Complete wetting near an edge of a rectangular-shaped substrate

NASA Astrophysics Data System (ADS)

Malijevský, Alexandr

2014-08-01

We consider fluid adsorption near a rectangular edge of a solid substrate that interacts with the fluid atoms via long range (dispersion) forces. The curved geometry of the liquid-vapour interface dictates that the local height of the interface above the edge ℓE must remain finite at any subcritical temperature, even when a macroscopically thick film is formed far from the edge. Using an interfacial Hamiltonian theory and a more microscopic fundamental measure density functional theory (DFT), we study the complete wetting near a single edge and show that {{\\ell}_{\\text{E}}}\\left(0\\right)-{{\\ell}_{\\text{E}}}\\left(\\delta \\mu \\right)\\sim \\delta {{\\mu}^{\\beta _{\\text{E}}^{\\text{co}}}} , as the chemical potential departure from the bulk coexistence δμ = μs(T) - μ tends to zero. The exponent \\beta _{\\text{E}}^{\\text{co}} depends on the range of the molecular forces and in particular \\beta _{\\text{E}}^{\\text{co}}=2/3 for three-dimensional systems with van der Waals forces. We further show that for a substrate model that is characterised by a finite linear dimension L, the height of the interface deviates from the one at the infinite substrate as δℓE(L) ˜ L-1 in the limit of large L. Both predictions are supported by numerical solutions of the DFT.

Steady boiling of vapor bubbles in rectangular channels

NASA Astrophysics Data System (ADS)

Ajaev, Vladimir S.; Homsy, George M.

2000-11-01

We consider vapor bubbles in microchannels in which the vapor is produced by a heater element and condenses in cooler parts of the interface. The free boundary problem is formulated for a long steady-state bubble in a rectangular channel with a heated bottom. The shape of the liquid-vapor interface is described using lubrication-type equations in the regime in which the vapor phase fills most of the cross-section. Contact lines may be present, marking the transitions between molecularly thin films and macroscopic ones. The main parameters are the differences between heater, saturation, and top wall temperatures. The equations are solved numerically over a range of parameter values with an integral condition requiring the evaporation near the heater to balance condensation in colder areas of the interface. Depending on the temperature, the side walls can be either dry or covered with a liquid film; we identify criteria for these two different regimes. The asymptotic method breaks down in the limit when capillary condensation becomes important near the bubble top and a different approach is used to determine the shape of the bubble in this limit. Solutions here involve localized regions of large mass fluxes, which are asymptotically matched to capillary-statics regions where the heat transfer is negligible.

A lift formula applied to low-Reynolds-number unsteady flows

NASA Astrophysics Data System (ADS)

Wang, Shizhao; Zhang, Xing; He, Guowei; Liu, Tianshu

2013-09-01

A lift formula for a wing in a rectangular control volume is given in a very simple and physically lucid form, providing a rational foundation for calculation of the lift of a flapping wing in highly unsteady and separated flows at low Reynolds numbers. Direct numerical simulations on the stationary and flapping two-dimensional flat plate and rectangular flat-plate wing are conducted to assess the accuracy of the lift formula along with the classical Kutta-Joukowski theorem. In particular, the Lamb vector integral for the vortex force and the acceleration term of fluid for the unsteady inertial effect are evaluated as the main contributions to the unsteady lift generation of a flapping wing.

Design of an Ultra-wide Band Waveguide Transition for the Ex-vessel Transmission Line of ITER Plasma Position Reflectometry

NASA Astrophysics Data System (ADS)

Simonetto, A.; Platania, P.; Garavaglia, S.; Gittini, G.; Granucci, G.; Pallotta, F.

2018-02-01

Plasma position reflectometry for ITER requires interfaces between in-vessel and ex-vessel waveguides. An ultra broadband interface (15-75 GHz) was designed between moderately oversized rectangular waveguide (20 × 12 mm), operated in TE01 (i.e., tall waveguide mode), and circular corrugated waveguide, with 88.9-mm internal diameter, propagating HE11. The interface was designed both as a sequence of waveguide components and as a quasi-optical confocal telescope. The design and the simulated performance are described for both concepts. The latter one requires more space but has better performance, and shall be prototyped.

Self-consistent simulation of an electron beam for a new autoresonant x-ray generator based on TE 102 rectangular mode

NASA Astrophysics Data System (ADS)

Dugar-Zhabon, V. D.; Orozco, E. A.; Herrera, A. M.

2016-02-01

The space cyclotron autoresonance interaction of an electron beam with microwaves of TE 102 rectangular mode is simulated. It is shown that in these conditions the beam electrons can achieve energies which are sufficient to generate hard x-rays. The physical model consists of a rectangular cavity fed by a magnetron oscillator through a waveguide with a ferrite isolator, an iris window and a system of dc current coils which generates an axially symmetric magnetic field. The 3D magnetic field profile is that which maintains the electron beam in the space autoresonance regime. To simulate the beam dynamics, a full self-consistent electromagnetic particle-in-cell code is developed. It is shown that the injected 12keV electron beam of 0.5A current is accelerated to energy of 225keV at a distance of an order of 17cm by 2.45GHz standing microwave field with amplitude of 14kV/cm.

ETF magnet design alternatives for the national MHD program

NASA Astrophysics Data System (ADS)

Marston, P. G.; Thome, R. J.; Dawson, A. M.; Bobrov, E. S.; Hatch, A. M.

1981-01-01

Five superconducting magnet designs are evaluated for a 200 MWe test facility requiring a magnet with an on-axis field of 6 T, an inlet bore area of 4 sq m, storing 6 x 10 to the 9th J. The designs include a straightforward rectangular saddle coil set, a 'Cask' configuration based on staves and corner blocks as the main support structure, and an internally cooled, cabled superconductor to minimize the substructure and eliminate the helium vessel. Also, a modular design using six coils with individual helium vessels and an integrated structure produces a simplest configuration which utilizes a natural rectangular interface for packaging the MHD channel and its connections, and results in a lower capital cost.

Exact nonstationary responses of rectangular thin plate on Pasternak foundation excited by stochastic moving loads

NASA Astrophysics Data System (ADS)

Chen, Guohai; Meng, Zeng; Yang, Dixiong

2018-01-01

This paper develops an efficient method termed as PE-PIM to address the exact nonstationary responses of pavement structure, which is modeled as a rectangular thin plate resting on bi-parametric Pasternak elastic foundation subjected to stochastic moving loads with constant acceleration. Firstly, analytical power spectral density (PSD) functions of random responses for thin plate are derived by integrating pseudo excitation method (PEM) with Duhamel's integral. Based on PEM, the new equivalent von Mises stress (NEVMS) is proposed, whose PSD function contains all cross-PSD functions between stress components. Then, the PE-PIM that combines the PEM with precise integration method (PIM) is presented to achieve efficiently stochastic responses of the plate by replacing Duhamel's integral with the PIM. Moreover, the semi-analytical Monte Carlo simulation is employed to verify the computational results of the developed PE-PIM. Finally, numerical examples demonstrate the high accuracy and efficiency of PE-PIM for nonstationary random vibration analysis. The effects of velocity and acceleration of moving load, boundary conditions of the plate and foundation stiffness on the deflection and NEVMS responses are scrutinized.

Equivalent square formula for determining the surface dose of rectangular field from 6 MV therapeutic photon beam.

PubMed

Apipunyasopon, Lukkana; Srisatit, Somyot; Phaisangittisakul, Nakorn

2013-09-06

The purpose of the study was to investigate the use of the equivalent square formula for determining the surface dose from a rectangular photon beam. A 6 MV therapeutic photon beam delivered from a Varian Clinac 23EX medical linear accelerator was modeled using the EGS4nrc Monte Carlo simulation package. It was then used to calculate the dose in the build-up region from both square and rectangular fields. The field patterns were defined by various settings of the X- and Y-collimator jaw ranging from 5 to 20 cm. Dose measurements were performed using a thermoluminescence dosimeter and a Markus parallel-plate ionization chamber on the four square fields (5 × 5, 10 × 10, 15 × 15, and 20 × 20 cm2). The surface dose was acquired by extrapolating the build-up doses to the surface. An equivalent square for a rectangular field was determined using the area-to-perimeter formula, and the surface dose of the equivalent square was estimated using the square-field data. The surface dose of square field increased linearly from approximately 10% to 28% as the side of the square field increased from 5 to 20 cm. The influence of collimator exchange on the surface dose was found to be not significant. The difference in the percentage surface dose of the rectangular field compared to that of the relevant equivalent square was insignificant and can be clinically neglected. The use of the area-to-perimeter formula for an equivalent square field can provide a clinically acceptable surface dose estimation for a rectangular field from a 6 MV therapy photon beam.

Digital control algorithms for microgravity isolation systems

NASA Technical Reports Server (NTRS)

Sinha, Alok; Wang, Yung-Peng

1992-01-01

New digital control algorithms were developed to achieve the desired acceleration transmissibility function. The attractive electromagnets have been taken as actuators. The relative displacement and the acceleration of the mass were used as feedback signals. Two approaches were developed to find that controller transfer function in Z-domain, which yields the desired transmissibility at each frequency. In the first approach, the controller transfer function is obtained by assuming that the desired transmissibility is known in Z-domain. Since the desired transmissibility H sub d(S) = 1/(tauS+1)(exp 2) is given in S-domain, the first task is to obtain the desired transmissibility in Z-domain. There are three methods to perform this task: bilinear transformation, and backward and forward rectangular rules. The bilinear transformation and backward rectangular rule lead to improper controller transfer functions, which are physically not realizable. The forward rectangular rule does lead to a physically realizable controller. However, this controller is found to be marginally stable because of a pole at Z=1. In order to eliminate this pole, a hybrid control structure is proposed. Here the control input is composed of two parts: analog and digital. The analog input simply represents the velocity (or the integral of acceleration) feedback; and the digital controller which uses only relative displacement signal, is then obtained to achieve the desired closed-loop transfer function. The stability analysis indicates that the controller transfer function is stable for typical values of sampling period. In the second approach, the aforementioned hybrid control structure is again used. First, an analog controller transfer function corresponding to relative displacement feedback is obtained to achieve the transmissibility as 1/(tauS+1)(exp 2). Then the transfer function for the digital control input is obtained by discretizing this analog controller transfer function via bilinear transformation. The stability of the resulting Z-domain closed loop system is analyzed. Also, the frequency response of the Z-domain closed-loop transfer function is determined to evaluate the performance of the control system.

Experimental Study of Large-Amplitude Faraday Waves in Rectangular Cylinders

NASA Technical Reports Server (NTRS)

Iek, Chanthy; Alexander, Iwan J.; Tin, Padetha; Adamovsky, Gregory

2005-01-01

Experiment on single-mode Faraday waves having two, thee, and four wavelengths across a rectangular cylinder of high aspect ratio is the subject of discussion. Previous experiments recently done by Henderson & Miles (1989) and by Lei Jiang et. a1 (1996) focused on Faraday waves with one and two wavelengths across rectangular cylinders. In this experimental study the waves steepness ranges from small at threshold levels to a large amplitude which according to Penny & Price theory (1952) approaches the maximum sustainable amplitude for a standing wave. The waves characteristics for small amplitudes are evaluated against an existing well known linear theory by Benjamin & Ursell (l954) and against a weakly nonlinear theory by J. Miles (1984) which includes the effect of viscous damping. The evaluation includes the wave neutral stability and damping rate. In addition, a wave amplitude differential equation of a linear theory including viscous effect by Cerda & Tirapegui (1998) is solved numerically to yield prediction of temporal profiles of both wave damping and wave formation at the threshold. An interesting finding from this exercise is that the fluid kinematic viscosity needs to increase ten times in order to obtain good agreement between the theoretical prediction and the experimental data for both wave damping and wave starting. For large amplitude waves, the experimental data are evaluated against the theory of Penny & Price which predicts wave characteristics of any amplitude up to the point at which the wave reaches its maximum amplitude attainable for a standing wave. The theory yields two criteria to show the maximum wave steepness, the vertical acceleration at the wave crest of half the earth gravity field acceleration and the including angle at the crest of 90 degrees. Comparison with experimental data shows close agreement for the wave crest acceleration but a large discrepancy for the including angle. Additional information is included in the original extended abstract.

Rectangular Ion Funnel: A New Ion Funnel Interface for Structures for Lossless Ion Manipulations

DOE PAGES

Chen, Tsung-Chi; Webb, Ian K.; Prost, Spencer A.; ...

2014-11-19

A recent achievement in Structures for Lossless Ion Manipulations (SLIM) is the ability for near lossless ion focusing, transfer, and trapping in sub-atmospheric pressure regions. While lossless ion manipulations are advantageously applied to the applications of ion mobility separations and gas phase reactions, ion introduction through ring electrode ion funnels or more conventional ion optics to SLIM can involve discontinuities in electric fields or other perturbations that result in ion losses. In this work, we investigated a new funnel design that aims to seamlessly couple to SLIM at the funnel exit. This rectangular ion funnel (RIF) was initially evaluated bymore » ion simulations, fabricated utilizing printed circuit board technology and tested experimentally. The RIF was integrated to a SLIM-TOFMS system, and the operating parameters, including RF, DC bias of the RIF electrodes, and electric fields for effectively interfacing with a SLIM were characterized. The RIF provided a 2-fold sensitivity increase without significant discrimination over a wide m/z range along with greatly improved SLIM operational stability.« less

The output power improvement and durability with different shape of MEMS piezoelectric energy harvester

NASA Astrophysics Data System (ADS)

Chen, C. T.; Fu, Y. H.; Tang, W. H.; Lin, S. C.; Wu, W. J.

2018-03-01

MEMS piezoelectric energy harvester (PEH) has been widely designed in cantilever beam style because of ease of fabrication and effective to generate large strain and output power. There are already several studies on tapered beam shapes to improve the overall performance of energy harvested. In this paper, we investigate cantilever beam type PEH in rectangular, trapezoidal and triangle shapes, and the devices are limited to the area smaller than 1cm × 1 cm for better flexibility in applications. The power output and the life time of each shape of devices are fabricated and characterized. The output power are tested with optimal resistance loads, and the output power are 145.3 μW, 125.3 μW and 107.8 μW for triangle, trapezoidal and rectangular shapes of devices respectively under excitation of 0.5g acceleration vibration level in the resonant frequency of the transducer. The tip displacements of the 3 devices are 3.05 mm, 2.66 mm, and 2.44 mm for triangular, trapezoidal and rectangular shape devices, respectively. To study the lifetime and durability issue, triangular and rectangular devices are excited under 0.2g to 1g for 24 hours. The resonant frequency shifting, tip displacement and open circuit voltage changing are monitored will be detailed in the paper.

Time-Dependent Thermally-Driven Interfacial Flows in Multilayered Fluid Structures

NASA Technical Reports Server (NTRS)

Haj-Hariri, Hossein; Borhan, A.

1996-01-01

A computational study of thermally-driven convection in multilayered fluid structures will be performed to examine the effect of interactions among deformable fluid-fluid interfaces on the structure of time-dependent flow in these systems. Multilayered fluid structures in two models configurations will be considered: the differentially heated rectangular cavity with a free surface, and the encapsulated cylindrical liquid bridge. An extension of a numerical method developed as part of our recent NASA Fluid Physics grant will be used to account for finite deformations of fluid-fluid interfaces.

Thermo-Oxidative Stability of Graphite/PMR-15 Composites: Effect of Fiber Surface Modification on Composite Shear Properties

NASA Technical Reports Server (NTRS)

Madhukar, Madhu S.; Bowles, Kenneth J.; Papadopolous, Demetrios S.

1994-01-01

Experiments were conducted to establish a correlation between the weight loss of a polyimide (PMR- 15) matrix and graphite fibers and the in-plane shear properties of their unidirectional composites subjected to different isothermal aging times up to 1000 hr at 316 C. The role of fiber surface treatment on the composite degradation during the thermo-oxidative aging was investigated by using A4 graphite fibers with three surface modifications: untreated (AU-4), surface treated (AS-4), and surface treated and sized with an epoxy-compatible sizing (AS-4G). The weight loss of the matrix fibers, and composites was determined during the aging. The effect of thermal aging was seen in all the fiber samples in terms of weight loss and reduction in fiber diameter. Calculated values of weight loss fluxes for different surfaces of rectangular unidirectional composite plates showed that the largest weight loss occurred at those cut surfaces where fibers were perpendicular to the surface. Consequently, the largest amount of damage was also noted on these cut surfaces. Optical observation of the neat matrix and composite plates subjected to different aging times revealed that the degradation (such as matrix microcracking and void growth) occurred in a thin surface layer near the specimen edges. The in-plane shear modulus of the composites was unaffected by the fiber surface treatment and the thermal aging. The shear strength of the composites with the untreated fibers was the lowest and it decreased with aging. A fracture surface examination of the composites with untreated fibers suggested that the weak interface allowed the oxidation reaction to proceed along the interface and thus expose the inner material to further oxidation. The results indicated that the fiber-matrix interface affected the composite degradation process during its thermal aging and that the the weak interface accelerated the composite degradation.

Bone bonding in bioactive glass ceramics combined with a new synthesized agent TAK-778.

PubMed

Kato, H; Neo, M; Tamura, J; Nakamura, T

2001-11-01

We studied the stimulatory effects of TAK-778, a new synthetic 3-benzothiepin derivative that promotes osteoblast differentiation, in the bonding of bone to bioactive glass ceramic implants in rabbit tibiae. Smooth-surfaced, rectangular plates (15 x 10 x 2 mm) made of apatite-wollastonite-containing glass ceramic were implanted bilaterally into the proximal metaphyses of rabbit tibiae. Sustained-release microcapsules containing TAK-778 were packed into the medullary cavity in one limb and untreated microcapsules were packed into the contralateral limb to serve as a paired control. At 4, 8, and 16 weeks after implantation, bonding at the bone/implant interfaces was evaluated using a detaching test and histological examination of undecalcified specimens. The tensile failure load increased during weeks 4 to 16 in both groups; the tensile failure load in the TAK-778-treated group was significantly greater than that in the control group at each interval after implantation. Histologically, the TAK-778-treated specimens showed greater active new bone formation mainly in the medullary cavity and more extensive bonding between the implant and bone than the untreated specimens. The results of this study suggest that adding the bone formation-promoting TAK-778 to bioactive glass ceramic implants may significantly accelerate bone apposition to the implants and improve the bonding process at the interface. This would help to establish earlier and stronger bonding of orthopedic ceramic implants to the surrounding bone tissue. Copyright 2001 John Wiley & Sons, Inc.

An immersed boundary formulation for simulating high-speed compressible viscous flows with moving solids

NASA Astrophysics Data System (ADS)

Qu, Yegao; Shi, Ruchao; Batra, Romesh C.

2018-02-01

We present a robust sharp-interface immersed boundary method for numerically studying high speed flows of compressible and viscous fluids interacting with arbitrarily shaped either stationary or moving rigid solids. The Navier-Stokes equations are discretized on a rectangular Cartesian grid based on a low-diffusion flux splitting method for inviscid fluxes and conservative high-order central-difference schemes for the viscous components. Discontinuities such as those introduced by shock waves and contact surfaces are captured by using a high-resolution weighted essentially non-oscillatory (WENO) scheme. Ghost cells in the vicinity of the fluid-solid interface are introduced to satisfy boundary conditions on the interface. Values of variables in the ghost cells are found by using a constrained moving least squares method (CMLS) that eliminates numerical instabilities encountered in the conventional MLS formulation. The solution of the fluid flow and the solid motion equations is advanced in time by using the third-order Runge-Kutta and the implicit Newmark integration schemes, respectively. The performance of the proposed method has been assessed by computing results for the following four problems: shock-boundary layer interaction, supersonic viscous flows past a rigid cylinder, moving piston in a shock tube and lifting off from a flat surface of circular, rectangular and elliptic cylinders triggered by shock waves, and comparing computed results with those available in the literature.

Coupling finite element and spectral methods: First results

NASA Technical Reports Server (NTRS)

Bernardi, Christine; Debit, Naima; Maday, Yvon

1987-01-01

A Poisson equation on a rectangular domain is solved by coupling two methods: the domain is divided in two squares, a finite element approximation is used on the first square and a spectral discretization is used on the second one. Two kinds of matching conditions on the interface are presented and compared. In both cases, error estimates are proved.

Tensile test and interface retention forces between wires and composites in lingual fixed retainers.

PubMed

Paolone, Maria Giacinta; Kaitsas, Roberto; Obach, Patricia; Kaitsas, Vasilios; Benedicenti, Stefano; Sorrenti, Eugenio; Barberi, Fabrizio

2015-06-01

In daily orthodontic clinical practice retention is very important, and lingual retainers are part of this challenge. The failure of lingual retainers may be due to many factors. The aim of this study was to assess the retention forces and mechanical behavior of different types of wires matched with different kinds of composites in lingual retainers. A tensile test was performed on cylindrical composite test specimens bonded to orthodontic wires. The specimens were constructed using four different wires: a straight wire (Remanium .016×.022″ Dentaurum), two round twisted wires (Penta One .0215″ Masel, Gold Penta Twisted .0215″ Gold N'braces) and a rectangular braided wire (D-Rect .016×.022″ Ormco); and three composites: two micro-hybrids (Micro-Hybrid Enamel Plus HFO Micerium, and Micro-Hybrid SDR U Dentsply) and a micro-nano-filled composite (Micro-Nano-Filled Transbond LR 3M). The test was performed at a speed of 10mm/min on an Inström device. The wire was fixed with a clamp. The results showed that the bonding between wires and composites in lingual fixed retainers seemed to be lowest for rectangular smooth wires and increased in round twisted and rectangular twisted wires where the bonding was so strong that the maximum tension/bond strength was greater than the ultimate tensile strength of the wire. The highest values were in rectangular twisted wires. Concerning the composites, hybrid composites had the lowest interface bonding values and broke very quickly, while the nano- and micro-composites tolerated stronger forces and displayed higher bonding values. The best results were observed with the golden twisted wire and reached 21.46 MPa with the Transbond composite. With the rectangular braided wire the retention forces were so high that the Enamel Plus composite fractured when the load exceeded 154.6 N/MPa. When the same wire was combined with the Transbond LR either the wire or the composite broke when the force exceeded 240 N. The results of this study show that, when selecting a lingual retainer in daily clinical practice, not only must the patient's compliance and dependability be considered but also the mechanical properties and composition of different combinations of composites and wires. Copyright © 2015 CEO. Published by Elsevier Masson SAS. All rights reserved.

Multiplexing of adjacent vortex modes with the forked grating coupler

NASA Astrophysics Data System (ADS)

Nadovich, Christopher T.; Kosciolek, Derek J.; Crouse, David T.; Jemison, William D.

2017-08-01

For vortex fiber multiplexing to reach practical commercial viability, simple silicon photonic interfaces with vortex fiber will be required. These interfaces must support multiplexing. Toward this goal, an efficient singlefed multimode Forked Grating Coupler (FGC) for coupling two different optical vortex OAM charges to or from the TE0 and TE1 rectangular waveguide modes has been developed. A simple, apodized device implemented with e-beam lithography and a conventional dual-etch processing on SOI wafer exhibits low crosstalk and reasonable mode match. Advanced designs using this concept are expected to further improve performance.

Fabrication of a negative PMMA master mold for soft-lithography by MeV ion beam lithography

NASA Astrophysics Data System (ADS)

Puttaraksa, Nitipon; Unai, Somrit; Rhodes, Michael W.; Singkarat, Kanda; Whitlow, Harry J.; Singkarat, Somsorn

2012-02-01

In this study, poly(methyl methacrylate) (PMMA) was investigated as a negative resist by irradiation with a high-fluence 2 MeV proton beam. The beam from a 1.7 MV Tandetron accelerator at the Plasma and Beam Physics Research Facility (PBP) of Chiang Mai University is shaped by a pair of computer-controlled L-shaped apertures which are used to expose rectangular pattern elements with 1-1000 μm side length. Repeated exposure of rectangular pattern elements allows a complex pattern to be built up. After subsequent development, the negative PMMA microstructure was used as a master mold for casting poly(dimethylsiloxane) (PDMS) following a standard soft-lithography process. The PDMS chip fabricated by this technique was demonstrated to be a microfluidic device.

Program EAGLE User’s Manual. Volume 3. Grid Generation Code

DTIC Science & Technology

1988-09-01

15 1. ompps.te Grid Structure ..... .. .................. . 15 2. Block Interfaces ......... ...................... . 18 3. Fundmental ...in principle it is possible to establish a correspondence between any physical region and a single empty rectangular block for general three...differences. Since this second surrounding layer is not involved in the grid generation, no further account will be taken of its presence in the present

3D printed, bio-inspired prototypes and analytical models for structured suture interfaces with geometrically-tuned deformation and failure behavior

NASA Astrophysics Data System (ADS)

Lin, Erica; Li, Yaning; Ortiz, Christine; Boyce, Mary C.

2014-12-01

Geometrically structured interfaces in nature possess enhanced, and often surprising, mechanical properties, and provide inspiration for materials design. This paper investigates the mechanics of deformation and failure mechanisms of suture interface designs through analytical models and experiments on 3D printed polymer physical prototypes. Suture waveforms with generalized trapezoidal geometries (trapezoidal, rectangular, anti-trapezoidal, and triangular) are studied and characterized by several important geometric parameters: the presence or absence of a bonded tip region, the tip angle, and the geometry. It is shown that a wide range (in some cases as great as an order of magnitude) in stiffness, strength, and toughness is achievable dependent on tip bonding, tip angle, and geometry. Suture interfaces with a bonded tip region exhibit a higher initial stiffness due to the greater load bearing by the skeletal teeth, a double peak in the stress-strain curve corresponding to the failure of the bonded tip and the failure of the slanted interface region or tooth, respectively, and an additional failure and toughening mechanism due to the failure of the bonded tip. Anti-trapezoidal geometries promote the greatest amplification of properties for suture interfaces with a bonded tip due the large tip interface area. The tip angle and geometry govern the stress distributions in the teeth and the ratio of normal to shear stresses in the interfacial layers, which together determine the failure mechanism of the interface and/or the teeth. Rectangular suture interfaces fail by simple shearing of the interfaces. Trapezoidal and triangular suture interfaces fail by a combination of shear and tensile normal stresses in the interface, leading to plastic deformation, cavitation events, and subsequent stretching of interface ligaments with mostly elastic deformation in the teeth. Anti-trapezoidal suture interfaces with small tip angles have high stress concentrations in the teeth and fail catastrophically by tooth failure, whereas larger tip angles exhibit a shear failure of the interfaces. Therefore, larger tip angles and trapezoidal or triangular geometries promote graceful failure, and smaller tip angles and anti-trapezoidal geometries promote more brittle-like failure. This dependence is reminiscent of biological systems, which exhibit a range of failure behaviors with limited materials and varied geometry. Triangular geometries uniquely exhibit uniform stress distributions in its teeth and promote the greatest amplification of mechanical properties. In both the bonded and unbonded cases, the predictions from the presented analytical models and experimental results on 3D printed prototypes show excellent agreement. This validates the analytical models and allows for the models to be used as a tool for the design of new materials and interfaces with tailored mechanical behavior.

Acceleration and Velocity Sensing from Measured Strain

NASA Technical Reports Server (NTRS)

Pak, Chan-Gi; Truax, Roger

2015-01-01

A simple approach for computing acceleration and velocity of a structure from the strain is proposed in this study. First, deflection and slope of the structure are computed from the strain using a two-step theory. Frequencies of the structure are computed from the time histories of strain using a parameter estimation technique together with an autoregressive moving average model. From deflection, slope, and frequencies of the structure, acceleration and velocity of the structure can be obtained using the proposed approach. Simple harmonic motion is assumed for the acceleration computations, and the central difference equation with a linear autoregressive model is used for the computations of velocity. A cantilevered rectangular wing model is used to validate the simple approach. Quality of the computed deflection, acceleration, and velocity values are independent of the number of fibers. The central difference equation with a linear autoregressive model proposed in this study follows the target response with reasonable accuracy. Therefore, the handicap of the backward difference equation, phase shift, is successfully overcome.

Permanent magnet edge-field quadrupole

DOEpatents

Tatchyn, R.O.

1997-01-21

Planar permanent magnet edge-field quadrupoles for use in particle accelerating machines and in insertion devices designed to generate spontaneous or coherent radiation from moving charged particles are disclosed. The invention comprises four magnetized rectangular pieces of permanent magnet material with substantially similar dimensions arranged into two planar arrays situated to generate a field with a substantially dominant quadrupole component in regions close to the device axis. 10 figs.

Permanent magnet edge-field quadrupole

DOEpatents

Tatchyn, Roman O.

1997-01-01

Planar permanent magnet edge-field quadrupoles for use in particle accelerating machines and in insertion devices designed to generate spontaneous or coherent radiation from moving charged particles are disclosed. The invention comprises four magnetized rectangular pieces of permanent magnet material with substantially similar dimensions arranged into two planar arrays situated to generate a field with a substantially dominant quadrupole component in regions close to the device axis.

Visualization of an air-water interface on superhydrophobic surfaces in turbulent channel flows

NASA Astrophysics Data System (ADS)

Kim, Hyunseok; Park, Hyungmin

2017-11-01

In the present study, three-dimensional deformation of air-water interface on superhydrophobic surfaces in turbulent channel flows at the Reynolds numbers of Re = 3000 and 10000 is measured with RICM (Reflection Interference Contrast Microscopy) technique. Two different types of roughness feature of circular hole and rectangular grate are considered, whose depth is 20 μm and diameter (or width) is varied between 20-200 μm. Since the air-water interface is always at de-pinned state at the considered condition, air-water interface shape and its sagging velocity is maintained to be almost constant as time goes one. In comparison with the previous results under the laminar flow, due to turbulent characteristics of the flow, sagging velocity is much faster. Based on the measured sagging profiles, a modified model to describe the air-water interface dynamics under turbulent flows is suggested. Supported by City of Seoul through Seoul Urban Data Science Laboratory Project (Grant No 0660-20170004) administered by SNU Big Data Institute.

Validation of Force Limited Vibration Testing at NASA Langley Research Center

NASA Technical Reports Server (NTRS)

Rice, Chad; Buehrle, Ralph D.

2003-01-01

Vibration tests were performed to develop and validate the forced limited vibration testing capability at the NASA Langley Research Center. The force limited vibration test technique has been utilized at the Jet Propulsion Laboratory and other NASA centers to provide more realistic vibration test environments for aerospace flight hardware. In standard random vibration tests, the payload is mounted to a rigid fixture and the interface acceleration is controlled to a specified level based on a conservative estimate of the expected flight environment. In force limited vibration tests, both the acceleration and force are controlled at the mounting interface to compensate for differences between the flexible flight mounting and rigid test fixture. This minimizes the over test at the payload natural frequencies and results in more realistic forces being transmitted at the mounting interface. Force and acceleration response data was provided by NASA Goddard Space Flight Center for a test article that was flown in 1998 on a Black Brant sounding rocket. The measured flight interface acceleration data was used as the reference acceleration spectrum. Using this acceleration spectrum, three analytical methods were used to estimate the force limits. Standard random and force limited vibration tests were performed and the results are compared with the flight data.

Elastic guided waves in a layered plate with rectangular cross section.

PubMed

Mukdadi, O M; Desai, Y M; Datta, S K; Shah, A H; Niklasson, A J

2002-11-01

Guided waves in a layered elastic plate of rectangular cross section (finite width and thickness) has been studied in this paper. A semianalytical finite element method in which the deformation of the cross section is modeled by two-dimensional finite elements and analytical representation of propagating waves along the length of the plate has been used. The method is applicable to arbitrary number of layers and general anisotropic material properties of each layer, and is similar to the stiffness method used earlier to study guided waves in a laminated composite plate of infinite width. Numerical results showing the effect of varying the width of the plate on the dispersion of guided waves are presented and are compared with those for an infinite plate. In addition, effect of thin anisotropic coating or interface layers on the guided waves is investigated.

Micromachined piezoresistive inclinometer with oscillator-based integrated interface circuit and temperature readout

NASA Astrophysics Data System (ADS)

Dalola, Simone; Ferrari, Vittorio; Marioli, Daniele

2012-03-01

In this paper a dual-chip system for inclination measurement is presented. It consists of a MEMS (microelectromechanical system) piezoresistive accelerometer manufactured in silicon bulk micromachining and a CMOS (complementary metal oxide semiconductor) ASIC (application specific integrated circuit) interface designed for resistive-bridge sensors. The sensor is composed of a seismic mass symmetrically suspended by means of four flexure beams that integrate two piezoresistors each to detect the applied static acceleration, which is related to inclination with respect to the gravity vector. The ASIC interface is based on a relaxation oscillator where the frequency and the duty cycle of a rectangular-wave output signal are related to the fractional bridge imbalance and the overall bridge resistance of the sensor, respectively. The latter is a function of temperature; therefore the sensing element itself can be advantageously used to derive information for its own thermal compensation. DC current excitation of the sensor makes the configuration unaffected by wire resistances and parasitic capacitances. Therefore, a modular system results where the sensor can be placed remotely from the electronics without suffering accuracy degradation. The inclination measurement system has been characterized as a function of the applied inclination angle at different temperatures. At room temperature, the experimental sensitivity of the system results in about 148 Hz/g, which corresponds to an angular sensitivity around zero inclination angle of about 2.58 Hz deg-1. This is in agreement with finite element method simulations. The measured output fluctuations at constant temperature determine an equivalent resolution of about 0.1° at midrange. In the temperature range of 25-65 °C the system sensitivity decreases by about 10%, which is less than the variation due to the microsensor alone thanks to thermal compensation provided by the current excitation of the bridge and the positive temperature coefficient of resistance of the piezoresistors.

Accelerator System Model (ASM) user manual with physics and engineering model documentation. ASM version 1.0

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

NONE

1993-07-01

The Accelerator System Model (ASM) is a computer program developed to model proton radiofrequency accelerators and to carry out system level trade studies. The ASM FORTRAN subroutines are incorporated into an intuitive graphical user interface which provides for the {open_quotes}construction{close_quotes} of the accelerator in a window on the computer screen. The interface is based on the Shell for Particle Accelerator Related Codes (SPARC) software technology written for the Macintosh operating system in the C programming language. This User Manual describes the operation and use of the ASM application within the SPARC interface. The Appendix provides a detailed description of themore » physics and engineering models used in ASM. ASM Version 1.0 is joint project of G. H. Gillespie Associates, Inc. and the Accelerator Technology (AT) Division of the Los Alamos National Laboratory. Neither the ASM Version 1.0 software nor this ASM Documentation may be reproduced without the expressed written consent of both the Los Alamos National Laboratory and G. H. Gillespie Associates, Inc.« less

Electron acceleration by surface plasma waves in double metal surface structure

NASA Astrophysics Data System (ADS)

Liu, C. S.; Kumar, Gagan; Singh, D. B.; Tripathi, V. K.

2007-12-01

Two parallel metal sheets, separated by a vacuum region, support a surface plasma wave whose amplitude is maximum on the two parallel interfaces and minimum in the middle. This mode can be excited by a laser using a glass prism. An electron beam launched into the middle region experiences a longitudinal ponderomotive force due to the surface plasma wave and gets accelerated to velocities of the order of phase velocity of the surface wave. The scheme is viable to achieve beams of tens of keV energy. In the case of a surface plasma wave excited on a single metal-vacuum interface, the field gradient normal to the interface pushes the electrons away from the high field region, limiting the acceleration process. The acceleration energy thus achieved is in agreement with the experimental observations.

MAPA: Implementation of the Standard Interchange Format and use for analyzing lattices

NASA Astrophysics Data System (ADS)

Shasharina, Svetlana G.; Cary, John R.

1997-05-01

MAPA (Modular Accelerator Physics Analysis) is an object oriented application for accelerator design and analysis with a Motif based graphical user interface. MAPA has been ported to AIX, Linux, HPUX, Solaris, and IRIX. MAPA provides an intuitive environment for accelerator study and design. The user can bring up windows for fully nonlinear analysis of accelerator lattices in any number of dimensions. The current graphical analysis methods of Lifetime plots and Surfaces of Section have been used to analyze the improved lattice designs of Wan, Cary, and Shasharina (this conference). MAPA can now read and write Standard Interchange Format (MAD) accelerator description files and it has a general graphical user interface for adding, changing, and deleting elements. MAPA's consistency checks prevent deletion of used elements and prevent creation of recursive beam lines. Plans include development of a richer set of modeling tools and the ability to invoke existing modeling codes through the MAPA interface. MAPA will be demonstrated on a Pentium 150 laptop running Linux.

Experimental and analytical studies on the vibration serviceability of long-span prestressed concrete floor

NASA Astrophysics Data System (ADS)

Cao, Liang; Liu, Jiepeng; Li, Jiang; Zhang, Ruizhi

2018-04-01

An extensive experimental and theoretical research study was undertaken to study the vibration serviceability of a long-span prestressed concrete floor system to be used in the lounge of a major airport. Specifically, jumping impact tests were carried out to obtain the floor's modal parameters, followed by an analysis of the distribution of peak accelerations. Running tests were also performed to capture the acceleration responses. The prestressed concrete floor was found to have a low fundamental natural frequency (≈ 8.86 Hz) corresponding to the average modal damping ratio of ≈ 2.17%. A coefficients β rp is proposed for convenient calculation of the maximum root-mean-square acceleration for running. In the theoretical analysis, the prestressed concrete floor under running excitation is treated as a two-span continuous anisotropic rectangular plate with simply-supported edges. The calculated analytical results (natural frequencies and root-mean-square acceleration) agree well with the experimental ones. The analytical approach is thus validated.

805 MHz Beta = 0.47 Elliptical Accelerating Structure R & D

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

S. Bricker; C. Compton; W. Hartung

2008-09-22

A 6-cell 805 MHz superconducting cavity for acceleration in the velocity range of about 0.4 to 0.53 times the speed of light was designed. After single-cell prototyping, three 6-cell niobium cavities were fabricated. In vertical RF tests of the 6-cell cavities, the measured quality factors (Q{sub 0}) were between 7 {center_dot} 10{sup 9} and 1.4 {center_dot} 10{sup 10} at the design field (accelerating gradient of 8 to 10 MV/m). A rectangular cryomodule was designed to house 4 cavities per cryomodule. The 4-cavity cryomodule could be used for acceleration of ions in a linear accelerator, with focusing elements between the cryomodules.more » A prototype cryomodule was fabricated to test 2 cavities under realistic operating conditions. Two of the 6-cell cavities were equipped with helium tanks, tuners, and input coupler and installed into the cryomodule. The prototype cryomodule was used to verify alignment, electromagnetic performance, frequency tuning, cryogenic performance, low-level RF control, and control of microphonics.« less

Reconstruction of transient vibration and sound radiation of an impacted plate using time domain plane wave superposition method

NASA Astrophysics Data System (ADS)

Geng, Lin; Zhang, Xiao-Zheng; Bi, Chuan-Xing

2015-05-01

Time domain plane wave superposition method is extended to reconstruct the transient pressure field radiated by an impacted plate and the normal acceleration of the plate. In the extended method, the pressure measured on the hologram plane is expressed as a superposition of time convolutions between the time-wavenumber normal acceleration spectrum on a virtual source plane and the time domain propagation kernel relating the pressure on the hologram plane to the normal acceleration spectrum on the virtual source plane. By performing an inverse operation, the normal acceleration spectrum on the virtual source plane can be obtained by an iterative solving process, and then taken as the input to reconstruct the whole pressure field and the normal acceleration of the plate. An experiment of a clamped rectangular steel plate impacted by a steel ball is presented. The experimental results demonstrate that the extended method is effective in visualizing the transient vibration and sound radiation of an impacted plate in both time and space domains, thus providing the important information for overall understanding the vibration and sound radiation of the plate.

X-Antenna: A graphical interface for antenna analysis codes

NASA Technical Reports Server (NTRS)

Goldstein, B. L.; Newman, E. H.; Shamansky, H. T.

1995-01-01

This report serves as the user's manual for the X-Antenna code. X-Antenna is intended to simplify the analysis of antennas by giving the user graphical interfaces in which to enter all relevant antenna and analysis code data. Essentially, X-Antenna creates a Motif interface to the user's antenna analysis codes. A command-file allows new antennas and codes to be added to the application. The menu system and graphical interface screens are created dynamically to conform to the data in the command-file. Antenna data can be saved and retrieved from disk. X-Antenna checks all antenna and code values to ensure they are of the correct type, writes an output file, and runs the appropriate antenna analysis code. Volumetric pattern data may be viewed in 3D space with an external viewer run directly from the application. Currently, X-Antenna includes analysis codes for thin wire antennas (dipoles, loops, and helices), rectangular microstrip antennas, and thin slot antennas.

Laser-driven proton and deuteron acceleration from a pure solid-density H2/D2 cryogenic jet

NASA Astrophysics Data System (ADS)

Kim, Jongjin; Gauthier, Maxence; Aurand, Bastian; Curry, Chandra; Goede, Sebastian; Goyon, Clement; Williams, Jackson; Kerr, Shaun; Ruby, John; Propp, Adrienne; Ramakrishna, Bhuvanesh; Pak, Art; Hazi, Andy; Glenzer, Siegfried; Roedel, Christian

2015-11-01

Laser-driven proton acceleration has become of tremendous interest for the fundamental science and the potential applications in tumor therapy and proton radiography. We have developed a cryogenic liquid hydrogen jet, which can deliver a self-replenishing target of pure solid-density hydrogen or deuterium. This allows for a target compatible with high-repetition-rate experiments and results in a pure hydrogen plasma, facilitating comparison with simulations. A new modification has allowed for the formation of jets with rectangular profiles, facilitating comparison with foil targets. This jet was installed at the Titan laser and driven by laser pulses of 40-60 J of 527 nm laser light in 1 ps. The resulting proton and deuteron spectra were measured in multiple directions with Thomson parabola spectrometers and RCF stacks. The spectral and angular information suggest contribution from both the TNSA and RPA acceleration mechanisms.

An analytical method to calculate equivalent fields to irregular symmetric and asymmetric photon fields.

PubMed

Tahmasebi Birgani, Mohamad J; Chegeni, Nahid; Zabihzadeh, Mansoor; Hamzian, Nima

2014-01-01

Equivalent field is frequently used for central axis depth-dose calculations of rectangular- and irregular-shaped photon beams. As most of the proposed models to calculate the equivalent square field are dosimetry based, a simple physical-based method to calculate the equivalent square field size was used as the basis of this study. The table of the sides of the equivalent square or rectangular fields was constructed and then compared with the well-known tables by BJR and Venselaar, et al. with the average relative error percentage of 2.5 ± 2.5% and 1.5 ± 1.5%, respectively. To evaluate the accuracy of this method, the percentage depth doses (PDDs) were measured for some special irregular symmetric and asymmetric treatment fields and their equivalent squares for Siemens Primus Plus linear accelerator for both energies, 6 and 18MV. The mean relative differences of PDDs measurement for these fields and their equivalent square was approximately 1% or less. As a result, this method can be employed to calculate equivalent field not only for rectangular fields but also for any irregular symmetric or asymmetric field. © 2013 American Association of Medical Dosimetrists Published by American Association of Medical Dosimetrists All rights reserved.

PRISM software—Processing and review interface for strong-motion data

USGS Publications Warehouse

Jones, Jeanne M.; Kalkan, Erol; Stephens, Christopher D.; Ng, Peter

2017-11-28

Rapidly available and accurate ground-motion acceleration time series (seismic recordings) and derived data products are essential to quickly providing scientific and engineering analysis and advice after an earthquake. To meet this need, the U.S. Geological Survey National Strong Motion Project has developed a software package called PRISM (Processing and Review Interface for Strong-Motion data). PRISM automatically processes strong-motion acceleration records, producing compatible acceleration, velocity, and displacement time series; acceleration, velocity, and displacement response spectra; Fourier amplitude spectra; and standard earthquake-intensity measures. PRISM is intended to be used by strong-motion seismic networks, as well as by earthquake engineers and seismologists.

Electron-phonon interactions in semiconductor nanostructures

NASA Astrophysics Data System (ADS)

Yu, Segi

In this dissertation, electron-phonon interactions are studied theoretically in semiconductor nanoscale heterostructures. Interactions of electrons with interface optical phonons dominate over other electron-phonon interactions in narrow width heterostructures. Hence, a transfer matrix method is used to establish a formalism for determining the dispersion relations and electrostatic potentials of the interface phonons for multiple-interface heterostructure within the macroscopic dielectric continuum model. This method facilitates systematic calculations for complex structures where the conventional method is difficult to implement. Several specific cases are treated to illustrate advantages of the formalism. Electrophonon resonance (EPR) is studied in cylindrical quantum wires using the confined/interface optical phonons representation and bulk phonon representation. It has been found that interface phonon contribution to EPR is small compared with confined phonon. Different selection rules for bulk phonons and confined phonons result in different EPR behaviors as the radius of cylindrical wire changes. Experiment is suggested to test which phonon representation is appropriate for EPR. The effects of phonon confinement on elect ron-acoustic-phonon scattering is studied in cylindrical and rectangular quantum wires. In the macroscopic elastic continuum model, the confined-phonon dispersion relations are obtained for several crystallographic directions with free-surface and clamped-surface boundary conditions in cylindrical wires. The scattering rates due to the deformation potential are obtained for these confined phonons and are compared with those of bulk-like phonons. The results show that the inclusion of acoustic phonon confinement may be crucial for calculating accurate low-energy electron scattering rates. Furthermore, it has been found that there is a scaling rule governing the directional dependence of the scattering rates. The Hamiltonian describing the deformation-potential of confined acoustic phonons is derived by quantizing the appropriate, experimentally verified approximate compressional acoustic-phonon modes in a free-standing rectangular quantum wire. The scattering rate is obtained for GaAs quantum wires with a range of cross-sectional dimensions. The results demonstrate that a proper treatment of confined acoustic phonons may be essential to correctly model electron scattering rates at low energies in nanoscale structures.

Shock tube Multiphase Experiments

NASA Astrophysics Data System (ADS)

Middlebrooks, John; Allen, Roy; Paudel, Manoj; Young, Calvin; Musick, Ben; McFarland, Jacob

2017-11-01

Shock driven multiphase instabilities (SDMI) are unique physical phenomena that have far-reaching practical applications in engineering and science. The instability is present in high energy explosions, scramjet combustors, and supernovae events. The SDMI arises when a multiphase interface is impulsively accelerated by the passage of a shockwave. It is similar in development to the Richtmyer-Meshkov (RM) instability however, particle-to-gas coupling is the driving mechanism of the SDMI. As particle effects such as lag and phase change become more prominent, the SDMI's development begins to significantly deviate from the RM instability. We have developed an experiment for studying the SDMI in our shock tube facility. In our experiments, a multiphase interface is created using a laminar jet and flowed into the shock tube where it is accelerated by the passage of a planar shockwave. The interface development is captured using CCD cameras synchronized with planar laser illumination. This talk will give an overview of new experiments conducted to examine the development of a shocked cylindrical multiphase interface. The effects of Atwood number, particle size, and a second acceleration (reshock) of the interface will be discussed.

Generation of light from free electrons.

PubMed

Salisbury, W W

1966-10-21

Experiments with the interaction of a rectangular cross- section beam of electrons which is brought into contact with a metallic diffraction grat e ng produce light variable in wavelength throughout the visible spectrum. Con tinuous variation of the beam thickness shows that light is produced by electrons hundreds of wavelengths from the grating, if the side of the beam near the grating is in contact with it. The results can be accounted for by periodic accelerations of the electrons passing over the surface of the grating. These accelerations are caused by electrostatic forces which in turn are due to the average spacecharge of sheets of elec trons reflected from the grating surface, so that in their space- charge structure the periodicity of the grating rulings is preserved.

Interaction of Porosity with a Planar Solid/Liquid Interface

NASA Technical Reports Server (NTRS)

Catalina, Adrian V.; Stefanescu, Doru M.; Sen, Subhayu; Kaukler, William F.

2004-01-01

In this article, an investigation of the interaction between gas porosity and a planar solid/liquid (SL) interface is reported. A two-dimensional numerical model able to accurately track sharp SL interfaces during solidification of pure metals and alloys is proposed. The finite-difference method and a rectangular undeformed grid are used for computation. The SL interface is described through the points of intersection with the grid lines. Its motion is determined by the thermal and solute gradients at each particular point. Changes of the interface temperature because of capillarity or solute redistribution as well as any perturbation of the thermal and solute field produced by the presence of non-metallic inclusions can be computed. To validate the model, the dynamics of the interaction between a gas pore and a solidification front in metal alloys was observed using a state of the art X-ray transmission microscope (XTM). The experiments included observation of the distortion of the SL interface near a pore, real-time measurements of the growth rate, and the change in shape of the porosity during interaction with the SL interface in pure Al and Al-0.25 wt pct Au alloy. In addition, porosity-induced solute segregation patterns surrounding a pore were also quantified.

Interface for the rapid analysis of liquid samples by accelerator mass spectrometry

DOEpatents

Turteltaub, Kenneth; Ognibene, Ted; Thomas, Avi; Daley, Paul F; Salazar Quintero, Gary A; Bench, Graham

2014-02-04

An interface for the analysis of liquid sample having carbon content by an accelerator mass spectrometer including a wire, defects on the wire, a system for moving the wire, a droplet maker for producing droplets of the liquid sample and placing the droplets of the liquid sample on the wire in the defects, a system that converts the carbon content of the droplets of the liquid sample to carbon dioxide gas in a helium stream, and a gas-accepting ion source connected to the accelerator mass spectrometer that receives the carbon dioxide gas of the sample in a helium stream and introduces the carbon dioxide gas of the sample into the accelerator mass spectrometer.

Mercury Thermal Hydraulic Loop (MTHL) Summary Report

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

Felde, David K.; Crye, Jason Michael; Wendel, Mark W.

2017-03-01

The Spallation Neutron Source (SNS) is a high-power linear accelerator built at Oak Ridge National Laboratory (ORNL) which incorporates the use of a flowing liquid mercury target. The Mercury Thermal Hydraulic Loop (MTHL) was constructed to investigate and verify the heat transfer characteristics of liquid mercury in a rectangular channel. This report provides a compilation of previously reported results from the water-cooled and electrically heated straight and curved test sections that simulate the geometry of the window cooling channel in the target nose region.

Experimental verification of the asymtotic modal analysis method as applied to a rectangular acoustic cavity excited by structural vibration

NASA Technical Reports Server (NTRS)

Peretti, L. F.; Dowell, E. H.

1992-01-01

An experiment was performed on a rigid wall rectangular acoustic cavity driven by a flexible plate mounted in a quarter of one end wall and excited by white noise. The experiment was designed so that the assumptions of Asymptotic Modal Analysis (AMA) were satisfied for certain bandwidths and center frequencies. Measurements of sound pressure levels at points along the boundaries and incrementally into tbe interior were taken. These were compared with the theoretical results predicted with AMA, and found to be in good agreement, particularly for moderate (1/3 octave) bandwidths and sufficiently high center frequencies. Sound pressure level measurements were also taken well into the cavity interior at various points along the 5 totally rigid walls. The AMA theory, including boundary intensification effects, was shown to be accurate provided the assumption of large number of acoustic modes is satisfied, and variables such as power spectra of the wall acceleration, frequency, and damping are slowly varying in the frequency of bandwidth.

Feasibility study for removing calcified material using a planar rectangular ultrasound transducer.

PubMed

Damianou, Christakis; Couppis, Andreas

2016-01-01

The aim of the proposed study was to conduct a feasibility study using a flat rectangular (3 mm × 10 mm) MRI compatible transducer operating at 5.3 MHz for destroying calcified material in an in vitro model. The proposed method can be used in the future for treating atherosclerosis plaques of the coronary, carotid or peripheral arteries. The system was tested initially on calcium rods. Another test was performed in a hydroxyapatite-polylactide model. A parametric study was performed where the mass of calcified material removed was studied as a function of intensity, pulse repetition frequency (PRF), duty factor (DF) and presence of bubbles. The amount of calcified material removed is directly related to the intensity, PRF and DF. It was found that the presence of bubbles accelerates the removal of calcified material. In order to ensure that pure mechanical mode ultrasound was used, the protocols were designed so that the temperature does not exceed 1 °C.

Rarefaction-driven Rayleigh–Taylor instability. Part 1. Diffuse-interface linear stability measurements and theory

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

Morgan, R. V.; Likhachev, O. A.; Jacobs, J. W.

Theory and experiments are reported that explore the behaviour of the Rayleigh–Taylor instability initiated with a diffuse interface. Experiments are performed in which an interface between two gases of differing density is made unstable by acceleration generated by a rarefaction wave. Well-controlled, diffuse, two-dimensional and three-dimensional, single-mode perturbations are generated by oscillating the gases either side to side, or vertically for the three-dimensional perturbations. The puncturing of a diaphragm separating a vacuum tank beneath the test section generates a rarefaction wave that travels upwards and accelerates the interface downwards. This rarefaction wave generates a large, but non-constant, acceleration of the order ofmore » $$1000g_{0}$$, where$$g_{0}$$is the acceleration due to gravity. Initial interface thicknesses are measured using a Rayleigh scattering diagnostic and the instability is visualized using planar laser-induced Mie scattering. Growth rates agree well with theoretical values, and with the inviscid, dynamic diffusion model of Duffet al. (Phys. Fluids, vol. 5, 1962, pp. 417–425) when diffusion thickness is accounted for, and the acceleration is weighted using inviscid Rayleigh–Taylor theory. The linear stability formulation of Chandrasekhar (Proc. Camb. Phil. Soc., vol. 51, 1955, pp. 162–178) is solved numerically with an error function diffusion profile using the Riccati method. This technique exhibits good agreement with the dynamic diffusion model of Duffet al. for small wavenumbers, but produces larger growth rates for large-wavenumber perturbations. Asymptotic analysis shows a$$1/k^{2}$$decay in growth rates as$$k\\rightarrow \\infty$$for large-wavenumber perturbations.« less

Rarefaction-driven Rayleigh–Taylor instability. Part 1. Diffuse-interface linear stability measurements and theory

DOE PAGES

Morgan, R. V.; Likhachev, O. A.; Jacobs, J. W.

2016-02-15

Theory and experiments are reported that explore the behaviour of the Rayleigh–Taylor instability initiated with a diffuse interface. Experiments are performed in which an interface between two gases of differing density is made unstable by acceleration generated by a rarefaction wave. Well-controlled, diffuse, two-dimensional and three-dimensional, single-mode perturbations are generated by oscillating the gases either side to side, or vertically for the three-dimensional perturbations. The puncturing of a diaphragm separating a vacuum tank beneath the test section generates a rarefaction wave that travels upwards and accelerates the interface downwards. This rarefaction wave generates a large, but non-constant, acceleration of the order ofmore » $$1000g_{0}$$, where$$g_{0}$$is the acceleration due to gravity. Initial interface thicknesses are measured using a Rayleigh scattering diagnostic and the instability is visualized using planar laser-induced Mie scattering. Growth rates agree well with theoretical values, and with the inviscid, dynamic diffusion model of Duffet al. (Phys. Fluids, vol. 5, 1962, pp. 417–425) when diffusion thickness is accounted for, and the acceleration is weighted using inviscid Rayleigh–Taylor theory. The linear stability formulation of Chandrasekhar (Proc. Camb. Phil. Soc., vol. 51, 1955, pp. 162–178) is solved numerically with an error function diffusion profile using the Riccati method. This technique exhibits good agreement with the dynamic diffusion model of Duffet al. for small wavenumbers, but produces larger growth rates for large-wavenumber perturbations. Asymptotic analysis shows a$$1/k^{2}$$decay in growth rates as$$k\\rightarrow \\infty$$for large-wavenumber perturbations.« less

Prediction of Spacecraft Vibration using Acceleration and Force Envelopes

NASA Technical Reports Server (NTRS)

Gordon, Scott; Kaufman, Daniel; Kern, Dennis; Scharton, Terry

2009-01-01

The base forces in the GLAST X- and Z-axis sine vibration tests were similar to those derived using generic inputs (from users guide and handbook), but the base forces in the sine test were generally greater than the flight data. Basedrive analyses using envelopes of flight acceleration data provided more accurate predictions of the base force than generic inputs, and as expected, using envelopes of both the flight acceleration and force provided even more accurate predictions The GLAST spacecraft interface accelerations and forces measured during the MECO transient were relatively low in the 60 to 150 Hz regime. One may expect the flight forces measured at the base of various spacecraft to be more dependent on the mass, frequencies, etc. of the spacecraft than are the corresponding interface acceleration data, which may depend more on the launch vehicle configuration.

Jammed systems of oriented needles always percolate on square lattices

NASA Astrophysics Data System (ADS)

Kondrat, Grzegorz; Koza, Zbigniew; Brzeski, Piotr

2017-08-01

Random sequential adsorption (RSA) is a standard method of modeling adsorption of large molecules at the liquid-solid interface. Several studies have recently conjectured that in the RSA of rectangular needles, or k -mers, on a square lattice, percolation is impossible if the needles are sufficiently long (k of order of several thousand). We refute these claims and present rigorous proof that in any jammed configuration of nonoverlapping, fixed-length, horizontal, or vertical needles on a square lattice, all clusters are percolating clusters.

Precise dielectric property measurements and E-field probe calibration for specific absorption rate measurements using a rectangular waveguide

PubMed Central

Hakim, B M; Beard, B B; Davis, C C

2018-01-01

Specific absorption rate (SAR) measurements require accurate calculations of the dielectric properties of tissue-equivalent liquids and associated calibration of E-field probes. We developed a precise tissue-equivalent dielectric measurement and E-field probe calibration system. The system consists of a rectangular waveguide, electric field probe, and data control and acquisition system. Dielectric properties are calculated using the field attenuation factor inside the tissue-equivalent liquid and power reflectance inside the waveguide at the air/dielectric-slab interface. Calibration factors were calculated using isotropicity measurements of the E-field probe. The frequencies used are 900 MHz and 1800 MHz. The uncertainties of the measured values are within ±3%, at the 95% confidence level. Using the same waveguide for dielectric measurements as well as calibrating E-field probes used in SAR assessments eliminates a source of uncertainty. Moreover, we clearly identified the system parameters that affect the overall uncertainty of the measurement system. PMID:29520129

Advanced designs for non-imaging submillimeter-wave Winston cone concentrators

NASA Astrophysics Data System (ADS)

Nelson, A. O.; Grossman, E. N.

2014-05-01

We describe the design and simulation of several non-imaging concentrators designed to couple submillimeter wavelength radiation from free space into highly overmoded, rectangular, WR-10 waveguide. Previous designs are altered to improve the uniformity of efficiency rather than the efficiency itself. The concentrators are intended for use as adapters between instruments using overmoded WR-10 waveguide as input or output and sources propagating through free space. Previous simulation and measurement have shown that the angular response is primarily determined by the Winston cone and is well predicted by geometric optics theory while the efficiencies are primarily determined by the transition section. Additionally, previous work has shown insensitivity to polarization, orientation and beam size. Several separate concentrator designs are studied, all of which use a Winston cone (also known as a compound parabolic concentrator) with an input diameter ranging from 4 mm to 16 mm, and "throat" diameters of less than 0.5 mm to 4 mm as the initial interface. The use of various length adiabatic circular-to-rectangular transition sections is investigated, along with the effect of an additional, 25 mm waveguide section designed to model the internal waveguide of the power meter. Adapters without a transition section and a rectangular Winston cone throat aperture and double cone configurations are also studied. Adapters are analyzed in simulation for consistent efficiency across the opening aperture.

Effect of a surface tension gradient on the slip flow along a superhydrophobic air-water interface

NASA Astrophysics Data System (ADS)

Song, Dong; Song, Baowei; Hu, Haibao; Du, Xiaosong; Du, Peng; Choi, Chang-Hwan; Rothstein, Jonathan P.

2018-03-01

Superhydrophobic surfaces have been shown to produce significant drag reduction in both laminar and turbulent flows by introducing an apparent slip velocity along an air-water interface trapped within the surface roughness. In the experiments presented within this study, we demonstrate the existence of a surface tension gradient associated with the resultant Marangoni flow along an air-water interface that causes the slip velocity and slip length to be significantly reduced. In this study, the slip velocity along a millimeter-sized air-water interface was investigated experimentally. This large-scale air-water interface facilitated a detailed investigation of the interfacial velocity profiles as the flow rate, interfacial curvature, and interface geometry were varied. For the air-water interfaces supported above continuous grooves (concentric rings within a torsional shear flow) where no surface tension gradient exists, a slip velocity as high as 30% of the bulk velocity was observed. However, for the air-water interfaces supported above discontinuous grooves (rectangular channels in a Poiseuille flow), the presence of a surface tension gradient reduced the slip velocity and in some cases resulted in an interfacial velocity that was opposite to the main flow direction. The curvature of the air-water interface in the spanwise direction was found to dictate the details of the interfacial flow profile with reverse flow in the center of the interface for concave surfaces and along the outside of the interface for convex surfaces. The deflection of the air-water interface was also found to greatly affect the magnitude of the slip. Numerical simulations imposed with a relatively small surface tension gradient along the air-water interface were able to predict both the reduced slip velocity and back flow along the air-water interface.

Evaluation of a magnetic resonance guided linear accelerator for stereotactic radiosurgery treatment.

PubMed

Wen, Ning; Kim, Joshua; Doemer, Anthony; Glide-Hurst, Carri; Chetty, Indrin J; Liu, Chang; Laugeman, Eric; Xhaferllari, Ilma; Kumarasiri, Akila; Victoria, James; Bellon, Maria; Kalkanis, Steve; Siddiqui, M Salim; Movsas, Benjamin

2018-06-01

The purpose of this study was to investigate the systematic localization accuracy, treatment planning capability, and delivery accuracy of an integrated magnetic resonance imaging guided Linear Accelerator (MR-Linac) platform for stereotactic radiosurgery. The phantom for the end-to-end test comprises three different compartments: a rectangular MR/CT target phantom, a Winston-Lutz cube, and a rectangular MR/CT isocenter phantom. Hidden target tests were performed at gantry angles of 0, 90, 180, and 270 degrees to quantify the systematic accuracy. Five patient plans with a total of eleven lesions were used to evaluate the dosimetric accuracy. Single-isocenter IMRT treatment plans using 10-15 coplanar beams were generated to treat the multiple metastases. The end-to-end localization accuracy of the system was 1.0 ± 0.1 mm. The conformity index, homogeneity index and gradient index of the plans were 1.26 ± 0.22, 1.22 ± 0.10, and 5.38 ± 1.44, respectively. The average absolute point dose difference between measured and calculated dose was 1.64 ± 1.90%, and the mean percentage of points passing the 3%/1 mm gamma criteria was 96.87%. Our experience demonstrates that excellent plan quality and delivery accuracy was achievable on the MR-Linac for treating multiple brain metastases with a single isocenter. Copyright © 2018 Elsevier B.V. All rights reserved.

Sloshing dynamics modulated fluid angular momentum and moment fluctuations driven by orbital gravity gradient and jitter accelerations in microgravity

NASA Technical Reports Server (NTRS)

Hung, R. J.; Pan, H. L.

1995-01-01

The dynamical behavior of spacecraft propellant affected by the asymmetric combined gravity gradient and jitter accelerations, in particular the effect of surface tension on partially-filled rotating fluids applicable to a full-scale Gravity Probe-B Spacecraft dewar tank has been investigated. Three different cases of orbital accelerations: (1) gravity gradient-dominated, (2) equally weighted between gravity gradient and jitter, and (3) gravity jitter-dominated accelerations are studied. The results of slosh wave excitation along the liquid-vapor interface induced by gravity gradient-dominated accelerations provide a torsional moment with tidal motion of bubble oscillations in the rotating dewar. The results are clearly seen from the twisting shape of the bubble oscillations driven by gravity gradient-dominated acceleration. The results of slosh wave excitation along the liquid-vapor interface induced by gravity jitter-dominated acceleration indicate the results of bubble motion in a manner of down-and-up and leftward-and-rightward movement of oscillation when the bubble is rotating with respect to rotating dewar axis. Fluctuations of angular momentum, fluid moment and bubble mass center caused by slosh wave excitations driven by gravity gradient acceleration or gravity jitter acceleration are also investigated.

Inviscid linear stability analysis of two vertical columns of different densities in a gravitational acceleration field

DOE PAGES

Prathama, Aditya Heru; Pantano, Carlos

2017-08-09

Here, we study the inviscid linear stability of a vertical interface separating two fluids of different densities and subject to a gravitational acceleration field parallel to the interface. In this arrangement, the two free streams are constantly accelerated, which means that the linear stability analysis is not amenable to Fourier or Laplace solution in time. Instead, we derive the equations analytically by the initial-value problem method and express the solution in terms of the well-known parabolic cylinder function. The results, which can be classified as an accelerating Kelvin–Helmholtz configuration, show that even in the presence of surface tension, the interfacemore » is unconditionally unstable at all wavemodes. This is a consequence of the ever increasing momentum of the free streams, as gravity accelerates them indefinitely. The instability can be shown to grow as the exponential of a quadratic function of time.« less

Computer Assistance in Information Work. Part I: Conceptual Framework for Improving the Computer/User Interface in Information Work. Part II: Catalog of Acceleration, Augmentation, and Delegation Functions in Information Work.

ERIC Educational Resources Information Center

Paisley, William; Butler, Matilda

This study of the computer/user interface investigated the role of the computer in performing information tasks that users now perform without computer assistance. Users' perceptual/cognitive processes are to be accelerated or augmented by the computer; a long term goal is to delegate information tasks entirely to the computer. Cybernetic and…

Instability of multi-layer fluid configurations in the presence of time-dependent accelerations in a microgravity environment

NASA Technical Reports Server (NTRS)

Lyell, M. J.; Roh, Michael

1991-01-01

The increasing number of research opportunities in a microgravity environment will benefit not only fundamental studies in fluid dynamics, but also technological applications such as those involving materials processing. In particular, fluid configurations which involve fluid-fluid interfaces would occur in a variety of experimental investigations. This work investigates the stability of a configuration involving fluid-fluid interfaces in the presence of a time-dependent forcing. Both periodic (g-jitter) and nonperiodic accelerations are considered. The fluid configuration is multilayered, and infinite in extent. The analysis is linear and inviscid, and the acceleration vector is oriented perpendicular to each interface. A Floquet analysis is employed in the case of the periodic forcing. In the problem of nonperiodic forcing, the resulting system of equations are integrated in time. Specific nondimensional parameters appear in each problem. The configuration behavior is investigated for a range of parameter values.

Three-dimensional numerical simulation of gradual opening in a wave rotor passage

NASA Technical Reports Server (NTRS)

Larosiliere, Louis M.

1993-01-01

The evolution of the contact interface and the propagation of compression waves inside a single wave rotor passage gradually opening to and traversing an inlet port is studied numerically using an inviscid formulation of the governing equations. Insights into the response of the interface and kinematics of the flow field to various opening times are given. Since the opening time is inversely proportional to the rotational speed of the rotor, the effects of passage rotation such as centripetal and Coriolis accelerations are intrinsically coupled to the gradual opening process. Certain three-dimensional features associated with the gradual opening process as a result of centripetal and Coriolis accelerations are illustrated. For the range of opening times or rotational speeds considered, a portion of the interface behaves like a vortex sheet that can degenerate into a complex interfacial structure. The vortices produced along the interface can serve as a stirring mechanism to promote local mixing. Coriolis and centripetal accelerations can introduce three dimensional effects such as interfacial distortions in meridional planes and spanwise migration of fluid elements.

Dislocation and Structural Studies at Metal-Metallic Glass Interface at Low Temperature

NASA Astrophysics Data System (ADS)

Gupta, Pradeep; Yedla, Natraj

2017-12-01

In this paper, molecular dynamics (MD) simulation deformation studies on the Al (metal)-Cu50Zr50 (metallic glass) model interface is carried out based on cohesive zone model. The interface is subjected to mode-I loading at a strain rate of 109 s-1 and temperature of 100 K. The dislocations reactions and evolution of dislocation densities during the deformation have been investigated. Atomic interactions between Al, Cu and Zr atoms are modeled using EAM (embedded atom method) potential, and a timestep of 0.002 ps is used for performing the MD simulations. A circular crack and rectangular notch are introduced at the interface to investigate the effect on the deformation behavior and fracture. Further, scale size effect is also investigated. The structural changes and evolution of dislocation density are also examined. It is found that the dominant deformation mechanism is by Shockley partial dislocation nucleation. Amorphization is observed in the Al regions close to the interface and occurs at a lower strain in the presence of a crack. The total dislocation density is found to be maximum after the first yield in both the perfect and defect interface models and is highest in the case of perfect interface with a density of 6.31 × 1017 m-2. In the perfect and circular crack defect interface models, it is observed that the fraction of Shockley partial dislocation density decreases, whereas that of strain rod dislocations increases with increase in strain.

KSC-97DC1286

NASA Image and Video Library

1997-08-19

Final prelaunch preparations are made at Launch Complex 17A, Cape Canaveral Air Station, for liftoff of the Boeing Delta II expendable launch vehicle with the Advanced Composition Explorer (ACE) spacecraft, at top. The black rectangular-shaped panel in front is one of ACE’s solar arrays. ACE will investigate the origin and evolution of solar phenomenon, the formation of solar corona, solar flares and acceleration of the solar wind. This will be the second Delta launch under the Boeing name and the first from Cape Canaveral. Liftoff is scheduled Aug. 24

Motion of Air Bubbles in Water Subjected to Microgravity Accelerations

NASA Technical Reports Server (NTRS)

DeLombard, Richard; Kelly, Eric M.; Hrovat, Kenneth; Nelson, Emily S.; Pettit, Donald R.

2006-01-01

The International Space Station (ISS) serves as a platform for microgravity research for the foreseeable future. A microgravity environment is one in which the effects of gravity are drastically reduced which then allows physical experiments to be conducted without the over powering effects of gravity. During his 6-month stay on the ISS, astronaut Donald R. Pettit performed many informal/impromptu science experiments with available equipment. One such experiment focused on the motion of air bubbles in a rectangular container nearly filled with de-ionized water. Bubbles were introduced by shaking and then the container was secured in place for several hours while motion of the bubbles was recorded using time-lapse photography. This paper shows correlation between bubble motion and quasi-steady acceleration levels during one such experiment operation. The quasi-steady acceleration vectors were measured by the Microgravity Acceleration Measurement System (MAMS). Essentially linear motion was observed in the condition considered here. Dr. Pettit also created other conditions which produced linear and circulating motion, which are the subjects of further study. Initial observations of this bubble motion agree with calculations from many microgravity physical science experiments conducted on shuttle microgravity science missions. Many crystal-growth furnaces involve heavy metals and high temperatures in which undesired acceleration-driven convection during solidification can adversely affect the crystal. Presented in this paper will be results showing correlation between bubble motion and the quasi-steady acceleration vector.

Rayleigh-Taylor instability at spherical interfaces between viscous fluids: Fluid/vacuum interface

DOE PAGES

Terrones, Guillermo; Carrara, Mark D.

2015-05-01

For a spherical interface of radius R separating two different homogeneous regions of incompressible viscous fluids under the action of a radially directed acceleration, we perform a linear stability analysis in terms of spherical surface harmonics Y n to derive the dispersion relation. The instability behavior is investigated by computing the growth rates and the most-unstable modes as a function of the spherical harmonic degree n. This general methodology is applicable to the entire parameter space spanned by the Atwood number, the viscosity ratio, and the dimensionless number B = (α RΡ² 2/μ² ²)¹ /³ R (where α R, Ρmore » 2 and μ 2 are the local radial acceleration at the interface, and the density and viscosity of the denser overlying fluid, respectively). While the mathematical formulation here is general, this paper focuses on instability that arises at a spherical viscous fluid/vacuum interface as there is a great deal to be learned from the effects of one-fluid viscosity and sphericity alone. To quantify and understand the effect that curvature and radial accelerationhave on the Rayleigh-Taylor instability, a comparison of the growth rates, under homologous driving conditions, between the planar and spherical interfaces is performed. The derived dispersion relation for the planar interface accounts for an underlying finite fluid region of thickness L and normal acceleration α R. Under certain conditions, the development of the most-unstable modes at a spherical interface can take place via the superposition of two adjacent spherical harmonics Y n and Y n+1. This bimodality in the evolution of disturbances in the linear regime does not have a counterpart in the planar configuration where the most-unstable modes are associated with a unique wave number.« less

A New Concept of Controller for Accelerators' Magnet Power Supplies

NASA Astrophysics Data System (ADS)

Visintini, Roberto; Cleva, Stefano; Cautero, Marco; Ciesla, Tomasz

2016-04-01

The complexity of a particle accelerator implies the remote control of very large numbers of devices, with many different typologies, either distributed along the accelerator or concentrated in locations, often far away from each other. Local and global control systems handle the devices through dedicated communication channels and interfaces. Each controlled device is practically a “smart node” performing a specific task. In addition, very often, those tasks are managed in real-time mode. The performances required to the control interface has an influence on the cost of the distributed nodes as well as on their hardware and software implementation. In large facilities (e.g. CERN) the “smart nodes” derive from specific in-house developments. Alternatively, it is possible to find on the market commercial devices, whose performances (and prices) are spread over a broad range, and spanning from proprietary design (customizable to the user's needs) to open source/design. In this paper, we will describe some applications of smart nodes in the particle accelerators field, with special focus on the power supplies for magnets. In modern accelerators, in fact, magnets and their associated power supplies constitute systems distributed along the accelerator itself, and strongly interfaced with the remote control system as well as with more specific (and often more demanding) orbit/trajectory feedback systems. We will give examples of actual systems, installed and operational on two light sources, Elettra and FERMI, located in the Elettra Research Center in Trieste, Italy.

DEC Ada interface to Screen Management Guidelines (SMG)

NASA Technical Reports Server (NTRS)

Laomanachareon, Somsak; Lekkos, Anthony A.

1986-01-01

DEC's Screen Management Guidelines are the Run-Time Library procedures that perform terminal-independent screen management functions on a VT100-class terminal. These procedures assist users in designing, composing, and keeping track of complex images on a video screen. There are three fundamental elements in the screen management model: the pasteboard, the virtual display, and the virtual keyboard. The pasteboard is like a two-dimensional area on which a user places and manipulates screen displays. The virtual display is a rectangular part of the terminal screen to which a program writes data with procedure calls. The virtual keyboard is a logical structure for input operation associated with a physical keyboard. SMG can be called by all major VAX languages. Through Ada, predefined language Pragmas are used to interface with SMG. These features and elements of SMG are briefly discussed.

Interfacial waves generated by electrowetting-driven contact line motion

NASA Astrophysics Data System (ADS)

Ha, Jonghyun; Park, Jaebum; Kim, Yunhee; Shin, Bongsu; Bae, Jungmok; Kim, Ho-Young

2016-10-01

The contact angle of a liquid-fluid interface can be effectively modulated by the electrowetting-on-dielectric (EWOD) technology. Rapid movement of the contact line can be achieved by swift changes of voltage at the electrodes, which can give rise to interfacial waves under the strong influence of surface tension. Here we experimentally demonstrate EWOD-driven interfacial waves of overlapping liquids and compare their wavelength and decay length with the theoretical results obtained by a perturbation analysis. Our theory also allows us to predict the temporal evolution of the interfacial profiles in either rectangular or cylindrical containers, as driven by slipping contact lines. This work builds a theoretical framework to understand and predict the dynamics of capillary waves of a liquid-liquid interface driven by EWOD, which has practical implications on optofluidic devices used to guide light.

General purpose programmable accelerator board

DOEpatents

Robertson, Perry J.; Witzke, Edward L.

2001-01-01

A general purpose accelerator board and acceleration method comprising use of: one or more programmable logic devices; a plurality of memory blocks; bus interface for communicating data between the memory blocks and devices external to the board; and dynamic programming capabilities for providing logic to the programmable logic device to be executed on data in the memory blocks.

Improved GO/PO method and its application to wideband SAR image of conducting objects over rough surface

NASA Astrophysics Data System (ADS)

Jiang, Wang-Qiang; Zhang, Min; Nie, Ding; Jiao, Yong-Chang

2018-04-01

To simulate the multiple scattering effect of target in synthetic aperture radar (SAR) image, the hybrid method GO/PO method, which combines the geometrical optics (GO) and physical optics (PO), is employed to simulate the scattering field of target. For ray tracing is time-consuming, the Open Graphics Library (OpenGL) is usually employed to accelerate the process of ray tracing. Furthermore, the GO/PO method is improved for the simulation in low pixel situation. For the improved GO/PO method, the pixels are arranged corresponding to the rectangular wave beams one by one, and the GO/PO result is the sum of the contribution values of all the rectangular wave beams. To get high-resolution SAR image, the wideband echo signal is simulated which includes information of many electromagnetic (EM) waves with different frequencies. Finally, the improved GO/PO method is used to simulate the SAR image of targets above rough surface. And the effects of reflected rays and the size of pixel matrix on the SAR image are also discussed.

Comparison of wing-span averaging effects on lift, rolling moment, and bending moment for two span load distributions and for two turbulence representations

NASA Technical Reports Server (NTRS)

Lichtenstein, J. H.

1978-01-01

An analytical method of computing the averaging effect of wing-span size on the loading of a wing induced by random turbulence was adapted for use on a digital electronic computer. The turbulence input was assumed to have a Dryden power spectral density. The computations were made for lift, rolling moment, and bending moment for two span load distributions, rectangular and elliptic. Data are presented to show the wing-span averaging effect for wing-span ratios encompassing current airplane sizes. The rectangular wing-span loading showed a slightly greater averaging effect than did the elliptic loading. In the frequency range most bothersome to airplane passengers, the wing-span averaging effect can reduce the normal lift load, and thus the acceleration, by about 7 percent for a typical medium-sized transport. Some calculations were made to evaluate the effect of using a Von Karman turbulence representation. These results showed that using the Von Karman representation generally resulted in a span averaging effect about 3 percent larger.

Estimation of payload loads using rigid body interface accelerations. [in structural design of launch vehicle systems

NASA Technical Reports Server (NTRS)

Chen, J. C.; Garba, J. A.; Wada, B. K.

1978-01-01

In the design/analysis process of a payload structural system, the accelerations at the payload/launch vehicle interface obtained from a system analysis using a rigid payload are often used as the input forcing function to the elastic payload to obtain structural design loads. Such an analysis is at best an approximation since the elastic coupling effects are neglected. This paper develops a method wherein the launch vehicle/rigid payload interface accelerations are modified to account for the payload elasticity. The advantage of the proposed method, which is exact to the extent that the physical system can be described by a truncated set of generalized coordinates, is that the complete design/analysis process can be performed within the organization responsible for the payload design. The method requires the updating of the system normal modes to account for payload changes, but does not require a complete transient solution using the composite system model. An application to a real complex structure, the Viking Spacecraft System, is given.

Catalysis by a de novo zinc-mediated protein interface: implications for natural enzyme evolution and rational enzyme engineering.

PubMed

Der, Bryan S; Edwards, David R; Kuhlman, Brian

2012-05-08

Here we show that a recent computationally designed zinc-mediated protein interface is serendipitously capable of catalyzing carboxyester and phosphoester hydrolysis. Although the original motivation was to design a de novo zinc-mediated protein-protein interaction (called MID1-zinc), we observed in the homodimer crystal structure a small cleft and open zinc coordination site. We investigated if the cleft and zinc site at the designed interface were sufficient for formation of a primitive active site that can perform hydrolysis. MID1-zinc hydrolyzes 4-nitrophenyl acetate with a rate acceleration of 10(5) and a k(cat)/K(M) of 630 M(-1) s(-1) and 4-nitrophenyl phosphate with a rate acceleration of 10(4) and a k(cat)/K(M) of 14 M(-1) s(-1). These rate accelerations by an unoptimized active site highlight the catalytic power of zinc and suggest that the clefts formed by protein-protein interactions are well-suited for creating enzyme active sites. This discovery has implications for protein evolution and engineering: from an evolutionary perspective, three-coordinated zinc at a homodimer interface cleft represents a simple evolutionary path to nascent enzymatic activity; from a protein engineering perspective, future efforts in de novo design of enzyme active sites may benefit from exploring clefts at protein interfaces for active site placement.

Thermocapillary Technique for Shaping and Fabricating Optical Ribbon Waveguides

NASA Astrophysics Data System (ADS)

Fiedler, Kevin; Troian, Sandra

The demand for ever increasing bandwidth and higher speed communication has ushered the next generation optoelectronic integrated circuits which directly incorporate polymer optical waveguide devices. Polymer melts are very versatile materials which have been successfully cast into planar single- and multimode waveguides using techniques such as embossing, photolithography and direct laser writing. In this talk, we describe a novel thermocapillary patterning method for fabricating waveguides in which the free surface of an ultrathin molten polymer film is exposed to a spatially inhomogeneous temperature field via thermal conduction from a nearby cooled mask pattern held in close proximity. The ensuring surface temperature distribution is purposely designed to pool liquid selectively into ribbon shapes suitable for optical waveguiding, but with rounded and not rectangular cross sectional areas due to capillary forces. The solidified waveguide patterns which result from this non-contact one step procedure exhibit ultrasmooth interfaces suitable for demanding optoelectronic applications. To complement these studies, we have also conducted finite element simulations for quantifying the influence of non-rectangular cross-sectional shapes on mode propagation and losses. Kf gratefully acknowledges support from a NASA Space Technology Research Fellowship.

Computational models for the analysis of three-dimensional internal and exhaust plume flowfields

NASA Technical Reports Server (NTRS)

Dash, S. M.; Delguidice, P. D.

1977-01-01

This paper describes computational procedures developed for the analysis of three-dimensional supersonic ducted flows and multinozzle exhaust plume flowfields. The models/codes embodying these procedures cater to a broad spectrum of geometric situations via the use of multiple reference plane grid networks in several coordinate systems. Shock capturing techniques are employed to trace the propagation and interaction of multiple shock surfaces while the plume interface, separating the exhaust and external flows, and the plume external shock are discretely analyzed. The computational grid within the reference planes follows the trace of streamlines to facilitate the incorporation of finite-rate chemistry and viscous computational capabilities. Exhaust gas properties consist of combustion products in chemical equilibrium. The computational accuracy of the models/codes is assessed via comparisons with exact solutions, results of other codes and experimental data. Results are presented for the flows in two-dimensional convergent and divergent ducts, expansive and compressive corner flows, flow in a rectangular nozzle and the plume flowfields for exhausts issuing out of single and multiple rectangular nozzles.

A Galerkin formulation of the MIB method for three dimensional elliptic interface problems

PubMed Central

Xia, Kelin; Wei, Guo-Wei

2014-01-01

We develop a three dimensional (3D) Galerkin formulation of the matched interface and boundary (MIB) method for solving elliptic partial differential equations (PDEs) with discontinuous coefficients, i.e., the elliptic interface problem. The present approach builds up two sets of elements respectively on two extended subdomains which both include the interface. As a result, two sets of elements overlap each other near the interface. Fictitious solutions are defined on the overlapping part of the elements, so that the differentiation operations of the original PDEs can be discretized as if there was no interface. The extra coefficients of polynomial basis functions, which furnish the overlapping elements and solve the fictitious solutions, are determined by interface jump conditions. Consequently, the interface jump conditions are rigorously enforced on the interface. The present method utilizes Cartesian meshes to avoid the mesh generation in conventional finite element methods (FEMs). We implement the proposed MIB Galerkin method with three different elements, namely, rectangular prism element, five-tetrahedron element and six-tetrahedron element, which tile the Cartesian mesh without introducing any new node. The accuracy, stability and robustness of the proposed 3D MIB Galerkin are extensively validated over three types of elliptic interface problems. In the first type, interfaces are analytically defined by level set functions. These interfaces are relatively simple but admit geometric singularities. In the second type, interfaces are defined by protein surfaces, which are truly arbitrarily complex. The last type of interfaces originates from multiprotein complexes, such as molecular motors. Near second order accuracy has been confirmed for all of these problems. To our knowledge, it is the first time for an FEM to show a near second order convergence in solving the Poisson equation with realistic protein surfaces. Additionally, the present work offers the first known near second order accurate method for C1 continuous or H2 continuous solutions associated with a Lipschitz continuous interface in a 3D setting. PMID:25309038

Droplet and multiphase effects in a shock-driven hydrodynamic instability with reshock

NASA Astrophysics Data System (ADS)

Middlebrooks, John B.; Avgoustopoulos, Constantine G.; Black, Wolfgang J.; Allen, Roy C.; McFarland, Jacob A.

2018-06-01

Shock-driven multiphase instabilities (SDMI) are unique physical phenomena that have far-reaching applications in engineering and science such as high energy explosions, scramjet combustors, and supernovae events. The SDMI arises when a multiphase field is impulsively accelerated by a shock wave and evolves as a result of gradients in particle-gas momentum transfer. A new shock tube facility has been constructed to study the SDMI. Experiments were conducted to investigate liquid particle and multiphase effects in the SDMI. A multiphase cylindrical interface was created with water droplet laden air in our horizontal shock tube facility. The interface was accelerated by a Mach 1.66 shock wave, and its reflection from the end wall. The interface development was captured using laser illumination and a high-resolution CCD camera. Laser interferometry was used to determine the droplet size distribution. A particle filtration technique was used to determine mass loading within an interface and verify particle size distribution. The effects of particle number density, particle size, and a secondary acceleration (reshock) of the interface were noted. Particle number density effects were found comparable to Atwood number effects in the Richtmyer-Meshkov instability for small (˜ 1.7 {μ }m) droplets. Evaporation was observed to alter droplet sizes and number density, markedly after reshock. For large diameter droplets (˜ 10.7 {μ }m), diminished development was observed with larger droplets lagging far behind the interface. These lagging droplets were also observed to breakup after reshock into structured clusters of smaller droplets. Mixing width values were reported to quantify mixing effects seen in images.

Beam Position Monitoring in the CSU Accelerator Facility

NASA Astrophysics Data System (ADS)

Einstein, Joshua; Vankeuren, Max; Watras, Stephen

2014-03-01

A Beam Position Monitoring (BPM) system is an integral part of an accelerator beamline, and modern accelerators can take advantage of newer technologies and designs when creating a BPM system. The Colorado State University (CSU) Accelerator Facility will include four stripline detectors mounted around the beamline, a low-noise analog front-end, and digitization and interface circuitry. The design will support a sampling rate greater than 10 Hz and sub-100 μm accuracy.

Droplet flow along the wall of rectangular channel with gradient of wettability

NASA Astrophysics Data System (ADS)

Kupershtokh, A. L.

2018-03-01

The lattice Boltzmann equations (LBE) method (LBM) is applicable for simulating the multiphysics problems of fluid flows with free boundaries, taking into account the viscosity, surface tension, evaporation and wetting degree of a solid surface. Modeling of the nonstationary motion of a drop of liquid along a solid surface with a variable level of wettability is carried out. For the computer simulation of such a problem, the three-dimensional lattice Boltzmann equations method D3Q19 is used. The LBE method allows us to parallelize the calculations on multiprocessor graphics accelerators using the CUDA programming technology.

Thermal residual stresses in silicon-carbide/titanium (0/90) laminate

NASA Technical Reports Server (NTRS)

Bigelow, C. A.

1992-01-01

The current work formulated a micromechanical analysis of a cross-ply laminate and calculated the thermal residual stress in a very thick (0/90)(sub 2n) silicon-carbide/titanium laminate. Results were also shown for a unidirectional laminate of the same material. Discrete fiber-matrix models assuming a rectangular array of fibers with a fiber volume fraction of 32.5 percent and a three-dimensional, finite-element analysis were used. Significant differences in the trends and magnitudes for the fiber, matrix, and interface stresses were calculated for unidirectional and (0/90) models. Larger hoop stresses calculated for the (0/90) model indicate that it may be more susceptible to radial cracking when subjected to mechanical loading than the unidirectional model. The axial stresses in the matrix were calculated to be slightly larger for the (0/90) model. The compressive axial stresses in the fiber were significantly larger in the (0/90) model. The presence of the cross-ply in the (0/90) model reduced the constraint on the fiber, producing radial interface stresses that were less compressive, which could lead to earlier failure of the fiber-matrix interface.

Interface and process for enhanced transmission of non-circular ion beams between stages at unequal pressure

DOEpatents

Tang, Keqi [Richland, WA; Shvartsburg, Alexandre A [Richland, WA; Smith, Richard D [Richland, WA

2008-03-04

The invention discloses a new interface with non-circular conductance limit aperture(s) useful for effective transmission of non-circular ion beams between stages with different gas pressure. In particular, the invention provides an improved coupling of field asymmetric waveform ion mobility spectrometry (FAIMS) analyzers of planar or side-to-side geometry to downstream stages such as mass spectrometry or ion mobility spectrometry. In this case, the non-circular aperture is rectangular; other geometries may be optimum in other applications. In the preferred embodiment, the non-circular aperture interface is followed by an electrodynamic ion funnel that may focus wide ion beams of any shape into tight circular beams with virtually no losses. The jet disrupter element of the funnel may also have a non-circular geometry, matching the shape of arriving ion beam. The improved sensitivity of planar FAIMS/MS has been demonstrated in experiments using a non-contiguous elongated aperture but other embodiments (e.g., with a contiguous slit aperture) may be preferable, especially in conjunction with an ion funnel operated at high pressures.

Monolayer phase coarsening using oscillatory flow

NASA Astrophysics Data System (ADS)

Leung, J.; Lopez, J. M.; Vogel, M. J.

2005-11-01

The co-existing phase domains of monolayers commonly observed via microscope are examined on flowing systems. Recent evidence shows that co-existing phase domains have profound effects on monolayer response to bulk flow. The present flow geometry consists of an open-top rectangular cavity in which the flow is driven by the periodic oscillation of the floor in its own plane. The oscillation of the floor dilates and compresses any film at the gas/liquid interface while still maintaining an essentially flat interface. A range of flow conditions (oscillation frequency and amplitude) is chosen so that the flow remains essentially two-dimensional. Measurements at the interface, initially covered by an insoluble monolayer (vitamin K1 or stearic acid), are made using a Brewster angle microscope system with a pulsed laser. Various phenomena such as fragmentation (breaking up of co-existing domains into finer ones) had previously been observed in sheared monolayer flows. In this new flow regime, we have seen dramatic coarsening of the domains. Interesting relaxation behavior at short and long time scales will also be discussed.

Free-surface flow of liquid oxygen under non-uniform magnetic field

NASA Astrophysics Data System (ADS)

Bao, Shi-Ran; Zhang, Rui-Ping; Wang, Kai; Zhi, Xiao-Qin; Qiu, Li-Min

2017-01-01

The paramagnetic property of oxygen makes it possible to control the two-phase flow at cryogenic temperatures by non-uniform magnetic fields. The free-surface flow of vapor-liquid oxygen in a rectangular channel was numerically studied using the two-dimensional phase field method. The effects of magnetic flux density and inlet velocity on the interface deformation, flow pattern and pressure drop were systematically revealed. The liquid level near the high-magnetic channel center was lifted upward by the inhomogeneous magnetic field. The interface height difference increased almost linearly with the magnetic force. For all inlet velocities, pressure drop under 0.25 T was reduced by 7-9% due to the expanded local cross-sectional area, compared to that without magnetic field. This work demonstrates the effectiveness of employing non-uniform magnetic field to control the free-surface flow of liquid oxygen. This non-contact method may be used for promoting the interface renewal, reducing the flow resistance, and improving the flow uniformity in the cryogenic distillation column, which may provide a potential for enhancing the operating efficiency of cryogenic air separation.

3D Numerical Simulation on the Sloshing Waves Excited by the Seismic Shacking

NASA Astrophysics Data System (ADS)

Zhang, Lin; Wu, Tso-Ren

2016-04-01

In the event of 2015 Nepal earthquake, a video clip broadcasted worldwide showed a violent water spilling in a hotel swimming pool. This sloshing phenomenon indicates a potential water loss in the sensitive facilities, e.g. the spent fuel pools in nuclear power plant, has to be taken into account carefully under the consideration of seismic-induced ground acceleration. In the previous studies, the simulation of sloshing mainly focused on the pressure force on the structure by using a simplified Spring-Mass Method developed in the field of solid mechanics. However, restricted by the assumptions of plane water surface and limited wave height, significant error will be made in evaluating the amount of water loss in the tank. In this paper, the computational fluid dynamical model, Splash3D, was adopted for studying the sloshing problem accurately. Splash3D solved 3D Navier-Stokes Equation directly with Large-Eddy Simulation (LES) turbulent closure. The Volume-of-fluid (VOF) method with piecewise linear interface calculation (PLIC) was used to track the complex breaking water surface. The time series acceleration of a design seismic was loaded to excite the water. With few restrictions from the assumptions, the accuracy of the simulation results were improved dramatically. A series model validations were conducted by compared to a 2D theoretical solution, and a 3D experimental data. Good comparisons can be seen. After the validation, we performed the simulation for considering a sloshing case in a rectangular water tank with a dimension of 12 m long, 8 m wide, 8 m deep, which contained water with 7 m in depth. The seismic movement was imported by considering time-series acceleration in three dimensions, which were about 0.5 g to 1.2 g in the horizontal directions, and 0.3 g to 1 g in the vertical direction. We focused the discussions on the kinematics of the water surface, wave breaking, velocity field, pressure field, water force on the side walls, and, most importantly, the amount of water loosed in the event. The simulated water movement excited by the seismic acceleration was visually similar to the video clip mentioned before. From the simulation results, we observed that the water was mainly leaked at the corner of the water tank with a nonlinear curve of the free-surface. This phenomenon can't be found in the conventional studies with acceleration in a sole direction. We also studied the effect from a porous body placed on the lower part of the tank. Detailed results and discussion will be presented in the full paper. Keywords Sloshing, Splash3D, LES, Breaking waves, VOF, spent fuel pool, Nuclear power plant

Quasistatic packings of droplets in flat microfluidic channels

NASA Astrophysics Data System (ADS)

Kadivar, Erfan

2016-02-01

As observed in recent experiments, monodisperse droplets self-assemble spontaneously in different ordered packings. In this work, we present a numerical study of the droplet packings in the flat rectangular microfluidic channels. Employing the boundary element method, we numerically solve the Stokes equation in two-dimension and investigate the appearance of droplet packing and transition between one and two-row packings of monodisperse emulsion droplets. By calculating packing force applied on the droplet interface, we investigate the effect of flow rate, droplet size, and surface tension on the packing configurations of droplets and transition between different topological packings.

A multi-channel coronal spectrophotometer.

NASA Technical Reports Server (NTRS)

Landman, D. A.; Orrall, F. Q.; Zane, R.

1973-01-01

We describe a new multi-channel coronal spectrophotometer system, presently being installed at Mees Solar Observatory, Mount Haleakala, Maui. The apparatus is designed to record and interpret intensities from many sections of the visible and near-visible spectral regions simultaneously, with relatively high spatial and temporal resolution. The detector, a thermoelectrically cooled silicon vidicon camera tube, has its central target area divided into a rectangular array of about 100,000 pixels and is read out in a slow-scan (about 2 sec/frame) mode. Instrument functioning is entirely under PDP 11/45 computer control, and interfacing is via the CAMAC system.

Reshocks, rarefactions, and the generalized Layzer model for hydrodynamic instabilities

NASA Astrophysics Data System (ADS)

Mikaelian, Karnig O.

2009-02-01

We report numerical simulations and analytic modeling of shock tube experiments on Rayleigh-Taylor and Richtmyer-Meshkov instabilities. We examine single interfaces of the type A /B where the incident shock is initiated in A and the transmitted shock proceeds into B. Examples are He/air and air/He. In addition, we study finite-thickness or double-interface A /B/A configurations such as air/SF6/air gas-curtain experiments. We first consider conventional shock tubes that have a "fixed" boundary: A solid endwall which reflects the transmitted shock and reshocks the interface(s). Then we focus on new experiments with a "free" boundary—a membrane disrupted mechanically or by the transmitted shock, sending back a rarefaction toward the interface(s). Complex acceleration histories are achieved, relevant for inertial confinement fusion implosions. We compare our simulation results with a generalized Layzer model for two fluids with time-dependent densities and derive a new freeze-out condition whereby accelerating and compressive forces cancel each other out. Except for the recently reported failures of the Layzer model, the generalized Layzer model and hydrocode simulations for reshocks and rarefactions agree well with each other and remain to be verified experimentally.

MuSim, a Graphical User Interface for Multiple Simulation Programs

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

Roberts, Thomas; Cummings, Mary Anne; Johnson, Rolland

2016-06-01

MuSim is a new user-friendly program designed to interface to many different particle simulation codes, regardless of their data formats or geometry descriptions. It presents the user with a compelling graphical user interface that includes a flexible 3-D view of the simulated world plus powerful editing and drag-and-drop capabilities. All aspects of the design can be parametrized so that parameter scans and optimizations are easy. It is simple to create plots and display events in the 3-D viewer (with a slider to vary the transparency of solids), allowing for an effortless comparison of different simulation codes. Simulation codes: G4beamline, MAD-X,more » and MCNP; more coming. Many accelerator design tools and beam optics codes were written long ago, with primitive user interfaces by today's standards. MuSim is specifically designed to make it easy to interface to such codes, providing a common user experience for all, and permitting the construction and exploration of models with very little overhead. For today's technology-driven students, graphical interfaces meet their expectations far better than text-based tools, and education in accelerator physics is one of our primary goals.« less

Predicting the Rate Constant of Electron Tunneling Reactions at the CdSe-TiO2 Interface.

PubMed

Hines, Douglas A; Forrest, Ryan P; Corcelli, Steven A; Kamat, Prashant V

2015-06-18

Current interest in quantum dot solar cells (QDSCs) motivates an understanding of the electron transfer dynamics at the quantum dot (QD)-metal oxide (MO) interface. Employing transient absorption spectroscopy, we have monitored the electron transfer rate (ket) at this interface as a function of the bridge molecules that link QDs to TiO2. Using mercaptoacetic acid, 3-mercaptopropionic acid, 8-mercaptooctanoic acid, and 16-mercaptohexadecanoic acid, we observe an exponential attenuation of ket with increasing linker length, and attribute this to the tunneling of the electron through the insulating linker molecule. We model the electron transfer reaction using both rectangular and trapezoidal barrier models that have been discussed in the literature. The one-electron reduction potential (equivalent to the lowest unoccupied molecular orbital) of each molecule as determined by cyclic voltammetry (CV) was used to estimate the effective barrier height presented by each ligand at the CdSe-TiO2 interface. The electron transfer rate (ket) calculated for each CdSe-ligand-TiO2 interface using both models showed the results in agreement with the experimentally determined trend. This demonstrates that electron transfer between CdSe and TiO2 can be viewed as electron tunneling through a layer of linking molecules and provides a useful method for predicting electron transfer rate constants.

High order solution of Poisson problems with piecewise constant coefficients and interface jumps

NASA Astrophysics Data System (ADS)

Marques, Alexandre Noll; Nave, Jean-Christophe; Rosales, Rodolfo Ruben

2017-04-01

We present a fast and accurate algorithm to solve Poisson problems in complex geometries, using regular Cartesian grids. We consider a variety of configurations, including Poisson problems with interfaces across which the solution is discontinuous (of the type arising in multi-fluid flows). The algorithm is based on a combination of the Correction Function Method (CFM) and Boundary Integral Methods (BIM). Interface and boundary conditions can be treated in a fast and accurate manner using boundary integral equations, and the associated BIM. Unfortunately, BIM can be costly when the solution is needed everywhere in a grid, e.g. fluid flow problems. We use the CFM to circumvent this issue. The solution from the BIM is used to rewrite the problem as a series of Poisson problems in rectangular domains-which requires the BIM solution at interfaces/boundaries only. These Poisson problems involve discontinuities at interfaces, of the type that the CFM can handle. Hence we use the CFM to solve them (to high order of accuracy) with finite differences and a Fast Fourier Transform based fast Poisson solver. We present 2-D examples of the algorithm applied to Poisson problems involving complex geometries, including cases in which the solution is discontinuous. We show that the algorithm produces solutions that converge with either 3rd or 4th order of accuracy, depending on the type of boundary condition and solution discontinuity.

Gas Gun Studies of Interface Wear Effects

NASA Astrophysics Data System (ADS)

Jackson, Tyler; Kennedy, Greg; Thadhani, Naresh

2011-06-01

The characteristics of interface wear were studied by performing gas gun experiments at velocities up to 1 km/s. The approach involved developing coefficients of constitutive strength models for Al 6061 and OFHC-Cu, then using those to design die geometry for interface wear gas gun experiments. Taylor rod-on-anvil impact experiments were performed to obtain coefficients of the Johnson-Cook constitutive strength model by correlating experimentally obtained deformed states of impacted samples with those predicted using ANSYS AUTODYN hydrocode. Simulations were used with validated strength models to design geometry involving acceleration of Al rods through a copper concentric cylindrical angular extrusion die. Experiments were conducted using 7.62 mm and 80 mm diameter gas guns. Differences in the microstructure of the interface layer and microhardness values illustrate that stress-strain conditions produced during acceleration of Al through the hollow concentric copper die, at velocities less than 800 m/s, result in formation of a layer via solid state alloying due to severe plastic deformation, while higher velocities produce an interface layer consisting of melted and re-solidified aluminum.

Interface behavior of a multi-layer fluid configuration subject to acceleration in a microgravity environment, supplement 1. M.S. Thesis

NASA Technical Reports Server (NTRS)

Lyell, M. J.; Roh, Michael

1991-01-01

With the increasing opportunities for research in a microgravity environment, there arises a need for understanding fluid mechanics under such conditions. In particular, a number of material processing configurations involve fluid-fluid interfaces which may experience instabilities in the presence of external forcing. In a microgravity environment, these accelerations may be periodic or impulse-type in nature. This research investigates the behavior of a multi-layer idealized fluid configuration which is infinite in extent. The analysis is linear, and each fluid region is considered inviscid, incompressible, and immiscible. An initial parametric study of confiquration stability in the presence of a constant acceleration field is performed. The zero mean gravity limit case serves as the base state for the subsequent time-dependent forcing cases. A stability analysis of the multi-layer fluid system in the presence of periodic forcing is investigated. Floquet theory is utilized. A parameter study is performed, and regions of stability are identified. For the impulse-type forcing case, asymptotic stability is established for the configuration. Using numerical integration, the time response of the interfaces is determined.

Cylindrical effects on Richtmyer-Meshkov instability for arbitrary Atwood numbers in weakly nonlinear regime

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

Liu, W. H.; He, X. T.; LCP, Institute of Applied Physics and Computational Mathematics, Beijing 100088

2012-07-15

When an incident shock collides with a corrugated interface separating two fluids of different densities, the interface is prone to Richtmyer-Meshkov instability (RMI). Based on the formal perturbation expansion method as well as the potential flow theory, we present a simple method to investigate the cylindrical effects in weakly nonlinear RMI with the transmitted and reflected cylindrical shocks by considering the nonlinear corrections up to fourth order. The cylindrical results associated with the material interface show that the interface expression consists of two parts: the result in the planar system and that from the cylindrical effects. In the limit ofmore » the cylindrical radius tending to infinity, the cylindrical results can be reduced to those in the planar system. Our explicit results show that the cylindrical effects exert an inward velocity on the whole perturbed interface, regardless of bubbles or spikes of the interface. On the one hand, outgoing bubbles are constrained and ingoing spikes are accelerated for different Atwood numbers (A) and mode numbers k'. On the other hand, for ingoing bubbles, when |A|k'{sup 3/2} Less-Than-Or-Equivalent-To 1, bubbles are considerably accelerated especially at the small |A| and k'; otherwise, bubbles are decelerated. For outgoing spikes, when |A|k' Greater-Than-Or-Equivalent-To 1, spikes are dramatically accelerated especially at large |A| and k'; otherwise, spikes are decelerated. Furthermore, the cylindrical effects have a significant influence on the amplitudes of the ingoing spike and bubble for large k'. Thus, it should be included in applications where the cylindrical effects play a role, such as inertial confinement fusion ignition target design.« less

A PIV Study of Drop-interface Coalescence with Surfactants

NASA Astrophysics Data System (ADS)

Weheliye, Weheliye Hashi; Dong, Teng; Angeli, Panagiota

2017-11-01

In this work, the coalescence of a drop with an aqueous-organic interface was studied by Particle Image Velocimetry (PIV). The effect of surfactants on the drop surface evolution, the vorticity field and the kinetic energy distribution in the drop during coalescence were investigated. The coalescence took place in an acrylic rectangular box with 79% glycerol solution at the bottom and Exxsol D80 oil above. The glycerol solution drop was generated through a nozzle fixed at 2cm above the aqueous/oil interface and was seeded with Rhodamine particles. The whole process was captured by a high-speed camera. Different mass ratios of non-ionic surfactant Span80 to oil were studied. The increase of surfactant concentration promoted deformation of the interface before the rupture of the trapped oil film. At the early stages after film rupture, two counter-rotating vortices appeared at the bottom of the drop which then travelled to the upper part. The propagation rates, as well as the intensities of the vortices decreased at high surfactant concentrations. At early stages, the kinetic energy was mainly distributed near the bottom part of the droplet, while at later stages it was distributed near the upper part of the droplet. Programme Grant MEMPHIS, Chinese Scholarship Council (CSC).

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

Piot, P.; Halavanau, A.

This paper discusses the implementation of a python- based high-level interface to the Fermilab acnet control system. The interface has been successfully employed during the commissioning of the Fermilab Accelerator Science & Technology (FAST) facility. Specifically, we present examples of applications at FAST which include the interfacing of the elegant program to assist lattice matching, an automated emittance measurement via the quadrupole-scan method and tranverse transport matrix measurement of a superconducting RF cavity.

Electron acceleration by laser produced wake field: Pulse shape effect

NASA Astrophysics Data System (ADS)

Malik, Hitendra K.; Kumar, Sandeep; Nishida, Yasushi

2007-12-01

Analytical expressions are obtained for the longitudinal field (wake field: Ex), density perturbations ( ne') and the potential ( ϕ) behind a laser pulse propagating in a plasma with the pulse duration of the electron plasma period. A feasibility study on the wake field is carried out with Gaussian-like (GL) pulse, rectangular-triangular (RT) pulse and rectangular-Gaussian (RG) pulse considering one-dimensional weakly nonlinear theory ( ne'/n0≪1), and the maximum energy gain acquired by an electron is calculated for all these three types of the laser pulse shapes. A comparative study infers that the RT pulse yields the best results: In its case maximum electron energy gain is 33.5 MeV for a 30 fs pulse duration whereas in case of GL (RG) pulse of the same duration the gain is 28.6 (28.8)MeV at the laser frequency of 1.6 PHz and the intensity of 3.0 × 10 18 W/m 2. The field of the wake and hence the energy gain get enhanced for the higher laser frequency, larger pulse duration and higher laser intensity for all types of the pulses.

Efficient three-dimensional Poisson solvers in open rectangular conducting pipe

NASA Astrophysics Data System (ADS)

Qiang, Ji

2016-06-01

Three-dimensional (3D) Poisson solver plays an important role in the study of space-charge effects on charged particle beam dynamics in particle accelerators. In this paper, we propose three new 3D Poisson solvers for a charged particle beam in an open rectangular conducting pipe. These three solvers include a spectral integrated Green function (IGF) solver, a 3D spectral solver, and a 3D integrated Green function solver. These solvers effectively handle the longitudinal open boundary condition using a finite computational domain that contains the beam itself. This saves the computational cost of using an extra larger longitudinal domain in order to set up an appropriate finite boundary condition. Using an integrated Green function also avoids the need to resolve rapid variation of the Green function inside the beam. The numerical operational cost of the spectral IGF solver and the 3D IGF solver scales as O(N log(N)) , where N is the number of grid points. The cost of the 3D spectral solver scales as O(Nn N) , where Nn is the maximum longitudinal mode number. We compare these three solvers using several numerical examples and discuss the advantageous regime of each solver in the physical application.

Interfacial states and far-from-equilibrium transitions in the epitaxial growth and erosion on (110) crystal surfaces

NASA Astrophysics Data System (ADS)

Levandovsky, Artem; Golubović, Leonardo; Moldovan, Dorel

2006-12-01

We discuss the far-from-equilibrium interfacial phenomena occurring in the multilayer homoepitaxial growth and erosion on (110) crystal surfaces. Experimentally, these rectangular symmetry surfaces exhibit a multitude of interesting nonequilibrium interfacial structures, such as the rippled one-dimensional periodic states that are not present in the homoepitaxial growth and erosion on the high symmetry (100) and (111) crystal surfaces. Within a unified phenomenological model, we reveal and elucidate this multitude of states on (110) surfaces as well as the transitions between them. By analytic arguments and numerical simulations, we address experimentally observed transitions between two types of rippled states on (110) surfaces. We discuss several intermediary interface states intervening, via consecutive transitions, between the two rippled states. One of them is the rhomboidal pyramid state, theoretically predicted by Golubovic [Phys. Rev. Lett. 89, 266104 (2002)] and subsequently seen, by de Mongeot and co-workers, in the epitaxial erosion of Cu(110) and Rh(110) surfaces [A. Molle , Phys. Rev. Lett. 93, 256103 (2004), and A. Molle , Phys. Rev. B 73, 155418 (2006)]. In addition, we find a number of interesting intermediary states having structural properties somewhere between those of rippled and pyramidal states. Prominent among them are the rectangular rippled states of long rooflike objects (huts) recently seen on Ag(110) surface. We also predict the existence of a striking interfacial structure that carries nonzero, persistent surface currents. Periodic surface currents vortex lattice formed in this so-called buckled rippled interface state is a far-from-equilibrium relative of the self-organized convective flow patterns in hydrodynamic systems. We discuss the coarsening growth of the multitude of the interfacial states on (110) crystal surfaces.

76 FR 9547 - Light-Walled Rectangular Pipe and Tube From Mexico; Final Results of Antidumping Duty...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-02-18

... DEPARTMENT OF COMMERCE International Trade Administration [A-201-836] Light-Walled Rectangular... preliminary results of the administrative review of the antidumping duty order on light-walled rectangular... light-walled rectangular pipe and tube from Mexico. See Light-Walled Rectangular Pipe and Tube From...

A simple procedure for the estimation of neutron skyshine from proton accelerators.

PubMed

Stevenson, G R; Thomas, R H

1984-01-01

Recent calculations of neutron diffusion at an air/ground interface have enabled the establishment of a very simple procedure for estimating neutron dose equivalent at large distances from proton accelerators in the energy range 10 MeV to several tens of GeV.

Compositional Reservoir Simulation of Highly Heterogeneous and Anisotropic Fractured Media in 2D and 3D Unstructured Gridding

NASA Astrophysics Data System (ADS)

Zidane, A.; Firoozabadi, A.

2017-12-01

We present an efficient and accurate numerical model for multicomponent compressible single-phase flow in 2D and 3D fractured media based on higher-order discretization. The numerical model accounts for heterogeneity and anisotropy in unstructured gridding with low mesh dependency. The efficiency of our model is demonstrated by having comparable CPU time between fractured and unfractured media. The fracture cross-flow equilibrium approach (FCFE) is applied on triangular finite elements (FE) in 2D. This allows simulating fractured reservoirs with all possible orientations of fractures as opposed to rectangular FE. In 3D we apply the FCFE approach on the prism FE. The prism FE with FCFE allows simulating realistic fractured domains compared to hexahedron FE. In addition, when using FCFE on triangular and prism FE there is no limitation on the number of intersecting fractures, whereas in rectangular and hexahedron FE the number is limited to 2 in 2D and 3 in 3D. To generate domains with complicated boundaries, we have developed a computer-aided design (CAD) interface in our model. The advances introduced in this work are demonstrated through various examples.

Debugging Nano-Bio Interfaces: Systematic Strategies to Accelerate Clinical Translation of Nanotechnologies.

PubMed

Mahmoudi, Morteza

2018-03-17

Despite considerable efforts in the field of nanomedicine that have been made by researchers, funding agencies, entrepreneurs, and the media, fewer nanoparticle (NP) technologies than expected have made it to clinical trials. The wide gap between the efforts and effective clinical translation is, at least in part, due to multiple overlooked factors in both in vitro and in vivo environments, a poor understanding of the nano-bio interface, and misinterpretation of the data collected in vitro, all of which reduce the accuracy of predictions regarding the NPs' fate and safety in humans. To minimize this bench-to-clinic gap, which may accelerate successful clinical translation of NPs, this opinion paper aims to introduce strategies for systematic debugging of nano-bio interfaces in the current literature. Copyright © 2018 Elsevier Ltd. All rights reserved.

Experiments on the Richtmyer-Meshkov Instability of Incompressible Fluids

NASA Technical Reports Server (NTRS)

Jacobs, J.; Niederhaus, C.

2000-01-01

Richtmyer-Meshkov (R-M) instability occurs when two different density fluids are impulsively accelerated in the direction normal to their nearly planar interface. The instability causes small perturbations on the interface to grow and possibly become turbulent given the proper initial conditions. R-M instability is similar to the Rayleigh-Taylor (R-T) instability, which is generated when the two fluids undergo a constant acceleration. R-M instability is a fundamental fluid instability that is important to fields ranging from astrophysics to high-speed combustion. For example, R-M instability is currently the limiting factor in achieving a net positive yield with inertial confinement fusion. The experiments described here utilize a novel technique that circumvents many of the experimental difficulties previously limiting the study of the R-M instability. A Plexiglas tank contains two unequal density liquids and is gently oscillated horizontally to produce a controlled initial fluid interface shape. The tank is mounted to a sled on a high speed, low friction linear rail system, constraining the main motion to the vertical direction. The sled is released from an initial height and falls vertically until it bounces off of a movable spring, imparting an impulsive acceleration in the upward direction. As the sled travels up and down the rails, the spring retracts out of the way, allowing the instability to evolve in free-fall until impacting a shock absorber at the end of the rails. The impulsive acceleration provided to the system is measured by a piezoelectric accelerometer mounted on the tank, and a capacitive accelerometer measures the low-level drag of the bearings. Planar Laser-Induced Fluorescence is used for flow visualization, which uses an Argon ion laser to illuminate the flow and a CCD camera, mounted to the sled, to capture images of the interface. This experimental study investigates the instability of an interface between incompressible, miscible liquids with an initial sinusoidal perturbation. The amplitude of the disturbance during the experiment is measured and compared to theory. The results show good agreement (within 10%) with linear stability theory up to nondimensional amplitude ka = 0.7 (wavenumber x amplitude). These results hold true for an initial ka (before acceleration) of -0.7 less than ka less than -0.06, while the linear theory was developed for absolute value of ka much less than 1. In addition, a third order weakly nonlinear perturbation theory is shown to be accurate for amplitudes as large as ka = 1.3, even though the interface becomes double-valued at ka = 1.1. As time progresses, the vorticity on the interface concentrates, and the interface spirals around the alternating sign vortex centers to form a mushroom pattern. At higher Reynolds Number (based on circulation), an instability of the vortex cores has been observed. While time limitations of the apparatus prevent determination of a critical Reynolds Number, the lowest Reynolds Number this vortex instability has been observed at is 5000.

A FORTRAN Program for Rectangular Microstrip Antennas.

DTIC Science & Technology

1982-04-01

accelerated by writing it as z -jko j cos(kyl)cos[k(b-yl)I 011 kasin(kb) + j i wx la)c osrxx /a) jAj mirdlI-I 1C0s(PnYi)cOS[Pm(b-Yi)1 a p.51n(pmb)Mi + jOM’OT...41 41 0. 4 i Q -4 -H -I rco .uU-4 ur -4c 10 -N > M 0) vi C ~ O 40 4w ~Ln U)4. 4814 aL. 00 a 0 00 0 00 r(A 410 00 0 Cl 4.49 0 td cc Nc~ ~44 0o tot E- 1

Voltera's Solution of the Wave Equation as Applied to Three-Dimensional Supersonic Airfoil Problems

NASA Technical Reports Server (NTRS)

Heslet, Max A; Lomax, Harvard; Jones, Arthur L

1947-01-01

A surface integral is developed which yields solutions of the linearized partial differential equation for supersonic flow. These solutions satisfy boundary conditions arising in wing theory. Particular applications of this general method are made, using acceleration potentials, to flat surfaces and to uniformly loaded lifting surfaces. Rectangular and trapezoidal plan forms are considered along with triangular forms adaptable to swept-forward and swept-back wings. The case of the triangular plan form in sideslip is also included. Emphasis is placed on the systematic application of the method to the lifting surfaces considered and on the possibility of further application.

Accelerated transport and growth with symmetrized dynamics

NASA Astrophysics Data System (ADS)

Merikoski, Juha

2013-12-01

In this paper we consider a model of accelerated dynamics with the rules modified from those of the recently proposed [Dong et al., Phys. Rev. Lett. 109, 130602 (2012), 10.1103/PhysRevLett.109.130602] accelerated exclusion process (AEP) such that particle-vacancy symmetry is restored to facilitate a mapping to a solid-on-solid growth model in 1+1 dimensions. In addition to kicking a particle ahead of the moving particle, as in the AEP, in our model another particle from behind is drawn, provided it is within the "distance of interaction" denoted by ℓmax. We call our model the doubly accelerated exclusion process (DAEP). We observe accelerated transport and interface growth and widening of the cluster size distribution for cluster sizes above ℓmax, when compared with the ordinary totally asymmetric exclusion process (TASEP). We also characterize the difference between the TASEP, AEP, and DAEP by computing a "staggered" order parameter, which reveals the local order in the steady state. This order in part explains the behavior of the particle current as a function of density. The differences of the steady states are also reflected by the behavior of the temporal and spatial correlation functions in the interface picture.

The g-LIMIT Microgravity Vibration Isolation System for the Microgravity Science Glovebox

NASA Technical Reports Server (NTRS)

Whorton, Mark S.; Ryan, Stephen G. (Technical Monitor)

2001-01-01

For many microgravity science experiments in the International Space Station, the ambient acceleration environment will be exceed desirable levels. To provide a more quiescent acceleration environment to the microgravity payloads, a vibration isolation system named g-LIMIT (GLovebox Integrated Microgravity Isolation Technology) is being designed. g-LIMIT is a sub-rack level isolation system for the Microgravity Science Glovebox that can be tailored to a variety of applications. Scheduled for launch on the UF-1 mission, the initial implementation of g-LIMIT will be a Characterization Test in the Microgravity Science Glovebox. g-LIMIT will be available to glovebox investigators immediately after characterization testing. Standard MSG structural and umbilical interfaces will be used so that the interface requirements are minimized. g-LIMIT consists of three integrated isolator modules, each of which is comprised of a dual axis actuator, two axes of acceleration sensing, two axes of position sensing, control electronics, and data transmission capabilities in a small-volume package. In addition, this system provides the unique capability for measuring quasi-steady acceleration of the experiment independent of accelerometers as a by-product of the control system and will have the capability of generating user-specified pristine accelerations to enhance experiment operations.

Dynamics of House Sparrows (Passer domesticus) in Newcastle disease virus transmission within the avifaunal-poultry interface: an epidemiological modeling approach

USDA-ARS?s Scientific Manuscript database

As emerging and persistent pathogens increase in prevalence, the agriculture-wildlife interface has been identified as a field requiring further research. Acceleration of wildlife urbanization, exotic species introductions, and habitat encroachment are disrupting barriers that once separated microb...

Second order finite-difference ghost-point multigrid methods for elliptic problems with discontinuous coefficients on an arbitrary interface

NASA Astrophysics Data System (ADS)

Coco, Armando; Russo, Giovanni

2018-05-01

In this paper we propose a second-order accurate numerical method to solve elliptic problems with discontinuous coefficients (with general non-homogeneous jumps in the solution and its gradient) in 2D and 3D. The method consists of a finite-difference method on a Cartesian grid in which complex geometries (boundaries and interfaces) are embedded, and is second order accurate in the solution and the gradient itself. In order to avoid the drop in accuracy caused by the discontinuity of the coefficients across the interface, two numerical values are assigned on grid points that are close to the interface: a real value, that represents the numerical solution on that grid point, and a ghost value, that represents the numerical solution extrapolated from the other side of the interface, obtained by enforcing the assigned non-homogeneous jump conditions on the solution and its flux. The method is also extended to the case of matrix coefficient. The linear system arising from the discretization is solved by an efficient multigrid approach. Unlike the 1D case, grid points are not necessarily aligned with the normal derivative and therefore suitable stencils must be chosen to discretize interface conditions in order to achieve second order accuracy in the solution and its gradient. A proper treatment of the interface conditions will allow the multigrid to attain the optimal convergence factor, comparable with the one obtained by Local Fourier Analysis for rectangular domains. The method is robust enough to handle large jump in the coefficients: order of accuracy, monotonicity of the errors and good convergence factor are maintained by the scheme.

Rectangularization of the survival curve in The Netherlands, 1950-1992.

PubMed

Nusselder, W J; Mackenbach, J P

1996-12-01

In this article we determine whether rectangularization of the survival curve occurred in the Netherlands in the period 1950-1992. Rectangularization is defined as a trend toward a more rectangular shape of the survival curve due to increased survival and concentration of deaths around the mean age at death. We distinguish between absolute and relative rectangularization, depending on whether an increase in life expectancy is accompanied by concentration of deaths into a smaller age interval or into a smaller proportion of total life expectancy. We used measures of variability based on Keyfitz' H and the standard deviation, both life table-based. Our results show that absolute and relative rectangularization of the entire survival curve occurred in both sexes and over the complete period (except for the years 1955-1959 and 1965-1969 in men). At older ages, results differ between sexes, periods, and an absolute versus a relative definition of rectangularization. Above age 60 1/2, relative rectangularization occurred in women over the complete period and in men since 1975-1979 only, whereas absolute rectangularization occurred in both sexes since the period of 1980-1984. The implications of the recent rectangularization at older ages for achieving compression of morbidity are discussed.

Evidence for asymmetric edge-on Langmuir monolayer: Application to surface potential measurements

NASA Astrophysics Data System (ADS)

El Abed, A.; Ionov, R.; Goldmann, M.; Fontaine, P.; Billard, J.; Peretti, P.

2001-10-01

We show, using surface pressure vs. molecular area isotherm measurements and synchrotron grazing X-ray diffraction, that 4BCD12 molecules, which consist of a central flexible bowl-like core to which eight long lateral hydrocarbon chains are bound, form a stable edge-on monolayer. Experimental data indicate that six lateral hydrocarbon chains orient upwards to form a quasi-rectangular lattice of 43° tilted hydrocarbon chains. The obtained axially asymmetric phase, which we label edge26-on, allows using surface potential measurements, for the validation of literature electric models of a single monolayer spread at the air-water interface.

Highly sensitive refractive index fiber inline Mach-Zehnder interferometer fabricated by femtosecond laser micromachining and chemical etching

NASA Astrophysics Data System (ADS)

Sun, Xiao-Yan; Chu, Dong-Kai; Dong, Xin-Ran; Zhou, Chu; Li, Hai-Tao; Luo-Zhi; Hu, You-Wang; Zhou, Jian-Ying; Cong-Wang; Duan, Ji-An

2016-03-01

A High sensitive refractive index (RI) sensor based on Mach-Zehnder interferometer (MZI) in a conventional single-mode optical fiber is proposed, which is fabricated by femtosecond laser transversal-scanning inscription method and chemical etching. A rectangular cavity structure is formed in part of fiber core and cladding interface. The MZI sensor shows excellent refractive index sensitivity and linearity, which exhibits an extremely high RI sensitivity of -17197 nm/RIU (refractive index unit) with the linearity of 0.9996 within the refractive index range of 1.3371-1.3407. The experimental results are consistent with theoretical analysis.

S3D: An interactive surface grid generation tool

NASA Technical Reports Server (NTRS)

Luh, Raymond Ching-Chung; Pierce, Lawrence E.; Yip, David

1992-01-01

S3D, an interactive software tool for surface grid generation, is described. S3D provides the means with which a geometry definition based either on a discretized curve set or a rectangular set can be quickly processed towards the generation of a surface grid for computational fluid dynamics (CFD) applications. This is made possible as a result of implementing commonly encountered surface gridding tasks in an environment with a highly efficient and user friendly graphical interface. Some of the more advanced features of S3D include surface-surface intersections, optimized surface domain decomposition and recomposition, and automated propagation of edge distributions to surrounding grids.

Taylor Instability of Incompressible Liquids

DOE R&D Accomplishments Database

Fermi, E.; von Neumann, J.

1955-11-01

A discussion is presented in simplified form of the problem of the growth of an initial ripple on the surface of an incompressible liquid in the presence of an acceleration, g, directed from the outside into the liquid. The model is that of a heavy liquid occupying at t = 0 the half space above the plane z = 0, and a rectangular wave profile is assumed. The theory is found to represent correctly one feature of experimental results, namely the fact that the half wave of the heavy liquid into the vacuum becomes rapidly narrower while the half wave pushing into the heavy liquid becomes more and more blunt. The theory fails to account for the experimental results according to which the front of the wave pushing into the heavy liquid moves with constant velocity. The case of instability at the boundary of 2 fluids of different densities is also explored. Similar results are obtained except that the acceleration of the heavy liquid into the light liquid is reduced.

Coherent and partially coherent dark hollow beams with rectangular symmetry and paraxial propagation properties

NASA Astrophysics Data System (ADS)

Cai, Yangjian; Zhang, Lei

2006-07-01

A theoretical model is proposed to describe coherent dark hollow beams (DHBs) with rectangular symmetry. The electric field of a coherent rectangular DHB is expressed as a superposition of a series of the electric field of a finite series of fundamental Gaussian beams. Analytical propagation formulas for a coherent rectangular DHB passing through paraxial optical systems are derived in a tensor form. Furthermore, for the more general case, we propose a theoretical model to describe a partially coherent rectangular DHB. Analytical propagation formulas for a partially coherent rectangular DHB passing through paraxial optical systems are derived. The beam propagation factor (M2 factor) for both coherent and partially coherent rectangular DHBs are studied. Numerical examples are given by using the derived formulas. Our models and method provide an effective way to describe and treat the propagation of coherent and partially coherent rectangular DHBs.

Compact waveguide circular polarizer

DOEpatents

Tantawi, Sami G.

2016-08-16

A multi-port waveguide is provided having a rectangular waveguide that includes a Y-shape structure with first top arm having a first rectangular waveguide port, a second top arm with second rectangular waveguide port, and a base arm with a third rectangular waveguide port for supporting a TE.sub.10 mode and a TE.sub.20 mode, where the end of the third rectangular waveguide port includes rounded edges that are parallel to a z-axis of the waveguide, a circular waveguide having a circular waveguide port for supporting a left hand and a right hand circular polarization TE.sub.11 mode and is coupled to a base arm broad wall, and a matching feature disposed on the base arm broad wall opposite of the circular waveguide for terminating the third rectangular waveguide port, where the first rectangular waveguide port, the second rectangular waveguide port and the circular waveguide port are capable of supporting 4-modes of operation.

Effect of accelerated crucible rotation on melt composition in high-pressure vertical Bridgman growth of cadmium zinc telluride

NASA Astrophysics Data System (ADS)

Yeckel, Andrew; Derby, Jeffrey J.

2000-02-01

Three-dimensional axisymmetric, time-dependent simulations of the high-pressure vertical Bridgman growth of large-diameter cadmium zinc telluride are performed to study the effect of accelerated crucible rotation (ACRT) on crystal growth dynamics. The model includes details of heat transfer, melt convection, solid-liquid interface shape, and dilute zinc segregation. Application of ACRT greatly improves mixing in the melt, but causes an overall increased deflection of the solid-liquid interface. The flow exhibits a Taylor-Görtler instability at the crucible sidewall, which further enhances melt mixing. The rate of mixing depends strongly on the length of the ACRT cycle, with an optimum half-cycle length between 2 and 4 Ekman time units. Significant melting of the crystal occurs during a portion of the rotation cycle, caused by periodic reversal of the secondary flow at the solid-liquid interface, indicating the possibility of compositional striations.

Front surface structured targets for enhancing laser-plasma interactions

NASA Astrophysics Data System (ADS)

Snyder, Joseph; George, Kevin; Ji, Liangliang; Yalamanchili, Sasir; Simonoff, Ethan; Cochran, Ginevra; Daskalova, Rebecca; Poole, Patrick; Willis, Christopher; Lewis, Nathan; Schumacher, Douglass

2016-10-01

We present recent progress made using front surface structured interfaces for enhancing ultrashort, relativistic laser-plasma interactions. Structured targets can increase laser absorption and enhance ion acceleration through a number of mechanisms such as direct laser acceleration and laser guiding. We detail experimental results obtained at the Scarlet laser facility on hollow, micron-scale plasma channels for enhancing electron acceleration. These targets show a greater than three times enhancement in the electron cutoff energy as well as an increased slope temperature for the electron distribution when compared to a flat interface. Using three-dimensional particle-in-cell (PIC) simulations, we have modeled the interaction to give insight into the physical processes responsible for the enhancement. Furthermore, we have used PIC simulations to design structures that are more advantageous for ion acceleration. Such targets necessitate advanced target fabrication methods and we describe techniques used to manufacture optimized structures, including vapor-liquid-solid growth, cryogenic etching, and 3D printing using two-photon-polymerization. This material is based upon work supported by the Air Force Office of Scientific Research under Award Number FA9550-14-1-0085.

ORBIT: A Code for Collective Beam Dynamics in High-Intensity Rings

NASA Astrophysics Data System (ADS)

Holmes, J. A.; Danilov, V.; Galambos, J.; Shishlo, A.; Cousineau, S.; Chou, W.; Michelotti, L.; Ostiguy, J.-F.; Wei, J.

2002-12-01

We are developing a computer code, ORBIT, specifically for beam dynamics calculations in high-intensity rings. Our approach allows detailed simulation of realistic accelerator problems. ORBIT is a particle-in-cell tracking code that transports bunches of interacting particles through a series of nodes representing elements, effects, or diagnostics that occur in the accelerator lattice. At present, ORBIT contains detailed models for strip-foil injection, including painting and foil scattering; rf focusing and acceleration; transport through various magnetic elements; longitudinal and transverse impedances; longitudinal, transverse, and three-dimensional space charge forces; collimation and limiting apertures; and the calculation of many useful diagnostic quantities. ORBIT is an object-oriented code, written in C++ and utilizing a scripting interface for the convenience of the user. Ongoing improvements include the addition of a library of accelerator maps, BEAMLINE/MXYZPTLK; the introduction of a treatment of magnet errors and fringe fields; the conversion of the scripting interface to the standard scripting language, Python; and the parallelization of the computations using MPI. The ORBIT code is an open source, powerful, and convenient tool for studying beam dynamics in high-intensity rings.

Accelerator controls at CERN: Some converging trends

NASA Astrophysics Data System (ADS)

Kuiper, B.

1990-08-01

CERN's growing services to the high-energy physics community using frozen resources has led to the implementation of "Technical Boards", mandated to assist the management by making recommendations for rationalizations in various technological domains. The Board on Process Control and Electronics for Accelerators, TEBOCO, has emphasized four main lines which might yield economy in resources. First, a common architecture for accelerator controls has been agreed between the three accelerator divisions. Second, a common hardware/software kit has been defined, from which the large majority of future process interfacing may be composed. A support service for this kit is an essential part of the plan. Third, high-level protocols have been developed for standardizing access to process devices. They derive from agreed standard models of the devices and involve a standard control message. This should ease application development and mobility of equipment. Fourth, a common software engineering methodology and a commercial package of application development tools have been adopted. Some rationalization in the field of the man-machine interface and in matters of synchronization is also under way.

A versatile program for the calculation of linear accelerator room shielding.

PubMed

Hassan, Zeinab El-Taher; Farag, Nehad M; Elshemey, Wael M

2018-03-22

This work aims at designing a computer program to calculate the necessary amount of shielding for a given or proposed linear accelerator room design in radiotherapy. The program (Shield Calculation in Radiotherapy, SCR) has been developed using Microsoft Visual Basic. It applies the treatment room shielding calculations of NCRP report no. 151 to calculate proper shielding thicknesses for a given linear accelerator treatment room design. The program is composed of six main user-friendly interfaces. The first enables the user to upload their choice of treatment room design and to measure the distances required for shielding calculations. The second interface enables the user to calculate the primary barrier thickness in case of three-dimensional conventional radiotherapy (3D-CRT), intensity modulated radiotherapy (IMRT) and total body irradiation (TBI). The third interface calculates the required secondary barrier thickness due to both scattered and leakage radiation. The fourth and fifth interfaces provide a means to calculate the photon dose equivalent for low and high energy radiation, respectively, in door and maze areas. The sixth interface enables the user to calculate the skyshine radiation for photons and neutrons. The SCR program has been successfully validated, precisely reproducing all of the calculated examples presented in NCRP report no. 151 in a simple and fast manner. Moreover, it easily performed the same calculations for a test design that was also calculated manually, and produced the same results. The program includes a new and important feature that is the ability to calculate required treatment room thickness in case of IMRT and TBI. It is characterised by simplicity, precision, data saving, printing and retrieval, in addition to providing a means for uploading and testing any proposed treatment room shielding design. The SCR program provides comprehensive, simple, fast and accurate room shielding calculations in radiotherapy.

ESMPy and OpenClimateGIS: Python Interfaces for High Performance Grid Remapping and Geospatial Dataset Manipulation

NASA Astrophysics Data System (ADS)

O'Kuinghttons, Ryan; Koziol, Benjamin; Oehmke, Robert; DeLuca, Cecelia; Theurich, Gerhard; Li, Peggy; Jacob, Joseph

2016-04-01

The Earth System Modeling Framework (ESMF) Python interface (ESMPy) supports analysis and visualization in Earth system modeling codes by providing access to a variety of tools for data manipulation. ESMPy started as a Python interface to the ESMF grid remapping package, which provides mature and robust high-performance and scalable grid remapping between 2D and 3D logically rectangular and unstructured grids and sets of unconnected data. ESMPy now also interfaces with OpenClimateGIS (OCGIS), a package that performs subsetting, reformatting, and computational operations on climate datasets. ESMPy exposes a subset of ESMF grid remapping utilities. This includes bilinear, finite element patch recovery, first-order conservative, and nearest neighbor grid remapping methods. There are also options to ignore unmapped destination points, mask points on source and destination grids, and provide grid structure in the polar regions. Grid remapping on the sphere takes place in 3D Cartesian space, so the pole problem is not an issue as it can be with other grid remapping software. Remapping can be done between any combination of 2D and 3D logically rectangular and unstructured grids with overlapping domains. Grid pairs where one side of the regridding is represented by an appropriate set of unconnected data points, as is commonly found with observational data streams, is also supported. There is a developing interoperability layer between ESMPy and OpenClimateGIS (OCGIS). OCGIS is a pure Python, open source package designed for geospatial manipulation, subsetting, and computation on climate datasets stored in local NetCDF files or accessible remotely via the OPeNDAP protocol. Interfacing with OCGIS has brought GIS-like functionality to ESMPy (i.e. subsetting, coordinate transformations) as well as additional file output formats (i.e. CSV, ESRI Shapefile). ESMPy is distinguished by its strong emphasis on open source, community governance, and distributed development. The user base has grown quickly, and the package is integrating with several other software tools and frameworks. These include the Ultrascale Visualization Climate Data Analysis Tools (UV-CDAT), Iris, PyFerret, cfpython, and the Community Surface Dynamics Modeling System (CSDMS). ESMPy minimum requirements include Python 2.6, Numpy 1.6.1 and an ESMF installation. Optional dependencies include NetCDF and OCGIS-related dependencies: GDAL, Shapely, and Fiona. ESMPy is regression tested nightly, and supported on Darwin, Linux and Cray systems with the GNU compiler suite and MPI communications. OCGIS is supported on Linux, and also undergoes nightly regression testing. Both packages are installable from Anaconda channels. Upcoming development plans for ESMPy involve development of a higher order conservative grid remapping method. Future OCGIS development will focus on mesh and location stream interoperability and streamlined access to ESMPy's MPI implementation.

WImpiBLAST: web interface for mpiBLAST to help biologists perform large-scale annotation using high performance computing.

PubMed

Sharma, Parichit; Mantri, Shrikant S

2014-01-01

The function of a newly sequenced gene can be discovered by determining its sequence homology with known proteins. BLAST is the most extensively used sequence analysis program for sequence similarity search in large databases of sequences. With the advent of next generation sequencing technologies it has now become possible to study genes and their expression at a genome-wide scale through RNA-seq and metagenome sequencing experiments. Functional annotation of all the genes is done by sequence similarity search against multiple protein databases. This annotation task is computationally very intensive and can take days to obtain complete results. The program mpiBLAST, an open-source parallelization of BLAST that achieves superlinear speedup, can be used to accelerate large-scale annotation by using supercomputers and high performance computing (HPC) clusters. Although many parallel bioinformatics applications using the Message Passing Interface (MPI) are available in the public domain, researchers are reluctant to use them due to lack of expertise in the Linux command line and relevant programming experience. With these limitations, it becomes difficult for biologists to use mpiBLAST for accelerating annotation. No web interface is available in the open-source domain for mpiBLAST. We have developed WImpiBLAST, a user-friendly open-source web interface for parallel BLAST searches. It is implemented in Struts 1.3 using a Java backbone and runs atop the open-source Apache Tomcat Server. WImpiBLAST supports script creation and job submission features and also provides a robust job management interface for system administrators. It combines script creation and modification features with job monitoring and management through the Torque resource manager on a Linux-based HPC cluster. Use case information highlights the acceleration of annotation analysis achieved by using WImpiBLAST. Here, we describe the WImpiBLAST web interface features and architecture, explain design decisions, describe workflows and provide a detailed analysis.

WImpiBLAST: Web Interface for mpiBLAST to Help Biologists Perform Large-Scale Annotation Using High Performance Computing

PubMed Central

Sharma, Parichit; Mantri, Shrikant S.

2014-01-01

The function of a newly sequenced gene can be discovered by determining its sequence homology with known proteins. BLAST is the most extensively used sequence analysis program for sequence similarity search in large databases of sequences. With the advent of next generation sequencing technologies it has now become possible to study genes and their expression at a genome-wide scale through RNA-seq and metagenome sequencing experiments. Functional annotation of all the genes is done by sequence similarity search against multiple protein databases. This annotation task is computationally very intensive and can take days to obtain complete results. The program mpiBLAST, an open-source parallelization of BLAST that achieves superlinear speedup, can be used to accelerate large-scale annotation by using supercomputers and high performance computing (HPC) clusters. Although many parallel bioinformatics applications using the Message Passing Interface (MPI) are available in the public domain, researchers are reluctant to use them due to lack of expertise in the Linux command line and relevant programming experience. With these limitations, it becomes difficult for biologists to use mpiBLAST for accelerating annotation. No web interface is available in the open-source domain for mpiBLAST. We have developed WImpiBLAST, a user-friendly open-source web interface for parallel BLAST searches. It is implemented in Struts 1.3 using a Java backbone and runs atop the open-source Apache Tomcat Server. WImpiBLAST supports script creation and job submission features and also provides a robust job management interface for system administrators. It combines script creation and modification features with job monitoring and management through the Torque resource manager on a Linux-based HPC cluster. Use case information highlights the acceleration of annotation analysis achieved by using WImpiBLAST. Here, we describe the WImpiBLAST web interface features and architecture, explain design decisions, describe workflows and provide a detailed analysis. PMID:24979410

Hydrodynamic instability of elastic-plastic solid plates at the early stage of acceleration.

PubMed

Piriz, A R; Sun, Y B; Tahir, N A

2015-03-01

A model is presented for the linear Rayleigh-Taylor instability taking place at the early stage of acceleration of an elastic-plastic solid, when the shock wave is still running into the solid and is driven by a time varying pressure on the interface. When the the shock is formed sufficiently close to the interface, this stage is considered to follow a previous initial phase controlled by the Ritchmyer-Meshkov instability that settles new initial conditions. The model reproduces the behavior of the instability observed in former numerical simulation results and provides a relatively simpler physical picture than the currently existing one for this stage of the instability evolution.

Experimental investigation of Rayleigh Taylor instability in elastic-plastic materials

NASA Astrophysics Data System (ADS)

Haley, Aaron Alan; Banerjee, Arindam

2010-11-01

The interface of an elastic-plastic plate accelerated by a fluid of lower density is Rayleigh Taylor (RT) unstable, the growth being mitigated by the mechanical strength of the plate. The instability is observed when metal plates are accelerated by high explosives, in explosive welding, and in volcanic island formation due to the strength of the inner crust. In contrast to the classical case involving Newtonian fluids, RT instability in accelerated solids is not well understood. The difficulties for constructing a theory for the linear growth phase in solids is essentially due to the character of elastic-plastic constitutive properties which has a nonlinear dependence on the magnitude of the rate of deformation. Experimental investigation of the phenomena is difficult due to the exceedingly small time scales (in high energy density experiments) and large measurement uncertainties of material properties. We performed experiments on our Two-Wheel facility to study the linear stage of the incompressible RT instability in elastic-plastic materials (yogurt) whose properties were well characterized. Rotation of the wheels imparted a constant centrifugal acceleration on the material interface that was cut with a small sinusoidal ripple. The controlled initial conditions and precise acceleration amplitudes are levied to investigate transition from elastic to plastic deformation and allow accurate and detailed measurements of flow properties.

QR-decomposition based SENSE reconstruction using parallel architecture.

PubMed

Ullah, Irfan; Nisar, Habab; Raza, Haseeb; Qasim, Malik; Inam, Omair; Omer, Hammad

2018-04-01

Magnetic Resonance Imaging (MRI) is a powerful medical imaging technique that provides essential clinical information about the human body. One major limitation of MRI is its long scan time. Implementation of advance MRI algorithms on a parallel architecture (to exploit inherent parallelism) has a great potential to reduce the scan time. Sensitivity Encoding (SENSE) is a Parallel Magnetic Resonance Imaging (pMRI) algorithm that utilizes receiver coil sensitivities to reconstruct MR images from the acquired under-sampled k-space data. At the heart of SENSE lies inversion of a rectangular encoding matrix. This work presents a novel implementation of GPU based SENSE algorithm, which employs QR decomposition for the inversion of the rectangular encoding matrix. For a fair comparison, the performance of the proposed GPU based SENSE reconstruction is evaluated against single and multicore CPU using openMP. Several experiments against various acceleration factors (AFs) are performed using multichannel (8, 12 and 30) phantom and in-vivo human head and cardiac datasets. Experimental results show that GPU significantly reduces the computation time of SENSE reconstruction as compared to multi-core CPU (approximately 12x speedup) and single-core CPU (approximately 53x speedup) without any degradation in the quality of the reconstructed images. Copyright © 2018 Elsevier Ltd. All rights reserved.

Interfacial instabilities in vibrated fluids

NASA Astrophysics Data System (ADS)

Porter, Jeff; Laverón-Simavilla, Ana; Tinao Perez-Miravete, Ignacio; Fernandez Fraile, Jose Javier

2016-07-01

Vibrations induce a range of different interfacial phenomena in fluid systems depending on the frequency and orientation of the forcing. With gravity, (large) interfaces are approximately flat and there is a qualitative difference between vertical and horizontal forcing. Sufficient vertical forcing produces subharmonic standing waves (Faraday waves) that extend over the whole interface. Horizontal forcing can excite both localized and extended interfacial phenomena. The vibrating solid boundaries act as wavemakers to excite traveling waves (or sloshing modes at low frequencies) but they also drive evanescent bulk modes whose oscillatory pressure gradient can parametrically excite subharmonic surface waves like cross-waves. Depending on the magnitude of the damping and the aspect ratio of the container, these locally generated surfaces waves may interact in the interior resulting in temporal modulation and other complex dynamics. In the case where the interface separates two fluids of different density in, for example, a rectangular container, the mass transfer due to vertical motion near the endwalls requires a counterflow in the interior region that can lead to a Kelvin-Helmholtz type instability and a ``frozen wave" pattern. In microgravity, the dominance of surface forces favors non-flat equilibrium configurations and the distinction between vertical and horizontal applied forcing can be lost. Hysteresis and multiplicity of solutions are more common, especially in non-wetting systems where disconnected (partial) volumes of fluid can be established. Furthermore, the vibrational field contributes a dynamic pressure term that competes with surface tension to select the (time averaged) shape of the surface. These new (quasi-static) surface configurations, known as vibroequilibria, can differ substantially from the hydrostatic state. There is a tendency for the interface to orient perpendicular to the vibrational axis and, in some cases, a bulge or cavity is induced that leads to splitting (fluid separation). We investigate the interaction of these prominent interfacial instabilities in the absence of gravity, concentrating on harmonically vibrated rectangular containers of fluid. We compare vibroequilibria theory with direct numerical simulations and consider the effect of surfaces waves, which can excite sloshing motion of the vibroequilibria. We systematically investigate the saddle-node bifurcation experienced by a symmetric singly connected vibroequilibria solution, for sufficiently deep containers, as forcing is increased. Beyond this instability, the fluid rapidly separates into (at least) two distinct masses. Pronounced hysteresis is associated with this transition, even in the presence of gravity. The interaction of vibroequilibria and frozen waves is investigated in two-fluid systems. Preparations for a parabolic flight experiment on fluids vibrated at high frequencies are discussed.

Two-dimensional radiant energy array computers and computing devices

NASA Technical Reports Server (NTRS)

Schaefer, D. H.; Strong, J. P., III (Inventor)

1976-01-01

Two dimensional digital computers and computer devices operate in parallel on rectangular arrays of digital radiant energy optical signal elements which are arranged in ordered rows and columns. Logic gate devices receive two input arrays and provide an output array having digital states dependent only on the digital states of the signal elements of the two input arrays at corresponding row and column positions. The logic devices include an array of photoconductors responsive to at least one of the input arrays for either selectively accelerating electrons to a phosphor output surface, applying potentials to an electroluminescent output layer, exciting an array of discrete radiant energy sources, or exciting a liquid crystal to influence crystal transparency or reflectivity.

Theoretical calculations of the pressure, forces, and moments at supersonic speeds due to various lateral motions acting on thin isolated vertical tails

NASA Technical Reports Server (NTRS)

Margolis, Kenneth; Bobbitt, Percy J

1956-01-01

Velocity potentials, pressure, distributions, and stability derivatives are derived by use of supersonic linearized theory for families of thin isolated vertical tails performing steady rolling, steady yawing, and constant-lateral-acceleration motions. Vertical-tail families (half-delta and rectangular plan forms) are considered for a broad Mach number range. Also considered are the vertical tail with arbitrary sweepback and taper ratio at Mach numbers for which both the leading edge and trailing edge of the tail are supersonic and the triangular vertical tail with a subsonic leading edge and a supersonic trailing edge. Expressions for potentials, pressures, and stability derivatives are tabulated.

Control Infrastructure for a Pulsed Ion Accelerator

NASA Astrophysics Data System (ADS)

Persaud, A.; Regis, M. J.; Stettler, M. W.; Vytla, V. K.

2016-10-01

We report on updates to the accelerator controls for the Neutralized Drift Compression Experiment II, a pulsed induction-type accelerator for heavy ions. The control infrastructure is built around a LabVIEW interface combined with an Apache Cassandra backend for data archiving. Recent upgrades added the storing and retrieving of device settings into the database, as well as ZeroMQ as a message broker that replaces LabVIEW's shared variables. Converting to ZeroMQ also allows easy access via other programming languages, such as Python.

Control Infrastructure for a Pulsed Ion Accelerator

DOE PAGES

Persaud, A.; Regis, M. J.; Stettler, M. W.; ...

2016-07-27

We report on updates to the accelerator controls for the Neutralized Drift Compression Experiment II, a pulsed induction-type accelerator for heavy ions. The control infrastructure is built around a LabVIEW interface combined with an Apache Cassandra backend for data archiving. Recent upgrades added the storing and retrieving of device settings into the database, as well as ZeroMQ as a message broker that replaces LabVIEW's shared variables. Converting to ZeroMQ also allows easy access via other programming languages, such as Python.

Mini-interfacial fracture toughness as a new validated enamel-bonding effectiveness test.

PubMed

Pongprueksa, Pong; De Munck, Jan; Barreto, Bruno C; Karunratanakul, Kavin; Van Meerbeek, Bart

2016-09-01

Today׳s most commonly applied bonding effectiveness tests are criticized for their high variability and low reliability, the latter in particular with regard to measuring the actual strength of the adhesive interface. in continuation of previous research conducted at dentin, we hereby aimed to validate the novel mini-interfacial fracture toughness (mini-iFT) test on its applicability to assess bonding effectiveness of contemporary adhesives when bonded to enamel. The 3-step etch&rinse (E&R) adhesive OptiBond FL (Kerr), the 2-step self-etch (SE) adhesive Clearfil SE Bond (Kuraray Noritake) and the two multi-mode adhesives Clearfil S(3) Bond Plus (Kuraray Noritake) and Scotchbond Universal (3M ESPE), both used following a 2-step E&R and 1-step SE mode, were applied to clinically relevant, flattened enamel surfaces. A composite (Filtek Z100; 3M ESPE) build-up was made in layers. After 1-week water storage at 37°C, all specimens were sectioned perpendicular to the interface to obtain rectangular sticks. A mini-iFT notch was prepared at the adhesive-enamel interface using a thin diamond blade under water cooling. Finally, the specimens were loaded in a 4-point bending test until failure. the mini-iFT onto human enamel was significantly higher for the adhesives applied in E&R mode versus those applied in SE mode. The lowest mini-iFT was found for the adhesives applied following a 1-step SE approach. SEM fracture analysis revealed that all fractures originated at the adhesive-enamel interface and that the induced crack propagated preferentially along this interface. mini-iFT appeared a valid alternative method to assess the mechanical properties of adhesive-enamel interfaces. Copyright © 2016 Elsevier Ltd. All rights reserved.

Multiple capillary biochemical analyzer

DOEpatents

Dovichi, N.J.; Zhang, J.Z.

1995-08-08

A multiple capillary analyzer allows detection of light from multiple capillaries with a reduced number of interfaces through which light must pass in detecting light emitted from a sample being analyzed, using a modified sheath flow cuvette. A linear or rectangular array of capillaries is introduced into a rectangular flow chamber. Sheath fluid draws individual sample streams through the cuvette. The capillaries are closely and evenly spaced and held by a transparent retainer in a fixed position in relation to an optical detection system. Collimated sample excitation radiation is applied simultaneously across the ends of the capillaries in the retainer. Light emitted from the excited sample is detected by the optical detection system. The retainer is provided by a transparent chamber having inward slanting end walls. The capillaries are wedged into the chamber. One sideways dimension of the chamber is equal to the diameter of the capillaries and one end to end dimension varies from, at the top of the chamber, slightly greater than the sum of the diameters of the capillaries to, at the bottom of the chamber, slightly smaller than the sum of the diameters of the capillaries. The optical system utilizes optic fibers to deliver light to individual photodetectors, one for each capillary tube. A filter or wavelength division demultiplexer may be used for isolating fluorescence at particular bands. 21 figs.

Multiple capillary biochemical analyzer

DOEpatents

Dovichi, Norman J.; Zhang, Jian Z.

1995-01-01

A multiple capillary analyzer allows detection of light from multiple capillaries with a reduced number of interfaces through which light must pass in detecting light emitted from a sample being analyzed, using a modified sheath flow cuvette. A linear or rectangular array of capillaries is introduced into a rectangular flow chamber. Sheath fluid draws individual sample streams through the cuvette. The capillaries are closely and evenly spaced and held by a transparent retainer in a fixed position in relation to an optical detection system. Collimated sample excitation radiation is applied simultaneously across the ends of the capillaries in the retainer. Light emitted from the excited sample is detected by the optical detection system. The retainer is provided by a transparent chamber having inward slanting end walls. The capillaries are wedged into the chamber. One sideways dimension of the chamber is equal to the diameter of the capillaries and one end to end dimension varies from, at the top of the chamber, slightly greater than the sum of the diameters of the capillaries to, at the bottom of the chamber, slightly smaller than the sum of the diameters of the capillaries. The optical system utilizes optic fibres to deliver light to individual photodetectors, one for each capillary tube. A filter or wavelength division demultiplexer may be used for isolating fluorescence at particular bands.

Micron-scale pattern formation in prestressed polygonal films

NASA Astrophysics Data System (ADS)

Annabattula, R. K.; Onck, P. R.

2011-02-01

In this paper we explore the spontaneous formation of micropatterns in thin prestressed polygonal films using finite element simulations. We study films with different size, thickness, and shape, including square, rectangular, pentagonal, and hexagonal films. Patterns form when the films release the internal eigenstrain by buckling-up, after which the films bond-back to the substrate. After an initial symmetric evolution of the buckling profile, the symmetry of the deflection pattern breaks when the wavelength of wriggles near the film edges decreases. During bond back the deflection morphology converges to a fourfold, fivefold, and sixfold ridging pattern for the square, pentagonal and hexagonal films, respectively, showing a close resemblance with experimental film systems of similar size and shape. Rectangular films of large length to width ratio go through a transition in buckling shapes from the initial Euler mode, through the varicose mode into the antisymmetric telephone-cord mode. For all the film shapes, the ratio of the film height to the effective film width scales with the square root of eigenstrain and is independent of thickness. The bond-back mechanism determines the final wrinkle morphology and is governed by the eigenstrain value at the end of the buckling-up stage and the dimensionless parameter (Γ /EWeq)(Weq/t)3, relating the interface energy to the strain energy in the film.

77 FR 1915 - Light-Walled Rectangular Pipe and Tube From Mexico; Final Results of Antidumping Duty...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-01-12

... DEPARTMENT OF COMMERCE International Trade Administration [A-201-836] Light-Walled Rectangular... preliminary results of the administrative review of the antidumping duty order on light-walled rectangular... period of review (POR) from August 1, 2009, through July 31, 2010. \\1\\ See Light-Walled Rectangular Pipe...

75 FR 55559 - Light-Walled Rectangular Pipe and Tube From Mexico: Preliminary Results of Antidumping Duty...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-09-13

... DEPARTMENT OF COMMERCE International Trade Administration [A-201-836] Light-Walled Rectangular... administrative review of the antidumping duty order on light-walled rectangular pipe and tube (LWRPT) from Mexico... Light-Walled Rectangular Pipe and Tube from Mexico, the People's Republic of China, and the Republic of...

Eigenvalues of Rectangular Waveguide Using FEM With Hybrid Elements

NASA Technical Reports Server (NTRS)

Deshpande, Manohar D.; Hall, John M.

2002-01-01

A finite element analysis using hybrid triangular-rectangular elements is developed to estimate eigenvalues of a rectangular waveguide. Use of rectangular vector-edge finite elements in the vicinity of the PEC boundary and triangular elements in the interior region more accurately models the physical nature of the electromagnetic field, and consequently quicken the convergence.

Force Limited Vibration Testing

NASA Technical Reports Server (NTRS)

Scharton, Terry; Chang, Kurng Y.

2005-01-01

This slide presentation reviews the concept and applications of Force Limited Vibration Testing. The goal of vibration testing of aerospace hardware is to identify problems that would result in flight failures. The commonly used aerospace vibration tests uses artificially high shaker forces and responses at the resonance frequencies of the test item. It has become common to limit the acceleration responses in the test to those predicted for the flight. This requires an analysis of the acceleration response, and requires placing accelerometers on the test item. With the advent of piezoelectric gages it has become possible to improve vibration testing. The basic equations have are reviewed. Force limits are analogous and complementary to the acceleration specifications used in conventional vibration testing. Just as the acceleration specification is the frequency spectrum envelope of the in-flight acceleration at the interface between the test item and flight mounting structure, the force limit is the envelope of the in-flight force at the interface . In force limited vibration tests, both the acceleration and force specifications are needed, and the force specification is generally based on and proportional to the acceleration specification. Therefore, force limiting does not compensate for errors in the development of the acceleration specification, e.g., too much conservatism or the lack thereof. These errors will carry over into the force specification. Since in-flight vibratory force data are scarce, force limits are often derived from coupled system analyses and impedance information obtained from measurements or finite element models (FEM). Fortunately, data on the interface forces between systems and components are now available from system acoustic and vibration tests of development test models and from a few flight experiments. Semi-empirical methods of predicting force limits are currently being developed on the basis of the limited flight and system test data. A simple two degree of freedom system is shown and the governing equations for basic force limiting results for this system are reviewed. The design and results of the shuttle vibration forces (SVF) experiments are reviewed. The Advanced Composition Explorer (ACE) also was used to validate force limiting. Test instrumentation and supporting equipment are reviewed including piezo-electric force transducers, signal processing and conditioning systems, test fixtures, and vibration controller systems. Several examples of force limited vibration testing are presented with some results.

Transfer Learning to Accelerate Interface Structure Searches

NASA Astrophysics Data System (ADS)

Oda, Hiromi; Kiyohara, Shin; Tsuda, Koji; Mizoguchi, Teruyasu

2017-12-01

Interfaces have atomic structures that are significantly different from those in the bulk, and play crucial roles in material properties. The central structures at the interfaces that provide properties have been extensively investigated. However, determination of even one interface structure requires searching for the stable configuration among many thousands of candidates. Here, a powerful combination of machine learning techniques based on kriging and transfer learning (TL) is proposed as a method for unveiling the interface structures. Using the kriging+TL method, thirty-three grain boundaries were systematically determined from 1,650,660 candidates in only 462 calculations, representing an increase in efficiency over conventional all-candidate calculation methods, by a factor of approximately 3,600.

Development of a Nondestructive Evaluation Technique for Degraded Thermal Barrier Coatings Using Microwave

NASA Astrophysics Data System (ADS)

Sayar, M.; Ogawa, K.; Shoji, T.

2008-02-01

Thermal barrier coatings have been widely used in gas turbine engines in order to protect substrate metal alloy against high temperature and to enhance turbine efficiency. Currently, there are no reliable nondestructive techniques available to monitor TBC integrity over lifetime of the coating. Hence, to detect top coating (TC) and TGO thicknesses, a microwave nondestructive technique that utilizes a rectangular waveguide was developed. The phase of the reflection coefficient at the interface of TC and waveguide varies for different TGO and TC thicknesses. Therefore, measuring the phase of the reflection coefficient enables us to accurately calculate these thicknesses. Finally, a theoretical analysis was used to evaluate the reliability of the experimental results.

RF window assembly comprising a ceramic disk disposed within a cylindrical waveguide which is connected to rectangular waveguides through elliptical joints

DOEpatents

Tantawi, Sami G.; Dolgashev, Valery A.; Yeremian, Anahid D.

2016-03-15

A high-power microwave RF window is provided that includes a cylindrical waveguide, where the cylindrical waveguide includes a ceramic disk concentrically housed in a central region of the cylindrical waveguide, a first rectangular waveguide, where the first rectangular waveguide is connected by a first elliptical joint to a proximal end of the cylindrical waveguide, and a second rectangular waveguide, where the second rectangular waveguide is connected by a second elliptical joint to a distal end of the cylindrical waveguide.

Effect of Baffle on Gravity-Gradient-Excited Slosh Waves and Spacecraft Moment and Angular-Momentum Fluctuations in Microgravity

NASA Technical Reports Server (NTRS)

Hung, R. J.; Lee, C. C.

1995-01-01

The dynamical behavior of fluids affected by the asymmetric gravity gradient acceleration has been investigated. In particular, the effects of surface tension on partially filled rotating fluids applicable to a full-scale Gravity Probe-B Spacecraft dewar tank with and without baffles are studied. Results of slosh wave excitation along the liquid-vapor interface induced by gravity gradient acceleration indicate that the gravity gradient acceleration is equivalent to the combined effect of a twisting force and a torsional moment acting on the spacecraft. The results are clearly seen from one-up one-down and one-down one-up oscillations in the cross-section profiles of two bubbles in the vertical (r, z)-plane of the rotating dewar, and from the eccentric contour of the bubble rotating around the axis of the dewar in a horizontal (r, theta)-plane. As the viscous force, between liquid and solid interface, greatly contributes to the damping of slosh wave excitation, a rotating dewar with baffles provides more areas of liquid-solid interface than that of a rotating dewar without baffles. Results show that the damping effect provided by the baffles reduces the amplitude of slosh wave excitation and lowers the degree of asymmetry in liquid-vapor distribution. Fluctuations of angular momentum and fluid moment caused by the slosh wave excited by gravity gradient acceleration with and without baffle boards are also investigated. It is also shown that the damping effect provided by the baffles greatly reduces the amplitudes of angular momentum and fluid moment fluctuations.

Dynamics of immiscible liquids in a rotating horizontal cylinder

NASA Astrophysics Data System (ADS)

Kozlov, N. V.; Kozlova, A. N.; Shuvalova, D. A.

2016-11-01

The dynamics of an interface between two immiscible liquids of different density is studied experimentally in a horizontal cylinder at rotation in the gravity field. Two liquids entirely fill the cavity volume, and the container is rotated sufficiently fast so that the liquids are centrifuged. The light liquid forms a column extended along the rotation axis, and the heavy liquid forms an annular layer. Under the action of gravity, the light liquid column displaces steadily along the radius, downwards in the laboratory frame. As a result, fluid oscillations in the cavity frame are excited at the interface, which lead to the generation of a steady streaming, and the fluid comes into a slow lagging rotation with respect to the cylinder walls. The dynamics of the studied system is determined by the ratio of the gravity acceleration to the centrifugal one—the dimensionless acceleration. In experiments, the system is controlled by the means of variation of the rotation rate, i.e., of the centrifugal force. At a critical value of the dimensionless acceleration the circular interface looses stability, and an azimuthal wave is excited. This leads to a strong increase in the interface differential velocity. A theoretical analysis is done based on the theory of centrifugal waves and a frequency equation is obtained. Experimental results are in good agreement with the theory at the condition of small wave amplitudes. Mechanism of steady streaming generation is analyzed based on previously published theoretical results obtained for the limiting case when the light phase is a solid cylinder. A qualitative agreement is found.

Diaphragm opening effects on shock wave formation and acceleration in a rectangular cross section channel

NASA Astrophysics Data System (ADS)

Pakdaman, S. A.; Garcia, M.; Teh, E.; Lincoln, D.; Trivedi, M.; Alves, M.; Johansen, C.

2016-11-01

Shock wave formation and acceleration in a high-aspect ratio cross section shock tube were studied experimentally and numerically. The relative importance of geometric effects and diaphragm opening time on shock formation are assessed. The diaphragm opening time was controlled through the use of slit-type (fast opening time) and petal-type (slow opening time) diaphragms. A novel method of fabricating the petal-type diaphragms, which results in a consistent burst pressure and symmetric opening without fragmentation, is presented. High-speed schlieren photography was used to visualize the unsteady propagation of the lead shock wave and trailing gas dynamic structures. Surface-mounted pressure sensors were used to capture the spatial and temporal development of the pressure field. Unsteady Reynolds-Averaged Navier-Stokes simulation predictions using the shear-stress-transport turbulence model are compared to the experimental data. Simulation results are used to explain the presence of high-frequency pressure oscillations observed experimentally in the driver section as well as the cause of the initial acceleration and subsequent rapid decay of shock velocity measured along the top and bottom channel surfaces. A one-dimensional theoretical model predicting the effect of the finite opening time of the diaphragm on the rate of driver depressurization and shock acceleration is proposed. The model removes the large amount of empiricism that accompanies existing models published in the literature. Model accuracy is assessed through comparisons with experiments and simulations. Limitations of and potential improvements in the model are discussed.

The ASTRO-1 preliminary design review coupled load analysis

NASA Technical Reports Server (NTRS)

Mcghee, D. S.

1984-01-01

Results of the ASTRO-1 preliminary design review coupled loads analysis are presented. The M6.0Y Generic Shuttle mathematical models were used. Internal accelerations, interface forces, relative displacements, and net e.g., accelerations were recovered for two ASTRO-1 payloads in a tandem configuration. Twenty-seven load cases were computed and summarized. Load exceedences were found and recommendations made.

Biomimetic approaches with smart interfaces for bone regeneration.

PubMed

Sailaja, G S; Ramesh, P; Vellappally, Sajith; Anil, Sukumaran; Varma, H K

2016-11-05

A 'smart tissue interface' is a host tissue-biomaterial interface capable of triggering favourable biochemical events inspired by stimuli responsive mechanisms. In other words, biomaterial surface is instrumental in dictating the interface functionality. This review aims to investigate the fundamental and favourable requirements of a 'smart tissue interface' that can positively influence the degree of healing and promote bone tissue regeneration. A biomaterial surface when interacts synergistically with the dynamic extracellular matrix, the healing process become accelerated through development of a smart interface. The interface functionality relies equally on bound functional groups and conjugated molecules belonging to the biomaterial and the biological milieu it interacts with. The essential conditions for such a special biomimetic environment are discussed. We highlight the impending prospects of smart interfaces and trying to relate the design approaches as well as critical factors that determine species-specific functionality with special reference to bone tissue regeneration.

Accelerated nucleation of the 2014 Iquique, Chile Mw 8.2 Earthquake.

PubMed

Kato, Aitaro; Fukuda, Jun'ichi; Kumazawa, Takao; Nakagawa, Shigeki

2016-04-25

The earthquake nucleation process has been vigorously investigated based on geophysical observations, laboratory experiments, and theoretical studies; however, a general consensus has yet to be achieved. Here, we studied nucleation process for the 2014 Iquique, Chile Mw 8.2 megathrust earthquake located within the current North Chile seismic gap, by analyzing a long-term earthquake catalog constructed from a cross-correlation detector using continuous seismic data. Accelerations in seismicity, the amount of aseismic slip inferred from repeating earthquakes, and the background seismicity, accompanied by an increasing frequency of earthquake migrations, started around 270 days before the mainshock at locations up-dip of the largest coseismic slip patch. These signals indicate that repetitive sequences of fast and slow slip took place on the plate interface at a transition zone between fully locked and creeping portions. We interpret that these different sliding modes interacted with each other and promoted accelerated unlocking of the plate interface during the nucleation phase.

Accelerated nucleation of the 2014 Iquique, Chile Mw 8.2 Earthquake

NASA Astrophysics Data System (ADS)

Kato, Aitaro; Fukuda, Jun'Ichi; Kumazawa, Takao; Nakagawa, Shigeki

2016-04-01

The earthquake nucleation process has been vigorously investigated based on geophysical observations, laboratory experiments, and theoretical studies; however, a general consensus has yet to be achieved. Here, we studied nucleation process for the 2014 Iquique, Chile Mw 8.2 megathrust earthquake located within the current North Chile seismic gap, by analyzing a long-term earthquake catalog constructed from a cross-correlation detector using continuous seismic data. Accelerations in seismicity, the amount of aseismic slip inferred from repeating earthquakes, and the background seismicity, accompanied by an increasing frequency of earthquake migrations, started around 270 days before the mainshock at locations up-dip of the largest coseismic slip patch. These signals indicate that repetitive sequences of fast and slow slip took place on the plate interface at a transition zone between fully locked and creeping portions. We interpret that these different sliding modes interacted with each other and promoted accelerated unlocking of the plate interface during the nucleation phase.

Accelerated nucleation of the 2014 Iquique, Chile Mw 8.2 Earthquake

PubMed Central

Kato, Aitaro; Fukuda, Jun’ichi; Kumazawa, Takao; Nakagawa, Shigeki

2016-01-01

The earthquake nucleation process has been vigorously investigated based on geophysical observations, laboratory experiments, and theoretical studies; however, a general consensus has yet to be achieved. Here, we studied nucleation process for the 2014 Iquique, Chile Mw 8.2 megathrust earthquake located within the current North Chile seismic gap, by analyzing a long-term earthquake catalog constructed from a cross-correlation detector using continuous seismic data. Accelerations in seismicity, the amount of aseismic slip inferred from repeating earthquakes, and the background seismicity, accompanied by an increasing frequency of earthquake migrations, started around 270 days before the mainshock at locations up-dip of the largest coseismic slip patch. These signals indicate that repetitive sequences of fast and slow slip took place on the plate interface at a transition zone between fully locked and creeping portions. We interpret that these different sliding modes interacted with each other and promoted accelerated unlocking of the plate interface during the nucleation phase. PMID:27109362

Passage of the discharge current through the plasma-electrode interface in the electromagnetic rail accelerator channel

NASA Astrophysics Data System (ADS)

Zhukov, B. G.; Reznikov, B. I.; Kurakin, R. O.; Ponyaev, S. A.; Bobashev, S. V.

2016-11-01

We investigate the phenomena that accompany the acceleration of a free plasma piston (without a striker) in the electromagnetic rail accelerator channel filled with different gases (argon, helium). An intense glow appears in the shock-compressed layer (SCL) in the case of strong shock waves that produce a high electron concentration ( 1017-1018 cm-3) behind the front. We have proposed that explosive electron emission (EEE) ensures the high-intensity emission of electrons, the passage of a part of the discharge current through the SCL, and the glow of the SCL. The velocity of a shock wave for which the strong electric field in the Debye layer at the cathode causes EEE from its surface and the passage of the current in the SCL has been determined. It has been concluded that, for high velocities of the plasma, the EEE is a universal mechanism that ensure the passage of a strong current through the interface between the cold electrode and the plasma.

PIV measurements of the single-mode Richtmyer-Meshkov instability.

NASA Astrophysics Data System (ADS)

Aure, Roger; Jacobs, Jeff

2006-11-01

Experiments will be presented where a system of two gases of different densities (A = 0.66) is impulsively accelerated to produce Richtmeyer-Meshkov (RM) instability. An interface is created by filling the driven section of a 9.8 meter long vertical shock tube with opposing gas flows of air and Sulfur Hexafluoride (SF6). The interface forms in the top of the Plexiglas test section where the two gasses meet and exit through two slots. The gases are seeded with 0.3 μm polystyrene Latex spheres. An initial 2-D perturbation in the form of a standing wave of sinusoidal shape is created by oscillating the driven section in the horizontal direction. The interface between the gases is impulsively accelerated by an M=1.2 shockwave. One image per experiment is captured with a cooled CCD camera. The image is doubly exposed by a double-pulsed ND-YAG laser and is analyzed using autocorrelation PIV techniques. Results will be presented showing velocity and vorticity distribution in the RM flow.

Inviscid linear stability analysis of two fluid columns of different densities subject to gravity

NASA Astrophysics Data System (ADS)

Prathama, Aditya; Pantano, Carlos

2017-11-01

We investigate the inviscid linear stability of vertical interface between two fluid columns of different densities under the influence of gravity. In this flow arrangement, the two free streams are continuously accelerating, in contrast to the canonical Kelvin-Helmholtz or Rayleigh-Taylor instabilities whose base flows are stationary (or weakly time dependent). In these classical cases, the temporal evolution of the interface can be expressed as Fourier or Laplace solutions in time. This is not possible in our case; instead, we employ the initial value problem method to solve the equations analytically. The results, expressed in terms of the well-known parabolic cylinder function, indicate that the instability grows as the exponential of a quadratic function of time. The analysis shows that in this accelerating Kelvin-Helmholtz configuration, the interface is unconditionally unstable at all wave modes, despite the presence of surface tension. Department of Energy, National Nuclear Security Administration (Award No. DE-NA0002382) and the California Institute of Technology.

Numerical modeling of crystal growth in Bridgman device

NASA Astrophysics Data System (ADS)

Vompe, Dmitry Aleksandrovich

1997-12-01

The standard model for the growth of a crystal from a pure substance or diluted binary mixture contains transport equations for heat and phase change conditions at the solidification front. A numerical method is constructed for simulations of crystal growth in a vertical Bridgman device. The method is based on a boundary fitting technique in which melted and solidified regions are mapped onto a fixed rectangular logical domain. The Alternating Directions scheme (ADI) is used to treat the diffusive terms implicitly, with explicit methods are used for the remaining terms in the mapped temperature equations with variable coefficients. The nonlinear equation for the solid/liquid interface motion is solved by the modified Euler technique. Results obtained from the calculations have been used to study the influence of various boundary conditions imposed on the sidewalls and the top and bottom of the ampoule. Conditions are identified that lead to a steadily growing crystal and results are compared with an asymptotic one- dimensional model. Criteria based on ampoule length and boundary conditions being derived and compared with a previously developed one-dimensional model. Various cases have been considered to determine conditions for maintaining a nearly flat interface. It was found that the interface amplitude can be decreased by a factor of 100 (even 1,000) by optimizing temperature boundary conditions.

Numerical study of the effects of icing on viscous flow over wings

NASA Technical Reports Server (NTRS)

Sankar, L. N.

1994-01-01

An improved hybrid method for computing unsteady compressible viscous flows is presented. This method divides the computational domain into two zones. In the outer zone, the unsteady full-potential equation (FPE) is solved. In the inner zone, the Navier-Stokes equations are solved using a diagonal form of an alternating-direction implicit (ADI) approximate factorization procedure. The two zones are tightly coupled so that steady and unsteady flows may be efficiently solved. Characteristic-based viscous/inviscid interface boundary conditions are employed to avoid spurious reflections at that interface. The resulting CPU times are less than 60 percent of that required for a full-blown Navier-Stokes analysis for steady flow applications and about 60 percent of the Navier-Stokes CPU times for unsteady flows in non-vector processing machines. Applications of the method are presented for a rectangular NACA 0012 wing in low subsonic steady flow at moderate and high angles of attack, and for an F-5 wing in steady and unsteady subsonic and transonic flows. Steady surface pressures are in very good agreement with experimental data and are essentially identical to Navier-Stokes predictions. Density contours show that shocks cross the viscous/inviscid interface smoothly, so that the accuracy of full Navier-Stokes equations can be retained with a significant savings in computational time.

Interface and Electronic Characterization of Thin Epitaxial Co3O4 Films

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

Vaz, C.A.; Zhu, Y.; Wang, H.-Q.

2009-01-15

The interface and electronic structure of thin ({approx} 20-74 nm) Co{sub 3}O{sub 4}(1 1 0) epitaxial films grown by oxygen-assisted molecular beam epitaxy on MgAl{sub 2}O{sub 4}(1 1 0) single crystal substrates have been investigated by means of real and reciprocal space techniques. As-grown film surfaces are found to be relatively disordered and exhibit an oblique low energy electron diffraction (LEED) pattern associated with the O-rich CoO{sub 2} bulk termination of the (1 1 0) surface. Interface and bulk film structure are found to improve significantly with post-growth annealing at 820 K in air and display sharp rectangular LEED patterns,more » suggesting a surface stoichiometry of the alternative Co{sub 2}O{sub 2} bulk termination of the (1 1 0) surface. Non-contact atomic force microscopy demonstrates the presence of wide terraces separated by atomic steps in the annealed films that are not present in the as-grown structures; the step height of {approx}2.7 {angstrom} corresponds to two atomic layers and confirms a single termination for the annealed films, consistent with the LEED results. A model of the (1 x 1) surfaces that allows for compensation of the polar surfaces is presented.« less

Experimental analysis of the flow near the boundary of random porous media

NASA Astrophysics Data System (ADS)

Wu, Zhenxing; Mirbod, Parisa

2018-04-01

The aim of this work is to experimentally examine flow over and near random porous media. Different porous materials were chosen to achieve porosity ranging from 0.95 to 0.99. In this study, we report the detailed velocity measurements of the flow over and near random porous material inside a rectangular duct using a planar particle image velocimetry (PIV) technique. By controlling the flow rate, two different Reynolds numbers were achieved. We determined the slip velocity at the interface between the porous media and free flow. Values of the slip velocity normalized either by the maximum flow velocity or by the shear rate at the interface and the screening distance K1/2 were found to depend on porosity. It was also shown that the depth of penetration inside the porous material was larger than the screening length using Brinkman's prediction. Moreover, we examined a model for the laminar coupled flow over and inside porous media and analyzed the permeability of a random porous medium. This study provided detailed analysis of flow over and at the interface of various specific random porous media using the PIV technique. This analysis has the potential to serve as a first step toward using random porous media as a new passive technique to control the flow over smooth surfaces.

On the Structure of the Mixing Zone at an Unstable Contact Boundary

NASA Astrophysics Data System (ADS)

Meshkov, E. E.

2018-01-01

The interface between two media of different densities (contact boundary) moving with an acceleration directed from the less dense medium to the more dense one is unstable (Rayleigh-Taylor instability) [1, 2]. The initial perturbations of the interface grow indefinitely and, as a result, a medium mixing zone growing with time is formed at the interface. The structure of such a mixing zone at gas-gas and gas-liquid interfaces is discussed on the basis of laboratory experiments on shock tubes of various types. It is concluded that the regions of turbulent and laminar flows are combined in the mixing zone.

Formation of intermetallics at the interface of explosively welded Ni-Al multilayered composites during annealing

NASA Astrophysics Data System (ADS)

Ogneva, T. S.; Lazurenko, D. V.; Bataev, I. A.; Mali, V. I.; Esikov, M. A.; Bataev, A. A.

2016-04-01

The Ni-Al multilayer composite was fabricated using explosive welding. The zones of mixing of Ni and Al are observed at the composite interfaces after the welding. The composition of these zones is inhomogeneous. Continuous homogeneous intermetallic layers are formed at the interface after heat treatment at 620 °C during 5 h These intermetallic layers consist of NiAl3 and Ni2Al3 phases. The presence of mixed zones significantly accelerates the growth rate of intermetallic phases at the initial stages of heating.

Pulsed particle beam vacuum-to-air interface

DOEpatents

Cruz, G.E.; Edwards, W.F.

1987-06-18

A vacuum-to-air interface is provided for a high-powered, pulsed particle beam accelerator. The interface comprises a pneumatic high speed gate valve, from which extends a vacuum-tight duct, that terminates in an aperture. Means are provided for periodically advancing a foil strip across the aperture at the repetition rate of the particle pulses. A pneumatically operated hollow sealing band urges foil strip, when stationary, against and into the aperture. Gas pressure means periodically lift off and separate foil strip from aperture, so that it may be readily advanced. 5 figs.

Simultaneous Interferometric Measurement of Corrosive or Demineralizing Bacteria and Their Mineral Interfaces

DTIC Science & Technology

2009-03-01

surface profile measurements of several bacterial species involved in micro- bially influenced corrosion and their solid-surface interfaces by using... influenced corrosion, involving the release of chemicals or the deposition of electrochemically active miner- als that accelerate surface...single cell, consistent with VSI height measurement variability (data not shown). To expand the range of VSI data acquisition to conditions that were

Acceleration of Semiempirical QM/MM Methods through Message Passage Interface (MPI), Hybrid MPI/Open Multiprocessing, and Self-Consistent Field Accelerator Implementations.

PubMed

Ojeda-May, Pedro; Nam, Kwangho

2017-08-08

The strategy and implementation of scalable and efficient semiempirical (SE) QM/MM methods in CHARMM are described. The serial version of the code was first profiled to identify routines that required parallelization. Afterward, the code was parallelized and accelerated with three approaches. The first approach was the parallelization of the entire QM/MM routines, including the Fock matrix diagonalization routines, using the CHARMM message passage interface (MPI) machinery. In the second approach, two different self-consistent field (SCF) energy convergence accelerators were implemented using density and Fock matrices as targets for their extrapolations in the SCF procedure. In the third approach, the entire QM/MM and MM energy routines were accelerated by implementing the hybrid MPI/open multiprocessing (OpenMP) model in which both the task- and loop-level parallelization strategies were adopted to balance loads between different OpenMP threads. The present implementation was tested on two solvated enzyme systems (including <100 QM atoms) and an S N 2 symmetric reaction in water. The MPI version exceeded existing SE QM methods in CHARMM, which include the SCC-DFTB and SQUANTUM methods, by at least 4-fold. The use of SCF convergence accelerators further accelerated the code by ∼12-35% depending on the size of the QM region and the number of CPU cores used. Although the MPI version displayed good scalability, the performance was diminished for large numbers of MPI processes due to the overhead associated with MPI communications between nodes. This issue was partially overcome by the hybrid MPI/OpenMP approach which displayed a better scalability for a larger number of CPU cores (up to 64 CPUs in the tested systems).

Numerical Calculations of Short-Range Wakefields of Collimators

NASA Astrophysics Data System (ADS)

Ng, C. K.

2001-12-01

The performance of future linear colliders are limited by the effect of short-range collimator wakefields on the beam. The beam quality is sensitive to the positioning of collimators at the end of the linac. The determination of collimator wakefields has been difficult, largely because of the scarcity of measurement data, and of the limitation of applicability of analytical results to realistic structures. In this paper, numerical methods using codes such as MAFIA are used to determine a series of tapered collimators with rectangular apertures that have been built for studies at SLAC (Stanford Linear Accelerator Center). We will study the dependences of the wakefield on the collimator taper angle, the collimator gap as well as the bunch length. Calculations are also compared with measurements.

Enhanced Circular Dichroism of Gold Bilayered Slit Arrays Embedded with Rectangular Holes.

PubMed

Zhang, Hao; Wang, Yongkai; Luo, Lina; Wang, Haiqing; Zhang, Zhongyue

2017-01-01

Gold bilayered slit arrays with rectangular holes embedded into the metal surface are designed to enhance the circular dichroism (CD) effect of gold bilayered slit arrays. The rectangular holes in these arrays block electric currents and generate localized surface plasmons around these holes, thereby strengthening the CD effect. The CD enhancement factor depends strongly on the rotational angle and the structural parameters of the rectangular holes; this factor can be enhanced further by drilling two additional rectangular holes into the metal surfaces of the arrays. These results help facilitate the design of chiral structures to produce a strong CD effect and large electric fields.

Propagation of THz pulses in rectangular subwavelength dielectric waveguides

NASA Astrophysics Data System (ADS)

Lu, Yao; Wu, Qiang; Zhang, Qi; Wang, Ride; Zhao, Wenjuan; Zhang, Deng; Pan, Chongpei; Qi, Jiwei; Xu, Jingjun

2018-06-01

Rectangular subwavelength waveguides are necessary for the development of micro/nanophotonic devices and on-chip platforms. Using a time-resolved imaging system, we studied the transient properties and the propagation modes of THz pulses in rectangular subwavelength dielectric waveguides. The dynamic process of THz pulses was systematically recorded to a movie. In addition, an anomalous group velocity dispersion was demonstrated in rectangular subwavelength waveguides. By using the effective index method, we theoretically calculated the modes in rectangular subwavelength waveguides, which agree well with the experiments and simulations. This work provides the opportunity to improve the analysis and design of the integrated platforms and photonic devices.

Testing of felt-ceramic materials for combustor applications

NASA Technical Reports Server (NTRS)

Venkat, R. S.; Roffe, G.

1983-01-01

The feasibility of using composite felt ceramic materials as combustor liners was experimentally studied. The material consists of a porous felt pad sandwiched between a layer of ceramic and one of solid metal. Flat, rectangular test panels, which encompassed several design variations of the basic composite material, were tested, two at a time, in a premixed gas turbine combustor as sections of the combustor wall. Tests were conducted at combustor inlet conditions of 0.5 MPa and 533 K with a reference velocity of 25 m/s. The panels were subjected to a hot gas temperature of 2170 K with 1% of the total airflow used to film cool the ceramic surface of the test panel. In general, thin ceramic layers yield low ceramic stress levels with high felt ceramic interface temperatures. On the other hand, thick ceramic layers result in low felt ceramic interface temperatures but high ceramic stress levels. Extensive thermal cycling appears to cause material degradation, but for a limited number of cycles, the survivability of felt ceramic materials, even under extremely severe combustor operating conditions, was conclusively demonstrated.

Interfacial free energy of the NaCl crystal-melt interface from capillary wave fluctuations.

PubMed

Benet, Jorge; MacDowell, Luis G; Sanz, Eduardo

2015-04-07

In this work we study, by means of molecular dynamics simulations, the solid-liquid interface of NaCl under coexistence conditions. By analysing capillary waves, we obtain the stiffness for different orientations of the solid and calculate the interfacial free energy by expanding the dependency of the interfacial free energy with the solid orientation in terms of cubic harmonics. We obtain an average value for the solid-fluid interfacial free energy of 89 ± 6 mN m(-1) that is consistent with previous results based on the measure of nucleation free energy barriers [Valeriani et al., J. Chem. Phys. 122, 194501 (2005)]. We analyse the influence of the simulation setup on interfacial properties and find that facets prepared as an elongated rectangular stripe give the same results as those prepared as squares for all cases but the 111 face. For some crystal orientations, we observe at small wave-vectors a behaviour not consistent with capillary wave theory and show that this behavior does not depend on the simulation setup.

Effect of inclusions on heterogeneous crack nucleation in nanocomposites

NASA Astrophysics Data System (ADS)

Gutkin, M. Yu.; Ovid'Ko, I. A.; Skiba, N. V.

2007-02-01

A two-dimensional theoretical model is proposed for the heterogeneous nucleation of a grain-boundary nanocrack in a nanocomposite consisting of a nanocrystalline matrix and nanoinclusions whose elastic moduli are identical to those of the matrix. The inclusions have the form of rods with a rectangular cross section and undergo dilatation eigenstrain induced by the differences in the lattice parameters and thermal expansion coefficients of the matrix and inclusions. In terms of the model, a mode-I-II nanocrack nucleates at the negative disclination of a biaxial dipole consisting of wedge grain-boundary (or junction) disclinations; then, the nanocrack opens along a grain boundary and reaches an inclusion boundary. Depending on the relative positions and orientations of the initial segment of the nanocrack and the inclusion, the nanocrack can either penetrate into the inclusion or bypass it along the matrix-inclusion interface. The nanocrack nucleation probability increases near an inclusion with negative (compressive) dilatation eigenstrain. A decrease in the inclusion size decreases (increases) the probability of a crack opening along the interface if the dilatation eigenstrain is negative (positive).

EPICS Controlled Collimator for Controlling Beam Sizes in HIPPO

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

Napolitano, Arthur Soriano; Vogel, Sven C.

2017-08-03

Controlling the beam spot size and shape in a diffraction experiment determines the probed sample volume. The HIPPO - High-Pressure-Preferred Orientation– neutron time-offlight diffractometer is located at the Lujan Neutron Scattering Center in Los Alamos National Laboratories. HIPPO characterizes microstructural parameters, such as phase composition, strains, grain size, or texture, of bulk (cm-sized) samples. In the current setup, the beam spot has a 10 mm diameter. Using a collimator, consisting of two pairs of neutron absorbing boron-nitride slabs, horizontal and vertical dimensions of a rectangular beam spot can be defined. Using the HIPPO robotic sample changer for sample motion, themore » collimator would enable scanning of e.g. cylindrical samples along the cylinder axis by probing slices of such samples. The project presented here describes implementation of such a collimator, in particular the motion control software. We utilized the EPICS (Experimental Physics Interface and Control System) software interface to integrate the collimator control into the HIPPO instrument control system. Using EPICS, commands are sent to commercial stepper motors that move the beam windows.« less

Reference manual for the Thermal Analyst's Help Desk Expert System

NASA Technical Reports Server (NTRS)

Ormsby, Rachel A.

1994-01-01

This document provides technical information and programming guidance for the maintenance and future development of the Thermal Analyst's Help Desk. Help Desk is an expert system that operates within the EXSYSTM expert system shell, and is used to determine first approximations of thermal capacity for spacecraft and instruments. The five analyses supported in Help Desk are: (1) surface area required for a radiating surface, (2) equilibrium temperature of a surface, (3) enclosure temperature and heat loads for a defined position in orbit, (4) enclosure temperature and heat loads over a complete orbit and, (5) selection of appropriate surface properties. The two geometries supported by Help Desk are a single flat plate and a rectangular box enclosure. The technical information includes the mathematical approach and analytical derivations used in the analyses such as: radiation heat balance, view factor calculation, and orbit determination with coordinate transformation. The programming guide for developers describes techniques for enhancement of Help Desk. Examples are provided showing the addition of new features, user interface development and enhancement, and external program interfaces.

Study on Orbital Liquid Transport and Interface Behavior in Vane Tank

NASA Astrophysics Data System (ADS)

Kang, Qi; Rui, Wei

2016-07-01

Liquid propellant tank is used to supply gas free liquid for spacecraft as an important part of propulsion system. The liquid behavior dominated by surface tension in microgravity is obviously different with that on the ground, which put forward a new challenge to the liquid transport and relocation. The experiments which are investigated at drop tower in National Microgravity Lab have concentrated on liquid relocation following thruster firing. Considered that the liquid located at the bottom in the direction of the acceleration vector, a sphere scale vane tank is used to study the liquid-gas interface behaviors with different acceleration vector and different filling independently and we obtain a series of stable equilibrium interface and relocation time. We find that there is an obvious sedimentation in the direction of acceleration vector when fill rate greater than 2% fill. Suggestions have been put forward that outer vanes transferring liquid to the outlet should be fixed and small holes should be dogged at the vane close to the center post to improve the liquid flow between different vanes when B0 is greater than 2.5. The research about liquid transport alone ribbon vanes is simulated though software Flow3D. The simulation process is verified by comparing the liquid lip and vapor-liquid interface obtained from drop tower experiment and simulation result when fill rate is 15%. Then the influence of fill rate, numbers of vanes and the gap between vane and wall is studied through the same simulate process. Vanes' configurations are also changed to study the effect on the lip and liquid volume below some section. Some suggestions are put forward for the design of vanes.

Bend losses in rectangular culverts.

DOT National Transportation Integrated Search

2008-09-01

This study investigated bend losses for open channel flow in rectangular channels or culverts. Laboratory experiments were performed for sub-critical flow in rectangular channels with abrupt bends. Bend angles of approximately 30, 45, 60, 75 and 90 d...

Finite element fatigue analysis of rectangular clutch spring of automatic slack adjuster

NASA Astrophysics Data System (ADS)

Xu, Chen-jie; Luo, Zai; Hu, Xiao-feng; Jiang, Wen-song

2015-02-01

The failure of rectangular clutch spring of automatic slack adjuster directly affects the work of automatic slack adjuster. We establish the structural mechanics model of automatic slack adjuster rectangular clutch spring based on its working principle and mechanical structure. In addition, we upload such structural mechanics model to ANSYS Workbench FEA system to predict the fatigue life of rectangular clutch spring. FEA results show that the fatigue life of rectangular clutch spring is 2.0403×105 cycle under the effect of braking loads. In the meantime, fatigue tests of 20 automatic slack adjusters are carried out on the fatigue test bench to verify the conclusion of the structural mechanics model. The experimental results show that the mean fatigue life of rectangular clutch spring is 1.9101×105, which meets the results based on the finite element analysis using ANSYS Workbench FEA system.

Analysis of junior high school students' difficulty in resolving rectangular conceptual problems

NASA Astrophysics Data System (ADS)

Utami, Aliksia Kristiana Dwi; Mardiyana, Pramudya, Ikrar

2017-08-01

Geometry is one part of the mathematics that must be learned in school and it has important effects on the development of creative thinking skills of learners, but in fact, there are some difficulties experienced by the students. This research focuses on analysis difficulty in resolving rectangular conceptual problems among junior high school students in every creative thinking skills level. This research used a descriptive method aimed to identify the difficulties and cause of the difficulties experienced by five students. The difficulties are associated with rectangular shapes and related problems. Data collection was done based on students' work through test, interview, and observations. The result revealed that student' difficulties in understanding the rectangular concept can be found at every creative thinking skills level. The difficulties are identifying the objects rectangular in the daily life except for a rectangle and square, analyzing the properties of rectangular shapes, and seeing the interrelationships between figures.

Linear Rayleigh-Taylor instability in an accelerated Newtonian fluid with finite width

NASA Astrophysics Data System (ADS)

Piriz, S. A.; Piriz, A. R.; Tahir, N. A.

2018-04-01

The linear theory of Rayleigh-Taylor instability is developed for the case of a viscous fluid layer accelerated by a semi-infinite viscous fluid, considering that the top interface is a free surface. Effects of the surface tensions at both interfaces are taken into account. When viscous effects dominate on surface tensions, an interplay of two mechanisms determines opposite behaviors of the instability growth rate with the thickness of the heavy layer for an Atwood number AT=1 and for sufficiently small values of AT. In the former case, viscosity is a less effective stabilizing mechanism for the thinnest layers. However, the finite thickness of the heavy layer enhances its viscous effects that, in general, prevail on the viscous effects of the semi-infinite medium.

Aerothermodynamic properties of stretched flames in enclosures

NASA Astrophysics Data System (ADS)

Rotman, D. A.; Oppenheim, A. K.

Flames are stretched by being pulled along their frontal surface by the flow field in which they reside. Their trajectories tend to approach particle paths, acquiring eventually the role of contact boundaries, -interfaces between the burnt and unburnt medium that may broaden solely as a consequence of diffusion. Fundamental properties of flow fields governing such flames are determined here on the basis of the zero Mach number model, providng a rational method of approach to the computational analysis of combustion fields in enclosures where, besides the aerodynamic properties flow, the thermodynamic process of compression must be taken into account. To illustrate its application, the method is used to reveal the mechanism of formation of a tulip-shape flame in a rectangular enclosure under nonturbulent flow conditions.

Friction and wear of single-crystal manganese-zinc ferrite

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1979-01-01

Sliding friction experiments were conducted with single crystal manganese-zinc ferrite in contact with itself and with transition metals. Results indicate mating highest atomic density directions (110) on matched crystallographic planes exhibit the lowest coefficient of friction, indicating that direction is important in the friction behavior of ferrite. Matched parallel high atomic density planes and crystallographic directions at the interface exhibit low coefficients of friction. The coefficients of friction for ferrite in contact with various metals are related to the relative chemical activity of these metals. The more active the metal, the higher the coefficient of friction. Cracking and the formation of hexagon- and rectangular-shaped platelet wear debris due to cleavages of (110) planes are observed on the ferrite surfaces as a result of sliding.

Wave radiation and diffraction by a two-dimensional floating body with an opening near a side wall

NASA Astrophysics Data System (ADS)

Zhang, Hong-sheng; Zhou, Hua-wei

2013-08-01

The radiation and diffraction problem of a two-dimensional rectangular body with an opening floating on a semi-infinite fluid domain of finite water depth is analysed based on the linearized velocity potential theory through an analytical solution procedure. The expressions for potentials are obtained by the method of variation separation, in which the unknown coefficients are determined by the boundary condition and matching requirement on the interface. The effects of the position of the hole and the gap between the body and side wall on hydrodynamic characteristics are investigated. Some resonance is observed like piston motion in a moon pool and sloshing in a closed tank because of the existence of restricted fluid domains.

Analysis and calculation of macrosegregation in a casting ingot, exhibits C and E

NASA Technical Reports Server (NTRS)

Poirier, D. R.; Maples, A. L.

1984-01-01

A computer model which describes the solidification of a binary metal alloy in an insulated rectangular mold with a temperature gradient is presented. A numerical technique, applicable to a broad class of moving boundary problems, was implemented therein. The solidification model described is used to calculate the macrosegregation within the solidified casting by coupling the equations for liquid flow in the solid/liquid or mushy zone with the energy equation for heat flow throughout the ingot and thermal convection in the bulk liquid portion. The rate of development of the solid can be automatically calculated by the model. Numerical analysis of such solidification parameters as enthalpy and boundary layer flow is displayed. On-line user interface and software documentation are presented.

Study on the mesophase development of pressure-responsive ABC triblock copolymers

NASA Astrophysics Data System (ADS)

Cho, Junhan

Here we focus on the revelation of new nanoscale morphologies for a molten compressible polymeric surfactant through a compressible self-consistent field approach. A linear ABC block copolymer is set to allow a disparity in the propensities for curved interfaces and in pressure responses of ij-pairs. Under these conditions, the copolymer evolves into noble morphologies at selected segregation levels such as networks with tetrapod connections, rectangularly packed cylinders in a 2-dimensional array, and also body-centered cubic phases. Those new structures are considered to turn up by interplay between disparity in the densities of block domains and packing frustration. Comparison with the classical mesophase structures is also given. The author acknowledges the support from the Center for Photofunctional Energy Materials (GRRC).

Experimental study of a fine structure of 2D wakes and mixing past an obstacle in a continuously stratified fluid

NASA Astrophysics Data System (ADS)

Chashechkin, Yuli. D.; Mitkin, Vladimir V.

2001-10-01

Experimental investigations of fine and macroscopic structures of density and velocity disturbances generated by a towing cylinder or a vertical strip in a linearly stratified liquid are carried out in a rectangular tank. A density gradient field is visualised by different Schlieren methods (direct shadow, 'slit-knife', 'slit-thread', 'natural rainbow') characterised by a high spatial resolution. Profiles of fluid velocity are visualised by density markers — wakes past a vertically descending sugar crystal or an ascending gas bubble. In a fluid at rest, the density marker acts as a vertical linear source of internal oscillations which allows us to measure buoyancy frequency over all depth by the Schlieren instrument directly or by a conductivity probe in a particular point. Sensitive methods reveal a set of high gradient interfaces inside and outside the downstream wake besides well-known large scale elements: upstream disturbances, attached internal waves and vortices. Solitary interfaces located inside the attached internal waves field have no features on their leading and trailing edges. A thickness of interfaces is defined by an appropriate diffusion coefficient and a buoyancy frequency. High gradient interfaces bound compact vortices. Vortices moving with respect to environment emit their own systems of internal waves randomising a regular pattern of attached antisymmetric internal waves. But after a rather long time a wave recurrence occurs and a regular but symmetric structure of the longest waves (similar to the pattern of initial attached internal waves) is observed again. High gradient interfaces and lines of their intersections act as collectors of a dye coming from a compact source or from a coloured liquid volume inside the tank and separate coloured and clear areas.

Ion response to relativistic electron bunches in the blowout regime of laser-plasma accelerators.

PubMed

Popov, K I; Rozmus, W; Bychenkov, V Yu; Naseri, N; Capjack, C E; Brantov, A V

2010-11-05

The ion response to relativistic electron bunches in the so called bubble or blowout regime of a laser-plasma accelerator is discussed. In response to the strong fields of the accelerated electrons the ions form a central filament along the laser axis that can be compressed to densities 2 orders of magnitude higher than the initial particle density. A theory of the filament formation and a model of ion self-compression are proposed. It is also shown that in the case of a sharp rear plasma-vacuum interface the ions can be accelerated by a combination of three basic mechanisms. The long time ion evolution that results from the strong electrostatic fields of an electron bunch provides a unique diagnostic of laser-plasma accelerators.

Effect of pressure fluctuations on Richtmyer-Meshkov coherent structures

NASA Astrophysics Data System (ADS)

Bhowmick, Aklant K.; Abarzhi, Snezhana

2016-11-01

We investigate the formation and evolution of Richtmyer Meshkov bubbles after the passage of a shock wave across a two fluid interface in the presence of pressure fluctuations. The fluids are ideal and incompressible and the pressure fluctuations are scale invariant in space and time, and are modeled by a power law time dependent acceleration field with exponent -2. Solutions indicate sensitivity to pressure fluctuations. In the linear regime, the growth of curvature and bubble velocity is linear. The growth rate is dominated by the initial velocity for weak pressure fluctuations, and by the acceleration term for strong pressure fluctuations. In the non-linear regime, the bubble curvature is constant and the solutions form a one parameter family (parametrized by the bubble curvature). The solutions are shown to be convergent and asymptotically stable. The physical solution (stable fastest growing) is a flat bubble for small pressure fluctuations and a curved bubble for large pressure fluctuations. The velocity field (in the frame of references accounting for the background motion) involves intense motion of the fluids in a vicinity of the interface, effectively no motion of the fluids away from the interfaces, and formation of vortical structures at the interface. The work is supported by the US National Science Foundation.

Effect of pressure fluctuations on Richtmyer-Meshkov coherent structures

NASA Astrophysics Data System (ADS)

Bhowmick, Aklant K.; Abarzhi, Snezhana

2016-10-01

We investigate the formation and evolution of Richtmyer Meshkov bubbles after the passage of a shock wave across a two fluid interface in the presence of pressure fluctuations. The fluids are ideal and incompressible and the pressure fluctuations are scale invariant in space and time, and are modeled by a power law time dependent acceleration field with exponent -2. Solutions indicate sensitivity to pressure fluctuations. In the linear regime, the growth of curvature and bubble velocity is linear. The growth rate is dominated by the initial velocity for weak pressure fluctuations, and by the acceleration term for strong pressure fluctuations. In the non-linear regime, the bubble curvature is constant and the solutions form a one parameter family (parametrized by the bubble curvature). The solutions are shown to be convergent and asymptotically stable. The physical solution (stable fastest growing) is a flat bubble for small pressure fluctuations and a curved bubble for large pressure fluctuations. The velocity field (in the frame of references accounting for the background motion) involves intense motion of the fluids in a vicinity of the interface, effectively no motion of the fluids away from the interfaces, and formation of vortical structures at the interface. The work is supported by the US National Science Foundation.

Analysis of ballistic transport in nanoscale devices by using an accelerated finite element contact block reduction approach

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

Li, H.; Li, G., E-mail: gli@clemson.edu

2014-08-28

An accelerated Finite Element Contact Block Reduction (FECBR) approach is presented for computational analysis of ballistic transport in nanoscale electronic devices with arbitrary geometry and unstructured mesh. Finite element formulation is developed for the theoretical CBR/Poisson model. The FECBR approach is accelerated through eigen-pair reduction, lead mode space projection, and component mode synthesis techniques. The accelerated FECBR is applied to perform quantum mechanical ballistic transport analysis of a DG-MOSFET with taper-shaped extensions and a DG-MOSFET with Si/SiO{sub 2} interface roughness. The computed electrical transport properties of the devices obtained from the accelerated FECBR approach and associated computational cost as amore » function of system degrees of freedom are compared with those obtained from the original CBR and direct inversion methods. The performance of the accelerated FECBR in both its accuracy and efficiency is demonstrated.« less

3D Printed Scintillators For Use in Field Emission Detection and Other Nuclear Physics Experiments

NASA Astrophysics Data System (ADS)

Ficenec, Karen

2015-10-01

In accelerator cavities, field emission electrons - electrons that get stripped away from the cavity walls due to the high electromagnetic field necessary to accelerate the main beam - are partially accelerated and can crash into the cavity walls, adding to the heat-load of the cryogenic system. Because these field electrons emit gamma rays when bent by the electromagnetic field, a scintillator, if made to fit the cavity enclosure, can detect their presence. Eliminating the waste of subtractive manufacturing techniques and allowing for the production of unique, varied shapes, 3D printing of scintillators may allow for an efficient detection system. UV light is used to start a chemical polymerization process that links the monomers of the liquid resin together into larger, intertwined molecules, forming the solid structure. Each shape requires slightly different calibration of its optimal printing parameters, such as slice thickness and exposure time to UV light. Thus far, calibration parameters have been optimized for cylinders of 20 mm diameter, cones of 30 mm diameter and 30 mm height, rectangular prisms 30 by 40 by 10 mm, and square pyramids 20 mm across. Calibration continues on creating holes in the prints (for optical fibers), as well as shapes with overhangs. Scintill This work was supported in part by the National Science Foundation under Grant No. PHY-1405857.

Effects of centrifugal acceleration on the flows and segregation in vertical Bridgman crystal growth with steady ampoule rotation

NASA Astrophysics Data System (ADS)

Lan, C. W.

2001-07-01

The effects of centrifugal acceleration on the flows and segregation in vertical Bridgman crystal growth with steady ampoule rotation are investigated through numerical simulation. The numerical model is based on the Boussinesq approximation in a rotating frame, and the fluid flow, heat and mass transfer, and the growth interface are solved simultaneously by a robust finite-volume/Newton method. The growth of gallium-doped germanium (GaGe) in the Grenoble furnace is adopted as an example. The calculated results at small Froude number (Fr<<1) are consistent with the previous prediction (Lan, J. Crystal growth 197 (1999) 983). However, at a high rotation speed or in reduced gravity, where the centrifugal acceleration becomes important (Fr˜1), the results are quite different due to the secondary flow induced. Since the direction of the induced flow is different from that of the buoyancy convection due to the concave interface, the flow damping is more effective than that due to the Coriolis force alone. More importantly, radial segregation can be reversed during the flow transition from one to the other.

G-cueing microcontroller (a microprocessor application in simulators)

NASA Technical Reports Server (NTRS)

Horattas, C. G.

1980-01-01

A g cueing microcontroller is described which consists of a tandem pair of microprocessors, dedicated to the task of simulating pilot sensed cues caused by gravity effects. This task includes execution of a g cueing model which drives actuators that alter the configuration of the pilot's seat. The g cueing microcontroller receives acceleration commands from the aerodynamics model in the main computer and creates the stimuli that produce physical acceleration effects of the aircraft seat on the pilots anatomy. One of the two microprocessors is a fixed instruction processor that performs all control and interface functions. The other, a specially designed bipolar bit slice microprocessor, is a microprogrammable processor dedicated to all arithmetic operations. The two processors communicate with each other by a shared memory. The g cueing microcontroller contains its own dedicated I/O conversion modules for interface with the seat actuators and controls, and a DMA controller for interfacing with the simulation computer. Any application which can be microcoded within the available memory, the available real time and the available I/O channels, could be implemented in the same controller.

Flight Force Measurements on a Spacecraft to Launch Vehicle Interface

NASA Astrophysics Data System (ADS)

Kaufman, Daniel S.; Gordon, Scott A.

2012-07-01

For several years we had wanted to measure interface forces between a launch vehicle and the Payload. Finally in July 2006 a proposal was made and funded to evaluate the use of flight force measurements (FFM) to improve the loads process of a Spacecraft in its design and test cycle. A NASA/Industry team was formed, the core Team consisted of 20 people. The proposal identified two questions that this assessment would attempt to address by obtaining the flight forces. These questions were: 1) Is flight correlation and reconstruction with acceleration methods sufficient? 2) How much can the loads and therefore the design and qualification be reduced by having force measurements? The objective was to predict the six interface driving forces between the Spacecraft and the Launch Vehicle throughout the boost phase. Then these forces would be compared with reconstructed loads analyses for evaluation in an attempt to answer them. The paper will present the development of a strain based force measurement system and also an acceleration method, actual flight results, post flight evaluations and lessons learned.

Method and structure for cache aware transposition via rectangular subsections

DOEpatents

Gustavson, Fred Gehrung; Gunnels, John A

2014-02-04

A method and structure for transposing a rectangular matrix A in a computer includes subdividing the rectangular matrix A into one or more square submatrices and executing an in-place transposition for each of the square submatrices A.sub.ij.

Lid design for low level waste container

DOEpatents

Holbrook, R.H.; Keener, W.E.

1995-02-28

A container for low level waste includes a shell and a lid. The lid has a frame to which a planar member is welded. The lid frame includes a rectangular outer portion made of square metal tubing, a longitudinal beam extending between axial ends of the rectangular outer portion, and a transverse beam extending between opposite lateral sides of the rectangular outer portion. Two pairs of diagonal braces extend between the longitudinal beam and the four corners of the rectangular outer portion of the frame. 6 figs.

Lid design for low level waste container

DOEpatents

Holbrook, Richard H.; Keener, Wendell E.

1995-01-01

A container for low level waste includes a shell and a lid. The lid has a frame to which a planar member is welded. The lid frame includes a rectangular outer portion made of square metal tubing, a longitudinal beam extending between axial ends of the rectangular outer portion, and a transverse beam extending between opposite lateral sides of the rectangular outer portion. Two pairs of diagonal braces extend between the longitudinal beam and the four corners of the rectangular outer portion of the frame.

Graduate Student Program in Materials and Engineering Research and Development for Future Accelerators

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

Spentzouris, Linda

The objective of the proposal was to develop graduate student training in materials and engineering research relevant to the development of particle accelerators. Many components used in today's accelerators or storage rings are at the limit of performance. The path forward in many cases requires the development of new materials or fabrication techniques, or a novel engineering approach. Often, accelerator-based laboratories find it difficult to get top-level engineers or materials experts with the motivation to work on these problems. The three years of funding provided by this grant was used to support development of accelerator components through a multidisciplinary approachmore » that cut across the disciplinary boundaries of accelerator physics, materials science, and surface chemistry. The following results were achieved: (1) significant scientific results on fabrication of novel photocathodes, (2) application of surface science and superconducting materials expertise to accelerator problems through faculty involvement, (3) development of instrumentation for fabrication and characterization of materials for accelerator components, (4) student involvement with problems at the interface of material science and accelerator physics.« less

Critical Nucleation Length for Accelerating Frictional Slip

NASA Astrophysics Data System (ADS)

Aldam, Michael; Weikamp, Marc; Spatschek, Robert; Brener, Efim A.; Bouchbinder, Eran

2017-11-01

The spontaneous nucleation of accelerating slip along slowly driven frictional interfaces is central to a broad range of geophysical, physical, and engineering systems, with particularly far-reaching implications for earthquake physics. A common approach to this problem associates nucleation with an instability of an expanding creep patch upon surpassing a critical length Lc. The critical nucleation length Lc is conventionally obtained from a spring-block linear stability analysis extended to interfaces separating elastically deformable bodies using model-dependent fracture mechanics estimates. We propose an alternative approach in which the critical nucleation length is obtained from a related linear stability analysis of homogeneous sliding along interfaces separating elastically deformable bodies. For elastically identical half-spaces and rate-and-state friction, the two approaches are shown to yield Lc that features the same scaling structure, but with substantially different numerical prefactors, resulting in a significantly larger Lc in our approach. The proposed approach is also shown to be naturally applicable to finite-size systems and bimaterial interfaces, for which various analytic results are derived. To quantitatively test the proposed approach, we performed inertial Finite-Element-Method calculations for a finite-size two-dimensional elastically deformable body in rate-and-state frictional contact with a rigid body under sideway loading. We show that the theoretically predicted Lc and its finite-size dependence are in reasonably good quantitative agreement with the full numerical solutions, lending support to the proposed approach. These results offer a theoretical framework for predicting rapid slip nucleation along frictional interfaces.

Stable radiation pressure acceleration of ions by suppressing transverse Rayleigh-Taylor instability with multiple Gaussian pulses

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

Zhou, M. L.; Liu, B.; Hu, R. H.

In the case of a thin plasma slab accelerated by the radiation pressure of an ultra-intense laser pulse, the development of Rayleigh-Taylor instability (RTI) will destroy the acceleration structure and terminate the acceleration process much sooner than theoretical limit. In this paper, a new scheme using multiple Gaussian pulses for ion acceleration in a radiation pressure acceleration regime is investigated with particle-in-cell simulation. We found that with multiple Gaussian pulses, the instability could be efficiently suppressed and the divergence of the ion bunch is greatly reduced, resulting in a longer acceleration time and much more collimated ion bunch with highermore » energy than using a single Gaussian pulse. An analytical model is developed to describe the suppression of RTI at the laser-plasma interface. The model shows that the suppression of RTI is due to the introduction of the long wavelength mode RTI by the multiple Gaussian pulses.« less

A wideband wireless neural stimulation platform for high-density microelectrode arrays.

PubMed

Myers, Frank B; Simpson, Jim A; Ghovanloo, Maysam

2006-01-01

We describe a system that allows researchers to control an implantable neural microstimulator from a PC via a USB 2.0 interface and a novel dual-carrier wireless link, which provides separate data and power transmission. Our wireless stimulator, Interestim-2B (IS-2B), is a modular device capable of generating controlled-current stimulation pulse trains across 32 sites per module with support for a variety of stimulation schemes (biphasic/monophasic, bipolar/monopolar). We have developed software to generate multi-site stimulation commands for the IS-2B based on streaming data from artificial sensory devices such as cameras and microphones. For PC interfacing, we have developed a USB 2.0 microcontroller-based interface. Data is transmitted using frequency-shift keying (FSK) at 6/12 MHz to achieve a data rate of 3 Mb/s via a pair of rectangular coils. Power is generated using a class-E power amplifier operating at 1 MHz and transmitted via a separate pair of spiral planar coils which are oriented perpendicular to the data coils to minimize cross-coupling. We have successfully demonstrated the operation of the system by applying it as a visual prosthesis. Pulse-frequency modulated stimuli are generated in real-time based on a grayscale image from a webcam. These pulses are projected onto an 11x11 LED matrix that represents a 2D microelectrode array.

Optimized operation of dielectric laser accelerators: Multibunch

NASA Astrophysics Data System (ADS)

Hanuka, Adi; Schächter, Levi

2018-06-01

We present a self-consistent analysis to determine the optimal charge, gradient, and efficiency for laser driven accelerators operating with a train of microbunches. Specifically, we account for the beam loading reduction on the material occurring at the dielectric-vacuum interface. In the case of a train of microbunches, such beam loading effect could be detrimental due to energy spread, however this may be compensated by a tapered laser pulse. We ultimately propose an optimization procedure with an analytical solution for group velocity which equals to half the speed of light. This optimization results in a maximum efficiency 20% lower than the single bunch case, and a total accelerated charge of 1 06 electrons in the train. The approach holds promise for improving operations of dielectric laser accelerators and may have an impact on emerging laser accelerators driven by high-power optical lasers.

Workload-Based Automated Interface Mode Selection

DTIC Science & Technology

2012-03-22

Process . . . . . . . . . . . . . . . . . . . . . 31 3.5.10 Agent Reward Function . . . . . . . . . . . . . . . . 31 3.5.11 Accelerated Learning... Strategies . . . . . . . . . . . . 31 4. Experimental Methodology . . . . . . . . . . . . . . . . . . . . . . . . 33 4.1 System Engineering Methodology...26 5. Agent state function. . . . . . . . . . . . . . . . . . . . . . . . . . . 28 6. Agent reward function

Space- and Ground-Based Crystal Growth Using a Baffle (CGB)

NASA Technical Reports Server (NTRS)

Ostrogorsky, A. G.; Marin, C.; Peignier, T.; Duffar, T.; Volz, M.; Jeter, L.; Luz, P.

2001-01-01

The composition of semiconductor crystals produced in space by conventional melt-growth processes (directional solidification and zone melting) is affected by minute levels of residual micro-acceleration, which causes natural convection. The residual acceleration has random magnitude, direction and frequency. Therefore, the velocity field in the melt is apriori unpredictable. As a result, the composition of the crystals grown in space can not be predicted and reproduced. The method for directional solidification with a submerged heater or a baffle was developed under NASA sponsorship. The disk-shaped baffle acts as a partition, creating a small melt zone at the solid-liquid interface. As a result, in ground based experiment the level of buoyancy-driven convection at the interface is significantly reduced. In several experiments with Te-doped GaSb, nearly diffusion controlled segregation was achieved.

Effects of local field and inherent strain in reflectance anisotropy spectra of A{sup III}B{sup V} semiconductors with naturally oxidized surfaces

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

Berkovits, V. L.; Kosobukin, V. A.; Gordeeva, A. B.

2015-12-28

Reflectance anisotropy (RA) spectra of naturally oxidized (001) surfaces of GaAs and InAs crystals are measured for photon energies from 1.5 up to 5.5 eV. The differential high-accuracy RA spectra reveal features substantially different from those caused by either a reconstruction of clean surface or a built-in near-surface electric field. Models of atomic structure with anisotropic transition layers of excess arsenic atoms specific for GaAs(001)/oxide and InAs(001)/oxide interfaces are proposed. In conformity with these models, a general theory of reflectance anisotropy is developed for semiconductor/oxide interfaces within the Green's function technique. The theory takes into account the combined effect of localmore » field due to interface dipoles and of intrinsic near-surface strain of the crystal. Measured RA spectra are analyzed in the model of valence-bond dipoles occupying a rectangular lattice in a multilayer medium. Comparing the measured and calculated spectra, we conclude that RA spectra of oxidized GaAs(001) and InAs(001) surfaces are simultaneously influenced by interface and near-surface anisotropies. The former is responsible for the broad-band spectral features which are associated with polarizability of the valence bonds attached to As atoms at the crystal/oxide interface. The near-surface anisotropy is due to inherent uniaxial straining the near-surface region of crystal. The effect of strain on RA spectra is experimentally and theoretically substantiated for GaAs crystal wafers undergone a uniaxial applied stress. Basically, this work results in the following. It establishes the physical nature of different levels of RA spectra observed in a majority of papers, but never analyzed. It demonstrates how the studied features of RA spectra could be applied for optical characterization of strained interfaces and atomic layers.« less

Effects of local field and inherent strain in reflectance anisotropy spectra of AIIIBV semiconductors with naturally oxidized surfaces

NASA Astrophysics Data System (ADS)

Berkovits, V. L.; Kosobukin, V. A.; Gordeeva, A. B.

2015-12-01

Reflectance anisotropy (RA) spectra of naturally oxidized (001) surfaces of GaAs and InAs crystals are measured for photon energies from 1.5 up to 5.5 eV. The differential high-accuracy RA spectra reveal features substantially different from those caused by either a reconstruction of clean surface or a built-in near-surface electric field. Models of atomic structure with anisotropic transition layers of excess arsenic atoms specific for GaAs(001)/oxide and InAs(001)/oxide interfaces are proposed. In conformity with these models, a general theory of reflectance anisotropy is developed for semiconductor/oxide interfaces within the Green's function technique. The theory takes into account the combined effect of local field due to interface dipoles and of intrinsic near-surface strain of the crystal. Measured RA spectra are analyzed in the model of valence-bond dipoles occupying a rectangular lattice in a multilayer medium. Comparing the measured and calculated spectra, we conclude that RA spectra of oxidized GaAs(001) and InAs(001) surfaces are simultaneously influenced by interface and near-surface anisotropies. The former is responsible for the broad-band spectral features which are associated with polarizability of the valence bonds attached to As atoms at the crystal/oxide interface. The near-surface anisotropy is due to inherent uniaxial straining the near-surface region of crystal. The effect of strain on RA spectra is experimentally and theoretically substantiated for GaAs crystal wafers undergone a uniaxial applied stress. Basically, this work results in the following. It establishes the physical nature of different levels of RA spectra observed in a majority of papers, but never analyzed. It demonstrates how the studied features of RA spectra could be applied for optical characterization of strained interfaces and atomic layers.

Dynamic equilibrium under vibrations of H2 liquid-vapor interface at various gravity levels

NASA Astrophysics Data System (ADS)

Gandikota, G.; Chatain, D.; Lyubimova, T.; Beysens, D.

2014-06-01

Horizontal vibration applied to the support of a simple pendulum can deviate from the equilibrium position of the pendulum to a nonvertical position. A similar phenomenon is expected when a liquid-vapor interface is subjected to strong horizontal vibration. Beyond a threshold value of vibrational velocity the interface should attain an equilibrium position at an angle to the initial horizontal position. In the present paper experimental investigation of this phenomenon is carried out in a magnetic levitation device to study the effect of the vibration parameters, gravity acceleration, and the liquid-vapor density on the interface position. The results compare well with the theoretical expression derived by Wolf [G. H. Wolf, Z. Phys. B 227, 291 (1969), 10.1007/BF01397662].

ForTrilinos

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

Evans, Katherine J; Johnson, Seth R; Prokopenko, Andrey V

'ForTrilinos' is related to The Trilinos Project, which contains a large and growing collection of solver capabilities that can utilize next-generation platforms, in particular scalable multicore, manycore, accelerator and heterogeneous systems. Trilinos is primarily written in C++, including its user interfaces. While C++ is advantageous for gaining access to the latest programming environments, it limits Trilinos usage via Fortran. Sever ad hoc translation interfaces exist to enable Fortran usage of Trilinos, but none of these interfaces is general-purpose or written for reusable and sustainable external use. 'ForTrilinos' provides a seamless pathway for large and complex Fortran-based codes to access Trilinosmore » without C/C++ interface code. This access includes Fortran versions of Kokkos abstractions for code execution and data management.« less

Understanding and managing trust at the climate science-policy interface

NASA Astrophysics Data System (ADS)

Lacey, Justine; Howden, Mark; Cvitanovic, Christopher; Colvin, R. M.

2018-01-01

Climate change effects are accelerating, making the need for appropriate actions informed by sound climate knowledge ever more pressing. A strong climate science-policy relationship facilitates the effective integration of climate knowledge into local, national and global policy processes, increases society's responsiveness to a changing climate, and aligns research activity to policy needs. This complex science-policy relationship requires trust between climate science `producers' and `users', but our understanding of trust at this interface remains largely uncritical. To assist climate scientists and policymakers, this Perspective provides insights into how trust develops and operates at the interface of climate science and policy, and examines the extent to which trust can manage — or even create — risk at this interface.

76 FR 64105 - Light-Walled Rectangular Pipe From Taiwan; Scheduling of an Expedited Five-Year Review Concerning...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-10-17

... INTERNATIONAL TRADE COMMISSION [Investigation No. 731-TA-410 (Third Review)] Light-Walled... Order on Light-Walled Rectangular Pipe From Taiwan AGENCY: United States International Trade Commission... determine whether revocation of the antidumping duty order on light-walled rectangular pipe from Taiwan...

77 FR 3497 - Light-Walled Rectangular Pipe and Tube From Taiwan

Federal Register 2010, 2011, 2012, 2013, 2014

2012-01-24

... INTERNATIONAL TRADE COMMISSION [Investigation No. 731-TA-410 (Third Review)] Light-Walled... order on light-walled rectangular pipe and tube from Taiwan would be likely to lead to continuation or... views of the Commission are contained in USITC Publication 4301 (January 2012), Light-Walled Rectangular...

Effective way of reducing coupling loss between rectangular microwaveguide and fiber.

PubMed

Zhou, Hang; Chen, Zilun; Xi, Xiaoming; Hou, Jing; Chen, Jinbao

2012-01-20

We introduce an anamorphic photonic crystal fiber (PCF) produced by postprocessing techniques to improve the coupling loss between a conventional single-mode fiber and rectangular microwaveguide. One end of the round core is connected with the conventional fiber, and the other end of the rectangular core is connected with the rectangular microwaveguide, then the PCF is tapered pro rata. In this way, the loss of mode mismatch between the output of the conventional fiber and the input of the waveguide would be reduced, which results in enhanced coupling efficiency. The conclusion was confirmed by numerical simulation: the new method is better than straight coupling between the optical fiber and the rectangular microwaveguide, and more than 2.8 dB improvement of coupling efficiency is achieved. © 2012 Optical Society of America

Electromagnetic Scattering from Arbitrarily Shaped Aperture Backed by Rectangular Cavity Recessed in Infinite Ground Plane

NASA Technical Reports Server (NTRS)

Cockrell, C. R.; Beck, Fred B.

1997-01-01

The electromagnetic scattering from an arbitrarily shaped aperture backed by a rectangular cavity recessed in an infinite ground plane is analyzed by the integral equation approach. In this approach, the problem is split into two parts: exterior and interior. The electromagnetic fields in the exterior part are obtained from an equivalent magnetic surface current density assumed to be flowing over the aperture and backed by an infinite ground plane. The electromagnetic fields in the interior part are obtained in terms of rectangular cavity modal expansion functions. The modal amplitudes of cavity modes are determined by enforcing the continuity of the electric field across the aperture. The integral equation with the aperture magnetic current density as an unknown is obtained by enforcing the continuity of magnetic fields across the aperture. The integral equation is then solved for the magnetic current density by the method of moments. The electromagnetic scattering properties of an aperture backed by a rectangular cavity are determined from the magnetic current density. Numerical results on the backscatter radar cross-section (RCS) patterns of rectangular apertures backed by rectangular cavities are compared with earlier published results. Also numerical results on the backscatter RCS patterns of a circular aperture backed by a rectangular cavity are presented.

A nonpolar, nonamphiphilic molecule can accelerate adsorption of phospholipids and lower their surface tension at the air/water interface.

PubMed

Nguyen, Phuc Nghia; Trinh Dang, Thuan Thao; Waton, Gilles; Vandamme, Thierry; Krafft, Marie Pierre

2011-10-04

The adsorption dynamics of a series of phospholipids (PLs) at the interface between an aqueous solution or dispersion of the PL and a gas phase containing the nonpolar, nonamphiphilic linear perfluorocarbon perfluorohexane (PFH) was studied by bubble profile analysis tensiometry. The PLs investigated were dioctanoylphosphatidylcholine (DiC(8)-PC), dilaurylphosphatidylcholine, dimyristoylphosphatidylcholine, and dipalmitoylphosphatidylcholine. The gas phase consisted of air or air saturated with PFH. The perfluorocarbon gas was found to have an unexpected, strong effect on both the adsorption rate and the equilibrium interfacial tension (γ(eq)) of the PLs. First, for all of the PLs, and at all concentrations investigated, the γ(eq) values were significantly lower (by up to 10 mN m(-1)) when PFH was present in the gas phase. The efficacy of PFH in decreasing γ(eq) depends on the ability of PLs to form micelles or vesicles in water. For vesicles, it also depends on the gel or fluid state of the membranes. Second, the adsorption rates of all the PLs at the interface (as assessed by the time required for the initial interfacial tension to be reduced by 30%) are significantly accelerated (by up to fivefold) by the presence of PFH for the lower PL concentrations. Both the surface-tension reducing effect and the adsorption rate increasing effect establish that PFH has a strong interaction with the PL monolayer and acts as a cosurfactant at the interface, despite the absence of any amphiphilic character. Fitting the adsorption profiles of DiC(8)-PC at the PFH-saturated air/aqueous solution interface with the modified Frumkin model indicated that the PFH molecule lay horizontally at the interface. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A study into the impact of interface roughness development on mechanical degradation of oxides formed on zirconium alloys

NASA Astrophysics Data System (ADS)

Platt, P.; Wedge, S.; Frankel, P.; Gass, M.; Howells, R.; Preuss, M.

2015-04-01

As a cladding material used to encapsulate nuclear fuel pellets, zirconium alloys are the primary barrier separating the fuel and a pressurised steam or lithiated water environment. Degradation mechanisms such as oxidation can be the limiting factor in the life-time of the fuel assembly. Key to controlling oxidation, and therefore allowing increased burn-up of fuel, is the development of a mechanistic understanding of the corrosion process. In an autoclave, the oxidation kinetics for zirconium alloys are typically cyclical, with periods of accelerated kinetics being observed in steps of ∼2 μm oxide growth. These periods of accelerated oxidation are immediately preceded by the development of a layer of lateral cracks near the metal-oxide interface, which may be associated with the development of interface roughness. The present work uses scanning electron microscopy to carry out a statistical analysis of changes in the metal-oxide interface roughness between three different alloys at different stages of autoclave oxidation. The first two alloys are Zircaloy-4 and ZIRLO™ for which analysis is carried out at stages before, during and after first transition. The third alloy is an experimental low tin alloy, which under the same oxidation conditions and during the same time period does not appear to go through transition. Assessment of the metal-oxide interface roughness is primarily carried out based on the root mean square of the interface slope known as the Rdq parameter. Results show clear trends with relation to transition points in the corrosion kinetics. Discussion is given to how this relates to the existing mechanistic understanding of the corrosion process, and the components required for possible future modelling approaches.

Hexagonal Pixels and Indexing Scheme for Binary Images

NASA Technical Reports Server (NTRS)

Johnson, Gordon G.

2004-01-01

A scheme for resampling binaryimage data from a rectangular grid to a regular hexagonal grid and an associated tree-structured pixel-indexing scheme keyed to the level of resolution have been devised. This scheme could be utilized in conjunction with appropriate image-data-processing algorithms to enable automated retrieval and/or recognition of images. For some purposes, this scheme is superior to a prior scheme that relies on rectangular pixels: one example of such a purpose is recognition of fingerprints, which can be approximated more closely by use of line segments along hexagonal axes than by line segments along rectangular axes. This scheme could also be combined with algorithms for query-image-based retrieval of images via the Internet. A binary image on a rectangular grid is generated by raster scanning or by sampling on a stationary grid of rectangular pixels. In either case, each pixel (each cell in the rectangular grid) is denoted as either bright or dark, depending on whether the light level in the pixel is above or below a prescribed threshold. The binary data on such an image are stored in a matrix form that lends itself readily to searches of line segments aligned with either or both of the perpendicular coordinate axes. The first step in resampling onto a regular hexagonal grid is to make the resolution of the hexagonal grid fine enough to capture all the binaryimage detail from the rectangular grid. In practice, this amounts to choosing a hexagonal-cell width equal to or less than a third of the rectangular- cell width. Once the data have been resampled onto the hexagonal grid, the image can readily be checked for line segments aligned with the hexagonal coordinate axes, which typically lie at angles of 30deg, 90deg, and 150deg with respect to say, the horizontal rectangular coordinate axis. Optionally, one can then rotate the rectangular image by 90deg, then again sample onto the hexagonal grid and check for line segments at angles of 0deg, 60deg, and 120deg to the original horizontal coordinate axis. The net result is that one has checked for line segments at angular intervals of 30deg. For even finer angular resolution, one could, for example, then rotate the rectangular-grid image +/-45deg before sampling to perform checking for line segments at angular intervals of 15deg.

Influence of the wavelet order on proper damage location in plate structures

NASA Astrophysics Data System (ADS)

Pawlak, Zdzisław; Knitter-Piątkowska, Anna

2018-01-01

The rectangular thin plates were analyzed in the paper. The static response in plate structure subjected to the uniform load was derived by applying the finite element method. In the dynamic, experimental tests the accelerations were obtained with the use of modal hammer and DEWEsoft® software. Next, the analysis of the signal was carried out with the use of Discrete Wavelet Transform (DWT), provided that damage exists in the considered plate structure. It was assumed, that in the middle of the structure a certain area of the plate is thinner or there is a crack across the entire plate thickness. The aim of this work was to choose the appropriate wavelet order to reveal the localization of defect. The results of selected numerical example proved the efficiency of proposed approach.

Development of procedures for calculating stiffness and damping properties of elastomers in engineering applications. Part 4: Testing of elastomers under a rotating load. [resonance testing

NASA Technical Reports Server (NTRS)

Darlow, M. S.; Smalley, A. J.

1977-01-01

A test rig designed to measure stiffness and damping of elastomer cartridges under a rotating load excitation is described. The test rig employs rotating unbalance in a rotor which runs to 60,000 RPM as the excitation mechanism. A variable resonant mass is supported on elastomer elements and the dynamic characteristics are determined from measurements of input and output acceleration. Five different cartridges are considered: three of these are buttons cartridges having buttons located in pairs, with 120 between each pair. Two of the cartridges consist of 360 elastomer rings with rectangular cross-sections. Dynamic stiffness and damping are measured for each cartridge and compared with predictions at different frequencies and different strains.

Analytical investigations on the thermal properties of microscale inorganic light-emitting diodes on an orthotropic substrate

NASA Astrophysics Data System (ADS)

Li, Y.; Chen, J.; Xing, Y.; Song, J.

2017-03-01

The microscale inorganic light-emitting diodes (μ-ILEDs) create novel opportunities in biointegrated applications such as wound healing acceleration and optogenetics. Analytical expressions, validated by finite element analysis, are obtained for the temperature increase of a rectangular μ-ILED device on an orthotropic substrate, which could offer an appealing advantage in controlling the heat flow direction to achieve the goal in thermal management. The influences of various parameters (e.g., thermal conductivities of orthotropic substrate, loading parameters) on the temperature increase of the μ-ILED are investigated based on the obtained closed-form solutions. These results provide a novel route to control the temperature distribution in the μ-ILED system and provide easily interpretable guidelines to minimize the adverse thermal effects.

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

Wang, Lifeng, E-mail: walfe@nuaa.edu.cn; Hu, Haiyan

The thermal vibration of a rectangular single-layered graphene sheet is investigated by using a rectangular nonlocal elastic plate model with quantum effects taken into account when the law of energy equipartition is unreliable. The relation between the temperature and the Root of Mean Squared (RMS) amplitude of vibration at any point of the rectangular single-layered graphene sheet in simply supported case is derived first from the rectangular nonlocal elastic plate model with the strain gradient of the second order taken into consideration so as to characterize the effect of microstructure of the graphene sheet. Then, the RMS amplitude of thermalmore » vibration of a rectangular single-layered graphene sheet simply supported on an elastic foundation is derived. The study shows that the RMS amplitude of the rectangular single-layered graphene sheet predicted from the quantum theory is lower than that predicted from the law of energy equipartition. The maximal relative difference of RMS amplitude of thermal vibration appears at the sheet corners. The microstructure of the graphene sheet has a little effect on the thermal vibrations of lower modes, but exhibits an obvious effect on the thermal vibrations of higher modes. The quantum effect is more important for the thermal vibration of higher modes in the case of smaller sides and lower temperature. The relative difference of maximal RMS amplitude of thermal vibration of a rectangular single-layered graphene sheet decreases monotonically with an increase of temperature. The absolute difference of maximal RMS amplitude of thermal vibration of a rectangular single-layered graphene sheet increases slowly with the rising of Winkler foundation modulus.« less

Microstructure stability during creep deformation of hard-oriented polysynthetically twinned crystal of TiAl alloy

NASA Astrophysics Data System (ADS)

Kim, Hee Y.; Maruyama, K.

2003-10-01

The hard-orientated polysynthetically twinned (PST) crystal with the lamellar plates oriented parallel to the compression axis was deformed at 1150 K under the applied stress of 158 to 316 MPa. Microstructural changes were examined quantitatively for the PST crystal during creep deformation. In the as-grown PST crystal of the present study, proportions of α 2/ γ, true twin, pseudotwin, and 120 deg rotational fault interfaces were 12, 59, 12, and 17 pct, respectively. After creep deformation, lamellar coarsening by dissolution of α 2 lamellae and migration of γ/γ interfaces were observed. The acceleration of creep rate after the minimum strain rate in the creep curve was attributed to the lamellar coarsening and destruction of lamellar structure during the creep deformation. Thirty-two percent of α 2/ γ interfaces, 51 pct of true twin interfaces, 74 pct of pseudotwin interfaces, and 80 pct of 120 deg rotational faults disappeared after 4 pct creep strain at 1150 K. The α 2/ γ interface was more stable than γ/γ interfaces during the creep deformation. The pseudotwin interface and 120 deg rotational fault were less thermally stable than the true twin interface for γ/γ interfaces.

The crack and wedging problem for an orthotropic strip

NASA Technical Reports Server (NTRS)

Cinar, A.; Erdogan, F.

1982-01-01

The plane elasticity problem for an orthotropic strip containing a crack parallel to its boundaries is considered. The problem is formulated under general mixed mode loading conditions. The stress intensity factors depend on two dimensionless orthotropic constants only. For the crack problem the results are given for a single crack and two collinear cracks. The calculated results show that of the two orthotropic constants the influence of the stiffness ratio on the stress intensity factors is much more significant than that of the shear parameter. The problem of loading the strip by a rigid rectangular lengths continuous contact is maintained along the wedge strip interface; at a certain critical wedge length the separation starts at the midsection of the wedge, and the length of the separation zone increases rapidly with increasing wedge length.

The GeoClaw software for depth-averaged flows with adaptive refinement

USGS Publications Warehouse

Berger, M.J.; George, D.L.; LeVeque, R.J.; Mandli, Kyle T.

2011-01-01

Many geophysical flow or wave propagation problems can be modeled with two-dimensional depth-averaged equations, of which the shallow water equations are the simplest example. We describe the GeoClaw software that has been designed to solve problems of this nature, consisting of open source Fortran programs together with Python tools for the user interface and flow visualization. This software uses high-resolution shock-capturing finite volume methods on logically rectangular grids, including latitude-longitude grids on the sphere. Dry states are handled automatically to model inundation. The code incorporates adaptive mesh refinement to allow the efficient solution of large-scale geophysical problems. Examples are given illustrating its use for modeling tsunamis and dam-break flooding problems. Documentation and download information is available at www.clawpack.org/geoclaw. ?? 2011.

A DNA aptamer recognising a malaria protein biomarker can function as part of a DNA origami assembly

PubMed Central

Godonoga, Maia; Lin, Ting-Yu; Oshima, Azusa; Sumitomo, Koji; Tang, Marco S. L.; Cheung, Yee-Wai; Kinghorn, Andrew B.; Dirkzwager, Roderick M.; Zhou, Cunshan; Kuzuya, Akinori; Tanner, Julian A.; Heddle, Jonathan G.

2016-01-01

DNA aptamers have potential for disease diagnosis and as therapeutics, particularly when interfaced with programmable molecular technology. Here we have combined DNA aptamers specific for the malaria biomarker Plasmodium falciparum lactate dehydrogenase (PfLDH) with a DNA origami scaffold. Twelve aptamers that recognise PfLDH were integrated into a rectangular DNA origami and atomic force microscopy demonstrated that the incorporated aptamers preserve their ability to specifically bind target protein. Captured PfLDH retained enzymatic activity and protein-aptamer binding was observed dynamically using high-speed AFM. This work demonstrates the ability of DNA aptamers to recognise a malaria biomarker whilst being integrated within a supramolecular DNA scaffold, opening new possibilities for malaria diagnostic approaches based on DNA nanotechnology. PMID:26891622

Frequency-independent radiation modes of interior sound radiation: An analytical study

NASA Astrophysics Data System (ADS)

Hesse, C.; Vivar Perez, J. M.; Sinapius, M.

2017-03-01

Global active control methods of sound radiation into acoustic cavities necessitate the formulation of the interior sound field in terms of the surrounding structural velocity. This paper proposes an efficient approach to do this by presenting an analytical method to describe the radiation modes of interior sound radiation. The method requires no knowledge of the structural modal properties, which are often difficult to obtain in control applications. The procedure is exemplified for two generic systems of fluid-structure interaction, namely a rectangular plate coupled to a cuboid cavity and a hollow cylinder with the fluid in its enclosed cavity. The radiation modes are described as a subset of the acoustic eigenvectors on the structural-acoustic interface. For the two studied systems, they are therefore independent of frequency.

Perception and performance in flight simulators: The contribution of vestibular, visual, and auditory information

NASA Technical Reports Server (NTRS)

1979-01-01

The pilot's perception and performance in flight simulators is examined. The areas investigated include: vestibular stimulation, flight management and man cockpit information interfacing, and visual perception in flight simulation. The effects of higher levels of rotary acceleration on response time to constant acceleration, tracking performance, and thresholds for angular acceleration are examined. Areas of flight management examined are cockpit display of traffic information, work load, synthetic speech call outs during the landing phase of flight, perceptual factors in the use of a microwave landing system, automatic speech recognition, automation of aircraft operation, and total simulation of flight training.

Overview of High Power Vacuum Dry RF Load Designs

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

Krasnykh, Anatoly

2015-08-27

A specific feature of RF linacs based on the pulsed traveling wave (TW) mode of operation is that only a portion of the RF energy is used for the beam acceleration. The residual RF energy has to be terminated into an RF load. Higher accelerating gradients require higher RF sources and RF loads, which can stably terminate the residual RF power. RF feeders (from the RF source though the accelerating section to the load) are vacuumed to transmit multi-megawatt high power RF. This overview will outline vacuumed RF loads only. A common method to terminate multi-MW RF power is tomore » use circulated water (or other liquid) as an absorbing medium. A solid dielectric interface (a high quality ceramic) is required to separate vacuum and liquid RF absorber mediums. Using such RF load approaches in TW linacs is troubling because there is a fragile ceramic window barrier and a failure could become catastrophic for linac vacuum and RF systems. Traditional loads comprising of a ceramic disk have limited peak and average power handling capability and are therefore not suitable for high gradient TW linacs. This overview will focus on ''vacuum dry'' or ''all-metal'' loads that do not employ any dielectric interface between vacuum and absorber. The first prototype is an original design of RF loads for the Stanford Two-Mile Accelerator.« less

78 FR 54864 - Light-Walled Rectangular Pipe and Tube From Mexico: Preliminary Results and Partial Rescission of...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-09-06

... DEPARTMENT OF COMMERCE International Trade Administration [A-201-836] Light-Walled Rectangular... the antidumping duty order on light-walled rectangular pipe and tube (LWR pipe and tube) from Mexico... The merchandise subject to the order is certain welded carbon- quality light-walled steel pipe and...

Experimental Modal Analysis of Rectangular and Circular Beams

ERIC Educational Resources Information Center

Emory, Benjamin H.; Zhu, Wei Dong

2006-01-01

Analytical and experimental methods are used to determine the natural frequencies and mode shapes of Aluminum 6061-T651 beams with rectangular and circular cross-sections. A unique test stand is developed to provide the rectangular beam with different boundary conditions including clamped-free, clamped-clamped, clamped-pinned, and pinned-pinned.…

77 FR 4278 - Light-Walled Rectangular Pipe and Tube From Turkey: Extension of Time Limits for Preliminary...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-01-27

... DEPARTMENT OF COMMERCE International Trade Administration [A-489-815] Light-Walled Rectangular Pipe and Tube From Turkey: Extension of Time Limits for Preliminary Results of Antidumping Duty..., light- walled rectangular pipe and tube from Turkey for the May 1, 2010, through April 30, 2011, period...

76 FR 57953 - Light-Walled Rectangular Pipe and Tube From Turkey; Notice of Final Results of Antidumping Duty...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-09-19

... Pipe and Tube From Turkey; Notice of Final Results of Antidumping Duty Administrative Review AGENCY... pipe and tube from Turkey. See Light-Walled Rectangular Pipe and Tube From Turkey; Notice of... order covering light- walled rectangular pipe and tube from Turkey. See Preliminary Results. The...

78 FR 74161 - Light-Walled Rectangular Pipe and Tube From China, Korea, Mexico, and Turkey; Scheduling of Full...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-12-10

...-Walled Rectangular Pipe and Tube From China, Korea, Mexico, and Turkey; Scheduling of Full Five-Year... Turkey AGENCY: United States International Trade Commission. ACTION: Notice. SUMMARY: The Commission... on light- walled rectangular pipe and tube from China, Korea, Mexico, and Turkey would be likely to...

Uncertainty Quantification of Non-linear Oscillation Triggering in a Multi-injector Liquid-propellant Rocket Combustion Chamber

NASA Astrophysics Data System (ADS)

Popov, Pavel; Sideris, Athanasios; Sirignano, William

2014-11-01

We examine the non-linear dynamics of the transverse modes of combustion-driven acoustic instability in a liquid-propellant rocket engine. Triggering can occur, whereby small perturbations from mean conditions decay, while larger disturbances grow to a limit-cycle of amplitude that may compare to the mean pressure. For a deterministic perturbation, the system is also deterministic, computed by coupled finite-volume solvers at low computational cost for a single realization. The randomness of the triggering disturbance is captured by treating the injector flow rates, local pressure disturbances, and sudden acceleration of the entire combustion chamber as random variables. The combustor chamber with its many sub-fields resulting from many injector ports may be viewed as a multi-scale complex system wherein the developing acoustic oscillation is the emergent structure. Numerical simulation of the resulting stochastic PDE system is performed using the polynomial chaos expansion method. The overall probability of unstable growth is assessed in different regions of the parameter space. We address, in particular, the seven-injector, rectangular Purdue University experimental combustion chamber. In addition to the novel geometry, new features include disturbances caused by engine acceleration and unsteady thruster nozzle flow.

Optical measurements of flyer plate acceleration by emulsion explosive

NASA Astrophysics Data System (ADS)

Kubota, Shiro; Shimada, Hideki; Matsui, Kikuo; Ogata, Yuji; Seto, Masahiro; Masui, Akira; Wada, Yuji; Liu, Zhi-Yue; Itoh, Shigeru

2001-04-01

This paper presents the study on the application of explosive welding technique to the field of the urgent repair of the gas and water pipe networks. The essential parameters related to the explosive welding are scrutinized from the point of view of the minimizing the damage to the steel pipe after welded explosively with a flyer plate. The emulsion explosive is contained in a rectangular hard-paper box whose bottom is the flyer plate with 100 mm length, 25 mm width and 1.5 mm thickness. The flyer motions of the flyer plates accelerated by emulsion explosive are observed by high-speed photography from the side and front view of the flyer plate. The damage to the pipe by the flyer plate is discussed with the results of the observation of flyer motion and explosive welding test under various experimental conditions. Moreover, one way to control the motion of the flyer plate is proposed. We put a PMMA buffer block into the explosive. The flying process of flyer plate is calculated by the finite different scheme based on the ALE method. The effectiveness of this method is demonstrated by the experimental and numerical studies.

Vertical structures in vibrated wormlike micellar solutions

NASA Astrophysics Data System (ADS)

Epstein, Tamir; Deegan, Robert

2008-11-01

Vertically vibrated shear thickening particulate suspensions can support a free-standing interfaces oriented parallel to gravity. We find that shear thickening worm-like micellar solutions also support such vertical interfaces. Above a threshold in acceleration, the solution spontaneously accumulates into a labyrinthine pattern characterized by a well-defined vertical edge. The formation of vertical structures is of interest because they are unique to shear-thickening fluids, and they indicate the existence of an unknown stress bearing mechanism.

Factorization of differential expansion for non-rectangular representations

NASA Astrophysics Data System (ADS)

Morozov, A.

2018-04-01

Factorization of the differential expansion (DE) coefficients for colored HOMFLY-PT polynomials of antiparallel double braids, originally discovered for rectangular representations R, in the case of rectangular representations R, is extended to the first non-rectangular representations R = [2, 1] and R = [3, 1]. This increases chances that such factorization will take place for generic R, thus fixing the shape of the DE. We illustrate the power of the method by conjecturing the DE-induced expression for double-braid polynomials for all R = [r, 1]. In variance with the rectangular case, the knowledge for double braids is not fully sufficient to deduce the exclusive Racah matrix S¯ — the entries in the sectors with nontrivial multiplicities sum up and remain unseparated. Still, a considerable piece of the matrix is extracted directly and its other elements can be found by solving the unitarity constraints.

Triple-band metamaterial absorption utilizing single rectangular hole

NASA Astrophysics Data System (ADS)

Kim, Seung Jik; Yoo, Young Joon; Kim, Young Ju; Lee, YoungPak

2017-01-01

In the general metamaterial absorber, the single absorption band is made by the single meta-pattern. Here, we introduce the triple-band metamaterial absorber only utilizing single rectangular hole. We also demonstrate the absorption mechanism of the triple absorption. The first absorption peak was caused by the fundamental magnetic resonance in the metallic part between rectangular holes. The second absorption was generated by induced tornado magnetic field. The process of realizing the second band is also presented. The third absorption was induced by the third-harmonic magnetic resonance in the metallic region between rectangular holes. In addition, the visible-range triple-band absorber was also realized by using similar but smaller single rectangular-hole structure. These results render the simple metamaterials for high frequency in large scale, which can be useful in the fabrication of metamaterials operating in the optical range.

The Moment of Inertia of a Rectangular Rod

NASA Astrophysics Data System (ADS)

Takeuchi, Takao

2007-11-01

Recently an inexpensive setup to obtain the moment of inertia of a rotating system was proposed by Peter E. Banks. An equally simple and inexpensive experiment to obtain the moment of inertia of a uniform rod is proposed in this paper. A rectangular rod with a hole somewhere in the rod was used for this purpose. The moment of inertia of a rectangular rod around the hole location was attempted. The experimental setup is shown in Fig. 1. Various supporting rods, clamps, and rubber stoppers to hold the rectangular rod in place at point p are not shown.

All-fiber optical filter with an ultranarrow and rectangular spectral response.

PubMed

Zou, Xihua; Li, Ming; Pan, Wei; Yan, Lianshan; Azaña, José; Yao, Jianping

2013-08-15

Optical filters with an ultranarrow and rectangular spectral response are highly desired for high-resolution optical/electrical signal processing. An all-fiber optical filter based on a fiber Bragg grating with a large number of phase shifts is designed and fabricated. The measured spectral response shows a 3 dB bandwidth of 650 MHz and a rectangular shape factor of 0.513 at the 25 dB bandwidth. This is the narrowest rectangular bandpass response ever reported for an all-fiber filter, to the best of our knowledge. The filter has also the intrinsic advantages of an all-fiber implementation.

Rectangular-cladding silicon slot waveguide with improved nonlinear performance

NASA Astrophysics Data System (ADS)

Huang, Zengzhi; Huang, Qingzhong; Wang, Yi; Xia, Jinsong

2018-04-01

Silicon slot waveguides have great potential in hybrid silicon integration to realize nonlinear optical applications. We propose a rectangular-cladding hybrid silicon slot waveguide. Simulation result shows that, with a rectangular-cladding, the slot waveguide can be formed by narrower silicon strips, so the two-photon absorption (TPA) loss in silicon is decreased. When the cladding material is a nonlinear polymer, the calculated TPA figure of merit (FOMTPA) is 4.4, close to the value of bulk nonlinear polymer of 5.0. This value confirms the good nonlinear performance of rectangular-cladding silicon slot waveguides.

The application of artificial intelligent techniques to accelerator operations at McMaster University

NASA Astrophysics Data System (ADS)

Poehlman, W. F. S.; Garland, Wm. J.; Stark, J. W.

1993-06-01

In an era of downsizing and a limited pool of skilled accelerator personnel from which to draw replacements for an aging workforce, the impetus to integrate intelligent computer automation into the accelerator operator's repertoire is strong. However, successful deployment of an "Operator's Companion" is not trivial. Both graphical and human factors need to be recognized as critical areas that require extra care when formulating the Companion. They include interactive graphical user's interface that mimics, for the operator, familiar accelerator controls; knowledge of acquisition phases during development must acknowledge the expert's mental model of machine operation; and automated operations must be seen as improvements to the operator's environment rather than threats of ultimate replacement. Experiences with the PACES Accelerator Operator Companion developed at two sites over the past three years are related and graphical examples are given. The scale of the work involves multi-computer control of various start-up/shutdown and tuning procedures for Model FN and KN Van de Graaff accelerators. The response from licensing agencies has been encouraging.

A Fast Method to Calculate the Spatial Impulse Response for 1-D Linear Ultrasonic Phased Array Transducers

PubMed Central

Zou, Cheng; Sun, Zhenguo; Cai, Dong; Muhammad, Salman; Zhang, Wenzeng; Chen, Qiang

2016-01-01

A method is developed to accurately determine the spatial impulse response at the specifically discretized observation points in the radiated field of 1-D linear ultrasonic phased array transducers with great efficiency. In contrast, the previously adopted solutions only optimize the calculation procedure for a single rectangular transducer and required approximation considerations or nonlinear calculation. In this research, an algorithm that follows an alternative approach to expedite the calculation of the spatial impulse response of a rectangular linear array is presented. The key assumption for this algorithm is that the transducer apertures are identical and linearly distributed on an infinite rigid plane baffled with the same pitch. Two points in the observation field, which have the same position relative to two transducer apertures, share the same spatial impulse response that contributed from corresponding transducer, respectively. The observation field is discretized specifically to meet the relationship of equality. The analytical expressions of the proposed algorithm, based on the specific selection of the observation points, are derived to remove redundant calculations. In order to measure the proposed methodology, the simulation results obtained from the proposed method and the classical summation method are compared. The outcomes demonstrate that the proposed strategy can speed up the calculation procedure since it accelerates the speed-up ratio which relies upon the number of discrete points and the number of the array transducers. This development will be valuable in the development of advanced and faster linear ultrasonic phased array systems. PMID:27834799

Surface Cracking and Interface Reaction Associated Delamination Failure of Thermal and Environmental Barrier Coatings

NASA Technical Reports Server (NTRS)

Zhu, Dong-Ming; Choi, Sung R.; Eldridge, Jeffrey I.; Lee, Kang N.; Miller, Robert A.

2003-01-01

In this paper, surface cracking and interface reactions of a BSAS coating and a multi-layer ZrO2-8wt%Y2O3 and mullite/BSAS/Si thermal and environmental barrier coating system on SiC/SiC ceramic matrix composites were characterized after long-term combined laser thermal gradient and furnace cyclic tests in a water vapor containing environment. The surface cracking was analyzed based on the coating thermal gradient sintering behavior and thermal expansion mismatch stress characteristics under the thermal cyclic conditions. The interface reactions, which were largely enhanced by the coating surface cracking in the water vapor environment, were investigated in detail, and the reaction phases were identified for the coating system after the long-term exposure. The accelerated coating delamination failure was attributed to the increased delamination driving force under the thermal gradient cyclic loading and the reduced interface adhesion due to the detrimental interface reactions.

Surface Cracking and Interface Reaction Associated Delamination Failure of Thermal and Environmental Barrier Coatings

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Choi, Sung R.; Eldridge, Jeffrey I.; Lee, Kang N.; Miller, Robert A.

2003-01-01

In this paper, surface cracking and interface reactions of a BSAS coating and a multi-layer ZTO2-8wt%Y2O3 and mullite/BSAS/Si thermal and environmental barrier coating system on SiC/SiC ceramic matrix composites were characterized after long-term combined laser thermal gradient and furnace cyclic tests in a water vapor containing environment. The surface cracking was analyzed based on the coating thermal gradient sintering behavior and thermal expansion mismatch stress characteristics under the thermal cyclic conditions. The interface reactions, which were largely enhanced by the coating surface cracking in the water vapor environment, were investigated in detail, and the reaction phases were identified for the coating system after the long- term exposure. The accelerated coating delamination failure was attributed to the increased delamination driving force under the thermal gradient cyclic loading and the reduced interface adhesion due to the detrimental interface reactions.

78 FR 1199 - Light-Walled Rectangular Pipe and Tube From Mexico: Final Results of Antidumping Duty...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-01-08

... DEPARTMENT OF COMMERCE International Trade Administration [A-201-836] Light-Walled Rectangular... order on light-walled rectangular pipe and tube (LWR pipe and tube) from Mexico. This review covers two... but received no such comments. We also did not receive a request for a hearing. \\1\\ See Light-Walled...

77 FR 21527 - Certain Cut-to-Length Carbon-Quality Steel Plate Products From the Republic of Korea: Final...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-04-10

... in coils) and without patterns in relief), of iron or non-alloy quality steel; and (2) flat-rolled... rectangular or non-rectangular cross section where such non-rectangular cross-section is achieved subsequent... characteristics that are painted, varnished, or coated with plastic or other non-metallic substances are included...

Sampling Scattered Data Onto Rectangular Grids for Volume Visualization

DTIC Science & Technology

1989-12-01

30 4.4 Building A Rectangular Grid ..... ................ 30 4.5 Sampling Methds ...... ...................... 34 4.6...dimensional data have been developed recently. In computational fluid flow analysis, methods for constructing three dimen- sional numerical grids are...structure of rectangular grids. Because finite element analysis is useful in fields other than fluid flow analysis and the numerical grid has promising

78 FR 42546 - Light-Walled Rectangular Pipe and Tube From China, Korea, Mexico, and Turkey: Notice of...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-07-16

...-Walled Rectangular Pipe and Tube From China, Korea, Mexico, and Turkey: Notice of Commission... light-walled rectangular pipe and tube from China, Korea, Mexico, and Turkey would be likely to lead to... institution from the Government of Turkey, the Commission found that the respondent interested party group...

75 FR 33779 - Light-Walled Rectangular Pipe and Tube from Turkey; Notice of Preliminary Results of Antidumping...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-06-15

... Pipe and Tube from Turkey; Notice of Preliminary Results of Antidumping Duty Administrative Review... review of the antidumping duty order on light-walled rectangular pipe and tube from Turkey. Atlas Tube... the antidumping duty order on light-walled rectangular ripe and tube from Turkey on May 30, 2008. See...

77 FR 55455 - Light-Walled Rectangular Pipe and Tube From Turkey: Notice of Final Results of Antidumping Duty...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-09-10

... Pipe and Tube From Turkey: Notice of Final Results of Antidumping Duty Administrative Review AGENCY... administrative review of the antidumping duty order on light-walled rectangular pipe and tube from Turkey.\\1\\ The... entitled ``Final Results of Review'' below. \\1\\ See Light-Walled Rectangular Pipe and Tube from Turkey...

Nanoparticles and amyloid systems: A fatal encounter?

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

Abel, Bernd

2014-10-06

Nanoparticles (NPs) are used in many products of our daily life, however, there has been concern that they may also be harmful to human health. Recently NPs have been found to accelerate the fibrillation kinetics of amyloid systems. In the past this has been preliminarily attributed to a nucleation effect. Nanoparticle surfaces and interfaces appear to limit the degrees of freedom of amyloid systems (i.e., peptides and proteins) due to a phase space constraint such that rapid cross-beta structures are formed faster than without interface interactions and in turn fibril formation is enhanced significantly. Here we explore if lipid bilayersmore » in the form of liposomes (140nm) also accelerate fibril formation for amyloid systems. We have investigated a fragment NNFGAIL of the Human islet amyloid polypeptide (hIAPP) in contact with 1,2-diphytanoyl-sn-glycero-3-phosphocholine (DPhPC) liposomes in aqueous solution. We found that the lipid bilayer vesicles do accelerate fibril formation in time-resolved off-line detected atomic force microscopy experiments. Characteristic Thioflavine-T fluorescence on the same structures verify that the structures consist of aggregated peptides in a typical cross-β-structure arrangement.« less

Large Eddy Simulations of the Tilted Rig Experiment: A Two-dimensional Rayleigh-Taylor Instability Case

NASA Astrophysics Data System (ADS)

Rollin, Bertrand; Denissen, Nicholas A.; Reisner, Jon M.; Andrews, Malcolm J.

2012-11-01

The tilted rig experiment is a derivative of the rocket rig experiment designed to investigate turbulent mixing induced by the Rayleigh-Taylor (RT) instability. A tank containing two fluids of different densities is accelerated downwards between two parallel guiding rods by rocket motors. The acceleration is such that the pressure and density gradients face opposite directions at the fluids interface, creating a Rayleigh-Taylor unstable configuration. The rig is tilted such that the tank is initially at an angle and the acceleration is not perpendicular to the fluids interface when the rockets fire. This results in a two dimensional Rayleigh-Taylor instability case where the fluids experience RT mixing and a bulk overturning motion. The tilted rig is therefore a valuable experiment to help calibrating two-dimensional mixing models. Large Eddy Simulations of the tilted rig experiments will be compared to available experimental results. A study of the behavior of turbulence variables relevant to turbulence modeling will be presented. LA-UR 12-23829. This work was performed for the U.S. Department of Energy by Los Alamos National Laboratory under Contract No.DEAC52- 06NA2-5396.

An analysis of the relaxation of laminar boundary layer on a flat plate after passage of an interface with application to expansion-tube flows

NASA Technical Reports Server (NTRS)

Gupta, R. N.

1972-01-01

The relaxation of the accelerating-gas boundary layer to the test-gas boundary layer over a flat plate in an expansion tube is analyzed. Several combinations of test gas and acceleration gas are considered. The problem is treated in two conically similar limits: (1) when the time lag between the arrival of the shock and the interface at the leading edge of the plate is very large, and (2) when this lag is negligible. The time-dependent laminar-boundary-layer equations of a binary mixture of perfect gases are taken as the flow-governing equations. This coupled set of differential equations, written in terms of the Lam-Crocco variables, has been solved by a line-relaxation finite-difference techniques. The results presented include the Stanton number and the local skin-friction coefficient as functions of shock Mach number and the nondimensional distance-time variable. The results indicate that more than 95 percent of the test-gas boundary layer exists over a length, measured from the leading edge of the plate, equal to about three-tenths of the distance traversed by the interface in the free stream.

Cohesive zone finite element analysis of crack initiation from a butt joint’s interface corner

DOE PAGES

Reedy, E. D.

2014-09-06

The Cohesive zone (CZ) fracture analysis techniques are used to predict the initiation of crack growth from the interface corner of an adhesively bonded butt joint. In this plane strain analysis, a thin linear elastic adhesive layer is sandwiched between rigid adherends. There is no preexisting crack in the problem analyzed, and the focus is on how the shape of the traction–separation (T–U) relationship affects the predicted joint strength. Unlike the case of a preexisting interfacial crack, the calculated results clearly indicate that the predicted joint strength depends on the shape of the T–U relationship. Most of the calculations usedmore » a rectangular T–U relationship whose shape (aspect ratio) is defined by two parameters: the interfacial strength σ* and the work of separation/unit area Γ. The principal finding of this study is that for a specified adhesive layer thickness, there is any number of σ*, Γ combinations that generate the same predicted joint strength. For each combination there is a corresponding CZ length. We developed an approximate CZ-like elasticity solution to show how such combinations arise and their connection with the CZ length.« less

Quasi-stationary states of an electron with linearly dependent effective mass in an open nanostructure within transmission coefficient and S-matrix methods

NASA Astrophysics Data System (ADS)

Seti, Julia; Tkach, Mykola; Voitsekhivska, Oxana

2018-03-01

The exact solutions of the Schrödinger equation for a double-barrier open semiconductor plane nanostructure are obtained by using two different approaches, within the model of the rectangular potential profile and the continuous position-dependent effective mass of the electron. The transmission coefficient and scattering matrix are calculated for the double-barrier nanostructure. The resonance energies and resonance widths of the electron quasi-stationary states are analyzed as a function of the size of the near-interface region between wells and barriers, where the effective mass linearly depends on the coordinate. It is established that, in both methods, the increasing size affects in a qualitatively similar way the spectral characteristics of the states, shifting the resonance energies into the low- or high-energy region and increasing the resonance widths. It is shown that the relative difference of resonance energies and widths of a certain state, obtained in the model of position-dependent effective mass and in the widespread abrupt model in physically correct range of near-interface sizes, does not exceed 0.5% and 5%, respectively, independently of the other geometrical characteristics of the structure.

Faster tissue interface analysis from Raman microscopy images using compressed factorisation

NASA Astrophysics Data System (ADS)

Palmer, Andrew D.; Bannerman, Alistair; Grover, Liam; Styles, Iain B.

2013-06-01

The structure of an artificial ligament was examined using Raman microscopy in combination with novel data analysis. Basis approximation and compressed principal component analysis are shown to provide efficient compression of confocal Raman microscopy images, alongside powerful methods for unsupervised analysis. This scheme allows the acceleration of data mining, such as principal component analysis, as they can be performed on the compressed data representation, providing a decrease in the factorisation time of a single image from five minutes to under a second. Using this workflow the interface region between a chemically engineered ligament construct and a bone-mimic anchor was examined. Natural ligament contains a striated interface between the bone and tissue that provides improved mechanical load tolerance, a similar interface was found in the ligament construct.

Computer code for the prediction of nozzle admittance

NASA Technical Reports Server (NTRS)

Nguyen, Thong V.

1988-01-01

A procedure which can accurately characterize injector designs for large thrust (0.5 to 1.5 million pounds), high pressure (500 to 3000 psia) LOX/hydrocarbon engines is currently under development. In this procedure, a rectangular cross-sectional combustion chamber is to be used to simulate the lower traverse frequency modes of the large scale chamber. The chamber will be sized so that the first width mode of the rectangular chamber corresponds to the first tangential mode of the full-scale chamber. Test data to be obtained from the rectangular chamber will be used to assess the full scale engine stability. This requires the development of combustion stability models for rectangular chambers. As part of the combustion stability model development, a computer code, NOAD based on existing theory was developed to calculate the nozzle admittances for both rectangular and axisymmetric nozzles. This code is detailed.

Runtime and Architecture Support for Efficient Data Exchange in Multi-Accelerator Applications.

PubMed

Cabezas, Javier; Gelado, Isaac; Stone, John E; Navarro, Nacho; Kirk, David B; Hwu, Wen-Mei

2015-05-01

Heterogeneous parallel computing applications often process large data sets that require multiple GPUs to jointly meet their needs for physical memory capacity and compute throughput. However, the lack of high-level abstractions in previous heterogeneous parallel programming models force programmers to resort to multiple code versions, complex data copy steps and synchronization schemes when exchanging data between multiple GPU devices, which results in high software development cost, poor maintainability, and even poor performance. This paper describes the HPE runtime system, and the associated architecture support, which enables a simple, efficient programming interface for exchanging data between multiple GPUs through either interconnects or cross-node network interfaces. The runtime and architecture support presented in this paper can also be used to support other types of accelerators. We show that the simplified programming interface reduces programming complexity. The research presented in this paper started in 2009. It has been implemented and tested extensively in several generations of HPE runtime systems as well as adopted into the NVIDIA GPU hardware and drivers for CUDA 4.0 and beyond since 2011. The availability of real hardware that support key HPE features gives rise to a rare opportunity for studying the effectiveness of the hardware support by running important benchmarks on real runtime and hardware. Experimental results show that in a exemplar heterogeneous system, peer DMA and double-buffering, pinned buffers, and software techniques can improve the inter-accelerator data communication bandwidth by 2×. They can also improve the execution speed by 1.6× for a 3D finite difference, 2.5× for 1D FFT, and 1.6× for merge sort, all measured on real hardware. The proposed architecture support enables the HPE runtime to transparently deploy these optimizations under simple portable user code, allowing system designers to freely employ devices of different capabilities. We further argue that simple interfaces such as HPE are needed for most applications to benefit from advanced hardware features in practice.

Runtime and Architecture Support for Efficient Data Exchange in Multi-Accelerator Applications

PubMed Central

Cabezas, Javier; Gelado, Isaac; Stone, John E.; Navarro, Nacho; Kirk, David B.; Hwu, Wen-mei

2014-01-01

Heterogeneous parallel computing applications often process large data sets that require multiple GPUs to jointly meet their needs for physical memory capacity and compute throughput. However, the lack of high-level abstractions in previous heterogeneous parallel programming models force programmers to resort to multiple code versions, complex data copy steps and synchronization schemes when exchanging data between multiple GPU devices, which results in high software development cost, poor maintainability, and even poor performance. This paper describes the HPE runtime system, and the associated architecture support, which enables a simple, efficient programming interface for exchanging data between multiple GPUs through either interconnects or cross-node network interfaces. The runtime and architecture support presented in this paper can also be used to support other types of accelerators. We show that the simplified programming interface reduces programming complexity. The research presented in this paper started in 2009. It has been implemented and tested extensively in several generations of HPE runtime systems as well as adopted into the NVIDIA GPU hardware and drivers for CUDA 4.0 and beyond since 2011. The availability of real hardware that support key HPE features gives rise to a rare opportunity for studying the effectiveness of the hardware support by running important benchmarks on real runtime and hardware. Experimental results show that in a exemplar heterogeneous system, peer DMA and double-buffering, pinned buffers, and software techniques can improve the inter-accelerator data communication bandwidth by 2×. They can also improve the execution speed by 1.6× for a 3D finite difference, 2.5× for 1D FFT, and 1.6× for merge sort, all measured on real hardware. The proposed architecture support enables the HPE runtime to transparently deploy these optimizations under simple portable user code, allowing system designers to freely employ devices of different capabilities. We further argue that simple interfaces such as HPE are needed for most applications to benefit from advanced hardware features in practice. PMID:26180487

Comparing the Richtmyer-Meshkov instability of thermal and ion-species interfaces in two-fluid plasmas

NASA Astrophysics Data System (ADS)

Wheatley, Vincent; Bond, Daryl; Li, Yuan; Samtaney, Ravi; Pullin, Dale

2017-11-01

The Richtmyer-Meshkov instability (RMI) of a shock accelerated perturbed density interface is important in both inertial confinement fusion and astrophysics, where the materials involved are typically in the plasma state. Initial density interfaces can be due to either temperature or ion-species discontinuities. If the Atwood number of the interfaces and specific heat ratios of the fluids are matched, these two cases behave similarly when modeled using the equations of either hydrodynamics or magnetohydrodynamics. In the two-fluid ion-electron plasma model, however, there is a significant difference between them: In the thermal interface case, there is a discontinuity in electron density that is also subject to the RMI, while for the ion-species interface case there is not. It will be shown via ideal two-fluid plasma simulations that this causes substantial differences in the dynamics of the flow between the two cases. This work was partially supported by the KAUST Office of Sponsored Research under Award URF/1/2162-01.

Analysis of 2D hyperbolic metamaterial dispersion by elementary excitation coupling

NASA Astrophysics Data System (ADS)

Vaianella, Fabio; Maes, Bjorn

2016-04-01

Hyperbolic metamaterials are examined for many applications thanks to the large density of states and extreme confinement of light they provide. For classical hyperbolic metal/dielectric multilayer structures, it was demon- strated that the properties originate from a specific coupling of the surface plasmon polaritons between the metal/dielectric interfaces. We show a similar analysis for 2D hyperbolic arrays of square (or rectangular) silver nanorods in a TiO2 host. In this case the properties derive from a specific coupling of the plasmons carried by the corners of the nanorods. The dispersion can be seen as the coupling of single rods for a through-metal connection of the corners, as the coupling of structures made of four semi-infinite metallic blocks separated by dielectric for a through-dielectric connection, or as the coupling of two semi-infinite rods for a through-metal and through-dielectric situation. For arrays of small square nanorods the elementary structure that explains the dispersion of the array is the single rod, and for arrays of large square nanorods it is four metallic corners. The medium size square nanorod case is more complicated, because the elementary structure can be one of the three basic designs, depending on the frequency and symmetry of the modes. Finally, we show that for arrays of rectangular nanorods the dispersion is explained by coupling of the two coupled rod structure. This work opens the way for a better understanding of a wide class of metamaterials via their elementary excitations.

Steady film flow over a substrate with rectangular trenches forming air inclusions

NASA Astrophysics Data System (ADS)

Varchanis, S.; Dimakopoulos, Y.; Tsamopoulos, J.

2017-12-01

Film flow along an inclined, solid substrate featuring periodic rectangular trenches may either completely wet the trench floor (Wenzel state) or get pinned on the entrance and exit corners of the trench (Cassie state) or assume other configurations in between these two extremes. Such intermediate configurations are examined in the present study. They are bounded by a second gas-liquid interface inside the trench, which adheres to its walls forming two three-phase contact lines, and encloses a different amount of air under different physical conditions. The Galerkin finite-element method is used to solve the Navier-Stokes equations in a physical domain, which is adaptively remeshed. Multiple steady solutions, connected by turning points and transcritical bifurcations as well as isolated solution branches, are revealed by pseudo-arc-length continuation. Two possible configurations of a single air inclusion inside the trench are examined: the inclusion either surrounds the upstream convex corner or is attached to the upstream trench wall. The penetration of the liquid inside the trench is enhanced primarily by increasing either the wettability of the substrate or capillary over viscous forces or by decreasing the flow rate. Flow hysteresis may occur when the liquid wetting of the upstream wall decreases abruptly, leading to drastically different flow patterns for the same parameter values. The interplay of inertia, viscous, gravity, and capillary forces along with substrate wettability determines the volume of the air encapsulated in the trench and the extent of deformation of the outer free surface.

Combining Acceleration and Displacement Dependent Modal Frequency Responses Using an MSC/NASTRAN DMAP Alter

NASA Technical Reports Server (NTRS)

Barnett, Alan R.; Widrick, Timothy W.; Ludwiczak, Damian R.

1996-01-01

Solving for dynamic responses of free-free launch vehicle/spacecraft systems acted upon by buffeting winds is commonly performed throughout the aerospace industry. Due to the unpredictable nature of this wind loading event, these problems are typically solved using frequency response random analysis techniques. To generate dynamic responses for spacecraft with statically-indeterminate interfaces, spacecraft contractors prefer to develop models which have response transformation matrices developed for mode acceleration data recovery. This method transforms spacecraft boundary accelerations and displacements into internal responses. Unfortunately, standard MSC/NASTRAN modal frequency response solution sequences cannot be used to combine acceleration- and displacement-dependent responses required for spacecraft mode acceleration data recovery. External user-written computer codes can be used with MSC/NASTRAN output to perform such combinations, but these methods can be labor and computer resource intensive. Taking advantage of the analytical and computer resource efficiencies inherent within MS C/NASTRAN, a DMAP Alter has been developed to combine acceleration- and displacement-dependent modal frequency responses for performing spacecraft mode acceleration data recovery. The Alter has been used successfully to efficiently solve a common aerospace buffeting wind analysis.

Transient aerodynamic characteristics of vans during the accelerated overtaking process

NASA Astrophysics Data System (ADS)

Liu, Li-ning; Wang, Xing-shen; Du, Guang-sheng; Liu, Zheng-gang; Lei, Li

2018-04-01

This paper studies the influence of the accelerated overtaking process on the vehicles' transient aerodynamic characteristics, through 3-D numerical simulations with dynamic meshes and sliding interface technique. Numerical accuracy is verified by experimental results. The aerodynamic characteristics of vehicles in the uniform overtaking process and the accelerated overtaking process are compared. It is shown that the speed variation of the overtaking van would influence the aerodynamic characteristics of the two vans, with greater influence on the overtaken van than on the overtaking van. The simulations of three different accelerated overtaking processes show that the greater the acceleration of the overtaking van, the larger the aerodynamic coefficients of the overtaken van. When the acceleration of the overtaking van increases by 1 m/s2, the maximum drag force, side force and yawing moment coefficients of the overtaken van all increase by more than 6%, to seriously affect the power performance and the stability of the vehicles. The analysis of the pressure fields under different accelerated conditions reveals the cause of variations of the aerodynamic characteristics of vehicles.

Numerical studies of surface tensions

NASA Technical Reports Server (NTRS)

Hung, R. J.

1995-01-01

Liquid-vapor (bubble) interface disturbances caused by various types of accelerations, including centrifugal, lateral and axial impulses, gravity gradient and g-jitter accelerations associated with spinning and slew motion in microgravity, are reviewed. Understanding of bubble deformations and fluctuations is important in the development of spacecraft orbital and attitude control techniques to secure its normal operation. This review discusses bubble deformations and oscillations driven by various forces in the microgravity environment. The corresponding bubble mass center fluctuations and slosh reaction forces and torques due to bubble deformations are also reviewed.

Accelerated aging of adhesive-mediated fiber post-resin composite bonds: A modeling approach.

PubMed

Radovic, Ivana; Monticelli, Francesca; Papacchini, Federica; Magni, Elisa; Cury, Alvaro Hafiz; Vulicevic, Zoran R; Ferrari, Marco

2007-08-01

Although fiber posts luted in root canals are not directly exposed to oral fluids, water storage is considered as in vitro accelerated aging test for bonded interfaces. The aim of the study was to evaluate the influence of accelerated water aging on fiber post-resin composite adhesion. Forty fiber posts (DT Light Post, RTD) were randomly divided into two main groups, according to the surface treatment performed. Group I: XPBond adhesive (Dentsply Caulk); Group II: sandblasting (Rocatec-Pre, 3M ESPE) and XPBond. Dual-cured resin cement (Calibra, Dentsply Caulk) and flowable composite (X-Flow, Dentsply Caulk) were applied on the posts to produce cylindrical specimens. The bond strength at the interface between post and cement/composite was measured with the microtensile test according to the non-trimming technique. Half of the sticks were tested immediately for bond strength, while in the other half testing was performed after 1 month of water storage at 37 degrees C. Post-cement/composite interfaces were evaluated under SEM prior and after water aging. Statistical analysis was performed using the Kruskal-Wallis ANOVA followed by Dunn's multiple range test (p<0.05). Immediate bond strength was higher on sandblasted posts. After water aging the two post surface treatments resulted comparable in bond strength. Resin cement achieved higher bond strength to fiber posts than flowable composite. Water aging significantly reduced bond strength. Sandblasting followed by adhesive coating may improve immediate post-resin bond strength in comparison to adhesive alone. However, fiber post-resin bond strength mediated by hydrophilic adhesive tends to decrease after water aging.

General image method in a plane-layered elastostatic medium

NASA Technical Reports Server (NTRS)

Fares, N.; Li, V. C.

1988-01-01

The general-image method presently used to obtain the elastostatic fields in plane-layered media relies on the use of potentials in order to represent elastic fields. For the case of a single interface, this method yields the displacement field in closed form, and is applicable to antiplane, plane, and three-dimensional problems. In the case of multiplane interfaces, the image method generates the displacement fields in terms of infinite series whose convergences can be accelerated to improve method efficiency.

Environmental Integrity of Coating/Metal Interface.

DTIC Science & Technology

1988-01-01

34. Report No. 1 FROM 02/01/87 TO 01/31/88 1988, JANUARY 32 * ’B SUPOLEMEN’ARY NOTATiON - 7 COSAT CODES 18 SUBJECT TERMS ,Co’r ’nXe on reverse ’,"ecessa’, ac ...AgCI accelerate disbonding by the formation of a weak fluid boundary layer at the coating/metal interface just ahead of electroosmotically produced...pockets of electroosmotically formed electrolyte or swollen regions of the heterogeneous polymer. A time series of micrographs allowed a virtually

The Design and Implementation of a Semi-Autonomous Surf-Zone Robot Using Advanced Sensors and a Common Robot Operating System

DTIC Science & Technology

2011-06-01

effective way- point navigation algorithm that interfaced with a Java based graphical user interface (GUI), written by Uzun, for a robot named Bender [2...the angular acceleration, θ̈, or angular rate, θ̇. When considering a joint driven by an electric motor, the inertia and friction can be divided into...interactive simulations that can receive input from user controls, scripts , and other applications, such as Excel and MATLAB. One drawback is that the

Thermal convection in a cylindrical enclosure

NASA Astrophysics Data System (ADS)

Shukla, K. N.

2005-02-01

The paper highlights the onset of convection in a fluid layer partially filled in an axisymmetric container. The equilibrium of the fluid is disturbed with the deformation of the interface due to residual acceleration. The general problem of deformable interface involves a dimensionless parameter, the Bond number. An analytical expression for the natural frequencies of the deformable surface is derived in terms of the Bond number, which determines the time period required for the stable location of the fluid for the propellant management of the spacecraft.

Method of manufacturing a large-area segmented photovoltaic module

DOEpatents

Lenox, Carl

2013-11-05

One embodiment of the invention relates to a segmented photovoltaic (PV) module which is manufactured from laminate segments. The segmented PV module includes rectangular-shaped laminate segments formed from rectangular-shaped PV laminates and further includes non-rectangular-shaped laminate segments formed from rectangular-shaped and approximately-triangular-shaped PV laminates. The laminate segments are mechanically joined and electrically interconnected to form the segmented module. Another embodiment relates to a method of manufacturing a large-area segmented photovoltaic module from laminate segments of various shapes. Other embodiments relate to processes for providing a photovoltaic array for installation at a site. Other embodiments and features are also disclosed.

Electromagnetic Field Penetration Studies

NASA Technical Reports Server (NTRS)

Deshpande, M.D.

2000-01-01

A numerical method is presented to determine electromagnetic shielding effectiveness of rectangular enclosure with apertures on its wall used for input and output connections, control panels, visual-access windows, ventilation panels, etc. Expressing EM fields in terms of cavity Green's function inside the enclosure and the free space Green's function outside the enclosure, integral equations with aperture tangential electric fields as unknown variables are obtained by enforcing the continuity of tangential electric and magnetic fields across the apertures. Using the Method of Moments, the integral equations are solved for unknown aperture fields. From these aperture fields, the EM field inside a rectangular enclosure due to external electromagnetic sources are determined. Numerical results on electric field shielding of a rectangular cavity with a thin rectangular slot obtained using the present method are compared with the results obtained using simple transmission line technique for code validation. The present technique is applied to determine field penetration inside a Boeing-757 by approximating its passenger cabin as a rectangular cavity filled with a homogeneous medium and its passenger windows by rectangular apertures. Preliminary results for, two windows, one on each side of fuselage were considered. Numerical results for Boeing-757 at frequencies 26 MHz, 171-175 MHz, and 428-432 MHz are presented.

Effect of application mode on interfacial morphology and chemistry between dentin and self-etch adhesives

PubMed Central

Zhang, Ying; Wang, Yong

2012-01-01

Objective To investigate the influence of application mode on the interfacial morphology and chemistry between dentin and self-etch adhesives with different aggressiveness. Methods The occlusal one-third of the crown was removed from un-erupted human third molars, followed by abrading with 600 grit SiC under water. Rectangular dentin slabs were prepared by sectioning the tooth specimens perpendicular to the abraded surfaces. The obtained dentin slabs were treated with one of the two one-step self-etch adhesives: Adper Easy Bond (AEB, PH~2.5) and Adper Prompt L-Pop (APLP, PH~0.8) with (15s, active application) or without (15s, inactive application) agitation. The dentin slabs were fractured and the exposed adhesive/dentin (A/D) interfaces were examined with micro-Raman spectroscopy and scanning electron microscopy (SEM). Results The interfacial morphology, degree of dentin demineralization (DD) and degree of conversion (DC) of the strong self-etch adhesive APLP showed more significant dependence on the application mode than the mild AEB. APLP exhibited inferior bonding at the A/D interface if applied without agitation, evidenced by debonding from the dentin substrate. The DDs and DCs of the APLP with agitation were higher than those of without agitation in the interface, in contrast to the comparable DD and DC values of two AEB specimen groups with different application modes. Raman spectral analysis revealed the important role of chemical interaction between acid monomers of self-etch adhesives and dentin in the above observations. Conclusion The chemical interaction with dentin is especially important for improving the DC of the strong self-etching adhesive at the A/D interface. Agitation could benefit polymerization efficacy of the strong self-etch adhesive through enhancing the chemical interaction with tooth substrate. PMID:23153573

Sample environment for in situ synchrotron XRD measurements for CO2 interaction with subsurface materials

NASA Astrophysics Data System (ADS)

Elbakhshwan, M.; Gill, S.; Weidner, R.; Ecker, L.

2017-12-01

Sequestration of CO2 in geological formations requires a deep understanding of its interaction with the cement-casing components in the depleted oil and gas wells. Portland cement is used to seal the wellbores; however it tends to interact with the CO2. Therefore it is critical to investigate the wellbore integrity over long term exposure to CO2. Studies showed that, CO2 leakage is due to the flow through the casing-cement microannulus, cement-cement fractures, or the cement-caprock interface. The objective of this work is to gain a better understanding of the dissolution process of the cement-casing in the CO2 flow channels alongside with the carbonation reactions at the interfaces using XRF, XANES and X-ray tomography techniques. In this study, a synthetic wellbore system, consisting of cement with an embedded rectangular length of steel casing that had grooves to accommodate fluid flow, was used to investigate the casing-cement microannulus through core-flood experiments. The objective of this work is to gain a better understanding of the dissolution process of the cement-casing in the CO2 flow channels alongside with the carbonation reactions at the interfaces using a sample environment designed and built for in situ X-ray diffraction in the National Synchrotron Light Source II (NSLS II). The formation of carbonate phases at cement -fluid and cement-steel/fluid interfaces will be monitored in real time. Samples may be exposed to super critical CO2 at pressures above 1100 psi and temperatures around 50°C. The reaction cell is built from hastealloy to provide corrosion resistance, while the experimental temperature and pressure are controlled with thermocouples and pressure vessel.

Pressure and partial wetting effects on superhydrophobic friction reduction in microchannel flow

NASA Astrophysics Data System (ADS)

Kim, Tae Jin; Hidrovo, Carlos

2012-11-01

Friction reduction in microchannel flows can help alleviate the inherently taxing pumping power requirements associated with the dimensions involved. One possible way of achieving friction reduction is through the introduction of surface microtexturing that can lead to a superhydrophobic Cassie-Baxter state. The Cassie-Baxter state is characterized by the presence of air pockets within the surface microtexturing believed to act as an effective "shear free" (or at least shear reduced) layer, decreasing the overall friction characteristics of the surface. Most work in this area has concentrated on optimizing the surface microtexturing geometry to maximize the friction reduction effects and overall stability of the Cassie-Baxter state. However, less attention has been paid to the effects of partially wetted conditions induced by pressure and the correlation between the liquid-gas interface location within the surface microtexturing and the microchannel flow characteristics. This is mainly attributed to the difficulty in tracking the interface shape and location within the microtexturing in the typical top-down view arrangements used in most studies. In this paper, a rectangular microchannel with regular microtexturing on the sidewalls is used to visualize and track the location of the air-water interface within the roughness elements. While visually tracking the wetting conditions in the microtextures, pressure drops versus flow rates for each microchannel are measured and analyzed in terms of the non-dimensional friction coefficient. The frictional behavior of the Poiseuille flow suggests that (1) the air-water interface more closely resembles a no-slip boundary rather than a shear-free one, (2) the friction is rather insensitive to the degree of microtexturing wetting, and (3) the fully wetted (Wenzel state) microtexturing provides lower friction than the non-wetted one (Cassie state), in corroboration with observations (1) and (2).

Development and Design of a User Interface for a Computer Automated Heating, Ventilation, and Air Conditioning System

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

Anderson, B.; /Fermilab

1999-10-08

A user interface is created to monitor and operate the heating, ventilation, and air conditioning system. The interface is networked to the system's programmable logic controller. The controller maintains automated control of the system. The user through the interface is able to see the status of the system and override or adjust the automatic control features. The interface is programmed to show digital readouts of system equipment as well as visual queues of system operational statuses. It also provides information for system design and component interaction. The interface is made easier to read by simple designs, color coordination, and graphics.more » Fermi National Accelerator Laboratory (Fermi lab) conducts high energy particle physics research. Part of this research involves collision experiments with protons, and anti-protons. These interactions are contained within one of two massive detectors along Fermilab's largest particle accelerator the Tevatron. The D-Zero Assembly Building houses one of these detectors. At this time detector systems are being upgraded for a second experiment run, titled Run II. Unlike the previous run, systems at D-Zero must be computer automated so operators do not have to continually monitor and adjust these systems during the run. Human intervention should only be necessary for system start up and shut down, and equipment failure. Part of this upgrade includes the heating, ventilation, and air conditioning system (HVAC system). The HVAC system is responsible for controlling two subsystems, the air temperatures of the D-Zero Assembly Building and associated collision hall, as well as six separate water systems used in the heating and cooling of the air and detector components. The BYAC system is automated by a programmable logic controller. In order to provide system monitoring and operator control a user interface is required. This paper will address methods and strategies used to design and implement an effective user interface. Background material pertinent to the BYAC system will cover the separate water and air subsystems and their purposes. In addition programming and system automation will also be covered.« less

Microgravity Acceleration Measurement System (MAMS) Flight Configuration Verification and Status

NASA Technical Reports Server (NTRS)

Wagar, William

2000-01-01

The Microgravity Acceleration Measurement System (MAMS) is a precision spaceflight instrument designed to measure and characterize the microgravity environment existing in the US Lab Module of the International Space Station. Both vibratory and quasi-steady triaxial acceleration data are acquired and provided to an Ethernet data link. The MAMS Double Mid-Deck Locker (DMDL) EXPRESS Rack payload meets all the ISS IDD and ICD interface requirements as discussed in the paper which also presents flight configuration illustrations. The overall MAMS sensor and data acquisition performance and verification data are presented in addition to a discussion of the Command and Data Handling features implemented via the ISS, downlink and the GRC Telescience Center displays.

Synergia: an accelerator modeling tool with 3-D space charge

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

Amundson, James F.; Spentzouris, P.; /Fermilab

2004-07-01

High precision modeling of space-charge effects, together with accurate treatment of single-particle dynamics, is essential for designing future accelerators as well as optimizing the performance of existing machines. We describe Synergia, a high-fidelity parallel beam dynamics simulation package with fully three dimensional space-charge capabilities and a higher order optics implementation. We describe the computational techniques, the advanced human interface, and the parallel performance obtained using large numbers of macroparticles. We also perform code benchmarks comparing to semi-analytic results and other codes. Finally, we present initial results on particle tune spread, beam halo creation, and emittance growth in the Fermilab boostermore » accelerator.« less

PERFORMANCE OF AN EARTHQUAKE EXCITED ROOF DIAPHRAGM.

USGS Publications Warehouse

Celebi, M.; Brady, G.; Safak, E.; Converse, A.; ,

1986-01-01

The objective of this paper is to study the earthquake performance of the roof diaphragm of the West Valley College gymnasium in Saratoga, California through a complete set of acceleration records obtained during the 24 April 1984 Morgan Hill Earthquake (M equals 6. 1). The roof diaphragm of the 112 ft. multiplied by 144 ft. rectangular, symmetric gymnasium consists of 3/8 in. plywood over tongue-and-groove sheathing attached to steel trusses supported by reinforced concrete columns and walls. Three sensors placed in the direction of each of the axes of the diaphragm facilitate the evaluation of in-plane deformation of the diaphragm. Other sensors placed at ground level measure vertical and horizontal motion of the building floor, and consequently allow the calculation of the relative motion of the diaphragm with respect to the ground level.

Low-frequency and wideband vibration energy harvester with flexible frame and interdigital structure

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

Li, Pengwei, E-mail: lipengwei@tyut.edu.cn; Wang, Yanfen; Luo, Cuixian

2015-04-15

As an alternative to traditional cantilever beam structures and their evolutions, a flexible beam based, interdigital structure, vibration energy harvester has been presented and investigated. The proposed interdigital-shaped oscillator consists of a rectangular flexible frame and series of cantilever beams interdigitally bonded to it. In order to achieve low frequency and wide-bandwidth harvesting, Young’s modulus of materials, frame size and the amount of the cantilevers have been studied systematically. The measured frequency responses of the designed device (PDMS frame, quintuple piezoelectric cantilever beams) show a 460% increase in bandwidth below 80Hz. When excited at an acceleration of 1.0 g, themore » energy harvester achieves to a maximum open-circuit voltage of 65V, and the maximum output power 4.5 mW.« less

Experimental study of the solid-liquid interface in a yield-stress fluid flow upstream of a step

NASA Astrophysics Data System (ADS)

Luu, Li-Hua; Pierre, Philippe; Guillaume, Chambon

2014-11-01

We present an experimental study where a yield-stress fluid is implemented to carefully examine the interface between a liquid-like unyielded region and a solid-like yielded region. The studied hydrodynamics consists of a rectangular pipe-flow disturbed by the presence of a step. Upstream of the step, a solid-liquid interface between a dead zone and a flow zone appears. This configuration can both model geophysical erosion phenomenon in debris flows or find applications for industrial extrusion processes. We aim to investigate the dominant physical mechanism underlying the formation of the static domain, by combining the rheological characterization of the yield-stress fluid with local measurements of the related hydrodynamic parameters. In this work, we use a model fluid, namely polymer micro-gel Carbopol, that exhibits a Hershel-Bulkley viscoplastic rheology. Exploiting the fluid transparency, the flow is monitored by Particle Image Velocimetry thanks to internal visualization technique. In particular, we demonstrate that the flow above the dead zone roughly behaves as a plug flow whose velocity profile can successfully be described by a Poiseuille equation including a Hershel-Bulkley rheology (PHB theory), with exception of a thin zone at the close vicinity of the static domain. The border inside the flow zone above which the so-called PHB flow starts, is found to be the same regardless of the flow rate and to move with a constant velocity that increases with the flow rate. We interpret this feature as a slip frontier.

Pulsed particle beam vacuum-to-air interface

DOEpatents

Cruz, Gilbert E.; Edwards, William F.

1988-01-01

A vacuum-to-air interface (10) is provided for a high-powered, pulsed particle beam accelerator. The interface comprises a pneumatic high speed gate valve (18), from which extends a vacuum-tight duct (26), that termintes in an aperture (28). Means (32, 34, 36, 38, 40, 42, 44, 46, 48) are provided for periodically advancing a foil strip (30) across the aperture (28) at the repetition rate of the particle pulses. A pneumatically operated hollow sealing band (62) urges foil strip (30), when stationary, against and into the aperture (28). Gas pressure means (68, 70) periodically lift off and separate foil strip (30) from aperture (28), so that it may be readily advanced.

Tack coat optimization for HMA overlays : accelerated pavement test report.

DOT National Transportation Integrated Search

2009-02-01

Interface bonding between hot-mix asphalt (HMA) overlays and Portland cement concrete (PCC) pavements is one : of the most significant factors affecting overlay service life. This study was performed to quantify the effects of HMA type, : tack coat t...

The Computer as Lab Partner.

ERIC Educational Resources Information Center

Nicklin, R. C.

1985-01-01

Microcomputers can record laboratory measurements which human laboratory partners can never collect. Simple, harder, and general-purpose interfaces are discussed, with suggestions for several experiments involving an exercise bike, acceleration, and pendulums. Additional applications with pH meters, spectrophotometers, and chromatographs are also…

Nonlinear theory of classical cylindrical Richtmyer-Meshkov instability for arbitrary Atwood numbers

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

Liu, Wan Hai; HEDPS and CAPT, Peking University, Beijing 100871; Ping Yu, Chang, E-mail: champion-yu@163.com

2014-06-15

A nonlinear theory is developed to describe the cylindrical Richtmyer-Meshkov instability (RMI) of an impulsively accelerated interface between incompressible fluids, which is based on both a technique of Padé approximation and an approach of perturbation expansion directly on the perturbed interface rather than the unperturbed interface. When cylindrical effect vanishes (i.e., in the large initial radius of the interface), our explicit results reproduce those [Q. Zhang and S.-I. Sohn, Phys. Fluids 9, 1106 (1996)] related to the planar RMI. The present prediction in agreement with previous simulations [C. Matsuoka and K. Nishihara, Phys. Rev. E 73, 055304(R) (2006)] leads usmore » to better understand the cylindrical RMI at arbitrary Atwood numbers for the whole nonlinear regime. The asymptotic growth rate of the cylindrical interface finger (bubble or spike) tends to its initial value or zero, depending upon mode number of the initial cylindrical interface and Atwood number. The explicit conditions, directly affecting asymptotic behavior of the cylindrical interface finger, are investigated in this paper. This theory allows a straightforward extension to other nonlinear problems related closely to an instable interface.« less

Lipid suppression via double inversion recovery with symmetric frequency sweep for robust 2D‐GRAPPA‐accelerated MRSI of the brain at 7 T

PubMed Central

Hangel, Gilbert; Strasser, Bernhard; Považan, Michal; Gruber, Stephan; Chmelík, Marek; Gajdošík, Martin; Trattnig, Siegfried

2015-01-01

This work presents a new approach for high‐resolution MRSI of the brain at 7 T in clinically feasible measurement times. Two major problems of MRSI are the long scan times for large matrix sizes and the possible spectral contamination by the transcranial lipid signal. We propose a combination of free induction decay (FID)‐MRSI with a short acquisition delay and acceleration via in‐plane two‐dimensional generalised autocalibrating partially parallel acquisition (2D‐GRAPPA) with adiabatic double inversion recovery (IR)‐based lipid suppression to allow robust high‐resolution MRSI. We performed Bloch simulations to evaluate the magnetisation pathways of lipids and metabolites, and compared the results with phantom measurements. Acceleration factors in the range 2–25 were tested in a phantom. Five volunteers were scanned to verify the value of our MRSI method in vivo. GRAPPA artefacts that cause fold‐in of transcranial lipids were suppressed via double IR, with a non‐selective symmetric frequency sweep. The use of long, low‐power inversion pulses (100 ms) reduced specific absorption rate requirements. The symmetric frequency sweep over both pulses provided good lipid suppression (>90%), in addition to a reduced loss in metabolite signal‐to‐noise ratio (SNR), compared with conventional IR suppression (52–70%). The metabolic mapping over the whole brain slice was not limited to a rectangular region of interest. 2D‐GRAPPA provided acceleration up to a factor of nine for in vivo FID‐MRSI without a substantial increase in g‐factors (<1.1). A 64 × 64 matrix can be acquired with a common repetition time of ~1.3 s in only 8 min without lipid artefacts caused by acceleration. Overall, we present a fast and robust MRSI method, using combined double IR fat suppression and 2D‐GRAPPA acceleration, which may be used in (pre)clinical studies of the brain at 7 T. © 2015 The Authors. NMR in Biomedicine published by John Wiley & Sons Ltd. PMID:26370781

Lipid suppression via double inversion recovery with symmetric frequency sweep for robust 2D-GRAPPA-accelerated MRSI of the brain at 7 T.

PubMed

Hangel, Gilbert; Strasser, Bernhard; Považan, Michal; Gruber, Stephan; Chmelík, Marek; Gajdošík, Martin; Trattnig, Siegfried; Bogner, Wolfgang

2015-11-01

This work presents a new approach for high-resolution MRSI of the brain at 7 T in clinically feasible measurement times. Two major problems of MRSI are the long scan times for large matrix sizes and the possible spectral contamination by the transcranial lipid signal. We propose a combination of free induction decay (FID)-MRSI with a short acquisition delay and acceleration via in-plane two-dimensional generalised autocalibrating partially parallel acquisition (2D-GRAPPA) with adiabatic double inversion recovery (IR)-based lipid suppression to allow robust high-resolution MRSI. We performed Bloch simulations to evaluate the magnetisation pathways of lipids and metabolites, and compared the results with phantom measurements. Acceleration factors in the range 2-25 were tested in a phantom. Five volunteers were scanned to verify the value of our MRSI method in vivo. GRAPPA artefacts that cause fold-in of transcranial lipids were suppressed via double IR, with a non-selective symmetric frequency sweep. The use of long, low-power inversion pulses (100 ms) reduced specific absorption rate requirements. The symmetric frequency sweep over both pulses provided good lipid suppression (>90%), in addition to a reduced loss in metabolite signal-to-noise ratio (SNR), compared with conventional IR suppression (52-70%). The metabolic mapping over the whole brain slice was not limited to a rectangular region of interest. 2D-GRAPPA provided acceleration up to a factor of nine for in vivo FID-MRSI without a substantial increase in g-factors (<1.1). A 64 × 64 matrix can be acquired with a common repetition time of ~1.3 s in only 8 min without lipid artefacts caused by acceleration. Overall, we present a fast and robust MRSI method, using combined double IR fat suppression and 2D-GRAPPA acceleration, which may be used in (pre)clinical studies of the brain at 7 T. © 2015 The Authors. NMR in Biomedicine published by John Wiley & Sons Ltd.

The crack and wedging problem for an orthotropic strip

NASA Technical Reports Server (NTRS)

Cinar, A.; Erdogan, F.

1983-01-01

The plane elasticity problem for an orthotropic strip containing a crack parallel to its boundaries is considered. The problem is formulated under general mixed mode loading conditions. The stress intensity factors depend on two dimensionless orthotropic constants only. For the crack problem the results are given for a single crack and two collinear cracks. The calculated results show that of the two orthotropic constants the influence of the stiffness ratio on the stress intensity factors is much more significant than that of the shear parameter. The problem of loading the strip by a rigid rectangular lengths continuous contact is maintained along the wedge strip interface; at a certain critical wedge length the separation starts at the midsection of the wedge, and the length of the separation zone increases rapidly with increasing wedge length. Previously announced in STAR as N82-26707

High-temperature, flexible, thermal barrier seal

NASA Technical Reports Server (NTRS)

Sirocky, Paul J. (Inventor); Steinetz, Bruce M. (Inventor)

1991-01-01

This device seals the sliding interfaces between structural panels that are roughly perpendicular to each other or whose edges are butted against one another. The nonuniformity of the gap between the panels requires significant flexibility along the seal length. The seal is mounted in a rectangular groove in a movable structural panel. A plurality of particles or balls is densely packed in an outer sheathing. The balls are laterally preloaded to maintain sealing contact with the adjacent wall using a pressurized linear bellows. Distortions in the adjacent panel are accommodated by rearrangement of the particles within the outer sheathing. Leakage through the seal is minimized by densely compacting the internal particles and by maintaining positive preload along the back side of the seal. The braid architecture of the outer sheathing is selected to minimize leakage through the seal and to resist mechanical abrasion.

Spacecraft Orbit Design and Analysis (SODA). Version 2.0: User's guide

NASA Technical Reports Server (NTRS)

Stallcup, Scott S.; Davis, John S.; Zsoldos, Jeffrey S.

1991-01-01

The Spacecraft Orbit Design and Analysis (SODA) computer program, Version 2.0, is discussed. SODA is a spaceflight mission planning system that consists of six program modules integrated around a common database and user interface. SODA runs on a VAX/VMS computer with an Evans and Sutherland PS300 graphics workstation. In the current version, three program modules produce an interactive three dimensional animation of one or more satellites in planetary orbit. Satellite visibility and sensor coverage capabilities are also provided. Circular and rectangular, off nadir, fixed and scanning sensors are supported. One module produces an interactive three dimensional animation of the solar system. Another module calculates cumulative satellite sensor coverage and revisit time for one or more satellites. Currently, Earth, Moon, and Mars systems are supported for all modules except the solar system module.

Extending the Solvation-Layer Interface Condition Continum Electrostatic Model to a Linearized Poisson-Boltzmann Solvent.

PubMed

Molavi Tabrizi, Amirhossein; Goossens, Spencer; Mehdizadeh Rahimi, Ali; Cooper, Christopher D; Knepley, Matthew G; Bardhan, Jaydeep P

2017-06-13

We extend the linearized Poisson-Boltzmann (LPB) continuum electrostatic model for molecular solvation to address charge-hydration asymmetry. Our new solvation-layer interface condition (SLIC)/LPB corrects for first-shell response by perturbing the traditional continuum-theory interface conditions at the protein-solvent and the Stern-layer interfaces. We also present a GPU-accelerated treecode implementation capable of simulating large proteins, and our results demonstrate that the new model exhibits significant accuracy improvements over traditional LPB models, while reducing the number of fitting parameters from dozens (atomic radii) to just five parameters, which have physical meanings related to first-shell water behavior at an uncharged interface. In particular, atom radii in the SLIC model are not optimized but uniformly scaled from their Lennard-Jones radii. Compared to explicit-solvent free-energy calculations of individual atoms in small molecules, SLIC/LPB is significantly more accurate than standard parametrizations (RMS error 0.55 kcal/mol for SLIC, compared to RMS error of 3.05 kcal/mol for standard LPB). On parametrizing the electrostatic model with a simple nonpolar component for total molecular solvation free energies, our model predicts octanol/water transfer free energies with an RMS error 1.07 kcal/mol. A more detailed assessment illustrates that standard continuum electrostatic models reproduce total charging free energies via a compensation of significant errors in atomic self-energies; this finding offers a window into improving the accuracy of Generalized-Born theories and other coarse-grained models. Most remarkably, the SLIC model also reproduces positive charging free energies for atoms in hydrophobic groups, whereas standard PB models are unable to generate positive charging free energies regardless of the parametrized radii. The GPU-accelerated solver is freely available online, as is a MATLAB implementation.

Accelerator-Reactor Coupling for Energy Production in Advanced Nuclear Fuel Cycles

NASA Astrophysics Data System (ADS)

Heidet, Florent; Brown, Nicholas R.; Haj Tahar, Malek

This article is a review of several accelerator-reactor interface issues and nuclear fuel cycle applications of accelerator-driven subcritical systems. The systems considered here have the primary goal of energy production, but that goal is accomplished via a specific application in various proposed nuclear fuel cycles, such as breed-and-burn of fertile material or burning of transuranic material. Several basic principles are reviewed, starting from the proton beam window including the target, blanket, reactor core, and up to the fuel cycle. We focus on issues of interest, such as the impact of the energy required to run the accelerator and associated systems on the potential electricity delivered to the grid. Accelerator-driven systems feature many of the constraints and issues associated with critical reactors, with the added challenges of subcritical operation and coupling to an accelerator. Reliable accelerator operation and avoidance of beam trips are critically important. One interesting challenge is measurement of blanket subcriticality level during operation. We also review the potential benefits of accelerator-driven systems in various nuclear fuel cycle applications. Ultimately, accelerator-driven subcritical systems with the goal of transmutation of transuranic material have lower 100,000-year radioactivity than a critical fast reactor with recycling of uranium and plutonium.

Shear flow control of cold and heated rectangular jets by mechanical tabs. Volume 1: Results and discussion

NASA Technical Reports Server (NTRS)

Brown, W. H.; Ahuja, K. K.

1989-01-01

The effects of mechanical protrusions on the jet mixing characteristics of rectangular nozzles for heated and unheated subsonic and supersonic jet plumes were studied. The characteristics of a rectangular nozzle of aspect ratio 4 without the mechanical protrusions were first investigated. Intrusive probes were used to make the flow measurements. Possible errors introduced by intrusive probes in making shear flow measurements were also examined. Several scaled sizes of mechanical tabs were then tested, configured around the perimeter of the rectangular jet. Both the number and the location of the tabs were varied. From this, the best configuration was selected. The conclusions derived were: (1) intrusive probes can produce significant errors in the measurements of the velocity of jets if they are large in diameter and penetrate beyond the jet center; (2) rectangular jets without tabs, compared to circular jets of the same exit area, provide faster jet mixing; and (3) further mixing enhancement is possible by using mechanical tabs.

Scattered acoustic field above a grating of parallel rectangular cavities

NASA Astrophysics Data System (ADS)

Khanfir, A.; Faiz, A.; Ducourneau, J.; Chatillon, J.; Skali Lami, S.

2013-02-01

The aim of this research project was to predict the sound pressure above a wall facing composed of N parallel rectangular cavities. The diffracted acoustic field is processed by generalizing the Kobayashi Potential (KP) method used for determining the electromagnetic field diffracted by a rectangular cavity set in a thick screen. This model enables the diffracted field to be expressed in modal form. Modal amplitudes are subsequently calculated using matrix equations obtained by enforcing boundary conditions. Solving these equations allows the determination of the total reflected acoustic field above the wall facing. This model was compared with experimental results obtained in a semi-anechoic room for a single cavity, a periodic array of three rectangular cavities and an aperiodic grating of nine rectangular cavities of different size and spacing. These facings were insonified by an incident spherical acoustic field, which was decomposed into plane waves. The validity of this model is supported by the agreement between the numerical and experimental results observed.

Rectangular optical filter based on high-order silicon microring resonators

NASA Astrophysics Data System (ADS)

Bao, Jia-qi; Yu, Kan; Wang, Li-jun; Yin, Juan-juan

2017-07-01

The rectangular optical filter is one of the most important optical switching components in the dense wavelength division multiplexing (DWDM) fiber-optic communication system and the intelligent optical network. The integrated highorder silicon microring resonator (MRR) is one of the best candidates to achieve rectangular filtering spectrum response. In general, the spectrum response rectangular degree of the single MRR is very low, so it cannot be used in the DWDM system. Using the high-order MRRs, the bandwidth of flat-top pass band, the out-of-band rejection degree and the roll-off coefficient of the edge will be improved obviously. In this paper, a rectangular optical filter based on highorder MRRs with uniform couplers is presented and demonstrated. Using 15 coupled race-track MRRs with 10 μm in radius, the 3 dB flat-top pass band of 2 nm, the out-of-band rejection ratio of 30 dB and the rising and falling edges of 48 dB/nm can be realized successfully.

A modal approach to piano soundboard vibroacoustic behavior.

PubMed

Trévisan, Benjamin; Ege, Kerem; Laulagnet, Bernard

2017-02-01

This paper presents an analytical method for modeling the vibro-acoustic behavior of ribbed non-rectangular orthotropic clamped plates. To do this, the non-rectangular plate is embedded in an extended rectangular simply supported plate on which a spring distribution is added, blocking the extended part of the surface, and allowing the description of any inner surface shapes. The acoustical radiation of the embedded plate is ensured using the radiation impedances of the extended rectangular simply supported plate. This method is applied to an upright piano soundboard: a non-rectangular orthotropic plate ribbed in both directions by several straight stiffeners. A modal decomposition is adopted on the basis of the rectangular extended simply supported plate modes, making it possible to calculate the modes of a piano soundboard in the frequency range [0;3000] Hz, showing the different associated mode families. Likewise, the acoustical radiation is calculated using the radiation impedances of a simply supported baffled plate, demonstrating the influence of the string coupling point positions on the acoustic radiated power. The paper ends with the introduction of indicators taking into account spatial and spectral variations of the excitation depending on the notes, which add to the accuracy of the study from the musical standpoint. A parametrical study, which includes several variations of soundboard design, highlights the complexity of rendering high-pitched notes homogeneous.

Turbulence Measurements of Rectangular Nozzles with Bevel

NASA Technical Reports Server (NTRS)

Bridges, James; Wernet, Mark P.

2015-01-01

This paper covers particle image velocimetry measurements of a family of rectangular nozzles with aspect ratios 2, 4, and 8, in the high subsonic flow regime. Far-field acoustic results, presented previously, showed that increasing aspect ratios increased the high frequency noise, especially directed in the polar plane containing the minor axis of the nozzle. The measurements presented here have important implications in the modeling of turbulent sources for acoustic analogy theories. While the nonaxisymmetric mean flow from the rectangular nozzles can be studied reliably using computational solutions, the nonaxisymmetry of the turbulent fluctuations, particularly at the level of velocity components, cannot; only measurements such as these can determine the impact of nozzle geometry on acoustic source anisotropy. Additional nozzles were constructed that extended the wide lip on one side of these nozzles to form beveled nozzles. The paper first documents the velocity fields, mean and variance, from the round, rectangular, and beveled rectangular nozzles at high subsonic speeds. A second section introduces measures of the isotropy of the turbulence, such as component ratios and lengthscales, first by showing them for a round jet and then for the rectangular nozzles. From these measures the source models of acoustic analogy codes can be judged or modified to account for these anisotropies.

Analysis of the rectangular resonator with butterfly MMI coupler using SOI

NASA Astrophysics Data System (ADS)

Kim, Sun-Ho; Park, Jun-Hee; Kim, Eudum; Jeon, Su-Jin; Kim, Ji-Hoon; Choi, Young-Wan

2018-02-01

We propose a rectangular resonator sensor structure with butterfly MMI coupler using SOI. It consists of the rectangular resonator, total internal reflection (TIR) mirror, and the butterfly MMI coupler. The rectangular resonator is expected to be used as bio and chemical sensors because of the advantages of using MMI coupler and the absence of bending loss unlike ring resonators. The butterfly MMI coupler can miniaturize the device compared to conventional MMI by using a linear butterfly shape instead of a square in the MMI part. The width, height, and slab height of the rib type waveguide are designed to be 1.5 μm, 1.5 μm, and 0.9 μm, respectively. This structure is designed as a single mode. When designing a TIR mirror, we considered the Goos-Hänchen shift and critical angle. We designed 3:1 MMI coupler because rectangular resonator has no bending loss. The width of MMI is designed to be 4.5 μm and we optimize the length of the butterfly MMI coupler using finite-difference time-domain (FDTD) method for higher Q-factor. It has the equal performance with conventional MMI even though the length is reduced by 1/3. As a result of the simulation, Qfactor of rectangular resonator can be obtained as 7381.

A Theoretical Investigation of the Input Characteristics of a Rectangular Cavity-Backed Slot Antenna

NASA Technical Reports Server (NTRS)

Cockrell, C. R.

1975-01-01

Equations which represent the magnetic and electric stored energies are derived for an infinite section of rectangular waveguide and a rectangular cavity. These representations which are referred to as being physically observable are obtained by considering the difference in the volume integrals appearing in the complex Poynting theorem. It is shown that the physically observable stored energies are determined by the field components that vanish in a reference plane outside the aperture. These physically observable representations are used to compute the input admittance of a rectangular cavity-backed slot antenna in which a single propagating wave is assumed to exist in the cavity. The slot is excited by a voltage source connected across its center; a sinusoidal distribution is assumed in the slot. Input-admittance calculations are compared with measured data. In addition, input-admittance curves as a function of electrical slot length are presented for several size cavities. For the rectangular cavity backed slot antenna, the quality factor and relative bandwidth were computed independently by using these energy relationships. It is shown that the asymptotic relationship which is usually assumed to exist between the quality bandwidth and the reciprocal of relative bandwidth is equally valid for the rectangular cavity backed slot antenna.

Two-step fabrication of single-layer rectangular SnSe flakes

NASA Astrophysics Data System (ADS)

Jiang, Jizhou; Wong, Calvin Pei Yu; Zou, Jing; Li, Shisheng; Wang, Qixing; Chen, Jianyi; Qi, Dianyu; Wang, Hongyu; Eda, Goki; Chua, Daniel H. C.; Shi, Yumeng; Zhang, Wenjing; Thye Shen Wee, Andrew

2017-06-01

Recent findings about ultrahigh thermoelectric performances in SnSe single crystals have stimulated research on this binary semiconductor material. Furthermore, single-layer SnSe is an interesting analogue of phosphorene, with potential applications in two-dimensional (2D) nanoelectronics. Although significant advances in the synthesis of SnSe nanocrystals have been made, fabrication of well-defined large-sized single-layer SnSe flakes in a facile way still remains a challenge. The growth of single-layer rectangular SnSe flakes with a thickness of ~6.8 Å and lateral dimensions of about 30 µm  ×  50 µm is demonstrated by a two-step synthesis method, where bulk rectangular SnSe flakes were synthesized first by a vapor transport deposition method followed by a nitrogen etching technique to fabricate single-layer rectangular SnSe flakes in an atmospheric pressure system. The as-obtained rectangular SnSe flakes exhibited a pure crystalline phase oriented along the a-axis direction. Field-effect transistor devices fabricated on individual single-layer rectangular SnSe flakes using gold electrodes exhibited p-doped ambipolar behavior and a hole mobility of about 0.16 cm2 V-1 s-1. This two-step fabrication method can be helpful for growing other similar 2D large-sized single-layer materials.

Empirical ground-motion relations for subduction-zone earthquakes and their application to Cascadia and other regions

USGS Publications Warehouse

Atkinson, G.M.; Boore, D.M.

2003-01-01

Ground-motion relations for earthquakes that occur in subduction zones are an important input to seismic-hazard analyses in many parts of the world. In the Cascadia region (Washington, Oregon, northern California, and British Columbia), for example, there is a significant hazard from megathrust earthquakes along the subduction interface and from large events within the subducting slab. These hazards are in addition to the hazard from shallow earthquakes in the overlying crust. We have compiled a response spectra database from thousands of strong-motion recordings from events of moment magnitude (M) 5-8.3 occurring in subduction zones around the world, including both interface and in-slab events. The 2001 M 6.8 Nisqually and 1999 M 5.9 Satsop earthquakes are included in the database, as are many records from subduction zones in Japan (Kyoshin-Net data), Mexico (Guerrero data), and Central America. The size of the database is four times larger than that available for previous empirical regressions to determine ground-motion relations for subduction-zone earthquakes. The large dataset enables improved determination of attenuation parameters and magnitude scaling, for both interface and in-slab events. Soil response parameters are also better determined by the data. We use the database to develop global ground-motion relations for interface and in-slab earthquakes, using a maximum likelihood regression method. We analyze regional variability of ground-motion amplitudes across the global database and find that there are significant regional differences. In particular, amplitudes in Cascadia differ by more than a factor of 2 from those in Japan for the same magnitude, distance, event type, and National Earthquake Hazards Reduction Program (NEHRP) soil class. This is believed to be due to regional differences in the depth of the soil profile, which are not captured by the NEHRP site classification scheme. Regional correction factors to account for these differences are proposed for Cascadia and Japan. The results of this study differ significantly from previous analyses based on more limited data and have important implications for seismic-hazard analysis. The ground-motion relations predict that a great megathrust earthquake (M ???8) at a fault distance of about 100 km would produce pseudoacceleration (PSA), 5% damped, horizontal component on soil sites of about 110 cm/sec2 at 0.5 Hz, 660 cm/sec2 at 2.5 Hz, and 410 cm/sec2 at 5 Hz, with a peak ground acceleration of about 180 cm/ sec2 . These damaging levels of motion would be experienced over a very large area, corresponding to a rectangular area about 300 km wide by 500 km long. Large in-slab events (M 7.5) would produce even higher PSA values within 100 km of the fault, but the in-slab motions attenuate much more rapidly with distance. Thus the hazard posed by moderate to large in-slab events such as the 2001 Nisqually earthquake is modest compared to that of a Cascadia megathrust earthquake of M ???8, in terms of the area that would experience damaging levels of ground motion.

Usability study of clinical exome analysis software: top lessons learned and recommendations.

PubMed

Shyr, Casper; Kushniruk, Andre; Wasserman, Wyeth W

2014-10-01

New DNA sequencing technologies have revolutionized the search for genetic disruptions. Targeted sequencing of all protein coding regions of the genome, called exome analysis, is actively used in research-oriented genetics clinics, with the transition to exomes as a standard procedure underway. This transition is challenging; identification of potentially causal mutation(s) amongst ∼10(6) variants requires specialized computation in combination with expert assessment. This study analyzes the usability of user interfaces for clinical exome analysis software. There are two study objectives: (1) To ascertain the key features of successful user interfaces for clinical exome analysis software based on the perspective of expert clinical geneticists, (2) To assess user-system interactions in order to reveal strengths and weaknesses of existing software, inform future design, and accelerate the clinical uptake of exome analysis. Surveys, interviews, and cognitive task analysis were performed for the assessment of two next-generation exome sequence analysis software packages. The subjects included ten clinical geneticists who interacted with the software packages using the "think aloud" method. Subjects' interactions with the software were recorded in their clinical office within an urban research and teaching hospital. All major user interface events (from the user interactions with the packages) were time-stamped and annotated with coding categories to identify usability issues in order to characterize desired features and deficiencies in the user experience. We detected 193 usability issues, the majority of which concern interface layout and navigation, and the resolution of reports. Our study highlights gaps in specific software features typical within exome analysis. The clinicians perform best when the flow of the system is structured into well-defined yet customizable layers for incorporation within the clinical workflow. The results highlight opportunities to dramatically accelerate clinician analysis and interpretation of patient genomic data. We present the first application of usability methods to evaluate software interfaces in the context of exome analysis. Our results highlight how the study of user responses can lead to identification of usability issues and challenges and reveal software reengineering opportunities for improving clinical next-generation sequencing analysis. While the evaluation focused on two distinctive software tools, the results are general and should inform active and future software development for genome analysis software. As large-scale genome analysis becomes increasingly common in healthcare, it is critical that efficient and effective software interfaces are provided to accelerate clinical adoption of the technology. Implications for improved design of such applications are discussed. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

ENDOR with band-selective shaped inversion pulses

NASA Astrophysics Data System (ADS)

Tait, Claudia E.; Stoll, Stefan

2017-04-01

Electron Nuclear DOuble Resonance (ENDOR) is based on the measurement of nuclear transition frequencies through detection of changes in the polarization of electron transitions. In Davies ENDOR, the initial polarization is generated by a selective microwave inversion pulse. The rectangular inversion pulses typically used are characterized by a relatively low selectivity, with full inversion achieved only for a limited number of spin packets with small resonance offsets. With the introduction of pulse shaping to EPR, the rectangular inversion pulses can be replaced with shaped pulses with increased selectivity. Band-selective inversion pulses are characterized by almost rectangular inversion profiles, leading to full inversion for spin packets with resonance offsets within the pulse excitation bandwidth and leaving spin packets outside the excitation bandwidth largely unaffected. Here, we explore the consequences of using different band-selective amplitude-modulated pulses designed for NMR as the inversion pulse in ENDOR. We find an increased sensitivity for small hyperfine couplings compared to rectangular pulses of the same bandwidth. In echo-detected Davies-type ENDOR, finite Fourier series inversion pulses combine the advantages of increased absolute ENDOR sensitivity of short rectangular inversion pulses and increased sensitivity for small hyperfine couplings of long rectangular inversion pulses. The use of pulses with an almost rectangular frequency-domain profile also allows for increased control of the hyperfine contrast selectivity. At X-band, acquisition of echo transients as a function of radiofrequency and appropriate selection of integration windows during data processing allows efficient separation of contributions from weakly and strongly coupled nuclei in overlapping ENDOR spectra within a single experiment.

Global field synchronization in gamma range of the sleep EEG tracks sleep depth: Artifact introduced by a rectangular analysis window.

PubMed

Rusterholz, Thomas; Achermann, Peter; Dürr, Roland; Koenig, Thomas; Tarokh, Leila

2017-06-01

Investigating functional connectivity between brain networks has become an area of interest in neuroscience. Several methods for investigating connectivity have recently been developed, however, these techniques need to be applied with care. We demonstrate that global field synchronization (GFS), a global measure of phase alignment in the EEG as a function of frequency, must be applied considering signal processing principles in order to yield valid results. Multichannel EEG (27 derivations) was analyzed for GFS based on the complex spectrum derived by the fast Fourier transform (FFT). We examined the effect of window functions on GFS, in particular of non-rectangular windows. Applying a rectangular window when calculating the FFT revealed high GFS values for high frequencies (>15Hz) that were highly correlated (r=0.9) with spectral power in the lower frequency range (0.75-4.5Hz) and tracked the depth of sleep. This turned out to be spurious synchronization. With a non-rectangular window (Tukey or Hanning window) these high frequency synchronization vanished. Both, GFS and power density spectra significantly differed for rectangular and non-rectangular windows. Previous papers using GFS typically did not specify the applied window and may have used a rectangular window function. However, the demonstrated impact of the window function raises the question of the validity of some previous findings at higher frequencies. We demonstrated that it is crucial to apply an appropriate window function for determining synchronization measures based on a spectral approach to avoid spurious synchronization in the beta/gamma range. Copyright © 2017 Elsevier B.V. All rights reserved.

Operation in the turbulent jet field of a linear array of multiple rectangular jets using a two-dimensional jet (Variation of mean velocity field)

NASA Astrophysics Data System (ADS)

Fujita, Shigetaka; Harima, Takashi

2016-03-01

The mean flowfield of a linear array of multiple rectangular jets run through transversely with a two-dimensional jet, has been investigated, experimentally. The object of this experiment is to operate both the velocity scale and the length scale of the multiple rectangular jets using a two-dimensional jet. The reason of the adoption of this nozzle exit shape was caused by the reports of authors in which the cruciform nozzle promoted the inward secondary flows strongly on both the two jet axes. Aspect ratio of the rectangular nozzle used in this experiment was 12.5. Reynolds number based on the nozzle width d and the exit mean velocity Ue (≅ 39 m / s) was kept constant 25000. Longitudinal mean velocity was measured using an X-array Hot-Wire Probe (lh = 3.1 μm in diameter, dh = 0.6 mm effective length : dh / lh = 194) operated by the linearized constant temperature anemometers (DANTEC), and the spanwise and the lateral mean velocities were measured using a yaw meter. The signals from the anemometers were passed through the low-pass filters and sampled using A.D. converter. The processing of the signals was made by a personal computer. Acquisition time of the signals was usually 60 seconds. From this experiment, it was revealed that the magnitude of the inward secondary flows on both the y and z axes in the upstream region of the present jet was promoted by a two-dimensional jet which run through transversely perpendicular to the multiple rectangular jets, therefore the potential core length on the x axis of the present jet extended 2.3 times longer than that of the multiple rectangular jets, and the half-velocity width on the rectangular jet axis of the present jet was suppressed 41% shorter compared with that of the multiple rectangular jets.

Mechanism of electromigration failure in Damascene processed copper interconnects

NASA Astrophysics Data System (ADS)

Michael, Nancy Lyn

2002-11-01

A major unresolved issue in Cu interconnect reliability is the interface role in the failure mechanism of real structures. The present study investigates failure in single-level damascene Cu interconnects with variations in interface condition, passivation and barrier, and linewidth. In the first phase, accelerated electromigration testing of 0.25mum Cu interconnects capped with SiN or SiCN, shows that lifetime and failure mode vary with capping layer. The first mode, seen primarily in SiN samples, is characterized by gradual resistance increase and extensive interface damage, believed to result from failure led by interface electromigration. The competing failure mode, found in SiCN capped samples, is characterized by abrupt resistance increase and localized voiding. The second phase fixes SiCN as the capping material and varies barrier material and line width. The three barrier materials, Ta, TaN, and Ta/TaN, produce similar lifetime statistics and failure is abrupt. Line width, however, does have a strong influence on failure time. The line width/grain size ratio ranged from 0.53 to 2.2 but does not correlate with mean time to failure (MTF). The strong dependence on interface fraction, combined with the conclusion from phase one that interface electromigration is not rate controlling, suggests another mechanism related to the interface is a controlling factor. The possibility that contamination and defects at the interface are key to this failure mode was investigated using electro-thermal fatigue (ETF). In ETF, where lines are simultaneously subjected to thermal cycling and constant current, damage caused by thermal stress is accelerated. Tests reveal that in 80 nm lines, transient failure occurs at times far below MTF in electromigration tests at higher temperatures. Failure found in ETF is clearly a result of damage growth due to thermal/mechanical stress rather than electromigration. At the stress levels created by the moderate ETF test conditions, the only place voids are likely to nucleate and grow is at pre-existing defects and impurities. In narrower lines, where smaller voids can cause catastrophic damage, defects have a greater effect on MTF. Results from this investigation suggest that impurities and defects in the Cu and at the interface, must be carefully controlled to make reliable narrow Cu interconnects.

The balance of electric field and interfacial catalysis in promoting water dissociation in bipolar membranes

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

Yan, Zhifei; Zhu, Liang; Li, Yuguang C.

Bipolar membranes maintain a steady pH in electrolytic cells through water autodissociation at the interface between their cation- and anion-exchange layers. We analyze the balance of electric field and catalysis in accelerating this reaction.

The balance of electric field and interfacial catalysis in promoting water dissociation in bipolar membranes

DOE PAGES

Yan, Zhifei; Zhu, Liang; Li, Yuguang C.; ...

2018-01-01

Bipolar membranes maintain a steady pH in electrolytic cells through water autodissociation at the interface between their cation- and anion-exchange layers. We analyze the balance of electric field and catalysis in accelerating this reaction.

Multifunctional Materials and Structures Gordon Research Conference

DTIC Science & Technology

2016-03-08

accelerating transport or dynamic chemical changes in strong, stiff materials, optimizing interfaces between hard and soft materials, multi-physics...Forms; Discuss Future Site and Scheduling Preferences; Election of the Next Vice Chair 7:30 pm - 9:30 pm Actuation and Morphing Discussion Leader

Fluid Physics Under a Stochastic Acceleration Field

NASA Technical Reports Server (NTRS)

Vinals, Jorge

2001-01-01

The research summarized in this report has involved a combined theoretical and computational study of fluid flow that results from the random acceleration environment present onboard space orbiters, also known as g-jitter. We have focused on a statistical description of the observed g-jitter, on the flows that such an acceleration field can induce in a number of experimental configurations of interest, and on extending previously developed methodology to boundary layer flows. Narrow band noise has been shown to describe many of the features of acceleration data collected during space missions. The scale of baroclinically induced flows when the driving acceleration is random is not given by the Rayleigh number. Spatially uniform g-jitter induces additional hydrodynamic forces among suspended particles in incompressible fluids. Stochastic modulation of the control parameter shifts the location of the onset of an oscillatory instability. Random vibration of solid boundaries leads to separation of boundary layers. Steady streaming ahead of a modulated solid-melt interface enhances solute transport, and modifies the stability boundaries of a planar front.

A beamline systems model for Accelerator-Driven Transmutation Technology (ADTT) facilities

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

Todd, A.M.M.; Paulson, C.C.; Peacock, M.A.

1995-10-01

A beamline systems code, that is being developed for Accelerator-Driven Transmutation Technology (ADTT) facility trade studies, is described. The overall program is a joint Grumman, G.H. Gillespie Associates (GHGA) and Los Alamos National Laboratory effort. The GHGA Accelerator Systems Model (ASM) has been adopted as the framework on which this effort is based. Relevant accelerator and beam transport models from earlier Grumman systems codes are being adapted to this framework. Preliminary physics and engineering models for each ADTT beamline component have been constructed. Examples noted include a Bridge Coupled Drift Tube Linac (BCDTL) and the accelerator thermal system. A decisionmore » has been made to confine the ASM framework principally to beamline modeling, while detailed target/blanket, balance-of-plant and facility costing analysis will be performed externally. An interfacing external balance-of-plant and facility costing model, which will permit the performance of iterative facility trade studies, is under separate development. An ABC (Accelerator Based Conversion) example is used to highlight the present models and capabilities.« less

A beamline systems model for Accelerator-Driven Transmutation Technology (ADTT) facilities

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

Todd, Alan M. M.; Paulson, C. C.; Peacock, M. A.

1995-09-15

A beamline systems code, that is being developed for Accelerator-Driven Transmutation Technology (ADTT) facility trade studies, is described. The overall program is a joint Grumman, G. H. Gillespie Associates (GHGA) and Los Alamos National Laboratory effort. The GHGA Accelerator Systems Model (ASM) has been adopted as the framework on which this effort is based. Relevant accelerator and beam transport models from earlier Grumman systems codes are being adapted to this framework. Preliminary physics and engineering models for each ADTT beamline component have been constructed. Examples noted include a Bridge Coupled Drift Tube Linac (BCDTL) and the accelerator thermal system. Amore » decision has been made to confine the ASM framework principally to beamline modeling, while detailed target/blanket, balance-of-plant and facility costing analysis will be performed externally. An interfacing external balance-of-plant and facility costing model, which will permit the performance of iterative facility trade studies, is under separate development. An ABC (Accelerator Based Conversion) example is used to highlight the present models and capabilities.« less

Experimental Characterization of a Plasma Deflagration Accelerator for Simulating Fusion Wall Response to Disruption Events

NASA Astrophysics Data System (ADS)

Underwood, Thomas; Loebner, Keith; Cappelli, Mark

2016-10-01

In this work, the suitability of a pulsed deflagration accelerator to simulate the interaction of edge-localized modes with plasma first wall materials is investigated. Experimental measurements derived from a suite of diagnostics are presented that focus on the both the properties of the plasma jet and the manner in which such jets couple with material interfaces. Detailed measurements of the thermodynamic plasma state variables within the jet are presented using a quadruple Langmuir probe operating in current-saturation mode. This data in conjunction with spectroscopic measurements of H α Stark broadening via a fast-framing, intensified CCD camera provide spatial and temporal measurements of how the plasma density and temperature scale as a function of input energy. Using these measurements, estimates for the energy flux associated with the deflagration accelerator are found to be completely tunable over a range spanning 150 MW m-2 - 30 GW m-2. The plasma-material interface is investigated using tungsten tokens exposed to the plasma plume under variable conditions. Visualizations of resulting shock structures are achieved through Schlieren cinematography and energy transfer dynamics are discussed by presenting temperature measurements of exposed materials. This work is supported by the U.S. Department of Energy Stewardship Science Academic Program in addition to the National Defense Science Engineering Graduate Fellowship.

Fluid-acoustic interactions in a low area ratio supersonic jet ejector

NASA Technical Reports Server (NTRS)

Krothapalli, Anjaneyulu; Ross, Christopher; Yamomoto, K.; Joshi, M. C.

1994-01-01

An experimental investigation carried out to determine aerodynamic and acoustic characteristics of a low area ratio rectangular jet ejector is reported. A supersonic primary jet issuing from a rectangular convergent-divergent nozzle of aspect ratio 4, into a rectangular duct of area ratio 3, was used. Improved performance was found when the ejector screech tone is most intense and appears to match the most unstable Strouhal number of the free rectangular jet. When the primary jet was operating at over and ideally expanded conditions, significant noise reduction was obtained with the ejector as compared to a corresponding free jet. Application of particle image velocimetry to high speed ejector flows was demonstrated through the measurement of instantaneous two dimensional velocity fields.

Low cost friction seismic base-isolation of residential new masonry buildings in developing countries: A small masonry house case study

NASA Astrophysics Data System (ADS)

Habieb, A. B.; Milani, G.; Tavio, T.; Milani, F.

2017-07-01

A Finite element model was established to examine performance of a low-cost friction base-isolation system in reducing seismic vulnerability of rural buildings. This study adopts an experimental investigation of the isolation system which was conducted in India. Four friction isolation interfaces, namely, marble-marble, marble-high-density polyethylene, marble-rubber sheet, and marble-geosynthetic were involved. Those interfaces differ in static and dynamic friction coefficient obtained through previous research. The FE model was performed based on a macroscopic approach and the masonry wall is assumed as an isotropic element. In order to observe structural response of the masonry house, elastic and plastic parameters of the brick wall were studied. Concrete damage plasticity (CDP) model was adopted to determine non-linear behavior of the brick wall. The results of FE model shows that involving these friction isolation systems could much decrease response acceleration at roof level. It was found that systems with marble-marble and marble-geosynthetic interfaces reduce the roof acceleration up to 50% comparing to the system without isolation. Another interesting result is there was no damage appearing in systems with friction isolation during the test. Meanwhile a severe failure was clearly visible for a system without isolation.

Kinetic Contributions to Gating by Interactions Unique to N-methyl-d-aspartate (NMDA) Receptors*

PubMed Central

Borschel, William F.; Cummings, Kirstie A.; Tindell, LeeAnn K.; Popescu, Gabriela K.

2015-01-01

Among glutamate-gated channels, NMDA receptors produce currents that subside with unusually slow kinetics, and this feature is essential to the physiology of central excitatory synapses. Relative to the homologous AMPA and kainate receptors, NMDA receptors have additional intersubunit contacts in the ligand binding domain that occur at both conserved and non-conserved sites. We examined GluN1/GluN2A single-channel currents with kinetic analyses and modeling to probe these class-specific intersubunit interactions for their role in glutamate binding and receptor gating. We found that substitutions that eliminate such interactions at non-conserved sites reduced stationary gating, accelerated deactivation, and imparted sensitivity to aniracetam, an AMPA receptor-selective positive modulator. Abolishing unique contacts at conserved sites also reduced stationary gating and accelerated deactivation. These results show that contacts specific to NMDA receptors, which brace the heterodimer interface within the ligand binding domain, stabilize actively gating receptor conformations and result in longer bursts and slower deactivations. They support the view that the strength of the heterodimer interface modulates gating in both NMDA and non-NMDA receptors and that unique interactions at this interface are responsible in part for basic differences between the kinetics of NMDA and non-NMDA currents at glutamatergic synapses. PMID:26370091

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

Shoup, R.W.; Long, F.; Martin, T.H.

Sandia has developed PBFA-Z, a 20-MA driver for z-pinch experiments by replacing the water lines, insulator stack. and MITLs on PBFA II with hardware of a new design. The PBFA-Z accelerator was designed to deliver 20 MA to a 15-mg z-pinch load in 100 ns. The accelerator was modeled using circuit codes to determine the time-dependent voltage and current waveforms at the input and output of the water lines, the insulator stack, and the MITLs. The design of the vacuum insulator stack was dictated by the drive voltage, the electric field stress and grading requirements, the water line and MITLmore » interface requirements, and the machine operations and maintenance requirements. The insulator stack consists of four separate modules, each of a different design because of different voltage drive and hardware interface requirements. The shape of the components in each module, i.e., grading rings, insulator rings, flux excluders, anode and cathode conductors, and the design of the water line and MITL interfaces, were optimized by using the electrostatic analysis codes, ELECTRO and JASON. The time-dependent performance of the insulator stacks was evaluated using IVORY, a 2-D PIC code. This paper will describe the insulator stack design, present the results of the ELECTRO and IVORY analyses, and show the results of the stack measurements.« less

Low-power, transparent optical network interface for high bandwidth off-chip interconnects.

PubMed

Liboiron-Ladouceur, Odile; Wang, Howard; Garg, Ajay S; Bergman, Keren

2009-04-13

The recent emergence of multicore architectures and chip multiprocessors (CMPs) has accelerated the bandwidth requirements in high-performance processors for both on-chip and off-chip interconnects. For next generation computing clusters, the delivery of scalable power efficient off-chip communications to each compute node has emerged as a key bottleneck to realizing the full computational performance of these systems. The power dissipation is dominated by the off-chip interface and the necessity to drive high-speed signals over long distances. We present a scalable photonic network interface approach that fully exploits the bandwidth capacity offered by optical interconnects while offering significant power savings over traditional E/O and O/E approaches. The power-efficient interface optically aggregates electronic serial data streams into a multiple WDM channel packet structure at time-of-flight latencies. We demonstrate a scalable optical network interface with 70% improvement in power efficiency for a complete end-to-end PCI Express data transfer.

Electron-irradiation-induced crystallization at metallic amorphous/silicon oxide interfaces caused by electronic excitation

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

Nagase, Takeshi, E-mail: t-nagase@uhvem.osaka-u.ac.jp; Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1, Yamada-Oka, Suita, Osaka 565-0871; Yamashita, Ryo

2016-04-28

Irradiation-induced crystallization of an amorphous phase was stimulated at a Pd-Si amorphous/silicon oxide (a(Pd-Si)/SiO{sub x}) interface at 298 K by electron irradiation at acceleration voltages ranging between 25 kV and 200 kV. Under irradiation, a Pd-Si amorphous phase was initially formed at the crystalline face-centered cubic palladium/silicon oxide (Pd/SiO{sub x}) interface, followed by the formation of a Pd{sub 2}Si intermetallic compound through irradiation-induced crystallization. The irradiation-induced crystallization can be considered to be stimulated not by defect introduction through the electron knock-on effects and electron-beam heating, but by the electronic excitation mechanism. The observed irradiation-induced structural change at the a(Pd-Si)/SiO{sub x} and Pd/SiO{sub x}more » interfaces indicates multiple structural modifications at the metal/silicon oxide interfaces through electronic excitation induced by the electron-beam processes.« less

Interfacial dilatational deformation accelerates particle formation in monoclonal antibody solutions.

PubMed

Lin, Gigi L; Pathak, Jai A; Kim, Dong Hyun; Carlson, Marcia; Riguero, Valeria; Kim, Yoen Joo; Buff, Jean S; Fuller, Gerald G

2016-04-14

Protein molecules are amphiphilic moieties that spontaneously adsorb at the air/solution (A/S) interface to lower the surface energy. Previous studies have shown that hydrodynamic disruptions to these A/S interfaces can result in the formation of protein aggregates that are of concern to the pharmaceutical industry. Interfacial hydrodynamic stresses encountered by protein therapeutic solutions under typical manufacturing, filling, and shipping conditions will impact protein stability, prompting a need to characterize the contribution of basic fluid kinematics to monoclonal antibody (mAb) destabilization. We demonstrate that dilatational surface deformations are more important to antibody stability when compared to constant-area shear of the A/S interface. We have constructed a dilatational interfacial rheometer that utilizes simultaneous pressure and bubble shape measurements to study the mechanical stability of mAbs under interfacial aging. It has a distinct advantage over methods utilizing the Young-Laplace equation, which incorrectly describes viscoelastic interfaces. We provide visual evidence of particle ejection from dilatated A/S interfaces and spectroscopic data of ejected mAb particles. These rheological studies frame a molecular understanding of the protein-protein interactions at the complex-fluid interface.

EPICS Channel Access Server for LabVIEW

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

Zhukov, Alexander P.

It can be challenging to interface National Instruments LabVIEW (http://www.ni.com/labview/) with EPICS (http://www.aps.anl.gov/epics/). Such interface is required when an instrument control program was developed in LabVIEW but it also has to be part of global control system. This is frequently useful in big accelerator facilities. The Channel Access Server is written in LabVIEW, so it works on any hardware/software platform where LabVIEW is available. It provides full server functionality, so any EPICS client can communicate with it.

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

Damiani, D.; Dubrovin, M.; Gaponenko, I.

Psana(Photon Science Analysis) is a software package that is used to analyze data produced by the Linac Coherent Light Source X-ray free-electron laser at the SLAC National Accelerator Laboratory. The project began in 2011, is written primarily in C++ with some Python, and provides user interfaces in both C++ and Python. Most users use the Python interface. The same code can be run in real time while data are being taken as well as offline, executing on many nodes/cores using MPI for parallelization. It is publicly available and installable on the RHEL5/6/7 operating systems.

Stable quasi-monoenergetic ion acceleration from the laser-driven shocks in a collisional plasma

NASA Astrophysics Data System (ADS)

Bhadoria, Shikha; Kumar, Naveen; Keitel, Christoph H.

2017-10-01

Effect of collisions on the shock formation and subsequent ion acceleration from the laser-plasma interaction is explored by the means of particle-in-cell simulations. In this setup, the incident laser pushes the laser-plasma interface inside the plasma target through the hole-boring effect and generates hot electrons. The propagation of these hot electrons inside the target excites a return plasma current, leading to filamentary structures caused by the Weibel/filamentation instability. Weakening of the space-charge effects due to collisions results in the shock formation with a higher density jump than in a collisionless plasma. This results in the formation of a stronger shock leading to a stable quasi-monoenergetic acceleration of ions.

Software package for modeling spin-orbit motion in storage rings

NASA Astrophysics Data System (ADS)

Zyuzin, D. V.

2015-12-01

A software package providing a graphical user interface for computer experiments on the motion of charged particle beams in accelerators, as well as analysis of obtained data, is presented. The software package was tested in the framework of the international project on electric dipole moment measurement JEDI (Jülich Electric Dipole moment Investigations). The specific features of particle spin motion imply the requirement to use a cyclic accelerator (storage ring) consisting of electrostatic elements, which makes it possible to preserve horizontal polarization for a long time. Computer experiments study the dynamics of 106-109 particles in a beam during 109 turns in an accelerator (about 1012-1015 integration steps for the equations of motion). For designing an optimal accelerator structure, a large number of computer experiments on polarized beam dynamics are required. The numerical core of the package is COSY Infinity, a program for modeling spin-orbit dynamics.

Investigation of accelerated stress factors and failure/degradation mechanisms in terrestrial solar cells

NASA Technical Reports Server (NTRS)

Lathrop, J. W.

1983-01-01

Results of an ongoing research program into the reliability of terrestrial solar cells are presented. Laboratory accelerated testing procedures are used to identify failure/degradation modes which are then related to basic physical, chemical, and metallurgical phenomena. In the most recent tests, ten different types of production cells, both with and without encapsulation, from eight different manufacturers were subjected to a variety of accelerated tests. Results indicated the presence of a number of hitherto undetected failure mechanisms, including Schottky barrier formation at back contacts and loss of adhesion of grid metallization. The mechanism of Schottky barrier formation is explained by hydrogen, formed by the dissociation of water molecules at the contact surface, diffusing to the metal semiconductor interface. This same mechanism accounts for the surprising increase in sensitivity to accelerated stress conditions that was observed in some cells when encapsulated.

Classroom: Efficient Grading

ERIC Educational Resources Information Center

Shaw, David D.; Pease, Leonard F., III.

2014-01-01

Grading can be accelerated to make time for more effective instruction. This article presents specific time management strategies selected to decrease administrative time required of faculty and teaching assistants, including a multiple answer multiple choice interface for exams, a three-tier grading system for open ended problem solving, and a…

Methodologies for launcher-payload coupled dynamic analysis

NASA Astrophysics Data System (ADS)

Fransen, S. H. J. A.

2012-06-01

An important step in the design and verification process of spacecraft structures is the coupled dynamic analysis with the launch vehicle in the low-frequency domain, also referred to as coupled loads analysis (CLA). The objective of such analyses is the computation of the dynamic environment of the spacecraft (payload) in terms of interface accelerations, interface forces, center of gravity (CoG) accelerations as well as the internal state of stress. In order to perform an efficient, fast and accurate launcher-payload coupled dynamic analysis, various methodologies have been applied and developed. The methods are related to substructuring techniques, data recovery techniques, the effects of prestress and fluids and time integration problems. The aim of this paper was to give an overview of these methodologies and to show why, how and where these techniques can be used in the process of launcher-payload coupled dynamic analysis. In addition, it will be shown how these methodologies fit together in a library of procedures which can be used with the MSC.Nastran™ solution sequences.

openPSTD: The open source pseudospectral time-domain method for acoustic propagation

NASA Astrophysics Data System (ADS)

Hornikx, Maarten; Krijnen, Thomas; van Harten, Louis

2016-06-01

An open source implementation of the Fourier pseudospectral time-domain (PSTD) method for computing the propagation of sound is presented, which is geared towards applications in the built environment. Being a wave-based method, PSTD captures phenomena like diffraction, but maintains efficiency in processing time and memory usage as it allows to spatially sample close to the Nyquist criterion, thus keeping both the required spatial and temporal resolution coarse. In the implementation it has been opted to model the physical geometry as a composition of rectangular two-dimensional subdomains, hence initially restricting the implementation to orthogonal and two-dimensional situations. The strategy of using subdomains divides the problem domain into local subsets, which enables the simulation software to be built according to Object-Oriented Programming best practices and allows room for further computational parallelization. The software is built using the open source components, Blender, Numpy and Python, and has been published under an open source license itself as well. For accelerating the software, an option has been included to accelerate the calculations by a partial implementation of the code on the Graphical Processing Unit (GPU), which increases the throughput by up to fifteen times. The details of the implementation are reported, as well as the accuracy of the code.

The structural response of a rail accelerator

NASA Technical Reports Server (NTRS)

Wang, S. Y.

1983-01-01

The transient response of a 0.4 by 0.6 cm rectangular bore rail accelerator was analyzed by a three dimensional finite element code. The copper rail deflected to a peak value of 0.08 mm in compression and then oscillated at an amplitude of 0.02 mm. Simultaneously the insulating side wall of glass fabric base, epoxy resin laminate (G-1o) was compressed to a peak value of 0.13 mm and rebounded to a steady state in extension. Projectile pinch or blowby due to the rail extension or compression, respectively, can be identified by examining the time history of the rail displacement. The effect of blowby was most significant at the side wall characterized by mm size displacement in compression. Dynamic stress calculations indicate that the G-10 supporting material behind the rail is subjected to over 21 MPa at which the G-10 could fail if the laminate was not carefully oriented. Results for a polycarbonate resin (Lexan) side wall show much larger displacements and stresses than for G-10. The tradeoff between the transparency of Lexan and the mechanical strength of G-10 for sidewall material is obvious. Displacement calculations from the modal method are smaller than the results from the direct integration method by almost an order of magnitude, because the high frequency effect is neglected.

Creep-Fatigue Cracking Near the Welded Interface in Friction Welding Dissimilar Superalloys INCONEL 718 and MAR-M247

NASA Astrophysics Data System (ADS)

Tra, Tran Hung; Okazaki, Masakazu

2017-08-01

A forged INCONEL 718 and a cast MAR-M247 alloy were joined by a friction welding process. The creep-fatigue strength of this joint was investigated. The life of the joint was significantly shorter than that of the base alloys. The joint failed near the interface of the INCONEL 718 side, although the life of INCONEL 718 was longer than that of MAR-M247. To understand this behavior, the stress field in the welding was numerically analyzed using a visco-elastic model. The results suggested that triaxiality in the stress state could be promoted near the welded interface and lead to an acceleration of creep-fatigue crack nucleation.

The Accelerated Late Adsorption of Pulmonary Surfactant

PubMed Central

2011-01-01

Adsorption of pulmonary surfactant to an air−water interface lowers surface tension (γ) at rates that initially decrease progressively, but which then accelerate close to the equilibrium γ. The studies here tested a series of hypotheses concerning mechanisms that might cause the late accelerated drop in γ. Experiments used captive bubbles and a Wilhelmy plate to measure γ during adsorption of vesicles containing constituents from extracted calf surfactant. The faster fall in γ reflects faster adsorption rather than any feature of the equation of state that relates γ to surface concentration (Γ). Adsorption accelerates when γ reaches a critical value rather than after an interval required to reach that γ. The hydrophobic surfactant proteins (SPs) represent key constituents, both for reaching the γ at which the acceleration occurs and for producing the acceleration itself. The γ at which rates of adsorption increase, however, is unaffected by the Γ of protein in the films. In the absence of the proteins, a phosphatidylethanolamine, which, like the SPs, induces fusion of the vesicles with the interfacial film, also causes adsorption to accelerate. Our results suggest that the late acceleration is characteristic of adsorption by fusion of vesicles with the nascent film, which proceeds more favorably when the Γ of the lipids exceeds a critical value. PMID:21417351

Accelerator–Reactor Coupling for Energy Production in Advanced Nuclear Fuel Cycles

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

Heidet, Florent; Brown, Nicholas R.; Haj Tahar, Malek

2015-01-01

This article is a review of several accelerator-reactor interface issues and nuclear fuel cycle applications of accelerator-driven subcritical systems. The systems considered here have the primary goal of energy production, but that goal is accomplished via a specific application in various proposed nuclear fuel cycles, such as breed-and-burn of fertile material or burning of transuranic material. Several basic principles are reviewed, starting from the proton beam window including the target, blanket, reactor core, and up to the fuel cycle. We focused on issues of interest, e.g. the impact of the energy required to run the accelerator and associated systems onmore » the potential electricity delivered to the grid. Accelerator-driven systems feature many of the constraints and issues associated with critical reactors, with the added challenges of subcritical operation and coupling to an accelerator. Reliable accelerator operation and avoidance of beam trips are a critically important. One interesting challenge is measurement of blanket subcriticality level during operation. We also reviewed the potential benefits of accelerator-driven systems in various nuclear fuel cycle applications. Ultimately, accelerator-driven subcritical systems with the goal of transmutation of transuranic material have lower 100,000-year radioactivity versus a critical fast reactor with recycle of uranium and plutonium.« less

[Light response characteristics of photosynthesis and model comparison of Distylium chinense in different flooding durations].

PubMed

Liu, Ze-bin; Cheng, Rui-mei; Xiao, Wen-fa; Guo, Quan-shui; Wang, Na

2015-04-01

The light responses of photosynthesis of two-year-old Distytum chinense seedlings subjected to a simulated reservoir flooding environment in autumn and winter seasons were measured by using a Li-6400 XT portable photosynthesis system, and the light response curves were fitted and analyzed by three models of the rectangular hyperbola, non-rectangular hyperbola and modified rectangular hyperbola to investigate the applicability of different light response models for the D. chinense in different flooding durations and the adaption regulation of light response parameters to flooding stress. The results showed that the fitting effect of the non-rectangular hyperbola model for light response process of D. chinense under normal growth condition and under short-term flooding (15 days of flooding) was better than that of the other two models, while the fitting effect of the modified rectangular hyperbola model for light response process of D. chinense under longer-term flooding (30, 45 and 60 days of flooding) was better than that of the other two models. The modified rectangular hyperbola model gave the best fitted results of light compensation point (LCP) , maximum net photosynthetic rate (P(n max)) and light saturation point (LSP), and the non-rectangular hyperbola model gave the best fitted result of dark respiration rate (R(d)). The apparent quantum yield (Φ), P(n max) and LSP of D. chinense gradually decreased, and the LCP and R(d) of D. chinense gradually increased in early flooding (30 days), but D. chinense gradually produced adaptability for flooding as the flooding duration continued to increase, and various physiological indexes were gradually stabilized. Thus, this species has adaptability to some degree to the flooding environment.

Design and validation of an improved graphical user interface with the 'Tool ball'.

PubMed

Lee, Kuo-Wei; Lee, Ying-Chu

2012-01-01

The purpose of this research is introduce the design of an improved graphical user interface (GUI) and verifies the operational efficiency of the proposed interface. Until now, clicking the toolbar with the mouse is the usual way to operate software functions. In our research, we designed an improved graphical user interface - a tool ball that is operated by a mouse wheel to perform software functions. Several experiments are conducted to measure the time needed to operate certain software functions with the traditional combination of "mouse click + tool button" and the proposed integration of "mouse wheel + tool ball". The results indicate that the tool ball design can accelerate the speed of operating software functions, decrease the number of icons on the screen, and enlarge the applications of the mouse wheel. Copyright © 2011 Elsevier Ltd and The Ergonomics Society. All rights reserved.

RF Magnetic Field Uniformity of Rectangular Planar Coils for Resonance Imaging

DTIC Science & Technology

2016-02-04

coil with square -shaped overlapping turns along the 135mm length of the coil. This paper compares these two coils to determine which has a more...in which, the coil arrays consist of a few square or circular coils side-by-side or overlapping. Mobile unilateral NMR/MRI scanners were...magnetic field along the length of a normal rectangular coil (NRC) and a rectangular coil with overlapping square -shaped turns (RCOS). The RCOS coil is

SU-E-T-598: The Effects of Arm Speed for Quality Assurance and Commissioning Measurements in Rectangular and Cylindrical Scanners

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

Bakhtiari, M; Schmitt, J

2014-06-01

Purpose: Cylindrical and rectangular scanning water tanks are examined with different scanning speeds to investigate the TG-106 criteria and the errors induced in the measurements. Methods: Beam profiles were measured in a depth of R50 for a low-energy electron beam (6 MeV) using rectangular and cylindrical tanks. The speeds of the measurements (arm movement) were varied in different profile measurements. Each profile was measured with a certain speed to obtain the average and standard deviation as a parameter for investigating the reproducibility and errors. Results: At arm speeds of ∼0.8 mm/s the errors were as large as 2% and 1%more » with rectangular and cylindrical tanks, respectively. The errors for electron beams and for photon beams in other depths were within the TG-106 criteria of 1% for both tank shapes. Conclusion: The measurements of low-energy electron beams in a depth of R50, as an extreme case scenario, are sensitive to the speed of the measurement arms for both rectangular and cylindrical tanks. The measurements in other depths, for electron beams and photon beams, with arm speeds of less than 1 cm/s are within the TG-106 criteria. An arm speed of 5 mm/s appeared to be optimal for fast and accurate measurements for both cylindrical and rectangular tanks.« less

A computer program for converting rectangular coordinates to latitude-longitude coordinates

USGS Publications Warehouse

Rutledge, A.T.

1989-01-01

A computer program was developed for converting the coordinates of any rectangular grid on a map to coordinates on a grid that is parallel to lines of equal latitude and longitude. Using this program in conjunction with groundwater flow models, the user can extract data and results from models with varying grid orientations and place these data into grid structure that is oriented parallel to lines of equal latitude and longitude. All cells in the rectangular grid must have equal dimensions, and all cells in the latitude-longitude grid measure one minute by one minute. This program is applicable if the map used shows lines of equal latitude as arcs and lines of equal longitude as straight lines and assumes that the Earth 's surface can be approximated as a sphere. The program user enters the row number , column number, and latitude and longitude of the midpoint of the cell for three test cells on the rectangular grid. The latitude and longitude of boundaries of the rectangular grid also are entered. By solving sets of simultaneous linear equations, the program calculates coefficients that are used for making the conversion. As an option in the program, the user may build a groundwater model file based on a grid that is parallel to lines of equal latitude and longitude. The program reads a data file based on the rectangular coordinates and automatically forms the new data file. (USGS)

Square and Rectangular Arrays from Directed Assembly of Sphere-forming Diblock Copolymers in Thin Films

NASA Astrophysics Data System (ADS)

Ji, Shengxiang; Nagpal, Umang; Liao, Wen; de Pablo, Juan; Nealey, Paul

2010-03-01

Patterns of square and rectangular arrays with nanoscale dimensions are scientifically and technologically important. Fabrication of square array patterns in thin films has been demonstrated by directed assembly of cylinder-forming diblock copolymers on chemically patterned substrates, supramolecular assembly of diblock copolymers, and self-assembly of triblock terpolymers. However, a macroscopic area of square array patterns with long-range order has not been achieved, and the fabrication of rectangular arrays has not been reported so far. Here we report a facile approach for fabricating patterns of square and rectangular arrays by directing the assembly of sphere-forming diblock copolymers on chemically patterned substrates. On stripe patterns, a square arrangement of half spheres, corresponding to the (100) plane of the body-centred cubic (BCC) lattice, formed on film surfaces. When the underlying pattern periods mismatched with the copolymer period, the square pattern could be stretched (up to ˜60%) or compressed (˜15%) to form rectangular arrays. Monte Carlo simulations have been further used to verify the experimental results and the 3-dimensional arrangements of spheres.

Psyplot: Visualizing rectangular and triangular Climate Model Data with Python

NASA Astrophysics Data System (ADS)

Sommer, Philipp

2016-04-01

The development and use of climate models often requires the visualization of geo-referenced data. Creating visualizations should be fast, attractive, flexible, easily applicable and easily reproducible. There is a wide range of software tools available for visualizing raster data, but they often are inaccessible to many users (e.g. because they are difficult to use in a script or have low flexibility). In order to facilitate easy visualization of geo-referenced data, we developed a new framework called "psyplot," which can aid earth system scientists with their daily work. It is purely written in the programming language Python and primarily built upon the python packages matplotlib, cartopy and xray. The package can visualize data stored on the hard disk (e.g. NetCDF, GeoTIFF, any other file format supported by the xray package), or directly from the memory or Climate Data Operators (CDOs). Furthermore, data can be visualized on a rectangular grid (following or not following the CF Conventions) and on a triangular grid (following the CF or UGRID Conventions). Psyplot visualizes 2D scalar and vector fields, enabling the user to easily manage and format multiple plots at the same time, and to export the plots into all common picture formats and movies covered by the matplotlib package. The package can currently be used in an interactive python session or in python scripts, and will soon be developed for use with a graphical user interface (GUI). Finally, the psyplot framework enables flexible configuration, allows easy integration into other scripts that uses matplotlib, and provides a flexible foundation for further development.

Exponential current pulse generation for efficient very high-impedance multisite stimulation.

PubMed

Ethier, S; Sawan, M

2011-02-01

We describe in this paper an intracortical current-pulse generator for high-impedance microstimulation. This dual-chip system features a stimuli generator and a high-voltage electrode driver. The stimuli generator produces flexible rising exponential pulses in addition to standard rectangular stimuli. This novel stimulation waveform is expected to provide superior energy efficiency for action potential triggering while releasing less toxic reduced ions in the cortical tissues. The proposed fully integrated electrode driver is used as the output stage where high-voltage supplies are generated on-chip to significantly increase the voltage compliance for stimulation through high-impedance electrode-tissue interfaces. The stimuli generator has been implemented in 0.18-μm CMOS technology while a 0.8-μm CMOS/DMOS process has been used to integrate the high-voltage output stage. Experimental results show that the rectangular pulses cover a range of 1.6 to 167.2 μA with a DNL and an INL of 0.098 and 0.163 least-significant bit, respectively. The maximal dynamic range of the generated exponential reaches 34.36 dB at full scale within an error of ± 0.5 dB while all of its parameters (amplitude, duration, and time constant) are independently programmable over wide ranges. This chip consumes a maximum of 88.3 μ W in the exponential mode. High-voltage supplies of 8.95 and -8.46 V are generated by the output stage, boosting the voltage swing up to 13.6 V for a load as high as 100 kΩ.

Deformable image registration with a featurelet algorithm: implementation as a 3D-slicer extension and validation

NASA Astrophysics Data System (ADS)

Renner, A.; Furtado, H.; Seppenwoolde, Y.; Birkfellner, W.; Georg, D.

2016-03-01

A radiotherapy (RT) treatment can last for several weeks. In that time organ motion and shape changes introduce uncertainty in dose application. Monitoring and quantifying the change can yield a more precise irradiation margin definition and thereby reduce dose delivery to healthy tissue and adjust tumor targeting. Deformable image registration (DIR) has the potential to fulfill this task by calculating a deformation field (DF) between a planning CT and a repeated CT of the altered anatomy. Application of the DF on the original contours yields new contours that can be used for an adapted treatment plan. DIR is a challenging method and therefore needs careful user interaction. Without a proper graphical user interface (GUI) a misregistration cannot be easily detected by visual inspection and the results cannot be fine-tuned by changing registration parameters. To provide a DIR algorithm with such a GUI available for everyone, we created the extension Featurelet-Registration for the open source software platform 3D Slicer. The registration logic is an upgrade of an in-house-developed DIR method, which is a featurelet-based piecewise rigid registration. The so called "featurelets" are equally sized rectangular subvolumes of the moving image which are rigidly registered to rectangular search regions on the fixed image. The output is a deformed image and a deformation field. Both can be visualized directly in 3D Slicer facilitating the interpretation and quantification of the results. For validation of the registration accuracy two deformable phantoms were used. The performance was benchmarked against a demons algorithm with comparable results.

Chemical Dissolution of Simulant FCA Cladding and Plates

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

Daniel, G.; Pierce, R.; O'Rourke, P.

The Savannah River Site (SRS) has received some fast critical assembly (FCA) fuel from the Japan Atomic Energy Agency (JAEA) for disposition. Among the JAEA FCA fuel are approximately 7090 rectangular Stainless Steel clad fuel elements. Each element has an internal Pu-10.6Al alloy metal wafer. The thickness of each element is either 1/16 inch or 1/32 inch. The dimensions of each element ranges from 2 inches x 1 inch to 2 inches x 4 inches. This report discusses the potential chemical dissolution of the FCA clad material or stainless steel. This technology uses nitric acid-potassium fluoride (HNO 3-KF) flowsheets ofmore » H-Canyon to dissolve the FCA elements from a rack of materials. Historically, dissolution flowsheets have aimed to maximize Pu dissolution rates while minimizing stainless steel dissolution (corrosion) rates. Because the FCA cladding is made of stainless steel, this work sought to accelerate stainless steel dissolution.« less

SEE rate estimation based on diffusion approximation of charge collection

NASA Astrophysics Data System (ADS)

Sogoyan, Armen V.; Chumakov, Alexander I.; Smolin, Anatoly A.

2018-03-01

The integral rectangular parallelepiped (IRPP) method remains the main approach to single event rate (SER) prediction for aerospace systems, despite the growing number of issues impairing method's validity when applied to scaled technology nodes. One of such issues is uncertainty in parameters extraction in the IRPP method, which can lead to a spread of several orders of magnitude in the subsequently calculated SER. The paper presents an alternative approach to SER estimation based on diffusion approximation of the charge collection by an IC element and geometrical interpretation of SEE cross-section. In contrast to the IRPP method, the proposed model includes only two parameters which are uniquely determined from the experimental data for normal incidence irradiation at an ion accelerator. This approach eliminates the necessity of arbitrary decisions during parameter extraction and, thus, greatly simplifies calculation procedure and increases the robustness of the forecast.

PREMIXED FLAME PROPAGATION AND MORPHOLOGY IN A CONSTANT VOLUME COMBUSTION CHAMBER

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

Hariharan, A; Wichman, IS

2014-06-04

This work presents an experimental and numerical investigation of premixed flame propagation in a constant volume rectangular channel with an aspect ratio of six (6) that serves as a combustion chamber. Ignition is followed by an accelerating cusped finger-shaped flame-front. A deceleration of the flame is followed by the formation of a "tulip"-shaped flame-front. Eventually, the flame is extinguished when it collides with the cold wall on the opposite channel end. Numerical computations are performed to understand the influence of pressure waves, instabilities, and flow field effects causing changes to the flame structure and morphology. The transient 2D numerical simulationmore » results are compared with transient 3D experimental results. Issues discussed are the appearance of oscillatory motions along the flame front and the influences of gravity on flame structure. An explanation is provided for the formation of the "tulip" shape of the premixed flame front.« less

Plane hydroelastic beam vibrations due to uniformly moving one axle vehicle

NASA Astrophysics Data System (ADS)

Fleischer, D.; Park, S.-K.

2004-06-01

The hydroelastic vibrations of a beam with rectangular cross-section is analyzed under the effect of an uniformly moving single axle vehicle using modal analysis and two-dimensional potential flow theory of the fluid neglecting the effect of surface waves aside the beam. For the special case of homogeneous beam resting on the surface of a water filled prismatic basin, the normal modes are determined considering surface waves in beam direction under the condition of compensating the volume of the enclosed fluid. The way to determine the vertical acceleration of the single axle vehicle is shown, which governs the response of the system. As analysis results the course of wheel load, the surface waves along the beam and the flow velocity distribution of the fluid is demonstrated for a continuous floating bridge under the passage of a rolling mass moving with uniform speed.

Development of a high-resolution cavity-beam position monitor

NASA Astrophysics Data System (ADS)

Inoue, Yoichi; Hayano, Hitoshi; Honda, Yosuke; Takatomi, Toshikazu; Tauchi, Toshiaki; Urakawa, Junji; Komamiya, Sachio; Nakamura, Tomoya; Sanuki, Tomoyuki; Kim, Eun-San; Shin, Seung-Hwan; Vogel, Vladimir

2008-06-01

We have developed a high-resolution cavity-beam position monitor (BPM) to be used at the focal point of the ATF2, which is a test beam line that is now being built to demonstrate stable orbit control at ˜nanometer resolution. The design of the cavity structure was optimized for the Accelerator Test Facility (ATF) beam in various ways. For example, the cavity has a rectangular shape in order to isolate two dipole modes in orthogonal directions, and a relatively thin gap that is less sensitive to trajectory inclination. A two stage homodyne mixer with highly sensitive electronics and phase-sensitive detection was also developed. Two BPM blocks, each containing two cavity BPMs, were installed in the existing ATF beam line using a rigid support frame. After testing the basic characteristics, we measured the resolution using three BPMs. The system demonstrated 8.7 nm position resolution over a dynamic range of 5μm.

Isentropic Compression with a Rectangular Configuration for Tungstene and Tantalum, Computations and Comparison with Experiments

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

Lefrancois, A.; Reisman, D. B.; Bastea, M.

2006-02-13

Isentropic compression experiments and numerical simulations on metals are performed at Z accelerator facility from Sandia National Laboratory and at Lawrence Livermore National Laboratory in order to study the isentrope, associated Hugoniot and phase changes of these metals. 3D configurations have been calculated here to benchmark the new beta version of the electromagnetism package coupled with the dynamics in Ls-Dyna and compared with the ICE Z shots 1511 and 1555. The electromagnetism module is being developed in the general-purpose explicit and implicit finite element program LS-DYNA{reg_sign} in order to perform coupled mechanical/thermal/electromagnetism simulations. The Maxwell equations are solved using amore » Finite Element Method (FEM) for the solid conductors coupled with a Boundary Element Method (BEM) for the surrounding air (or vacuum). More details can be read in the references.« less

Simulation of multipactor on the rectangular grooved dielectric surface

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

Cai, Libing; Wang, Jianguo, E-mail: wanguiuc@mail.xjtu.edu.cn; Northwest Institute of Nuclear Technology, Xi'an, Shaanxi 710024

2015-11-15

Multipactor discharge on the rectangular grooved dielectric surface is simulated self-consistently by using a two-and-a-half dimensional (2.5 D) electrostatic particle-in-cell (PIC) code. Compared with the electromagnetic PIC code, the former can give much more accurate solution for the space charge field caused by the multipactor electrons and the deposited surface charge. According to the rectangular groove width and height, the multipactor can be divided into four models, the spatial distributions of the multipactor electrons and the space charge fields are presented for these models. It shows that the rectangular groove in different models gives very different suppression effect on themore » multipactor, effective and efficient suppression on the multipactor can only be reached with a proper groove size.« less

Propellant Feed System for Swirl-Coaxial Injection

NASA Technical Reports Server (NTRS)

Reynolds, David Christopher (Inventor)

2015-01-01

A propellant feed system for swirl-coaxial injection of a liquid propellant includes a reservoir having a bottom plate and at least one tube originating in the bottom plate and extending therefrom. The tube has rectangular slits defined in and distributed tangentially and evenly about a portion of the tube that is disposed in the bottom plate. Drain holes are provided in the bottom plate and tunnels are defined in the bottom plate. Each tunnel fluidly couples one of the drain holes to a corresponding one of the rectangular slits. Each tunnel includes (i) a bend of at least 90.degree., and (ii) a straight portion leading to its corresponding rectangular slit wherein the straight portion is at least five times as long as a hydraulic diameter of the corresponding rectangular slit.

Three-dimensional thermocapillary flow regimes with evaporation

NASA Astrophysics Data System (ADS)

Bekezhanova, V. B.; Goncharova, O. N.

2017-10-01

A three-dimensional problem of evaporative convection in a system of the immiscible media with a common thermocapillary interface is studied. New exact solution, which is a generalization of the Ostroumov - Birikh solution of the Navier - Stokes equations in the Oberbeck - Boussinesq approximation, is presented in order to describe the joint flows of the liquid and gas - vapor mixture in an infinite channel with a rectangular cross-section. The motion occurs in the bulk force field under action of a constant longitudinal temperature gradient. The velocity components depend only on the transverse coordinates. The functions of pressure, temperature and concentration of vapor in the gas are characterized by the linear dependence on the longitudinal coordinate. In the framework of the problem statement, which takes into account diffusive mass flux through the interface and zero vapor flux at the upper boundary of the channel, the influence of the gravity and intensity of the thermal action on flow structure is studied. The original three-dimensional problem is reduced to a chain of two-dimensional problems which are solved numerically with help of modification of the method of alternating directions. Arising flows can be characterized as a translational-rotational motion, under that the symmetrical double, quadruple or sextuple vortex structures are formed. Quantity, shape and structure of the vortexes also depend on properties of the working media.

Control of jet noise

NASA Technical Reports Server (NTRS)

Schreck, Stefan

1992-01-01

To investigate the possibility of active control of jet noise, knowledge of the noise generation mechanisms in natural jets is essential. Once these mechanisms are determined, active control can be used to manipulate the noise production processes. We investigated the evolution of the flow fields and the acoustic fields of rectangular and circular jets. A predominant flapping mode was found in the supersonic rectangular jets. We hope to increase the spreading of supersonic jets by active control of the flapping mode found in rectangular supersonic jets.

Synchronizability of random rectangular graphs

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

Estrada, Ernesto, E-mail: ernesto.estrada@strath.ac.uk; Chen, Guanrong

2015-08-15

Random rectangular graphs (RRGs) represent a generalization of the random geometric graphs in which the nodes are embedded into hyperrectangles instead of on hypercubes. The synchronizability of RRG model is studied. Both upper and lower bounds of the eigenratio of the network Laplacian matrix are determined analytically. It is proven that as the rectangular network is more elongated, the network becomes harder to synchronize. The synchronization processing behavior of a RRG network of chaotic Lorenz system nodes is numerically investigated, showing complete consistence with the theoretical results.

Experimental Sloshing Reference Test

NASA Astrophysics Data System (ADS)

Lada, C.; Such-Taboada, M.; Ngan, I.; Grigore, L.; Appolloni, M.; Roure, S.; Murray, N.; Mendes Leal, M.; de Wilde, D.; Longo, J.; Bureo-Dacal, R.; Cozzani, A.; Laine, B.

2014-06-01

This article describes the sloshing experiment performed on the HYDRA multi-axis hydraulic shaker at ESTEC. Two tank geometries, a rectangular tank and a pill shaped tank, were excited in the lateral direction. Both tanks, manufactured from a transparent material in order to provide high visibility of the phenomenon, were filled with water and several fill ratios were tested, varying the amplitude of the input and the sweep rate. The results of the test are presented from a structural point of view, with the main objective to study the interface force due to dynamic fluid sloshing motion. An investigation of the behaviour of the water around the main resonance of the assembly is conducted through the observation of the identified modes and the damping values. The experimental results confirm the amplification effect at low frequency caused by water sloshing motion and a comparison with data from numerical simulation is provided.

GRC-2008-C-00349

NASA Image and Video Library

2004-02-26

Code R and Code D hosted NESC Principal Engineer Mike Kirsch who is Program Leader for Composite Crew Module (CCM). The purpose of the visit was to review/observe experiments that GRC is performing in support of the CCM program. The test object is the critical Low Impact Docking System/Tunnel interface joint that links the metal docking ring with the polymer composite tunnel element of the crew module pressure vessel. The rectangular specimens simulated the splice joint between the aluminum and the PMC sheets, including a PMC doubler sheet. GRC was selected for these tests due to our expertise in composite testing and our ability to perform 3D fullfield displacement and strain measurements of the complex bond geometry using digital image correlation. The specimens performed above their minimum load requirements and the full field strain measurements showed the strain levels at the critical bond line. This work is part of a joint Code D & R investigation.

Combination of the discontinuous Galerkin method with finite differences for simulation of seismic wave propagation

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

Lisitsa, Vadim, E-mail: lisitsavv@ipgg.sbras.ru; Novosibirsk State University, Novosibirsk; Tcheverda, Vladimir

We present an algorithm for the numerical simulation of seismic wave propagation in models with a complex near surface part and free surface topography. The approach is based on the combination of finite differences with the discontinuous Galerkin method. The discontinuous Galerkin method can be used on polyhedral meshes; thus, it is easy to handle the complex surfaces in the models. However, this approach is computationally intense in comparison with finite differences. Finite differences are computationally efficient, but in general, they require rectangular grids, leading to the stair-step approximation of the interfaces, which causes strong diffraction of the wavefield. Inmore » this research we present a hybrid algorithm where the discontinuous Galerkin method is used in a relatively small upper part of the model and finite differences are applied to the main part of the model.« less

Plasmonic reflectance anisotropy spectroscopy of metal nanoparticles on a semiconductor surface

NASA Astrophysics Data System (ADS)

Kosobukin, V. A.; Korotchenkov, A. V.

2016-12-01

A theory of plasmonic differential anisotropic reflection of light from nanoparticles located near the interface between media is developed. The model of a monolayer consisting of identical ellipsoidal metal particles occupying sites of a rectangular lattice is investigated. Effective plasmonic polarizabilities of nanoparticles in the layer are calculated self-consistently using the Green's function technique in the quasipoint dipole approximation. The local-field effect caused by anisotropic dipole plasmons of particles in the layer and their image dipoles is taken into account. The lately observed resonant reflectance anisotropy spectra of indium nanoclusters on InAs surface are explained by the difference between frequencies of plasmons with the orthogonal polarizations in the surface plane. The difference between the plasmon frequencies is attributed to anisotropy of the particles shape or/and the layer structure; the signs of frequency difference for the two types of anisotropy being different.

Near-field thermal rectification devices using phase change periodic nanostructure.

PubMed

Ghanekar, Alok; Tian, Yanpei; Ricci, Matthew; Zhang, Sinong; Gregory, Otto; Zheng, Yi

2018-01-22

We theoretically analyze two near-field thermal rectification devices: a radiative thermal diode and a thermal transistor that utilize a phase change material to achieve dynamic control over heat flow by exploiting metal-insulator transition of VO 2 near 341 K. The thermal analogue of electronic diode allows high heat flow in one direction while it restricts the heat flow when the polarity of temperature gradient is reversed. We show that with the introduction of 1-D rectangular grating, thermal rectification is dramatically enhanced in the near-field due to reduced tunneling of surface waves across the interfaces for negative polarity. The radiative thermal transistor also works around phase transition temperature of VO 2 and controls heat flow. We demonstrate a transistor-like behavior wherein heat flow across the source and the drain can be greatly varied by making a small change in gate temperature.

An Interactive, Design and Educational Tool for Supersonic External-Compression Inlets

NASA Technical Reports Server (NTRS)

Benson, Thomas J.

1994-01-01

A workstation-based interactive design tool called VU-INLET was developed for the inviscid flow in rectangular, supersonic, external-compression inlets. VU-INLET solves for the flow conditions from free stream, through the supersonic compression ramps, across the terminal normal shock region and the subsonic diffuser to the engine face. It calculates the shock locations, the capture streamtube, and the additive drag of the inlet. The inlet geometry can be modified using a graphical user interface and the new flow conditions recalculated interactively. Free stream conditions and engine airflow can also be interactively varied and off-design performance evaluated. Flow results from VU-INLET can be saved to a file for a permanent record, and a series of help screens make the simulator easy to learn and use. This paper will detail the underlying assumptions of the models and the numerical methods used in the simulator.

Power density of piezoelectric transformers improved using a contact heat transfer structure.

PubMed

Shao, Wei Wei; Chen, Li Juan; Pan, Cheng Liang; Liu, Yong Bin; Feng, Zhi Hua

2012-01-01

Based on contact heat transfer, a novel method to increase power density of piezoelectric transformers is proposed. A heat transfer structure is realized by directly attaching a dissipater to the piezoelectric transformer plate. By maintaining the vibration mode of the transformer and limiting additional energy losses from the contact interface, an appropriate design can improve power density of the transformer on a large scale, resulting from effective suppression of its working temperature rise. A prototype device was fabricated from a rectangular piezoelectric transformer, a copper heat transfer sheet, a thermal grease insulation pad, and an aluminum heat radiator. The experimental results show the transformer maintains a maximum power density of 135 W/cm(3) and an efficiency of 90.8% with a temperature rise of less than 10 °C after more than 36 h, without notable changes in performance. © 2012 IEEE

Surfactant effect on drop coalescence and film drainage hydrodynamics

NASA Astrophysics Data System (ADS)

Weheliye, Weheliye; Chinaud, Maxime; Voulgaropoulos, Victor; Angeli, Panagiota

2015-11-01

Coalescence of a drop on an aqueous-organic interface is studied in two test geometries A rectangular acrylic vessel and a Hele-Shaw cell (two parallel plates placed 2mm apart) are investigated for the experiments. Time resolved Particle Image Velocimetry (PIV) measurements provide information on the hydrodynamics during the bouncing stage of the droplet and on the vortices generated at the bulk fluid after the droplet has coalesced. The velocity field inside the droplet during its coalescence is presented. By localizing the rupture point of the coalescence in the quasi two dimensional cell, the film drainage dynamics are discussed by acquiring its flow velocity by PIV measurements with a straddling camera. The effect of surface tension forces in the coalescence of the droplet is investigated by introducing surface active agents at various concentrations extending on both sides of the critical micelle concentration.

Thermal conductance of interfaces with molecular layers - low temperature transient absorption study on gold nanorods supported on self assembled monolayers

NASA Astrophysics Data System (ADS)

Wang, Wei; Huang, Jingyu; Murphy, Catherine; Cahill, David; University of Illinois At Urbana Champaign, Department of Materials Science; Engineering Team; Department Collaboration

2011-03-01

While heat transfer via phonons across solid-solid boundary has been a core field in condense matter physics for many years, vibrational energy transport across molecular layers has been less well elucidated. We heat rectangular-shaped gold nanocrystals (nanorods) with Ti-sapphire femtosecond pulsed laser at their longitudinal surface plasmon absorption wavelength to watch how their temperature evolves in picoseconds transient. We observed single exponential decay behavior, which suggests that the heat dissipation is only governed by a single interfacial conductance value. The ``RC'' time constant was 300ps, corresponding to a conductance value of 95MW/ m 2 K. This interfacial conductance value is also a function of ambient temperature since at temperatures as low as 80K, which are below the Debye temperature of organic layers, several phonon modes were quenched, which shut down the dominating channels that conduct heat at room temperature.

Frequencies of gravity-capillary waves on highly curved interfaces with edge constraints

NASA Astrophysics Data System (ADS)

Shankar, P. N.

2007-06-01

A recently developed technique to calculate the natural frequencies of gravity-capillary waves in a confined liquid mass with a possibly highly curved free surface is extended to the case where the contact line is pinned. The general technique is worked out in detail for the cases of rectangular and cylindrical containers of circular section, the cases for which experimental data are available. The results of the present method are in excellent agreement with all earlier experimental and theoretical data for the flat static interface case [Benjamin and Scott, 1979. Gravity-capillary waves with edge constraints. J. Fluid Mech. 92, 241-267; Graham-Eagle, 1983. A new method for calculating eigenvalues with applications to gravity-capillary waves with edge constraints. Math. Proc. Camb. Phil. Soc. 94, 553-564; Henderson and Miles, 1994. Surface-wave damping in a circular cylinder with a fixed contact line. J. Fluid Mech. 275, 285-299]. However, the present method is applicable even when the contact angle is not π/2 and the static interface is curved. As a consequence we are able to work out the effects of a curved meniscus on the results of Cocciaro et al. [1993. Experimental investigation of capillary effects on surface gravity waves: non-wetting boundary conditions. J. Fluid Mech. 246, 43-66] where the measured contact angle was 62∘. We find that the meniscus does indeed account, as suggested by Cocciaro et al., for the earlier discrepancy between theory and experiment of about 20 mHz and there is now excellent agreement between the two.

Diagnostic X-Multi-Axis Beamline

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

Paul, A C

Tomographic reconstruction of explosive events require time resolved multipal lines of sight. Considered here is a four (or eight) line of sight beam layout for a nominal 20 MeV 2000 Ampere 2 microsecond electron beam for generation of x-rays 0.9 to 5 meters from a given point, the ''firing point''. The requirement of a millimeter spatial x-ray source requires that the electron beam be delivered to the converter targets with sub-millimeter precision independent of small variations in beam energy and initial conditions. The 2 usec electron beam pulse allows for four bursts in each line, separated in time by aboutmore » 500 microseconds. Each burst is divided by a electro-magnetic kicker into four (or eight) pulses, one for each beamline. The arrival time of the four (or eight) beam pulses at the x-ray target can be adjusted by the kicker timing and the sequence that the beams of each burst are switched into the different beamlines. There exists a simple conceptual path from a four beamline to a eight beamline upgrade. The eight line beamline is built up from seven unique types of sub-systems or ''blocks''. The beamline consists of 22 of these functional blocks and contains a total of 455 individual magnets, figure 1. The 22 blocks are inter-connected by a total of 30 straight line inter-block sections (IBS). Beamlines 1-4 are built from 12 blocks with conceptual layout structure shown in figure 2. Beamlines 5-8 are built with an additional 10 blocks with conceptual layout structure shown in figure 3. This beamline can be thought of as looking like a lollipop consisting of a 42 meter long stick leading to a 60 by 70 meter rectangular candy blob consisting of the eight lines of sight. The accelerator providing the electron beam is at the end of the stick and the firing point is at the center of the blob. The design allows for a two stage implementation. Beamlines 1-3 can be installed to provide a tomographic azimuthal resolution of 45 degrees. An upgrade can later be made by adding beamlines 5-8 azimuthally indexed so as to provide an azimuthal resolution of 22.5 degrees. All eight beamlines point down by 10 degrees (pitch). The x-ray converter target can be located along each beamline anywhere between 0 to 5 meters from the firing point. An example of inter-facing the Diagnostic X facility with the Darht II accelerator located at LANL will be given.« less

Highly Productive Application Development with ViennaCL for Accelerators

NASA Astrophysics Data System (ADS)

Rupp, K.; Weinbub, J.; Rudolf, F.

2012-12-01

The use of graphics processing units (GPUs) for the acceleration of general purpose computations has become very attractive over the last years, and accelerators based on many integrated CPU cores are about to hit the market. However, there are discussions about the benefit of GPU computing when comparing the reduction of execution times with the increased development effort [1]. To counter these concerns, our open-source linear algebra library ViennaCL [2,3] uses modern programming techniques such as generic programming in order to provide a convenient access layer for accelerator and GPU computing. Other GPU-accelerated libraries are primarily tuned for performance, but less tailored to productivity and portability: MAGMA [4] provides dense linear algebra operations via a LAPACK-comparable interface, but no dedicated matrix and vector types. Cusp [5] is closest in functionality to ViennaCL for sparse matrices, but is based on CUDA and thus restricted to devices from NVIDIA. However, no convenience layer for dense linear algebra is provided with Cusp. ViennaCL is written in C++ and uses OpenCL to access the resources of accelerators, GPUs and multi-core CPUs in a unified way. On the one hand, the library provides iterative solvers from the family of Krylov methods, including various preconditioners, for the solution of linear systems typically obtained from the discretization of partial differential equations. On the other hand, dense linear algebra operations are supported, including algorithms such as QR factorization and singular value decomposition. The user application interface of ViennaCL is compatible to uBLAS [6], which is part of the peer-reviewed Boost C++ libraries [7]. This allows to port existing applications based on uBLAS with a minimum of effort to ViennaCL. Conversely, the interface compatibility allows to use the iterative solvers from ViennaCL with uBLAS types directly, thus enabling code reuse beyond CPU-GPU boundaries. Out-of-the-box support for types from the Eigen library [8] and MTL 4 [9] are provided as well, enabling a seamless transition from single-core CPU to GPU and multi-core CPU computations. Case studies from the numerical solution of PDEs are given and isolated performance benchmarks are discussed. Also, pitfalls in scientific computing with GPUs and accelerators are addressed, allowing for a first evaluation of whether these novel devices can be mapped well to certain applications. References: [1] R. Bordawekar et al., Technical Report, IBM, 2010 [2] ViennaCL library. Online: http://viennacl.sourceforge.net/ [3] K. Rupp et al., GPUScA, 2010 [4] MAGMA library. Online: http://icl.cs.utk.edu/magma/ [5] Cusp library. Online: http://code.google.com/p/cusp-library/ [6] uBLAS library. Online: http://www.boost.org/libs/numeric/ublas/ [7] Boost C++ Libraries. Online: http://www.boost.org/ [8] Eigen library. Online: http://eigen.tuxfamily.org/ [9] MTL 4 Library. Online: http://www.mtl4.org/

CTD² Dashboard: a searchable web interface to connect validated results from the Cancer Target Discovery and Development Network* | Office of Cancer Genomics

Cancer.gov

The Cancer Target Discovery and Development (CTD2) Network aims to use functional genomics to accelerate the translation of high-throughput and high-content genomic and small-molecule data towards use in precision oncology.

Orthonormal aberration polynomials for anamorphic optical imaging systems with rectangular pupils.

PubMed

Mahajan, Virendra N

2010-12-20

The classical aberrations of an anamorphic optical imaging system, representing the terms of a power-series expansion of its aberration function, are separable in the Cartesian coordinates of a point on its pupil. We discuss the balancing of a classical aberration of a certain order with one or more such aberrations of lower order to minimize its variance across a rectangular pupil of such a system. We show that the balanced aberrations are the products of two Legendre polynomials, one for each of the two Cartesian coordinates of the pupil point. The compound Legendre polynomials are orthogonal across a rectangular pupil and, like the classical aberrations, are inherently separable in the Cartesian coordinates of the pupil point. They are different from the balanced aberrations and the corresponding orthogonal polynomials for a system with rotational symmetry but a rectangular pupil.

Shear flow control of cold and heated rectangular jets by mechanical tabs. Volume 2: Tabulated data

NASA Technical Reports Server (NTRS)

Brown, W. H.; Ahuja, K. K.

1989-01-01

The effects of mechanical protrusions on the jet mixing characteristics of rectangular nozzles for heated and unheated subsonic and supersonic jet plumes were studied. The characteristics of a rectangular nozzle of aspect ratio 4 without the mechanical protrusions were first investigated. Intrusive probes were used to make the flow measurements. Possible errors introduced by intrusive probes in making shear flow measurements were also examined. Several scaled sizes of mechanical tabs were then tested, configured around the perimeter of the rectangular jet. Both the number and the location of the tabs were varied. From this, the best configuration was selected. This volume contains tabulated data for each of the data runs cited in Volume 1. Baseline characteristics, mixing modifications (subsonic and supersonic, heated and unheated) and miscellaneous charts are included.

Modeling of a multileaf collimator

NASA Astrophysics Data System (ADS)

Kim, Siyong

A comprehensive physics model of a multileaf collimator (MLC) field for treatment planning was developed. Specifically, an MLC user interface module that includes a geometric optimization tool and a general method of in- air output factor calculation were developed. An automatic tool for optimization of MLC conformation is needed to realize the potential benefits of MLC. It is also necessary that a radiation therapy treatment planning (RTTP) system is capable of modeling MLC completely. An MLC geometric optimization and user interface module was developed. The planning time has been reduced significantly by incorporating the MLC module into the main RTTP system, Radiation Oncology Computer System (ROCS). The dosimetric parameter that has the most profound effect on the accuracy of the dose delivered with an MLC is the change in the in-air output factor that occurs with field shaping. It has been reported that the conventional method of calculating an in-air output factor cannot be used for MLC shaped fields accurately. Therefore, it is necessary to develop algorithms that allow accurate calculation of the in-air output factor. A generalized solution for an in-air output factor calculation was developed. Three major contributors of scatter to the in-air output-flattening filter, wedge, and tertiary collimator-were considered separately. By virtue of a field mapping method, in which a source plane field determined by detector's eye view is mapped into a detector plane field, no additional dosimetric data acquisition other than the standard data set for a range of square fields is required for the calculation of head scatter. Comparisons of in-air output factors between calculated and measured values show a good agreement for both open and wedge fields. For rectangular fields, a simple equivalent square formula was derived based on the configuration of a linear accelerator treatment head. This method predicts in-air output to within 1% accuracy. A two-effective-source algorithm was developed to account for the effect of source to detector distance on in-air output for wedge fields. Two effective sources, one for head scatter and the other for wedge scatter, were dealt with independently. Calculations provided less than 1% difference of in-air output factors from measurements. This approach offers the best comprehensive accuracy in radiation delivery with field shapes defined using MLC. This generalized model works equally well with fields shaped by any type of tertiary collimator and have the necessary framework to extend its application to intensity modulated radiation therapy.

Generation of quasi-monoenergetic heavy ion beams via staged shock wave acceleration driven by intense laser pulses in near-critical plasmas

NASA Astrophysics Data System (ADS)

Zhang, W. L.; Qiao, B.; Shen, X. F.; You, W. Y.; Huang, T. W.; Yan, X. Q.; Wu, S. Z.; Zhou, C. T.; He, X. T.

2016-09-01

Laser-driven ion acceleration potentially offers a compact, cost-effective alternative to conventional accelerators for scientific, technological, and health-care applications. A novel scheme for heavy ion acceleration in near-critical plasmas via staged shock waves driven by intense laser pulses is proposed, where, in front of the heavy ion target, a light ion layer is used for launching a high-speed electrostatic shock wave. This shock is enhanced at the interface before it is transmitted into the heavy ion plasmas. Monoenergetic heavy ion beam with much higher energy can be generated by the transmitted shock, comparing to the shock wave acceleration in pure heavy ion target. Two-dimensional particle-in-cell simulations show that quasi-monoenergetic {{{C}}}6+ ion beams with peak energy 168 MeV and considerable particle number 2.1 × {10}11 are obtained by laser pulses at intensity of 1.66 × {10}20 {{W}} {{cm}}-2 in such staged shock wave acceleration scheme. Similarly a high-quality {{Al}}10+ ion beam with a well-defined peak with energy 250 MeV and spread δ E/{E}0=30 % can also be obtained in this scheme.

Explosive decomposition of hydrazine by rapid compression of a gas volume

NASA Technical Reports Server (NTRS)

Bunker, R. L.; Baker, D. L.; Lee, J. H. S.

1991-01-01

In the present investigation of the initiation mechanism and the explosion mode of hydrazine decomposition, a 20 cm-long column of liquid hydrazine was accelerated into a column of gaseous nitrogen, from which it was separated by a thin Teflon diaphragm, in a close-ended cylindrical chamber. Video data obtained reveal the formation of a froth generated by the acceleration of hydrazine into nitrogen at the liquid hydrazine-gaseous nitrogen interface. The explosive hydrazine decomposition had as its initiation mechanism the formation of a froth at a critical temperature; the explosion mode of hydrazine is a confined thermal runaway reaction.

Vertebrate gravity sensors as dynamic systems

NASA Technical Reports Server (NTRS)

Ross, M. D.

1985-01-01

This paper considers verterbrate gravity receptors as dynamic sensors. That is, it is hypothesized that gravity is a constant force to which an acceleration-sensing system would readily adapt. Premises are considered in light of the presence of kinocilia on hair cells of vertebrate gravity sensors; differences in loading of the sensors among species; and of possible reduction in loading by inclusion of much organic material in otoconia. Moreover, organic-inorganic interfaces may confer a piezoelectric property upon otoconia, which increase the sensitivity of the sensory system to small accelerations. Comparisons with man-made accelerometers are briefly taken up.

Slippage on a particle-laden liquid-gas interface in textured microchannels

NASA Astrophysics Data System (ADS)

Gaddam, Anvesh; Agrawal, Amit; Joshi, Suhas S.; Thompson, Mark C.

2018-03-01

Despite numerous investigations in the literature on slip flows in textured microchannels, experimental results were seldom in agreement with the theory. It is conjectured that contamination of the liquid-gas interface by impurities might be one of the sources of this discrepancy. However, the effect of impurities on slippage at the liquid-gas interface is neither understood nor previously reported. To this end, this work presents numerical investigation on the flow past a liquid-gas interface embedded with solid particles in textured microchannels. Initially, we present numerical simulations past transverse ribs with cylindrical particles on the liquid-gas interface. A reduction in effective slip length (or slip loss) with respect to the particle-free interface as a function of gas fraction, constriction ratio, and particle position was quantified. A significant slip loss (˜20-80%) was induced, owing to acceleration-deceleration cycles experienced by the liquid advecting across the particle-laden liquid-gas interface. Even a small number of solid particles adsorbed on a liquid-gas interface were shown to reduce the effective slip length considerably. This renders a textured microchannel with the particle-laden interface to be ineffective as compared to a completely wetted textured microchannel under certain conditions. Furthermore, a flow past two bi-dimensional textures, viz. posts and holes, with their interfaces embedded with spherical particles was also simulated. Our results show that texture configurations with an unbounded liquid-gas interface can mitigate the detrimental effects of particles adsorbed at the interface. The results presented here will help guide in designing efficient textured surfaces in future.

Accelerator Reactor Coupling for Energy Production in Advanced Nuclear Fuel Cycles

DOE PAGES

Brown, Nicholas R.; Heidet, Florent; Haj Tahar, Malek

2016-01-01

This article is a review of several accelerator–reactor interface issues and nuclear fuel cycle applications of acceleratordriven subcritical systems. The systems considered here have the primary goal of energy production, but that goal is accomplished via a specific application in various proposed nuclear fuel cycles, such as breed-and-burn of fertile material or burning of transuranic material. Several basic principles are reviewed, starting from the proton beam window including the target, blanket, reactor core, and up to the fuel cycle. We focus on issues of interest, such as the impact of the energy required to run the accelerator and associated systemsmore » on the potential electricity delivered to the grid. Accelerator-driven systems feature many of the constraints and issues associated with critical reactors, with the added challenges of subcritical operation and coupling to an accelerator. Reliable accelerator operation and avoidance of beam trips are critically important. One interesting challenge is measurement of blanket subcriticality level during operation. We also review the potential benefits of accelerator-driven systems in various nuclear fuel cycle applications. Ultimately, accelerator-driven subcritical systems with the goal of transmutation of transuranic material have lower 100,000-year radioactivity than a critical fast reactor with recycling of uranium and plutonium.« less

Compound scale-up at the discovery-development interface.

PubMed

Nikitenko, Antonia A

2006-11-01

As a result of an economically challenging environment within the pharmaceutical industry, pharmaceutical companies and their departments must increase productivity and cut costs to stay in line with the market. Discovery-led departments such as the medicinal chemistry and lead optimization groups focus on synthesizing large varieties of compounds in minimal amounts, while the chemical development groups must then deliver a few chosen leads employing an optimized synthesis method and using multi-kilogram quantities of material. A research group at the discovery-development interface has the task of medium-scale synthesis which is important in the lead selection stage. The primary objective of this group is the initial scale-up of promising leads for extensive physicochemical and biological testing. The challenge of the interface group involves overcoming synthetic issues within the rigid, accelerated timelines.

Accelerated decarburization of Fe-C metal alloys

DOEpatents

Pal, Uday B.; Sadoway, Donald R.

1997-01-01

A process for improving the rate of metal production and FeO utilization in a steelmaking process or a process combining iron-making and steelmaking in a single reactor that uses or generates Fe-C metal alloy droplets submerged in an FeO-containing slag. The process involves discharging a charge build-up (electron accumulation) in the slag at the slag-metal alloy interface by means of an electron conductor connected between the metal alloy droplets and a gas at a gas-slag interface, said gas having an oxygen partial pressure of at least about 0.01 atmosphere.

Accelerated decarburization of Fe-C metal alloys

DOEpatents

Pal, U.B.; Sadoway, D.R.

1997-05-27

A process is described for improving the rate of metal production and FeO utilization in a steelmaking process or a process combining iron-making and steelmaking in a single reactor that uses or generates Fe-C metal alloy droplets submerged in an FeO-containing slag. The process involves discharging a charge build-up (electron accumulation) in the slag at the slag-metal alloy interface by means of an electron conductor connected between the metal alloy droplets and a gas at a gas-slag interface, said gas having an oxygen partial pressure of at least about 0.01 atmosphere. 2 figs.

Rectangular Microstrip Antenna with Slot Embedded Geometry

NASA Astrophysics Data System (ADS)

Ambresh, P. A.; Hadalgi, P. M.; Hunagund, P. V.; Sujata, A. A.

2014-09-01

In this paper, a novel design that improves the performance of conventional rectangular microstrip antenna is discussed. Design adopts basic techniques such as probe feeding technique with rectangular inverted patch structure as superstrate, air filled dielectric medium as substrate and slot embedded patch. Prototype of the proposed antenna has been fabricated and various antenna performance parameters such as impedance bandwidth, return loss, radiation pattern and antenna gain are considered for Electromagnetic-study. The antennas are designed for the wireless application operating in the frequency range of 3.3 GHz to 3.6 GHz, and UK based fixed satellite service application (3 GHz to 4 GHz), and are named as single inverted patch conventional rectangular microstrip antenna (SIP-CRMSA) and slots embedded inverted patch rectangular microstrip antenna (SEIP-RMSA), respectively. Measurement outcomes for SEIP-RMSA1 and SEIP-RMSA2 showed the satisfactory performance with an achievable impedance bandwidth of 260 MHz (7 %) and 250 MHz (6.72 %), with return loss (RL) of -11.06 dB and -17.98 dB, achieved gain of 8.17 dB and 5.17 dB with 10% and 8% size reduction in comparison with the conventional patch antenna.

Sensorimotor-Conceptual Integration in Free Walking Enhances Divergent Thinking for Young and Older Adults

PubMed Central

Kuo, Chun-Yu; Yeh, Yei-Yu

2016-01-01

Prior research has shown that free walking can enhance creative thinking. Nevertheless, it remains unclear whether bidirectional body-mind links are essential for the positive effect of free walking on creative thinking. Moreover, it is unknown whether the positive effect can be generalized to older adults. In Experiment 1, we replicated previous findings with two additional groups of young participants. Participants in the rectangular-walking condition walked along a rectangular path while generating unusual uses for chopsticks. Participants in the free-walking group walked freely as they wished, and participants in the free-generation condition generated unconstrained free paths while the participants in the random-experienced condition walked those paths. Only the free-walking group showed better performance in fluency, flexibility, and originality. In Experiment 2, two groups of older adults were randomly assigned to the free-walking and rectangular-walking conditions. The free-walking group showed better performance than the rectangular-walking group. Moreover, older adults in the free-walking group outperformed young adults in the rectangular-walking group in originality and performed comparably in fluency and flexibility. Bidirectional links between proprioceptive-motor kinematics and metaphorical abstract concepts can enhance divergent thinking for both young and older adults. PMID:27790178

Treatment of mandibular angle fracture with a 2mm, 3 dimensional rectangular grid compression miniplates: A prospective clinical study.

PubMed

Mansuri, Samir; Abdulkhayum, Abdul Mujeeb; Gazal, Giath; Hussain, Mohammed Abid Zahir

2013-12-01

Surgical treatment of fracture mandible using an internal fixation has changed in the last decades to achieve the required rigidity, stability and immediate restoration of function. The aim of the study was to do a Prospective study of 10 patients to determine the efficacy of rectangular grid compression miniplates in mandibular fractures. This study was carried out using 2.0 rectangular grid compression miniplates and 8 mm multidirectional screws as a rigid internal fixation in 10 patients without post operative intermaxillary fixation (IMF). Follow up was done for period of 6 months. All fractures were healed with an absolute stability in post operative period. None of the patient complained of post operative difficulty in occlusion. Within the limits of this study, it can be concluded that rectangular grid compression miniplates was rigid, reliable and thus can be recommended for the treatment of mandibular angle fractures. How to cite this article: Mansuri S, Abdulkhayum AM, Gazal G, Hussain MA. Treatment of mandibular angle fracture with a 2mm, 3 dimensional rectangular grid compression miniplates: A prospective clinical study. J Int Oral Health 2013;5(6):93-100 .

Influence of surface rectangular defect winding layer on burst pressure of CNG-II composite cylinder

NASA Astrophysics Data System (ADS)

You, H. X.; Peng, L.; Zhao, C.; Ma, K.; Zhang, S.

2018-01-01

To study the influence of composite materials’ surface defect on the burst pressure of CNG-II composite cylinder, the surface defect was simplified as a rectangular slot of certain size on the basis of actually investigating the shape of cylinder’s surface defect. A CNG-II composite cylinder with a rectangular slot defect (2mm in depth) was used for burst test, and the numerical simulation software ANSYS was used to calculate its burst pressure. Through comparison between the burst pressure in the test and the numerical analysis result, the correctness of the numerical analysis method was verified. On this basis, the numerical analysis method was conducted for composite cylinders with surface defect in other depth. The result showed that surface defect in the form of rectangular slot had no significant effect on the liner stress of composite cylinder. Instead, it had a great influence on the stress of fiber-wrapped layer. The burst pressure of the composite cylinder decreased as the defect depth increasing. The hoop stress at the bottom of the defect in the shape of rectangular slot exceeded the maximum of the composite materials’ tensile strength, which could result in the burst pressure of composite cylinders decreasing.

The study and development of the empirical correlations equation of natural convection heat transfer on vertical rectangular sub-channels

NASA Astrophysics Data System (ADS)

Kamajaya, Ketut; Umar, Efrizon; Sudjatmi, K. S.

2012-06-01

This study focused on natural convection heat transfer using a vertical rectangular sub-channel and water as the coolant fluid. To conduct this study has been made pipe heaters are equipped with thermocouples. Each heater is equipped with five thermocouples along the heating pipes. The diameter of each heater is 2.54 cm and 45 cm in length. The distance between the central heating and the pitch is 29.5 cm. Test equipment is equipped with a primary cooling system, a secondary cooling system and a heat exchanger. The purpose of this study is to obtain new empirical correlations equations of the vertical rectangular sub-channel, especially for the natural convection heat transfer within a bundle of vertical cylinders rectangular arrangement sub-channels. The empirical correlation equation can support the thermo-hydraulic analysis of research nuclear reactors that utilize cylindrical fuel rods, and also can be used in designing of baffle-free vertical shell and tube heat exchangers. The results of this study that the empirical correlation equations of natural convection heat transfer coefficients with rectangular arrangement is Nu = 6.3357 (Ra.Dh/x)0.0740.

Interface engineering of CsPbBr3/TiO2 heterostructure with enhanced optoelectronic properties for all-inorganic perovskite solar cells

NASA Astrophysics Data System (ADS)

Qian, Chong-Xin; Deng, Zun-Yi; Yang, Kang; Feng, Jiangshan; Wang, Ming-Zi; Yang, Zhou; Liu, Shengzhong Frank; Feng, Hong-Jian

2018-02-01

Interface engineering has become a vital method in accelerating the development of perovskite solar cells in the past few years. To investigate the effect of different contacted surfaces of a light absorber with an electron transporting layer, TiO2, we synthesize CsPbBr3/TiO2 thin films with two different interfaces (CsBr/TiO2 and PbBr2/TiO2). Both interfacial heterostructures exhibit enhanced visible light absorption, and the CsBr/TiO2 thin film presents higher absorption than the PbBr2/TiO2 interface, which is attributed to the formation of interface states and the decreased interface bandgap. Furthermore, compared with the PbBr2/TiO2 interface, CsBr/TiO2 solar devices present larger output short circuit current and shorter photoluminescence decay time, which indicates that the CsBr contacting layer with TiO2 can better extract and separate the photo-induced carriers. The first-principles calculations confirm that, due to the existence of staggered gap (type II) offset junction and the interface states, the CsBr/TiO2 interface can more effectively separate the photo-induced carriers and thus drive the electron transfer from the CsPbBr3 perovskite layer to the TiO2 layer. These results may be beneficial to exploit the potential application of all-inorganic perovskite CsPbBr3-based solar cells through the interface engineering route.

The evolution of slip pulses within bimaterial interfaces with rupture velocity

NASA Astrophysics Data System (ADS)

Shlomai, H.; Fineberg, J.

2017-12-01

The most general frictional motion in nature involves bimaterial interfaces, when contacting bodies possess different elastic properties. Frictional motion occurs when the contacts composing the interface separating these bodies detach via propagating rupture fronts. Coupling between slip and normal stress variations is unique to bimaterial interfaces. Here we use high speed simultaneous measurements of slip velocities, real contact area and stresses to explicitly reveal this bimaterial coupling and its role in determining different classes of rupture modes and their structures. Our experiments study the rupture of a spatially extended interface formed by brittle plastics whose shear wave speeds differ by 30%. Any slip within a bimaterial interface will break the stress symmetry across the interface. One important result of this is that local values of normal stress variations at the interface couple to interface slip, `bimaterial coupling'. The sign of the coupling depends on the front propagation direction. When we consider ruptures propagating in the direction of motion of the more compliant material, the `positive' direction, slip reduces the normal stress. We focus on this direction. We show that, in this direction, interface ruptures develop from crack-like behavior at low rupture velocities, whose structure corresponds to theoretical predictions: As the ruptures accelerate towards their asymptotic speed, the structures of the strain and stress fields near the rupture tip deviate significantly from this crack-like form, and systematically sharpen to a pulse-like rupture mode called slip-pulses. We conclude with a description of slip-pulse properties.

Tyrosine phosphorylation switching of a G protein.

PubMed

Li, Bo; Tunc-Ozdemir, Meral; Urano, Daisuke; Jia, Haiyan; Werth, Emily G; Mowrey, David D; Hicks, Leslie M; Dokholyan, Nikolay V; Torres, Matthew P; Jones, Alan M

2018-03-30

Heterotrimeric G protein complexes are molecular switches relaying extracellular signals sensed by G protein-coupled receptors (GPCRs) to downstream targets in the cytoplasm, which effect cellular responses. In the plant heterotrimeric GTPase cycle, GTP hydrolysis, rather than nucleotide exchange, is the rate-limiting reaction and is accelerated by a receptor-like regulator of G signaling (RGS) protein. We hypothesized that posttranslational modification of the Gα subunit in the G protein complex regulates the RGS-dependent GTPase cycle. Our structural analyses identified an invariant phosphorylated tyrosine residue (Tyr 166 in the Arabidopsis Gα subunit AtGPA1) located in the intramolecular domain interface where nucleotide binding and hydrolysis occur. We also identified a receptor-like kinase that phosphorylates AtGPA1 in a Tyr 166 -dependent manner. Discrete molecular dynamics simulations predicted that phosphorylated Tyr 166 forms a salt bridge in this interface and potentially affects the RGS protein-accelerated GTPase cycle. Using a Tyr 166 phosphomimetic substitution, we found that the cognate RGS protein binds more tightly to the GDP-bound Gα substrate, consequently reducing its ability to accelerate GTPase activity. In conclusion, we propose that phosphorylation of Tyr 166 in AtGPA1 changes the binding pattern with AtRGS1 and thereby attenuates the steady-state rate of the GTPase cycle. We coin this newly identified mechanism "substrate phosphoswitching." © 2018 by The American Society for Biochemistry and Molecular Biology, Inc.

Modification of growth interface of CdZnTe crystals in THM process by ACRT

NASA Astrophysics Data System (ADS)

Zhou, Boru; Jie, Wanqi; Wang, Tao; Yin, Liying; Yang, Fan; Zhang, Binbin; Xi, Shouzhi; Dong, Jiangpeng

2018-02-01

The accelerated crucible rotation technique (ACRT) was introduced in the traveling heater method (THM) growth process of detector-grade CdZnTe (CZT) crystals to regulate the convection in the melt and to modify the growth interface morphology. Several ingots with the diameter of 53 mm were grown by THM with/without ACRT. The ingots were quenched during the growth to show both macroscopic and microscopic morphologies of the growth interfaces. The results show that by using ACRT the growth interface can be changed from a concave one to the flat or even convex one depending on the ACRT parameters, which is favorable for reducing nucleation in the melt to get larger CZT grains. Meanwhile, by using ACRT in THM process, the microscopic interface was changed from a diffused one to cellular or even planar one (at suitable ACRT parameters), through which the trapped Te inclusions was decreased for one order. An ingot grown by THM with constant rotation rate of 40 rpm was also grown, which have also reduced the interface curvature in macro-scale and Te inclusions to some extent, but the effects are not as significant as ACRT with high crucible rotation rate.

A new metamaterial-based wideband rectangular invisibility cloak

NASA Astrophysics Data System (ADS)

Islam, S. S.; Hasan, M. M.; Faruque, M. R. I.

2018-02-01

A new metamaterial-based wideband electromagnetic rectangular cloak is being introduced in this study. The metamaterial unit cell shows sharp transmittances in the C- and X-bands and displays wideband negative effective permittivity region there. The metamaterial unit cell was then applied in designing a rectangular-shaped electromagnetic cloak. The scattering reduction technique was adopted for the cloaking operation. The cloak operates in the certain portion of C-and X-bands that covers more than 4 GHz bandwidth region. The experimental results were provided as well for the metamaterial and the cloak.

Natural frequencies of thin rectangular plates clamped on contour using the Finite Element Method

NASA Astrophysics Data System (ADS)

(Barboni Haţiegan, L.; Haţiegan, C.; Gillich, G. R.; Hamat, C. O.; Vasile, O.; Stroia, M. D.

2018-01-01

This paper presents the determining of natural frequencies of plates without and with damages using the finite element method of SolidWorks program. The first thirty natural frequencies obtained for thin rectangular rectangular plates clamped on contour without and with central damages a for different dimensions. The relative variation of natural frequency was determined and the obtained results by the finite element method (FEM) respectively relative variation of natural frequency, were graphically represented according to their vibration natural modes. Finally, the obtained results were compared.

Computational and experimental investigation of plasma deflagration jets and detonation shocks in coaxial plasma accelerators

NASA Astrophysics Data System (ADS)

Subramaniam, Vivek; Underwood, Thomas C.; Raja, Laxminarayan L.; Cappelli, Mark A.

2018-02-01

We present a magnetohydrodynamic (MHD) numerical simulation to study the physical mechanisms underlying plasma acceleration in a coaxial plasma gun. Coaxial plasma accelerators are known to exhibit two distinct modes of operation depending on the delay between gas loading and capacitor discharging. Shorter delays lead to a high velocity plasma deflagration jet and longer delays produce detonation shocks. During a single operational cycle that typically consists of two discharge events, the plasma acceleration exhibits a behavior characterized by a mode transition from deflagration to detonation. The first of the discharge events, a deflagration that occurs when the discharge expands into an initially evacuated domain, requires a modification of the standard MHD algorithm to account for rarefied regions of the simulation domain. The conventional approach of using a low background density gas to mimic the vacuum background results in the formation of an artificial shock, inconsistent with the physics of free expansion. To this end, we present a plasma-vacuum interface tracking framework with the objective of predicting a physically consistent free expansion, devoid of the spurious shock obtained with the low background density approach. The interface tracking formulation is integrated within the MHD framework to simulate the plasma deflagration and the second discharge event, a plasma detonation, formed due to its initiation in a background prefilled with gas remnant from the deflagration. The mode transition behavior obtained in the simulations is qualitatively compared to that observed in the experiments using high framing rate Schlieren videography. The deflagration mode is further investigated to understand the jet formation process and the axial velocities obtained are compared against experimentally obtained deflagration plasma front velocities. The simulations are also used to provide insight into the conditions responsible for the generation and sustenance of the magnetic pinch. The pinch width and number density distribution are compared to experimentally obtained data to calibrate the inlet boundary conditions used to set up the plasma acceleration problem.

Research on the comparison of extension mechanism of cellular automaton based on hexagon grid and rectangular grid

NASA Astrophysics Data System (ADS)

Zhai, Xiaofang; Zhu, Xinyan; Xiao, Zhifeng; Weng, Jie

2009-10-01

Historically, cellular automata (CA) is a discrete dynamical mathematical structure defined on spatial grid. Research on cellular automata system (CAS) has focused on rule sets and initial condition and has not discussed its adjacency. Thus, the main focus of our study is the effect of adjacency on CA behavior. This paper is to compare rectangular grids with hexagonal grids on their characteristics, strengths and weaknesses. They have great influence on modeling effects and other applications including the role of nearest neighborhood in experimental design. Our researches present that rectangular and hexagonal grids have different characteristics. They are adapted to distinct aspects, and the regular rectangular or square grid is used more often than the hexagonal grid. But their relative merits have not been widely discussed. The rectangular grid is generally preferred because of its symmetry, especially in orthogonal co-ordinate system and the frequent use of raster from Geographic Information System (GIS). However, in terms of complex terrain, uncertain and multidirectional region, we have preferred hexagonal grids and methods to facilitate and simplify the problem. Hexagonal grids can overcome directional warp and have some unique characteristics. For example, hexagonal grids have a simpler and more symmetric nearest neighborhood, which avoids the ambiguities of the rectangular grids. Movement paths or connectivity, the most compact arrangement of pixels, make hexagonal appear great dominance in the process of modeling and analysis. The selection of an appropriate grid should be based on the requirements and objectives of the application. We use rectangular and hexagonal grids respectively for developing city model. At the same time we make use of remote sensing images and acquire 2002 and 2005 land state of Wuhan. On the base of city land state in 2002, we make use of CA to simulate reasonable form of city in 2005. Hereby, these results provide a proof of concept for hexagonal which has great dominance.

25. DETAIL OF THE MASONRY ARCH OF A RECTANGULAR COKE ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

25. DETAIL OF THE MASONRY ARCH OF A RECTANGULAR COKE OVEN. - Tower Hill No. 2 Mine, Approximately 0.47 mile Southwest of intersection of Stone Church Road & Township Route 561, Hibbs, Fayette County, PA

VIEW OF INTERIOR SPACE WITH RECTANGULAR SHAPE STRETCH PRESS CONTAINMENT ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

VIEW OF INTERIOR SPACE WITH RECTANGULAR SHAPE STRETCH PRESS CONTAINMENT PIT IN BACKGROUND, FACING NORTH. - Douglas Aircraft Company Long Beach Plant, Aircraft Parts Shipping & Receiving Building, 3855 Lakewood Boulevard, Long Beach, Los Angeles County, CA

Strength and stiffness of reinforced rectangular columns under biaxially eccentric thrust.

DOT National Transportation Integrated Search

1976-01-01

Compression tests on nine reinforced concrete rectangular columns subjected to : constant thrust and biaxially eccentric moments were conducted at the off-campus : research facility of The University of Texas, The Civil Engineering Structures : Labor...

Design of Three-Dimensional Hypersonic Inlets with Rectangular to Elliptical Shape Transition

NASA Technical Reports Server (NTRS)

Smart, M. K.

1998-01-01

A methodology has been devised for the design of three-dimensional hypersonic inlets which include a rectangular to elliptical shape transition. This methodology makes extensive use of inviscid streamtracing techniques to generate a smooth shape transition from a rectangular-like capture to an elliptical throat. Highly swept leading edges and a significantly notched cowl enable use of these inlets in fixed geometry configurations. The design procedure includes a three dimensional displacement thickness calculation and uses established correlations to check for boundary layer separation due to shock wave interactions. Complete details of the design procedure are presented and the characteristics of a modular inlet with rectangular to elliptical shape transition and a design point of Mach 7.1 are examined. Comparison with a classical two-dimensional inlet optimized for maximum total pressure recovery indicates that this three-dimensional inlet demonstrates good performance even well below its design point.

Mode instability in a Yb-doped stretched core fiber

NASA Astrophysics Data System (ADS)

Xia, N.; Yoo, S.

2017-02-01

In this work we present the theoretical study of transverse mode instability (TMI) in ytterbium (Yb)-doped rectangular core fibers with different core aspect ratios using the fast Fourier transform (FFT) beam propagation method (BPM). As expected, the rectangular core fiber with larger aspect ratio (AR.) offers more efficient heat dissipation than a circular core fiber. However, it is found that the rectangular core fiber does not benefit from the better heat dissipation to suppress the TMI when compared to the circular core counterpart. The temperature building in the rectangular core fiber decreases by up to 24.6% with a 10:1 aspect ratio core, while threshold pump power drops by up to 38.3% when compared with a circular core fiber with the same core area. Our study reveals that a smaller effective refractive index difference between modes and a weaker gain saturation effect compensate the thermal advantage from more efficient heat dissipation.

Cos-Gaussian modal field of a terahertz rectangular metal waveguide filled with multiple slices of dielectric

NASA Astrophysics Data System (ADS)

Wang, Kai; Cao, Qing; Zhang, Huifang; Shen, Pengcheng; Xing, Lujing

2018-06-01

Based on the TE01 mode of a rectangular metal waveguide and the Gaussian mode of a fiber, we propose the cos-Gaussian mode of a terahertz rectangular metal waveguide filled with multiple slices of dielectric. First, we consider a rectangular metal waveguide filled with an ideal graded-index dielectric along one direction. Furthermore, we replace the graded-index dielectric with multiple slices of dielectric according to the effective medium theory. The modal field, the effective index, and the coupling efficiency of this waveguide are investigated. It is found that the approximately linearly polarized electric field is Gaussian along one dimensionality and cosine along the other one. In addition, the low loss and high coupling efficiency with a Gaussian beam can be acquired at 0.9 THz. By optimization, the coupling efficiency could reach 88.5%.

Evolution of low-aspect-ratio rectangular synthetic jets in a quiescent environment

NASA Astrophysics Data System (ADS)

Wang, Lei; Feng, Li-Hao; Wang, Jin-Jun; Li, Tian

2018-06-01

An experimental study was conducted on the evolution of low-aspect-ratio (AR) rectangular synthetic jets using time-resolved two-dimensional particle image velocimetry and stereoscopic particle image velocimetry. Five orifice ARs ranging from 1 to 5 were found to have an obvious effect on the axis switching of vortex rings and the near-field flow physics at a uniform Reynolds number of 166 and non-dimensional stroke length of 4.5. Compared with conventional continuous jets, rectangular synthetic jets displayed more times of axis switching and the first axis-switching location was closer to the jet exit. Two types of different streamwise vortices, SV-I and SV-II, were detected in the near field as the characteristic products of axis switching. Influenced by the axis switching and streamwise vortices, significant entrainment and mixing enhancement was demonstrated for low-AR rectangular synthetic jets.

Numerical Investigation of Flow Around Rectangular Cylinders with and Without Jets

NASA Technical Reports Server (NTRS)

Tiwari, S. N .; Pidugu, S. B.

1999-01-01

The problem of flow past bluff bodies was studied extensively in the past. The problem of drag reduction is very important in many high speed flow applications. Considerable work has been done in this subject area in case of circular cylinders. The present study attempts to investigate the feasibility of drag reduction on a rectangular cylinder by flow injection by flow injection from the rear stagnation region. The physical problem is modeled as two-dimensional body and numerical analysis is carried out with and without trailing jets. A commercial code is used for this purpose. Unsteady computation is performed in case of rectangular cylinders with no trailing jets where as steady state computation is performed when jet is introduced. It is found that drag can be reduced by introducing jets with small intensity in rear stagnation region of the rectangular cylinders.

Analysis and numerical simulation research of the heating process in the oven

NASA Astrophysics Data System (ADS)

Chen, Yawei; Lei, Dingyou

2016-10-01

How to use the oven to bake delicious food is the most concerned problem of the designers and users of the oven. For this intent, this paper analyzed the heat distribution in the oven based on the basic operation principles and proceeded the data simulation of the temperature distribution on the rack section. Constructing the differential equation model of the temperature distribution changes in the pan when the oven works based on the heat radiation and heat transmission, based on the idea of utilizing cellular automation to simulate heat transfer process, used ANSYS software to proceed the numerical simulation analysis to the rectangular, round-cornered rectangular, elliptical and circular pans and giving out the instantaneous temperature distribution of the corresponding shapes of the pans. The temperature distribution of the rectangular and circular pans proves that the product gets overcooked easily at the corners and edges of rectangular pans but not of a round pan.

On solving three-dimensional open-dimension rectangular packing problems

NASA Astrophysics Data System (ADS)

Junqueira, Leonardo; Morabito, Reinaldo

2017-05-01

In this article, a recently proposed three-dimensional open-dimension rectangular packing problem is considered, in which the objective is to find a minimal volume rectangular container that packs a set of rectangular boxes. The literature has tackled small-sized instances of this problem by means of optimization solvers, position-free mixed-integer programming (MIP) formulations and piecewise linearization approaches. In this study, the problem is alternatively addressed by means of grid-based position MIP formulations, whereas still considering optimization solvers and the same piecewise linearization techniques. A comparison of the computational performance of both models is then presented, when tested with benchmark problem instances and with new instances, and it is shown that the grid-based position MIP formulation can be competitive, depending on the characteristics of the instances. The grid-based position MIP formulation is also embedded with real-world practical constraints, such as cargo stability, and results are additionally presented.

One-dimensional nonlinear theory for rectangular helix traveling-wave tube

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

Fu, Chengfang, E-mail: fchffchf@126.com; Zhao, Bo; Yang, Yudong

A 1-D nonlinear theory of a rectangular helix traveling-wave tube (TWT) interacting with a ribbon beam is presented in this paper. The RF field is modeled by a transmission line equivalent circuit, the ribbon beam is divided into a sequence of thin rectangular electron discs with the same cross section as the beam, and the charges are assumed to be uniformly distributed over these discs. Then a method of computing the space-charge field by solving Green's Function in the Cartesian Coordinate-system is fully described. Nonlinear partial differential equations for field amplitudes and Lorentz force equations for particles are solved numericallymore » using the fourth-order Runge-Kutta technique. The tube's gain, output power, and efficiency of the above TWT are computed. The results show that increasing the cross section of the ribbon beam will improve a rectangular helix TWT's efficiency and reduce the saturated length.« less

Experimental growth of inertial forced Richtmyer-Meshkov instabilities for different Atwood numbers

NASA Astrophysics Data System (ADS)

Redondo, J. M.; Castilla, R.

2009-04-01

Richtmyer-Meshkov instability occurs when a shock wave impinges on an interface separating two fluids having different densities [1,2]. The instability causes perturbations on the interface to grow, bubbles and spikes, producing vortical structures which potentially result in a turbulent mixing layer. In addition to shock tube experiments, the incompressible Richtmyer-Meshkov instability has also been studied by impulsively accelerating containers of incompressible fluids. Castilla and Redondo (1994) [3] first exploited this technique by dropping tanks containing a liquid and air or two liquids onto a cushioned surface. This technique was improved upon by Niederhaus and Jacobs (2003)[4] by mounting the tank onto a rail system and then allowing it to bounce off of a fixed spring. A range of both miscible and inmiscible liquids were used, giving a wide range of Atwood numbers using the combinations of air, water, alcohol, oil and mercury. Experimental results show the different pattern selection of both the bubbles and spikes for the different Atwood numbers. Visual analysis of the marked interfaces allows to distinguish the regions of strong mixing and compare self-similarity growth of the mixing region. [1] Meshkov, E. E. 1969 Instability of the interface of two gases accelerated by a shock wave. Fluid Dynamics 4, 101-104. [2] Brouillette, M. & Sturtevant, B. 1994 Experiments on the Richtmyer-Meshkov instability: single-scale perturbations on a continuous interface. Journal of Fluid Mechanics 263, 271-292. [3] Castilla, R. & Redondo, J. M. 1994 Mixing Front Growth in RT and RM Instabilities. Proceedings of the Fourth International Workshop on the Physics of Compressible Turbulent Mixing, Cambridge, United Kingdom, edited by P. F. Linden, D. L. Youngs, and S. B. Dalziel, 11-31. [4] Niederhaus, C. E. & Jacobs, J. W. 2003 Experimental study of the Richtmyer-Meshkov instability of incompressible fluids. Journal of Fluid Mechanics 485, 243-277.

Petabyte Class Storage at Jefferson Lab (CEBAF)

NASA Technical Reports Server (NTRS)

Chambers, Rita; Davis, Mark

1996-01-01

By 1997, the Thomas Jefferson National Accelerator Facility will collect over one Terabyte of raw information per day of Accelerator operation from three concurrently operating Experimental Halls. When post-processing is included, roughly 250 TB of raw and formatted experimental data will be generated each year. By the year 2000, a total of one Petabyte will be stored on-line. Critical to the experimental program at Jefferson Lab (JLab) is the networking and computational capability to collect, store, retrieve, and reconstruct data on this scale. The design criteria include support of a raw data stream of 10-12 MB/second from Experimental Hall B, which will operate the CEBAF (Continuous Electron Beam Accelerator Facility) Large Acceptance Spectrometer (CLAS). Keeping up with this data stream implies design strategies that provide storage guarantees during accelerator operation, minimize the number of times data is buffered allow seamless access to specific data sets for the researcher, synchronize data retrievals with the scheduling of postprocessing calculations on the data reconstruction CPU farms, as well as support the site capability to perform data reconstruction and reduction at the same overall rate at which new data is being collected. The current implementation employs state-of-the-art StorageTek Redwood tape drives and robotics library integrated with the Open Storage Manager (OSM) Hierarchical Storage Management software (Computer Associates, International), the use of Fibre Channel RAID disks dual-ported between Sun Microsystems SMP servers, and a network-based interface to a 10,000 SPECint92 data processing CPU farm. Issues of efficiency, scalability, and manageability will become critical to meet the year 2000 requirements for a Petabyte of near-line storage interfaced to over 30,000 SPECint92 of data processing power.

Real-time orthorectification by FPGA-based hardware acceleration

NASA Astrophysics Data System (ADS)

Kuo, David; Gordon, Don

2010-10-01

Orthorectification that corrects the perspective distortion of remote sensing imagery, providing accurate geolocation and ease of correlation to other images is a valuable first-step in image processing for information extraction. However, the large amount of metadata and the floating-point matrix transformations required to operate on each pixel make this a computation and I/O (Input/Output) intensive process. As result much imagery is either left unprocessed or loses timesensitive value in the long processing cycle. However, the computation on each pixel can be reduced substantially by using computational results of the neighboring pixels and accelerated by special pipelined hardware architecture in one to two orders of magnitude. A specialized coprocessor that is implemented inside an FPGA (Field Programmable Gate Array) chip and surrounded by vendorsupported hardware IP (Intellectual Property) shares the computation workload with CPU through PCI-Express interface. The ultimate speed of one pixel per clock (125 MHz) is achieved by the pipelined systolic array architecture. The optimal partition between software and hardware, the timing profile among image I/O and computation, and the highly automated GUI (Graphical User Interface) that fully exploits this speed increase to maximize overall image production throughput will also be discussed. The software that runs on a workstation with the acceleration hardware orthorectifies 16 Megapixels per second, which is 16 times faster than without the hardware. It turns the production time from months to days. A real-life successful story of an imaging satellite company that adopted such workstations for their orthorectified imagery production will be presented. The potential candidacy of the image processing computation that can be accelerated more efficiently by the same approach will also be analyzed.

Microjet Generator for Highly Viscous Fluids

NASA Astrophysics Data System (ADS)

Onuki, Hajime; Oi, Yuto; Tagawa, Yoshiyuki

2018-01-01

This paper describes a simple system for generating a highly viscous microjet. The jet is produced inside a wettable thin tube partially submerged in a liquid. The gas-liquid interface inside the tube, which is initially concave, is kept much deeper than that outside the tube. An impulsive force applied at the bottom of a liquid container leads to significant acceleration of the liquid inside the tube followed by flow focusing due to the concave interface. The jet generation process can be divided into two parts that occur in different time scales, i.e., the impact interval [impact duration ≤O (10-4) s ] and the focusing interval [focusing duration ≫O (10-4) s ]. During the impact interval, the liquid accelerates suddenly due to the impact. During the focusing interval, the microjet emerges due to flow focusing. In order to explain the sudden acceleration inside the tube during the impact interval, we develop a physical model based on a pressure impulse approach. Numerical simulations confirm the proposed model, indicating that the basic mechanism of the acceleration of the liquid due to the impulsive force is elucidated. Remarkably, the viscous effect is negligible during the impact interval. In contrast, during the focusing interval, the viscosity plays an important role in the microjet generation. We experimentally and numerically investigate the velocity of microjets with various viscosities. We find that higher viscosities lead to reduction of the jet velocity, which can be described by using the Reynolds number (the ratio between the inertia force and the viscous force). This device may be a starting point for next-generation technologies, such as high-viscosity inkjet printers including bioprinters and needle-free injection devices for minimally invasive medical treatments.

Software package for modeling spin–orbit motion in storage rings

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

Zyuzin, D. V., E-mail: d.zyuzin@fz-juelich.de

2015-12-15

A software package providing a graphical user interface for computer experiments on the motion of charged particle beams in accelerators, as well as analysis of obtained data, is presented. The software package was tested in the framework of the international project on electric dipole moment measurement JEDI (Jülich Electric Dipole moment Investigations). The specific features of particle spin motion imply the requirement to use a cyclic accelerator (storage ring) consisting of electrostatic elements, which makes it possible to preserve horizontal polarization for a long time. Computer experiments study the dynamics of 10{sup 6}–10{sup 9} particles in a beam during 10{supmore » 9} turns in an accelerator (about 10{sup 12}–10{sup 15} integration steps for the equations of motion). For designing an optimal accelerator structure, a large number of computer experiments on polarized beam dynamics are required. The numerical core of the package is COSY Infinity, a program for modeling spin–orbit dynamics.« less

Relaxation of the accelerating-gas boundary layer to the test-gas boundary layer on a flat plate in an expansion tube

NASA Technical Reports Server (NTRS)

Gupta, R. N.; Trimpi, R. L.

1973-01-01

An analytic investigation of the relaxation of the accelerating-gas boundary layer to the test-gas boundary layer over a flat plate mounted in an expansion tube has been conducted. In this treatment, nitrogen has been considered as the test gas and helium as the accelerating gas. The problem is analyzed in two conically similar limits: (1) when the time lag between the arrival of the shock and the interface at the leading edge of the plate is very large, and (2) when this time lag is negligible. The transient laminar boundary-layer equations of a perfect binary-gas mixture are taken as the flow governing equations. These coupled equations have been solved numerically by Gauss-Seidel line-relaxation method. The results predict the transient behavior as well as the time required for an all-helium accelerating-gas boundary layer to relax to an all-nitrogen boundary layer.

Dual Ion Species Plasma Expansion from Isotopically Layered Cryogenic Targets

NASA Astrophysics Data System (ADS)

Scott, G. G.; Carroll, D. C.; Astbury, S.; Clarke, R. J.; Hernandez-Gomez, C.; King, M.; Alejo, A.; Arteaga, I. Y.; Dance, R. J.; Higginson, A.; Hook, S.; Liao, G.; Liu, H.; Mirfayzi, S. R.; Rusby, D. R.; Selwood, M. P.; Spindloe, C.; Tolley, M. K.; Wagner, F.; Zemaityte, E.; Borghesi, M.; Kar, S.; Li, Y.; Roth, M.; McKenna, P.; Neely, D.

2018-05-01

A dual ion species plasma expansion scheme from a novel target structure is introduced, in which a nanometer-thick layer of pure deuterium exists as a buffer species at the target-vacuum interface of a hydrogen plasma. Modeling shows that by controlling the deuterium layer thickness, a composite H+/D+ ion beam can be produced by target normal sheath acceleration (TNSA), with an adjustable ratio of ion densities, as high energy proton acceleration is suppressed by the acceleration of a spectrally peaked deuteron beam. Particle in cell modeling shows that a (4.3 ±0.7 ) MeV per nucleon deuteron beam is accelerated, in a directional cone of half angle 9°. Experimentally, this was investigated using state of the art cryogenic targetry and a spectrally peaked deuteron beam of (3.4 ±0.7 ) MeV per nucleon was measured in a cone of half angle 7°-9°, while maintaining a significant TNSA proton component.

[Effect of sintering gold paste coating on the bonding strength of pure titanium and three low-fusing porcelains].

PubMed

Zhang, Ya-li; Luo, Xiao-ping; Zhou, Li

2012-05-01

To study the effect of sintering gold paste coating of pure titanium on the adhesion of three porcelains following the protocol ISO 9693, and to investigate the titanium-porcelains interfaces. Sixty machined pure titanium samples were prepared in a rectangular shape according to ISO 9693 and divided equally into six groups. Half of the strips were coated with gold paste (Deckgold) and sintered. Three ultra-low-fusing dental porcelains (I: Initial Ti, S: Super porcelain Ti-22, T: TitanKeramik) were fused onto the titanium surfaces. A thin layer of bonding agent was only applied on the surfaces of uncoated gold specimens. The interface of the porcelain and titanium was observed with a field emission scanning electron microscope (FE-SEM) after metallographic preparation and sputtered with a very thin carbon layer of the embedded titanium-porcelain interface. After three-point bending test was performed, optical stereomicroscope was used to characterize the titanium-porcelains adhesion and determine the mode of failure. FE-SEM illustrated intermetallic compounds of Au-Ti formed with some visible microcracks in the gold layer and the interface of gold layer and ceramic. All the uncoated gold titanium-porcelain system showed predominately adhesive fracture at the titanium oxidation, whereas the failure modes in all gold coated systems were cohesive and adhesive, mainly cohesive. The three-point-bending test showed that the bonding strength of GS and GI groups [(37.08 ± 4.32) and (36.20 ± 2.40) MPa] were higher than those in uncoated groups [(31.56 ± 3.74) and (30.88 ± 2.60) MPa, P < 0.05], while no significant difference was found between T group and GT group (P > 0.05). The gold paste intermediate coatings can improve bond strengths of Super porcelain Ti-22 system and Initial Ti system, which have potential applications in clinical fields.

Teaching Hyporheic and Groundwater Flow Concepts Using an Interactive Computer Simulation

NASA Astrophysics Data System (ADS)

Stonedahl, S. H.; Stonedahl, F.

2016-12-01

We built an educational flow simulator with an interactive web-based interface that allows students to investigate the effects of arbitrary head functions on water flowing through various configurations of permeable/impermeable sediments. The domain consists of a 24 by 48 rectangular grid of sediments with no-flow bottom and side boundaries and a constant head surface water-groundwater (SWGW) interface boundary. The SWGW interface head function can be drawn freehand with the mouse or specified to be a step function, a sine curve, or a zig-zag function, where the amplitude and wavenumber parameters of the head functions are chosen by the user. The subsurface domain may be modified by drawing no-flow (impermeable) barriers in the sediment, changing any number of the 1152 grid cells into no flow cells. The program iteratively solves the Laplace equation to calculate head values at each grid cell within the sediment. Users can then start water particles along the SWGW interface and track their paths through the system to visualize the head-induced flow. Sediment cells can be color coded by head values or water speed. Exploring these systems with the simulator allows users to improve their understanding of the relationship between head and velocity as well as how the position of no-flow barriers impacts water flow in saturated sediments. These learning objectives are amenable to our target audience of undergraduate students, but younger (middle/high school) students may also be able to absorb key concepts by playing with the simulation. The structure of the simulation itself highlights the broader idea of simulation of natural processes through the discretization of continuous environments. The simulation was developed using the NetLogo platform and runs embedded in a webpage: http://susa.stonedahl.com/swgwsimulator. The simulation source code is available and can readily be modified by other educators (or students) to create additional features and options.

Northrop P-61 Black Widow Flight Testing a Ramjet

NASA Image and Video Library

1947-01-21

The National Advisory Committee for Aeronautics (NACA) Lewis Flight Propulsion Laboratory obtained a Northrop P-61 Black Widow in October 1945 and modified it to serve as a subsonic testbed for ramjet engines and swept-wing aircraft models. The P-61 was developed during World War II specifically for nighttime attacks. It was the largest and heaviest US fighter in the war. The P-61’s unique design included an abbreviated fuselage and twin booms that were joined by a single tail. To facilitate its nighttime missions, the P-61 was painted black and carried a radar system in its nose. It was designed so the crew could perform their flight and tracking tasks in complete darkness. NACA Lewis was in the midst of a massive research effort on ramjets when it acquired the Black Widow. Researchers used the aircraft to accelerate the ramjet until it reached a velocity at which it could be ignited. A ramjet can be seen being fired underneath the aircraft in this photograph. Sensors and instrumentation fed data from the ramjet to the pilot and researchers on the ground. The NACA researchers created a rectangular ramjet with a V-shaped gutter flameholder. The researchers installed the ramjet on the P-61 and flew it at subsonic speeds over a range of altitudes up to 29,000 feet. The ramjet had been previously tested at low speeds on a test stand on the hangar apron. The rectangular ramjet was also used to study different types of flameholders and nozzles used to spray fuel into the combustion chamber. The Black Widow was transferred from Lewis in October 1948.

Investigation of test methods, material properties, and processes for solar cell encapsulants

NASA Technical Reports Server (NTRS)

Willis, P. B.

1981-01-01

Encapsulant materials and processes for the production of cost-effective, long-life solar cell modules were investigated. The following areas were explored: (1) soil resistant surface treatment; (2) corrosion protecting coatings from mild steel substrates; (3) primers for bonding module interfaces; and (4) RS/4 accelerated aging of candidate encapsulation compounds

Methods to Account for Accelerated Semi-Conductor Device Wearout in Longlife Aerospace Applications

DTIC Science & Technology

2003-01-01

Vasi, “Device scalling effects on hot-carrier induced interface and oxide-trappoing charge distributions in MOSFETs,” IEEE Transactions on Electron...Symposium Proceedings, pp. 248–254, 2002. [104] S. I. A. ( SIA ), “International technology roadmap for semiconductors.” <www.semichips.org>, 1999. 113

The emerging infectious disease crisis and pathogen pollution: a question of ecology and evolution

USDA-ARS?s Scientific Manuscript database

Risk of emerging infectious diseases (EID) on a global scale has accelerated over the past 10,000 years in conjunction with agriculture, domestication, and globalization as the interfaces for people and environments have been altered over time. EID exist at the junction of 3 ongoing global challenge...

A Computational Study of a Circular Interface Richtmyer-Meshkov Instability in MHD

NASA Astrophysics Data System (ADS)

Maxon, William; Black, Wolfgang; Denissen, Nicholas; McFarland, Jacob; Los Alamos National Laboratory Collaboration; University of Missouri Shock Tube Laboratory Team

2017-11-01

The Richtmyer-Meshkov instability (RMI) is a hydrodynamic instability that appears in several high energy density applications such as inertial confinement fusion (ICF). In ICF, as the thermonuclear fuel is being compressed it begins to mix due to fluid instabilities including the RMI. This mixing greatly decreases the energy output. The RMI occurs when two fluids of different densities are impulsively accelerated and the pressure and density gradients are misaligned. In magnetohydrodynamics (MHD), the RMI may be suppressed by introducing a magnetic field in an electrically conducting fluid, such as a plasma. This suppression has been studied as a possible mechanism for improving confinement in ICF targets. In this study,ideal MHD simulations are performed with a circular interface impulsively accelerated by a shock wave in the presence of a magnetic field. These simulations are executed with the research code FLAG, a multiphysics, arbitrary Lagrangian/Eulerian, hydrocode developed and utilized at Los Alamos National Laboratory. The simulation results will be assessed both quantitatively and qualitatively to examine the stabilization mechanism. These simulations will guide ongoing MHD experiments at the University of Missouri Shock Tube Facility.

Extending fields in a level set method by solving a biharmonic equation

NASA Astrophysics Data System (ADS)

Moroney, Timothy J.; Lusmore, Dylan R.; McCue, Scott W.; McElwain, D. L. Sean

2017-08-01

We present an approach for computing extensions of velocities or other fields in level set methods by solving a biharmonic equation. The approach differs from other commonly used approaches to velocity extension because it deals with the interface fully implicitly through the level set function. No explicit properties of the interface, such as its location or the velocity on the interface, are required in computing the extension. These features lead to a particularly simple implementation using either a sparse direct solver or a matrix-free conjugate gradient solver. Furthermore, we propose a fast Poisson preconditioner that can be used to accelerate the convergence of the latter. We demonstrate the biharmonic extension on a number of test problems that serve to illustrate its effectiveness at producing smooth and accurate extensions near interfaces. A further feature of the method is the natural way in which it deals with symmetry and periodicity, ensuring through its construction that the extension field also respects these symmetries.

Adsorption and Distribution of Edible Gliadin Nanoparticles at the Air/Water Interface.

PubMed

Peng, Dengfeng; Jin, Weiping; Li, Jing; Xiong, Wenfei; Pei, Yaqiong; Wang, Yuntao; Li, Yan; Li, Bin

2017-03-22

Edible gliadin nanoparticles (GNPs) were fabricated using the anti-solvent method. They possessed unique high foamability and foam stability. An increasing concentration of GNPs accelerated their initial adsorption speed from the bulk phase to the interface and raised the viscoelastic modulus of interfacial films. High foamability (174.2 ± 6.4%) was achieved at the very low concentration of GNPs (1 mg/mL), which was much better than that of ovalbumin and sodium caseinate. Three stages of adsorption kinetics at the air/water interface were characterized. First, they quickly diffused and adsorbed at the interface, resulting in a fast increase of the surface pressure. Then, nanoparticles started to fuse into a film, and finally, the smooth film became a firm and rigid layer to protect bubbles against coalescence and disproportionation. These results explained that GNPs had good foamability and high foam stability simultaneously. That provides GNPs as a potential candidate for new foaming agents applied in edible and biodegradable products.

The Importance of Reconnection at Sector Boundaries: Another Space Weather Hazard?

NASA Astrophysics Data System (ADS)

Qi, Y.; Lai, H.; Russell, C. T.

2017-12-01

Sector Boundaries are interfaces between nearly oppositely directed magnetic flux in the solar wind. When the leading solar wind stream is moving more slowly than the following stream a high-pressure ridge appears at the interface, that compresses the plasma sometimes leading to a forward and reverse shock pair that slows the fast stream and accelerate the slow stream. If reconnection at the interface between the streams occurs part of the magnetic flux will be annihilated but the plasma once associated with that magnetic flux remains near the interface causing a sometimes significant short-lived dynamic pressure increase. The declining phase of solar cycle 24 exhibits several examples of the phenomenon with densities reaching over 80 protons cm-3 at speed of about 400 km sec-1. We examine the solar wind context of the phenomenon and the consequences at the magnetosphere using space-based and ground-based observations and comment on their possible generation of geomagnetically-induced currents.

A computer program for the simulation of folds of different sizes under the influence of gravity

NASA Astrophysics Data System (ADS)

Vacas Peña, José M.; Martínez Catalán, José R.

2004-02-01

Folding&g is a computer program, based on the finite element method, developed to simulate the process of natural folding from small to large scales in two dimensions. Written in Pascal code and compiled with Borland Delphi 3.0, the program has a friendly interactive user interface and can be used for research as well as educational purposes. Four main menu options allow the user to import or to build and to save a model data file, select the type of graphic output, introduce and modify several physical parameters and enter the calculation routines. The program employs isoparametric, initially rectangular elements with eight nodes, which can sustain large deformations. The mathematical procedure is based on the elasticity equations, but has been modified to simulate a viscous rheology, either linear or of power-law type. The parameters to be introduced include either the linear viscosity, or, when the viscosity is non-linear, the material constant, activation energy, temperature and power of the differential stress. All the parameters can be set by rows, which simulate layers. A toggle permits gravity to be introduced into the calculations. In this case, the density of the different rows must be specified, and the sizes of the finite elements and of the whole model become meaningful. Viscosity values can also be assigned to blocks of several rows and columns, which permits the modelling of heterogeneities such as rectangular areas of high strength, which can be used to simulate shearing components interfering with the buckling process. The program is applied to several cases of folding, including a single competent bed and multilayers, and its results compared with analytical and experimental results. The influence of gravity is illustrated by the modelling of diapiric structures and of a large recumbent fold.

Optimization of H2 thermal annealing process for the fabrication of ultra-low loss sub-micron silicon-on-insulator rib waveguides

NASA Astrophysics Data System (ADS)

Bellegarde, Cyril; Pargon, Erwine; Sciancalepore, Corrado; Petit-Etienne, Camille; Lemonnier, Olivier; Ribaud, Karen; Hartmann, Jean-Michel; Lyan, Philippe

2018-02-01

The superior confinement of light provided by the high refractive index contrast in Si/SiO2 waveguides allows the use of sub-micron photonic waveguides. However, when downscaling waveguides to sub-micron dimensions, propagation losses become dominated by sidewall roughness scattering. In a previous study, we have shown that hydrogen annealing after waveguide patterning yielded smooth silicon sidewalls. Our optimized silicon patterning process flow allowed us to reduce the sidewall roughness down to 0.25 nm (1σ) while maintaining rectangular Strip waveguides. As a result, record low optical losses of less than 1 dB/cm were measured at telecom wavelengths for waveguides with dimensions larger than 350 nm. With Rib waveguides, losses are expected to be even lower. However, in this case the Si reflow during the H2 anneal leads to the formation of a foot at the bottom of the structure and to a rounding of its top. A compromise is thus to be found between low losses and conservation of the rectangular shape of the Rib waveguide. This work proposes to investigate the impact of temperature and duration of the H2 anneal on the Rib profile, sidewalls roughness and optical performances. The impact of a Si/SiO2 interface is also studied. The introduction of H2 thermal annealing allows to obtain very low losses of 0.5 dB/cm at 1310 nm wavelength for waveguide dimensions of 300-400 nm, but it comes along an increase of the pattern bottom width of 41%, with a final bottom width of 502 nm.

28. CROSS SECTION OF A RECTANGULAR COKE OVEN SHOWING THE ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

28. CROSS SECTION OF A RECTANGULAR COKE OVEN SHOWING THE INTERNAL STRUCTURE OF THE OVEN. - Tower Hill No. 2 Mine, Approximately 0.47 mile Southwest of intersection of Stone Church Road & Township Route 561, Hibbs, Fayette County, PA

Natural Vibration Analysis of Clamped Rectangular Orthotropic Plates

NASA Astrophysics Data System (ADS)

dalaei, m.; kerr, a. d.

The natural vibrations of clamped rectangular orthotropic plates are analyzed using the extended Kantorovich method. The developed iterative scheme converges very rapidly to the final result. The obtained natural frequencies are evaluated for a square plate made of Kevlar 49 Epoxy and the obtained results are compared with those published by Kanazawa and Kawai, and by Leissa. The agreement was found to be very close. As there are no exact analytical solutions for clamped rectangular plates, the generated closed form expression for the natural modes, and the corresponding natural frequencies, are very suitable for use in engineering analyses.

Numerical evaluation of the surface deformation of elastic solids subjected to a hertzian contact stress

NASA Technical Reports Server (NTRS)

Hamrock, B. J.; Dowson, D.

1974-01-01

The elastic deformation of two ellipsoidal solids in contact and subjected to Hertzian stress distribution was evaluated numerically as part of a general study of the elastic deformation of such solids in elastohydrodynamic contacts. In the analysis the contact zone was divided into equal rectangular areas, and it was assumed that a uniform pressure is applied over each rectangular area. The influence of the size of the rectangular area upon accuracy was also studied. The results indicate the distance from the center of the contact at which elastic deformation becomes insignificant.

Study of proton radiation effects among diamond and rectangular gate MOSFET layouts

NASA Astrophysics Data System (ADS)

Seixas, L. E., Jr.; Finco, S.; Silveira, M. A. G.; Medina, N. H.; Gimenez, S. P.

2017-01-01

This paper describes an experimental comparative study of proton ionizing radiation effects between the metal-oxide-semiconductor (MOS) Field Effect Transistors (MOSFETs) implemented with hexagonal gate shapes (diamond) and their respective counterparts designed with the classical rectangular ones, regarding the same gate areas, channel widths and geometrical ratios (W/L). The devices were manufactured by using the 350 nm bulk complementary MOS (CMOS) integrated circuits technology. The diamond MOSFET with α angles higher or equal to 90° tends to present a smaller vulnerability to the high doses ionizing radiation than those observed in the typical rectangular MOSFET counterparts.

A design method for entrance sections of transonic wind tunnels with rectangular cross sections

NASA Technical Reports Server (NTRS)

Lionel, L.; Mcdevitt, J. B.

1975-01-01

A mathematical technique developed to design entrance sections for transonic or high-speed subsonic wind tunnels with rectangular cross sections is discribed. The transition from a circular cross-section setting chamber to a rectangular test section is accomplished smoothly so as not to introduce secondary flows (vortices or boundary-layer separation) into a uniform test stream. The results of static-pressure measurements in the transition region and of static and total-pressure surveys in the test section of a pilot model for a new facility at the Ames Research Center are presented.

Space-Charge Waves and Instabilities in Intense Beams

NASA Astrophysics Data System (ADS)

Wang, J. G.

1997-11-01

Advancced accelerator applications, such as drivers for heavy ion inertial fusion, high-intensity synchrotrons for spallation neutron sources, high energy boosters, free electron lasers, high-power microwave generators, etc., require ever-increasing beam intensity. An important beam dynamics issue in such beams is the collective behavior of charged particles due to their space charge effects. This includes the phenomena of space-charge waves and instabilities excited on beams by external perturbations. It is very crucial to fully understand these phenomena in order to develop advanced accelerators for various applications. At the University of Maryland we have been conducting experimental programs to study space-charge waves and longitudinal instabilities by employing low-energy, high-current, space-charge dominated electron beams. Localized perturbations on the beams are generated from a gridded electron gun. In a conducting transport channel focused by short solenoids, these perturbations evolve into space-charge waves propagating on the beams. The wave speed is measured and many beam parameters are determined with this technique. The reflection of space-charge waves at the shoulder of an initially rectangular beam bunch is also observed. In a resistive-wall channel focused by a uniform long solenoid, the space-charge waves suffer longitudinal instability. The properties of the instabilities are studied in detail in the long wavelength range. In this talk we review our experimental results on the waves and instabilities and compare with theory.

Do the accelerating actions of tianeptine and l-arginine on cortical spreading depression interact? An electrophysiological analysis in young and adult rats.

PubMed

Maia, Luciana Maria Silva de Seixas; Amancio-Dos-Santos, Angela; Germano, Paula Catirina Pereira da Silva; Falcão, Anna Carolina Santos Marinho; Duda-de-Oliveira, Desirré; Guedes, Rubem Carlos Araújo

2017-05-22

In the rat, we previously demonstrated that serotonin-enhancing drugs impair cortical spreading depression (CSD) and that l-arginine (arginine) treatment enhances CSD. Here, we investigated the interaction between topical application of the serotonin uptake enhancer tianeptine and systemic arginine administration on CSD. From postnatal day 7-28, female Wistar rats (n=40) received by gavage 300mg/Kg/day arginine (n=20) or water (n=20). Half of the arginine- or water-treated rats underwent CSD recording at 30-40days of age (young), while the other half was recorded at 90-120days (adult). Following baseline recording (four episodes of CSD), we applied tianeptine solution (10mg/ml) to a rectangular portion of the intact dura mater for 10-min and then elicited CSD. This procedure was repeated three times. Compared to baseline values, CSD velocities and amplitudes following tianeptine application increased, and CSD duration decreased significantly (p<0.05) in both young and adult rats, regardless of treatment group. CSD acceleration caused by systemic treatment with arginine is in agreement with previous findings. Topical cortical application of tianeptine replicated the effect of systemic application, suggesting a cortically based mechanism for tianeptine's action. However, the absence of interaction between arginine and tianeptine treatments suggests that they probably act through separate mechanisms. Copyright © 2017 Elsevier B.V. All rights reserved.

Semiconductor Crystal Growth in Static and Rotating Magnetic fields

NASA Technical Reports Server (NTRS)

Volz, Martin

2004-01-01

Magnetic fields have been applied during the growth of bulk semiconductor crystals to control the convective flow behavior of the melt. A static magnetic field established Lorentz forces which tend to reduce the convective intensity in the melt. At sufficiently high magnetic field strengths, a boundary layer is established ahead of the solid-liquid interface where mass transport is dominated by diffusion. This can have a significant effect on segregation behavior and can eliminate striations in grown crystals resulting from convective instabilities. Experiments on dilute (Ge:Ga) and solid solution (Ge-Si) semiconductor systems show a transition from a completely mixed convective state to a diffusion-controlled state between 0 and 5 Tesla. In HgCdTe, radial segregation approached the diffusion limited regime and the curvature of the solid-liquid interface was reduced by a factor of 3 during growth in magnetic fields in excess of 0.5 Tesla. Convection can also be controlled during growth at reduced gravitational levels. However, the direction of the residual steady-state acceleration vector can compromise this effect if it cannot be controlled. A magnetic field in reduced gravity can suppress disturbances caused by residual transverse accelerations and by random non-steady accelerations. Indeed, a joint program between NASA and the NHMFL resulted in the construction of a prototype spaceflight magnet for crystal growth applications. An alternative to the suppression of convection by static magnetic fields and reduced gravity is the imposition of controlled steady flow generated by rotating magnetic fields (RMF)'s. The potential benefits of an RMF include homogenization of the melt temperature and concentration distribution, and control of the solid-liquid interface shape. Adjusting the strength and frequency of the applied magnetic field allows tailoring of the resultant flow field. A limitation of RMF's is that they introduce deleterious instabilities above a critical magnetic field value. Growth conditions in which static magnetic fields rotational magnetic fields, and reduced gravitational levels can have a beneficial role will be described.

PRISM, Processing and Review Interface for Strong Motion Data Software

NASA Astrophysics Data System (ADS)

Kalkan, E.; Jones, J. M.; Stephens, C. D.; Ng, P.

2016-12-01

A continually increasing number of high-quality digital strong-motion records from stations of the National Strong Motion Project (NSMP) of the U.S. Geological Survey (USGS), as well as data from regional seismic networks within the U.S., calls for automated processing of strong-motion records with human review limited to selected significant or flagged records. The NSMP has developed the Processing and Review Interface for Strong Motion data (PRISM) software to meet this need. PRISM automates the processing of strong-motion records by providing batch-processing capabilities. The PRISM software is platform-independent (coded in Java), open-source, and does not depend on any closed-source or proprietary software. The software consists of two major components: a record processing engine composed of modules for each processing step, and a graphical user interface (GUI) for manual review and processing. To facilitate the use by non-NSMP earthquake engineers and scientists, PRISM (both its processing engine and GUI components) is easy to install and run as a stand-alone system on common operating systems such as Linux, OS X and Windows. PRISM was designed to be flexible and extensible in order to accommodate implementation of new processing techniques. Input to PRISM currently is limited to data files in the Consortium of Organizations for Strong-Motion Observation Systems (COSMOS) V0 format, so that all retrieved acceleration time series need to be converted to this format. Output products include COSMOS V1, V2 and V3 files as: (i) raw acceleration time series in physical units with mean removed (V1), (ii) baseline-corrected and filtered acceleration, velocity, and displacement time series (V2), and (iii) response spectra, Fourier amplitude spectra and common earthquake-engineering intensity measures (V3). A thorough description of the record processing features supported by PRISM is presented with examples and validation results. All computing features have been thoroughly tested.

The Richtmyer-Meshkov Instability on a Circular Interface in Magnetohydrodynamics

NASA Astrophysics Data System (ADS)

Black, Wolfgang; Maxon, W. Curtis; Denissen, Nicholas; McFarland, Jacob

2017-11-01

Hydrodynamic instabilities (HI) are ubiquitous in high energy density (HED) applications such as astrophysics, thermonuclear weapons, and inertial fusion. In these systems, fluid mixing is encouraged by the HI which can reduce the energy yield and eventually drive the system to equilibrium. The Richtmyer-Meshkov (RM) instability is one such HI and is created when a perturbed interface between a density gradient is impulsively accelerated. The physics can be complicated one step further by the inclusion of Magnetohydrodynamics (MHD), where HED systems experience the effects of magnetic and electric fields. These systems provide unique challenges and as such can be used to validate hydrodynamic codes capable of predicting HI. The work presented here will outline efforts to study the RMI in MHD for a circular interface utilizing the hydrocode FLAG, developed at Los Alamos National Laboratory.

Toward more versatile and intuitive cortical brain-machine interfaces.

PubMed

Andersen, Richard A; Kellis, Spencer; Klaes, Christian; Aflalo, Tyson

2014-09-22

Brain-machine interfaces have great potential for the development of neuroprosthetic applications to assist patients suffering from brain injury or neurodegenerative disease. One type of brain-machine interface is a cortical motor prosthetic, which is used to assist paralyzed subjects. Motor prosthetics to date have typically used the motor cortex as a source of neural signals for controlling external devices. The review will focus on several new topics in the arena of cortical prosthetics. These include using: recordings from cortical areas outside motor cortex; local field potentials as a source of recorded signals; somatosensory feedback for more dexterous control of robotics; and new decoding methods that work in concert to form an ecology of decode algorithms. These new advances promise to greatly accelerate the applicability and ease of operation of motor prosthetics. Copyright © 2014 Elsevier Ltd. All rights reserved.

Caracterisation de l'effet du vieillissement en milieu aqueux sur les proprietes mecaniques de composites a matrice elastomere

NASA Astrophysics Data System (ADS)

Favre, Audrey

Rubber composites are widely used in several engineering fields, such as automotive, and more recently for inflatable dams and other innovative underwater applications. These rubber materials are composed by an elastomeric matrix while the reinforcing phase is a synthetic fabric. Since these components are expected to operate several years in water environment, their durability must be guaranteed. The use of rubber materials immersed in water is not new, in fact, these materials have been studied for almost one century. However, the knowledge on reinforced rubber composites immersed several years in water is still limited. In this work, investigations on reinforced rubbers were carried out in the framework of a research project in partnership with Alstom and Hydro-Quebec. The objective of this study was to identify rubber composites that could be used under water for long periods. Various rubber composites with ethylene-propylene-diene monomer (EPDM), silicone, EPDM/silicone and polychloroprene (Neoprene) matrices reinforced with E-glass fabric were studied. Thus, these materials were exposed to an accelerated ageing at 85 °C underwater for periods varying from 14 to 365 days. For comparison purposes, they were also immersed and aged one year at room temperature (21 °C). The impact of accelerated aging was estimated through three different characterization methods. Scanning electron microscopy (SEM) was first used to assess the quality of fiber-matrix interface. Then, water absorption tests were performed to quantify the rate of water absorption during immersion. Finally the evolution of the mechanical properties was followed by the determination of Young's modulus (E) and ultimate stress (sigmau) using a dedicated traction test. This analysis allowed to point out that the quality of the fiber-matrix interface was the main factor influencing the drop of the mechanical properties and their durability. Moreover, it was noticed that this interface could be improved by using appropriate coupling agent as confirmed by the silicone composite with treated fabric. It was also observed that fiber-matrix interface could be a place where high stresses were localized because of differential swelling leading to an important loss of mechanical properties. The results revealed very different behaviors from one composite to another. The accelerated aging of EPDM/silicone and Neoprene composites led to a rapid diminution of mechanical properties in only 14 days. Conversely, silicone composites showed a 20 % increase of mechanical properties after 75 days of immersion. EPDM composites exhibited an important variability from one sample to another. It can be concluded from this study that composites made from silicone matrix with treated E-glass result in a better durability underwater. Keywords: composite elastomer, accelerated ageing, immersion in the water

ADC interface for data server with data preselection for luminosity detector in AIDA-2020 project

NASA Astrophysics Data System (ADS)

Daniluk, W.; Dziedzic, B.; Korcyl, G.; Wojtoń, T.; Zawiejski, L.

2017-08-01

Main aim of the AIDA-2020 project is development of detectors for future accelerators. In FCAL Colaboration we are working on forward subdetectors for ILC and CLIC accelerators. My team is developing prototype module which receives data from ADC, provides the data preselection, and transmits them as packages to the data server for further their analysis. Common prototype is based on AC701 evaluation board which contains Artix-7 FPGA and is equipped with SMA connectors for gigabit transceivers and ethernet connector. In my talk I will describe architecture of the device and current state of module development.

Dynamic Modeling and Testing of MSRR-1 for Use in Microgravity Environments Analysis

NASA Technical Reports Server (NTRS)

Gattis, Christy; LaVerde, Bruce; Howell, Mike; Phelps, Lisa H. (Technical Monitor)

2001-01-01

Delicate microgravity science is unlikely to succeed on the International Space Station if vibratory and transient disturbers corrupt the environment. An analytical approach to compute the on-orbit acceleration environment at science experiment locations within a standard payload rack resulting from these disturbers is presented. This approach has been grounded by correlation and comparison to test verified transfer functions. The method combines the results of finite element and statistical energy analysis using tested damping and modal characteristics to provide a reasonable approximation of the total root-mean-square (RMS) acceleration spectra at the interface to microgravity science experiment hardware.

Implementation of the beamline controls at the Florence accelerator laboratory

NASA Astrophysics Data System (ADS)

Carraresi, L.; Mirto, F. A.

2008-05-01

The new Tandetron accelerator in Florence, with many different beamlines, has required a new organization of all the control signals of the used equipment (slow control). We present our solution, which allows us the control of all the employed instruments simultaneously from a number of different workplaces. All of our equipment has been designed to be Ethernet based and this is the key to accomplish two very important requirements: simultaneous remote control from many computers and electrical isolation to achieve a lower noise level. The control of the instruments requires only one Ethernet network and no particular interfaces or drivers on the computers.

Fingering dynamics on the adsorbed solute with influence of less viscous and strong sample solvent.

PubMed

Rana, Chinar; Mishra, Manoranjan

2014-12-07

Viscous fingering is a hydrodynamic instability that sets in when a low viscous fluid displaces a high viscous fluid and creates complex patterns in porous media flows. Fundamental facets of the displacement process, such as the solute concentration distribution, spreading length, and the solute mixing, depend strongly on the type of pattern created by the unstable interface of the underlying fluids. In the present study, the frontal interface of the sample shows viscous fingering and the strong solvent causes the retention of the solute to depend on the solvent concentration. This work presents a computational investigation to explore the effect of the underlying physico-chemical phenomena, (i.e., the combined effects of solvent strength, retention, and viscous fingering) on the dynamics of the adsorbed solute. A linear adsorption isotherm has been assumed between the mobile and stationary phases of the solute. We carried out the numerical simulations by considering a rectangular Hele-Shaw cell as an analog to 2D-porous media containing a three component system (displacing fluid, sample solvent, solute) to map out the evolution of the solute concentration. We observed that viscous fingering at the frontal interface of the strong sample solvent intensifies the band broadening of the solute zone. Also notable increase in the spreading dynamics of the solute has been observed for less viscous and strong sample solvent as compared to the high viscous sample slices or in the pure dispersive case. On the contrary, the solute gets intensively mixed at early times for more viscous sample in comparison to less viscous one. The results of the simulations are in qualitative agreement with the behavior observed in the liquid chromatography column experiments.

Numerical Modeling of Poroelastic-Fluid Systems Using High-Resolution Finite Volume Methods

NASA Astrophysics Data System (ADS)

Lemoine, Grady

Poroelasticity theory models the mechanics of porous, fluid-saturated, deformable solids. It was originally developed by Maurice Biot to model geophysical problems, such as seismic waves in oil reservoirs, but has also been applied to modeling living bone and other porous media. Poroelastic media often interact with fluids, such as in ocean bottom acoustics or propagation of waves from soft tissue into bone. This thesis describes the development and testing of high-resolution finite volume numerical methods, and simulation codes implementing these methods, for modeling systems of poroelastic media and fluids in two and three dimensions. These methods operate on both rectilinear grids and logically rectangular mapped grids. To allow the use of these methods, Biot's equations of poroelasticity are formulated as a first-order hyperbolic system with a source term; this source term is incorporated using operator splitting. Some modifications are required to the classical high-resolution finite volume method. Obtaining correct solutions at interfaces between poroelastic media and fluids requires a novel transverse propagation scheme and the removal of the classical second-order correction term at the interface, and in three dimensions a new wave limiting algorithm is also needed to correctly limit shear waves. The accuracy and convergence rates of the methods of this thesis are examined for a variety of analytical solutions, including simple plane waves, reflection and transmission of waves at an interface between different media, and scattering of acoustic waves by a poroelastic cylinder. Solutions are also computed for a variety of test problems from the computational poroelasticity literature, as well as some original test problems designed to mimic possible applications for the simulation code.

Quantum Chemical Calculations Using Accelerators: Migrating Matrix Operations to the NVIDIA Kepler GPU and the Intel Xeon Phi.

PubMed

Leang, Sarom S; Rendell, Alistair P; Gordon, Mark S

2014-03-11

Increasingly, modern computer systems comprise a multicore general-purpose processor augmented with a number of special purpose devices or accelerators connected via an external interface such as a PCI bus. The NVIDIA Kepler Graphical Processing Unit (GPU) and the Intel Phi are two examples of such accelerators. Accelerators offer peak performances that can be well above those of the host processor. How to exploit this heterogeneous environment for legacy application codes is not, however, straightforward. This paper considers how matrix operations in typical quantum chemical calculations can be migrated to the GPU and Phi systems. Double precision general matrix multiply operations are endemic in electronic structure calculations, especially methods that include electron correlation, such as density functional theory, second order perturbation theory, and coupled cluster theory. The use of approaches that automatically determine whether to use the host or an accelerator, based on problem size, is explored, with computations that are occurring on the accelerator and/or the host. For data-transfers over PCI-e, the GPU provides the best overall performance for data sizes up to 4096 MB with consistent upload and download rates between 5-5.6 GB/s and 5.4-6.3 GB/s, respectively. The GPU outperforms the Phi for both square and nonsquare matrix multiplications.

Detector shape in hexagonal sampling grids

NASA Astrophysics Data System (ADS)

Baronti, Stefano; Capanni, Annalisa; Romoli, Andrea; Santurri, Leonardo; Vitulli, Raffaele

2001-12-01

Recent improvements in CCD technology make hexagonal sampling attractive for practical applications and bring a new interest on this topic. In the following the performances of hexagonal sampling are analyzed under general assumptions and compared with the performances of conventional rectangular sampling. This analysis will take into account both the lattice form (squared, rectangular, hexagonal, and regular hexagonal), and the pixel shape. The analyzed hexagonal grid will not based a-priori on a regular hexagon tessellation, i.e., no constraints will be made on the ratio between the sampling frequencies in the two spatial directions. By assuming an elliptic support for the spectrum of the signal being sampled, sampling conditions will be expressed for a generic hexagonal sampling grid, and a comaprison with the well-known sampling conditions for a comparable rectangular lattice will be performed. Further, by considering for sake of clarity a spectrum with a circular support, the comparison will be performed under the assumption of same number of pixels for unity of surface, and the particular case of regular hexagonal sampling grid will also be considered. Regular hexagonal lattice with regular hexagonal sensitivity shape of the detector elements will result as the best trade-off between the proposed sampling requirement. Concerning the detector shape, the hexagonal is more advantageous than the rectangular. To show that a figure of merit is defined which takes into account that the MTF (modulation transfer function) of a hexagonal detector is not separable, conversely from that of a rectangular detector. As a final result, octagonal shape detectors are compared to those with rectangular and hexagonal shape in the two hypotheses of equal and ideal fill factor, respectively.

Electronic Structure of a Self-Assembled Monolayer with Two Surface Anchors: 6-Mercaptopurine on Au(111).

PubMed

Fernández, Cynthia C; Pensa, Evangelina; Carro, Pilar; Salvarezza, Roberto; Williams, Federico J

2018-05-22

The electronic structure of aromatic and aliphatic thiols on Au(111) has been extensively studied in relation to possible applications in molecular electronics. In this work, the effect on the electronic structure of an additional anchor to the S-Au bond using 6-mercaptopurine as a model system has been investigated. Results from X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure spectroscopy, and density functional theory (DFT) confirm that this molecule adsorbs on Au(111) with S-Au and iminic N-Au bonds. Combined ultraviolet photoelectron spectroscopy and DFT data reveal that formation of the 6MP self-assembled monolayer generates a molecular dipole perpendicular to the surface, with negative charges residing at the metal/monolayer interface and positive charges at the monolayer/vacuum interface, which lowers the substrate work function. Scanning tunneling microscopy shows two surface molecular domains: a well-ordered rectangular lattice where molecules are tilted on average 30° with respect to the substrate and aligned 6MP islands where molecules are standing upright. Finally, we found a new electronic state located at -1.7 eV with respect to the Fermi level that corresponds to a localized π molecular state, while the state corresponding to the N-Au bond is hybridized with Au d electrons and stabilized at much lower energies (-3 eV).

Improved locality of the phase-field lattice-Boltzmann model for immiscible fluids at high density ratios

NASA Astrophysics Data System (ADS)

Fakhari, Abbas; Mitchell, Travis; Leonardi, Christopher; Bolster, Diogo

2017-11-01

Based on phase-field theory, we introduce a robust lattice-Boltzmann equation for modeling immiscible multiphase flows at large density and viscosity contrasts. Our approach is built by modifying the method proposed by Zu and He [Phys. Rev. E 87, 043301 (2013), 10.1103/PhysRevE.87.043301] in such a way as to improve efficiency and numerical stability. In particular, we employ a different interface-tracking equation based on the so-called conservative phase-field model, a simplified equilibrium distribution that decouples pressure and velocity calculations, and a local scheme based on the hydrodynamic distribution functions for calculation of the stress tensor. In addition to two distribution functions for interface tracking and recovery of hydrodynamic properties, the only nonlocal variable in the proposed model is the phase field. Moreover, within our framework there is no need to use biased or mixed difference stencils for numerical stability and accuracy at high density ratios. This not only simplifies the implementation and efficiency of the model, but also leads to a model that is better suited to parallel implementation on distributed-memory machines. Several benchmark cases are considered to assess the efficacy of the proposed model, including the layered Poiseuille flow in a rectangular channel, Rayleigh-Taylor instability, and the rise of a Taylor bubble in a duct. The numerical results are in good agreement with available numerical and experimental data.

Insights from depth-averaged numerical simulation of flow at bridge abutments in compound channels.

DOT National Transportation Integrated Search

2011-07-01

Two-dimensional, depth-averaged flow models are used to study the distribution of flow around spill-through abutments situated on floodplains in compound channels and rectangular channels (flow on very wide floodplains may be treated as rectangular c...

75 FR 57456 - Light-Walled Rectangular Pipe and Tube from the People's Republic of China: Final Results of the...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-09-21

...'') U.S. affiliated importer FitMAX Inc. (``FitMAX'') on June 2, 2010 and June 16, 2010. FitMAX... carbon- quality light-walled steel pipe and tube, of rectangular (including square) cross section, having...

Whole article corrigendum: "Surface-plasmon-enhanced GaN-LED based on the multilayered rectangular nano-grating" [Optics Communications 322 (2014) 66-72

NASA Astrophysics Data System (ADS)

Zhu, Jun; Zhang, Haosu; Zhu, Zhendong; Li, Qunqing; Jin, Guofan

2017-02-01

This article proposes a surface-plasmon-enhanced GaN-LED based on the multilayered rectangular nano-grating. This structure contains a SiO2 film, an Ag film and a HfO2 film sequentially coated on the rectangularly-patterned p-GaN layer. The Ag film is used to enhance the internal quantum efficiency. The HfO2 cover-layer symmetrizes the distribution of refractive index besides the Ag film to improve the light extraction efficiency and surface-plasmon (SP) extraction efficiency. The inserted SiO2 layer is utilized to further improve the SP extraction efficiency. The properties of SP modes and Purcell effect in this structure are investigated. The photoluminescence experiments demonstrate that its peak intensity of top-emission is about 2.5 times greater than that from the reference structure covered by a single-layer Ag film on the rectangularly-patterned p-GaN layer.

A high-power microwave circular polarizer and its application on phase shifter.

PubMed

Shao, Hao; Hu, Yongmei; Chang, Chao; Guo, Letian

2016-04-01

A high-power waveguide dual circular polarizer was theoretically designed and proof-of-principle was experimentally tested. It consists of two incident rectangular waveguides with a perpendicular H-plane junction, one circular waveguide with a pair of trapezoidal grooves coupled in E-plane at the top, a spherical crown located at the bottom, and an iris at the perpendicular junction of two rectangular waveguides. When wave incidents at one of the two separated rectangular waveguides, it, respectively, generates a left-hand circular polarized wave or a right-hand circular polarized wave in the circular waveguide. By adding a dumbbell-like metal plug driven with a high speed servomotor, a movable short circuit is formed along the circular waveguide to adjust the output RF phase of the rectangular port, realizing a high-speed high-power phase shifter. The C-band high power microwave (HPM) experiments were carried out, and the power capacity of the HPM polarizer and phase shifter was demonstrated to reach gigawatt level.

Free vibration of rectangular plates with a small initial curvature

NASA Technical Reports Server (NTRS)

Adeniji-Fashola, A. A.; Oyediran, A. A.

1988-01-01

The method of matched asymptotic expansions is used to solve the transverse free vibration of a slightly curved, thin rectangular plate. Analytical results for natural frequencies and mode shapes are presented in the limit when the dimensionless bending rigidity, epsilon, is small compared with in-plane forces. Results for different boundary conditions are obtained when the initial deflection is: (1) a polynomial in both directions, and (2) the product of a polynomial and a trigonometric function, and arbitrary. For the arbitrary initial deflection case, the Fourier series technique is used to define the initial deflection. The results obtained show that the natural frequencies of vibration of slightly curved plates are coincident with those of perfectly flat, prestressed rectangular plates. However, the eigenmodes are very different from those of initially flat prestressed rectangular plates. The total deflection is found to be the sum of the initial deflection, the deflection resulting from the solution of the flat plate problem, and the deflection resulting from the static problem.

Evaluation of radiation exposure with Tru-Align intraoral rectangular collimation system using OSL dosimeters.

PubMed

Goren, Arthur D; Bonvento, Michael J; Fernandez, Thomas J; Abramovitch, Kenneth; Zhang, Wenjian; Roe, Nadine; Seltzer, Jared; Steinberg, Mitchell; Colosi, Dan C

2011-03-01

A pilot study to compare radiation exposure with the Tru-Align rectangular collimation system to round collimation exposures was undertaken. Radiation exposure at various points within the cross sections of the collimators and entrance, intraoral and exit dose measurements were measured using InLight OSL dosimeters. Overall dose reduction with the use of the rectangular collimation system was estimated by taking into account the ratios of collimator openings and the average radiation exposure at the measurement points. Use of the Tru-Align system resulted in an average radiation exposure within the perimeter of the projected outline of the rectangular collimator of 36.1 mR, compared to 148.5 mR with the round collimator. Our calculations indicate a dose reduction by a factor of approximately 3.2 in the case of the Tru-Align system compared to round collimation. The Tru-Align system was easy to use, but in some situations failed to allow Xray coverage of the entire surface of the image receptor, leading to cone cuts.

Steady-state propagation speed of rupture fronts along one-dimensional frictional interfaces.

PubMed

Amundsen, David Skålid; Trømborg, Jørgen Kjoshagen; Thøgersen, Kjetil; Katzav, Eytan; Malthe-Sørenssen, Anders; Scheibert, Julien

2015-09-01

The rupture of dry frictional interfaces occurs through the propagation of fronts breaking the contacts at the interface. Recent experiments have shown that the velocities of these rupture fronts range from quasistatic velocities proportional to the external loading rate to velocities larger than the shear wave speed. The way system parameters influence front speed is still poorly understood. Here we study steady-state rupture propagation in a one-dimensional (1D) spring-block model of an extended frictional interface for various friction laws. With the classical Amontons-Coulomb friction law, we derive a closed-form expression for the steady-state rupture velocity as a function of the interfacial shear stress just prior to rupture. We then consider an additional shear stiffness of the interface and show that the softer the interface, the slower the rupture fronts. We provide an approximate closed form expression for this effect. We finally show that adding a bulk viscosity on the relative motion of blocks accelerates steady-state rupture fronts and we give an approximate expression for this effect. We demonstrate that the 1D results are qualitatively valid in 2D. Our results provide insights into the qualitative role of various key parameters of a frictional interface on its rupture dynamics. They will be useful to better understand the many systems in which spring-block models have proved adequate, from friction to granular matter and earthquake dynamics.

g-LIMIT Status Briefing

NASA Technical Reports Server (NTRS)

Whorton, Mark; Perkins, Brad T.

2000-01-01

For many microgravity science experiments in the International Space Station, the ambient acceleration environment will be exceed desirable levels. To provide a more quiescent acceleration environment to the microgravity payloads, a vibration isolation system named g-LIMIT (GLovebox Integrated Microgravity Isolation Technology) is being designed. g-LIMIT is a sub-rack level isolation system that can be tailored to a variety of applications. Scheduled for launch on the UF-1 mission, the initial implementation of g-LIMIT will be a Characterization Test in the Microgravity Science Glovebox (MSG). g-LIMIT will be available to glovebox investigators immediately after characterization testing. Standard MSG structural and umbilical interfaces will be used so that the isolation mount is transparent to the user with no additional accommodation requirements. g-LIMIT consists of three integrated isolator modules, each of which is comprised of a dual axis actuator, two axes of acceleration sensing, two axes of position sensing, control electronics, and data transmission capabilities in a minimum-volume package. In addition, this system provides the unique capability for measuring absolute acceleration of the experiment independent of accelerometers as a by-product of the control system and will have the capability of generating pristine accelerations to enhance experiment operations.

Optimization of Monte Carlo dose calculations: The interface problem

NASA Astrophysics Data System (ADS)

Soudentas, Edward

1998-05-01

High energy photon beams are widely used for radiation treatment of deep-seated tumors. The human body contains many types of interfaces between dissimilar materials that affect dose distribution in radiation therapy. Experimentally, significant radiation dose perturbations has been observed at such interfaces. The EGS4 Monte Carlo code was used to calculate dose perturbations at boundaries between dissimilar materials (such as bone/water) for 60Co and 6 MeV linear accelerator beams using a UNIX workstation. A simple test of the reliability of a random number generator was also developed. A systematic study of the adjustable parameters in EGS4 was performed in order to minimize calculational artifacts at boundaries. Calculations of dose perturbations at boundaries between different materials showed that there is a 12% increase in dose at water/bone interface, and a 44% increase in dose at water/copper interface. with the increase mainly due to electrons produced in water and backscattered from the high atomic number material. The dependence of the dose increase on the atomic number was also investigated. The clinically important case of using two parallel opposed beams for radiation therapy was investigated where increased doses at boundaries has been observed. The Monte Carlo calculations can provide accurate dosimetry data under conditions of electronic non-equilibrium at tissue interfaces.

Versatile dual organic interface layer for performance enhancement of polymer solar cells

NASA Astrophysics Data System (ADS)

Li, Zhiqi; Liu, Chunyu; Zhang, Zhihui; Li, Jinfeng; Zhang, Liu; Zhang, Xinyuan; Shen, Liang; Guo, Wenbin; Ruan, Shengping

2016-11-01

The electron transport layer plays a crucial role on determining electron injection and extraction, resulting from the effect of balancing charge transport and reducing the interfacial energy barrier. Decreasing the inherent incompatibility and enhancing electrical contact via employing appropriate buffer layer at the surface of hydrophobic organic active layer and hydrophilic inorganic electrode are also essential for charge collection. Herein, we demonstrate that an efficient dual polyelectrolytes interfacial layer composed of polyethylenimine (PEI) and conducting poly(9,9-dihexylfluorenyl-2,7-diyl) (PDHFD) is incorporated to investigate the interface energetics and electron transport in polymer solar cells (PSCs). The composited PEI/PDHFD interface layer (PPIL) overcomed the low conductivity of bare PEI polymer, which decreased series resistance and facilitated electron extraction at the ITO/PPIL-active layer interface. The introduction of the interface energy state of the PPIL reduced the work function of ITO so that it can mate the top of the valence band of the photoactive materials and promoted the formation of ohmic contact at ITO electrode interface. As a result, the composited PPIL tuned energy alignment and accelerated the electron transfer, leading to significantly increased photocurrent and power conversion efficiency (PCE) of the devices based on various representative polymer:fullerene systems.

Spontaneous emission of Bloch oscillation radiation under the competing influences of microcavity enhancement and inhomogeneous interface degradation

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

Sokolov, V. N.; Iafrate, G. J.

2014-02-07

A theory for the spontaneous emission (SE) of terahertz radiation for a Bloch electron traversing a single energy miniband of a superlattice (SL) in a cavity, while undergoing elastic scattering is presented. The Bloch electron is accelerated under the influence of a superimposed external constant electric field and an internal inhomogeneous electric field, while radiating into a microcavity. The analysis of the SE accounts for both the spectral structure of nonharmonic miniband components and the Bloch oscillation degradation effects arising from elastic scattering due to SL interface roughness. The interface roughness effects are decomposed into contributions arising from independent planarmore » and cross-correlated neighboring planar interfaces; parametric numerical estimates show that the cross-correlated contribution to the SE relaxation rate is relatively small, representing less than roughly 10% of the total relaxation rate. It is shown that the degradation effects from SL interface roughness can be more than compensated for by the enhancements derived from microcavity-based tuning of the emission frequency to the cavity density of states peak. The theoretical approach developed herein has general applicability beyond its use for elastic scattering due to interface roughness. As well, the results obtained in this analysis can be useful in the development of SL-based Bloch-oscillator terahertz devices.« less

A Computer Code for Dynamic Stress Analysis of Media-Structure Problems with Nonlinearities (SAMSON). Volume III. User’s Manual.

DTIC Science & Technology

NONLINEAR SYSTEMS, LINEAR SYSTEMS, SUBROUTINES , SOIL MECHANICS, INTERFACES, DYNAMICS, LOADS(FORCES), FORCE(MECHANICS), DAMPING, ACCELERATION, ELASTIC...PROPERTIES, PLASTIC PROPERTIES, CRACKS , REINFORCING MATERIALS , COMPOSITE MATERIALS , FAILURE(MECHANICS), MECHANICAL PROPERTIES, INSTRUCTION MANUALS, DIGITAL COMPUTERS...STRESSES, *COMPUTER PROGRAMS), (*STRUCTURES, STRESSES), (*DATA PROCESSING, STRUCTURAL PROPERTIES), SOILS , STRAIN(MECHANICS), MATHEMATICAL MODELS

An Inexpensive Autosampler to Maximize Throughput for an Ion Source that Samples Surfaces in Open Air

EPA Science Inventory

An autosampler was built to pull cotton swab heads mounted into a 3-foot long, square Al rod in ambient air through the He ionizing beam of a Direct Analysis in Real Time (DART) ion source interfaced to an orthogonal acceleration, time-of-flight mass spectrometer. The cost of th...

Living more safely in the chaparral-urban interface

Treesearch

Klaus W. H. Radtke

1983-01-01

Urban encroachment into chaparral areas has accelerated the fire-flood-erosion cycle. Preventative maintenance measures can help reduce the damage from fire and flood. This report describes the chaparral environment; how to cope with problems in watershed management, how to landscape for fire and soil erosion control, how to plan for home safety from fire, how to treat...

Variation in flexural properties of photo-pultruded composite archwires: analyses of round and rectangular profiles.

PubMed

Fallis, D W; Kusy, R P

2000-11-01

Prototype continuous, unidirectional, fiber-reinforced composite archwires were manufactured into round and rectangular profiles utilizing a photo-pultrusion process. Both 0.022 inch (0.56 mm) diameter and 0.021 x 0.028 inch (0.53 x 0.71 mm) rectangular composites were formed utilizing commercially available S2-glass reinforcement within a polymeric matrix. Reinforcement was varied according to the number, denier and twists per inch (TPI) of four S2-glass yarns to volume levels of 32-74% for round and 41-61% for rectangular profiles. Cross-sectional geometry was evaluated via light microscopy to determine loading characteristics; whereas two flexural properties (the elastic moduli and flexural strengths) were determined by 3-point bending tests. Morphological evaluation of samples revealed that as the TPI increased from 1 to 8, the yarns were more separated from one another and distributed more peripherally within a profile. For round and rectangular profiles utilizing 1 TPI fibers, moduli increased with fiber content approaching theoretical values. For round profiles utilizing 1 TPI and 4 TPI fibers, flexural strengths increased until the loading geometry was optimized. In contrast, the flexural strengths of composites that were pultruded with 8 TPI fibers were not improved at any loading level. Doubling the denier of the yarn, without altering the loading, increased both the moduli and flexural strengths in rectangular samples; whereas, the increases observed in round samples were not statistically significant. At optimal loading the maximum mean moduli and strengths equaled 53.6 +/- 2.0 and 1.36 +/- 0.17 GPa for round wire and equaled 45.7 +/- 0.8 and 1.40 +/- 0.05 GPa for rectangular wires, respectively. These moduli were midway between that of martensitic NiTi (33.4 GPa) and beta-titanium (72.4 GPa), and produced about one-quarter the force of a stainless steel wire per unit of activation. Values of strengths placed this composite material in the range of published values for beta-titanium wires (1.3-1.5 GPa). Copyright 2000 Kluwer Academic Publishers

Parallel image registration with a thin client interface

NASA Astrophysics Data System (ADS)

Saiprasad, Ganesh; Lo, Yi-Jung; Plishker, William; Lei, Peng; Ahmad, Tabassum; Shekhar, Raj

2010-03-01

Despite its high significance, the clinical utilization of image registration remains limited because of its lengthy execution time and a lack of easy access. The focus of this work was twofold. First, we accelerated our course-to-fine, volume subdivision-based image registration algorithm by a novel parallel implementation that maintains the accuracy of our uniprocessor implementation. Second, we developed a thin-client computing model with a user-friendly interface to perform rigid and nonrigid image registration. Our novel parallel computing model uses the message passing interface model on a 32-core cluster. The results show that, compared with the uniprocessor implementation, the parallel implementation of our image registration algorithm is approximately 5 times faster for rigid image registration and approximately 9 times faster for nonrigid registration for the images used. To test the viability of such systems for clinical use, we developed a thin client in the form of a plug-in in OsiriX, a well-known open source PACS workstation and DICOM viewer, and used it for two applications. The first application registered the baseline and follow-up MR brain images, whose subtraction was used to track progression of multiple sclerosis. The second application registered pretreatment PET and intratreatment CT of radiofrequency ablation patients to demonstrate a new capability of multimodality imaging guidance. The registration acceleration coupled with the remote implementation using a thin client should ultimately increase accuracy, speed, and access of image registration-based interpretations in a number of diagnostic and interventional applications.

High Quality Facade Segmentation Based on Structured Random Forest, Region Proposal Network and Rectangular Fitting

NASA Astrophysics Data System (ADS)

Rahmani, K.; Mayer, H.

2018-05-01

In this paper we present a pipeline for high quality semantic segmentation of building facades using Structured Random Forest (SRF), Region Proposal Network (RPN) based on a Convolutional Neural Network (CNN) as well as rectangular fitting optimization. Our main contribution is that we employ features created by the RPN as channels in the SRF.We empirically show that this is very effective especially for doors and windows. Our pipeline is evaluated on two datasets where we outperform current state-of-the-art methods. Additionally, we quantify the contribution of the RPN and the rectangular fitting optimization on the accuracy of the result.

Numerical calculation of flow fields about rectangular wings of finite thickness in supersonic flow. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Vogel, J. M.

1973-01-01

The calculation of the outer inviscid flow about a rectangular wing moving at supersonic speeds is reported. The inviscid equations of motion governing the flow generated by the wing form a set of hyperbolic differential equations. The flow field about the rectangular wing is separated into three regions consisting of the forebody, the afterbody, and the wing wake. Solutions for the forebody are obtained using conical flow techniques while the afterbody and the wing wake regions are treated as initial value problems. The numerical solutions are compared in the two dimensional regions with known exact solutions.

27. VIEW LOOKING THROUGH A RECTANGULAR COKE OVEN. NOTE THE ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

27. VIEW LOOKING THROUGH A RECTANGULAR COKE OVEN. NOTE THE USE OF BOTH BRICK AND STONE IN THE CONSTRUCTION OF THE OVEN. - Tower Hill No. 2 Mine, Approximately 0.47 mile Southwest of intersection of Stone Church Road & Township Route 561, Hibbs, Fayette County, PA

Reflections on the Gall-Peters Projection.

ERIC Educational Resources Information Center

Robinson, Arthur H.

1987-01-01

Explains the cartographic qualities of rectangular world maps and compares the merits of various projections such as the Mercator and the recently-created Gall-Peters. States that the Gall-Peters projection does not provide a reasonable base for a general world map; that no rectangular projection does. (JDH)

75 FR 1751 - Light-Walled Rectangular Pipe and Tube from Turkey: Extension of Time Limits for Preliminary...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-01-13

... DEPARTMENT OF COMMERCE International Trade Administration [A-489-815] Light-Walled Rectangular Pipe and Tube from Turkey: Extension of Time Limits for Preliminary Results of Antidumping Duty Administrative Review AGENCY: Import Administration, International Trade Administration, Department of Commerce...

76 FR 4289 - Light-Walled Rectangular Pipe and Tube From Turkey: Extension of Time Limit for Preliminary...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-01-25

... DEPARTMENT OF COMMERCE International Trade Administration [A-489-815] Light-Walled Rectangular Pipe and Tube From Turkey: Extension of Time Limit for Preliminary Results of Antidumping Duty Administrative Review AGENCY: Import Administration, International Trade Administration, Department of Commerce...

The interface microstructure, mechanical properties and corrosion resistance of dissimilar joints during multipass laser welding for nuclear power plants

NASA Astrophysics Data System (ADS)

Li, Gang; Lu, Xiaofeng; Zhu, Xiaolei; Huang, Jian; Liu, Luwei; Wu, Yixiong

2018-05-01

This study presents the interface microstructure, mechanical properties and corrosion resistance of dissimilar joints between Inconel 52M overlays and 316L stainless steel during multipass laser welding for nuclear power plants. The results indicate that the microstructure at the interface beside 316L stainless steel consists of cellular with the width of 30-40 μm, which also exhibits numerous Cr and Mo-rich precipitates like flocculent structure and in chains along grain boundaries as a mixed chemical solution for etching. Many dendritic structure with local melting characteristics and Nb-rich precipitates are exhibited at the interface beside Inconel 52M overlays. Such Nb-rich precipitates at the interface beside Inconel 52M overlays deteriorate the tensile strength and toughness of dissimilar joints at room temperature. The tensile strength of 316L stainless steel at 350 °C significantly decreases with the result that dissimilar joints are fractured in 316L stainless steel. The correlation between corrosion behavior and microstructure of weld metals is also discussed. The difference in high corrosion potential between Nb-rich precipitates and the matrix could result in establishing effective galvanic couples, and thus accelerating the corrosion of weld metals.

Ice-sheet modelling accelerated by graphics cards

NASA Astrophysics Data System (ADS)

Brædstrup, Christian Fredborg; Damsgaard, Anders; Egholm, David Lundbek

2014-11-01

Studies of glaciers and ice sheets have increased the demand for high performance numerical ice flow models over the past decades. When exploring the highly non-linear dynamics of fast flowing glaciers and ice streams, or when coupling multiple flow processes for ice, water, and sediment, researchers are often forced to use super-computing clusters. As an alternative to conventional high-performance computing hardware, the Graphical Processing Unit (GPU) is capable of massively parallel computing while retaining a compact design and low cost. In this study, we present a strategy for accelerating a higher-order ice flow model using a GPU. By applying the newest GPU hardware, we achieve up to 180× speedup compared to a similar but serial CPU implementation. Our results suggest that GPU acceleration is a competitive option for ice-flow modelling when compared to CPU-optimised algorithms parallelised by the OpenMP or Message Passing Interface (MPI) protocols.

Accelerating Time Integration for the Shallow Water Equations on the Sphere Using GPUs

DOE PAGES

Archibald, R.; Evans, K. J.; Salinger, A.

2015-06-01

The push towards larger and larger computational platforms has made it possible for climate simulations to resolve climate dynamics across multiple spatial and temporal scales. This direction in climate simulation has created a strong need to develop scalable timestepping methods capable of accelerating throughput on high performance computing. This study details the recent advances in the implementation of implicit time stepping of the spectral element dynamical core within the United States Department of Energy (DOE) Accelerated Climate Model for Energy (ACME) on graphical processing units (GPU) based machines. We demonstrate how solvers in the Trilinos project are interfaced with ACMEmore » and GPU kernels to increase computational speed of the residual calculations in the implicit time stepping method for the atmosphere dynamics. We demonstrate the optimization gains and data structure reorganization that facilitates the performance improvements.« less

Limits of the potential flow approach to the single-mode Rayleigh-Taylor problem

NASA Astrophysics Data System (ADS)

Ramaprabhu, P.; Dimonte, Guy; Young, Yuan-Nan; Calder, A. C.; Fryxell, B.

2006-12-01

We report on the behavior of a single-wavelength Rayleigh-Taylor flow at late times. The calculations were performed in a long square duct (λ×λ×8λ) , using four different numerical simulations. In contradiction with potential flow theories that predict a constant terminal velocity, the single-wavelength Rayleigh-Taylor problem exhibits late-time acceleration. The onset of acceleration occurs as the bubble penetration depth exceeds the diameter of bubbles, and is observed for low and moderate density differences. Based on our simulations, we provide a phenomenological description of the observed acceleration, and ascribe this behavior to the formation of Kelvin-Helmholtz vortices on the bubble-spike interface that diminish the friction drag, while the associated induced flow propels the bubbles forward. For large density ratios, the formation of secondary instabilities is suppressed, and the bubbles remain terminal consistent with potential flow models.

A preliminary study of a cryogenic equivalence principle experiment on Shuttle

NASA Technical Reports Server (NTRS)

Everitt, C. W. F.; Worden, P. W., Jr.

1985-01-01

The Weak Equivalence Principle is the hypothesis that all test bodies fall with the same acceleration in the same gravitational field. The current limit on violations of the Weak Equivalence Principle, measured by the ratio of the difference in acceleration of two test masses to their average acceleration, is about 3 parts in one-hundred billion. It is anticipated that this can be improved in a shuttle experiment to a part in one quadrillion. Topics covered include: (1) studies of the shuttle environment, including interference with the experiment, interfacing to the experiment, and possible alternatives; (2) numerical simulations of the proposed experiment, including analytic solutions for special cases of the mass motion and preliminary estimates of sensitivity and time required; (3) error analysis of several noise sources such as thermal distortion, gas and radiation pressure effects, and mechanical distortion; and (4) development and performance tests of a laboratory version of the instrument.

Reaction Acceleration in Thin Films with Continuous Product Deposition for Organic Synthesis.

PubMed

Wei, Zhenwei; Wleklinski, Michael; Ferreira, Christina; Cooks, R Graham

2017-08-01

Thin film formats are used to study the Claisen-Schmidt base-catalyzed condensation of 6-hydroxy-1-indanone with substituted benzaldehydes and to compare the reaction acceleration relative to the bulk. Relative acceleration factors initially exceeded 10 3 and were on the order of 10 2 at steady state, although the confined volume reaction was not electrostatically driven. Substituent effects were muted compared to those in the corresponding bulk and microdroplet reactions and it is concluded that the rate-limiting step at steady state is reagent transport to the interface. Conditions were found that allowed product deposition from the thin film to occur continuously as the reaction mixture was added and as the solvent evaporated. Yields of 74 % and production rates of 98 mg h -1 were reached in a very simple experimental system that could be multiplexed to greater scales. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Optical implementation of (3, 3, 2) regular rectangular CC-Banyan optical network

NASA Astrophysics Data System (ADS)

Yang, Junbo; Su, Xianyu

2007-07-01

CC-Banyan network plays an important role in the optical interconnection network. Based on previous reports of (2, 2, 3) the CC-Banyan network, another rectangular-Banyan network, i.e. (3, 3, 2) rectangular CC-Banyan network, has been discussed. First, according to its construction principle, the topological graph and the routing rule of (3, 3, 2) rectangular CC-Banyan network have been proposed. Then, the optically experimental setup of (3, 3, 2) rectangular CC-Banyan network has been designed and achieved. Each stage of node switch consists of phase spatial light modulator (PSLM) and polarizing beam-splitter (PBS), and fiber has been used to perform connection between adjacent stages. PBS features that s-component (perpendicular to the incident plane) of the incident light beam is reflected, and p-component (parallel to the incident plane) passes through it. According to switching logic, under the control of external electrical signals, PSLM functions to control routing paths of the signal beams, i.e. the polarization of each optical signal is rotated or not rotated 90° by a programmable PSLM. Finally, the discussion and analysis show that the experimental setup designed here can realize many functions such as optical signal switch and permutation. It has advantages of large number of input/output-ports, compact in structure, and low energy loss. Hence, the experimental setup can be used in optical communication and optical information processing.

Method for exciting inductive-resistive loads with high and controllable direct current

DOEpatents

Hill, Jr., Homer M.

1976-01-01

Apparatus and method for transmitting dc power to a load circuit by applying a dc voltage from a standard waveform synthesizer to duration modulate a bipolar rectangular wave generator. As the amplitude of the dc voltage increases, the widths of the rectangular wave generator output pulses increase, and as the amplitude of the dc voltage decreases, the widths of the rectangular wave generator output pulses decrease. Thus, the waveform synthesizer selectively changes the durations of the rectangular wave generator bipolar output pulses so as to produce a rectangular wave ac carrier that is duration modulated in accordance with and in direct proportion to the voltage amplitude from the synthesizer. Thereupon, by transferring the carrier to the load circuit through an amplifier and a rectifier, the load current also corresponds directly to the voltage amplitude from the synthesizer. To this end, the rectified wave at less than 100% duty factor, amounts to a doubled frequency direct voltage pulse train for applying a direct current to the load, while the current ripple is minimized by a high L/R in the load circuit. In one embodiment, a power transmitting power amplifier means having a dc power supply is matched to the load circuit through a transformer for current magnification without sacrificing load current duration capability, while negative voltage and current feedback are provided in order to insure good output fidelity.

Multi-Sensor Distributive On-line Processing, Visualization, and Analysis Infrastructure for an Agricultural Information System at the NASA Goddard Earth Sciences DAAC

NASA Astrophysics Data System (ADS)

Teng, W.; Berrick, S.; Leptoukh, G.; Liu, Z.; Rui, H.; Pham, L.; Shen, S.; Zhu, T.

2004-12-01

The Goddard Space Flight Center Earth Sciences Data and Information Services Center (GES DISC) Distributed Active Archive Center (DAAC) is developing an Agricultural Information System (AIS), evolved from an existing TRMM Online Visualization and Analysis System (TOVAS), which will operationally provide precipitation and other satellite data products and services. AIS outputs will be integrated into existing operational decision support systems for global crop monitoring, such as that of the U.N. World Food Program. The ability to use the raw data stored in the GES DAAC archives is highly dependent on having a detailed understanding of the data's internal structure and physical implementation. To gain this understanding is a time-consuming process and not a productive investment of the user's time. This is an especially difficult challenge when users need to deal with multi-sensor data that usually are of different structures and resolutions. The AIS has taken a major step towards meeting this challenge by incorporating an underlying infrastructure, called the GES-DISC Interactive Online Visualization and Analysis Infrastructure or "Giovanni," that integrates various components to support web interfaces that allow users to perform interactive analysis on-line without downloading any data. Several instances of the Giovanni-based interface have been or are being created to serve users of TRMM precipitation, MODIS aerosol, and SeaWiFS ocean color data, as well as agricultural applications users. Giovanni-based interfaces are simple to use but powerful. The user selects geophysical parameters, area of interest, and time period; and the system generates an output on screen in a matter of seconds. The currently available output options are (1) area plot - averaged or accumulated over any available data period for any rectangular area; (2) time plot - time series averaged over any rectangular area; (3) Hovmoller plots - longitude-time and latitude-time plots; (4) ASCII output - for all plot types; and (5) image animation - for area plot. Planned output options for the near-future include correlation plots and GIS-compatible outputs. The AIS will enable the remote, interoperable access to distributed data, because the current Giovanni implementation incorporates the GrADS-DODS Server (GDS), a stable, secure data server that provides subsetting and analysis services across the Internet, for any GrADS-readable data set. The subsetting capability allows users to retrieve a specified spatial region from a large data set, eliminating the need to first download the entire data set. The analysis capability allows users to retrieve the results of an operation applied to one or more data sets on the server. The Giovanni-GDS technology allows the serving of data, through convenient on-line analysis tools, from any location where GDS and a few GrADS scripts are installed. The GES-DISC implementation of this technology is unique in the way it enables multi-sensor processing and analysis.

Recoil polarization measurements

NASA Astrophysics Data System (ADS)

Brinkmann, Kai-Thomas

2017-01-01

Polarization observables in photon-induced meson production off nucleons have long been recognized to hold the promise of a detailed understanding of the excited states in the excitation spectrum of the nucleon. Photon beam and proton target polarization are routinely used at the ELSA facility in the Crystal Barrel/TAPS experiment and have yielded a wealth of data on contributing partial waves and nucleon resonances. A detector study on how to complement these ongoing studies by recoil polarization measurements that offer an orthogonal approach with otherwise unmeasurable observables in the field of non-strange meson photoproduction has been performed. Building on experience with silicon detectors operated in the photon beamline environment, first possible layouts of Si detector telescopes for recoil protons were developed. Various geometries, e.g. Archimedean spiral design of annular sensors, sector shapes and rectangular sensors were studied and have been used during test measurements. A prototype for the recoil polarimeter was built and subjected to performance tests in protonproton scattering at the COSY-accelerator in Jülich.

Gust alleviation for a STOL transport by using elevator, spoilers, and flaps

NASA Technical Reports Server (NTRS)

Lallman, F. J.

1974-01-01

Control laws were developed to investigate methods of alleviating the response of a STOL transport to gusty air. The transport considered in the study had triple-slotted, externally blown jet flaps and a large T-tail. The control devices used were the elevator, spoilers, and flaps. A hybrid computing system was used to simulate linearized longitudinal dynamics of the aircraft and to implement a conjugate gradient optimal search algorithm. The aircraft was simulated in the low-speed approach condition only. Feedback control matrices were found which minimized the average of a quadratic functional involving passenger compartment accelerations, pitch angle and rate, flight path angle and speed variations. The optimization was performed for artificially designed gust inputs in the form of predetermined rectangular waveforms. Results were obtained for elevator, spoilers, and flaps acting singly and in combination. Additional results were obtained for unit sinusoidal gust inputs by using the gain matrices computed for the artificial test gusts. Various sensor configurations were also investigated.

RESONATOR PARTICLE SEPARATOR

DOEpatents

Blewett, J.P.; Kiesling, J.D.

1963-06-11

A wave-guide resonator structure is designed for use in separating particles of equal momentum but differing in mass, having energies exceeding one billion eiectron volts. The particles referred to are those of sub-atomic size and are generally produced as a result of the bombardment of a target by a beam such as protons produced in a high energy accelerator. In the resonator a travelling electric wave is produced which travels at the same rate of speed as the unwanted particle which is thus deflected continuously over the length of the resonator. The wanted particle is slightly out of phase with the travelling wave so that over the whole length of the resonator it has a net deflection of substantially zero. The travelling wave is established in a wave guide of rectangular cross section in which stubs are provided to store magnetic wave energy leaving the electric wave energy in the main structure to obtain the desired travelling wave and deflection. The stubs are of such shape and spacing to establish a critical mathemitical relationship. (AEC)

Direct Synthesis of Carbon Nanotube Field Emitters on Metal Substrate for Open-Type X-ray Source in Medical Imaging.

PubMed

Gupta, Amar Prasad; Park, Sangjun; Yeo, Seung Jun; Jung, Jaeik; Cho, Chonggil; Paik, Sang Hyun; Park, Hunkuk; Cho, Young Chul; Kim, Seung Hoon; Shin, Ji Hoon; Ahn, Jeung Sun; Ryu, Jehwang

2017-07-29

We report the design, fabrication and characterization of a carbon nanotube enabled open-type X-ray system for medical imaging. We directly grew the carbon nanotubes used as electron emitter for electron gun on a non-polished raw metallic rectangular-rounded substrate with an area of 0.1377 cm² through a plasma enhanced chemical vapor deposition system. The stable field emission properties with triode electrodes after electrical aging treatment showed an anode emission current of 0.63 mA at a gate field of 7.51 V/μm. The 4.5-inch cubic shape open type X-ray system was developed consisting of an X-ray aperture, a vacuum part, an anode high voltage part, and a field emission electron gun including three electrodes with focusing, gate and cathode electrodes. Using this system, we obtained high-resolution X-ray images accelerated at 42-70 kV voltage by digital switching control between emitter and ground electrode.

Direct Synthesis of Carbon Nanotube Field Emitters on Metal Substrate for Open-Type X-ray Source in Medical Imaging

PubMed Central

Gupta, Amar Prasad; Park, Sangjun; Yeo, Seung Jun; Jung, Jaeik; Cho, Chonggil; Paik, Sang Hyun; Park, Hunkuk; Cho, Young Chul; Kim, Seung Hoon; Shin, Ji Hoon; Ahn, Jeung Sun; Ryu, Jehwang

2017-01-01

We report the design, fabrication and characterization of a carbon nanotube enabled open-type X-ray system for medical imaging. We directly grew the carbon nanotubes used as electron emitter for electron gun on a non-polished raw metallic rectangular-rounded substrate with an area of 0.1377 cm2 through a plasma enhanced chemical vapor deposition system. The stable field emission properties with triode electrodes after electrical aging treatment showed an anode emission current of 0.63 mA at a gate field of 7.51 V/μm. The 4.5-inch cubic shape open type X-ray system was developed consisting of an X-ray aperture, a vacuum part, an anode high voltage part, and a field emission electron gun including three electrodes with focusing, gate and cathode electrodes. Using this system, we obtained high-resolution X-ray images accelerated at 42–70 kV voltage by digital switching control between emitter and ground electrode. PMID:28773237

Investigation on dynamical interaction between a heavy vehicle and road pavement

NASA Astrophysics Data System (ADS)

Yang, Shaopu; Li, Shaohua; Lu, Yongjie

2010-08-01

This paper presents a model for three-dimensional, heavy vehicle-pavement-foundation coupled system, which is modelled as a seven-DOF vehicle moving along a simply supported double-layer rectangular thin plate on a linear viscoelastic foundation. The vertical tyre force is described by a single point-contact model, while the pavement-foundation is modelled as a double-layer plate on a linear viscoelastic foundation. Using the Galerkin method and quick direct integral method, the dynamical behaviour of the vehicle-pavement-foundation coupled system is investigated numerically and compared with that of traditional vehicle system and pavement system. The effects of coupling action on vehicle body vertical acceleration, suspension deformations, tyre forces and pavement displacements are also obtained. The investigation shows that the coupling action could not be neglected even on a smooth road surface, such as highway. Thus, it is necessary to investigate the dynamics of vehicle and pavement simultaneously based on the vehicle-pavement-foundation coupled system.

Highly efficient catalytic systems based on Pd-coated microbeads

NASA Astrophysics Data System (ADS)

Lim, Jin Hyun; Cho, Ahyoung; Lee, Seung Hwan; Park, Bumkyo; Kang, Dong Woo; Koo, Chong Min; Yu, Taekyung; Park, Bum Jun

2018-01-01

The efficiency of two prototype catalysis systems using palladium (Pd)-coated microparticles was investigated with regard to the recovery and recyclability of the catalytic particles. One such system was the interface-adsorption method, in which polymer particles coated with Pd nanoparticles strongly and irreversibly attach to the oil-water interface. Due to the irreversible adsorption of the catalytic particles to the interface, particle loss was completely prevented while mixing the aqueous solution and while collecting the products. The other system was based on the magnetic field-associated particle recovery method. The use of polymeric microparticles containing Pd nanoparticles and magnetite nanoparticles accelerated the sedimentation of the particles in the aqueous phase by applying a strong magnetic field, consequently suppressing drainage of the particles from the reactor along the product stream. Upon multiple runs of the catalytic reactions, it was found that conversion does not change significantly, demonstrating the excellent recyclability and performance efficiency in the catalytic processes.

CAST: a new program package for the accurate characterization of large and flexible molecular systems.

PubMed

Grebner, Christoph; Becker, Johannes; Weber, Daniel; Bellinger, Daniel; Tafipolski, Maxim; Brückner, Charlotte; Engels, Bernd

2014-09-15

The presented program package, Conformational Analysis and Search Tool (CAST) allows the accurate treatment of large and flexible (macro) molecular systems. For the determination of thermally accessible minima CAST offers the newly developed TabuSearch algorithm, but algorithms such as Monte Carlo (MC), MC with minimization, and molecular dynamics are implemented as well. For the determination of reaction paths, CAST provides the PathOpt, the Nudge Elastic band, and the umbrella sampling approach. Access to free energies is possible through the free energy perturbation approach. Along with a number of standard force fields, a newly developed symmetry-adapted perturbation theory-based force field is included. Semiempirical computations are possible through DFTB+ and MOPAC interfaces. For calculations based on density functional theory, a Message Passing Interface (MPI) interface to the Graphics Processing Unit (GPU)-accelerated TeraChem program is available. The program is available on request. Copyright © 2014 Wiley Periodicals, Inc.

On the radiation impedance of a rectangular piston

NASA Technical Reports Server (NTRS)

Levine, H.

1982-01-01

Single integral representations for the resistive and reactive components of the radiation impedance appropriate to a rectangular piston are established, thereby enabling a systematic refinement of estimates at both short and long wave lengths. Comparisons with previous analyses are made explicit as well as extensions and corrections thereto.

46 CFR 72.05-20 - Stairways, ladders, and elevators.

Code of Federal Regulations, 2010 CFR

2010-10-01

... factor of safety of 4 based on the ultimate strength. (j) The stringers, treads, and all platforms and... means of an intermediate landing of rectangular or nearly rectangular shape based on the actual...) Except as further noted the provisions of this section apply to all vessels. (2) For small vessels...

46 CFR 72.05-20 - Stairways, ladders, and elevators.

Code of Federal Regulations, 2011 CFR

2011-10-01

... factor of safety of 4 based on the ultimate strength. (j) The stringers, treads, and all platforms and... means of an intermediate landing of rectangular or nearly rectangular shape based on the actual...) Except as further noted the provisions of this section apply to all vessels. (2) For small vessels...

Effect of wall roughness on liquid oscillations damping in rectangular tanks

NASA Technical Reports Server (NTRS)

Bugg, F. M.

1970-01-01

Tests were conducted in two rectangular glass tanks using silicon carbide grit bonded to walls to determine effect of wall roughness for damping liquid oscillations. Tests included effects of roughness height, roughness location, roughness at various values, amplitude decay, Reynolds number, and boundary layer thickness.

Evaluation of a rectangular rapid flashing beacon system at the Belmont Ridge Road and W&OD Trail mid-block crosswalk.

DOT National Transportation Integrated Search

2015-05-01

On April 8, 2013, the Virginia Department of Transportation (VDOT) installed a Rectangular Rapid Flashing Beacon : (RRFB) system at Belmont Ridge Road in Loudoun County that included two units at the Washington and Old Dominion : (W&OD) Trail crossin...

Students' Reasoning about Invariance of Volume as a Quantity

ERIC Educational Resources Information Center

Kara, Melike

2013-01-01

The aims of this study were to investigate how upper-elementary-grade students compare the volume of rectangular prisms of equal volume (specifically, students' noticing and reasoning for invariance of volume and coordination of the three linear dimensions of rectangular prisms) and how students' levels of sophistication in volume measurement…