Configuration study for a 30 GHz monolithic receive array, volume 2

NASA Technical Reports Server (NTRS)

Nester, W. H.; Cleaveland, B.; Edward, B.; Gotkis, S.; Hesserbacker, G.; Loh, J.; Mitchell, B.

1984-01-01

The formalism of the sidelobe suppression algorithm and the method used to calculate the system noise figure for a 30 GHz monolithic receive array are presented. Results of array element weight determination and performance studies of a Gregorian aperture image system are also given.

Fast imaging with inelastically scattered electrons by off-axis chromatic confocal electron microscopy.

PubMed

Zheng, Changlin; Zhu, Ye; Lazar, Sorin; Etheridge, Joanne

2014-04-25

We introduce off-axis chromatic scanning confocal electron microscopy, a technique for fast mapping of inelastically scattered electrons in a scanning transmission electron microscope without a spectrometer. The off-axis confocal mode enables the inelastically scattered electrons to be chromatically dispersed both parallel and perpendicular to the optic axis. This enables electrons with different energy losses to be separated and detected in the image plane, enabling efficient energy filtering in a confocal mode with an integrating detector. We describe the experimental configuration and demonstrate the method with nanoscale core-loss chemical mapping of silver (M4,5) in an aluminium-silver alloy and atomic scale imaging of the low intensity core-loss La (M4,5@840  eV) signal in LaB6. Scan rates up to 2 orders of magnitude faster than conventional methods were used, enabling a corresponding reduction in radiation dose and increase in the field of view. If coupled with the enhanced depth and lateral resolution of the incoherent confocal configuration, this offers an approach for nanoscale three-dimensional chemical mapping.

Analysis of off-axis incoherent digital holographic microscopy

NASA Astrophysics Data System (ADS)

Quan, Xiangyu; Matoba, Osamu; Awatsuji, Yasuhiro

2017-05-01

Off-axis incoherent digital holography that enables single-shot three-dimensional (3D) distribution is introduced in the paper. Conventional fluorescence microscopy images 3D fields by sectioning, this prevents instant imaging of fast reactions of living cells. In order to realize digital holography from incoherent light, we adapted common path configuration to achieve the best temporal coherence. And by introducing gratings, we shifted the direction of each light to achieve off-axis interference. Simulations and preliminary experiments using LED light have confirmed the results. We expect to use this method to realize 3D phase imaging and fluorescent imaging at the same time from the same biological sample.

Feasibility study of a synthesis procedure for array feeds to improve radiation performance of large distorted reflector antennas

NASA Technical Reports Server (NTRS)

Stutzman, W. L.; Takamizawa, K.; Werntz, P.; Lapean, J.; Barts, R.; Shen, B.; Dunn, D.

1992-01-01

The topics covered include the following: (1) performance analysis of the Gregorian tri-reflector; (2) design and performance of the type 6 reflector antenna; (3) a new spherical main reflector system design; (4) optimization of reflector configurations using physical optics; (5) radiometric array design; and (7) beam efficiency studies.

Design study of imaging techniques for the Starprobe mission

NASA Technical Reports Server (NTRS)

Bottema, M.

1981-01-01

A 10 cm aperture, off-axis aplanatic gregorian telescope is investigated as a candidate instrument for imaging from Starprobe in the 115 nm to 900 nm wavelength range. Focal lengths of 300 cm (f/30) and 150 cm (f/15) are compared in terms of optical performance, compatibility with the Starprobe spacecraft and response to the thermal environment in a 20-hour time interval, centered on perihelion. Ultraviolet/visible imaging from Starprobe concluded should be technically feasible. A 10 cm aperture telescope with focal length close to 300 cm is recommended for further study. This instrument should be capable of a detector-limited angular resoluton of about 2 arc sec. The estimated overall dimensions should not exceed 105 cm by 40 cm by 25 cm and its mass be less than 28 kg. The recommended concept assumes solid blank ULE mirrors, a graphite-epoxy optical bench, and an aluminum thermal enclosure, covered with multilayer insulation. These materials must be carefully selected to minimize the risk of UV photopolymerization of contaminants at the mirror surfaces during observtions.

Dependence of L-mode confinement on the electron cyclotron power deposition profile in the TCV tokamak

NASA Astrophysics Data System (ADS)

Kirneva, N. A.; Razumova, K. A.; Pochelon, A.; Behn, R.; Coda, S.; Curchod, L.; Duval, B. P.; Goodman, T. P.; Labit, B.; Karpushov, A. N.; Rancic, M.; Sauter, O.; Silva, M.; TCV Team

2012-01-01

Scenarios with different electron cyclotron heating power profile distributions and widths were compared for the first time in experiments on the Tokamak à Configuration Variable (TCV). The heating profile was changed from shot to shot over a wide range from localized on-axis, with normalized minor radius half-width at half maximum σ1/2 ~ 0.1, up to a widely distributed heating power profile with σ1/2 ~ 0.4 and finally to a profile peaked far off-axis. The global confinement, MHD activity, density, temperature and electron pressure profile evolution were compared. In particular, the energy confinement properties of discharges with localized on-axis heating and distributed on-axis heating were very similar, with degradation close to that predicted by the ITER L-mode scaling; in the case of off-axis heating, on the other hand, the confinement degradation was even stronger.

A dual-porosity reactive-transport model of off-axis hydrothermal systems

NASA Astrophysics Data System (ADS)

Farahat, N. X.; Abbot, D. S.; Archer, D. E.

2017-12-01

We built a dual-porosity reactive-transport 2D numerical model of off-axis pillow basalt alteration. An "outer chamber" full of porous glassy material supports significant seawater flushing, and an "inner chamber", which represents the more crystalline interior of a pillow, supports diffusive alteration. Hydrothermal fluids in the two chambers interact, and the two chambers are coupled to 2D flows. In a few million years of low-temperature alteration, the dual-porosity model predicts progressive stages of alteration that have been observed in drilled crust. A single-porosity model, with all else being equal, does not predict alteration stages as well. The dual-chamber model also does a better job than the single-chamber model at predicting the types of minerals expected in off-axis environments. We validate the model's ability to reproduce observations by configuring it to represent a thoroughly-studied transect of the Juan de Fuca Ridge eastern flank.

Validation of the BASALT model for simulating off-axis hydrothermal circulation in oceanic crust

NASA Astrophysics Data System (ADS)

Farahat, Navah X.; Archer, David; Abbot, Dorian S.

2017-08-01

Fluid recharge and discharge between the deep ocean and the porous upper layer of off-axis oceanic crust tends to concentrate in small volumes of rock, such as seamounts and fractures, that are unimpeded by low-permeability sediments. Basement structure, sediment burial, heat flow, and other regional characteristics of off-axis hydrothermal systems appear to produce considerable diversity of circulation behaviors. Circulation of seawater and seawater-derived fluids controls the extent of fluid-rock interaction, resulting in significant geochemical impacts. However, the primary regional characteristics that control how seawater is distributed within upper oceanic crust are still poorly understood. In this paper we present the details of the two-dimensional (2-D) BASALT (Basement Activity Simulated At Low Temperatures) numerical model of heat and fluid transport in an off-axis hydrothermal system. This model is designed to simulate a wide range of conditions in order to explore the dominant controls on circulation. We validate the BASALT model's ability to reproduce observations by configuring it to represent a thoroughly studied transect of the Juan de Fuca Ridge eastern flank. The results demonstrate that including series of narrow, ridge-parallel fractures as subgrid features produces a realistic circulation scenario at the validation site. In future projects, a full reactive transport version of the validated BASALT model will be used to explore geochemical fluxes in a variety of off-axis hydrothermal environments.

Generation of vortex array laser beams with Dove prism embedded unbalanced Mach-Zehnder interferometer

NASA Astrophysics Data System (ADS)

Chu, Shu-Chun

2009-02-01

This paper introduces a scheme for generation of vortex laser beams from a solid-state laser with off-axis laser-diode pumping. The proposed system consists of a Dove prism embedded in an unbalanced Mach-Zehnder interferometer configuration. This configuration allows controlled construction of p × p vortex array beams from Ince-Gaussian modes, IGep,p modes. An incident IGe p,p laser beam of variety order p can easily be generated from an end-pumped solid-state laser with an off-axis pumping mechanism. This study simulates this type of vortex array laser beam generation and discusses beam propagation effects. The formation of ordered transverse emission patterns have applications in a variety of areas such as optical data storage, distribution, and processing that exploit the robustness of soliton and vortex fields and optical manipulations of small particles and atoms in the featured intensity distribution.

Motion of Optically Heated Spheres at the Water-Air Interface.

PubMed

Girot, A; Danné, N; Würger, A; Bickel, T; Ren, F; Loudet, J C; Pouligny, B

2016-03-22

A micrometer-sized spherical particle classically equilibrates at the water-air interface in partial wetting configuration, causing about no deformation to the interface. In condition of thermal equilibrium, the particle just undergoes faint Brownian motion, well visible under a microscope. We report experimental observations when the particle is made of a light-absorbing material and is heated up by a vertical laser beam. We show that, at small laser power, the particle is trapped in on-axis configuration, similarly to 2-dimensional trapping of a transparent sphere by optical forces. Conversely, on-axis trapping becomes unstable at higher power. The particle escapes off the laser axis and starts orbiting around the axis. We show that the laser-heated particle behaves as a microswimmer with velocities on the order of several 100 μm/s with just a few milliwatts of laser power.

Testing the TPF Interferometry Approach before Launch

NASA Technical Reports Server (NTRS)

Serabyn, Eugene; Mennesson, Bertrand

2006-01-01

One way to directly detect nearby extra-solar planets is via their thermal infrared emission, and with this goal in mind, both NASA and ESA are investigating cryogenic infrared interferometers. Common to both agencies' approaches to faint off-axis source detection near bright stars is the use of a rotating nulling interferometer, such as the Terrestrial Planet Finder interferometer (TPF-I), or Darwin. In this approach, the central star is nulled, while the emission from off-axis sources is transmitted and modulated by the rotation of the off-axis fringes. Because of the high contrasts involved, and the novelty of the measurement technique, it is essential to gain experience with this technique before launch. Here we describe a simple ground-based experiment that can test the essential aspects of the TPF signal measurement and image reconstruction approaches by generating a rotating interferometric baseline within the pupil of a large singleaperture telescope. This approach can mimic potential space-based interferometric configurations, and allow the extraction of signals from off-axis sources using the same algorithms proposed for the space-based missions. This approach should thus allow for testing of the applicability of proposed signal extraction algorithms for the detection of single and multiple near-neighbor companions...

A medium-scale measurement of the cosmic microwave background at 3.3 millimeters

NASA Technical Reports Server (NTRS)

Meinhold, Peter; Lubin, Philip

1991-01-01

A system has been developed for making measurements of spatial fluctuations in the cosmic microwave background radiation, on an angular scale of 5 arcmin to a few degrees. The system consists of an off-axis Gregorian telescope with a nearly Gaussian response with FWHM adjustable from 20 to 50 arcmin, an SIS coherent receiver operating at 3.3 mm, and a pointing system capable of better than 1 arcmin rms stabilization. This paper reports on results from the system's first balloon flight in August 1988, and ground-based measurements made from the South Pole in December 1988. A portion of the South Pole data is used to place a 95-percent confidence level upper limit of Delta T/T less than 0.000035 for Gaussian sky fluctuations in the background radiation at 20-arcmin angular scale and a limit of Delta T/T less than 0.000033 on overall excess intrinsic sky noise. In addition, dust contamination in cosmic background radiation data is estimated using measurements of the Galaxy from this flight and a previous one, along with the IRAS 100-micron map. These anisotropy results give the most stringent limits on cold dark matter theories to date.

Use of off-axis injection as an alternative to geometrically merging beams in an energy-recovering linac

DOEpatents

Douglas, David R [York County, VA

2012-01-10

A method of using off-axis particle beam injection in energy-recovering linear accelerators that increases operational efficiency while eliminating the need to merge the high energy re-circulating beam with an injected low energy beam. In this arrangement, the high energy re-circulating beam and the low energy beam are manipulated such that they are within a predetermined distance from one another and then the two immerged beams are injected into the linac and propagated through the system. The configuration permits injection without geometric beam merging as well as decelerated beam extraction without the use of typical beamline elements.

Effects of multi-directional vibrotactile feedback on vestibular-deficient postural performance during continuous multi-directional support surface perturbations.

PubMed

Sienko, K H; Balkwill, M D; Oddsson, L I E; Wall, C

2008-01-01

Single-axis vibrotactile feedback of trunk tilt provided in real-time has previously been shown to significantly reduce the root-mean-square (RMS) trunk sway in subjects with vestibular loss during single-axis perturbation. This research examines the effect of multi-directional vibrotactile feedback on postural sway during continuous multi-directional surface perturbations when the subjects' eyes are closed. Eight subjects with vestibular loss donned a multi-axis feedback device that mapped body tilt estimates onto their torsos with a 3-row by 16-column array of tactile actuators (tactors). Tactor row indicated tilt magnitude and tactor column indicated tilt direction. Root-mean-square trunk tilt, elliptical fits to trunk sway trajectory areas, percentage of time spent outside a no vibrotactile feedback zone, RMS center of pressure, and anchoring index parameters indicating intersegmental coordination were used to assess the efficacy of the multi-directional vibrotactile balance aid. Four tactor display configurations in addition to the tactors off configuration were evaluated. Subjects had significantly reduced RMS trunk sway, significantly smaller elliptical fits of the trajectory area, and spent significantly less time outside of the no feedback zone in the tactors on versus the tactors off configuration. Among the displays evaluated in this study, there was not an optimal tactor column configuration for standing tasks involving continuous surface perturbations. Furthermore, subjects performed worse when erroneous information was displayed. Therefore, a spatial resolution of 90 degrees (4 columns) seems to be as effective as a spatial resolution of 22.5 degrees (16 columns) for control of standing.

Off-axis digital holographic microscopy with LED illumination based on polarization filtering.

PubMed

Guo, Rongli; Yao, Baoli; Gao, Peng; Min, Junwei; Zhou, Meiling; Han, Jun; Yu, Xun; Yu, Xianghua; Lei, Ming; Yan, Shaohui; Yang, Yanlong; Dan, Dan; Ye, Tong

2013-12-01

A reflection mode digital holographic microscope with light emitting diode (LED) illumination and off-axis interferometry is proposed. The setup is comprised of a Linnik interferometer and a grating-based 4f imaging unit. Both object and reference waves travel coaxially and are split into multiple diffraction orders in the Fourier plane by the grating. The zeroth and first orders are filtered by a polarizing array to select orthogonally polarized object waves and reference waves. Subsequently, the object and reference waves are combined again in the output plane of the 4f system, and then the hologram with uniform contrast over the entire field of view can be acquired with the aid of a polarizer. The one-shot nature in the off-axis configuration enables an interferometric recording time on a millisecond scale. The validity of the proposed setup is illustrated by imaging nanostructured substrates, and the experimental results demonstrate that the phase noise is reduced drastically by an order of 68% when compared to a He-Ne laser-based result.

Rotorcraft flight control design using quantitative feedback theory and dynamic crossfeeds

NASA Technical Reports Server (NTRS)

Cheng, Rendy P.

1995-01-01

A multi-input, multi-output controls design with robust crossfeeds is presented for a rotorcraft in near-hovering flight using quantitative feedback theory (QFT). Decoupling criteria are developed for dynamic crossfeed design and implementation. Frequency dependent performance metrics focusing on piloted flight are developed and tested on 23 flight configurations. The metrics show that the resulting design is superior to alternative control system designs using conventional fixed-gain crossfeeds and to feedback-only designs which rely on high gains to suppress undesired off-axis responses. The use of dynamic, robust crossfeeds prior to the QFT design reduces the magnitude of required feedback gain and results in performance that meets current handling qualities specifications relative to the decoupling of off-axis responses. The combined effect of the QFT feedback design following the implementation of low-order, dynamic crossfeed compensator successfully decouples ten of twelve off-axis channels. For the other two channels it was not possible to find a single, low-order crossfeed that was effective.

A study of rotor and platform design trade-offs for large-scale floating vertical axis wind turbines

NASA Astrophysics Data System (ADS)

Griffith, D. Todd; Paquette, Joshua; Barone, Matthew; Goupee, Andrew J.; Fowler, Matthew J.; Bull, Diana; Owens, Brian

2016-09-01

Vertical axis wind turbines are receiving significant attention for offshore siting. In general, offshore wind offers proximity to large populations centers, a vast & more consistent wind resource, and a scale-up opportunity, to name a few beneficial characteristics. On the other hand, offshore wind suffers from high levelized cost of energy (LCOE) and in particular high balance of system (BoS) costs owing to accessibility challenges and limited project experience. To address these challenges associated with offshore wind, Sandia National Laboratories is researching large-scale (MW class) offshore floating vertical axis wind turbines (VAWTs). The motivation for this work is that floating VAWTs are a potential transformative technology solution to reduce offshore wind LCOE in deep-water locations. This paper explores performance and cost trade-offs within the design space for floating VAWTs between the configurations for the rotor and platform.

Far-ultraviolet observations of comet C/2012 S1 (ISON) with a sounding-rocket-borne instrument

NASA Astrophysics Data System (ADS)

Feldman, P.; McCandliss, S.; Weaver, H.; Fleming, B.; Redwine, K.; Li, M.; Kutyrev, A.; Moseley, S.

2014-07-01

We report on a far-ultraviolet observation of comet C/2012 S1 (ISON) made from a Black Brant IX sounding rocket that was launched on 20 November 2013 at 04:40 MST from the White Sands Missile Range, New Mexico, when the comet was 0.44 au from the Sun, 0.86 au from the Earth, and at a solar elongation of 26.3 degrees pre-perihelion. At the time of launch the comet was 0.1 degrees below ground horizon. The payload reached an apogee of 279 km and the total time pointed at the comet was 353 s. The sounding rocket borne instrument was our wide-field multi-object spectro-telescope called FORTIS (Far-UV Off Rowland-circle Telescope for Imaging and Spectroscopy), which is a Gregorian telescope (concave primary and secondary optics) with a triaxial figured diffractive secondary that provides an on-axis imaging channel and two off-axis spectral channels in a common focal plane. A multi-object spectroscopic capability is provided by an array of microshutters placed at the prime focus of the telescope. Our microshutter array (MSA) is based on prototype devices of the large area arrays developed at Goddard Space Flight Center (GSFC) for use in the Near Infrared Spectrograph (NIRSpec) on the James Webb Space Telescope (JWST). The imaging channel on FORTIS has a field-of-view (FOV) of 0.5 degrees square. The MSA allows selection of up to 43 individual regions, each with a solid angle of 12.4'' × 36.9'', for spectral acquisition over the 800--1950 Ångstroms bandpass at a resolution of 6 Ångstroms. However a problem with addressing the MSA prevented the acquisition of spectra through individual slits. Nonetheless spectrally confused images, dominated by Lyman-alpha emission from the comet, were acquired in both off-axis spectral channels. The imaging channel uses a CaF_2/MgF_2 cylindrical doublet to correct for astigmatism introduced by the triaxial secondary, which restricts the bandpass to wavelengths longward of 1280 Ångstroms. The corrected imaging resolution is approximately 4''. Broadband images of the comet acquired in the on-axis imaging channel throughout the duration of the flight show a variation in count rate proportional to altitude due to absorption of cometary emissions by terrestrial molecular oxygen located in the lower thermosphere. Molecular oxygen absorption has a strong dependence on wavelength, which will selectively attenuate cometary emissions from different atomic and molecular species and allow us to constrain their production rates relative to hydrogen observed in the spectral channels. Analysis is ongoing and preliminary results will be presented.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rodrigues, A; Yin, F; Wu, Q

2015-06-15

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

Configuration study for a 30 GHz monolithic receive array, volume 1

NASA Technical Reports Server (NTRS)

Nester, W. H.; Cleaveland, B.; Edward, B.; Gotkis, S.; Hesserbacker, G.; Loh, J.; Mitchell, B.

1984-01-01

Gregorian, Cassegrain, and single reflector systems were analyzed in configuration studies for communications satellite receive antennas. Parametric design and performance curves were generated. A preliminary design of each reflector/feed system was derived including radiating elements, beam-former network, beamsteering system, and MMIC module architecture. Performance estimates and component requirements were developed for each design. A recommended design was selected for both the scanning beam and the fixed beam case. Detailed design and performance analysis results are presented for the selected Cassegrain configurations. The final design point is characterized in detail and performance measures evaluated in terms of gain, sidelobe level, noise figure, carrier-to-interference ratio, prime power, and beamsteering. The effects of mutual coupling and excitation errors (including phase and amplitude quantization errors) are evaluated. Mechanical assembly drawings are given for the final design point. Thermal design requirements are addressed in the mechanical design.

WHAT? A Large Reflective Schmidt Telescope for the Antarctic Plateau

NASA Astrophysics Data System (ADS)

Saunders, W.; McGrath, A. J.

We present a design concept for WHAT the Wide-field Antarctic Horizontal Telescope to take advantage of the unique possibilities of Antarctica for both optical and near infrared astronomy. The design is an 8 metre, wide-field, fixed-axis, all-reflective, f/4 Schmidt telescope. Prime and Cassegrain (or Gregorian) foci are provided, giving plate scales 150-1500 μ m/'', over fields of view 3'-3circ. Diffraction limited, NGSAO-corrected K_dark images are possible over arc-minute sized fields, over most of the sky. The sensitivity, resolution, field of view and cost all compare favourably with current or proposed space or ground-based telescopes.

Imaging Spectropolarimeter for the Multi-Application Solar Telescope at Udaipur Solar Observatory: Characterization of Polarimeter and Preliminary Observations

NASA Astrophysics Data System (ADS)

Tiwary, Alok Ranjan; Mathew, Shibu K.; Bayanna, A. Raja; Venkatakrishnan, P.; Yadav, Rahul

2017-04-01

The Multi-Application Solar Telescope (MAST) is a 50 cm off-axis Gregorian telescope that has recently become operational at the Udaipur Solar Observatory (USO). An imaging spectropolarimeter is being developed as one of the back-end instruments of MAST to gain a better understanding of the evolution and dynamics of solar magnetic and velocity fields. This system consists of a narrow-band filter and a polarimeter. The polarimeter includes a linear polarizer and two sets of liquid crystal variable retarders (LCVRs). The instrument is intended for simultaneous observations in the spectral lines 6173 Å and 8542 Å, which are formed in the photosphere and chromosphere, respectively. In this article, we present results from the characterization of the LCVRs for the spectral lines of interest and the response matrix of the polarimeter. We also present preliminary observations of an active region obtained using the spectropolarimeter. For verification purposes, we compare the Stokes observations of the active region obtained from the Helioseismic Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO) with that of MAST observations in the spectral line 6173 Å. We find good agreement between the two observations, considering the fact that MAST observations are limited by seeing.

Fast Imaging Solar Spectrograph System in New Solar Telescope

NASA Astrophysics Data System (ADS)

Park, Y.-D.; Kim, Y. H.; Chae, J.; Goode, P. R.; Cho, K. S.; Park, H. M.; Nah, J. K.; Jang, B. H.

2010-12-01

In 2004, Big Bear Solar Observatory in California, USA launched a project for construction of the world's largest aperture solar telescope (D = 1.6m) called New Solar Telescope(NST). University of Hawaii (UH) and Korea Astronomy and Space Science Institute(KASI) partly collaborate on the project. NST is a designed off-axis parabolic Gregorian reflector with very high spatial resolution(0.07 arcsec at 5000A) and is equipped with several scientific instruments such as Visible Imaging Magnetograph (VIM), InfraRed Imaging Magnetograph IRIM), and so on. Since these scientific instruments are focused on studies of the solar photosphere, we need a post-focus instrument for the NST to study the fine structures and dynamic patterns of the solar chromosphere and low Transition Region (TR) layer, including filaments/prominences, spicules, jets, micro flares, etc. For this reason, we developed and installed a fast imaging solar spectrograph(FISS) system on the NST withadvantages of achieving compact design with high spectral resolution and small aberration as well as recording many solar spectral lines in a single and/or dual band mode. FISS was installed in May, 2010 and now we carry out a test observation. In this talk, we introduce the FISS system and the results of the test observation after FISS installation.

Stable donutlike vortex beam generation from lasers with controlled Ince-Gaussian modes

NASA Astrophysics Data System (ADS)

Chu, Shu-Chun; Otsuka, Kenju

2007-11-01

This study proposes a three-lens configuration for generating a stable donutlike vortex laser beam with controlled Ince-Gaussian mode (IGM) operation in the model of laser-diode (LD)-pumped solid-state lasers. Simply controlling the lateral off-axis position of the pump beam's focus on the laser crystal can generate a desired donutlike vortex beam from the proposed simple and easily made three-lens configuration, a proposed astigmatic mode converter assembled into one body with a concave-convex laser cavity.

High-accuracy Aspheric X-ray Mirror Metrology Using Software Configurable Optical Test System/deflectometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Run; Su, Peng; Burge, James H.

The Software Configurable Optical Test System (SCOTS) uses deflectometry to measure surface slopes of general optical shapes without the need for additional null optics. Careful alignment of test geometry and calibration of inherent system error improve the accuracy of SCOTS to a level where it competes with interferometry. We report a SCOTS surface measurement of an off-axis superpolished elliptical x-ray mirror that achieves <1 nm<1 nm root-mean-square accuracy for the surface measurement with low-order term included.

Recent off-axis volcanism in the eastern Gulf of Aden: Implications for plume-ridge interaction

NASA Astrophysics Data System (ADS)

Leroy, Sylvie; d'Acremont, Elia; Tiberi, Christel; Basuyau, Clémence; Autin, Julia; Lucazeau, Francis; Sloan, Heather

2010-04-01

Evidence of anomalous volcanism is readily observed in the Gulf of Aden, although, much of this oceanic basin remains as yet unmapped. In this paper, we investigate the possible connection of the Afar hotspot with a major off-axis volcanic structure and its interpretation as a consequence of a the anomalous presence of melt by integrating several data sets, both published and unpublished, from the Encens-Sheba cruise, the Aden New Century (ANC) cruise and several other onshore and marine surveys. These include bathymetric, gravity, magnetic, magneto-telluric data, and rock samples. Based upon these observations, interpretations were made of seafloor morphology, gravity and magnetic models, seafloor age, geochemical analyses and tectonic setting. We discuss the possible existence of a regional melting anomaly in the Gulf of Aden area and of the probability of its connection to the Afar plume. Several models that might explain the anomalous volcanism are taken into account, such as a local melting anomaly unrelated to the Afar plume, an anomalously large volume of melt associated with seafloor spreading, and interaction of the ridge with the Afar plume. A local melting anomaly and atypical seafloor spreading prove inconsistent with our observations. Two previously proposed models of plume-ridge interactions are examined: the diffuse plume dispersion called pancaked flow and channelized along-axis flow. We conclude that the configuration and structure of this young ocean basin may have the effect of channeling material away from the Afar plume along the Aden and Sheba Ridges to produce the off-axis volcanism observed on the ridge flanks. This interpretation implies that the influence of the Afar hotspot may extend much farther eastwards into the Gulf of Aden than previously believed. The segmentation of the Gulf of Aden and the configuration of the Aden-Sheba system may provide a potential opportunity to study channeled flow of solid plume mantle from the plume along a segmented ridge and nearby continental margins.

Grating tuned unstable resonator laser cavity

DOEpatents

Johnson, Larry C.

1982-01-01

An unstable resonator to be used in high power, narrow line CO.sub.2 pump lasers comprises an array of four reflectors in a ring configuration wherein spherical and planar wavefronts are separated from each other along separate optical paths and only the planar wavefronts are impinged on a plane grating for line tuning. The reflector array comprises a concave mirror for reflecting incident spherical waves as plane waves along an output axis to form an output beam. A plane grating on the output axis is oriented to reflect a portion of the output beam off axis onto a planar relay mirror spaced apart from the output axis in proximity to the concave mirror. The relay mirror reflects plane waves from the grating to impinge on a convex expanding mirror spaced apart from the output axis in proximity to the grating. The expanding mirror reflects the incident planar waves as spherical waves to illuminate the concave mirror. Tuning is provided by rotating the plane grating about an axis normal to the output axis.

Large Binocular Telescope project

NASA Astrophysics Data System (ADS)

Hill, John M.; Salinari, Piero

2003-02-01

The Large Binocular Telescope (LBT) Project is a collaboration between institutions in Arizona, Germany, Italy, and Ohio. The first of two 8.4-meter borosilicate honeycomb primary mirrors for LBT is being polished at the Steward Observatory Mirror Lab this year. The second of the two 8.4-meter mirror blanks waits its turn in the polishing queue. The baseline optical configuration of LBT includes adaptive infrared secondaries of a Gregorian design. The F/15 secondaries are undersized to provide a low thermal background focal plane which is unvignetted over a 4-arcminute diameter field-of-view. These adaptive secondary mirrors with 672 voice-coil actuators are now in the early stages of fabrication. The interferometric focus combining the light from the two 8.4-meter primaries will reimage the two folded Gregorian focal planes to three central locations for phased array imaging. The telescope elevation structure accommodates swing arm spiders which allow rapid interchange of the various secondary and tertiary mirrors as well as prime focus cameras. The telescope structure accommodates installation of a vacuum bell jar for aluminizing the primary mirrors in-situ on the telescope. The telescope structure was fabricated and pre-assembled in Italy by Ansaldo-Camozzi in Milan. The structure was disassembled, packed and shipped to Arizona. The enclosure was built on Mt. Graham and is ready for telescope installation.

Cost analysis of a mini-facet heliostat

NASA Astrophysics Data System (ADS)

Hall, Colin; Pratt, Rodney; Farrant, David; Corsi, Clotilde; Pye, John; Coventry, Joe

2017-06-01

A significant problem with conventional heliostats is off-axis astigmatism, which increases the spot size at the central receiver, limiting the temperature and efficiency of solar thermal systems. Inspired by low-cost mini-actuators used for car wing mirrors, we examine the economic feasibility of a heliostat with individually adjustable mini-facets to correct astigmatic effects, and we compare three alternative tracking configurations.

Simulation study of terahertz radiation generation by circularly polarized laser pulses propagating in axially magnetized plasma

NASA Astrophysics Data System (ADS)

Saroch, Akanksha; Jha, Pallavi

2017-12-01

This paper deals with a two-dimensional simulation study of terahertz radiation emission in the wake of circularly polarized laser pulses propagating in uniformly magnetized plasma, using the XOOPIC code. The external magnetic field is applied along the direction of propagation of the laser pulse. It is seen that linearly polarized terahertz radiation is emitted off-axis, along the propagation direction, in plasma. This emitted radiation is also seen to be transmitted in vacuum. Simulation studies reveal that no such radiation is generated on-axis for the given configuration.

Optical control of the Advanced Technology Solar Telescope.

PubMed

Upton, Robert

2006-08-10

The Advanced Technology Solar Telescope (ATST) is an off-axis Gregorian astronomical telescope design. The ATST is expected to be subject to thermal and gravitational effects that result in misalignments of its mirrors and warping of its primary mirror. These effects require active, closed-loop correction to maintain its as-designed diffraction-limited optical performance. The simulation and modeling of the ATST with a closed-loop correction strategy are presented. The correction strategy is derived from the linear mathematical properties of two Jacobian, or influence, matrices that map the ATST rigid-body (RB) misalignments and primary mirror figure errors to wavefront sensor (WFS) measurements. The two Jacobian matrices also quantify the sensitivities of the ATST to RB and primary mirror figure perturbations. The modeled active correction strategy results in a decrease of the rms wavefront error averaged over the field of view (FOV) from 500 to 19 nm, subject to 10 nm rms WFS noise. This result is obtained utilizing nine WFSs distributed in the FOV with a 300 nm rms astigmatism figure error on the primary mirror. Correction of the ATST RB perturbations is demonstrated for an optimum subset of three WFSs with corrections improving the ATST rms wavefront error from 340 to 17.8 nm. In addition to the active correction of the ATST, an analytically robust sensitivity analysis that can be generally extended to a wider class of optical systems is presented.

Petascale Computing for Ground-Based Solar Physics with the DKIST Data Center

NASA Astrophysics Data System (ADS)

Berukoff, Steven J.; Hays, Tony; Reardon, Kevin P.; Spiess, DJ; Watson, Fraser; Wiant, Scott

2016-05-01

When construction is complete in 2019, the Daniel K. Inouye Solar Telescope will be the most-capable large aperture, high-resolution, multi-instrument solar physics facility in the world. The telescope is designed as a four-meter off-axis Gregorian, with a rotating Coude laboratory designed to simultaneously house and support five first-light imaging and spectropolarimetric instruments. At current design, the facility and its instruments will generate data volumes of 3 PB per year, and produce 107-109 metadata elements.The DKIST Data Center is being designed to store, curate, and process this flood of information, while providing association of science data and metadata to its acquisition and processing provenance. The Data Center will produce quality-controlled calibrated data sets, and make them available freely and openly through modern search interfaces and APIs. Documented software and algorithms will also be made available through community repositories like Github for further collaboration and improvement.We discuss the current design and approach of the DKIST Data Center, describing the development cycle, early technology analysis and prototyping, and the roadmap ahead. We discuss our iterative development approach, the underappreciated challenges of calibrating ground-based solar data, the crucial integration of the Data Center within the larger Operations lifecycle, and how software and hardware support, intelligently deployed, will enable high-caliber solar physics research and community growth for the DKIST's 40-year lifespan.

Muses on the Gregorian Calendar

ERIC Educational Resources Information Center

Staples, Ed

2013-01-01

This article begins with an exploration of the origins of the Gregorian Calendar. Next it describes the function of school inspector Christian Zeller (1822-1899) used to determine the number of the elapsed days of a year up to and including a specified date and how Zeller's function can be used to determine the number of days that have elapsed in…

Full range line-field parallel swept source imaging utilizing digital refocusing

NASA Astrophysics Data System (ADS)

Fechtig, Daniel J.; Kumar, Abhishek; Drexler, Wolfgang; Leitgeb, Rainer A.

2015-12-01

We present geometric optics-based refocusing applied to a novel off-axis line-field parallel swept source imaging (LPSI) system. LPSI is an imaging modality based on line-field swept source optical coherence tomography, which permits 3-D imaging at acquisition speeds of up to 1 MHz. The digital refocusing algorithm applies a defocus-correcting phase term to the Fourier representation of complex-valued interferometric image data, which is based on the geometrical optics information of the LPSI system. We introduce the off-axis LPSI system configuration, the digital refocusing algorithm and demonstrate the effectiveness of our method for refocusing volumetric images of technical and biological samples. An increase of effective in-focus depth range from 255 μm to 4.7 mm is achieved. The recovery of the full in-focus depth range might be especially valuable for future high-speed and high-resolution diagnostic applications of LPSI in ophthalmology.

Characteristics of phase-correcting fresnel zone plates and elliptical waveguides

NASA Astrophysics Data System (ADS)

Wiltse, James C.

1994-02-01

The primary area of activity has been concentrated on the investigations relating to Fresnel zone plate antennas. A secondary effort has dealt with the characteristics of propagation in waveguides of elliptical cross section. In both cases, applications at microwave and millimeter-wavelengths have been emphasized. Thorough literature searches were conducted, and the results are given in Appendices A and B. The zone plate work has dealt with both transmission and reflection types, and has included considering the off-axis-fed cases. In the latter case, the plate may consist of elliptical zones, rather than the usual circular configuration. In general, the characteristics studied include far-field patterns, focal region fields, off-axis performance, bandwidth, and aberrations. In the case of propagation in elliptical waveguides, the attenuation and modal properties were studied for enclosed metal waveguides, coaxial transmission lines, and various surface waveguides.

Robustness of an artificially tailored fisheye imaging system with a curvilinear image surface

NASA Astrophysics Data System (ADS)

Lee, Gil Ju; Nam, Won Il; Song, Young Min

2017-11-01

Curved image sensors inspired by animal and insect eyes have provided a new development direction in next-generation digital cameras. It is known that natural fish eyes afford an extremely wide field of view (FOV) imaging due to the geometrical properties of the spherical lens and hemispherical retina. However, its inherent drawbacks, such as the low off-axis illumination and the fabrication difficulty of a 'dome-like' hemispherical imager, limit the development of bio-inspired wide FOV cameras. Here, a new type of fisheye imaging system is introduced that has simple lens configurations with a curvilinear image surface, while maintaining high off-axis illumination and a wide FOV. Moreover, through comparisons with commercial conventional fisheye designs, it is determined that the volume and required number of optical elements of the proposed design is practical while capturing the fundamental optical performances. Detailed design guidelines for tailoring the proposed optic system are also discussed.

Design and analysis of multilayer x ray/XUV microscope

NASA Technical Reports Server (NTRS)

Shealy, David L.

1990-01-01

The design and analysis of a large number of normal incidence multilayer x ray microscopes based on the spherical mirror Schwarzschild configuration is examined. Design equations for the spherical mirror Schwarzschild microscopes are summarized and used to evaluate mirror parameters for microscopes with magnifications ranging from 2 to 50x. Ray tracing and diffraction analyses are carried out for many microscope configurations to determine image resolution as a function of system parameters. The results are summarized in three publication included herein. A preliminary study of advanced reflecting microscope configurations, where aspherics are used in place of the spherical microscope mirror elements, has indicated that the aspherical elements will improve off-axis image resolution and increase the effective field of view.

Far-field noise and internal modes from a ducted propeller at simulated aircraft takeoff conditions

NASA Astrophysics Data System (ADS)

Woodward, Richard P.; Bock, Lawrence A.; Heidelberg, Laurence J.; Hall, David G.

1992-01-01

The ducted propeller offers structural and acoustic benefits typical of conventional turbofan engines while retaining much of the aeroacoustic benefits of the unducted propeller. A model Advanced Ducted Propeller (ADP) was tested in the NASA Lewis Low-Speed Anechoic Wind Tunnel at a simulated takeoff velocity of Mach 0.2. The ADP model was designed and manufactured by the Pratt and Whitney Division of United Technologies. The 16-blade rotor ADP was tested with 22- and 40-vane stators to achieve cut-on and cut-off criterion with respect to propagation of the fundamental rotor-stator interaction tone. Additional test parameters included three inlet lengths, three nozzle sizes, two spinner configurations, and two rotor rub strip configurations. The model was tested over a range of rotor blade setting angles and propeller axis angles-of-attack. Acoustic data were taken with a sideline translating microphone probe and with a unique inlet microphone probe which identified inlet rotating acoustic modes. The beneficial acoustic effects of cut-off were clearly demonstrated. A 5 dB fundamental tone reduction was associated with the long inlet and 40-vane sector, which may relate to inlet propeller axis angle-of-attack at rotor speeds of at least 96 percent design.

Far-field noise and internal modes from a ducted propeller at simulated aircraft takeoff conditions

NASA Astrophysics Data System (ADS)

Woodward, Richard P.; Bock, Lawrence A.; Heidelberg, Laurence J.; Hall, David G.

The ducted propeller offers structural and acoustic benefits typical of conventional turbofan engines while retaining much of the aeroacoustic benefits of the unducted propeller. A model Advanced Ducted Propeller (ADP) was tested in the NASA Lewis Low-Speed Anechoic Wind Tunnel at a simulated takeoff velocity of Mach 0.2. The ADP model was designed and manufactured by the Pratt and Whitney Division of United Technologies. The 16-blade rotor ADP was tested with 22- and 40-vane stators to achieve cut-on and cut-off criterion with respect to propagation of the fundamental rotor-stator interaction tone. Additional test parameters included three inlet lengths, three nozzle sizes, two spinner configurations, and two rotor rub strip configurations. The model was tested over a range of rotor blade setting angles and propeller axis angles-of-attack. Acoustic data were taken with a sideline translating microphone probe and with a unique inlet microphone probe which identified inlet rotating acoustic modes. The beneficial acoustic effects of cut-off were clearly demonstrated. A 5 dB fundamental tone reduction was associated with the long inlet and 40-vane sector, which may relate to inlet duct geometry. The fundamental tone level was essentially unaffected by propeller axis angle-of-attack at rotor speeds of at least 96 percent design.

Far-field noise and internal modes from a ducted propeller at simulated aircraft takeoff conditions

NASA Technical Reports Server (NTRS)

Woodward, Richard P.; Bock, Lawrence A.; Heidelberg, Laurence J.; Hall, David G.

1992-01-01

The ducted propeller offers structural and acoustic benefits typical of conventional turbofan engines while retaining much of the aeroacoustic benefits of the unducted propeller. A model Advanced Ducted Propeller (ADP) was tested in the NASA Lewis Low-Speed Anechoic Wind Tunnel at a simulated takeoff velocity of Mach 0.2. The ADP model was designed and manufactured by the Pratt and Whitney Division of United Technologies. The 16-blade rotor ADP was tested with 22- and 40-vane stators to achieve cut-on and cut-off criterion with respect to propagation of the fundamental rotor-stator interaction tone. Additional test parameters included three inlet lengths, three nozzle sizes, two spinner configurations, and two rotor rub strip configurations. The model was tested over a range of rotor blade setting angles and propeller axis angles-of-attack. Acoustic data were taken with a sideline translating microphone probe and with a unique inlet microphone probe which identified inlet rotating acoustic modes. The beneficial acoustic effects of cut-off were clearly demonstrated. A 5 dB fundamental tone reduction was associated with the long inlet and 40-vane sector, which may relate to inlet duct geometry. The fundamental tone level was essentially unaffected by propeller axis angle-of-attack at rotor speeds of at least 96 percent design.

Optimization of a rod pinch diode radiography source at 2.3 MV

NASA Astrophysics Data System (ADS)

Menge, P. R.; Johnson, D. L.; Maenchen, J. E.; Rovang, D. C.; Oliver, B. V.; Rose, D. V.; Welch, D. R.

2003-08-01

Rod pinch diodes have shown considerable capability as high-brightness flash x-ray sources for penetrating dynamic radiography. The rod pinch diode uses a small diameter (0.4-2 mm) anode rod extended through a cathode aperture. When properly configured, the electron beam born off of the aperture edge can self-insulate and pinch onto the tip of the rod creating an intense, small x-ray source. Sandia's SABRE accelerator (2.3 MV, 40 Ω, 70 ns) has been utilized to optimize the source experimentally by maximizing the figure of merit (dose/spot diameter2) and minimizing the diode impedance droop. Many diode parameters have been examined including rod diameter, rod length, rod material, cathode aperture diameter, cathode thickness, power flow gap, vacuum quality, and severity of rod-cathode misalignment. The configuration producing the greatest figure of merit uses a 0.5 mm diameter gold rod, a 6 mm rod extension beyond the cathode aperture (diameter=8 mm), and a 10 cm power flow gap to produce up to 3.5 rad (filtered dose) at 1 m from a 0.85 mm x-ray on-axis spot (1.02 mm at 3° off axis). The resultant survey of parameter space has elucidated several physics issues that are discussed.

A PENELOPE-based system for the automated Monte Carlo simulation of clinacs and voxelized geometries - application to far-from-axis fields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sempau, Josep; Badal, Andreu; Brualla, Lorenzo

Purpose: Two new codes, PENEASY and PENEASYLINAC, which automate the Monte Carlo simulation of Varian Clinacs of the 600, 1800, 2100, and 2300 series, together with their electron applicators and multileaf collimators, are introduced. The challenging case of a relatively small and far-from-axis field has been studied with these tools. Methods: PENEASY is a modular, general-purpose main program for the PENELOPE Monte Carlo system that includes various source models, tallies and variance-reduction techniques (VRT). The code includes a new geometry model that allows the superposition of voxels and objects limited by quadric surfaces. A variant of the VRT known asmore » particle splitting, called fan splitting, is also introduced. PENEASYLINAC, in turn, automatically generates detailed geometry and configuration files to simulate linacs with PENEASY. These tools are applied to the generation of phase-space files, and of the corresponding absorbed dose distributions in water, for two 6 MV photon beams from a Varian Clinac 2100 C/D: a 40 x 40 cm{sup 2} centered field; and a 3 x 5 cm{sup 2} field centered at (4.5, -11.5) cm from the beam central axis. This latter configuration implies the largest possible over-traveling values of two of the jaws. Simulation results for the depth dose and lateral profiles at various depths are compared, by using the gamma index, with experimental values obtained with a PTW 31002 ionization chamber. The contribution of several VRTs to the computing speed of the more demanding off-axis case is analyzed. Results: For the 40 x 40 cm{sup 2} field, the percentages {gamma}{sub 1} and {gamma}{sub 1.2} of voxels with gamma indices (using 0.2 cm and 2% criteria) larger than unity and larger than 1.2 are 0.2% and 0%, respectively. For the 3 x 5 cm{sup 2} field, {gamma}{sub 1} = 0%. These figures indicate an excellent agreement between simulation and experiment. The dose distribution for the off-axis case with voxels of 2.5 x 2.5 x 2.5 mm{sup 3} and an average standard statistical uncertainty of 2% (1{sigma}) is computed in 3.1 h on a single core of a 2.8 GHz Intel Core 2 Duo processor. This result is obtained with the optimal combination of the tested VRTs. In particular, fan splitting for the off-axis case accelerates execution by a factor of 240 with respect to standard particle splitting. Conclusions: PENEASY and PENEASYLINAC can simulate the considered Varian Clinacs both in an accurate and efficient manner. Fan splitting is crucial to achieve simulation results for the off-axis field in an affordable amount of CPU time. Work to include Elekta linacs and to develop a graphical interface that will facilitate user input is underway.« less

Characterization and optimization of slanted well designs for microfluidic mixing under electroosmotic flow.

PubMed

Johnson, Timothy J; Locascio, Laurie E

2002-08-01

Recently, a series of slanted wells on the floor of a microfluidic channel were experimentally shown to successfully induce off-axis transport and mixing of two confluent streams when operating under electroosmotic (EO) flow. This paper will further explore, through numerical simulations, the parameters that affect off-axis transport under EO flow with an emphasis on optimizing the mixing rate of (a). two confluent streams in steady-state or (b). the transient scenario of two confluent plugs of material, which simulates mixing after an injection. For the steady-state scenario, the degree of mixing was determined to increase by changing any of the following parameters: (1). increasing the well depth, (2). decreasing the well angle relative to the axis of the channel, and (3). increasing the EO mobility of the well walls relative to the mobility of the main channel. Also, it will be shown that folding of the fluid can occur when the well angle is sufficiently reduced and/or when the EO mobility of the wells is increased relative to the channel. The optimum configuration for the transient problem of mixing two confluent plugs includes shallow wells to minimize the well residence time, and an increased EO mobility of the well walls relative to the main channel as well as small well angles to maximize off-axis transport. The final design reported here for the transient study reduces the standard deviation of the concentration across the channel by 72% while only increasing the axial dispersion of the injected plug by 8.6 % when compared to a plug injected into a channel with no wells present. These results indicate that a series of slanted wells on the wall of a microchannel provides a means for controlling and achieving a high degree of off-axis transport and mixing in a passive manner for micro total analysis system (microTAS) devices that are driven by electroosmosis.

Recommended conceptual optical system design for China's Large Optical-infrared Telescope (LOT).

PubMed

Ma, Donglin

2018-01-08

Recently, China is planning to construct a new large optical-infrared telescope (LOT), in which the aperture of the primary mirror is as large as 12m. China's LOT is a general-purpose telescope, which is aimed to work with multiple scientific instruments such as spectrographs. Based on the requirements of LOT telescope, we have compared the performance of Ritchey-Chrétien (RC) design and Aplanatic-Gregorian (AG) design from the perspective of scientific performance and construction cost. By taking the primary focal ratio, Nasmyth focal ratio, and telescope's site condition into consideration, we finally recommend a RC f/1.6 design configuration for LOT's Nasmyth telescope system. Unlike the general identical configuration, we choose a non-identical configuration for the telescope system which has a shorter Cassegrain focal ratio compared to the designed Nasmyth focal ratio. The non-identical design can allow for a shorter back focal distance and therefore a shorter telescope fork to guarantee the gravitational stability of the whole telescope structure, as well as relatively lower construction cost. Detailed analysis for the feasibility of our recommended design is provided in this paper.

A parametric study of various synthetic aperture telescope configurations for coherent imaging applications

NASA Technical Reports Server (NTRS)

Harvey, James E.; Wissinger, Alan B.; Bunner, Alan N.

1986-01-01

The comparative advantages of synthetic aperture telescopes (SATs) of segmented primary mirror and common secondary mirror type, on the one hand, and on the other those employing an array of independent telescopes, are discussed. The diffraction-limited optical performance of both redundant and nonredundant subaperture configurations are compared in terms of point spread function characteristics and encircled energy plots. Coherent imaging with afocal telescope SATs involves a pupil-mapping operation followed by a Fourier transform one. A quantitative analysis of the off-axis optical performance degradation due to pupil-mapping errors is presented, together with the field-dependent effects of residual design aberrations of independent telescopes.

System and method for incremental forming

DOEpatents

Beltran, Michael; Cao, Jian; Roth, John T.

2015-12-29

A system includes a frame configured to hold a workpiece and first and second tool positioning assemblies configured to be opposed to each other on opposite sides of the workpiece. The first and second tool positioning assemblies each include a toolholder configured to secure a tool to the tool positioning assembly, a first axis assembly, a second axis assembly, and a third axis assembly. The first, second, and third axis assemblies are each configured to articulate the toolholder along a respective axis. Each axis assembly includes first and second guides extending generally parallel to the corresponding axis and disposed on opposing sides of the toolholder with respect to the corresponding axis. Each axis assembly includes first and second carriages articulable along the first and second guides of the axis assembly, respectively, in the direction of the corresponding axis.

Videoexoscopic real-time intraoperative navigation for spinal neurosurgery: a novel co-adaptation of two existing technology platforms, technical note.

PubMed

Huang, Meng; Barber, Sean Michael; Steele, William James; Boghani, Zain; Desai, Viren Rajendrakumar; Britz, Gavin Wayne; West, George Alexander; Trask, Todd Wilson; Holman, Paul Joseph

2018-06-01

Image-guided approaches to spinal instrumentation and interbody fusion have been widely popularized in the last decade [1-5]. Navigated pedicle screws are significantly less likely to breach [2, 3, 5, 6]. Navigation otherwise remains a point reference tool because the projection is off-axis to the surgeon's inline loupe or microscope view. The Synaptive robotic brightmatter drive videoexoscope monitor system represents a new paradigm for off-axis high-definition (HD) surgical visualization. It has many advantages over the traditional microscope and loupes, which have already been demonstrated in a cadaveric study [7]. An auxiliary, but powerful capability of this system is projection of a second, modifiable image in a split-screen configuration. We hypothesized that integration of both Medtronic and Synaptive platforms could permit the visualization of reconstructed navigation and surgical field images simultaneously. By utilizing navigated instruments, this configuration has the ability to support live image-guided surgery or real-time navigation (RTN). Medtronic O-arm/Stealth S7 navigation, MetRx, NavLock, and SureTrak spinal systems were implemented on a prone cadaveric specimen with a stream output to the Synaptive Display. Surgical visualization was provided using a Storz Image S1 platform and camera mounted to the Synaptive robotic brightmatter drive. We were able to successfully technically co-adapt both platforms. A minimally invasive transforaminal lumbar interbody fusion (MIS TLIF) and an open pedicle subtraction osteotomy (PSO) were performed using a navigated high-speed drill under RTN. Disc Shaver and Trials under RTN were implemented on the MIS TLIF. The synergy of Synaptive HD videoexoscope robotic drive and Medtronic Stealth platforms allow for live image-guided surgery or real-time navigation (RTN). Off-axis projection also allows upright neutral cervical spine operative ergonomics for the surgeons and improved surgical team visualization and education compared to traditional means. This technique has the potential to augment existing minimally invasive and open approaches, but will require long-term outcome measurements for efficacy.

A new method for designing dual foil electron beam forming systems. II. Feasibility of practical implementation of the method

NASA Astrophysics Data System (ADS)

Adrich, Przemysław

2016-05-01

In Part I of this work a new method for designing dual foil electron beam forming systems was introduced. In this method, an optimal configuration of the dual foil system is found by means of a systematic, automatized scan of system performance in function of its parameters. At each point of the scan, Monte Carlo method is used to calculate the off-axis dose profile in water taking into account detailed and complete geometry of the system. The new method, while being computationally intensive, minimizes the involvement of the designer. In this Part II paper, feasibility of practical implementation of the new method is demonstrated. For this, a prototype software tools were developed and applied to solve a real life design problem. It is demonstrated that system optimization can be completed within few hours time using rather moderate computing resources. It is also demonstrated that, perhaps for the first time, the designer can gain deep insight into system behavior, such that the construction can be simultaneously optimized in respect to a number of functional characteristics besides the flatness of the off-axis dose profile. In the presented example, the system is optimized in respect to both, flatness of the off-axis dose profile and the beam transmission. A number of practical issues related to application of the new method as well as its possible extensions are discussed.

Impetus of composite mechanics on test methods for fiber composites

NASA Technical Reports Server (NTRS)

Chamis, C. C.

1978-01-01

The impetus of composite mechanics on composite test methods and/or on interpreting test results is described by using examples from composite micromechanics, composite macromechanics and laminate theory. The specific examples included contributions such as criteria for selecting resin matrices for improved composite strength, the 10 deg off-axis tensile test, criteria for configuring hybrids and superhybrids for improved impact resistance and the reduced bending rigidities concept for buckling and vibration analyses.

Fused off-axis object illumination direct-to-digital holography with a plurality of illumination sources

DOEpatents

Price, Jeffery R.; Bingham, Philip R.

2005-11-08

Systems and methods are described for rapid acquisition of fused off-axis illumination direct-to-digital holography. A method of recording a plurality of off-axis object illuminated spatially heterodyne holograms, each of the off-axis object illuminated spatially heterodyne holograms including spatially heterodyne fringes for Fourier analysis, includes digitally recording, with a first illumination source of an interferometer, a first off-axis object illuminated spatially heterodyne hologram including spatially heterodyne fringes for Fourier analysis; and digitally recording, with a second illumination source of the interferometer, a second off-axis object illuminated spatially heterodyne hologram including spatially heterodyne fringes for Fourier analysis.

Fracture modes in off-axis fiber composites

NASA Technical Reports Server (NTRS)

Sinclair, J. H.; Chamis, C. C.

1978-01-01

Criteria were developed for identifying, characterizing, and quantifying fracture modes in high-modulus graphite-fiber/resin unidirectional composites subjected to off-axis tensile loading. Procedures are described which use sensitivity analyses and off-axis data to determine the uniaxial strength of fiber composites. It was found that off-axis composites fail by three fracture modes which produce unique fracture surface characteristics. The stress that dominates each fracture mode and the load angle range of its dominance can be identified. Linear composite mechanics is adequate to describe quantitatively the mechanical behavior of off-axis composites. The uniaxial strengths predicted from off-axis data are comparable to these measured in uniaxial tests.

Integrated manufacture of a freeform off-axis multi-reflective imaging system without optical alignment.

PubMed

Li, Zexiao; Liu, Xianlei; Fang, Fengzhou; Zhang, Xiaodong; Zeng, Zhen; Zhu, Linlin; Yan, Ning

2018-03-19

Multi-reflective imaging systems find wide applications in optical imaging and space detection. However, it is faced with difficulties in adjusting the freeform mirrors with high accuracy to guarantee the optical function. Motivated by this, an alignment-free manufacture approach is proposed to machine the optical system. The direct optical performance-guided manufacture route is established without measuring the form error of freeform optics. An analytical model is established to investigate the effects of machine errors to serve the error identification and compensation in machining. Based on the integrated manufactured system, an ingenious self-designed testing configuration is constructed to evaluate the optical performance by directly measuring the wavefront aberration. Experiments are carried out to manufacture a three-mirror anastigmat, surface topographical details and optical performance shows agreement to the designed expectation. The final system works as an off-axis infrared imaging system. Results validate the feasibility of the proposed method to achieve excellent optical application.

Off-axis holographic laser speckle contrast imaging of blood vessels in tissues

NASA Astrophysics Data System (ADS)

Abdurashitov, Arkady; Bragina, Olga; Sindeeva, Olga; Sergey, Sindeev; Semyachkina-Glushkovskaya, Oxana V.; Tuchin, Valery V.

2017-09-01

Laser speckle contrast imaging (LSCI) has become one of the most common tools for functional imaging in tissues. Incomplete theoretical description and sophisticated interpretation of measurement results are completely sidelined by a low-cost and simple hardware, fastness, consistent results, and repeatability. In addition to the relatively low measuring volume with around 700 μm of the probing depth for the visible spectral range of illumination, there is no depth selectivity in conventional LSCI configuration; furthermore, in a case of high NA objective, the actual penetration depth of light in tissues is greater than depth of field (DOF) of an imaging system. Thus, the information about these out-of-focus regions persists in the recorded frames but cannot be retrieved due to intensity-based registration method. We propose a simple modification of LSCI system based on the off-axis holography to introduce after-registration refocusing ability to overcome both depth-selectivity and DOF problems as well as to get the potential possibility of producing a cross-section view of the specimen.

Off-axis digital holographic camera for quantitative phase microscopy.

PubMed

Monemhaghdoust, Zahra; Montfort, Frédéric; Emery, Yves; Depeursinge, Christian; Moser, Christophe

2014-06-01

We propose and experimentally demonstrate a digital holographic camera which can be attached to the camera port of a conventional microscope for obtaining digital holograms in a self-reference configuration, under short coherence illumination and in a single shot. A thick holographic grating filters the beam containing the sample information in two dimensions through diffraction. The filtered beam creates the reference arm of the interferometer. The spatial filtering method, based on the high angular selectivity of the thick grating, reduces the alignment sensitivity to angular displacements compared with pinhole based Fourier filtering. The addition of a thin holographic grating alters the coherence plane tilt introduced by the thick grating so as to create high-visibility interference over the entire field of view. The acquired full-field off-axis holograms are processed to retrieve the amplitude and phase information of the sample. The system produces phase images of cheek cells qualitatively similar to phase images extracted with a standard commercial DHM.

Single and two-shot quantitative phase imaging using Hilbert-Huang Transform based fringe pattern analysis

NASA Astrophysics Data System (ADS)

Trusiak, Maciej; Micó, Vicente; Patorski, Krzysztof; García-Monreal, Javier; Sluzewski, Lukasz; Ferreira, Carlos

2016-08-01

In this contribution we propose two Hilbert-Huang Transform based algorithms for fast and accurate single-shot and two-shot quantitative phase imaging applicable in both on-axis and off-axis configurations. In the first scheme a single fringe pattern containing information about biological phase-sample under study is adaptively pre-filtered using empirical mode decomposition based approach. Further it is phase demodulated by the Hilbert Spiral Transform aided by the Principal Component Analysis for the local fringe orientation estimation. Orientation calculation enables closed fringes efficient analysis and can be avoided using arbitrary phase-shifted two-shot Gram-Schmidt Orthonormalization scheme aided by Hilbert-Huang Transform pre-filtering. This two-shot approach is a trade-off between single-frame and temporal phase shifting demodulation. Robustness of the proposed techniques is corroborated using experimental digital holographic microscopy studies of polystyrene micro-beads and red blood cells. Both algorithms compare favorably with the temporal phase shifting scheme which is used as a reference method.

MHD and resonant instabilities in JT-60SA during current ramp-up with off-axis N-NB injection

NASA Astrophysics Data System (ADS)

Bierwage, A.; Toma, M.; Shinohara, K.

2017-12-01

The excitation of magnetohydrodynamic (MHD) and resonant instabilities and their effect on the plasma profiles during the current ramp-up phase of a beam-driven JT-60SA tokamak plasma is studied using the MHD-PIC hybrid code MEGA. In the simple scenario considered, the plasma is only driven by one negative-ion-based neutral beam, depositing 500 keV deuterons at 5 MW power off-axis at about mid-radius. The beam injection starts half-way in the ramp-up phase. Within 1 s, the beam-driven plasma current and fast ion pressure produce a configuration that is strongly unstable to rapidly growing MHD and resonant modes. Using MEGA, modes with low toroidal mode numbers in the range n = 1-4 are examined in detail and shown to cause substantial changes in the plasma profiles. The necessity to develop reduced models and incorporate the effects of such instabilities in integrated codes used to simulate the evolution of entire plasma discharges is discussed.

Optical alignment of the VLTI

NASA Astrophysics Data System (ADS)

Guisard, Stephane

2003-02-01

When completed the VLTI project will be composed by four 8.2 m Unit Telescopes (UT) and four 1.8 m Auxiliay Telescopes (AT) with their respective Coude trains and relay optics, two test siderostats, 6 (up to 8) Delay lines and 8 Beam compressors with their corresponding feeding mirrors. There will be more than 200 optical components, mirrors and lenses, with diameters ranging from 5 mm to 8200 mm. Their surface shapes range from flat to off-axis ellipsoid, including also spherical, on and off-axis hyperbolae and parabolas as well as cylindrical surfaces. Depending on the interferometer configuration, the different possible optical path lengths are of the order of 100 to 300 meters. We describe briefly the principles chosen as well as the types of criteria and method used for the alignment. The method can certainly be applied to other optical systems. The explanations given are understandable to the non-optician, this text is not intended to be an alignment procedure.

Electron Cyclotron Current Drive Efficiency in General Tokamak Geometry and Its Application to Advanced Tokamak Plasmas

NASA Astrophysics Data System (ADS)

Lin-Liu, Y. R.; Chan, V. S.; Luce, T. C.; Prater, R.

1998-11-01

Owing to relativistic mass shift in the cyclotron resonance condition, a simple and accurate interpolation formula for estimating the current drive efficiency, such as those(S.C. Chiu et al.), Nucl. Fusion 29, 2175 (1989).^,(D.A. Ehst and C.F.F. Karney, Nucl. Fusion 31), 1933 (1991). commonly used in FWCD, is not available in the case of ECCD. In this work, we model ECCD using the adjoint techniques. A semi-analytic adjoint function appropriate for general tokamak geometry is obtained using Fisch's relativistic collision model. Predictions of off-axis ECCD qualitatively and semi-quantitatively agrees with those of Cohen,(R.H. Cohen, Phys. Fluids 30), 2442 (1987). currently implemented in the raytracing code TORAY. The dependences of the current drive efficiency on the wave launch configuration and the plasma parameters will be presented. Strong absorption of the wave away from the resonance layer is shown to be an important factor in optimizing the off-axis ECCD for application to advanced tokamak operations.

High-speed volume measurement system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lane, Michael H.; Doyle, Jr., James L.; Brinkman, Michael J.

2018-01-30

Disclosed is a volume sensor having a first axis, a second axis, and a third axis, each axis including a laser source configured to emit a beam; a parallel beam generating assembly configured to receive the beam and split the beam into a first parallel beam and a second parallel beam, a beam-collimating assembly configured to receive the first parallel beam and the second parallel beam and output a first beam sheet and a second beam sheet, the first beam sheet and the second beam sheet being configured to traverse the object aperture; a first collecting lens and a secondmore » collecting lens; and a first photodetector and a second photodetector, the first photodetector and the second photodetector configured to output an electrical signal proportional to the object; wherein the first axis, the second axis, and the third axis are arranged at an angular offset with respect to each other.« less

Off-axis illumination direct-to-digital holography

DOEpatents

Thomas, Clarence E.; Price, Jeffery R.; Voelkl, Edgar; Hanson, Gregory R.

2004-06-08

Systems and methods are described for off-axis illumination direct-to-digital holography. A method of recording an off-axis illuminated spatially heterodyne hologram including spatially heterodyne fringes for Fourier analysis, includes: reflecting a reference beam from a reference mirror at a non-normal angle; reflecting an object beam from an object at an angle with respect to an optical axis defined by a focusing lens; focusing the reference beam and the object beam at a focal plane of a digital recorder to form the off-axis illuminated spatially heterodyne hologram including spatially heterodyne fringes for Fourier analysis; digitally recording the off-axis illuminated spatially heterodyne hologram including spatially heterodyne fringes for Fourier analysis; Fourier analyzing the recorded off-axis illuminated spatially heterodyne hologram including spatially heterodyne fringes by transforming axes of the recorded off-axis illuminated spatially heterodyne hologram including spatially heterodyne fringes in Fourier space to sit on top of a heterodyne carrier frequency defined as an angle between the reference beam and the object beam; applying a digital filter to cut off signals around an original origin; and then performing an inverse Fourier transform.

Analysis of a generalized dual reflector antenna system using physical optics

NASA Technical Reports Server (NTRS)

Acosta, Roberto J.; Lagin, Alan R.

1992-01-01

Reflector antennas are widely used in communication satellite systems because they provide high gain at low cost. Offset-fed single paraboloids and dual reflector offset Cassegrain and Gregorian antennas with multiple focal region feeds provide a simple, blockage-free means of forming multiple, shaped, and isolated beams with low sidelobes. Such antennas are applicable to communications satellite frequency reuse systems and earth stations requiring access to several satellites. While the single offset paraboloid has been the most extensively used configuration for the satellite multiple-beam antenna, the trend toward large apertures requiring minimum scanned beam degradation over the field of view 18 degrees for full earth coverage from geostationary orbit may lead to impractically long focal length and large feed arrays. Dual reflector antennas offer packaging advantages and more degrees of design freedom to improve beam scanning and cross-polarization properties. The Cassegrain and Gregorian antennas are the most commonly used dual reflector antennas. A computer program for calculating the secondary pattern and directivity of a generalized dual reflector antenna system was developed and implemented at LeRC. The theoretical foundation for this program is based on the use of physical optics methodology for describing the induced currents on the sub-reflector and main reflector. The resulting induced currents on the main reflector are integrated to obtain the antenna far-zone electric fields. The computer program is verified with other physical optics programs and with measured antenna patterns. The comparison shows good agreement in far-field sidelobe reproduction and directivity.

Large Binocular Telescope project

NASA Astrophysics Data System (ADS)

Hill, John M.; Salinari, Piero

2000-08-01

The Large Binocular Telescope (LBT) Project is a collaboration between institutions in Arizona, Germany, Italy, and Ohio. The telescope will have two 8.4 meter diameter primary mirrors phased on a common mounting with a 22.8 meter baseline. The second of two borosilicate honeycomb primary mirrors for LBT is being case at the Steward Observatory Mirror Lab this year. The baseline optical configuration of LBT includes adaptive infrared secondaries of a Gregorian design. The F/15 secondaries are undersized to provide a low thermal background focal plane which is unvignetted over a 4 arcminute diameter field-of- view. The interferometric focus combining the light from the two 8.4 meter primaries will reimage the two folded Gregorian focal planes to three central locations. The telescope elevation structure accommodates swing arm spiders which allow rapid interchange of the various secondary and tertiary mirrors as well as prime focus cameras. Maximum stiffness and minimal thermal disturbance were important drivers for the design of the telescope in order to provide the best possible images for interferometric observations. The telescope structure accommodates installation of a vacuum bell jar for aluminizing the primary mirrors in-situ on the telescope. The telescope structure is being fabricated in Italy by Ansaldo Energia S.p.A. in Milan. After pre-erection in the factory, the telescope will be shipped to Arizona in early 2001. The enclosure is being built on Mt. Graham under the auspices of Hart Construction Management Services of Safford, Arizona. The enclosure will be completed by late 2001 and ready for telescope installation.

Off-axis points encoding/decoding with orbital angular momentum spectrum

PubMed Central

Chu, Jiaqi; Chu, Daping; Smithwitck, Quinn

2017-01-01

Encoding/decoding off-axis points with discrete orbital angular momentum (OAM) modes is investigated. On-axis Laguerre-Gaussian (LG) beams are expanded into off-axis OAM spectra, with which off-axis points are encoded. The influence of the mode and the displacement of the LG beam on the spread of the OAM spectrum is analysed. The results show that not only the conventional on-axis point, but also off-axis points, can be encoded and decoded with OAM of light. This is confirmed experimentally. The analytical result here provides a solid foundation to use OAM modes to encode two-dimensional high density information for multiplexing and to analyse the effect of mis-alignment in practical OAM applications. PMID:28272543

Dynamic/Jitter Assessment of Multiple Potential HabEx Structural Designs

NASA Technical Reports Server (NTRS)

Knight, J. Brent; Stahl, H. Philip; Singleton, Andy; Hunt, Ron; Therrell, Melissa; Caldwell, Kate; Garcia, Jay; Baysinger, Mike

2017-01-01

One of the driving structural requirements of the Habitable Exo-Planet (HabEx) telescope is to maintain Line Of Sight (LOS) stability between the Primary Mirror (PM) and Secondary Mirror (SM) of = 5 mas. Dynamic analyses of two configurations of a proposed (HabEx) 4 meter off-axis telescope structure were performed to predict effects of jitter on primary/secondary mirror alignment. The dynamic disturbance used as the forcing function was the James Webb Space Telescope reaction wheel assembly vibration emission specification level. The objective of these analyses was to predict "order-of-magnitude" performance for various structural configurations which will roll into efforts to define the HabEx structural design's global architecture. Two variations of the basic architectural design were analyzed. Relative motion between the PM and the SM for each design configuration are reported.

Dynamic/jitter assessment of multiple potential HabEx structural designs

NASA Astrophysics Data System (ADS)

Knight, J. Brent; Stahl, H. Philip; Singleton, Andy; Hunt, Ron; Therrell, Melissa; Caldwell, Kate; Garcia, Jay; Baysinger, Mike

2017-09-01

One of the driving structural requirements of the Habitable Exo-Planet (HabEx) telescope is to maintain Line Of Sight (LOS) stability between the Primary Mirror (PM) and Secondary Mirror (SM) of <= 5 milli-arc seconds (mas). Dynamic analyses of two configurations of a proposed HabEx 4 meter off-axis telescope structure were performed to predict effects of a vibration input on primary/secondary mirror alignment. The dynamic disturbance used as the forcing function was the James Webb Space Telescope reaction wheel assembly vibration emission specification level. The objective of these analyses was to predict "order-of-magnitude" performance for various structural configurations which contribute to efforts in defining the HabEx structural design's global architecture. Two variations of the basic architectural design were analyzed. Relative motion between the PM and the SM for each design configuration are reported.

Prospects for Off-axis Current Drive via High Field Side Lower Hybrid Current Drive in DIII-D

NASA Astrophysics Data System (ADS)

Wukitch, S. J.; Shiraiwa, S.; Wallace, G. M.; Bonoli, P. T.; Holcomb, C.; Park, J. M.; Pinsker, R. I.

2017-10-01

An outstanding challenge for an economical, steady state tokamak is efficient off-axis current drive scalable to reactors. Previous studies have focused on high field side (HFS) launch of lower hybrid waves for current drive (LHCD) in double null configurations in reactor grade plasmas. The goal of this work is to find a HFS LHCD scenario for DIII-D that balances coupling, power penetration and damping. The higher magnetic field on the HFS improves wave accessibility, which allows for lower n||waves to be launched. These waves penetrate farther into the plasma core before damping at higher Te yielding a higher current drive efficiency. Utilizing advanced ray tracing and Fokker Planck simulation tools (GENRAY+CQL3D), wave penetration, absorption and drive current profiles in high performance DIII-D H-Mode plasmas were investigated. We found LH scenarios with single pass absorption, excellent wave penetration to r/a 0.6-0.8, FWHM r/a=0.2 and driven current up to 0.37 MA/MW coupled. These simulations indicate that HFS LHCD has potential to achieve efficient off-axis current drive in DIII-D and the latest results will be presented. Work supported by U.S. Dept. of Energy, Office of Science, Office of Fusion Energy Sciences, using User Facility DIII-D, under Award No. DE-FC02-04ER54698 and Contract No. DE-FC02-01ER54648 under Scientific Discovery through Advanced Computing Initiative.

Planning the 8-meter Chinese Giant Solar Telescope

NASA Astrophysics Data System (ADS)

Beckers, Jacques M.; Liu, Z.; Deng, Y.; Ji, H.

2013-07-01

The Chinese Giant Solar Telescope (CGST) will be a diffraction limited solar telescope optimized for the near-infrared (NIR) spectral region (0.8 - 2.5 microns). Its diffraction limit will be reached by the incorporation of Multi-Conjugate Adaptive Optics (MCAO) enhanced by image restoration techniques to achieve uniform (u.v) plane coverage over the angular spatial frequency region allowed by its 8-meter aperture. Thus it will complement the imaging capabilities of 4-meter telescopes being planned elsewhere which are optimized for the visible (VIS) spectral region (300 - 1000 nm) In the NIR spectral regions the CGST will have access to unique spectral features which will improve the diagnostics of the solar atmosphere. These include the CaII lines near 860 nm , the HeI lines near 1083 nm, the 1074 nm FeXIII coronal lines, the large Zeeman-split FeI line at 1548 nm, and (v) the H- continuum absorption minimum at 1.6 micron. Especially in sunspot umbrae the simultaneous observation of continua and lines across the NIR spectral range will cover a substantial depth range in the solar atmosphere. Of course the mid- and far- infrared regions are also available for unequalled high-angular resolution solar observations, for example, in the Hydrogen Bracket lines, CO molecular bands, and the MgI emission line at 12.3 microns. The CGST is a so-called ring telescope in which the light is captured by a 1 meter wide segmented ring or by a ring of 7 smaller off-axis aperture telescopes. The open central area of the telescope is large. The advantages of such a ring configuration is that (a) it covers all the spatial frequencies out to those corresponding to its outer diameter, (b) its circular symmetry makes it polarization neutral, (c) its large central hole helps thermal control, and (d) it provides ample space for the MCAO system and instrumentation in the Gregorian focus. Even though optimized for the NIR, we expect to use the CGST also at visible wavelengths in the so-called “Partial Adaptive Optics” (PAO) mode (Applied Optics 31,424,1992) to obtain angular resolution twice that of a 4-meter telescope if their observations indicate that higher resolution is desirable. The CGST is a Chinese solar community project.

A first-order treatment of aberrations in Cassegrainian and Gregorian antennas

NASA Astrophysics Data System (ADS)

Dragone, C.

1982-05-01

The decrease in aperture efficiency caused by small aberrations in a reflector antenna is determined. The important case of a Cassegrainian (or Gregorian) antenna with a feed placed in the vicinity of the focal point is treated in detail. For this case the various aberration components due to astigmatism, coma, etc., are derived explicitly, their effect on aperture efficiency is shown, and the conditions that optimize performance are given. The results are useful for the design of multibeam antennas in ground stations and satellites.

Internal energy flows in composite optical vortices

NASA Astrophysics Data System (ADS)

Ferrer-Garcia, Manuel F.; Lopez-Mago, Dorilian; Hernandez-Aranda, Raul I.

2016-09-01

We study the energy ow pattern in the superposition of two off-axis optical vortices with orthogonal polarization states. This system presents a rich structure of polarization singularities, which allows us to study the transverse spin and orbital angular momentum of different polarization morphologies, which includes C points (stars, lemons and monstars) and L lines. We perform numerical simulations of the optical forces acting on submicron particles and show interesting configurations. We provide the set of control parameters to unambiguously distinguish between the spin and orbital ow contributions.

High-precision processing and detection of the high-caliber off-axis aspheric mirror

NASA Astrophysics Data System (ADS)

Dai, Chen; Li, Ang; Xu, Lingdi; Zhang, Yingjie

2017-10-01

To achieve the efficient, controllable, digital processing and high-precision detection of the high-caliber off-axis aspheric mirror, meeting the high-level development needs of the modern high-resolution, large field of space optical remote sensing camera, we carried out the research on high precision machining and testing technology of off-axis aspheric mirror. First, we forming the off-axis aspheric sample with diameter of 574mm × 302mm by milling it with milling machine, and then the intelligent robot equipment was used for off-axis aspheric high precision polishing. Surface detection of the sample will be proceed with the off-axis aspheric contact contour detection technology and offaxis non-spherical surface interference detection technology after its fine polishing using ion beam equipment. The final surface accuracy RMS is 12nm.

On safe configurations of a natural-artificial space tether system

NASA Astrophysics Data System (ADS)

Rodnikov, A. V.

2018-05-01

We study the dynamics of a particle moving under gravitation of precessing dynamically symmetric rigid body if the particle motion is restricted by two unilateral (flexible) constraints realized by two weightless unstretchable tethers with ends fixed at body poles, formed as the intersection of the body surface with the axis of its dynamical symmetry. The system under consideration is a simple model of an original natural-artificial space construction consisting of an asteroid and a space station tethered to each other via two cables. We note that the problem is integrable for the system safe configurations, i.e. for motions along the constraints common boundary (both tethers are tensed) if the body gravitational potential is invariant with respect to rotation about the axis of dynamical symmetry. We study these motions depicting phase portraits for possible values of system parameters. We also deduce conditions for the particle coming off the boundary of constraint(s) (if the tether(s) are slackened) and analyze these conditions, eliminating corresponding areas from phase portraits. We also formulate some statements, concerning the particle safety.

A very wide band telescope for Planck using optical and radio frequency techniques

NASA Astrophysics Data System (ADS)

Fargant, Guy; Dubruel, Denis; Cornut, Myriam; Riti, Jean-Bernard; Passvogel, Thomas; de Maagt, Peter; Anderegg, Michel; Tauber, Jan

2017-11-01

Planck associated to FIRST is one of the ESA scientific missions belonging to the Horizon 2000 programme. It will be launched by an Ariane 5 in 2007. Planck aims at obtaining very accurate images of the Cosmic Microwave Background fluctuations, thanks to a spaceborne telescope featuring a wide wavelength range and an excellent control of straylight and thermal variations. The telescope is based on an off-axis gregorian design consisting of two concave ellipsoidal mirrors with a 1.5-meter pupil, derived from radio frequency antenna, but with a very wide spectral domain which ranges from far infrared (350 μm) up to millimetric wavelengths (10 mm). Its field of view is large (10 degrees) owing to a high number of detectors in the focal plane. The short wavelength detectors (bolometers operating at 0.1 K) are located at the centre of the focal plane unit while the long wavelength ones (based on HEMT amplifier technology operating at 20 K) are located at the periphery. The Planck telescope operates at a temperature below 60 K. This level is achieved in a passive way, i.e. using a cryogenic radiator. Furthermore, this radiator must accommodate a set of coolers dedicated to the focal plane unit, cooling one of the experiments down to 0.1 K. The Planck mission leads to very stringent requirements (straylight, thermal stability) that can only be achieved by designing the spacecraft at system level, combining optical, radio frequency and thermal techniques in order to achieve the required performance.

Experimental evaluation of expendable supersonic nozzle concepts

NASA Technical Reports Server (NTRS)

Baker, V.; Kwon, O.; Vittal, B.; Berrier, B.; Re, R.

1990-01-01

Exhaust nozzles for expendable supersonic turbojet engine missile propulsion systems are required to be simple, short and compact, in addition to having good broad-range thrust-minus-drag performance. A series of convergent-divergent nozzle scale model configurations were designed and wind tunnel tested for a wide range of free stream Mach numbers and nozzle pressure ratios. The models included fixed geometry and simple variable exit area concepts. The experimental and analytical results show that the fixed geometry configurations tested have inferior off-design thrust-minus-drag performance in the transonic Mach range. A simple variable exit area configuration called the Axi-Quad nozzle, combining features of both axisymmetric and two-dimensional convergent-divergent nozzles, performed well over a broad range of operating conditions. Analytical predictions of the flow pattern as well as overall performance of the nozzles, using a fully viscous, compressible CFD code, compared very well with the test data.

Off-axis astigmatism in the isolated chicken crystalline lens.

PubMed

Maier, Felix; Wahl, Siegfried; Schaeffel, Frank

2016-12-01

The chicken eye was previously found to have little off-axis astigmatism which is not explained by its special corneal shape but rather by the optical properties of the crystalline lens. To learn more about lens design, we studied off-axis astigmatism in the chicken lens in situ and compared it to a glass lens of similar power but with homogenous refractive index. After euthanasia, enucleated eye balls were cut in the equatorial plane right behind the scleral ossicles. The anterior segment was placed in a water-filled chamber. Several thin laser beams were projected in two perpendicular meridians through the lens under various eccentricities and the focal lengths were determined. Off-axis astigmatism across the horizontal visual field was determined as the differences in power in the two meridians. The same procedure was used for the glass lens. On-axis, the chicken crystalline lens had slightly more power in the vertical than in the horizontal meridian (-2.8±0.7D (SEM)). Astigmatism flipped sign and increased with eccentricity to reach +6.1±2.1D (SEM) at 33.5deg off-axis, as expected from off-axis astigmatism. Even though this value appears high, it was still 2.5 times lower than in the glass lens. A ZEMAX model of a lens with a homogeneous index and with surface profiles taken of the natural chicken lens revealed even higher levels of off-axis astigmatism. Obviously, the natural chicken lens displays much less off-axis astigmatism than a glass lens with similar power. Since its shape does not explain the low off-axis astigmatism, it must be due to a refined internal refractive index structure. Copyright © 2016 Elsevier Ltd. All rights reserved.

Imaging phased telescope array study

NASA Technical Reports Server (NTRS)

Harvey, James E.

1989-01-01

The problems encountered in obtaining a wide field-of-view with large, space-based direct imaging phased telescope arrays were considered. After defining some of the critical systems issues, previous relevant work in the literature was reviewed and summarized. An extensive list was made of potential error sources and the error sources were categorized in the form of an error budget tree including optical design errors, optical fabrication errors, assembly and alignment errors, and environmental errors. After choosing a top level image quality requirment as a goal, a preliminary tops-down error budget allocation was performed; then, based upon engineering experience, detailed analysis, or data from the literature, a bottoms-up error budget reallocation was performed in an attempt to achieve an equitable distribution of difficulty in satisfying the various allocations. This exercise provided a realistic allocation for residual off-axis optical design errors in the presence of state-of-the-art optical fabrication and alignment errors. Three different computational techniques were developed for computing the image degradation of phased telescope arrays due to aberrations of the individual telescopes. Parametric studies and sensitivity analyses were then performed for a variety of subaperture configurations and telescope design parameters in an attempt to determine how the off-axis performance of a phased telescope array varies as the telescopes are scaled up in size. The Air Force Weapons Laboratory (AFWL) multipurpose telescope testbed (MMTT) configuration was analyzed in detail with regard to image degradation due to field curvature and distortion of the individual telescopes as they are scaled up in size.

A compact and lightweight off-axis lightguide prism in near to eye display

NASA Astrophysics Data System (ADS)

Zhuang, Zhenfeng; Cheng, Qijia; Surman, Phil; Zheng, Yuanjin; Sun, Xiao Wei

2017-06-01

We propose a method to improve the design of an off-axis lightguide configuration for near to eye displays (NED) using freeform optics technology. The advantage of this modified optical system, which includes an organic light-emitting diode (OLED), a doublet lens, an imaging lightguide prism and a compensation prism, is that it increases optical length path, offers a smaller size, as well as avoids the obstructed views, and matches the user's head shape. In this system, the light emitted from the OLED passes through the doublet lens and is refracted/reflected by the imaging lightguide prism, which is used to magnify the image from the microdisplay, while the compensation prism is utilized to correct the light ray shift so that a low-distortion image can be observed in a real-world setting. A NED with a 4 mm diameter exit pupil, 21.5° diagonal full field of view (FoV), 23 mm eye relief, and a size of 33 mm by 9.3 mm by 16 mm is designed. The developed system is compact, lightweight and suitable for entertainment and education application.

Electromagnetic scattering by a uniaxial anisotropic sphere located in an off-axis Bessel beam.

PubMed

Qu, Tan; Wu, Zhen-Sen; Shang, Qing-Chao; Li, Zheng-Jun; Bai, Lu

2013-08-01

Electromagnetic scattering of a zero-order Bessel beam by an anisotropic spherical particle in the off-axis configuration is investigated. Based on the spherical vector wave functions, the expansion expression of the zero-order Bessel beam is derived, and its convergence is numerically discussed in detail. Utilizing the tangential continuity of the electromagnetic fields, the expressions of scattering coefficients are given. The effects of the conical angle of the wave vector components of the zero-order Bessel beam, the ratio of the radius of the sphere to the central spot radius of the zero-order Bessel beam, the shift of the beam waist center position along both the x and y axes, the permittivity and permeability tensor elements, and the loss of the sphere on the radar cross section (RCS) are numerically analyzed. It is revealed that the maximum RCS appears in the conical direction or neighboring direction when the sphere is illuminated by a zero-order Bessel beam. Furthermore, the RCS will decrease and the symmetry is broken with the shift of the beam waist center.

Analysis of nodal aberration properties in off-axis freeform system design.

PubMed

Shi, Haodong; Jiang, Huilin; Zhang, Xin; Wang, Chao; Liu, Tao

2016-08-20

Freeform surfaces have the advantage of balancing off-axis aberration. In this paper, based on the framework of nodal aberration theory (NAT) applied to the coaxial system, the third-order astigmatism and coma wave aberration expressions of an off-axis system with Zernike polynomial surfaces are derived. The relationship between the off-axis and surface shape acting on the nodal distributions is revealed. The nodal aberration properties of the off-axis freeform system are analyzed and validated by using full-field displays (FFDs). It has been demonstrated that adding Zernike terms, up to nine, to the off-axis system modifies the nodal locations, but the field dependence of the third-order aberration does not change. On this basis, an off-axis two-mirror freeform system with 500 mm effective focal length (EFL) and 300 mm entrance pupil diameter (EPD) working in long-wave infrared is designed. The field constant aberrations induced by surface tilting are corrected by selecting specific Zernike terms. The design results show that the nodes of third-order astigmatism and coma move back into the field of view (FOV). The modulation transfer function (MTF) curves are above 0.4 at 20 line pairs per millimeter (lp/mm) which meets the infrared reconnaissance requirement. This work provides essential insight and guidance for aberration correction in off-axis freeform system design.

Off-axis reflective optical apparatus

NASA Technical Reports Server (NTRS)

Ames, Lawrence L. (Inventor); Leary, David F. (Inventor); Mammini, Paul V. (Inventor)

2005-01-01

Embodiments of the present invention are directed to a simple apparatus and a convenient and accurate method of mounting the components to form an off-axis reflective optical apparatus such as a collimator. In one embodiment, an off-axis reflective optical apparatus comprises a mounting block having a ferrule holder support surface and an off-axis reflector support surface which is generally perpendicular to the ferrule holder support surface. An optical reflector is mounted on the off-axis reflector support surface and has a reflected beam centerline. The optical reflector has a conic reflective surface and a conic center. A ferrule holder is mounted on the ferrule holder support surface. The ferrule holder provides a ferrule for coupling to an optical fiber and orienting a fiber tip of the optical fiber along a fiber axis toward the optical reflector. The fiber axis is nonparallel to the reflected beam centerline. Prior to mounting the optical reflector to the off-axis reflector support surface and prior to mounting the ferrule holder to the ferrule holder support surface, the optical reflector is movable on the off-axis reflector surface and the ferrule holder is movable on the ferrule holder support surface to align the conic center of the optical reflector with respect to the fiber tip of the optical fiber, and the apparatus has at least one of the following features: (1) the optical reflector is movable on the off-axis reflector support surface to adjust a focus of the fiber tip with respect to the optical reflector, and (2) the ferrule holder is movable on the ferrule holder support surface to adjust the focus of the fiber tip with respect to the optical reflector.

Study on off-axis detection of pulsed laser in atmosphere

NASA Astrophysics Data System (ADS)

Liang, Weiwei

2018-02-01

Laser communication, designation, and ranging are point to point and have a high degree of specificity, current laser detection, such as laser warning receiver system, could detect the scattering laser from the off-axis distance by scattering track on natural aerosols, which is helpful to locate the laser source. However, the intensity of the scattering laser is extremely weak and affected by many factors, in order to evaluate the detection characteristic, a simplified model of off-axis detection for scattering laser in the lower atmosphere based on the Mie scattering theory is presented in this paper, the performances of the off-axis laser detection in different conditions such as off-axis distance, visibility, incidence angle, and delay time are investigated.

Re-evaluating across-axis geochemical variations at the East Pacific Rise and Juan de Fuca Ridge: on- and off-axis melt delivery

NASA Astrophysics Data System (ADS)

Perfit, M. R.; Walters, R. L.

2014-12-01

High spatial density geochemical data sets from the N-EPR and S-JdFR are used to re-evaluate the across-axis geochemical variations in major and trace elements at mid-ocean ridges (MORs). At two axial melt lens (AML) segments, north and south, at the 9-10°N EPR, N-MORB MgO varies across-axis from the most primitive above the AML to more evolved away from the axis. This trend is distinct at the northern (magmatically more robust) segment with an axial MgO range of 8-9 wt% and off-axis (>2km) range of 6.5-8 wt%. This decrease is also reflected in E-MORB MgO variation. There is more variability at the southern segment but, off-axis progression to more evolved MgO is still evident. Interestingly, the Cleft segment, JdFR, displays similar geochemical behavior to the EPR with an axial MgO range of 7-8.5 wt% and off-axis (>2km) range of 6-7.5 wt%. EPR geochemical studies over the past 30 years have described models of upper crustal accumulation ranging from eruptions limited to the axis, to temporal variation in the composition of magma in the AML, to multiple eruption sites across the ridge crest and flanks (<5km). Eruptions limited to the axis, with topographically controlled flow off-axis, cannot reproduce the observed off-axis change to more evolved N-MORB. Time-dependence could explain one instance of evolved lavas off-axis but, similar geochemical behavior is observed at two separate AML segments. Multiple instances of consistent compositional variability at multiple AML segments, and at different ridges, point to a common process of crustal accretion at MORs. In light of recent geophysical discoveries of Off-axis AMLs (OAMLs) at the EPR and JdFR, we propose that the trend of more evolved lavas for the majority of N-MORB lavas with distance from the axis is controlled by thermal distribution in the underlying crystal mush zone (CMZ). Higher magma flux beneath the axis facilitates higher temperatures and high porosity melt pathways, reducing crustal residence times, and erupting more primitive lava compositions. OAMLs at the edges of the CMZ, where it is cooler, feed more evolved off-axis eruptions. Lower magma flux at the edges increases crustal residence time and the extent to which magmas crystallize. OAMLs outside of the CMZ host magmas that may escaped any central mixing and erupt a greater range of compositions.

Generation of Multiple Vortex Beams with Specified Vortex Number from Lasers with Controlled Ince-Gaussian Modes

NASA Astrophysics Data System (ADS)

Chu, Shu-Chun

2008-07-01

This study proposes a systematic method of selecting excitations of part of Ince-Gaussian modes (IGMs) and a three-lens configuration for generating multiple vortex beams with forced IGMs in the model of laser-diode (LD)-pumped solid-state lasers. Simply changing the lateral off-axis position of the tight pump beam focus on the laser crystal can produce the desired multiple optical vortex beam from the laser in a well-controlled manner using a proposed astigmatic mode converter assembled into one body with the laser cavity.

The effect of ball impact location on racket and forearm joint angle changes for one-handed tennis backhand groundstrokes.

PubMed

King, Mark; Hau, Agnes; Blenkinsop, Glen

2017-07-01

Recreational tennis players tend to have higher incidence of tennis elbow, and this has been hypothesised to be related to one-handed backhand technique and off-centre ball impacts on the racket face. This study aimed to investigate for a range of participants the effect of off-longitudinal axis and off-lateral axis ball-racket impact locations on racket and forearm joint angle changes immediately following impact in one-handed tennis backhand groundstrokes. Three-dimensional racket and wrist angular kinematic data were recorded for 14 university tennis players each performing 30 "flat" one-handed backhand groundstrokes. Off-longitudinal axis ball-racket impact locations explained over 70% of the variation in racket rotation about the longitudinal axis and wrist flexion/extension angles during the 30 ms immediately following impact. Off-lateral axis ball-racket impact locations had a less clear cut influence on racket and forearm rotations. Specifically off-longitudinal impacts below the longitudinal axis forced the wrist into flexion for all participants with there being between 11° and 32° of forced wrist flexion for an off-longitudinal axis impact that was 1 ball diameter away from the midline. This study has confirmed that off-longitudinal impacts below the longitudinal axis contribute to forced wrist flexion and eccentric stretch of the wrist extensors and there can be large differences in the amount of forced wrist flexion from individual to individual and between strokes with different impact locations.

Opto-mechanical architecture of the LISA instrument

NASA Astrophysics Data System (ADS)

Weise, Dennis; Marenaci, Pierangelo; Weimer, Peter; Berger, Marcel; Schulte, Hans R.; Gath, Peter; Johann, Ulrich

2017-11-01

We report on the latest iteration of the baseline opto-mechanical architecture of the LISA instru- ment, which has been developed within the current LISA Mission Formulation study under ESA con- tract. The collective features of the current architec- ture have been consolidated in an extensive trade of various alternative payload configurations, including variants with only one active proof mass per space- craft and the application of "In-Field Pointing" for accommodation of constellation breathing. With respect to the original configuration [1], the newly established architecture most notably distin- guishes itself by the use of an off-axis telescope and a "non-frequency-swap" science interferometer for stray light mitigation, as well as the implementa- tion of ancillary pathlength metrology in terms of an "Optical Truss" and Point Ahead Angle sensing.

Field investigation of a wake structure downwind of a VANT (Vertical-Axis Wind Turbine) in a wind farm array

NASA Astrophysics Data System (ADS)

Liu, H. T.; Buck, J. W.; Germain, A. C.; Hinchee, M. E.; Solt, T. S.; Leroy, G. M.; Srnsky, R. A.

1988-09-01

The effects of upwind turbine wakes on the performance of a FloWind 17-m vertical-axis wind turbine (VAWT) were investigated through a series of field experiments conducted at the FloWind wind farm on Cameron Ridge, Tehachapi, California. From the field measurements, we derived the velocity and power/energy deficits under various turbine on/off configurations. Much information was provided to characterize the structure of VAWT wakes and to assess their effects on the performance of downwind turbines. A method to estimate the energy deficit was developed based on the measured power deficit and the wind speed distributions. This method may be adopted for other turbine types and sites. Recommendations are made for optimizing wind farm design and operations, as well as for wind energy management.

Acquisition and replay systems for direct-to-digital holography and holovision

DOEpatents

Thomas, Clarence E.; Hanson, Gregory R.

2003-02-25

Improvements to the acquisition and replay systems for direct-to-digital holography and holovision are described. A method of recording an off-axis hologram includes: splitting a laser beam into an object beam and a reference beam; reflecting the reference beam from a reference beam mirror; reflecting the object beam from an illumination beamsplitter; passing the object beam through an objective lens; reflecting the object beam from an object; focusing the reference beam and the object beam at a focal plane of a digital recorder to form an off-axis hologram; digitally recording the off-axis hologram; and transforming the off-axis hologram in accordance with a Fourier transform to obtain a set of results. A method of writing an off-axis hologram includes: passing a laser beam through a spatial light modulator; and focusing the laser beam at a focal plane of a photorefractive crystal to impose a holographic diffraction grating pattern on the photorefractive crystal. A method of replaying an off-axis hologram includes: illuminating a photorefractive crystal having a holographic diffraction grating with a replay beam.

Tower wake/blade interaction noise of a wind turbine

NASA Astrophysics Data System (ADS)

Nishiwaki, Hideo; Takeda, Katsumi

1987-10-01

A scale model of a 1.5m dia. two-bladed windturbine was used in an anechoic chamber that provided a free-stream velocity of 8m/s. The blades used were a 1.5/8 scale model of a test machine for a local energy utilization project promoted by the Science and Technology Agency. The height of the tower from the ground level was 1.8m. The acoustic measurements were made in a circle of 1.6m downstream from the machine at the height of the windmill centerline. The noise level of the on-axis spectra was about 15dB larger than that of the off-axis. This is a result of the dipole nature of the acoustic impulse. The Wortmann airfoil (FX 77-W series) was employed for the blade profiles and the Reynolds number was 10(5), based on the tip chord length. The experiment revealed that the sound intensity at each harmonic was not proportional to the axial and radial extents of the wake. The elliptic slender configuration was the quietest, while the square configuration was the loudest. From a practical point of view, it is suggested that the circular section is most suitable for the tower leg.

Wide acceptance angle, high concentration ratio, optical collector

NASA Technical Reports Server (NTRS)

Kruer, Mark A. (Inventor)

1991-01-01

A cassegrain optical system provides improved collection of off-axis light yet is still characterized by a high concentration ratio. The optical system includes a primary mirror for collecting incoming light and reflecting the light to a secondary mirror which, in turn, reflects the light to a solar cell or other radiation collection device. The primary mirror reflects incoming on-axis light onto an annular section of the secondary mirror and results in the reflection of a substantial amount of incoming off-axis light onto the remainder of the secondary mirror. Thus light which would otherwise be lost to the system will be captured by the collector. Furthermore, the off-axis sections of the secondary mirror may be of a different geometrical shape than the on-axis annular section so as to optimize the amount of off-axis light collected.

Effects of off-axis loading on the tensile behavior of a ceramic-matrix composite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lynch, C.S.; Evans, A.G.

A 0{degree}/90{degree} ceramic-matrix composite (CMC) comprised of Nicalon fibers in magnesium aluminosilicate (MAS) has been loaded in tension in three orientations relative to the fiber direction: 0, 30, and 45{degree}. The off-axis loaded samples exhibit inelastic deformation at appreciably lower stresses than samples loads at 0{degree}. Matrix cracking governs the inelastic strains in all orientations. But, important differences in the morphologies and sequencing of the cracks account for the differences in the stress levels. Off-axis failure also occurs at substantially lower stresses than on-axis failure. On-axis composite failure is governed by fiber fracture, but off-axis failure involves matrix-crack coalescence. Tomore » facilitate interpretation and modeling of these behaviors, the interface friction and debond stresses have been determined from hysteresis measurements.« less

Analysis on influence of installation error of off-axis three-mirror optical system on imaging line-of-sight

NASA Astrophysics Data System (ADS)

Gao, Lingyu; Li, Xinghua; Guo, Qianrui; Quan, Jing; Hu, Zhengyue; Su, Zhikun; Zhang, Dong; Liu, Peilu; Li, Haopeng

2018-01-01

The internal structure of off-axis three-mirror system is commonly complex. The mirror installation error in assembly always affects the imaging line-of-sight and further degrades the image quality. Due to the complexity of the optical path in off-axis three-mirror optical system, the straightforward theoretical analysis on the variations of imaging line-of-sight is extremely difficult. In order to simplify the theoretical analysis, an equivalent single-mirror system is proposed and presented in this paper. In addition, the mathematical model of single-mirror system is established and the accurate expressions of imaging coordinate are derived. Utilizing the simulation software ZEMAX, off-axis three-mirror model and single-mirror model are both established. By adjusting the position of mirror and simulating the line-of-sight rotation of optical system, the variations of imaging coordinates are clearly observed. The final simulation results include: in off-axis three-mirror system, the varying sensitivity of the imaging coordinate to the rotation of line-of-sight is approximately 30 um/″; in single-mirror system, the varying sensitivity of the imaging coordinate to the rotation of line-of-sight is 31.5 um/″. Compared to the simulation results of the off-axis three-mirror model, the 5% relative error of single-mirror model analysis highly satisfies the requirement of equivalent analysis and also verifies its validity. This paper presents a new method to analyze the installation error of the mirror in the off-axis three-mirror system influencing on the imaging line-of-sight. Moreover, the off-axis three-mirror model is totally equivalent to the single-mirror model in theoretical analysis.

Assembly and alignment method for optimized spatial resolution of off-axis three-mirror fore optics of hyperspectral imager.

PubMed

Kim, Youngsoo; Hong, Jinsuk; Choi, Byungin; Lee, Jong-Ung; Kim, Yeonsoo; Kim, Hyunsook

2017-08-21

A fore optics for the hyperspectral spectrometer is designed, manufactured, assembled, and aligned. The optics has a telecentric off-axis three-mirror configuration with a field of view wider than 14 degrees and an f-number as small as 2.3. The primary mirror (M1) and the secondary mirror (M2) are axially symmetric aspheric surfaces to minimize the sensitivity. The tertiary mirror (M3) is a decentered aspheric surface to minimize the coma and astigmatism aberration. The M2 also has a hole for the slit to maintain the optical performance while maximizing the telecentricity. To ensure the spatial resolution performance of the optical system, an alignment procedure is established to assemble and align the entrance slit of the spectrometer to the rear end of the fore optics. It has a great advantage to confirm and maintain the alignment integrity of the fore optics module throughout the alignment procedure. To perform the alignment procedure successfully, the precision movement control requirements are calculated and applied. As a result, the alignment goal of the RMS wave front error (WFE) to be smaller than 90 nm at all fields is achieved.

Measurement of the cosmic microwave background using BEAST for the determination of cosmological parameters

NASA Astrophysics Data System (ADS)

Childers, Jeffery Dale

The Background Emission Anisotropy Scanning Telescope (BEAST) is a millimeter wavelength experiment designed to generate maps of fluctuations in the cosmic microwave background (CMB). The telescope is composed of an off-axis Gregorian optical system with a 2.2 meter primary that focuses the collected microwave radiation onto an array of cryogenically cooled high electron mobility transistor (HEMT) receivers. This array is composed of six corrugated scalar feed horns in the Q band (38 to 45 GHz) and two more in the Ka band (26 to 36 GHz) with one of the six Q-band horns connected to an ortho-mode transducer for extraction of both polarizations incident on the single feed. The system has a minimum beam size of 20' with an average sensitivity of 900 m K [Special characters omitted.] per receiver. A map of the CMB centered on the north celestial pole has been generated from the BEAST telescope in a 9 ° wide annulus at declination 37° with a typical pixel error of 57 ± 5 m K when smoothed to 30' resolution. Cosmological parameter estimation of the power spectrum resulting from the map provides a measure of O k == 1- O total = -0.0= 74 ± .070, which is consistent with a flat universe. This paper describes the design and performance of the BEAST instrument and provides the details of subsystems developed and used toward the goal of generating a map of CMB fluctuations on 20' scales with sensitivity in l space between l ~100 and l ~500. A summary of the map and results generated by an observing campaign at the University of California White Mountain Research Station are also included.

VizieR Online Data Catalog: 44 SZ-selected galaxy clusters ACT observations (Sifon+, 2016)

NASA Astrophysics Data System (ADS)

Sifon, C.; Battaglia, N.; Hasselfield, M.; Menanteau, F.; Barrientos, L. F.; Bond, J. R.; Crichton, D.; Devlin, M. J.; Dunner, R.; Hilton, M.; Hincks, A. D.; Hlozek, R.; Huffenberger, K. M.; Hughes, J. P.; Infante, L.; Kosowsky, A.; Marsden, D.; Marriage, T. A.; Moodley, K.; Niemack, M. D.; Page, L. A.; Spergel, D. N.; Staggs, S. T.; Trac, H.; Wollack, E. J.

2017-11-01

ACT is a 6-metre off-axis Gregorian telescope located at an altitude of 5200um in the Atacama desert in Chile, designed to observe the CMB at arcminute resolution. Galaxy clusters were detected in the 148GHz band by matched-filtering the maps with the pressure profile suggested by Arnaud et al. (2010A&A...517A..92A), fit to X-ray selected local (z<0.2) clusters, with varying cluster sizes,θ500, from 1.18 to 27-arcmin. Because of the complete overlap of ACT equatorial observations with Sloan Digital Sky Survey Data Release 8 (SDSS DR8; Aihara et al., 2011ApJS..193...29A) imaging, all cluster candidates were assessed with optical data (Menanteau et al., 2013ApJ...765...67M). We observed 20 clusters from the equatorial sample with the Gemini Multi-Object Spectrograph (GMOS) on the Gemini-South telescope, split in semesters 2011B (ObsID:GS-2011B-C-1, PI:Barrientos/Menanteau) and 2012A (ObsID:GS-2012A-C-1, PI:Menanteau), prioritizing clusters in the cosmological sample at 0.3

Intermittent bursts induced by double tearing mode reconnection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wei, Lai; Wang, Zheng-Xiong, E-mail: zxwang@dlut.edu.cn

Reversed magnetic shear (RMS) configuration is assumed to be the steady-state operation scenario for the future advanced tokamaks like International Thermonuclear Experimental Reactor. In this work, we numerically discover a phenomenon of violent intermittent bursts induced by self-organized double tearing mode (DTM) reconnection in the RMS configuration during the very long evolution, which may continuously lead to annular sawtooth crashes and thus badly impact the desired steady-state operation of the future advanced RMS tokamaks. The key process of the intermittent bursts in the off-axis region is similar to that of the typical sawtooth relaxation oscillation in the positive magnetic shearmore » configuration. It is interestingly found that in the decay phase of the DTM reconnection, the zonal field significantly counteracts equilibrium field to make the magnetic shear between the two rational surfaces so weak that the residual self-generated vortices of the previous DTM burst are able to trigger a reverse DTM reconnection by curling the field lines.« less

Intermittent bursts induced by double tearing mode reconnection

NASA Astrophysics Data System (ADS)

Wei, Lai; Wang, Zheng-Xiong

2014-06-01

Reversed magnetic shear (RMS) configuration is assumed to be the steady-state operation scenario for the future advanced tokamaks like International Thermonuclear Experimental Reactor. In this work, we numerically discover a phenomenon of violent intermittent bursts induced by self-organized double tearing mode (DTM) reconnection in the RMS configuration during the very long evolution, which may continuously lead to annular sawtooth crashes and thus badly impact the desired steady-state operation of the future advanced RMS tokamaks. The key process of the intermittent bursts in the off-axis region is similar to that of the typical sawtooth relaxation oscillation in the positive magnetic shear configuration. It is interestingly found that in the decay phase of the DTM reconnection, the zonal field significantly counteracts equilibrium field to make the magnetic shear between the two rational surfaces so weak that the residual self-generated vortices of the previous DTM burst are able to trigger a reverse DTM reconnection by curling the field lines.

A polar-region-adaptable systematic bias collaborative measurement method for shipboard redundant rotational inertial navigation systems

NASA Astrophysics Data System (ADS)

Wang, Lin; Wu, Wenqi; Wei, Guo; Lian, Junxiang; Yu, Ruihang

2018-05-01

The shipboard redundant rotational inertial navigation system (RINS) configuration, including a dual-axis RINS and a single-axis RINS, can satisfy the demand of marine INSs of especially high reliability as well as achieving trade-off between position accuracy and cost. Generally, the dual-axis RINS is the master INS, and the single-axis RINS is the hot backup INS for high reliability purposes. An integrity monitoring system performs a fault detection function to ensure sailing safety. However, improving the accuracy of the backup INS in case of master INS failure has not been given enough attention. Without the aid of any external information, a systematic bias collaborative measurement method based on an augmented Kalman filter is proposed for the redundant RINSs. Estimates of inertial sensor biases can be used by the built-in integrity monitoring system to monitor the RINS running condition. On the other hand, a position error prediction model is designed for the single-axis RINS to estimate the systematic error caused by its azimuth gyro bias. After position error compensation, the position information provided by the single-axis RINS still remains highly accurate, even if the integrity monitoring system detects a dual-axis RINS fault. Moreover, use of a grid frame as a navigation frame makes the proposed method applicable in any area, including the polar regions. Semi-physical simulation and experiments including sea trials verify the validity of the method.

Structural Performance of a Hybrid FRP-Aluminum Modular Triangular Truss System Subjected to Various Loading Conditions

PubMed Central

Zhang, Dongdong; Huang, Yaxin; Zhao, Qilin; Li, Fei; Gao, Yifeng

2014-01-01

A novel hybrid FRP-aluminum truss system has been employed in a two-rut modular bridge superstructure composed of twin inverted triangular trusses. The actual flexural behavior of a one-rut truss has been previously investigated under the on-axis loading test; however, the structural performance of the one-rut truss subjected to an off-axis load is still not fully understood. In this paper, a geometrical linear finite element model is introduced and validated by the on-axis loading test; the structural performance of the one-rut truss subjected to off-axis load was numerically obtained; the dissimilarities of the structural performance between the two different loading cases are investigated in detail. The results indicated that (1) the structural behavior of the off-axis load differs from that of the on-axis load, and the off-axis load is the critical loading condition controlling the structural performance of the triangular truss; (2) under the off-axis load, the FRP trussed members and connectors bear certain out-of-plane bending moments and are subjected to a complicated stress state; and (3) the stress state of these members does not match that of the initial design, and optimization for the redesign of these members is needed, especially for the pretightened teeth connectors. PMID:25254254

Large-aperture interferometer using local reference beam

NASA Technical Reports Server (NTRS)

Howes, W. L.

1982-01-01

A large-aperture interferometer was devised by adding a local-reference-beam-generating optical system to a schlieren system. Two versions of the interferometer are demonstrated, one employing 12.7 cm (5 in.) diameter schlieren optics, the other employing 30.48 cm (12 in.) diameter parabolic mirrors in an off-axis system. In the latter configuration a cylindrical lens is introduced near the light source to correct for astigmatism. A zone plate is a satisfactory decollimating element in the reference-beam arm of the interferometer. Attempts to increase the flux and uniformity of irradiance in the reference beam by using a diffuser are discussed.

Content-based fused off-axis object illumination direct-to-digital holography

DOEpatents

Price, Jeffery R.

2006-05-02

Systems and methods are described for content-based fused off-axis illumination direct-to-digital holography. A method includes calculating an illumination angle with respect to an optical axis defined by a focusing lens as a function of data representing a Fourier analyzed spatially heterodyne hologram; reflecting a reference beam from a reference mirror at a non-normal angle; reflecting an object beam from an object the object beam incident upon the object at the illumination angle; focusing the reference beam and the object beam at a focal plane of a digital recorder to from the content-based off-axis illuminated spatially heterodyne hologram including spatially heterodyne fringes for Fourier analysis; and digitally recording the content based off-axis illuminated spatially heterodyne hologram including spatially heterodyne fringes for Fourier analysis.

Rippled disc electrostatic generator/motor configurations utilizing magnetic insulation

DOEpatents

Post, Richard F

2017-04-04

Electrostatic generators/motors designs are provided that generally may include a first rippled stator centered about a longitudinal axis; a second rippled stator centered about the axis, a first rippled rotor centered about the axis and located between the first rippled stator and the second rippled stator. A magnetic field having field lines about parallel with the average plane of at least one of the first rippled stator or the second rippled stator is provided with either a Halbach array configuration or a conductor array configuration.

Malaligned dynamic anterior cervical plate: a biomechanical analysis of effectiveness.

PubMed

Lawrence, Brandon D; Patel, Alpesh A; Guss, Andrew; Ryan Spiker, W; Brodke, Darrel S

2014-12-01

Biomechanical evaluation. To evaluate the kinematic and load-sharing differences of dynamic anterior cervical plates when placed in-line at 0° and off-axis at 20°. The use of dynamic anterior cervical plating systems has recently gained popularity due to the theoretical benefit of improved load sharing with graft subsidence. Occasionally, due to anatomical restraints, the anterior cervical plate may be placed off-axis in the coronal plane. This may potentially decrease the dynamization capability of the plate, leading to less load sharing and potentially decreased fusion rates. The purpose of this study was to comprehensively evaluate the kinematic and load-sharing differences of a dynamic plate placed in-line versus off-axis in the coronal plane. Thirteen fresh-frozen human cadaveric cervical spines (C2-T1) were used. Nondestructive range-of-motion testing was performed with a pneumatically controlled spine simulator in flexion/extension, lateral bending, and axial rotation using the OptoTrak motion measurement system. A C5 corpectomy was performed, and a custom interbody spacer with an integrated load cell collected load-sharing data under axial compression at varying loads. A dynamic anterior cervical plate was placed in-line at 0° and then off-axis at 20°. Testing conditions ensued using a full-length spacer, followed by simulated subsidence by removing 10% of the height of the original spacer. There were no kinematic differences noted in the in-line model versus the off-axis model. After simulated subsidence, the small decreases in stiffness and increases in motion were similar whether the plate was placed in-line or off-axis in all 3 planes of motion. There were also no significant differences in the load-sharing characteristics of the in-line plate versus the off-axis plate in either the full-length model or the subsided interbody model. This study suggests that off-axis dynamic plate positioning does not significantly impact construct kinematics or graft load sharing. As such, we do not recommend removal or repositioning of an off-axis placed dynamic plate because the kinematic and load-sharing biomechanical properties are similar. N/A.

Off-axis dose equivalent due to secondary neutrons from uniform scanning proton beams during proton radiotherapy

NASA Astrophysics Data System (ADS)

Islam, M. R.; Collums, T. L.; Zheng, Y.; Monson, J.; Benton, E. R.

2013-11-01

The production of secondary neutrons is an undesirable byproduct of proton therapy and it is important to quantify the contribution from secondary neutrons to patient dose received outside the treatment volume. The purpose of this study is to investigate the off-axis dose equivalent from secondary neutrons experimentally using CR-39 plastic nuclear track detectors (PNTD) at ProCure Proton Therapy Center, Oklahoma City, OK. In this experiment, we placed several layers of CR-39 PNTD laterally outside the treatment volume inside a phantom and in air at various depths and angles with respect to the primary beam axis. Three different proton beams with max energies of 78, 162 and 226 MeV and 4 cm modulation width, a 5 cm diameter brass aperture, and a small snout located 38 cm from isocenter were used for the entire experiment. Monte Carlo simulations were also performed based on the experimental setup using a simplified snout configuration and the FLUKA Monte Carlo radiation transport code. The measured ratio of secondary neutron dose equivalent to therapeutic primary proton dose (H/D) ranged from 0.3 ± 0.08 mSv Gy-1 for 78 MeV proton beam to 37.4 ± 2.42 mSv Gy-1 for 226 MeV proton beam. Both experiment and simulation showed a similar decreasing trend in dose equivalent with distance to the central axis and the magnitude varied by a factor of about 2 in most locations. H/D was found to increase as the energy of the primary proton beam increased and higher H/D was observed at 135° compared to 45° and 90°. The overall higher H/D in air indicates the predominance of external neutrons produced in the nozzle rather than inside the body.

The effects of transducer geometry on artifacts common to diagnostic bone imaging with conventional medical ultrasound.

PubMed

Mauldin, F William; Owen, Kevin; Tiouririne, Mohamed; Hossack, John A

2012-06-01

The portability, low cost, and non-ionizing radiation associated with medical ultrasound suggest that it has potential as a superior alternative to X-ray for bone imaging. However, when conventional ultrasound imaging systems are used for bone imaging, clinical acceptance is frequently limited by artifacts derived from reflections occurring away from the main axis of the acoustic beam. In this paper, the physical source of off-axis artifacts and the effect of transducer geometry on these artifacts are investigated in simulation and experimental studies. In agreement with diffraction theory, the sampled linear-array geometry possessed increased off-axis energy compared with single-element piston geometry, and therefore, exhibited greater levels of artifact signal. Simulation and experimental results demonstrated that the linear-array geometry exhibited increased artifact signal when the center frequency increased, when energy off-axis to the main acoustic beam (i.e., grating lobes) was perpendicularly incident upon off-axis surfaces, and when off-axis surfaces were specular rather than diffusive. The simulation model used to simulate specular reflections was validated experimentally and a correlation coefficient of 0.97 between experimental and simulated peak reflection contrast was observed. In ex vivo experiments, the piston geometry yielded 4 and 6.2 dB average contrast improvement compared with the linear array when imaging the spinous process and interlaminar space of an animal spine, respectively. This work indicates that off-axis reflections are a major source of ultrasound image artifacts, particularly in environments comprising specular reflecting (i.e., bone or bone-like) objects. Transducer geometries with reduced sensitivity to off-axis surface reflections, such as a piston transducer geometry, yield significant reductions in image artifact.

Photographic simulation of off-axis blurring due to chromatic aberration in spectacle lenses.

PubMed

Doroslovački, Pavle; Guyton, David L

2015-02-01

Spectacle lens materials of high refractive index (nd) tend to have high chromatic dispersion (low Abbé number [V]), which may contribute to visual blurring with oblique viewing. A patient who noted off-axis blurring with new high-refractive-index spectacle lenses prompted us to do a photographic simulation of the off-axis aberrations in 3 readily available spectacle lens materials, CR-39 (nd = 1.50), polyurethane (nd = 1.60), and polycarbonate (nd = 1.59). Both chromatic and monochromatic aberrations were found to cause off-axis image degradation. Chromatic aberration was more prominent in the higher-index materials (especially polycarbonate), whereas the lower-index CR-39 had more astigmatism of oblique incidence. It is important to consider off-axis aberrations when a patient complains of otherwise unexplained blurred vision with a new pair of spectacle lenses, especially given the increasing promotion of high-refractive-index materials with high chromatic dispersion. Copyright © 2015 American Association for Pediatric Ophthalmology and Strabismus. Published by Elsevier Inc. All rights reserved.

Expected neutrino fluence from short Gamma-Ray Burst 170817A and off-axis angle constraints

NASA Astrophysics Data System (ADS)

Biehl, D.; Heinze, J.; Winter, W.

2018-05-01

We compute the expected neutrino fluence from SGRB 170817A, associated with the gravitational wave event GW 170817, directly based on Fermi observations in two scenarios: structured jet and off-axis (observed) top-hat jet. While the expected neutrino fluence for the structured jet case is very small, large off-axis angles imply high radiation densities in the jet, which can enhance the neutrino production efficiency. In the most optimistic allowed scenario, the neutrino fluence can reach only 10-4 of the sensitivity of the neutrino telescopes. We furthermore demonstrate that the fact that gamma-rays can escape limits the baryonic loading (energy in protons versus photons) and the off-axis angle for the internal shock scenario. In particular, for a baryonic loading of 10, the off-axis angle is more strongly constrained by the baryonic loading than by the time delay between the gravitational wave event and the onset of the gamma-ray emission.

Coma of modified Gregorian and Cassegrainian mirror systems

NASA Technical Reports Server (NTRS)

Jones, R. T.

1976-01-01

The equivalence of the classical Newtonian, Cassegrainian, and Gregorian mirror systems with respect to the first two Seidel aberrations is rederived by means of a simple congruence. The effects of arbitrary small modifications of the two mirror systems are then studied and general formulas are derived for the effects of such modifications on the spherical aberration and coma. Spherical aberration is corrected to the third order if the amount of glass removed from one surface is replaced at the corresponding zone of the other surface. Modifications in which one surface is made spherical while the other is adjusted to eliminate spherical aberration result in large increases of coma for systems having the usual amplifying ratios.

Hybrid shallow on-axis and deep off-axis hydrothermal circulation at fast-spreading ridges.

PubMed

Hasenclever, Jörg; Theissen-Krah, Sonja; Rüpke, Lars H; Morgan, Jason P; Iyer, Karthik; Petersen, Sven; Devey, Colin W

2014-04-24

Hydrothermal flow at oceanic spreading centres accounts for about ten per cent of all heat flux in the oceans and controls the thermal structure of young oceanic plates. It also influences ocean and crustal chemistry, provides a basis for chemosynthetic ecosystems, and has formed massive sulphide ore deposits throughout Earth's history. Despite this, how and under what conditions heat is extracted, in particular from the lower crust, remains largely unclear. Here we present high-resolution, whole-crust, two- and three-dimensional simulations of hydrothermal flow beneath fast-spreading ridges that predict the existence of two interacting flow components, controlled by different physical mechanisms, that merge above the melt lens to feed ridge-centred vent sites. Shallow on-axis flow structures develop owing to the thermodynamic properties of water, whereas deeper off-axis flow is strongly shaped by crustal permeability, particularly the brittle-ductile transition. About 60 per cent of the discharging fluid mass is replenished on-axis by warm (up to 300 degrees Celsius) recharge flow surrounding the hot thermal plumes, and the remaining 40 per cent or so occurs as colder and broader recharge up to several kilometres away from the axis that feeds hot (500-700 degrees Celsius) deep-rooted off-axis flow towards the ridge. Despite its lower contribution to the total mass flux, this deep off-axis flow carries about 70 per cent of the thermal energy released at the ridge axis. This combination of two flow components explains the seismically determined thermal structure of the crust and reconciles previously incompatible models favouring either shallower on-axis or deeper off-axis hydrothermal circulation.

Off Axis Growth of Strontium Titanate Films with High Dielectric Constant Tuning and Low Loss

DTIC Science & Technology

2003-04-03

80309, U.S.A. ABSTRACT We have measured the nonlinear dielectric properties of strontium titanate (STO) thin films grown on neodymium gallate (NGO...and lanthanum aluminate (LAO) substrates. The films prepared by off-axis pulsed laser deposition were characterized by their dielectric constant and...performed on the films prepared with the off axis growth. EXPERIMENTAL Pulsed laser deposition (PLD) was used to deposit STO films on lanthanum

Design of CMOS compatible and compact, thermally-compensated electro-optic modulator based on off-axis microring resonator for dense wavelength division multiplexing applications.

PubMed

Haldar, Raktim; Banik, Abhik D; Varshney, Shailendra K

2014-09-22

In this work, we propose and demonstrate the performance of silicon-on-insulator (SOI) off-axis microring resonator (MRR) as electro-optic modulator (EOM). Adding an extra off-axis inner-ring in conventional microring structure provides control to compensate thermal effects on EOM. It is shown that dynamically controlled bias-voltage applied to the outer ring has the potency to quell the thermal effects over a wide range of temperature. Thus, besides the appositely biased conventional microring, off-axis inner microring with pre-emphasized electrical input message signal enables our proposed structure suitable for high data-rate dense wavelength division multiplexing scheme of optical communication within a very compact device size.

Geometric & radiometric vignetting associated with a 72-facet, off-axis, polygon mirror for swept source optical coherence tomography (SS-OCT)

NASA Astrophysics Data System (ADS)

Everson, Michael; Duma, Virgil-Florin; Dobre, George

2017-01-01

Optical Coherence Tomography (OCT) has a broad range of applications in 2D and volumetric imaging of micron scale structures typically used on inaccessible objects such as the retina of the eye. This report focuses on Swept Source OCT (SS-OCT), favoured for its faster scanning speeds and therefore faster data acquisition (highly favourable when imaging live patients). SS-OCT relies on the scanning of a narrow laser line at speeds typically in excess of 100 kHz. We have employed ZemaxTM ray tracing software to simulate one method of splitting the spectrum of a broadband, near-infrared source, into its component wavelengths by reflecting the spectrum from an off-axis, 72-facet polygon mirror at a frequency of 48 kHz. We specifically addressed the geometric and radiometric vignetting associated with the reflected spectrum off an individual mirrored facet and how this may impose limitations to the incident beam size and hence lead to a loss in the power available from the source. It was found that for certain configurations up to 44% of the light was lost at the edges of the spectrum due to both radiometric and geometric vignetting, which may result in an effective swept range of <50 nm from an initial bandwidth of 100 nm. Our simulations account for real refractive errors and losses in the beam caused by lens aberrations, and produce a model of the sampling function of wavelength against time.

Wavefront division digital holography

NASA Astrophysics Data System (ADS)

Zhang, Wenhui; Cao, Liangcai; Li, Rujia; Zhang, Hua; Zhang, Hao; Jiang, Qiang; Jin, Guofan

2018-05-01

Digital holography (DH), mostly Mach-Zehnder configuration based, belongs to non-common path amplitude splitting interference imaging whose stability and fringe contrast are environmental sensitive. This paper presents a wavefront division DH configuration with both high stability and high-contrast fringes benefitting from quasi common path wavefront-splitting interference. In our proposal, two spherical waves with similar curvature coming from the same wavefront are used, which makes full use of the physical sampling capacity of the detectors. The interference fringe spacing can be adjusted flexibly for both in-line and off-axis mode due to the independent modulation to these two waves. Only a few optical elements, including the mirror-beam splitter interference component, are used without strict alignments, which makes it robust and easy-to-implement. The proposed wavefront division DH promotes interference imaging physics into the practical and miniaturized a step forward. The feasibility of this method is proved by the imaging of a resolution target and a water flea.

DIII-D accomplishments and plans in support of fusion next steps

DOE PAGES

Buttery, R. J; Eidietis, N.; Holcomb, C.; ...

2013-06-01

DIII-D is using its flexibility and diagnostics to address the critical science required to enable next step fusion devices. We have adapted operating scenarios for ITER to low torque and are now being optimized for transport. Three ELM mitigation scenarios have been developed to near-ITER parameters. New control techniques are managing the most challenging plasma instabilities. Disruption mitigation tools show promising dissipation strategies for runaway electrons and heat load. An off axis neutral beam upgrade has enabled sustainment of high βN capable steady state regimes. Divertor research is identifying the challenge, physics and candidate solutions for handling the hot plasmamore » exhaust with notable progress in heat flux reduction using the snowflake configuration. Our work is helping optimize design choices and prepare the scientific tools for operation in ITER, and resolve key elements of the plasma configuration and divertor solution for an FNSF.« less

Integrated Scenario Modeling of NSTX Advanced Plasma Configurations

NASA Astrophysics Data System (ADS)

Kessel, Charles; Synakowski, Edward

2003-10-01

The Spherical Torus will provide an attractive fusion energy source if it can demonstrate the following major features: high elongation and triangularity, 100% non-inductive current with a credible path to high bootstrap fractions, non-solenoidal startup and current rampup, high beta with stabilization of RWM instabilities, and sufficiently high energy confinement. NSTX has specific experimental milestones to examine these features, and integrated scenario modeling is helping to understand how these configurations might be produced and what tools are needed to access this operating space. Simulations with the Tokamak Simulation Code (TSC), CURRAY, and JSOLVER/BALMSC/PEST2 have identified fully non-inductively sustained, high beta plasmas that rely on strong plasma shaping accomplished with a PF coil modification, off-axis current drive from Electron Bernstein Waves (EBW), flexible on-axis heating and CD from High Harmonic Fast Wave (HHFW) and Neutral Beam Injection (NBI), and density control. Ideal MHD stability shows that with wall stabilization through plasma rotation and/or RWM feedback coils, a beta of 40% is achievable, with 100% non-inductive current sustained for 4 current diffusion times. Experimental data and theory are combined to produce a best extrapolation to these regimes, which is continuously improved as the discharges approach these parameters, and theoretical/computational methods expand. Further investigations and development for integrated scenario modeling on NSTX is discussed.

Diamond Machining of an Off-Axis Biconic Aspherical Mirror

NASA Technical Reports Server (NTRS)

Ohl, Raymond G.; Preuss, Werner; Sohn, Alex; MacKenty, John

2009-01-01

Two diamond-machining methods have been developed as part of an effort to design and fabricate an off-axis, biconic ellipsoidal, concave aluminum mirror for an infrared spectrometer at the Kitt Peak National Observatory. Beyond this initial application, the methods can be expected to enable satisfaction of requirements for future instrument mirrors having increasingly complex (including asymmetrical), precise shapes that, heretofore, could not readily be fabricated by diamond machining or, in some cases, could not be fabricated at all. In the initial application, the mirror is prescribed, in terms of Cartesian coordinates x and y, by aperture dimensions of 94 by 76 mm, placements of -2 mm off axis in x and 227 mm off axis in y, an x radius of curvature of 377 mm, a y radius of curvature of 407 mm, an x conic constant of 0.078, and a y conic constant of 0.127. The aspect ratio of the mirror blank is about 6. One common, "diamond machining" process uses single-point diamond turning (SPDT). However, it is impossible to generate the required off-axis, biconic ellipsoidal shape by conventional SPDT because (1) rotational symmetry is an essential element of conventional SPDT and (2) the present off-axis biconic mirror shape lacks rotational symmetry. Following conventional practice, it would be necessary to make this mirror from a glass blank by computer-controlled polishing, which costs more than diamond machining and yields a mirror that is more difficult to mount to a metal bench. One of the two present diamond machining methods involves the use of an SPDT machine equipped with a fast tool servo (FTS). The SPDT machine is programmed to follow the rotationally symmetric asphere that best fits the desired off-axis, biconic ellipsoidal surface. The FTS is actuated in synchronism with the rotation of the SPDT machine to generate the difference between the desired surface and the best-fit rotationally symmetric asphere. In order to minimize the required stroke of the FTS, the blanks were positioned at a large off-axis distance and angle, and the axis of the FTS was not parallel to the axis of the spindle of the SPDT machine. The spindle was rotated at a speed of 120 rpm, and the maximum FTS speed was 8.2 mm/s.

Multileaf collimator tongue-and-groove effect on depth and off-axis doses: A comparison of treatment planning data with measurements and Monte Carlo calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Hee Jung; Department of Biomedical Engineering, Seoul National University, Seoul; Department of Radiation Oncology, Soonchunhyang University Hospital, Seoul

2015-01-01

To investigate how accurately treatment planning systems (TPSs) account for the tongue-and-groove (TG) effect, Monte Carlo (MC) simulations and radiochromic film (RCF) measurements were performed for comparison with TPS results. Two commercial TPSs computed the TG effect for Varian Millennium 120 multileaf collimator (MLC). The TG effect on off-axis dose profile at 3 depths of solid water was estimated as the maximum depth and the full width at half maximum (FWHM) of the dose dip at an interleaf position. When compared with the off-axis dose of open field, the maximum depth of the dose dip for MC and RCF rangedmore » from 10.1% to 20.6%; the maximum depth of the dose dip gradually decreased by up to 8.7% with increasing depths of 1.5 to 10 cm and also by up to 4.1% with increasing off-axis distances of 0 to 13 cm. However, TPS results showed at most a 2.7% decrease for the same depth range and a negligible variation for the same off-axis distances. The FWHM of the dose dip was approximately 0.19 cm for MC and 0.17 cm for RCF, but 0.30 cm for Eclipse TPS and 0.45 cm for Pinnacle TPS. Accordingly, the integrated value of TG dose dip for TPS was larger than that for MC and RCF and almost invariant along the depths and off-axis distances. We concluded that the TG dependence on depth and off-axis doses shown in the MC and RCF results could not be appropriately modeled by the TPS versions in this study.« less

Experimental Validation Techniques for the Heleeos Off-Axis Laser Propagation Model

DTIC Science & Technology

2010-03-01

EXPERIMENTAL VALIDATION TECHNIQUES FOR THE HELEEOS OFF-AXIS LASER PROPAGATION MODEL THESIS John Haiducek, 1st Lt, USAF AFIT/GAP/ENP/10-M07 DEPARTMENT...Department of Defense, or the United States Government. AFIT/GAP/ENP/10-M07 EXPERIMENTAL VALIDATION TECHNIQUES FOR THE HELEEOS OFF-AXIS LASER ...BS, Physics 1st Lt, USAF March 2010 APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED. AFIT/GAP/ENP/10-M07 Abstract The High Energy Laser End-to-End

Off-Axis Ratcheting Behavior of Unidirectional Carbon/Epoxy Laminate under Asymmetric Cyclic Loading at High Temperature

DTIC Science & Technology

2011-11-01

ply unidirectional carbon/epoxy laminates [0]12 were fabricated from the prepreg tape of P3252-20 (TORAY). They were laid up by hand and cured in...Off-Axis Ratcheting Behavior of Unidirectional Carbon/Epoxy Laminate under Asymmetric Cyclic Loading at High Temperature Takafumi Suzuki 1 and...Development of an engineering model for predicting the off-axis ratcheting behavior of a unidirectional CFRP laminate has been attempted. For this purpose

Ridge-crossing mantle plumes and gaps in tracks

NASA Astrophysics Data System (ADS)

Sleep, Norman H.

2002-12-01

Hot spot tracks approach, cross, and leave ridge axes. The complications of this process make it difficult to determine the track followed by a plume and the evolution of its vigor. When a plume is sufficiently near the ridge axis, buoyant plume material flows along the base of the lithosphere toward the axis, forming an on-axis hot spot. The track of the on-axis hot spot is a symmetric V on both plates and an unreliable indication of the path followed by the plume. Aseismic ridges form more or less along flowlines from a plume to a ridge axis when channels form at the base of the lithosphere. A dynamic effect is that off-axis hot spots appear to shut off at the time that an on-axis hot spot becomes active along an axis-approaching track. This produces a gap in the obvious track and a jump of the hot spot to the ridge axis. The gap results from the effects of ponded plume material on intraplate (membrane) stress. Membrane tension lets dikes ascend efficiently to produce obvious tracks of edifices. An off-axis hot spot shuts down when the plume is sufficiently near the ridge axis that plume material flows there, putting the nearby lithosphere above the plume into compression, preventing dikes. In addition, the off-axis thickness of plume material, which produces membrane tension, decreases as the slope of the base of the lithosphere increases beneath young lithosphere. Slow spreading rates favor gaps produced in this way. Gaps are observed near both fast and slow ridges.

Propagation dynamics of off-axis symmetrical and asymmetrical vortices embedded in flat-topped beams

NASA Astrophysics Data System (ADS)

Zhang, Xu; Wang, Haiyan

2017-11-01

In this paper, propagation dynamics of off-axis symmetrical and asymmetrical optical vortices(OVs) embedded in flat-topped beams have been explored numerically based on rigorous scalar diffraction theory. The distribution properties of phase and intensity play an important role in driving the propagation dynamics of OVs. Numerical results show that the single off-axis vortex moves in a straight line. The displacement of the single off-axis vortex becomes smaller, when either the order of flatness N and the beam size ω0are increased or the off-axis displacement d is decreased. In addition, the phase singularities of high order vortex beams can be split after propagating a certain distance. It is also demonstrated that the movement of OVs are closely related with the spatial symmetrical or asymmetrical distribution of vortex singularities field. Multiple symmetrical and asymmetrical optical vortices(OVs) embedded in flat-topped beams can interact and rotate. The investment of the propagation dynamics of OVs may have many applications in optical micro-manipulation and optical tweezers.

Off-axis Gamma-ray Burst Afterglow Modeling Based on a Two-dimensional Axisymmetric Hydrodynamics Simulation

NASA Astrophysics Data System (ADS)

van Eerten, Hendrik; Zhang, Weiqun; MacFadyen, Andrew

2010-10-01

Starting as highly relativistic collimated jets, gamma-ray burst outflows gradually slow down and become nonrelativistic spherical blast waves. Although detailed analytical solutions describing the afterglow emission received by an on-axis observer during both the early and late phases of the outflow evolution exist, a calculation of the received flux during the intermediate phase and for an off-axis observer requires either a more simplified analytical model or direct numerical simulations of the outflow dynamics. In this paper, we present light curves for off-axis observers covering the long-term evolution of the blast wave, calculated from a high-resolution two-dimensional relativistic hydrodynamics simulation using a synchrotron radiation model. We compare our results to earlier analytical work and calculate the consequence of the observer angle with respect to the jet axis both for the detection of orphan afterglows and for jet break fits to the observational data. We confirm earlier results in the literature finding that only a very small number of local type Ibc supernovae can harbor an orphan afterglow. For off-axis observers, the observable jet break can be delayed up to several weeks, potentially leading to overestimation of the beaming-corrected total energy. In addition we find that, when using our off-axis light curves to create synthetic Swift X-ray data, jet breaks are likely to remain hidden in the data.

Fracture modes of high modulus graphite/epoxy angleplied laminates subjected to off-axis tensile loads

NASA Technical Reports Server (NTRS)

Sinclair, J. H.

1980-01-01

Angelplied laminates of high modulus graphite fiber/epoxy were studied in several ply configurations at various tensile loading angles to the zero ply direction in order to determine the effects of ply orientations on tensile properties, fracture modes, and fracture surface characteristics of the various plies. It was found that fracture modes in the plies of angleplied laminates can be characterized by scanning electron microscope observation. The characteristics for a given fracture mode are similar to those for the same fracture mode in unidirectional specimens. However, no simple load angle range can be associated with a given fracture mode.

Theoretical performance of cross-wind axis turbines with results for a catenary vertical axis configuration

NASA Technical Reports Server (NTRS)

Muraca, R. J.; Stephens, M. V.; Dagenhart, J. R.

1975-01-01

A general analysis capable of predicting performance characteristics of cross-wind axis turbines was developed, including the effects of airfoil geometry, support struts, blade aspect ratio, windmill solidity, blade interference and curved flow. The results were compared with available wind tunnel results for a catenary blade shape. A theoretical performance curve for an aerodynamically efficient straight blade configuration was also presented. In addition, a linearized analytical solution applicable for straight configurations was developed. A listing of the computer program developed for numerical solutions of the general performance equations is included in the appendix.

A dark-line two-dimensional magneto-optical trap of 85Rb atoms with high optical depth.

PubMed

Zhang, Shanchao; Chen, J F; Liu, Chang; Zhou, Shuyu; Loy, M M T; Wong, G K L; Du, Shengwang

2012-07-01

We describe the apparatus of a dark-line two-dimensional (2D) magneto-optical trap (MOT) of (85)Rb cold atoms with high optical depth (OD). Different from the conventional configuration, two (of three) pairs of trapping laser beams in our 2D MOT setup do not follow the symmetry axes of the quadrupole magnetic field: they are aligned with 45° angles to the longitudinal axis. Two orthogonal repumping laser beams have a dark-line volume in the longitudinal axis at their cross over. With a total trapping laser power of 40 mW and repumping laser power of 18 mW, we obtain an atomic OD up to 160 in an electromagnetically induced transparency (EIT) scheme, which corresponds to an atomic-density-length product NL = 2.05 × 10(15) m(-2). In a closed two-state system, the OD can become as large as more than 600. Our 2D MOT configuration allows full optical access of the atoms in its longitudinal direction without interfering with the trapping and repumping laser beams spatially. Moreover, the zero magnetic field along the longitudinal axis allows the cold atoms maintain a long ground-state coherence time without switching off the MOT magnetic field, which makes it possible to operate the MOT at a high repetition rate and a high duty cycle. Our 2D MOT is ideal for atomic-ensemble-based quantum optics applications, such as EIT, entangled photon pair generation, optical quantum memory, and quantum information processing.

Measurement of νμ and νe Events in an Off-Axis Horn-Focused Neutrino Beam

NASA Astrophysics Data System (ADS)

Adamson, P.; Aguilar-Arevalo, A. A.; Anderson, C. E.; Bazarko, A. O.; Bishai, M.; Brice, S. J.; Brown, B. C.; Bugel, L.; Cao, J.; Choudhary, B. C.; Coney, L.; Conrad, J. M.; Cox, D. C.; Curioni, A.; Djurcic, Z.; Finley, D. A.; Fleming, B. T.; Ford, R.; Gallagher, H. R.; Garcia, F. G.; Garvey, G. T.; Green, C.; Green, J. A.; Harris, D.; Hart, T. L.; Hawker, E.; Hylen, J.; Imlay, R.; Johnson, R. A.; Karagiorgi, G.; Kasper, P.; Katori, T.; Kobilarcik, T.; Kopp, S.; Kourbanis, I.; Koutsoliotas, S.; Laird, E. M.; Linden, S. K.; Link, J. M.; Liu, Y.; Liu, Y.; Loiacono, L.; Louis, W. C.; Marchionni, A.; Mahn, K. B. M.; Marsh, W.; McGregor, G.; Messier, M. D.; Metcalf, W.; Meyers, P. D.; Mills, F.; Mills, G. B.; Monroe, J.; Moore, C. D.; Nelson, J. K.; Nelson, R. H.; Nguyen, V. T.; Nienaber, P.; Nowak, J. A.; Ouedraogo, S.; Patterson, R. B.; Pavlovic, Z.; Perevalov, D.; Polly, C. C.; Prebys, E.; Raaf, J. L.; Ray, H.; Roe, B. P.; Russell, A. D.; Sandberg, V.; Schirato, R.; Schmitz, D.; Shaevitz, M. H.; Shoemaker, F. C.; Smart, W.; Smith, D.; Sodeberg, M.; Sorel, M.; Spentzouris, P.; Stancu, I.; Stefanski, R. J.; Sung, M.; Tanaka, H. A.; Tayloe, R.; Tzanov, M.; Vahle, P.; van de Water, R.; Viren, B.; Wascko, M. O.; White, D. H.; Wilking, M. J.; Yang, H. J.; Yumiceva, F. X.; Zeller, G. P.; Zimmerman, E. D.; Zwaska, R.

2009-05-01

We report the first observation of off-axis neutrino interactions in the MiniBooNE detector from the NuMI beam line at Fermilab. The MiniBooNE detector is located 745 m from the NuMI production target, at 110 mrad angle (6.3°) with respect to the NuMI beam axis. Samples of charged-current quasielastic νμ and νe interactions are analyzed and found to be in agreement with expectation. This provides a direct verification of the expected pion and kaon contributions to the neutrino flux and validates the modeling of the NuMI off-axis beam.

Off-axis spectral beam combining of Bragg reflection waveguide photonic crystal diode lasers

NASA Astrophysics Data System (ADS)

Sun, Fangyuan; Wang, Lijie; Zhao, Yufei; Hou, Guanyu; Shu, Shili; Zhang, Jun; Peng, Hangyu; Tian, Sicong; Tong, Cunzhu; Wang, Lijun

2018-06-01

The spectral beam combining (SBC) of Bragg reflection waveguide photonic crystal (BRW-PC) diode lasers was studied for the first time. An off-axis feedback system was constructed using a stripe mirror and a spatial filter to control beam quality in the external cavity. It was found that the BRW-PC diode lasers with a low divergence and a circular beam provided a simplified and cost-effective SBC. The off-axis feedback broke the beam quality limit of a single element, and an M 2 factor of 3.8 times lower than that of a single emitter in the slow axis was demonstrated.

The effects of eccentricities on the fracture of off-axis fiber composites. [carbon fiber reinforced plastics

NASA Technical Reports Server (NTRS)

Chamis, C. C.; Sinclair, J. H.

1978-01-01

Finite element analyses were performed to investigate theoretically the effects of in-plane and out-of-plane eccentricities, bending or twisting, and thickness nonuniformity on the axial stress and strain variations across the width of off-axis specimens. The results are compared with measured data and are also used to assess the effects of these eccentricities on the fracture stress of off-axis fiber composites. Guidelines for detecting and minimizing the presence of eccentricities are described.

The effects of eccentricities on the fracture of off-axis fiber composites

NASA Technical Reports Server (NTRS)

Chamis, C. C.; Sinclair, J. H.

1978-01-01

Finite element analyses were performed to investigate theoretically the effects of in-plane and out-of plane eccentricities, bending or twisting, and thickness nonuniformity on the axial stress and strain variations across the width of off-axis specimens. The results are compared with measured data and are also used to access the effects of these eccentricities on the fracture stress of off-axis fiber composites. Guidelines for detecting and minimizing the presence of eccentricities are described.

Multifactor Determinants of Visual Accommodation as a Critical Intervening Variable in the Perception of Size and Distance: Phase I Report

DTIC Science & Technology

1997-11-01

Expanded subset of the illustration to clarify the locus of the off-axis end point of retinal stimulation for correct accommodation. 55 Figure...12c. Expanded illustration to clarify the locus of the off -axis end point of retinal stimulation for myopic accommodation. 55 Figure 12d...Expanded illustration to clarify the locus of the off -axis end point of retinal stimulation for hyperopic accommodation. 56 Figure 13. Simplified

Binocular Coordination of the Human Vestibulo-Ocular Reflex during Off-axis Pitch Rotation

NASA Technical Reports Server (NTRS)

Wood, S. J.; Reschke, M. F.; Kaufman, G. D.; Black, F. O.; Paloski, W. H.

2006-01-01

Head movements in the sagittal pitch plane typically involve off-axis rotation requiring both vertical and horizontal vergence ocular reflexes to compensate for angular and translational motion relative to visual targets of interest. The purpose of this study was to compare passive pitch VOR responses during rotation about an Earth-vertical axis (canal only cues) with off-axis rotation (canal and otolith cues). Methods. Eleven human subjects were oscillated sinusoidally at 0.13, 0.3 and 0.56 Hz while lying left-side down with the interaural axis either aligned with the axis of rotation or offset by 50 cm. In a second set of measurements, twelve subjects were also tested during sinusoidally varying centrifugation over the same frequency range. The modulation of vertical and horizontal vergence ocular responses was measured with a binocular videography system. Results. Off-axis pitch rotation enhanced the vertical VOR at lower frequencies and enhanced the vergence VOR at higher frequencies. During sinusoidally varying centrifugation, the opposite trend was observed for vergence, with both vertical and vergence vestibulo-ocular reflexes being suppressed at the highest frequency. Discussion. These differential effects of off-axis rotation over the 0.13 to 0.56 Hz range are consistent with the hypothesis that otolith-ocular reflexes are segregated in part on the basis of stimulus frequency. At the lower frequencies, tilt otolith-ocular responses compensate for declining canal input. At higher frequencies, translational otolith-ocular reflexes compensate for declining visual contributions to the kinematic demands required for fixating near targets.

New configuration for efficient and durable copper coating on the outer surface of a tube

DOE PAGES

Ahmad, Irfan; Chapman, Steven F.; Velas, Katherine M.; ...

2017-03-27

A well-adhered copper coating on stainless steel power coupler parts is required in superconducting radio frequency (SRF) accelerators. Radio frequency power coupler parts are complex, tubelike stainless steel structures, which require copper coating on their outer and inner surfaces. Conventional copper electroplating sometimes produces films with inadequate adhesion strength for SRF applications. Electroplating also requires a thin nickel strike layer under the copper coating, whose magnetic properties can be detrimental to SRF applications. Coaxial energetic deposition (CED) and sputtering methods have demonstrated efficient conformal coating on the inner surfaces of tubes but coating the outer surface of a tube ismore » challenging because these coating methods are line of sight. When the substrate is off axis and the plasma source is on axis, only a small section of the substrate’s outer surface is exposed to the source cathode. The conventional approach is to rotate the tube to achieve uniformity across the outer surface. This method results in poor film thickness uniformity and wastes most of the source plasma. Alameda Applied Sciences Corporation (AASC) has developed a novel configuration called hollow external cathode CED (HEC-CED) to overcome these issues. HEC-CED produces a film with uniform thickness and efficiently uses all eroded source material. Furthermore, the Cu film deposited on the outside of a stainless steel tube using the new HEC-CED configuration survived a high pressure water rinse adhesion test. HEC-CED can be used to coat the outside of any cylindrical structure.« less

New configuration for efficient and durable copper coating on the outer surface of a tube

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ahmad, Irfan; Chapman, Steven F.; Velas, Katherine M.

A well-adhered copper coating on stainless steel power coupler parts is required in superconducting radio frequency (SRF) accelerators. Radio frequency power coupler parts are complex, tubelike stainless steel structures, which require copper coating on their outer and inner surfaces. Conventional copper electroplating sometimes produces films with inadequate adhesion strength for SRF applications. Electroplating also requires a thin nickel strike layer under the copper coating, whose magnetic properties can be detrimental to SRF applications. Coaxial energetic deposition (CED) and sputtering methods have demonstrated efficient conformal coating on the inner surfaces of tubes but coating the outer surface of a tube ismore » challenging because these coating methods are line of sight. When the substrate is off axis and the plasma source is on axis, only a small section of the substrate’s outer surface is exposed to the source cathode. The conventional approach is to rotate the tube to achieve uniformity across the outer surface. This method results in poor film thickness uniformity and wastes most of the source plasma. Alameda Applied Sciences Corporation (AASC) has developed a novel configuration called hollow external cathode CED (HEC-CED) to overcome these issues. HEC-CED produces a film with uniform thickness and efficiently uses all eroded source material. Furthermore, the Cu film deposited on the outside of a stainless steel tube using the new HEC-CED configuration survived a high pressure water rinse adhesion test. HEC-CED can be used to coat the outside of any cylindrical structure.« less

Comparison of calculations and measurements of the off-axis radiation dose (SI) in liquid nitrogen as a function of radiation length

NASA Astrophysics Data System (ADS)

Cromar, P. F.

1984-12-01

In this thesis results are presented from a study of the off-axis X and Gamma radiation field caused by a highly relativistic electron beam in liquid Nitrogen at various path lengths out to 2 radiation lengths. The off-axis dose in Silicon was calculated using electron/photon transport code CYLTRAN and measured using thermal luminescent dosimeters (TLD's). Calculations were performed on a CDC-7600 computer ar Los Alamos National Laboratory and measurements were made using the Naval Postgraduate School 100 Mev Linac. Comparison of the results is made and CYLTRAN is found to be in agreement with experimentally measured values. The CYLTRAN results are extended to the off-axis dose caused by a 100 Mev electron beam in air at Standard Temperature and Pressure (STP).

Mechanical behavior and fracture characteristics of off-axis fiber composites. 1: Experimental investigation. [at the Lewis Research Center

NASA Technical Reports Server (NTRS)

Sinclair, J. H.; Chamis, C. C.

1977-01-01

The mechanical behavior, fracture surfaces, and fracture modes of unidirectional high-modulus graphite-fiber/epoxy composites subjected to off-axis tensile loads were investigated experimentally. The investigation included the generation of stress-strain-to-fracture data and scanning electron microscope studies of the fractured surfaces. The results led to the identification of fracture modes and distinct fracture surface characteristics for off-axis tensile loading. The results also led to the formulation of critical for identifying and characterizing these fracture modes and their associated fracture surfaces. The results presented and discussed herein were used in the theoretical investigation and comparisons described in Part 2. These results should also provide a good foundation for identifying, characterizing, and quantifying fracture modes in both off-axis and angle-plied laminates.

Single-shot dual-wavelength in-line and off-axis hybrid digital holography

NASA Astrophysics Data System (ADS)

Wang, Fengpeng; Wang, Dayong; Rong, Lu; Wang, Yunxin; Zhao, Jie

2018-02-01

We propose an in-line and off-axis hybrid holographic real-time imaging technique. The in-line and off-axis digital holograms are generated simultaneously by two lasers with different wavelengths, and they are recorded using a color camera with a single shot. The reconstruction is carried using an iterative algorithm in which the initial input is designed to include the intensity of the in-line hologram and the approximate phase distributions obtained from the off-axis hologram. In this way, the complex field in the object plane and the output by the iterative procedure can produce higher quality amplitude and phase images compared to traditional iterative phase retrieval. The performance of the technique has been demonstrated by acquiring the amplitude and phase images of a green lacewing's wing and a living moon jellyfish.

Off-axis beam dynamics in rf-gun-based electron photoinjectors

DOE PAGES

Huang, R.; Mitchell, Chad; Papadopoulos, C.; ...

2016-11-22

The need to operate an rf-gun-based electron photoinjector with a beam emitted away from the cathode center can occur under various circumstances. First, in some cases the cathode can be affected by ion back-bombardment that progressively reduces the quantum efficiency (QE) in its center, making off-axis operation mandatory; second, in some cases the drive laser intensity can be sufficiently high to generate QE depletion in the cathode area illuminated by the laser, forcing off-axis operation; last, in cathodes with nonuniform QE distribution it could be convenient to operate off axis to exploit a better QE. However, operation in this modemore » may lead to growth of the projected transverse beam emittances due to correlations between the transverse and longitudinal degrees of freedom that are introduced within the gun and downstream rf cavities. A strategy is described to mitigate this emittance growth by allowing the beam to propagate along a carefully tuned off-axis trajectory in downstream rf cavities to remove the time-dependent rf kicks introduced in the gun. Along this trajectory, short range wakefields do not degrade the emittance, and long range wakefields degrade the emittance for very high repetition rate only.« less

Off-axis low coherence digital holographic interferometry for quantitative phase imaging with an LED

NASA Astrophysics Data System (ADS)

Guo, Rongli; Wang, Fan; Hu, Xiaoying; Yang, Wenqian

2017-11-01

Off-axis digital holographic interferometry with the light source of a light emitting diode (LED) is presented and its application for quantitative phase imaging in a large range with low noise is demonstrated. The scheme is implemented in a grating based Mach-Zehnder interferometer. To achieve off-axis interferometry, firstly, the collimated beam emitted from an LED is diffracted into multiple orders by a grating and they are split into two copies by a beam splitter; secondly, in the object arm the zero order of one copy is filtered in the Fourier plane and is reshaped to illuminate the sample, while in the reference arm one of its first order of another copy is selected to serve as the reference beam, and then an off-axis hologram can be obtained at the image plane. The main advantage stemming from an LED illumination is its high spatial phase resolution, due to the subdued speckle effect. The off-axis geometry enables one-shot recording of the hologram in the millisecond scale. The utility of the proposed setup is illustrated with measurements of a resolution target and part of a wing of green-lacewing, and dynamic evaporation process of an ethanol film.

Off-axis beam dynamics in rf-gun-based electron photoinjectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, R.; Mitchell, Chad; Papadopoulos, C.

The need to operate an rf-gun-based electron photoinjector with a beam emitted away from the cathode center can occur under various circumstances. First, in some cases the cathode can be affected by ion back-bombardment that progressively reduces the quantum efficiency (QE) in its center, making off-axis operation mandatory; second, in some cases the drive laser intensity can be sufficiently high to generate QE depletion in the cathode area illuminated by the laser, forcing off-axis operation; last, in cathodes with nonuniform QE distribution it could be convenient to operate off axis to exploit a better QE. However, operation in this modemore » may lead to growth of the projected transverse beam emittances due to correlations between the transverse and longitudinal degrees of freedom that are introduced within the gun and downstream rf cavities. A strategy is described to mitigate this emittance growth by allowing the beam to propagate along a carefully tuned off-axis trajectory in downstream rf cavities to remove the time-dependent rf kicks introduced in the gun. Along this trajectory, short range wakefields do not degrade the emittance, and long range wakefields degrade the emittance for very high repetition rate only.« less

Extremely Soft X-Ray Flash as the Indicator of Off-axis Orphan GRB Afterglow

NASA Astrophysics Data System (ADS)

Urata, Yuji; Huang, Kuiyun; Yamazaki, Ryo; Sakamoto, Takanori

2015-06-01

We verified the off-axis jet model of X-ray flashes (XRFs) and examined a discovery of off-axis orphan gamma-ray burst (GRB) afterglows. The XRF sample was selected on the basis of the following three factors: (1) a constraint on the lower peak energy of the prompt spectrum {E}{obs}{src}, (2) redshift measurements, and (3) multicolor observations of an earlier (or brightening) phase. XRF 020903 was the only sample selected on the basis of these criteria. A complete optical multicolor afterglow light curve of XRF 020903 obtained from archived data and photometric results in the literature showed an achromatic brightening around 0.7 days. An off-axis jet model with a large observing angle (0.21 rad, which is twice the jet opening half-angle, {θ }{jet}) can naturally describe the achromatic brightening and the prompt X-ray spectral properties. This result indicates the existence of off-axis orphan GRB afterglow light curves. Events with a larger viewing angle (\\gt ∼ 2{θ }{jet}) could be discovered using an 8 m class telescope with wide-field imagers such as the Subaru Hyper-Suprime-Cam and the Large Synoptic Survey Telescope.

Properties of perpendicular-anisotropy magnetic tunnel junctions fabricated over the bottom electrode contact

NASA Astrophysics Data System (ADS)

Miura, Sadahiko; Honjo, Hiroaki; Kinoshita, Keizo; Tokutome, Keiichi; Koike, Hiroaki; Ikeda, Shoji; Endoh, Tetsuo; Ohno, Hideo

2015-04-01

Perpendicular-anisotropy magnetic tunnel junctions (MTJs) were prepared on four substrate geometries, i.e., directly on the axis of the bottom electrode contact, directly off the axis of the bottom electrode contact, on the axis of the bottom electrode contact with a polished bottom electrode, and off the axis of the bottom electrode contact with a polished bottom electrode. Electrical shorts were observed for direct on-axis geometry at a certain extent, whereas there were no electrical shorts for the other three geometries. The MR ratio/σR, JC0, and thermal stability factor of the devices for polish on-axis geometry were almost the same as those for polish off-axis geometry. From TEM observations of the polish on-axis device, the interface between the bottom contact and the base electrode was determined to be rough, whereas the MgO barrier layer was determined to be smooth, indicating that the polish process was effective for smooth magnetic tunnel junction fabrication over the bottom contact. MTJs for polish on-axis geometry eliminated the base electrode resistance and increased the magnetoresistance ratio. This technology contributes to the higher density of spin transfer torque magnetic random access memory.

Development of vibration isolation platform for low amplitude vibration

NASA Astrophysics Data System (ADS)

Lee, Dae-Oen; Park, Geeyong; Han, Jae-Hung

2014-03-01

The performance of high precision payloads on board a satellite is extremely sensitive to vibration. Although vibration environment of a satellite on orbit is very gentle compared to the launch environment, even a low amplitude vibration disturbances generated by reaction wheel assembly, cryocoolers, etc may cause serious problems in performing tasks such as capturing high resolution images. The most commonly taken approach to protect sensitive payloads from performance degrading vibration is application of vibration isolator. In this paper, development of vibration isolation platform for low amplitude vibration is discussed. Firstly, single axis vibration isolator is developed by adapting three parameter model using bellows and viscous fluid. The isolation performance of the developed single axis isolator is evaluated by measuring force transmissibility. The measured transmissibility shows that both the low Q-factor (about 2) and the high roll-off rate (about -40 dB/dec) are achieved with the developed isolator. Then, six single axis isolators are combined to form Stewart platform in cubic configuration to provide multi-axis vibration isolation. The isolation performance of the developed multi-axis isolator is evaluated using a simple prototype reaction wheel model in which wheel imbalance is the major source of vibration. The transmitted force without vibration isolator is measured and compared with the transmitted force with vibration isolator. More than 20 dB reduction of the X and Y direction (radial direction of flywheel) disturbance is observed for rotating wheel speed of 100 Hz and higher.

Fabrication challenges associated with conformal optics

NASA Astrophysics Data System (ADS)

Schaefer, John; Eichholtz, Richard A.; Sulzbach, Frank C.

2001-09-01

A conformal optic is typically an optical window that conforms smoothly to the external shape of a system platform to improve aerodynamics. Conformal optics can be on-axis, such as an ogive missile dome, or off-axis, such as in a free form airplane wing. A common example of conformal optics is the automotive head light window that conforms to the body of the car aerodynamics and aesthetics. The unusual shape of conformal optics creates tremendous challenges for design, manufacturing, and testing. This paper will discuss fabrication methods that have been successfully demonstrated to produce conformal missile domes and associated wavefront corrector elements. It will identify challenges foreseen with more complex free-form configurations. Work presented in this paper was directed by the Precision Conformal Optics Consortium (PCOT). PCOT is comprised of both industrial and academic members who teamed to develop and demonstrate conformal optical systems suitable for insertion into future military programs. The consortium was funded under DARPA agreement number MDA972-96-9-08000.

Off-Axis Seamount Lavas at 8°20' N Span the Entire Range of East Pacific Rise MORB Compositions

NASA Astrophysics Data System (ADS)

Anderson, M.; Wanless, V. D.; Perfit, M. R.; Gregg, P. M.; Fornari, D. J.; McCully, E.; Ridley, W. I.

2017-12-01

Lavas erupted at off-axis seamounts can provide a window into mantle heterogeneity and melting systematics that are not easily observed on-axis at fast-spreading mid-ocean ridges (MORs), where melts are efficiently mixed and homogenized within shallow axial magma chambers. To investigate off-axis magmatism, we systematically mapped the 8°20' N seamount chain in November of 2016 on R/V Atlantis using shipboard EM122 multibeam system and AUV Sentry. This 160-km long chain of off-axis seamounts and ridges is located perpendicular to the ridge axis, west of the East Pacific Rise (EPR) and north of the Siqueiros Fracture Zone. The high-resolution surface and AUV-based multibeam and AUV sidescan maps are combined with geochemical analyses of 300 basalt samples, collected using HOV Alvin and dredging, to evaluate magmatic plumbing and sources off-axis. Preliminary major and trace element concentrations reveal remarkable geochemical heterogeneity (including both normal and enriched basalt compositions) across the entire seamount chain and within individual seamounts. For example, (La/Sm)N contents span the entire range of known values for basalts from northern Pacific MORs and seamounts (0.45—2.76). MgO contents vary from 10.25 to 4.56 wt. % across the seamount chain and by as much as 3.61 wt. % from volcanic features sampled at an individual seamount (Beryl). Additionally, K2O/TiO2 ratios range from 4.9 to 61.3 across the seamount chain, and by as much as 54.4 at a single seamount (Beryl), indicating heterogeneous mantle sources or variable extents of melting occur at both regional and local scales. We combine the geochemical results and bathymetric maps with petrologic models to evaluate extents and depths of fractional crystallization and mantle melting in the off-axis environment.

Stable operating regime for traveling wave devices

DOEpatents

Carlsten, Bruce E.

2000-01-01

Autophase stability is provided for a traveling wave device (TWD) electron beam for amplifying an RF electromagnetic wave in walls defining a waveguide for said electromagnetic wave. An off-axis electron beam is generated at a selected energy and has an energy noise inherently arising from electron gun. The off-axis electron beam is introduced into the waveguide. The off-axis electron beam is introduced into the waveguide at a second radius. The waveguide structure is designed to obtain a selected detuning of the electron beam. The off-axis electron beam has a velocity and the second radius to place the electron beam at a selected distance from the walls defining the waveguide, wherein changes in a density of the electron beam due to the RF electromagnetic wave are independent of the energy of the electron beam to provide a concomitant stable operating regime relative to the energy noise.

Geometrical optics design of a compact range Gregorian subreflector system by the principle of the central ray

NASA Technical Reports Server (NTRS)

Clerici, Giancarlo; Burnside, Walter D.

1989-01-01

In recent years, the compact range has become very popular for measuring Radar Cross Section (RCS) and antenna patterns. The compact range, in fact, offers several advantages due to reduced size, a controlled environment, and privacy. On the other hand, it has some problems of its own, which must be solved properly in order to achieve high quality measurement results. For example, diffraction from the edges of the main reflector corrupts the plane wave in the target zone and creates spurious scattering centers in RCS measurements. While diffraction can be minimized by using rolled edges, the field of an offset single reflector compact range is corrupted by three other errors: the taper of the reflected field, the cross polarization introduced by the tilt of the feed and the aperture blockage introduced by the feed itself. These three errors can be eliminated by the use of a subreflector system. A properly designed subreflector system offers very little aperture blockage, no cross-polarization introduced and a minimization of the taper of the reflected field. A Gregorian configuration has been adopted in order to enclose the feed and the ellipsoidal subreflector in a lower chamber, which is isolated by absorbers from the upper chamber, where the main parabolic reflector and the target zone are enclosed. The coupling between the two rooms is performed through a coupling aperture. The first cut design for such a subreflector system is performed through Geometrical Optics ray tracing techniques (GO), and is greatly simplified by the use of the concept of the central ray introduced by Dragone. The purpose of the GO design is to establish the basic dimensions of the main reflector and subreflector, the size of the primary and secondary illuminating surfaces, the tilt angles of the subreflector and feed, and estimate the feed beamwidth. At the same time, the shape of the coupling aperture is initially determined.

Speed control system for an access gate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bzorgi, Fariborz M

2012-03-20

An access control apparatus for an access gate. The access gate typically has a rotator that is configured to rotate around a rotator axis at a first variable speed in a forward direction. The access control apparatus may include a transmission that typically has an input element that is operatively connected to the rotator. The input element is generally configured to rotate at an input speed that is proportional to the first variable speed. The transmission typically also has an output element that has an output speed that is higher than the input speed. The input element and the outputmore » element may rotate around a common transmission axis. A retardation mechanism may be employed. The retardation mechanism is typically configured to rotate around a retardation mechanism axis. Generally the retardation mechanism is operatively connected to the output element of the transmission and is configured to retard motion of the access gate in the forward direction when the first variable speed is above a control-limit speed. In many embodiments the transmission axis and the retardation mechanism axis are substantially co-axial. Some embodiments include a freewheel/catch mechanism that has an input connection that is operatively connected to the rotator. The input connection may be configured to engage an output connection when the rotator is rotated at the first variable speed in a forward direction and configured for substantially unrestricted rotation when the rotator is rotated in a reverse direction opposite the forward direction. The input element of the transmission is typically operatively connected to the output connection of the freewheel/catch mechanism.« less

Point Spread Function of ASTRO-H Soft X-Ray Telescope (SXT)

NASA Technical Reports Server (NTRS)

Hayashi, Takayuki; Sato, Toshiki; Kikuchi, Naomichi; Iizuka, Ryo; Maeda, Yoshitomo; Ishida, Manabu; Kurashima, Sho; Nakaniwa, Nozomi; Okajima, Takashi; Mori, Hideyuki;

A Miniature Magnetic-Force-Based Three-Axis AC Magnetic Sensor with Piezoelectric/Vibrational Energy-Harvesting Functions.

PubMed

Hung, Chiao-Fang; Yeh, Po-Chen; Chung, Tien-Kan

2017-02-08

In this paper, we demonstrate a miniature magnetic-force-based, three-axis, AC magnetic sensor with piezoelectric/vibrational energy-harvesting functions. For magnetic sensing, the sensor employs a magnetic-mechanical-piezoelectric configuration (which uses magnetic force and torque, a compact, single, mechanical mechanism, and the piezoelectric effect) to convert x -axis and y -axis in-plane and z -axis magnetic fields into piezoelectric voltage outputs. Under the x -axis magnetic field (sine-wave, 100 Hz, 0.2-3.2 gauss) and the z -axis magnetic field (sine-wave, 142 Hz, 0.2-3.2 gauss), the voltage output with the sensitivity of the sensor are 1.13-26.15 mV with 8.79 mV/gauss and 1.31-8.92 mV with 2.63 mV/gauss, respectively. In addition, through this configuration, the sensor can harness ambient vibrational energy, i.e., possessing piezoelectric/vibrational energy-harvesting functions. Under x -axis vibration (sine-wave, 100 Hz, 3.5 g) and z -axis vibration (sine-wave, 142 Hz, 3.8 g), the root-mean-square voltage output with power output of the sensor is 439 mV with 0.333 μW and 138 mV with 0.051 μW, respectively. These results show that the sensor, using this configuration, successfully achieves three-axis magnetic field sensing and three-axis vibration energy-harvesting. Due to these features, the three-axis AC magnetic sensor could be an important design reference in order to develop future three-axis AC magnetic sensors, which possess energy-harvesting functions, for practical industrial applications, such as intelligent vehicle/traffic monitoring, processes monitoring, security systems, and so on.

A Miniature Magnetic-Force-Based Three-Axis AC Magnetic Sensor with Piezoelectric/Vibrational Energy-Harvesting Functions

PubMed Central

Hung, Chiao-Fang; Yeh, Po-Chen; Chung, Tien-Kan

2017-01-01

In this paper, we demonstrate a miniature magnetic-force-based, three-axis, AC magnetic sensor with piezoelectric/vibrational energy-harvesting functions. For magnetic sensing, the sensor employs a magnetic–mechanical–piezoelectric configuration (which uses magnetic force and torque, a compact, single, mechanical mechanism, and the piezoelectric effect) to convert x-axis and y-axis in-plane and z-axis magnetic fields into piezoelectric voltage outputs. Under the x-axis magnetic field (sine-wave, 100 Hz, 0.2–3.2 gauss) and the z-axis magnetic field (sine-wave, 142 Hz, 0.2–3.2 gauss), the voltage output with the sensitivity of the sensor are 1.13–26.15 mV with 8.79 mV/gauss and 1.31–8.92 mV with 2.63 mV/gauss, respectively. In addition, through this configuration, the sensor can harness ambient vibrational energy, i.e., possessing piezoelectric/vibrational energy-harvesting functions. Under x-axis vibration (sine-wave, 100 Hz, 3.5 g) and z-axis vibration (sine-wave, 142 Hz, 3.8 g), the root-mean-square voltage output with power output of the sensor is 439 mV with 0.333 μW and 138 mV with 0.051 μW, respectively. These results show that the sensor, using this configuration, successfully achieves three-axis magnetic field sensing and three-axis vibration energy-harvesting. Due to these features, the three-axis AC magnetic sensor could be an important design reference in order to develop future three-axis AC magnetic sensors, which possess energy-harvesting functions, for practical industrial applications, such as intelligent vehicle/traffic monitoring, processes monitoring, security systems, and so on. PMID:28208693

Instrument Line Shape Modeling and Correction for Off-Axis Detectors in Fourier Transform Spectrometry

NASA Technical Reports Server (NTRS)

Bowman, K.; Worden, H.; Beer, R.

1999-01-01

Spectra measured by off-axis detectors in a high-resolution Fourier transform spectrometer (FTS) are characterized by frequency scaling, asymmetry and broadening of their line shape, and self-apodization in the corresponding interferogram.

Off-axis full-field swept-source optical coherence tomography using holographic refocusing

NASA Astrophysics Data System (ADS)

Hillmann, Dierck; Franke, Gesa; Hinkel, Laura; Bonin, Tim; Koch, Peter; Hüttmann, Gereon

2013-03-01

We demonstrate a full-field swept-source OCT using an off-axis geometry of the reference illumination. By using holographic refocusing techniques, a uniform lateral resolution is achieved over the measurement depth of approximately 80 Rayleigh lengths. Compared to a standard on-axis setup, artifacts and autocorrelation signals are suppressed and the measurement depth is doubled by resolving the complex conjugate ambiguity. Holographic refocusing was done efficiently by Fourier-domain resampling as demonstrated before in inverse scattering and holoscopy. It allowed to reconstruct a complete volume with about 10μm resolution over the complete measurement depth of more than 10mm. Off-axis full-field swept-source OCT enables high measurement depths, spanning many Rayleigh lengths with reduced artifacts.

From the Cradle of Liberty

NASA Astrophysics Data System (ADS)

Fried, Bart

A discussion of several antique telescopes in the Philadelphia area. Included are: a Gregorian once owned by General 'Mad' Anthony Wayne; General George Washington's spyglass, a 5 inch Bardou; and a few unknowns.

Reflective baffle for BepiColombo mission

NASA Astrophysics Data System (ADS)

Rugi-Grond, E.; Weigel, T.; Herren, A.; Dominguez Calvo, M.; Krähenbühl, U.; Mouricaud, D.; Vayssade, H.

2017-11-01

The BepiColombo Spacecraft can't tolerate to absorb a major fraction of the off-axis sunlight through larger payload apertures. Fortunately, there are solutions to design baffles such that they reflect the incoming radiation back through the front aperture rather than absorbing it. A Design Study, sponsored by ESA and performed by Contraves Space together with SAGEM Défense Securité, has analysed the potential of various solutions and assessed the options to manufacture them. The selected configuration has been analysed in detail for the optical, mechanical and thermal performance as well as the impact on mass and power dissipation. The size of the baffle was adapted to the needs of the BepiColombo Laser Altimeter (BELA) payload.

Optimizing Facility Configurations and Operating Conditions for Improved Performance in the NASA Ames 24 Inch Shock Tube

NASA Technical Reports Server (NTRS)

Bogdanoff, David W.; Cruden, Brett A.

2016-01-01

The Ames Electric Arc Shock Tube (EAST) is a shock tube wherein the driver gas can be heated by an electric arc discharge. The electrical energy is stored in a 1.2 MJ capacitor bank. Four inch and 24 inch diameter driven tubes are available. The facility is described and the need for testing in the 24 inch tube to better simulate low density NASA mission profiles is discussed. Three test entries, 53, 53B and 59, are discussed. Tests are done with air or Mars gas (95.7% CO2/2.7% N2/1.6% Ar) at pressures of 0.01 to 0.14 Torr. Velocities spanned 6.3-9.2 km/s, with a nominal center of 7 km/s. Many facility configurations are studied in an effort to improve data quality. Various driver and driven tube configurations and the use of a buffer section between the driver and the driven tube are studied. Diagnostics include test times, time histories of the shock light pulses and tilts of the shock wave off the plane normal to the tube axis. The report will detail the results of the various trials, give the best configuration/operating conditions found to date and provide recommendations for further improvements. Finally, diaphragm performance is discussed.

CFD simulations of power coefficients for an innovative Darrieus style vertical axis wind turbine with auxiliary straight blades

NASA Astrophysics Data System (ADS)

Arpino, F.; Cortellessa, G.; Dell'Isola, M.; Scungio, M.; Focanti, V.; Profili, M.; Rotondi, M.

2017-11-01

The increasing price of fossil derivatives, global warming and energy market instabilities, have led to an increasing interest in renewable energy sources such as wind energy. Amongst the different typologies of wind generators, small scale Vertical Axis Wind Turbines (VAWT) present the greatest potential for off grid power generation at low wind speeds. In the present work, Computational Fluid Dynamic (CFD) simulations were performed in order to investigate the performance of an innovative configuration of straight-blades Darrieus-style vertical axis micro wind turbine, specifically developed for small scale energy conversion at low wind speeds. The micro turbine under investigation is composed of three pairs of airfoils, consisting of a main and auxiliary blades with different chord lengths. The simulations were made using the open source finite volume based CFD toolbox OpenFOAM, considering different turbulence models and adopting a moving mesh approach for the turbine rotor. The simulated data were reported in terms of dimensionless power coefficients for dynamic performance analysis. The results from the simulations were compared to the data obtained from experiments on a scaled model of the same VAWT configuration, conducted in a closed circuit open chamber wind tunnel facility available at the Laboratory of Industrial Measurements (LaMI) of the University of Cassino and Lazio Meridionale (UNICLAM). From the proposed analysis, it was observed that the most suitable model for the simulation of the performances of the micro turbine under investigation is the one-equation Spalart-Allmaras, even if under the conditions analysed in the present work and for TSR values higher than 1.1, some discrepancies between numerical and experimental data can be observed.

Normalized Point Source Sensitivity for Off-Axis Optical Performance Evaluation of the Thirty Meter Telescope

NASA Technical Reports Server (NTRS)

Seo, Byoung-Joon; Nissly, Carl; Troy, Mitchell; Angeli, George

2010-01-01

The Normalized Point Source Sensitivity (PSSN) has previously been defined and analyzed as an On-Axis seeing-limited telescope performance metric. In this paper, we expand the scope of the PSSN definition to include Off-Axis field of view (FoV) points and apply this generalized metric for performance evaluation of the Thirty Meter Telescope (TMT). We first propose various possible choices for the PSSN definition and select one as our baseline. We show that our baseline metric has useful properties including the multiplicative feature even when considering Off-Axis FoV points, which has proven to be useful for optimizing the telescope error budget. Various TMT optical errors are considered for the performance evaluation including segment alignment and phasing, segment surface figures, temperature, and gravity, whose On-Axis PSSN values have previously been published by our group.

A two-dimensional matrix correction for off-axis portal dose prediction errors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bailey, Daniel W.; Department of Radiation Medicine, Roswell Park Cancer Institute, Buffalo, New York 14263; Kumaraswamy, Lalith

2013-05-15

Purpose: This study presents a follow-up to a modified calibration procedure for portal dosimetry published by Bailey et al. ['An effective correction algorithm for off-axis portal dosimetry errors,' Med. Phys. 36, 4089-4094 (2009)]. A commercial portal dose prediction system exhibits disagreement of up to 15% (calibrated units) between measured and predicted images as off-axis distance increases. The previous modified calibration procedure accounts for these off-axis effects in most regions of the detecting surface, but is limited by the simplistic assumption of radial symmetry. Methods: We find that a two-dimensional (2D) matrix correction, applied to each calibrated image, accounts for off-axismore » prediction errors in all regions of the detecting surface, including those still problematic after the radial correction is performed. The correction matrix is calculated by quantitative comparison of predicted and measured images that span the entire detecting surface. The correction matrix was verified for dose-linearity, and its effectiveness was verified on a number of test fields. The 2D correction was employed to retrospectively examine 22 off-axis, asymmetric electronic-compensation breast fields, five intensity-modulated brain fields (moderate-high modulation) manipulated for far off-axis delivery, and 29 intensity-modulated clinical fields of varying complexity in the central portion of the detecting surface. Results: Employing the matrix correction to the off-axis test fields and clinical fields, predicted vs measured portal dose agreement improves by up to 15%, producing up to 10% better agreement than the radial correction in some areas of the detecting surface. Gamma evaluation analyses (3 mm, 3% global, 10% dose threshold) of predicted vs measured portal dose images demonstrate pass rate improvement of up to 75% with the matrix correction, producing pass rates that are up to 30% higher than those resulting from the radial correction technique alone. As in the 1D correction case, the 2D algorithm leaves the portal dosimetry process virtually unchanged in the central portion of the detector, and thus these correction algorithms are not needed for centrally located fields of moderate size (at least, in the case of 6 MV beam energy).Conclusion: The 2D correction improves the portal dosimetry results for those fields for which the 1D correction proves insufficient, especially in the inplane, off-axis regions of the detector. This 2D correction neglects the relatively smaller discrepancies that may be caused by backscatter from nonuniform machine components downstream from the detecting layer.« less

Demonstration of a Monolithic Micro-Spectrometer System

NASA Technical Reports Server (NTRS)

Rajic, S.; Egert, C. M.

1995-01-01

The starting design of a spectrometer based on a modified Czerny-Turner configuration containing five precision surfaces encapsulated in a monolithic structure is described. Since the purpose at the early stages of the development was to demonstrate the feasibility of the technology and not an attempt to address a specific sensing problem, the first substrate material chosen was optical quality polymethyl methacrylate (PMMA). The final system design decision was narrowed down to two possible configurations containing five and six precision surfaces. The five surface design was chosen since it contained one less precision optical surface, yet included multiple off-axis spheres. In this particular design and material system, the mass was kept below 7 g. The wavelength range (bandpass) design goal was 1 micrometer (0.6 - 1.6 micrometers). The PMMA is particularly transparent in this wavelength region and there are interesting effects to monitor within this band. The optical system was designed and optimized using the ZEMAX optical design software program to be entirely alignment free (self aligning).

Imaging Polarimeter for a Sub-MeV Gamma-Ray All-sky Survey Using an Electron-tracking Compton Camera

DOE Office of Scientific and Technical Information (OSTI.GOV)

Komura, S.; Takada, A.; Mizumura, Y.

2017-04-10

X-ray and gamma-ray polarimetry is a promising tool to study the geometry and the magnetic configuration of various celestial objects, such as binary black holes or gamma-ray bursts (GRBs). However, statistically significant polarizations have been detected in few of the brightest objects. Even though future polarimeters using X-ray telescopes are expected to observe weak persistent sources, there are no effective approaches to survey transient and serendipitous sources with a wide field of view (FoV). Here we present an electron-tracking Compton camera (ETCC) as a highly sensitive gamma-ray imaging polarimeter. The ETCC provides powerful background rejection and a high modulation factormore » over an FoV of up to 2 π sr thanks to its excellent imaging based on a well-defined point-spread function. Importantly, we demonstrated for the first time the stability of the modulation factor under realistic conditions of off-axis incidence and huge backgrounds using the SPring-8 polarized X-ray beam. The measured modulation factor of the ETCC was 0.65 ± 0.01 at 150 keV for an off-axis incidence with an oblique angle of 30° and was not degraded compared to the 0.58 ± 0.02 at 130 keV for on-axis incidence. These measured results are consistent with the simulation results. Consequently, we found that the satellite-ETCC proposed in Tanimori et al. would provide all-sky surveys of weak persistent sources of 13 mCrab with 10% polarization for a 10{sup 7} s exposure and over 20 GRBs down to a 6 × 10{sup −6} erg cm{sup −2} fluence and 10% polarization during a one-year observation.« less

Imaging Polarimeter for a Sub-MeV Gamma-Ray All-sky Survey Using an Electron-tracking Compton Camera

NASA Astrophysics Data System (ADS)

Komura, S.; Takada, A.; Mizumura, Y.; Miyamoto, S.; Takemura, T.; Kishimoto, T.; Kubo, H.; Kurosawa, S.; Matsuoka, Y.; Miuchi, K.; Mizumoto, T.; Nakamasu, Y.; Nakamura, K.; Oda, M.; Parker, J. D.; Sawano, T.; Sonoda, S.; Tanimori, T.; Tomono, D.; Yoshikawa, K.

2017-04-01

X-ray and gamma-ray polarimetry is a promising tool to study the geometry and the magnetic configuration of various celestial objects, such as binary black holes or gamma-ray bursts (GRBs). However, statistically significant polarizations have been detected in few of the brightest objects. Even though future polarimeters using X-ray telescopes are expected to observe weak persistent sources, there are no effective approaches to survey transient and serendipitous sources with a wide field of view (FoV). Here we present an electron-tracking Compton camera (ETCC) as a highly sensitive gamma-ray imaging polarimeter. The ETCC provides powerful background rejection and a high modulation factor over an FoV of up to 2π sr thanks to its excellent imaging based on a well-defined point-spread function. Importantly, we demonstrated for the first time the stability of the modulation factor under realistic conditions of off-axis incidence and huge backgrounds using the SPring-8 polarized X-ray beam. The measured modulation factor of the ETCC was 0.65 ± 0.01 at 150 keV for an off-axis incidence with an oblique angle of 30° and was not degraded compared to the 0.58 ± 0.02 at 130 keV for on-axis incidence. These measured results are consistent with the simulation results. Consequently, we found that the satellite-ETCC proposed in Tanimori et al. would provide all-sky surveys of weak persistent sources of 13 mCrab with 10% polarization for a 107 s exposure and over 20 GRBs down to a 6 × 10-6 erg cm-2 fluence and 10% polarization during a one-year observation.

Improvements in dose calculation accuracy for small off-axis targets in high dose per fraction tomotherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hardcastle, Nicholas; Bayliss, Adam; Wong, Jeannie Hsiu Ding

2012-08-15

Purpose: A recent field safety notice from TomoTherapy detailed the underdosing of small, off-axis targets when receiving high doses per fraction. This is due to angular undersampling in the dose calculation gantry angles. This study evaluates a correction method to reduce the underdosing, to be implemented in the current version (v4.1) of the TomoTherapy treatment planning software. Methods: The correction method, termed 'Super Sampling' involved the tripling of the number of gantry angles from which the dose is calculated during optimization and dose calculation. Radiochromic film was used to measure the dose to small targets at various off-axis distances receivingmore » a minimum of 21 Gy in one fraction. Measurements were also performed for single small targets at the center of the Lucy phantom, using radiochromic film and the dose magnifying glass (DMG). Results: Without super sampling, the peak dose deficit increased from 0% to 18% for a 10 mm target and 0% to 30% for a 5 mm target as off-axis target distances increased from 0 to 16.5 cm. When super sampling was turned on, the dose deficit trend was removed and all peak doses were within 5% of the planned dose. For measurements in the Lucy phantom at 9.7 cm off-axis, the positional and dose magnitude accuracy using super sampling was verified using radiochromic film and the DMG. Conclusions: A correction method implemented in the TomoTherapy treatment planning system which triples the angular sampling of the gantry angles used during optimization and dose calculation removes the underdosing for targets as small as 5 mm diameter, up to 16.5 cm off-axis receiving up to 21 Gy.« less

Effect of Off-Axis Screw Insertion, Insertion Torque, and Plate Contouring on Locked Screw Strength

PubMed Central

Gallagher, Bethany; Silva, Matthew J.; Ricci, William M.

2015-01-01

Objectives This study quantifies the effects of insertion torque, off-axis screw angulation, and plate contouring on the strength of locking plate constructs. Methods Groups of locking screws (n = 6–11 screws) were inserted at 50%, 100%, 150%, and 200% of the manufacturer-recommended torque (3.2 Nm) into locking compression plates at various angles: orthogonal (control), 5-degree angle off-axis, and 10-degree angle off-axis. Screws were loaded to failure by a transverse force (parallel to the plate) either in the same (“+”) or opposite direction (“−”) of the initial screw angulation. Separately, locking plates were bent to 5 and 10-degree angles, with the bend apex at a screw hole. Locking screws inserted orthogonally into the apex hole at 100% torque were loaded to failure. Results Orthogonal insertion resulted in the highest average load to failure, 2577 ± 141 N (range, 2413–2778 N), whereas any off-axis insertion significantly weakened constructs (165–1285 N, at 100% torque) (P < 0.05). For “+” loading, torque beyond 100% did not increase strength, but 50% torque reduced screw strength (P < 0.05). Loading in the “−” direction consistently resulted in higher strengths than “+” loading (P < 0.05). Plate contouring of 5-degree angle did not significantly change screw strength compared with straight plates but contouring of 10-degree angle significantly reduced load to failure (P < 0.05). Conclusions To maximize the screw plate interface strength, locking screws should be inserted without cross-threading. The mechanical stability of locked screws is significantly compromised by loose insertion, off-axis insertion, or severe distortion of the locking mechanism. PMID:24343255

SU-F-T-425: Head-Scatter Off-Axis for FFF Megavoltage Photon Beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, T; Penjweini, R; Dimofte, A

Purpose: Head-scatter photons inside a clinical accelerator cause the output to change with collimator setting. On the central-axis, this contribution is well-described by output factor in air (or head-scatter factor). However, a few studies have examined this component at off-axis points. Methods: We define the head-scatter off-axis ratio, HOA, as the ratio of the water kerma in air due to head-scatter photons at the off-axis position x to the water kerma from direct primary photons on the central axis: HOA(cx,cy,xy) = (Q(cx,cy,x) – QP(cx,cy,x))/QP(cx,cy,0), where Q(cx, cy,x), QP(cx,cy,x) are charges measured by an ionization chamber in a miniphantom for collimatormore » setting cx × cy and cx × 3 cm, respectively, at off-axis point x. “Direct primary” is those photons that come from the source without interactions in the intervening structures. Results: We measured HOA for two energies (6XFFF and 6X) along X and Y jaw directions for various collimator settings. The shape of HOA has well defined penumbra for collimator setting larger than 10 × 10 cm2. Conclusion: The narrow gaussian component is interpreted as the source of photons scattered in the flattening filter and the primary collimator. The broad component is attributed to photons scattered in the secondary (variable) collimators. By a direct comparison between 6X and 6XFFF beams, we can confirm that the second component is indeed coming from collimator jaws and identify the parts coming from the primary collimator and the flattening filter, respectively.« less

Building Petascale Cyberinfrastructure and Science Support for Solar Physics: Approach of the DKIST Data Center

NASA Astrophysics Data System (ADS)

Berukoff, Steven; Reardon, Kevin; Hays, Tony; Spiess, DJ; Watson, Fraser

2015-08-01

When construction is complete in 2019, the Daniel K. Inouye Solar Telescope will be the most-capable large aperture, high-resolution, multi-instrument solar physics facility in the world. The telescope is designed as a four-meter off-axis Gregorian, with a rotating Coude laboratory designed to simultaneously house and support five first-light imaging and spectropolarimetric instruments. At current design, the facility and its instruments will generate data volumes of 5 PB, produce 108 images, and 107-109 metadata elements annually. This data will not only forge new understanding of solar phenomena at high resolution, but enhance participation in solar physics and further grow a small but vibrant international community.The DKIST Data Center is being designed to store, curate, and process this flood of information, while augmenting its value by providing association of science data and metadata to its acquisition and processing provenance. In early Operations, the Data Center will produce, by autonomous, semi-automatic, and manual means, quality-controlled and -assured calibrated data sets, closely linked to facility and instrument performance during the Operations lifecycle. These data sets will be made available to the community openly and freely, and software and algorithms made available through community repositories like Github for further collaboration and improvement.We discuss the current design and approach of the DKIST Data Center, describing the development cycle, early technology analysis and prototyping, and the roadmap ahead. In this budget-conscious era, a key design criterion is elasticity, the ability of the built system to adapt to changing work volumes, types, and the shifting scientific landscape, without undue cost or operational impact. We discuss our deep iterative development approach, the underappreciated challenges of calibrating ground-based solar data, the crucial integration of the Data Center within the larger Operations lifecycle, and how software and hardware support, intelligently deployed, will enable high-caliber solar physics research and community growth for the DKIST's 40-year lifespan.

Design and analysis of a worm gear turntable off-axis assembly method in a three-grating monochromator.

PubMed

Chen, Jianjun; Cui, Jicheng; Yao, Xuefeng; Liu, Jianan; Sun, Ci

2018-04-01

To solve the problem where the actual grating aperture decreases with an increasing scanning angle during the scanning of a three-grating monochromator, we propose an off-axis assembly method for the worm gear turntable that makes it possible to suppress this aperture reduction. We simulated and compared the traditional assembly method with the off-axis assembly method in the three-grating monochromator. Results show that the actual grating aperture can be improved by the off-axis assembly method. In fact, for any one of the three gratings, when the monochromator outputs the longest wavelength in the corresponding wavelength band, the actual grating aperture increases by 45.93%. Over the entire monochromator output band, the actual grating aperture increased by an average of 32.56% and can thus improve the monochromator's output energy. Improvement of the actual grating aperture can also reduce the stray light intensity in the monochromator and improve its output signal-to-noise ratio.

Off-axis mirror fabrication from spherical surfaces under mechanical stress

NASA Astrophysics Data System (ADS)

Izazaga-Pérez, R.; Aguirre-Aguirre, D.; Percino-Zacarías, M. E.; Granados-Agustín, Fermin-Salomon

2013-09-01

The preliminary results in the fabrication of off-axis optical surfaces are presented. The propose using the conventional polishing method and with the surface under mechanical stress at its edges. It starts fabricating a spherical surface using ZERODUR® optical glass with the conventional polishing method, the surface is deformed by applying tension and/or compression at the surface edges using a specially designed mechanical mount. To know the necessary deformation, the interferogram of the deformed surface is analyzed in real time with a ZYGO® Mark II Fizeau type interferometer, the mechanical stress is applied until obtain the inverse interferogram associated to the off-axis surface that we need to fabricate. Polishing process is carried out again until obtain a spherical surface, then mechanical stress in the edges are removed and compares the actual interferogram with the theoretical associated to the off-axis surface. To analyze the resulting interferograms of the surface we used the phase shifting analysis method by using a piezoelectric phase-shifter and Durango® interferometry software from Diffraction International™.

Calculating broad neutron resonances in a cut-off Woods-Saxon potential

NASA Astrophysics Data System (ADS)

Baran, Á.; Noszály, Cs.; Salamon, P.; Vertse, T.

2015-07-01

In a cut-off Woods-Saxon (CWS) potential with realistic depth S -matrix poles being far from the imaginary wave number axis form a sequence where the distances of the consecutive resonances are inversely proportional with the cut-off radius value, which is an unphysical parameter. Other poles lying closer to the imaginary wave number axis might have trajectories with irregular shapes as the depth of the potential increases. Poles being close repel each other, and their repulsion is responsible for the changes of the directions of the corresponding trajectories. The repulsion might cause that certain resonances become antibound and later resonances again when they collide on the imaginary axis. The interaction is extremely sensitive to the cut-off radius value, which is an apparent handicap of the CWS potential.

Instrument for underwater high-angular resolution volume scattering function measurements

NASA Astrophysics Data System (ADS)

Dueweke, Paul W.; Bolstad, Jay; Leonard, Donald A.; Sweeney, Harold E.; Boyer, Philip A.; Winkler, Erik M.

1997-02-01

A prototype instrument for in situ measurements of the volume scattering function (VSF) and the beam attenuation of water has been built and tested in the EOO laboratory. The intended application of the instrument is the enhancement of Navy operational optical systems for finding and imaging underwater objects such as mines. A description of the apparatus that was built and preliminary laboratory data will be presented. The instrument measures the VSF, (beta) ((theta) ), near the optical axis in both the forward and back directions from approximately 0.2 degrees off axis to approximately 5 degrees in 0.1 degree steps and at side angles of 45 degrees, 90 degrees, and 135 degrees. A diode- pumped, frequency-doubled, Nd:YAG laser provides the 532 nm light. This is the most used wavelength for underwater optical systems. The forward and back scattered light is collected and focused to a plane where scattering angles in the water are mapped onto concentric rings. At this focal plane, a conical reflector compresses the annular optical data onto a line along the cone axis where it is read by a MOS linear image array providing over 500 separate angular measurements. The beam attenuation coefficient, c, is also measured by means of a unique dual path configuration.

Cylindrical laser resonator

DOEpatents

Casperson, Lee W.

1976-02-24

The properties of an improved class of lasers is presented. In one configuration of these lasers the radiation propagates radially within the amplifying medium, resulting in high fields and symmetric illumination at the resonator axis. Thus there is a strong focusing of energy at the axis of the resonator. In a second configuration the radiation propagates back and forth in a tubular region of space.

An Off-Axis Four-Quadrant Phase Mask (FQPM) Coronagraph for Palomar: High-Contrast Near Bright Stars Imager

NASA Technical Reports Server (NTRS)

Haguenauer, Pierre; Serabyn, Eugene; Bloemhof, Eric E.; Troy, Mitchell; Wallace, James K.; Koresko, Chris D.; Mennesson, Bertrand

2005-01-01

Direct detection of planets around nearby stars requires the development of high-contrast imaging techniques because of the high difference between their respective fluxes. This led us to test a new coronagraphic approach based on the use of phase mask instead of dark occulting ones. Combined with high-level wavefront correction on an unobscured off-axis section of a large telescope, this method allows imaging very close to the star. Calculations indicate that for a given ground-based on-axis telescope, use of such an off-axis coronagraph provides a near-neighbor detection capability superior to that of a traditional coronagraph utilizing the full telescope aperture. Setting up a laboratory experiment working in near infrared allowed us to demonstrate the principle of the method, and a rejection of 2000:1 has already been achieved.

Prompt and Afterglow Emission from Short GRB Cocoons

NASA Astrophysics Data System (ADS)

Morsony, Brian; Lazzati, Davide; López-Cámara, Diego; Workman, Jared; Moskal, Jeremiah; Cantiello, Matteo; Perna, Rosalba

2018-01-01

We present simulations of short GRB jets that create a wide cocoon of mildly relativistic material surrounding the narrow, highly relativistic jet. We model the prompt and afterglow emission from the jet and cocoon at a range of observer angles relative to the jet axis. Even far off axis, prompt X-ray and gamma-ray emission from the cocoon may be detectable by FERMI GBM out to several 10’s of Mpc. Afterglow emission off-axis is dominated by cocoon material at early times (hours - days). The afterglow should be detectable at a wide range of frequencies (radio, optical, X-ray) for a large fraction of off-axis short GRBs within 200 Mpc, the detection range of aLIGO at design sensitivity. Given recent events, cocoon emission may be very important in the future for localizing LIGO-detected neutron star mergers.

Multi-Axis Thrust Measurements of the EO-1 Pulsed Plasma Thruster

NASA Technical Reports Server (NTRS)

Arrington, Lynn A.; Haag, Thomas W.

1999-01-01

Pulsed plasma thrusters are low thrust propulsive devices which have a high specific impulse at low power. A pulsed plasma thruster is currently scheduled to fly as an experiment on NASA's Earth Observing-1 satellite mission. The pulsed plasma thruster will be used to replace one of the reaction wheels. As part of the qualification testing of the thruster it is necessary to determine the nominal thrust as a function of charge energy. These data will be used to determine control algorithms. Testing was first completed on a breadboard pulsed plasma thruster to determine nominal or primary axis thrust and associated propellant mass consumption as a function of energy and then later to determine if any significant off-axis thrust component existed. On conclusion that there was a significant off-axis thrust component with the bread-board in the direction of the anode electrode, the test matrix was expanded on the flight hardware to include thrust measurements along all three orthogonal axes. Similar off-axis components were found with the flight unit.

Optical re-injection in cavity-enhanced absorption spectroscopy

PubMed Central

Leen, J. Brian; O’Keefe, Anthony

2014-01-01

Non-mode-matched cavity-enhanced absorption spectrometry (e.g., cavity ringdown spectroscopy and integrated cavity output spectroscopy) is commonly used for the ultrasensitive detection of trace gases. These techniques are attractive for their simplicity and robustness, but their performance may be limited by the reflection of light from the front mirror and the resulting low optical transmission. Although this low transmitted power can sometimes be overcome with higher power lasers and lower noise detectors (e.g., in the near-infrared), many regimes exist where the available light intensity or photodetector sensitivity limits instrument performance (e.g., in the mid-infrared). In this article, we describe a method of repeatedly re-injecting light reflected off the front mirror of the optical cavity to boost the cavity's circulating power and deliver more light to the photodetector and thus increase the signal-to-noise ratio of the absorption measurement. We model and experimentally demonstrate the method's performance using off-axis cavity ringdown spectroscopy (OA-CRDS) with a broadly tunable external cavity quantum cascade laser. The power coupled through the cavity to the detector is increased by a factor of 22.5. The cavity loss is measured with a precision of 2 × 10−10 cm−1/\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} }{}$\\sqrt {{\\rm Hz;}}$\\end{document} Hz ; an increase of 12 times over the standard off-axis configuration without reinjection and comparable to the best reported sensitivities in the mid-infrared. Finally, the re-injected CRDS system is used to measure the spectrum of several volatile organic compounds, demonstrating the improved ability to resolve weakly absorbing spectroscopic features. PMID:25273701

Development of a 3-D Defocusing Liquid Crystal Particle Thermometry and Velocimetry (3DDLCPTV) System

DTIC Science & Technology

2007-05-01

general, off axis imaging can cause distortion and astigmatism in the image if proper precautions are not taken. In this case, the lens selection... astigmatism into the optical system. This astigmatism takes the form of a blurring in each image directed away from the optical axis. This blurring...is non-trivial and makes particle identification nearly impossible. Images of particles from two of the off axis cameras with the astigmatism present

The Perpetual Calendar

ERIC Educational Resources Information Center

Rogosinski, H. P.

1972-01-01

A brief history of the development of our present day Gregorian calendar is given. Methods are then given, based on congruences, to determine such things as the week-day for any given date and the date for Easter in any year. (LS)

Two spinning ways for precession dynamo.

PubMed

Cappanera, L; Guermond, J-L; Léorat, J; Nore, C

2016-04-01

It is numerically demonstrated by means of a magnetohydrodynamic code that precession can trigger dynamo action in a cylindrical container. Fixing the angle between the spin and the precession axis to be 1/2π, two limit configurations of the spinning axis are explored: either the symmetry axis of the cylinder is parallel to the spin axis (this configuration is henceforth referred to as the axial spin case), or it is perpendicular to the spin axis (this configuration is referred to as the equatorial spin case). In both cases, the centro-symmetry of the flow breaks when the kinetic Reynolds number increases. Equatorial spinning is found to be more efficient in breaking the centro-symmetry of the flow. In both cases, the average flow in the reference frame of the mantle converges to a counter-rotation with respect to the spin axis as the Reynolds number grows. We find a scaling law for the average kinetic energy in term of the Reynolds number in the axial spin case. In the equatorial spin case, the unsteady asymmetric flow is shown to be capable of sustaining dynamo action in the linear and nonlinear regimes. The magnetic field is mainly dipolar in the equatorial spin case, while it is is mainly quadrupolar in the axial spin case.

Structure and Dynamics of the Southeast Indian Ridge, 129°E to 140°E, and Off-axis Volcanism: Preliminary Results of the STORM Cruise

NASA Astrophysics Data System (ADS)

Briais, Anne; Barrère, Fabienne; Boulart, Cédric; Ceuleneer, Georges; Ferreira, Nicolas; Hanan, Barry; Hémond, Christophe; Macleod, Sarah; Maia, Marcia; Maillard, Agnès; Merkuryev, Sergey; Park, Sung-Hyun; Révillon, Sidonie; Ruellan, Etienne; Schohn, Alexandre; Watson, Sally; Yang, Yun-Seok

2016-04-01

We present observations of the South-East Indian Ridge (SEIR) collected during the STORM cruise (South Tasmania Ocean Ridge and Mantle) on the N/O L'Atalante early 2015. The SEIR between Australia and Antarctica displays large variations of axial morphology despite an almost constant intermediate spreading rate. The Australia-Antarctic Discordance (AAD) between 120°E and 128°E is a section of the mid-ocean ridge where the magma budget is abnormally low, and which marks the boundary between Indian and Pacific mantle domains with distinct geochemical isotopic compositions. The STORM project focuses on the area east of the discordance from 128 to 140°E, where gravity highs observed on satellite-derived maps of the flanks of the SEIR reveal numerous volcanic seamounts. A major objective of the STORM cruise was to test the hypothesis of a mantle flow from the Pacific to the Indian domains. We collected multibeam bathymetry and magnetic data between 136 and 138°E to map off-axis volcanic ridges up to 10 Ma-old crust. We mapped the SEIR axis between 129 and 140°E, and the northern part of the George V transform fault. We collected rock samples on seamounts and in the transform fault, basaltic glass samples along the ridge axis, and near-bottom samples and in-situ measurements in the water column. Our observations reveal that the off-axis seamounts form near the SEIR axis, are not associated to off-axis deformation of the ocean floor, and are often located near the traces of ridge axis discontinuities. We also observe a general shallowing of the ridge axis from the AAD to the George V TF and the presence of robust axial segments near the transform fault. Our new data allow us to describe the complex evolution of the transform fault system. They also permit to locate new hydrothermal systems along the ridge axis.

Documentation of the Recirculation in a Closed-Chamber Rotor Hover Test

NASA Technical Reports Server (NTRS)

McCoy, Miranda; Wadcock, Alan J.; Young, Larry A.

2016-01-01

A rotor hover test was performed inside the JPL 25-foot-diameter Space Simulator. The 40-inch-diameter rotor was tested at two locations in the chamber-on the chamber centerline and 2m off-axis. The rotor was tested in both upright and inverted configurations for 500 < RPM < 2000. Fluorescent tufts were used to identify regions of recirculation. Velocities on the entrainment side of the rotor were measured. Tabulated values for the mean entrainment velocity components and the corresponding root mean square velocity fluctuations are provided. Unsteady velocity measurements provide a description of the turbulence ingested into the rotor plane and quantify the unsteady velocity field that the Mars Scout Helicopter can expect to encounter during free flight inside the Space Simulator.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Braig, Christoph; Lochel, Heike; Firsov, Alexander

Here, the feasibility of an off-axis x-ray reflection zone plate to perform wavelength-dispersive spectroscopy, on-axis point focusing, and two-dimensional imaging is demonstrated by means of one and the same diffractive optical element (DOE) at a synchrotron radiation facility. The resolving power varies between 3 × 10 1 and 4 × 10 2 in the range of 7.6 keV to 9.0 keV, with its maximum at the design energy of 8.3 keV. This result is verified using an adjustable entrance slit, by which horizontal (H) and vertical (V) focusing to 0.85 μm(H) and 1.29 μm(V) is obtained near the sagittal focalmore » plane of the astigmatic configuration. An angular and axial scan proves an accessible field of view of at least 0.6 arcmin × 0.8 arcmin and a focal depth of ±0.86 mm. Supported by the grating efficiency of around 17.5% and a very short pulse elongation, future precision x-ray fluorescence and absorption studies of transition metals at their K-edge on an ultrashort timescale could benefit from our findings.« less

METHOD AND APPARATUS FOR PULSING A CHARGED PARTICLE BEAM

DOEpatents

Aaland, K.; Kuenning, R.W.; Harmon, R.K.

1961-05-01

A system is offered for pulsing a continuous beam of charged particles to form beam pulses that are consistently rectangular and of precise time durations which may be varied over an extremely wide range at a widely variable range of repetition rates. The system generally comprises spaced deflection plates on opposite sides of a beam axis in between which a unidirectional bias field is established to deflect the beam for impingement on an off-axis collector. The bias field is periodically neutralized by the application of fast rise time substantially rectangular pulses to one of the deflection plates in opposition to the bias field and then after a time delay to the other deflection plate in aiding relation to the bias field and during the flat crest portion of the bias opposing pulses. The voltage distribution of the resulting deflection field then includes neutral or zero portions which are of symmetrical substantially rectangular configuration relative to time and during which the beam axially passes the collector in the form of a substantially rectangular beam pulse.

SU-C-201-05: Silicon Array Dosimeter in Situ with Electronic Portal Image Device for Simultaneous Transit Dose and Image Verification in Radiotherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deshpande, S; Alhujaili, S; Vial, P

Purpose: To investigate an Electronic Portal Imaging Device (EPID) coupled to a 2D array dosimeter to provide simultaneous imaging and dose verification. Methods: The novel dual detector configuration comprised of a 2D diode array dosimeter, referred to as a Magic Plate (MP) placed directly on a standard EPID. Dose response of the MP was evaluated by measuring the detector’s response with respect to off-axis position and field size with 30 cm of solid water (SW) acting as a transit object in the beam. Measurements were performed with 3, 5, 10 and 15 mm SW build-up and compared to 2D ionisationmore » chamber array (ICA) measurements and the PinnacleTM treatment planning system (TPS) at a source to detector distance of 150 cm with a 6 MV beam. Clinical dosimetric performance was evaluated by measuring a number of intensity-modulated radiation therapy (IMRT) beams in transit geometry. Imaging performance of the EPID was quantified by measuring the contrast-to-noise ratio (CNR) and spatial resolution. Images of a Rando phantom were used for qualitative assessment. Results: Measured MP off-axis and field size response agreed within 2% of TPS and ICA responses when measured using 15 mm SW build-up. Clinical IMRT beams had gamma pass rates of ≥95% at 3%/3mm criteria. Measured CNR and spatial resolution (f50) were 264.96, 210.6, and 0.41, 0.40 with build-up of 5 and 15 mm respectively for the dual detector configuration. CNR and spatial resolution of 643.9 and 0.41 were measured for standard EPID. CNR was quantitatively worse in the dual detector configuration. Differences in imaging performance were not visible in a qualitative assessment using a Rando phantom. Conclusion: Combining a prototype MP 2D dosimeter with a conventional EPID did not significantly detract from the performance of either device and has the potential for simultaneous on-line patient transit dosimetry and image assessment in radiation therapy. Cancer Institute NSW Australia(Research Equipment Grant 10/REG/1-20) and Cancer Council NSW (Grant ID RG 1-06)« less

Stable and simple quantitative phase-contrast imaging by Fresnel biprism

NASA Astrophysics Data System (ADS)

Ebrahimi, Samira; Dashtdar, Masoomeh; Sánchez-Ortiga, Emilio; Martínez-Corral, Manuel; Javidi, Bahram

2018-03-01

Digital holographic (DH) microscopy has grown into a powerful nondestructive technique for the real-time study of living cells including dynamic membrane changes and cell fluctuations in nanometer and sub-nanometer scales. The conventional DH microscopy configurations require a separately generated coherent reference wave that results in a low phase stability and a necessity to precisely adjust the intensity ratio between two overlapping beams. In this work, we present a compact, simple, and very stable common-path DH microscope, employing a self-referencing configuration. The microscope is implemented by a diode laser as the source and a Fresnel biprism for splitting and recombining the beams simultaneously. In the overlapping area, linear interference fringes with high contrast are produced. The frequency of the interference pattern could be easily adjusted by displacement of the biprism along the optical axis without a decrease in fringe contrast. To evaluate the validity of the method, the spatial noise and temporal stability of the setup are compared with the common off-axis DH microscope based on a Mach-Zehnder interferometer. It is shown that the proposed technique has low mechanical noise as well as superb temporal stability with sub-nanometer precision without any external vibration isolation. The higher temporal stability improves the capabilities of the microscope for studying micro-object fluctuations, particularly in the case of biological specimens. Experimental results are presented using red blood cells and silica microspheres to demonstrate the system performance.

Comparison of Calculations and Measurements of the Off-Axis Radiation Dose (SI) in Liquid Nitrogen as a Function of Radiation Length.

DTIC Science & Technology

1984-12-01

radiation lengths. The off-axis dose in Silicon was calculated using the electron/photon transport code CYLTRAN and measured using thermal luminescent...various path lengths out to 2 radiation lengths. The cff-axis dose in Silicon was calculated using the electron/photon transport code CYLTRAN and measured... using thermal luminescent dosimeters (TLD’s). Calculations were performed on a CDC-7600 computer at Los Alamos National Laboratory and measurements

Pulsed ultrasonic stir welding method

NASA Technical Reports Server (NTRS)

Ding, R. Jeffrey (Inventor)

2013-01-01

A method of performing ultrasonic stir welding uses a welding head assembly to include a plate and a rod passing through the plate. The rod is rotatable about a longitudinal axis thereof. In the method, the rod is rotated about its longitudinal axis during a welding operation. During the welding operation, a series of on-off ultrasonic pulses are applied to the rod such that they propagate parallel to the rod's longitudinal axis. At least a pulse rate associated with the on-off ultrasonic pulses is controlled.

Second harmonic generation of off axial vortex beam in the case of walk-off effect

NASA Astrophysics Data System (ADS)

Chen, Shunyi; Ding, Panfeng; Pu, Jixiong

2016-07-01

Process of off axial vortex beam propagating in negative uniaxial crystal is investigated in this work. Firstly, we get the formulae of the normalized electric field and calculate the location of vortices for second harmonic beam in two type of phase matching. Then, numerical analysis verifies that the intensity distribution and location of vortices of the first order original vortex beam depend on the walk-off angle and off axial magnitude. It is shown that, in type I phase matching, the distribution of vortices is symmetrical about the horizontal axis, the separation distance increases as the off axial magnitude increases or the off axial magnitude deceases. However, in type II phase matching, the vortices are symmetrical along with some vertical axis, and increase of the walk-off angle or off axial magnitude leads to larger separation distance. Finally, the case of high order original off axial vortex beam is also investigated.

Conjugation of both on-axis and off-axis light in Nipkow disk confocal microscope to increase availability of incoherent light source.

PubMed

Saito, Kenta; Arai, Yoshiyuki; Zhang, Jize; Kobayashi, Kentaro; Tani, Tomomi; Nagai, Takeharu

2011-01-01

Laser-scanning confocal microscopy has been employed for exploring structures at subcellular, cellular and tissue level in three dimensions. To acquire the confocal image, a coherent light source, such as laser, is generally required in conventional single-point scanning microscopy. The illuminating beam must be focused onto a small spot with diffraction-limited size, and this determines the spatial resolution of the microscopy system. In contrast, multipoint scanning confocal microscopy using a Nipkow disk enables the use of an incoherent light source. We previously demonstrated successful application of a 100 W mercury arc lamp as a light source for the Yokogawa confocal scanner unit in which a microlens array was coupled with a Nipkow disk to focus the collimated incident light onto a pinhole (Saito et al., Cell Struct. Funct., 33: 133-141, 2008). However, transmission efficiency of incident light through the pinhole array was low because off-axis light, the major component of the incident light, was blocked by the non-aperture area of the disk. To improve transmission efficiency, we propose an optical system in which off-axis light is able to be transmitted through pinholes surrounding the pinhole located on the optical axis of the collimator lens. This optical system facilitates the use of not only the on-axis but also the off-axis light such that the available incident light is considerably improved. As a result, we apply the proposed system to high-speed confocal and multicolor imaging both with a satisfactory signal-to-noise ratio.

OFF-AXIS THERMAL AND SYNCHROTRON EMISSION FOR SHORT GAMMA RAY BURST

NASA Astrophysics Data System (ADS)

Xie, Xiaoyi

2018-01-01

We present light curves of photospheric and synchrotron emission from a relativistic jet propagating through the ejecta cloud of a neutron star merger. We use a moving-mesh relativistic hydrodynamics code with adaptive mesh refinement to compute the continuous evolution of jet over 13 orders of magnitude in radius from the scale of the central merger engine all the way through the late afterglow phase. As the jet propagates through the cloud it forms a hot cocoon surrounding the jet core. We find that the photospheric emission released by the hot cocoon is bright for on-axis observers and is detectable for off-axis observers at a wide range of observing angles for sufficiently close sources. As the jet and cocoon drive an external shock into the surrounding medium we compute synchrotron light curves and find bright emission for off-axis observers which differs from top-hat Blandford-McKee jets, especially for lower explosion energies.

Orbital Verification of the CXO High-Resolution Mirror Assembly Alignment and Vignetting

NASA Technical Reports Server (NTRS)

Gaetz, T. J.; Jerius, D.; Edgar, R. J.; VanSpeybroeck, L. P.; Schwartz, D. A.; Markevitch, M.; Schulz, N. S.

2000-01-01

Prior to launch, the High Resolution Mirror Assembly (HRMA) of the Chandra X-ray Observatory underwent extensive ground testing at the X-ray Calibration Facility (XRCF) at the Marshall Space Flight Center in Huntsville. Observations made during the post-launch Orbital Activation and Calibration period, allow the on-orbit condition of the X-ray optics to be assessed. Based on these ground-based and on-orbit data, we examine the alignment of the x-ray optics based on the PSF, and the boresight and alignment of the optical axis alignment relative to the detectors. We examine the vignetting and the single reflection ghost suppression properties of the telescope. Slight imperfections in alignment lead to a small azimuthal dependence of the off-axis area; the morphology of off-axis images also shows an additional small azimuthal dependence varying as 1/2 the off-axis azimuth angle.

Shaping off-axis metallic membrane reflectors using optimal boundary shapes and inelastic strains

NASA Technical Reports Server (NTRS)

White, C. V.; Dragovan, M.

2004-01-01

This paper will describe a novel concept for constructing off-axis membrane reflector surfaces. Membrane reflectors have been extensively studied, including investigations into inflated lenticular architectures, shaping by spin casting, shaping using electrostatic forces, and shaping by evacuating behind a membrane surface stretched between circular or annular-shaped supports.

When Will It Be …?: U.S. Naval Observatory Religious Calendar Computers Expanded

NASA Astrophysics Data System (ADS)

Bartlett, Jennifer L.; Chizek Frouard, Malynda; Ziegler, Cross; Lesniak, Michael V.

2017-01-01

Reflecting increasing sensitivity to differing religious practices, the U.S. Naval Observatory (USNO) has expanded its on-line calendar resources to compute additional religious dates for specific years via an Application Programming Interface (API). This flexible method now identifies Christian, Islamic, and Jewish events in JavaScript Object Notation (JSON) that anyone can use.Selected Christian Observances (http://aa.usno.navy.mil/data/docs/easter.php) returns dates of eight events for years after 1582 C.E. (A.D. 1582): Ash Wednesday, Palm Sunday, Good Friday, Easter, Ascension, Whit Sunday, Trinity Sunday, and the first Sunday of Advent. The determination of Easter, a moveable feast, uses the method of western Christian churches.Selected Islamic Observances (http://aa.usno.navy.mil/data/docs/islamic.php) returns approximate Gregorian dates of three events for years after 1582 C.E. (A.H. 990) and Julian dates for 622-1582 C.E. (A.H. 1-990) along with the corresponding Islamic year (anno Hegirae). Ramadân, Shawwál, and the Islamic year begin at sunset on the preceding Gregorian or Julian date. For planning purposes, the determination of these dates uses a tabular calendar; in practice, observation of the appropriate waxing crescent Moon determines the actual date, which may vary.Selected Jewish Observances (http://aa.usno.navy.mil/data/docs/passover.php) returns Gregorian dates of six events for years after 1582 C.E. (A.M. 5342) and Julian dates for the years 360-1582 C.E. (A.M. 4120-5342) along with the corresponding Jewish year (anno Mundi). Passover, Shavuot, Rosh Hashanah, Yom Kippur, and Hanukkah begin at sunset on the preceding Gregorian or Julian date.On-line documentation for using the API-enabled calendar computers, including sample calls, is available (http://aa.usno.navy.mil/data/docs/api.php). The webpage also describes how to use the API with the Complete Sun and Moon Data for One Day, Phases of the Moon, Solar Eclipse Computer, Day and Night Across the Earth, Apparent Disk of a Solar System Object, Julian Date Conversion, and Sidereal Time services.Introduction to Calendars (http://aa.usno.navy.mil/faq/docs/calendars.php) provides an overview of the topic and links to additional resources.

Enantioselective route to 5-methyl- and 5,7-dimethyl-6,7-dihydro-5H-dibenz[c,e]azepine: secondary amines with switchable axial chirality.

PubMed

Pira, Silvain L; Wallace, Timothy W; Graham, Jonathan P

2009-04-02

(-)-5-Methyl-6,7-dihydro-5H-dibenz[c,e]azepine 4, a new secondary amine featuring an axis-center stereochemical relay, was prepared enantioselectively from 2'-acetylbiphenyl-2-carboxylic acid, using (R)-2-phenylglycinol as an auxiliary for the control of both elements of chirality. The biaryl axis in 4 preferentially adopts the aS-configuration, with the methyl substituent pseudoequatorial, but conversion into the corresponding N-Boc derivative locks the axis into the aR-configuration, as predicted on the basis of molecular mechanics calculations.

Design and resolution analysis of parabolic mirror spectrometer

NASA Astrophysics Data System (ADS)

Wu, Su; Wang, Guodong; Xia, Guo; Sun, Yanchao; Hu, Mingyong

2017-10-01

In order to further eliminate aberration and improve resolution, the paper employs parabolic mirror as the collimating mirror and the focusing mirror to design "Z" configuration and "U" configuration optical structure of parabolic spectrometer with the F number 2.5 and the spectral range varying from 250 nm to 850 nm. We conduct experiments on ZEMAX to simulate and optimize the initial parameters of two structures with the root-mean-square (RMS) radius of spots along Y axis as the optimization goal. Through analyzing the spot diagram and the root-mean-square (RMS) of Y axis, we can see that the "U" configuration spectrometers can achieve much better spectral resolution than the "Z" configuration.

Effects of off-axis elliptical training on reducing pain and improving knee function in individuals with patellofemoral pain

PubMed Central

Tsai, Liang-Ching; Lee, Song Joo; Yang, Aaron J.; Ren, Yupeng; Press, Joel M.; Zhang, Li-Qun

2014-01-01

Objective To examine whether an off-axis elliptical training program reduces pain and improves knee function in individuals with patellofemoral pain (PFP). Design Controlled laboratory study, pre-test-post-test. Setting University rehabilitation center. Participants Twelve adult subjects with PFP. Interventions Subjects with PFP completed an exercise program consisting of 18 sessions of lower extremity off-axis training using a custom-made elliptical trainer that allows frontal-plane sliding and transverse-plane pivoting of the footplates. Main Outcome Measures Changes in knee pain and function post-training and 6 weeks following training were evaluated using the Knee Injury and Osteoarthritis Outcome Score (KOOS) and International Knee Documentation Committee (IKDC) scores. Lower extremity off-axis control was assessed by pivoting and sliding instability, calculated as the root mean square (RMS) of the footplate pivoting angle and sliding distance during elliptical exercise. Subjects’ single-leg hop distance and proprioception in detecting lower extremity pivoting motion were also evaluated. Results Subjects reported significantly greater KOOS and IKDC scores (increased by 12–18 points) and hop distance (increased by 0.2 m) following training. A significant decrease in the pivoting and sliding RMS was also observed following training. Additionally, subjects with PFP demonstrated improved pivoting proprioception when tested under a minimum-weight-bearing position. Conclusions An off-axis elliptical training program was effective in enhancing lower extremity neuromuscular control on the frontal and transverse planes, reducing pain and improving knee function in persons with PFP. PMID:25591131

Ultrasensitive, real-time analysis of biomarkers in breath using tunable external cavity laser and off-axis cavity-enhanced absorption spectroscopy

NASA Astrophysics Data System (ADS)

Bayrakli, Ismail; Akman, Hatice

2015-03-01

A robust biomedical sensor for ultrasensitive detection of biomarkers in breath based on a tunable external cavity laser (ECL) and an off-axis cavity-enhanced absorption spectroscopy (OA-CEAS) using an amplitude stabilizer is developed. A single-mode, narrow-linewidth, tunable ECL is demonstrated. A broadly coarse wavelength tuning range of 720 cm-1 for the spectral range between 6890 and 6170 cm-1 is achieved by rotating the diffraction grating forming a Littrow-type external-cavity configuration. A mode-hop-free tuning range of 1.85 cm-1 is obtained. The linewidths below 140 kHz are recorded. The ECL is combined with an OA-CEAS to perform laser chemical sensing. Our system is able to detect any molecule in breath at concentrations to the ppbv range that have absorption lines in the spectral range between 1450 and 1620 nm. Ammonia is selected as target molecule to evaluate the performance of the sensor. Using the absorption line of ammonia at 6528.76 cm-1, a minimum detectable absorption coefficient of approximately 1×10-8 cm-1 is demonstrated for 256 averages. This is achieved for a 1.4-km absorption path length and a 2-s data-acquisition time. These results yield a detection sensitivity of approximately 8.6×10-10 cm-1 Hz-1/2. Ammonia in exhaled breath is analyzed and found in a concentration of 870 ppb for our example.

Physics Basis for the Advanced Tokamak Fusion Power Plant ARIES-AT

DOE Office of Scientific and Technical Information (OSTI.GOV)

S.C. Jardin; C.E. Kessel; T.K. Mau

2003-10-07

The advanced tokamak is considered as the basis for a fusion power plant. The ARIES-AT design has an aspect ratio of A always equal to R/a = 4.0, an elongation and triangularity of kappa = 2.20, delta = 0.90 (evaluated at the separatrix surface), a toroidal beta of beta = 9.1% (normalized to the vacuum toroidal field at the plasma center), which corresponds to a normalized beta of bN * 100 x b/(I(sub)P(MA)/a(m)B(T)) = 5.4. These beta values are chosen to be 10% below the ideal-MHD stability limit. The bootstrap-current fraction is fBS * I(sub)BS/I(sub)P = 0.91. This leads tomore » a design with total plasma current I(sub)P = 12.8 MA, and toroidal field of 11.1 T (at the coil edge) and 5.8 T (at the plasma center). The major and minor radii are 5.2 and 1.3 m, respectively. The effects of H-mode edge gradients and the stability of this configuration to non-ideal modes is analyzed. The current-drive system consists of ICRF/FW for on-axis current drive and a lower-hybrid system for off-axis. Tran sport projections are presented using the drift-wave based GLF23 model. The approach to power and particle exhaust using both plasma core and scrape-off-layer radiation is presented.« less

Ultrasensitive, real-time analysis of biomarkers in breath using tunable external cavity laser and off-axis cavity-enhanced absorption spectroscopy.

PubMed

Bayrakli, Ismail; Akman, Hatice

2015-03-01

A robust biomedical sensor for ultrasensitive detection of biomarkers in breath based on a tunable external cavity laser (ECL) and an off-axis cavity-enhanced absorption spectroscopy (OA-CEAS) using an amplitude stabilizer is developed. A single-mode, narrow-linewidth, tunable ECL is demonstrated. A broadly coarse wavelength tuning range of 720 cm⁻¹ for the spectral range between 6890 and 6170 cm⁻¹ is achieved by rotating the diffraction grating forming a Littrow-type external-cavity configuration. A mode-hop-free tuning range of 1.85 cm⁻¹ is obtained. The linewidths below 140 kHz are recorded. The ECL is combined with an OA-CEAS to perform laser chemical sensing. Our system is able to detect any molecule in breath at concentrations to the ppbv range that have absorption lines in the spectral range between 1450 and 1620 nm. Ammonia is selected as target molecule to evaluate the performance of the sensor. Using the absorption line of ammonia at 6528.76 cm⁻¹, a minimum detectable absorption coefficient of approximately 1×10⁻⁸ cm⁻¹ is demonstrated for 256 averages. This is achieved for a 1.4-km absorption path length and a 2-s data-acquisition time. These results yield a detection sensitivity of approximately 8.6×10⁻¹⁰ cm⁻¹ Hz(-1/2). Ammonia in exhaled breath is analyzed and found in a concentration of 870 ppb for our example.

Bootstrap current control studies in the Wendelstein 7-X stellarator using the free-plasma-boundary version of the SIESTA MHD equilibrium code

NASA Astrophysics Data System (ADS)

Peraza-Rodriguez, H.; Reynolds-Barredo, J. M.; Sanchez, R.; Tribaldos, V.; Geiger, J.

2018-02-01

The recently developed free-plasma-boundary version of the SIESTA MHD equilibrium code (Hirshman et al 2011 Phys. Plasmas 18 062504; Peraza-Rodriguez et al 2017 Phys. Plasmas 24 082516) is used for the first time to study scenarios with considerable bootstrap currents for the Wendelstein 7-X (W7-X) stellarator. Bootstrap currents in the range of tens of kAs can lead to the formation of unwanted magnetic island chains or stochastic regions within the plasma and alter the boundary rotational transform due to the small shear in W7-X. The latter issue is of relevance since the island divertor operation of W7-X relies on a proper positioning of magnetic island chains at the plasma edge to control the particle and energy exhaust towards the divertor plates. Two scenarios are examined with the new free-plasma-boundary capabilities of SIESTA: a freely evolving bootstrap current one that illustrates the difficulties arising from the dislocation of the boundary islands, and a second one in which off-axis electron cyclotron current drive (ECCD) is applied to compensate the effects of the bootstrap current and keep the island divertor configuration intact. SIESTA finds that off-axis ECCD is indeed able to keep the location and phase of the edge magnetic island chain unchanged, but it may also lead to an undesired stochastization of parts of the confined plasma if the EC deposition radial profile becomes too narrow.

Production of primary mirror segments for the Giant Magellan Telescope

NASA Astrophysics Data System (ADS)

Martin, H. M.; Allen, R. G.; Burge, J. H.; Davis, J. M.; Davison, W. B.; Johns, M.; Kim, D. W.; Kingsley, J. S.; Law, K.; Lutz, R. D.; Strittmatter, P. A.; Su, P.; Tuell, M. T.; West, S. C.; Zhou, P.

2014-07-01

Segment production for the Giant Magellan Telescope is well underway, with the off-axis Segment 1 completed, off-axis Segments 2 and 3 already cast, and mold construction in progress for the casting of Segment 4, the center segment. All equipment and techniques required for segment fabrication and testing have been demonstrated in the manufacture of Segment 1. The equipment includes a 28 m test tower that incorporates four independent measurements of the segment's figure and geometry. The interferometric test uses a large asymmetric null corrector with three elements including a 3.75 m spherical mirror and a computer-generated hologram. For independent verification of the large-scale segment shape, we use a scanning pentaprism test that exploits the natural geometry of the telescope to focus collimated light to a point. The Software Configurable Optical Test System, loosely based on the Hartmann test, measures slope errors to submicroradian accuracy at high resolution over the full aperture. An enhanced laser tracker system guides the figuring through grinding and initial polishing. All measurements agree within the expected uncertainties, including three independent measurements of radius of curvature that agree within 0.3 mm. Segment 1 was polished using a 1.2 m stressed lap for smoothing and large-scale figuring, and a set of smaller passive rigid-conformal laps on an orbital polisher for deterministic small-scale figuring. For the remaining segments, the Mirror Lab is building a smaller, orbital stressed lap to combine the smoothing capability with deterministic figuring.

Regularized Biot-Savart Laws for Modeling Magnetic Configurations with Flux Ropes

NASA Astrophysics Data System (ADS)

Titov, V. S.; Downs, C.; Mikic, Z.; Torok, T.; Linker, J.

2017-12-01

Many existing models assume that magnetic flux ropes play a key role in solar flares and coronal mass ejections (CMEs). It is therefore important to develop efficient methods for constructing flux-rope configurations constrained by observed magnetic data and the initial morphology of CMEs. For this purpose, we have derived and implemented a compact analytical form that represents the magnetic field of a thin flux rope with an axis of arbitrary shape and a circular cross-section. This form implies that the flux rope carries axial current I and axial flux F, so that the respective magnetic field is the curl of the sum of toroidal and poloidal vector potentials proportional to I and F, respectively. We expressed the vector potentials in terms of modified Biot-Savart laws whose kernels are regularized at the axis in such a way that these laws define a cylindrical force-free flux rope with a parabolic profile of the axial current density, when the axis is straight. For the cases we have studied so far, we determined the shape of the rope axis by following the polarity inversion line of the eruptions' source region, using observed magnetograms. The height variation along the axis and other flux-rope parameters are estimated by means of potential field extrapolations. Using this heuristic approach, we were able to construct pre-eruption configurations for the 2009 February13 and 2011 October 1 CME events. These applications demonstrate the flexibility and efficiency of our new method for energizing pre-eruptive configurations in MHD simulations of CMEs. We discuss possible ways of optimizing the axis paths and other extensions of the method in order to make it more useful and robust. Research supported by NSF, NASA's HSR and LWS Programs, and AFOSR.

Correlating off-axis tension tests to shear modulus of wood-based panels

Treesearch

Edmond P. Saliklis; Robert H. Falk

2000-01-01

The weakness of existing relationships correlating off-axis modulus of elasticity E q to shear modulus G 12 for wood composite panels is demonstrated through presentation of extensive experimental data. A new relationship is proposed that performs better than existing equations found in the literature. This relationship can be manipulated to calculate the shear modulus...

Study on imaging spectrometer with smile and keystone eliminated

NASA Astrophysics Data System (ADS)

Zhang, Xiaolong; Yu, Kun; Zhang, Jun

2017-03-01

The formulas of image height in two-dimensional field about Gaussian and tilted imaging system of grating-based imaging spectrometer instrument (GISI) are deduced firstly, and the determined expressions of smile and keystone of GISI are obtained. It is proposed to correct the smile with off-axis lens, and the elimination effect of the smile is studied by means of spatial ray tracing. By controlling the degree of off-axis and the distribution of focal power of the off-axis lens, the long-wave infrared imaging spectrometer with well-eliminated smile and keystone is designed. The maximum of smile and keystone at working wavelengths in all fields of view are less than 8.57 μm and 13.33 μm, respectively.

Observation of hole accumulation in Ge/Si core/shell nanowires using off-axis electron holography.

PubMed

Li, Luying; Smith, David J; Dailey, Eric; Madras, Prashanth; Drucker, Jeff; McCartney, Martha R

2011-02-09

Hole accumulation in Ge/Si core/shell nanowires (NWs) has been observed and quantified using off-axis electron holography and other electron microscopy techniques. The epitaxial [110]-oriented Ge/Si core/shell NWs were grown on Si (111) substrates by chemical vapor deposition through the vapor-liquid-solid growth mechanism. High-angle annular-dark-field scanning transmission electron microscopy images and off-axis electron holograms were obtained from specific NWs. The excess phase shifts measured by electron holography across the NWs indicated the presence of holes inside the Ge cores. Calculations based on a simplified coaxial cylindrical model gave hole densities of (0.4 ± 0.2) /nm(3) in the core regions.

Electromagnetic fields backscattered from an s-shaped inlet cavity with an absorber coating on its inner walls

NASA Technical Reports Server (NTRS)

Burkholder, R. J.; Chuang, C. W.; Pathak, P. H.

1987-01-01

The EM backscatter from a two-dimensional S-shaped inlet cavity is analyzed using three different techniques, namely a hybrid combination of asymptotic high frequency and modal methods, an integral equation method, and the geometrical optics ray method, respectively. This inlet has a thin absorber coating on its perfectly conducting inner walls and the planar interior termination is made perfectly conducting. The effect of the absorber on the inner wall is treated via a perturbation scheme in the hybrid approach where it is assumed that the loss is sufficiently small for the method to be valid. The results are compared with the backscatter from a straight inlet cavity to evaluate the effect of offsetting the termination in the S-bend configuration such that it is not visible from the open end of the inlet. The envelope of the backscatter pattern for the straight inlet is always seen to peak around the forward axis due to the large return from the directly visible termination, and the pattern envelope tapers off away from the forward axis. Offsetting the termination causes the envelope of the backscatter pattern to flatten out, thereby reducing the return near the forward axis by several dB. The absorber coating reduces the pattern level of the straight inlet in directions away from the forward axis but has little effect on the peak near the axis; furthermore, the absorber coating is seen to consistently reduce the backscatter from the S-bend inlet for almost all incidence angles. The hybrid method gives excellent agreement with experimental data and with the integral equation solution, whereas, the geometrical optics ray tracing method is able to generally predict the average of the bachscatter pattern but not the pattern details.

Steerable vertical to horizontal energy transducer for mobile robots

DOEpatents

Spletzer, Barry L.; Fischer, Gary J.; Feddema, John T.

2001-01-01

The present invention provides a steerable vertical to horizontal energy transducer for mobile robots that less complex and requires less power than two degree of freedom tilt mechanisms. The present invention comprises an end effector that, when mounted with a hopping actuator, translates along axis (typically vertical) actuation into combined vertical and horizontal motion. The end effector, or foot, mounts with an end of the actuator that moves toward the support surface (typically a floor or the earth). The foot is shaped so that the first contact with the support surface is off the axis of the actuator. Off-axis contact with the support surface generates an on-axis force (typically resulting in vertical motion) and a moment orthogonal to the axis. The moment initiates a horizontal tumbling motion, and tilts the actuator so that its axis is oriented with a horizontal component and continued actuation generates both vertical and horizontal force.

Reactor Pressure Vessel Fracture Analysis Capabilities in Grizzly

DOE Office of Scientific and Technical Information (OSTI.GOV)

Spencer, Benjamin; Backman, Marie; Chakraborty, Pritam

2015-03-01

Efforts have been underway to develop fracture mechanics capabilities in the Grizzly code to enable it to be used to perform deterministic fracture assessments of degraded reactor pressure vessels (RPVs). Development in prior years has resulted a capability to calculate -integrals. For this application, these are used to calculate stress intensity factors for cracks to be used in deterministic linear elastic fracture mechanics (LEFM) assessments of fracture in degraded RPVs. The -integral can only be used to evaluate stress intensity factors for axis-aligned flaws because it can only be used to obtain the stress intensity factor for pure Mode Imore » loading. Off-axis flaws will be subjected to mixed-mode loading. For this reason, work has continued to expand the set of fracture mechanics capabilities to permit it to evaluate off-axis flaws. This report documents the following work to enhance Grizzly’s engineering fracture mechanics capabilities for RPVs: • Interaction Integral and -stress: To obtain mixed-mode stress intensity factors, a capability to evaluate interaction integrals for 2D or 3D flaws has been developed. A -stress evaluation capability has been developed to evaluate the constraint at crack tips in 2D or 3D. Initial verification testing of these capabilities is documented here. • Benchmarking for axis-aligned flaws: Grizzly’s capabilities to evaluate stress intensity factors for axis-aligned flaws have been benchmarked against calculations for the same conditions in FAVOR. • Off-axis flaw demonstration: The newly-developed interaction integral capabilities are demon- strated in an application to calculate the mixed-mode stress intensity factors for off-axis flaws. • Other code enhancements: Other enhancements to the thermomechanics capabilities that relate to the solution of the engineering RPV fracture problem are documented here.« less

High frequency capacitance-voltage characteristics of thermally grown SiO2 films on beta-SiC

NASA Technical Reports Server (NTRS)

Tang, S. M.; Berry, W. B.; Kwor, R.; Zeller, M. V.; Matus, L. G.

1990-01-01

Silicon dioxide films grown under dry and wet oxidation environment on beta-SiC films have been studied. The beta-SiC films had been heteroepitaxially grown on both on-axis and 2-deg off-axis (001) Si substrates. Capacitance-voltage and conductance-voltage characteristics of metal-oxide-semiconductor structures were measured in a frequency range of 10 kHz to 1 MHz. From these measurements, the interface trap density and the effective fixed oxide charge density were observed to be generally lower for off-axis samples.

On the maximum off-axis gain of symmetrical pencil-beam antennas

NASA Technical Reports Server (NTRS)

Sawitz, P. H.

1977-01-01

For a general class of symmetrical pencil-beam antennas, the gain at a given off-axis angle can be maximized by choosing the proper antenna size. The maximum gain at the given angle relative to the on-axis gain is independent of the given angle and dependent only on the main-beam pattern. It is computed here for four commonly used gain functions. Its value, in all cases, is close to 4 dB. This result is important in the definition of service areas for communication and broadcast satellites.

Endurance testing of downstream cathodes on a low-power MPD thruster

NASA Technical Reports Server (NTRS)

Burkhart, J. A.; Rose, J. R.

1974-01-01

A low-power MPD thruster with downstream cathode was tested for endurance with a series of hollow cathode designs. Failure modes and failure mechanisms were identified. A new hollow cathode (with rod inserts) has emerged which shows promise for long life. The downstream positioning of the cathode was also changed from an on-axis location to an off-axis location. Data are presented for a 1332-hour life test of this new hollow cathode located at the new off-axis location. Xenon propellant was used.

Flat-field anastigmatic mirror objective for high-magnification extreme ultraviolet microscopy

NASA Astrophysics Data System (ADS)

Toyoda, Mitsunori

2015-08-01

To apply high-definition microscopy to the extreme ultraviolet (EUV) region in practice, i.e. to enable in situ observation of living tissue and the at-wavelength inspection of lithography masks, we constructed a novel reflective objective made of three multilayer mirrors. This objective is configured as a two-stage imaging system made of a Schwarzschild two-mirror system as the primary objective and an additional magnifier with a single curved mirror. This two-stage configuration can provide a high magnification of 1500, which is suitable for real-time observation with an EUV charge coupled device (CCD) camera. Besides, since off-axis aberrations can be corrected by the magnifier, which provides field flattener optics, we are able to configure the objective as a flat-field anastigmatic system, in which we will have a diffraction-limited spatial resolution over a large field-of-view. This paper describes in detail the optical design of the present objective. After calculating the closed-form equations representing the third-order aberrations of the objective, we apply these equations to practical design examples with a numerical aperture of 0.25 and an operation wavelength of 13.5 nm. We also confirm the imaging performances of this novel design by using the numerical ray-tracing method.

Two-point motional Stark effect diagnostic for Madison Symmetric Torus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ko, J.; Den Hartog, D. J.; Caspary, K. J.

2010-10-15

A high-precision spectral motional Stark effect (MSE) diagnostic provides internal magnetic field measurements for Madison Symmetric Torus (MST) plasmas. Currently, MST uses two spatial views - on the magnetic axis and on the midminor (off-axis) radius, the latter added recently. A new analysis scheme has been developed to infer both the pitch angle and the magnitude of the magnetic field from MSE spectra. Systematic errors are reduced by using atomic data from atomic data and analysis structure in the fit. Reconstructed current density and safety factor profiles are more strongly and globally constrained with the addition of the off-axis radiusmore » measurement than with the on-axis one only.« less

Off-axis current drive and real-time control of current profile in JT-60U

NASA Astrophysics Data System (ADS)

Suzuki, T.; Ide, S.; Oikawa, T.; Fujita, T.; Ishikawa, M.; Seki, M.; Matsunaga, G.; Hatae, T.; Naito, O.; Hamamatsu, K.; Sueoka, M.; Hosoyama, H.; Nakazato, M.; JT-60 Team

2008-04-01

Aiming at optimization of current profile in high-β plasmas for higher confinement and stability, a real-time control system of the minimum of the safety factor (qmin) using the off-axis current drive has been developed. The off-axis current drive can raise the safety factor in the centre and help to avoid instability that limits the performance of the plasma. The system controls the injection power of lower-hybrid waves, and hence its off-axis driven current in order to control qmin. The real-time control of qmin is demonstrated in a high-β plasma, where qmin follows the temporally changing reference qmin,ref from 1.3 to 1.7. Applying the control to another high-β discharge (βN = 1.7, βp = 1.5) with m/n = 2/1 neo-classical tearing mode (NTM), qmin was raised above 2 and the NTM was suppressed. The stored energy increased by 16% with the NTM suppressed, since the resonant rational surface was eliminated. For the future use for current profile control, current density profile for off-axis neutral beam current drive (NBCD) is for the first time measured, using the motional Stark effect diagnostic. Spatially localized NBCD profile was clearly observed at the normalized minor radius ρ of about 0.6-0.8. The location was also confirmed by multi-chordal neutron emission profile measurement. The total amount of the measured beam driven current was consistent with the theoretical calculation using the ACCOME code. The CD location in the calculation was inward shifted than the measurement.

When Will It Be ...?: U.S. Naval Observatory Sidereal Time and Julian Date Calculators

NASA Astrophysics Data System (ADS)

Chizek Frouard, Malynda R.; Lesniak, Michael V.; Bartlett, Jennifer L.

2017-01-01

Sidereal time and Julian date are two values often used in observational astronomy that can be tedious to calculate. Fortunately, the U.S. Naval Observatory (USNO) has redesigned its on-line Sidereal Time and Julian Date (JD) calculators to provide data through an Application Programming Interface (API). This flexible interface returns dates and times in JavaScript Object Notation (JSON) that can be incorporated into third-party websites or applications.Via the API, Sidereal Time can be obtained for any location on Earth for any date occurring in the current, previous, or subsequent year. Up to 9999 iterations of sidereal time data with intervals from 1 second to 1095 days can be generated, as long as the data doesn’t extend past the date limits. The API provides the Gregorian calendar date and time (in UT1), Greenwich Mean Sidereal Time, Greenwich Apparent Sidereal Time, Local Mean Sidereal Time, Local Apparent Sidereal Time, and the Equation of the Equinoxes.Julian Date can be converted to calendar date, either Julian or Gregorian as appropriate, for any date between JD 0 (January 1, 4713 BCE proleptic Julian) and JD 5373484 (December 31, 9999 CE Gregorian); the reverse calendar date to Julian Date conversion is also available. The calendar date and Julian Date are returned for all API requests; the day of the week is also returned for Julian Date to calendar date conversions.On-line documentation for using all USNO API-enabled calculators, including sample calls, is available (http://aa.usno.navy.mil/data/docs/api.php).For those who prefer using traditional data input forms, Sidereal Time can still be accessed at http://aa.usno.navy.mil/data/docs/siderealtime.php, and the Julian Date Converter at http://aa.usno.navy.mil/data/docs/JulianDate.php.

Analysis of off-axis tension test of wood specimens

Treesearch

Jen Y. Liu

2002-01-01

This paper presents a stress analysis of the off-axis tension test of clear wood specimens based on orthotropic elasticity theory. The effects of Poisson's ratio and shear coupling coefficient on stress distribution are analyzed in detail. The analysis also provides a theoretical foundation for the selection of a 10° grain angle in wood specimens for the...

High aperture off-axis parabolic mirror applied in digital holographic microscopy

NASA Astrophysics Data System (ADS)

Kalenkov, Georgy S.; Kalenkov, Sergey G.; Shtanko, Alexander E.

2018-04-01

An optical scheme of recording digital holograms of micro-objects based on high numerical aperture off-axis parabolic mirror forming a high aperture reference wave is suggested. Registration of digital holograms based on the proposed optical scheme is confirmed experimentally. Application of the proposed approach for hyperspectral holograms registration of micro-objects in incoherent light is discussed.

Description of the 3 MW SWT-3 wind turbine at San Gorgonio Pass, California

NASA Technical Reports Server (NTRS)

Rybak, S. C.

1982-01-01

The SWT-3 wind turbine, a microprocessor controlled three bladed variable speed upwind machine with a 3MW rating that is presently operational and undergoing system testing, is discussed. The tower, a rigid triangular truss configuration, is rotated about its vertical axis to position the wind turbine into the prevailing wind. The blades rotate at variable speed in order to maintain an optimum 6 to 1 tip speed ratio between cut in and fated wind velocity, thereby maximizing power extraction from the wind. Rotor variable speed is implemented by the use of a hydrostatic transmission consisting of fourteen fixed displacement pumps operating in conjunction with eighteen variable displacement motors. Full blade pitch with on-off hydraulic actuation is used to maintain 3MW of output power.

Development of a high brightness ultrafast Transmission Electron Microscope based on a laser-driven cold field emission source.

PubMed

Houdellier, F; Caruso, G M; Weber, S; Kociak, M; Arbouet, A

2018-03-01

We report on the development of an ultrafast Transmission Electron Microscope based on a cold field emission source which can operate in either DC or ultrafast mode. Electron emission from a tungsten nanotip is triggered by femtosecond laser pulses which are tightly focused by optical components integrated inside a cold field emission source close to the cathode. The properties of the electron probe (brightness, angular current density, stability) are quantitatively determined. The measured brightness is the largest reported so far for UTEMs. Examples of imaging, diffraction and spectroscopy using ultrashort electron pulses are given. Finally, the potential of this instrument is illustrated by performing electron holography in the off-axis configuration using ultrashort electron pulses. Copyright © 2017 Elsevier B.V. All rights reserved.

Two-dimensional straightness measurement based on optical knife-edge sensing

NASA Astrophysics Data System (ADS)

Wang, Chen; Zhong, Fenghe; Ellis, Jonathan D.

2017-09-01

Straightness error is a parasitic translation along a perpendicular direction to the primary displacement axis of a linear stage. The parasitic translations could be coupled into other primary displacement directions of a multi-axis platform. Hence, its measurement and compensation are critical in precision multi-axis metrology, calibration, and manufacturing. This paper presents a two-dimensional (2D) straightness measurement configuration based on 2D optical knife-edge sensing, which is simple, light-weight, compact, and easy to align. It applies a 2D optical knife-edge to manipulate the diffraction pattern sensed by a quadrant photodetector, whose output voltages could derive 2D straightness errors after a calibration process. This paper analyzes the physical model of the configuration and performs simulations and experiments to study the system sensitivity, measurement nonlinearity, and error sources. The results demonstrate that the proposed configuration has higher sensitivity and insensitive to beam's vibration, compared with the conventional configurations without using the knife-edge, and could achieve ±0.25 μ m within a ±40 μ m measurement range along a 40 mm primary axial motion.

RESONATORS. MODES: Modes of a plano - spherical laser resonator with the Gaussian gain distribution of the active medium

NASA Astrophysics Data System (ADS)

Malyutin, A. A.

2007-03-01

Modes of a laser with plano-spherical degenerate and nondegenerate resonators are calculated upon diode pumping producing the Gaussian gain distribution in the active medium. Axially symmetric and off-axis pumpings are considered. It is shown that in the first case the lowest Hermite-Gaussian mode is excited with the largest weight both in the degenerate and nondegenerate resonator if the pump level is sufficiently high or the characteristic size wg of the amplifying region greatly exceeds the mode radius w0. The high-order Ince-Gaussian modes are excited upon weak off-axis pumping in the nondegenerate resonator both in the absence and presence of the symmetry of the gain distribution with respect to the resonator axis. It is found that when the level of off-axis symmetric pumping of the resonator is high enough, modes with the parameters of the TEM00 mode periodically propagating over a closed path in the resonator can exist. The explanation of this effect is given.

Ten Deg Off-Axis Test for Shear Properties in Fiber Composites

NASA Technical Reports Server (NTRS)

Chamis, C. C.; Sinclair, J. H.

1977-01-01

A combined theoretical and experimental investigation was conducted to assess the suitability of the 10 deg off-axis tensile test specimen for the intralaminar shear characterization of unidirectional composites. Composite mechanics, a combined-stress failure criterion, and a finite variation across the specimen width and the relative stress and strain magnitudes at the 10 deg plane. Strain gages were used to measure the strain variation across the specimen width at specimen midlength and near the end tabs. Specimens from Mod-I/epoxy, T-300/epoxy, and S-glass/epoxy were used in the experimental program. It was found that the 10 deg off-axis tensile test specimen is suitable for intralaminar shear characterization, and it is recommended that it should be considered as a possible standard test specimen for such a characterization.

Sparsity based terahertz reflective off-axis digital holography

NASA Astrophysics Data System (ADS)

Wan, Min; Muniraj, Inbarasan; Malallah, Ra'ed; Zhao, Liang; Ryle, James P.; Rong, Lu; Healy, John J.; Wang, Dayong; Sheridan, John T.

2017-05-01

Terahertz radiation lies between the microwave and infrared regions in the electromagnetic spectrum. Emitted frequencies range from 0.1 to 10 THz with corresponding wavelengths ranging from 30 μm to 3 mm. In this paper, a continuous-wave Terahertz off-axis digital holographic system is described. A Gaussian fitting method and image normalisation techniques were employed on the recorded hologram to improve the image resolution. A synthesised contrast enhanced hologram is then digitally constructed. Numerical reconstruction is achieved using the angular spectrum method of the filtered off-axis hologram. A sparsity based compression technique is introduced before numerical data reconstruction in order to reduce the dataset required for hologram reconstruction. Results prove that a tiny amount of sparse dataset is sufficient in order to reconstruct the hologram with good image quality.

High speed phase retrieval of in-line holograms by the assistance of corresponding off-axis holograms.

PubMed

Orzó, László

2015-06-29

Retrieving correct phase information from an in-line hologram is difficult as the object wave field and the diffractions of the zero order and the conjugate object term overlap. The existing iterative numerical phase retrieval methods are slow, especially in the case of high Fresnel number systems. Conversely, the reconstruction of the object wave field from an off-axis hologram is simple, but due to the applied spatial frequency filtering the achievable resolution is confined. Here, a new, high-speed algorithm is introduced that efficiently incorporates the data of an auxiliary off-axis hologram in the phase retrieval of the corresponding in-line hologram. The efficiency of the introduced combined phase retrieval method is demonstrated by simulated and measured holograms.

Apparatus for and method of correcting for astigmatism in a light beam reflected off of a light reflecting surface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sawicki, R.H.; Sweatt, W.

1987-03-03

An apparatus is described for correcting for astigmatism in a light beam reflected off of a light reflecting surface, comprising: (a) a first means defining a flat, rectangular light reflecting surface which is resiliently bendable, to a limited extent, into different concave and/or convex cylindrical curvatures about a particular axis. The first means is configured so that the light reflecting surface can be adjustably bent into the selected cylindrical curvature by applying a particular bending moment to the first means with respect to the surface, depending upon the curvature desired. The first means includes an integrally formed body member havingmore » a main plate-like segment including a front fact defining the light reflecting surface and a pair of spaced-apart flange segments extending rearwardly of the main segment; and (b) second means acting on the first means for adjustably bending the light reflecting surface into a particular selected one of the different cylindrical curvatures, depending upon the astigmatism to be corrected for.« less

Life cycle cost modeling of conceptual space vehicles

NASA Technical Reports Server (NTRS)

Ebeling, Charles

1993-01-01

This paper documents progress to date by the University of Dayton on the development of a life cycle cost model for use during the conceptual design of new launch vehicles and spacecraft. This research is being conducted under NASA Research Grant NAG-1-1327. This research effort changes the focus from that of the first two years in which a reliability and maintainability model was developed to the initial development of a life cycle cost model. Cost categories are initially patterned after NASA's three axis work breakdown structure consisting of a configuration axis (vehicle), a function axis, and a cost axis. The focus will be on operations and maintenance costs and other recurring costs. Secondary tasks performed concurrent with the development of the life cycle costing model include continual support and upgrade of the R&M model. The primary result of the completed research will be a methodology and a computer implementation of the methodology to provide for timely cost analysis in support of the conceptual design activities. The major objectives of this research are: to obtain and to develop improved methods for estimating manpower, spares, software and hardware costs, facilities costs, and other cost categories as identified by NASA personnel; to construct a life cycle cost model of a space transportation system for budget exercises and performance-cost trade-off analysis during the conceptual and development stages; to continue to support modifications and enhancements to the R&M model; and to continue to assist in the development of a simulation model to provide an integrated view of the operations and support of the proposed system.

Ethics, a neglected dimension of power relationships of physician leaders.

PubMed

Chervenak, Frank A; McCullough, Laurence B; Baril, Thomas E

2006-09-01

Physician leaders in obstetrics and gynecology find themselves in complex power relationships with administrative subordinates, administrative peers, and administrative superiors. The ethical dimensions of these power relationships have not been examined previously. The authors draw on the work of 3 major historic figures (John Gregory, Thomas Hobbes, and Friedrich Hoffmann) to identify for the first time 3 major types of power relationships and organizational cultures. Gregorian power relationships and organizational cultures are characterized by shared fiduciary responsibility that advances the core mission of a health care organization. Hobbesian power relationships and organizational cultures are characterized by relentless self-interest in a zero-sum game. Hoffmannian power relationships and organizational cultures are characterized by enlightened self-interest in a win-win game. The authors analyze the ethical dimensions of power relationships of physician leaders with subordinates, peers, and superiors and of organizational cultures. The authors support transformational leadership toward Gregorian power relationships and organizational cultures, using, when necessary, Hoffmannian power relationships and organizational cultures as a way station.

Large-field high-contrast hard x-ray Zernike phase-contrast nano-imaging beamline at Pohang Light Source.

PubMed

Lim, Jun; Park, So Yeong; Huang, Jung Yun; Han, Sung Mi; Kim, Hong-Tae

2013-01-01

We developed an off-axis-illuminated zone-plate-based hard x-ray Zernike phase-contrast microscope beamline at Pohang Light Source. Owing to condenser optics-free and off-axis illumination, a large field of view was achieved. The pinhole-type Zernike phase plate affords high-contrast images of a cell with minimal artifacts such as the shade-off and halo effects. The setup, including the optics and the alignment, is simple and easy, and allows faster and easier imaging of large bio-samples.

Axis-1 diode simulations I: standard 2-inch cathode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ekdahl, Carl

2011-01-11

The standard configuration of the DARHT Axis-I diode features a 5.08-cm diameter velvet emitter mounted in the flat surface of the cathode shroud. The surface of the velvet is slightly recessed {approx}2.5 mm. This configuration produces a 1.75 kA beam when a 3.8-MV pulse is applied to the anode-cathode (AK) gap. This note addresses some of the physics of this diode through the use of finite-element simulations.

Soft actuators and soft actuating devices

DOEpatents

Yang, Dian; Whitesides, George M.

2017-10-17

A soft buckling linear actuator is described, including: a plurality of substantially parallel bucklable, elastic structural components each having its longest dimension along a first axis; and a plurality of secondary structural components each disposed between and bridging two adjacent bucklable, elastic structural components; wherein every two adjacent bucklable, elastic structural components and the secondary structural components in-between define a layer comprising a plurality of cells each capable of being connected with a fluid inflation or deflation source; the secondary structural components from two adjacent layers are not aligned along a second axis perpendicular to the first axis; and the secondary structural components are configured not to buckle, the bucklable, elastic structural components are configured to buckle along the second axis to generate a linear force, upon the inflation or deflation of the cells. Methods of actuation using the same are also described.

Improved Strength and Toughness of Carbon Woven Fabric Composites with Functionalized MWCNTs

PubMed Central

Soliman, Eslam; Kandil, Usama; Reda Taha, Mahmoud

2014-01-01

This investigation examines the role of carboxyl functionalized multi-walled carbon nanotubes (COOH-MWCNTs) in the on- and off-axis flexure and the shear responses of thin carbon woven fabric composite plates. The chemically functionalized COOH-MWCNTs were used to fabricate epoxy nanocomposites and, subsequently, carbon woven fabric plates to be tested on flexure and shear. In addition to the neat epoxy, three loadings of COOH-MWCNTs were examined: 0.5 wt%, 1.0 wt% and 1.5 wt% of epoxy. While no significant statistical difference in the flexure response of the on-axis specimens was observed, significant increases in the flexure strength, modulus and toughness of the off-axis specimens were observed. The average increase in flexure strength and flexure modulus with the addition of 1.5 wt% COOH-MWCNTs improved by 28% and 19%, respectively. Finite element modeling is used to demonstrate fiber domination in on-axis flexure behavior and matrix domination in off-axis flexure behavior. Furthermore, the 1.5 wt% COOH-MWCNTs increased the toughness of carbon woven composites tested on shear by 33%. Microstructural investigation using Fourier Transform Infrared Spectroscopy (FTIR) proves the existence of chemical bonds between the COOH-MWCNTs and the epoxy matrix. PMID:28788698

47 CFR 25.223 - Off-axis EIRP spectral density limits for feeder link earth stations in the 17/24 GHz BSS.

Code of Federal Regulations, 2013 CFR

2013-10-01

... feeder link earth stations in the 17/24 GHz BSS. 25.223 Section 25.223 Telecommunication FEDERAL....223 Off-axis EIRP spectral density limits for feeder link earth stations in the 17/24 GHz BSS. (a) This section applies to all applications for earth station licenses in the 17/24 GHz BSS frequency...

47 CFR 25.223 - Off-axis EIRP spectral density limits for feeder link earth stations in the 17/24 GHz BSS.

Code of Federal Regulations, 2011 CFR

2011-10-01

... feeder link earth stations in the 17/24 GHz BSS. 25.223 Section 25.223 Telecommunication FEDERAL....223 Off-axis EIRP spectral density limits for feeder link earth stations in the 17/24 GHz BSS. (a) This section applies to all applications for earth station licenses in the 17/24 GHz BSS frequency...

47 CFR 25.223 - Off-axis EIRP spectral density limits for feeder link earth stations in the 17/24 GHz BSS.

Code of Federal Regulations, 2012 CFR

2012-10-01

... feeder link earth stations in the 17/24 GHz BSS. 25.223 Section 25.223 Telecommunication FEDERAL....223 Off-axis EIRP spectral density limits for feeder link earth stations in the 17/24 GHz BSS. (a) This section applies to all applications for earth station licenses in the 17/24 GHz BSS frequency...

47 CFR 25.223 - Off-axis EIRP spectral density limits for feeder link earth stations in the 17/24 GHz BSS.

Code of Federal Regulations, 2010 CFR

2010-10-01

... feeder link earth stations in the 17/24 GHz BSS. 25.223 Section 25.223 Telecommunication FEDERAL....223 Off-axis EIRP spectral density limits for feeder link earth stations in the 17/24 GHz BSS. (a) This section applies to all applications for earth station licenses in the 17/24 GHz BSS frequency...

Dust Tolerant Connectors

NASA Technical Reports Server (NTRS)

Mueller, Robert P. (Inventor); Lewis, Mark E. (Inventor); Bastin, Gary L. (Inventor); Branch, Matthew C. (Inventor); Carlson, Jeffrey W. (Inventor); Dokos, Adam G. (Inventor); Murtland, Kevin A. (Inventor); Nugent, Matthew W. (Inventor); Tamasy, Gabor J. (Inventor); Townsend, III, Ivan I. (Inventor)

2016-01-01

Methods and systems may provide for debris exclusion and removal apparatuses for connectors which have inverting end caps with a multi-axis lever configuration, inverting end caps with enlarged handle and/or side rail configurations, rotating end cap configurations, poppet valve configurations, O-ring configurations, filament barrier configurations, retractable cover configurations, clamshell end cap configurations, or any combination thereof. Apparatuses may also provide for an intelligent electrical connector system capable of detecting damage to or faults within a plurality of conductors and then rerouting the energy through a non-damaged spare conductor.

Refraction of sound by a shear layer - Experimental assessment

NASA Technical Reports Server (NTRS)

Schlinker, R. H.; Amiet, R. K.

1979-01-01

An experimental study was conducted to determine the refraction angle and amplitude changes associated with sound transmission through a circular, open jet shear layer. Both on-axis and off-axis acoustic source locations were used. Source frequency varied from 1 kHz to 10 kHz while freestream Mach number varied from 0.1 to 0.4. The experimental results were compared with an existing refraction theory which was extended to account for off-axis source positions. A simple experiment was also conducted to assess the importance of turbulence scattering between 1 kHz and 25 kHz.

Orientation-dependent tensile deformation and damage of a T700 carbon fiber/epoxy composite: A synchrotron-based study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bie, B. X.; Huang, J. Y.; Fan, D.

Uniaxial tensile experiments are conducted on a T700 carbon fiber/epoxy composite along various offaxis angles. Stressestrain curves are measured along with strain fields mapped via synchrotron x-ray digital image correlation, as well as computerized tomography. Elastic modulus and tensile strength decrease with increasing off-axis angles, while fracture strain exhibits a nonmonotonic trend as a combined result of tensile strength decrease and fracture mode transition. At high off-axis angles, strain field mapping demonstrates distinct tensile and shear strain localizations and deformation bands approximately along the fiber directions, while deformation is mainly achieved via continuous growth of tensile strain at low off-axismore » angles. Roughness of fracture planes decreases exponentially as the off-axis angle increases. The stressestrain curves, strain fields, tomography and fractographs show consistent features, and reveal a fracture mode transition from mainly tension (fiber fracture) to in-plane shear (interface debonding).« less

Production of Internal Transport Barriers via self-generated flows in Alcator C-Mod

NASA Astrophysics Data System (ADS)

Fiore, Catherine L.

2011-10-01

New results suggest that changes observed in the intrinsic toroidal rotation influence ITB formation in Alcator C-Mod that arise when the resonance for ICRF minority heating is positioned off-axis at or outside of the plasma half-radius. These ITBs form in a reactor relevant regime, without particle or momentum injection, with Ti ~Te, and with monotonic q profiles (qmin < 1). C-Mod H-mode plasmas exhibit strong intrinsic co-current rotation that increases with increasing stored energy without external drive. With the resonance position off-axis, the rotation decreases in the center of the plasma resulting in a radial rotation profile with a central well which deepens and moves farther off-axis when the ICRF resonance is at the plasma half-radius. This profile results in strong ExB shear (>1.5x105 Rad/sec) in the region where the ITB foot is observed. The self generated ExB shearing increases rapidly after the H-mode transition in off-axis ICRF heated discharges, before other profile changes are observed. Gyrokinetic analyses indicate that this spontaneous shearing rate is comparable to the linear ITG growth rate at the ITB location and may be responsible for stabilizing the underlying turbulence. Detailed measurement of the ion temperature demonstrates that the radial profile also flattens as the ICRF resonance position moves off axis. This decreases R/LTi in the barrier region, lessening the drive for the ITG turbulence and the resulting particle transport. The reduction in particle transport resulting from increase in core stability allows the neoclassical pinch to peak the density and pressure on axis. This suggests that spontaneous rotation is a potential tool for plasma profile control in reactor plasmas. The experimental results and corresponding gyrokinetic study will be presented. US-DoE DE-FC02-99ER54512 and DE-FG03-96ER54373.

Adjustable permanent magnet assembly for NMR and MRI

DOEpatents

Pines, Alexander; Paulsen, Jeffrey; Bouchard, Louis S; Blumich, Bernhard

2013-10-29

System and methods for designing and using single-sided magnet assemblies for magnetic resonance imaging (MRI) are disclosed. The single-sided magnet assemblies can include an array of permanent magnets disposed at selected positions. At least one of the permanent magnets can be configured to rotate about an axis of rotation in the range of at least +/-10 degrees and can include a magnetization having a vector component perpendicular to the axis of rotation. The single-sided magnet assemblies can further include a magnet frame that is configured to hold the permanent magnets in place while allowing the at least one of the permanent magnets to rotate about the axis of rotation.

Ion Beam Characterization of a NEXT Multi-Thruster Array Plume

NASA Technical Reports Server (NTRS)

Pencil, Eric J.; Foster, John E.; Patterson, Michael J.; Diaz, Esther M.; Van Noord, Jonathan L.; McEwen, Heather K.

2006-01-01

Three operational, engineering model, 7-kW ion thrusters and one instrumented, dormant thruster were installed in a cluster array in a large vacuum facility at NASA Glenn Research Center. A series of engineering demonstration tests were performed to evaluate the system performance impacts of operating various multiple-thruster configurations in an array. A suite of diagnostics was installed to investigate multiple-thruster operation impact on thruster performance and life, thermal interactions, and alternative system modes and architectures. The ion beam characterization included measuring ion current density profiles and ion energy distribution with Faraday probes and retarding potential analyzers, respectively. This report focuses on the ion beam characterization during single thruster operation, multiple thruster operation, various neutralizer configurations, and thruster gimbal articulation. Comparison of beam profiles collected during single and multiple thruster operation demonstrated the utility of superimposing single engine beam profiles to predict multi-thruster beam profiles. High energy ions were detected in the region 45 off the thruster axis, independent of thruster power, number of operating thrusters, and facility background pressure, which indicated that the most probable ion energy was not effected by multiple-thruster operation. There were no significant changes to the beam profiles collected during alternate thruster-neutralizer configurations, therefore supporting the viability of alternative system configuration options. Articulation of one thruster shifted its beam profile, whereas the beam profile of a stationary thruster nearby did not change, indicating there were no beam interactions which was consistent with the behavior of a collisionless beam expansion.

Structure and Dynamics of the Southeast Indian Ridge and Off-axis Volcanism, 129°E to 140°E: Preliminary Results of the STORM Cruise

NASA Astrophysics Data System (ADS)

Maia, M.; Briais, A.; Barrere, F.; Boulart, C.; Ceuleneer, G.; Ferreira, N.; Hanan, B. B.; Hemond, C.; MacLeod, S.; Maillard, A. L.; Merkuryev, S. A.; Park, S. H.; Revillon, S.; Ruellan, E.; Schohn, A.; Watson, S. J.; Yang, Y. S.

2015-12-01

We present observations of the South-East Indian Ridge (SEIR) collected during the STORM cruise (South Tasmania Ocean Ridge and Mantle) on the N/O L'Atalante early 2015. The SEIR between Australia and Antarctica displays large variations of axial morphology despite an almost constant intermediate spreading rate. The Australia-Antarctic Discordance (AAD) between 120°E and 128°E is a section of the mid-ocean ridge where the magma budget is abnormally low, and which marks the boundary between Indian and Pacific mantle domains with distinct geochemical isotopic compositions. The STORM project focuses on the area east of the discordance from 128 to 140°E, where gravity highs observed on satellite-derived maps of the flanks of the SEIR reveal numerous volcanic seamounts. A major objective of the STORM cruise was to test the hypothesis of a mantle flow from the Pacific to the Indian domains. We collected multibeam bathymetry and magnetic data between 136 and 138°E to map off-axis volcanic ridges up to 10 Ma-old crust. We mapped the SEIR axis between 129 and 140°E, and the northern part of the George V transform fault. We collected rock samples on seamounts and in the transform fault, basaltic glass samples along the ridge axis, and near-bottom samples and in-situ measurements in the water column. Our observations reveal that the off-axis seamounts form near the SEIR axis, and are not associated to off-axis deformation of the ocean floor. They show a general shallowing of the ridge axis from the AAD to the George V TF and the presence of robust axial segments near the transform fault. They allow us to describe the complex evolution of the transform fault system. They also permit to locate new hydrothermal systems along the ridge axis. STORM cruise scientific party: F. Barrere, C. Boulart, G. Ceuleneer, N. Ferreira, B. Hanan, C. Hémond, S. Macleod, M. Maia, A. Maillard, S. Merkuryev, S.H. Park, S. Révillon, E. Ruellan, A. Schohn, S. Watson, and Y.S. Yang.

Fos-defined activity in rat brainstem following centripetal acceleration.

PubMed

Kaufman, G D; Anderson, J H; Beitz, A J

1992-11-01

To identify rat brainstem nuclei involved in the initial, short-term response to a change in gravito-inertial force, adult Long-Evans rats were rotated in the horizontal plane for 90 min in complete darkness after they were eccentrically positioned off the axis of rotation (off-axis) causing a centripetal acceleration of 2 g. Neural activation was defined by the brainstem distribution of the c-fos primary response gene protein, Fos, using immunohistochemistry. The Fos labeling in off-axis animals was compared with that of control animals who were rotated on the axis of rotation (on-axis) with no centripetal acceleration, or who were restrained but not rotated. In the off-axis animals there was a significant labeling of neurons: in the inferior, medial, and y-group subnuclei of the vestibular complex; in subnuclei of the inferior olive, especially the dorsomedial cell column; in midbrain nuclei, including the interstitial nucleus of Cajal, nucleus of Darkschewitsch, Edinger-Westphal nucleus, and dorsolateral periaqueductal gray; in autonomic centers including the solitary nucleus, area postrema, and locus coeruleus; and in reticular nuclei including the lateral reticular nucleus and the lateral parabrachial nucleus. Also, there was greater Fos expression in the dorsomedial cell column, the principal inferior olive subnuclei, inferior vestibular nucleus, the dorsolateral central gray, and the locus coeruleus in animals who had their heads restrained compared to animals whose heads were not restrained. As one control, the vestibular neuroepithelium was destroyed by injecting sodium arsanilate into the middle ear, bilaterally. This resulted in a complete lack of Fos labeling in the vestibular nuclei and the inferior olive, and a significant reduction in labeling in other nuclei in the off-axis condition, indicating that these nuclei have a significant labyrinth-sensitive component to their Fos labeling. The data indicate that several novel brainstem regions, including the dorsomedial cell column of the inferior olive and the periaqueductal gray, as well as more traditional brainstem nuclei including vestibular and oculomotor related nuclei, respond to otolith activation during a sustained centripetal acceleration.

Highly Automated Module Production Incorporating Advanced Light Management

DOE Office of Scientific and Technical Information (OSTI.GOV)

Perelli-Minetti, Michael; Roof, Kyle

2015-08-11

The objective was to enable a high volume, cost effective solution for increasing the amount of light captured by PV modules through utilization of an advanced Light Re-directing Film and to follow a phased approach to develop and implement this new technology in order to achieve an expected power gain of up to 12 watts per module. Full size PV modules were manufactured using a new Light Redirecting Film (LRF) material applied to two different areas of PV modules in order to increase the amount of light captured by the modules. One configuration involved applying thin strips of LRF filmmore » over the tabbing ribbon on the cells in order to redirect the light that is normally absorbed by the tabbing ribbon to the active areas of the cells. A second configuration involved applying thin strips of LRF film over the white spaces between cells within a module in order to capture some of the light that is normally reflected from the white areas back through the front glass of the modules. Significant power increases of 1.4% (3.9 watts) and 1.0% (3.2 watts), respectively, compared to standard PV modules were measured under standard test conditions. The performance of PV modules with LRF applied to the tabbing ribbon was modeled. The results showed that the power increase provided by LRF depended greatly on the angle of incident light with the optimum performance only occurring when the light was within a narrow range of being perpendicular to the solar module. The modeling showed that most of the performance gain would be lost when the angle of incident light was greater than 28 degrees off axis. This effect made the orientation of modules with LRF applied to tabbing ribbons very important as modules mounted in “portrait” mode were predicted to provide little to no power gain from LRF under real world conditions. Based on these results, modules with LRF on tabbing ribbons would have to be mounted in “landscape” mode to realize a performance advantage. In addition, modeling showed that under diffuse lighting conditions such as when the sky is overcast, there would be no significant performance advantage for modules with LRF. Modules were sent to an outside contractor to measure the power performance under different angles of incident light in order to validate the modeling results. The measured data agreed very well with the modeling predictions and showed that the power gain for modules with LRF applied to tabbing ribbons was completely lost at an angle of 25 degrees off of perpendicular. At even larger angles, the power was lower than standard modules. From 35 degrees to 55 degrees off axis, the power loss was about 1.4% or equal to the power gain at the optimum condition of perfectly on-axis light.« less

Examination of the suitability of an implementation of the Jette localized heterogeneities fluence term L(1)(x,y,z) in an electron beam treatment planning algorithm

NASA Astrophysics Data System (ADS)

Rodebaugh, Raymond Francis, Jr.

2000-11-01

In this project we applied modifications of the Fermi- Eyges multiple scattering theory to attempt to achieve the goals of a fast, accurate electron dose calculation algorithm. The dose was first calculated for an ``average configuration'' based on the patient's anatomy using a modification of the Hogstrom algorithm. It was split into a measured central axis depth dose component based on the material between the source and the dose calculation point, and an off-axis component based on the physics of multiple coulomb scattering for the average configuration. The former provided the general depth dose characteristics along the beam fan lines, while the latter provided the effects of collimation. The Gaussian localized heterogeneities theory of Jette provided the lateral redistribution of the electron fluence by heterogeneities. Here we terminated Jette's infinite series of fluence redistribution terms after the second term. Experimental comparison data were collected for 1 cm thick x 1 cm diameter air and aluminum pillboxes using the Varian 2100C linear accelerator at Rush-Presbyterian- St. Luke's Medical Center. For an air pillbox, the algorithm results were in reasonable agreement with measured data at both 9 and 20 MeV. For the Aluminum pill box, there were significant discrepancies between the results of this algorithm and experiment. This was particularly apparent for the 9 MeV beam. Of course a one cm thick Aluminum heterogeneity is unlikely to be encountered in a clinical situation; the thickness, linear stopping power, and linear scattering power of Aluminum are all well above what would normally be encountered. We found that the algorithm is highly sensitive to the choice of the average configuration. This is an indication that the series of fluence redistribution terms does not converge fast enough to terminate after the second term. It also makes it difficult to apply the algorithm to cases where there are no a priori means of choosing the best average configuration or where there is a complex geometry containing both lowly and highly scattering heterogeneities. There is some hope of decreasing the sensitivity to the average configuration by including portions of the next term of the localized heterogeneities series.

Effects of an Off-Axis Pivoting Elliptical Training Program on Gait Function in Persons With Spastic Cerebral Palsy: A Preliminary Study.

PubMed

Tsai, Liang-Ching; Ren, Yupeng; Gaebler-Spira, Deborah J; Revivo, Gadi A; Zhang, Li-Qun

2017-07-01

This preliminary study examined the effects of off-axis elliptical training on reducing transverse-plane gait deviations and improving gait function in 8 individuals with cerebral palsy (CP) (15.5 ± 4.1 years) who completed an training program using a custom-made elliptical trainer that allows transverse-plane pivoting of the footplates during exercise. Lower-extremity off-axis control during elliptical exercise was evaluated by quantifying the root-mean-square and maximal angular displacement of the footplate pivoting angle. Lower-extremity pivoting strength was assessed. Gait function and balance were evaluated using 10-m walk test, 6-minute-walk test, and Pediatric Balance Scale. Toe-in angles during gait were quantified. Participants with CP demonstrated a significant decrease in the pivoting angle (root mean square and maximal angular displacement; effect size, 1.00-2.00) and increase in the lower-extremity pivoting strength (effect size = 0.91-1.09) after training. Reduced 10-m walk test time (11.9 ± 3.7 seconds vs. 10.8 ± 3.0 seconds; P = 0.004; effect size = 1.46), increased Pediatric Balance Scale score (43.6 ± 12.9 vs. 45.6 ± 10.8; P = 0.042; effect size = 0.79), and decreased toe-in angle (3.7 ± 10.5 degrees vs. 0.7 ± 11.7 degrees; P = 0.011; effect size = 1.22) were observed after training. We present an intervention to challenge lower-extremity off-axis control during a weight-bearing and functional activity for individuals with CP. Our preliminary findings suggest that this intervention was effective in enhancing off-axis control, gait function, and balance and reducing in-toeing gait in persons with CP.

Visual Costs of the Inhomogeneity of Luminance and Contrast by Viewing LCD-TFT Screens Off-Axis.

PubMed

Ziefle, Martina; Groeger, Thomas; Sommer, Dietmar

2003-01-01

In this study the anisotropic characteristics of TFT-LCD (Thin-Film-Transistor-Liquid Crystal Display) screens were examined. Anisotropy occurs as the distribution of luminance and contrast changes over the screen surface due to different viewing angles. On the basis of detailed photometric measurements the detection performance in a visual reaction task was measured in different viewing conditions. Viewing angle (0 degrees, frontal view; 30 degrees, off-axis; 50 degrees, off-axis) as well as ambient lighting (a dark or illuminated room) were varied. Reaction times and accuracy of detection performance were recorded. Results showed TFT's anisotropy to be a crucial factor deteriorating performance. With an increasing viewing angle performance decreased. It is concluded that TFT's anisotropy is a limiting factor for overall suitability and usefulness of this new display technology.

A hydrostatic stress-dependent anisotropic model of viscoplasticity

NASA Technical Reports Server (NTRS)

Robinson, D. N.; Tao, Q.; Verrilli, M. J.

1994-01-01

A hydrostatic stress-dependent, anisotropic model of viscoplasticity is formulated as an extension of Bodner's model. This represents a further extension of the isotropic Bodner model over that made to anisotropy by Robinson and MitiKavuma. Account is made of the inelastic deformation that can occur in metallic composites under hydrostatic stress. A procedure for determining the material parameters is identified that is virtually identical to the established characterization procedure for the original Bodner model. Characterization can be achieved using longitudinal/transverse tensile and shear tests and hydrostatic stress tests; alternatively, four off-axis tensile tests can be used. Conditions for a yield stress minimum under off-axis tension are discussed. The model is applied to a W/Cu composite; characterization is made using off-axis tensile data generated at NASA Lewis Research Center (LeRC).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wagner, Michael; Ma, Zhiwen; Martinek, Janna

An aspect of the present disclosure is a receiver for receiving radiation from a heliostat array that includes at least one external panel configured to form an internal cavity and an open face. The open face is positioned substantially perpendicular to a longitudinal axis and forms an entrance to the internal cavity. The receiver also includes at least one internal panel positioned within the cavity and aligned substantially parallel to the longitudinal axis, and the at least one internal panel includes at least one channel configured to distribute a heat transfer medium.

Mechanical conceptual design of 6.5 meter telescope: Telescopio San Pedro Mártir (TSPM)

NASA Astrophysics Data System (ADS)

Uribe, Jorge; Bringas, Vicente; Reyes, Noe; Tovar, Carlos; López, Aldo; Caballero, Xóchitl; Martínez, César; Toledo, Gengis; Lee, William; Carramiñana, Alberto; González, Jesús; Richer, Michael; Sánchez, Beatriz; Lucero, Diana; Manuel, Rogelio; Rubio, Saúl; González, Germán.; Hernández, Obed; Segura, José; Macias, Eduardo; García, Mary; Lazaro, José; Rosales, Fabián.; del Llano, Luis

2016-07-01

Telescopio San Pedro Mártir (TSPM) project intends to build a 6.5 meters telescope with alt-azimuth design, currently at the conceptual design. The project is an association between Instituto de Astronomía de la Universidad Nacional Autónoma de México (IA-UNAM) and the Instituto Nacional de Astrofísica, Óptica Electrónica (INAOE) in partnership with department of Astronomy and Steward Observatory of University of Arizona and Smithsonian Astrophysical Observatory of Harvard University. Conceptual design of the telescope is lead and developed by the Centro de Ingeniería y Desarrollo Industrial (CIDESI). An overview of the feasibility study and the structural conceptual design are summarized in this paper. The telescope concept is based on telescopes already commissioned such as MMT and the Baade and Clay Magellan telescopes, building up on these proven concepts. The main differences relative to the Magellan pair are; the elevation axis is located 1 meter above the primary mirror vertex, allowing for a similar field of view at the Cassegrain and both Nasmyth focal stations; instead of using a vane ends to position the secondary mirror TSPM considers an Steward platform like MMT; finally TSPM has a larger floor distance to m1 cell than Magellans and MMT. Initially TSPM will operate with an f/5 Cassegrain station, but the design considers further Nasmyth configurations from a Cassegrain f/5 up to a Gregorian f/11. The telescope design includes 7 focal stations: 1 Cassegrain; 2 Nasmyth; and 4 folded-Cassegrain. The telescope will be designed and manufactured in Mexico, will be design in Queretaro by CIDESI and built between Queretaro and Michoacán manufacturing facilities; it will be preassembled in these facilities and disassembled to send it to the San Pedro Mártir Observatory for final integration. The azimuth and altitude structure is planned to be constructed in modules and transported by truck and shipped to Ensenada and finally to the OAN where is going to be finally assembled, verified and tested.

Experimental validation of a novel stictionless magnetorheological fluid isolator

NASA Astrophysics Data System (ADS)

Kelso, Shawn P.; Denoyer, Keith K.; Blankinship, Ross M.; Potter, Kenneth; Lindler, Jason E.

2003-07-01

Magnetorheological (MR) fluid damper design typically constitutes a piston/dashpot configuration. During reciprocation, the fluid is circulated through the device with the generated pressure providing viscous damping. In addition, the damper is also intended to accommodate off-axis loading; i.e., rotation moments and lateral loads orthogonal to the axis of operation. Typically two sets of seals, one where the piston shaft enters and exits the device and one between the piston and the cylinder wall, maintain alignment of the damper and seal the fluid from leaking. With MR fluid, these seals can act as sources of non-linear friction effects (stiction) and oftentimes possess a shorter lifespan due to the abrasive nature of the ferrous particles suspended in the fluid. Intelligently controlling damping forces must also accommodate the non-linear stiction behavior, which degrades performance. A new, unique MR fluid isolator was designed, fabricated and tested that directly addresses these concerns. The goal of this research was the development of a stiction-free MR isolator whose damping force can be predicted and precisely controlled. This paper presents experimental results for a prototype device and compares those results to model predictions.

Hard x-ray spectroscopy and imaging by a reflection zone plate in the presence of astigmatism

DOE PAGES

Braig, Christoph; Lochel, Heike; Firsov, Alexander; ...

2015-12-17

Here, the feasibility of an off-axis x-ray reflection zone plate to perform wavelength-dispersive spectroscopy, on-axis point focusing, and two-dimensional imaging is demonstrated by means of one and the same diffractive optical element (DOE) at a synchrotron radiation facility. The resolving power varies between 3 × 10 1 and 4 × 10 2 in the range of 7.6 keV to 9.0 keV, with its maximum at the design energy of 8.3 keV. This result is verified using an adjustable entrance slit, by which horizontal (H) and vertical (V) focusing to 0.85 μm(H) and 1.29 μm(V) is obtained near the sagittal focalmore » plane of the astigmatic configuration. An angular and axial scan proves an accessible field of view of at least 0.6 arcmin × 0.8 arcmin and a focal depth of ±0.86 mm. Supported by the grating efficiency of around 17.5% and a very short pulse elongation, future precision x-ray fluorescence and absorption studies of transition metals at their K-edge on an ultrashort timescale could benefit from our findings.« less

An experimental investigation of the structural dynamics of a torsionally soft rotor in vacuum

NASA Technical Reports Server (NTRS)

Srinivasan, A. V.; Cutts, D. G.; Shu, H. T.

1986-01-01

An extensive data base of structural dynamic characteristics has been generated from an experimental program conducted on a torsionally soft two-bladed model helicopter rotor system. Measurements of vibratory strains for five modes of vibration were made at twenty-one locations on the two blades at speeds varying from 0 to 1000 RPM and for several combinations of precone, droop and flexure stiffness. Tests were conducted in vacuum under carefully controlled conditions using a unique excitation device with a system of piezoelectric crystals bonded to the blade surface near the root. Frequencies, strain mode shapes and dampings are extracted from the time histories and can be used to validate structural dynamics codes. The dynamics of the system are such that there is a clear tendency for the first torsion and second flap modes to couple within the speed range considered. Strain mode shapes vary significantly with speed and configuration. This feature is important in the calcualtion of aeroelastic instabilities. The tension axis tests confirmed that the modulus-weighted centroid for the nonhomogeneous airfoil is slightly off the mass centroid and validated previous static tests done to determine location of the tension axis.

Laser scanning confocal microscope with programmable amplitude, phase, and polarization of the illumination beam.

PubMed

Boruah, B R; Neil, M A A

2009-01-01

We describe the design and construction of a laser scanning confocal microscope with programmable beam forming optics. The amplitude, phase, and polarization of the laser beam used in the microscope can be controlled in real time with the help of a liquid crystal spatial light modulator, acting as a computer generated hologram, in conjunction with a polarizing beam splitter and two right angled prisms assembly. Two scan mirrors, comprising an on-axis fast moving scan mirror for line scanning and an off-axis slow moving scan mirror for frame scanning, configured in a way to minimize the movement of the scanned beam over the pupil plane of the microscope objective, form the XY scan unit. The confocal system, that incorporates the programmable beam forming unit and the scan unit, has been implemented to image in both reflected and fluorescence light from the specimen. Efficiency of the system to programmably generate custom defined vector beams has been demonstrated by generating a bottle structured focal volume, which in fact is the overlap of two cross polarized beams, that can simultaneously improve both the lateral and axial resolutions if used as the de-excitation beam in a stimulated emission depletion confocal microscope.

Radius of Curvature of Off-Axis Paraboloids

NASA Technical Reports Server (NTRS)

Robinson, Brian; Reardon, Patrick; Hadaway, James; Geary, Joseph; Russell, Kevin (Technical Monitor)

2002-01-01

We present several methods for measuring the vertex radius of curvature of off-axis paraboloidal mirrors. One is based on least-squares fitting of interferometer output, one on comparison of sagittal and tangential radii of curvature, and another on measurement of displacement of the nulled test article from the ideal reference wave. Each method defines radius of curvature differently and, as a consequence, produces its own sort of errors.

Effect of rotor configuration on guyed tower and foundation designs and estimated costs for intermediate site horizontal axis wind turbines

NASA Technical Reports Server (NTRS)

Frederick, G. R.; Winemiller, J. R.; Savino, J. M.

1982-01-01

Three designs of a guyed cylindrical tower and its foundation for an intermediate size horizontal axis wind turbine generator are discussed. The primary difference in the three designs is the configuration of the rotor. Two configurations are two-blade rotors with teetering hubs - one with full span pitchable blades, the other with fixed pitch blades. The third configuration is a three-bladed rotor with a rigid hub and fixed pitch blades. In all configurations the diameter of the rotor is 38 meters and the axis of rotation is 30.4 meters above grade, and the power output is 200 kW and 400 kW. For each configuration the design is based upon for the most severe loading condition either operating wind or hurricane conditions. The diameter of the tower is selected to be 1.5 meters (since it was determined that this would provide sufficient space for access ladders within the tower) with guy rods attached at 10.7 meters above grade. Completing a design requires selecting the required thicknesses of the various cylindrical segments, the number and diameter of the guy rods, the number and size of soil anchors, and the size of the central foundation. The lower natural frequencies of vibration are determined for each design to ensure that operation near resonance does not occur. Finally, a cost estimate is prepared for each design. A preliminary design and cost estimate of a cantilever tower (cylindrical and not guyed) and its foundation is also presented for each of the three configurations.

Control System for Bearingless Motor-generator

NASA Technical Reports Server (NTRS)

Kascak, Peter E. (Inventor); Jansen, Ralph H. (Inventor); Dever, Timothy P. (Inventor)

2008-01-01

A control system for an electromagnetic rotary drive for bearingless motor-generators comprises a winding configuration comprising a plurality of individual pole pairs through which phase current flows, each phase current producing both a lateral force and a torque. A motor-generator comprises a stator, a rotor supported for movement relative to the stator, and a control system. The motor-generator comprises a winding configuration supported by the stator. The winding configuration comprises at least three pole pairs through which phase current flows resulting in three three-phase systems. Each phase system has a first rotor reference frame axis current that produces a levitating force with no average torque and a second rotor reference frame axis current that produces torque.

Control system for bearingless motor-generator

NASA Technical Reports Server (NTRS)

Jansen, Ralph H. (Inventor); Dever, Timothy P. (Inventor); Kascak, Peter E. (Inventor)

2010-01-01

A control system for an electromagnetic rotary drive for bearingless motor-generators comprises a winding configuration comprising a plurality of individual pole pairs through which phase current flows, each phase current producing both a lateral force and a torque. A motor-generator comprises a stator, a rotor supported for movement relative to the stator, and a control system. The motor-generator comprises a winding configuration supported by the stator. The winding configuration comprises at least three pole pairs through which phase current flows resulting in three three-phase systems. Each phase system has a first rotor reference frame axis current that produces a levitating force with no average torque and a second rotor reference frame axis current that produces torque.

Design and Analysis of an Axisymmetric Phased Array Fed Gregorian Reflector System for Limited Scanning

DTIC Science & Technology

2016-01-22

applications. For space applications, attitude control systems can provide good angular control of the antenna aperture with small residual angular...Bilyeu, and G.R. Veal, Development of Flight Hardware for a Large Inflatable- Deployable Antenna Experiment , Acta Astronautica, Vol. 38, Nos. 4-8

Stuck threaded member extractor tool and extraction methods

DOEpatents

Roscosky, James M.; Essay, Shane M.

2016-02-02

Disclosed is a tool having a tapered first portion configured to translate a rotational force to the stuck member, a second portion connecting with the first portion and configured to translate the rotational force to the tapered first portion, a planar tip at an end of the first portion and perpendicular to a central axis passing through the first portion and the second portion, a plurality of left-handed splines extending helically around the central axis from the tip toward the second portion, a driver engaged with the second portion and configured to receive a third rotational force from a mechanical manipulator, and a leak seal connected to the driver and configured to form a seal around the stuck member and at least a portion of the driver and prevent gases opposite the stuck member from escaping.

SU-E-T-441: Comparison of Dose Distributions for Spot-Scanned Pencil-Beam and Scattered-Beam Proton Treatments of Ocular Tumors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deisher, A; Whitaker, T; Kruse, J

2014-06-01

Purpose: To study the cross-field and depth dose profiles of spot-scanned pencil beam configurations for the treatment of ocular tumors and to compare their performance to a simulated scattered beam. Methods: Dose distributions in a cubic water phantom were compared for beams that passed through a final 24mm diameter aperture to deposit maximum dose at 2.4cm depth. The pencil-beam spots formed a hexagonally-packed ring with a center-to-center spacing of 4mm. The protons exited the nozzle with energy 95.5MeV, traversed a 4.5cm water-equivalent range shifter, and travelled either 42.5cm or 100cm to the phantom surface. The aperture-to-phantom distance (APD) was 5.7cmmore » to allow room for eye-tracking hardware. A configuration with APD=0 was also tested. The scattered beam was generated with energy 159MeV, passed through 127mm of Lexan, exited the final aperture, and travelled 5.7cm to the phantom surface. This latter configuration is comparable to the MGH single scattered beamline. All beams were modelled with TOPAS1.0-beta6 compiled with GEANT4.9.6p2. Results: The modeled scattered beam produced a distal fall-off along the central axis of zd90%-zd10%=3.6mm. For the pencil beam, the zd90%-zd10% was 1.6mm in all configurations. The scattered beam's cross-field penumbra at depth of maximum dose was r90%- r10%=1.9mm. For the spot-scanned configuration with the range-shifter-tophantom distance (RsPD) of 100cm, similar cross-field profiles were achieved with r90%-r10%=2.0mm. At shorter RsPD of 42.5cm, the crossfield penumbras were 5.6mm and 7.7mm for APD=0cm and APD=5.7cm, respectively. Conclusion: For proton treatments employing a range shifter, the cross-field and central axis dose profiles depend on the quality of the original beam, the size of the range shifter, the distance from the range shifter exit to the patient, and the distance from the final aperture to the patient. A spot-scanned pencil beam configuration can achieve cross-field penumbras equal to a scattered beam and superior distal gradients.« less

Driver-witness electron beam acceleration in dielectric mm-scale capillaries

NASA Astrophysics Data System (ADS)

Lekomtsev, K.; Aryshev, A.; Tishchenko, A. A.; Shevelev, M.; Lyapin, A.; Boogert, S.; Karataev, P.; Terunuma, N.; Urakawa, J.

2018-05-01

We investigated a corrugated mm-scale capillary as a compact accelerating structure in the driver-witness acceleration scheme, and suggested a methodology to measure the acceleration of the witness bunch. The accelerating fields produced by the driver bunch and the energy spread of the witness bunch in a corrugated capillary and in a capillary with a constant inner radius were measured and simulated for both on-axis and off-axis beam propagation. Our simulations predicted a change in the accelerating field structure for the corrugated capillary. Also, an approximately twofold increase of the witness bunch energy gain on the first accelerating cycle was expected for both capillaries for the off-axis beam propagation. These results were confirmed in the experiment, and the maximum measured acceleration of 170 keV /m at 20 pC driver beam charge was achieved for off-axis beam propagation. The driver bunch showed an increase in energy spread of up to 11%, depending on the capillary geometry and beam propagation, with a suppression of the longitudinal energy spread in the witness bunch of up to 15%.

The role of turbulent suppression in the triggering ITBs on C-Mod

NASA Astrophysics Data System (ADS)

Zhurovich, K.; Fiore, C. L.; Ernst, D. R.; Bonoli, P. T.; Greenwald, M. J.; Hubbard, A. E.; Hughes, J. W.; Marmar, E. S.; Mikkelsen, D. R.; Phillips, P.; Rice, J. E.

2007-11-01

Internal transport barriers can be routinely produced in C-Mod steady EDA H-mode plasmas by applying ICRF at |r/a|>= 0.5. Access to the off-axis ICRF heated ITBs may be understood within the paradigm of marginal stability. Analysis of the Te profiles shows a decrease of R/LTe in the ITB region as the RF resonance is moved off axis. Ti profiles broaden as the ICRF power deposition changes from on-axis to off-axis. TRANSP calculations of the Ti profiles support this trend. Linear GS2 calculations do not reveal any difference in ETG growth rate profiles for ITB vs. non-ITB discharges. However, they do show that the region of stability to ITG modes widens as the ICRF resonance is moved outward. Non-linear simulations show that the outward turbulent particle flux exceeds the Ware pinch by factor of 2 in the outer plasma region. Reducing the temperature gradient significantly decreases the diffusive flux and allows the Ware pinch to peak the density profile. Details of these experiments and simulations will be presented.

An afocal telescope configuration for the ESA Ariel mission

NASA Astrophysics Data System (ADS)

Da Deppo, V.; Middleton, K.; Focardi, M.; Morgante, G.; Pace, E.; Claudi, R.; Micela, G.

2017-09-01

ARIEL (Atmospheric Remote-sensing Infrared Exoplanet Large-survey) is one of the three candidates for the next ESA medium-class science mission (M4) expected to be launched in 2026. This mission will be devoted to observing spectroscopically in the infrared (IR) a large population of known transiting planets in the neighborhood of the Solar System, opening a new discovery space in the field of extrasolar planets and enabling the understanding of the physics and chemistry of these far away worlds. ARIEL is based on a 1-m class telescope ahead of two spectrometer channels covering the band 1.95 to 7.8 microns. In addition there are four photometric channels: two wide band, also used as fine guidance sensors, and two narrow band. During its 3.5 years of operations from L2 orbit, ARIEL will continuously observe exoplanets transiting their host star. The ARIEL optical design is conceived as a fore-module common afocal telescope that will feed the spectrometer and photometric channels. The telescope optical design is composed of an off-axis portion of a two-mirror classic Cassegrain coupled to a tertiary off-axis paraboloidal mirror. The telescope and optical bench operating temperatures, as well as those of some subsystems, will be monitored and fine tuned/stabilised mainly by means of a thermal control subsystem (TCU-Telescope Control Unit) working in closed-loop feedback and hosted by the main Payload electronics unit, the Instrument Control Unit (ICU). Another important function of the TCU will be to monitor the telescope and optical bench thermistors when the Payload decontamination heaters will be switched on (when operating the instrument in Decontamination Mode) during the Commissioning Phase and cyclically, if required. Then the thermistors data will be sent by the ICU to the On Board Computer by means of a proper formatted telemetry. The latter (OBC) will be in charge of switching on and off the decontamination heaters on the basis of the thermistors readout values.

Study of tethered satellite active attitude control

NASA Technical Reports Server (NTRS)

Colombo, G.

1982-01-01

Existing software was adapted for the study of tethered subsatellite rotational dynamics, an analytic solution for a stable configuration of a tethered subsatellite was developed, the analytic and numerical integrator (computer) solutions for this "test case' was compared in a two mass tether model program (DUMBEL), the existing multiple mass tether model (SKYHOOK) was modified to include subsatellite rotational dynamics, the analytic "test case,' was verified, and the use of the SKYHOOK rotational dynamics capability with a computer run showing the effect of a single off axis thruster on the behavior of the subsatellite was demonstrated. Subroutines for specific attitude control systems are developed and applied to the study of the behavior of the tethered subsatellite under realistic on orbit conditions. The effect of all tether "inputs,' including pendular oscillations, air drag, and electrodynamic interactions, on the dynamic behavior of the tether are included.

A new vertical axis wind turbine design for urban areas

NASA Astrophysics Data System (ADS)

Frunzulica, Florin; Cismilianu, Alexandru; Boros, Alexandru; Dumitrache, Alexandru; Suatean, Bogdan

2016-06-01

In this paper we aim at developing the model of a Vertical Axis Wind Turbine (VAWT) with the short-term goal of physically realising this turbine to operate at a maximmum power of 5 kW. The turbine is designed for household users in the urban or rural areas and remote or isolated residential areas (hardly accsessible). The proposed model has a biplane configuration on each arm of the VAWT (3 × 2 = 6 blades), allowing for increased performance of the turbine at TSR between 2 and 2.5 (urban area operation) compared to the classic vertical axis turbines. Results that validate the proposed configuration as well as passive control methods to increase the performance of the classic VAWTs are presented.

Fine alignment of a large segmented mirror

NASA Technical Reports Server (NTRS)

Dey, Thomas William (Inventor)

2010-01-01

A system for aligning a segmented mirror includes a source of radiation directed along a first axis to the segmented mirror and a beamsplitter removably inserted along the first axis for redirecting radiation from the first axis to a second axis, substantially perpendicular to the first axis. An imaging array is positioned along the second axis for imaging the redirected radiation, and a knife-edge configured for cutting the redirected radiation is serially positioned to occlude and not occlude the redirected radiation, effectively providing a variable radiation pattern detected by the imaging array for aligning the segmented mirror.

Core break-off mechanism

NASA Technical Reports Server (NTRS)

Myrick, Thomas M. (Inventor)

2003-01-01

A mechanism for breaking off and retaining a core sample of a drill drilled into a ground substrate has an outer drill tube and an inner core break-off tube sleeved inside the drill tube. The break-off tube breaks off and retains the core sample by a varying geometric relationship of inner and outer diameters with the drill tube. The inside diameter (ID) of the drill tube is offset by a given amount with respect to its outer diameter (OD). Similarly, the outside diameter (OD) of the break-off tube is offset by the same amount with respect to its inner diameter (ID). When the break-off tube and drill tube are in one rotational alignment, the two offsets cancel each other such that the drill can operate the two tubes together in alignment with the drill axis. When the tubes are rotated 180 degrees to another positional alignment, the two offsets add together causing the core sample in the break-off tube to be displaced from the drill axis and applying shear forces to break off the core sample.

Conformal Stereotactic Radiosurgery With Multileaf Collimation.

DTIC Science & Technology

1992-01-01

Hartmann, W. Schlegel, V. Sturm, B. Kober, 0. Pastyr, W.J. Lorenz, "Cerebral radiation surgery using moving field irradiation at a linear ac ...Kober, 0. Pastyr, W.J. Lorenz, "Cerebral radiation surgery using moving field irradiation at a linear ac - celerator facility," Int. J. Radiation...scattered photons), off-axis ratios (for points off of the central axis of the incident beam), percent depth dose or tissue maximum ratio (to ac - count for

Mechanical behavior and fracture characteristics of off-axis fiber composites. 2: Theory and comparisons

NASA Technical Reports Server (NTRS)

Chamis, C. C.; Sinclair, J. H.

1978-01-01

The mechanical behavior and stresses inducing fracture modes of unidirectional high-modulus graphite-fiber/epoxy composites subjected to off-axis tensile loads were investigated theoretically. The investigation included the use of composite mechanics, combined-stress failure criteria, and finite-element stress analysis. The results are compared with experimental data and led to the formulation of criteria and convenient plotting procedures for identifying, characterizing, and quantifying these fracture modes.

Fabrication, Testing, Coating and Alignment of Fast Segmented Optics

DTIC Science & Technology

2006-05-25

mirror segment, a 100 mm thick Zerodur mirror blank was purchased from Schott. Figure 2 shows the segment and its support for polishing and testing in...Polishing large off-axis segments of fast primary mirrors 2. Testing large segments in an off-axis geometry 3. Alignment of multiple segments of a large... mirror 4. Coatings that reflect high-intensity light without distorting the substrate These technologies are critical because of several unique

Thin glass shells for AO: from plano to off-axis aspherics

NASA Astrophysics Data System (ADS)

Harel, Emmanuelle; Anretar, Alain; Antelme, Jean-Pierre; Caillon, Stéphane; Dussourd, Adrien; Foucaud, Guillaume; Jaury, Hervé; Roure, Océane; William, Jean-Philippe; Wuillaume, Philippe; Ruch, Eric; Geyl, Roland

2016-07-01

Reosc has been working on thin glass shells for many years and was recently selected by ESO for the production of the E-ELT M4 mirror thin glass shells. Previously Reosc also produced the aspheric thin shell for the VLT-M2 AO Facility. Based on this experience we will discuss how off axis thin glass shells can be made for the next generation AO systems like the GMT one.

Off-axis impact of unidirectional composites with cracks: Dynamic stress intensification

NASA Technical Reports Server (NTRS)

Sih, G. C.; Chen, E. P.

1979-01-01

The dynamic response of unidirectional composites under off axis (angle loading) impact is analyzed by assuming that the composite contains an initial flaw in the matrix material. The analytical method utilizes Fourier transform for the space variable and Laplace transform for the time variable. The off axis impact is separated into two parts, one being symmetric and the other skew-symmetric with reference to the crack plane. Transient boundary conditions of normal and shear tractions are applied to a crack embedded in the matrix of the unidirectional composite. The two boundary conditions are solved independently and the results superimposed. Mathematically, these conditions reduce the problem to a system of dual integral equations which are solved in the Laplace transform plane for the transformation of the dynamic stress intensity factor. The time inversion is carried out numerically for various combinations of the material properties of the composite and the results are displayed graphically.

Ten deg off-axis tensile test for intralaminar shear characterization of fiber composites

NASA Technical Reports Server (NTRS)

Chamis, C. C.; Sinclair, J. H.

1976-01-01

A combined theoretical and experimental investigation was conducted to assess the suitability of the 10 deg off-axis tensile test specimen for the intralaminar shear characterization of unidirectional composites. Composite mechanics, a combined-stress failure criterion, and a finite element analysis were used to determine theoretically the stress-strain variation across the specimen width and the relative stress and strain magnitudes at the 10 deg plane. Strain gages were used to measure the strain variation across the specimen width at specimen midlength and near the end tabs. Specimens from Mod-I/epoxy, T-300/epoxy, and S-glass/epoxy were used in the experimental program. It was found that the 10 deg off-axis tensile test specimen is suitable for intralaminar shear characterization and it is recommended that it should be considered as a possible standard test specimen for such a characterization.

Human otolith-ocular reflexes during off-vertical axis rotation: effect of frequency on tilt-translation ambiguity and motion sickness

NASA Technical Reports Server (NTRS)

Wood, Scott J.; Paloski, W. H. (Principal Investigator)

2002-01-01

The purpose of this study was to examine how the modulation of tilt and translation otolith-ocular responses during constant velocity off-vertical axis rotation varies as a function of stimulus frequency. Eighteen human subjects were rotated in darkness about their longitudinal axis 30 degrees off-vertical at stimulus frequencies between 0.05 and 0.8 Hz. The modulation of torsion decreased while the modulation of horizontal slow phase velocity (SPV) increased with increasing frequency. It is inferred that the ambiguity of otolith afferent information is greatest in the frequency region where tilt (torsion) and translational (horizontal SPV) otolith-ocular responses crossover. It is postulated that the previously demonstrated peak in motion sickness susceptibility during linear accelerations around 0.3 Hz is the result of frequency segregation of ambiguous otolith information being inadequate to distinguish between tilt and translation.

Wavelength-tunable Hermite-Gaussian modes and an orbital-angular-momentum-tunable vortex beam in a dual-off-axis pumped Yb:CALGO laser.

PubMed

Shen, Yijie; Meng, Yuan; Fu, Xing; Gong, Mali

2018-01-15

A dual-off-axis pumping scheme is presented to generate wavelength-tunable high-order Hermite-Gaussian (HG) modes in Yb:CaGdAlO 4 lasers. The mode and wavelength can be actively controlled by the off-axis displacements and pump power. The purities of the output HG modes are quantified by intensity distributions and the measured M 2 values. The highest order reaches m=15 for stable HG m,0 mode, and wavelength-tunable width is about 10 nm. Moreover, through externally converting the HG m,0 modes, the vortex beams carrying orbital angular momentum (OAM) with a large OAM-tunable range from ±1ℏ to ±15ℏ are produced. This work is effective for largely scaling the spectral and OAM tunable ranges of optical vortex beams.

Parallel-quadrature phase-shifting digital holographic microscopy using polarization beam splitter

PubMed Central

Das, Bhargab; Yelleswarapu, Chandra S; Rao, DVGLN

2012-01-01

We present a digital holography microscopy technique based on parallel-quadrature phase-shifting method. Two π/2 phase-shifted holograms are recorded simultaneously using polarization phase-shifting principle, slightly off-axis recording geometry, and two identical CCD sensors. The parallel phase-shifting is realized by combining circularly polarized object beam with a 45° degree polarized reference beam through a polarizing beam splitter. DC term is eliminated by subtracting the two holograms from each other and the object information is reconstructed after selecting the frequency spectrum of the real image. Both amplitude and phase object reconstruction results are presented. Simultaneous recording eliminates phase errors caused by mechanical vibrations and air turbulences. The slightly off-axis recording geometry with phase-shifting allows a much larger dimension of the spatial filter for reconstruction of the object information. This leads to better reconstruction capability than traditional off-axis holography. PMID:23109732

Fast reconstruction of off-axis digital holograms based on digital spatial multiplexing.

PubMed

Sha, Bei; Liu, Xuan; Ge, Xiao-Lu; Guo, Cheng-Shan

2014-09-22

A method for fast reconstruction of off-axis digital holograms based on digital multiplexing algorithm is proposed. Instead of the existed angular multiplexing (AM), the new method utilizes a spatial multiplexing (SM) algorithm, in which four off-axis holograms recorded in sequence are synthesized into one SM function through multiplying each hologram with a tilted plane wave and then adding them up. In comparison with the conventional methods, the SM algorithm simplifies two-dimensional (2-D) Fourier transforms (FTs) of four N*N arrays into a 1.25-D FTs of one N*N arrays. Experimental results demonstrate that, using the SM algorithm, the computational efficiency can be improved and the reconstructed wavefronts keep the same quality as those retrieved based on the existed AM method. This algorithm may be useful in design of a fast preview system of dynamic wavefront imaging in digital holography.

Averaging scheme for atomic resolution off-axis electron holograms.

PubMed

Niermann, T; Lehmann, M

2014-08-01

All micrographs are limited by shot-noise, which is intrinsic to the detection process of electrons. For beam insensitive specimen this limitation can in principle easily be circumvented by prolonged exposure times. However, in the high-resolution regime several instrumental instabilities limit the applicable exposure time. Particularly in the case of off-axis holography the holograms are highly sensitive to the position and voltage of the electron-optical biprism. We present a novel reconstruction algorithm to average series of off-axis holograms while compensating for specimen drift, biprism drift, drift of biprism voltage, and drift of defocus, which all might cause problematic changes from exposure to exposure. We show an application of the algorithm utilizing also the possibilities of double biprism holography, which results in a high quality exit-wave reconstruction with 75 pm resolution at a very high signal-to-noise ratio. Copyright © 2014 Elsevier Ltd. All rights reserved.

Design of off-axis four-mirror optical system without obscuration based on free-form surface

NASA Astrophysics Data System (ADS)

Huang, Chenxu; Liu, Xin

2015-11-01

With the development of modern military technology, the requirements of airborne electro-optical search and tracking system are increasing on target detection and recognition. However, traditional off-axis three-mirror system couldn't meet the requirements for reducing weight and compacting size in some circumstances. Based on Seidel aberration theory, by restricting the aberration functions, the optical system could achieve initial construction parameters. During the designing process, decenters and tilts of mirrors were adjusted continuously to eliminate the obscurations. To balance off-axis aberration and increase angle of view, the free-form mirror was introduced into the optical system. Then an unobstructed optical system with effective focal length of 100 mm, FOV of 16°×16°, and relative aperture as F/7 is designed. The results show that the system structure is compact, with imaging qualities approaching diffraction limit.

Optics ellipticity performance of an unobscured off-axis space telescope.

PubMed

Zeng, Fei; Zhang, Xin; Zhang, Jianping; Shi, Guangwei; Wu, Hongbo

2014-10-20

With the development of astronomy, more and more attention is paid to the survey of dark matter. Dark matter cannot be seen directly but can be detected by weak gravitational lensing measurement. Ellipticity is an important parameter used to define the shape of a galaxy. Galaxy ellipticity changes with weak gravitational lensing and nonideal optics. With our design of an unobscured off-axis telescope, we implement the simulation and calculation of optics ellipticity. With an accurate model of optics PSF, the characteristic of ellipticity is modeled and analyzed. It is shown that with good optical design, the full field ellipticity can be quite small. The spatial ellipticity change can be modeled by cubic interpolation with very high accuracy. We also modeled the ellipticity variance with time and analyzed the tolerance. It is shown that the unobscured off-axis telescope has good ellipticity performance and fulfills the requirement of dark matter survey.

A Simple Method to Determine the "R" or "S" Configuration of Molecules with an Axis of Chirality

ERIC Educational Resources Information Center

Wang, Cunde; Wu, Weiming

2011-01-01

A simple method for the "R" or "S" designation of molecules with an axis of chirality is described. The method involves projection of the substituents along the chiral axis, utilizes the Cahn-Ingold-Prelog sequence rules in assigning priority to the substituents, is easy to use, and has broad applicability. (Contains 5 figures.)

Static internal performance of a single-engine onaxisymmetric-nozzle vaned-thrust-reverser design with thrust modulation capabilities

NASA Technical Reports Server (NTRS)

Leavitt, L. D.; Burley, J. R., II

1985-01-01

An investigation has been conducted at wind-off conditions in the stati-test facility of the Langley 16-Foot Transonic Tunnel. The tests were conducted on a single-engine reverser configuration with partial and full reverse-thrust modulation capabilities. The reverser design had four ports with equal areas. These ports were angled outboard 30 deg from the vertical impart of a splay angle to the reverse exhaust flow. This splaying of reverser flow was intended to prevent impingement of exhaust flow on empennage surfaces and to help avoid inlet reingestion of exhaust gas when the reverser is integrated into an actual airplane configuration. External vane boxes were located directly over each of the four ports to provide variation of reverser efflux angle from 140 deg to 26 deg (measured forward from the horizontal reference axis). The reverser model was tested with both a butterfly-type inner door and an internal slider door to provide area control for each individual port. In addition, main nozzle throat area and vector angle were varied to examine various methods of modulating thrust levels. Other model variables included vane box configuration (four or six vanes per box), orientation of external vane boxes with respect to internal port walls (splay angle shims), and vane box sideplates. Nozzle pressure ratio was varied from 2.0 approximately 7.0.

Decoupled dimensions of leaf economic and anti-herbivore defense strategies in a tropical canopy tree community.

PubMed

Chauvin, K McManus; Asner, G P; Martin, R E; Kress, W J; Wright, S J; Field, C B

2018-03-01

Trade-offs among plant functional traits indicate diversity in plant strategies of growth and survival. The leaf economics spectrum (LES) reflects a trade-off between short-term carbon gain and long-term leaf persistence. A related trade-off, between foliar growth and anti-herbivore defense, occurs among plants growing in contrasting resource regimes, but it is unclear whether this trade-off is maintained within plant communities, where resource gradients are minimized. The LES and the growth-defense trade-off involve related traits, but the extent to which these trade-off dimensions are correlated is poorly understood. We assessed the relationship between leaf economic and anti-herbivore defense traits among sunlit foliage of 345 canopy trees in 83 species on Barro Colorado Island, Panama. We quantified ten traits related to resource allocation and defense, and identified patterns of trait co-variation using multivariate ordination. We tested whether traits and ordination axes were correlated with patterns of phylogenetic relatedness, juvenile demographic trade-offs, or topo-edaphic variation. Two independent axes described ~ 60% of the variation among canopy trees. Axis 1 revealed a trade-off between leaf nutritional and structural investment, consistent with the LES. Physical defense traits were largely oriented along this axis. Axis 2 revealed a trade-off between investments in phenolic defenses versus other foliar defenses, which we term the leaf defense spectrum. Phylogenetic relationships and topo-edaphic variation largely did not explain trait co-variation. Our results suggest that some trade-offs among the growth and defense traits of outer-canopy trees may be captured by the LES, while others may occur along additional resource allocation dimensions.

Study of turbine and guide vanes integration to enhance the performance of cross flow vertical axis wind turbine

NASA Astrophysics Data System (ADS)

Wibowo, Andreas; Tjahjana, Dominicus Danardono Dwi Prija; Santoso, Budi; Situmorang, Marcelinus Risky Clinton

2018-02-01

The main purpose of this study is to investigate the best configuration between guide vanes and cross flow vertical axis wind turbine with variation of several parameters including guide vanes tilt angle and the number of turbine and guide vane blades. The experimental test were conducted under various wind speed and directions for testing cross flow wind turbine, consisted of 8, 12 and 16 blades. Two types of guide vane were developed in this study, employing 20° and 60° tilt angle. Both of the two types of guide vane had three variations of blade numbers which had same blade numbers variations as the turbines. The result showed that the configurations between 60° guide vane with 16 blade numbers and turbine with 16 blade numbers had the best configurations. The result also showed that for certain configuration, guide vane was able to increase the power generated by the turbine significantly by 271.39% compared to the baseline configuration without using of guide vane.

Cosmic microwave background polarimetry with ABS and ACT: Instrumental design, characterization, and analysis

NASA Astrophysics Data System (ADS)

Simon, Sara Michelle

The LCDM model of the universe is supported by an abundance of astronomical observations, but it does not confirm a period of inflation in the early universe or explain the nature of dark energy and dark matter. The polarization of the cosmic microwave background (CMB) may hold the key to addressing these profound questions. If a period of inflation occurred in the early universe, it could have left a detectable odd-parity pattern called B-modes in the polarization of the CMB on large angular scales. Additionally, the CMB can be used to probe the structure of the universe on small angular scales through lensing and the detection of galaxy clusters and their motions via the Sunyaev-Zel'dovich effect, which can improve our understanding of neutrinos, dark matter, and dark energy. The Atacama B-mode Search (ABS) instrument was a cryogenic crossed-Dragone telescope located at an elevation of 5190m in the Atacama Desert in Chile that observed from February 2012 until October 2014. ABS searched on degree-angular scales for inflationary B-modes in the CMB and pioneered the use of a rapidly-rotating half-wave plate (HWP), which modulates the polarization of incoming light to permit the measurement of celestial polarization on large angular scales that would otherwise be obscured by 1/f noise from the atmosphere. Located next to ABS in the Atacama is the Atacama Cosmology Telescope (ACT), which is an off-axis Gregorian telescope. Its large 6m primary mirror facilitates measurements of the CMB on small angular scales. HWPs are baselined for use with the upgraded polarization-sensitive camera for ACT, called Advanced ACTPol, to extend observations of the polarized CMB to larger angular scales while also retaining sensitivity to small angular scales. The B-mode signal is extremely faint, and measuring it poses an instrumental challenge that requires the development of new technologies and well-characterized instruments. I will discuss the use of novel instrumentation and methods on the ABS telescope and Advanced ACTPol, the characterization of the ABS instrument, and the first two seasons of ABS data, including an overview of the data selection process.

A handheld MEMS-based line-scanned dual-axis confocal microscope for early cancer detection and surgical guidance (Conference Presentation)

NASA Astrophysics Data System (ADS)

Chen, Ye; Yin, Chengbo; Wei, Linpeng; Glaser, Adam K.; Abeytunge, Sanjee; Peterson, Gary; Mandella, Michael J.; Sanai, Nader; Rajadhyaksha, Milind; Liu, Jonathan T.

2017-02-01

Considerable efforts have been recently undertaken to develop miniature optical-sectioning microscopes for in vivo microendoscopy and point-of-care pathology. These devices enable in vivo interrogation of disease as a real-time and noninvasive alternative to gold-standard histopathology, and therefore could have a transformative impact for the early detection of cancer as well as for guiding tumor-resection procedures. Regardless of the specific modality, various trade-offs in size, speed, field of view, resolution, contrast, and sensitivity are necessary to optimize a device for a particular application. Here, a miniature MEMS-based line-scanned dual-axis confocal (LS-DAC) microscope, with a 12-mm diameter distal tip, has been developed for point-of-care pathology. The dual-axis architecture has demonstrated superior rejection of out-of-focus and multiply scattered photons compared to a conventional single-axis confocal configuration. The use of line scanning enables fast frame rates (≥15 frames/sec), which mitigates motion artifacts of a handheld device during clinical use. We have developed a method to actively align the illumination and collection beams in this miniature LS-DAC microscope through the use of a pair of rotatable alignment mirrors. Incorporation of a custom objective lens, with a small form factor for in vivo application, enables the device to achieve an axial and lateral resolution of 2.0 and 1.1 microns, respectively. Validation measurements with reflective targets, as well as in vivo and ex vivo images of tissues, demonstrate that this high-speed LS-DAC microscope can achieve high-contrast imaging of fluorescently labeled tissues with sufficient sensitivity for applications such as oral cancer detection and guiding brain-tumor resections.

Miniature in vivo MEMS-based line-scanned dual-axis confocal microscope for point-of-care pathology

PubMed Central

Yin, C.; Glaser, A.K.; Leigh, S. Y.; Chen, Y.; Wei, L.; Pillai, P. C. S.; Rosenberg, M. C.; Abeytunge, S.; Peterson, G.; Glazowski, C.; Sanai, N.; Mandella, M. J.; Rajadhyaksha, M.; Liu, J. T. C.

2016-01-01

There is a need for miniature optical-sectioning microscopes to enable in vivo interrogation of tissues as a real-time and noninvasive alternative to gold-standard histopathology. Such devices could have a transformative impact for the early detection of cancer as well as for guiding tumor-resection procedures. Miniature confocal microscopes have been developed by various researchers and corporations to enable optical sectioning of highly scattering tissues, all of which have necessitated various trade-offs in size, speed, depth selectivity, field of view, resolution, image contrast, and sensitivity. In this study, a miniature line-scanned (LS) dual-axis confocal (DAC) microscope, with a 12-mm diameter distal tip, has been developed for clinical point-of-care pathology. The dual-axis architecture has demonstrated an advantage over the conventional single-axis confocal configuration for reducing background noise from out-of-focus and multiply scattered light. The use of line scanning enables fast frame rates (16 frames/sec is demonstrated here, but faster rates are possible), which mitigates motion artifacts of a hand-held device during clinical use. We have developed a method to actively align the illumination and collection beams in a DAC microscope through the use of a pair of rotatable alignment mirrors. Incorporation of a custom objective lens, with a small form factor for in vivo clinical use, enables our device to achieve an optical-sectioning thickness and lateral resolution of 2.0 and 1.1 microns respectively. Validation measurements with reflective targets, as well as in vivo and ex vivo images of tissues, demonstrate the clinical potential of this high-speed optical-sectioning microscopy device. PMID:26977337

A methodology for TLD postal dosimetry audit of high-energy radiotherapy photon beams in non-reference conditions.

PubMed

Izewska, Joanna; Georg, Dietmar; Bera, Pranabes; Thwaites, David; Arib, Mehenna; Saravi, Margarita; Sergieva, Katia; Li, Kaibao; Yip, Fernando Garcia; Mahant, Ashok Kumar; Bulski, Wojciech

2007-07-01

A strategy for national TLD audit programmes has been developed by the International Atomic Energy Agency (IAEA). It involves progression through three sequential dosimetry audit steps. The first step audits are for the beam output in reference conditions for high-energy photon beams. The second step audits are for the dose in reference and non-reference conditions on the beam axis for photon and electron beams. The third step audits involve measurements of the dose in reference, and non-reference conditions off-axis for open and wedged symmetric and asymmetric fields for photon beams. Through a co-ordinated research project the IAEA developed the methodology to extend the scope of national TLD auditing activities to more complex audit measurements for regular fields. Based on the IAEA standard TLD holder for high-energy photon beams, a TLD holder was developed with horizontal arm to enable measurements 5cm off the central axis. Basic correction factors were determined for the holder in the energy range between Co-60 and 25MV photon beams. New procedures were developed for the TLD irradiation in hospitals. The off-axis measurement methodology for photon beams was tested in a multi-national pilot study. The statistical distribution of dosimetric parameters (off-axis ratios for open and wedge beam profiles, output factors, wedge transmission factors) checked in 146 measurements was 0.999+/-0.012. The methodology of TLD audits in non-reference conditions with a modified IAEA TLD holder has been shown to be feasible.

Characterizing the Impact of Off-Axis Scan Acquisition on the Reproducibility of Total Retinal Thickness Measurements in SDOCT Volumes.

PubMed

Antony, Bhavna J; Stetson, Paul F; Abramoff, Michael D; Lee, Kyungmoo; Colijn, Johanna M; Buitendijk, Gabriëlle H S; Klaver, Caroline C W; Roorda, Austin; Lujan, Brandon J

2015-07-01

Off-axis acquisition of spectral domain optical coherence tomography (SDOCT) images has been shown to increase total retinal thickness (TRT) measurements. We analyzed the reproducibility of TRT measurements obtained using either the retinal pigment epithelium (RPE) or Bruch's membrane as reference surfaces in off-axis scans intentionally acquired through multiple pupil positions. Five volumetric SDOCT scans of the macula were obtained from one eye of 25 normal subjects. One scan was acquired through a central pupil position, while subsequent scans were acquired through four peripheral pupil positions. The internal limiting membrane, the RPE, and Bruch's membrane were segmented using automated approaches. These volumes were registered to each other and the TRT was evaluated in 9 Early Treatment of Diabetic Retinopathy Study (ETDRS) regions. The reproducibility of the TRT obtained using the RPE was computed using the mean difference, coefficient of variation (CV), and the intraclass correlation coefficient (ICC), and compared to those obtained using Bruch's membrane as the reference surface. A secondary set of 1545 SDOCT scans was also analyzed in order to gauge the incidence of off-axis scans in a typical acquisition environment. The photoreceptor tips were dimmer in off-axis images, which affected the RPE segmentation. The overall mean TRT difference and CV obtained using the RPE were 7.04 ± 4.31 μm and 1.46%, respectively, whereas Bruch's membrane was 1.16 ± 1.00 μm and 0.32%, respectively. The ICCs at the subfoveal TRT were 0.982 and 0.999, respectively. Forty-one percent of the scans in the secondary set showed large tilts (> 6%). RPE segmentation is confounded by its proximity to the interdigitation zone, a structure strongly affected by the optical Stiles-Crawford effect. Bruch's membrane, however, is unaffected leading to a more robust segmentation that is less dependent upon pupil position. The way in which OCT images are acquired can independently affect the accuracy of automated retinal thickness measurements. Assessment of scan angle in a clinical dataset demonstrates that off-axis scans are common, which emphasizes the need for caution when relying on automated thickness parameters when this component of scan acquisition is not controlled for.

PREVAIL: IBM's e-beam technology for next generation lithography

NASA Astrophysics Data System (ADS)

Pfeiffer, Hans C.

2000-07-01

PREVAIL - Projection Reduction Exposure with Variable Axis Immersion Lenses represents the high throughput e-beam projection approach to NGL which IBM is pursuing in cooperation with Nikon Corporation as alliance partner. This paper discusses the challenges and accomplishments of the PREVAIL project. The supreme challenge facing all e-beam lithography approaches has been and still is throughput. Since the throughput of e-beam projection systems is severely limited by the available optical field size, the key to success is the ability to overcome this limitation. The PREVAIL technique overcomes field-limiting off-axis aberrations through the use of variable axis lenses, which electronically shift the optical axis simultaneously with the deflected beam so that the beam effectively remains on axis. The resist images obtained with the Proof-of-Concept (POC) system demonstrate that PREVAIL effectively eliminates off- axis aberrations affecting both resolution and placement accuracy of pixels. As part of the POC system a high emittance gun has been developed to provide uniform illumination of the patterned subfield and to fill the large numerical aperture projection optics designed to significantly reduce beam blur caused by Coulomb interaction.

Projection Reduction Exposure with Variable Axis Immersion Lenses (PREVAIL)-A High Throughput E-Beam Projection Approach for Next Generation Lithography

NASA Astrophysics Data System (ADS)

Pfeiffer, Hans

1999-12-01

Projection reduction exposure with variable axis immersion lenses (PREVAIL) represents the high throughput e-beam projection approach to next generation lithography (NGL), which IBM is pursuing in cooperation with Nikon Corporation as an alliance partner. This paper discusses the challenges and accomplishments of the PREVAIL project. The supreme challenge facing all e-beam lithography approaches has been and still is throughput. Since the throughput of e-beam projection systems is severely limited by the available optical field size, the key to success is the ability to overcome this limitation. The PREVAIL technique overcomes field-limiting off-axis aberrations through the use of variable axis lenses, which electronically shift the optical axis simultaneously with the deflected beam, so that the beam effectively remains on axis. The resist images obtained with the proof-of-concept (POC) system demonstrate that PREVAIL effectively eliminates off-axis aberrations affecting both the resolution and placement accuracy of pixels. As part of the POC system a high emittance gun has been developed to provide uniform illumination of the patterned subfield, and to fill the large numerical aperture projection optics designed to significantly reduce beam blur caused by Coulombinteraction.

Submacropulse electron-beam dynamics correlated with higher-order modes in Tesla-type superconducting rf cavities

NASA Astrophysics Data System (ADS)

Lumpkin, A. H.; Thurman-Keup, R.; Edstrom, D.; Ruan, J.; Eddy, N.; Prieto, P.; Napoly, O.; Carlsten, B. E.; Bishofberger, K.

2018-06-01

We report the direct observations of submacropulse beam centroid oscillations correlated with higher order modes (HOMs) which were generated by off-axis electron beam steering in TESLA-type superconducting rf cavities. The experiments were performed at the Fermilab Accelerator Science and Technology (FAST) facility using its unique configuration of a photocathode rf gun injecting beam into two separated nine-cell cavities in series with corrector magnets and beam position monitors (BPMs) located before, between, and after them. Oscillations of ˜100 kHz in the vertical plane and ˜380 kHz in the horizontal plane with up to 600 -μ m amplitudes were observed in a 3-MHz micropulse repetition rate beam with charges of 100, 300, 500, and 1000 pC /b . However, the effects were much reduced at 100 pC /b . The measurements were based on HOM detector circuitry targeting the first and second dipole passbands, rf BPM bunch-by-bunch array data, imaging cameras, and a framing camera. Calculations reproduced the oscillation frequencies of the phenomena in the vertical case. In principle, these fundamental results may be scaled to cryomodule configurations of major accelerator facilities.

Three junction holographic micro-scale PV system

NASA Astrophysics Data System (ADS)

Wu, Yuechen; Vorndran, Shelby; Ayala Pelaez, Silvana; Kostuk, Raymond K.

2016-09-01

In this work a spectrum splitting micro-scale concentrating PV system is evaluated to increase the conversion efficiency of flat panel PV systems. In this approach, the dispersed spectrum splitting concentration systems is scaled down to a small size and structured in an array. The spectrum splitting configuration allows the use of separate single bandgap PV cells that increase spectral overlap with the incident solar spectrum. This results in an overall increase in the spectral conversion efficiency of the resulting system. In addition other benefits of the micro-scale PV system are retained such reduced PV cell material requirements, more versatile interconnect configurations, and lower heat rejection requirements that can lead to a lower cost system. The system proposed in this work consists of two cascaded off-axis holograms in combination with a micro lens array, and three types of PV cells. An aspherical lens design is made to minimize the dispersion so that higher concentration ratios can be achieved for a three-junction system. An analysis methodology is also developed to determine the optical efficiency of the resulting system, the characteristics of the dispersed spectrum, and the overall system conversion efficiency for a combination of three types of PV cells.

Submacropulse electron-beam dynamics correlated with higher-order modes in Tesla-type superconducting rf cavities

DOE PAGES

Lumpkin, A. H.; Thurman-Keup, R.; Edstrom, D.; ...

2018-06-04

Here, we report the direct observations of submacropulse beam centroid oscillations correlated with higher order modes (HOMs) which were generated by off-axis electron beam steering in TESLA-type superconducting rf cavities. The experiments were performed at the Fermilab Accelerator Science and Technology (FAST) facility using its unique configuration of a photocathode rf gun injecting beam into two separated nine-cell cavities in series with corrector magnets and beam position monitors (BPMs) located before, between, and after them. Oscillations of ~100 kHz in the vertical plane and ~380 kHz in the horizontal plane with up to 600-μm amplitudes were observed in a 3-MHzmore » micropulse repetition rate beam with charges of 100, 300, 500, and 1000 pC/b. However, the effects were much reduced at 100 pC/b. The measurements were based on HOM detector circuitry targeting the first and second dipole passbands, rf BPM bunch-by-bunch array data, imaging cameras, and a framing camera. Calculations reproduced the oscillation frequencies of the phenomena in the vertical case. In principle, these fundamental results may be scaled to cryomodule configurations of major accelerator facilities.« less

Accelerated characterization of graphite/epoxy composites

NASA Technical Reports Server (NTRS)

Griffith, W. I.; Morris, D. H.; Brinson, H. F.

1980-01-01

A method to predict the long term compliance of unidirectional off-axis laminates from short term laboratory tests is presented. The method uses an orthotropic transformation equation and the time-stress-temperature superposition principle. Short term tests are used to construct master curves for two off-axis unidirectional laminates with fiber angles of 10 and 90 degrees. Analytical predictions of long term compliance for 30 and 60 degrees laminates are made. Comparisons with experimental data are also given.

Optical cylinder designs to increase the field of vision in the osteo-odonto-keratoprosthesis.

PubMed

Hull, C C; Liu, C S; Sciscio, A; Eleftheriadis, H; Herold, J

2000-12-01

The single optical cylinders used in the osteo-odonto-keratoprosthesis (OOKP) are known to produce very small visual fields. Values of 40 degrees are typically quoted. The purpose of this paper is to present designs for new optical cylinders that significantly increase the field of view and therefore improve the visual rehabilitation of patients having an OOKP. Computer ray-tracing techniques were used to design and analyse improved one- and two-piece optical cylinders made from polymethyl methacrylate. All designs were required to have a potential visual acuity of 6/6 before consideration was given to the visual field and optimising off-axis image quality. Aspheric surfaces were used where this significantly improved off-axis image quality. Single optical cylinders, with increased posterior cylinder (intraocular) diameters, gave an increase in the theoretical visual field of 18% (from 76 degrees to 90 degrees) over current designs. Two-piece designs based on an inverted telephoto principle gave theoretical field angles over 120 degrees. Aspheric surfaces were shown to improve the off-axis image quality while maintaining a potential visual acuity of at least 6/6. This may well increase the measured visual field by improving the retinal illuminance off-axis. Results demonstrate that it is possible to significantly increase the theoretical maximum visual field through OOKP optical cylinders. Such designs will improve the visual rehabilitation of patients undergoing this procedure.

A Study of Electron Modes in Off-axis Heated Alcator C-Mod Plasmas

NASA Astrophysics Data System (ADS)

Fiore, C. L.; Ernst, D. R.; Mikkelsen, D.; Ennever, P. C.; Howard, N. T.; Gao, C.; Reinke, M. L.; Rice, J. E.; Hughes, J. W.; Walk, J. R.

2013-10-01

Understanding the underlying physics and stability of the peaked density internal transport barriers (ITB) that have been observed during off-axis ICRF heating of Alcator C-Mod plasmas is the goal of recent gyro-kinetic simulations. Two scenarios are examined: an ITB plasma formed with maximal (4.5 MW) off-axis heating power; also the use of off-axis heating in an I-mode plasma as a target in the hopes of establishing an ITB. In the former, it is expected that evidence of trapped electron mode instabilities could be found if a sufficiently high electron temperature is achieved in the core. Linear simulations show unstable modes are present across the plasma core from r/a = 0.2 and greater. In the latter case, despite establishing similar conditions to those in which ITBS were formed, none developed in the I-mode plasmas. Linear gyrokinetic analyses show no unstable ion modes at r/a < 0.55 in these I-mode plasmas, with both ITG and ETG modes present beyond r/a = 0.65. The details of the experimental results will be presented. Linear and non-linear simulations of both of these cases will attempt to explore the underlying role of electron and ion gradient driven instabilities to explain the observations. This work was supported by US-DoE DE-FC02-99ER54512 and DE-AC02-09CH11466.

Destabilization of counter-propagating TAEs by off-axis, co-current Neutral Beam Injection

NASA Astrophysics Data System (ADS)

Podesta', M.; Fredrickson, E.; Gorelenkova, M.

2017-10-01

Neutral Beam injection (NBI) is a common tool to heat the plasma and drive current non-inductively in fusion devices. Energetic particles (EP) resulting from NBI can drive instabilities that are detrimental for the performance and the predictability of plasma discharges. A broad NBI deposition profile, e.g. by off-axis injection aiming near the plasma mid-radius, is often assumed to limit those undesired effects by reducing the radial gradient of the EP density, thus reducing the ``universal'' drive for instabilities. However, this work presents new evidence that off-axis NBI can also lead to undesired effects such as the destabilization of Alfvénic instabilities, as observed in NSTX-U plasmas. Experimental observations indicate that counter propagating toroidal AEs are destabilized as the radial EP density profile becomes hollow as a result of off-axis NBI. Time-dependent analysis with the TRANSP code, augmented by a reduced fast ion transport model (known as kick model), indicates that instabilities are driven by a combination of radial and energy gradients in the EP distribution. Understanding the mechanisms for wave-particle interaction, revealed by the phase space resolved analysis, is the basis to identify strategies to mitigate or suppress the observed instabilities. Work supported by the U.S. Department of Energy, Office of Science, Office of Fusion Energy Sciences under Contract Number DE-AC02-09CH11466.

Exploring for Volcanic and Hydrothermal Activity Above Off-axis Melt Lenses near the East Pacific Rise

NASA Astrophysics Data System (ADS)

White, S. M.; Lee, A. J.; Rubin, K. H.

2015-12-01

Two Alvin dives (AL 4771 and 4774) transected the seafloor directly above the two largest Off-Axis Melt Lenses (O-AML) east of the East Pacific Rise (EPR) axis at 9 39'N and 9 54'N. In 2008, a 3D high-resolution seismic reflection survey (MGL-0812) discovered O-AMLs 3-7 km from the EPR at 2-3 km below the seafloor. Several other O-AML in the crust have been subsequently detected in several locations up to 20 km from the spreading axis at fast and intermediate spreading ridges; understanding their impacts is increasingly important. During the dives, no currently active hydrothermal venting or fresh lava was seen, suggesting that these features do not constantly power off-axis geological activity. However, the seafloor appears much younger at small volcanic seamounts in the 9 39'N than at the 9 54'N site. At 9 39'N, we used Alvin to explore the off-axis volcanic mound complex, reaching the summit of the three largest mounds. Although no evidence for on-going hydrothermal or volcanic activity was detected, the seafloor wore a thin sediment layer of ~10cm and thin Mn-coatings on 9 rock samples, suggesting volcanism more recently than would be expected based on the spreading-rate age of the crust. At 9 54'N, the Alvin trackline started south of a prominent abyssal hill, which has an unusual D-shape over 1 km wide in the center, crossed the abyssal hill, visited two local hummocks on top, and then attempted to find volcanic activity on the near slope of EPR axis by going as far west was possible during the dive. Heavy sediment everywhere on the abyssal hill, to the depth of push cores (~30 cm) and probably much deeper in many areas and 4 rock samples from the abyssal hill were quite weathered with little glass intact, suggest that this site is unaffected by the underlying O-AML. Upslope toward the EPR west of the abyssal hill, 4 rocks collected appear somewhat younger, and sediment became thinner. In addition, 3 CTD tow-yos over each O-AML found no evidence of active hydrothermal vents at either site. While these results do not support the idea of on-going and widespread volcanic activity associated with O-AMLs, a comprehensive survey may reveal smaller pockets of activity. A viable alternative is that off-axis activity is sparse and sporadic, perhaps focused by faults that tap into O-AML heat, and that O-AMLs warrant further investigation.

Exploring for Volcanic and Hydrothermal Activity Above Off-axis Melt Lenses near the East Pacific Rise

NASA Astrophysics Data System (ADS)

West, A. J.; Torres, M. A.; Nealson, K. H.

2014-12-01

Two Alvin dives (AL 4771 and 4774) transected the seafloor directly above the two largest Off-Axis Melt Lenses (O-AML) east of the East Pacific Rise (EPR) axis at 9 39'N and 9 54'N. In 2008, a 3D high-resolution seismic reflection survey (MGL-0812) discovered O-AMLs 3-7 km from the EPR at 2-3 km below the seafloor. Several other O-AML in the crust have been subsequently detected in several locations up to 20 km from the spreading axis at fast and intermediate spreading ridges; understanding their impacts is increasingly important. During the dives, no currently active hydrothermal venting or fresh lava was seen, suggesting that these features do not constantly power off-axis geological activity. However, the seafloor appears much younger at small volcanic seamounts in the 9 39'N than at the 9 54'N site. At 9 39'N, we used Alvin to explore the off-axis volcanic mound complex, reaching the summit of the three largest mounds. Although no evidence for on-going hydrothermal or volcanic activity was detected, the seafloor wore a thin sediment layer of ~10cm and thin Mn-coatings on 9 rock samples, suggesting volcanism more recently than would be expected based on the spreading-rate age of the crust. At 9 54'N, the Alvin trackline started south of a prominent abyssal hill, which has an unusual D-shape over 1 km wide in the center, crossed the abyssal hill, visited two local hummocks on top, and then attempted to find volcanic activity on the near slope of EPR axis by going as far west was possible during the dive. Heavy sediment everywhere on the abyssal hill, to the depth of push cores (~30 cm) and probably much deeper in many areas and 4 rock samples from the abyssal hill were quite weathered with little glass intact, suggest that this site is unaffected by the underlying O-AML. Upslope toward the EPR west of the abyssal hill, 4 rocks collected appear somewhat younger, and sediment became thinner. In addition, 3 CTD tow-yos over each O-AML found no evidence of active hydrothermal vents at either site. While these results do not support the idea of on-going and widespread volcanic activity associated with O-AMLs, a comprehensive survey may reveal smaller pockets of activity. A viable alternative is that off-axis activity is sparse and sporadic, perhaps focused by faults that tap into O-AML heat, and that O-AMLs warrant further investigation.

Effect of grain orientation and coating on thermal fatigue resistance of a directionally solidified superalloy (MAR-M 247)

NASA Technical Reports Server (NTRS)

Bizon, P. T.; Dreshfield, R. L.; Calfo, F. D.

1979-01-01

The effect of off-axis directionally solidified (DS) grain growth on thermal fatigue life of Mar-M 247 alloy was evaluated. Uncoated conventionally cast as well as DS wedge bars were cycled in a burner rig between 1070 C and room temperature. The longitudinal axis and leading edge of the specimen coincided. As the angle between the specimen longitudinal axis and growth axis increased, the thermal fatigue life decreased for both the uncoated and aluminide-coated bars. Life increases of about 50 cycles for the DS conditions were attributed to coating. The decrease in thermal fatigue life with increasing angle is primarily attributed to the increase in modulus of elasticity with increasing angle and not to the intersection of DS grain boundaries with the specimen leading edge. The thermal fatigue cracks were observed to be transgranular in the DS material. Limited tensile and stress-rupture properties of conventionally cast and off-axis DS Mar-M 247 alloy are also presented.

The application of image processing in the measurement for three-light-axis parallelity of laser ranger

NASA Astrophysics Data System (ADS)

Wang, Yang; Wang, Qianqian

2008-12-01

When laser ranger is transported or used in field operations, the transmitting axis, receiving axis and aiming axis may be not parallel. The nonparallelism of the three-light-axis will affect the range-measuring ability or make laser ranger not be operated exactly. So testing and adjusting the three-light-axis parallelity in the production and maintenance of laser ranger is important to ensure using laser ranger reliably. The paper proposes a new measurement method using digital image processing based on the comparison of some common measurement methods for the three-light-axis parallelity. It uses large aperture off-axis paraboloid reflector to get the images of laser spot and white light cross line, and then process the images on LabVIEW platform. The center of white light cross line can be achieved by the matching arithmetic in LABVIEW DLL. And the center of laser spot can be achieved by gradation transformation, binarization and area filter in turn. The software system can set CCD, detect the off-axis paraboloid reflector, measure the parallelity of transmitting axis and aiming axis and control the attenuation device. The hardware system selects SAA7111A, a programmable vedio decoding chip, to perform A/D conversion. FIFO (first-in first-out) is selected as buffer.USB bus is used to transmit data to PC. The three-light-axis parallelity can be achieved according to the position bias between them. The device based on this method has been already used. The application proves this method has high precision, speediness and automatization.

Aeroelastically coupled blades for vertical axis wind turbines

DOEpatents

Paquette, Joshua; Barone, Matthew F.

2016-02-23

Various technologies described herein pertain to a vertical axis wind turbine blade configured to rotate about a rotation axis. The vertical axis wind turbine blade includes at least an attachment segment, a rear swept segment, and optionally, a forward swept segment. The attachment segment is contiguous with the forward swept segment, and the forward swept segment is contiguous with the rear swept segment. The attachment segment includes a first portion of a centroid axis, the forward swept segment includes a second portion of the centroid axis, and the rear swept segment includes a third portion of the centroid axis. The second portion of the centroid axis is angularly displaced ahead of the first portion of the centroid axis and the third portion of the centroid axis is angularly displaced behind the first portion of the centroid axis in the direction of rotation about the rotation axis.

The influence of isotropic and anisotropic crustal permeability on hydrothermal flow at fast spreading ridges

NASA Astrophysics Data System (ADS)

Hasenclever, Jörg; Rüpke, Lars; Theissen-Krah, Sonja; Morgan, Jason

2016-04-01

We use 3-D numerical models of hydrothermal fluid flow to assess the magnitude and spatial distribution of hydrothermal mass and energy fluxes within the upper and lower oceanic crust. A better understanding of the hydrothermal flow pattern (e.g. predominantly on-axis above the axial melt lens vs. predominantly off-axis and ridge-perpendicular over the entire crustal thickness) is essential for quantifying the volume of oceanic crust exposed to high-temperature fluid flow and the associated leaching and redistribution of economically interesting metals. The initial setup of all 3-D models is based on our previous 2-D studies (Theissen-Krah et al., 2011), in which we have coupled numerical models for crustal accretion and hydrothermal fluid flow. One result of these 2-D calculations is a crustal permeability field that leads to a thermal structure in the crust that matches seismic tomography data at the East Pacific Rise. Our reference 3-D model for hydrothermal flow at fast-spreading ridges predicts the existence of a hybrid hydrothermal system (Hasenclever et al., 2014) with two interacting flow components that are controlled by different physical mechanisms. Shallow on-axis flow structures develop owing to the thermodynamic properties of water, whereas deeper off-axis flow is strongly shaped by crustal permeability, particularly the brittle-ductile transition. About ˜60% of the discharging fluid mass is replenished on-axis by warm (up to 300oC) recharge flow surrounding the hot thermal plumes. The remaining ˜40%, however, occurs as colder and broader recharge up to several kilometres away from the ridge axis that feeds hot (500-700oC) deep off-axis flow in the lower crust towards the ridge. Both flow components merge above the melt lens to feed ridge-centred vent sites. In a suite of 3-D model calculations we vary the isotropic crustal permeability to quantify its influence on on-axis vs. off-axis hydrothermal fluxes as well as on along-axis hydrothermal activity. We also explore the effect of anisotropic permeability that is likely to be a feature of the diking region above the melt lens where the repeated emplacement of meter-size dikes should lead to higher permeability in vertical and along-ridge direction and to lower permeability across the ridge. We further study the effect of along-ridge depth-variations of the axial melt lens on the distribution of hydrothermal vent sites.

Influence of temperature on the optical system with large diameter off-axis parabolic lenses

NASA Astrophysics Data System (ADS)

Su, Yaru; Ruan, Hao; Liu, Jie

2016-10-01

In this work, an optical system with large diameter off-axis parabolic lenses was adopted to achieve diffraction gratings by laser interference exposure. The diffraction wavefront aberration caused by temperature variations was simulated using ZEMAX. Through theoretical analysis and optical simulation, it is proved that the diffraction wavefront aberration of holographic grating caused by the pinhole's location errors (it is assumed that when the displacement of pinhole exists along one axis, the locations of the pinhole along the other two orthogonal axes are in a state of precise adjustment ) is much larger when the displacement occurs along z axis than along the other two axes, and the diffraction wavefront aberration is the smallest when the displacement occurs along x axis. If the ambient temperature changes by 1 degree, the PV value is 0.0631λ when the location of the pinhole changes by 0.121mm along z axis, 0.0034λor 0.0672λ when the location of the pinhole changes by 0.002mm along x axis or 0.03mm along y axis. To reach the diffraction limit (that means the PV value is 0.25λ), the decentering value of the pinhole along z axis should be less than 0.0341mm. In conclusion, the position error along z axis is an important factor to influence the PV value of diffraction grating, and the effect of temperature on the PV value of diffraction grating can be neglected.

Three-dimensional organization of vestibular-related eye movements to off-vertical axis rotation and linear translation in pigeons

NASA Technical Reports Server (NTRS)

Dickman, J. D.; Angelaki, D. E.

1999-01-01

During linear accelerations, compensatory reflexes should continually occur in order to maintain objects of visual interest as stable images on the retina. In the present study, the three-dimensional organization of the vestibulo-ocular reflex in pigeons was quantitatively examined during linear accelerations produced by constant velocity off-vertical axis yaw rotations and translational motion in darkness. With off-vertical axis rotations, sinusoidally modulated eye-position and velocity responses were observed in all three components, with the vertical and torsional eye movements predominating the response. Peak torsional and vertical eye positions occurred when the head was oriented with the lateral visual axis of the right eye directed orthogonal to or aligned with the gravity vector, respectively. No steady-state horizontal nystagmus was obtained with any of the rotational velocities (8-58 degrees /s) tested. During translational motion, delivered along or perpendicular to the lateral visual axis, vertical and torsional eye movements were elicited. No significant horizontal eye movements were observed during lateral translation at frequencies up to 3 Hz. These responses suggest that, in pigeons, all linear accelerations generate eye movements that are compensatory to the direction of actual or perceived tilt of the head relative to gravity. In contrast, no translational horizontal eye movements, which are known to be compensatory to lateral translational motion in primates, were observed under the present experimental conditions.

Split in phase singularities of an optical vortex by off-axis diffraction through a simple circular aperture

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taira, Yoshitaka; Zhang, Shukui

Here, diffraction patterns of an optical vortex through several shaped apertures reveal its topological charge. In this letter, we theoretically and experimentally show that diffraction of a Laguerre Gaussian beam through a circular aperture at an off-axis position can be used to determine the magnitude and sign of the topological charge. To our knowledge, this is the first time that a simple circular aperture has been used to detect orbital angular momentum of an incident optical vortex.

Split in phase singularities of an optical vortex by off-axis diffraction through a simple circular aperture.

PubMed

Taira, Yoshitaka; Zhang, Shukui

2017-04-01

Diffraction patterns of an optical vortex through several shaped apertures reveal its topological charge. In this Letter, we theoretically and experimentally show that diffraction of a Laguerre Gaussian beam through a circular aperture at an off-axis position can be used to determine the magnitude and sign of the topological charge. To our knowledge, this is the first time that a simple circular aperture has been used to detect orbital angular momentum of an incident optical vortex.

Feasibility study of complex wavefield retrieval in off-axis acoustic holography employing an acousto-optic sensor

PubMed Central

Rodríguez, Guillermo López; Weber, Joshua; Sandhu, Jaswinder Singh; Anastasio, Mark A.

2011-01-01

We propose and experimentally demonstrate a new method for complex-valued wavefield retrieval in off-axis acoustic holography. The method involves use of an intensity-sensitive acousto-optic (AO) sensor, optimized for use at 3.3 MHz, to record the acoustic hologram and a computational method for reconstruction of the object wavefield. The proposed method may circumvent limitations of conventional implementations of acoustic holography and may facilitate the development of acoustic-holography-based biomedical imaging methods. PMID:21669451

Transverse Cracking in a Fiber Reinforced Ceramic Matrix Composite

DTIC Science & Technology

1990-12-01

failure if the off-axis ply was very thin. Wang and Parvizi- Majidi (3) investigated transverse cracking in Nicalon/CAS, a ceramic composite with silicon...the off-axis ply was very thin. 7 Wang and Parvizi- Majidi (3) investigated transverse I cracking in Nicalon/CAS, a ceramic composite with silicon...were quite 3 prevalent in the three lay-ups with the 900 plies in the center, less so in the 0/90/04/90/0 lay-up. Wang and Parvizi- Majidi also

Split in phase singularities of an optical vortex by off-axis diffraction through a simple circular aperture

DOE PAGES

Taira, Yoshitaka; Zhang, Shukui

2017-03-29

Here, diffraction patterns of an optical vortex through several shaped apertures reveal its topological charge. In this letter, we theoretically and experimentally show that diffraction of a Laguerre Gaussian beam through a circular aperture at an off-axis position can be used to determine the magnitude and sign of the topological charge. To our knowledge, this is the first time that a simple circular aperture has been used to detect orbital angular momentum of an incident optical vortex.

Accelerated characterization of graphite/epoxy composites

NASA Technical Reports Server (NTRS)

Griffith, W. I.; Morris, D. H.; Brinson, H. F.

1980-01-01

A method to predict the long-term compliance of unidirectional off-axis laminates from short-term laboratory tests is presented. The method uses an orthotropic transformation equation and the time-stress-temperature superposition principle. Short-term tests are used to construct master curves for two off-axis unidirectional laminates with fiber angles of 10 deg and 90 deg. In addition, analytical predictions of long-term compliance for 30 deg and 60 deg laminates are made. Comparisons with experimental data are also given.

Simultaneous off-axis multiplexed holography and regular fluorescence microscopy of biological cells.

PubMed

Nygate, Yoav N; Singh, Gyanendra; Barnea, Itay; Shaked, Natan T

2018-06-01

We present a new technique for obtaining simultaneous multimodal quantitative phase and fluorescence microscopy of biological cells, providing both quantitative phase imaging and molecular specificity using a single camera. Our system is based on an interferometric multiplexing module, externally positioned at the exit of an optical microscope. In contrast to previous approaches, the presented technique allows conventional fluorescence imaging, rather than interferometric off-axis fluorescence imaging. We demonstrate the presented technique for imaging fluorescent beads and live biological cells.

Structural design of off-axis aspheric surface reflective zoom optical system

NASA Astrophysics Data System (ADS)

Zhang, Ke; Chang, Jun; Song, Haiping; Niu, Yajun

2018-01-01

Designed an off-axis aspheric reflective zoom optical system, and produced a prototype. The system consists of three aspheric reflective lens, the zoom range is 30mm { 90mm. This system gave up the traditional structure of zoom cam, the lens moved using linear guide rail driven by motor, the positioning precision of which was 0.01mm. And introduced the design of support frames of each lens. The practice tests verified the rationality of the prototype structure design.

Optomechanical stability design of space optical mapping camera

NASA Astrophysics Data System (ADS)

Li, Fuqiang; Cai, Weijun; Zhang, Fengqin; Li, Na; Fan, Junjie

2018-01-01

According to the interior orientation elements and imaging quality requirements of mapping application to mapping camera and combined with off-axis three-mirror anastigmat(TMA) system, high optomechanical stability design of a space optical mapping camera is introduced in this paper. The configuration is a coaxial TMA system used in off-axis situation. Firstly, the overall optical arrangement is described., and an overview of the optomechanical packaging is provided. Zerodurglass, carbon fiber composite and carbon-fiber reinforced silicon carbon (C/SiC) are widely used in the optomechanical structure, because their low coefficient of thermal expansion (CTE) can reduce the thermal sensitivity of the mirrors and focal plane. Flexible and unloading support are used in reflector and camera supporting structure. Epoxy structural adhesives is used for bonding optics to metal structure is also introduced in this paper. The primary mirror is mounted by means of three-point ball joint flexures system, which is attach to the back of the mirror. Then, In order to predict flexural displacements due to gravity, static finite element analysis (FEA) is performed on the primary mirror. The optical performance peak-to-valley (PV) and root-mean-square (RMS) wavefront errors are detected before and after assemble. Also, the dynamic finite element analysis(FEA) of the whole optical arrangement is carried out as to investigate the performance of optomechanical. Finally, in order to evaluate the stability of the design, the thermal vacuum test and vibration test are carried out and the Modulation Transfer Function (MTF) and elements of interior orientation are presented as the evaluation index. Before and after the thermal vacuum test and vibration test, the MTF, focal distance and position of the principal point of optical system are measured and the result is as expected.

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

NASA Technical Reports Server (NTRS)

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.

Tablet based distributed intelligent load management

DOEpatents

Lu, Yan; Zhou, Siyuan

2018-01-09

A facility is connected to an electricity utility and is responsive to Demand Response Events. A plurality of devices is each individually connected to the electricity grid via an addressable switch connected to a secure network that is enabled to be individually switched off by a server. An occupant of a room in control of the plurality of devices provides via a Human Machine Interface on a tablet a preferred order of switching off the plurality of devices in case of a Demand Response Event. A configuration file based at least partially on the preferred order and on a severity of the Demand Response Events determines which devices which of the plurality devices will be switched off. The server accesses the configuration file and switches off the devices included in the configuration file.

Analysis and testing of a new method for drop size measurement using laser scatter interferometry

NASA Technical Reports Server (NTRS)

Bachalo, W. D.; Houser, M. J.

1984-01-01

Research was conducted on a laser light scatter detection method for measuring the size and velocity of spherical particles. The method is based upon the measurement of the interference fringe pattern produced by spheres passing through the intersection of two laser beams. A theoretical analysis of the method was carried out using the geometrical optics theory. Experimental verification of the theory was obtained by using monodisperse droplet streams. Several optical configurations were tested to identify all of the parametric effects upon the size measurements. Both off-axis forward and backscatter light detection were utilized. Simulated spray environments and fuel spray nozzles were used in the evaluation of the method. The measurements of the monodisperse drops showed complete agreement with the theoretical predictions. The method was demonstrated to be independent of the beam intensity and extinction resulting from the surrounding drops. Signal processing concepts were considered and a method was selected for development.

The design concept of the 6-degree-of-freedom hydraulic shaker at ESTEC

NASA Technical Reports Server (NTRS)

Brinkman, P. W.; Kretz, D.

1992-01-01

The European Space Agency (ESA) has decided to extend its test facilities at the European Space and Technology Center (ESTEC) at Noordwijk, The Netherlands, by implementing a 6-degree-of-freedom hydraulic shaker. This shaker will permit vibration testing of large payloads in the frequency range from 0.1 Hz to 100 Hz. Conventional single axis sine and random vibration modes can be applied without the need for a configuration change of the test set-up for vertical and lateral excitations. Transients occurring during launch and/or landing of space vehicles can be accurately simulated in 6-degrees-of-freedom. The performance requirements of the shaker are outlined and the results of the various trade-offs, which are investigated during the initial phase of the design and engineering program are provided. Finally, the resulting baseline concept and the anticipated implementation plan of the new test facility are presented.

Steering and filtering white light with resonant waveguide gratings

NASA Astrophysics Data System (ADS)

Quaranta, Giorgio; Basset, Guillaume; Martin, Olivier J. F.; Gallinet, Benjamin

2017-08-01

A novel thin-film single-layer structure based on resonant waveguide gratings (RWGs) allows to engineer selective color filtering and steering of white light. The unit cell of the structure consists of two adjacent finite-length and cross-talking RWGs, where the former acts as in-coupler and the latter acts as out-coupler. The structure is made by only one nano-imprint lithography replication and one thin film layer deposition, making it fully compatible with up-scalable fabrication processes. We characterize a fabricated optical security element designed to work with the flash and the camera of a smartphone in off-axis light steering configuration, where the pattern is revealed only by placing the smartphone in the proper position. Widespread applications are foreseen in a variety of fields, such as multifocal or monochromatic lenses, solar cells, biosensors, security devices and seethrough optical combiners for near-eye displays.

Portable waveguide display system with a large field of view by integrating freeform elements and volume holograms.

PubMed

Han, Jian; Liu, Juan; Yao, Xincheng; Wang, Yongtian

2015-02-09

A compact waveguide display system integrating freeform elements and volume holograms is presented here for the first time. The use of freeform elements can broaden the field of view, which limits the applications of a holographic waveguide. An optimized system can achieve a diagonal field of view of 45° when the thickness of the waveguide planar is 3mm. Freeform-elements in-coupler and the volume holograms out-coupler were designed in detail in our study, and the influence of grating configurations on diffraction efficiency was analyzed thoroughly. The off-axis aberrations were well compensated by the in-coupler and the diffraction efficiency of the optimized waveguide display system could reach 87.57%. With integrated design, stability and reliability of this monochromatic display system were achieved and the alignment of the system was easily controlled by the record of the volume holograms, which makes mass production possible.

Portable waveguide display system with a large field of view by integrating freeform elements and volume holograms

PubMed Central

Han, Jian; Liu, Juan; Yao, Xincheng; Wang, Yongtian

2015-01-01

A compact waveguide display system integrating freeform elements and volume holograms is presented here for the first time. The use of freeform elements can broaden the field of view, which limits the applications of a holographic waveguide. An optimized system can achieve a diagonal field of view of 45° when the thickness of the waveguide planar is 3mm. Freeform-elements in-coupler and the volume holograms out-coupler were designed in detail in our study, and the influence of grating configurations on diffraction efficiency was analyzed thoroughly. The off-axis aberrations were well compensated by the in-coupler and the diffraction efficiency of the optimized waveguide display system could reach 87.57%. With integrated design, stability and reliability of this monochromatic display system were achieved and the alignment of the system was easily controlled by the record of the volume holograms, which makes mass production possible. PMID:25836207

Holographic line field en-face OCT with digital adaptive optics in the retina in vivo.

PubMed

Ginner, Laurin; Schmoll, Tilman; Kumar, Abhishek; Salas, Matthias; Pricoupenko, Nastassia; Wurster, Lara M; Leitgeb, Rainer A

2018-02-01

We demonstrate a high-resolution line field en-face time domain optical coherence tomography (OCT) system using an off-axis holography configuration. Line field en-face OCT produces high speed en-face images at rates of up to 100 Hz. The high frame rate favors good phase stability across the lateral field-of-view which is indispensable for digital adaptive optics (DAO). Human retinal structures are acquired in-vivo with a broadband light source at 840 nm, and line rates of 10 kHz to 100 kHz. Structures of different retinal layers, such as photoreceptors, capillaries, and nerve fibers are visualized with high resolution of 2.8 µm and 5.5 µm in lateral directions. Subaperture based DAO is successfully applied to increase the visibility of cone-photoreceptors and nerve fibers. Furthermore, en-face Doppler OCT maps are generated based on calculating the differential phase shifts between recorded lines.

Effect of canard position and wing leading-edge flap deflection on wing buffet at transonic speeds

NASA Technical Reports Server (NTRS)

Gloss, B. B.; Henderson, W. P.; Huffman, J. K.

1974-01-01

A generalized wind-tunnel model, with canard and wing planform typical of highly maneuverable aircraft, was tested. The addition of a canard above the wing chord plane, for the configuration with leading-edge flaps undeflected, produced substantially higher total configuration lift coefficients before buffet onset than the configuration with the canard off and leading-edge flaps undeflected. The wing buffet intensity was substantially lower for the canard-wing configuration than the wing-alone configuration. The low-canard configuration generally displayed the poorest buffet characteristics. Deflecting the wing leading-edge flaps substantially improved the wing buffet characteristics for canard-off configurations. The addition of the high canard did not appear to substantially improve the wing buffet characteristics of the wing with leading-edge flaps deflected.

Methods and apparatus for cooling wind turbine generators

DOEpatents

Salamah, Samir A [Niskayuna, NY; Gadre, Aniruddha Dattatraya [Rexford, NY; Garg, Jivtesh [Schenectady, NY; Bagepalli, Bharat Sampathkumaran [Niskayuna, NY; Jansen, Patrick Lee [Alplaus, NY; Carl, Jr., Ralph James

2008-10-28

A wind turbine generator includes a stator having a core and a plurality of stator windings circumferentially spaced about a generator longitudinal axis. A rotor is rotatable about the generator longitudinal axis, and the rotor includes a plurality of magnetic elements coupled to the rotor and cooperating with the stator windings. The magnetic elements are configured to generate a magnetic field and the stator windings are configured to interact with the magnetic field to generate a voltage in the stator windings. A heat pipe assembly thermally engaging one of the stator and the rotor to dissipate heat generated in the stator or rotor.

Portable low-coherence interferometry for quantitatively imaging fast dynamics with extended field of view

NASA Astrophysics Data System (ADS)

Shaked, Natan T.; Girshovitz, Pinhas; Frenklach, Irena

2014-06-01

We present our recent advances in the development of compact, highly portable and inexpensive wide-field interferometric modules. By a smart design of the interferometric system, including the usage of low-coherence illumination sources and common-path off-axis geometry of the interferometers, spatial and temporal noise levels of the resulting quantitative thickness profile can be sub-nanometric, while processing the phase profile in real time. In addition, due to novel experimentally-implemented multiplexing methods, we can capture low-coherence off-axis interferograms with significantly extended field of view and in faster acquisition rates. Using these techniques, we quantitatively imaged rapid dynamics of live biological cells including sperm cells and unicellular microorganisms. Then, we demonstrated dynamic profiling during lithography processes of microscopic elements, with thicknesses that may vary from several nanometers to hundreds of microns. Finally, we present new algorithms for fast reconstruction (including digital phase unwrapping) of off-axis interferograms, which allow real-time processing in more than video rate on regular single-core computers.

Phase derivative method for reconstruction of slightly off-axis digital holograms.

PubMed

Guo, Cheng-Shan; Wang, Ben-Yi; Sha, Bei; Lu, Yu-Jie; Xu, Ming-Yuan

2014-12-15

A phase derivative (PD) method is proposed for reconstruction of off-axis holograms. In this method, a phase distribution of the tested object wave constrained within 0 to pi radian is firstly worked out by a simple analytical formula; then it is corrected to its right range from -pi to pi according to the sign characteristics of its first-order derivative. A theoretical analysis indicates that this PD method is particularly suitable for reconstruction of slightly off-axis holograms because it only requires the spatial frequency of the reference beam larger than spatial frequency of the tested object wave in principle. In addition, because the PD method belongs to a pure local method with no need of any integral operation or phase shifting algorithm in process of the phase retrieval, it could have some advantages in reducing computer load and memory requirements to the image processing system. Some experimental results are given to demonstrate the feasibility of the method.

Measurement of multiaxial ply strength by an off-axis flexure test

NASA Technical Reports Server (NTRS)

Crews, John H., Jr.; Naik, Rajiv A.

1992-01-01

An off-axis flexure (OAF) test was performed to measure ply strength under multiaxial stress states. This test involves unidirectional off-axis specimens loaded in bending, using an apparatus that allows these anisotropic specimens to twist as well as flex without the complications of a resisting torque. A 3D finite element stress analysis verified that simple beam theory could be used to compute the specimen bending stresses at failure. Unidirectional graphite/epoxy specimens with fiber angles ranging from 90 deg to 15 deg have combined normal and shear stresses on their failure planes that are typical of 45 deg plies in structural laminates. Tests for a range of stress states with AS4/3501-6 specimens showed that both normal and shear stresses on the failure plane influenced cracking resistance. This OAF test may prove to be useful for generating data needed to predict ply cracking in composite structures and may also provide an approach for studying fiber-matrix interface failures under stress states typical of structures.

A simulation investigation of scout/attack helicopter directional control requirements for hover and low-speed tasks

NASA Technical Reports Server (NTRS)

Bivens, Courtland C.; Guercio, Joseph G.

1987-01-01

A piloted simulator experiment was conducted to investigate directional axis handling qualities requirements for low speed and hover tasks performed by a Scout/Attack helicopter. Included were the directional characteristics of various candidate light helicopter family configurations. Also, the experiment focused on conventional single main/tail rotor configurations of the OH-58 series aircraft, where the first-order yaw-axis dynamic effects that contributed to the loss of tail rotor control were modeled. Five pilots flew 22 configurations under various wind conditions. Cooper-Harper handling quality ratings were used as the primary measure of merit of each configuration. The results of the experiment indicate that rotorcraft configurations with high directional gust sensitivity require greater minimum yaw damping to maintain satisfactory handling qualities during nap-of-the-Earth flying tasks. It was also determined that both yaw damping and control response are critical handling qualities parameters in performing the air-to-air target acquisition and tracking task. Finally, the lack of substantial yaw damping and larger values of gust sensitivity increased the possibility of loss of directional control at low airspeeds for the single main/tail rotor configurations.

Telescope-optical system performance analysis for the Cryogenic Limb Array Etalon Spectrometer (CLAES) on the Upper Atmospheric Research Satellite

NASA Technical Reports Server (NTRS)

Roche, A. E.; Forney, P. B.; Morrow, H. E.; Anapol, M.

1983-01-01

A first-order performance analysis of the CLAES telescope-optical system is presented. The experiment involves the passive measurement of earth-limb radiance over a 10-60 km tangent altitude range, and is based on a solid Fabry-Perot spectrometer which provides spectral resolution of 0.25/cm for atmospheric emission spectroscopy over the 3.5-12 micron IR range. The optical system is required to provide a high degree of off-axis rejection and stray-light control, primarily to suppress intense emission from the earth surface. The astigmatism and other geometric aberrations are corrected by a secondary mirror which produces an excellent image of the primary one, allowing for location of a diffraction control or Lyot stop. The off-axis scattering performance of the telescope is examined in terms of the mirror scatter coefficient and point source rejection ratio. A mirror bidirectional reflectance distribution function of 0.0001 at 1 deg with a 1/theta-squared roll-off between 1 and 0.2 deg is realizable based on recent measurements. This results in an off-axis radiance term that is generally small in comparison with the system-limiting NER.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Santos-Villalobos, Hector J; Barstow, Del R; Karakaya, Mahmut

Iris recognition has been proven to be an accurate and reliable biometric. However, the recognition of non-ideal iris images such as off angle images is still an unsolved problem. We propose a new biometric targeted eye model and a method to reconstruct the off-axis eye to its frontal view allowing for recognition using existing methods and algorithms. This allows for existing enterprise level algorithms and approaches to be largely unmodified by using our work as a pre-processor to improve performance. In addition, we describe the `Limbus effect' and its importance for an accurate segmentation of off-axis irides. Our method usesmore » an anatomically accurate human eye model and ray-tracing techniques to compute a transformation function, which reconstructs the iris to its frontal, non-refracted state. Then, the same eye model is used to render a frontal view of the reconstructed iris. The proposed method is fully described and results from synthetic data are shown to establish an upper limit on performance improvement and establish the importance of the proposed approach over traditional linear elliptical unwrapping methods. Our results with synthetic data demonstrate the ability to perform an accurate iris recognition with an image taken as much as 70 degrees off-axis.« less

Geophysical and Geochemical Analysis of the 8°20' N Seamount Chain: Studies of Off-Axis Volcanism

NASA Astrophysics Data System (ADS)

McCully, E.; Fornari, D. J.; Gregg, P. M.; Perfit, M. R.; Wanless, V. D.; Anderson, M.; Lubetkin, M.

2017-12-01

The 8°20' N Seamount Chain is an off-axis lineament of volcanoes located west of the East Pacific Rise (EPR) and 15 km north of the Siqueiros Fracture Zone. The volcanoes are located 11 km west of the EPR axis and extend 160 km to the west. The OASIS (Off-Axis Seamount Investigations at Siqueiros) expedition in November 2016 collected ship-based EM122 bathymetry aboard the R/V Atlantis over the entire seamount chain at a 50 m resolution, and AUV Sentry bathymetric and sidescan sonar data were collected over 11 selected areas on some of the seamount summits and flanks at 1-2 m resolution. 90,000 high-resolution digital images were acquired using DSV Alvin and analyzed and classified according to morphology, structure, sediment and manganese presence, and biology. These data are used to create geologic facies maps to correlate seafloor morphology and type with acoustic reflectivity. Major and trace element data of samples collected by Alvin and dredging are also correlated to geological parameters of the seafloor features on each studied seamount. Initial estimates for the volumes of individual constructional features (e.g., mounds, cones) that comprise the seamounts were derived from the high-resolution EM122 multibeam and Sentry AUV bathymetric data and calculated using IVS Fledermaus and plotted as a function of distance from the EPR. These individually constructed volcanic features, dependent on geochemical diversity, may ultimately be grouped into larger eruptive volumes. Thus far, Sentry-derived volumes range from 0.0011-2.96 km3, while EM122-derived volumes range from 0.13-123 km3. The seamounts were classified into 3 shapes; circular, volcanic lineaments aligning parallel to the ridge-axis, and ridge-like constructions, trending perpendicular to the EPR axis. The central 60 km of the chain (60-120 km off-axis) is dominated by ridges and circular seamounts, which exhibit the largest volumes observed along the 8°20' N chain. The seamounts with the lowest volumes are observed in the eastern-most 50 km of the lineament, nearest to the ridge axis. Future work includes distinguishing monogenetic and polygenetic cones and better quantifying how many eruptive periods occurred to form the present seamount morphology.

Resolving the Shell of the Superbubble 30 Doradus C with Chandra

NASA Astrophysics Data System (ADS)

Lopez, Laura

2017-09-01

We propose to observe the superbubble (SB) 30 Doradus C (30 Dor C) with ACIS-S for 100 ks to resolve and characterize the non-thermal shell, point sources, and the young supernova remnant (SNR) J0536 6913 at sub-arcsecond scales. 30 Dor C has been imaged off axis repeatedly by Chandra due to its proximity to SN 1987A, but the majority of the shell has only been observed <20 ks at off-axis distances of >10 arcminutes. The on-axis spatial resolution, sensitivity, and low background of ACIS-S are necessary to disentangle point sources from diffuse emission, to localize synchrotron filaments associated with accelerated electrons, and to investigate the SNR J0536 6913.

Regularized Biot–Savart Laws for Modeling Magnetic Flux Ropes

NASA Astrophysics Data System (ADS)

Titov, Viacheslav S.; Downs, Cooper; Mikić, Zoran; Török, Tibor; Linker, Jon A.; Caplan, Ronald M.

2018-01-01

Many existing models assume that magnetic flux ropes play a key role in solar flares and coronal mass ejections (CMEs). It is therefore important to develop efficient methods for constructing flux-rope configurations constrained by observed magnetic data and the morphology of the pre-eruptive source region. For this purpose, we have derived and implemented a compact analytical form that represents the magnetic field of a thin flux rope with an axis of arbitrary shape and circular cross-sections. This form implies that the flux rope carries axial current I and axial flux F, so that the respective magnetic field is the curl of the sum of axial and azimuthal vector potentials proportional to I and F, respectively. We expressed the vector potentials in terms of modified Biot–Savart laws, whose kernels are regularized at the axis in such a way that, when the axis is straight, these laws define a cylindrical force-free flux rope with a parabolic profile for the axial current density. For the cases we have studied so far, we determined the shape of the rope axis by following the polarity inversion line of the eruptions’ source region, using observed magnetograms. The height variation along the axis and other flux-rope parameters are estimated by means of potential-field extrapolations. Using this heuristic approach, we were able to construct pre-eruption configurations for the 2009 February 13 and 2011 October 1 CME events. These applications demonstrate the flexibility and efficiency of our new method for energizing pre-eruptive configurations in simulations of CMEs.

Solar C: Scatter-Free Observatory for Limb Active Regions and Coronae

NASA Technical Reports Server (NTRS)

2004-01-01

The SOLARC observatory is a 0.5m off-axis reflecting coronagraph. NASA SRT funding has allowed the completion of this telescope facility, which we believe is now the world's largest operational coronagraph. We have achieved our proposal goals both in the development of the new technology for this facility and in the demonstration of its scientific and educational potential: 1) The SOLARC engineering development was successful and has spawned other similar instruments. The off-axis design of ATST (a new 4m telescope) has benefited from the SOLARC development. The off-axis 1.6m NST facility at BBSO is also now under construction and will be the world's largest solar disk observing telescope until ATST is completed. Both of these telescope designs are derivatives of the SOLARC 0.5m off-axis. Some of this technical development is described in the publications. 2) The most important scientific goal of SOLARC has been to demonstrate that coronal magnetic fields can be measured using infrared spectropolarimetry techniques. With the completion of the optical fiber-bundle imaging spectropolarimeter we have measured the coronal field strength with a sensitivity to the line-of-sight field component of 2G at 150,OOOkm above the limb. We believe this capability opens new opportunities for space weather, and coronal physics research. In particular we have demonstrated a new tool for understanding the effect of the Sun on the terrestrial space environment. A paper reporting these results has recently been submitted to the Astrophysical Journal Letters.

Nonlinear evolution of magnetic flux ropes. I - Low-beta limit

NASA Technical Reports Server (NTRS)

Osherovich, V. A.; Farrugia, C. J.; Burlaga, L. F.

1993-01-01

We study the nonlinear self-similar evolution of a cylindrical magnetic flux tube with two components of the magnetic field, axial and azimuthal. We restrict ourselves to the case of a plasma of low beta. Introducing a special class of configurations we call 'separable fields', we reduce the problem to an ordinary differential equation. Two cases are to be distinguished: (1) when the total field minimizes on the symmetry axis, the magnetic configuration inexorably collapses, and (2) when, on the other hand, the total field maximizes on the symmetry axis, the magnetic configuration behaves analogously to a nonlinear oscillator. Here we focus on the latter case. The effective potential of the motion contains two terms: a strong repulsive term and a weak restoring term associated with the pinch. We solve the nonlinear differential equation of motion numerically and find that the period of oscillations grows exponentially with the energy of the oscillator. Our treatment emphasizes the role of the force-free configuration as the lowest potential energy state about which the system oscillates.

A Thin-Flux-Rope Approximation as a Basis for Modeling of Pre- and Post-Eruptive Magnetic Configurations

NASA Astrophysics Data System (ADS)

Titov, V. S.; Mikic, Z.; Torok, T.; Linker, J.

2016-12-01

Many existing models of solar flares and coronal mass ejections (CMEs) assume a key role of magnetic flux ropes in these phenomena. It is therefore important to have efficient methods for constructing flux-rope configurations consistent with the observed photospheric magnetic data and morphology of CMEs. As our new step in this direction, we propose an analytical formulation that succinctly represents the magnetic field of a thin flux rope, which has an axis of arbitrary shape and a circular cross-section with the diameter slowly varying along the axis. This representation implies also that the flux rope carries axial current I and axial flux F, so that the respective magnetic field is a curl of the sum of toroidal and poloidal vector potentials proportional to I and F, respectively. Each of the two potentials is individually expressed in terms of a modified Biot-Savart law with separate kernels, both regularized at the rope axis. We argue that the proposed representation is flexible enough to be used in MHD simulations for initializing pre-eruptive configurations in the low corona or post-eruptive configurations (interplanetary CMEs) in the heliosphere. We discuss the potential advantages of our approach, and the subsequent steps to be performed, to develop a fully operative and highly competitive method compared to existing methods. Research supported by NSF, NASA's HSR and LWS Programs, and AFOSR.

Computational Aerodynamic Analysis of Offshore Upwind and Downwind Turbines

DOE PAGES

Zhao, Qiuying; Sheng, Chunhua; Afjeh, Abdollah

2014-01-01

Aerodynamic interactions of the model NREL 5 MW offshore horizontal axis wind turbines (HAWT) are investigated using a high-fidelity computational fluid dynamics (CFD) analysis. Four wind turbine configurations are considered; three-bladed upwind and downwind and two-bladed upwind and downwind configurations, which operate at two different rotor speeds of 12.1 and 16 RPM. In the present study, both steady and unsteady aerodynamic loads, such as the rotor torque, blade hub bending moment, and base the tower bending moment of the tower, are evaluated in detail to provide overall assessment of different wind turbine configurations. Aerodynamic interactions between the rotor and tower are analyzed,more » including the rotor wake development downstream. The computational analysis provides insight into aerodynamic performance of the upwind and downwind, two- and three-bladed horizontal axis wind turbines.« less

SU-F-J-179: Commissioning Dosimetric Data of a New 2.5 Megavoltage Imaging Beam from a TrueBeam Linear

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ding, G

2016-06-15

Purpose: Recently a new 2.5 megavoltage imaging beam has become available in a TrueBeam linear accelerator for image guidance. There is limited information available related to the beam characteristics. Commissioning dosimetric data of the new imaging is necessary for configuration of the beam in a treatment planning system in order to calculate imaging doses to patients resulting from this new imaging beam. The purpose of this study is to provide measured commissioning data recommended for a beam configuration in a treatment planning system. Methods: A recently installed TrueBeam linear accelerator is equipped with a new low energy photon beam withmore » a nominal energy of 2.5 MV which provides better image quality in addition to other therapeutic megavoltage beams. Dosimetric characteristics of the 2.5 MV are measured for commissioning. An ionization chamber was used to measure dosimetric data including depth-dose curves and dose profiles at different depths for field sizes ranging from 5×5 cm{sup 2} to 40×40 cm{sup 2}. Results: Although the new 2.5 MV beam is a flattening-filter-free (FFF) beam, its dose profiles are much flatter compared to a 6 MV FFF beam. The dose decrease at 20 cm away from the central axis is less than 30% for a 40×40 cm{sup 2} field. This moderately lower dose at off-axis distances benefits the imaging quality. The values of percentage depth-dose (PDD) curves are 53% and 63% for 10×10 cm{sup 2} and 40×40 cm{sup 2} fields respectively. The measured beam output is 0.85 cGy/MU for a reference field size at depth 5 cm obtained according to the AAPM TG-51 protocol. Conclusion: This systematically measured commissioning data is useful for configuring the new imaging beam in a treatment planning system for patient imaging dose calculations resulting from the application of this 2.5 MV beam which is commonly set as a default in imaging procedures.« less

Dexterous Humanoid Robotic Wrist

NASA Technical Reports Server (NTRS)

Ihrke, Chris A. (Inventor); Bridgwater, Lyndon (Inventor); Reich, David M. (Inventor); Wampler, II, Charles W. (Inventor); Askew, Scott R. (Inventor); Diftler, Myron A. (Inventor); Nguyen, Vienny (Inventor)

2013-01-01

A humanoid robot includes a torso, a pair of arms, a neck, a head, a wrist joint assembly, and a control system. The arms and the neck movably extend from the torso. Each of the arms includes a lower arm and a hand that is rotatable relative to the lower arm. The wrist joint assembly is operatively defined between the lower arm and the hand. The wrist joint assembly includes a yaw axis and a pitch axis. The pitch axis is disposed in a spaced relationship to the yaw axis such that the axes are generally perpendicular. The pitch axis extends between the yaw axis and the lower arm. The hand is rotatable relative to the lower arm about each of the yaw axis and the pitch axis. The control system is configured for determining a yaw angle and a pitch angle of the wrist joint assembly.

Wide-field-of-view millimeter-wave telescope design with ultra-low cross-polarization

NASA Astrophysics Data System (ADS)

Bernacki, Bruce E.; Kelly, James F.; Sheen, David; Hatchell, Brian; Valdez, Patrick; Tedeschi, Jonathan; Hall, Thomas; McMakin, Douglas

2012-06-01

As millimeter-wave arrays become available, off-axis imaging performance of the fore optics increases in importance due to the relatively large physical extent of the arrays. Typically, simple optical telescope designs are adapted to millimeter-wave imaging but single-mirror spherical or classic conic designs cannot deliver adequate image quality except near the optical axis. Since millimeter-wave designs are quasi-optical, optical ray tracing and commercial design software can be used to optimize designs to improve off-axis imaging as well as minimize cross-polarization. Methods that obey the Dragone-Mizuguchi condition for the design of reflective millimeter-wave telescopes with low cross-polarization also provide additional degrees of freedom that offer larger fields of view than possible with single-reflector designs. Dragone's graphical design method does not lend itself readily to computer-based optical design approaches, but subsequent authors expanded on Dragone's geometric design approach with analytic expressions that describe the location, shape, off-axis height and tilt of the telescope elements that satisfy Dragone's design rules and can be used as a first-order design for subsequent computer-based design and optimization. We investigate two design variants that obey the Dragone-Mizuguchi conditions that exhibit ultra-low cross-polarization and a large diffraction-limited field of view well suited to millimeter-wave imaging arrays.

Role of ion magnetization in formation of radial density profile in magnetically expanding plasma produced by helicon antenna

NASA Astrophysics Data System (ADS)

Yadav, Sonu; Ghosh, Soumen; Bose, Sayak; Barada, Kshitish K.; Pal, Rabindranath; Chattopadhyay, Prabal K.

2018-04-01

Experimentally, the density profile in the magnetic nozzle of a helicon antenna based plasma device is seen to be modified from being centrally peaked to that of hollow nature as the external magnetic field is increased. It occurs above a characteristic field value when the ions become magnetized in the expansion chamber. The density profile in the source chamber behind the nozzle, however, remains peaked on-axis irrespective of the magnetic field. The electron temperature there is observed to be hollow and this nature is carried to the expansion chamber along the field line. In the electron energy distribution near the off axis peak location, a high energy tail exists. Rotation of these tail electrons in the azimuthal direction due to the gradient-B drift in the expansion chamber leads to an additional off-axis ionization and forms the hollow density profile. It seems that if the ions are not magnetized, then the off-axially produced additional plasma is not confined and the density profile retains the on-axis peak nature. The present experiment successfully demonstrates how the knowledge of the ion magnetization together with tail electrons significantly contributes to the design of an efficient helicon plasma based thruster.

Design and manufacture of 8.4 m primary mirror segments and supports for the GMT

NASA Astrophysics Data System (ADS)

Martin, H. M.; Angel, J. R. P.; Burge, J. H.; Cuerden, B.; Davison, W. B.; Johns, M.; Kingsley, J. S.; Kot, L. B.; Lutz, R. D.; Miller, S. M.; Shectman, S. A.; Strittmatter, P. A.; Zhao, C.

2006-06-01

The design, manufacture and support of the primary mirror segments for the GMT build on the successful primary mirror systems of the MMT, Magellan and Large Binocular telescopes. The mirror segment and its support system are based on a proven design, and the experience gained in the existing telescopes has led to significant refinements that will provide even better performance in the GMT. The first 8.4 m segment has been cast at the Steward Observatory Mirror Lab, and optical processing is underway. Measurement of the off-axis surface is the greatest challenge in the manufacture of the segments. A set of tests that meets the requirements has been defined and the concepts have been developed in some detail. The most critical parts of the tests have been demonstrated in the measurement of a 1.7 m off-axis prototype. The principal optical test is a full-aperture, high-resolution null test in which a hybrid reflective-diffractive null corrector compensates for the 14 mm aspheric departure of the off-axis segment. The mirror support uses the same synthetic floatation principle as the MMT, Magellan, and LBT mirrors. Refinements for GMT include 3-axis actuators to accommodate the varying orientations of segments in the telescope.

Off-axis phase-only holograms of 3D objects using accelerated point-based Fresnel diffraction algorithm

NASA Astrophysics Data System (ADS)

Zeng, Zhenxiang; Zheng, Huadong; Yu, Yingjie; Asundi, Anand K.

2017-06-01

A method for calculating off-axis phase-only holograms of three-dimensional (3D) object using accelerated point-based Fresnel diffraction algorithm (PB-FDA) is proposed. The complex amplitude of the object points on the z-axis in hologram plane is calculated using Fresnel diffraction formula, called principal complex amplitudes (PCAs). The complex amplitudes of those off-axis object points of the same depth can be obtained by 2D shifting of PCAs. In order to improve the calculating speed of the PB-FDA, the convolution operation based on fast Fourier transform (FFT) is used to calculate the holograms rather than using the point-by-point spatial 2D shifting of the PCAs. The shortest recording distance of the PB-FDA is analyzed in order to remove the influence of multiple-order images in reconstructed images. The optimal recording distance of the PB-FDA is also analyzed to improve the quality of reconstructed images. Numerical reconstructions and optical reconstructions with a phase-only spatial light modulator (SLM) show that holographic 3D display is feasible with the proposed algorithm. The proposed PB-FDA can also avoid the influence of the zero-order image introduced by SLM in optical reconstructed images.

The Effect of Microgravity on the Growth of Lead Tin Telluride

NASA Technical Reports Server (NTRS)

Narayanan, R.

2000-01-01

The main objective of this research was to present a model for the prediction of the effect of the microgravity environment on the growth of Lead Tin Telluride. The attitude change and its relation to the experimental objectives: The main objective for the AADSF experiment on USMP 3 involving LTT growth was to estimate the effect of ampoule orientation on the axial and radial segregation of tin telluride. As the furnace was not situated on a gimbal there was no possibility to reorient the ampoule during the flight. Instead the only way to change the growth orientation was to change the attitude of the orbiter. This was accomplished by vernier rocket firings. In what follows it must be noted that the orbiter body coordinates are such that the positive z axis points outward from the 'belly', the positive 'x' axis points outwards from the nose and the positive 'y' axis points outwards from the starboard side. The furnace which was in the pay load had its axis aligned with the orbiter's 'z' axis with the hot end closest to the shuttle body. There were basically three orientations that were desired. These corresponded to the ampoule being seen as a heated from above (thermally stable-solutally unstable) configuration, the heated from below (where the instabilities were reversed from the first orientation) configuration and an 'in between' case where the ampoule axis was misaligned with respect to the orbiters 'g(sub z)' axis.

An afocal telescope configuration for the ESA ARIEL mission

NASA Astrophysics Data System (ADS)

Da Deppo, Vania; Focardi, Mauro; Middleton, Kevin; Morgante, Gianluca; Pascale, Enzo; Grella, Samuele; Pace, Emanuele; Claudi, Riccardo; Amiaux, Jérôme; Colomé Ferrer, Josep; Hunt, Thomas; Rataj, Miroslaw; Sierra-Roig, Carles; Ficai Veltroni, Iacopo; Eccleston, Paul; Micela, Giuseppina; Tinetti, Giovanna

2017-12-01

Atmospheric Remote-Sensing Infrared Exoplanet Large Survey (ARIEL) is a candidate as an M4 ESA mission to launch in 2026. During its 3.5 years of scientific operations, ARIEL will observe spectroscopically in the infrared (IR) a large population of known transiting planets in the neighbourhood of the solar system. ARIEL aims to give a breakthrough in the observation of exoplanet atmospheres and understanding of the physics and chemistry of these far-away worlds. ARIEL is based on a 1 m class telescope feeding a collimated beam into two separate instrument modules: a spectrometer module covering the waveband between 1.95 and 7.8 μm and a combined fine guidance system/visible photometer/NIR spectrometer. The telescope configuration is a classic Cassegrain layout used with an eccentric pupil and coupled to a tertiary off-axis paraboloidal mirror. To constrain the thermo-mechanically induced optical aberrations, the primary mirror (M1) temperature will be monitored and finely tuned using an active thermal control system based on thermistors and heaters. They will be switched on and off to maintain the M1 temperature within ± 1 K by the telescope control unit (TCU). The TCU is a payload electronics subsystem also responsible for the thermal control of the spectrometer module detectors as well as the secondary mirror mechanism and IR calibration source management. The TCU, being a slave subsystem of the instrument control unit, will collect the housekeeping data from the monitored subsystems and will forward them to the master unit. The latter will run the application software, devoted to the main spectrometer management and to the scientific data on-board processing.

Gauß and beyond: the making of Easter algorithms

NASA Astrophysics Data System (ADS)

Bien, Reinhold

2004-07-01

It is amazing to see how many webpages are devoted to the art of finding the date of Easter Sunday. Just for illustration, the reader may search for terms such as Gregorian calendar, date of Easter, or Easter algorithm. Sophisticated essays as well as less enlightening contributions are presented, and many a doubt is expressed about the reliability of some results obtained with some Easter algorithms. In short, there is still a great interest in those problems. Gregorian Easter algorithms exist for two centuries (or more?), but most of their history is rather obscure. Some reasons may be that some important sources are written in Latin or in the German of Goethe's time, or they are difficult to discover. Without being complete, the following paper is intended to shed light on how those techniques emerged and evolved. Like a microcosm, the history of Easter algorithms resembles the history of any science: it is a story of trials, errors, and successes, and, last but not least, a story of offended pride. A number of articles, published before 1910, are cited in: A. Fraenkel, Die Berechnung des Osterfestes. Journal für die reine und angewandte Mathematik, Volume 138 (1910), 133-146.

Adaptive Changes in the Perception of Fast and Slow Movement at Different Head Positions.

PubMed

Panichi, Roberto; Occhigrossi, Chiara; Ferraresi, Aldo; Faralli, Mario; Lucertini, Marco; Pettorossi, Vito E

2017-05-01

This paper examines the subjective sense of orientation during asymmetric body rotations in normal subjects. Self-motion perception was investigated in 10 healthy individuals during asymmetric whole-body rotation with different head orientations. Both on-vertical axis and off-vertical axis rotations were employed. Subjects tracked a remembered earth-fixed visual target while rotating in the dark for four cycles of asymmetric rotation (two half-sinusoidal cycles of the same amplitude, but of different duration). The rotations induced a bias in the perception of velocity (more pronounced with fast than with slow motion). At the end of rotation, a marked target position error (TPE) was present. For the on-vertical axis rotations, the TPE was no different if the rotations were performed with a 30° nose-down, a 60° nose-up, or a 90° side-down head tilt. With off-vertical axis rotations, the simultaneous activation of the semicircular canals and otolithic receptors produced a significant increase of TPE for all head positions. This difference between on-vertical and off-vertical axis rotation was probably partly due to the vestibular transfer function and partly due to different adaptation to the speed of rotation. Such a phenomenon might be generated in different components of the vestibular system. The adaptive process enhancing the perception of dynamic movement around the vertical axis is not related to the specific semicircular canals that are activated; the addition of an otolithic component results in a significant increase of the TPE.Panichi R, Occhigrossi C, Ferraresi A, Faralli M, Lucertini M, Pettorossi VE. Adaptive changes in the perception of fast and slow movement at different head positions. Aerosp Med Hum Perform. 2017; 88(5):463-468.

Summary of tower designs for large horizontal axis wind turbines

NASA Technical Reports Server (NTRS)

Frederick, G. R.; Savino, J. M.

1986-01-01

Towers for large horizontal axis wind turbines, machines with a rotor axis height above 30 meters and rated at more than 500 kW, have varied in configuration, materials of construction, type of construction, height, and stiffness. For example, the U.S. large HAWTs have utilized steel truss type towers and free-standing steel cylindrical towers. In Europe, the trend has been to use only free-standing and guyed cylindrical towers, but both steel and reinforced concrete have been used as materials of construction. These variations in materials of construction and type of construction reflect different engineering approaches to the design of cost effective towers for large HAWTs. Tower designs are the NASA/DOE Mod-5B presently being fabricated. Design goals and requirements that influence tower configuration, height and materials are discussed. In particular, experiences with United States large wind turbine towers are elucidated. Finally, current trends in tower designs for large HAWTs are highlighted.

Actuation method and apparatus, micropump, and PCR enhancement method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ullakko, Kari; Mullner, Peter; Hampikian, Greg

An actuation apparatus includes at least one magnetic shape memory (MSM) element containing a material configured to expand and/or contract in response to exposure to a magnetic field. Among other things, the MSM element may be configured to pump fluid through a micropump by expanding and/or contracting in response to the magnetic field. The magnetic field may rotate about an axis of rotation and exhibit a distribution having a component substantially perpendicular to the axis of rotation. Further, the magnetic field distribution may include at least two components substantially orthogonal to one another lying in one or more planes perpendicularmore » to the axis of rotation. The at least one MSM element may contain nickel, manganese, and gallium. A polymerase chain reaction (PCR) may be enhanced by contacting a PCR reagent and DNA material with the MSM element.« less

Design of an off-axis visual display based on a free-form projection screen to realize stereo vision

NASA Astrophysics Data System (ADS)

Zhao, Yuanming; Cui, Qingfeng; Piao, Mingxu; Zhao, Lidong

2017-10-01

A free-form projection screen is designed for an off-axis visual display, which shows great potential in applications such as flight training for providing both accommodation and convergence cues for pilots. The method based on point cloud is proposed for the design of the free-form surface, and the design of the point cloud is controlled by a program written in the macro-language. In the visual display based on the free-form projection screen, when the error of the screen along Z-axis is 1 mm, the error of visual distance at each filed is less than 1%. And the resolution of the design for full field is better than 1‧, which meet the requirement of resolution for human eyes.

Analysis of off-axis solenoid fields using the magnetic scalar potential: An application to a Zeeman-slower for cold atoms

NASA Astrophysics Data System (ADS)

Muniz, Sérgio R.; Bagnato, Vanderlei S.; Bhattacharya, M.

2015-06-01

In a region free of currents, magnetostatics can be described by the Laplace equation of a scalar magnetic potential, and one can apply the same methods commonly used in electrostatics. Here, we show how to calculate the general vector field inside a real (finite) solenoid, using only the magnitude of the field along the symmetry axis. Our method does not require integration or knowledge of the current distribution and is presented through practical examples, including a nonuniform finite solenoid used to produce cold atomic beams via laser cooling. These examples allow educators to discuss the nontrivial calculation of fields off-axis using concepts familiar to most students, while offering the opportunity to introduce themes of current modern research.

Efficiency of the DOMUS 750 vertical-axis wind turbine

NASA Astrophysics Data System (ADS)

Hallock, Kyle; Rasch, Tyler; Ju, Guoqiang; Alonso-Marroquin, Fernando

2017-06-01

The aim of this paper is to present some preliminary results on the efficiency of a wind turbine for an off-grid housing unit. To generate power, the unit uses a photovoltaic solar array and a vertical-axis wind turbine (VAWT). The existing VAWT was analysed to improve efficiency and increase power generation. There were found to be two main sources of inefficiency: 1. the 750W DC epicyclic generator performed poorly in low winds, and 2. the turbine blades wobbled, allowing for energy loss due to off-axis rotation. A 12V DC permanent magnet alternator was chosen that met the power requirements of the housing unit and would generate power at lower wind speeds. A support bracket was designed to prevent the turbine blades from wobbling.

Three-dimensional organization of otolith-ocular reflexes in rhesus monkeys. II. Inertial detection of angular velocity

NASA Technical Reports Server (NTRS)

Angelaki, D. E.; Hess, B. J.

1996-01-01

1. The dynamic contribution of otolith signals to three-dimensional angular vestibuloocular reflex (VOR) was studied during off-vertical axis rotations in rhesus monkeys. In an attempt to separate response components to head velocity from those to head position relative to gravity during low-frequency sinusoidal oscillations, large oscillation amplitudes were chosen such that peak-to-peak head displacements exceeded 360 degrees. Because the waveforms of head position and velocity differed in shape and frequency content, the particular head position and angular velocity sensitivity of otolith-ocular responses could be independently assessed. 2. During both constant velocity rotation and low-frequency sinusoidal oscillations, the otolith system generated two different types of oculomotor responses: 1) modulation of three-dimensional eye position and/or eye velocity as a function of head position relative to gravity, as presented in the preceding paper, and 2) slow-phase eye velocity as a function of head angular velocity. These two types of otolith-ocular responses have been analyzed separately. In this paper we focus on the angular velocity responses of the otolith system. 3. During constant velocity off-vertical axis rotations, a steady-state nystagmus was elicited that was maintained throughout rotation. During low-frequency sinusoidal off-vertical axis oscillations, dynamic otolith stimulation resulted primarily in a reduction of phase leads that characterize low-frequency VOR during earth-vertical axis rotations. Both of these effects are the result of an internally generated head angular velocity signal of otolithic origin that is coupled through a low-pass filter to the VOR. No change in either VOR gain or phase was observed at stimulus frequencies larger than 0.1 Hz. 4. The dynamic otolith contribution to low-frequency angular VOR exhibited three-dimensional response characteristics with some quantitative differences in the different response components. For horizontal VOR, the amplitude of the steady-state slow-phase velocity during constant velocity rotation and the reduction of phase leads during sinusoidal oscillation were relatively independent of tilt angle (for angles larger than approximately 10 degrees). For vertical and torsional VOR, the amplitude of steady-state slow-phase eye velocity during constant velocity rotation increased, and the phase leads during sinusoidal oscillation decreased with increasing tilt angle. The largest steady-state response amplitudes and smallest phase leads were observed during vertical/torsional VOR about an earth-horizontal axis. 5. The dynamic range of otolith-borne head angular velocity information in the VOR was limited to velocities up to approximately 110 degrees/s. Higher head velocities resulted in saturation and a decrease in the amplitude of the steady-state response components during constant velocity rotation and in increased phase leads during sinusoidal oscillations. 6. The response characteristics of otolith-borne angular VORs were also studied in animals after selective semicircular canal inactivation. Otolith angular VORs exhibited clear low-pass filtered properties with a corner frequency of approximately 0.05-0.1 Hz. Vectorial summation of canal VOR alone (elicited during earth-vertical axis rotations) and otolith VOR alone (elicited during off-vertical axis oscillations after semicircular canal inactivation) could not predict VOR gain and phase during off-vertical axis rotations in intact animals. This suggests a more complex interaction of semicircular canal and otolith signals. 7. The results of this study show that the primate low-frequency enhancement of VOR dynamics during off-vertical axis rotation is independent of a simultaneous activation of the vertical and torsional "tilt" otolith-ocular reflexes that have been characterized in the preceding paper. (ABSTRACT TRUNCATED).

In-Plane Cracking Behavior and Ultimate Strength for 2D Woven and Braided Melt-Infiltrated SiC/SiC Composites Tensile Loaded in Off-Axis Fiber Directions

NASA Technical Reports Server (NTRS)

Morscher, Gregory N.; Yun, Hee Mann; DiCarlo, James A.

2007-01-01

The tensile mechanical properties of ceramic matrix composites (CMC) in directions off the primary axes of the reinforcing fibers are important for architectural design of CMC components that are subjected to multi-axial stress states. In this study, 2D-woven melt-infiltrated (MI) SiC/SiC composite panels with balanced fiber content in the 0 degree and 90 degree directions were tensile loaded in-plane in the 0 degree direction and at 45 degree to this direction. In addition, a 2D triaxially-braided MI composite panel with balanced fiber content in the plus or minus 67 degree bias directions and reduced fiber content in the axial direction was tensile loaded perpendicular to the axial direction tows (i.e., 23 degrees from the bias fibers). Stress-strain behavior, acoustic emission, and optical microscopy were used to quantify stress-dependent matrix cracking and ultimate strength in the panels. It was observed that both off-axis loaded panels displayed higher composite onset stresses for through-thickness matrix cracking than the 2D-woven 0/90 panels loaded in the primary 0 degree direction. These improvements for off-axis cracking strength can in part be attributed to higher effective fiber fractions in the loading direction, which in turn reduces internal stresses on critical matrix flaws for a given composite stress. Also for the 0/90 panel loaded in the 45 degree direction, an improved distribution of matrix flaws existed due to the absence of fiber tows perpendicular to the loading direction. In addition, for the +67/0/-67 braided panel, the axial tows perpendicular to the loading direction were not only low in volume fraction, but were also were well separated from one another. Both off-axis oriented panels also showed relatively good ultimate tensile strength when compared to other off-axis oriented composites in the literature, both on an absolute strength basis as well as when normalized by the average fiber strength within the composites. Initial implications are discussed for constituent and architecture design to improve the directional cracking of SiC/SiC CMC components with MI matrices.

Detector-specific correction factors in radiosurgery beams and their impact on dose distribution calculations.

PubMed

García-Garduño, Olivia A; Rodríguez-Ávila, Manuel A; Lárraga-Gutiérrez, José M

2018-01-01

Silicon-diode-based detectors are commonly used for the dosimetry of small radiotherapy beams due to their relatively small volumes and high sensitivity to ionizing radiation. Nevertheless, silicon-diode-based detectors tend to over-respond in small fields because of their high density relative to water. For that reason, detector-specific beam correction factors ([Formula: see text]) have been recommended not only to correct the total scatter factors but also to correct the tissue maximum and off-axis ratios. However, the application of [Formula: see text] to in-depth and off-axis locations has not been studied. The goal of this work is to address the impact of the correction factors on the calculated dose distribution in static non-conventional photon beams (specifically, in stereotactic radiosurgery with circular collimators). To achieve this goal, the total scatter factors, tissue maximum, and off-axis ratios were measured with a stereotactic field diode for 4.0-, 10.0-, and 20.0-mm circular collimators. The irradiation was performed with a Novalis® linear accelerator using a 6-MV photon beam. The detector-specific correction factors were calculated and applied to the experimental dosimetry data for in-depth and off-axis locations. The corrected and uncorrected dosimetry data were used to commission a treatment planning system for radiosurgery planning. Various plans were calculated with simulated lesions using the uncorrected and corrected dosimetry. The resulting dose calculations were compared using the gamma index test with several criteria. The results of this work presented important conclusions for the use of detector-specific beam correction factors ([Formula: see text] in a treatment planning system. The use of [Formula: see text] for total scatter factors has an important impact on monitor unit calculation. On the contrary, the use of [Formula: see text] for tissue-maximum and off-axis ratios has not an important impact on the dose distribution calculation by the treatment planning system. This conclusion is only valid for the combination of treatment planning system, detector, and correction factors used in this work; however, this technique can be applied to other treatment planning systems, detectors, and correction factors.

Regularized Biot-Savart Laws for Modeling Magnetic Flux Ropes

NASA Astrophysics Data System (ADS)

Titov, Viacheslav; Downs, Cooper; Mikic, Zoran; Torok, Tibor; Linker, Jon A.

2017-08-01

Many existing models assume that magnetic flux ropes play a key role in solar flares and coronal mass ejections (CMEs). It is therefore important to develop efficient methods for constructing flux-rope configurations constrained by observed magnetic data and the initial morphology of CMEs. As our new step in this direction, we have derived and implemented a compact analytical form that represents the magnetic field of a thin flux rope with an axis of arbitrary shape and a circular cross-section. This form implies that the flux rope carries axial current I and axial flux F, so that the respective magnetic field is a curl of the sum of toroidal and poloidal vector potentials proportional to I and F, respectively. The vector potentials are expressed in terms of Biot-Savart laws whose kernels are regularized at the rope axis. We regularized them in such a way that for a straight-line axis the form provides a cylindrical force-free flux rope with a parabolic profile of the axial current density. So far, we set the shape of the rope axis by tracking the polarity inversion lines of observed magnetograms and estimating its height and other parameters of the rope from a calculated potential field above these lines. In spite of this heuristic approach, we were able to successfully construct pre-eruption configurations for the 2009 February13 and 2011 October 1 CME events. These applications demonstrate that our regularized Biot-Savart laws are indeed a very flexible and efficient method for energizing initial configurations in MHD simulations of CMEs. We discuss possible ways of optimizing the axis paths and other extensions of the method in order to make it more useful and robust.Research supported by NSF, NASA's HSR and LWS Programs, and AFOSR.

Research on the magnetorheological finishing of large aperture off-axis aspheric optical surfaces for zinc sulfide

NASA Astrophysics Data System (ADS)

Zhang, Yunfei; Huang, Wen; Zheng, Yongcheng; Ji, Fang; Xu, Min; Duan, Zhixin; Luo, Qing; Liu, Qian; Xiao, Hong

2016-03-01

Zinc sulfide is a kind of typical infrared optical material, commonly produced using single point diamond turning (SPDT). SPDT can efficiently produce zinc sulfide aspheric surfaces with micro-roughness and acceptable figure error. However the tool marks left by the diamond turning process cause high micro-roughness that degrades the optical performance when used in the visible region of the spectrum. Magnetorheological finishing (MRF) is a deterministic, sub-aperture polishing technology that is very helpful in improving both surface micro-roughness and surface figure.This paper mainly investigates the MRF technology of large aperture off-axis aspheric optical surfaces for zinc sulfide. The topological structure and coordinate transformation of a MRF machine tool PKC1200Q2 are analyzed and its kinematics is calculated, then the post-processing algorithm model of MRF for an optical lens is established. By taking the post-processing of off-axis aspheric surfacefor example, a post-processing algorithm that can be used for a raster tool path is deduced and the errors produced by the approximate treatment are analyzed. A polishing algorithm of trajectory planning and dwell time based on matrix equation and optimization theory is presented in this paper. Adopting this algorithm an experiment is performed to machining a large-aperture off-axis aspheric surface on the MRF machine developed by ourselves. After several times' polishing, the figure accuracy PV is proved from 3.3λ to 2.0λ and RMS from 0.451λ to 0.327λ. This algorithm is used to polish the other shapes including spheres, aspheres and prisms.

Production of internal transport barriers via self-generated mean flows in Alcator C-Moda)

NASA Astrophysics Data System (ADS)

Fiore, C. L.; Ernst, D. R.; Podpaly, Y. A.; Mikkelsen, D.; Howard, N. T.; Lee, Jungpyo; Reinke, M. L.; Rice, J. E.; Hughes, J. W.; Ma, Y.; Rowan, W. L.; Bespamyatnov, I.

2012-05-01

New results suggest that changes observed in the intrinsic toroidal rotation influence the internal transport barrier (ITB) formation in the Alcator C-Mod tokamak [E. S. Marmar and Alcator C-Mod group, Fusion Sci. Technol. 51, 261 (2007)]. These arise when the resonance for ion cyclotron range of frequencies (ICRF) minority heating is positioned off-axis at or outside of the plasma half-radius. These ITBs form in a reactor relevant regime, without particle or momentum injection, with Ti ≈ Te, and with monotonic q profiles (qmin < 1). C-Mod H-mode plasmas exhibit strong intrinsic co-current rotation that increases with increasing stored energy without external drive. When the resonance position is moved off-axis, the rotation decreases in the center of the plasma resulting in a radial toroidal rotation profile with a central well which deepens and moves farther off-axis when the ICRF resonance location reaches the plasma half-radius. This profile results in strong E × B shear (>1.5 × 105 rad/s) in the region where the ITB foot is observed. Gyrokinetic analyses indicate that this spontaneous shearing rate is comparable to the linear ion temperature gradient (ITG) growth rate at the ITB location and is sufficient to reduce the turbulent particle and energy transport. New and detailed measurement of the ion temperature demonstrates that the radial profile flattens as the ICRF resonance position moves off axis, decreasing the drive for the ITG the instability as well. These results are the first evidence that intrinsic rotation can affect confinement in ITB plasmas.

Low-loss off-axis feeds for symmetric dual-reflector antennas

NASA Technical Reports Server (NTRS)

Veruttipong, T.; Galindo-Israel, V.; Imbriale, W.

1986-01-01

Circularly symmetric, dual reflector, high gain antenna systems often require feeds placed off the system's axis because of the need for multiple feeds to use the reflector antenna. Also, the constraint requiring the hyperboloid or shaped subreflector to remain circularly symmetric is sometimes added. In a Cassegrainian system, the subreflector and feed may be rotated off axis around the paraboloid focus and retain main reflector focusing. However, substantial spillover results in considerable noise with a high gain/low noise temperature system. In a shaped system, the tilt of the shaped subreflector and feed together results in substantial defocusing as well as spillover noise. If the subreflector is tilted approximately one-half the angle of the feed tilt in either the Cassegrainian or the dual shaped reflector antenna, it is found that spillover and noise are substantially reduced with tolerable defocusing. An extensive numerical analysis of these effects was conducted to determine the characteristics of a planned 70-meter, dual shaped reflector versus Cassegrainian antenna and to gain some understanding of the cause of the observed effects.

Measurement of vortex flow fields

NASA Technical Reports Server (NTRS)

Mcdevitt, T. Kevin; Ambur, Todd A.; Orngard, Gary M.; Owen, F. Kevin

1992-01-01

A 3-D laser fluorescence anemometer (LFA) was designed, built, and demonstrated for use in the Langley 16 x 24 inch Water Tunnel. Innovative optical design flexibility combined with compact and portable data acquisition and control systems were incorporated into the instrument. This will allow its use by NASA in other test facilities. A versatile fiber optic system facilities normal and off-axis laser beam alignment, removes mirror losses and improves laser safety. This added optical flexibility will also enable simple adaptation for use in the adjacent jet facility. New proprietary concepts in transmitting color separation, light collection, and novel prism separation of the scattered light was also designed and built into the system. Off-axis beam traverse and alignment complexity led to the requirement for a specialized, programmable transverse controller, and the inclusion of an additional traverse for the off-axis arm. To meet this challenge, an 'in-house' prototype unit was designed and built and traverse control software developed specifically for the water tunnel traverse applications. A specialized data acquisition interface was also required. This was designed and built for the LFA system.

White-light diffraction phase microscopy at doubled space-bandwidth product.

PubMed

Shan, Mingguang; Kandel, Mikhail E; Majeed, Hassaan; Nastasa, Viorel; Popescu, Gabriel

2016-12-12

White light diffraction microscopy (wDPM) is a quantitative phase imaging method that benefits from both temporal and spatial phase sensitivity, granted, respectively, by the common-path geometry and white light illumination. However, like all off-axis quantitative phase imaging methods, wDPM is characterized by a reduced space-bandwidth product compared to phase shifting approaches. This happens essentially because the ultimate resolution of the image is governed by the period of the interferogram and not just the diffraction limit. As a result, off-axis techniques generates single-shot, i.e., high time-bandwidth, phase measurements, at the expense of either spatial resolution or field of view. Here, we show that combining phase-shifting and off-axis, the original space-bandwidth is preserved. Specifically, we developed phase-shifting diffraction phase microscopy with white light, in which we measure and combine two phase shifted interferograms. Due to the white light illumination, the phase images are characterized by low spatial noise, i.e., <1nm pathlength. We illustrate the operation of the instrument with test samples, blood cells, and unlabeled prostate tissue biopsy.

Field experiment of 800× off-axis XR-Köhler concentrator module on a carousel tracker

NASA Astrophysics Data System (ADS)

Yamada, Noboru; Okamoto, Kazuya; Ijiro, Toshikazu; Suzuki, Takao; Maemura, Toshihiko; Kawaguchi, Takashi; Takahashi, Hiroshi; Sato, Takashi; Hernandez, Maikel; Benitez, Pablo; Chaves, Julio; Cvetkovic, Aleksandra; Vilaplana, Juan; Mohedano, Ruben; Mendes-Lopes, Joao; Miñano, Juan Carlos

2013-09-01

This paper presents the design and preliminary experimental results of a concentrator-type photovoltaic module based on a free-form off-axis 800×XR-Köhler concentrator. The off-axis XR-Köhler concentrator is one of the advanced concentrators that perform high concentration with a large acceptance angle and excellent irradiance uniformity on a solar cell. As a result of on-sun characterization of the unglazed single-cell unit test rig, the temperature-corrected DC module efficiency was 32.2% at 25 °C without an anti-reflective (AR) coating on the secondary optics, and the acceptance angle was more than ±1.0°. In addition, the non-corrected DC efficiency of an individual cell in a glazed 8-cell unit module mounted on a carousel tracking system was measured. The individual efficiency deviated in the range of 24.3-27.4%, owing to the mirror shape and alignment errors. The resultant series-connected efficiency was approximately 25% at direct normal irradiation (DNI) of 770 W/m2.

The role of the hypothalamus-pituitary-adrenal/interrenal axis in mediating predator-avoidance trade-offs.

PubMed

Harris, Breanna N; Carr, James A

2016-05-01

Maintaining energy balance and reproducing are important for fitness, yet animals have evolved mechanisms by which the hypothalamus-pituitary-adrenal/interrenal (HPA/HPI) axis can shut these activities off. While HPA/HPI axis inhibition of feeding and reproduction may have evolved as a predator defense, to date there has been no review across taxa of the causal evidence for such a relationship. Here we review the literature on this topic by addressing evidence for three predictions: that exposure to predators decreases reproduction and feeding, that exposure to predators activates the HPA/HPI axis, and that predator-induced activation of the HPA/HPI axis inhibits foraging and reproduction. Weight of evidence indicates that exposure to predator cues inhibits several aspects of foraging and reproduction. While the evidence from fish and mammals supports the hypothesis that predator cues activate the HPA/HPI axis, the existing data in other vertebrate taxa are equivocal. A causal role for the HPA axis in predator-induced suppression of feeding and reproduction has not been demonstrated to date, although many studies report correlative relationships between HPA activity and reproduction and/or feeding. Manipulation of HPA/HPI axis signaling will be required in future studies to demonstrate direct mediation of predator-induced inhibition of feeding and reproduction. Understanding the circuitry linking sensory pathways to their control of the HPA/HPI axis also is needed. Finally, the role that fear and anxiety pathways play in the response of the HPA axis to predator cues is needed to better understand the role that predators have played in shaping anxiety related behaviors in all species, including humans. Copyright © 2016 Elsevier Inc. All rights reserved.

Thermal stability of bubble domains in ferromagnetic discs

NASA Astrophysics Data System (ADS)

Hrkac, G.; Bance, S.; Goncharov, A.; Schrefl, T.; Suess, D.

2007-05-01

The transition and thermal stability of disc-shaped ferromagnetic particles at the temperature of T = 300 K with a uniaxial anisotropy along the symmetry axis from a bi-domain to a single domain state has been studied. The nudge elastic band method was used to map the energy landscape and to calculate the energy barrier between the transition states. For single FePt disc-shaped particles with perpendicular anisotropy three transition configurations have been found: single domain, stripe- and stable bubble domains at zero applied field. The single domain configuration along the positive anisotropy axis is reached by an annihilation process of the domain wall and the all-down state by a complex domain expansion process. Magnetization configurations in two interacting discs show an increase in thermal stability compared with single disc systems, which is attributed to the interacting magnetostatic energy between the two particles.

Torque ripple reduction in electric machines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reddy, Patel Bhageerath; Huh, Kum-Kang; El-Refaie, Ayman Mohamed Fawzi

An electric machine, such as an Internal Permanent magnet or Synchronous Reluctance machine, having X phases, that includes a stator assembly, having M slots, with a stator core and stator teeth, that is further configured with stator windings to generate a stator magnetic field when excited with alternating currents and extends along a longitudinal axis with an inner surface that defines a cavity; and a rotor assembly, having N poles, disposed within the cavity which is configured to rotate about the longitudinal axis, wherein the rotor assembly includes a shaft, a rotor core located circumferentially around the shaft. The machinemore » is configured such that a value k=M/(X*N) wherein k is a non-integer greater than about 1.3. The electric machine may alternatively, or additionally, include a non-uniformed gap between the exterior surface of the rotor spokes and the interior stator surface of the stator.« less

Cam-controlled boring bar

DOEpatents

Glatthorn, Raymond H.

1986-01-01

A cam-controlled boring bar system (100) includes a first housing (152) which is rotatable about its longitudinal axis (154), and a second housing in the form of a cam-controlled slide (158) which is also rotatable about the axis (154) as well as being translatable therealong. A tool-holder (180) is mounted within the slide (158) for holding a single point cutting tool. Slide (158) has a rectangular configuration and is disposed within a rectangularly configured portion of the first housing (152). Arcuate cam slots (192) are defined within a side plate (172) of the housing (152), while cam followers (194) are mounted upon the cam slide (158) for cooperative engagement with the cam slots (192). In this manner, as the housing (152) and slide (158) rotate, and as the slide (158) also translates, a through-bore (14) having an hourglass configuration will be formed within a workpiece (16) which may be, for example, a nuclear reactor steam generator tube support plate.

TIGER: A user-friendly interactive grid generation system for complicated turbomachinery and axis-symmetric configurations

NASA Technical Reports Server (NTRS)

Shih, Ming H.; Soni, Bharat K.

1993-01-01

The issue of time efficiency in grid generation is addressed by developing a user friendly graphical interface for interactive/automatic construction of structured grids around complex turbomachinery/axis-symmetric configurations. The accuracy of geometry modeling and its fidelity is accomplished by adapting the nonuniform rational b-spline (NURBS) representation. A customized interactive grid generation code, TIGER, has been developed to facilitate the grid generation process for complicated internal, external, and internal-external turbomachinery fields simulations. The FORMS Library is utilized to build user-friendly graphical interface. The algorithm allows a user to redistribute grid points interactively on curves/surfaces using NURBS formulation with accurate geometric definition. TIGER's features include multiblock, multiduct/shroud, multiblade row, uneven blade count, and patched/overlapping block interfaces. It has been applied to generate grids for various complicated turbomachinery geometries, as well as rocket and missile configurations.

Design, Fabrication, Optical Testing, and Performance of Diamond Machined Aspheric Mirrors for Ground-Based Near-IR Astronomy

NASA Technical Reports Server (NTRS)

Ohl, Raymond G.; Mink, Ronald; Chambers, V. John; Connelly, Joseph A.; Mentzell, J. Eric; Tveekrem, June L.; Howard, Joseph M.; Preuss, Werner; Schroeder, Mechthild; Sohn, Alex;

Linear and Non-Linear Response of Liquid and Solid Particles to Energetic Radiation

DTIC Science & Technology

1991-03-11

for particle 2 located on the + x6 axis (perpendicular to the beam propagation axis) one diameter surface-to-surface from particle 1 (i 12 = 4.0, Obd2 ...axis direction. Off is the far field scattering angle relative to the beam propagation axis. Obd2 is the orientation angle of particle 2 relative to...Particle 2 in the Xb - Zb plane and positioned one diameter surface-to-surface from particle 1 (P12 = 4.0). a.) Obd2 = 00, b.) Obd2 = 30 ° , c.) ebd

System and method for manufacture of airfoil components

DOEpatents

Moors, Thomas Michael

2016-11-29

Embodiments of the present disclosure relate generally to systems and methods for manufacturing an airfoil component. The system can include: a geometrical mold; an elongated flexible sleeve having a closed-off interior and positioned within the geometrical mold, wherein the elongated flexible sleeve is further positioned to have a desired geometry; an infusing channel in fluid communication with the closed-off interior of the elongated flexible sleeve and configured to communicate a resinous material thereto; a vacuum channel in fluid communication with the closed-off interior of the elongated flexible sleeve and configured to vacuum seal the closed-off interior of the elongated flexible sleeve; and a glass fiber layer positioned within the closed-off interior of the elongated flexible sleeve.

Major off-axis hydrothermal activity on the northern Gorda Ridge

USGS Publications Warehouse

Rona, Peter A.; Denlinger, Roger P.; Fisk, M. R.; Howard, K. J.; Taghon, G. L.; Klitgord, Kim D.; McClain, James S.; McMurray, G. R.; Wiltshire, J. C.

1990-01-01

The first hydrothermal field on the northern Gorda Ridge, the Sea Cliff hydrothermal field, was discovered and geologic controls of hydrothermal activity in the rift valley were investigated on a dive series using the DSV Sea Cliff. The Sea Cliff hydrothermal field was discovered where predicted at the intersection of axis-oblique and axis-parallel faults at the south end of a linear ridge at mid-depth (2700 m) on the east wall. Preliminary mapping and sampling of the field reveal: a setting nested on nearly sediment-free fault blocks 300 m above the rift valley floor 2.6 km from the axis; a spectrum of venting types from seeps to black smokers; high conductive heat flow estimated to be equivalent to the convective flux of multiple black smokers through areas of the sea floor sealed by a caprock of elastic breccia primarily derived from basalt with siliceous cement and barite pore fillings; and a vent biota with Juan de Fuca Ridge affinites. These findings demonstrate the importance of off-axis hydrothermal activity and the role of the intersection of tectonic lineations in controlling hydrothermal sites at sea-floor spreading centers.

Off-axis integrated cavity output spectroscopy with a mid-infrared interband cascade laser for real-time breath ethane measurements.

PubMed

Parameswaran, Krishnan R; Rosen, David I; Allen, Mark G; Ganz, Alan M; Risby, Terence H

2009-02-01

Cavity-enhanced tunable diode laser absorption spectroscopy is an attractive method for measuring small concentrations of gaseous species. Ethane is a breath biomarker of lipid peroxidation initiated by reactive oxygen species. A noninvasive means of quickly quantifying oxidative stress status has the potential for broad clinical application. We present a simple, compact system using off-axis integrated cavity output spectroscopy with an interband cascade laser and demonstrate its use in real-time measurements of breath ethane. We demonstrate a detection sensitivity of 0.48 ppb/Hz(1/2).

Off-axis targets maximize bearing Fisher Information in broadband active sonar.

PubMed

Kloepper, Laura N; Buck, John R; Liu, Yang; Nachtigall, Paul E

2018-01-01

Broadband active sonar systems estimate range from time delay and velocity from Doppler shift. Relatively little attention has been paid to how the received echo spectrum encodes information about the bearing of an object. This letter derives the bearing Fisher Information encoded in the frequency dependent transmitter beampattern. This leads to a counter-intuitive result: directing the sonar beam so that a target of interest is slightly off-axis maximizes the bearing information about the target. Beam aim data from a dolphin biosonar experiment agree closely with the angle predicted to maximize bearing information.

VizieR Online Data Catalog: ChaMP. I. First X-ray source catalog (Kim+, 2004)

NASA Astrophysics Data System (ADS)

Kim, D.-W.; Cameron, R. A.; Drake, J. J.; Evans, N. R.; Freeman, P.; Gaetz, T. J.; Ghosh, H.; Green, P. J.; Harnden, F. R. Jr; Karovska, M.; Kashyap, V.; Maksym, P. W.; Ratzlaff, P. W.; Schlegel, E. M.; Silverman, J. D.; Tananbaum, H. D.; Vikhlinin, A. A.; Wilkes, B. J.; Grimes, J. P.

2004-01-01

The Chandra Multiwavelength Project (ChaMP) is a wide-area (~14deg2 < survey of serendipitous Chandra X-ray sources, aiming to establish fair statistical samples covering a wide range of characteristics (such as absorbed active galactic nuclei, high-z clusters of galaxies) at flux levels (fX~10-15 to 10-14erg/s/cm2) ) intermediate between the Chandra deep surveys and previous missions. We present the first ChaMP catalog, which consists of 991 near on-axis, bright X-ray sources obtained from the initial sample of 62 observations. The data have been uniformly reduced and analyzed with techniques specifically developed for the ChaMP and then validated by visual examination. To assess source reliability and positional uncertainty, we perform a series of simulations and also use Chandra data to complement the simulation study. The false source detection rate is found to be as good as or better than expected for a given limiting threshold. On the other hand, the chance of missing a real source is rather complex, depending on the source counts, off-axis distance (or PSF), and background rate. The positional error (95% confidence level) is usually less than 1" for a bright source, regardless of its off-axis distance, while it can be as large as 4" for a weak source (~20counts) at a large off-axis distance (Doff-axis>8'). We have also developed new methods to find spatially extended or temporary variable sources, and those sources are listed in the catalog. (5 data files).

CACTUS (Calculator and Computer Technology User Service): Some Easter Mathematics

ERIC Educational Resources Information Center

Hyde, Hartley

2007-01-01

In the Western Gregorian Calendar, the date of Easter Sunday is defined as the Sunday following the ecclesiastical Full Moon that falls on or next after March 21. While the pattern of dates so defined usually repeats each 19 years, there is a 0.08 day difference between the cycles. More accurately, the system has a period of 70 499 183 lunations…

Electromagnetic Simulations for an Axisymmetric Gregorian Reflector System for a Space Deployed Inflatable Antenna

DTIC Science & Technology

2016-01-22

Q. J. Wei, S. Pan, S. Mohan, and S. Seager, Inflatable antenna for CubeSat : fabrication, deployment and results of experimental tests, 2014 IEEE...Aerospace Conference, pp. 1- 12. [8] A. Babuscia, T. Choi, C. Lee, and K-M. Cheung, Inflatable antennas and arrays for interplanetary communication using CubeSats and SmallSats, 2015 IEEE Aerospace Conference, pp. 1-9.

Design and Analysis of an Axisymmetric Phased Array Fed Gregorian Reflector System for Limited Scanning

DTIC Science & Technology

2016-01-22

Numerical electromagnetic simulations based on the multilevel fast multipole method (MLFMM) were used to analyze and optimize the antenna...and are not necessarily endorsed by the United States Government. numerical simulations with the multilevel fast multipole method (MLFMM...and optimized using numerical simulations conducted with the multilevel fast multipole method (MLFMM) using FEKO software (www.feko.info). The

Ohmic ITBs in Alcator C-Mod

NASA Astrophysics Data System (ADS)

Rowan, William L.; Bespamyatnov, Igor O.; Fiore, C. L.; Dominguez, A.; Hubbard, A. E.; Ince-Cushman, A.; Greenwald, M. J.; Lin, L.; Marmar, E. S.; Reinke, M.; Rice, J. E.; Zhurovich, K.

2007-11-01

Internal transport barrier (ITB) plasmas can arise spontaneously in Ohmic Alcator C-Mod plasmas. The operational prescription for the ITB include formation of an EDA H-mode in a toroidal magnetic field that is ramping down and a subsequent increase in the toroidal magnetic field. Like ITBs generated with off-axis ICRF heating, these have peaked pressure profiles which can be suppressed by on-axis ICRF heating. Recent work on onset conditions for the ICRF generated ITB (K. Zhurovich, et al., To be published in Nuclear Fusion) demonstrates that the broadening of the ion temperature profile due to off-axis ICRF reduces the ion temperature gradient and suppreses the ITG instability driven particle flux as the primary mechanism for ITB formation. The object of this study is to examine the characteristics of Ohmic ITBs to find whether this model for onset is supported.

Structural Design of a 4-Meter Off-Axis Space Telescope for the Habitable-Zone Exoplanet Direct Imaging Mission

NASA Technical Reports Server (NTRS)

Arnold, William, Sr.; Stahl, H Philip

2017-01-01

This design study was conducted to support the HABEX project. There are a number of companion papers at this conference which go into detail on what all the HABEX goals are. The objective of this paper is to establish a baseline primary mirror design which satisfies the following structural related requirements. The designs in this study have a high TRL (Technology Readiness Level), realistic manufacturing limits and performance in line with the HABEX mission. A secondary goal of the study was to evaluate a number competing criteria for the selection. Questions such as differences in the on axis versus off axis static and dynamic response to disturbances. This study concentrates on the structural behavior, companion papers cover thermal and long term stability aspects of the problem.

Mini-lidar sensor for the remote stand-off sensing of chemical/biological substances and method for sensing same

DOEpatents

Ray, Mark D.; Sedlacek, Arthur J.

2003-08-19

A method and apparatus for remote, stand-off, and high efficiency spectroscopic detection of biological and chemical substances. The apparatus including an optical beam transmitter which transmits a beam having an axis of transmission to a target, the beam comprising at least a laser emission. An optical detector having an optical detection path to the target is provided for gathering optical information. The optical detection path has an axis of optical detection. A beam alignment device fixes the transmitter proximal to the detector and directs the beam to the target along the optical detection path such that the axis of transmission is within the optical detection path. Optical information gathered by the optical detector is analyzed by an analyzer which is operatively connected to the detector.

Horizontal Axis Levitron--A Physics Demonstration

ERIC Educational Resources Information Center

Michaelis, Max M.

2014-01-01

After a brief history of the Levitron, the first horizontal axis Levitron is reported. Because it is easy to operate, it lends itself to educational physics experiments and analogies. Precession and nutation are visualized by reflecting the beam from a laser pointer off the "spignet". Precession is fundamental to nuclear magnetic…

Results of investigation on an 0.004-scale 140c modified configuration space shuttle vehicle orbiter model (74-0) in the NASA/Langley Research Center hypersonic nitrogen tunnel (OA89)

NASA Technical Reports Server (NTRS)

Hawthorne, P. J.

1975-01-01

Wind tunnel test data for the modified space shuttle vehicle orbiter is documented. Tests were made at various elevon settings and additionally in wing off/bodyflap off configuration at angles of attack from -5 to 42.5 degrees at zero yaw. Data obtained on high hypersonic longitudinal and lateral directional stability and control characteristics of the updated SSV configuration in an initially diatomic medium are included.

The ASTRO-H SXT Performance to the Large Off-Set Angles

NASA Technical Reports Server (NTRS)

Sato, Toshiki; Iizuka, Ryo; Mori, Hideyuki; Hayashi, Takayuki; Maeda, Yoshitomo; Ishida, Manabu; Kikuchi, Naomichi; Kurashima, Sho; Nakaniwa, Nozomi; Okajima, Takashi;

Optimization of a bundle divertor for FED

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hively, L.M.; Rothe, K.E.; Minkoff, M.

1982-01-01

Optimal double-T bundle divertor configurations have been obtained for the Fusion Engineering Device (FED). On-axis ripple is minimized, while satisfying a series of engineering constraints. The ensuing non-linear optimization problem is solved via a sequence of quadratic programming subproblems, using the VMCON algorithm. The resulting divertor designs are substantially improved over previous configurations.

Wide-Field-of-View Millimeter-Wave Telescope Design with Ultra-Low Cross-Polarization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bernacki, Bruce E.; Kelly, James F.; Sheen, David M.

2012-05-01

As millimeter-wave arrays become available, off-axis imaging performance of the fore optics increases in importance due to the relatively large physical extent of the arrays. Typically, simple optical telescope designs are adapted to millimeter-wave imaging but single-mirror spherical or classic conic designs cannot deliver adequate image quality except near the optical axis. Since most millimeter-wave designs are quasi-optical, optical ray tracing and commercial design software can be used to optimize designs to improve off-axis imaging as well as minimize cross-polarization. Methods that obey the Dragone-Mizuguchi condition for the design of reflective millimeter-wave telescopes with low cross-polarization also provide additional degreesmore » of freedom that offer larger fields of view than possible with single-reflector designs. Dragone’s graphical design method does not lend itself readily to computer-based optical design approaches, but subsequent authors expanded on Dragone’s geometric design approach with analytic expressions that describe the location, shape, off-axis height and tilt of the telescope elements that satisfy Dragone’s design rules and can be used as a first-order design for subsequent computer-based design and optimization. We investigate two design variants that obey the Dragone-Mizuguchi conditions that exhibit ultra-low polarization crosstalk and a large diffraction-limited field of view well suited to millimeter-wave imaging arrays.« less

Rolled-up inductor structure for a radiofrequency integrated circuit (RFIC)

DOEpatents

Li, Xiuling; Huang, Wen; Ferreira, Placid M.; Yu, Xin

2015-12-29

A rolled-up inductor structure for a radiofrequency integrated circuit (RFIC) comprises a multilayer sheet in a rolled configuration comprising multiple turns about a longitudinal axis. The multilayer sheet comprises a conductive pattern layer on a strain-relieved layer, and the conductive pattern layer comprises at least one conductive strip having a length extending in a rolling direction. The at least one conductive strip thereby wraps around the longitudinal axis in the rolled configuration. The conductive pattern layer may also comprise two conductive feed lines connected to the conductive strip for passage of electrical current therethrough. The conductive strip serves as an inductor cell of the rolled-up inductor structure.

Rolled-up transmission line structure for a radiofrequency integrated circuit (RFIC)

DOEpatents

Li, Xiuling; Huang, Wen

2015-04-28

A rolled-up transmission line structure for a radiofrequency integrated circuit (RFIC) comprises a multilayer sheet in a rolled configuration comprising multiple turns about a longitudinal axis, where the multilayer sheet comprises a conductive pattern layer on a strain-relieved layer. The conductive pattern layer comprises a first conductive film and a second conductive film separated from the first conductive film in a rolling direction. In the rolled configuration, the first conductive film surrounds the longitudinal axis, and the second conductive film surrounds the first conductive film. The first conductive film serves as a signal line and the second conductive film serves as a conductive shield for the rolled-up transmission line structure.

NMR of samples containing metal foils.

PubMed

Xiong, J; Lock, H; Tao, T; Keeler, C; Maciel, G E

1999-07-01

By using spool configurations of a sample containing aluminum foil, in which the axis of the spool is collinear with the RF coil axis, one can obtain high-quality 13C NMR spectra of static samples of organic material attached to the aluminum foil. By combining such a spool configuration (or, alternatively, analogous samples containing equivalent amounts of fine aluminum powder) with the magic-angle hopping (MAH) technique, one can achieve a high degree of isotropic averaging of the 13C spectrum. This opens to NMR techniques the study of a variety of samples containing macroscopic pieces of metal foils, e.g., thin films deposited on metal foils and electrochemical systems with species adsorbed on metal-foil electrodes.

Tank Investigation of the EDO Model 142 Hydro-Ski Research Airplane

NASA Technical Reports Server (NTRS)

Ramsen, John A.; Wadlin, Kenneth L.; Gray, George R.

1951-01-01

A tank investigation has been conducted of a 1/10-size powered-dynamic model of the Edo model 142 hydra-ski research airplane. The results of tests of two configurations are presented: One included a large ski and a ski well; the other, a small ski without a well. Water take-offs would be possible with the available thrust for either configuration: however, the configuration with the large ski emerged sooner and had less resistance from ski emergence until take-off. Longitudinal stability and landing behavior in smooth water were satisfactory for both configurations. Some alteration to the design of the tail would be desirable in order to reduce the spray loads.

Vertical axis wind turbine airfoil

DOEpatents

Krivcov, Vladimir; Krivospitski, Vladimir; Maksimov, Vasili; Halstead, Richard; Grahov, Jurij Vasiljevich

2012-12-18

A vertical axis wind turbine airfoil is described. The wind turbine airfoil can include a leading edge, a trailing edge, an upper curved surface, a lower curved surface, and a centerline running between the upper surface and the lower surface and from the leading edge to the trailing edge. The airfoil can be configured so that the distance between the centerline and the upper surface is the same as the distance between the centerline and the lower surface at all points along the length of the airfoil. A plurality of such airfoils can be included in a vertical axis wind turbine. These airfoils can be vertically disposed and can rotate about a vertical axis.

Experimenting with concentrated sunlight using the DLR solar furnace

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neumann, A.; Groer, U.

1996-10-01

The high flux solar furnace that is operated by the Deutsche Forschungsanstalt fuer Luft- und Raumfahrt (DLR) at Cologne was inaugurated in June 1994 and we are now able to look back onto one year of successful operation. The solar furnace project was founded by the government of the State Northrhine Westfalia within the Study Group AG Solar. The optical design is a two-stage off-axis configuration which uses a flat 52 m{sup 2} heliostat and a concentrator composed of 147 spherical mirror facets. The heliostat redirects the solar light onto the concentrator which focuses the beam out of the opticalmore » axis of the system into the laboratory building. At high insolation levels (>800W/m{sup 2}) it is possible to collect a total power of 20 kW with peak flux densities of 4 MW/m{sup 2}. Sixteen different experiment campaigns were carried out during this first year of operation. The main research fields for these experiments were material science, component development and solar chemistry. The furnace also has its own research program leading to develop sophisticated measurement techniques like remote infrared temperature sensing and flux mapping. Another future goal to be realized within the next five years is the improvement of the performance of the furnace itself. 6 refs., 9 figs., 1 tab.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Corsi, Alessandra; Gal-Yam, A.; Kulkarni, S. R.

Long duration γ-ray bursts are a rare subclass of stripped-envelope core-collapse supernovae (SNe) that launch collimated relativistic outflows (jets). All γ-ray-burst-associated SNe are spectroscopically Type Ic, with broad-lines, but the fraction of broad-lined SNe Ic harboring low-luminosity γ-ray bursts remains largely unconstrained. Some SNe should be accompanied by off-axis γ-ray burst jets that initially remain invisible, but then emerge as strong radio sources (as the jets decelerate). However, this critical prediction of the jet model for γ-ray bursts has yet to be verified observationally. Here, we present K. G. Jansky Very Large Array observations of 15 broad-lined SNe of Type Ic discovered by the Palomar Transient Factory in an untargeted manner. Most of the SNe in our sample exclude radio emission observationally similar to that of the radio-loud, relativistic SN 1998bw. We constrain the fraction of 1998bw-like broad-lined SNe Ic to bemore » $$\\lesssim 41 \\% $$ (99.865% confidence). Most of the events in our sample also exclude off-axis jets similar to GRB 031203 and GRB 030329, but we cannot rule out off-axis γ-ray bursts expanding in a low-density wind environment. Three SNe in our sample are detected in the radio. PTF11qcj and PTF14dby show late-time radio emission with average ejecta speeds of ≈0.3–0.4 c, on the dividing line between relativistic and "ordinary" SNe. The speed of PTF11cmh radio ejecta is poorly constrained. We estimate that $$\\lesssim 85 \\% $$ (99.865% confidence) of the broad-lined SNe Ic in our sample may harbor off-axis γ-ray bursts expanding in media with densities in the range probed by this study.« less

Modeling free energy availability from Hadean hydrothermal systems to the first metabolism.

PubMed

Simoncini, E; Russell, M J; Kleidon, A

2011-12-01

Off-axis Hydrothermal Systems (HSs) are seen as the possible setting for the emergence of life. As the availability of free energy is a general requirement to drive any form of metabolism, we ask here under which conditions free energy generation by geologic processes is greatest and relate these to the conditions found at off-axis HSs. To do so, we present a conceptual model in which we explicitly capture the energetics of fluid motion and its interaction with exothermic reactions to maintain a state of chemical disequilibrium. Central to the interaction is the temperature at which the exothermic reactions take place. This temperature not only sets the equilibrium constant of the chemical reactions and thereby the distance of the actual state to chemical equilibrium, but these reactions also shape the temperature gradient that drives convection and thereby the advection of reactants to the reaction sites and the removal of the products that relate to geochemical free energy generation. What this conceptual model shows is that the positive feedback between convection and the chemical kinetics that is found at HSs favors a greater rate of free energy generation than in the absence of convection. Because of the lower temperatures and because the temperature of reactions is determined more strongly by these dynamics rather than an external heat flux, the conditions found at off-axis HSs should result in the greatest rates of geochemical free energy generation. Hence, we hypothesize from these thermodynamic considerations that off-axis HSs seem most conducive for the emergence of protometabolic pathways as these provide the greatest, abiotic generation rates of chemical free energy.

Reduction of optically observed artillery blast wave trajectories using low dimensionality models

NASA Astrophysics Data System (ADS)

Steward, Bryan J.; Gross, Kevin C.; Perram, Glen P.

2011-05-01

Muzzle blast trajectories from firings of a 152 mm caliber gun howitzer were obtained with high-speed optical imagers and used to assess the fidelity with which low dimensionality models can be used for data reduction. Characteristic flow regions were defined for the blast waves. The near-field region was estimated to extend to 0.98 - 1.25 meters from the muzzle and the far-field region was estimated to begin at 2.61 - 3.31 meters. Blast wave geometries and radial trajectories were collected in the near through far-fields with visible imagers operating at 1,600 Hz. Beyond the near-field the blast waves exhibited a near-spherical geometry in which the major axis of the blast lay along the axis of the gun barrel and measured within 95% of the minor axis. Several blast wave propagation models were applied to the mid and far-field data to determine their ability to reduce the blast wave trajectories to fewer parameters while retaining the ability to distinguish amongst three munitions configurations. A total of 147 firings were observed and used to assess within-configuration variability relative to separation between configurations. Results show that all models perform well, and drag and point blast model parameters additionally provide insight into phenomenology of the blast.

How Confocal Is Confocal Raman Microspectroscopy on the Skin? Impact of Microscope Configuration and Sample Preparation on Penetration Depth Profiles.

PubMed

Lunter, Dominique Jasmin

2016-01-01

The aim of the study was to elucidate the effect of sample preparation and microscope configuration on the results of confocal Raman microspectroscopic evaluation of the penetration of a pharmaceutical active into the skin (depth profiling). Pig ear skin and a hydrophilic formulation containing procaine HCl were used as a model system. The formulation was either left on the skin during the measurement, or was wiped off or washed off prior to the analysis. The microscope configuration was varied with respect to objectives and pinholes used. Sample preparation and microscope configuration had a tremendous effect on the results of depth profiling. Regarding sample preparation, the best results could be observed when the formulation was washed off the skin prior to the analysis. Concerning microscope configuration, the use of a 40 × 0.6 numerical aperture (NA) objective in combination with a 25-µm pinhole or a 100 × 1.25 NA objective in combination with a 50-µm pinhole was found to be advantageous. Complete removal of the sample from the skin before the analysis was found to be crucial. A thorough analysis of the suitability of the chosen microscope configuration should be performed before acquiring concentration depth profiles. © 2016 S. Karger AG, Basel.

A new phosphine oxide host based on ortho-disubstituted dibenzofuran for efficient electrophosphorescence: towards high triplet state excited levels and excellent thermal, morphological and efficiency stability.

PubMed

Han, Chunmiao; Xie, Guohua; Li, Jing; Zhang, Zhensong; Xu, Hui; Deng, Zhaopeng; Zhao, Yi; Yan, Pengfei; Liu, Shiyong

2011-08-01

An efficient host for blue and green electrophosphorescence, 4,6-bis(diphenylphosphoryl)dibenzofuran (o-DBFDPO), with the structure of a short-axis-substituted dibenzofuran was designed and synthesised. It appears that the greater density of the diphenylphosphine oxide (DPPO) moieties in the short-axis substitution configuration effectively restrains the intermolecular interactions, because only very weak π-π stacking interactions could be observed, with a centroid-to-centroid distance of 3.960 Å. The improved thermal stability of o-DBFDPO was corroborated by its very high glass transition temperature (T(g)) of 191 °C, which is the result of the symmetric disubstitution structure. Photophysical investigation showed o-DBFDPO to be superior to the monosubstituted derivative, with a longer lifetime (1.95 ns) and a higher photoluminescent quantum efficiency (61 %). The lower first singlet state excited level (3.63 eV) of o-DBFDPO demonstrates the stronger polarisation effect attributable to the greater number of DPPO moieties. Simultaneously, an extremely high first triplet state excited level (T(1)) of 3.16 eV is observed, demonstrating the tiny influence of short-axis substitution on T(1). The improved carrier injection ability, which contributed to low driving voltages of blue- and green-emitting phosphorescent organic light-emitting diodes (PHOLEDs), was further confirmed by Gaussian calculation. Furthermore, the better thermal and morphological properties of o-DBFDPO and the matched frontier molecular orbital (FMO) levels in the devices significantly reduced efficiency roll-offs. Efficient blue and green electrophosphorescence based on the o-DBFDPO host was demonstrated. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Deep-level dominated electrical characteristics of Au contacts on beta-SiC

NASA Technical Reports Server (NTRS)

Das, K.; Kong, H. S.; Petit, J. B.; Bumgarner, J. W.; Davis, R. F.; Matus, L. G.

1990-01-01

Electrical characteristics of Au contacts on beta-SiC films, grown epitaxially on both nominal and off-axis (100) silicon substrates, are reported. An analysis of the logarithmic I-V plots of the Au/beta-SiC diodes revealed information pertaining to the deep states present in the materials. It was found that while the beta-SiC films grown on nominally (100) oriented substrates show the presence of two deep levels located between 0.26 and 0.38 eV below the conduction bandedge, the beta-SiC films deposited on off-axis substrates have only one deep level, located about 0.49 eV below the conduction bandedge for the 2-deg off (100) substrates and 0.57 eV for the 4-deg off (100) substrates. The presence of the shallower deep states in the beta-SiC films grown on nominal (100) substrates is attributed to the electrical activity of antiphase domain boundaries.

Four-mirror extreme ultraviolet (EUV) lithography projection system

DOEpatents

Cohen, Simon J; Jeong, Hwan J; Shafer, David R

2000-01-01

The invention is directed to a four-mirror catoptric projection system for extreme ultraviolet (EUV) lithography to transfer a pattern from a reflective reticle to a wafer substrate. In order along the light path followed by light from the reticle to the wafer substrate, the system includes a dominantly hyperbolic convex mirror, a dominantly elliptical concave mirror, spherical convex mirror, and spherical concave mirror. The reticle and wafer substrate are positioned along the system's optical axis on opposite sides of the mirrors. The hyperbolic and elliptical mirrors are positioned on the same side of the system's optical axis as the reticle, and are relatively large in diameter as they are positioned on the high magnification side of the system. The hyperbolic and elliptical mirrors are relatively far off the optical axis and hence they have significant aspherical components in their curvatures. The convex spherical mirror is positioned on the optical axis, and has a substantially or perfectly spherical shape. The spherical concave mirror is positioned substantially on the opposite side of the optical axis from the hyperbolic and elliptical mirrors. Because it is positioned off-axis to a degree, the spherical concave mirror has some asphericity to counter aberrations. The spherical concave mirror forms a relatively large, uniform field on the wafer substrate. The mirrors can be tilted or decentered slightly to achieve further increase in the field size.

Real-Time Grazing Incidence Small Angle X-Ray Scattering Studies of the Growth Kinetics of Sputter-Deposited Silicon Thin Films

NASA Astrophysics Data System (ADS)

Demasi, Alexander; Erdem, Gozde; Chinta, Priya; Headrick, Randall; Ludwig, Karl

2012-02-01

The fundamental kinetics of thin film growth remains an active area of investigation. In this study, silicon thin films were grown at room temperature on silicon substrates via both on-axis and off-axis plasma sputter deposition, while the evolution of surface morphology was measured in real time with in-situ grazing incidence small angle x-ray scattering (GISAXS) at the National Synchrotron Light Source. GISAXS is a surface-sensitive, non-destructive technique, and is therefore ideally suited to a study of this nature. In addition to investigating the effect of on-axis versus off-axis bombardment, the effect of sputter gas partial pressure was examined. Post-facto, ex-situ atomic force microscopy (AFM) was used to measure the final surface morphology of the films, which could subsequently be compared with the surface morphology determined by GISAXS. Comparisons are made between the observed surface evolution during growth and theoretical predictions. This work was supported by the Department of Energy, Office of Basic Energy Sciences.

Gimbaled multispectral imaging system and method

DOEpatents

Brown, Kevin H.; Crollett, Seferino; Henson, Tammy D.; Napier, Matthew; Stromberg, Peter G.

2016-01-26

A gimbaled multispectral imaging system and method is described herein. In an general embodiment, the gimbaled multispectral imaging system has a cross support that defines a first gimbal axis and a second gimbal axis, wherein the cross support is rotatable about the first gimbal axis. The gimbaled multispectral imaging system comprises a telescope that fixed to an upper end of the cross support, such that rotation of the cross support about the first gimbal axis causes the tilt of the telescope to alter. The gimbaled multispectral imaging system includes optics that facilitate on-gimbal detection of visible light and off-gimbal detection of infrared light.

APS-U LATTICE DESIGN FOR OFF-AXIS ACCUMULATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Yipeng; Borland, M.; Lindberg, R.

2017-06-25

A 67-pm hybrid-seven-bend achromat (H7BA) lattice is being proposed for a future Advanced Photon Source (APS) multi-bend-achromat (MBA) upgrade project. This lattice design pushes for smaller emittance and requires use of a swap-out (on-axis) injection scheme due to limited dynamic acceptance. Alternate lattice design work has also been performed for the APS upgrade to achieve better beam dynamics performance than the nominal APS MBA lattice, in order to allow off-axis accumulation. Two such alternate H7BA lattice designs, which target a still-low emittance of 90 pm, are discussed in detail in this paper. Although the single-particle-dynamics performance is good, simulations ofmore » collective effects indicate that surprising difficulty would be expected accumulating high single-bunch charge in this lattice. The brightness of the 90-pm lattice is also a factor of two lower than the 67-pm H7BA lattice.« less

Off-Axis Nulling Transfer Function Measurement: A First Assessment

NASA Technical Reports Server (NTRS)

Vedova, G. Dalla; Menut, J.-L.; Millour, F.; Petrov, R.; Cassaing, F.; Danchi, W. C.; Jacquinod, S.; Lhome, E.; Lopez, B.; Lozi, J.;

Islamic Fundamentalism in South Asia

DTIC Science & Technology

2007-08-20

Dhaka in March 1948, that Urdu would be the country’s official language . Nearly 99% of the population of East Bengal spoke Bengali, a language that...In 1955 East Bengal’s name was changed to East Pakistan. On April 19, 1954, Bengali was finally made an official state language , and 1956 it...word of God. Dhaka newspapers, reflecting the conflicts in Bengali culture, list three dates: in the Bengali ( Bangla ), Muslim, and Gregorian

Study of shuttle imaging microwave system antenna. Volume 1: Conceptual design

NASA Technical Reports Server (NTRS)

Wesley, R. W.; Waineo, D. K.; Barton, C. R.; Love, A. W.

1975-01-01

A detailed preliminary design and complete performance evaluation are presented of an 11-channel large aperture scanning radiometer antenna for the shuttle imaging microwave system (SIMS) program. Provisions for interfacing the antenna with the space shuttle orbiter are presented and discussed. A program plan for hardware development and a rough order of magnitude (ROM) cost are also included. The conceptual design of the antenna is presented. It consists of a four-meter diameter parabolic torus main reflector, which is a graphite/epoxy shell supported by a graphite/epoxy truss. A rotating feed wheel assembly supports six Gregorian subreflectors covering the upper eight frequency channels from 6.6 GHz through 118.7 GHz, and two three-channel prime forms feed assemblies for 0.6, 1.4, and 2.7 GHz. The feed wheel assembly also holds the radiometers and power supplies, and a drive system using a 400 Hz synchronous motor is described. The RF analysis of the antenna is performed using physical optics procedures for both the dual reflector Gregorian concept and the single reflector prime focus concept. A unique aberration correcting feed for 2.7 GHz is analyzed. A structural analysis is also included. The analyses indicate that the antenna will meet system requirements.

High-speed optical three-axis vector magnetometry based on nonlinear Hanle effect in rubidium vapor

NASA Astrophysics Data System (ADS)

Azizbekyan, Hrayr; Shmavonyan, Svetlana; Khanbekyan, Aleksandr; Movsisyan, Marina; Papoyan, Aram

2017-07-01

The magnetic-field-compensation optical vector magnetometer based on the nonlinear Hanle effect in alkali metal vapor allowing two-axis measurement operation has been further elaborated for three-axis performance, along with significant reduction of measurement time. The upgrade was achieved by implementing a two-beam resonant excitation configuration and a fast maximum searching algorithm. Results of the proof-of-concept experiments, demonstrating 1 μT B-field resolution, are presented. The applied interest and capability of the proposed technique is analyzed.

Solutions on a high-speed wide-angle zoom lens with aspheric surfaces

NASA Astrophysics Data System (ADS)

Yamanashi, Takanori

2012-10-01

Recent development in CMOS and digital camera technology has accelerated the business and market share of digital cinematography. In terms of optical design, this technology has increased the need to carefully consider pixel pitch and characteristics of the imager. When the field angle at the wide end, zoom ratio, and F-number are specified, choosing an appropriate zoom lens type is crucial. In addition, appropriate power distributions and lens configurations are required. At points near the wide end of a zoom lens, it is known that an aspheric surface is an effective means to correct off-axis aberrations. On the other hand, optical designers have to focus on manufacturability of aspheric surfaces and perform required analysis with respect to the surface shape. Centration errors aside, it is also important to know the sensitivity to aspheric shape errors and their effect on image quality. In this paper, wide angle cine zoom lens design examples are introduced and their main characteristics are described. Moreover, technical challenges are pointed out and solutions are proposed.

Estimation of Aerodynamic Stability Derivatives for Space Launch System and Impact on Stability Margins

NASA Technical Reports Server (NTRS)

Pei, Jing; Wall, John

2013-01-01

This paper describes the techniques involved in determining the aerodynamic stability derivatives for the frequency domain analysis of the Space Launch System (SLS) vehicle. Generally for launch vehicles, determination of the derivatives is fairly straightforward since the aerodynamic data is usually linear through a moderate range of angle of attack. However, if the wind tunnel data lacks proper corrections then nonlinearities and asymmetric behavior may appear in the aerodynamic database coefficients. In this case, computing the derivatives becomes a non-trivial task. Errors in computing the nominal derivatives could lead to improper interpretation regarding the natural stability of the system and tuning of the controller parameters, which would impact both stability and performance. The aerodynamic derivatives are also provided at off nominal operating conditions used for dispersed frequency domain Monte Carlo analysis. Finally, results are shown to illustrate that the effects of aerodynamic cross axis coupling can be neglected for the SLS configuration studied

Qualification of a High Accuracy Dual-Axis Antenna Deployment and Trimming Mechanism

NASA Technical Reports Server (NTRS)

Gossant, Alain; Morichon, Francois

2010-01-01

The Antenna Deployment and Trimming Mechanism Mark 2 (ADTM Mk2) has been developed to answer today's need for a generic antenna deployment and high accuracy pointing mechanism, allowing RF sensing applications and easier dual deployments configurations. This paper presents the design and evolution from its predecessor, the experience of the design team from kick off to qualification and batch manufacture, as well as some lessons learned from ramping up "mass-production" capabilities while implementing customer driven changes. Astrium has manufactured and flown ADTM units for the past 20 years, from an initial deployment-only mechanism developed for the Orion program to today's Eurostar E3000 ADTM family. The Antenna ADTM Mk2 is an evolution of the original ADTM Mk1. Although it uses Mk1 building blocks to minimize risks associated with the development of a new product, it incorporates major evolutions and is the new baseline for Astrium latest generation of Eurostar E3000 telecom satellites.

Parallel pumping of a ferromagnetic nanostripe: Confinement quantization and off-resonant driving

NASA Astrophysics Data System (ADS)

Yarbrough, P. M.; Livesey, K. L.

2018-01-01

The parametric excitation of spin waves in a rectangular, ferromagnetic nanowire in the parallel pump configuration and with an applied field along the long axis of the wire is studied theoretically, using a semi-classical and semi-analytic Hamiltonian approach. We find that as a function of static applied field strength, there are jumps in the pump power needed to excite thermal spin waves. At these jumps, there is the possibility to non-resonantly excite spin waves near kz = 0. Spin waves with negative or positive group velocity and with different standing wave structures across the wire width can be excited by tuning the applied field. By using a magnetostatic Green's function that depends on both the nanowire's width and thickness—rather than just its aspect ratio—we also find that the threshold field strength varies considerably for nanowires with the same aspect ratio but of different sizes. Comparisons between different methods of calculations are made and the advantages and disadvantages of each are discussed.

Efficiency bounds of molecular motors under a trade-off figure of merit

NASA Astrophysics Data System (ADS)

Zhang, Yanchao; Huang, Chuankun; Lin, Guoxing; Chen, Jincan

2017-05-01

On the basis of the theory of irreversible thermodynamics and an elementary model of the molecular motors converting chemical energy by ATP hydrolysis to mechanical work exerted against an external force, the efficiencies of the molecular motors at two different optimization configurations for trade-off figure of merit representing a best compromise between the useful energy and the lost energy are calculated. The upper and lower bounds for the efficiency at two different optimization configurations are determined. It is found that the optimal efficiencies at the two different optimization configurations are always larger than 1 / 2.

Improving the off-axis spatial resolution and dynamic range of the NIF X-ray streak cameras (invited)

DOE PAGES

MacPhee, A. G.; Dymoke-Bradshaw, A. K. L.; Hares, J. D.; ...

2016-08-08

Here, we report simulationsand experiments that demonstrate an increasein spatial resolution ofthe NIF core diagnostic x-ray streak camerasby a factor of two, especially off axis. A designwas achieved by usinga corrector electron optic to flatten the field curvature at the detector planeand corroborated by measurement. In addition, particle in cell simulations were performed to identify theregions in the streak camera that contribute most to space charge blurring. Our simulations provide a tool for convolving syntheticpre-shot spectra with the instrument functionso signal levels can be set to maximize dynamic range for the relevant part of the streak record.

Quantitative DIC microscopy using an off-axis self-interference approach.

PubMed

Fu, Dan; Oh, Seungeun; Choi, Wonshik; Yamauchi, Toyohiko; Dorn, August; Yaqoob, Zahid; Dasari, Ramachandra R; Feld, Michael S

2010-07-15

Traditional Normarski differential interference contrast (DIC) microscopy is a very powerful method for imaging nonstained biological samples. However, one of its major limitations is the nonquantitative nature of the imaging. To overcome this problem, we developed a quantitative DIC microscopy method based on off-axis sample self-interference. The digital holography algorithm is applied to obtain quantitative phase gradients in orthogonal directions, which leads to a quantitative phase image through a spiral integration of the phase gradients. This method is practically simple to implement on any standard microscope without stringent requirements on polarization optics. Optical sectioning can be obtained through enlarged illumination NA.

Coherent and incoherent off-axis Hermite-Gaussian beam combinations.

PubMed

Lü, B; Ma, H

2000-03-10

A detailed study of the coherent and the incoherent combinations of two-dimensional off-axis Hermite-Gaussian beams with rectangular symmetry is made. The closed-form propagation formulas of the resulting beam are derived, and the resulting beam quality in terms of the M(2) factor and power in the bucket is discussed and compared for the coherent and the incoherent combinations. In addition, it is shown that the resulting astigmatic beam can be symmetrized in the sense of the second-moment definition of beam width. However, the symmetrizing transformation of the resulting astigmatic beams is incomplete, because there exist different irradiance profiles.

Absolute Scale Quantitative Off-Axis Electron Holography at Atomic Resolution

NASA Astrophysics Data System (ADS)

Winkler, Florian; Barthel, Juri; Tavabi, Amir H.; Borghardt, Sven; Kardynal, Beata E.; Dunin-Borkowski, Rafal E.

2018-04-01

An absolute scale match between experiment and simulation in atomic-resolution off-axis electron holography is demonstrated, with unknown experimental parameters determined directly from the recorded electron wave function using an automated numerical algorithm. We show that the local thickness and tilt of a pristine thin WSe2 flake can be measured uniquely, whereas some electron optical aberrations cannot be determined unambiguously for a periodic object. The ability to determine local specimen and imaging parameters directly from electron wave functions is of great importance for quantitative studies of electrostatic potentials in nanoscale materials, in particular when performing in situ experiments and considering that aberrations change over time.

Characterisation of a resolution enhancing image inversion interferometer.

PubMed

Wicker, Kai; Sindbert, Simon; Heintzmann, Rainer

2009-08-31

Image inversion interferometers have the potential to significantly enhance the lateral resolution and light efficiency of scanning fluorescence microscopes. Self-interference of a point source's coherent point spread function with its inverted copy leads to a reduction in the integrated signal for off-axis sources compared to sources on the inversion axis. This can be used to enhance the resolution in a confocal laser scanning microscope. We present a simple image inversion interferometer relying solely on reflections off planar surfaces. Measurements of the detection point spread function for several types of light sources confirm the predicted performance and suggest its usability for scanning confocal fluorescence microscopy.

Gigantic transverse voltage induced via off-diagonal thermoelectric effect in CaxCoO2 thin films

NASA Astrophysics Data System (ADS)

Takahashi, Kouhei; Kanno, Tsutomu; Sakai, Akihiro; Adachi, Hideaki; Yamada, Yuka

2010-07-01

Gigantic transverse voltages exceeding several tens volt have been observed in CaxCoO2 thin films with tilted c-axis orientation upon illumination of nanosecond laser pulses. The voltage signals were highly anisotropic within the film surface showing close relation with the c-axis tilt direction. The magnitude and the decay time of the voltage strongly depended on the film thickness. These results confirm that the large laser-induced voltage originates from a phenomenon termed the off-diagonal thermoelectric effect, by which a film out-of-plane temperature gradient leads to generation of a film in-plane voltage.

Dynamic modulation of ocular orientation during visually guided saccades and smooth-pursuit eye movements

NASA Technical Reports Server (NTRS)

Hess, Bernhard J M.; Angelaki, Dora E.

2003-01-01

Rotational disturbances of the head about an off-vertical yaw axis induce a complex vestibuloocular reflex pattern that reflects the brain's estimate of head angular velocity as well as its estimate of instantaneous head orientation (at a reduced scale) in space coordinates. We show that semicircular canal and otolith inputs modulate torsional and, to a certain extent, also vertical ocular orientation of visually guided saccades and smooth-pursuit eye movements in a similar manner as during off-vertical axis rotations in complete darkness. It is suggested that this graviceptive control of eye orientation facilitates rapid visual spatial orientation during motion.

Off-axis Doas Measurements At Observatoire De Haute Provence During 2001

NASA Astrophysics Data System (ADS)

Roozendael, M. Van; de Mazière, M.; Fayt, C.; Hendrick, F.; Hermans, C.

Since December 2000, a ground-based off-axis DOAS spectrometer has been operated by BIRA-IASB in the South of France at the Observatoire de Haute Provence (OHP, 44°N). The design of the instrument allows automated observations of the scattered light alternatively in the zenith direction and at 10° above the horizon (off-axis geometry). The spectrometer is polarised and follows the azimuth of the sun. Its temperature is regulated and it is equipped with a Princeton Instruments/ Hammamatsu cooled diode array detector. Observations are made every 5 minutes in the 320-390 nm range. The analysis of the spectra recorded between January and December 2001 demonstrates the sensitivity of the measurements to tropospheric contents of NO2, HCHO, O3 and BrO. Results show a large seasonality in the HCHO content with maximum values in summer. The tropospheric BrO column is found to be stable over the year in the range of approximately 1.5-2 x1013 molec/cm2, roughly consistent with GOME observations at Northern mid-latitudes. Large increases of the BrO concentration are observed in summer likely due to local pollution in the vicinity of the station.

Initial system design method for non-rotationally symmetric systems based on Gaussian brackets and Nodal aberration theory.

PubMed

Zhong, Yi; Gross, Herbert

2017-05-01

Freeform surfaces play important roles in improving the imaging performance of off-axis optical systems. However, for some systems with high requirements in specifications, the structure of the freeform surfaces could be very complicated and the number of freeform surfaces could be large. That brings challenges in fabrication and increases the cost. Therefore, to achieve a good initial system with minimum aberrations and reasonable structure before implementing freeform surfaces is essential for optical designers. The already existing initial system design methods are limited to certain types of systems. A universal tool or method to achieve a good initial system efficiently is very important. In this paper, based on the Nodal aberration theory and the system design method using Gaussian Brackets, the initial system design method is extended from rotationally symmetric systems to general non-rotationally symmetric systems. The design steps are introduced and on this basis, two off-axis three-mirror systems are pre-designed using spherical shape surfaces. The primary aberrations are minimized using the nonlinear least-squares solver. This work provides insight and guidance for initial system design of off-axis mirror systems.

Determination of fiber-matrix interface failure parameters from off-axis tests

NASA Technical Reports Server (NTRS)

Naik, Rajiv A.; Crews, John H., Jr.

1993-01-01

Critical fiber-matrix (FM) interface strength parameters were determined using a micromechanics-based approach together with failure data from off-axis tension (OAT) tests. The ply stresses at failure for a range of off-axis angles were used as input to a micromechanics analysis that was performed using the personal computer-based MICSTRAN code. FM interface stresses at the failure loads were calculated for both the square and the diamond array models. A simple procedure was developed to determine which array had the more severe FM interface stresses and the location of these critical stresses on the interface. For the cases analyzed, critical FM interface stresses were found to occur with the square array model and were located at a point where adjacent fibers were closest together. The critical FM interface stresses were used together with the Tsai-Wu failure theory to determine a failure criterion for the FM interface. This criterion was then used to predict the onset of ply cracking in angle-ply laminates for a range of laminate angles. Predictions for the onset of ply cracking in angle-ply laminates agreed with the test data trends.

Reduction of structural defects in thick 4H-SiC epitaxial layers grown on 4° off-axis substrates

NASA Astrophysics Data System (ADS)

Yazdanfar, M.; Ivanov, I. G.; Pedersen, H.; Kordina, O.; Janzén, E.

2013-06-01

By carefully controlling the surface chemistry of the chemical vapor deposition process for silicon carbide (SiC), 100 μm thick epitaxial layers with excellent morphology were grown on 4° off-axis SiC substrates at growth rates exceeding 100 μm/h. In order to reduce the formation of step bunching and structural defects, mainly triangular defects, the effect of varying parameters such as growth temperature, C/Si ratio, Cl/Si ratio, Si/H2 ratio, and in situ pre-growth surface etching time are studied. It was found that an in-situ pre growth etch at growth temperature and pressure using 0.6% HCl in hydrogen for 12 min reduced the structural defects by etching preferentially on surface damages of the substrate surface. By then applying a slightly lower growth temperature of 1575 °C, a C/Si ratio of 0.8, and a Cl/Si ratio of 5, 100 μm thick, step-bunch free epitaxial layer with a minimum triangular defect density and excellent morphology could be grown, thus enabling SiC power device structures to be grown on 4° off axis SiC substrates.

Positioning of the carboxamide side chain in 11-oxo-11H-indeno[1,2-b]quinolinecarboxamide anticancer agents: effects on cytotoxicity.

PubMed

Deady, L W; Desneves, J; Kaye, A J; Finlay, G J; Baguley, B C; Denny, W A

2001-02-01

A series of 11-oxo-11H-indeno[1,2-b]quinolines bearing a carboxamide-linked cationic side chain at various positions on the chromophore was studied to determine structure-activity relationships between cytotoxicity and the position of the side chain. The compounds were prepared by Pfitzinger synthesis from an appropriate isatin and 1-indanone, followed by various oxidative steps, to generate the required carboxylic acids. The 4- and 6-carboxamides (with the side chain on a terminal ring, off the short axis of the chromophore) were effective cytotoxins. The dimeric 4- and 6-linked analogues were considerably more cytotoxic than the parent monomers, but had broadly similar activities. In contrast, analogues with side chains at the 8-position (on a terminal ring but off the long axis of the chromophore) or 10-position (off the short axis of the chromophore but in a central ring) were drastically less effective. The 4,10- and 6,10-biscarboxamides had activities between those of the corresponding parent monocarboxamides. The first of these showed good activity against advanced subcutaneous colon 38 tumours in mice.

Propagation of a melting anomaly along the ultraslow Southwest Indian Ridge between 46°E and 52°20'E: interaction with the Crozet hotspot?

NASA Astrophysics Data System (ADS)

Sauter, Daniel; Cannat, Mathilde; Meyzen, Christine; Bezos, Antoine; Patriat, Philippe; Humler, Eric; Debayle, Eric

2009-11-01

Regional axial depths, mantle Bouguer anomaly values, geochemical proxies for the extent of partial melting and tomographic models along the Southwest Indian Ridge (SWIR) all concur in indicating the presence of thicker crust and hotter mantle between the Indomed and Gallieni transform faults (TFs; 46°E and 52°20'E) relative to the neighbouring ridge sections. Accreted seafloor between these TFs over the past ~10 Myr is also locally much shallower (>1000 m) and corresponds to thicker crust (>1.7 km) than previously accreted seafloor along the same ridge region. Two large outward facing topographic gradients mark the outer edges of two anomalously shallow off-axis domains on the African and Antarctic plates. Their vertical relief (>2000 m locally) and their geometry, parallel to the present-day axis along a >210-km-long ridge section, suggest an extremely sudden and large event dated between ~8 (magnetic anomaly C4n) and ~11 Ma (magnetic anomaly C5n). Asymmetric spreading and small ridge jumps occur at the onset of the formation of the anomalously shallow off-axis domains, leading to a re-organization of the ridge segmentation. We interpret these anomalously shallow off-axis domains as the relicts of a volcanic plateau due to a sudden increase of the magma supply. This event of enhanced magmatism started in the central part of the ridge section and then propagated along axis to the east and probably also to the west. However, it did not cross the Gallieni and Indomed TFs suggesting that large offsets can curtail or even block along-axis melt flow. We propose that this melting anomaly may be ascribed to a regionally higher mantle temperature provided by mantle outpouring from the Crozet hotspot towards the SWIR.

Results of investigations on an 0.004-scale 140A/B configuration space shuttle vehicle orbiter model (34-0) in the NASA/Langley Research Center hypersonic helium tunnel (OA88)

NASA Technical Reports Server (NTRS)

Hawthorne, P. J.

1974-01-01

Data obtained during a wind tunnel test of an 0.004-scale 140A/B configuration SSV Orbiter are reported. The test was conducted at a nominal Mach number of 20 and at Reynolds numbers of 0.7, 1.1, 2.0, and 4 x 10 to the 6th power per foot. The complete 140A/B model was tested with various elevon settings and additionally in wing off/bodyflap off configurations at angles of attack from 18 to 54 degrees at zero yaw. This test was performed to obtain high hypersonic longitudinal and lateral-directional stability and control characteristics of the SSV configuration.

Latching micro optical switch

DOEpatents

Garcia, Ernest J; Polosky, Marc A

2013-05-21

An optical switch reliably maintains its on or off state even when subjected to environments where the switch is bumped or otherwise moved. In addition, the optical switch maintains its on or off state indefinitely without requiring external power. External power is used only to transition the switch from one state to the other. The optical switch is configured with a fixed optical fiber and a movable optical fiber. The movable optical fiber is guided by various actuators in conjunction with a latching mechanism that configure the switch in one position that corresponds to the on state and in another position that corresponds to the off state.

Crustal Thickness on the South East Indian Ridge from OBH data

NASA Astrophysics Data System (ADS)

Tolstoy, M.; Cochran, J. R.; Carbotte, S. M.; Floyd, J. S.

2002-12-01

Seismic reflection and refraction data were collected on the intermediate-rate spreading South East Indian Ridge during December 2001 and January 2002 aboard the RV Ewing. A total of six lines of Ocean Bottom Hydrophone (OBH) refraction data were collected along four segments with contrasting ridge axis morphology. All lines were shot ridge parallel, with four lines on-axis, and two lines approximately 20 km off-axis. Each line used four OBHs and the line lengths varied between 102 km and 124 km, depending on the length of each ridge segment. For the two western most segments, an axial magma chamber is observed with crustal arrivals disappearing or being significantly delayed in the 15-20 km range. This indicates a magma chamber deeper than those observed on the faster spreading East Pacific Rise. Off-axis in this area clear crustal arrivals are seen out to 40-50 km. This indicates relatively thick crust in this most inflated of the sections studied, consistent with a higher magma supply. The two eastern most segments have on-axis lines only, and both of these indicate relatively thin crust. This is consistent with the more magma starved character of the bathymetry in these areas. Data will be presented, along with preliminary crustal velocity and thickness models.

Acceleration feedback of a current-following synchronized control algorithm for telescope elevation axis

NASA Astrophysics Data System (ADS)

Tang, Tao; Zhang, Tong; Du, Jun-Feng; Ren, Ge; Tian, Jing

2016-11-01

This paper proposes a dual-motor configuration to enhance closed-loop performance of a telescope control system. Two identical motors are mounted on each side of a U-type frame to drive the telescope elevation axis instead of a single motor drive, which is usually used in a classical design. This new configuration and mechanism can reduce the motor to half the size used in the former design, and it also provides some other advantages. A master-slave current control mode is employed to synchronize the two motors. Acceleration feedback control is utilized to further enhance the servo performance. Extensive experiments are used to validate the effectiveness of the proposed control algorithm in synchronization, disturbance attenuation and low-velocity tracking.

Real-time simulator for designing electron dual scattering foil systems.

PubMed

Carver, Robert L; Hogstrom, Kenneth R; Price, Michael J; LeBlanc, Justin D; Pitcher, Garrett M

2014-11-08

The purpose of this work was to develop a user friendly, accurate, real-time com- puter simulator to facilitate the design of dual foil scattering systems for electron beams on radiotherapy accelerators. The simulator allows for a relatively quick, initial design that can be refined and verified with subsequent Monte Carlo (MC) calculations and measurements. The simulator also is a powerful educational tool. The simulator consists of an analytical algorithm for calculating electron fluence and X-ray dose and a graphical user interface (GUI) C++ program. The algorithm predicts electron fluence using Fermi-Eyges multiple Coulomb scattering theory with the reduced Gaussian formalism for scattering powers. The simulator also estimates central-axis and off-axis X-ray dose arising from the dual foil system. Once the geometry of the accelerator is specified, the simulator allows the user to continuously vary primary scattering foil material and thickness, secondary scat- tering foil material and Gaussian shape (thickness and sigma), and beam energy. The off-axis electron relative fluence or total dose profile and central-axis X-ray dose contamination are computed and displayed in real time. The simulator was validated by comparison of off-axis electron relative fluence and X-ray percent dose profiles with those calculated using EGSnrc MC. Over the energy range 7-20 MeV, using present foils on an Elekta radiotherapy accelerator, the simulator was able to reproduce MC profiles to within 2% out to 20 cm from the central axis. The central-axis X-ray percent dose predictions matched measured data to within 0.5%. The calculation time was approximately 100 ms using a single Intel 2.93 GHz processor, which allows for real-time variation of foil geometrical parameters using slider bars. This work demonstrates how the user-friendly GUI and real-time nature of the simulator make it an effective educational tool for gaining a better understanding of the effects that various system parameters have on a relative dose profile. This work also demonstrates a method for using the simulator as a design tool for creating custom dual scattering foil systems in the clinical range of beam energies (6-20 MeV). 

Developments in blade shape design for a Darrieus vertical axis wind turbine

NASA Astrophysics Data System (ADS)

Ashwill, T. D.; Leonard, T. M.

1986-09-01

A new computer program package has been developed that determines the troposkein shape for a Darrieus Vertical Axis Wind Turbine Blade with any geometrical configuration or rotation rate. This package allows users to interact and develop a buildable blade whose shape closely approximates the troposkein. Use of this package can significantly reduce flatwise mean bending stresses in the blade and increase fatigue life.

Fabrication of FORTIS

NASA Astrophysics Data System (ADS)

McCandliss, Stephan R.; Fleming, Brian; Kaiser, Mary Elizabeth; Kruk, Jeffrey; Feldman, Paul D.; Kutyrev, Alexander S.; Li, Mary J.; Goodwin, Phillip A.; Rapchun, David; Lyness, Eric; Brown, Ari D.; Moseley, Harvey; Siegmund, Oswald; Vallerga, John

2010-07-01

The Johns Hopkins University sounding rocket group is building the Far-ultraviolet Off Rowland-circle Telescope for Imaging and Spectroscopy (FORTIS), which is a Gregorian telescope with rulings on the secondary mirror. FORTIS will be launched on a sounding rocket from White Sand Missile Range to study the relationship between Lyman alpha escape and the local gas-to-dust ratio in star forming galaxies with non-zero redshifts. It is designed to acquire images of a 30' x 30' field and provide fully redundant "on-the-fly" spectral acquisition of 43 separate targets in the field with a bandpass of 900 - 1800 Angstroms. FORTIS is an enabling scientific and technical activity for future cutting edge far- and near-uv survey missions seeking to: search for Lyman continuum radiation leaking from star forming galaxies, determine the epoch of He II reionization and characterize baryon acoustic oscillations using the Lyman forest. In addition to the high efficiency "two bounce" dual-order spectro-telescope design, FORTIS incorporates a number of innovative technologies including: an image dissecting microshutter array developed by GSFC; a large area (~ 45 mm x 170 mm) microchannel plate detector with central imaging and "outrigger" spectral channels provided by Sensor Sciences; and an autonomous targeting microprocessor incorporating commercially available field programable gate arrays. We discuss progress to date in developing our pathfinder instrument.

Asymmetric vortex pair in the wake of a circular cylinder

NASA Astrophysics Data System (ADS)

Iosilevskii, G.; Seginer, A.

1994-10-01

Stationary configurations of two asymmetric point vortices in the wake of an infinite circular cylinder, spinning or not about its axis, are analytically investigated using an ideal fluid approximation. Four different vortex configurations (patterns) in the wake of a spinning cylinder are found in the case when vortex asymmetry is weak; each configuration is associated with a certain direction of the Magnus force. The qualitative relation between a pattern and a direction of the Magnus force is in agreement with experimental data. Also obtained are asymmetrical vortex configurations in the wake of a nonspinning cylinder.

THE ABUNDANCE OF X-SHAPED RADIO SOURCES. I. VLA SURVEY OF 52 SOURCES WITH OFF-AXIS DISTORTIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roberts, David H.; Cohen, Jake P.; Lu, Jing

Cheung identified a sample of 100 candidate X-shaped radio galaxies using the NRAO FIRST survey; these are small-axial-ratio extended radio sources with off-axis emission. Here, we present radio images of 52 of these sources that have been made from archival Very Large Array data with resolution of about 1″. Fifty-one of the 52 were observed at 1.4 GHz, 7 were observed at 1.4 and 5 GHz, and 1 was observed only at 5 GHz. We also present overlays of the Sloan Digital Sky Survey red images for 48 of the sources, and DSS II overlays for the remainder. Optical counterpartsmore » have been identified for most sources, but there remain a few empty fields. Our higher resolution VLA images along with FIRST survey images of the sources in the sample reveal that extended extragalactic radio sources with small axial ratios are largely (60%) cases of double radio sources with twin lobes that have off-axis extensions, usually with inversion-symmetric structure. The available radio images indicate that at most 20% of sources might be genuine X-shaped radio sources that could have formed by a restarting of beams in a new direction following an interruption and axis flip. The remaining 20% are in neither of these categories. The implications of this result for the gravitational wave background are discussed in Roberts et al.« less

Petrological Constraints on Melt Generation Beneath the Asal Rift (Djibouti)

NASA Astrophysics Data System (ADS)

Pinzuti, P.; Humler, E.; Manighetti, I.; Gaudemer, Y.; Bézos, A.

2010-12-01

The temporal evolution of the mantle melting processes in the Asal Rift is evaluated from the chemical composition of 95 lava flows sampled along 10 km of the rift axis and 8 km off-axis (that is for the last 650 ky). The major element composition and the trace element ratios of aphyric basalts across the Asal Rift show a symmetric pattern relative to the rift axis and preserved a clear signal of mantle melting depth variations. FeO, Fe8.0, Sm/YbN and Zr/Y increase, whereas SiO2 and Lu/HfN decrease from the rift axis to the rift shoulders. These variations are qualitatively consistent with a shallower melting beneath the rift axis than off-axis and the data show that the melting regime is inconsistent with a passive upwelling model. In order to quantify the depth range and extent of melting, we invert Na8.0 and Fe8.0 contents of basalts based on a pure active upwelling model. Beneath the rift axis, melting paths are shallow, from 60 to 30 km. These melting paths are consistent with adiabatic melting in normal-temperature asthenosphere, beneath an extensively thinned mantle lithosphere. In contrast, melting on the rift shoulders occurred beneath a thick mantle lithosphere and required mantle solidus temperature 180°C hotter than normal (melting paths from 110 to 75 km). The calculated rate of lithospheric thinning is high (6.0 cm yr-1) and could explain the survival of a metastable garnet within the mantle at depth shallower than 90 km beneath the modern Asal Rift.

Articulated transition duct in turbomachine

DOEpatents

Flanagan, James Scott; McMahan, Kevin Weston; LeBegue, Jeffrey Scott; Pentecost, Ronnie Ray

2014-04-29

Turbine systems are provided. A turbine system includes a transition duct comprising an inlet, an outlet, and a duct passage extending between the inlet and the outlet and defining a longitudinal axis, a radial axis, and a tangential axis. The outlet of the transition duct is offset from the inlet along the longitudinal axis and the tangential axis. The duct passage includes an upstream portion and a downstream portion. The upstream portion extends from the inlet between an inlet end and an aft end. The downstream portion extends from the outlet between an outlet end and a head end. The turbine system further includes a joint coupling the aft end of the upstream portion and the head end of the downstream portion together. The joint is configured to allow movement of the upstream portion and the downstream portion relative to each other about or along at least one axis.

Propagation of angular errors in two-axis rotation systems

NASA Astrophysics Data System (ADS)

Torrington, Geoffrey K.

2003-10-01

Two-Axis Rotation Systems, or "goniometers," are used in diverse applications including telescope pointing, automotive headlamp testing, and display testing. There are three basic configurations in which a goniometer can be built depending on the orientation and order of the stages. Each configuration has a governing set of equations which convert motion between the system "native" coordinates to other base systems, such as direction cosines, optical field angles, or spherical-polar coordinates. In their simplest form, these equations neglect errors present in real systems. In this paper, a statistical treatment of error source propagation is developed which uses only tolerance data, such as can be obtained from the system mechanical drawings prior to fabrication. It is shown that certain error sources are fully correctable, partially correctable, or uncorrectable, depending upon the goniometer configuration and zeroing technique. The system error budget can be described by a root-sum-of-squares technique with weighting factors describing the sensitivity of each error source. This paper tabulates weighting factors at 67% (k=1) and 95% (k=2) confidence for various levels of maximum travel for each goniometer configuration. As a practical example, this paper works through an error budget used for the procurement of a system at Sandia National Laboratories.

Superradiance in a Large and Dilute Cloud of Cold Atoms in the Linear-Optics Regime.

PubMed

Araújo, Michelle O; Krešić, Ivor; Kaiser, Robin; Guerin, William

2016-08-12

Superradiance has been extensively studied in the 1970s and 1980s in the regime of superfluorescence, where a large number of atoms are initially excited. Cooperative scattering in the linear-optics regime, or "single-photon superradiance," has been investigated much more recently, and superradiant decay has also been predicted, even for a spherical sample of large extent and low density, where the distance between atoms is much larger than the wavelength. Here, we demonstrate this effect experimentally by directly measuring the decay rate of the off-axis fluorescence of a large and dilute cloud of cold rubidium atoms after the sudden switch off of a low-intensity laser driving the atomic transition. We show that, at large detuning, the decay rate increases with the on-resonance optical depth. In contrast to forward scattering, the superradiant decay of off-axis fluorescence is suppressed near resonance due to attenuation and multiple-scattering effects.

RF/optical shared aperture for high availability wideband communication RF/FSO links

DOEpatents

Ruggiero, Anthony J; Pao, Hsueh-yuan; Sargis, Paul

2014-04-29

An RF/Optical shared aperture is capable of transmitting and receiving optical signals and RF signals simultaneously. This technology enables compact wide bandwidth communications systems with 100% availability in clear air turbulence, rain and fog. The functions of an optical telescope and an RF reflector antenna are combined into a single compact package by installing an RF feed at either of the focal points of a modified Gregorian telescope.

RF/optical shared aperture for high availability wideband communication RF/FSO links

DOEpatents

Ruggiero, Anthony J; Pao, Hsueh-yuan; Sargis, Paul

2015-03-24

An RF/Optical shared aperture is capable of transmitting and receiving optical signals and RF signals simultaneously. This technology enables compact wide bandwidth communications systems with 100% availability in clear air turbulence, rain and fog. The functions of an optical telescope and an RF reflector antenna are combined into a single compact package by installing an RF feed at either of the focal points of a modified Gregorian telescope.

A DirtI Application for LBT Commissioning Campaigns

NASA Astrophysics Data System (ADS)

Borelli, J. L.

2009-09-01

In order to characterize the Gregorian focal stations and test the performance achieved by the Large Binocular Telescope (LBT) adaptive optics system, two infrared test cameras were constructed within a joint project between INAF (Observatorio Astronomico di Bologna, Italy) and the Max Planck Institute for Astronomy (Germany). Is intended here to describe the functionality and successful results obtained with the Daemon for the Infrared Test Camera Interface (DirtI) during commissioning campaigns.

Polarization-Insensitive Tunable Optical Filters based on Liquid Crystal Polarization Gratings

NASA Astrophysics Data System (ADS)

Nicolescu, Elena

Tunable optical filters are widely used for a variety of applications including spectroscopy, optical communication networks, remote sensing, and biomedical imaging and diagnostics. All of these application areas can greatly benefit from improvements in the key characteristics of the tunable optical filters embedded in them. Some of these key parameters include peak transmittance, bandwidth, tuning range, and transition width. In recent years research efforts have also focused on miniaturizing tunable optical filters into physically small packages for compact portable spectroscopy and hyperspectral imaging applications such as real-time medical diagnostics and defense applications. However, it is important that miniaturization not have a detrimental effect on filter performance. The overarching theme of this dissertation is to explore novel configurations of Polarization Gratings (PGs) as simple, low-cost, polarization-insensitive alternatives to conventional optical filtering technologies for applications including hyperspectral imaging and telecommunications. We approach this goal from several directions with a combination of theory and experimental demonstration leading to, in our opinion, a significant contribution to the field. We present three classes of tunable optical filters, the first of which is an angle-filtering scheme where the stop-band wavelengths are redirected off axis and the passband is transmitted on-axis. This is achieved using a stacked configuration of polarization gratings of various thicknesses. To improve this class of filter, we also introduce a novel optical element, the Bilayer Polarization Grating, exhibiting unique optical properties and demonstrating complex anchoring conditions with high quality. The second class of optical filter is analogous to a Lyot filter, utilizing stacks of static or tunable waveplates sandwiched with polarizing elements. However, we introduce a new configuration using PGs and static waveplates to replace the polarizers in the system, thereby greatly increasing the filter throughput. We then turn our attention to a Fourier filtering technique. This is a fundamentally different filtering approach involving a single PG where the filtering functionality involves selecting a spectral band with a movable aperture or slit and a diffractive element (PG in our case). Finally, we study the integration of a PG in a multi-channel wavelength blocker system focusing on the practical and fundamental limitations of using a PG as a variable optical attenuator/wavelength blocker in a commercial optical telecommunications network.

Computational and experimental aftbody flow fields for hypersonic, airbreathing configurations with scramjet exhaust flow simulation

NASA Technical Reports Server (NTRS)

Huebner, Lawrence D.; Tatum, Kenneth E.

1991-01-01

Computational results are presented for three issues pertinent to hypersonic, airbreathing vehicles employing scramjet exhaust flow simulation. The first issue consists of a comparison of schlieren photographs obtained on the aftbody of a cruise missile configuration under powered conditions with two-dimensional computational solutions. The second issue presents the powered aftbody effects of modeling the inlet with a fairing to divert the external flow as compared to an operating flow-through inlet on a generic hypersonic vehicle. Finally, a comparison of solutions examining the potential of testing powered configurations in a wind-off, instead of a wind-on, environment, indicate that, depending on the extent of the three-dimensional plume, it may be possible to test aftbody powered hypersonic, airbreathing configurations in a wind-off environment.

Pathway Ranking for In-place Sediment Management (CU1209). Site 2 Report - Pearl Harbor

DTIC Science & Technology

2006-04-01

type resistance cell. The probe is configured with two pairs of stainless steel electrodes, the outer pair through which a known current is imposed...the “bioinhibited” (no oxygen control) deployment at BPA . Vertical axis is dissolved oxygen concentration, and horizontal axis is sample record at 6...99 Table 5-7. BFSD results from site BPA . Numbers in the Flux Rate Confidence column indicate the

Evaluation of simulation motion fidelity criteria in the vertical and directional axes

NASA Technical Reports Server (NTRS)

Schroeder, Jeffery A.

1993-01-01

An evaluation of existing motion fidelity criteria was conducted on the NASA Ames Vertical Motion Simulator. Experienced test pilots flew single-axis repositioning tasks in both the vertical and the directional axes. Using a first-order approximation of a hovering helicopter, tasks were flown with variations only in the filters that attenuate the commands to the simulator motion system. These filters had second-order high-pass characteristics, and the variations were made in the filter gain and natural frequency. The variations spanned motion response characteristics from nearly full math-model motion to fixed-base. Between configurations, pilots recalibrated their motion response perception by flying the task with full motion. Pilots subjectively rated the motion fidelity of subsequent configurations relative to this full motion case, which was considered the standard for comparison. The results suggested that the existing vertical-axis criterion was accurate for combinations of gain and natural frequency changes. However, if only the gain or the natural frequency was changed, the rated motion fidelity was better than the criterion predicted. In the vertical axis, the objective and subjective results indicated that a larger gain reduction was tolerated than the existing criterion allowed. The limited data collected in the yaw axis revealed that pilots had difficulty in distinguishing among the variations in the pure yaw motion cues.

Robotic tool positioning process using a multi-line off-axis laser triangulation sensor

NASA Astrophysics Data System (ADS)

Pinto, T. C.; Matos, G.

2018-03-01

Proper positioning of a friction stir welding head for pin insertion, driven by a closed chain robot, is important to ensure quality repair of cracks. A multi-line off-axis laser triangulation sensor was designed to be integrated to the robot, allowing relative measurements of the surface to be repaired. This work describes the sensor characteristics, its evaluation and the measurement process for tool positioning to a surface point of interest. The developed process uses a point of interest image and a measured point cloud to define the translation and rotation for tool positioning. Sensor evaluation and tests are described. Keywords: laser triangulation, 3D measurement, tool positioning, robotics.

RF current profile control studies in the alcator C-mod tokamak

NASA Astrophysics Data System (ADS)

Bonoli, P. T.; Porkolab, M.; Wukitch, S. J.; Bernabei, S.; Kaita, R.; Mikkelsen, D.; Phillips, C. K.; Schilling, G.

1999-09-01

Time dependent calculations of lower hybrid (LH) current profile control in Alcator C-Mod have been done using the TRANSP [1], FPPRF [2], and LSC [3] codes. Up to 3 MW of LH current drive power was applied in plasmas with high power ICRF minority heating (PICH=1.8-3 MW) and fast current ramp up. Using the experimentally measured temperature profiles, off-axis current generation resulted in nonmonotonic q-profiles with qmin~=1.6. Self-consistent effects of off-axis electron heating by the LH power were also included in the analysis and significant broadening of the electron temperature profile was found with qmin>~2 and a larger shear reversal radius.

Flipping interferometry and its application for quantitative phase microscopy in a micro-channel.

PubMed

Roitshtain, Darina; Turko, Nir A; Javidi, Bahram; Shaked, Natan T

2016-05-15

We present a portable, off-axis interferometric module for quantitative phase microscopy of live cells, positioned at the exit port of a coherently illuminated inverted microscope. The module creates on the digital camera an interference pattern between the image of the sample and its flipped version. The proposed simplified module is based on a retro-reflector modification in an external Michelson interferometer. The module does not contain any lenses, pinholes, or gratings and its alignment is straightforward. Still, it allows full control of the off-axis angle and does not suffer from ghost images. As experimentally demonstrated, the module is useful for quantitative phase microscopy of live cells rapidly flowing in a micro-channel.

Wavelet-based tracking of bacteria in unreconstructed off-axis holograms.

PubMed

Marin, Zach; Wallace, J Kent; Nadeau, Jay; Khalil, Andre

2018-03-01

We propose an automated wavelet-based method of tracking particles in unreconstructed off-axis holograms to provide rough estimates of the presence of motion and particle trajectories in digital holographic microscopy (DHM) time series. The wavelet transform modulus maxima segmentation method is adapted and tailored to extract Airy-like diffraction disks, which represent bacteria, from DHM time series. In this exploratory analysis, the method shows potential for estimating bacterial tracks in low-particle-density time series, based on a preliminary analysis of both living and dead Serratia marcescens, and for rapidly providing a single-bit answer to whether a sample chamber contains living or dead microbes or is empty. Copyright © 2017 Elsevier Inc. All rights reserved.

Orthotropic elastic-plastic behavior of AS4/APC-2 thermoplastic composite at elevated temperatures

NASA Technical Reports Server (NTRS)

Sun, C. T.; Yoon, K. J.

1989-01-01

Inelastic and strength properties of AS4/APC-2 composites were characterized with respect to temperature variation by using a one parameter orthotropic plasticity model and a one parameter failure criterion. Simple uniaxial off-axis tension tests were performed on coupon specimens of unidirectional AS4/APC-2 thermoplastic composite at various temperatures. To avoid the complication caused by the extension-shear coupling effect in off-axis testing, new tabs were designed and used on the test specimens. The experimental results showed that the nonlinear behavior of constitutive relations and the strength can be characterized quite well using the one parameter plasticity model and the failure criterion, respectively.

Characterization of elastic-plastic properties of AS4/APC-2 thermoplastic composite

NASA Technical Reports Server (NTRS)

Sun, C. T.; Yoon, K. J.

1988-01-01

Elastic and inelastic properties of AS4/APC-2 composites were characterized with respect to temperature variation by using a one-parameter orthotropic plasticity model and a one parameter failure criterion. Simple uniaxial off-axis tension tests were performed on coupon specimens of unidirectional AS4/APC-2 thermoplastic composite at various temperatures. To avoid the complication caused by the extension-shear coupling effect in off-axis testing, new tabs were designed and used on the test specimens. The experimental results showed that the nonlinear behavior of constitutive relations and the failure strengths can be characterized quite well using the one parameter plasticity model and the failure criterion, respectively.

Role of switching-on and -off effects in the vacuum instability

NASA Astrophysics Data System (ADS)

Adorno, T. C.; Ferreira, R.; Gavrilov, S. P.; Gitman, D. M.

2018-04-01

We find exact differential mean numbers of fermions and bosons created from the vacuum due to a composite electric field of special configuration. This configuration imitates a finite switching-on and -off regime and consists of fields that switch on exponentially from the infinitely remote past, remains constant during a certain interval T and switch off exponentially to the infinitely remote future. We show that calculations in the slowly varying field approximation are completely predictable in the framework of a locally constant field approximation. Beyond the slowly varying field approximation, we study effects of fast switching on and off in a number of cases when the size of the dimensionless parameter eET is either close or exceeds the threshold value that determines the transition from a regime sensitive to on-off parameters to the slowly varying regime for which these effects are secondary.

Sonic boom prediction for the Langley Mach 2 low-boom configuration

NASA Technical Reports Server (NTRS)

Madson, Michael D.

1992-01-01

Sonic boom pressure signatures and aerodynamic force data for the Langley Mach 2 low sonic boom configuration were computed using the TranAir full-potential code. A solution-adaptive Cartesian grid scheme is utilized to compute off-body flow field data. Computations were performed with and without nacelles at several angles of attack. Force and moment data were computed to measure nacelle effects on the aerodynamic characteristics and sonic boom footprints of the model. Pressure signatures were computed both on and off ground-track. Near-field pressure signature computations on ground-track were in good agreement with experimental data. Computed off ground-track signatures showed that maximum pressure peaks were located off ground-track and were significantly higher than the signatures on ground-track. Bow shocks from the nacelle inlets increased lift and drag, and also increased the magnitude of the maximum pressure both on and off ground-track.

Off Axis Growth of Strontium Titanate Films with High Dielectric Constant Tuning and Low Loss

NASA Astrophysics Data System (ADS)

Kampangkeaw, Satreerat

2002-03-01

Using off-axis pulsed laser deposition, we have grown strontium titanate (STO) films on neodymium gallate (NGO) and lanthanum aluminate (LAO) substrates. We measured the film dielectric constant and loss tangent as a function of temperature in the 10kHz to 1 MHz frequency range. We found that the loss is less than 0.01 We also obtained a figure of merit from the relative variation of the dielectric constant divided by the loss tangent. The obtained figured of merit at 35K and 1MHz is about 1000 comparable to bulk values. The dielectric constant of these films can be changed by a factor of 4-8 in the presence of a DC electric field up to 5V/μm. The films show significant variations of dielectric properties grown on different substrates at different locations respect to the axis of the plume. The STO films on LAO having high dielectric constant and dielectric tuning were grown in region near the center of the plume. On the other hand, STO on NGO shows this effect only on the films grown far from the plume axis.

Probing Nucleation and Growth Behavior of Twisted Kebabs from Shish Scaffold in Sheared Polyethylene Melts by in situ X-ray Studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Keum,J.; Burger, C.; Zuo, F.

2007-01-01

By utilizing synchrotron rheo-WAXD (wide-angle X-ray diffraction) and rheo-SAXS (small-angle X-ray scattering) techniques, the nucleation and growth behavior of twisted kebabs from the shear-induced shish scaffold in entangled high-density polyethylene (HDPE) melts were investigated. The evolution of the (110) reflection intensity in WAXD at the early stages of crystallization could be described by a simplified Avrami equation, while the corresponding long period of kebabs determined by SAXS was found to decrease with time. The combined SAXS and WAXD results indicate that the kebab growth in sheared HDPE melts consists of two-dimensional geometry with thermal (sporadic) nucleation. The WAXD data clearlymore » exhibited the transformations of (110) reflection from equatorial 2-arc to off-axis 4-arc and of (200) reflection from off-axis 4-arc to meridional 2-arc, which can be explained by the rotation of crystallographic a-axis around the b-axis during twisted kebab growth. This observation is also consistent with the orientation mode changes from 'Keller/Machin II' to 'intermediate' and then to 'Keller/Machin I'.« less

Soft buckling actuators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Dian; Whitesides, George M.

A soft actuator is described, including: a rotation center having a center of mass; a plurality of bucklable, elastic structural components each comprising a wall defining an axis along its longest dimension, the wall connected to the rotation center in a way that the axis is offset from the center of mass in a predetermined direction; and a plurality of cells each disposed between two adjacent bucklable, elastic structural components and configured for connection with a fluid inflation or deflation source; wherein upon the deflation of the cell, the bucklable, elastic structural components are configured to buckle in the predeterminedmore » direction. A soft actuating device including a plurality of the soft actuators and methods of actuation using the soft actuator or soft actuating device disclosed herein are also described.« less

Navigation Assistance: A Trade-Off between Wayfinding Support and Configural Learning Support

ERIC Educational Resources Information Center

Munzer, Stefan; Zimmer, Hubert D.; Baus, Jorg

2012-01-01

Current GPS-based mobile navigation assistance systems support wayfinding, but they do not support learning about the spatial configuration of an environment. The present study examined effects of visual presentation modes for navigation assistance on wayfinding accuracy, route learning, and configural learning. Participants (high-school students)…

Method and apparatus for characterizing and enhancing the dynamic performance of machine tools

DOEpatents

Barkman, William E; Babelay, Jr., Edwin F

2013-12-17

Disclosed are various systems and methods for assessing and improving the capability of a machine tool. The disclosure applies to machine tools having at least one slide configured to move along a motion axis. Various patterns of dynamic excitation commands are employed to drive the one or more slides, typically involving repetitive short distance displacements. A quantification of a measurable merit of machine tool response to the one or more patterns of dynamic excitation commands is typically derived for the machine tool. Examples of measurable merits of machine tool performance include dynamic one axis positional accuracy of the machine tool, dynamic cross-axis stability of the machine tool, and dynamic multi-axis positional accuracy of the machine tool.

JPEG 2000-based compression of fringe patterns for digital holographic microscopy

NASA Astrophysics Data System (ADS)

Blinder, David; Bruylants, Tim; Ottevaere, Heidi; Munteanu, Adrian; Schelkens, Peter

2014-12-01

With the advent of modern computing and imaging technologies, digital holography is becoming widespread in various scientific disciplines such as microscopy, interferometry, surface shape measurements, vibration analysis, data encoding, and certification. Therefore, designing an efficient data representation technology is of particular importance. Off-axis holograms have very different signal properties with respect to regular imagery, because they represent a recorded interference pattern with its energy biased toward the high-frequency bands. This causes traditional images' coders, which assume an underlying 1/f2 power spectral density distribution, to perform suboptimally for this type of imagery. We propose a JPEG 2000-based codec framework that provides a generic architecture suitable for the compression of many types of off-axis holograms. This framework has a JPEG 2000 codec at its core, extended with (1) fully arbitrary wavelet decomposition styles and (2) directional wavelet transforms. Using this codec, we report significant improvements in coding performance for off-axis holography relative to the conventional JPEG 2000 standard, with Bjøntegaard delta-peak signal-to-noise ratio improvements ranging from 1.3 to 11.6 dB for lossy compression in the 0.125 to 2.00 bpp range and bit-rate reductions of up to 1.6 bpp for lossless compression.

Real-Time Amplitude and Phase Imaging of Optically Opaque Objects by Combining Full-Field Off-Axis Terahertz Digital Holography with Angular Spectrum Reconstruction

NASA Astrophysics Data System (ADS)

Yamagiwa, Masatomo; Ogawa, Takayuki; Minamikawa, Takeo; Abdelsalam, Dahi Ghareab; Okabe, Kyosuke; Tsurumachi, Noriaki; Mizutani, Yasuhiro; Iwata, Testuo; Yamamoto, Hirotsugu; Yasui, Takeshi

2018-06-01

Terahertz digital holography (THz-DH) has the potential to be used for non-destructive inspection of visibly opaque soft materials due to its good immunity to optical scattering and absorption. Although previous research on full-field off-axis THz-DH has usually been performed using Fresnel diffraction reconstruction, its minimum reconstruction distance occasionally prevents a sample from being placed near a THz imager to increase the signal-to-noise ratio in the hologram. In this article, we apply the angular spectrum method (ASM) for wavefront reconstruction in full-filed off-axis THz-DH because ASM is more accurate at short reconstruction distances. We demonstrate real-time phase imaging of a visibly opaque plastic sample with a phase resolution power of λ/49 at a frame rate of 3.5 Hz in addition to real-time amplitude imaging. We also perform digital focusing of the amplitude image for the same object with a depth selectivity of 447 μm. Furthermore, 3D imaging of visibly opaque silicon objects was achieved with a depth precision of 1.7 μm. The demonstrated results indicate the high potential of the proposed method for in-line or in-process non-destructive inspection of soft materials.

Application of very high harmonic fast waves for off-axis current drive in the DIII-D and FNSF-AT tokamaks

DOE PAGES

Prater, Ronald; Moeller, Charles P.; Pinsker, Robert I.; ...

2014-06-26

Fast waves at frequencies far above the ion cyclotron frequency and approaching the lower hybrid frequency (also called “helicons” or “whistlers”) have application to off-axis current drive in tokamaks with high electron beta. The high frequency causes the whistler-like behavior of the wave power nearly following field lines, but with a small radial component, so the waves spiral slowly toward the plasma center. The high frequency also contributes to strong damping. Modeling predicts robust off-axis current drive with good efficiency compared to alternatives in high performance discharges in DIII-D and Fusion Nuclear Science Facility (FNSF) when the electron beta ismore » above about 1.8%. Detailed analysis of ray behavior shows that ray trajectories and damping are deterministic (that is, not strongly affected by plasma profiles or initial ray conditions), unlike the chaotic ray behavior in lower frequency fast wave experiments. Current drive was found to not be sensitive to the launched value of the parallel index of refraction n||, so wave accessibility issues can be reduced. Finally, use of a traveling wave antenna provides a very narrow n|| spectrum, which also helps avoid accessibility problems.« less

Photon collider: a four-channel autoguider solution

NASA Astrophysics Data System (ADS)

Hygelund, John C.; Haynes, Rachel; Burleson, Ben; Fulton, Benjamin J.

2010-07-01

The "Photon Collider" uses a compact array of four off axis autoguider cameras positioned with independent filtering and focus. The photon collider is two way symmetric and robustly mounted with the off axis light crossing the science field which allows the compact single frame construction to have extremely small relative deflections between guide and science CCDs. The photon collider provides four independent guiding signals with a total of 15 square arc minutes of sky coverage. These signals allow for simultaneous altitude, azimuth, field rotation and focus guiding. Guide cameras read out without exposure overhead increasing the tracking cadence. The independent focus allows the photon collider to maintain in focus guide stars when the main science camera is taking defocused exposures as well as track for telescope focus changes. Independent filters allow auto guiding in the science camera wavelength bandpass. The four cameras are controlled with a custom web services interface from a single Linux based industrial PC, and the autoguider mechanism and telemetry is built around a uCLinux based Analog Devices BlackFin embedded microprocessor. Off axis light is corrected with a custom meniscus correcting lens. Guide CCDs are cooled with ethylene glycol with an advanced leak detection system. The photon collider was built for use on Las Cumbres Observatory's 2 meter Faulks telescopes and currently used to guide the alt-az mount.

Fabrication and testing of the first 8.4-m off-axis segment for the Giant Magellan Telescope

NASA Astrophysics Data System (ADS)

Martin, H. M.; Allen, R. G.; Burge, J. H.; Kim, D. W.; Kingsley, J. S.; Tuell, M. T.; West, S. C.; Zhao, C.; Zobrist, T.

2010-07-01

The primary mirror of the Giant Magellan Telescope consists of seven 8.4 m segments which are borosilicate honeycomb sandwich mirrors. Fabrication and testing of the off-axis segments is challenging and has led to a number of innovations in manufacturing technology. The polishing system includes an actively stressed lap that follows the shape of the aspheric surface, used for large-scale figuring and smoothing, and a passive "rigid conformal lap" for small-scale figuring and smoothing. Four independent measurement systems support all stages of fabrication and provide redundant measurements of all critical parameters including mirror figure, radius of curvature, off-axis distance and clocking. The first measurement uses a laser tracker to scan the surface, with external references to compensate for rigid body displacements and refractive index variations. The main optical test is a full-aperture interferometric measurement, but it requires an asymmetric null corrector with three elements, including a 3.75 m mirror and a computer-generated hologram, to compensate for the surface's 14 mm departure from the best-fit sphere. Two additional optical tests measure large-scale and small-scale structure, with some overlap. Together these measurements provide high confidence that the segments meet all requirements.

Real-Time Amplitude and Phase Imaging of Optically Opaque Objects by Combining Full-Field Off-Axis Terahertz Digital Holography with Angular Spectrum Reconstruction

NASA Astrophysics Data System (ADS)

Yamagiwa, Masatomo; Ogawa, Takayuki; Minamikawa, Takeo; Abdelsalam, Dahi Ghareab; Okabe, Kyosuke; Tsurumachi, Noriaki; Mizutani, Yasuhiro; Iwata, Testuo; Yamamoto, Hirotsugu; Yasui, Takeshi

2018-04-01

Terahertz digital holography (THz-DH) has the potential to be used for non-destructive inspection of visibly opaque soft materials due to its good immunity to optical scattering and absorption. Although previous research on full-field off-axis THz-DH has usually been performed using Fresnel diffraction reconstruction, its minimum reconstruction distance occasionally prevents a sample from being placed near a THz imager to increase the signal-to-noise ratio in the hologram. In this article, we apply the angular spectrum method (ASM) for wavefront reconstruction in full-filed off-axis THz-DH because ASM is more accurate at short reconstruction distances. We demonstrate real-time phase imaging of a visibly opaque plastic sample with a phase resolution power of λ/49 at a frame rate of 3.5 Hz in addition to real-time amplitude imaging. We also perform digital focusing of the amplitude image for the same object with a depth selectivity of 447 μm. Furthermore, 3D imaging of visibly opaque silicon objects was achieved with a depth precision of 1.7 μm. The demonstrated results indicate the high potential of the proposed method for in-line or in-process non-destructive inspection of soft materials.

Marker Configuration Model-Based Roentgen Fluoroscopic Analysis.

PubMed

Garling, Eric H; Kaptein, Bart L; Geleijns, Koos; Nelissen, Rob G H H; Valstar, Edward R

2005-04-01

It remains unknown if and how the polyethylene bearing in mobile bearing knees moves during dynamic activities with respect to the tibial base plate. Marker Configuration Model-Based Roentgen Fluoroscopic Analysis (MCM-based RFA) uses a marker configuration model of inserted tantalum markers in order to accurately estimate the pose of an implant or bone using single plane Roentgen images or fluoroscopic images. The goal of this study is to assess the accuracy of (MCM-Based RFA) in a standard fluoroscopic set-up using phantom experiments and to determine the error propagation with computer simulations. The experimental set-up of the phantom study was calibrated using a calibration box equipped with 600 tantalum markers, which corrected for image distortion and determined the focus position. In the computer simulation study the influence of image distortion, MC-model accuracy, focus position, the relative distance between MC-models and MC-model configuration on the accuracy of MCM-Based RFA were assessed. The phantom study established that the in-plane accuracy of MCM-Based RFA is 0.1 mm and the out-of-plane accuracy is 0.9 mm. The rotational accuracy is 0.1 degrees. A ninth-order polynomial model was used to correct for image distortion. Marker-Based RFA was estimated to have, in a worst case scenario, an in vivo translational accuracy of 0.14 mm (x-axis), 0.17 mm (y-axis), 1.9 mm (z-axis), respectively, and a rotational accuracy of 0.3 degrees. When using fluoroscopy to study kinematics, image distortion and the accuracy of models are important factors, which influence the accuracy of the measurements. MCM-Based RFA has the potential to be an accurate, clinically useful tool for studying kinematics after total joint replacement using standard equipment.

Comparison of Magnetic Properties in a Magnetic Cloud and Its Solar Source on 2013 April 11-14

NASA Astrophysics Data System (ADS)

Vemareddy, P.; Möstl, C.; Amerstorfer, T.; Mishra, W.; Farrugia, C.; Leitner, M.

2016-09-01

In the context of the Sun-Earth connection of coronal mass ejections and magnetic flux ropes (MFRs), we studied the solar active region (AR) and the magnetic properties of magnetic cloud (MC) event during 2013 April 14-15. We use in situ observations from the Advanced Composition Explorer and source AR measurements from the Solar Dynamics Observatory. The MCs magnetic structure is reconstructed from the Grad-Shafranov method, which reveals a northern component of the axial field with left handed helicity. The MC invariant axis is highly inclined to the ecliptic plane pointing northward and is rotated by 117° with respect to the source region PIL. The net axial flux and current in the MC are comparatively higher than from the source region. Linear force-free alpha distribution (10-7-10-6 m-1) at the sigmoid leg matches the range of twist number in the MC of 1-2 au MFR. The MFR is nonlinear force-free with decreasing twist from the axis (9 turns/au) toward the edge. Therefore, a Gold-Hoyle (GH) configuration, assuming a constant twist, is more consistent with the MC structure than the Lundquist configuration of increasing twist from the axis to boundary. As an indication of that, the GH configuration yields a better fitting to the global trend of in situ magnetic field components, in terms of rms, than the Lundquist model. These cylindrical configurations improved the MC fitting results when the effect of self-similar expansion of MFR was considered. For such twisting behavior, this study suggests an alternative fitting procedure to better characterize the MC magnetic structure and its source region links.

COMPARISON OF MAGNETIC PROPERTIES IN A MAGNETIC CLOUD AND ITS SOLAR SOURCE ON 2013 APRIL 11–14

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vemareddy, P.; Möstl, C.; Amerstorfer, T.

2016-09-01

In the context of the Sun–Earth connection of coronal mass ejections and magnetic flux ropes (MFRs), we studied the solar active region (AR) and the magnetic properties of magnetic cloud (MC) event during 2013 April 14–15. We use in situ observations from the Advanced Composition Explorer and source AR measurements from the Solar Dynamics Observatory . The MCs magnetic structure is reconstructed from the Grad–Shafranov method, which reveals a northern component of the axial field with left handed helicity. The MC invariant axis is highly inclined to the ecliptic plane pointing northward and is rotated by 117° with respect tomore » the source region PIL. The net axial flux and current in the MC are comparatively higher than from the source region. Linear force-free alpha distribution (10{sup −7}–10{sup −6} m{sup −1}) at the sigmoid leg matches the range of twist number in the MC of 1–2 au MFR. The MFR is nonlinear force-free with decreasing twist from the axis (9 turns/au) toward the edge. Therefore, a Gold–Hoyle (GH) configuration, assuming a constant twist, is more consistent with the MC structure than the Lundquist configuration of increasing twist from the axis to boundary. As an indication of that, the GH configuration yields a better fitting to the global trend of in situ magnetic field components, in terms of rms, than the Lundquist model. These cylindrical configurations improved the MC fitting results when the effect of self-similar expansion of MFR was considered. For such twisting behavior, this study suggests an alternative fitting procedure to better characterize the MC magnetic structure and its source region links.« less

The immunomodulatory role of the hypothalamus-pituitary-gonad axis: Proximate mechanism for reproduction-immune trade offs?

PubMed

Segner, Helmut; Verburg-van Kemenade, B M Lidy; Chadzinska, Magdalena

2017-01-01

The present review discusses the communication between the hypothalamic-pituitary-gonad (HPG) axis and the immune system of vertebrates, attempting to situate the HPG-immune interaction into the context of life history trade-offs between reproductive and immune functions. More specifically, (i) we review molecular and cellular interactions between hormones of the HPG axis, and, as far as known, the involved mechanisms on immune functions, (ii) we evaluate whether the HPG-immune crosstalk serves as proximate mechanism mediating reproductive-immune trade-offs, and (iii) we ask whether the nature of the HPG-immune interaction is conserved throughout vertebrate evolution, despite the changes in immune functions, reproductive modes, and life histories. In all vertebrate classes studied so far, HPG hormones have immunomodulatory functions, and indications exist that they contribute to reproduction-immunity resource trade-offs, although the very limited information available for most non-mammalian vertebrates makes it difficult to judge how comparable or different the interactions are. There is good evidence that the HPG-immune crosstalk is part of the proximate mechanisms underlying the reproductive-immune trade-offs of vertebrates, but it is only one factor in a complex network of factors and processes. The fact that the HPG-immune interaction is flexible and can adapt to the functional and physiological requirements of specific life histories. Moreover, the assumption of a relatively fixed pattern of HPG influence on immune functions, with, for example, androgens always leading to immunosuppression and estrogens always being immunoprotective, is probably oversimplified, but the HPG-immune interaction can vary depending on the physiological and envoironmental context. Finally, the HPG-immune interaction is not only driven by resource trade-offs, but additional factors such as, for instance, the evolution of viviparity shape this neuroendocrine-immune relationship. Copyright © 2016 Elsevier Ltd. All rights reserved.

Design, experimental analysis, and unsteady Reynolds-averaged Navier-Stokes simulation of laboratory-scale counter-rotating vertical-axis turbines in marine environment

NASA Astrophysics Data System (ADS)

Doan, Minh; Padricelli, Claudrio; Obi, Shinnosuke; Totsuka, Yoshitaka

2017-11-01

We present the torque and power measurement of laboratory-scale counter-rotating vertical-axis hydrokinetic turbines, built around a magnetic hysteresis brake as the speed controller and a Hall-effect sensor as the rotational speed transducer. A couple of straight-three-bladed turbines were linked through a transmission of spur gears and timing pulleys and coupled to the electronic instrumentation via flexible shaft couplers. A total of 8 experiments in 2 configurations were conducted in the water channel facility (4-m long, 0.3-m wide, and 0.15-m deep). Power generation of the turbines (0.06-m rotor diameter) was measured and compared with that of single turbines of the same size. The wakes generated by these experiments were also measured by particle image velocimetry (PIV) and numerically simulated by unsteady Reynolds-averaged Navier-Stokes (URANS) simulation using OpenFOAM. Preliminary results from wake measurement indicated the mechanism of enhanced power production behind the counter-rotating configuration of vertical-axis turbines. Current address: Politecnico di Milano.

Polytype Stability and Microstructural Characterization of Silicon Carbide Epitaxial Films Grown on [ {11}overline{{2}} {0} ]- and [0001]-Oriented Silicon Carbide Substrates

NASA Astrophysics Data System (ADS)

Bishop, S. M.; Reynolds, C. L.; Liliental-Weber, Z.; Uprety, Y.; Zhu, J.; Wang, D.; Park, M.; Molstad, J. C.; Barnhardt, D. E.; Shrivastava, A.; Sudarshan, T. S.; Davis, R. F.

2007-04-01

The polytype and surface and defect microstructure of epitaxial layers grown on 4H( {11}overline{{2}} {0} ), 4H(0001) on-axis, 4H(0001) 8° off-axis, and 6H(0001) on-axis substrates have been investigated. High-resolution x-ray diffraction (XRD) revealed the epitaxial layers on 4H( {11}overline{{2}} {0} ) and 4H(0001) 8° off-axis to have the 4H-SiC (silicon carbide) polytype, while the 3C-SiC polytype was identified for epitaxial layers on 4H(0001) and 6H(0001) on-axis substrates. Cathodoluminescence (CL), Raman spectroscopy, and transmission electron microscopy (TEM) confirmed these results. The epitaxial surface of 4H( {11}overline{{2}} {0} ) films was specular with a roughness of 0.16-nm root-mean-square (RMS), in contrast to the surfaces of the other epitaxial layer-substrate orientations, which contained curvilinear boundaries, growth pits (˜3 × 104 cm-2), triangular defects >100 μm, and significant step bunching. Molten KOH etching revealed large defect densities within 4H( {11}overline{{2}} {0} ) films that decreased with film thickness to ˜106 cm-2 at 2.5 μm, while cross-sectional TEM studies showed areas free of defects and an indistinguishable film-substrate interface for 4H( {11}overline{{2}} {0} ) epitaxial layers.

Parametric study of ion heating in a burnout device (HIP-1)

NASA Technical Reports Server (NTRS)

Sigman, D. R.; Reinmann, J. J.; Lauver, M. R.

1974-01-01

Results of further studies on the Lewis Research Center hot-ion plasma source (HIP-1) are reported. Changes have been made in both the electrode geometry and materials to produce higher ion temperatures. Ion temperature increased significantly with increased vacuum pumping speed. The best ion temperatures achieved, so far, for H(+), D(+), and He(+) plasmas are estimated to be equal to, or greater than 0.6, equal to, or greater than 0.9, and equal to, greater than 2.0 keV, respectively. Electrode pairs produced high ion temperatures whether on the magnetic axis or off it by 5.5 cm. Multiple sources, one on-axis and one off-axis, were run simultaneously from a single power supply by using independent gas feed rates. A momentum analyzer has been added to the charge-exchange neutral particle analyzer to identify particles according to mass, as well as energy. Under any given plasma condition, the higher mass ions have higher average energies but not by as much as the ratio of their respective masses.

What Are “X-shaped” Radio Sources Telling Us? II. Properties of a Sample of 87

NASA Astrophysics Data System (ADS)

Saripalli, Lakshmi; Roberts, David H.

2018-01-01

In an earlier paper, we presented Jansky Very Large Array multi-frequency, multi-array continuum imaging of a unique sample of low-axial ratio radio galaxies. In this paper, the second in the series, we examine the images to learn the phenomenology of how the off-axis emission relates to the main radio source. Inversion-symmetric offset emission appears to be bimodal and to originate from one of two strategic locations: outer ends of radio lobes (outer-deviation) or from inner ends (inner-deviation). The latter sources are almost always associated with edge-brightened sources. With S- and Z-shaped sources being a subset of outer-deviation sources, this class lends itself naturally to explanations involving black hole axis precession. Our data allow us to present a plausible model for the more enigmatic inner-deviation sources with impressive wings; as for outer-deviation sources these too require black hole axis shifts, although they also require plasma backflows into relic channels. Evolution in morphology over time relates the variety in structures in inner-deviation sources including XRGs. With features such as non-collinearities, central inner-S “spine,” corresponding lobe emission peaks, double and protruding hotspots not uncommon, black hole axis precession, drifts, or flips could be active in a significant fraction of radio sources with prominent off-axis emission. At least 4% of radio galaxies appear to undergo black hole axis rotation. Quasars offer a key signature for recognizing rotating axes. With a rich haul of sources that have likely undergone axis rotation, our work shows the usefulness of low-axial ratio sources in pursuing searches for binary supermassive black holes.

Petrological constraints on melt generation beneath the Asal Rift (Djibouti) using quaternary basalts

NASA Astrophysics Data System (ADS)

Pinzuti, Paul; Humler, Eric; Manighetti, Isabelle; Gaudemer, Yves

2013-08-01

The temporal evolution of the mantle melting processes in the Asal Rift is evaluated from the chemical composition of 56 new lava flows sampled along 10 km of the rift axis and 9 km off-axis (i.e., erupted within the last 620 kyr). Petrological and primary geochemical results show that most of the samples of the inner floor of the Asal Rift are affected by plagioclase accumulation. Trace element ratios and major element compositions corrected for mineral accumulation and crystallization show a symmetric pattern relative to the rift axis and preserved a clear signal of mantle melting depth variations. While FeO, Fe8.0, Zr/Y, and (Dy/Yb)N decrease from the rift shoulders to the rift axis, SiO2, Na/Ti, Lu/Hf increase and Na2O and Na8.0 are constant across the rift. These variations are qualitatively consistent with shallow melting beneath the rift axis and deeper melting for off-axis lava flows. Na8.0 and Fe8.0 contents show that beneath the rift axis, melting paths are shallow, from 81 ± 4 to 43 ± 5 km. These melting paths are consistent with adiabatic melting in normal-temperature fertile asthenosphere, beneath an extensively thinned mantle lithosphere. On the contrary, melting on the rift shoulders (from 107 ± 7 to 67 ± 8 km) occurred beneath thicker lithosphere, requiring a mantle solidus temperature 100 ± 40°C hotter. In this geodynamic environment, the calculated rate of lithospheric thinning appears to be 4.0 ± 2.0 cm yr-1, a value close to the mean spreading rate (2.9 ± 0.2 cm yr-1) over the last 620 kyr.

The off-axis viewing device: a rifle-mounted sighting system for search and engagement from covered positions

NASA Astrophysics Data System (ADS)

Chapman, Thomas; Brady, Christopher

2007-04-01

Soldiers involved in urban operations are at a higher risk of receiving a bullet or fragment wound to the head or face compared to other parts of their body. One reason for this vulnerability is the need for the soldier to expose their head when looking and shooting from behind cover. Research conducted by DSTO Australia, using weapon-mounted cameras, has validated the concept of off-axis shooting but has emphasized the requirement for a system that closely integrates with both the soldier and his weapon. A system was required that would not adversely effect the usability, utility or accuracy of the weapon. Several Concept Demonstrators were developed over a two-year period and the result of this development is the Off-Axis Viewing Device (OAVD). The OAVD is an un-powered sighting attachment that integrates with a red dot reflex sight and enables the soldier to scan for and engage targets from a position of cover. The image from the weapon's scope is transmitted through the OAVD's periscopic mirror system to the soldier. Mounted directly behind the sight, the OAVD can also be swiveled to a redundant position on the side of the weapon to allow normal on-axis use of the sight. The OAVD can be rotated back into place behind the sight with one hand, or removed and stored in the soldier's webbing. In May 2004, a rapid acquisition program was initiated to develop the concept to an in-service capability and the OAVD is currently being deployed with the Australian Defence Force.

Ocular Reflex Phase During Off-Vertical Axis Rotation In Humans Is Modified By Head-On-Trunk Position

NASA Technical Reports Server (NTRS)

Wood, Scott; Clement, Gilles; Denise, Pierre; Reschke, Millard

2005-01-01

Constant velocity Off-Vertical Axis Rotation (OVAR) imposes a continuously varying orientation of the head and body relative to gravity. The ensuing ocular reflexes include modulation of both horizontal and torsional eye velocity as a function of the varying linear acceleration along the lateral plane. The purpose of this study was to examine whether the modulation of these ocular reflexes would be modified by different head-on-trunk positions. Ten human subjects were rotated in darkness about their longitudinal axis 20 deg off-vertical at constant rates of 45 and 180 deg/s, corresponding to 0.125 and 0.5 Hz. Binocular responses were obtained with video-oculography with the head and trunk aligned, and then with the head turned relative to the trunk 40 deg to the right or left of center. Sinusoidal curve fits were used to derive amplitude, phase and bias velocity of the eye movements across multiple cycles for each head-on-trunk position. Consistent with previous studies, the modulation of torsional eye movements was greater at 0.125 Hz while the modulation of horizontal eye movements was greater at 0.5 Hz. Neither amplitude nor bias velocities were significantly altered by head-on-trunk position. The phases of both torsional and horizontal ocular reflexes, on the other hand, shifted towards alignment with the head. These results are consistent with the modulation of torsional and horizontal ocular reflexes during OVAR being primarily mediated by the otoliths in response to the sinusoidally varying linear acceleration along the interaural head axis.

Active optics: off axis aspherics generation for high contrast imaging

NASA Astrophysics Data System (ADS)

Hugot, E.; Laslandes, M.; Ferrari, M.; Vives, S.; Moindrot, S.; El Hadi, K.; Dohlen, K.

2017-11-01

Active Optics methods, based on elasticity theory, allow the aspherisation of optical surfaces by stress polishing but also active aspherisation in situ. Researches in this field will impact the final performance and the final cost of any telescope or instrument. The stress polishing method is well suited for the superpolishing of aspheric components for astronomy. Its principle relies on spherical polishing with a full-sized tool of a warped substrate, which becomes aspherical once unwarped. The main advantage of this technique is the very high optical quality obtained either on form or on high spatial frequency errors. Furthermore, the roughness can be decreased down to a few angstroms, thanks the classical polishing with a large pitch tool, providing a substantial gain on the final scientific performance, for instance on the contrast on coronagraphic images, but also on the polishing time and cost. Stress polishing is based on elasticity theory, and requires an optimised deformation system able to provide the right aspherical form on the optical surface during polishing. The optical quality of the deformation is validated using extensive Finite Element Analysis, allowing an estimation of residuals and an optimisation of the warping harness. We describe here the work realised on stress polishing of toric mirrors for VLT-SPHERE and then our actual work on off axis aspherics (OAA) for the ASPIICS-Proba3 mission for solar coronagraphy. The ASPIICS optical design made by Vives et al is a three mirrors anastigmat including a concave off axis hyperboloid and a convex off axis parabola (OAP). We are developing a prototype in order to demonstrate the feasibility of this type of surface, using a multi-mode warping harness (Lemaitre et al). Furthermore, we present our work on variable OAP, meaning the possibility to adjust the shape of a simple OAP in situ with a minimal number of actuators, typically one actuator per optical mode (Focus, Coma and Astigmatism). Applications for future space telescopes and instrumentation are discussed.

Effect of Off-Axis Fluoroscopy Imaging on Two-Dimensional Kinematics in the Lumbar Spine: A Dynamic In Vitro Validation Study

PubMed Central

Zhao, Kristin D.; Ben-Abraham, Ephraim I.; Magnuson, Dixon J.; Camp, Jon J.; Berglund, Lawrence J.; An, Kai-Nan; Bronfort, Gert; Gay, Ralph E.

2016-01-01

Spine intersegmental motion parameters and the resultant regional patterns may be useful for biomechanical classification of low back pain (LBP) as well as assessing the appropriate intervention strategy. Because of its availability and reasonable cost, two-dimensional (2D) fluoroscopy has great potential as a diagnostic and evaluative tool. However, the technique of quantifying intervertebral motion in the lumbar spine must be validated, and the sensitivity assessed. The purpose of this investigation was to (1) compare synchronous fluoroscopic and optoelectronic measures of intervertebral rotations during dynamic flexion–extension movements in vitro and (2) assess the effect of C-arm rotation to simulate off-axis patient alignment on intervertebral kinematics measures. Six cadaveric lumbar–sacrum specimens were dissected, and active marker optoelectronic sensors were rigidly attached to the bodies of L2–S1. Fluoroscopic sequences and optoelectronic kinematic data (0.15-mm linear, 0.17–0.20 deg rotational, accuracy) were obtained simultaneously. After images were obtained in a true sagittal plane, the image receptor was rotated in 5 deg increments (posterior oblique angulations) from 5 deg to 15 deg. Quantitative motion analysis (qma) software was used to determine the intersegmental rotations from the fluoroscopic images. The mean absolute rotation differences between optoelectronic values and dynamic fluoroscopic values were less than 0.5 deg for all the motion segments at each off-axis fluoroscopic rotation and were not significantly different (P > 0.05) for any of the off-axis rotations of the fluoroscope. Small misalignments of the lumbar spine relative to the fluoroscope did not introduce measurement variation in relative segmental rotations greater than that observed when the spine and fluoroscope were perpendicular to each other, suggesting that fluoroscopic measures of relative segmental rotation during flexion–extension are likely robust, even when patient alignment is not perfect. PMID:26974192

Radio Observations of a Sample of Broad-Line Type IC Supernovae Discovered by PTF/IPTF: A Search for Relativistic Explosions

DOE PAGES

Corsi, Alessandra; Gal-Yam, A.; Kulkarni, S. R.; ...

2016-10-10

Long duration γ-ray bursts are a rare subclass of stripped-envelope core-collapse supernovae (SNe) that launch collimated relativistic outflows (jets). All γ-ray-burst-associated SNe are spectroscopically Type Ic, with broad-lines, but the fraction of broad-lined SNe Ic harboring low-luminosity γ-ray bursts remains largely unconstrained. Some SNe should be accompanied by off-axis γ-ray burst jets that initially remain invisible, but then emerge as strong radio sources (as the jets decelerate). However, this critical prediction of the jet model for γ-ray bursts has yet to be verified observationally. Here, we present K. G. Jansky Very Large Array observations of 15 broad-lined SNe of Type Ic discovered by the Palomar Transient Factory in an untargeted manner. Most of the SNe in our sample exclude radio emission observationally similar to that of the radio-loud, relativistic SN 1998bw. We constrain the fraction of 1998bw-like broad-lined SNe Ic to bemore » $$\\lesssim 41 \\% $$ (99.865% confidence). Most of the events in our sample also exclude off-axis jets similar to GRB 031203 and GRB 030329, but we cannot rule out off-axis γ-ray bursts expanding in a low-density wind environment. Three SNe in our sample are detected in the radio. PTF11qcj and PTF14dby show late-time radio emission with average ejecta speeds of ≈0.3–0.4 c, on the dividing line between relativistic and "ordinary" SNe. The speed of PTF11cmh radio ejecta is poorly constrained. We estimate that $$\\lesssim 85 \\% $$ (99.865% confidence) of the broad-lined SNe Ic in our sample may harbor off-axis γ-ray bursts expanding in media with densities in the range probed by this study.« less

Effect of Off-Axis Fluoroscopy Imaging on Two-Dimensional Kinematics in the Lumbar Spine: A Dynamic In Vitro Validation Study.

PubMed

Zhao, Kristin D; Ben-Abraham, Ephraim I; Magnuson, Dixon J; Camp, Jon J; Berglund, Lawrence J; An, Kai-Nan; Bronfort, Gert; Gay, Ralph E

2016-05-01

Spine intersegmental motion parameters and the resultant regional patterns may be useful for biomechanical classification of low back pain (LBP) as well as assessing the appropriate intervention strategy. Because of its availability and reasonable cost, two-dimensional (2D) fluoroscopy has great potential as a diagnostic and evaluative tool. However, the technique of quantifying intervertebral motion in the lumbar spine must be validated, and the sensitivity assessed. The purpose of this investigation was to (1) compare synchronous fluoroscopic and optoelectronic measures of intervertebral rotations during dynamic flexion-extension movements in vitro and (2) assess the effect of C-arm rotation to simulate off-axis patient alignment on intervertebral kinematics measures. Six cadaveric lumbar-sacrum specimens were dissected, and active marker optoelectronic sensors were rigidly attached to the bodies of L2-S1. Fluoroscopic sequences and optoelectronic kinematic data (0.15-mm linear, 0.17-0.20 deg rotational, accuracy) were obtained simultaneously. After images were obtained in a true sagittal plane, the image receptor was rotated in 5 deg increments (posterior oblique angulations) from 5 deg to 15 deg. Quantitative motion analysis (qma) software was used to determine the intersegmental rotations from the fluoroscopic images. The mean absolute rotation differences between optoelectronic values and dynamic fluoroscopic values were less than 0.5 deg for all the motion segments at each off-axis fluoroscopic rotation and were not significantly different (P > 0.05) for any of the off-axis rotations of the fluoroscope. Small misalignments of the lumbar spine relative to the fluoroscope did not introduce measurement variation in relative segmental rotations greater than that observed when the spine and fluoroscope were perpendicular to each other, suggesting that fluoroscopic measures of relative segmental rotation during flexion-extension are likely robust, even when patient alignment is not perfect.

Active deformation and evolution of the upper forearc slope of the central Ryukyu Arc, northwestern Pacific

NASA Astrophysics Data System (ADS)

Arai, K.; Inoue, T.; Sato, T.

2016-12-01

The Ryukyu Arc, which extend for over 1200 km along the east coast of Asia from Kyushu to Taiwan, and the associated Ryukyu Trench, are products of the subduction of the Philippine Sea Plate beneath the Eurasian Plate. The Okinawa Trough, a back-arc basin located landward of the Ryukyu Arc, formed in the Late Miocene (Gungor et al., 2012) or the Late Pliocene-Early Pleistocene (Sibuet et al., 1998); its formation is a key geologic event associated with complex tectonic movements and changes in the topographic configuration of the Ryukyu Arc. Geological Survey of Japan (GSJ), AIST has started the marine geological mapping project around Ryukyu Arc since the 2008 FY. Multi channel (16 ch) high-resolution seismic profiles were acquired during these cruises by the GI-gun (355cu. inch) or the Cluster-gun (30+30 cu. inch) systems. Survey area in the southeast off Okinawa Island is located on the upper forearc slope along the Ryukyu Trench. Seismic reflections of shelf and the upper forearc slope show no obvious deformation such as the fold and faults parallel to the Ryukyu Trench axis. In contrast, some active faults, which were perpendicular to the Ryukyu Trench axis (NW-SE direction), were observed. An acoustic basement, which is characterized distinct reflector had tilted southeastward (trenchward) and was unconformable overlain by the stratified sediments. These sediments divided into four seismic units. We present the geological history and tectonics of the central Ryukyu Arc.

Experiment definition phase shuttle laboratory LDRL-10.6 experiment. [using a molniya satellite and ground communication links

NASA Technical Reports Server (NTRS)

1975-01-01

The acquisition and tracking links of shuttle to molniya satellite and shuttle to ground are established. Link parameters and tolerance are analyzed. A 10-micromillimeter optomechanical subsystem brassboard model was designed and measured for optical properties and weight optimization. The design incorporates an afocal rotating Gregorian telescope in a two-gimbal berylium structure with beam steering control mechanisms. Parameters for both the optomechanical subsystem and spaceborne terminals are included.

Gregorian optical system with non-linear optical technology for protection against intense optical transients

DOEpatents

Ackermann, Mark R [Albuquerque, NM; Diels, Jean-Claude M [Albuquerque, NM

2007-06-26

An optical system comprising a concave primary mirror reflects light through an intermediate focus to a secondary mirror. The secondary mirror re-focuses the image to a final image plane. Optical limiter material is placed near the intermediate focus to optically limit the intensity of light so that downstream components of the optical system are protected from intense optical transients. Additional lenses before and/or after the intermediate focus correct optical aberrations.

METALLICITY DISTRIBUTION FUNCTIONS, RADIAL VELOCITIES, AND ALPHA ELEMENT ABUNDANCES IN THREE OFF-AXIS BULGE FIELDS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Christian I.; Rich, R. Michael; Kobayashi, Chiaki

2013-03-10

We present radial velocities and chemical abundance ratios of [Fe/H], [O/Fe], [Si/Fe], and [Ca/Fe] for 264 red giant branch stars in three Galactic bulge off-axis fields located near (l, b) = (-5.5, -7), (-4, -9), and (+8.5, +9). The results are based on equivalent width and spectrum synthesis analyses of moderate resolution (R Almost-Equal-To 18,000), high signal-to-noise ratio (S/N {approx} 75-300 pixel{sup -1}) spectra obtained with the Hydra spectrographs on the Blanco 4 m and WIYN 3.5 m telescopes. The targets were selected from the blue side of the giant branch to avoid cool stars that would be strongly affectedmore » by CN and TiO; however, a comparison of the color-metallicity distribution in literature samples suggests that our selection of bluer targets should not present a significant bias against metal-rich stars. We find a full range in metallicity that spans [Fe/H] Almost-Equal-To -1.5 to +0.5, and that, in accordance with the previously observed minor-axis vertical metallicity gradient, the median [Fe/H] also declines with increasing Galactic latitude in off-axis fields. The off-axis vertical [Fe/H] gradient in the southern bulge is estimated to be {approx}0.4 dex kpc{sup -1}; however, comparison with the minor-axis data suggests that a strong radial gradient does not exist. The (+8.5, +9) field exhibits a higher than expected metallicity, with a median [Fe/H] = -0.23, that might be related to a stronger presence of the X-shaped bulge structure along that line-of-sight. This could also be the cause of an anomalous increase in the median radial velocity for intermediate metallicity stars in the (+8.5, +9) field. However, the overall radial velocity and dispersion for each field are in good agreement with recent surveys and bulge models. All fields exhibit an identical, strong decrease in velocity dispersion with increasing metallicity that is consistent with observations in similar minor-axis outer bulge fields. Additionally, the [O/Fe], [Si/Fe], and [Ca/Fe] versus [Fe/H] trends are identical among our three fields, and are in good agreement with past bulge studies. We find that stars with [Fe/H] {approx}< -0.5 are {alpha}-enhanced, and that the [{alpha}/Fe] ratios decline at higher metallicity. At [Fe/H] {approx}< 0, the {alpha}-element trends are indistinguishable from the halo and thick disk, and the variations in the behavior of individual {alpha}-elements are consistent with production in massive stars and a rapid bulge formation timescale.« less

Natural History of Gas Configurations and Encapsulation in Necrotic Collections During Necrotizing Pancreatitis.

PubMed

van Grinsven, Janneke; van Brunschot, Sandra; van Baal, Mark C; Besselink, Marc G; Fockens, Paul; van Goor, Harry; van Santvoort, Hjalmar C; Bollen, Thomas L

2018-05-11

Decision-making on invasive intervention in patients with clinical signs of infected necrotizing pancreatitis is often related to the presence of gas configurations and the degree of encapsulation in necrotic collections on imaging. Data on the natural history of gas configurations and encapsulation in necrotizing pancreatitis are, however, lacking. A post hoc analysis was performed of a previously described prospective cohort in 21 Dutch hospitals (2004-2008). All computed tomography scans (CTs) performed during hospitalization for necrotizing pancreatitis were categorized per week (1 to 8, and thereafter) and re-assessed by an abdominal radiologist. A total of 639 patients with necrotizing pancreatitis were included, with median four (IQR 2-7) CTs per patient. The incidence of first onset of gas configurations varied per week without a linear correlation: 2-3-13-11-10-19-12-21-12%, respectively. Overall, gas configurations were found in 113/639 (18%) patients and in 113/202 (56%) patients with infected necrosis. The incidence of walled-off necrosis increased per week: 0-3-12-39-62-76-93-97-100% for weeks 1-8 and thereafter respectively. Clinically relevant walled-off necrosis (largely or fully encapsulated necrotic collections) was seen in 162/379 (43%) patients within the first 3 weeks. Gas configurations occur in every phase of the disease and develop in half of the patients with infected necrotizing pancreatitis. Opposed to traditional views, clinically relevant walled-off necrosis occurs frequently within the first 3 weeks.