchers tackling it from different angles, and especially for circular drumheads with constant tension. Such drums include the conga which usually produces rhythmic sounds. But little or no attempt has been made.

  6. the mathematics of ghanaian circular musical drumheads

    African Journals Online (AJOL)

    User

    overtones. INTRODUCTION. The mathematics of percussion drums and other musical instruments has been delved into by lots of researchers tackling it from different angles, and especially for circular drumheads with constant tension. Such drums include the conga which usually produces rhythmic sounds. But little or no ...

  7. Compliance Supplement. OMB Circular A-133.

    Science.gov (United States)

    Office of Management and Budget, Washington, DC.

    This document is a supplement to Circular A-133 (1990) from the Office of Management and Budget (OMB), which extended the government's "single audit process" for agencies that administer federal financial assistance programs to higher education institutions and non-profit organizations. This supplement is based on the 1996 Amendments …

  8. A yarn interaction model for circular braiding

    NARCIS (Netherlands)

    van Ravenhorst, J.H.; Akkerman, Remko

    2016-01-01

    Machine control data for the automation of the circular braiding process has been generated using previously published mathematical models that neglect yarn interaction. This resulted in a significant deviation from the required braid angle at mandrel cross-sectional changes, likely caused by an

  9. 77 FR 52116 - Title VI; Final Circular

    Science.gov (United States)

    2012-08-28

    ... inclusive as the U.S. Department of Health and Human Services (HHS) poverty guidelines. A few commenters... Civil Rights Act of 1964. The purpose of this Circular is to provide recipients of FTA financial... Rights, Federal Transit Administration, 1200 New Jersey Ave. SE., Room E54-422, Washington, DC 20590...

  10. Cold Rydberg atoms in circular states

    Science.gov (United States)

    Anderson, David; Schwarzkopf, Andrew; Raithel, Georg

    2012-06-01

    Circular-state Rydberg atoms are interesting in that they exhibit a unique combination of extraordinary properties; long lifetimes (˜n^5), large magnetic moments (l=|m|=n-1) and no first order Stark shift. Circular states have found applications in cavity quantum electrodynamics and precision measurements [1,2], among other studies. In this work we present the production of circular states in an atom trapping apparatus using an adiabatic state-switching method (the crossed-field method [3]). To date, we have observed lifetimes of adiabatically prepared states of several milliseconds. Their relatively large ionization electric fields have been verified by time-of-flight signatures of ion trajectories. We intend to explore the magnetic trapping of circular state Rydberg atoms, as well as their production and interaction properties in ultra-cold and degenerate samples.[4pt] [1] P. Bertet et al., Phys. Rev. Lett., 88, 14 (2002)[0pt] [2] M. Brune et al., Phys. Rev. Lett., 72, 21 (1994)[0pt] [3] D. Delande and J.C. Gay, Europhys. Lett., 5, 303-308 (1988).

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

    International Nuclear Information System (INIS)

    Farkas, Z.D.

    1988-09-01

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

  12. Permeability and dispersivity of variable-aperture fracture systems

    International Nuclear Information System (INIS)

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

    1990-01-01

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

  13. Central obscuration effects on optical synthetic aperture imaging

    Science.gov (United States)

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

    2014-02-01

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

  14. 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).

  15. 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

  16. Aperture determination of RHIC92 from randomly generated initial coordinates

    International Nuclear Information System (INIS)

    Dell, G.F.

    1992-01-01

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

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

    Science.gov (United States)

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

    2017-12-01

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

  18. Synthetic aperture radar processing with polar formatted subapertures

    Science.gov (United States)

    Doerry, Armin W.

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

  19. 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.

  20. Synthetic Aperture Sequential Beamformation applied to medical imaging

    DEFF Research Database (Denmark)

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

    2012-01-01

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

  1. Highly efficient machining of non-circular freeform optics using fast tool servo assisted ultra-precision turning.

    Science.gov (United States)

    Li, Zexiao; Fang, Fengzhou; Zhang, Xiaodong; Liu, Xianlei; Gao, Huimin

    2017-10-16

    Freeform optics has been regarded as the next generation of the optical components, especially those with non-circular apertures are playing an increasingly significant role in scanning field and specialized optical system. However, there still exist challenges to machine non-circular optical freeform surface. This paper is focused on highly efficiently generating freeform surfaces with optical surface quality by ultra-precision turning using a fast tool servo (FTS). A systematic strategy of machining smooth freeform surfaces with rectangular aperture is proposed in this paper. The contour of freeform optics is decomposed and assigned to the motions of slide and FTS back-and-forth. An optimized model is established for deriving the profile of the rotational component to cater for the capacity of FTS. Tool path reconstruction is carried out to generate a smooth tool trajectory and modified the contour to cater for the stroke of FTS. Simulation is adopted to analyze the machining property of a typical rectangular freeform surface. A rectangular freeform surface is efficiently machined via the proposed method, where a micron level profile error and nanometric finish in Ra are realized. Characteristics of reflection are analyzed via experiment and simulation. Prospects of such machining approach are discussed to provide guidance to future study.

  2. A simple circular-polarized antenna: Circular waveguide horn coated with lossy magnetic material

    Science.gov (United States)

    Lee, Choon S.; Justice, D. W.; Lee, Shung-Wu

    1988-01-01

    It is shown that a circular waveguide horn coated with a lossy material in its interior wall can be used as an alternative to a corrugated waveguide for radiating a circularly polarized (CP) field. To achieve good CP radiation, the diameter of the structure must be larger than the free-space wavelength, and the coating material must be sufficiently lossy and magnetic. The device is cheaper and lighter in weight than the corrugated one.

  3. Circular depolarization ratios of single water droplets and finite ice circular cylinders: a modeling study

    Directory of Open Access Journals (Sweden)

    M. Nicolet

    2012-05-01

    Full Text Available Computations of the phase matrix elements for single water droplets and ice crystals in fixed orientations are presented to determine if circular depolarization δC is more accurate than linear depolarization for phase discrimination. T-matrix simulations were performed to calculate right-handed and left-handed circular depolarization ratios δ+C, respectively δ−C and to compare them with linear ones. Ice crystals are assumed to have a circular cylindrical shape where their surface-equivalent diameters range up to 5 μm. The circular depolarization ratios of ice particles were generally higher than linear depolarization and depended mostly on the particle orientation as well as their sizes. The fraction of non-detectable ice crystals (δ<0.05 was smaller considering a circular polarized light source, reaching 4.5%. However, water droplets also depolarized light circularly for scattering angles smaller than 179° and size parameters smaller than 6 at side- and backscattering regions. Differentiation between ice crystals and water droplets might be difficult for experiments performed at backscattering angles which deviate from 180° unlike LIDAR applications. Instruments exploiting the difference in the P44/P11 ratio at a scattering angle around 115° are significantly constrained in distinguishing between water and ice because small droplets with size parameters between 5 and 10 do cause very high circular depolarizations at this angle. If the absence of the liquid phase is confirmed, the use of circular depolarization in single particle detection is more sensitive and less affected by particle orientation.

  4. A Direction Finding Method with A 3-D Array Based on Aperture Synthesis

    Science.gov (United States)

    Li, Shiwen; Chen, Liangbing; Gao, Zhaozhao; Ma, Wenfeng

    2018-01-01

    Direction finding for electronic warfare application should provide a wider field of view as possible. But the maximum unambiguous field of view for conventional direction finding methods is a hemisphere. It cannot distinguish the direction of arrival of the signals from the back lobe of the array. In this paper, a full 3-D direction finding method based on aperture synthesis radiometry is proposed. The model of the direction finding system is illustrated, and the fundamentals are presented. The relationship between the outputs of the measurements of a 3-D array and the 3-D power distribution of the point sources can be represented by a 3-D Fourier transform, and then the 3-D power distribution of the point sources can be reconstructed by an inverse 3-D Fourier transform. And in order to display the 3-D power distribution of the point sources conveniently, the whole spherical distribution is represented by two 2-D circular distribution images, one of which is for the upper hemisphere, and the other is for the lower hemisphere. Then a numeric simulation is designed and conducted to demonstrate the feasibility of the method. The results show that the method can estimate the arbitrary direction of arrival of the signals in the 3-D space correctly.

  5. Three-dimensional bubble field resolution using synthetic aperture imaging: application to a plunging jet

    Science.gov (United States)

    Belden, Jesse; Ravela, Sai; Truscott, Tadd T.; Techet, Alexandra H.

    2012-09-01

    A methodology for resolving three-dimensional (3D) bubble fields using 3D synthetic aperture imaging (SA imaging) is developed and applied to the bubbly flows induced by a turbulent circular plunging jet. 3D SA imaging involves capturing entirely in-focus images in an array of cameras with multiple viewpoints, then reprojecting the images into the measurement volume and combining them post capture. The result is a stack of synthetically refocused images that span the measurement volume with each refocused image having a narrow focus on a particular plane. In this paper, bubble shadow images are captured by projecting diffuse backlight onto the measurement volume. 3D SA imaging is ideally suited to investigate optically dense multiphase flows due to the ability to reconstruct volumes that contain partial occlusions. Instantaneous bubble sizes and locations in the plunging jet bubble fields are extracted from the volumes using two feature extraction algorithms and presented for various jet heights. The data are compared with existing literature on bubble penetration depth and size distributions. A scaling law for the integrated air concentration as a function of depth below the free-surface is proposed. Coupled with scaling laws for a parameter describing the radius of the bubble cone and radial concentration profiles, this new scaling law can be used to determine the entire air concentration profile given a minimal number of single-point measurements.

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

    International Nuclear Information System (INIS)

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

    2006-01-01

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

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

    Science.gov (United States)

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

    2006-10-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2006-10-07

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

  9. Circular magnetic bistability in Co-rich amorphous microwires

    International Nuclear Information System (INIS)

    Chizhik, A; Gonzalez, J; Zhukov, A; Blanco, J M

    2003-01-01

    Circular magnetic bistability associated with a large Barkhausen jump between two states with opposite directions of circular magnetization have been observed by magneto-optical Kerr effect in nearly-zero magnetostrictive glass covered Co-rich amorphous microwire. The influence of external axial tensile stress on the circular switching field has been studied. Observed results have been related with a circular magneto-elastic anisotropy induced by a tensile stress in the outer transversally magnetized shell of the microwire

  10. Development pattern of circular economy in Jiangsu coastland

    OpenAIRE

    Wang, Liang

    2009-01-01

    Circular economy is an effective development pattern to balance economic growth, social development and environmental protection. Based on apprehending the connotation of circular economy, this paper fully considers and studies on the future trends in this area according to the theory of circular economy and the empirical circumstances of Jiangsu Coastland. This paper also discusses the circular economy development pattern adopted by Jiangsu coastland during economic and social development fr...

  11. Supply chain in a circular economy: a multidimensional research agenda

    OpenAIRE

    Dora, M; Manjot Singh Bhatia; Gallear, D

    2016-01-01

    This paper focuses on analysing and synthesising the extant research published on supply chains in the context of circular economy. Circular supply chain (CSC) broadly relates to remanufacturing, reusing and recycling processes in the circular economy in which at every stage of a product’s lifecycle consideration is given to the most efficient use of resources (Genovese et al., 2015). The Circular Economy promoted by the European Commission includes industrial systems that are restorative by ...

  12. Synthetic Aperture Sequential Beamforming using Spatial Matched Filtering

    DEFF Research Database (Denmark)

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

    2017-01-01

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

  13. Velocity estimation using synthetic aperture imaging [blood flow

    DEFF Research Database (Denmark)

    Nikolov, Svetoslav; Jensen, Jørgen Arendt

    2001-01-01

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

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

    Science.gov (United States)

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

    2014-01-01

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

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

    DEFF Research Database (Denmark)

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

    2003-01-01

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

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

    CERN Document Server

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

    2014-01-01

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

  17. Synthetic aperture ultrasound Fourier beamformation using virtual sources

    DEFF Research Database (Denmark)

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

    2016-01-01

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

  18. Fourier beamformation of multistatic synthetic aperture ultrasound imaging

    DEFF Research Database (Denmark)

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

    2015-01-01

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

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

    DEFF Research Database (Denmark)

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

    2014-01-01

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

  20. Comparison between different encoding schemes for synthetic aperture imaging

    DEFF Research Database (Denmark)

    Nikolov, Svetoslav; Jensen, Jørgen Arendt

    2002-01-01

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

  1. Large aperture components for solid state laser fusion systems

    International Nuclear Information System (INIS)

    Simmons, W.W.

    1978-01-01

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

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

    Indian Academy of Sciences (India)

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

  3. Exploitation of distributed scatterers in synthetic aperture radar interferometry

    NARCIS (Netherlands)

    Samiei Esfahany, S.

    2017-01-01

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

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

    Science.gov (United States)

    2015-10-26

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

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

    Science.gov (United States)

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

    2017-11-01

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

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

    Indian Academy of Sciences (India)

    29

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

  7. Motion compensated beamforming in synthetic aperture vector flow imaging

    DEFF Research Database (Denmark)

    Oddershede, Niels; Jensen, Jørgen Arendt

    2006-01-01

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

  8. In Vivo Evaluation of Synthetic Aperture Sequential Beamforming

    DEFF Research Database (Denmark)

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

    2012-01-01

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

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

    NARCIS (Netherlands)

    Ernst, G.J.

    1982-01-01

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

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

    Indian Academy of Sciences (India)

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

  11. Brightness-temperature retrival methods in synthetic aperture radiometers

    OpenAIRE

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

    2009-01-01

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

  12. Implementation and investigation of circular slot UWB antenna with dual-band-notched characteristics

    Directory of Open Access Journals (Sweden)

    DadashZadeh Gholamreza

    2011-01-01

    Full Text Available Abstract The design and analysis of an ultra wideband aperture antenna with dual-band-notched characteristics are presented. The proposed antenna consists of a circular ring exciting stub on the front side and a circular slot on the back ground plane. By utilizing a parasitic strip and a T-shaped stub on the antenna structure, two notched bands of 850 MHz (3.5-4.35 GHz and 900 MHz (5.05-5.95 GHz are achieved. The proposed antenna is fabricated and measured. Measured results show that this antenna operates from 2.3 GHz to upper 11 GHz for voltage standing wave ratio less than 2, except two frequency notched bands of 3.5-4.35 and 5.05-5.95 GHz. Moreover, the experimental results show that proposed antenna has stable radiation patterns and constant gain. A conceptual circuit model, which is based on the measured impedance of the proposed antenna, is also shown to investigate the dual-band-notched characteristics.

  13. A multifocal collimator with circularly distributed focal points for SPECT imaging

    International Nuclear Information System (INIS)

    Guillemaud, R.; Grangeat, P.

    1994-01-01

    The authors propose a new circular multifocal collimator which has multiple axial focal points distributed on a transverse circle. This distribution provides a strong focusing at the center of the detector like a cone-beam collimator, with a good sensitivity, and a weak transverse focusing at the periphery, to ensure acquisition of sufficient data, in order to prevent truncation artifacts. For a circular acquisition trajectory, each projection set of the multifocal geometry is equivalent to a virtual cone-beam projection set with a larger detector. Due to this equivalence, the authors derive a first solution for an analytical multifocal reconstruction algorithm: to rebin the projection set from multifocal to cone-beam geometry, then to use a 3D cone-beam reconstruction algorithm. The authors propose to use the Grangeat algorithm in order to deal with a large cone-beam aperture. Finally, the authors present results on simulated data for heart phantom, for a Defrise phantom and for a MTF study. The conclusion is that, from a multifocal projection set, objects are reconstructed without truncation artifacts, with a good precision at their center and with a loss of resolution at the periphery. In addition, the 3D cone-beam artifacts are reduced with the use of the Grangeat algorithm for the reconstruction step

  14. A product design framework for a circular economy

    NARCIS (Netherlands)

    Van den Berg, M.R.; Bakker, C.A.

    2015-01-01

    The paper provides a circular economy framework from a product design perspective with tools to aid product designers in applying circular product design in practice. Design research for circular economy has so far mainly been limited to referring to existing fields of research such as design for

  15. Circular on early marriage, March 1988.

    Science.gov (United States)

    1988-01-01

    This Circular calls on government at all levels in Hunan, China, to summon the departments concerned thoroughly to investigate the problem of early child-bearing so that they can do a good job in managing the problems of unregistered cohabiting and of unmarried mothers. The Circular recommends that: "It is necessary to criticize and educate, and even punish by discipline, those parents who connive with their sons and daughters in practicing unregistered cohabiting." It also states the following: "It is necessary to keep a strict check on registry personnel who do not carry out their duties properly. Those who violate laws and discipline, engage in malpractices for selfish ends, and practice bribery and corruption, resulting in early marriage and child-bearing, must be dealt with strictly. Legal sanctions must be enforced against those who break the law." full text

  16. Realization of Bohr-like circular wavepackets

    Science.gov (United States)

    Mestayer, Jeff; Wyker, B.; Dunning, F. B.; Reinhold, C.; Yoshida, S.; Burgdörfer, J.

    2008-05-01

    We demonstrate a protocol to create localized wavepackets in very-high n Rydberg states that travel in near-circular orbits around the nucleus. Although these wavepackets slowly dephase and eventually lose their localization, their motion can be followed for several orbital periods. These wavepackets represent the closest analog yet achieved to the original Bohr model of the atom, i.e., an electron in circular classical orbit around the nucleus. The time evolution of the momentum and position of the wavepackets is monitored using, respectively, short half-cycle pulses and sudden field steps, which are applied after a variable time delay and along different directions. The present technique is explained with the aid of CTMC simulations, and possible extension to creation of elusive ``planetary atoms'' in highly correlated stable multiply-excited states is discussed. Research supported by the NSF, the Robert A. Welch Foundation, the OBES, U.S. DoE to ORNL, and by the FWF (Austria).

  17. The Biogenesis of Nascent Circular RNAs

    Directory of Open Access Journals (Sweden)

    Yang Zhang

    2016-04-01

    Full Text Available Steady-state circular RNAs (circRNAs have been mapped to thousands of genomic loci in mammals. We studied circRNA processing using metabolic tagging of nascent RNAs with 4-thiouridine (4sU. Strikingly, the efficiency of circRNA processing from pre-mRNA is extremely low endogenously. Additional studies revealed that back-splicing outcomes correlate with fast RNA Polymerase II elongation rate and are tightly controlled by cis-elements in vivo. Additionally, prolonged 4sU labeling in cells shows that circRNAs are largely processed post-transcriptionally and that circRNAs are stable. Circular RNAs that are abundant at a steady-state level tend to accumulate. This is particularly true in cells, such as neurons, that have slow division rates. This study uncovers features of circRNA biogenesis by investigating the link between nascent circRNA processing and transcription.

  18. Design of circular differential microphone arrays

    CERN Document Server

    Benesty, Jacob; Cohen, Israel

    2015-01-01

    Recently, we proposed a completely novel and efficient way to design differential beamforming algorithms for linear microphone arrays. Thanks to this very flexible approach, any order of differential arrays can be designed. Moreover, they can be made robust against white noise amplification, which is the main inconvenience in these types of arrays. The other well-known problem with linear arrays is that electronic steering is not really feasible.  In this book, we extend all these fundamental ideas to circular microphone arrays and show that we can design small and compact differential arrays of any order that can be electronically steered in many different directions and offer a good degree of control of the white noise amplification problem, high directional gain, and frequency-independent response. We also present a number of practical examples, demonstrating that differential beamforming with circular microphone arrays is likely one of the best candidates for applications involving speech enhancement (i....

  19. Self-organization in circular shear layers

    DEFF Research Database (Denmark)

    Bergeron, K.; Coutsias, E.A.; Lynov, Jens-Peter

    1996-01-01

    Experiments on forced circular shear layers performed in both magnetized plasmas and in rotating fluids reveal qualitatively similar self-organization processes leading to the formation of patterns of coherent vortical structures with varying complexity. In this paper results are presented from...... both weakly nonlinear analysis and full numerical simulations that closely reproduce the experimental observations. Varying the Reynolds number leads to bifurcation sequences accompanied by topological changes in the distribution of the coherent structures as well as clear transitions in the total...

  20. Vibration of circular bladed disk with imperfections

    Czech Academy of Sciences Publication Activity Database

    Půst, Ladislav; Pešek, Luděk

    2011-01-01

    Roč. 21, č. 10 (2011), s. 2893-2904 ISSN 0218-1274 R&D Projects: GA ČR GA101/09/1166 Institutional research plan: CEZ:AV0Z20760514 Keywords : circular bladed disk * vibration * imperfection * nonlinear damping Subject RIV: BI - Acoustics Impact factor: 0.755, year: 2011 http://www.worldscinet.com/ijbc/21/2110/S0218127411030210.html

  1. Circular Intensity Differential Scattering of chiral molecules

    Energy Technology Data Exchange (ETDEWEB)

    Bustamante, C.J.

    1980-12-01

    In this thesis a theory of the Circular Intensity Differential Scattering (CIDS) of chiral molecules as modelled by a helix oriented with respect to the direction of incidence of light is presented. It is shown that a necessary condition for the existence of CIDS is the presence of an asymmetric polarizability in the scatterer. The polarizability of the scatterer is assumed generally complex, so that both refractive and absorptive phenomena are taken into account.

  2. Moving beyond the circular economy [forthcoming

    OpenAIRE

    Moreno, MA; Braithwaite, N; Cooper, T

    2014-01-01

    The production model, which currently underpins our material prosperity, remains highly resource-intensive, and the volume of minerals, ores and fossil fuels consumed annually is set to triple by 2050 unless economic growth is decoupled from resource consumption [1]. One response that has been attracting significant attention is the idea of a circular economy (or close loop economy), in which waste is transformed into value rather than disposed of to landfill [2]. While acknowledging potentia...

  3. Notas sobre una escuela circular prefabricada

    Directory of Open Access Journals (Sweden)

    Neutra, Richard J.

    1961-09-01

    Full Text Available En 1930, la idea de una planta circular para escuela, abarcando un espacio exterior frente a un edificio de usos varios, era ya antigua por lo menos en diez años. El Museo de Arte Moderno de Nueva York, que por aquellos tiempos instaló y preparó en sus nuevas dependencias la primera exposición masiva de Arquitectura moderna, dispuso una magnífica maqueta de este proyecto de Richard J. Neutra.

  4. Nuclear collisions at the Future Circular Collider

    Energy Technology Data Exchange (ETDEWEB)

    Armesto, N., E-mail: nestor.armesto@usc.es [Departamento de Física de Partículas and IGFAE, Universidade de Santiago de Compostela, 15706 Santiago de Compostela, Galicia-Spain (Spain); Dainese, A. [INFN – Sezione di Padova, 35131 Padova (Italy); D' Enterria, D. [Physics Department, CERN, CH-1211 Genéve 23 (Switzerland); Masciocchi, S. [EMMI and GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, Darmstadt (Germany); Roland, C. [Massachusetts Institute of Technology, Cambridge, MA 02139-4307 (United States); Salgado, C.A. [Departamento de Física de Partículas and IGFAE, Universidade de Santiago de Compostela, 15706 Santiago de Compostela, Galicia-Spain (Spain); Leeuwen, M. van [Nikhef, National Institute for Subatomic Physics, Amsterdam (Netherlands); Institute for Subatomic Physics of Utrecht University, Utrecht (Netherlands); Wiedemann, U.A. [Physics Department, CERN, CH-1211 Genéve 23 (Switzerland)

    2016-12-15

    The Future Circular Collider is a new proposed collider at CERN with centre-of-mass energies around 100 TeV in the pp mode. Ongoing studies aim at assessing its physics potential and technical feasibility. Here we focus on updates in physics opportunities accessible in pA and AA collisions not covered in previous Quark Matter contributions, including Quark-Gluon Plasma and gluon saturation studies, novel hard probes of QCD matter, and photon-induced collisions.

  5. Nuclear collisions at the Future Circular Collider

    CERN Document Server

    Armesto, N.; d'Enterria, D.; Masciocchi, S.; Roland, C.; Salgado, C.A.; van Leeuwen, M.; Wiedemann, U.A.

    2016-01-01

    The Future Circular Collider is a new proposed collider at CERN with centre-of-mass energies around 100 TeV in the pp mode. Ongoing studies aim at assessing its physics potential and technical feasibility. Here we focus on updates in physics opportunities accessible in pA and AA collisions not covered in previous Quark Matter contributions, including Quark-Gluon Plasma and gluon saturation studies, novel hard probes of QCD matter, and photon-induced collisions.

  6. FROM CIRCULAR ECONOMY TO BLUE ECONOMY

    Directory of Open Access Journals (Sweden)

    Iustin-Emanuel, ALEXANDRU

    2014-11-01

    Full Text Available Addressing the subject of this essay is based on the background ideas generated by a new branch of science - Biomimicry. According to European Commissioner for the Environment, "Nature is the perfect model of circular economy". Therefore, by imitating nature, we are witnessing a process of cycle redesign: production-consumption-recycling. The authors present some reflections on the European Commission's decision to adopt after July 1, 2014 new measures concerning the development of more circular economies. Starting from the principles of Ecolonomy, which is based on the whole living paradigm, this paper argues for the development within each economy of entrepreneurial policies related to the Blue economy. In its turn, Blue economy is based on scientific analyses that identify the best solutions in a business. Thus, formation of social capital will lead to healthier and cheaper products, which will stimulate entrepreneurship. Blue economy is another way of thinking economic practice and is a new model of business design. It is a healthy, sustainable business, designed for people. In fact, it is the core of the whole living paradigm through which, towards 2020, circular economy will grow more and more.

  7. System for circular and complex tomography

    International Nuclear Information System (INIS)

    Hellstrom, M.J.

    1979-01-01

    This invention discloses a system for conducting circular as well as complex tomographic procedures utilizing apparatus which has no mechanical linkage between the X-ray source and the X-ray receptor. The path of travel of the X-ray source both circularly and linearly is sensed by electromagnetic radiation and more particularly by light radiation which is generated by a laser. The linear travel is sensed by means of reflected laser radiation directed to the X-ray source and fed to an interferometer. The circular travel, on the other hand, is sensed by means of a laser gyroscope also receiving light radiation from a laser. Optical energy sensing means is thus used to generate command signals which are coupled to respective drive motors which act to rotate and when desirable, translate the X-ray receptor so that its motion follows the motion, both orbital and linear, of the X-ray source for performing any desired type of tomographic procedure

  8. Circular Polarization in Turbulent Blazar Jets

    Directory of Open Access Journals (Sweden)

    Nicholas Roy MacDonald

    2017-11-01

    Full Text Available Circular polarization (CP provides an invaluable probe into the underlying plasma content of relativistic jets. CP can be generated within the jet through a physical process known as linear birefringence. This is a physical mechanism through which initially linearly polarized emission produced in one region of the jet is attenuated by Faraday rotation as it passes through other regions of the jet with distinct magnetic field orientations. Marscher developed the turbulent extreme multi-zone (TEMZ model of blazar emission which mimics these types of magnetic geometries with collections of thousands of plasma cells passing through a standing conical shock. I have recently developed a radiative transfer algorithm to generate synthetic images of the time-dependent circularly polarized intensity emanating from the TEMZ model at different radio frequencies. In this study, we produce synthetic multi-epoch observations that highlight the temporal variability in the circular polarization produced by the TEMZ model. We also explore the effect that different plasma compositions within the jet have on the resultant levels of CP.

  9. Architectural Surfaces and Structures from Circular Arcs

    KAUST Repository

    Shi, Ling

    2013-12-01

    In recent decades, the popularity of freeform shapes in contemporary architecture poses new challenges to digital design. One of them is the process of rationalization, i.e. to make freeform skins or structures affordable to manufacture, which draws the most attention from geometry researchers. In this thesis, we aim to realize this process with simple geometric primitives, circular arcs. We investigate architectural surfaces and structures consisting of circular arcs. Our focus is lying on how to employ them nicely and repetitively in architectural design, in order to decrease the cost in manufacturing. Firstly, we study Darboux cyclides, which are algebraic surfaces of order ≤ 4. We provide a computational tool to identify all families of circles on a given cyclide based on the spherical model of M ̈obius geometry. Practical ways to design cyclide patches that pass through certain inputs are presented. In particular, certain triples of circle families on Darboux cyclides may be suitably arranged as 3-webs. We provide a complete classification of all possible 3-webs of circles on Darboux cyclides. We then investigate the circular arc snakes, which are smooth sequences of circu- lar arcs. We evolve the snakes such that their curvature, as a function of arc length, remains unchanged. The evolution of snakes is utilized to approximate given surfaces by circular arcs or to generated freeform shapes, and it is realized by a 2-step pro- cess. More interestingly, certain 6-arc snake with boundary constraints can produce a smooth self motion, which can be employed to build flexible structures. Another challenging topic is approximating smooth freeform skins with simple panels. We contribute to this problem area by approximating a negatively-curved 5 surface with a smooth union of rational bilinear patches. We provide a proof for vertex consistency of hyperbolic nets using the CAGD approach of the rational B ́ezier form. Moreover, we use Darboux transformations for the

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

    CSIR Research Space (South Africa)

    Chiranjan, Ashill

    2016-12-01

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

  11. New environmental supplier selection criteria for circular supply chains

    DEFF Research Database (Denmark)

    Prosman, Ernst Johannes; Sacchi, Romain

    2017-01-01

    Although circular supply chains are widely perceived as a leap towards a more environmentally friendly economy, the environmental impact across circular supply chains differs. This article sets out to develop environmental supplier selection criteria for circular supply chains. The method draws...... also show how three supplier selection criteria explain most of the environmental impact of selecting a supplier in a circular supply chain. First, supplier selection might impact environmentally preferred waste handling activities. Second, sourcing from a supplier located on an under-supplied market...... simultaneously when selecting suppliers in circular supply chains since focusing on a single criterion may negatively affect the other criteria. The findings contribute to circular supply chain literature by proposing and demonstrating the need for environmental supplier selection criteria in circular supply...

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

    International Nuclear Information System (INIS)

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

    2014-01-01

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

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

    DEFF Research Database (Denmark)

    Bisdom, Kevin; Bertotti, Giovanni; Nick, Hamid

    2016-01-01

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

  14. MHD stability of an almost circular tokamak

    International Nuclear Information System (INIS)

    Roy, A.

    1990-10-01

    In a tokamak, the ratio β between the plasma pressure and that of the magnetic field is limited by the appearance of instabilities. The magnetic field in a tokamak reactor will always be limited by technological constraints. It is therefore crucial to know what factors have an effect on the β limit, since a zero resistivity plasma fluid model allows for theoretical reproduction of the β limits observed experimentally. Theoretical studies have shown that the distributions of pressure and current density may have a substantial effect on the β limit. The effect of the current density and pressure distributions on the β limit has been studied for tokamak with a circular core section. The best results are obtained when the current density is concentrated in the centre of the section and is nil at the periphery. But the second region of stability against ballooning modes cannot be obtained in a circular tokamak owing to the destabilisation of the universal modes. This study was then extended to the stability of plasmas the section of which is almost circular and has a point of reflection. Such configurations are vital for fusion since they allow systems in which the confinement time does not deteriorate with an increase in the additional heating power. The β limit was calculated for different positions of the reflection point. The results show that when it is displaced from the interior towards the exterior of the torus, the stability of the overall modes is progressively improved until it is vertical. But if the point of reflection is further displaced from this vertical position towards the exterior of the torus, localised modes close to the edge of the plasma are destabilised and bring about a drop in the β limit. (author) figs., tabs., 80 refs

  15. Multipole Analysis of Circular Cylindircal Magnetic Systems

    Energy Technology Data Exchange (ETDEWEB)

    Selvaggi, Jerry P. [Rensselaer Polytechnic Inst., Troy, NY (United States)

    2005-12-01

    This thesis deals with an alternate method for computing the external magnetic field from a circular cylindrical magnetic source. The primary objective is to characterize the magnetic source in terms of its equivalent multipole distribution. This multipole distribution must be valid at points close to the cylindrical source and a spherical multipole expansion is ill-equipped to handle this problem; therefore a new method must be introduced. This method, based upon the free-space Green's function in cylindrical coordinates, is developed as an alternative to the more familiar spherical harmonic expansion. A family of special functions, called the toroidal functions or Q-functions, are found to exhibit the necessary properties for analyzing circular cylindrical geometries. In particular, the toroidal function of zeroth order, which comes from the integral formulation of the free-space Green's function in cylindrical coordinates, is employed to handle magnetic sources which exhibit circular cylindrical symmetry. The toroidal functions, also called Q-functions, are the weighting coefficients in a ''Fourier series-like'' expansion which represents the free-space Green's function. It is also called a toroidal expansion. This expansion can be directly employed in electrostatic, magnetostatic, and electrodynamic problems which exhibit cylindrical symmetry. Also, it is shown that they can be used as an alternative to the Elliptic integral formulation. In fact, anywhere that an Elliptic integral appears, one can replace it with its corresponding Q-function representation. A number of problems, using the toroidal expansion formulation, are analyzed and compared to existing known methods in order to validate the results. Also, the equivalent multipole distribution is found for most of the solved problems along with its corresponding physical interpretation. The main application is to characterize the external magnetic field due to a six

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

    Science.gov (United States)

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

    1993-02-01

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

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

    Science.gov (United States)

    Jolly, Alistair D.; Thompson, Peter

    2002-07-01

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

  18. Synthetic aperture flow imaging using dual stage beamforming

    DEFF Research Database (Denmark)

    Li, Ye; Jensen, Jørgen Arendt

    2013-01-01

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

  19. Synthetic Aperture Flow Imaging Using a Dual Beamformer Approach

    DEFF Research Database (Denmark)

    Li, Ye

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

  20. Pressure independence of granular flow through an aperture.

    Science.gov (United States)

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

    2010-06-11

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

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

    CERN Document Server

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

    2017-01-01

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

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

    DEFF Research Database (Denmark)

    Hansen, Jens Munk; Jensen, Jørgen Arendt

    2011-01-01

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

  3. Random mask optimization for fast neutron coded aperture imaging

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-05-01

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

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

    Science.gov (United States)

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

    2015-09-01

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

  5. Circular waveguide bifurcation for asymmetric modes

    Science.gov (United States)

    Schilling, H. W.; Collin, R. E.

    1984-12-01

    An analytical solution for a circular waveguide bifurcation with incident TE(11)- and TM(11)-modes is presented using the residue calculus method. It is shown how the coupling between the TE(1n)- and TM(1n)-modes can be taken into account by expressing the coupling factor as a contour integral, which is the key step enabling the residue calculus method to be applied. Graphical results for the scattering matrix parameters of the junction are given for a range of waveguide radii of interest in the design of dual-mode coaxial prime focus feeds for paraboloidal antennas.

  6. Porphyrin Protonation Studied by Magnetic Circular Dichroism

    Czech Academy of Sciences Publication Activity Database

    Štěpánek, Petr; Andrushchenko, Valery; Ruud, K.; Bouř, Petr

    2012-01-01

    Roč. 116, č. 1 (2012), s. 778-783 ISSN 1089-5639 R&D Projects: GA ČR GAP208/11/0105; GA ČR GA203/09/2037; GA ČR GAP208/10/0559; GA MŠk(CZ) LH11033 Institutional research plan: CEZ:AV0Z40550506 Keywords : magnetic circular dichroism (MCD) * TPPS * spectra simulations * porphyrin protonation Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.771, year: 2012

  7. Symmetric Circular Matchings and RNA Folding

    DEFF Research Database (Denmark)

    Hofacker, Ivo L.; Reidys, Christian; Stadler, Peter F.

    2012-01-01

    or the co-folding of two or more identical RNAs. Here, we show that the RNA folding problem with symmetry terms can still be solved with polynomial-time algorithms. Empirically, the fraction of symmetric ground state structures decreases with chain length, so that the error introduced by neglecting......RNA secondary structures can be computed as optimal solutions of certain circular matching problems. An accurate treatment of this energy minimization problem has to account for the small --- but non-negligible --- entropic destabilization of secondary structures with non-trivial automorphisms...

  8. Acceleration of polarized protons in circular accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Courant, E.D.; Ruth, R.D.

    1980-09-12

    The theory of depolarization in circular accelerators is presented. The spin equation is first expressed in terms of the particle orbit and then converted to the equivalent spinor equation. The spinor equation is then solved for three different situations: (1) a beam on a flat top near a resonance, (2) uniform acceleration through an isolated resonance, and (3) a model of a fast resonance jump. Finally, the depolarization coefficient, epsilon, is calculated in terms of properties of the particle orbit and the results are applied to a calculation of depolarization in the AGS.

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

    DEFF Research Database (Denmark)

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

    2012-01-01

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

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

    International Nuclear Information System (INIS)

    He Xiaoyong; Cao Juncheng

    2008-01-01

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

  11. The modular design of large-aperture zoom system

    Science.gov (United States)

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

    2016-10-01

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

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

    DEFF Research Database (Denmark)

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

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

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

    Science.gov (United States)

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

    2013-01-01

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

  14. Implementation of real-time duplex synthetic aperture ultrasonography

    DEFF Research Database (Denmark)

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

    2015-01-01

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

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

    OpenAIRE

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

    2015-01-01

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

  16. Digital filtering and reconstruction of coded aperture images

    International Nuclear Information System (INIS)

    Tobin, K.W. Jr.

    1987-01-01

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

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

    Science.gov (United States)

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

    2011-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-03-01

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

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

    CERN Document Server

    Chen , Victor C

    2014-01-01

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

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

    OpenAIRE

    Yong Jin; Min Jiang; Yunshan Hou; Jianguo Huang

    2010-01-01

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

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

    Science.gov (United States)

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

    2012-07-01

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

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

    Science.gov (United States)

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

    2013-08-01

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

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

    International Nuclear Information System (INIS)

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

    2008-01-01

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

  4. Coded aperture material motion detection system for the ACPR

    International Nuclear Information System (INIS)

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

    1975-01-01

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

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

    Science.gov (United States)

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

    2013-09-01

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

  6. Coded aperture imaging system for nuclear fuel motion detection

    International Nuclear Information System (INIS)

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

    1980-01-01

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

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

    Science.gov (United States)

    Stepinski, Tadeusz

    2007-07-01

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

  8. High Performance Circularly Polarized Microstrip Antenna

    Science.gov (United States)

    Bondyopadhyay, Probir K. (Inventor)

    1997-01-01

    A microstrip antenna for radiating circularly polarized electromagnetic waves comprising a cluster array of at least four microstrip radiator elements, each of which is provided with dual orthogonal coplanar feeds in phase quadrature relation achieved by connection to an asymmetric T-junction power divider impedance notched at resonance. The dual fed circularly polarized reference element is positioned with its axis at a 45 deg angle with respect to the unit cell axis. The other three dual fed elements in the unit cell are positioned and fed with a coplanar feed structure with sequential rotation and phasing to enhance the axial ratio and impedance matching performance over a wide bandwidth. The centers of the radiator elements are disposed at the corners of a square with each side of a length d in the range of 0.7 to 0.9 times the free space wavelength of the antenna radiation and the radiator elements reside in a square unit cell area of sides equal to 2d and thereby permit the array to be used as a phased array antenna for electronic scanning and is realizable in a high temperature superconducting thin film material for high efficiency.

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

    Science.gov (United States)

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

    2017-12-01

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

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

    Science.gov (United States)

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

    2010-06-01

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

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

    Science.gov (United States)

    Luo, Yujuan; Ji, Xiaoling; Yu, Hong

    2018-01-01

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

  12. The Circular Economy: In Practice-focused Undergraduate Engineering Education

    DEFF Research Database (Denmark)

    Knudby, Torben; Larsen, Samuel

    The growth of the planet’s population makes the traditional industrial model of “take, make and waste” unsustainable. The circular economy, in which resources are continuously reused, offers a solution. For manufacturers of durable goods the circular economy requires a well-functioning circular...... circular supply chains is un-explored and the purpose of the paper is to identify a suitable teaching method. Because courses in circular supply chain topics are currently non existent, the paper first develops a set of learning goals based on the skillset necessary to design, implement, and operate...... a circular supply chain. Second, the paper examines whether the teaching method of a similar cross-disciplinary course in innovation can be successfully applied. This teaching method is based on cross-disciplinary team projects that work with innovation in cooperation with a participating firm. The study...

  13. Proposal of a Sustainable Circular Index for Manufacturing Companies

    Directory of Open Access Journals (Sweden)

    Susana Garrido Azevedo

    2017-11-01

    Full Text Available Recently the circular economy has increasingly received attention worldwide due to the recognition that the security of the supply of resources and environmental sustainability are crucial for the prosperity of all the countries and businesses. G20 countries are stimulating the development of frameworks that enhance the circular economy and generally more sustainable production and consumption modes. In this context, this paper aims to suggest an index to assess the sustainability and the circularity of manufacturing companies. With this tenet, a Sustainable Circular Index (SCI is proposed based on a five-phase framework. This index could support managers in assessing their level of sustainability and circularity and in implementing some practices that could improve the performances of their companies regarding these two topics. This index represents an important benchmarking tool for manufacturing companies to assess their sustainable and circular behavior and represents a guideline for managers.

  14. Zernike vs. Bessel circular functions in visual optics.

    Science.gov (United States)

    Trevino, Juan P; Gómez-Correa, Jesus E; Iskander, D Robert; Chávez-Cerda, Sabino

    2013-07-01

    We propose the Bessel Circular Functions as alternatives of the Zernike Circle Polynomials to represent relevant circular ophthalmic surfaces. We assess the fitting capabilities of the orthogonal Bessel Circular Functions by comparing them to Zernike Circle Polynomials for approximating a variety of computationally generated surfaces which can represent ophthalmic surfaces. The Bessel Circular Functions showed better modelling capabilities for surfaces with abrupt variations such as the anterior eye surface at the limbus region, and influence functions. From our studies we find that the Bessel Circular Functions can be more suitable for studying particular features of post surgical corneal surfaces. We show that given their boundary conditions and free oscillating properties, the Bessel Circular Functions are an alternative for representing specific wavefronts and can be better than the Zernike Circle Polynomials for some important cases of corneal surfaces, influence functions and the complete anterior corneal surface. © 2013 The Authors Ophthalmic & Physiological Optics © 2013 The College of Optometrists.

  15. Critical Raw Materials and the Circular Economy – Background report

    OpenAIRE

    MATHIEUX FABRICE; ARDENTE FULVIO; BOBBA SILVIA; NUSS PHILIP; BLENGINI GIOVANNI; ALVES DIAS PATRICIA; BLAGOEVA DARINA; TORRES DE MATOS CRISTINA; WITTMER DOMINIC; PAVEL CLAUDIU; HAMOR TAMAS; SAVEYN HANS; GAWLIK BERND; ORVEILLON GLENN; HUYGENS DRIES

    2017-01-01

    This report is a background document used by several European Commission services to prepare the EC report on critical raw materials and the circular economy, a commitment of the European Commission made in its Communication ‘EU action plan for the Circular Economy’. It represents a JRC contribution to the Raw Material Initiative and to the EU Circular Economy Action Plan. It combines the results of several research programmes and activities of the JRC on critical raw materials in a context o...

  16. A bullet shaped tip for the circular stapling device.

    Science.gov (United States)

    Brodman, H R; Brodman, R F

    1984-06-01

    A stainless steel bullet shaped tip has been designed for attachment to the shaft of the circular stapling device. It is useful when the shaft of this circular stapling device must transverse a viscus wall. This modification of the circular stapler has been used in vertical stapling of the stomach for morbid obesity, in low intestinal anastomoses using the side-to-end technique and in re-establishing intestinal continuity after a Hartmann procedure.

  17. The consequences of multiplexing and limited view angle in coded-aperture imaging

    International Nuclear Information System (INIS)

    Smith, W.E.; Barrett, H.H.; Paxman, R.G.

    1984-01-01

    Coded-aperture imaging (CAI) is a method for reconstructing distributions of radionuclide tracers that offers advantages over ECT and PET; namely, many views can be taken simultaneously without detector motion, and large numbers of photons are utilized since collimators are not required. However, because of this type of data acquisition, the coded image suffers from multiplexing; i.e., more than one object point may be mapped to each detector in the coded image. To investigate the dependence of the reconstruction on multiplexing, the authors reconstruct a simulated two-dimensional circular object from multiplexed one-dimensional coded-image data, then perform the reconstruction from un-multiplexed data. Each of these reconstructions are produced both from noise-free and noisy simulated data. To investigate the dependence on view angle, the authors reconstruct two simulated three-dimensional objects; a spherical phantom, and a series of point-like objects arranged nearly in a plane. Each of these reconstructions are from multiplexed two-dimensional coded-image data, first using two orthogonal views, and then a single viewing direction. The two-dimensional reconstructions demonstrate that, in the noise-free case, the multiplexing of the data does not seriously affect the reconstruction equality and that in the noisy-data case, the multiplexing helps, due to the fact that more photons are collected. Also, for point-like objects confined to a near-planar region of space, the authors show that restricted views can give satisfactory results, but that, for a large, three-dimensional object, a more complete viewing geometry is required

  18. Circularly Polarized Microwave Antenna Element with Very Low Off-Axis Cross-Polarization

    Science.gov (United States)

    Greem. David; DuToit, Cornelis

    2013-01-01

    The goal of this work was to improve off-axis cross-polarization performance and ease of assembly of a circularly polarized microwave antenna element. To ease assembly, the initial design requirement of Hexweb support for the internal circuit part, as well as the radiating disks, was eliminated. There is a need for different plating techniques to improve soldering. It was also desirable to change the design to eliminate soldering as well as the need to use the Hexweb support. Thus, a technique was developed to build the feed without using solder, solving the lathing and soldering issue. Internal parts were strengthened by adding curvature to eliminate Hexweb support, and in the process, the new geometries of the internal parts opened the way for improving the off-axis cross-polarization performance as well. The radiating disks curvatures were increased for increased strength, but it was found that this also improved crosspolarization. Optimization of the curvatures leads to very low off-axis cross-polarization. The feed circuit was curved into a cylinder for improved strength, eliminating Hexweb support. An aperture coupling feed mechanism eliminated the need for feed pins to the disks, which would have required soldering. The aperture coupling technique also improves cross-polarization performance by effectively exciting the radiating disks very close to the antenna s central axis of symmetry. Because of the shape of the parts, it allowed for an all-aluminum design bolted together and assembled with no solder needed. The advantage of a solderless design is that the reliability is higher, with no single-point failure (solder), and no need for special plating techniques in order to solder the unit together. The shapes (curved or round) make for a more robust build without extra support materials, as well as improved offaxis cross-polarization.

  19. NUMERICAL MODELING OF STRESSES NEAR THE SURFACE IN THE INGOT OF CIRCULAR SECTION, CRYSTALLIZABLE AT CIRCULAR TORCH SECONDARY COOLING

    Directory of Open Access Journals (Sweden)

    A. N. Chichko

    2004-01-01

    Full Text Available The results of computer calculations of the stresses, generated in outside layer of ingot of steel 20 of circular section with diameter 300 mm, in application to one of the industrial technological schemas of RUP “BMZ”, are presented. The segments of compressive and tensile stresses formation along the length of ingot are determined and the principal possibility of production of continuously cast slug of circular section at circular-torch spray cooling is shown.

  20. Tangent hyperbolic circular frequency diverse array radars

    Directory of Open Access Journals (Sweden)

    Sarah Saeed

    2016-03-01

    Full Text Available Frequency diverse array (FDA with uniform frequency offset (UFO has been in spot light of research for past few years. Not much attention has been devoted to non-UFOs in FDA. This study investigates tangent hyperbolic (TH function for frequency offset selection scheme in circular FDAs (CFDAs. Investigation reveals a three-dimensional single-maximum beampattern, which promises to enhance system detection capability and signal-to-interference plus noise ratio. Furthermore, by utilising the versatility of TH function, a highly configurable type array system is achieved, where beampatterns of three different configurations of FDA can be generated, just by adjusting a single function parameter. This study further examines the utility of the proposed TH-CFDA in some practical radar scenarios.

  1. Circular structures of the earth's continents

    Science.gov (United States)

    Briukhanov, Vladimir Nikolaevich; Bush, Vil'iam Arturovich; Glukhovskii, Marat Zinov'evich; Zverev, A. T.; Kats, Ia. G.

    The relationship between the composition of the lithosphere and the circular structures (CSs) visible on remote images of the earth surface is investigated using space observations and geological, geophysical, geomorphological, and mapping data. The CSs are divided into classes according to their structural, or size, parameters (megastructures, macrostructures, mesostructures, ministructures, and microstructures) and their genetic types (e.g., nuclear, abyssal, metagenic, and exogenic). The distribution of these structural-genetic CS types on the earth's continents (with the exception of the Antarctic) is discussed, and the specificity of the features of these CS types is examined. Special attention is given to the correlations between the distribution of CSs and the regional distribution of metallogenic rocks.

  2. Perturbation analysis of octupoles in circular accelerators

    International Nuclear Information System (INIS)

    Moohyun Yoon

    1998-01-01

    The octupole effects in a circular accelerator are analyzed using a first-order canonical perturbation theory. It is shown that, to the first order, the nonlinear amplitude-dependent tune shifts due to an octupole are composed of two types: terms of second order and terms of fourth order in betatron-oscillation amplitudes. The fourth-order part of tune shifts is expressed in terms of distortion functions. Distortion functions are also expanded in harmonics to express the higher-order tune shifts in harmonically expanded form. Finally, the results are applied to an accelerator and compared with the results of numerical tracking of particles. Laskar's algorithm for numerical analysis of the fundamental frequency is used to determine tunes from the tracking data, in which the error becomes inversely proportional to the cube of the number of data points. (author)

  3. Resolving capacity of the circular Zernike polynomials.

    Science.gov (United States)

    Svechnikov, M V; Chkhalo, N I; Toropov, M N; Salashchenko, N N

    2015-06-01

    Circular Zernike polynomials are often used for approximation and analysis of optical surfaces. In this paper, we analyse their lateral resolving capacity, illustrating the effects of a lack of approximation by a finite set of polynomials and answering the following questions: What is the minimum number of polynomials that is necessary to describe a local deformation of a certain size? What is the relationship between the number of approximating polynomials and the spatial spectrum of the approximation? What is the connection between the mean-square error of approximation and the number of polynomials? The main results of this work are the formulas for calculating the error of fitting the relief and the connection between the width of the spatial spectrum and the order of approximation.

  4. Circular arc snakes and kinematic surface generation

    KAUST Repository

    Barton, Michael

    2013-05-01

    We discuss the theory, discretization, and numerics of curves which are evolving such that part of their shape, or at least their curvature as a function of arc length, remains unchanged. The discretization of a curve as a smooth sequence of circular arcs is well suited for such purposes, and allows us to reduce evolution of curves to the evolution of a control point collection in a certain finite-dimensional shape space. We approach this evolution by a 2-step process: linearized evolution via optimized velocity fields, followed by optimization in order to exactly fulfill all geometric side conditions. We give applications to freeform architecture, including "rationalization" of a surface by congruent arcs, form finding and, most interestingly, non-static architecture. © 2013 The Author(s) Computer Graphics Forum © 2013 The Eurographics Association and Blackwell Publishing Ltd.

  5. Towards Quantum Simulation with Circular Rydberg Atoms

    Directory of Open Access Journals (Sweden)

    T. L. Nguyen

    2018-02-01

    Full Text Available The main objective of quantum simulation is an in-depth understanding of many-body physics, which is important for fundamental issues (quantum phase transitions, transport, … and for the development of innovative materials. Analytic approaches to many-body systems are limited, and the huge size of their Hilbert space makes numerical simulations on classical computers intractable. A quantum simulator avoids these limitations by transcribing the system of interest into another, with the same dynamics but with interaction parameters under control and with experimental access to all relevant observables. Quantum simulation of spin systems is being explored with trapped ions, neutral atoms, and superconducting devices. We propose here a new paradigm for quantum simulation of spin-1/2 arrays, providing unprecedented flexibility and allowing one to explore domains beyond the reach of other platforms. It is based on laser-trapped circular Rydberg atoms. Their long intrinsic lifetimes, combined with the inhibition of their microwave spontaneous emission and their low sensitivity to collisions and photoionization, make trapping lifetimes in the minute range realistic with state-of-the-art techniques. Ultracold defect-free circular atom chains can be prepared by a variant of the evaporative cooling method. This method also leads to the detection of arbitrary spin observables with single-site resolution. The proposed simulator realizes an XXZ spin-1/2 Hamiltonian with nearest-neighbor couplings ranging from a few to tens of kilohertz. All the model parameters can be dynamically tuned at will, making a large range of simulations accessible. The system evolution can be followed over times in the range of seconds, long enough to be relevant for ground-state adiabatic preparation and for the study of thermalization, disorder, or Floquet time crystals. The proposed platform already presents unrivaled features for quantum simulation of regular spin chains. We

  6. Towards Quantum Simulation with Circular Rydberg Atoms

    Science.gov (United States)

    Nguyen, T. L.; Raimond, J. M.; Sayrin, C.; Cortiñas, R.; Cantat-Moltrecht, T.; Assemat, F.; Dotsenko, I.; Gleyzes, S.; Haroche, S.; Roux, G.; Jolicoeur, Th.; Brune, M.

    2018-01-01

    The main objective of quantum simulation is an in-depth understanding of many-body physics, which is important for fundamental issues (quantum phase transitions, transport, …) and for the development of innovative materials. Analytic approaches to many-body systems are limited, and the huge size of their Hilbert space makes numerical simulations on classical computers intractable. A quantum simulator avoids these limitations by transcribing the system of interest into another, with the same dynamics but with interaction parameters under control and with experimental access to all relevant observables. Quantum simulation of spin systems is being explored with trapped ions, neutral atoms, and superconducting devices. We propose here a new paradigm for quantum simulation of spin-1 /2 arrays, providing unprecedented flexibility and allowing one to explore domains beyond the reach of other platforms. It is based on laser-trapped circular Rydberg atoms. Their long intrinsic lifetimes, combined with the inhibition of their microwave spontaneous emission and their low sensitivity to collisions and photoionization, make trapping lifetimes in the minute range realistic with state-of-the-art techniques. Ultracold defect-free circular atom chains can be prepared by a variant of the evaporative cooling method. This method also leads to the detection of arbitrary spin observables with single-site resolution. The proposed simulator realizes an X X Z spin-1 /2 Hamiltonian with nearest-neighbor couplings ranging from a few to tens of kilohertz. All the model parameters can be dynamically tuned at will, making a large range of simulations accessible. The system evolution can be followed over times in the range of seconds, long enough to be relevant for ground-state adiabatic preparation and for the study of thermalization, disorder, or Floquet time crystals. The proposed platform already presents unrivaled features for quantum simulation of regular spin chains. We discuss

  7. A computational protocol for the study of circularly polarized phosphorescence and circular dichroism in spin-forbidden absorption

    DEFF Research Database (Denmark)

    Kaminski, Maciej; Cukras, Janusz; Pecul, Magdalena

    2015-01-01

    We present a computational methodology to calculate the intensity of circular dichroism (CD) in spinforbidden absorption and of circularly polarized phosphorescence (CPP) signals, a manifestation of the optical activity of the triplet–singlet transitions in chiral compounds. The protocol is based...... on the response function formalism and is implemented at the level of time-dependent density functional theory. It has been employed to calculate the spin-forbidden circular dichroism and circularly polarized phosphorescence signals of valence n - p* and n ’ p* transitions, respectively, in several chiral enones...

  8. Synthetic aperture ladar based on a MOPAW laser

    Science.gov (United States)

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

    2016-10-01

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

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

    Science.gov (United States)

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

    2003-09-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-12-15

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

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

    OpenAIRE

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

    2009-01-01

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

  12. Multielement Synthetic Transmit Aperture Imaging Using Temporal Encoding

    DEFF Research Database (Denmark)

    Gammelmark, Kim; Jensen, Jørgen Arendt

    2003-01-01

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

  13. Apodized RFI filtering of synthetic aperture radar images

    Energy Technology Data Exchange (ETDEWEB)

    Doerry, Armin Walter

    2014-02-01

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

  14. Beaconless search and rescue using polarimetric synthetic aperture radar

    Science.gov (United States)

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

    1996-03-01

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

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

    DEFF Research Database (Denmark)

    Gran, Fredrik; Jensen, Jørgen Arendt

    2003-01-01

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

  16. Chinese very small aperture terminal system for ministries

    Science.gov (United States)

    Dan, Sen

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

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

    Science.gov (United States)

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

    2017-11-01

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

  18. MYRaf: An Easy Aperture Photometry GUI for IRAF

    Science.gov (United States)

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

    2015-07-01

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

  19. A fast autofocus algorithm for synthetic aperture radar processing

    DEFF Research Database (Denmark)

    Dall, Jørgen

    1992-01-01

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

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

    Science.gov (United States)

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

    1987-01-01

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

  1. Convolutional neural networks for synthetic aperture radar classification

    Science.gov (United States)

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

    2016-05-01

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

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

    Science.gov (United States)

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

    1981-01-01

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

  3. Resonant Transmission of Cold Atoms through Subwavelength Apertures

    International Nuclear Information System (INIS)

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

    2005-01-01

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

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

    DEFF Research Database (Denmark)

    Nikolov, Svetoslav; Jensen, Jørgen Arendt

    2003-01-01

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

  5. Implementation of Synthetic Aperture Imaging in Medical Ultrasound

    DEFF Research Database (Denmark)

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

    2010-01-01

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

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

    Science.gov (United States)

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

    2003-02-01

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

  7. The generation of a complete spiral spot and multi split rings by focusing three circularly polarized vortex beams

    Science.gov (United States)

    Chen, Jiannong; Gao, Xiumin; Zhu, Linwei; Xu, Qinfeng; Ma, Wangzi

    2014-05-01

    We demonstrate that a complete right-handed or left-handed spiral-shaped focus can be created by focusing circularly polarized and three spatially shifted vortex beams through high numerical objective. By dividing the back aperture into multi annular zones and applying an additional phase term, the multi focal spots aligned along z axis of individual three dimensional focal shapes can be generated. The spiral shaped focus provides a pathway of manipulating the micro-particles in a curved trajectory and opens up a possibility of measuring mechanical torque of biological large molecules such as DNA by chemically binding one end on the cover-glass. The multi focal spots aligned along the z axis can eliminate the need of z axis scanning in the direct laser writing fabrication of some metamaterials which is composed of three-dimensional array of specific shapes of building blocks.

  8. PCDDB: the Protein Circular Dichroism Data Bank, a repository for circular dichroism spectral and metadata.

    Science.gov (United States)

    Whitmore, Lee; Woollett, Benjamin; Miles, Andrew John; Klose, D P; Janes, Robert W; Wallace, B A

    2011-01-01

    The Protein Circular Dichroism Data Bank (PCDDB) is a public repository that archives and freely distributes circular dichroism (CD) and synchrotron radiation CD (SRCD) spectral data and their associated experimental metadata. All entries undergo validation and curation procedures to ensure completeness, consistency and quality of the data included. A web-based interface enables users to browse and query sample types, sample conditions, experimental parameters and provides spectra in both graphical display format and as downloadable text files. The entries are linked, when appropriate, to primary sequence (UniProt) and structural (PDB) databases, as well as to secondary databases such as the Enzyme Commission functional classification database and the CATH fold classification database, as well as to literature citations. The PCDDB is available at: http://pcddb.cryst.bbk.ac.uk.

  9. Product design and business model strategies for a circular economy

    NARCIS (Netherlands)

    Bocken, N.M.P.; de Pauw, I.C.; Bakker, C.A.; van der Grinten, B.

    The transition within business from a linear to a circular economy brings with it a range of practical challenges for companies. The following question is addressed: What are the product design and business model strategies for
    companies that want to move to a circular economy model? This paper

  10. static analysis of circular cylindrical shell under hydrostatic and ring ...

    African Journals Online (AJOL)

    DEPT OF AGRICULTURAL ENGINEERING

    University of Nigeria, Nsukka. ABSTRACT. Analysis of circular cylindrical shell under the action of hydrostatic and stiffening ring forces is ... The economy or feasibility of many modern constructions necessitates lightweight, thin- ... concerned with the analysis of circular cylindri- cal shell subjected to hydrostatic pressure in.

  11. Band vs. Circular Sawmills: Relative Labor & Maintenance Costs

    Science.gov (United States)

    Philip H. Steele; Philip A. Araman

    1997-01-01

    Substantial sawmill lumber yield increases from kerf and sawing variation reductions can be realized by employing band rather than circular headrigs. Softwood sawmills rapidly adopted bandsaw headrig technology to the extent that it is currently unusual to find circular saw headrigs in a softwood sawmill. Hardwood sawmills, faced with a different economic situation,...

  12. Equal distribution of satellite constellations on circular target orbits

    NARCIS (Netherlands)

    Vos, E.; Scherpen, J.M.A.; van der Schaft, A. J.

    2014-01-01

    This paper addresses the problem of equal distribution of satellite constellations on circular target orbits. The control goal is to make the constellation converge to a circular target orbit, while spatially distributing the satellites at equal inter-satellite distances. The solution is defined in

  13. Three-dimensional free vibration analysis of thick laminated circular ...

    African Journals Online (AJOL)

    Dr Oke

    Laminated circular plates are commonly used structural component having a broad application in aerospace, civil, mechanical, nuclear, electronic as well as marine ..... sufficient to obtain satisfactory convergence for first five frequency parameters of glass/epoxy laminated circular plates. It is seen that the first axisymmetric ...

  14. A Survey of Records Management Practices in Circular Primary ...

    African Journals Online (AJOL)

    The study was a survey of records management practices in circular primary schools of metropolitan local government area of Kano state. There was a total of 8 local government areas in the metropolitan with a population of 233 circular schools. Out of the number, 104 were randomly selected for the study. A minimum of 10 ...

  15. Modeling magnetic circular dichroism within the polarizable embedding approach

    DEFF Research Database (Denmark)

    Nørby, Morten Steen; Coriani, Sonia; Kongsted, Jacob

    2018-01-01

    Magnetic circular dichroism (MCD) is defined as the differential absorption of left and right circularly polarized light in a sample subjected to an external magnetic field. In order to interpret the results of MCD measurements, theoretical predictions of key MCD parameters can be of utmost...... of the more conventional dielectric continuum approach. Results are presented for cytosine and hypoxanthine solvated in water....

  16. Circular integrated optical microresonators: Analytical methods and computational aspects

    NARCIS (Netherlands)

    Hiremath, K.R.; Hammer, Manfred; Chremmos, I.; Schwelb, O.; Uzunoglu, N.

    2010-01-01

    This chapter discusses an ab-initio frequency-domain model of circular microresonators, built on the physical notions that commonly enter the description of the resonator functioning in terms of interaction between fields in the circular cavity with the modes supported by the straight bus

  17. Experience with Penile Circular Fasciocutaneous Flap in the ...

    African Journals Online (AJOL)

    Objective: To evaluate our experience with penile circular fasciocutaneous flap urethroplasty for the repair of long penile and bulbar strictures. Patients and Methods: Between February 2003 and April 2005, a total of 21 circumcised patients with a mean age of 39 (range 11 – 79) years underwent penile circular ...

  18. Analysis of radial vibrations of poroelastic circular cylindrical shells ...

    African Journals Online (AJOL)

    Waves propagating in radial direction of a poroelastic circular cylinder are termed as radial vibrations. Radial vibrations of poroelastic circular cylindrical shell of infinite extent immersed in an inviscid elastic fluid are examined employing Biot's theory. Biot's model consists of an elastic matrix permeated by a network of ...

  19. Role of Food Logistics Management in a circular economy

    NARCIS (Netherlands)

    Bloemhof-Ruwaard, J.M.; Groot, J.J.; Snels, J.C.M.A.

    2016-01-01

    In this paper we will discuss the role of food logistics management in a circular economy. Specific pillars in Circular Economy such as Closed Loop supply Chain management and Industrial Ecology will be discussed. Apart from a research agenda, we will provide exemplary cases in practice showing the

  20. An analysis of near-circular lunar mapping orbits

    Indian Academy of Sciences (India)

    Numerical investigations have been carried out to analyse the evolution of lunar circular orbits and the influence of the higher order harmonics of the lunar gravity field. The aim is to select the appropriate near-circular orbit characteristics, which extend orbit life through passive orbit maintenance. The spherical harmonic ...

  1. On the Recognition of Fuzzy Circular Interval Graphs

    OpenAIRE

    Oriolo, Gianpaolo; Pietropaoli, Ugo; Stauffer, Gautier

    2011-01-01

    Fuzzy circular interval graphs are a generalization of proper circular arc graphs and have been recently introduced by Chudnovsky and Seymour as a fundamental subclass of claw-free graphs. In this paper, we provide a polynomial-time algorithm for recognizing such graphs, and more importantly for building a suitable representation.

  2. Chemical detection of cysteine-rich circular petides in selected ...

    African Journals Online (AJOL)

    Cysteine-rich circular peptides (CRCs) comprise a large family of gene encoded and low molecular weight polypeptides that has recently engaged the attention of scientists. This class of peptides exhibit a continuous circular configuration and a cystine knot backbone, which defines their resilient nature-directed structural ...

  3. Flow-induced vibration of circular cylindrical structures

    International Nuclear Information System (INIS)

    Chen, S.S.

    1985-06-01

    This report summarizes the flow-induced vibration of circular cylinders in quiescent fluid, axial flow, and crossflow, and applications of the analytical methods and experimental data in design evaluation of various system components consisting of circular cylinders. 219 figs., 30 tabs

  4. Three-dimensional free vibration analysis of thick laminated circular ...

    African Journals Online (AJOL)

    Three-dimensional free vibration analysis of thick laminated circular plates. Sumit Khare, N.D. Mittal. Abstract. In this communication, a numerical analysis regarding free vibration of thick laminated circular plates, having free, clamped as well as simply-supported boundary conditions at outer edges of plates is presented.

  5. Investigation of accuracy characteristics of circular photodetector: Multiscan

    Science.gov (United States)

    Povarov, Kirill S.; Mitrofanov, Sergey S.

    2017-06-01

    This article is about the research of precision characteristics of a circular sensor "Multiscan". The research was conducted on installation which base was a goniometer GS-5. Such characteristics as nonlinearity, stability, error of reproducibility of results of measurements were investigated. A scheme for arranging the encoder on the basis of a circular photodetector "Multiscan" is proposed.

  6. MHD natural convection in open inclined square cavity with a heated circular cylinder

    Science.gov (United States)

    Hosain, Sheikh Anwar; Alim, M. A.; Saha, Satrajit Kumar

    2017-06-01

    MHD natural convection in open cavity becomes very important in many scientific and engineering problems, because of it's application in the design of electronic devices, solar thermal receivers, uncovered flat plate solar collectors having rows of vertical strips, geothermal reservoirs, etc. Several experiments and numerical investigations have been presented for describing the phenomenon of natural convection in open cavity for two decades. MHD natural convection and fluid flow in a two-dimensional open inclined square cavity with a heated circular cylinder was considered. The opposite wall to the opening side of the cavity was first kept to constant heat flux q, at the same time the surrounding fluid interacting with the aperture was maintained to an ambient temperature T∞. The top and bottom wall was kept to low and high temperature respectively. The fluid with different Prandtl numbers. The properties of the fluid are assumed to be constant. As a result a buoyancy force is created inside the cavity due to temperature difference and natural convection is formed inside the cavity. The Computational Fluid Dynamics (CFD) code are used to discretize the solution domain and represent the numerical result to graphical form.. Triangular meshes are used to obtain the solution of the problem. The streamlines and isotherms are produced, heat transfer parameter Nu are obtained. The results are presented in graphical as well as tabular form. The results show that heat flux decreases for increasing inclination of the cavity and the heat flux is a increasing function of Prandtl number Pr and decreasing function of Hartmann number Ha. It is observed that fluid moves counterclockwise around the cylinder in the cavity. Various recirculations are formed around the cylinder. The almost all isotherm lines are concentrated at the right lower corner of the cavity. The object of this work is to develop a Mathematical model regarding the effect of MHD natural convection flow around

  7. Administrative Circular No. 26 (Rev.10) - Recognition of merit

    CERN Multimedia

    2014-01-01

    Administrative Circular No. 26 (Rev. 10) entitled “Recognition of Merit”, approved by the Director-General following discussion at the Standing Concertation Committee meeting of 5 December 2013 and entering into force on 1 January 2014, is available on the intranet site of the Human Resources Department (see here).   This circular is applicable to staff members. It cancels and replaces Administrative Circular No. 26 (Rev. 9) entitled “Recognition of Merit” of December 2011. The circular was revised in order to take into account the work performed in the framework of an elective mandate during the exercise of merit recognition of staff members. In addition, the circular was revised to provide that, in the case of staff members on special leave for professional reasons for a period equal to or longer than half a year, it will no longer be possible to grant an exceptional advancement. Department Head Office HR Department

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2017-06-01

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

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

    International Nuclear Information System (INIS)

    Byard, Kevin; Shutler, Paul M.E.

    2017-01-01

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

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

    Directory of Open Access Journals (Sweden)

    H. Guo

    2014-09-01

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

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

    Directory of Open Access Journals (Sweden)

    Joseph Moody

    2017-10-01

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

  12. Study of Wide Swath Synthetic Aperture Ladar Imaging Techology

    Directory of Open Access Journals (Sweden)

    Zhang Keshu

    2017-02-01

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

  13. Dynamic Aperture and Resonance Correction for JPARC-RCS

    CERN Document Server

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

    2005-01-01

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

  14. Super Unit Cells in Aperture-Based Metamaterials

    Directory of Open Access Journals (Sweden)

    Dragan Tanasković

    2015-01-01

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

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

    Science.gov (United States)

    Liu, Jing; He, Qiong; Luo, Jianwen

    2017-04-01

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

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

    Directory of Open Access Journals (Sweden)

    Michele Grassi

    2009-06-01

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

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

    Directory of Open Access Journals (Sweden)

    Stephen A. Boppart

    2008-06-01

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

  18. Fabrication of large aperture SiC brazing mirror

    Science.gov (United States)

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

    2016-10-01

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

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

    Science.gov (United States)

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

    2017-04-01

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

  20. Direct aperture deformation: An interfraction image guidance strategy

    International Nuclear Information System (INIS)

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

    2006-01-01

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

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

    Science.gov (United States)

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

    2017-11-01

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

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

    International Nuclear Information System (INIS)

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

    1995-01-01

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

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

    OpenAIRE

    Qiufeng Yan; Jianhui Zhang; Jun Huang; Ying Wang

    2018-01-01

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

  4. 2 inch diameter single crystal growth and scintillation properties of Ce:Gd.sub.3./sub.Al.sub.2./sub.Ga.sub.3./sub.O.sub.12./sub..

    Czech Academy of Sciences Publication Activity Database

    Kamada, K.; Yanagida, T.; Endo, T.; Tsutumi, K.; Usuki, Y.; Nikl, Martin; Fujimoto, Y.; Fukabori, A.; Yoshikawa, A.

    2012-01-01

    Roč. 352, č. 1 (2012), s. 88-90 ISSN 0022-0248 Grant - others:AV ČR(CZ) M100100910 Institutional research plan: CEZ:AV0Z10100521 Keywords : Czochralski method * oxides * scintillator materials Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.552, year: 2012

  5. 11 T Twin-Aperture Nb$_3$Sn Dipole Development for LHC Upgrades

    CERN Document Server

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

    2015-01-01

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

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

    Science.gov (United States)

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

    2017-08-01

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

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

    Directory of Open Access Journals (Sweden)

    SİBEL YENİKAYA

    2011-03-01

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

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

    CERN Document Server

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

    2015-01-01

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

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

    OpenAIRE

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

    2004-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Yuan Wang

    2017-01-01

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

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

    International Nuclear Information System (INIS)

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

    2005-01-01

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

  12. On Introducing Asymmetry into Circular Distributions

    Directory of Open Access Journals (Sweden)

    Dale Umbach

    2012-07-01

    Full Text Available Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman","serif";} We give a brief history of the results which led to the introduction of asymmetry into symmetric circular distributions. This is followed by the presentation of another method of introducing asymmetry. Some properties of the induced distributions are studied. Finally, this new distribution is shown to be a reasonable fit to the Jander ant data as presented in Fisher (1993.

  13. Detection of HBV Covalently Closed Circular DNA

    Directory of Open Access Journals (Sweden)

    Xiaoling Li

    2017-06-01

    Full Text Available Chronic hepatitis B virus (HBV infection affects approximately 240 million people worldwide and remains a serious public health concern because its complete cure is impossible with current treatments. Covalently closed circular DNA (cccDNA in the nucleus of infected cells cannot be eliminated by present therapeutics and may result in persistence and relapse. Drug development targeting cccDNA formation and maintenance is hindered by the lack of efficient cccDNA models and reliable cccDNA detection methods. Southern blotting is regarded as the gold standard for quantitative cccDNA detection, but it is complicated and not suitable for high-throughput drug screening, so more sensitive and simple methods, including polymerase chain reaction (PCR-based methods, Invader assays, in situ hybridization and surrogates, have been developed for cccDNA detection. However, most methods are not reliable enough, and there are no unified standards for these approaches. This review will summarize available methods for cccDNA detection. It is hoped that more robust methods for cccDNA monitoring will be developed and that standard operation procedures for routine cccDNA detection in scientific research and clinical monitoring will be established.

  14. SEAMLESS TECHNOLOGY ON CIRCULAR KNITTING MACHINES

    Directory of Open Access Journals (Sweden)

    CRETU Viorica

    2014-05-01

    Full Text Available With industrial progress, the advancements in garment manufacturing have evolved from cut & sew to complete garment knitting, which produces one entire garment without sewing or linking process. Seamless knitting technology is similar to sock manufacture, the specialized circular knitting machines producing 3 dimensional garments with no side seams, with the waistband integrated with body of the garment and with knitted washing instructions and logos. The paper starts by presenting the main advantages of seamless garments but also some limitations because the technology. Because for a seamless garment, which is realized as a knitted tub, is very important to ensure the required final chest size, it was presented the main components involved: the knitting machine, the garment design and the yarns used. The knitting machines, beside the values of diameters and gauges with a great impact on the chest size, are characterized by a very innovative and complex construction. The design of a seamless garment is fundamental different compared to garments produced on a traditional way because the designer must to work backwards from a finished garment to create the knitting programme that will ultimately give the correct finished size. On the end of the paper it was presented some of the applications of the seamless products that cover intimate apparel and other bodywear, outwear, activewear and functional sportswear, upholstery, industrial, automotive and medical textiles.

  15. Administrative Circular No. 14 (Rev. 2)

    CERN Multimedia

    HR Department

    2007-01-01

    The HR Department wishes to draw the attention of members of the personnel to a number of amendments to Administrative Circular No. 14 (Rev. 2) entitled "Protection of members of the personnel against the financial consequences of illness, accident and disability" which came into force on 1st July 2006 (cf. Weekly Bulletin of 14 and 21 August 2006). Occupational Accident Declaration Form (HS50) https://cern.ch/service-procedures/AdminMan/Forms/HS50E.doc •\tIt must be completed within 10 working days of the date on which the accident occurred (§ 29.2.1), unless the person concerned is materially unable to meet this deadline. • The completed formula must be accompanied by a medical certificate giving details of any bodily injuries resulting from the accident (Annex 1, § 5). The medical certificate must be obtained from the doctor who has been consulted for that purpose. Benefits resulting from illnesses and accidents Medical treatment will cease to be reimbursed under ...

  16. Resonance and coupling effects in circular accelerators

    International Nuclear Information System (INIS)

    Corsten, C.J.A.

    1982-01-01

    This thesis deals with a general theory for the description of resonance and coupling effects in circular particle accelerators. The theory is mainly applied to the proposed proton accumulator ring IKOR in West Germany and to an electron storage ring which is characteristic of existing synchrotron radiation facilities (PAMPUS; this project has since been dismissed by the Dutch government). In chapter 1 the author expands the general Hamilton function for the description of the relativistic particle motion in a time-dependent magnetic field and a HF accelerating electric field (in order to study transverse-longitudinal coupling effects) as well as for the motion in a time-independent magnetic field without acceleration (to study transverse coupling effects). The linear transverse motion is discussed in chapter 2. Analytical formulae for the so-called Twiss parameters are derived from the linear Hamilton theory. The simultaneous treatment of the betatron and synchrotron motion is developed in chapter 3 and a theory for the description of the one-dimensional non-linear betatron motion is elaborated in chapter 4. The two-dimensional non-linear betatron resonances are treated in chapter 5. The description of these resonances can be reduced rather simply to a one-dimensional problem and are treated by examination of trajectories in a phase plane. (Auth.)

  17. Status of the Future Circular Collider Study

    CERN Document Server

    AUTHOR|(CDS)2108454; Zimmermann, Frank

    2016-01-01

    Following the 2013 update of the European Strategy for Particle Physics, the international Future Circular Collider (FCC) Study has been launched by CERN as host institute. Its main purpose and long-term goal is to design an energyfrontier hadron collider (FCC-hh) with a centre-of-mass energy of about 100 TeV in a new 80–100 km tunnel. The FCC study also includes the design of a 90–350 GeV highluminosity lepton collider (FCC-ee) installed in the same tunnel, serving as Higgs, top and Z factory, as a potential intermediate step, as well as an electron-proton collider option (FCC-he). The physics cases for such machines are being assessed and concepts for experiments will be developed by the end of 2018, in time for the next update of the European Strategy for Particle Physics. This overview summarizes the status of machine designs and parameters, and it discusses the essential technical components being developed in the frame of the FCC study. Key elements are superconducting accelerator-dipole magnets wit...

  18. On Stellar Flash Echoes from Circular Rings

    Science.gov (United States)

    Nemiroff, Robert; Mukherjee, Oindabi

    2018-01-01

    A flash -- or any episode of variability -- that occurs in the vicinity of a circular ring might be seen several times later, simultaneously, as echoes on the ring. Effective images of the flash are created and annihilated in pairs, with as many as four flash images visible concurrently. Videos detailing sequences of image pair creation, tandem motion, and subsequent image annihilation are shown, given simple opacity and scattering assumptions. It is proven that, surprisingly, images from a second pair creation event always annihilate with images from the first. Caustic surfaces between flash locations yielding two and four images are computed. Although such ring echos surely occur, their practical detection might be difficult as it could require dedicated observing programs involving sensitive photometry of extended objects. Potential flash sources include planetary and interstellar gas and dust rings near and around variable stars, flare stars, novae, supernovae, and GRBs. Potentially recoverable information includes size, distance, temporal history, and angular isotropy of both the ring and flash.

  19. Coulomb-interacting billiards in circular cavities

    International Nuclear Information System (INIS)

    Solanpää, J; Räsänen, E; Nokelainen, J; Luukko, P J J

    2013-01-01

    We apply a molecular dynamics scheme to analyze classically chaotic properties of a two-dimensional circular billiard system containing two Coulomb-interacting electrons. As such, the system resembles a prototype model for a semiconductor quantum dot. The interaction strength is varied from the noninteracting limit with zero potential energy up to the strongly interacting regime where the relative kinetic energy approaches zero. At weak interactions the bouncing maps show jumps between quasi-regular orbits. In the strong-interaction limit we find an analytic expression for the bouncing map. Its validity in the general case is assessed by comparison with our numerical data. To obtain a more quantitative view on the dynamics as the interaction strength is varied, we compute and analyze the escape rates of the system. Apart from very weak or strong interactions, the escape rates show consistently exponential behavior, thus suggesting strongly chaotic dynamics and a phase space without significant sticky regions within the considered time scales. (paper)

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

    Science.gov (United States)

    Yarbrough, L. D.

    2009-12-01

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