Effect of medullary cavity in cancellous bone on two-wave phenomenon

NASA Astrophysics Data System (ADS)

Hachiken, Takuma; Nakanishi, Shoko; Matsukawa, Mami

2016-07-01

Osteoporotic patients have a larger medullary cavity in their cancellous bone than healthy people. In this study, the effect of the medullary cavity on the two-wave phenomenon was experimentally investigated using a cancellous bone model and a radius bone model. In the cancellous bone model, with the increase in hole (medullary cavity) diameter, the amplitudes of the fast waves became smaller, whereas the amplitudes of the slow waves became larger. In the radius bone model, the fast wave overlapped with the circumferential wave. The slow wave became larger with increasing hole diameter. The analysis of the slow wave thus seems to be useful for the in vivo diagnosis of the degree of osteoporosis.

Single-drop impingement onto a wavy liquid film and description of the asymmetrical cavity dynamics

NASA Astrophysics Data System (ADS)

van Hinsberg, Nils Paul; Charbonneau-Grandmaison, Marie

2015-07-01

The present paper is devoted to an experimental investigation of the cavity formed upon a single-drop impingement onto a traveling solitary surface wave on a deep pool of the same liquid. The dynamics of the cavity throughout its complete expansion and receding phase are analyzed using high-speed shadowgraphy and compared to the outcomes of drop impingements onto steady liquid surface films having equal thickness. The effects of the surface wave velocity, amplitude and phase, drop impingement velocity, and liquid viscosity on the cavity's diameter and depth evolution are accurately characterized at various time instants. The wave velocity induces a distinct and in time increasing inclination of the cavity in the wave propagation direction. In particular for strong waves an asymmetrical distribution of the radial expansion and retraction velocity along the cavity's circumference is observed. A linear dependency between the absolute Weber number and the typical length and time scales associated with the cavity's maximum depth and maximum diameter is reported.

Effects of discharge parameters on the micro-hollow cathode sustained glow discharge

NASA Astrophysics Data System (ADS)

Shoujie, HE; Peng, WANG; Jing, HA; Baoming, ZHANG; Zhao, ZHANG; Qing, LI

2018-05-01

The effects of parameters such as pressure, first anode radius, and the cavity diameter on the micro-hollow cathode sustained glow discharge are investigated by using a two-dimensional self-consistent fluid model in pure argon. The results indicate that the three parameters influence the discharge in the regions inside and outside of the cavity. Under a fixed voltage on each electrode, a larger volume of high density plasma can be produced in the region between the first and the second anodes by selecting the appropriate pressure, the higher first anode, and the appropriate cavity diameter. As the pressure increases, the electron density inside the hollow cathode, the high density plasma volume between the first anode and second anodes, and the radial electric field in the cathode cavity initially increase and subsequently decrease. As the cavity diameter increases, the high-density plasma volume between the first and second anodes initially increases and subsequently decreases; whereas the electron density inside the hollow cathode decreases. As the first anode radius increases, the electron density increases both inside and outside of the cavity. Moreover, the increase of the electron density is more obvious in the microcathode sustained region than in the micro cavity region. The results reveal that the discharge inside the cavity interacts with that outside the cavity. The strong hollow cathode effect and the high-density plasma inside the cavity favor the formation of a sustained discharge between the first anode and the second anodes. Results also show that the radial boundary conditions exert a considerably weaker influence on the discharge except for a little change in the region close to the radial boundary.

Tethers as Debris: Simulating Impacts of Tether Fragments on Shuttle Tiles

NASA Technical Reports Server (NTRS)

Evans, Steven W.

2004-01-01

The SPHC hydrodynamic code was used to simulate impacts of Kevlar and aluminum projectiles on a model of the LI-900 type insulating tiles used on Space Shuffle Orbiters The intent was to examine likely damage that such tiles might experience if impacted by orbital debris consisting of tether fragments. Projectile speeds ranged from 300 meters per second to 10 kilometers per second. Damage is characterized by penetration depth, tile surface-hole diameter, tile body-cavity diameter, coating fracture diameter, tether and cavity wall material phases, and deformation of the aluminum backwall.

Crescent shaped Fabry-Perot fiber cavity for ultra-sensitive strain measurement.

PubMed

Liu, Ye; Wang, D N; Chen, W P

2016-12-02

Optical Fabry-Perot interferometer sensors based on inner air-cavity is featured with compact size, good robustness and high strain sensitivity, especially when an ultra-thin air-cavity is adopted. The typical shape of Fabry-Perot inner air-cavity with reflection mode of operation is elliptic, with minor axis along with and major axis perpendicular to the fiber length. The first reflection surface is diverging whereas the second one is converging. To increase the visibility of the output interference pattern, the length of major axis should be large for a given cavity length. However, the largest value of the major axis is limited by the optical fiber diameter. If the major axis length reaches the fiber diameter, the robustness of the Fabry-Perot cavity device would be decreased. Here we demonstrate an ultra-thin crescent shaped Fabry-Perot cavity for strain sensing with ultra-high sensitivity and low temperature cross-sensitivity. The crescent-shape cavity consists of two converging reflection surfaces, which provide the advantages of enhanced strain sensitivity when compared with elliptic or D-shaped FP cavity. The device is fabricated by fusion splicing an etched multimode fiber with a single mode fiber, and hence is simple in structure and economic in cost.

Crescent shaped Fabry-Perot fiber cavity for ultra-sensitive strain measurement

NASA Astrophysics Data System (ADS)

Liu, Ye; Wang, D. N.; Chen, W. P.

2016-12-01

Optical Fabry-Perot interferometer sensors based on inner air-cavity is featured with compact size, good robustness and high strain sensitivity, especially when an ultra-thin air-cavity is adopted. The typical shape of Fabry-Perot inner air-cavity with reflection mode of operation is elliptic, with minor axis along with and major axis perpendicular to the fiber length. The first reflection surface is diverging whereas the second one is converging. To increase the visibility of the output interference pattern, the length of major axis should be large for a given cavity length. However, the largest value of the major axis is limited by the optical fiber diameter. If the major axis length reaches the fiber diameter, the robustness of the Fabry-Perot cavity device would be decreased. Here we demonstrate an ultra-thin crescent shaped Fabry-Perot cavity for strain sensing with ultra-high sensitivity and low temperature cross-sensitivity. The crescent-shape cavity consists of two converging reflection surfaces, which provide the advantages of enhanced strain sensitivity when compared with elliptic or D-shaped FP cavity. The device is fabricated by fusion splicing an etched multimode fiber with a single mode fiber, and hence is simple in structure and economic in cost.

Fabrication of Yolk-Shell Cu@C Nanocomposites as High-Performance Catalysts in Oxidative Carbonylation of Methanol to Dimethyl Carbonate

NASA Astrophysics Data System (ADS)

Wang, Juan; Hao, Panpan; Shi, Ruina; Yang, Leilei; Liu, Shusen; Zhao, Jinxian; Ren, Jun; Li, Zhong

2017-08-01

A facile way was developed to fabricate yolk-shell composites with tunable Cu cores encapsulated within hollow carbon spheres (Cu@C) with an average diameter about 210 nm and cavity size about 80 nm. During pyrolysis, the confined nanospace of hollow cavity ensures that the nucleation-and-growth process of Cu nanocrystals take place exclusively inside the cavities. The size of Cu cores can be easily tuned from 30 to 55 nm by varying the copper salt concentration. By deliberately creating shell porosity through KOH chemical activation, at an optimized KOH/HCS mass ratio of 1/4, the catalytic performance for the oxidative carbonylation of methanol to dimethyl carbonate (DMC) of the activated sample is enhanced remarkably with TOF up to 8.6 h-1 at methanol conversion of 17.1%. The activated yolk-shell catalyst shows promising catalytic properties involving the reusability with slight loss of catalytic activity and negligible leaching of activated components even after seven recycles, which is beneficial to the implementation of clean production for the eco-friendly chemical DMC thoroughly.

Distribution of cavity trees in midwestern old-growth and second-growth forests

Treesearch

Zhaofei Fan; Stephen R. Shifley; Martin A. Spetich; Frank R. Thompson; David R. Larsen

2003-01-01

We used classification and regression tree analysis to determine the primary variables associated with the occurrence of cavity trees and the hierarchical structure among those variables. We applied that information to develop logistic models predicting cavity tree probability as a function of diameter, species group, and decay class. Inventories of cavity abundance in...

Distribution of cavity trees in midwesternold-growth and second-growth forests

Treesearch

Zhaofei Fan; Stephen R. Shifley; Martin A. Spetich; Frank R., III Thompson; David R. Larsen

2003-01-01

We used classification and regression tree analysis to determine the primary variables associated with the occurrence of cavity trees and the hierarchical structure among those variables. We applied that information to develop logistic models predicting cavity tree probability as a function of diameter, species group, and decay class. Inventories of cavity abundance in...

Apparatus and method for plasma processing of SRF cavities

NASA Astrophysics Data System (ADS)

Upadhyay, J.; Im, Do; Peshl, J.; Bašović, M.; Popović, S.; Valente-Feliciano, A.-M.; Phillips, L.; Vušković, L.

2016-05-01

An apparatus and a method are described for plasma etching of the inner surface of superconducting radio frequency (SRF) cavities. Accelerator SRF cavities are formed into a variable-diameter cylindrical structure made of bulk niobium, for resonant generation of the particle accelerating field. The etch rate non-uniformity due to depletion of the radicals has been overcome by the simultaneous movement of the gas flow inlet and the inner electrode. An effective shape of the inner electrode to reduce the plasma asymmetry for the coaxial cylindrical rf plasma reactor is determined and implemented in the cavity processing method. The processing was accomplished by moving axially the inner electrode and the gas flow inlet in a step-wise way to establish segmented plasma columns. The test structure was a pillbox cavity made of steel of similar dimension to the standard SRF cavity. This was adopted to experimentally verify the plasma surface reaction on cylindrical structures with variable diameter using the segmented plasma generation approach. The pill box cavity is filled with niobium ring- and disk-type samples and the etch rate of these samples was measured.

Raccoon (Procyon lotor) diurnal den use within an intensively managed forest in central West Virginia

USGS Publications Warehouse

Owen, Sheldon F.; Berl, Jacob L.; Edwards, John W.; Ford, W. Mark; Wood, Petra Bohall

2015-01-01

Intensive forest management may influence the availability of suitable den sites for large den-seeking species, such as Procyon lotor (Raccoon). As part of a Raccoon ecology study on an industrial forest in the Allegheny Mountains of central West Virginia, we radio-tracked 32 Raccoons to 175 diurnal den sites to determine relative use of dens that included cavity trees, rock dens, log piles, slash piles, and exposed limbs. Patterns of den use significantly differed between sexes and among seasons. Overall, we recorded 58 cavity dens in 12 tree species with 7 maternal dens found in 5 tree species. Raccoons selected larger-diameter den trees than available cavity trees and non-cavity trees. Because the abundance of suitable tree cavities is known to influence Raccoon densities and recruitment at fine spatial scales and female Raccoons in this study used tree cavities as maternal den sites, the continued harvest of large-diameter trees (i.e., those capable of developing den cavities) without replacement may impact Raccoon recruitment within intensively managed forests throughout the central Appalachians.

Time resolved flow-field measurements of a turbulent mixing layer over a rectangular cavity

NASA Astrophysics Data System (ADS)

Bian, Shiyao; Driscoll, James F.; Elbing, Brian R.; Ceccio, Steven L.

2011-07-01

High Reynolds number, low Mach number, turbulent shear flow past a rectangular, shallow cavity has been experimentally investigated with the use of dual-camera cinematographic particle image velocimetry (CPIV). The CPIV had a 3 kHz sampling rate, which was sufficient to monitor the time evolution of large-scale vortices as they formed, evolved downstream and impinged on the downstream cavity wall. The time-averaged flow properties (velocity and vorticity fields, streamwise velocity profiles and momentum and vorticity thickness) were in agreement with previous cavity flow studies under similar operating conditions. The time-resolved results show that the separated shear layer quickly rolled-up and formed eddies immediately downstream of the separation point. The vortices convect downstream at approximately half the free-stream speed. Vorticity strength intermittency as the structures approach the downstream edge suggests an increase in the three-dimensionality of the flow. Time-resolved correlations reveal that the in-plane coherence of the vortices decays within 2-3 structure diameters, and quasi-periodic flow features are present with a vortex passage frequency of ~1 kHz. The power spectra of the vertical velocity fluctuations within the shear layer revealed a peak at a non-dimensional frequency corresponding to that predicted using linear, inviscid instability theory.

Superconductive wire

DOEpatents

Korzekwa, David A.; Bingert, John F.; Peterson, Dean E.; Sheinberg, Haskell

1995-01-01

A superconductive article is made by inserting a rigid mandrel into an internal cavity of a first metallic tube, said tube having an interior surface and an exterior surface, said interior surface defining the interior cavity, forming a layer of a superconductive material or superconductive precursor upon the exterior surface of said first metallic tube, machining the layer of superconductive material or superconductive precursor to a predetermined diameter to form an intermediate article configured for insertion into a second metallic tube having an interior diameter corresponding to the predetermined diameter, inserting the machined intermediate article into a second metallic tube having an internal diameter corresponding to the predetermined diameter of the intermediate article to form a composite intermediate article, reducing or ironing the composite intermediate article to a predetermined cross-sectional diameter, and sintering the reduced or ironed composite intermediate article at temperatures and for time sufficient for the superconductive material or superconductive precursor to exhibit superconductivity.

Superconductive wire

DOEpatents

Korzekwa, D.A.; Bingert, J.F.; Peterson, D.E.; Sheinberg, H.

1995-07-18

A superconductive article is made by inserting a rigid mandrel into an internal cavity of a first metallic tube, said tube having an interior surface and an exterior surface, said interior surface defining the interior cavity, forming a layer of a superconductive material or superconductive precursor upon the exterior surface of said first metallic tube, machining the layer of superconductive material or superconductive precursor to a predetermined diameter to form an intermediate article configured for insertion into a second metallic tube having an interior diameter corresponding to the predetermined diameter, inserting the machined intermediate article into a second metallic tube having an internal diameter corresponding to the predetermined diameter of the intermediate article to form a composite intermediate article, reducing or ironing the composite intermediate article to a predetermined cross-sectional diameter, and sintering the reduced or ironed composite intermediate article at temperatures and for time sufficient for the superconductive material or superconductive precursor to exhibit superconductivity. 2 figs.

Constructing Artifical Red-Cockaded Woodpecker Cavities

Treesearch

David H. Allen

1991-01-01

A complete guide is provided for excavating red-cockaded woodpecker (Picoides borealis) cavities. A hole 4 inches wide by 10 inches high by 6 inches deep is cut from a live pine(Pinusspp.) tree with a chainsaw, and a prefabricated cavity is inserted. Cavities can be excavated in pines of any age, but the diameter of the tree at the height of insertion must be greater...

Biosensing operations based on whispering-gallery-mode optical cavities in single 1.0-µm diameter hexagonal GaN microdisks grown by radio-frequency plasma-assisted molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Kouno, Tetsuya; Sakai, Masaru; Kishino, Katsumi; Hara, Kazuhiko

2016-05-01

Biosensing operations based on a whispering-gallery-mode optical cavity in a single hexagonal GaN microdisk of approximately 1.0 µm diameter were demonstrated here. The sharp resonant peak in the photoluminescence spectrum obtained from the microdisk in aqueous sucrose solution redshifts with a change in sucrose concentration. The results indicate that an extremely small microdisk could be used as an optical transducer for sensing sugar, namely, as a biosensor. Furthermore, we investigate the relationship between the diameter of the microdisk and the sensitivity of the biosensor.

Droplet impact dynamics for two liquids impinging on anisotropic superhydrophobic surfaces

NASA Astrophysics Data System (ADS)

Pearson, John T.; Maynes, Daniel; Webb, Brent W.

2012-09-01

Droplet impingement experiments were performed on grooved hydrophobic surfaces with cavity fractions of 0, 80, and 93 % using droplets of water and a 50 %/50 % water/glycerol mixture. The influence of liquid viscosity, cavity fraction, and spreading direction, relative to the surface grooves, is explored qualitatively and quantitatively. The maximum droplet spread diameter, velocity of the rebounding jet, and the time delay between droplet impact and jet emission were characterized for Weber numbers, We, based on droplet impact speed and diameter, up to 500. The unequal shear stresses and contact angles influence the maximum spread diameters in the two primary spread directions. At We > 100, the ratio of the spread diameter along the direction of the grooves to the spread diameter perpendicular to the grooves increases above unity with increasing We. The maximum droplet spread diameter is compared to recent predictive models, and the data reveal differing behavior for the two fluids considered. The results also reveal the existence of very high relative jet velocities in the range 5 ≤ We ≤ 15 for water droplets, while such jets were not observed for the more viscous mixture. Further, in the range 115 ≤ We ≤ 265, the water/glycerol jet formation dynamics are radically different from the water behavior. Most evident is the existence of two-pronged jets, which arise from the anisotropy of the surface and the unequal shear stresses and contact angles that prevail on the surfaces. It is these influences that give rise to differences in the maximum spread diameters in the two primary spread directions. Similar two-pronged jet emission was observed for water over the very narrow range of We from 91 to 96. The issuing jet velocities were also observed to increase with increasing cavity fraction for both fluids and over the entire range of We explored. Lastly, the elapsed time between droplet impact and jet emission decreased with increasing cavity fraction.

Synthesis of nickel entities: From highly stable zerovalent nanoclusters to nanowires. Growth control and catalytic behavior.

PubMed

Peinetti, Ana S; Mizrahi, Martín; Requejo, Félix G; Buceta, David; López-Quintela, M Arturo; González, Graciela A; Battaglini, Fernando

2018-04-15

Non-noble metal nanoclusters synthesis is receiving increased attention due to their unique catalytic properties and lower cost. Herein, the synthesis of ligand-free Ni nanoclusters with an average diameter of 0.7 nm corresponding to a structure of 13 atoms is presented; they exhibit a zero-valence state and a high stability toward oxidation and thermal treatment. The nanoclusters formation method consists in the electroreduction of nickel ions inside an ordered mesoporous alumina; also, by increasing the current density, other structures can be obtained reaching to nanowires of 10 nm diameter. A seed-mediated mechanism is proposed to explain the growth to nanowires inside these mesoporous cavities. The size dependence on the catalytic behavior of these entities is illustrated by studying the reduction of methylene blue where the nanoclusters show an outstanding performance. Copyright © 2018 Elsevier Inc. All rights reserved.

A New Differential Pressure Flow Meter for Measurement of Human Breath Flow: Simulation and Experimental Investigation

PubMed Central

Bridgeman, Devon; Tsow, Francis; Xian, Xiaojun; Forzani, Erica

2016-01-01

The development and performance characterization of a new differential pressure-based flow meter for human breath measurements is presented in this article. The device, called a “Confined Pitot Tube,” is comprised of a pipe with an elliptically shaped expansion cavity located in the pipe center, and an elliptical disk inside the expansion cavity. The elliptical disk, named Pitot Tube, is exchangeable, and has different diameters, which are smaller than the diameter of the elliptical cavity. The gap between the disk and the cavity allows the flow of human breath to pass through. The disk causes an obstruction in the flow inside the pipe, but the elliptical cavity provides an expansion for the flow to circulate around the disk, decreasing the overall flow resistance. We characterize the new sensor flow experimentally and theoretically, using Comsol Multiphysics® software with laminar and turbulent models. We also validate the sensor, using inhalation and exhalation tests and a reference method. PMID:27818521

High peak-power kilohertz laser system employing single-stage multi-pass amplification

DOEpatents

Shan, Bing; Wang, Chun; Chang, Zenghu

2006-05-23

The present invention describes a technique for achieving high peak power output in a laser employing single-stage, multi-pass amplification. High gain is achieved by employing a very small "seed" beam diameter in gain medium, and maintaining the small beam diameter for multiple high-gain pre-amplification passes through a pumped gain medium, then leading the beam out of the amplifier cavity, changing the beam diameter and sending it back to the amplifier cavity for additional, high-power amplification passes through the gain medium. In these power amplification passes, the beam diameter in gain medium is increased and carefully matched to the pump laser's beam diameter for high efficiency extraction of energy from the pumped gain medium. A method of "grooming" the beam by means of a far-field spatial filter in the process of changing the beam size within the single-stage amplifier is also described.

Passively Q-switched of EDFL employing multi-walled carbon nanotubes with diameter less than 8 nm as saturable absorber

NASA Astrophysics Data System (ADS)

Nur Fatin Zuikafly, Siti; Ahmad, Fauzan; Haniff Ibrahim, Mohd; Wadi Harun, Sulaiman

2017-11-01

The paper demonstrates passively Q-switched erbium-doped fiber laser implementing multiwalled carbon nanotubes (MWCNTs) based saturable absorber. The paper is the first to report the use of the MWCNTs with diameter less than 8 nm as typically, the diameter used is 10 to 20 nm. The MWCNTs is incorporated with water soluble host polymer, polyvinyl alcohol (PVA) to produce a MWCNTs polymer composite thin film which is then sandwiched between two fiber connectors. The fabricated SA is employed in the laser experimental setup in ring cavity. The Q-switching regime started at threshold pump power of 103 mW and increasable to 215 mW. The stable pulse train from 41.6 kHz to 76.92 kHz with maximum average output power and pulse energy of 0.17 mW and 3.39 nJ are produced. The shortest pulse width of 1.9 μs is obtained in the proposed experimental work, making it the lowest pulse width ever reported using MWCNTs-based saturable absorber.

Apparatus for Leak Testing Pressurized Hoses

NASA Technical Reports Server (NTRS)

Underwood, Steve D. (Inventor); Garrison, Steve G. (Inventor); Gant, Bobby D. (Inventor); Palmer, John R. (Inventor)

2015-01-01

A hose-attaching apparatus for leak-testing a pressurized hose may include a hose-attaching member. A bore may extend through the hose-attaching member. An internal annular cavity may extend coaxially around the bore. At least one of a detector probe hole and a detector probe may be connected to the internal annular cavity. At least a portion of the bore may have a diameter which is at least one of substantially equal to and less than a diameter of a hose to be leak-tested.

Snag characteristics and dynamics following natural and artificially induced mortality in a managed loblolly pine forest

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

Zarnoch, Stanley J.; Vukovich, Mark A.; Kilgo, John C.

A 14-year study of snag characteristics was established in 41- to 44-year old loblolly pine (Pinus taeda L.) stands in southeastern USA. During the initial 5.5 years, no stand manipulation or unusually high-mortality events occurred. Afterwards, three treatments were applied consisting of trees thinned and removed, trees felled and not removed, and artificial creation of snags produced by girdling and herbicide injection. The thinned treatments were designed to maintain the same live canopy density as the snag-created treatment, disregarding snags that remained standing.We monitored snag height, diameter, density, volume, and bark percentage; the number of cavities was monitored in naturalmore » snags only. During the first 5.5 years, recruitment and loss rates were stable, resulting in a stable snag population. Large snags (≥25 cm diameter) were common, but subcanopy small snags (10 to <25 cm diameter) dominated numerically. Large natural snags survived (90% quantile) significantly longer (6.0–9.4 years) than smaller snags (4.4–6.9 years). Large artificial snags persisted the longest (11.8 years). Cavities in natural snags developed within 3 years following tree death. The mean number of cavities per snag was five times greater in large versus small snags and large snags were more likely to have multiple cavities, emphasizing the importance of mature pine stands for cavity-dependent wildlife species.« less

Interpretation of Data from Uphole Refraction Surveys

DTIC Science & Technology

1980-06-01

Seismic refraction Seismic refraction method Seismic surveys Subsurface exploration ""-. 20, AI0SrRACT -(CmtuamU 00MvaO eL If naaaaamr and Identlfyby...by the presence of subsurface cavities and large cavities are identifiable, the sensitivity of the method is marginal for practical use in cavity...detection. Some cavities large enough to be of engineering signifi- cance (e.g., a tunnel of h-m diameter) may be practically undetectable by this method

Cylindrical acoustic levitator/concentrator

DOEpatents

Kaduchak, Gregory; Sinha, Dipen N.

2002-01-01

A low-power, inexpensive acoustic apparatus for levitation and/or concentration of aerosols and small liquid/solid samples having particulates up to several millimeters in diameter in air or other fluids is described. It is constructed from a commercially available, hollow cylindrical piezoelectric crystal which has been modified to tune the resonance frequency of the breathing mode resonance of the crystal to that of the interior cavity of the cylinder. When the resonance frequency of the interior cylindrical cavity is matched to the breathing mode resonance of the cylindrical piezoelectric transducer, the acoustic efficiency for establishing a standing wave pattern in the cavity is high. The cylinder does not require accurate alignment of a resonant cavity. Water droplets having diameters greater than 1 mm have been levitated against the force of gravity using; less than 1 W of input electrical power. Concentration of aerosol particles in air is also demonstrated.

HOT WATER DRILL FOR TEMPERATE ICE.

USGS Publications Warehouse

Taylor, Philip L.

1984-01-01

The development of a high-pressure hot-water drill is described, which has been used reliably in temperate ice to depths of 400 meters with an average drill rate of about 1. 5 meters per minute. One arrangement of the equipment weighs about 500 kilograms, and can be contained on two sleds, each about 3 meters long. Simplified performance equations are given, and experiments with nozzle design suggest a characteristic number describing the efficiency of each design, and a minimum bore-hole diameter very close to 6 centimeters for a hot water drill. Also discussed is field experience with cold weather, water supply, and contact with englacial cavities and the glacier bed.

Competition for red-cockaded woodpecker roost and nest cavities: effects of resin age and entrance diameter

Treesearch

D. Craig Rudolph; Richard N. Conner; Janet Turner

1990-01-01

Competition for roost and nest cavities was investigated in a Texas population of Red-cockaded Woodpeckers (Picoides borealis) in longleaf pine (Pinus palustris) habitat. Twenty-two percent of all examined cavities were occupied by Red-cockaded Woodpeckers, and 46% were occupied by other species. Red-cockaded Woodpeckers did not roost in the open or...

Influence of cervical preflaring on apical file size determination.

PubMed

Pecora, J D; Capelli, A; Guerisoli, D M Z; Spanó, J C E; Estrela, C

2005-07-01

To investigate the influence of cervical preflaring with different instruments (Gates-Glidden drills, Quantec Flare series instruments and LA Axxess burs) on the first file that binds at working length (WL) in maxillary central incisors. Forty human maxillary central incisors with complete root formation were used. After standard access cavities, a size 06 K-file was inserted into each canal until the apical foramen was reached. The WL was set 1 mm short of the apical foramen. Group 1 received the initial apical instrument without previous preflaring of the cervical and middle thirds of the root canal. Group 2 had the cervical and middle portion of the root canals enlarged with Gates-Glidden drills sizes 90, 110 and 130. Group 3 had the cervical and middle thirds of the root canals enlarged with nickel-titanium Quantec Flare series instruments. Titanium-nitrite treated, stainless steel LA Axxess burs were used for preflaring the cervical and middle portions of root canals from group 4. Each canal was sized using manual K-files, starting with size 08 files with passive movements until the WL was reached. File sizes were increased until a binding sensation was felt at the WL, and the instrument size was recorded for each tooth. The apical region was then observed under a stereoscopic magnifier, images were recorded digitally and the differences between root canal and maximum file diameters were evaluated for each sample. Significant differences were found between experimental groups regarding anatomical diameter at the WL and the first file to bind in the canal (P < 0.01, 95% confidence interval). The major discrepancy was found when no preflaring was performed (0.151 mm average). The LA Axxess burs produced the smallest differences between anatomical diameter and first file to bind (0.016 mm average). Gates-Glidden drills and Flare instruments were ranked in an intermediary position, with no statistically significant differences between them (0.093 mm average). The instrument binding technique for determining anatomical diameter at WL is not precise. Preflaring of the cervical and middle thirds of the root canal improved anatomical diameter determination; the instrument used for preflaring played a major role in determining the anatomical diameter at the WL. Canals preflared with LA Axxess burs created a more accurate relationship between file size and anatomical diameter.

Observation of enhanced spontaneous emission in dielectrically apertured microcavities

NASA Astrophysics Data System (ADS)

Graham, Luke Alan

The effects of enhanced spontaneous emission are important in determining the low threshold characteristics of oxide confined vertical cavity semiconductor lasers. This enhancement effect increases as Q/V, where Q = λ/Δλ for the cavity and V is the mode volume. In particular we investigate the effects of mode diameter on enhancement in microcavity structures with successively smaller dielectric apertures. These structures were fabricated by etching and back filling with SiO 2 and by lateral steam oxidation. For both cavities, InAlGaAs quantum dot emitters were used in the active region in order to avoid carrier diffusion and recombination at the side walls. Decay data was obtained at 10 K using time resolved photoluminescence of individual microcavities, and arrays. The detector used here is based on a silicon avalanche photodiode operated in ``Geiger'' mode. It provides a resolution of 350 ps and a quantum efficiency of ~1% at a wavelength of 1 μm. For the etched aperture structures we observed enhancement factors as high as 1.4 for the 1 μm diameter cavities with a maximum Q ~ 200. The enhancement is limited by the low Qs induced by etched side wall scattering. For 1 μm apertures fabricated by lateral steam oxidation, a Q of 450 is obtained with an enhancement factor of 2.3. In these devices we show that the enhancement is limited by distribution of quantum dots throughout the aperture region. Dots resonant with the cavity and located along the aperture edge decay more slowly than those in the center, leading to spatial hole burning effects in the decay data. Microcavities with aperture sizes ranging from 1-5 μm and Qs greater than 5000 are also demonstrated. We show 0th and 1 st order mode spacings as a function of aperture size and from this data calculate the transverse optical mode diameter as a function of aperture diameter. We find that the optical mode size becomes larger than the aperture size for diameters of ~2.5 μm and below and that this is correlated with a steep drop in Q for smaller apertures. We also find that the upper limit in cavity Q in these structures appears to come from losses induced by the MgF2/ZnSe e-beam deposited DBRs.

Simulation of Flow Through Breach in Leading Edge at Mach 24

NASA Technical Reports Server (NTRS)

Gnoffo, Peter A.; Alter, Stephen J.

2004-01-01

A baseline solution for CFD Point 1 (Mach 24) in the STS-107 accident investigation was modified to include effects of holes through the leading edge into a vented cavity. The simulations were generated relatively quickly and early in the investigation by making simplifications to the leading edge cavity geometry. These simplifications in the breach simulations enabled: 1) A very quick grid generation procedure; 2) High fidelity corroboration of jet physics with internal surface impingements ensuing from a breach through the leading edge, fully coupled to the external shock layer flow at flight conditions. These simulations provided early evidence that the flow through a 2 inch diameter (or larger) breach enters the cavity with significant retention of external flow directionality. A normal jet directed into the cavity was not an appropriate model for these conditions at CFD Point 1 (Mach 24). The breach diameters were of the same order or larger than the local, external boundary-layer thickness. High impingement heating and pressures on the downstream lip of the breach were computed. It is likely that hole shape would evolve as a slot cut in the direction of the external streamlines. In the case of the 6 inch diameter breach the boundary layer is fully ingested.

Water Entry by a Train of Droplets

NASA Astrophysics Data System (ADS)

Ohl, Claus-Dieter; Huang, Xin; Chan, Chon U.; Frommhold, Philipp Erhard; Lippert, Alexander

2014-11-01

The impact of single droplets on a deep pool is a well-studied phenomenon which reveals reach fluid mechanics. Lesser studied is the impact of a train of droplet and the accompanied formation of largely elongated cavities, in particular for well controlled droplets. The droplets with diameters of 20-40 μm and velocities of approx. 20 m/s are generated with a piezo-actuated nozzle at rates of 200-300 kHz. Individual droplets are selected by electric charging and deflection and the impact is visualized with stroboscopic photography and high-speed videos. We study in particular the formation and shape of the cavity as by varying the number of droplets from one to 64. The cavities reach centimetres in length with lateral diameters of the order of 100 of micrometres.

Inter-assemblage facilitation: the functional diversity of cavity-producing beetles drives the size diversity of cavity-nesting bees.

PubMed

Sydenham, Markus A K; Häusler, Lise D; Moe, Stein R; Eldegard, Katrine

2016-01-01

Inter-specific interactions are important drivers and maintainers of biodiversity. Compared to trophic and competitive interactions, the role of non-trophic facilitation among species has received less attention. Cavity-nesting bees nest in old beetle borings in dead wood, with restricted diameters corresponding to the body size of the bee species. The aim of this study was to test the hypothesis that the functional diversity of cavity-producing wood boring beetles - in terms of cavity diameters - drives the size diversity of cavity-nesting bees. The invertebrate communities were sampled in 30 sites, located in forested landscapes along an elevational gradient. We regressed the species richness and abundance of cavity nesting bees against the species richness and abundance of wood boring beetles, non-wood boring beetles and elevation. The proportion of cavity nesting bees in bee species assemblage was regressed against the species richness and abundance of wood boring beetles. We also tested the relationships between the size diversity of cavity nesting bees and wood boring beetles. The species richness and abundance of cavity nesting bees increased with the species richness and abundance of wood boring beetles. No such relationship was found for non-wood boring beetles. The abundance of wood boring beetles was also related to an increased proportion of cavity nesting bee individuals. Moreover, the size diversity of cavity-nesting bees increased with the functional diversity of wood boring beetles. Specifically, the mean and dispersion of bee body sizes increased with the functional dispersion of large wood boring beetles. The positive relationships between cavity producing bees and cavity nesting bees suggest that non-trophic facilitative interactions between species assemblages play important roles in organizing bee species assemblages. Considering a community-wide approach may therefore be required if we are to successfully understand and conserve wild bee species assemblages in forested landscapes.

[The acoustics of the open mastoid cavity (so-called "radical cavity") and its modification by surgical measures. II. Clinical studies].

PubMed

Hartwein, J

1992-09-01

The acoustic resonance of a severely altered outer ear channel (radical mastoid cavity) is investigated in a series of 18 patients who underwent revision surgery by means of in-situ measurements of the sound-pressure-level near the tympanic membrane. While the average volume of the open cavity differs from the normal ear channel for the factor 2.5, the size of the external meatus is--in average--only 20% larger. This leads to an average frequency in patients with open cavity of 1939 Hz, more than 1000 Hz less than in a series (n = 20) of normal ears (average resonance frequency: 2942 Hz). The altered acoustic behaviour of the open cavity leads to partial extensive discrepancies of the resonance-caused sound-pressure augmentation in the frequencies of 3 and 4 kHz, which are important for speech perception. The average difference is more than 10 dB (SPL). Proved surgical techniques of cavity obliteration and meatoplasty can lead to a nearly normalized acoustic behaviour of the outer ear in a statistic significant way. Due to these surgical procedures, an average postoperative resonance frequency of 2421 Hz could be reached in our patients. Especially, the resonance-caused sound-pressure augmentation in 3-4 kHz could nearly be equalized to such of a normal outer ear. Differences in the acoustic behaviour of the outer ear as can be found between patients with an open mastoid cavity and normal ears can almost be eliminated surgically.(ABSTRACT TRUNCATED AT 250 WORDS)

Experimental investigation into vortex structure and pressure drop across microcavities in 3D integrated electronics

NASA Astrophysics Data System (ADS)

Renfer, Adrian; Tiwari, Manish K.; Brunschwiler, Thomas; Michel, Bruno; Poulikakos, Dimos

2011-09-01

Hydrodynamics in microcavities with cylindrical micropin fin arrays simulating a single layer of a water-cooled electronic chip stack is investigated experimentally. Both inline and staggered pin arrangements are investigated using pressure drop and microparticle image velocimetry (μPIV) measurements. The pressure drop across the cavity shows a flow transition at pin diameter-based Reynolds numbers ( Re d ) ~200. Instantaneous μPIV, performed using a pH-controlled high seeding density of tracer microspheres, helps visualize vortex structure unreported till date in microscale geometries. The post-transition flow field shows vortex shedding and flow impingement onto the pins explaining the pressure drop increase. The flow fluctuations start at the chip outlet and shift upstream with increasing Re d . No fluctuations are observed for a cavity with pin height-to-diameter ratio h/ d = 1 up to Re d ~330; however, its pressure drop was higher than for a cavity with h/d = 2 due to pronounced influence of cavity walls.

[The sural medial perforator flap: Anatomical bases, surgical technique and indications in head and neck reconstruction].

PubMed

Struk, S; Schaff, J-B; Qassemyar, Q

2018-04-01

The medial sural artery perforator (MSAP) flap is defined as a thin cutaneo-adipose perforator flap harvested on the medial aspect of the leg. The aims of this study were to describe the anatomical basis as well as the surgical technique and discuss the indications in head and neck reconstructive surgery. We harvested 10 MSAP flap on 5 fresh cadavers. For each case, the number and the location of the perforators were recorded. For each flap, the length of pedicle, the diameter of source vessels and the thickness of the flap were studied. Finally, we performed a clinical application of a MSAP flap. A total of 23 perforators with a diameter superior than 1mm were dissected on 10 legs. The medial sural artery provided between 1 and 4 musculocutaneous perforators. Perforators were located in average at 10.3cm±2cm from the popliteal fossa and at 3.6cm±1cm from the median line of the calf. The mean pedicle length was 12.1cm±2.5cm. At its origin, the source artery diameter was 1.8mm±0.25mm and source veins diameters were 2.45mm±0.9mm in average. There was no complication in our clinical application. This study confirms the reliability of previous anatomical descriptions of the medial sural artery perforator flap. This flap was reported as thin and particularly adapted for oral cavity reconstruction and for facial or limb resurfacing. Sequelae might be reduced as compared to those of the radial forearm flap with comparable results. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Thermal modeling of a pressurized air cavity receiver for solar dish Stirling system

NASA Astrophysics Data System (ADS)

Zou, Chongzhe; Zhang, Yanping; Falcoz, Quentin; Neveu, Pierre; Li, Jianlan; Zhang, Cheng

2017-06-01

A solar cavity receiver model for the dish collector system is designed in response to growing demand of renewable energy. In the present research field, no investigations into the geometric parameters of a cavity receiver have been performed. The cylindrical receiver in this study is composed of an enclosed bottom at the back, an aperture at the front, a helical pipe inside the cavity and an insulation layer on the external surface of the cavity. The influence of several critical receiver parameters on the thermal efficiency is analyzed in this paper: cavity inner diameter and cavity length. The thermal model in this paper is solved considering the cavity dimensions as variables. Implementing the model into EES, each parameter influence is separately investigated, and a preliminary optimization method is proposed.

Pool boiling on surfaces with mini-fins and micro-cavities

NASA Astrophysics Data System (ADS)

Pastuszko, Robert; Piasecka, Magdalena

2012-11-01

The experimental studies presented here focused on pool boiling heat transfer on mini-fin arrays, mini-fins with perforated covering and surfaces with micro-cavities. The experiments were carried out for water and fluorinert FC-72 at atmospheric pressure. Mini-fins of 0.5 and 1 mm in height were uniformly spaced on the base surface. The copper foil with holes of 0.1 mm in diameter (pitch 0.2/0.4 mm), sintered with the fin tips, formed a system of connected perpendicular and horizontal tunnels. The micro-cavities were obtained through spark erosion. The maximal depth of the craters of these cavities was 15 - 30 μm and depended on the parameters of the branding-pen settings. At medium and small heat fluxes, structures with mini-fins showed the best boiling heat transfer performance both for water and FC-72. At medium and high heat fluxes (above 70 kW/m2 for water and 25 kW/m2 for FC-72), surfaces with mini-fins without porous covering and micro-cavities produced the highest heat transfer coefficients. The surfaces obtained with spark erosion require a proper selection of geometrical parameters for particular liquids - smaller diameters of cavities are suitable for liquids with lower surface tension (FC-72).

Reproducibility of WC-C High-Temperature Fixed Point

NASA Astrophysics Data System (ADS)

Grigoryeva, I. A.; Khlevnoy, B. B.; Solodilov, M. V.

2017-05-01

Reproducibility of the tungsten carbide-carbon peritectic (WC-C) fixed point (3021 K) was investigated by comparing six WC-C blackbody-type cells with each other. All the cells were built at VNIIOFI and had the same design with a cell outer diameter of 24 mm and a cavity opening diameter of 3 mm. Four cells were built using tungsten powder supplied by Alfa Aesar, while the other two cells used powder from Zhuzhou KETE (China). The nominal purity of both suppliers was 99.999 %. All the cells were compared in the same furnace. A reference cell in the second furnace was used for monitoring the stability of a radiation thermometer. Melting temperatures (given by the point of inflection) of all six cells agreed within ±45 mK. The reproducibility, as a standard deviation of the measured temperatures, can be estimated as 35 mK. The Zhuzhou KETE cells showed a slightly lower temperature than the Alfa Aesar cells: by 32 mK on average, which is comparable with repeatability of the measurements.

Overview of pulsed-power-driven high-energy-density plasma research at the University of Michigan

NASA Astrophysics Data System (ADS)

McBride, R. D.; Campbell, P. C.; Miller, S. M.; Woolstrum, J. M.; Yager-Elorriaga, D. A.; Steiner, A. M.; Jordan, N. M.; Lau, Y. Y.; Gilgenbach, R. M.; Safronova, A. S.; Kantsyrev, V. L.; Shlyaptseva, V. V.; Shrestha, I. K.; Butcher, C. J.; Laity, G. R.; Leckbee, J. J.; Wisher, M. L.; Slutz, S. A.; Cuneo, M. E.

2017-10-01

The Michigan Accelerator for Inductive Z-pinch Experiments (MAIZE) is a 3-m-diameter, single-cavity Linear Transformer Driver (LTD) at the University of Michigan (UM). MAIZE supplies a fast electrical pulse (0-1 MA in 100 ns for matched loads) to various experimental configurations, including wire-array z-pinches and cylindrical foil loads. This talk will report on projects aimed at upgrading the MAIZE facility (e.g., a new power feed and new diagnostics) as well as various physics campaigns on MAIZE (e.g., radiation source development, power flow, implosion instabilities, and other projects relevant to the MagLIF program at Sandia). In addition to MAIZE, UM is constructing a second, smaller LTD facility consisting of four 1.25-m-diameter cavities. These cavities were previously part of Sandia's 21-cavity Ursa Minor facility. The status of the four Ursa Minor cavities at UM will also be presented. This research was funded in part by the University of Michigan, a Faculty Development Grant from the Nuclear Regulatory Commission, the NNSA under DOE Grant DE-NA0003047 for UNR, and Sandia National Laboratories under DOE-NNSA contract DE-NA0003525.

TH-AB-BRA-11: Using 3D Dosimeters for the Investigation of the Electron Return Effect (ERE) in MR-Guided Radiation Therapy: A Feasibility Study

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

Choi, G; Lee, H; Alqathami, M

Purpose: To demonstrate the capability of 3D radiochromic PRESAGE and Fricke-type dosimeters to measure the influence of magnetic fields on dose distribution, including the electron return effect (ERE), for MR-guided radiation therapy applications. Methods: Short cylindrical 3D dosimeters with PRESAGE and Fricke-type formulations were created in-house prior to irradiations in a 1.5T/7MV MR-linac. Each dosimeter was prepared with a concentric cylindrical air cavity with diameters of 1.5 cm and 2.5 cm, and the diameters of the dosimeters were 7.2 cm and 8.8 cm for PRESAGE and Fricke-type respectively. The dosimeters were irradiated within the bore of the MR-linac with themore » flat face of the dosimeters perpendicular to the magnetic field. Dosimeters were irradiated to approximately 9 Gy and 29 Gy to the center of dosimeters with a 15×15 cm{sup 2} field. The PRESAGE dosimeter was scanned using an optical-CT 2 hours post-irradiation; the Fricke-type dosimeter was immediately imaged with the MR component of the MR-linac post-irradiation. Results: Axial slices of the dose distributions show a clear demonstration of the dose enhancement due to the ERE above the cavity and the region of reduced dose below the cavity. The regions of increased and reduced dose are rotated with respect to the radiation beam axis due to the average directional change of the electrons. Measurements from line profiles show the dose enhanced up to ∼0.5 cm around the cavity by up to a factor of 1.3 and 1.4 for PRESAGE and Fricke-type dosimeters respectively. Conclusion: PRESAGE and Fricke-type dosimeters are able to qualitatively measure the ERE with good agreement with previously published simulation and 2D dosimetry demonstrations of the ERE. Further investigation of these 3D dosimeters as promising candidates for quality assurance of MR-guided radiation therapy systems is encouraged to assess changes in response and measurement accuracy due to the magnetic field.« less

Heartwood, sapwood, and fungal decay associated with red-cockaded woodpecker cavity trees

Treesearch

Richard N. Conner; D. Craig Rudolph; Daniel Saenz; Richard R. Schaefer

1994-01-01

Provision of suitable sites for red-cockaded woodpecker (Picotdes borealis) cavity excavation is essential for successful management of the woodpecker. To evaluate internal characteristics of pines used by the woodpecker, we increment-cored longleaf pines (Pinus palustris) to determine heartwood diameter, sapwood thickness, and...

Accuracy improvement of interferometric Rayleigh scattering diagnostic

NASA Astrophysics Data System (ADS)

Yan, Bo; Chen, Li; Yin, Kewei; Chen, Shuang; Yang, Furong; Tu, Xiaobo

2017-10-01

Cavity structure is used to increase the Interferometric Rayleigh scattering signal intensity. By using ZEMAX method, we simulate a special cavity mode comprising two spherical reflectors with different size, including the focal length and the diameter. The simulations suggest that the parallel beam can reflect repeatedly in the resonant cavity and concentrate on the focus. Besides, the reflection times and the ray width can reach about 50 and 2.1 cm after some feasible solutions.

Fabrication of 1-D Photonic Crystal Cavity on a Nanofiber Using Femtosecond Laser-induced Ablation.

PubMed

Nayak, Kali Prasanna; Keloth, Jameesh; Hakuta, Kohzo

2017-02-25

We present a protocol for fabricating 1-D Photonic Crystal (PhC) cavities on subwavelength-diameter tapered optical fibers, optical nanofibers, using femtosecond laser-induced ablation. We show that thousands of periodic nano-craters are fabricated on an optical nanofiber by irradiating with just a single femtosecond laser pulse. For a typical sample, periodic nano-craters with a period of 350 nm and with diameter gradually varying from 50 - 250 nm over a length of 1 mm are fabricated on a nanofiber with diameter around 450 - 550 nm. A key aspect of such a nanofabrication is that the nanofiber itself acts as a cylindrical lens and focuses the femtosecond laser beam on its shadow surface. Moreover, the single-shot fabrication makes it immune to mechanical instabilities and other fabrication imperfections. Such periodic nano-craters on nanofiber, act as a 1-D PhC and enable strong and broadband reflection while maintaining the high transmission out of the stopband. We also present a method to control the profile of the nano-crater array to fabricate apodized and defect-induced PhC cavities on the nanofiber. The strong confinement of the field, both transverse and longitudinal, in the nanofiber-based PhC cavities and the efficient integration to the fiber networks, may open new possibilities for nanophotonic applications and quantum information science.

High-resolution and fast-response fiber-optic temperature sensor using silicon Fabry-Pérot cavity.

PubMed

Liu, Guigen; Han, Ming; Hou, Weilin

2015-03-23

We report a fiber-optic sensor based on a silicon Fabry-Pérot cavity, fabricated by attaching a silicon pillar on the tip of a single-mode fiber, for high-resolution and high-speed temperature measurement. The large thermo-optic coefficient and thermal expansion coefficient of the silicon material give rise to an experimental sensitivity of 84.6 pm/°C. The excellent transparency and large refractive index of silicon over the infrared wavelength range result in a visibility of 33 dB for the reflection spectrum. A novel average wavelength tracking method has been proposed and demonstrated for sensor demodulation with improved signal-to-noise ratio, which leads to a temperature resolution of 6 × 10⁻⁴ °C. Due to the high thermal diffusivity of silicon, a response time as short as 0.51 ms for a sensor with an 80-µm-diameter and 200-µm-long silicon pillar has been experimentally achieved, suggesting a maximum frequency of ~2 kHz can be reached, to address the needs for highly dynamic environmental variations such as those found in the ocean.

Assessment of the effect of deviated nasal septum on the structure of nasal cavity.

PubMed

Wang, Junguo; Dou, Xin; Liu, Dingding; Song, Panpan; Qian, Xiaoyun; Wang, Shoulin; Gao, Xia

2016-06-01

The present study was aimed to investigate the effects of DNS on the structure of nasal cavity. The paranasal sinus coronal view CT of 108 patients with DNS and 129 hospitalized patients without DNS was retrospectively analyzed. The transverse diameter of nasal cavity (a), transverse diameter of nasal cavity and paranasal sinus (b), angle between maxillary and palatal bone, interalveolar distance, and maxillary rotation distance were measured. The ratio of a/b in experimental group was 0.367 ± 0.006 which was significantly (P = 0.0023) less than that in control group (0.391 ± 0.005). For the angle between maxillary and palatal bone, there was no significant difference found between DNS and control group for both right and left sides. The interalveolar distance was 40.75 mm in experimental group, and 38.8 mm in control (P = 0.0002). For the maxillary rotation distance, findings were considered as significant (P < 0.0001) in experimental group (11.25 mm) compared with control (10.1 mm). The present study demonstrates that long-term DNS affects the development of nasal cavity and paranasal sinus, as well as increases the interalveolar distance and maxillary rotation distance. These influences may be caused by the alteration of airflow inside the nasal cavities.

Experimental investigation for cavity dimensions of highly porous small bodies

NASA Astrophysics Data System (ADS)

Okamoto, T.; Nakamura, A.; Hasegawa, S.

2014-07-01

Small bodies were probably very porous during the formation of the solar system. In order to understand the surface evolution of highly porous bodies, it is necessary to investigate the impact process for targets with such high porosity. In this study, impact experiments with sintered glass-bead targets of 87 and 94 % porosities were conducted. Growth of cavities with time and the final cavity dimensions were analyzed and compared with previous studies of porous targets. Impact experiments were conducted using a two-stage light-gas gun at ISAS, Japan. The projectiles of a few millimeters were composed of titanium, aluminum, nylon, and basalt. The impact velocities ranged from 1.8 to 7.2 km s^{-1}. In order to observe the inside of the targets, we used a flash X-ray system and a micro-X-ray tomography instrument. The track shape was found to be divided into two types, elongated 'carrot' shape and short 'bulb' shape [1]. The figures on the left and right present a transmission image of the bulb shape track and a sketch of a cross section of the cavity, respectively. The results of the final maximum diameter, D_max and the final entrance-hole diameter, D_ent show that both dimensions tend to increase with impact velocity and decrease with target porosity. We adopted the scaling law of crater diameter [2] for our analysis of D_max and D_ent. The following empirical relations are obtained for targets with porosity ≥ 87 %: {D_max}/{d_p}(ρ_t/ρ_p)^{0.4} =10^{-1.52±0.27} ({Y}/ρ_t{v_0^2})^{-0.49 ± 0.07}, {D_ent}/{d_p}(ρ_t/ρ_p)^{0.4} =10^{-2.12±0.39} ({Y}/ρ_t{v_0^2})^{-0.53 ± 0.11}, where d_p, ρ_t, ρ_p, Y, and v_0 are the projectile diameter, target density, projectile density, target compressive strength, and the impact velocity, respectively. The results of the depth from the entrance hole to the maximum diameter of the cavity, L_max, shows that L_max decreases with impact velocity and increases with target porosity. If we assume that a projectile decelerates by inertial drag [1], the characteristic length L_0, which is the depth from the surface where the kinetic energy of the projectile becomes 1/e of the initial energy, is described as follows: L_0={2ρ_p}/{3C_dρ_t}d_p, where C_d is the drag coefficient that increases with dynamic pressure normalized by tensile strength of the projectile [1]. We found that L_max/d_p increases with L_0/d_p. It indicates that L_max depends on the degree of projectile deformation or disruption through the drag coefficient and also depends on the projectile-target density ratio. We will also discuss the growth of the cavity volume, maximum diameter, and depth of the cavity with time using dimensionless parameters of crater scaling [3].

Wind turbine/generator set and method of making same

DOEpatents

Bevington, Christopher M.; Bywaters, Garrett L.; Coleman, Clint C.; Costin, Daniel P.; Danforth, William L.; Lynch, Jonathan A.; Rolland, Robert H.

2013-06-04

A wind turbine comprising an electrical generator that includes a rotor assembly. A wind rotor that includes a wind rotor hub is directly coupled to the rotor assembly via a simplified connection. The wind rotor and generator rotor assembly are rotatably mounted on a central spindle via a bearing assembly. The wind rotor hub includes an opening having a diameter larger than the outside diameter of the central spindle adjacent the bearing assembly so as to allow access to the bearing assembly from a cavity inside the wind rotor hub. The spindle is attached to a turret supported by a tower. Each of the spindle, turret and tower has an interior cavity that permits personnel to traverse therethrough to the cavity of the wind rotor hub. The wind turbine further includes a frictional braking system for slowing, stopping or keeping stopped the rotation of the wind rotor and rotor assembly.

Wind turbine/generator set having a stator cooling system located between stator frame and active coils

DOEpatents

Bevington, Christopher M.; Bywaters, Garrett L.; Coleman, Clint C.; Costin, Daniel P.; Danforth, William L.; Lynch, Jonathan A.; Rolland, Robert H.

2012-11-13

A wind turbine comprising an electrical generator that includes a rotor assembly. A wind rotor that includes a wind rotor hub is directly coupled to the rotor assembly via a simplified connection. The wind rotor and generator rotor assembly are rotatably mounted on a central spindle via a bearing assembly. The wind rotor hub includes an opening having a diameter larger than the outside diameter of the central spindle adjacent the bearing assembly so as to allow access to the bearing assembly from a cavity inside the wind rotor hub. The spindle is attached to a turret supported by a tower. Each of the spindle, turret and tower has an interior cavity that permits personnel to traverse therethrough to the cavity of the wind rotor hub. The wind turbine further includes a frictional braking system for slowing, stopping or keeping stopped the rotation of the wind rotor and rotor assembly.

Wind turbine having a direct-drive drivetrain

DOEpatents

Bevington, Christopher M.; Bywaters, Garrett L.; Coleman, Clint C.; Costin, Daniel P.; Danforth, William L.; Lynch, Jonathan A.; Rolland, Robert H.

2011-02-22

A wind turbine comprising an electrical generator that includes a rotor assembly. A wind rotor that includes a wind rotor hub is directly coupled to the rotor assembly via a simplified connection. The wind rotor and generator rotor assembly are rotatably mounted on a central spindle via a bearing assembly. The wind rotor hub includes an opening having a diameter larger than the outside diameter of the central spindle adjacent the bearing assembly so as to allow access to the bearing assembly from a cavity inside the wind rotor hub. The spindle is attached to a turret supported by a tower. Each of the spindle, turret and tower has an interior cavity that permits personnel to traverse therethrough to the cavity of the wind rotor hub. The wind turbine further includes a frictional braking system for slowing, stopping or keeping stopped the rotation of the wind rotor and rotor assembly.

Long Elastic Open Neck Acoustic Resonator for low frequency absorption

NASA Astrophysics Data System (ADS)

Simon, Frank

2018-05-01

Passive acoustic liners, used in aeronautic engine nacelles to reduce radiated fan noise, have a quarter-wavelength behavior, because of perforated sheets backed by honeycombs (with one or two degrees of freedom). However, their acoustic absorption ability is naturally limited to medium and high frequencies because of constraints in thickness. The low ratio "plate thickness/hole diameter" generates impedance levels dependent on the incident sound pressure level and the grazing mean flow (by a mechanism of nonlinear dissipation through vortex shedding), which penalises the optimal design of liners. The aim of this paper is to overcome this problem by a concept called LEONAR ("Long Elastic Open Neck Acoustic Resonator"), in which a perforated plate is coupled with tubes of variable lengths inserted in a limited volume of a back cavity. To do this, experimental and theoretical studies, using different types of liners (material nature, hole diameter, tube length, cavity thickness) are described in this paper. It is shown that the impedance can be precisely determined with an analytical approach based on parallel transfer matrices of tubes coupled to the cavity. Moreover, the introduction of tubes in a cavity of a conventional resonator generates a significant shift in the frequency range of absorption towards lower frequencies or allows a reduction of cavity thickness. The impedance is practically independent of sound pressure level because of a high ratio "tube length/tube hole diameter". Finally, a test led in an aeroacoustic bench suggests that a grazing flow at a bulk Mach number of 0.3 has little impact on the impedance value. These first results allow considering these resonators with linear behavior as an alternative to classical resonators, in particular, as needed for future Ultra High Bypass Ratio engines with shorter and thinner nacelles.

Short communication: A reproductive tract scoring system to manage fertility in lactating dairy cows.

PubMed

Young, C D; Schrick, F N; Pohler, K G; Saxton, A M; Di Croce, F A; Roper, D A; Wilkerson, J B; Edwards, J L

2017-07-01

We developed a reproductive tract size and position score (SPS) system as a reproductive management tool to identify lactating dairy cows with decreased fertility. This system, relying solely on transrectal palpation, considers the size (cervical and uterine) and position of the reproductive tract relative to the pelvis. Cows undergoing pre-breeding exams were identified as having reproductive tracts that were small (SPS1), medium (SPS2), or large (SPS3). Cows designated SPS1 had small and compact uterine horns that rested within the pelvic cavity; SPS2 cows had reproductive tracts that were intermediate in cervical and uterine horn diameter, with longer uterine horns resting partially outside the pelvic cavity; and SPS3 cows had reproductive tracts that were larger and rested mostly outside the pelvic cavity. Cows that were SPS1 had a higher rate of pregnancy per artificial insemination (43.3 ± 3.7%) than cows that were SPS2 (36.9 ± 3.6%) or SPS3 (27.7 ± 4.3%). The percentage of cows with an SPS2 score differed in pregnancies per artificial insemination compared with SPS3 cows. The average days in milk was similar for SPS1, SPS2, and SPS3 cows (104.3 ± 3.5, 98.4 ± 3.4, and 94.7 ± 7.7, respectively). Ultrasound measurements of the uterine horn and cervical diameter, and length measurements of the uterine horns, cervix, and vagina confirmed differences among the SPS groups derived by transrectal palpation. The ease with which transrectal palpation can be used to determine the size and position of the reproductive tract attests to the relevance and usefulness of this scoring system to identify less fertile lactating dairy cows. The ability to do so with ease provides an opportunity to make economically relevant management decisions and maximize reproductive efficiency in a given herd. Copyright © 2017 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Electrowetting Lens Employing Hemispherical Cavity Formed by Hydrofluoric Acid, Nitric Acid, and Acetic Acid Etching of Silicon

NASA Astrophysics Data System (ADS)

Lee, June Kyoo; Choi, Ju Chan; Jang, Won Ick; Kim, Hak-Rin; Kong, Seong Ho

2012-06-01

We demonstrate the design of an electrowetting lens employing a high-aspect-ratio hemispherical lens cavity and its micro-electro-mechanical-system (MEMS) fabrication process in this study. Our preliminary simulation results showed that the physical and electrical durability of the lens can be improved by the mitigation of stresses on the insulator at the hemispherical cavity. High-aspect-ratio hemispherical cavities with various diameters and very smooth sidewall surfaces were uniformly fabricated on a silicon wafer by a sophisticated isotropic wet etching technique. Moreover, we experimentally investigated the optical properties of the MEMS-based electrowetting lens with the proposed cavity. Two immiscible liquids in the proposed lens cavity were electrostatically controlled with negligible optical distortion and low focal-length hysteresis due to the fully axis-symmetrical geometry and smooth sidewall of the cavity.

Carbon dioxide insufflation deflects airborne particles from an open surgical wound model.

PubMed

Kokhanenko, P; Papotti, G; Cater, J E; Lynch, A C; van der Linden, J A; Spence, C J T

2017-01-01

Surgical site infections remain a significant burden on healthcare systems and may benefit from new countermeasures. To assess the merits of open surgical wound CO 2 insufflation via a gas diffuser to reduce airborne contamination, and to determine the distribution of CO 2 in and over a wound. An experimental approach with engineers and clinical researchers was employed to measure the gas flow pattern and motion of airborne particles in a model of an open surgical wound in a simulated theatre setting. Laser-illuminated flow visualizations were performed and the degree of protection was quantified by collecting and characterizing particles deposited in and outside the wound cavity. The average number of particles entering the wound with a diameter of <5μm was reduced 1000-fold with 10L/min CO 2 insufflation. Larger and heavier particles had a greater penetration potential and were reduced by a factor of 20. The degree of protection was found to be unaffected by exaggerated movements of hands in and out of the wound cavity. The steady-state CO 2 concentration within the majority of the wound cavity was >95% and diminished rapidly above the wound to an atmospheric level (∼0%) at a height of 25mm. Airborne particles were deflected from entering the wound by the CO 2 in the cavity akin to a protective barrier. Insufflation of CO 2 may be an effective means of reducing intraoperative infection rates in open surgeries. Copyright © 2016 The Author(s). Published by Elsevier Ltd.. All rights reserved.

Cavity cooling a single charged levitated nanosphere.

PubMed

Millen, J; Fonseca, P Z G; Mavrogordatos, T; Monteiro, T S; Barker, P F

2015-03-27

Optomechanical cavity cooling of levitated objects offers the possibility for laboratory investigation of the macroscopic quantum behavior of systems that are largely decoupled from their environment. However, experimental progress has been hindered by particle loss mechanisms, which have prevented levitation and cavity cooling in a vacuum. We overcome this problem with a new type of hybrid electro-optical trap formed from a Paul trap within a single-mode optical cavity. We demonstrate a factor of 100 cavity cooling of 400 nm diameter silica spheres trapped in vacuum. This paves the way for ground-state cooling in a smaller, higher finesse cavity, as we show that a novel feature of the hybrid trap is that the optomechanical cooling becomes actively driven by the Paul trap, even for singly charged nanospheres.

Cavity Cooling a Single Charged Levitated Nanosphere

NASA Astrophysics Data System (ADS)

Millen, J.; Fonseca, P. Z. G.; Mavrogordatos, T.; Monteiro, T. S.; Barker, P. F.

2015-03-01

Optomechanical cavity cooling of levitated objects offers the possibility for laboratory investigation of the macroscopic quantum behavior of systems that are largely decoupled from their environment. However, experimental progress has been hindered by particle loss mechanisms, which have prevented levitation and cavity cooling in a vacuum. We overcome this problem with a new type of hybrid electro-optical trap formed from a Paul trap within a single-mode optical cavity. We demonstrate a factor of 100 cavity cooling of 400 nm diameter silica spheres trapped in vacuum. This paves the way for ground-state cooling in a smaller, higher finesse cavity, as we show that a novel feature of the hybrid trap is that the optomechanical cooling becomes actively driven by the Paul trap, even for singly charged nanospheres.

Wide angle near-field optical probes by reverse tube etching.

PubMed

Patanè, S; Cefalì, E; Arena, A; Gucciardi, P G; Allegrini, M

2006-04-01

We present a simple modification of the tube etching process for the fabrication of fiber probes for near-field optical microscopy. It increases the taper angle of the probe by a factor of two. The novelty is that the fiber is immersed in hydrofluoric acid and chemically etched in an upside-down geometry. The tip formation occurs inside the micrometer tube cavity formed by the polymeric jacket. By applying this approach, called reverse tube etching, to multimode fibers with 200/250 microm core/cladding diameter, we have fabricated tapered regions featuring high surface smoothness and average cone angles of approximately 30 degrees . A simple model based on the crucial role of the gravity in removing the etching products, explains the tip formation process.

On the siting of gases shock-emplaced from internal cavities in basalt

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

Wiens, R.C.

1988-12-01

Noble gases were extracted by stepped combustion and crushing from basalts which contained gas-filled cavities of controlled sizes prior to shock at 40 GPa. Analysis of fractions enriched and depleted in shock glass from a single sample gave a factor of 2 higher gas abundances in the glass-rich separate. Release patterns were nearly identical, suggesting similar siting (in glass) in both fractions. Crushing of a sample released {approximately}45% of implanted noble gases, but only {approximately}17% of N{sub 2}, indicating that most or all of the noble gas was trapped in vesicles. Analysis by SEM/EDS confirmed the presence of vesicles inmore » glassy areas, with an average diameter of {approximately}10 {mu}m. Samples with relatively large pre-shock cavities were found to consist of up to 70-80% glass locally and generally exhibit greater local shock effects than solid and densely-packed particulate targets at the same shock pressure, though the latter give higher glass emplacement efficiencies. The petrographic results indicate that in situ production of glassy pockets grossly similar to those in the shergottite EETA 79001 is possible from shock reverberations in the vicinity of a vug. However, the siting of the gases points to a more complex scenario, in which SPB gas and melt material were probably injected into EETA 79001.« less

LINEAR ACCELERATOR

DOEpatents

Christofilos, N.C.; Polk, I.J.

1959-02-17

Improvements in linear particle accelerators are described. A drift tube system for a linear ion accelerator reduces gap capacity between adjacent drift tube ends. This is accomplished by reducing the ratio of the diameter of the drift tube to the diameter of the resonant cavity. Concentration of magnetic field intensity at the longitudinal midpoint of the external sunface of each drift tube is reduced by increasing the external drift tube diameter at the longitudinal center region.

Effects of urban sprawl on snags and the abundance and productivity of cavity-nesting birds

Treesearch

Christina M. Blewett; John M. Marzluff

2005-01-01

We investigated the occurrence of, and relationships among, snags and cavity-nesting birds in the rapidly urbanizing region around Seattle, Washington in 2001 and 2002. We measured the density of snags in 49 sites (1-km2 "suburban landscapes" that included built and forested portions), and determined the diameter, height, decay status,...

Pollen-imprinted polyurethanes for QCM allergen sensors.

PubMed

Jenik, Michael; Seifner, Alexandra; Lieberzeit, Peter; Dickert, Franz L

2009-05-01

Molecularly imprinted polymers for detecting plant pollen were designed as artificial recognition materials for quartz crystal microbalances in the gaseous phase. Imprints of birch (diameter, 25 mum) and nettle (diameter, 15 mum) pollen can be generated by polydimethylsiloxane stamping technique as proven by atomic force microscopy. If pollen grains are able to access the cavities and thus are incorporated, the resulting sensors display Sauerbrey-like negative frequency shifts. Non-Sauerbrey behaviour can be observed as soon as pollen is prevented from entering the selective hollows: this results in grain mobility on the electrode surface leading to frequency increases. Access to the cavities is determined by the diameter ratio between pollen grains and imprints as can be revealed during cross-selectivity measurements of nettle and birch pollen imprinted layers. When the amount of pollen grains on the electrode surface exceeds the number of available imprints, the excess particles move freely, resulting in positive, non-Sauerbrey frequency shifts.

Thermal radiation characteristics of nonisothermal cylindrical enclosures using a numerical ray tracing technique

NASA Technical Reports Server (NTRS)

Baumeister, Joseph F.

1990-01-01

Analysis of energy emitted from simple or complex cavity designs can lead to intricate solutions due to nonuniform radiosity and irradiation within a cavity. A numerical ray tracing technique was applied to simulate radiation propagating within and from various cavity designs. To obtain the energy balance relationships between isothermal and nonisothermal cavity surfaces and space, the computer code NEVADA was utilized for its statistical technique applied to numerical ray tracing. The analysis method was validated by comparing results with known theoretical and limiting solutions, and the electrical resistance network method. In general, for nonisothermal cavities the performance (apparent emissivity) is a function of cylinder length-to-diameter ratio, surface emissivity, and cylinder surface temperatures. The extent of nonisothermal conditions in a cylindrical cavity significantly affects the overall cavity performance. Results are presented over a wide range of parametric variables for use as a possible design reference.

Laminar flow in a microchannel with superhydrophobic walls exhibiting transverse ribs

NASA Astrophysics Data System (ADS)

Davies, J.; Maynes, D.; Webb, B. W.; Woolford, B.

2006-08-01

One approach recently proposed for reducing the frictional resistance to liquid flow in microchannels is the patterning of microribs and cavities on the channel walls. When treated with a hydrophobic coating, the liquid flowing in the microchannel wets only the surfaces of the ribs, and does not penetrate the cavities, provided the pressure is not too high. The net result is a reduction in the surface contact area between channel walls and the flowing liquid. For microribs and cavities that are aligned normal to the channel axis (principal flow direction), these micropatterns form a repeating, periodic structure. This paper presents results of a study exploring the momentum transport in a parallel-plate microchannel with such microengineered walls. The investigation explored the entire laminar flow Reynolds number range and characterized the influence of the vapor cavity depth on the overall flow field. The liquid-vapor interface (meniscus) in the cavity regions is treated as flat in the numerical analysis and two conditions are explored with regard to the cavity region: (1) The liquid flow at the liquid-vapor interface is treated as shear-free (vanishing viscosity in the vapor region), and (2) the liquid flow in the microchannel core and the vapor flow within the cavity are coupled by matching the velocity and shear stress at the interface. Regions of slip and no-slip behavior exist and the velocity field shows distinct variations from classical laminar flow in a parallel-plate channel. The local streamwise velocity profiles, interfacial velocity distributions, and maximum interfacial velocities are presented for a number of scenarios and provide a sound understanding of the local flow physics. The predictions and accompanying measurements reveal that significant reductions in the frictional pressure drop (enhancement in effective fluid slip at the channel walls) can be achieved relative to the classical smooth-channel Stokes flow. Reductions in the friction factor and enhancements in the fluid slip are greater as the cavity-to-rib length ratio is increased (increasing shear-free fraction) and as the channel hydraulic diameter is decreased. The results also show that the slip length and average friction factor-Reynolds number product exhibit a flow Reynolds dependence. Furthermore, the predictions reveal the global impact of the vapor cavity depth on the overall frictional resistance.

Space shuttle main engine high pressure fuel pump aft platform seal cavity flow analysis

NASA Technical Reports Server (NTRS)

Lowry, S. A.; Keeton, L. W.

1987-01-01

A general purpose, three-dimensional computational fluid dynamics code named PHOENICS, developed by CHAM Inc., is used to model the flow in the aft-platform seal cavity in the high pressure fuel pump of the space shuttle main engine. The model is used to predict the temperatures, velocities, and pressures in the cavity for six different sets of boundary conditions. The results are presented as input for further analysis of two known problems in the region, specifically: erratic pressures and temperatures in the adjacent coolant liner cavity and cracks in the blade shanks near the outer diameter of the aft-platform seal.

Dynamics of tongue shaped cavity generated during the impact of high-speed microdrops

NASA Astrophysics Data System (ADS)

Deka, Hiranya; Ray, Bahni; Biswas, Gautam; Dalal, Amaresh

2018-04-01

Tongue shaped cavities are seen during the hydrophobic sphere impact, jet impact, and impact of a train of microdrops on a deep liquid pool. For the multiple microdrops' impact, the mechanisms, which lead to deep cavity formation and later bubble entrapment inside the liquid pool, are presented here. The investigations are performed in an air-water system at large values of Froude numbers, thus having a negligible effect of gravity. Depending on the train length, the capillary wave generating from each drop impact affects the necking. The temporal variation of the neck radius shows power law behavior. We delineate the distinctive feature of pinch-off of the cavity in terms of the critical length of the train. Pinch-off is observed when the penetration depth of the cavity is more than three times the diameter of the cavity.

Nucleate boiling performance evaluation of cavities at mesoscale level

DOE PAGES

Mu, Yu-Tong; Chen, Li; He, Ya-Ling; ...

2016-09-29

Nucleate boiling heat transfer (NBHT) from enhanced structures is an effective way to dissipate high heat flux. Here, a 3D multi-relaxation-time (MRT) phase-change lattice Boltzmann method in conjunction with conjugated heat transfer treatment is proposed and then applied to the study of cavities behaviours for nucleation on roughened surfaces for an entire ebullition cycle without introducing any artificial disturbance. The bubble departure diameter, departure frequency and total boiling heat transfer rate are also explored. We demonstrate that the cavity shapes show significant influence on the features of NBHT. The total heat transfer rate increases with the cavity mouth and cavitymore » base area while decreases with the increase in cavity bottom wall thickness. The cavity with low wetting can enhance the heat transfer and improve the bubble release frequency.« less

Vertical-cavity surface-emitting lasers - Design, growth, fabrication, characterization

NASA Astrophysics Data System (ADS)

Jewell, Jack L.; Lee, Y. H.; Harbison, J. P.; Scherer, A.; Florez, L. T.

1991-06-01

The authors have designed, fabricated, and tested vertical-cavity surface-emitting lasers (VCSEL) with diameters ranging from 0.5 microns to above 50 microns. Design issues, molecular beam epitaxial growth, fabrication, and lasing characteristics are discussed. The topics considered in fabrication of VCSELs are microlaser geometries; ion implementation and masks; ion beam etching; packaging and arrays; and ultrasmall devices.

Double high refractive-index contrast grating VCSEL

NASA Astrophysics Data System (ADS)

Gebski, Marcin; Dems, Maciej; Wasiak, Michał; Sarzała, Robert P.; Lott, J. A.; Czyszanowski, Tomasz

2015-03-01

Distributed Bragg reflectors (DBRs) are typically used as the highly reflecting mirrors of vertical-cavity surface-emitting lasers (VCSELs). In order to provide optical field confinement, oxide apertures are often incorporated in the process of the selective wet oxidation of high aluminum-content DBR layers. This technology has some potential drawbacks such as difficulty in controlling the uniformity of the oxide aperture diameters across a large-diameter (≥ 6 inch) production wafers, high DBR series resistance especially for small diameters below about 5 μm despite elaborate grading and doping schemes, free carrier absorption at longer emission wavelengths in the p-doped DBRs, reduced reliability for oxide apertures placed close to the quantum wells, and low thermal conductivity for transporting heat away from the active region. A prospective alternative mirror is a high refractive index contrast grating (HCG) monolithically integrated with the VCSEL cavity. Two HCG mirrors potentially offer a very compact and simplified VCSEL design although the problems of resistance, heat dissipation, and reliability are not completely solved. We present an analysis of a double HCG 980 nm GaAs-based ultra-thin VCSEL. We analyze the optical confinement of such a structure with a total optical thickness is ~1.0λ including the optical cavity and the two opposing and parallel HCG mirrors.

Operation and investigation of a tilted bottom cavity for pyrgeometer characterizations.

PubMed

Gröbner, Julian

2008-08-20

A new cavity for pyrgeometer characterizations has been built at the Infrared Radiometry Section of the World Radiation Center (WRC-IRS) at PMOD/WRC. The calculated effective emissivity of 0.99993+/-0.00033 was obtained from Monte Carlo simulations taking into account the geometry and the measured temperature distributions of the cavity. The cavity is operated in a temperature range of -30 degrees C to +30 degrees C and is initially flushed with nitrogen to reduce the relative humidity in the cavity. The estimated uncertainties of retrieved pyrgeometer parameters k1, k2, and k3 are +/-0.024, +/-0.0008, and +/-0.03, respectively. The relative uncertainty of pyrgeometer sensitivity C is 0.8%. The comparison with the cavity used since 1995 at PMOD/WRC gave average differences of 0.005, 0.00026, and 0.08 for k1, k2, and k3, respectively. The pyrgeometer sensitivity retrieved with the new cavity is on average 1.0% higher than with the original cavity.

Exponentially decaying interaction potential of cavity solitons

NASA Astrophysics Data System (ADS)

Anbardan, Shayesteh Rahmani; Rimoldi, Cristina; Kheradmand, Reza; Tissoni, Giovanna; Prati, Franco

2018-03-01

We analyze the interaction of two cavity solitons in an optically injected vertical cavity surface emitting laser above threshold. We show that they experience an attractive force even when their distance is much larger than their diameter, and eventually they merge. Since the merging time depends exponentially on the initial distance, we suggest that the attraction could be associated with an exponentially decaying interaction potential, similarly to what is found for hydrophobic materials. We also show that the merging time is simply related to the characteristic times of the laser, photon lifetime, and carrier lifetime.

(QC Themes) Type-Two Quantum Computing in PBG-Based Cavities for Efficient Simulation of Lattice Gas Dynamics

DTIC Science & Technology

2008-04-26

substrate Si3N4 Diameter : 540 nm Pitch : 760 nm Diamond Holes in Diamond (HID) Pillars of Diamond (POD) POD with Electrooptic Polymer at Center 3D ...Diamond film : 2 um Si- substrate Al : 0.2 um PMMA : 0.5um 1. Deposit UNCD film 2. Deposit Al metal 3. Deposit PMMA on Al 4. E-beam Lithography 5...band-gap (PBG) based cavities. The cavities are etched directly on to the diamond substrate . The set of coupled qubits in each spot represents an

Wind turbine having a direct-drive drivetrain

DOEpatents

Bevington, Christopher M.; Bywaters, Garrett L.; Coleman, Clint C.; Costin, Daniel P.; Danforth, William L.; Lynch, Jonathan A.; Rolland, Robert H.

2008-10-07

A wind turbine (100) comprising an electrical generator (108) that includes a rotor assembly (112). A wind rotor (104) that includes a wind rotor hub (124) is directly coupled to the rotor assembly via a simplified connection. The wind rotor and generator rotor assembly are rotatably mounted on a central spindle (160) via a bearing assembly (180). The wind rotor hub includes an opening (244) having a diameter larger than the outside diameter of the central spindle adjacent the bearing assembly so as to allow access to the bearing assembly from a cavity (380) inside the wind rotor hub. The spindle is attached to a turret (140) supported by a tower (136). Each of the spindle, turret and tower has an interior cavity (172, 176, 368) that permits personnel to traverse therethrough to the cavity of the wind rotor hub. The wind turbine further includes a frictional braking system (276) for slowing, stopping or keeping stopped the rotation of the wind rotor and rotor assembly.

Large mirror surface control by corrective coating

NASA Astrophysics Data System (ADS)

Bonnand, Romain; Degallaix, Jerome; Flaminio, Raffaele; Giacobone, Laurent; Lagrange, Bernard; Marion, Fréderique; Michel, Christophe; Mours, Benoit; Mugnier, Pierre; Pacaud, Emmanuel; Pinard, Laurent

2013-08-01

The Advanced Virgo gravitational wave detector aims at a sensitivity ten times better than the initial LIGO and Virgo detectors. This implies very stringent requirement on the optical losses in the interferometer arm cavities. In this paper we focus on the mirrors which form the interferometer arm cavities and that require a surface figure error to be well below one nanometre on a diameter of 150 mm. This ‘sub-nanometric flatness’ is not achievable by classical polishing on such a large diameter. Therefore we present the corrective coating technique which has been developed to reach this requirement. Its principle is to add a non-uniform thin film on top of the substrate in order to flatten its surface. In this paper we will introduce the Advanced Virgo requirements and present the basic principle of the corrective coating technique. Then we show the results obtained experimentally on an initial Virgo substrate. Finally we provide an evaluation of the round-trip losses in the Fabry-Perot arm cavities once the corrected surface is used.

Effects of wind on the dynamics of the central jet during drop impact onto a deep-water surface

NASA Astrophysics Data System (ADS)

Liu, Xinan; Wang, An; Wang, Shuang; Dai, Dejun

2018-05-01

The cavity and central jet generated by the impact of a single water drop on a deep-water surface in a wind field are experimentally studied. Different experiments are performed by varying the impacting drop diameter and wind speed. The contour profile histories of the cavity (also called crater) and central jet (also called stalk) are measured in detail with a backlit cinematic shadowgraph technique. The results show that shortly after the drop hits the water surface an asymmetrical cavity appears along the wind direction, with a train of capillary waves on the cavity wall. This is followed by the formation of an inclined central jet at the location of the drop impact. It is found that the wind has little effect on the penetration depth of the cavity at the early stage of the cavity expansion, but markedly changes the capillary waves during the retraction of the cavity. The capillary waves in turn shift the position of the central jet formation leeward. The dynamics of the central jet are dominated by two mechanisms: (i) the oblique drop impact produced by the wind and (ii) the wind drag force directly acting on the jet. The maximum height of the central jet, called the stalk height, is drastically affected by the wind, and the nondimensional stalk height H /D decreases with increasing θ Re-1 , where D is the drop diameter, θ is the impingement angle of drop impact, and Re=ρaUwD /μa is the Reynolds number with air density ρa, wind speed Uw, and air viscosity μa.

L-band Dielectric Constant Measurements of Seawater (Oral presentation and SMOS Poster)

NASA Technical Reports Server (NTRS)

Lang, Roger H.; Utku, Cuneyt; LeVine, David M.

2003-01-01

This paper describes a resonant cavity technique for the measurement of the dielectric constant of seawater as a function of its salinity. Accurate relationships between salinity and dielectric constant (which determines emissivity) are needed for sensor systems such as SMOS and Aquarius that will monitor salinity from space in the near future. The purpose of the new measurements is to establish the dependence of the dielectric constant of seawater on salinity in contemporary units (e.g. psu) and to take advantage of modern instrumentation to increase the accuracy of these measurements. The measurement device is a brass cylindrical cavity 16cm in diameter and 7cm in height. The seawater is introduced into the cavity through a slender glass tube having an inner diameter of 0.1 mm. By assuming that this small amount of seawater slightly perturbs the internal fields in the cavity, perturbation theory can be employed. A simple formula results relating the real part of the dielectric constant to the change in resonant frequency of the cavity. In a similar manner, the imaginary part of the dielectric constant is related to the change in the cavity s Q. The expected accuracy of the cavity technique is better than 1% for the real part and 1 to 2% for the imaginary part. Presently, measurements of methanol have been made and agree with precision measurements in the literature to within 1% in both real and imaginary parts. Measurements have been made of the dielectric constant of seawater samples from Ocean Scientific in the United Kingdom with salinities of 10, 30, 35 and 38 psu. All measurements were made at room temperature. Plans to make measurements at a range of temperatures and salinities will be discussed.

Polymerization shrinkage and spherical glass mega fillers: effects on cuspal deflection

PubMed Central

BASSI, M. ANDREASI; SERRA, S.; ANDRISANI, C.; LICO, S.; BAGGI, L.; LAURITANO, D.

2016-01-01

SUMMARY Purpose The Authors analyzed the effect of spherical glass mega fillers (SGMF) on reducing contraction stress in dental composite resins, by means of a cavity model simulating the cuspal deflection which occurs on filled tooth cavity walls in clinical condition. Materials and methods 20 stylized MOD cavities (C-factor = 0.83) were performed in acrylic resin. The inner surface of each cavity was sand blasted and adhesively treated in order to ensure a valid bond with the composite resin. Three different diameter of SGMF were used (i.e. 1, 1,5, 2 mm). The samples were divided in 4 groups of 5 each: Group 1 samples filled with the composite only; Group 2 samples filled with composite added with SGMFs, Ø1mm (16 spheres for each sample); Group 3 samples filled with composite added with SGMFs, Ø1,5 mm (5 spheres for each sample); Group 4 samples filled with composite added with SGMFs, Ø2 mm (2 spheres for each sample). Digital pictures were taken, in standardized settings, before and immediately after the polymerization of the composite material, placed into the cavities. With a digital image analysis software the distances from the coronal reference points of the cavity walls were measured. Then the difference between the first and second measurement was calculated. The data were analyzed by means of the ANOVA test. Results A significative reduction on cavity walls deflection, when the composite resin is used in addiction with the SGMFs was observed. The SGMFs of smallest diameter (1mm) showed the better outcome. Conclusion The SGMFs are reliable in reducing contraction stress in dental composite resins. PMID:28280535

Snag distributions in relation to human access in ponderosa pine forests

Treesearch

Jeff P. Hollenbeck; Lisa J. Bate; Victoria A. Saab; John F. Lehmkuhl

2013-01-01

Ponderosa pine (Pinus ponderosa) forests in western North America provide habitat for numerous cavity-using wildlife species that often select large-diameter snags for nesting and roosting. Yet large snags are often removed for their commercial and firewood values. Consequently we evaluated effects of human access on snag densities and diameter-class distributions at...

Theory of hydrophobicity: transient cavities in molecular liquids

NASA Technical Reports Server (NTRS)

Pratt, L. R.; Pohorille, A.

1992-01-01

Observation of the size distribution of transient cavities in computer simulations of water, n-hexane, and n-dodecane under benchtop conditions shows that the sizes of cavities are more sharply defined in liquid water but the most-probable-size cavities are about the same size in each of these liquids. The calculated solvent atomic density in contact with these cavities shows that water applies more force per unit area of cavity surface than do the hydrocarbon liquids. This contact density, or "squeezing" force, reaches a maximum near cavity diameters of 2.4 angstroms. The results for liquid water are compared to the predictions of simple theories and, in addition, to results for a reference simple liquid. The numerical data for water at a range of temperatures are analyzed to extract a surface free energy contribution to the work of formation of atomic-size cavities. Comparison with the liquid-vapor interfacial tensions of the model liquids studied here indicates that the surface free energies extracted for atomic-size cavities cannot be accurately identified with the macroscopic surface tensions of the systems.

Theory of hydrophobicity: Transient cavities in molecular liquids

PubMed Central

Pratt, Lawrence R.; Pohorille, Andrew

1992-01-01

Observation of the size distribution of transient cavities in computer simulations of water, n-hexane, and n-dodecane under benchtop conditions shows that the sizes of cavities are more sharply defined in liquid water but the most-probable-size cavities are about the same size in each of these liquids. The calculated solvent atomic density in contact with these cavities shows that water applies more force per unit area of cavity surface than do the hydrocarbon liquids. This contact density, or “squeezing” force, reaches a maximum near cavity diameters of 2.4 Å. The results for liquid water are compared to the predictions of simple theories and, in addition, to results for a reference simple liquid. The numerical data for water at a range of temperatures are analyzed to extract a surface free energy contribution to the work of formation of atomic-size cavities. Comparison with the liquid-vapor interfacial tensions of the model liquids studies here indicates that the surface free energies extracted for atomic-size cavities cannot be accurately identified with the macroscopic surface tensions of the systems. PMID:11537863

Collapsing cavities in reactive and nonreactive media

NASA Astrophysics Data System (ADS)

Bourne, Neil K.; Field, John E.

1991-04-01

This paper presents results of a high-speed photographic study of cavities collapsed asymmetrically by shocks of strengths in the range 0.26 GPa to 3.5 GPa. Two-dimensional collapses of cavity configurations punched into a 12% by weight gelatine in water sheet, and an ammonium nitrate/sodium nitrate (AN/SN) emulsion explosive were photographed using schlieren optics. The single cavity collapses were characterized by the velocity of the liquid jet formed by the upstream wall as it was accelerated by the shock and by the time taken for the cavity to collapse. The shock pressure did not qualitatively affect the collapse behaviour but jet velocities were found to exceed incident shock velocities at higher pressures. The more violent collapses induced light emission from the compressed gas in the cavity. When an array of cavities collapsed, a wave, characterized by the particle velocity in the medium, the cavity diameter and the inter-cavity spacing, was found to run through the array. When such an array was created within an emulsion explosive, ignition of the reactive matrix occurred ahead of the collapse wave when the incident shock was strong.

Beam Test of a Dielectric Loaded High Pressure RF Cavity for Use in Muon Cooling Channels

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

Freemire, Ben; Bowring, Daniel; Kochemirovskiy, Alexey

2016-06-01

Bright muon sources require six dimensional cooling to achieve acceptable luminosities. Ionization cooling is the only known method able to do so within the muon lifetime. One proposed cooling channel, the Helical Cooling Channel, utilizes gas filled radio frequency cavities to both mitigate RF breakdown in the presence of strong, external magnetic fields, and provide the cooling medium. Engineering constraints on the diameter of the magnets within which these cavities operate dictate the radius of the cavities be decreased at their nominal operating frequency. To accomplish this, one may load the cavities with a larger dielectric material. A 99.5% aluminamore » ring was inserted in a high pressure RF test cell and subjected to an intense proton beam at the MuCool Test Area at Fermilab. The results of the performance of this dielectric loaded high pressure RF cavity will be presented.« less

Nuclear characteristics of a fissioning uranium plasma test reactor with light-water cooling

NASA Technical Reports Server (NTRS)

Whitmarsh, C. L., Jr.

1973-01-01

An analytical study was performed to determine a design configuration for a cavity test reactor. Test section criteria were that an average flux of 10 to the 15th power neutrons/sq cm/sec (E less than or equal to 0.12 eV) be supplied to a 61-cm-diameter spherical cavity at 200-atm pressure. Design objectives were to minimize required driver power, to use existing fuel-element technology, and to obtain fuel-element life of 10 to 100 full-power hours. Parameter calculations were made on moderator region size and material, driver fuel arrangement, control system, and structure in order to determine a feasible configuration. Although not optimized, a configuration was selected which would meet design criteria. The driver fuel region was a cylindrical annular region, one element thick, of 33 MTR-type H2O-cooled elements (Al-U fuel plate configuration), each 101 cm long. The region between the spherical test cavity and the cylindrical driver fuel region was Be (10 vol. % H2O coolant) with a midplane dimension of 8 cm. Exterior to the driver fuel, the 25-cm-thick cylindrical and axial reflectors were also Be with 10 vol. % H2O coolant. The entire reactor was contained in a 10-cm-thick steel pressure vessel, and the 200-atm cavity pressure was equalized throughout the driver reactor. Fuel-element life was 50 hr at the required driver power of 200 MW. Reactor control would be achieved with rotating poison drums located in the cylindrical reflector region. A control range of about 18 percent delta k/k was required for reactor operation.

Snag densities in old-growth stands on the Gasquet Ranger District, Six Rivers National Forest, California

Treesearch

Thomas M. Jimerson

1989-01-01

Baseline levels for densities of snags (standing dead trees) wered etermined in undisturbed old-growth stands on the Gasquet Ranger District. Six Riven National Forest, California. Snag species, number, diameter at breast height (d.b.h.), height, cavity type, cavity use, decay class, and snag origin were recorded on 317 plots over a 2-year period. The 2121 snags...

Experimental Evaluation of an Isolated Synthetic Jet IN Crossflow

NASA Technical Reports Server (NTRS)

Schaeffler, Norman W.; Jenkins, Luther N.; Hepner, Timothy E.

2007-01-01

The second case for this workshop builds upon the isolated synthetic jet of Case 1 by adding a crossflow, with no streamwise pressure gradient, for the developing jet to interact with. Formally, Case 2 examines the interaction of a single, isolated, synthetic jet and a fully turbulent zero-pressure gradient boundary layer. The resulting flow has many of the characteristics that need to be modeled with fidelity if the results of the calculations are to serve as the basis for research and design with active flow control devices. These include the turbulence in the boundary layer, the time-evolution of the large vortical structure emanating from the jet orifice and its subsequent interaction with and distortion by the boundary layer turbulence, and the effect of the suction cycle on the boundary layer flow. In a synthetic jet, the flow through the orifice and out into the outer flowfield alternates between an exhaust and a suction cycle, driven by the contraction and expansion of a cavity internal to the actuator. In the present experiment, the volume changes in the internal cavity are accomplished by replacing one of the rigid walls of the cavity, the wall opposite the orifice exit, with a deformable wall. This flexible wall is driven by a bottom-mounted moveable piston. The piston is driven electro-mechanically. The synthetic jet issues into the external flow through a circular orifice. In the present experiment, this orifice has a diameter of 0.250 inches (6.35 mm). The flow is conceptually similar to that documented in Schaeffler [1]. To document the flow, several measurement techniques were utilized. The upstream boundary conditions (in-flow conditions), and several key phase-averaged velocity profiles were measured with a 3-component laser-Doppler velocimetry system. Phase-averaged velocity field measurements were made with both stereo digital particle image velocimetry and 2-D digital particle image velocimetry as the primary measurement system. Surface pressure measurements were made utilizing an electronically scanned pressure system.

Thermal conditions within tree cavities in ponderosa pine (Pinus ponderosa) forests: potential implications for cavity users.

PubMed

Vierling, Kerri T; Lorenz, Teresa J; Cunningham, Patrick; Potterf, Kelsi

2018-04-01

Tree cavities provide critical roosting and breeding sites for multiple species, and thermal environments in these cavities are important to understand. Our objectives were to (1) describe thermal characteristics in cavities between June 3 and August 9, 2014, and (2) investigate the environmental factors that influence cavity temperatures. We placed iButtons in 84 different cavities in ponderosa pine (Pinus ponderosa) forests in central Washington, and took hourly measurements for at least 8 days in each cavity. Temperatures above 40 °C are generally lethal to developing avian embryos, and ~ 18% of the cavities had internal temperatures of ≥ 40 °C for at least 1 h of each day. We modeled daily maximum cavity temperature, the amplitude of daily cavity temperatures, and the difference between the mean internal cavity and mean ambient temperatures as a function of several environmental variables. These variables included canopy cover, tree diameter at cavity height, cavity volume, entrance area, the hardness of the cavity body, the hardness of the cavity sill (which is the wood below the cavity entrance which forms the barrier between the cavity and the external environment), and sill width. Ambient temperature had the largest effect size for maximum cavity temperature and amplitude. Larger trees with harder sills may provide more thermally stable cavity environments, and decayed sills were positively associated with maximum cavity temperatures. Summer temperatures are projected to increase in this region, and additional research is needed to determine how the thermal environments of cavities will influence species occupancy, breeding, and survival.

Thermal conditions within tree cavities in ponderosa pine (Pinus ponderosa) forests: potential implications for cavity users

NASA Astrophysics Data System (ADS)

Vierling, Kerri T.; Lorenz, Teresa J.; Cunningham, Patrick; Potterf, Kelsi

2017-11-01

Tree cavities provide critical roosting and breeding sites for multiple species, and thermal environments in these cavities are important to understand. Our objectives were to (1) describe thermal characteristics in cavities between June 3 and August 9, 2014, and (2) investigate the environmental factors that influence cavity temperatures. We placed iButtons in 84 different cavities in ponderosa pine (Pinus ponderosa) forests in central Washington, and took hourly measurements for at least 8 days in each cavity. Temperatures above 40 °C are generally lethal to developing avian embryos, and 18% of the cavities had internal temperatures of ≥ 40 °C for at least 1 h of each day. We modeled daily maximum cavity temperature, the amplitude of daily cavity temperatures, and the difference between the mean internal cavity and mean ambient temperatures as a function of several environmental variables. These variables included canopy cover, tree diameter at cavity height, cavity volume, entrance area, the hardness of the cavity body, the hardness of the cavity sill (which is the wood below the cavity entrance which forms the barrier between the cavity and the external environment), and sill width. Ambient temperature had the largest effect size for maximum cavity temperature and amplitude. Larger trees with harder sills may provide more thermally stable cavity environments, and decayed sills were positively associated with maximum cavity temperatures. Summer temperatures are projected to increase in this region, and additional research is needed to determine how the thermal environments of cavities will influence species occupancy, breeding, and survival.

The importance of old growth refugia in the Yukon boreal forest to cavity-nesting owls

Treesearch

D. H. Mossop

1997-01-01

The Yukon's boreal forest is a slow-growing yet dynamic system greatly affected by wildfire. Trees of a diameter and age to accommodate cavity-nesting owls and other larger birds should be rare. An experiment was conducted by erecting just over 100 nest boxes throughout the southern Yukon to test the availability of nest holes for small owls. After 5 years an...

Biomechanical behavior of cavity configuration on micropush-out test: a finite-element-study.

PubMed

Cekic-Nagas, Isil; Shinya, Akikazu; Ergun, Gulfem; Vallittu, Pekka K; Lassila, Lippo V J

2011-01-01

The objective of this study was to simulate the micropush-out bond strength test from a biomechanical point of view. For this purpose, stress analysis using finite element (FE) method was performed. Three different occlusal cavity shapes were simulated in disc specimens (model A: 1.5 mm cervical, 2 mm occlusal diameter; model B: 1.5 mm cervical, 1.75 mm occlusal diameter; model C: 1.5 mm cervical, 1.5 mm occlusal diameter). Quarter sizes of 3D FE specimen models of 4.0 x 4.0 x 1.25 mm3 were constructed. In order to avoid quantitative differences in the stress value in the models, models were derived from a single mapping mesh pattern that generated 47.182 elements and 66.853 nodes. The materials that were used were resin composite (Filtek Z250, 3M ESPE), bonding agent (Adper Scotchbond Multi-Purpose, 3M ESPE) and dentin as an isotropic material. Loading conditions consisted of subjecting a press of 4 MPa to the top of the resin composite discs. The postprocessing files allowed the calculation of the maximum principal stress, minimum principal stress and displacement within the disc specimens and stresses at the bonding layer. FE model construction and analysis were performed on PC workstation (Precision Work Station 670, Dell Inc.) using FE analysis program (ANSYS 10 Sp, ANSYS Inc.). Compressive stress concentrations were observed equally in the bottom interface edge of dentin. Tensile stresses were observed on the top area of dentin and at the half of lower side of composite under the loading point in all of the FE models. The FE model revealed differences in displacement and stress between different cavity shaped disc specimens. As the slope of the cavity was increased, the maximum displacement, compressive and tensile stresses also increased.

Effect of fibroids not distorting the endometrial cavity on the outcome of in vitro fertilization treatment: a retrospective cohort study.

PubMed

Yan, Lei; Ding, Lingling; Li, Chunyan; Wang, Yu; Tang, Rong; Chen, Zi-Jiang

2014-03-01

To investigate the effect of fibroids that do not distort the endometrial cavity on IVF/intracytoplasmic sperm injection (ICSI) outcomes and to identify certain fibroid subgroups that may be deleterious to fertility outcomes. Retrospective cohort study. University-based reproductive medicine center. A total of 10,268 patients undergoing IVF/ICSI between 2009 and 2011 in our unit. Transvaginal ultrasound and hysteroscopy; controlled ovarian hyperstimulation and IVF/ICSI; strict matching criteria. Cycle cancellation, clinical pregnancy, miscarriage, and delivery rates. We included 249 patients with fibroids who underwent IVF/ICSI. Higher day 3 FSH levels were found in women with fibroids compared with in control subjects. No significant differences were found in IVF/ICSI outcomes between the two groups. Patients with intramural fibroids with the largest diameter <2.85 cm or the sum of reported diameters <2.95 cm had a significantly higher delivery rate than patients with larger fibroids. A significant negative effect on delivery rate was noted when intramural fibroids with the largest diameter greater than 2.85 cm were considered, compared with matched controls without fibroids. Our results suggest that although non-cavity-distorting fibroids do not affect IVF/ICSI outcomes, intramural fibroids greater than 2.85 cm in size significantly impair the delivery rate of patients undergoing IVF/ICSI. Copyright © 2014 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.

Experimental and numerical study of shock-driven collapse of multiple cavity arrays

NASA Astrophysics Data System (ADS)

Betney, Matthew; Anderson, Phillip; Tully, Brett; Doyle, Hugo; Hawker, Nicholas; Ventikos, Yiannis

2014-10-01

This study presents a numerical and experimental investigation of the interaction of a single shock wave with multiple air-filled spherical cavities. The 5 mm diameter cavities are cast in a hydrogel, and collapsed by a shock wave generated by the impact of a projectile fired from a single-stage light-gas gun. Incident shock pressures of up to 1 GPa have been measured, and the results compared to simulations conducted using a front-tracking approach. The authors have previously studied the collapse dynamics of a single cavity. An important process is the formation of a high-speed transverse jet, which impacts the leeward cavity wall and produces a shockwave. The speed of this shock has been measured using schlieren imaging, and the density has been measured with a fibre optic probe. This confirmed the computational prediction that the produced shock is of a higher pressure than the original incident shock. When employing multiple cavity arrays, the strong shock produced by the collapse of one cavity can substantially affect the collapse of further cavities. With control over cavity placement, these effects may be utilised to intensify collapse. This intensification is experimentally measured via analysis of the optical emission.

Development of a sapphire fiber thermometer using two wavelength bands

NASA Astrophysics Data System (ADS)

Ye, Linhua; Shen, Yonghang

1996-09-01

This paper reports the development of a sapphire ((alpha) - Al2O3) single crystal optical fiber thermometer using two wavelength bands. A thin film of precious metal or ceramic deposited onto one end of the sapphire fiber forms a mini-radiation cavity. The other end of the sapphire fiber is coupled to a low-loss silica fiber. Radiation from the small cavity is transmitted along the silica fiber into a photodetection system which consists of a lens, beam splitter, two interference filters (820 nm and 940 nm center wavelength, 30 nm bandwidth) and two silicon photocells. The temperature measurement is based on the detection of radiation from the small cavity. The sapphire fiber (0.25 - 1.0 mm diameter, 100 - 450 mm length) was grown by the laser heated pedestal growth (LHPG) methods. Transmission loss in the sapphire fiber was experimentally measured. Theoretical analysis shows the apparent emittance of the small cavity with a length to diameter (L/D) ratio greater than eight is a constant value near to one, so the small cavity can be considered as a small black-body cavity. Using the developed sapphire fiber temperature sensor, we have built a sapphire fiber thermometer based on a 8098 single-chip microcomputer system. It was calibrated at some known stable temperature point and uses the fundamental radiation law to extrapolate to other temperatures. By taking the ratio of the optical power at two wavelengths, errors due to changes in the system, such as emissivity and transmission losses, can be canceled out. The thermometer has an operating temperature range of 800 to 1900 degrees Celsius, and an accuracy of 0.2% at 1000 degrees Celsius. There are a number of applications of the thermometer both in science and industry.

System for producing a uniform rubble bed for in situ processes

DOEpatents

Galloway, T.R.

1983-07-05

A method and a cutter are disclosed for producing a large cavity filled with a uniform bed of rubblized oil shale or other material, for in situ processing. A raise drill head has a hollow body with a generally circular base and sloping upper surface. A hollow shaft extends from the hollow body. Cutter teeth are mounted on the upper surface of the body and relatively small holes are formed in the body between the cutter teeth. Relatively large peripheral flutes around the body allow material to drop below the drill head. A pilot hole is drilled into the oil shale deposit. The pilot hole is reamed into a large diameter hole by means of a large diameter raise drill head or cutter to produce a cavity filled with rubble. A flushing fluid, such as air, is circulated through the pilot hole during the reaming operation to remove fines through the raise drill, thereby removing sufficient material to create sufficient void space, and allowing the larger particles to fill the cavity and provide a uniform bed of rubblized oil shale. 4 figs.

Effect of diameter of metal nanowires on pool boiling heat transfer with FC-72

NASA Astrophysics Data System (ADS)

Kumar G., Udaya; S., Suresh; M. R., Thansekhar; Babu P., Dinesh

2017-11-01

Effect of varying diameter of metal nanowires on pool boiling heat transfer performance is presented in this study. Copper nanowires (CuNWs) of four different diameters (∼35 nm, ∼70 nm, ∼130 nm and ∼200 nm) were grown directly on copper specimen using template-based electrodeposition technique. Both critical heat flux (CHF) and boiling heat transfer coefficient (h) were found to be improved in surfaces with nanowires as compared to the bare copper surface. Moreover, both the parameters were found to increase with increasing diameter of the nanowires. The percentage increases observed in CHF for the samples with nanowires were 38.37%, 40.16%, 48.48% and 45.57% whereas the percentage increase in the heat transfer coefficient were 86.36%, 95.45%, 184.1% and 131.82% respectively as compared to the bare copper surface. Important reasons believed for this enhancement were improvement in micron scale cavity density and cavity size which arises as a result of the coagulation and grouping of nanowires during the drying process. In addition to this, superhydrophilic nature, capillary effect, and enhanced bubble dynamics parameters (bubble frequency, bubble departure diameter, and nucleation site density) were found to be the concurring mechanisms responsible for this enhancement in heat transfer performance. Qualitative bubble dynamics analysis was done for the surfaces involved and the visual observations are provided to support the results presented and discussed.

Apparatus for irradiating a continuously flowing stream of fluid. [For neutron activation analysis

DOEpatents

Speir, L.G.; Adams, E.L.

1982-05-13

An apparatus for irradiating a continuously flowing stream of fluid is disclosed. The apparatus consists of a housing having a spherical cavity and a spherical moderator containing a radiation source positioned within the spherical cavity. The spherical moderator is of lesser diameter than the spherical cavity so as to define a spherical annular volume around the moderator. The housing includes fluid intake and output conduits which open onto the spherical cavity at diametrically opposite positions. Fluid flows through the cavity around the spherical moderator and is uniformly irradiated due to the 4..pi.. radiation geometry. The irradiation source, for example a /sup 252/Cf neutron source, is removable from the spherical moderator through a radial bore which extends outwardly to an opening on the outside of the housing. The radiation source may be routinely removed without interrupting the flow of fluid or breaching the containment of the fluid.

Apparatus for irradiating a continuously flowing stream of fluid

DOEpatents

Speir, Leslie G.; Adams, Edwin L.

1984-01-01

An apparatus for irradiating a continuously flowing stream of fluid is diosed. The apparatus consists of a housing having a spherical cavity and a spherical moderator containing a radiation source positioned within the spherical cavity. The spherical moderator is of lesser diameter than the spherical cavity so as to define a spherical annular volume around the moderator. The housing includes fluid intake and output conduits which open onto the spherical cavity at diametrically opposite positions. Fluid flows through the cavity around the spherical moderator and is uniformly irradiated due to the 4.pi. radiation geometry. The irradiation source, for example a .sup.252 CF neutron source, is removable from the spherical moderator through a radial bore which extends outwardly to an opening on the outside of the housing. The radiation source may be routinely removed without interrupting the flow of fluid or breaching the containment of the fluid.

High average power laser using a transverse flowing liquid host

DOEpatents

Ault, Earl R.; Comaskey, Brian J.; Kuklo, Thomas C.

2003-07-29

A laser includes an optical cavity. A diode laser pumping device is located within the optical cavity. An aprotic lasing liquid containing neodymium rare earth ions fills the optical cavity. A circulation system that provides a closed loop for circulating the aprotic lasing liquid into and out of the optical cavity includes a pump and a heat exchanger.

Experimental measurements of heat transfer coefficient in a partially/fully opened tilted cavity

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

Chakroun, W.; Elsayed, M.M.; Al-Fahed, S.F.

1997-11-01

An experimental investigation was carried out to determine the heat transfer coefficient from a rectangular tilted cavity to the ambient due to the buoyancy driven flow in the cavity. The cavity is partially or fully open from one side. All the walls of the cavity are adiabatic except the wall facing the cavity opening which is heated at a constant heat flux. Air was used as the cavity fluid and the experiments were carried out at a flux Grashof number of 5.5 {times} 10{sup 8}. The tilt angle of the cavity, measured from the vertical direction, was changed between {minus}90more » deg to +90 deg in 15 deg increments. Also, geometries of aspect ratio (height-to-width of cavity) of 1.0, 0.5, and 0.25 and of opening ratio (opening height to cavity height) of 1.0, 0.5, and 0.25 were considered in the study. The results are presented in terms of the average Nusselt number for different values of the above experimental parameters. Conclusions are derived for the effect of changing the tilt angle, the aspect ratio, or the opening ratio of the cavity on the average heat transfer coefficient between the cavity and the ambient air. Buoyancy-driven flow in rectangular cavities has been widely investigated by many researchers. This geometry is of special interest in many solar applications such as in solar passive heating, solar concentrators, and solar central receivers. The importance of the geometry extends to other engineering applications such as electronic equipment, fire research, and energy conservation in buildings.« less

Performance in the vertical test of the 832 nine-cell 1.3 GHz cavities for the European X-ray Free Electron Laser

NASA Astrophysics Data System (ADS)

Reschke, D.; Gubarev, V.; Schaffran, J.; Steder, L.; Walker, N.; Wenskat, M.; Monaco, L.

2017-04-01

The successful production and associated vertical testing of over 800 superconducting 1.3 GHz accelerating cavities for the European X-ray Free Electron Laser (XFEL) represents the culmination of over 20 years of superconducting radio-frequency R&D. The cavity production took place at two industrial vendors under the shared responsibility of INFN Milano-LASA and DESY. Average vertical testing rates at DESY exceeded 10 cavities per week, peaking at up to 15 cavities per week. The cavities sent for cryomodule assembly at Commissariat à l'énergie atomique (CEA) Saclay achieved an average maximum gradient of approximately 33 MV /m , reducing to ˜30 MV /m when the operational specifications on quality factor (Q) and field emission were included (the so-called usable gradient). Only 16% of the cavities required an additional surface retreatment to recover their low performance (usable gradient less than 20 MV /m ). These cavities were predominantly limited by excessive field emission for which a simple high pressure water rinse (HPR) was sufficient. Approximately 16% of the cavities also received an additional HPR, e.g. due to vacuum problems before or during the tests or other reasons, but these were not directly related to gradient performance. The in-depth statistical analyses presented in this report have revealed several features of the series produced cavities.

Quantum dynamics of a Josephson junction driven cavity mode system in the presence of voltage bias noise

NASA Astrophysics Data System (ADS)

Wang, Hui; Blencowe, M. P.; Armour, A. D.; Rimberg, A. J.

2017-09-01

We give a semiclassical analysis of the average photon number as well as photon number variance (Fano factor F ) for a Josephson junction (JJ) embedded microwave cavity system, where the JJ is subject to a fluctuating (i.e., noisy) bias voltage with finite dc average. Through the ac Josephson effect, the dc voltage bias drives the effectively nonlinear microwave cavity mode into an amplitude squeezed state (F <1 ), as has been established previously [Armour et al., Phys. Rev. Lett. 111, 247001 (2013), 10.1103/PhysRevLett.111.247001], but bias noise acts to degrade this squeezing. We find that the sensitivity of the Fano factor to bias voltage noise depends qualitatively on which stable fixed point regime the system is in for the corresponding classical nonlinear steady-state dynamics. Furthermore, we show that the impact of voltage bias noise is most significant when the cavity is excited to states with large average photon number.

Comparative histopathological analysis of human pulps after class I cavity preparation with a high-speed air-turbine handpiece or Er:YAG laser

NASA Astrophysics Data System (ADS)

Kina, J. F.; Benitez, P. C.; Lizarelli, R. F. Z.; Bagnato, V. S.; Martinez, T. C.; Oliveira, C. F.; Hebling, J.; Costa, C. A. S.

2008-12-01

The purpose of this study was to comparatively evaluate the response of human pulps after cavity preparation with different devices. Deep class I cavities were prepared in sound mandibular premolars using either a high-speed air-turbine handpiece (Group 1) or an Er:YAG laser (Group 2). Following total acid etching and the application of an adhesive system, all cavities were restored with composite resin. Fifteen days after the clinical procedure, the teeth were extracted and processed for analysis under optical microscopy. In Group 1 in which the average for the remaining dentin thickness (RDT) between the cavity floor and the coronal pulp was 909.5 μm, a discrete inflammatory response occurred in only one specimen with an RDT of 214 μm. However, tissue disorganization occurred in most specimens. In Group 2 (average RDT = 935.2 μm), the discrete inflammatory pulp response was observed in only one specimen (average RDT = 413 μm). It may be concluded that the high-speed air-turbine handpiece caused greater structural alterations in the pulp, although without inducing inflammatory processes.

Experimental demonstration of passive acoustic imaging in the human skull cavity using CT-based aberration corrections.

PubMed

Jones, Ryan M; O'Reilly, Meaghan A; Hynynen, Kullervo

2015-07-01

Experimentally verify a previously described technique for performing passive acoustic imaging through an intact human skull using noninvasive, computed tomography (CT)-based aberration corrections Jones et al. [Phys. Med. Biol. 58, 4981-5005 (2013)]. A sparse hemispherical receiver array (30 cm diameter) consisting of 128 piezoceramic discs (2.5 mm diameter, 612 kHz center frequency) was used to passively listen through ex vivo human skullcaps (n = 4) to acoustic emissions from a narrow-band fixed source (1 mm diameter, 516 kHz center frequency) and from ultrasound-stimulated (5 cycle bursts, 1 Hz pulse repetition frequency, estimated in situ peak negative pressure 0.11-0.33 MPa, 306 kHz driving frequency) Definity™ microbubbles flowing through a thin-walled tube phantom. Initial in vivo feasibility testing of the method was performed. The performance of the method was assessed through comparisons to images generated without skull corrections, with invasive source-based corrections, and with water-path control images. For source locations at least 25 mm from the inner skull surface, the modified reconstruction algorithm successfully restored a single focus within the skull cavity at a location within 1.25 mm from the true position of the narrow-band source. The results obtained from imaging single bubbles are in good agreement with numerical simulations of point source emitters and the authors' previous experimental measurements using source-based skull corrections O'Reilly et al. [IEEE Trans. Biomed. Eng. 61, 1285-1294 (2014)]. In a rat model, microbubble activity was mapped through an intact human skull at pressure levels below and above the threshold for focused ultrasound-induced blood-brain barrier opening. During bursts that led to coherent bubble activity, the location of maximum intensity in images generated with CT-based skull corrections was found to deviate by less than 1 mm, on average, from the position obtained using source-based corrections. Taken together, these results demonstrate the feasibility of using the method to guide bubble-mediated ultrasound therapies in the brain. The technique may also have application in ultrasound-based cerebral angiography.

Experimental demonstration of passive acoustic imaging in the human skull cavity using CT-based aberration corrections

PubMed Central

Jones, Ryan M.; O’Reilly, Meaghan A.; Hynynen, Kullervo

2015-01-01

Purpose: Experimentally verify a previously described technique for performing passive acoustic imaging through an intact human skull using noninvasive, computed tomography (CT)-based aberration corrections Jones et al. [Phys. Med. Biol. 58, 4981–5005 (2013)]. Methods: A sparse hemispherical receiver array (30 cm diameter) consisting of 128 piezoceramic discs (2.5 mm diameter, 612 kHz center frequency) was used to passively listen through ex vivo human skullcaps (n = 4) to acoustic emissions from a narrow-band fixed source (1 mm diameter, 516 kHz center frequency) and from ultrasound-stimulated (5 cycle bursts, 1 Hz pulse repetition frequency, estimated in situ peak negative pressure 0.11–0.33 MPa, 306 kHz driving frequency) Definity™ microbubbles flowing through a thin-walled tube phantom. Initial in vivo feasibility testing of the method was performed. The performance of the method was assessed through comparisons to images generated without skull corrections, with invasive source-based corrections, and with water-path control images. Results: For source locations at least 25 mm from the inner skull surface, the modified reconstruction algorithm successfully restored a single focus within the skull cavity at a location within 1.25 mm from the true position of the narrow-band source. The results obtained from imaging single bubbles are in good agreement with numerical simulations of point source emitters and the authors’ previous experimental measurements using source-based skull corrections O’Reilly et al. [IEEE Trans. Biomed. Eng. 61, 1285–1294 (2014)]. In a rat model, microbubble activity was mapped through an intact human skull at pressure levels below and above the threshold for focused ultrasound-induced blood–brain barrier opening. During bursts that led to coherent bubble activity, the location of maximum intensity in images generated with CT-based skull corrections was found to deviate by less than 1 mm, on average, from the position obtained using source-based corrections. Conclusions: Taken together, these results demonstrate the feasibility of using the method to guide bubble-mediated ultrasound therapies in the brain. The technique may also have application in ultrasound-based cerebral angiography. PMID:26133635

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.

Experimental characterization of mm-wave detection by a micro-array of Golay cells

NASA Astrophysics Data System (ADS)

Denison, Douglas R.; Knotts, Michael E.; McConney, Michael E.; Tsukruk, Vladimir V.

2009-05-01

We present experimental results for an uncooled imaging focal plane array technology that consists of a polymer/metal/polymer layered membrane suspended over a micro-fabricated array of cavities. The device operation is Golay-like (heating of air in the cavity causes a detectable deflection of the membrane proportional to incident EM power), but potentially offers both greater sensitivity and more read-out options (optical or electrical) than a traditional Golay cell through tailoring of the membrane properties. The membrane is formed from a layer-by-layer deposition of polymer with one or more monolayers of gold nanoparticles (or other metal) that help control the membrane's elasticity and deformation-dependent optical reflectivity/electrical conductivity. Baseline capabilities of the device have been established through optical measurements of membrane deflection due to incident mm-wave radiation modulated at 30 Hz (corresponding to a video refresh rate). The device demonstrates an NEP of 300 nW/√Hz at 105 GHz for a 19-layer membrane (9 poly/1 Au/9 poly) suspended over an array of 80 μm diameter cavities (depth = 100 μm) etched in a 500 μm thick substrate of Si. Calculations of membrane sensitivity show that this NEP could be reduced to ~ 100 pW/√Hz with enlarged cavity diameters on the order of 600 μm.

Method of fabricating a scalable nanoporous membrane filter

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

Tringe, Joseph W; Balhorn, Rodney L; Zaidi, Saleem

A method of fabricating a nanoporous membrane filter having a uniform array of nanopores etch-formed in a thin film structure (e.g. (100)-oriented single crystal silicon) having a predetermined thickness, by (a) using interferometric lithography to create an etch pattern comprising a plurality array of unit patterns having a predetermined width/diameter, (b) using the etch pattern to etch frustum-shaped cavities or pits in the thin film structure such that the dimension of the frustum floors of the cavities are substantially equal to a desired pore size based on the predetermined thickness of the thin film structure and the predetermined width/diameter ofmore » the unit patterns, and (c) removing the frustum floors at a boundary plane of the thin film structure to expose, open, and thereby create the nanopores substantially having the desired pore size.« less

An efficient multi-dimensional implementation of VSIAM3 and its applications to free surface flows

NASA Astrophysics Data System (ADS)

Yokoi, Kensuke; Furuichi, Mikito; Sakai, Mikio

2017-12-01

We propose an efficient multidimensional implementation of VSIAM3 (volume/surface integrated average-based multi-moment method). Although VSIAM3 is a highly capable fluid solver based on a multi-moment concept and has been used for a wide variety of fluid problems, VSIAM3 could not simulate some simple benchmark problems well (for instance, lid-driven cavity flows) due to relatively high numerical viscosity. In this paper, we resolve the issue by using the efficient multidimensional approach. The proposed VSIAM3 is shown to capture lid-driven cavity flows of the Reynolds number up to Re = 7500 with a Cartesian grid of 128 × 128, which was not capable for the original VSIAM3. We also tested the proposed framework in free surface flow problems (droplet collision and separation of We = 40 and droplet splashing on a superhydrophobic substrate). The numerical results by the proposed VSIAM3 showed reasonable agreements with these experiments. The proposed VSIAM3 could capture droplet collision and separation of We = 40 with a low numerical resolution (8 meshes for the initial diameter of droplets). We also simulated free surface flows including particles toward non-Newtonian flow applications. These numerical results have showed that the proposed VSIAM3 can robustly simulate interactions among air, particles (solid), and liquid.

Quench Studies of Six High Temperature Nitrogen Doped 9 Cell Cavities for Use in the LCLS-II Baseline Prototype Cryomodule at Jefferson Laboratory

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

Palczewski, Ari; Geng, Rongli; Eremeev, Grigory

Jefferson Lab (JLab) processed six nine-cell cavities as part of a small-scale production for LCLS-II cavity processing development utilizing the promising nitrogen-doping process. Various nitrogen-doping recipes have been scrutinized to optimize process parameters with the aim to guarantee an unloaded quality factor (Q_0) of 2.7∙10 10 at an accelerating field (Eacc) of 16 MV/m at 2.0 K in the cryomodule. During the R&D phase the characteristic Q0 vs. Eacc performance curve of the cavities has been measured in JLab’s vertical test area at 2 K. The findings showed the characteristic rise of the Q0 with Eacc as expected from nitrogen-doping.more » Initially, five cavities achieved an average Q0 of 3.3·10 10 at the limiting Eacc averaging to 16.8 MV/m, while one cavity experienced an early quench accompanied by an unusual Q_0 vs. Eacc curve. The project accounts for a cavity performance loss from the vertical dewar test (with or without the helium vessel) to the horizontal performance in a cryomodule, such that these results leave no save margin to the cryomodule specification. Consequently, a refinement of the nitrogen-doping has been initiated to guarantee an average quench field above 20 MV/m without impeding the Q_0. This paper covers the refinement work performed for each cavity, which depends on the initial results, as well as a quench analysis carried out before and after the rework during the vertical RF tests as far as applicable.« less

Morphology and morphometry of the reproductive system of female Saguinus midas (Linnaeus, 1758).

PubMed

Monteiro, Nathaly Cristine Da Silva; De Lima, Ana Rita; De Carvalho, Ana Flávia; De Carvalho Garcia, Rafael; Therrier, Joanne; Souza, Ana Carla Barros; Pereira, Luiza Correia; Branco, Erika

2012-06-01

In this article, the reproductive system's morphology of three young animals of the species Saguinus midas, from the bauxite mine in Paragominas, is described. The specimens were fixed and preserved in a solution of 10% aqueous formaldehyde, followed by dissection, measurement of the genital organs (uterus, vagina, ovaries, and uterine tubes), and histological processing. The vulva is delimited by the labia, with a clitoris. It is lined by keratinized stratified squamous epithelium with sebaceous glands of holocrine secretion. The vagina is an elongated tube with an average length of 26 mm and diameter of 1 mm, presenting a non-keratinized squamous epithelium, disposed between the vestibule of the vagina and cervix, the latter being relatively short. The uterus is simple, has globular shape and is located in the caudal portion of the abdominal cavity, with an average length of 14 mm and average width of 7 mm. It is formed by vascular and serous layers of muscles, and undergoes a bifurcation to form two structures on the bottom of blind sac. The uterine tubes are long and convoluted with an average length of 35 mm (right) and 36 mm (left), consisting of loose connective tissue and muscle layer lined by simple ciliated columnar epithelium. The ovaries are large and ellipsoid with smooth surface. Histologically, one animal showed ovulation fosse. Copyright © 2011 Wiley Periodicals, Inc.

A bone marrow toxicity model for 223Ra alpha-emitter radiopharmaceutical therapy

NASA Astrophysics Data System (ADS)

Hobbs, Robert F.; Song, Hong; Watchman, Christopher J.; Bolch, Wesley E.; Aksnes, Anne-Kirsti; Ramdahl, Thomas; Flux, Glenn D.; Sgouros, George

2012-05-01

Ra-223, an α-particle emitting bone-seeking radionuclide, has recently been used in clinical trials for osseous metastases of prostate cancer. We investigated the relationship between absorbed fraction-based red marrow dosimetry and cell level-dosimetry using a model that accounts for the expected localization of this agent relative to marrow cavity architecture. We show that cell level-based dosimetry is essential to understanding potential marrow toxicity. The GEANT4 software package was used to create simple spheres representing marrow cavities. Ra-223 was positioned on the trabecular bone surface or in the endosteal layer and simulated for decay, along with the descendants. The interior of the sphere was divided into cell-size voxels and the energy was collected in each voxel and interpreted as dose cell histograms. The average absorbed dose values and absorbed fractions were also calculated in order to compare those results with previously published values. The absorbed dose was predominantly deposited near the trabecular surface. The dose cell histogram results were used to plot the percentage of cells that received a potentially toxic absorbed dose (2 or 4 Gy) as a function of the average absorbed dose over the marrow cavity. The results show (1) a heterogeneous distribution of cellular absorbed dose, strongly dependent on the position of the cell within the marrow cavity; and (2) that increasing the average marrow cavity absorbed dose, or equivalently, increasing the administered activity resulted in only a small increase in potential marrow toxicity (i.e. the number of cells receiving more than 4 or 2 Gy), for a range of average marrow cavity absorbed doses from 1 to 20 Gy. The results from the trabecular model differ markedly from a standard absorbed fraction method while presenting comparable average dose values. These suggest that increasing the amount of radioactivity may not substantially increase the risk of toxicity, a result unavailable to the absorbed fraction method of dose calculation.

Structure and function of bordered pits: new discoveries and impacts on whole-plant hydraulic function.

PubMed

Choat, Brendan; Cobb, Alexander R; Jansen, Steven

2008-01-01

Bordered pits are cavities in the lignified cell walls of xylem conduits (vessels and tracheids) that are essential components in the water-transport system of higher plants. The pit membrane, which lies in the center of each pit, allows water to pass between xylem conduits but limits the spread of embolism and vascular pathogens in the xylem. Averaged across a wide range of species, pits account for > 50% of total xylem hydraulic resistance, indicating that they are an important factor in the overall hydraulic efficiency of plants. The structure of pits varies dramatically across species, with large differences evident in the porosity and thickness of pit membranes. Because greater porosity reduces hydraulic resistance but increases vulnerability to embolism, differences in pit structure are expected to correlate with trade-offs between efficiency and safety of water transport. However, trade-offs in hydraulic function are influenced both by pit-level differences in structure (e.g. average porosity of pit membranes) and by tissue-level changes in conduit allometry (average length, diameter) and the total surface area of pit membranes that connects vessels. In this review we address the impact of variation in pit structure on water transport in plants from the level of individual pits to the whole plant.

Impact cratering on porous targets in the strength regime

NASA Astrophysics Data System (ADS)

Nakamura, Akiko M.

2017-12-01

Cratering on small bodies is crucial for the collision cascade and also contributes to the ejection of dust particles into interplanetary space. A crater cavity forms against the mechanical strength of the surface, gravitational acceleration, or both. The formation of moderately sized craters that are sufficiently larger than the thickness of the regolith on small bodies, in which mechanical strength plays the dominant role rather than gravitational acceleration, is in the strength regime. The formation of microcraters on blocks on the surface is also within the strength regime. On the other hand, the formation of a crater of a size comparable to the thickness of the regolith is affected by both gravitational acceleration and cohesion between regolith particles. In this short review, we compile data from the literature pertaining to impact cratering experiments on porous targets, and summarize the ratio of spall diameter to pit diameter, the depth, diameter, and volume of the crater cavity, and the ratio of depth to diameter. Among targets with various porosities studied in the laboratory to date, based on conventional scaling laws (Holsapple and Schmidt, J. Geophys. Res., 87, 1849-1870, 1982) the cratering efficiency obtained for porous sedimentary rocks (Suzuki et al., J. Geophys. Res. 117, E08012, 2012) is intermediate. A comparison with microcraters formed on a glass target with impact velocities up to 14 km s-1 indicates a different dependence of cratering efficiency and depth-to-diameter ratio on impact velocity.

Synthesis of an ultradense forest of vertically aligned triple-walled carbon nanotubes of uniform diameter and length using hollow catalytic nanoparticles.

PubMed

Baliyan, Ankur; Nakajima, Yoshikata; Fukuda, Takahiro; Uchida, Takashi; Hanajiri, Tatsuro; Maekawa, Toru

2014-01-22

It still remains a crucial challenge to actively control carbon nanotube (CNT) structure such as the alignment, area density, diameter, length, chirality, and number of walls. Here, we synthesize an ultradense forest of CNTs of a uniform internal diameter by the plasma-enhanced chemical vapor deposition (PECVD) method using hollow nanoparticles (HNPs) modified with ligand as a catalyst. The diameters of the HNPs and internal cavities in the HNPs are uniform. A monolayer of densely packed HNPs is self-assembled on a silicon substrate by spin coating. HNPs shrink via the collapse of the internal cavities and phase transition from iron oxide to metallic iron in hydrogen plasma during the PECVD process. Agglomeration of catalytic NPs is avoided on account of the shrinkage of the NPs and ligand attached to the NPs. Diffusion of NPs into the substrate, which would inactivate the growth of CNTs, is also avoided on account of the ligand. As a result, an ultradense forest of triple-walled CNTs of a uniform internal diameter is successfully synthesized. The area density of the grown CNTs is as high as 0.6 × 10(12) cm(-2). Finally, the activity of the catalytic NPs and the NP/carbon interactions during the growth process of CNTs are investigated and discussed. We believe that the present approach may make a great contribution to the development of an innovative synthetic method for CNTs with selective properties.

Turbulent Supersonic/Hypersonic Heating Correlations for Open and Closed Cavities

NASA Technical Reports Server (NTRS)

Everhart, Joel L.; Greene, Francis A.

2009-01-01

Supersonic/hypersonic laminar heating correlations that were developed for damage assessment analysis of atmospheric re-entry vehicles have been modified and extended to cover fully-turbulent conditions over rectangular cavity geometries that are aligned with the local velocity. Turbulent boundary layer properties were computationally determined and used to develop the cavity geometry parametrics and to correlate experimental closed cavity heating data to yield new relationships for the floor-averaged and centerline endwall peak-heating augmentation. With the form of the closed-cavity correlations established, historical data were used to develop new correlations for turbulent open-cavity heating.

Turbulent Supersonic/Hypersonic Heating Correlations for Open and Closed Cavities

NASA Technical Reports Server (NTRS)

Everhart, Joel L.; Greene, Francis A.

2009-01-01

Supersonic/hypersonic laminar heating correlations that were developed for damage assessment analysis of atmospheric re-entry vehicles have been modified and extended to cover fully-turbulent conditions over rectangular cavity geometries that are aligned with the local velocity. Turbulent boundary layer properties were computationally determined and used to develop the cavity geometry parametrics and to correlate experimental closed cavity heating data to yield new relationships for the floor-averaged and centerline endwall peakheating augmentation. With the form of the closed-cavity correlations established, historical data were used to develop new correlations for turbulent open-cavity heating.

Cavitation in liquid cryogens. 3: Ogives

NASA Technical Reports Server (NTRS)

Hord, J.

1973-01-01

Experimental results for three, scaled, quarter-caliber ogives are given. Both desinent and developed cavity data, using liquid hydrogen and liquid nitrogen, are reported. The desinent data do not exhibit a consistent ogive size effect, but the developed cavity data were consistently influenced by ogive size; B-factor increases with increasing ogive diameter. The developed cavity data indicated that stable thermodynamic equilibrium exists throughout the vaporous cavities. These data were correlated by using the extended theory derived in NASA-CR-2156 (volume II of this report series). The new correlating parameter MTWO, improves data correlation for the ogives, hydrofoil, and venturi and appears attractive for future predictive applications. The cavitation coefficient and equipment size effects are shown to vary with specific equipment-fluid combinations. A method of estimating cavitation coefficient from knowledge of the noncavitating pressure coefficient is suggested.

Dielectric magnetic microparticles as photomagnonic cavities: Enhancing the modulation of near-infrared light by spin waves

NASA Astrophysics Data System (ADS)

Almpanis, Evangelos

2018-05-01

The coupling between spin waves and optical Mie resonances inside a dielectric magnetic spherical particle, which acts simultaneously as a photonic and magnonic (photomagnonic) cavity, is investigated by means of numerical calculations accurate to arbitrary order in the magnetooptical coupling coefficient. Isolated dielectric magnetic particles with diameters of just a few microns support high-Q optical Mie resonances at near-infrared frequencies and localized spin waves, providing an ultrasmall and compact platform in the emerging field of cavity optomagnonics. Our results predict the occurrence of strong interaction effects, beyond the linear-response approximation, which lead to enhanced modulation of near-infrared light by spin waves through multimagnon absorption and emission mechanisms.

System for producing a uniform rubble bed for in situ processes

DOEpatents

Galloway, Terry R.

1983-01-01

A method and a cutter for producing a large cavity filled with a uniform bed of rubblized oil shale or other material, for in situ processing. A raise drill head (72) has a hollow body (76) with a generally circular base and sloping upper surface. A hollow shaft (74) extends from the hollow body (76). Cutter teeth (78) are mounted on the upper surface of the body (76) and relatively small holes (77) are formed in the body (76) between the cutter teeth (78). Relatively large peripheral flutes (80) around the body (76) allow material to drop below the drill head (72). A pilot hole is drilled into the oil shale deposit. The pilot hole is reamed into a large diameter hole by means of a large diameter raise drill head or cutter to produce a cavity filled with rubble. A flushing fluid, such as air, is circulated through the pilot hole during the reaming operation to remove fines through the raise drill, thereby removing sufficient material to create sufficient void space, and allowing the larger particles to fill the cavity and provide a uniform bed of rubblized oil shale.

Measurement of the Dielectric Constant of Seawater at L-Band: Techniques and Measurements

NASA Technical Reports Server (NTRS)

Lang, R.; Utku, C.; Tarkocin, Y.; LeVine, D.

2009-01-01

Satellite instruments, that will monitor salinity from space in the near future, require an accurate relationship between salinity/temperature and seawater dielectric constant. This paper will review measurements that were made of the dielectric constant of seawater during the past several years. The objective of the measurements is to determine the dependence of the dielectric constant of seawater on salinity and on temperature, more accurately than in the past. by taking advantage of modem instrumentation. The measurements of seawater permittivity have been performed as a function of salinity and temperature using a transmission resonant cavity technique. The measurements have been made in the salinity range of 10 to 38 psu and in the temperature range of IOU C to 35 C. These results will be useful in algorithm development for sensor systems such as SMOS and Aquarius. The measurement system consists of a brass microwave cavity that is resonant at 1.413 GHz. The seawater is introduced into the cavity through a capillary glass tube having an inner diameter of 0.1 mm. The diameter of the tube has been made very small so that the amount of seawater introduced in the cavity is small - thus maintaining the sensitivity of the measurements and allowing the use of perturbation theory predicting the seawater permittivity. The change in resonant frequency and the change in cavity Q can be used to determine the real and imaginary pare of the dielectric constant of seawater introduced into the slender tube. The microwave measurements are made by an HPS722D network analyzer. The cavity has been immersed in a uateriethylene-glycol bath which is connected to a Lauda circulator. The circulator keeps the brass cavity at a temperature constant to within 0.01 degrees. The system is automated using a Visual Basic program to control the analyzer and to collect the data. The results of the dielectric constant measurements of seawater will be presented. The measurement results will be compared with permittivity values generated from the Kline and Swift relationship. Two methods of calibration will be discussed, The errors that each technique introduces into the measurement resulls will be reviewed. Temperature stability, frequency drift and the effect of increasing cavity transmission loss on the unloaded cavity Q will also be discussed.

The Apollo peak-ring impact basin: Insights into the structure and evolution of the South Pole-Aitken basin

NASA Astrophysics Data System (ADS)

Potter, Ross W. K.; Head, James W.; Guo, Dijun; Liu, Jianzhong; Xiao, Long

2018-05-01

The 492 km-diameter Apollo impact basin post-dates, and is located at the inner edge of, the ∼2240 km-diameter South Pole-Aitken (SPA) basin, providing an opportunity to assess the SPA substructure and lateral heterogeneity. Gravity Recovery and Interior Laboratory gravity data suggest an average crustal thickness on the floor of SPA of ∼20 km and within the Apollo basin of ∼5 km, yet remote sensing data reveal no conclusive evidence for the presence of exposed mantle material. We use the iSALE shock physics code to model the formation of the Apollo basin and find that the observational data are best fit by the impact of a 40 km diameter body traveling at 15 km/s into 20-40 km thick crustal material. These results strongly suggest that the Apollo impact occurred on ejecta deposits and collapsed crustal material of the SPA basin and could help place constraints on the location, size and geometry of the SPA transient cavity. The peak ring in the interior of Apollo basin is plausibly interpreted to be composed of inwardly collapsed lower crustal material that experienced peak shock pressures in excess of 35 GPa, consistent with remote sensing observations that suggest shocked plagioclase. Proposed robotic and/or human missions to SPA and Apollo would present an excellent opportunity to test the predictions of this work and address many scientific questions about SPA basin evolution and structure.

Sensitizing of pyrene fluorescence by β-cyclodextrin-modified TiO2 nanoparticles.

PubMed

Shown, Indrajit; Ujihara, Masaki; Imae, Toyoko

2010-12-15

TiO(2) nanoparticles were synthesized by hydrolysis of tetraisopropyl orthotitanate in an aqueous solution of cyclodextrin. The β-cyclodextrin-modified spherical TiO(2) nanoparticles were water-dispersible and had an average particle diameter of 4.4 ± 1 nm. Pyrene fluorescence was enhanced by increasing the concentration of β-cyclodextrin-modified TiO(2) nanoparticle and the sensitization effect was triply stronger than the case of the β-cyclodextrin only. The increase in a concentration of host (β-cyclodextrin) changes its microenvironment for guest (pyrene), that is, the interaction of pyrene with apolar cavity of β-cyclodextrin increases, resulting in enhancement of fluorescence. The sensitization behavior of pyrene fluorescence in the presence of TiO(2) nanoparticles occurs from the increase in the extinction coefficient of pyrene, demonstrating the charge transfer between pyrene and metal oxide nanoparticle. Crown Copyright © 2010. Published by Elsevier Inc. All rights reserved.

Lasing in strongly scattering dielectric microstructures

NASA Astrophysics Data System (ADS)

Florescu, Lucia

In the first part of this thesis, a detailed analysis of lasing in random multiple-light-scattering media with gain is presented. Random laser emission is analyzed using a time-dependent diffusion model for light propagating in the medium containing active atoms. We demonstrate the effects of scatterers to narrow the emission spectral linewidth and to shorten the emitted pulse duration at a specific threshold pump intensity. This threshold pump intensity decreases with scatterer density and excitation spot diameter, in excellent agreement with experimental results. The coherence properties of the random laser are studied using a generalized master equation. The random laser medium is treated as a collection of low quality-factor cavities, coupled by random photon diffusion. Laser-like coherence, on average, is demonstrated above a specific pumping threshold. We demonstrate that with stronger scattering, the pumping threshold for the transition from chaotic to isotropic coherent light emission decreases and enhanced optical coherence for the emitted light is achieved above threshold. The second part of this thesis presents a study of lasing in photonic crystals (PCs). The emission from an incoherently pumped atomic system in interaction with the electro-magnetic reservoir of a PC is analyzed using a set of generalized semiclassical Maxwell-Bloch equations. We demonstrate that the photonic band edge facilitates the enhancement of stimulated emission and the reduction of internal losses, leading to an important lowering of the laser threshold. In addition, an increase of the laser output at a photonic band edge is demonstrated. We next develop a detailed quantum theory of a coherently pumped two-level atom in a photonic band gap material, coupled to both a multi-mode wave-guide channel and a high-quality micro-cavity embedded within the PC. The cavity field characteristics are highly distinct from that of a corresponding high-Q cavity in ordinary vacuum. We demonstrate enhanced, inversionless, and nearly coherent light generation when the photon density of states (DOS) jump between the Mollow spectral components of atomic resonance fluorescence is large. In the case of a vanishing photon DOS on the lower Mollow sideband and no dipolar dephasing, the emitted photon statistics is Poissonian and the cavity field exhibits quadrature coherence.

SU-E-T-280: Reconstructed Rectal Wall Dose Map-Based Verification of Rectal Dose Sparing Effect According to Rectum Definition Methods and Dose Perturbation by Air Cavity in Endo-Rectal Balloon

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

Park, J; Research Institute of Biomedical Engineering, The Catholic University of Korea, Seoul; Park, H

Purpose: Dosimetric effect and discrepancy according to the rectum definition methods and dose perturbation by air cavity in an endo-rectal balloon (ERB) were verified using rectal-wall (Rwall) dose maps considering systematic errors in dose optimization and calculation accuracy in intensity-modulated radiation treatment (IMRT) for prostate cancer patients. Methods: When the inflated ERB having average diameter of 4.5 cm and air volume of 100 cc is used for patient, Rwall doses were predicted by pencil-beam convolution (PBC), anisotropic analytic algorithm (AAA), and AcurosXB (AXB) with material assignment function. The errors of dose optimization and calculation by separating air cavity from themore » whole rectum (Rwhole) were verified with measured rectal doses. The Rwall doses affected by the dose perturbation of air cavity were evaluated using a featured rectal phantom allowing insert of rolled-up gafchromic films and glass rod detectors placed along the rectum perimeter. Inner and outer Rwall doses were verified with reconstructed predicted rectal wall dose maps. Dose errors and extent at dose levels were evaluated with estimated rectal toxicity. Results: While AXB showed insignificant difference of target dose coverage, Rwall doses underestimated by up to 20% in dose optimization for the Rwhole than Rwall at all dose range except for the maximum dose. As dose optimization for Rwall was applied, the Rwall doses presented dose error less than 3% between dose calculation algorithm except for overestimation of maximum rectal dose up to 5% in PBC. Dose optimization for Rwhole caused dose difference of Rwall especially at intermediate doses. Conclusion: Dose optimization for Rwall could be suggested for more accurate prediction of rectal wall dose prediction and dose perturbation effect by air cavity in IMRT for prostate cancer. This research was supported by the Leading Foreign Research Institute Recruitment Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning (MSIP) (Grant No. 200900420)« less

WE-G-BRD-08: End-To-End Targeting Accuracy of the Gamma Knife for Trigeminal Neuralgia

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

Brezovich, I; Wu, X; Duan, J

2014-06-15

Purpose: Current QA procedures verify accuracy of individual equipment parameters, but may not include CT and MRI localizers. This study uses an end-to-end approach to measure the overall targeting errors in individual patients previously treated for trigeminal neuralgia. Methods: The trigeminal nerve is simulated by a 3 mm long, 3.175 mm (1/8 inch) diameter MRI contrast-filled cavity embedded within a PMMA plastic capsule. The capsule is positioned within the head frame such that the cavity position matches the Gamma Knife coordinates of 10 previously treated patients. Gafchromic EBT2 film is placed at the center of the cavity in coronal andmore » sagittal orientations. The films are marked with a pin prick to identify the cavity center. Treatments are planned for delivery with 4 mm collimators using MRI and CT scans acquired with the clinical localizer boxes and acquisition protocols. Coordinates of shots are chosen so that the cavity is centered within the 50% isodose volume. Following irradiation, the films are scanned and analyzed. Targeting errors are defined as the distance between the pin prick and the centroid of the 50% isodose line. Results: Averaged over 10 patient simulations, targeting errors along the x, y and z coordinates (patient left-to-right, posterior-anterior, head-to-foot) were, respectively, −0.060 +/− 0.363, −0.350 +/− 0.253, and 0.364 +/− 0.191 mm when MRI was used for treatment planning. Planning according to CT exhibited generally smaller errors, namely 0.109 +/− 0.167, −0.191 +/− 0.144, and 0.211 +/− 0.94 mm. The largest errors in MRI and CT planned treatments were, respectively, y = −0.761 and x = 0.428 mm. Conclusion: Unless patient motion or stronger MRI image distortion in actual treatments caused additional errors, all patients received the prescribed dose, i.e., the targeted section of the trig±eminal nerve was contained within the 50% isodose surface in all cases.« less

A microwave cavity for measurement of the mass of hydrogen pellets

NASA Astrophysics Data System (ADS)

Sørensen, H.; Hansen, J. E.; Michelsen, P.; Sass, B.; Weisberg, K.-V.; Knudsen, O.; Michelsen, E.

1990-11-01

A description is given of a nondestructive method utilizing a microwave cavity for measuring the mass of high-speed pellets of solid hydrogen. The cavity is designed for use on a multishot pellet injector, where eight pellets are fired successively with trajectories being parallel and symmetrical around the injector axis. The cavity is cylindrical with the axis coinciding with the injector axis. When a pellet passes through the cavity through holes of 15-16 mm diameter, the change in resonant frequency is proportional to the pellet mass. As a result of the cylindrical symmetry the sensitivity will be identical for all pellets. The frequency shift is measured directly and is converted to a signal proportional to the size of the pellet. The cavity was calibrated with pellets of H2 and D2 containing around 6×1020 atoms and with velocities between 1200 and 1500 m/s. The sensitivity was found to be 300±15 mV/1020 atoms in both cases. This is in fair agreement with estimates made from the dielectric constants of solid H2 and D2. The cavity is built together with two optical detectors for time of flight measurements to form an integrated diagnostic unit.

Orion EFT-1 Cavity Heating Tile Experiments and Environment Reconstruction

NASA Technical Reports Server (NTRS)

Salazar, Giovanni; Amar, Adam; Oliver, Brandon; Hyatt, Andrew; Rezin, Marc

2016-01-01

Developing aerothermodynamic environments for deep cavities, such as those produced by micrometeoroids and orbital debris impacts, poses a great challenge for engineers. In order to assess existing cavity heating models, two one-inch diameter cavities were flown on the Orion Multi-Purpose Crew Vehicle during Exploration Flight Test 1 (EFT1). These cavities were manufactured with depths of 1.0 in and 1.4 in, and they were both instrumented. Instrumentation included surface thermocouples upstream, downstream and within the cavities, and additional thermocouples at the TPS-structure interface. This paper will present the data obtained, and comparisons with computational predictions will be shown. Additionally, the development of a 3D material thermal model will be described, which will be used to account for the three-dimensionality of the problem when interpreting the data. Furthermore, using a multi-dimensional inverse heat conduction approach, a reconstruction of a time- and space-dependent flight heating distribution during EFT1 will be presented. Additional discussions will focus on instrumentation challenges and calibration techniques specific to these experiments. The analysis shown will highlight the accuracies and/or deficiencies of current computational techniques to model cavity flows during hypersonic re-entry.

Effects of Wing Leading Edge Penetration with Venting and Exhaust Flow from Wheel Well at Mach 24 in Flight

NASA Technical Reports Server (NTRS)

Gnoffo, Peter A.

2003-01-01

A baseline solution for CFD Point 1 (Mach 24) in the STS-107 accident investigation was modified to include effects of: (1) holes through the leading edge into a vented cavity; and (2) a scarfed, conical nozzle directed toward the centerline of the vehicle from the forward, inboard corner of the landing gear door. The simulations were generated relatively quickly and early in the investigation because simplifications were made to the leading edge cavity geometry and an existing utility to merge scarfed nozzle grid domains with structured baseline external domains was implemented. These simplifications in the breach simulations enabled: (1) a very quick grid generation procedure; and (2) high fidelity corroboration of jet physics with internal surface impingements ensuing from a breach through the leading edge, fully coupled to the external shock layer flow at flight conditions. These simulations provided early evidence that the flow through a two-inch diameter (or larger) breach enters the cavity with significant retention of external flow directionality. A normal jet directed into the cavity was not an appropriate model for these conditions at CFD Point 1 (Mach 24). The breach diameters were of the same order or larger than the local, external boundary-layer thickness. High impingement heating and pressures on the downstream lip of the breach were computed. It is likely that hole shape would evolve as a slot cut in the direction of the external streamlines. In the case of the six-inch diameter breach the boundary layer is fully ingested. The intent of externally directed jet simulations in the second scenario was to approximately model aerodynamic effects of a relatively large internal wing pressure, fueled by combusting aluminum, which deforms the corner of the landing gear door and directs a jet across the windside surface. These jet interactions, in and of themselves, were not sufficiently large to explain observed aerodynamic behavior.

Bottom-up photonic crystal cavities formed by patterned III-V nanopillars.

PubMed

Scofield, Adam C; Shapiro, Joshua N; Lin, Andrew; Williams, Alex D; Wong, Ping-Show; Liang, Baolai L; Huffaker, Diana L

2011-06-08

We report on the formation and optical properties of bottom-up photonic crystal (PC) cavities formed by III-V nanopillars (NPs) via catalyst-free selective-area metal-organic chemical vapor deposition on masked GaAs substrates. This method of NP synthesis allows for precise lithographic control of NP position and diameter enabling simultaneous formation of both the photonic band gap (PBG) region and active gain region. The PBG and cavity resonance are determined by independently tuning the NP radius r, pitch a, and height h in the respective masked areas. Near-infrared emission at 970 nm is achieved from axial GaAs/InGaAs heterostructures with in situ passivation by laterally grown InGaP shells. To achieve out-of-plane optical confinement, the PC cavities are embedded in polydimethylsiloxane (PDMS) and removed from the growth substrate. Spatially and spectrally resolved 77 K photoluminescence demonstrates a strong influence of the PBG resonance on device emission. Resonant peaks are observed in the emission spectra of PC cavities embedded in PDMS.

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

Freemire, Ben; Bowring, Daniel; Kochemirovskiy, Alexey

Bright muon sources require six dimensional cooling to achieve acceptable luminosities. Ionization cooling is the only known method able to do so within the muon lifetime. One proposed cooling channel, the Helical Cooling Channel, utilizes gas filled radio frequency cavities to both mitigate RF breakdown in the presence of strong, external magnetic fields, and provide the cooling medium. Engineering constraints on the diameter of the magnets within which these cavities operate dictate the radius of the cavities be decreased at their nominal operating frequency. To accomplish this, one may load the cavities with a larger dielectric material. Alumina of puritiesmore » ranging from 96 to 99.8% was tested in a high pressure RF test cell at the MuCool Test Area at Fermilab. The results of breakdown studies with pure nitrogen gas, and oxygen-doped nitrogen gas indicate the peak surface electric field on the alumina ranges between 10 and 15 MV/m. How these results affect the design of a prototype cooling channel cavity will be discussed.« less

Picosecond laser system with 30-W average power via cavity dumping and amplifying

NASA Astrophysics Data System (ADS)

Fu, J.; Pang, Q. S.; Chang, L.; Bai, Z. A.; Ai, Q. K.; Chen, L. Y.; Chen, M.; Li, G.; Ma, Y. F.; Fan, Z. W.; Niu, G.; Yu, J.; Liu, Y.; Zhang, X.; Kang, W. Y.; He, K.

2011-06-01

We present a picosecond laser system with high energy by technologies of cavity dumping and amplifying. Firstly, pulses with 10 ps and ˜520 nJ were obtained by cavity-dumped mode-locked laser at 10 kHz repetition rate. Secondly those pulses were seeded into a side-pumped regenerative amplifier (RA). Then pulses output from the regenerative amplifier were amplified by two four-pass post amplifiers. From the laser system pulses with an average power of 30 W corresponding to 3 mJ pulse energy were achieved with the pulse-width of 25.4 ps at repetition rate of 10 kHz.

Explicit and implicit calculations of turbulent cavity flows with and without yaw angle

NASA Astrophysics Data System (ADS)

Yen, Guan-Wei

1989-08-01

Computations were performed to simulate turbulent supersonic flows past three-dimensional deep cavities with and without yaw. Simulation of these self-sustained oscillatory flows were generated through time accurate solutions of the Reynolds averaged complete Navier-Stokes equations using two different schemes: (1) MacCormack, finite-difference; and (2) implicit, upwind, finite-volume schemes. The second scheme, which is approximately 30 percent faster, is found to produce better time accurate results. The Reynolds stresses were modeled, using the Baldwin-Lomax algebraic turbulence model with certain modifications. The computational results include instantaneous and time averaged flow properties everywhere in the computational domain. Time series analyses were performed for the instantaneous pressure values on the cavity floor. The time averaged computational results show good agreement with the experimental data along the cavity floor and walls. When the yaw angle is nonzero, there is no longer a single length scale (length-to-depth ratio) for the flow, as is the case for zero yaw angle flow. The dominant directions and inclinations of the vortices are dramatically different for this nonsymmetric flow. The vortex shedding from the cavity into the mainstream flow is captured computationally. This phenomenon, which is due to the oscillation of the shear layer, is confirmed by the solutions of both schemes.

Explicit and implicit calculations of turbulent cavity flows with and without yaw angle. M.S. Thesis

NASA Technical Reports Server (NTRS)

Yen, Guan-Wei

1989-01-01

Computations were performed to simulate turbulent supersonic flows past three-dimensional deep cavities with and without yaw. Simulation of these self-sustained oscillatory flows were generated through time accurate solutions of the Reynolds averaged complete Navier-Stokes equations using two different schemes: (1) MacCormack, finite-difference; and (2) implicit, upwind, finite-volume schemes. The second scheme, which is approximately 30 percent faster, is found to produce better time accurate results. The Reynolds stresses were modeled, using the Baldwin-Lomax algebraic turbulence model with certain modifications. The computational results include instantaneous and time averaged flow properties everywhere in the computational domain. Time series analyses were performed for the instantaneous pressure values on the cavity floor. The time averaged computational results show good agreement with the experimental data along the cavity floor and walls. When the yaw angle is nonzero, there is no longer a single length scale (length-to-depth ratio) for the flow, as is the case for zero yaw angle flow. The dominant directions and inclinations of the vortices are dramatically different for this nonsymmetric flow. The vortex shedding from the cavity into the mainstream flow is captured computationally. This phenomenon, which is due to the oscillation of the shear layer, is confirmed by the solutions of both schemes.

25  W/m² collection efficiency solar-pumped Nd:YAG laser by a heliostat-parabolic mirror system.

PubMed

Liang, D; Almeida, J; Vistas, C R

2016-09-20

A large aspheric fused silica lens was used to couple efficiently the concentrated solar radiation from the focal zone of a 1.5-m-diameter primary concentrator into a 4-mm-diameter, 35-mm-long Nd:YAG single-crystal rod within a conical pump cavity. Continuous-wave laser power of 29.3 W was measured, attaining 25.0  W/m² solar laser collection efficiency, corresponding to a 19% increase over the previous record. Its laser beam figure of merit-the ratio between laser power and the product of Mx2, My2 beam quality factors-of 0.01 W is 1.6 times higher than that of a direct tracking solar laser with 30  W/m² collection efficiency. A strong dependency of solar laser power on laser resonator cavity length was found.

Flow-induced resonance of screen-covered cavities

NASA Technical Reports Server (NTRS)

Soderman, Paul T.

1990-01-01

An experimental study of screen-covered cavities exposed to airflow tangent to the screen is described. The term screen refers to a thin metal plate perforated with a repetitive pattern of round holes. The purpose was to find the detailed aerodynamic and acoustic mechanisms responsible for screen-covered cavity resonance and to find ways to control the pressure oscillations. Results indicate that strong cavity acoustic resonances are created by screen orifices that shed vortices which couple resonance by choosing hole spacings such that shed vortices do not arrive at a downstream orifice in synchronization with cavity pressure oscillations. The proper hole pattern is effective at all airspeeds. It was also discovered that a reduction of orifice size tended to weaken the screen/cavity interaction regardless of hole pattern, probably because of viscous flow losses at the orifices. The screened cavities that resonated did so at much higher frequencies than the equivalent open cavity. The classical large eddy phenomenon occurs at the relatively small scale of the orifices (the excitation is typically of high frequency). The wind tunnel study was made at airspeeds from 0 to 100m/sec. The 457-mm-long by 1.09-m-high rectangular cavities had length-to-depth ratios greater than one, which is indicative of shallow cavities. The cavity screens were perforated in straight rows and columns with hole diameters ranging from 1.59 to 6.35 mm and with porosities from 2.6 to 19.6 percent.

All fiber passively Q-switched laser

DOEpatents

Soh, Daniel B. S.; Bisson, Scott E

2015-05-12

Embodiments relate to an all fiber passively Q-switched laser. The laser includes a large core doped gain fiber having a first end. The large core doped gain fiber has a first core diameter. The laser includes a doped single mode fiber (saturable absorber) having a second core diameter that is smaller than the first core diameter. The laser includes a mode transformer positioned between a second end of the large core doped gain fiber and a first end of the single mode fiber. The mode transformer has a core diameter that transitions from the first core diameter to the second core diameter and filters out light modes not supported by the doped single mode fiber. The laser includes a laser cavity formed between a first reflector positioned adjacent the large core doped gain fiber and a second reflector positioned adjacent the doped single mode fiber.

Oversized 250 GHz Traveling Wave Tube with a Photonic Band-Gap Structure

NASA Astrophysics Data System (ADS)

Rosenzweig, Guy; Shapiro, Michael A.; Temkin, Richard J.

2017-10-01

The challenge in manufacturing traveling wave tubes (TWTs) at high frequencies is that the sizes of the structures scale with, and are much smaller than, the wavelength. We have designed and are building a 250 GHz TWT that uses an oversized structure to overcome fabrication and power handling issues that result from the small dimensions. Using a photonic band-gap (PBG) structure, we succeeded to design the TWT with a beam tunnel diameter of 0.72 mm. The circuit consists of metal plates with the beam tunnel drilled down their center. Twelve posts are protruding on one side of each plate in a triangular array and corresponding sockets are drilled on the other side. The posts of each plate are inserted into the sockets of an adjacent plate, forming a PBG lattice. The vacuum spacing between adjacent plates forms the `PBG cavity''. The full structure is a series of PBG coupled cavities, with microwave power coupling through the beam tunnel. The PBG lattice provides confinement of microwave power in each of the cavities and can be tuned to give the right amount of diffraction per cavity so that no sever is needed to suppress oscillations in the operating mode. CST PIC simulations predict over 38 dB gain with 67 W peak power, using a 30 kV, 310 mA electron beam, 0.6 mm in diameter. Research supported by the AFOSR Program on Plasma and Electro-Energetic Physics and by the NIH National Institute of Biomedical Imaging and Bioengineering.

Heating Augmentation Due to Compression Pad Cavities on the Project Orion CEV Heat Shield

NASA Technical Reports Server (NTRS)

Hollis, Brian R.

2009-01-01

An experimental study has been conducted to assess the effects of compression pad cavities on the aeroheating environment of the Project Orion CEV heat-shield. Testing was conducted in Mach 6 and Mach 10 perfect-gas wind tunnels to obtain heating measurements in and around the compression pads cavities using global phosphor thermography. Data were obtained over a wide range of Reynolds numbers that produced laminar, transitional, and turbulent flow within and downstream of the cavities. The effects of cavity dimensions on boundary-layer transition and heating augmentation levels were studied. Correlations were developed for transition onset and for the average cavity-heating augmentation.

Compression Pad Cavity Heating Augmentation on Orion Heat Shield

NASA Technical Reports Server (NTRS)

Hollis, Brian R.

2011-01-01

An experimental study has been conducted to assess the effects of compression pad cavities on the aeroheating environment of the Project Orion Crew Exploration Vehicle heat shield. Testing was conducted in Mach 6 and 10 perfect-gas wind tunnels to obtain heating measurements in and around the compression pads cavities using global phosphor thermography. Data were obtained over a wide range of Reynolds numbers that produced laminar, transitional, and turbulent flow within and downstream of the cavities. The effects of cavity dimensions on boundary-layer transition and heating augmentation levels were studied. Correlations were developed for transition onset and for the average cavity-heating augmentation.

Specificities of Acoustic Streaming in Cylindrical Cavity with Increasing Nonlinearity of the Process

NASA Astrophysics Data System (ADS)

Gubaidullin, A. A.; Pyatkova, A. V.

2018-01-01

This paper presents a numerical study of a gas acoustic streaming in a cylindrical cavity under a vibratory action. The walls of the cavity are considered impermeable and maintained at a constant temperature. The test gas is air. Variations in acoustic streaming and period-average temperature of the gas in the cavity with increasing nonlinearity of the process are shown. The increase in the nonlinearity is caused by an increase in the vibration amplitude.

Electromagnetic coupling to centimeter-scale mechanical membrane resonators via RF cylindrical cavities

NASA Astrophysics Data System (ADS)

Martinez, Luis A.; Castelli, Alessandro R.; Delmas, William; Sharping, Jay E.; Chiao, Raymond

2016-11-01

We present experimental and theoretical results for the excitation of a mechanical oscillator via radiation pressure with a room-temperature system employing a relatively low-(Q) centimeter-size mechanical oscillator coupled to a relatively low-Q standard three-dimensional radio-frequency (RF) cavity resonator. We describe the forces giving rise to optomechanical coupling using the Maxwell stress tensor and show that nanometer-scale displacements are possible and experimentally observable. The experimental system is composed of a 35 mm diameter silicon nitride membrane sputtered with a 300 nm gold conducting film and attached to the end of a RF copper cylindrical cavity. The RF cavity is operated in its {{TE}}011 mode and amplitude modulated on resonance with the fundamental drum modes of the membrane. Membrane motion is monitored using an unbalanced, non-zero optical path difference, optically filtered Michelson interferometer capable of measuring sub-nanometer displacements.

Near-threshold harmonics from a femtosecond enhancement cavity-based EUV source: effects of multiple quantum pathways on spatial profile and yield.

PubMed

Hammond, T J; Mills, Arthur K; Jones, David J

2011-12-05

We investigate the photon flux and far-field spatial profiles for near-threshold harmonics produced with a 66 MHz femtosecond enhancement cavity-based EUV source operating in the tight-focus regime. The effects of multiple quantum pathways in the far-field spatial profile and harmonic yield show a strong dependence on gas jet dynamics, particularly nozzle diameter and position. This simple system, consisting of only a 700 mW Ti:Sapphire oscillator and an enhancement cavity produces harmonics up to 20 eV with an estimated 30-100 μW of power (intracavity) and > 1μW (measured) of power spectrally-resolved and out-coupled from the cavity. While this power is already suitable for applications, a quantum mechanical model of the system indicates substantial improvements should be possible with technical upgrades.

Brillouin lasing in coupled silica toroid microcavities

NASA Astrophysics Data System (ADS)

Honda, Yoshihiro; Yoshiki, Wataru; Tetsumoto, Tomohiro; Fujii, Shun; Furusawa, Kentaro; Sekine, Norihiko; Tanabe, Takasumi

2018-05-01

We demonstrate stimulated Brillouin scattering lasing in a strongly coupled microcavity system. By coupling two silica toroid microcavities, we achieve large mode splitting of 11 GHz, whose frequency separation matches the Brillouin frequency shift of silica. The stimulated Brillouin scattering light is resonantly amplified by pumping at the higher frequency side of the supermode splitting resonance. Since the mode splitting is adjusted by changing the gap distance between the two cavities, our system does not require precise control of a mm-sized cavity diameter to match the free-spectral spacing with the Brillouin frequency shift. It also allows us to use a small cavity, and hence, our system has the potential to achieve the lasing threshold at a very low power.

Quantum transport in chaotic and integrable ballistic cavities with tunable shape

NASA Astrophysics Data System (ADS)

Lee, Y.; Faini, G.; Mailly, D.

1997-10-01

We have performed magnetotransport measurements in ballistic cavities and obtained the average by small modulations on the shapes and/or on the Fermi level. We work with cavities whose underlying classical dynamics is chaotic (stadia and Sinaï billiards) and integrable (circles and rectangles). The former show a Lorentzian weak-localization peak, in agreement with semiclassical predictions and other averaging methods that have been used in recent measurements. For integrable cavities our measurements show that the shape of the weak localization is very sensitive to the exact geometry of the sample: a linear magnetoconductance has been observed for rectangles as expected by the theory for integrable cavities, whereas for circles the shape is always Lorentzian. These discrepancies illustrate the nongeneric behavior of scattering through integrable geometries, that we analyze taking into account the interplay of integrability with smooth disorder and geometrical effects. The power spectra of the conductance fluctuations are also analyzed, the deduced typical areas are in good agreement with those obtained from the weak localization. Periodic orbits in nonaveraged Fourier transforms of the magnetoconductance for regular cavities are clearly identified indicating the good quality of our samples.

Line splitting and modified atomic decay of atoms coupled with N quantized cavity modes

NASA Astrophysics Data System (ADS)

Zhu, Yifu

1992-05-01

We study the interaction of a two-level atom with N non-degenerate quantized cavity modes including dissipations from atomic decay and cavity damps. In the strong coupling regime, the absorption or emission spectrum of weakly excited atom-cavity system possesses N + 1 spectral peaks whose linewidths are the weighted averages of atomic and cavity linewidths. The coupled system shows subnatural (supernatural) atomic decay behavior if the photon loss rates from the N cavity modes are smaller (larger) than the atomic decay rate. If N cavity modes are degenerate, they can be treated effectively as a single mode. In addition, we present numerical calculations for N = 2 to characterize the system evolution from the weak coupling to strong coupling limits.

SRF test facility for the superconducting LINAC ``RAON'' — RRR property and e-beam welding

NASA Astrophysics Data System (ADS)

Jung, Yoochul; Hyun, Myungook; Joo, Jongdae; Joung, Mijoung

2015-02-01

Equipment, such as a vacuum furnace, high pressure rinse (HPR), eddy current test (ECT) and buffered chemical polishing (BCP), are installed in the superconducting radio frequency (SRF) test facility. Three different sizes of cryostats (diameters of 600 mm for a quarter wave resonator (QWR), 900 mm for a half wave resonator (HWR), and 1200 mm for single spoke resonator 1&2 (SSR 1&2)) for vertical RF tests are installed for testing cavities. We confirmed that as-received niobium sheets (ASTM B393, RRR300) good electrical properties because they showed average residual resistance ratio (RRR) values higher than 300. However, serious RRR degradation occurred after joining two pieces of Nb by e-beam welding because the average RRR values of the samples were ˜179, which was only ˜60% of as-received RRR value. From various e-beam welding experiments in which the welding current and a speed at a fixed welding voltage were changed, we confirmed that good welding results were obtained at a 53 mA welding current and a 20-mm/s welding speed at a fixed welding voltage of 150 kV.

Controlling diameter distribution of catalyst nanoparticles in arc discharge.

PubMed

Li, Jian; Volotskova, Olga; Shashurin, Alexey; Keidar, Michael

2011-11-01

It is demonstrated that the diameter distribution of catalyst nanoparticles in arc discharge can be controlled by a magnetic field. The magnetic field affects the arc shape, shortens the diffusing time of the catalyst nanoparticles through the nucleation zone, and consequentially reduces the average diameters of nanoparticles. The average diameter is reduced from about 7.5 nm without magnetic field to about 5 nm is the case of a magnetic field. Decrease of the catalyst nanoparticle diameter with magnetic field correlates well with decrease in the single-wall carbon nanotube and their bundles diameters.

Bellholes: Ceiling Cavities Eroded By Bats in Caves of the Neotropical Climates

NASA Astrophysics Data System (ADS)

Miller, T.

2014-12-01

Hundreds of thousands of symmetrical, vertical, bullet-shaped cavities known as bellholes are present in the ceilings of caves restricted to the tropical Americas. Most have circular diameters (rarely influenced by joints or bedding) of at least 30 cm, and may be several meters in height. They are often paired with bellbasins (shallow depressions located vertically beneath them that contain guano produced by bats). Members of the species Artibeus jamaicensis (Jamaican Fruit Bat) are almost exclusive users of these roosts. Brown streaks flowing down the sides of the bellholes and centimeters-thick rinds of the basins below are largely apatite minerals produced by the reaction of the host limestone with phosphoric acids in the guano.Many bellholes have developed in speleothem in the cave ceilings, disproving early theories that they are the result of solution by phreatic currents in flooded caves. A. jamaicensis roosts singly or in harem groups of 2-14 that commonly cluster in the bellholes and it is likely that these social habits of this species focus corrosion resulting from the transfer of feces to rock (producing altered rock then removed by claws) to create discretely-spaced upward-growing cavities. Fossil evidence from Jamaica supports an arrival there from the mainland in the past 12,000 years, suggesting bellholes and bellbasins are geologically recent features in the Caribbean islands. Their locations (not all cave passages have bellholes) can provide information on the hydrological history or microclimate of a cave, due to the absence of both bellholes and bats in some specific situations, e.g. where physical barriers exist such as sumps, small airspaces above streams or through rock collapses, or with increasing distance from an entrance.Smaller circular, increasingly-indented ceiling cavities demonstrate a sequence of bellhole development. Small (23 cm diameter, 9 cm high), circular, streaked cavities in a limestone drainage tunnel constructed in 1927 in Puerto Rico suggest that a 30 cm diameter, 50 cm high bellhole could develop in fewer than 900 years. The numbers of bellholes and bellbasins suggest they may be an important post-formational erosional process in tropical caves, e.g. 4.8 linear cm of ceiling rock has been eroded just from the bellholes of only the first 600 m of a single cave in Puerto Rico.

Cavity turnover and equilibrium cavity densities in a cottonwood bottomland

USGS Publications Warehouse

Sedgwick, James A.; Knopf, Fritz L.

1992-01-01

A fundamental factor regulating the numbers of secondary cavity nesting (SCN) birds is the number of extant cavities available for nesting. The number of available cavities may be thought of as being in an approximate equilibrium maintained by a very rough balance between recruitment and loss of cavities. Based on estimates of cavity recruitment and loss, we ascertained equilibrium cavity densities in a mature plains cottonwood (Populus sargentii) bottomland along the South Platte River in northeastern Colorado. Annual cavity recruitment, derived from density estimates of primary cavity nesting (PCN) birds and cavity excavation rates, was estimated to be 71-86 new cavities excavated/100 ha. Of 180 active cavities of 11 species of cavity-nesting birds found in 1985 and 1986, 83 were no longer usable by 1990, giving an average instantaneous rate of cavity loss of r = -0.230. From these values of cavity recruitment and cavity loss, equilibrium cavity density along the South Platte is 238-289 cavities/100 ha. This range of equilibrium cavity density is only slightly above the minimum of 205 cavities/100 ha required by SCN's and suggests that cavity availability may be limiting SCN densities along the South Platte River. We submit that snag management alone does not adequately address SCN habitat needs, and that cavity management, expressed in terms of cavity turnover and cavity densities, may be more useful.

Randomized trial of oral misoprostol treatment for cervical ripening before tandem application in cervix cancer.

PubMed

Cepni, Kimia; Gul, Sule; Cepni, Ismail; Güralp, Onur; Sal, Veysel; Mayadagli, Alpaslan

2011-11-01

To investigate the efficacy of oral misoprostol administered to facilitate tandem application to the cervix as a part of brachytherapy in patients with cervical cancer. Eighty patients with cervical cancer who had been planned to undergo brachytherapy at Dr. Lütfi Kırdar Kartal Training and Research Hospital were evaluated in a double-blind, prospective, randomized trial. Patients were divided randomly into two groups of 40 patients. The first and second groups received 400 μg of misoprostol orally and placebo, respectively, 3 h before tandem application. The two groups were compared in terms of age, diameter of tumor, parity, age at first intercourse, amount of bleeding and pain at first tandem application, length of endometrial cavity measured by hysterometer, and size of Hegar dilators used for cervical dilatation. Of all cases, 63.6%, 16.3%, 10%, 6.3%, 2.5%, and 1.3% were Stage IIB, IIIB, IIIA, IVA, IIA and IIC, respectively. Mean (±SD) age (range) was 49.3 ± 13.1 (25-83) years and 56.6 ± 13.2 (30-78) years in the study and control groups, respectively (p = 0.015). Age at first intercourse, diameter of tumor, parity, amount of bleeding at first tandem application, and length of endometrial cavity measured by hysterometer were not significantly different between the two groups. Pain score was significantly higher in the control group (p < 0.001). Application was significantly easier in the study group compared with controls (p < 0.001). Average size of initial Hegar dilators used for cervical dilatation was significantly higher in the study group compared with controls (p = 0.017). Administration of misoprostol 400 μg orally for cervical ripening before tandem application facilitates the procedure, increases patient tolerability and comfort, and may decrease complication rates. Copyright © 2011 Elsevier Inc. All rights reserved.

Effect of cathode shape on vertical buffered electropolishing for niobium SRF cavities

NASA Astrophysics Data System (ADS)

Jin, S.; Wu, A. T.; Lu, X. Y.; Rimmer, R. A.; Lin, L.; Zhao, K.; Mammosser, J.; Gao, J.

2013-09-01

This paper reports the research results of the effect of cathode shape during vertical buffered electropolishing (BEP) by employing a demountable single cell niobium (Nb) superconducting radio frequency (SRF) cavity. Several different cathode shapes such as, for instance, bar, ball, ellipsoid, and wheels of different diameters have been tested. Detailed electropolishing parameters including I-V characteristic, removal rate, surface roughness, and polishing uniformity at different locations inside the demountable cavity are measured. Similar studies are also done on conventional electropolishing (EP) for comparison. It is revealed that cathode shape has dominant effects for BEP especially on the obtaining of a suitable polishing condition and a uniform polishing rate in an Nb SRF single cell cavity. EP appears to have the same tendency. This paper demonstrates that a more homogeneous polishing result can be obtained by optimizing the electric field distribution inside the cavity through the modification of the cathode shape given the conditions that temperature and electrolyte flow are kept constant. Electric field distribution and electrolyte flow patterns inside the cavity are simulated via Poisson-Superfish and Solidworks respectively. With the optimal cathode shape, BEP shows a much faster polishing rate of ∼2.5 μm/min and is able to produce a smoother surface finish in the treatments of single cell cavities in comparison with EP.

Blowing bubbles in Lennard-Jonesium along the saturation curve.

PubMed

Ashbaugh, Henry S

2009-05-28

Extensive molecular simulations of the Lennard-Jones fluid have been performed to determine its liquid-vapor coexistence properties and solvent contact densities with cavities up to ten times the diameter of the solvent from the triple point to the critical point. These simulations are analyzed using a revised scaled-particle theory [H. S. Ashbaugh and L. R. Pratt, Rev. Mod. Phys. 78, 159 (2006)] to evaluate the thermodynamics of cavity solvation and curvature dependent interfacial properties along the saturation curve. While the thermodynamic signatures of cavity solvation are distinct from those in water, exhibiting a chemical potential dominated by a large temperature independent enthalpy, the solvent dewets cavities of increasing size similar with water near coexistence. The interfacial tension for forming a liquid-wall interface is found to be consistently greater than the liquid-vapor surface tension of the Lennard-Jones fluid by up to 10% and potentially reflects the suppression of high amplitude fluctuations at the cavity surface. The first-order curvature correction for the surface tension is negative and appears to diverge to negative infinity at temperatures approaching the critical point. Our results point to the success of the revised scaled-particle theory at bridging molecular and macroscopic descriptions of cavity solvation.

Growth of lodgepole pine stands and its relation to mountain pine beetle susceptibility

Treesearch

S.A. Mata; J.M. Schmid; W.K. Olsen

2003-01-01

Periodic diameter and basal area growth were determined for partially cut stands of lodgepole pine at five locations over approximately 10 year periods. After cutting, average diameters in the partially cut plots generally increased by 0.8 inches or more, while average diameter in the uncut controls increased by 0.6 inches or less. Diameter growth in the partially cut...

Fast discharge in a spherical cavity

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

Antsiferov, P. S., E-mail: Ants@isan.troitsk.ru; Dorokhin, L. A.

2014-04-15

The work is devoted to the study of the plasma, created by a fast discharge in a spherical cavity. The discharge was driven by an inductive storage with plasma erosion opening switch (dI/dt ∼10{sup 12} A/s). The plasma was produced in a spherical cavity (alumina, 11 mm diameter). Xe, Ar, and He at the pressure 80 Pa were used as working gases. The time evolution of the spatial structure and of extreme ultraviolet (EUV) spectra of the discharge plasma was studied by means of micro channel plate detector. The discharges with Xe and Ar resulted in the stable appearance of the spherically shapedmore » plasma with the diameter about 1–3 mm. The plasma emission in the EUV region lasts ∼500 ns. The EUV spectrum of Ar discharge at the moment of maximum of the electron temperature T{sub e} contains the lines of Ar X (ionization potential 478.7 eV), that indicates a value of T{sub e} in the range 50–100 eV. The mechanism of plasma appearance can be the cumulation of the convergent spherical shock wave, generated by fast heat deposition and magnetic pressure in working media near the inner surface of the discharge volume.« less

Experimental characterization of HOTNES: A new thermal neutron facility with large homogeneity area

NASA Astrophysics Data System (ADS)

Bedogni, R.; Sperduti, A.; Pietropaolo, A.; Pillon, M.; Pola, A.; Gómez-Ros, J. M.

2017-01-01

A new thermal neutron irradiation facility, called HOTNES (HOmogeneous Thermal NEutron Source), was established in the framework of a collaboration between INFN-LNF and ENEA-Frascati. HOTNES is a polyethylene assembly, with about 70 cmx70 cm square section and 100 cm height, including a large, cylindrical cavity with diameter 30 cm and height 70 cm. The facility is supplied by a 241Am-B source located at the bottom of this cavity. The facility was designed in such a way that the iso-thermal-fluence surfaces, characterizing the irradiation volume, coincide with planes parallel to the cavity bottom. The thermal fluence rate across a given isofluence plane is as uniform as 1% on a disk with 30 cm diameter. Thermal fluence rate values from about 700 cm-2 s-1 to 1000 cm-2 s-1 can be achieved. The facility design, previously optimized by Monte Carlo simulation, was experimentally verified. The following techniques were used: gold activation foils to assess the thermal fluence rate, semiconductor-based active detector for mapping the irradiation volume, and Bonner Sphere Spectrometer to determine the complete neutron spectrum. HOTNES is expected to be attractive for the scientific community involved in neutron metrology, neutron dosimetry and neutron detector testing.

Cucurbit[7]uril Enables Multi-Stimuli-Responsive Release from the Self-Assembled Hydrophobic Phase of a Metal Organic Polyhedron.

PubMed

Samanta, Soumen K; Quigley, Jeffrey; Vinciguerra, Brittany; Briken, Volker; Isaacs, Lyle

2017-07-05

Mixed self-assembly of ligands 1, 2, 1,6-hexanediamine (HDA), and Pd(NO 3 ) 2 afforded Fujita-type metal organic polyhedron MOP1 (diameter ≈ 8.2 nm), which is covalently functionalized with an average of 18 cucurbit[7]uril (CB[7]) units, as evidenced by 1 H NMR, diffusion-ordered spectroscopy NMR, and transmission electron microscopy measurements. By virtue of the host-guest properties of CB[7], the inner cavity of MOP can be rendered hydrophobic by using octadecyl HDA (3) as guest during the self-assembly process. The hydrophobic cavity was successfully utilized to trap the hydrophobic dye Nile Red (NR) and the anticancer drug doxorubicin (DOX). The stimuli-responsive release of encapsulated NR or DOX occurs (1) upon addition of a competitive binder (e.g., adamantane ammonium (ADA)) for CB[7], (2) by a dual pH-chemical stimulus involving the protonation state change of adamantane carboxylate at pH 5.8, and (3) by a dual pH-photochemical stimulus involving photoisomerization of trans-6 to cis-6 at pH 5.8. NR is released from NR@MOP2 within HeLa cancer cells. This body of work suggests that the covalent attachment of cucurbit[n]uril to metal organic polyhedra constitutes a promising vehicle for the development of both diagnostic and therapeutic nanoparticles.

Assessment by Monte Carlo computer simulations of the phase behavior of hard spherocylinders confined within cylindrical cavities.

PubMed

Viveros-Méndez, Perla X; Gil-Villegas, Alejandro; Aranda Espinoza, Said

2017-12-21

The phase behavior of hard spherocylinders (HSCs) confined in cylindrical cavities is studied using Monte Carlo simulations in the canonical ensemble. Results are presented for different values of the particles' aspect ratio l/σ, where l and σ are the length and diameter of the cylinder and hemispherical caps, respectively. Finite cavities with periodic boundary conditions along the principal axis of the cavities have been considered, where the cavity's principal axis is along the z-direction. We first focus our study in the structure induced by varying the degree of confinement, determining the HSC phase diagram for aspect ratios l/σ = 3, 5, 7, and 9, at a fixed packing fraction η = 0.071. By compressing the cavities along the radial direction, the isotropic phase becomes stable before the nematic phase as the length of the cavities is increased, resulting in a second-order transition. The occurrence of phase transitions has also been determined by varying η for constant values of the cavity's length L. Systems with low aspect ratios, l/σ = 3, 5, 7, and 9, exhibit first-order transitions with chiral, paranematic, and isotropic phases, whereas for larger HSCs, l/σ = 50, 70, and 100, the transitions are second order with paranematic, nematic, and isotropic phases, in contrast with the behavior of non-confined systems, with first-order transitions for isotropic, nematic, smectic-A, and solid phases.

Large-Scale Impact Cratering and Early Earth Evolution

NASA Technical Reports Server (NTRS)

Grieve, R. A. F.; Cintala, M. J.

1997-01-01

The surface of the Moon attests to the importance of large-scale impact in its early crustal evolution. Previous models of the effects of a massive bombardment on terrestrial crustal evolution have relied on analogies with the Moon, with allowances for the presence of water and a thinner lithosphere. It is now apparent that strict lunar-terrestrial analogies are incorrect because of the "differential scaling" of crater dimensions and melt volumes with event size and planetary gravity. Impact melt volumes and "ancient cavity dimensions for specific impacts were modeled according to previous procedures. In the terrestrial case, the melt volume (V(sub m)) exceeds that of the transient cavity (V(sub tc)) at diameters > or = 400 km. This condition is reached on the Moon only with transient cavity diameters > or = 3000 km, equivalent to whole Moon melting. The melt volumes in these large impact events are minimum estimates, since, at these sizes, the higher temperature of the target rocks at depth will increase melt production. Using the modification-scaling relation of Croft, a transient cavity diameter of about 400 km in the terrestrial environment corresponds to an expected final impact "basin" diameter of about 900 km. Such a "basin" would be comparable in dimensions to the lunar basin Orientale. This 900-km "basin" on the early Earth, however, would not have had the appearance of Orientale. It would have been essentially a melt pool, and, morphologically, would have had more in common with the palimpsests structures on Callisto and Ganymede. With the terrestrial equivalents to the large multiring basins of the Moon being manifested as muted palimpsest-like structures filled with impact melt, it is unlikely they played a role in establishing the freeboard on the early Earth. The composition of the massive impact melt sheets (> 10 (exp 7) cu km) produced in "basin-forming" events on the early Earth would have most likely ranged from basaltic to more mafic for the largest impacts, where the melt volume would have reached well into the mantle. Any contribution from adiabatic melting or shock heating of the asthenosphere would have had similar mafic compositions. The depth of the melt sheets is unknown but would have been in the multilkilometer range. Bodies of basaltic melt > or = 300 m thick differentiate in the terrestrial environment, with the degree of differentiation being a function of the thickness of the body. We therefore expect that these thick, closed-system melt pools would have differentiated into an ultramafic-mafic base and felsic top. If only 10% of the impact melt produced in a single event creating a 400-km diameter transient cavity evolved into felsic differentiates, they would be comparable in volume to the Columbia River basalts. It has been estimated that at least 200 impact events of this size or larger occurred on the early Earth during a period of heavy bombardment. We speculate that these massive differentiated melt sheets may have had a role in the formation of the initial felsic component of the Earth's crust. Additional information is contained in the original.

Proof-of-principle demonstration of Nb3Sn superconducting radiofrequency cavities for high Q0 applications

NASA Astrophysics Data System (ADS)

Posen, S.; Liepe, M.; Hall, D. L.

2015-02-01

Many future particle accelerators require hundreds of superconducting radiofrequency (SRF) cavities operating with high duty factor. The large dynamic heat load of the cavities causes the cryogenic plant to make up a significant part of the overall cost of the facility. This contribution can be reduced by replacing standard niobium cavities with ones coated with a low-dissipation superconductor such as Nb3Sn. In this paper, we present results for single cell cavities coated with Nb3Sn at Cornell. Five coatings were carried out, showing that at 4.2 K, high Q0 out to medium fields was reproducible, resulting in an average quench field of 14 MV/m and an average 4.2 K Q0 at quench of 8 × 109. In each case, the peak surface magnetic field at quench was well above Hc1, showing that it is not a limiting field in these cavities. The coating with the best performance had a quench field of 17 MV/m, exceeding gradient requirements for state-of-the-art high duty factor SRF accelerators. It is also shown that—taking into account the thermodynamic efficiency of the cryogenic plant—the 4.2 K Q0 values obtained meet the AC power consumption requirements of state-of-the-art high duty factor accelerators, making this a proof-of-principle demonstration for Nb3Sn cavities in future applications.

Large-scale testing of in-vessel debris cooling through external flooding of the reactor pressure vessel in the CYBL facility

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

Chu, T.Y.; Bentz, J.H.; Bergeron, K.D.

1994-04-01

The possibility of achieving in-vessel core retention by flooding the reactor cavity, or the ``flooded cavity``, is an accident management concept currently under consideration for advanced light water reactors (ALWR), as well as for existing light water reactors (LWR). The CYBL (CYlindrical BoiLing) facility is a facility specifically designed to perform large-scale confirmatory testing of the flooded cavity concept. CYBL has a tank-within-a-tank design; the inner 3.7 m diameter tank simulates the reactor vessel, and the outer tank simulates the reactor cavity. The energy deposition on the bottom head is simulated with an array of radiant heaters. The array canmore » deliver a tailored heat flux distribution corresponding to that resulting from core melt convection. The present paper provides a detailed description of the capabilities of the facility, as well as results of recent experiments with heat flux in the range of interest to those required for in-vessel retention in typical ALWRs. The paper concludes with a discussion of other experiments for the flooded cavity applications.« less

Molecular Structure and Equilibrium Forces of Bovine Submaxillary Mucin Adsorbed at a Solid-Liquid Interface.

PubMed

Zappone, Bruno; Patil, Navinkumar J; Madsen, Jan B; Pakkanen, Kirsi I; Lee, Seunghwan

2015-04-21

By combining dynamic light scattering, circular dichroism spectroscopy, atomic force microscopy, and surface force apparatus, the conformation of bovine submaxillary mucin in dilute solution and nanomechanical properties of mucin layers adsorbed on mica have been investigated. The samples were prepared by additional chromatographic purification of commercially available products. The mucin molecule was found to have a z-average hydrodynamic diameter of ca. 35 nm in phosphate buffered solution, without any particular secondary or tertiary structure. The contour length of the mucin is larger than, yet of the same order of magnitude as the diameter, indicating that the molecule can be modeled as a relatively rigid polymeric chain due to the large persistence length of the central glycosylated domain. Mucin molecules adsorbed abundantly onto mica from saline buffer, generating polymer-like, long-ranged, repulsive, and nonhysteretic forces upon compression of the adsorbed layers. Detailed analysis of such forces suggests that adsorbed mucins had an elongated conformation favored by the stiffness of the central domain. Acidification of aqueous media was chosen as means to reduce mucin-mucin and mucin-substrate electrostatic interactions. The hydrodynamic diameter in solution did not significantly change when the pH was lowered, showing that the large persistence length of the mucin molecule is due to steric hindrance between sugar chains, rather than electrostatic interactions. Remarkably, the force generated by an adsorbed layer with a fixed surface coverage also remained unaltered upon acidification. This observation can be linked to the surface-protective, pH-resistant role of bovine submaxillary mucin in the variable environmental conditions of the oral cavity.

Dimensional analysis of the endometrial cavity: how many dimensions should the ideal intrauterine device or system have?

PubMed

Goldstuck, Norman D

2018-01-01

The geometrical shape of the human uterus most closely approximates that of a prolate ellipsoid. The endometrial cavity itself is more likely to also have the shape of a prolate ellipsoid especially when the extension of the cervix is omitted. Using this information and known endometrial cavity volumes and lateral and vertical dimensions, it is possible to calculate the anteroposterior (AP) dimensions and get a complete evaluation of all possible dimensions of the endometrial cavity. These are singular observations and not part of any other study. The AP dimensions of the endometrial cavity of the uterus were calculated using the formula for the volume of the prolate ellipsoid to complete a three-dimensional picture of the endometrial cavity. Calculations confirm ultrasound imaging which shows large variations in cavity size and shape. Known cavity volumes and length and breadth measurements indicate that the AP diameter may vary from 6.29 to 38.2 mm. These measurements confirm the difficulty of getting a fixed-frame intrauterine device (IUD) to accommodate to a space of highly variable dimensions. This is especially true of three-dimension IUDs. A one-dimensional frameless IUD is most likely to be able to conform to this highly variable space and shape. The endometrial cavity may assume many varied prolate ellipsoid configurations where one or more measurements may be too small to accommodate standard IUDs. A one-dimensional device is most likely to be able to be accommodated by most uterine cavities as compared to two- and three-dimensional devices.

Insensitive detonator apparatus for initiating large failure diameter explosives

DOEpatents

Perry, III, William Leroy

2015-07-28

A munition according to a preferred embodiment can include a detonator system having a detonator that is selectively coupled to a microwave source that functions to selectively prime, activate, initiate, and/or sensitize an insensitive explosive material for detonation. The preferred detonator can include an explosive cavity having a barrier within which an insensitive explosive material is disposed and a waveguide coupled to the explosive cavity. The preferred system can further include a microwave source coupled to the waveguide such that microwaves enter the explosive cavity and impinge on the insensitive explosive material to sensitize the explosive material for detonation. In use the preferred embodiments permit the deployment and use of munitions that are maintained in an insensitive state until the actual time of use, thereby substantially preventing unauthorized or unintended detonation thereof.

A mini-cavity probe reactor.

NASA Technical Reports Server (NTRS)

Hyland, R. E.

1971-01-01

The mini-cavity reactor is a rocket engine concept which combines the high specific impulse from a central gaseous fueled cavity (0.6 m diam) and NERVA type fuel elements in a driver region that is external to a moderator-reflector zone to produce a compact light weight reactor. The overall dimension including a pressure vessel that is located outside of the spherical reactor is approximately 1.21 m in diameter. Specific impulses up to 2000 sec are obtainable for 220 to 890 N of thrust with pressures less than 1000 atm. Powerplant weights including a radiator for disposing of the power in the driver region are between 4600 and 32,000 kg - less than payloads of the shuttle. This reactor could also be used as a test reactor for gas-core, MHD, breeding and materials research.

Adiabatic transfer of energy fluctuations between membranes inside an optical cavity

NASA Astrophysics Data System (ADS)

Garg, Devender; Chauhan, Anil K.; Biswas, Asoka

2017-08-01

A scheme is presented for the adiabatic transfer of average fluctuations in the phonon number between two membranes in an optical cavity. We show that by driving the cavity modes with external time-delayed pulses, one can obtain an effect analogous to stimulated Raman adiabatic passage in the atomic systems. The adiabatic transfer of fluctuations from one membrane to the other is attained through a "dark" mode, which is robust against decay of the mediating cavity mode. The results are supported with analytical and numerical calculations with experimentally feasible parameters.

Atom detection and photon production in a scalable, open, optical microcavity.

PubMed

Trupke, M; Goldwin, J; Darquié, B; Dutier, G; Eriksson, S; Ashmore, J; Hinds, E A

2007-08-10

A microfabricated Fabry-Perot optical resonator has been used for atom detection and photon production with less than 1 atom on average in the cavity mode. Our cavity design combines the intrinsic scalability of microfabrication processes with direct coupling of the cavity field to single-mode optical waveguides or fibers. The presence of the atom is seen through changes in both the intensity and the noise characteristics of probe light reflected from the cavity input mirror. An excitation laser passing transversely through the cavity triggers photon emission into the cavity mode and hence into the single-mode fiber. These are first steps toward building an optical microcavity network on an atom chip for applications in quantum information processing.

Cavitation induced by high speed impact of a solid surface on a liquid jet

NASA Astrophysics Data System (ADS)

Farhat, Mohamed; Tinguely, Marc; Rouvinez, Mathieu

2009-11-01

A solid surface may suffer from severe erosion if it impacts a liquid jet at high speed. The physics behind the erosion process remains unclear. In the present study, we have investigated the impact of a gun bullet on a laminar water jet with the help of a high speed camera. The bullet has a flat front and 11 mm diameter, which is half of jet diameter. The impact speed was varied between 200 and 500 ms-1. Immediately after the impact, a systematic shock wave and high speed jetting were observed. As the compression waves reflect on the jet boundary, a spectacular number of vapour cavities are generated within the jet. Depending on the bullet velocity, these cavities may grow and collapse violently on the bullet surface with a risk of cavitation erosion. We strongly believe that this transient cavitation is the main cause of erosion observed in many industrial applications such as Pelton turbines.

Space shuttle orbit maneuvering engine reusable thrust chamber program

NASA Technical Reports Server (NTRS)

Senneff, J. M.

1975-01-01

Reusable thrust chamber and injector concepts were evaluated for the space shuttle orbit maneuvering engine (OME). Parametric engine calculations were carried out by computer program for N2O4/amine, LOX/amine and LOX/hydrocarbon propellant combinations for engines incorporating regenerative cooled and insulated columbium thrust chambers. The calculation methods are described including the fuel vortex film cooling method of combustion gas temperature control, and performance prediction. A method of acceptance of a regeneratively cooled heat rejection reduction using a silicone oil additive was also demonstrated by heated tube heat transfer testing. Regeneratively cooled thrust chamber operation was also demonstrated where the injector was characterized for the OME application with a channel wall regenerative thrust chamber. Bomb stability testing of the demonstration chambers/injectors demonstrated recovery for the nominal design of acoustic cavities. Cavity geometry changes were also evaluated to assess their damping margin. Performance and combustion stability was demonstrated of the originally developed 10 inch diameter combustion pattern operating in an 8 inch diameter thrust chamber.

Classification of reflected signals from cavitated tooth surfaces using an artificial intelligence technique incorporating a fiber optic displacement sensor

NASA Astrophysics Data System (ADS)

Rahman, Husna Abdul; Harun, Sulaiman Wadi; Arof, Hamzah; Irawati, Ninik; Musirin, Ismail; Ibrahim, Fatimah; Ahmad, Harith

2014-05-01

An enhanced dental cavity diameter measurement mechanism using an intensity-modulated fiber optic displacement sensor (FODS) scanning and imaging system, fuzzy logic as well as a single-layer perceptron (SLP) neural network, is presented. The SLP network was employed for the classification of the reflected signals, which were obtained from the surfaces of teeth samples and captured using FODS. Two features were used for the classification of the reflected signals with one of them being the output of a fuzzy logic. The test results showed that the combined fuzzy logic and SLP network methodology contributed to a 100% classification accuracy of the network. The high-classification accuracy significantly demonstrates the suitability of the proposed features and classification using SLP networks for classifying the reflected signals from teeth surfaces, enabling the sensor to accurately measure small diameters of tooth cavity of up to 0.6 mm. The method remains simple enough to allow its easy integration in existing dental restoration support systems.

A blackbody-pumped CO2-N2 transfer laser

NASA Astrophysics Data System (ADS)

Deyoung, R. J.; Higdon, N. S.

1984-08-01

A compact blackbody-pumped CO2-N2 transfer laser was constructed and the significant operating parameters were investigated. Lasing was achieved at 10.6 microns by passing preheated N2 through a 1.5-mm-diameter nozzle to a laser cavity where the N2 was mixed with CO2 and He. An intrinsic efficiency of 0.7 percent was achieved for an oven temperature of 1473 K and N2 oven pressure of 440 torr. The optimum laser cavity consisted of a back mirror with maximum reflectivity and an output mirror with 97.5-percent reflectivity. The optimum gas mixture was 1CO2/.5He/6N2. The variation of laser output was measured as a function of oven temperature, nozzle diameter, N2 oven pressure, He and CO2 partial pressures, nozzle-to-oven separation, laser cell temperature, and output laser mirror reflectivity. With these parameters optimized, outputs approaching 1.4 watts were achieved.

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

NASA Technical Reports Server (NTRS)

1983-01-01

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

Modification of multi-ring basins - The Imbrium model

NASA Technical Reports Server (NTRS)

Whitford-Stark, J. L.

1981-01-01

It is shown that the gross variations in wall height around Imbrium result largely from intersection of the Imbrium basin with pre-existing basins and faulting: angle of impact and slumping played a lesser modifying role. The gross irregularities in plan of the northern part of Imbrium is hypothesized to result from the collapse of large crustal blocks into the Imbrium and Serenitatis cavities. Lithosphere thickness is believed to play an important role in the mechanisms of formation and modification of large craters and basins. The deduction of slow sub-lithospheric flow of material toward the cavity centers does not lend support to the tsunami model, requires a minor modification of the nested-crater model and provides a mechanism for the production of megaterraces. Spatial and temporal lithosphere variations satisfy constraints requiring the overlap of morphology/diameter characteristics, variable onset diameters between planets, variable ring spacings from planet to planet and provide a mechanism for producing local irregularities in ring structures.

A blackbody-pumped CO2-N2 transfer laser

NASA Technical Reports Server (NTRS)

Deyoung, R. J.; Higdon, N. S.

1984-01-01

A compact blackbody-pumped CO2-N2 transfer laser was constructed and the significant operating parameters were investigated. Lasing was achieved at 10.6 microns by passing preheated N2 through a 1.5-mm-diameter nozzle to a laser cavity where the N2 was mixed with CO2 and He. An intrinsic efficiency of 0.7 percent was achieved for an oven temperature of 1473 K and N2 oven pressure of 440 torr. The optimum laser cavity consisted of a back mirror with maximum reflectivity and an output mirror with 97.5-percent reflectivity. The optimum gas mixture was 1CO2/.5He/6N2. The variation of laser output was measured as a function of oven temperature, nozzle diameter, N2 oven pressure, He and CO2 partial pressures, nozzle-to-oven separation, laser cell temperature, and output laser mirror reflectivity. With these parameters optimized, outputs approaching 1.4 watts were achieved.

Classification of reflected signals from cavitated tooth surfaces using an artificial intelligence technique incorporating a fiber optic displacement sensor.

PubMed

Rahman, Husna Abdul; Harun, Sulaiman Wadi; Arof, Hamzah; Irawati, Ninik; Musirin, Ismail; Ibrahim, Fatimah; Ahmad, Harith

2014-05-01

An enhanced dental cavity diameter measurement mechanism using an intensity-modulated fiber optic displacement sensor (FODS) scanning and imaging system, fuzzy logic as well as a single-layer perceptron (SLP) neural network, is presented. The SLP network was employed for the classification of the reflected signals, which were obtained from the surfaces of teeth samples and captured using FODS. Two features were used for the classification of the reflected signals with one of them being the output of a fuzzy logic. The test results showed that the combined fuzzy logic and SLP network methodology contributed to a 100% classification accuracy of the network. The high-classification accuracy significantly demonstrates the suitability of the proposed features and classification using SLP networks for classifying the reflected signals from teeth surfaces, enabling the sensor to accurately measure small diameters of tooth cavity of up to 0.6 mm. The method remains simple enough to allow its easy integration in existing dental restoration support systems.

Relationship between non-destructive OCT evaluation of resins composites and bond strength in a cavity

NASA Astrophysics Data System (ADS)

Bakhsh, T. A.; Sadr, A.; Shimada, Y.; Khunkar, S.; Tagami, J.; Sumi, Y.

2012-01-01

Objectives: Formation of microgaps under the composite restorations due to polymerization stress and other causes compromise the adhesion to the dental substrate and restoration durability. However, the relationship between cavity adaptation and bond strength is not clear. In this paper, we introduce a new testing method to assess cavity adaptation by swept-source optical coherence tomography (SS-OCT) and microtensile bond strength (MTBS) in the same class-I cavity. Methods: Round class-I cavities 3 mm in diameter and 1.5 mm in depth were prepared on 10 human premolars. After application of Tokuyama Bond Force adhesive, the cavities were filled by one of the two techniques; incremental technique using Estelite Sigma Quick universal composite or flowable lining using Palfique Estelite LV with bulk filling using the universal composite. Ten serial B-scan images were obtained throughout each cavity by SS-OCT. Significant peaks in the signal intensity were detected at the bonded interface of the cavity floor and to compare the different filling techniques. The specimens were later cut into beams (0.7x0.7 mm) and tested to measure MTBS at the cavity floor. Results: Flowable lining followed by bulk filling was inferior in terms of cavity adaptation and MTBS compared to the incremental technique (p<0.05, t-test). The adaptation (gap free cavity floor) and MTBS followed similar trends in both groups. Conclusion: Quantitative assessment of dental restorations by OCT can provide additional information on the performance and effectiveness of dental composites and restoration techniques. This study was supported by Global Center of Excellence, Tokyo Medical and Dental University and King Abdulaziz University.

An empirical model for transient crater growth in granular targets based on direct observations

NASA Astrophysics Data System (ADS)

Yamamoto, Satoru; Barnouin-Jha, Olivier S.; Toriumi, Takashi; Sugita, Seiji; Matsui, Takafumi

2009-09-01

The present paper describes observations of crater growth up to the time of transient crater formation and presents a new empirical model for transient crater growth as a function of time. Polycarbonate projectiles were impacted vertically into soda-lime glass sphere targets using a single-stage light-gas gun. Using a new technique with a laser sheet illuminating the target [Barnouin-Jha, O.S., Yamamoto, S., Toriumi, T., Sugita, S., Matsui, T., 2007. Non-intrusive measurements of the crater growth. Icarus, 188, 506-521], we measured the temporal change in diameter of crater cavities (diameter growth). The rate of increase in diameter at early times follows a power law relation, but the data at later times (before the end of transient crater formation) deviates from the power law relation. In addition, the power law exponent at early times and the degree of deviation from a power law at later times depend on the target. In order to interpret these features, we proposed to modify Maxwell's Z-model under the assumption that the strength of the excavation flow field decreases exponentially with time. We also derived a diameter growth model as: d(t)∝[1-exp(-βt)]γ, where d(t) is the apparent diameter of the crater cavity at time t after impact, and β and γ are constants. We demonstrated that the diameter growth model could represent well the experimental data for various targets with different target material properties, such as porosity or angle of repose. We also investigated the diameter growth for a dry sand target, which has been used to formulate previous scaling relations. The obtained results showed that the dry sand target has larger degree of deviation from a power law, indicating that the target material properties of the dry sand target have a significant effect on diameter growth, especially at later times. This may suggest that the previously reported scaling relations should be reexamined in order to account for the late-stage behavior with the effect of target material properties.

The Transition from Complex Crater to Peak-Ring Basin on the Moon: New Observations from the Lunar Orbiter Laser Altimeter (LOLA) Instrument

NASA Technical Reports Server (NTRS)

Baker, David M. H.; Head, James W.; Fassett, Caleb I.; Kadish, Seth J.; Smith, Dave E.; Zuber, Maria T.; Neumann, Gregory A.

2012-01-01

Impact craters on planetary bodies transition with increasing size from simple, to complex, to peak-ring basins and finally to multi-ring basins. Important to understanding the relationship between complex craters with central peaks and multi-ring basins is the analysis of protobasins (exhibiting a rim crest and interior ring plus a central peak) and peak-ring basins (exhibiting a rim crest and an interior ring). New data have permitted improved portrayal and classification of these transitional features on the Moon. We used new 128 pixel/degree gridded topographic data from the Lunar Orbiter Laser Altimeter (LOLA) instrument onboard the Lunar Reconnaissance Orbiter, combined with image mosaics, to conduct a survey of craters >50 km in diameter on the Moon and to update the existing catalogs of lunar peak-ring basins and protobasins. Our updated catalog includes 17 peak-ring basins (rim-crest diameters range from 207 km to 582 km, geometric mean = 343 km) and 3 protobasins (137-170 km, geometric mean = 157 km). Several basins inferred to be multi-ring basins in prior studies (Apollo, Moscoviense, Grimaldi, Freundlich-Sharonov, Coulomb-Sarton, and Korolev) are now classified as peak-ring basins due to their similarities with lunar peak-ring basin morphologies and absence of definitive topographic ring structures greater than two in number. We also include in our catalog 23 craters exhibiting small ring-like clusters of peaks (50-205 km, geometric mean = 81 km); one (Humboldt) exhibits a rim-crest diameter and an interior morphology that may be uniquely transitional to the process of forming peak rings. Comparisons of the predictions of models for the formation of peak-ring basins with the characteristics of the new basin catalog for the Moon suggest that formation and modification of an interior melt cavity and nonlinear scaling of impact melt volume with crater diameter provide important controls on the development of peak rings. In particular, a power-law model of growth of an interior melt cavity with increasing crater diameter is consistent with power-law fits to the peak-ring basin data for the Moon and Mercury. We suggest that the relationship between the depth of melting and depth of the transient cavity offers a plausible control on the onset diameter and subsequent development of peak-ring basins and also multi-ring basins, which is consistent with both planetary gravitational acceleration and mean impact velocity being important in determining the onset of basin morphological forms on the terrestrial planets.

Experimental study of cryogen spray properties for application in dermatologic laser surgery.

PubMed

Aguilar, Guillermo; Majaron, Boris; Karapetian, Emil; Lavernia, Enrique J; Nelson, J Stuart

2003-07-01

Cryogenic sprays are used for cooling human skin during laser dermatologic surgery. In this paper, six straight-tube nozzles are characterized by photographs of cryogenic spray shapes, as well as measurements of average droplet diameter, velocity, and temperature. A single-droplet evaporation model to predict average spray droplet diameter and temperature is tested using the experimental data presented here. The results show two distinct spray patterns--sprays for 1.4-mm-diameter nozzles (wide nozzles) show significantly larger average droplet diameters and higher temperatures as a function of distance from the nozzle compared with those for 0.5-0.8-mm-diameter nozzles (narrow nozzles). These results complement and support previously reported studies, indicating that wide nozzles induce more efficient heat extraction than the narrow nozzles.

Silicon-on-insulator based nanopore cavity arrays for lipid membrane investigation.

PubMed

Buchholz, K; Tinazli, A; Kleefen, A; Dorfner, D; Pedone, D; Rant, U; Tampé, R; Abstreiter, G; Tornow, M

2008-11-05

We present the fabrication and characterization of nanopore microcavities for the investigation of transport processes in suspended lipid membranes. The cavities are situated below the surface of silicon-on-insulator (SOI) substrates. Single cavities and large area arrays were prepared using high resolution electron-beam lithography in combination with reactive ion etching (RIE) and wet chemical sacrificial underetching. The locally separated compartments have a circular shape and allow the enclosure of picoliter volume aqueous solutions. They are sealed at their top by a 250 nm thin Si membrane featuring pores with diameters from 2 µm down to 220 nm. The Si surface exhibits excellent smoothness and homogeneity as verified by AFM analysis. As biophysical test system we deposited lipid membranes by vesicle fusion, and demonstrated their fluid-like properties by fluorescence recovery after photobleaching. As clearly indicated by AFM measurements in aqueous buffer solution, intact lipid membranes successfully spanned the pores. The nanopore cavity arrays have potential applications in diagnostics and pharmaceutical research on transmembrane proteins.

Onyx embolization of an intraosseous pseudoaneurysm of the middle meningeal artery in a patient with meningiomatosis, McCune-Albright syndrome, and gray platelet syndrome.

PubMed

Settecase, Fabio; Nicholson, Andrew D; Amans, Matthew R; Higashida, Randall T; Halbach, Van V; Cooke, Daniel L; Dowd, Christopher F; Hetts, Steven W

2016-03-01

A 13-year-old boy with meningiomatosis, McCune-Albright syndrome, and gray platelet syndrome presented with an enlarging "lump" on his right forehead. A head CT scan revealed a polyostotic fibrous dysplasia involving the entire skull. A 3.4-cm right frontal osseous cavity and an overlying right forehead subcutaneous soft-tissue mass were seen, measuring 5.2 cm in diameter and 1.6 cm thick. Ultrasound of the cavity and overlying mass showed swirling of blood and an arterialized waveform. MRI revealed an en plaque meningioma underlying the cavity. An intraosseous pseudoaneurysm fed by 3 distal anterior division branches of the right middle meningeal artery (MMA) with contrast extravasation was found on angiography. Two MMA feeders were embolized with Onyx, with anterograde filling of the intraosseous cavity with Onyx. A small pocket of residual intracavity contrast filling postembolization from a smaller third MMA feeder eventually thrombosed and the forehead lump regressed.

Cylindrical acoustic levitator/concentrator having non-circular cross-section

DOEpatents

Kaduchak, Gregory; Sinha, Dipen N.

2003-11-11

A low-power, inexpensive acoustic apparatus for levitation and/or concentration of aerosols and small liquid/solid samples having particulates up to several millimeters in diameter in air or other fluids is described. It is constructed from a commercially available, hollow piezoelectric crystal which has been formed with a cylindrical cross-section to tune the resonance frequency of the breathing mode resonance of the crystal to that of the interior cavity of the cylinder. When the resonance frequency of the interior cylindrical cavity is matched to the breathing mode resonance of the cylindrical piezoelectric transducer, the acoustic efficiency for establishing a standing wave pattern in the cavity is high. By deforming the circular cross-section of the transducer, the acoustic force is concentrated along axial regions parallel to the axis of the transducer. The cylinder does not require accurate alignment of a resonant cavity. The concentrated regions of acoustic force cause particles in the fluid to concentrate within the regions of acoustic force for separation from the fluid.

Shell-NASA Vibration-Based Damage Characterization

NASA Technical Reports Server (NTRS)

Rollins, John M.

2014-01-01

This article describes collaborative research between Shell International Exploration and Production (IE&P) scientists and ISAG personnel to investigate the feasibility of ultrasonic-based characterization of spacecraft tile damage for in-space inspection applications. The approach was proposed by Shell personnel in a Shell-NASA "speed-matching" session in early 2011 after ISAG personnel described challenges inherent in the inspection of MMOD damage deep within spacecraft thermal protection system (TPS) tiles. The approach leveraged Shell's relevant sensor and analytical expertise. The research addressed the difficulties associated with producing 3D models of MMOD damage cavities under the surface of a TPS tile, given that simple image-based sensing is constrained by line of sight through entry holes that have diameters considerably smaller than the underlying damage cavities. Damage cavity characterization is needed as part of a vehicle inspection and risk reduction capability for long-duration, human-flown space missions. It was hoped that cavity characterization could be accomplished through the use of ultrasonic techniques that allow for signal penetration through solid material.

The behavior of glass fibers in the rat following intraperitoneal injection.

PubMed

Collier, C G; Morris, K J; Launder, K A; Humphreys, J A; Morgan, A; Eastes, W; Townsend, S

1994-12-01

Potential carcinogenicity of fibers is believed to be determined by three factors: the dose, dimensions and durability of the fibers concerned. Currently there is considerable debate on the appropriateness of using results from intraperitoneal (i.p.) injection studies to predict the potential carcinogenicity of airborne fibers following inhalation. For ip results to have any significance to potential inhalation hazards, there should be some relation between the biopersistence, dose, and dose distribution of fibers in the serosal cavity and in the lung. Preliminary results on the durability of one experimental glass fiber in the peritoneal cavity suggest differences in dissolution when compared with durability in the lung. In the lung, the diameters of the long fibers (> 20 microns) were observed to decline at a rate consistent with their exposure to a neutral pH environment. The diameter of shorter fibers declined much more slowly, consistent with exposure to a more acidic environment such as is found in the phagolysosomes of alveolar macrophages. In the peritoneal cavity all fibers, regardless of length, dissolved at the same rate as short fibers in the lung. The effect of dose on the distribution of fibers in the peritoneal cavity was investigated using similar experimental glass fibers and compared with that of a powder made from ground fibers. For both materials at doses up to 1.5 mg, material was taken up by the peritoneal organs roughly in proportion to their surface area. This uptake was complete 1-2 days after injection. At higher doses, the majority of the material in excess of this 1.5 mg formed clumps of fibers (nodules) which were either free in the peritoneal cavity or loosely bound to peritoneal organs. These nodules displayed classic foreign body reactions with an associated granulomatous inflammatory response. The findings on both durability in the peritoneal cavity and the presence of two distinct populations of material following i.p. injection have implications for the justification of the use of i.p. injections to assess potential carcinogenicity of fibers following inhalation.

Diode-pumped Alexandrite laser with passive SESAM Q-switching and wavelength tunability

NASA Astrophysics Data System (ADS)

Parali, Ufuk; Sheng, Xin; Minassian, Ara; Tawy, Goronwy; Sathian, Juna; Thomas, Gabrielle M.; Damzen, Michael J.

2018-03-01

We report the first experimental demonstration of a wavelength tunable passively Q-switched red-diode-end pumped Alexandrite laser using a semiconductor saturable absorber mirror (SESAM). We present the results of the study of passive SESAM Q-switching and wavelength-tuning in continuous diode-pumped Alexandrite lasers in both linear cavity and X-cavity configurations. In the linear cavity configuration, pulsed operation up to 27 kHz repetition rate in fundamental TEM00 mode was achieved and maximum average power was 41 mW. The shortest pulse generated was 550 ns (FWHM) and the Q-switched wavelength tuning band spanned was between 740 nm and 755 nm. In the X-cavity configuration, a higher average power up to 73 mW, and obtained with higher pulse energy 6 . 5 μJ at 11.2 kHz repetition rate, in fundamental TEM00 mode with excellent spatial quality M2 < 1 . 1. The Q-switched wavelength tuning band spanned was between 775 nm and 781 nm.

Behavior of a Light Solid in a Rotating Horizontal Cylinder with Liquid Under Vibration

NASA Astrophysics Data System (ADS)

Karpunin, I. E.; Kozlova, A. N.; Kozlov, N. V.

2018-06-01

Dynamics of a cylindrical body in a rotating cavity is experimentally studied under transversal translational vibrations of the cavity rotation axis. Experiments are run at high rotation rate, when under the action of centrifugal force the body shifts to the rotation axis (the centrifuged state). In the absence of vibrations, the lagging rotation of the body is observed, due to the body radial shift from the axis of rotation caused by gravity. The body average rotation regime depends on the cavity rotation rate. The vibrations lead to the excitation of different regimes of body differential rotation (leading or lagging) associated with the excitation of its inertial oscillations. The dependence of the differential speed of the body rotation on the vibration frequency is investigated. The body dynamics has a complex character depending on the dimensionless vibration frequency. The analysis of body oscillation trajectory revealed that the body oscillatory motion consists of several modes, which contribute to the averaged dynamics of the body and the flows in the cavity.

Detailed Validation Assessment of Turbine Stage Disc Cavity Rotating Flows

NASA Astrophysics Data System (ADS)

Kanjiyani, Shezan

The subject of this thesis is concerned with the amount of cooling air assigned to seal high pressure turbine rim cavities which is critical for performance as well as component life. Insufficient air leads to excessive hot annulus gas ingestion and its penetration deep into the cavity compromising disc life. Excessive purge air, adversely affects performance. Experiments on a rotating turbine stage rig which included a rotor-stator forward disc cavity were performed at Arizona State University. The turbine rig has 22 vanes and 28 blades, while the rim cavity is composed of a single-tooth rim lab seal and a rim platform overlap seal. Time-averaged static pressures were measured in the gas path and the cavity, while mainstream gas ingestion into the cavity was determined by measuring the concentration distribution of tracer gas (carbon dioxide). Additionally, particle image velocimetry (PIV) was used to measure fluid velocity inside the rim cavity between the lab seal and the overlap. The data from the experiments were compared to an 360-degree unsteady RANS (URANS) CFD simulations. Although not able to match the time-averaged test data satisfactorily, the CFD simulations brought to light the unsteadiness present in the flow during the experiment which the slower response data did not fully capture. To interrogate the validity of URANS simulations in capturing complex rotating flow physics, the scope of this work also included to validating the CFD tool by comparing its predictions against experimental LDV data in a closed rotor-stator cavity. The enclosed cavity has a stationary shroud, a rotating hub, and mass flow does not enter or exit the system. A full 360 degree numerical simulation was performed comparing Fluent LES, with URANS turbulence models. Results from these investigations point to URANS state of art under-predicting closed cavity tangential velocity by 32% to 43%, and open rim cavity effectiveness by 50% compared to test data. The goal of this thesis is to assess the validity of URANS turbulence models in more complex rotating flows, compare accuracy with LES simulations, suggest CFD settings to better simulate turbine stage mainstream/disc cavity interaction with ingestion, and recommend experimentation techniques.

A study of thermal conductivity in graphene diodes and transistors with intrinsic defects and subjected to metal impurities

NASA Astrophysics Data System (ADS)

Sadeghzadeh, Sadegh; Rezapour, Navid

2016-12-01

In this paper, the effect of the presence of cavities resulting from the fabrication process and the effect of common metal impurities added during the synthesis process on the thermal conductivity of single-layer graphene sheets, diodes and transistors have been investigated by using the Reverse Non Equilibrium Molecular Dynamics (RNEMD) method. The obtained results show that thermal conductivity generally diminishes by increasing the concentration of nanoparticles and increases when porosities and impurities are at the edges of sheets. Regarding a better thermal management in graphene with the addition of nanoparticles, and considering its existing porosity, a lower thermal conductivity is achieved by adding more nanoparticles. By increasing the diameter of pores from 0.5 nm to 4.4 nm in a specific single-layer graphene sheet, thermal conductivity diminishes from 67 W/mk to 1.43 W/mk; while it diminishes from 45 to 1.0 W/mk for the same structure containing both the defects and nanoparticles over the defects. In evaluating the influences of cavities and metallic nanoparticles on thermal conductivity, it was observed that changing the share of cavities or nanoparticles has a significant effect on the thermal conductivity of graphene diodes and transistors. The rectification efficiency of diodes diminished from about 100% for the defect-free diode to about 19% for the diode containing 2 nm cavities and then increased to 75% for the diode with 5 nm cavities. While, with the increase in the concentration of iron nanoparticles, the rectification efficiency increased from about 100% for the diode with no iron particles to about 255% for the diode containing 13 wt % of iron particles. Final results demonstrate that the metallic nanoparticles and also defects with specific diameters can be effectively exploited to increase or decrease the efficiency of nanodiodes and nanotransistors. This leads to engineered design of nanodiodes and nanotransistors for various applications.

Survival and growth of black walnut families after 7 years in West Virginia

Treesearch

G. W. Wendel; Donald E. Dorn; Donald E. Dorn

1985-01-01

Average survival, 7-year stem diameter, and stem diameter growth differed significantly among 34 black walnut families planted in West Virginia. Average total height, height growth, and diameter at breast height were not significantly different among families. Families were from seed collected in West Virginia, Pennsylvania, North Carolina, and Tennessee. The 7-year...

Diameter Growth of Southern Bottomland Hardwoods

Treesearch

Henry Bull

1945-01-01

There is very little published information on average rates of diameter growth of southern bottomland hardwoods. Probably the best information of this kind is given by Winters, Putnam, and Eldredge,2 who summarize forest survey data on average rates of diameter growth for 4 size classes and 20 species or species groups (including pine and cyress), and for all species...

Height diameter relations of maple street trees

Treesearch

David J. Nowak

1990-01-01

Height and diameter measurements were taken for silver, sugar and Norway maple street trees in Rochester and Syracuse, New York. Mature silver maples proved to be the tallest of the three species. Average sugar maple height was consistently taller than Norway maple height until diameters reached 28 inches. Average mature tree height for all three species level off in...

New host record of avian tuberculosis in an American white pelican, Pelecanus erythrorhynchos

USGS Publications Warehouse

Nol, P.; Brannian, R.E.; Berlowski, B.M.; Wolcott, M.J.; Rocke, T.E.

2003-01-01

An American white pelican (P. erythrorhyncos) was captured in August 1999 in California, USA. The bird was unable to fly away or evade the boat, and showed considerable aggression when captured. Numerous multifocal, 1 mm diameter, yellow masses were observed throughout the lungs and air sacs. The liver was yellow. A 6 cm diameter, firm spherical mass was present in the abdominal cavity, distal to the liver. Aspergillus spp. were cultured from the air sac tissue. Mycobacterium avium was identified from the splenic mass.

Proof-of-principle demonstration of Nb 3Sn superconducting radiofrequency cavities for high Q 0 applications

DOE PAGES

Posen, S.; Liepe, M.; Hall, D. L.

2015-02-23

Many future particle accelerators require hundreds of superconducting radiofrequency (SRF) cavities operating with high duty factor. The large dynamic heat load of the cavities causes the cryogenic plant to make up a significant part of the overall cost of the facility. Our contribution can be reduced by replacing standard niobium cavities with ones coated with a low-dissipation superconductor such as Nb 3Sn. Here, we present results for single cell cavities coated with Nb 3Sn at Cornell. Five coatings were carried out, showing that at 4.2 K, high Q 0 out to medium fields was reproducible, resulting in an average quenchmore » field of 14 MV/m and an average 4.2 K Q 0 at quench of 8 x 10 9 . In each case, the peak surface magnetic field at quench was well above H c1, showing that it is not a limiting field in these cavities. Furthermore, the coating with the best performance had a quench field of 17 MV/m, exceeding gradient requirements for state-of-the-art high duty factor SRF accelerators. It is also shown that—taking into account the thermodynamic efficiency of the cryogenic plant—the 4.2 K Q 0 values obtained meet the AC power consumption requirements of state-of-the-art high duty factor accelerators, making this a proof-of-principle demonstration for Nb 3Sn cavities in future applications.« less

High-pulse-energy mode-locked picosecond oscillator

NASA Astrophysics Data System (ADS)

Chao, Yang; Chen, Meng; Li, Gang

2014-02-01

We report on a high-pulse-energy solid-state picosecond Nd:YVO4 oscillator with cavity-dumping. The laser is end-pumped by an 808 nm laser diode and passively mode-locked with a semiconductor saturable absorption mirror (SESAM). In pure cw-mode-locking, this laser produced 2.5 W of average power at a pulse repetition rate of 40 MHz and pulse duration around 12 ps. A cavity dumping technique using an intra-cavity BBO electro-optic crystal to which bidirectional voltage was applied was adopted, effectively improving the cavity-dumping rate. Tunable high repetition rate from 100 kHz to 1 MHz was achieved. With electro-optic cavity dumper working at 1 MHz repetition rate, we achieved average power 594 mW. The laser includes a 5 mm long, a-cut, 0.5% doped Nd:YVO4 crystal with a 5-degree angle at one end face. Laser radiation is coupled out from the crystal end face with a 5-degree angle, without requiring insertion of a thin-film polarizer (TFP), thus simplifying the laser structure. This picosecond laser system has the advantages of compact structure and high stability, providing a good oscillator for regenerative amplifiers.

Application of boundary element method to Stokes flows over a striped superhydrophobic surface with trapped gas bubbles

NASA Astrophysics Data System (ADS)

Ageev, A. I.; Golubkina, I. V.; Osiptsov, A. N.

2018-01-01

A slow steady flow of a viscous fluid over a superhydrophobic surface with a periodic striped system of 2D rectangular microcavities is considered. The microcavities contain small gas bubbles on the curved surface of which the shear stress vanishes. The general case is analyzed when the bubble occupies only a part of the cavity, and the flow velocity far from the surface is directed at an arbitrary angle to the cavity edge. Due to the linearity of the Stokes flow problem, the solution is split into two parts, corresponding to the flows perpendicular and along the cavities. Two variants of a boundary element method are developed and used to construct numerical solutions on the scale of a single cavity with periodic boundary conditions. By averaging these solutions, the average slip velocity and the slip length tensor components are calculated over a wide range of variation of governing parameters for the cases of a shear-driven flow and a pressure-driven channel flow. For a sufficiently high pressure drop in a microchannel of finite length, the variation of the bubble surface shift into the cavities induced by the streamwise pressure variation is estimated from numerical calculations.

Simultaneous Bistability of a Qubit and Resonator in Circuit Quantum Electrodynamics

NASA Astrophysics Data System (ADS)

Mavrogordatos, Th. K.; Tancredi, G.; Elliott, M.; Peterer, M. J.; Patterson, A.; Rahamim, J.; Leek, P. J.; Ginossar, E.; Szymańska, M. H.

2017-01-01

We explore the joint activated dynamics exhibited by two quantum degrees of freedom: a cavity mode oscillator which is strongly coupled to a superconducting qubit in the strongly coherently driven dispersive regime. Dynamical simulations and complementary measurements show a range of parameters where both the cavity and the qubit exhibit sudden simultaneous switching between two metastable states. This manifests in ensemble averaged amplitudes of both the cavity and qubit exhibiting a partial coherent cancellation. Transmission measurements of driven microwave cavities coupled to transmon qubits show detailed features which agree with the theory in the regime of simultaneous switching.

Development for a supercompact X -band pulse compression system and its application at SLAC

DOE PAGES

Wang, Juwen W.; Tantawi, Sami G.; Xu, Chen; ...

2017-11-09

Here, we have successfully designed, fabricated, installed, and tested a super compact X -band SLAC Energy Doubler system at SLAC. It is composed of an elegant 3 dB coupler–mode converter–polarizer coupled to a single spherical energy storage cavity with high Q 0 of 94000 and a diameter less than 12 cm. The available rf peak power of 50 MW can be compressed to a peak average power of more than 200 MW in order to double the kick for the electron bunches in a rf transverse deflector system and greatly improve the measurement resolution of both the electron bunches andmore » the x-ray free-electron laser pulses. The design physics and fabrication as well as the measurement results will be presented in detail. High-power operation has demonstrated the excellent performance of this rf compression system without rf breakdown, sign of pulse heating, and rf radiation.« less

Development for a supercompact X -band pulse compression system and its application at SLAC

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

Wang, Juwen W.; Tantawi, Sami G.; Xu, Chen

Here, we have successfully designed, fabricated, installed, and tested a super compact X -band SLAC Energy Doubler system at SLAC. It is composed of an elegant 3 dB coupler–mode converter–polarizer coupled to a single spherical energy storage cavity with high Q 0 of 94000 and a diameter less than 12 cm. The available rf peak power of 50 MW can be compressed to a peak average power of more than 200 MW in order to double the kick for the electron bunches in a rf transverse deflector system and greatly improve the measurement resolution of both the electron bunches andmore » the x-ray free-electron laser pulses. The design physics and fabrication as well as the measurement results will be presented in detail. High-power operation has demonstrated the excellent performance of this rf compression system without rf breakdown, sign of pulse heating, and rf radiation.« less

Validation of an interior noise prediction model for a composite cylinder

NASA Technical Reports Server (NTRS)

Beyer, Todd B.; Grosveld, Ferdinand W.

1987-01-01

An acoustic modal analysis has been performed in the cavity of a composite cylinder model of an aircraft fuselage. The filament wound, composite shell is 12 feet long and 5.5 feet in diameter. A one-half-in. thick plywood floor is attached to the shell 69 deg from the vertical centerline through the bottom of the shell. The acoustic modal frequencies were obtained from a sound pressure level and phase survey conducted throughout the interior volume bounded by the floor, endcaps and stiffened shell, while being excited by white noise from a loudspeaker source. The measured acoustic resonance frequencies and mode shapes compare well with analytical predictions from the Propeller Aircraft Interior Noise (PAIN) model. Details of the theory and derivation of the acoustic characteristics have been included. Reverberation time measurements, using the integrated impulse technique, have been performed to determine acoustic loss factors. These measured loss factors have been input to the PAIN program in order to more accurately predict the space-averaged interior noise of the composite cylinder.

A diameter distribution approach to estimating average stand dominant height in Appalachian hardwoods

Treesearch

John R. Brooks

2007-01-01

A technique for estimating stand average dominant height based solely on field inventory data is investigated. Using only 45.0919 percent of the largest trees per acre in the diameter distribution resulted in estimates of average dominant height that were within 4.3 feet of the actual value, when averaged over stands of very different structure and history. Cubic foot...

Formation of quasi-single crystalline porous ZnO nanostructures with a single large cavity

NASA Astrophysics Data System (ADS)

Cho, Seungho; Kim, Semi; Jung, Dae-Won; Lee, Kun-Hong

2011-09-01

We report a method for synthesizing quasi-single crystalline porous ZnO nanostructures containing a single large cavity. The microwave-assisted route consists of a short (about 2 min) temperature ramping stage (from room temperature to 120 °C) and a stage in which the temperature is maintained at 120 °C for 2 h. The structures produced by this route were 200-480 nm in diameter. The morphological yields of this method were very high. The temperature- and time-dependent evolution of the synthesized powders and the effects of an additive, vitamin C, were studied. Spherical amorphous/polycrystalline structures (70-170 nm in diameter), which appeared transitorily, may play a key role in the formation of the single crystalline porous hollow ZnO nanostructures. Studies and characterization of the nanostructures suggested a possible mechanism for formation of the quasi-single crystalline porous ZnO nanostructures with an interior space.We report a method for synthesizing quasi-single crystalline porous ZnO nanostructures containing a single large cavity. The microwave-assisted route consists of a short (about 2 min) temperature ramping stage (from room temperature to 120 °C) and a stage in which the temperature is maintained at 120 °C for 2 h. The structures produced by this route were 200-480 nm in diameter. The morphological yields of this method were very high. The temperature- and time-dependent evolution of the synthesized powders and the effects of an additive, vitamin C, were studied. Spherical amorphous/polycrystalline structures (70-170 nm in diameter), which appeared transitorily, may play a key role in the formation of the single crystalline porous hollow ZnO nanostructures. Studies and characterization of the nanostructures suggested a possible mechanism for formation of the quasi-single crystalline porous ZnO nanostructures with an interior space. Electronic supplementary information (ESI) available: TEM images and the corresponding SAED image of a ZnO nanostructure synthesized from the reaction without l(+)-ascorbic acid at the 85 °C time point (Fig. S1). See DOI: 10.1039/c1nr10609k

Unsteady viscous calculations of supersonic flows past deep and shallow three-dimensional cavities

NASA Technical Reports Server (NTRS)

Baysal, O.; Srinivasan, S.; Stallings, R. L.

1988-01-01

Computational simulations were performed for supersonic, turbulent flows over deep and shallow three-dimensional cavities. The width and the depth of these cavities were fixed at 2.5 in. and 0.5 in., respectively. Length-to-depth ratio of the deep cavity was 6 and that of the shallow cavity was 16. Freestream values of Mach number and Reynolds number were 1.50 and 2.0 x 10 to the 6th/ft., respectively, at a total temperature of 585 R. The thickness of the turbulent boundary layer at the front lip of the cavity was 0.2 in. Simulations of these oscillatory flows were generated through time-accurate solutions of Reynolds-averaged full Navier-Stokes equations using the explicit MacCormack scheme. The solutions are validated through comparisons with experimental data. The features of open and closed cavity flows and effects of the third dimension are illustrated through computational graphics.

Scalable fabrication of coupled NV center - photonic crystal cavity systems by self-aligned N ion implantation

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

Schröder, T.; Walsh, M.; Zheng, J.

2017-04-06

Towards building large-scale integrated photonic systems for quantum information processing, spatial and spectral alignment of single quantum systems to photonic nanocavities is required. In this paper, we demonstrate spatially targeted implantation of nitrogen vacancy (NV) centers into the mode maximum of 2-d diamond photonic crystal cavities with quality factors up to 8000, achieving an average of 1.1 ± 0.2 NVs per cavity. Nearly all NV-cavity systems have significant emission intensity enhancement, reaching a cavity-fed spectrally selective intensity enhancement, F int, of up to 93. Although spatial NV-cavity overlap is nearly guaranteed within about 40 nm, spectral tuning of the NV’smore » zero-phonon-line (ZPL) is still necessary after fabrication. To demonstrate spectral control, we temperature tune a cavity into an NV ZPL, yielding F ZPL int~5 at cryogenic temperatures.« less

Munitions having an insensitive detonator system for initiating large failure diameter explosives

DOEpatents

Perry, III, William Leroy

2015-08-04

A munition according to a preferred embodiment can include a detonator system having a detonator that is selectively coupled to a microwave source that functions to selectively prime, activate, initiate, and/or sensitize an insensitive explosive material for detonation. The preferred detonator can include an explosive cavity having a barrier within which an insensitive explosive material is disposed and a waveguide coupled to the explosive cavity. The preferred system can further include a microwave source coupled to the waveguide such that microwaves enter the explosive cavity and impinge on the insensitive explosive material to sensitize the explosive material for detonation. In use the preferred embodiments permit the deployment and use of munitions that are maintained in an insensitive state until the actual time of use, thereby substantially preventing unauthorized or unintended detonation thereof.

Growth of ponderosa pine stands in relation to mountain pine beetle susceptibility

Treesearch

R. A. Obedzinski; J. M. Schmid; S. A. Mata; W. K. Olsen; R. R. Kessler

1999-01-01

Ten-year diameter and basal area growth were determined for partially cut stands at 4 locations. Average diameters in the partially cut plots generally increased by 1 inch or more, while average diameter in the uncut controls increased by 0.9 inches or less. Individual tree growth is discussed in relation to potential susceptibility to mountain pine beetle infestation...

Supersonic/Hypersonic Correlations for In-Cavity Transition and Heating Augmentation

NASA Technical Reports Server (NTRS)

Everhart, Joel L.

2011-01-01

Laminar-entry cavity heating data with a non-laminar boundary layer exit flow have been retrieved from the database developed at Mach 6 and 10 in air on large flat plate models for the Space Shuttle Return-To-Flight Program. Building on previously published fully laminar and fully turbulent analysis methods, new descriptive correlations of the in-cavity floor-averaged heating and endwall maximum heating have been developed for transitional-to-turbulent exit flow. These new local-cavity correlations provide the expected flow and geometry conditions for transition onset; they provide the incremental heating augmentation induced by transitional flow; and, they provide the transitional-to-turbulent exit cavity length. Furthermore, they provide an upper application limit for the previously developed fully-laminar heating correlations. An example is provided that demonstrates simplicity of application. Heating augmentation factors of 12 and 3 above the fully laminar values are shown to exist on the cavity floor and endwall, respectively, if the flow exits in fully tripped-to-turbulent boundary layer state. Cavity floor heating data in geometries installed on the windward surface of 0.075-scale Shuttle wind tunnel models have also been retrieved from the boundary layer transition database developed for the Return-To-Flight Program. These data were independently acquired at Mach 6 and Mach 10 in air, and at Mach 6 in CF4. The correlation parameters for the floor-averaged heating have been developed and they offer an exceptionally positive comparison to previously developed laminar-cavity heating correlations. Non-laminar increments have been extracted from the Shuttle data and they fall on the newly developed transitional in-cavity correlations, and they are bounded by the 95% correlation prediction limits. Because the ratio of specific heats changes along the re-entry trajectory, turning angle into a cavity and boundary layer flow properties may be affected, raising concerns regarding the application validity of the heating augmentation predictions.

Cellulosic nanowhiskers. Theory and application of light scattering from polydisperse spheroids in the Rayleigh-Gans-Debye regime.

PubMed

Braun, Birgit; Dorgan, John R; Chandler, John P

2008-04-01

Mathematical treatment of light scattering within the Rayleigh-Gans-Debye limit for spheroids with polydispersity in both length and diameter is developed and experimentally tested using cellulosic nanowhiskers (CNW). Polydispersity indices are obtained by fitting the theoretical formfactor to experimental data. Good agreement is achieved using a polydispersity of 2.3 for the length, independent of the type of acid used. Diameter polydispersities are 2.1 and 3.0 for sulfuric and hydrochloric acids, respectively. These polydispersities allow the determination of average dimensions from the z-average mean-square radius (z) and the weight-average molecular weight (M w) easily obtained from Berry plots. For cotton linter hydrolyzed by hydrochloric acid, the average length and diameter are 244 and 22 nm. This compares to average length and diameter of 272 and 13 nm for sulfuric acid. This study establishes a new light-scattering methodology as a quick and robust tool for size characterization of polydisperse spheroidal nanoparticles.

Use of novel nest boxes by carmine bee-eaters (Merops nubicus) in captivity.

PubMed

Elston, Jennifer J; Carney, Jennifer; Quinones, Glorieli; Sky, Christy; Plasse, Chelle; Bettinger, Tammie

2007-01-01

Carmine bee-eaters make attractive additions to zoo aviaries but breeding programs have had challenges and limited success. The objectives of this study were to document nesting behavior of Carmine bee-eaters in a captive setting and compare reproductive success between a novel nest box (plastic, 17 x 30 x 22 cm) and a PVC pipe model used previously (30 cm long, 8 cm in diameter). Three bee-eater pairs were given access to seven nest chambers (six novel boxes, one PVC model). Behavioral observations occurred during a 15-min period in the morning or afternoon before egg production and continued until chicks fledged for a total of 87 observation periods (21.75 hr). All occurrences by an individual bird entering or exiting a nest tunnel, food provision, and the time (min) spent inside a nest cavity were documented. Additionally, daily temperature within each nest chamber was recorded. Before eggs were produced the average daily temperature (23.02 degrees C) within the nest chambers did not differ, suggesting that nest cavity choice was not influenced by temperature. No differences were detected among pairs in percent of observed time spent inside their nest cavities or number of times a nest tunnel was entered during the incubation or fledging periods. During incubation females spent a greater percent of observed time inside the nest cavity than males (P=0.02). During the fledging period food provision did not differ between the pairs, however males entered their nest tunnels more often per hour than females (P=0.03), and males tended to provide food more often than females (P=0.053). Two pairs nested in novel nest boxes and successfully fledged one chick each. The pair that nested in the PVC model did not fledge a chick. A nest box that aids in keeping eggs intact is essential for breeding bee-eaters in captivity, and maintaining captive populations will provide opportunities for zoo visitors to enjoy these birds and will reduce the need to remove birds from the wild. Zoo Biol 0:1-13, 2007. (c) 2007 Wiley-Liss, Inc.

Roost selection by Rafinesque’s big-eared bats (Corynorhinus rafinesquii) in a pristine habitat at three spatial scales

USGS Publications Warehouse

Lucas, Jessica S.; Loeb, Susan C.; Jodice, Patrick G.R.

2015-01-01

Although several studies have described roost use by Rafinesque's big-eared bats (Corynorhinus rafinesquii), few studies have examined roost selection. We examined roost use and selection by Rafinesque's big-eared bat at the tree, stand, and landscape scales during the maternity season in pristine old-growth habitat in the Coastal Plain of South Carolina. We located 43 roosts (14 maternity, 29 solitary) through cavity searches and radio-telemetry. Maternity colonies and solitary individuals selected roosts based on similar characteristics. The best model explaining roost selection by all bats included tree and stand characteristics; landscape factors had little influence on roost use. Bats selected large diameter trees in areas with a high density of trees with cavities in the surrounding area. Most roosts (67.4%) were in water tupelo (Nyssa aquatica) in semi-permanently flooded and saturated areas. Half of maternity roost cavities had upper bole openings whereas only 25.8% of solitary roosts had upper bole openings. Bats that roosted with maternity groups stayed in roosts for significantly shorter periods of time (1.3 ± 0.1 days) and used significantly more roost trees (5.0 ± 0.6 roosts) than adult males (3.8 ± 1.10 days, 2.3 ± 0.4 roosts, respectively). Maternity colony use of cavities with upper bole openings and shorter residency times suggest that predator avoidance may have been an important factor governing roosting behavior of maternity colonies in this area. Our results suggest that retention of large diameter, hollow trees in wetland areas will benefit Rafinesque's big-eared bat individuals and maternity colonies in this area.

Flowable resin and marginal gap on tooth third medial cavity involving enamel and radicular cementum: a SEM evaluation of two restoration techniques.

PubMed

Lo Giudice, G; Cicciù, M; Cervino, G; Lizio, A; Visco, A M

2012-01-01

The aim of this study is to investigate the presence and the extent of a possible marginal gap after the interposition of a flowable composite between the composite restoration and the dental structures (enamel and cementum). This technique is also used to eliminate the infiltration in a zone of the cavity preparation that is frequently at a risk of secondary decay. Fifteen human premolars extracted for orthodontic reasons were used for the study. A cavity with mesial and distal margin in enamel and cementum was realized in every tooth. The cavities were then restored with an adhesive system (ScotchBond 3MÔ) and composite (Filtek Supreme 3MÔ); and, a fine layer of flowable composite was applied in the distal margin of each cavity. Scanning electron microscopy (SEM) in secondary electron imaging (S.E.I.) modality was used for the study and identifying the marginal gaps in the composite restorations. Data was investigated on the mesial and distal margin of each cavity at the restoration-enamel interface, and at the restoration-cementum interface. The interfaces were divided in four groups: Group A (enamel/composite); Group B (enamel/flow/composite); Group C (cementum/composite); and, Group D (cementum/flow/composite). By the comparison of the gap's average width found in each group, it is evidenced that the average width of the gap increases when the interface moves from the coronal to the radicular end (Group A 0,1 ± 0,4 μm Vs Group C 12,3 ± 11,6 μm; Group B 0,2 ± 0,8 μm Vs Group D 2,8 ± 6,6 μm). Correlating the measurements of the marginal gap's average width among the Group A and Group B, no significant variations were obtained; and instead, on comparing Group C with Group D, the gap's average width decreases. The interposition of a low elastic modulus composite between the adhesive layer and the composite resin allows an improvement of the cementum-restoration interface by the means of a lower shrinkage stress during polymerization.

Transition between bulk and surface refractive index sensitivity of micro-cavity in-line Mach-Zehnder interferometer induced by thin film deposition.

PubMed

Śmietana, Mateusz; Janik, Monika; Koba, Marcin; Bock, Wojtek J

2017-10-16

In this work we discuss the refractive index (RI) sensitivity of a micro-cavity in-line Mach-Zehnder interferometer in the form of a cylindrical hole (40-50 μm in diameter) fabricated in a standard single-mode optical fiber using a femtosecond laser. The surface of the micro-cavity was coated with up to 400 nm aluminum oxide thin film using the atomic layer deposition method. Next, the film was progressively chemically etched and the influence on changes in the RI of liquid in the micro-cavity was determined at different stages of the experiment, i.e., at different thicknesses of the film. An effect of transition between sensitivity to the film thickness (surface) and the RI of liquid in the cavity (bulk) is demonstrated for the first time. We have found that depending on the interferometer working conditions determined by thin film properties, the device can be used for investigation of phenomena taking place at the surface, such as in case of specific label-free biosensing applications, or for small-volume RI analysis as required in analytical chemistry.

Lasers with intra-cavity phase elements

NASA Astrophysics Data System (ADS)

Gulses, A. Alkan; Kurtz, Russell; Islas, Gabriel; Anisimov, Igor

2018-02-01

Conventional laser resonators yield multimodal output, especially at high powers and short cavity lengths. Since highorder modes exhibit large divergence, it is desirable to suppress them to improve laser quality. Traditionally, such modal discriminations can be achieved by simple apertures that provide absorptive loss for large diameter modes, while allowing the lower orders, such as the fundamental Gaussian, to pass through. However, modal discrimination may not be sufficient for short-cavity lasers, resulting in multimodal operation as well as power loss and overheating in the absorptive part of the aperture. In research to improve laser mode control with minimal energy loss, systematic experiments have been executed using phase-only elements. These were composed of an intra-cavity step function and a diffractive out-coupler made of a computer-generated hologram. The platform was a 15-cm long solid-state laser that employs a neodymium-doped yttrium orthovanadate crystal rod, producing 1064 nm multimodal laser output. The intra-cavity phase elements (PEs) were shown to be highly effective in obtaining beams with reduced M-squared values and increased output powers, yielding improved values of radiance. The utilization of more sophisticated diffractive elements is promising for more difficult laser systems.

Accuracy improvement of quantitative analysis by spatial confinement in laser-induced breakdown spectroscopy.

PubMed

Guo, L B; Hao, Z Q; Shen, M; Xiong, W; He, X N; Xie, Z Q; Gao, M; Li, X Y; Zeng, X Y; Lu, Y F

2013-07-29

To improve the accuracy of quantitative analysis in laser-induced breakdown spectroscopy, the plasma produced by a Nd:YAG laser from steel targets was confined by a cavity. A number of elements with low concentrations, such as vanadium (V), chromium (Cr), and manganese (Mn), in the steel samples were investigated. After the optimization of the cavity dimension and laser fluence, significant enhancement factors of 4.2, 3.1, and 2.87 in the emission intensity of V, Cr, and Mn lines, respectively, were achieved at a laser fluence of 42.9 J/cm(2) using a hemispherical cavity (diameter: 5 mm). More importantly, the correlation coefficient of the V I 440.85/Fe I 438.35 nm was increased from 0.946 (without the cavity) to 0.981 (with the cavity); and similar results for Cr I 425.43/Fe I 425.08 nm and Mn I 476.64/Fe I 492.05 nm were also obtained. Therefore, it was demonstrated that the accuracy of quantitative analysis with low concentration elements in steel samples was improved, because the plasma became uniform with spatial confinement. The results of this study provide a new pathway for improving the accuracy of quantitative analysis of LIBS.

Anatomical investigations on intraosseous access in stillborns - Comparison of different devices and techniques.

PubMed

Fuchs, Zeynep; Scaal, Martin; Haverkamp, Heinz; Koerber, Friederike; Persigehl, Thorsten; Eifinger, Frank

2018-06-01

Intraosseous (IO)-access plays an alternative route during resuscitation. Our study was performed to investigate the successful rate of IO-access in preterm and term stillborns using different devices and techniques. The cadavers used were legal donations. 16 stillborns, median: 29.2 weeks (IQR 27.2-38.4) were investigated. Two different needles (a: Butterfly needle, 21G, Venofix ® Fa.Braun; b: Arrow ® EZ-IO ® 15G, Teleflex, Dublin, Ireland) were used. Needles were inserted i: manually, using a Butterfly needle; ii: manually, using EZ-IO ® needle or iii: using a battery-powered semi-automatic drill (Arrow ® EZ-IO ® ). Spectral-CT's were performed. The diameter of the corticalis was determined from the CT-images. Successful hit rates with 95% confidence intervals (CI) and odds ratios between the three methods were estimated using a generalised linear mixed model (GLMM). Estimated success rate was 61.1% (95%CI:39.7%-78.9%) for the Butterfly needle, 43.0% (95%CI:23.4%-65.0%) for hand-twisted EZ-IO ® screwing and 39.7% (95%CI:24.1-57.7%) for the semi-automatic drill (Arrow ® EZ-IO ® ), all referring to an average diameter of the corticalis of 1.2 mm. The odds of a correct position were 2.4 times higher (95%CI:0.8-7.6) when using the Butterfly needle than with the drill. In contrast, the odds of correct positioning when inserting the needle by hand were not significantly different from using the drill (odds ratio 1.1, 95%CI: 0.4-3.3). Neither of these effects nor the diameter of the corticalis with an odds ratio near one were significant in the model. Median diameter of the bone marrow cavity was 4.0 mm [IQR 3.3-4.7]. Intraosseous access for premature and neonatal infants could be best achieved by using a manually twisted Butterfly needle. Copyright © 2018 Elsevier B.V. All rights reserved.

Tumorigenicity of fine man-made fibers after intratracheal administrations to hamsters.

PubMed

Adachi, S; Takemoto, K; Kimura, K

1991-02-01

Six types of man-made fibers were administered intratracheally (2.0 mg/animal each a week, for 5 weeks; total 10 mg/animal) to female Syrian hamsters that were observed histologically for 2 years after administration. The fibers were rock wool [average diameter (D) = 6.1 microns, average length (L) = 296 microns], fiberglass (D = 0.65 microns, L = 16.8 microns), potassium titanate fiber (D = 0.36 microns, L = 7.17 microns), calcium sulfate fiber (D = 1.0 microns, L = 17.8 microns), basic magnesium sulfate fiber (D = 0.45 microns, L = 22.4 microns), and metaphosphate fiber (D = 2.38 microns, L = 64.1 microns). Tumors were observed in hamsters that had received basic magnesium sulfate fiber (9/20), metaphosphate fiber (6/20), calcium sulfate fiber (3/20), and fiberglass (2/20) but not in the control, rock wool, or potassium titanate fiber groups. The primary sites of the tumors were not only in the pleural cavity but also in the intracelial organs, kidney, adrenal gland, bladder, and uterus. Only a few of the tumors were identified as mesotheliomas by histological examination. In addition to neoplastic lesions, fibrosis, pleural thickening, and chronic inflammatory changes in the lungs were observed in the hamsters, but these changes appeared too mild to foster a pneumoconiosis such as asbestosis.

Selected computations of transonic cavity flows

NASA Technical Reports Server (NTRS)

Atwood, Christopher A.

1993-01-01

An efficient diagonal scheme implemented in an overset mesh framework has permitted the analysis of geometrically complex cavity flows via the Reynolds averaged Navier-Stokes equations. Use of rapid hyperbolic and algebraic grid methods has allowed simple specification of critical turbulent regions with an algebraic turbulence model. Comparisons between numerical and experimental results are made in two dimensions for the following problems: a backward-facing step; a resonating cavity; and two quieted cavity configurations. In three-dimensions the flow about three early concepts of the stratospheric Observatory For Infrared Astronomy (SOFIA) are compared to wind-tunnel data. Shedding frequencies of resolved shear layer structures are compared against experiment for the quieted cavities. The results demonstrate the progress of computational assessment of configuration safety and performance.

Heating Augmentation in Laminar Flow Due to Heat-Shield Cavities on the Project Orion CEV

NASA Technical Reports Server (NTRS)

Hollis, Brian R.

2008-01-01

An experimental study has been conducted to assess the effects of compression pad cavities on the aeroheating environment of the Project Orion CEV heat-shield at laminar conditions. Testing was conducted in Mach 6 and Mach 10 perfect-gas wind tunnels to obtain heating measurements on and around the compression pads using global phosphor thermography. Consistent trends in heating augmentation levels were observed in the data and correlations of average and maximum heating at the cavities were formulated in terms of the local boundary-layer parameters and cavity dimensions. Additional heating data from prior testing of Genesis and Mars Science Laboratory models were also examined to extend the parametric range of cavity heating correlations.

Synthesis of iron oxide nanoparticles in Listeria innocua Dps (DNA-binding protein from starved cells): a study with the wild-type protein and a catalytic centre mutant.

PubMed

Ceci, Pierpaolo; Chiancone, Emilia; Kasyutich, Oksana; Bellapadrona, Giuliano; Castelli, Lisa; Fittipaldi, Maria; Gatteschi, Dante; Innocenti, Claudia; Sangregorio, Claudio

2010-01-11

A comparative analysis of the magnetic properties of iron oxide nanoparticles grown in the cavity of the DNA-binding protein from starved cells of the bacterium Listeria innocua, LiDps, and of its triple-mutant lacking the catalytic ferroxidase centre, LiDps-tm, is presented. TEM images and static and dynamic magnetic and electron magnetic resonance (EMR) measurements reveal that, under the applied preparation conditions, namely alkaline pH, high temperature (65 degrees C), exclusion of oxygen, and the presence of hydrogen peroxide, maghemite and/or magnetite nanoparticles with an average diameter of about 3 nm are mineralised inside the cavities of both LiDps and LiDps-tm. The magnetic nanoparticles (MNPs) thus formed show similar magnetic properties, with superparamagnetic behaviour above 4.5 K and a large magnetic anisotropy. Interestingly, in the EMR spectra an absorption at half-field is observed, which can be considered as a manifestation of the quantum behaviour of the MNPs. These results indicate that Dps proteins can be advantageously used for the production of nanomagnets at the interface between molecular clusters and traditional MNPs and that the presence of the ferroxidase centre, though increasing the efficiency of nanoparticle formation, does not affect the nature and fine structure of the MNPs. Importantly, the self-organisation of MNP-containing Dps on HRTEM grids suggests that Dps-enclosed MNPs can be deposited on surfaces in an ordered fashion.

Titanium based flat heat pipes for computer chip cooling

NASA Astrophysics Data System (ADS)

Soni, Gaurav; Ding, Changsong; Sigurdson, Marin; Bozorgi, Payam; Piorek, Brian; MacDonald, Noel; Meinhart, Carl

2008-11-01

We are developing a highly conductive flat heat pipe (called Thermal Ground Plane or TGP) for cooling computer chips. Conventional heat pipes have circular cross sections and thus can't make good contact with chip surface. The flatness of our TGP will enable conformal contact with the chip surface and thus enhance cooling efficiency. Another limiting factor in conventional heat pipes is the capillary flow of the working fluid through a wick structure. In order to overcome this limitation we have created a highly porous wick structure on a flat titanium substrate by using micro fabrication technology. We first etch titanium to create very tall micro pillars with a diameter of 5 μm, a height of 40 μm and a pitch of 10 μm. We then grow a very fine nano structured titania (NST) hairs on all surfaces of the pillars by oxidation in H202. In this way we achieve a wick structure which utilizes multiple length scales to yield high performance wicking of water. It's capable of wicking water at an average velocity of 1 cm/s over a distance of several cm. A titanium cavity is laser-welded onto the wicking substrate and a small quantity of water is hermetically sealed inside the cavity to achieve a TGP. The thermal conductivity of our preliminary TGP was measured to be 350 W/m-K, but has the potential to be several orders of magnitude higher.

Effect of root canal treatment procedures with a novel rotary nickel titanium instrument (TRUShape) on stress in mandibular molars: a comparative finite element analysis.

PubMed

Bonessio, Noemi; Arias, Ana; Lomiento, Guiseppe; Peters, Ove A

2017-01-01

The aim of this study was to investigate and compare, via finite element analysis (FEA), the effects of endodontic access and canal preparation on stress distribution under functional loading of a mandibular molar treated with novel (TRUShape) and conventional (Vortex) rotary root canal preparation instruments. Identical plastic mandibular molars with natural anatomy had all 4 canals shaped with either TRUShape or a conventional rotary, Vortex (#20 and #30, both by Dentsply Tulsa Dental). Finite element analysis was used to evaluate stress distribution in untreated and treated models. Micro-computed tomography (MCT) of the extracted teeth shaped in vitro was used to inform the FEA model regarding the geometry of root canals and external surfaces. Modeling the intact periodontal support and cancellous/cortical bone was based on anatomical data. Profiles of average and maximum von Mises stresses in dentin of the four treated conditions under functional loading were compared to the untreated model. This comparison was performed for each tooth model with and without root canal obturation and composite restoration. On average, the dentin sections with the most changes after preparation were located in the access cavity, with average stress increase up to +5.7, +8.5, +8.9, and +10.2 % for the TRUShape #20, Vortex #20, TRUShape #30 and Vortex #30, respectively, relative to the untreated model. Within the root canal system, the average stress differences were smaller than <5 % with lower values for TRUShape preparation. A reduction of the average stress in the access cavity was observed as an effect of the composite restoration, while about the same von Mises stress' profiles were found into the root canal. In this finite element analysis, preparation of the access cavity resulted in increased von Mises stresses under functional occlusal load. The limited (up to 0.7 %) retained radicular dentin in the TRUShape versus the Vortex cavity proved effective in reducing masticatory stresses. The bonded restoration modeled in this study only partially counterbalance the combined effects of access cavity and root canal preparation.

Quantum cooling and squeezing of a levitating nanosphere via time-continuous measurements

NASA Astrophysics Data System (ADS)

Genoni, Marco G.; Zhang, Jinglei; Millen, James; Barker, Peter F.; Serafini, Alessio

2015-07-01

With the purpose of controlling the steady state of a dielectric nanosphere levitated within an optical cavity, we study its conditional dynamics under simultaneous sideband cooling and additional time-continuous measurement of either the output cavity mode or the nanosphere’s position. We find that the average phonon number, purity and quantum squeezing of the steady-states can all be made more non-classical through the addition of time-continuous measurement. We predict that the continuous monitoring of the system, together with Markovian feedback, allows one to stabilize the dynamics for any value of the laser frequency driving the cavity. By considering state of the art values of the experimental parameters, we prove that one can in principle obtain a non-classical (squeezed) steady-state with an average phonon number {n}{ph}≈ 0.5.

Availability of nest cavity trees for wood ducks (Aix sponsa) at Sunkhaze Meadows National Wildlife Refuge, Maine

USGS Publications Warehouse

Clugston, D.A.

1999-01-01

The availability of natural cavities for cavitynesting waterfowl, especially wood ducks (Aix sponsa), was unknown ferating forest of Sunkhaze Meadows National Wildlife Refuge, ME. An assessment of cavity availability was needed to determine if the existing nesting box program should be increased. During November to March, 199697 and 199798, I sampled 56 onehalf ha random plots, stratified into 5 types (upland hardwood, upland conifer, upland mixwood, wetland conifer, and wetland hardwood) to assess availability of trees with cavities. The predominant tree species with cavities were red maple (Acer rubrum; 39%) and aspen (Populus sp.; 31%); 72% of all trees with cavities were alive. Density ees/plot averaged from 1.0 +0.4 (x +SE) in wetland softwoods to 1.9 +0.4 in upland hardwoods. This low density of potential cavity trees and the small mean dbh (39.4 +1.6 cm) indicate a young forest with few suitable cavities. Forested areas, especially hardwoods near canopy openings, need to be allowed to mature to increase the number and quality of future cavities. An expanded nest box program seems justified.

Picosecond passively mode-locked mid-infrared fiber laser

NASA Astrophysics Data System (ADS)

Wei, C.; Zhu, X.; Norwood, R. A.; Kieu, K.; Peyghambarian, N.

2013-02-01

Mode-locked mid-infrared (mid-IR) fiber lasers are of increasing interest due to their many potential applications in spectroscopic sensors, infrared countermeasures, laser surgery, and high-efficiency pump sources for nonlinear wavelength convertors. Er3+-doped ZBLAN (ZrF4-BaF2-LaF3-AlF3-NaF) fiber lasers, which can emit mid-IR light at 2.65-2.9 μm through the transition from the upper energy level 4I11/2 to the lower laser level 4I13/2, have attracted much attention because of their broad emission range, high optical efficiency, and the ready availability of diode pump lasers at the two absorption peaks of Er3+ ions (975 nm and 976 nm). In recent years, significant progress on high power Er3+- doped ZBLAN fiber lasers has been achieved and over 20 watt cw output at 2.8 μm has been demonstrated; however, there has been little progress on ultrafast mid-IR ZBLAN fiber lasers to date. We report a passively mode-locked Er3+- doped ZBLAN fiber laser in which a Fe2+:ZnSe crystal was used as the intracavity saturable absorber. Fe2+:ZnSe is an ideal material for mid-IR laser pulse generation because of its large saturable absorption cross-section and small saturation energy along with the excellent opto-mechanical (damage threshold ~2 J/cm2) and physical characteristics of the crystalline ZnSe host. A 1.6 m double-clad 8 mol% Er3+-doped ZBLAN fiber was used in our experiment. The fiber core has a diameter of 15 μm and a numerical aperture (NA) of 0.1. The inner circular cladding has a diameter of 125 μm and an NA of 0.5. Both continuous-wave and Q-switched mode-locking pulses at 2.8 μm were obtained. Continuous-wave mode locking operation with a pulse duration of 19 ps and an average power of 51 mW were achieved when a collimated beam traversed the Fe2+:ZnSe crystal. When the cavity was modified to provide a focused beam at the Fe2+:ZnSe crystal, Q-switched mode-locked operation with a pulse duration of 60 ps and an average power of 4.6 mW was achieved. More powerful and narrower pulses are expected if the dispersion of the cavity can be properly managed.

Strong Magnetic Field Fluctuations within Filamentary Auroral Density Cavities Interpreted as VLF Saucer Sources

NASA Technical Reports Server (NTRS)

Knudsen, D. L.; Kabirzadeh, R.; Burchill, J. K.; Pfaff, Robert F.; Wallis, D. D.; Bounds, S. R.; Clemmons, J. H.; Pincon, J.-L.

2012-01-01

The Geoelectrodynamics and Electro-Optical Detection of Electron and SuprathermalIon Currents (GEODESIC) sounding rocket encountered more than 100 filamentary densitycavities associated with enhanced plasma waves at ELF (3 kHz) and VLF (310 kHz)frequencies and at altitudes of 800990 km during an auroral substorm. These cavities weresimilar in size (20 m diameter in most cases) to so-called lower-hybrid cavities (LHCs)observed by previous sounding rockets and satellites; however, in contrast, many of theGEODESIC cavities exhibited up to tenfold enhancements in magnetic wave powerthroughout the VLF band. GEODESIC also observed enhancements of ELF and VLFelectric fields both parallel and perpendicular to the geomagnetic field B0 within cavities,though the VLF E field increases were often not as large proportionally as seen in themagnetic fields. This behavior is opposite to that predicted by previously published theoriesof LHCs based on passive scattering of externally incident auroral hiss. We argue thatthe GEODESIC cavities are active wave generation sites capable of radiating VLF wavesinto the surrounding plasma and producing VLF saucers, with energy supplied by cold,upward flowing electron beams composing the auroral return current. This interpretation issupported by the observation that the most intense waves, both inside and outside cavities,occurred in regions where energetic electron precipitation was largely inhibited orabsent altogether. We suggest that the wave-enhanced cavities encountered by GEODESICwere qualitatively different from those observed by earlier spacecraft because of thefortuitous timing of the GEODESIC launch, which placed the payload at apogee within asubstorm-related return current during its most intense phase, lasting only a few minutes.

The violent interstellar medium in Messier 31

NASA Technical Reports Server (NTRS)

Brinks, Elias; Braun, Robert; Unger, Stephen W.

1990-01-01

Taurus observations in the line of H alpha and Very Large Array (VLA) HI mapping of the HII complex No. 722 in M31, reveal what seems to be a spherical cavity 330 pc in diameter blown out by a stellar association of over 20(exp 6) years old. Evidence of induced star formation which was initiated less than 5(exp 6) years ago is present in the form of bright HII emission and numerous O, B and Wolf-Rayet stars which are found within the shell surrounding the cavity. The energy necessary to create the HI shell is estimated to be about 5(exp 51) erg.

Preliminary laboratory testing on the sound absorption of coupled cavity sonic crystal

NASA Astrophysics Data System (ADS)

Kristiani, R.; Yahya, I.; Harjana; Suparmi

2016-11-01

This paper focuses on the sound absorption performance of coupled cavity sonic crystal. It constructed by a pair of a cylindrical tube with different values in diameters. A laboratory test procedure after ASTM E1050 has been conducted to measure the sound absorption of the sonic crystal elements. The test procedures were implemented to a single coupled scatterer and also to a pair of similar structure. The results showed that using the paired structure bring a better possibility for increase the sound absorption to a wider absorption range. It also bring a practical advantage for setting the local Helmholtz resonant frequency to certain intended frequency.

Self-consistent Maxwell-Bloch model of quantum-dot photonic-crystal-cavity lasers

NASA Astrophysics Data System (ADS)

Cartar, William; Mørk, Jesper; Hughes, Stephen

2017-08-01

We present a powerful computational approach to simulate the threshold behavior of photonic-crystal quantum-dot (QD) lasers. Using a finite-difference time-domain (FDTD) technique, Maxwell-Bloch equations representing a system of thousands of statistically independent and randomly positioned two-level emitters are solved numerically. Phenomenological pure dephasing and incoherent pumping is added to the optical Bloch equations to allow for a dynamical lasing regime, but the cavity-mediated radiative dynamics and gain coupling of each QD dipole (artificial atom) is contained self-consistently within the model. These Maxwell-Bloch equations are implemented by using Lumerical's flexible material plug-in tool, which allows a user to define additional equations of motion for the nonlinear polarization. We implement the gain ensemble within triangular-lattice photonic-crystal cavities of various length N (where N refers to the number of missing holes), and investigate the cavity mode characteristics and the threshold regime as a function of cavity length. We develop effective two-dimensional model simulations which are derived after studying the full three-dimensional passive material structures by matching the cavity quality factors and resonance properties. We also demonstrate how to obtain the correct point-dipole radiative decay rate from Fermi's golden rule, which is captured naturally by the FDTD method. Our numerical simulations predict that the pump threshold plateaus around cavity lengths greater than N =9 , which we identify as a consequence of the complex spatial dynamics and gain coupling from the inhomogeneous QD ensemble. This behavior is not expected from simple rate-equation analysis commonly adopted in the literature, but is in qualitative agreement with recent experiments. Single-mode to multimode lasing is also observed, depending on the spectral peak frequency of the QD ensemble. Using a statistical modal analysis of the average decay rates, we also show how the average radiative decay rate decreases as a function of cavity size. In addition, we investigate the role of structural disorder on both the passive cavity and active lasers, where the latter show a general increase in the pump threshold for cavity lengths greater than N =7 , and a reduction in the nominal cavity mode volume for increasing amounts of disorder.

Design and fabrication of plasmonic cavities for magneto-optical sensing

NASA Astrophysics Data System (ADS)

Loughran, T. H. J.; Roth, J.; Keatley, P. S.; Hendry, E.; Barnes, W. L.; Hicken, R. J.; Einsle, J. F.; Amy, A.; Hendren, W.; Bowman, R. M.; Dawson, P.

2018-05-01

The design and fabrication of a novel plasmonic cavity, intended to allow far-field recovery of signals arising from near field magneto-optical interactions, is presented. Finite element modeling is used to describe the interaction between a gold film, containing cross-shaped cavities, with a nearby magnetic under-layer. The modeling revealed strong electric field confinement near the center of the cross structure for certain optical wavelengths, which may be tuned by varying the length of the cross through a range that is compatible with available fabrication techniques. Furthermore, the magneto optical Kerr effect (MOKE) response of the composite structure can be enhanced with respect to that of the bare magnetic film. To confirm these findings, cavities were milled within gold films deposited upon a soluble film, allowing relocation to a ferromagnetic film using a float transfer technique. Cross cavity arrays were fabricated and characterized by optical transmission spectroscopy prior to floating, revealing resonances at optical wavelengths in good agreement with the finite element modeling. Following transfer to the magnetic film, circular test apertures within the gold film yielded clear magneto-optical signals even for diameters within the sub-wavelength regime. However, no magneto-optical signal was observed for the cross cavity arrays, since the FIB milling process was found to produce nanotube structures within the soluble under-layer that adhered to the gold. Further optimization of the fabrication process should allow recovery of magneto-optical signal from cross cavity structures.

Jet dynamics post drop impact on a deep pool

NASA Astrophysics Data System (ADS)

Michon, Guy-Jean; Josserand, Christophe; Séon, Thomas

2017-02-01

We investigate experimentally the jet formed by the collapse of a cavity created by the impact of a drop on a pool of the same aqueous liquid. We show that jets can emerge with very different shapes and velocities, depending on the impact parameters, thus generating droplets with various initial sizes and velocities. After presenting the jet velocity and top drop radius variation as a function of the impact parameters, we discuss the influence of the liquid parameters on the jet velocity. This allows us to define two different regimes: the singular jet and the cavity jet regimes, where the mechanisms leading to the cavity retraction and subsequent jet dynamics are drastically different. In particular, we demonstrate that in the first regime, a singular capillary wave collapse sparks the whole jet dynamics, making the jet's fast, thin, liquid parameters dependent and barely reproducible. On the contrary, in the cavity jet regime, defined for higher impact Froude numbers, the jets are fat and slow. We show that jet velocity is simply proportional to the capillary velocity √{γ /ρlDd }, where γ is the liquid surface tension, ρl the liquid density, and Dd the impacting drop diameter, and it is in particular independent of viscosity, impact velocity, and gravity, even though the cavity is larger than the capillary length. Finally, we demonstrate that capillary wave collapse and cavity retraction are correlated in the singular regime and decorrelated in the cavity jet regime.

Integration of Fluorescence Differential Path-Length Spectroscopy to Photodynamic Therapy of the Head and Neck Tumors is Useful in Monitoring Clinical Outcome

NASA Astrophysics Data System (ADS)

Karakullukcu, Baris; Kanick, Stephen; Aans, Jan Bonne; Sterenborg, Henricus; Tan, Bing; Amelink, Arjen; Robinson, Dominic

2015-04-01

The use of fluorescence differential pathlength spectroscopy (FDPS) has the potential to provide real-time information on photosensitiser pharmacokinetics, vascular physiology and photosensitizer photobleaching based dosimetry of tumors in the oral cavity receiving m-tetrahydroxyphenylchlorin (mTHPC) photodynamic therapy (PDT). Reflectance spectra can be used provide quantitative values of oxygen saturation, blood volume fraction, blood vessel diameter, and to determine the local optical properties that can be used to correct raw fluorescence for tissue absorption. Patients and methods: Twenty-seven lesions in the oral cavity, either dysplasias or cancer were interrogated using FDPS, before and immediately after the therapeutic illumination. The average tumor center to normal mucosa ratio of fluorescence was 1.50 ± 0.66. mTHPC photobleaching was observed in 24 of the lesions treated. The average extent of photobleaching was 81% ± 17%. Information from FDPS spectroscopy coupled with the clinical results of the treatment identified 3 types of correctable errors in the application of mTHPC-PDT: Two patients exhibited very low concentrations of photosensitizer in tumour center, indicating an ineffective i.v. injection of photosensitiser or an erroneous systemic distribution of mTHPC. In one in tumor we observed no photobleaching accompanied by a high blood volume fraction in the illuminated tissue, suggesting that the presence of blood prevented therapeutic light reaching the target tissue. All 3 of the these lesions had no clinical response to PDT. In four patients we observed less than 50% photobleaching at the tumor margins , suggesting a possible geographic miss. One patient in this group had a recurrence within 2 months after PDT even though the initial response was good. The integration of FDPS to clinical PDT yields data on tissue physiology, photosensitiser content and photobleaching that can help identify treatment errors that can potentially be corrected.

High average-power 2 μm radiation generated by intracavity KTP OPO

NASA Astrophysics Data System (ADS)

He, Guangyuan; Guo, Jing; Jiao, Zhongxing; Wang, Biao

2015-09-01

A high average-power 2 μm laser with good beam quality based on an intracavity potassium titanium oxide phosphate (KTP) optical parametric oscillator (OPO) is demonstrated. A concave lens is used in the 1064 nm Nd:YAG pumped laser cavity to compensate for the thermal lensing of the laser rod. The cavity length of the KTP OPO is enlarged to improve the 2 μm beam quality. The maximum average output of the 2 μm laser is up to 18 W at 7 kHz with M 2 less than 6 and pulse width of 70 ns. The FWHM of the signal and idle lights are both less than 3 nm.

Correlation between morphometry of the suprascapular notch and anthropometric measurements of the scapula.

PubMed

Polguj, M; Jędrzejewski, K S; Podgórski, M; Topol, M

2011-05-01

The concept of the study was to find the correlation between the morphometry of the suprascapular notch and basic anthropometric measurements of the human scapula. The measurements of the human scapulae included: morphological length and width, maximal width and length projection of scapular spine, length of acromion, and maximal length of the coracoid process. The glenoid cavity was measured in two perpendicular directions to evaluate its width and length. The width-length scapular and glenoid cavity indexes were calculated for every bone. In addition to standard anthropometric measurements two other measurements were defined and evaluated for every suprascapular notch: maximal depth (MD) and superior transverse diameter (STD). The superior transverse suprascapular ligament was completely ossified in 7% of cases. Ten (11.6%) scapulae had a discrete notch. In the studied material, in 21 (24.4%) scapulae the MD was longer than the STD. Two (2.3%) scapulae had equal maximal depth and superior transverse diameter. In 47 (57.7%) scapulae the superior transverse diameter was longer than the maximal depth. There was no statistically significant difference between anthropometric measurements in the group with higher MD and the group with higher STD. The maximal depth of the suprascapular notch negatively correlated with the scapular width-length index. The maximal depth of the scapular notch correlated with the morphological length of the scapulae.

Soil Penetration by Earthworms and Plant Roots—Mechanical Energetics of Bioturbation of Compacted Soils

PubMed Central

2015-01-01

We quantify mechanical processes common to soil penetration by earthworms and growing plant roots, including the energetic requirements for soil plastic displacement. The basic mechanical model considers cavity expansion into a plastic wet soil involving wedging by root tips or earthworms via cone-like penetration followed by cavity expansion due to pressurized earthworm hydroskeleton or root radial growth. The mechanical stresses and resulting soil strains determine the mechanical energy required for bioturbation under different soil hydro-mechanical conditions for a realistic range of root/earthworm geometries. Modeling results suggest that higher soil water content and reduced clay content reduce the strain energy required for soil penetration. The critical earthworm or root pressure increases with increased diameter of root or earthworm, however, results are insensitive to the cone apex (shape of the tip). The invested mechanical energy per unit length increase with increasing earthworm and plant root diameters, whereas mechanical energy per unit of displaced soil volume decreases with larger diameters. The study provides a quantitative framework for estimating energy requirements for soil penetration work done by earthworms and plant roots, and delineates intrinsic and external mechanical limits for bioturbation processes. Estimated energy requirements for earthworm biopore networks are linked to consumption of soil organic matter and suggest that earthworm populations are likely to consume a significant fraction of ecosystem net primary production to sustain their subterranean activities. PMID:26087130

Optimization of Turbine Rim Seals

NASA Technical Reports Server (NTRS)

Wagner, J. H.; Tew, D. E.; Stetson, G. M.; Sabnis, J. S.

2006-01-01

Experiments are being conducted to gain an understanding of the physics of rim scale cavity ingestion in a turbine stage with the high-work, single-stage characteristics envisioned for Advanced Subsonic Transport (AST) aircraft gas turbine engines fo the early 21st century. Initial experimental measurements to be presented include time-averaged turbine rim cavity and main gas path static pressure measurements for rim seal coolant to main gas path mass flow ratios between 0 and 0.02. The ultimate objective of this work is develop improved rim seal design concepts for use in modern high-work, single sage turbines n order to minimize the use of secondary coolant flow. Toward this objective the time averaged and unsteady data to be obtained in these experiments will be used to 1) Quantify the impact of the rim cavity cooling air on the ingestion process. 2) Quantify the film cooling benefits of the rim cavity purge flow in the main gas path. 3) Quantify the impact of the cooling air on turbine efficiency. 4) Develop/evaluate both 3D CFD and analytical models of the ingestion/cooling process.

A physics based multiscale modeling of cavitating flows.

PubMed

Ma, Jingsen; Hsiao, Chao-Tsung; Chahine, Georges L

2017-03-02

Numerical modeling of cavitating bubbly flows is challenging due to the wide range of characteristic lengths of the physics at play: from micrometers (e.g., bubble nuclei radius) to meters (e.g., propeller diameter or sheet cavity length). To address this, we present here a multiscale approach which integrates a Discrete Singularities Model (DSM) for dispersed microbubbles and a two-phase Navier Stokes solver for the bubbly medium, which includes a level set approach to describe large cavities or gaseous pockets. Inter-scale schemes are used to smoothly bridge the two transitioning subgrid DSM bubbles into larger discretized cavities. This approach is demonstrated on several problems including cavitation inception and vapor core formation in a vortex flow, sheet-to-cloud cavitation over a hydrofoil, cavitation behind a blunt body, and cavitation on a propeller. These examples highlight the capabilities of the developed multiscale model in simulating various form of cavitation.

A physics based multiscale modeling of cavitating flows

PubMed Central

Ma, Jingsen; Hsiao, Chao-Tsung; Chahine, Georges L.

2018-01-01

Numerical modeling of cavitating bubbly flows is challenging due to the wide range of characteristic lengths of the physics at play: from micrometers (e.g., bubble nuclei radius) to meters (e.g., propeller diameter or sheet cavity length). To address this, we present here a multiscale approach which integrates a Discrete Singularities Model (DSM) for dispersed microbubbles and a two-phase Navier Stokes solver for the bubbly medium, which includes a level set approach to describe large cavities or gaseous pockets. Inter-scale schemes are used to smoothly bridge the two transitioning subgrid DSM bubbles into larger discretized cavities. This approach is demonstrated on several problems including cavitation inception and vapor core formation in a vortex flow, sheet-to-cloud cavitation over a hydrofoil, cavitation behind a blunt body, and cavitation on a propeller. These examples highlight the capabilities of the developed multiscale model in simulating various form of cavitation. PMID:29720773

Fiber cavity ring-down using an optical time-domain reflectometer

NASA Astrophysics Data System (ADS)

Passos, D. J.; Silva, S. O.; Fernandes, J. R. A.; Marques, M. B.; Frazão, O.

2014-12-01

This work presented a demonstration of the potential for a fiber based cavity ring-down (CRD) using an optical time-domain reflectometer (OTDR). The OTDR was used to send the impulses down into about 20 km of a standard single optical fiber, at the end of which the fiber cavity ring-down was placed. The OTDR measured no appreciable losses, so other CRDs multiplexed could be spliced in parallel along the same optical fiber. To demonstrate the behavior and sensitivity of the proposed configuration, a displacement sensor based on a fiber taper with a diameter of 50 μm was placed inside the fiber loop, and the induced losses were measured on the CRD signal — a sensitivity of 11.8 ± 0.5 μs/mm was achieved. The dynamic range of the sensing head used in this configuration was about 2 mm. Finally, this work was also compared with different works published in the literature.

Silicon Alignment Pins: An Easy Way to Realize a Wafer-To-Wafer Alignment

NASA Technical Reports Server (NTRS)

Peralta, Alejandro (Inventor); Gill, John J. (Inventor); Toda, Risaku (Inventor); Lin, Robert H. (Inventor); Jung-Kubiak, Cecile (Inventor); Reck, Theodore (Inventor); Thomas, Bertrand (Inventor); Siles, Jose V. (Inventor); Lee, Choonsup (Inventor); Chattopadhyay, Goutam (Inventor)

2016-01-01

A silicon alignment pin is used to align successive layers of components made in semiconductor chips and/or metallic components to make easier the assembly of devices having a layered structure. The pin is made as a compressible structure which can be squeezed to reduce its outer diameter, have one end fit into a corresponding alignment pocket or cavity defined in a layer of material to be assembled into a layered structure, and then allowed to expand to produce an interference fit with the cavity. The other end can then be inserted into a corresponding cavity defined in a surface of a second layer of material that mates with the first layer. The two layers are in registry when the pin is mated to both. Multiple layers can be assembled to create a multilayer structure. Examples of such devices are presented.

Growth of magnesium diboride films on 2 inch diameter copper discs by hybrid physical–chemical vapor deposition

DOE PAGES

Withanage, Wenura K.; Xi, X. X.; Nassiri, Alireza; ...

2017-02-16

Here, magnesium diboride (MgB 2) coating is a potential candidate to replace bulk niobium (Nb) for superconducting radio frequency cavities due to the appealing superconducting properties of MgB 2. MgB 2 coating on copper may allow cavity operation near 20–25 K as a result of the high transition temperature (T c) of MgB 2 and excellent thermal conductivity of Cu. We have grown MgB 2 films on 2 inch diameter Cu discs by hybrid physical–chemical vapor deposition for radio frequency characterization. Structural and elemental analyses showed a uniform MgB 2 coating on top of a Mg–Cu alloy layer with occasionalmore » intrusion of Mg–Cu alloy regions. High T c values of around 37 K and high critical current density (J c) on the order of 107 A cm –2 at zero field were observed. Radio frequency measurements at 11.4 GHz confirmed a high T c and showed a quality factor (Q 0) much higher than for Cu and close to that of Nb.« less

Growth of magnesium diboride films on 2 inch diameter copper discs by hybrid physical–chemical vapor deposition

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

Withanage, Wenura K.; Xi, X. X.; Nassiri, Alireza

Here, magnesium diboride (MgB 2) coating is a potential candidate to replace bulk niobium (Nb) for superconducting radio frequency cavities due to the appealing superconducting properties of MgB 2. MgB 2 coating on copper may allow cavity operation near 20–25 K as a result of the high transition temperature (T c) of MgB 2 and excellent thermal conductivity of Cu. We have grown MgB 2 films on 2 inch diameter Cu discs by hybrid physical–chemical vapor deposition for radio frequency characterization. Structural and elemental analyses showed a uniform MgB 2 coating on top of a Mg–Cu alloy layer with occasionalmore » intrusion of Mg–Cu alloy regions. High T c values of around 37 K and high critical current density (J c) on the order of 107 A cm –2 at zero field were observed. Radio frequency measurements at 11.4 GHz confirmed a high T c and showed a quality factor (Q 0) much higher than for Cu and close to that of Nb.« less

Growth of magnesium diboride films on 2 inch diameter copper discs by hybrid physical–chemical vapor deposition

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

Withanage, Wenura K.; Xi, X. X.; Nassiri, Alireza

Magnesium diboride (MgB2) coating is a potential candidate to replace bulk niobium (Nb) for superconducting radio frequency cavities due to the appealing superconducting properties of MgB2. MgB2 coating on copper may allow cavity operation near 20–25 K as a result of the high transition temperature (T c) of MgB2 and excellent thermal conductivity of Cu. We have grown MgB2 films on 2 inch diameter Cu discs by hybrid physical–chemical vapor deposition for radio frequency characterization. Structural and elemental analyses showed a uniform MgB2 coating on top of a Mg–Cu alloy layer with occasional intrusion of Mg–Cu alloy regions. High Tmore » c values of around 37 K and high critical current density (J c) on the order of 107 A cm-2 at zero field were observed. Radio frequency measurements at 11.4 GHz confirmed a high T c and showed a quality factor (Q 0) much higher than for Cu and close to that of Nb.« less

Control of the shell structural properties and cavity diameter of hollow magnesium fluoride particles.

PubMed

Nandiyanto, Asep Bayu Dani; Ogi, Takashi; Okuyama, Kikuo

2014-03-26

Control of the shell structural properties [i.e., thickness (8-25 nm) and morphology (dense and raspberry)] and cavity diameter (100-350 nm) of hollow particles was investigated experimentally, and the results were qualitatively explained based on the available theory. We found that the selective deposition size and formation of the shell component on the surface of a core template played important roles in controlling the structure of the resulting shell. To achieve the selective deposition size and formation of the shell component, various process parameters (i.e., reaction temperature and charge, size, and composition of the core template and shell components) were tested. Magnesium fluoride (MgF2) and polystyrene spheres were used as models for shell and core components, respectively. MgF2 was selected because, to the best of our knowledge, the current reported approaches to date were limited to synthesis of MgF2 in film and particle forms only. Therefore, understanding how to control the formation of MgF2 with various structures (both the thickness and morphology) is a prospective for advanced lens synthesis and applications.

Experimental investigation on laser-induced plasma ignition of hydrocarbon fuel in scramjet engine at takeover flight conditions

NASA Astrophysics Data System (ADS)

Li, Xipeng; Liu, Weidong; Pan, Yu; Yang, Leichao; An, Bin

2017-09-01

Laser-induced plasma ignition of an ethylene fuelled cavity is successfully conducted in a model scramjet engine combustor with dual cavities. The simulated flight condition corresponds to takeover flight Mach 4, with isolator entrance Mach number of 2.1, the total pressure of 0.65 MPa and stagnation temperature of 947 K. Ethylene is injected 35 mm upstream of cavity flameholder from four orifices with 2-mm-diameter. The 1064 nm laser beam, from a Q-switched Nd:YAG laser source running at 10 Hz and 940 mJ per pulse, is focused into cavity for ignition. High speed photography is used to capture the transient ignition process. The laser-induced gas breakdown, flame kernel generation and propagation are all recorded and ensuing stable supersonic combustion is established in cavity. The highly ionized plasma zone is almost round at starting, and then the surface of the flame kernel is wrinkled severely in 150 μs after the laser pulse due to the strong turbulence flow in cavity. The flame kernel is found rotating anti-clockwise and gradually moves upstream as the entrainment of circulation flow in cavity. The flame is stabilized at the corner of the cavity for about 200 μs, and then spreads from leading edge to trailing edge via the under part of shear layer to fully fill the entire cavity. The corner recirculation zone of cavity is of great importance for flame spreading. Eventually, a cavity shear-layer stabilized combustion is established in the supersonic flow roughly 2.9 ms after the laser pulse. Both the temporal evolution of normalized chemiluminescence intensity and normalized flame area show that the entire ignition process can be divided into four stages, which are referred as turbulent dissipation stage, combustion enhancement stage, reverting stage and combustion stabilization stage. The results show promising potentials of laser induced plasma for ignition in real scramjets.

Effects of air temperature and velocity on the drying kinetics and product particle size of starch from arrowroot (Maranta arundinacae)

NASA Astrophysics Data System (ADS)

Caparanga, Alvin R.; Reyes, Rachael Anne L.; Rivas, Reiner L.; De Vera, Flordeliza C.; Retnasamy, Vithyacharan; Aris, Hasnizah

2017-11-01

This study utilized the 3k factorial design with k as the two varying factors namely, temperature and air velocity. The effects of temperature and air velocity on the drying rate curves and on the average particle diameter of the arrowroot starch were investigated. Extracted arrowroot starch samples were dried based on the designed parameters until constant weight was obtained. The resulting initial moisture content of the arrowroot starch was 49.4%. Higher temperatures correspond to higher drying rates and faster drying time while air velocity effects were approximately negligible or had little effect. Drying rate is a function of temperature and time. The constant rate period was not observed for the drying rate of arrowroot starch. The drying curves were fitted against five mathematical models: Lewis, Page, Henderson and Pabis, Logarithmic and Midili. The Midili Model was the best fit for the experimental data since it yielded the highest R2 and the lowest RSME values for all runs. Scanning electron microscopy (SEM) was used for qualitative analysis and for determination of average particle diameter of the starch granules. The starch granules average particle diameter had a range of 12.06 - 24.60 μm. The use of ANOVA proved that particle diameters for each run varied significantly with each other. And, the Taguchi Design proved that high temperatures yield lower average particle diameter, while high air velocities yield higher average particle diameter.

More Insight of Piezoelectric-based Synthetic Jet Actuators

NASA Astrophysics Data System (ADS)

Housley, Kevin; Amitay, Michael

2016-11-01

Increased understanding of the internal flow of piezoelectric-based synthetic jet actuators is needed for the development of specialized actuator cavity geometries to increase jet momentum coefficients and tailor acoustic resonant frequencies. Synthetic jet actuators can benefit from tuning of the structural resonant frequency of the piezoelectric diaphragm(s) and the acoustic resonant frequency of the actuator cavity such that they experience constructive coupling. The resulting coupled behavior produces increased jet velocities. The ability to design synthetic jet actuators to operate with this behavior at select driving frequencies allows for them to be better used in flow control applications, which sometimes require specific jet frequencies in order to utilize the natural instabilities of a given flow field. A parametric study of varying actuator diameters was conducted to this end. Phase-locked data were collected on the jet velocity, the cavity pressure at various locations, and the three-dimensional deformation of the surface of the diaphragm. These results were compared to previous analytical work on the interaction between the structural resonance of the diaphragm and the acoustic resonance of the cavity. Funded by the Boeing Company.

Increases of Chamber Height and Base Diameter Have Contrasting Effects on Grazing Rate of Two Cladoceran Species: Implications for Microcosm Studies.

PubMed

Pan, Ying; Zhang, Yunshu; Peng, Yan; Zhao, Qinghua; Sun, Shucun

2015-01-01

Aquatic microcosm studies often increase either chamber height or base diameter (to increase water volume) to test spatial ecology theories such as "scale" effects on ecological processes, but it is unclear whether the increase of chamber height or base diameter have the same effect on the processes, i.e., whether the effect of the shape of three-dimensional spaces is significant. We orthogonally manipulated chamber height and base diameter and determined swimming activity, average swimming velocity and grazing rates of the cladocerans Daphnia magna and Moina micrura (on two algae Scenedesmus quadricauda and Chlorella vulgaris; leading to four aquatic algae-cladoceran systems in total) under different microcosm conditions. Across all the four aquatic systems, increasing chamber height at a given base diameter significantly decreased the duration and velocity of horizontal swimming, and it tended to increase the duration but decrease the velocity of vertical swimming. These collectively led to decreases in both average swimming velocity and grazing rate of the cladocerans in the tall chambers (at a given base diameter), in accordance with the positive relationship between average swimming velocity and grazing rate. In contrast, an increase of base diameter at a given chamber height showed contrasting effects on the above parameters. Consistently, at a given chamber volume increasing ratio of chamber height to base diameter decreased the average swimming velocity and grazing rate across all the aquatic systems. In general, increasing chamber depth and base diameter may exert contrasting effects on zooplankton behavior and thus phytoplankton-zooplankton interactions. We suggest that spatial shape plays an important role in determining ecological process and thus should be considered in a theoretical framework of spatial ecology and also the physical setting of aquatic microcosm experiments.

Increases of Chamber Height and Base Diameter Have Contrasting Effects on Grazing Rate of Two Cladoceran Species: Implications for Microcosm Studies

PubMed Central

Pan, Ying; Zhang, Yunshu; Peng, Yan; Zhao, Qinghua; Sun, Shucun

2015-01-01

Aquatic microcosm studies often increase either chamber height or base diameter (to increase water volume) to test spatial ecology theories such as “scale” effects on ecological processes, but it is unclear whether the increase of chamber height or base diameter have the same effect on the processes, i.e., whether the effect of the shape of three-dimensional spaces is significant. We orthogonally manipulated chamber height and base diameter and determined swimming activity, average swimming velocity and grazing rates of the cladocerans Daphnia magna and Moina micrura (on two algae Scenedesmus quadricauda and Chlorella vulgaris; leading to four aquatic algae-cladoceran systems in total) under different microcosm conditions. Across all the four aquatic systems, increasing chamber height at a given base diameter significantly decreased the duration and velocity of horizontal swimming, and it tended to increase the duration but decrease the velocity of vertical swimming. These collectively led to decreases in both average swimming velocity and grazing rate of the cladocerans in the tall chambers (at a given base diameter), in accordance with the positive relationship between average swimming velocity and grazing rate. In contrast, an increase of base diameter at a given chamber height showed contrasting effects on the above parameters. Consistently, at a given chamber volume increasing ratio of chamber height to base diameter decreased the average swimming velocity and grazing rate across all the aquatic systems. In general, increasing chamber depth and base diameter may exert contrasting effects on zooplankton behavior and thus phytoplankton-zooplankton interactions. We suggest that spatial shape plays an important role in determining ecological process and thus should be considered in a theoretical framework of spatial ecology and also the physical setting of aquatic microcosm experiments. PMID:26273836

Analysis of coupled-bunch instabilities for the NSLS-II storage ring with a 500MHz 7-cell PETRA-III cavity

DOE PAGES

Bassi, G.; Blednykh, A.; Cheng, W.; ...

2015-12-11

We present the NSLS-II storage ring that is designed to operate with superconducting RF-cavities with the aim to store an average current of 500 mA distributed in 1080 bunches, with a gap in the uniform filling for ion clearing. At the early stage of the commissioning (phase 1), characterized by a bare lattice without damping wigglers and without Landau cavities, a normal conducting 7-cell PETRA-III RF-cavity structure has been installed with the goal to store an average current of 25 mA. In this paper we discuss our analysis of coupled-bunch instabilities driven by the Higher Order Modes (HOMs) of themore » 7-cell PETRA-III RF-cavity. As a cure of the instabilities, we apply a well-known scheme based on a proper detuning of the HOMs frequencies based upon cavity temperature change, and the use of the beneficial effect of the slow head–tail damping at positive chromaticity to increase the transverse coupled-bunch instability thresholds. In addition, we discuss measurements of coupled-bunch instabilities observed during the phase 1 commissioning of the NSLS-II storage ring. In our analysis we rely, in the longitudinal case, on the theory of coupled-bunch instability for uniform fillings, while in the transverse case we complement our studies with numerical simulations with OASIS, a novel parallel particle tracking code for self-consistent simulations of collective effects driven by short and long-range wakefields.« less

Interaction of a parabolic-shaped pulse pair in a passively mode-locked Yb-doped fiber laser

NASA Astrophysics Data System (ADS)

Wang, Da-Shuai; Wu, Ge; Gao, Bo; Tian, Xiao-Jian

2013-01-01

We numerically investigate the formation and interaction of a parabolic-shaped pulse pair in a passively mode-locked Yb-doped fiber laser. Based on a lumped model, the parabolic-shaped pulse pair is obtained by controlling the inter-cavity average dispersion and gain saturation energy, Moreover, pulse repulsive and attractive motion are also achieved with different pulse separations. Simulation results show that the phase shift plays an important role in pulse interaction, and the interaction is determined by the inter-cavity average dispersion and gain saturation energy, i.e., the strength of the interaction is proportional to the gain saturation energy, a stronger gain saturation energy will result in a higher interaction intensity. On the contrary, the increase of the inter-cavity dispersion will counterbalance some interaction force. The results also show that the interaction of a parabolic-shaped pulse pair has a larger interaction distance compared to conventional solitons.

Utility of Early Post-operative High Resolution Volumetric MR Imaging after Transsphenoidal Pituitary Tumor Surgery

PubMed Central

Patel, Kunal S.; Kazam, Jacob; Tsiouris, Apostolos J.; Anand, Vijay K.; Schwartz, Theodore H.

2014-01-01

Objective Controversy exists over the utility of early post-operative magnetic resonance imaging (MRI) after transsphenoidal pituitary surgery for macroadenomas. We investigate whether valuable information can be derived from current higher resolution scans. Methods Volumetric MRI scans were obtained in the early (<10 days) and late (>30 days) post-operative periods in a series of patients undergoing transsphenoidal pituitary surgery. The volume of the residual tumor, resection cavity, and corresponding visual field tests were recorded at each time point. Statistical analyses of changes in tumor volume and cavity size were calculated using the late MRI as the gold standard. Results 40 patients met the inclusion criteria. Pre-operative tumor volume averaged 8.8 cm3. Early postoperative assessment of average residual tumor volume (1.18 cm3) was quite accurate and did not differ statistically from late post-operative volume (1.23 cm3, p=.64), indicating the utility of early scans to measure residual tumor. Early scans were 100% sensitive and 91% specific for predicting ≥ 98% resection (p<.001, Fisher’s exact test). The average percent decrease in cavity volume from pre-operative MRI (tumor volume) to early post-operative imaging was 45% with decreases in all but 3 patients. There was no correlation between the size of the early cavity and the visual outcome. Conclusions Early high resolution volumetric MRI is valuable in determining the presence or absence of residual tumor. Cavity volume almost always decreases after surgery and a lack of decrease should alert the surgeon to possible persistent compression of the optic apparatus that may warrant re-operation. PMID:25045791

Natural cavities used by wood ducks in north-central Minnesota

USGS Publications Warehouse

Gilmer, D.S.; Ball, I.J.; Cowardin, L.M.; Mathisen, J.

1978-01-01

Radio telemetry was used to locate 31 wood duck (Aix sponsa) nest cavity sites in 16 forest stands. Stands were of 2 types: (1) mature (mean = 107 years) northern hardwoods (10 nest sites), and (2) mature (mean = 68 years) quaking aspen (Populus tremuloides) (21 nest sites). Aspen was the most important cavity-producing tree used by wood ducks and accounted for 57 percent of 28 cavities inspected. In stands used by wood ducks, the average density of suitable cavities was about 4 per hectare. Trees containing nests were closer to water areas (P < 0.05) and the nearest forest canopy openings (P < 0.01) than was a random sample of trees from the same stands. A significant (P < 0.005) relationship existed between the orientation of the cavity entrance and the nearest canopy opening. Potential wood duck cavities usually were clustered within a stand rather than randomly distributed. Selection of trees by woodpeckers for nest hole construction probably influenced the availability of cavities used by wood ducks. A plan for managing forests to benefit wood ducks and other wildlife dependent on old-growth timber is discussed.

Optimal spacing within a tubed, volumetric, cavity receiver suitable for modular molten salt solar towers

NASA Astrophysics Data System (ADS)

Turner, Peter

2016-05-01

A 2-dimensional radiation analysis has been developed to analyse the radiative efficiency of an arrangement of heat transfer tubes distributed in layers but spaced apart to form a tubed, volumetric receiver. Such an arrangement could be suitable for incorporation into a cavity receiver. Much of the benefit of this volumetric approach is gained after using 5 layers although improvements do continue with further layers. The radiation analysis splits each tube into multiple segments in which each segment surface can absorb, reflect and radiate rays depending on its surface temperature. An iterative technique is used to calculate appropriate temperatures depending on the distribution of the net energy absorbed and assuming that the cool heat transfer fluid (molten salt) starts at the front layer and flows back through successive layers to the rear of the cavity. Modelling the finite diameter of each layer of tubes increases the ability of a layer to block radiation scattered at acute angles and this effect is shown to reduce radiation losses by nearly 25% compared to the earlier 1-d analysis. Optimum efficient designs tend to occur when the blockage factor is 0.2 plus the inverse of the number of tube layers. It is beneficial if the distance between successive layers is ≥ 2 times the diameter of individual tubes and in this situation, if the incoming radiation is spread over a range of angles, the performance is insensitive to the degree of any tube positional offset or stagger between layers.

Why do complex impact craters have elevated crater rims?

NASA Astrophysics Data System (ADS)

Kenkmann, Thomas; Sturm, Sebastian; Krueger, Tim

2014-05-01

Most of the complex impact craters on the Moon and on Mars have elevated crater rims like their simple counterparts. The raised rim of simple craters is the result of (i) the deposition of a coherent proximal ejecta blanket at the edge of the transient cavity (overturned flap) and (ii) a structural uplift of the pre-impact surface near the transient cavity rim during the excavation stage of cratering [1]. The latter occurs either by plastic thickening or localized buckling of target rocks, as well as by the emplacement of interthrust wedges [2] or by the injection of dike material. Ejecta and the structural uplift contribute equally to the total elevation of simple crater rims. The cause of elevated crater rims of large complex craters [3] is less obvious, but still, the rim height scales with the final crater diameter. Depending on crater size, gravity, and target rheology, the final crater rim of complex craters can be situated up to 1.5-2.0 transient crater radii distance from the crater center. Here the thickness of the ejecta blanket is only a fraction of that occurring at the rim of simple craters, e.g. [4], and thus cannot account for a strong elevation. Likewise, plastic thickening including dike injection of the underlying target may not play a significant role at this distance any more. We started to systematically investigate the structural uplift and ejecta thickness along the rim of complex impact craters to understand the cause of their elevation. Our studies of two lunar craters (Bessel, 16 km diameter and Euler, 28 km diameter) [5] and one unnamed complex martian crater (16 km diameter) [6] showed that the structural uplift at the final crater rim makes 56-67% of the total rim elevation while the ejecta thickness contributes 33-44%. Thus with increasing distance from the transient cavity rim, the structural uplift seems to dominate. As dike injection and plastic thickening are unlikely at such a distance from the transient cavity, we propose that reverse faulting induced by radially outward directed maximum stresses during the excavation flow may be responsible for the elevation of complex crater rims. This hypothesis is tested at terrestrial craters whose apparent crater rims are often confined by circumferential faults [7]. References:[1] Shoemaker, E. M. (1963) The Solar System, 4, 301-336. [2] Poelchau M.H. et al. (2009), JGR, 114, E01006. [3] Settle, M., and Head, J.W., (1977), Icarus, 31, 123. [4] McGetchin, T. R., et al., (1973), EPSL, 20, 226.[5] Krüger T. et al. (2014), LPSC 45, #1834. [6] Sturm, S. et al. (2014), LPSC 45, 1801. [7] Turtle, E. et al. (2005), GSA-SP. 384, 1.

Characterization of high speed synthetic jet actuators

NASA Astrophysics Data System (ADS)

Pikcilingis, Lucia

Over the last 20 years, synthetic jets have been studied as a means for aerodynamic active flow control. Specifically, synthetic jets provide momentum transfer with zero-net mass flux, which has been proven to be effective for controlling flow fields. A synthetic jet is created by the periodic formation of vortex rings at its orifice due to the periodic motion of a piezoelectric disk(s). The present study seeks to optimize the performance of a synthetic jet actuator by utilizing different geometrical parameters such as disk thickness, orifice width and length, cavity height and cavity diameter, and different input parameters such as driving voltage and frequency. Two apparatuses were used with a cavity diameter of either 80 mm or 160 mm. Piezoelectric-based disks were provided by the Mide Corporation. Experiments were conducted using several synthetic jet apparatuses designed for various geometrical parameters utilizing a dual disk configuration. Velocity and temperature measurements were acquired at the center of the synthetic jet orifice using a temperature compensated hotwire and thermocouple probe. The disk(s) displacement was measured at the center of the disk with a laser displacement sensor. It was shown that the synthetic jets, having the 80 mm cavity diameter, are capable of exceeding peak velocities of 200 m/s with a relatively large orifice of dimensions AR = 12, hc* = 3, and hn* = 4. In addition, the conditions at which the disks were manufactured had minimal effect on the performance of the jet, except for the pair with overnight resting time as opposed to less than an hour resting time for the control units. Altering the tab style of the disks, where the tab allows the electrical circuit to be exposed for external power connection, showed that a thin fragile tab versus a tab of the same thickness as the disk has minimal effect on the performance but affects the durability of the disk due to the fragility or robustness of the tab. The synthetic jets, having a 160 mm cavity diameter, yielded jet velocities greater than 300 m/s. Altering the clamping conditions, at which the disks are clamped, showed that increasing the number of clamping points where the disks are clamped, improved the performance of the jet. Coupling this with a flexible clamping boundary condition yielded the best performing jets. Fatigue tests were conducted for both apparatuses using several different disk designs. These tests showed that there is a degradation of the disks that causes the jet performance to decay and eventually cause a fracture in the disk. It is apparent from this work that, though the conditions at which the disks are manufactured have a small effect on performance, the disks do exhibit a threshold where beyond it the performance decays. Though desired jet velocities and momentums are achievable, the abnormality of the disks needs to be addressed before applying the actuator to practical situations. As this research continues, the synthetic jet actuator will become more robust and reliable to be an effective and reliable source of active flow control.

Coupled thermal-fluid analysis with flowpath-cavity interaction in a gas turbine engine

NASA Astrophysics Data System (ADS)

Fitzpatrick, John Nathan

This study seeks to improve the understanding of inlet conditions of a large rotor-stator cavity in a turbofan engine, often referred to as the drive cone cavity (DCC). The inlet flow is better understood through a higher fidelity computational fluid dynamics (CFD) modeling of the inlet to the cavity, and a coupled finite element (FE) thermal to CFD fluid analysis of the cavity in order to accurately predict engine component temperatures. Accurately predicting temperature distribution in the cavity is important because temperatures directly affect the material properties including Young's modulus, yield strength, fatigue strength, creep properties. All of these properties directly affect the life of critical engine components. In addition, temperatures cause thermal expansion which changes clearances and in turn affects engine efficiency. The DCC is fed from the last stage of the high pressure compressor. One of its primary functions is to purge the air over the rotor wall to prevent it from overheating. Aero-thermal conditions within the DCC cavity are particularly challenging to predict due to the complex air flow and high heat transfer in the rotating component. Thus, in order to accurately predict metal temperatures a two-way coupled CFD-FE analysis is needed. Historically, when the cavity airflow is modeled for engine design purposes, the inlet condition has been over-simplified for the CFD analysis which impacts the results, particularly in the region around the compressor disc rim. The inlet is typically simplified by circumferentially averaging the velocity field at the inlet to the cavity which removes the effect of pressure wakes from the upstream rotor blades. The way in which these non-axisymmetric flow characteristics affect metal temperatures is not well understood. In addition, a constant air temperature scaled from a previous analysis is used as the simplified cavity inlet air temperature. Therefore, the objectives of this study are: (a) model the DCC cavity with a more physically representative inlet condition while coupling the solid thermal analysis and compressible air flow analysis that includes the fluid velocity, pressure, and temperature fields; (b) run a coupled analysis whose boundary conditions come from computational models, rather than thermocouple data; (c) validate the model using available experimental data; and (d) based on the validation, determine if the model can be used to predict air inlet and metal temperatures for new engine geometries. Verification with experimental results showed that the coupled analysis with the 3D no-bolt CFD model with predictive boundary conditions, over-predicted the HP6 offtake temperature by 16k. The maximum error was an over-prediction of 50k while the average error was 17k. The predictive model with 3D bolts also predicted cavity temperatures with an average error of 17k. For the two CFD models with predicted boundary conditions, the case without bolts performed better than the case with bolts. This is due to the flow errors caused by placing stationary bolts in a rotating reference frame. Therefore it is recommended that this type of analysis only be attempted for drive cone cavities with no bolts or shielded bolts.

Fluid and microfluidic dielectric measurement using a cavity perturbation method at microwave C-band

NASA Astrophysics Data System (ADS)

Asghari, Aref

The utilization of cavity perturbation technique in dielectric property measurement of fluid and micro-fluid is investigated in this thesis to better assist the ever-growing needs of science and technology for analysis and characterization of such materials in various applications from genetics, MEMS devices, to consumer product industry. Development of different techniques for measuring complex dielectric properties of fluid and micro-fluids at Giga (10 9)-Hz frequencies is of significant importance as their usage is increasingly coupled with infrared and microwave electromagnetic wavelengths. Conventional cavity perturbation method could provide a sensitive and convenient system for measuring fluids of low (e.g., epsilonr <10) permittivity that meets the assumptions of negligible perturbation to the electromagnetic field distribution in the cavity. Developing a methodology that uses conventional cavity perturbation method that is however suitable for a sensitive, accurate, and reliable measurement of high permittivity polar liquids at microwave C-band is the goal in the current work. Systematic studies are carried out, using de-ionic (DI) water as test specimens, to evaluate the influence of sample's container, volume, dimension, and temperature on the sensitivity and reliability of microwave dielectric measurement. The cavity perturbation measurement of DI water in a 1 mm diameter capillary tube showed well-defined temperature dependence of dielectric permittivity and loss coefficients of water. Observation of a permittivity peak in temperature range tested at 4GHz around -10 °C implies an important relaxation in low temperatures at microwave C-band, which corresponds to a critical slowing down of polarization reorientation in crystallized (icy) H2O. Numerical simulations using Finite Element Analysis (FEA) COMSOL suites were conducted to established the optimum amount of liquid water for cavity perturbation testing at microwave C-band (in perfectly conducting condition). The results showed at TE103 mode the tube D4= 4mm diameter (272 muL liquid volume capacity) provides the best measurement sensitivity in terms of resonant shift and low loss while for TE105 the 2mm 68 (muL liquid volume capacity) tube is the most promising. The experimental results yielded a shape factor of around 2 and 1 for epsilon' and epsilon", respectively. The examination of epsilon' and epsilon" interdependence using Kramers-Kronig concept showed the permittivity loss values is 4 times more dependent to the quality factor of resonant peak than permittivity. On the other hand, the dielectric permittivity dependence to resonant frequency was calculated around 2 times bigger than dielectric loss which signifies the importance of epsilon" in high loss liquid measurement by the cavity resonant perturbation method.

Measurement and interpretation of skin prick test results.

PubMed

van der Valk, J P M; Gerth van Wijk, R; Hoorn, E; Groenendijk, L; Groenendijk, I M; de Jong, N W

2015-01-01

There are several methods to read skin prick test results in type-I allergy testing. A commonly used method is to characterize the wheal size by its 'average diameter'. A more accurate method is to scan the area of the wheal to calculate the actual size. In both methods, skin prick test (SPT) results can be corrected for histamine-sensitivity of the skin by dividing the results of the allergic reaction by the histamine control. The objectives of this study are to compare different techniques of quantifying SPT results, to determine a cut-off value for a positive SPT for histamine equivalent prick -index (HEP) area, and to study the accuracy of predicting cashew nut reactions in double-blind placebo-controlled food challenge (DBPCFC) tests with the different SPT methods. Data of 172 children with cashew nut sensitisation were used for the analysis. All patients underwent a DBPCFC with cashew nut. Per patient, the average diameter and scanned area of the wheal size were recorded. In addition, the same data for the histamine-induced wheal were collected for each patient. The accuracy in predicting the outcome of the DBPCFC using four different SPT readings (i.e. average diameter, area, HEP-index diameter, HEP-index area) were compared in a Receiver-Operating Characteristic (ROC) plot. Characterizing the wheal size by the average diameter method is inaccurate compared to scanning method. A wheal average diameter of 3 mm is generally considered as a positive SPT cut-off value and an equivalent HEP-index area cut-off value of 0.4 was calculated. The four SPT methods yielded a comparable area under the curve (AUC) of 0.84, 0.85, 0.83 and 0.83, respectively. The four methods showed comparable accuracy in predicting cashew nut reactions in a DBPCFC. The 'scanned area method' is theoretically more accurate in determining the wheal area than the 'average diameter method' and is recommended in academic research. A HEP-index area of 0.4 is determined as cut-off value for a positive SPT. However, in clinical practice, the 'average diameter method' is also useful, because this method provides similar accuracy in predicting cashew nut allergic reactions in the DBPCFC. Trial number NTR3572.

Studies on Creep Deformation and Rupture Behavior of 316LN SS Multi-Pass Weld Joints Fabricated with Two Different Electrode Sizes

NASA Astrophysics Data System (ADS)

Vijayanand, V. D.; Kumar, J. Ganesh; Parida, P. K.; Ganesan, V.; Laha, K.

2017-02-01

Effect of electrode size on creep deformation and rupture behavior has been assessed by carrying out creep tests at 923 K (650 °C) over the stress range 140 to 225 MPa on 316LN stainless steel weld joints fabricated employing 2.5 and 4 mm diameter electrodes. The multi-pass welding technique not only changes the morphology of delta ferrite from vermicular to globular in the previous weld bead region near to the weld bead interface, but also subjects the region to thermo-mechanical heat treatment to generate appreciable strength gradient. Electron backscatter diffraction analysis revealed significant localized strain gradients in regions adjoining the weld pass interface for the joint fabricated with large electrode size. Larger electrode diameter joint exhibited higher creep rupture strength than the smaller diameter electrode joint. However, both the joints had lower creep rupture strength than the base metal. Failure in the joints was associated with microstructural instability in the fusion zone, and the vermicular delta ferrite zone was more prone to creep cavitation. Larger electrode diameter joint was found to be more resistant to failure caused by creep cavitation than the smaller diameter electrode joint. This has been attributed to the larger strength gradient between the beads and significant separation between the cavity prone vermicular delta ferrite zones which hindered the cavity growth. Close proximity of cavitated zones in smaller electrode joint facilitated their faster coalescence leading to more reduction in creep rupture strength. Failure location in the joints was found to depend on the electrode size and applied stress. The change in failure location has been assessed on performing finite element analysis of stress distribution across the joint on incorporating tensile and creep strengths of different constituents of joints, estimated by ball indentation and impression creep testing techniques.

InGaAsP/InP-air-aperture microcavities for single-photon sources at 1.55-μm telecommunication band

NASA Astrophysics Data System (ADS)

Guo, Sijie; Zheng, Yanzhen; Weng, Zhuo; Yao, Haicheng; Ju, Yuhao; Zhang, Lei; Ren, Zhilei; Gao, Ruoyao; Wang, Zhiming M.; Song, Hai-Zhi

2016-11-01

InGaAsP/InP-air-aperture micropillar cavities are proposed to serve as 1.55-μm single photon sources, which are indispensable in silica-fiber based quantum information processing. Owing to air-apertures introduced to InP layers, and adiabatically tapered distributed Bragg-reflector structures used in the central cavity layers, the pillar diameters can be less than 1 μm, achieving mode volume as small as (λ/n)3, and the quality factors are more than 104 - 105, sufficient to increase the quantum dot emission rate for 100 times and create strong coupling between the optical mode and the 1.55- μm InAs/InP quantum dot emitter. The mode wavelengths and quality factors are found weakly changing with the cavity size and the deviation from the ideal shape, indicating the robustness against the imperfection of the fabrication technique. The fabrication, simply epitaxial growth, dry and chemical etching, is a damage-free and monolithic process, which is advantageous over previous hybrid cavities. The above properties satisfy the requirements of efficient, photonindistinguishable and coherent 1.55-μm quantum dot single photon sources, so the proposed InGaAsP/InP-air-aperture micropillar cavities are prospective candidates for quantum information devices at telecommunication band.

Solar Collector With Image-Forming Mirror Cavity to Irradiate Small Central Volume

NASA Technical Reports Server (NTRS)

Buchele, Don; Castle, Charles; Bonoetti, Joseph A.

2001-01-01

A unique solar thermal chamber has been designed and fabricated to produce the maximum concentration of solar energy and higher temperature possible. Its primary purpose was for solar plasma propulsion experiments and related material specimen testing above 3000 K. The design not only maximized solar concentration, but also, minimized infrared heat loss. This paper provides the underlying theory and operation of the chamber and initial optical correlation to the actual fabricated hardware. The chamber is placed at the focal point of an existing primary concentrator with a 2.74 m (9 ft) focal length. A quartz lens focuses a small sun image at the inlet hole of the mirrored cavity. The lens focuses two image planes at prescribed positions; the sun at the cavity's entrance hole and the primary concentrator at the junction plane of two surfaces that form the cavity chamber. The back half is an ellipsoid reflector that produces a 1.27 cm diameter final sun image. The image is "suspended in space," 7.1 cm away from the nearest cavity surface, to minimize thermal and contaminate damage to the mirror surfaces. A hemisphere mirror makes up the front chamber and has its center of curvature at the target image, where rays leaving the target are reflected back upon themselves, minimizing radiation losses.

High power infrared super-Gaussian beams: generation, propagation, and application

NASA Astrophysics Data System (ADS)

du Preez, Neil C.; Forbes, Andrew; Botha, Lourens R.

2008-10-01

In this paper we present the design of a CO2 laser resonator that produces as the stable transverse mode a super-Gaussian laser beam. The resonator makes use of an intra-cavity diffractive mirror and a flat output coupler, generating the desired intensity profile at the output coupler with a flat wavefront. We consider the modal build-up in such a resonator and show that such a resonator mode has the ability to extract more energy from the cavity that a standard cavity single mode beam (e.g., Gaussian mode cavity). We demonstrate the design experimentally on a high average power TEA CO2 laser for paint stripping applications.

Three-dimensional Characterization of Resorption Cavity Size and Location in Human Vertebral Trabecular Bone

PubMed Central

Goff, M.G.; Slyfield, C.R.; Kummari, S.R.; Tkachenko, E.V.; Fischer, S. E.; Yi, Y.H.; Jekir, M.; Keaveny, T.M.; Hernandez, C.J.

2012-01-01

The number and size of resorption cavities in cancellous bone are believed to influence rates of bone loss, local tissue stress and strain and potentially whole bone strength. Traditional two-dimensional approaches to measuring resorption cavities in cancellous bone report the percent of the bone surface covered by cavities or osteoclasts, but cannot measure cavity number or size. Here we use three-dimensional imaging (voxel size 0.7 × 0.7 × 5.0 μm) to characterize resorption cavity location, number and size in human vertebral cancellous bone from nine elderly donors (7 male, 2 female, ages 47–80 years). Cavities were 30.10 ± 8.56 μm in maximum depth, 80.60 ± 22.23 *103 μm2 in surface area and 614.16 ± 311.93 *103 μm3 in volume (mean ± SD). The average number of cavities per unit tissue volume (N.Cv/TV) was 1.25 ± 0.77 mm−3. The ratio of maximum cavity depth to local trabecular thickness was 30.46 ± 7.03 % and maximum cavity depth was greater on thicker trabeculae (p < 0.05, r2 = 0.14). Half of the resorption cavities were located entirely on nodes (the intersection of two or more trabeculae) within the trabecular structure. Cavities that were not entirely on nodes were predominately on plate-like trabeculae oriented in the cranial-caudal (longitudinal) direction. Cavities on plate-like trabeculae were larger in maximum cavity depth, cavity surface area and cavity volume than cavities on rod-like trabeculae (p < 0.05). We conclude from these findings that cavity size and location are related to local trabecular microarchitecture. PMID:22507299

Melt production in large-scale impact events: Implications and observations at terrestrial craters

NASA Technical Reports Server (NTRS)

Grieve, Richard A. F.; Cintala, Mark J.

1992-01-01

The volume of impact melt relative to the volume of the transient cavity increases with the size of the impact event. Here, we use the impact of chondrite into granite at 15, 25, and 50 km s(sup -1) to model impact-melt volumes at terrestrial craters in crystalline targets and explore the implications for terrestrial craters. Figures are presented that illustrate the relationships between melt volume and final crater diameter D(sub R) for observed terrestrial craters in crystalline targets; also included are model curves for the three different impact velocities. One implication of the increase in melt volumes with increasing crater size is that the depth of melting will also increase. This requires that shock effects occurring at the base of the cavity in simple craters and in the uplifted peaks of central structures at complex craters record progressively higher pressures with increasing crater size, up to a maximum of partial melting (approx. 45 GPa). Higher pressures cannot be recorded in the parautochthonous rocks of the cavity floor as they will be represented by impact melt, which will not remain in place. We have estimated maximum recorded pressures from a review of the literature, using such observations as planar features in quartz and feldspar, diaplectic glasses of feldspar and quartz, and partial fusion and vesiculation, as calibrated with estimates of the pressures required for their formation. Erosion complicates the picture by removing the surficial (most highly shocked) rocks in uplifted structures, thereby reducing the maximum shock pressures observed. In addition, the range of pressures that can be recorded is limited. Nevertheless, the data define a trend to higher recorded pressures with crater diameter, which is consistent with the implications of the model. A second implication is that, as the limit of melting intersects the base of the cavity, central topographic peaks will be modified in appearance and ultimately will not occur. That is, the peak will first develop a central depression, due to the flow of low-strength melted materials, when the melt volume begins to intersect the transient-cavity base.

Experimental investigation of the effect of air cavity size in cylindrical ionization chambers on the measurements in 60Co radiotherapy beams

NASA Astrophysics Data System (ADS)

Swanpalmer, John; Johansson, Karl-Axel

2011-11-01

In the late 1970s, Johansson et al (1978 Int. Symp. National and International Standardization of Radiation Dosimetry (Atlanta 1977) vol 2 (Vienna: IAEA) pp 243-70) reported experimentally determined displacement correction factors (pdis) for cylindrical ionization chamber dosimetry in 60Co and high-energy photon beams. These pdis factors have been implemented and are currently in use in a number of dosimetry protocols. However, the accuracy of these factors has recently been questioned by Wang and Rogers (2009a Phys. Med. Biol. 54 1609-20), who performed Monte Carlo simulations of the experiments performed by Johansson et al. They reported that the inaccuracy of the pdis factors originated from the normalization procedure used by Johansson et al. In their experiments, Johansson et al normalized the measured depth-ionization curves at the depth of maximum ionization for each of the different ionization chambers. In this study, we experimentally investigated the effect of air cavity size of cylindrical ionization chambers in a PMMA phantom and 60Co γ-beam. Two different pairs of air-filled cylindrical ionization chambers were used. The chambers in each pair had identical construction and materials but different air cavity volume (diameter). A 20 MeV electron beam was utilized to determine the ratio of the mass of air in the cavity of the two chambers in each pair. This ratio of the mass of air in each pair was then used to compare the ratios of the ionizations obtained at different depths in the PMMA phantom and 60Co γ-beam using the two pairs of chambers. The diameter of the air cavity of cylindrical ionization chambers influences both the depth at which the maximum ionization is observed and the ionization per unit mass of air at this depth. The correction determined at depths of 50 mm and 100 mm is smaller than the correction currently used in many dosimetry protocols. The results presented here agree with the findings of Wang and Rogers' Monte Carlo simulations and show that the normalization procedure employed by Johansson et al is not correct.

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

Small, Katherine; Kelly, Chris; Beldham-Collins, Rachael

A comparative study was conducted comparing the difference between (1) conformal radiotherapy (CRT) to the whole breast with sequential boost excision cavity plans and (2) intensity-modulated radiation therapy (IMRT) to the whole breast with simultaneously integrated boost to the excision cavity. The computed tomography (CT) data sets of 25 breast cancer patients were used and the results analysed to determine if either planning method produced superior plans. CT data sets from 25 past breast cancer patients were planned using (1) CRT prescribed to 50 Gy in 25 fractions (Fx) to the whole-breast planning target volume (PTV) and 10 Gy inmore » 5Fx to the excision cavity and (2) IMRT prescribed to 60 Gy in 25Fx, with 60 Gy delivered to the excision cavity PTV and 50 Gy delivered to the whole-breast PTV, treated simultaneously. In total, 50 plans were created, with each plan evaluated by PTV coverage using conformity indices, plan maximum dose, lung dose, and heart maximum dose for patients with left-side lesions. CRT plans delivered the lowest plan maximum doses in 56% of cases (average CRT = 6314.34 cGy, IMRT = 6371.52 cGy). They also delivered the lowest mean lung dose in 68% of cases (average CRT = 1206.64 cGy, IMRT = 1288.37 cGy) and V20 in 88% of cases (average CRT = 20.03%, IMRT = 21.73%) and V30 doses in 92% of cases (average CRT = 16.82%, IMRT = 17.97%). IMRT created more conformal plans, using both conformity index and conformation number, in every instance, and lower heart maximum doses in 78.6% of cases (average CRT = 5295.26 cGy, IMRT = 5209.87 cGy). IMRT plans produced superior dose conformity and shorter treatment duration, but a slightly higher planning maximum and increased lung doses. IMRT plans are also faster to treat on a daily basis, with shorter fractionation.« less

Brain Arterial Diameters as a Risk Factor for Vascular Events.

PubMed

Gutierrez, Jose; Cheung, Ken; Bagci, Ahmet; Rundek, Tatjana; Alperin, Noam; Sacco, Ralph L; Wright, Clinton B; Elkind, Mitchell S V

2015-08-06

Arterial luminal diameters are routinely used to assess for vascular disease. Although small diameters are typically considered pathological, arterial dilatation has also been associated with disease. We hypothesize that extreme arterial diameters are biomarkers of the risk of vascular events. Participants in the Northern Manhattan Study who had a time-of-flight magnetic resonance angiography were included in this analysis (N=1034). A global arterial Z-score, called the brain arterial remodeling (BAR) score, was obtained by averaging the measured diameters within each individual. Individuals with a BAR score <-2 SDs were considered to have the smallest diameters, individuals with a BAR score >-2 and <2 SDs had average diameters, and individuals with a BAR score >2 SDs had the largest diameters. All vascular events were recorded prospectively after the brain magnetic resonance imaging. Spline curves and incidence rates were used to test our hypothesis. The association of the BAR score with death (P=0.001), vascular death (P=0.02), any vascular event (P=0.05), and myocardial infarction (P=0.10) was U-shaped except for ischemic stroke (P=0.74). Consequently, incidence rates for death, vascular death, myocardial infarction, and any vascular event were higher in individuals with the largest diameters, whereas individuals with the smallest diameters had a higher incidence of death, vascular death, any vascular event, and ischemic stroke compared with individuals with average diameters. The risk of death, vascular death, and any vascular event increased at both extremes of brain arterial diameters. The pathophysiology linking brain arterial remodeling to systemic vascular events needs further research. © 2015 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley Blackwell.

Ultrafast Directional Beam Switching in Coupled VCSELs

NASA Technical Reports Server (NTRS)

Ning, Cun-Zheng; Goorjian, Peter

2001-01-01

We propose a new approach to performing ultrafast directional beam switching using two coupled Vertical-Cavity Surface-Emitting Lasers (VCSELs). The proposed strategy is demonstrated for two VCSELs of 5.6 microns in diameter placed about 1 micron apart from the edges, showing a switching speed of 42 GHz with a maximum far-field angle span of about 10 degrees.

The Manicouagan impact structure - An analysis of its original dimensions and form

NASA Technical Reports Server (NTRS)

Grieve, R. A. F.; Head, J. W., III

1983-01-01

A reanalysis of the preerosional geology of the Canadian impact crater, Manicouagan, is presented. Although most of the current features of the annular moat are primarily a result of erosional processes, the original dimensions of the cavity have been determined to include a transient cavity 60 km in diam. The final floor of the crater was studied and found to be an impact melt-covered inner plateau 55 km in diam. Comparisons with similar crater bottoms on the moon are used to estimate a final crater rim diameter of 85-95 km. The inner plateau and relatively smooth deposits on the crater floor are noted to be most similar to the lunar crater Copernicus.

Very large scale characterization of graphene mechanical devices using a colorimetry technique.

PubMed

Cartamil-Bueno, Santiago Jose; Centeno, Alba; Zurutuza, Amaia; Steeneken, Peter Gerard; van der Zant, Herre Sjoerd Jan; Houri, Samer

2017-06-08

We use a scalable optical technique to characterize more than 21 000 circular nanomechanical devices made of suspended single- and double-layer graphene on cavities with different diameters (D) and depths (g). To maximize the contrast between suspended and broken membranes we used a model for selecting the optimal color filter. The method enables parallel and automatized image processing for yield statistics. We find the survival probability to be correlated with a structural mechanics scaling parameter given by D 4 /g 3 . Moreover, we extract a median adhesion energy of Γ = 0.9 J m -2 between the membrane and the native SiO 2 at the bottom of the cavities.

High power 808 nm vertical cavity surface emitting laser with multi-ring-shaped-aperture structure

NASA Astrophysics Data System (ADS)

Hao, Y. Q.; Shang, C. Y.; Feng, Y.; Yan, C. L.; Zhao, Y. J.; Wang, Y. X.; Wang, X. H.; Liu, G. J.

2011-02-01

The carrier conglomeration effect has been one of the main problems in developing electrically pumped high power vertical cavity surface emitting laser (VCSEL) with large aperture. We demonstrate a high power 808 nm VCSEL with multi-ring-shaped-aperture (MRSA) to weaken the carrier conglomeration effect. Compared with typical VCSEL with single large aperture (SLA), the 300-μm-diameter VCSEL with MRSA has more uniform near field and far field patterns. Moreover, MRSA laser exhibits maximal CW light output power 0.3 W which is about 3 times that of SLA laser. And the maximal wall-plug efficiency of 17.4% is achieved, higher than that of SLA laser by 10%.

Absorption spectroscopy of microalgae, cyanobacteria, and dissolved organic matter: Measurements in an integrating sphere cavity

NASA Astrophysics Data System (ADS)

Pogosyan, S. I.; Durgaryan, A. M.; Konyukhov, I. V.; Chivkunova, O. B.; Merzlyak, M. N.

2009-12-01

A device for integrating cavity absorption measurements (ICAM) with an internal diameter of 80 mm suitable for field research is described. The spectral features of the light absorption by some cyanobacteria, green algae, and diatoms in the integrating sphere were studied and the dependences of the absorption on the cell concentration were determined in comparison with the conventional measurements in a 1-cm cuvette. The sensitivity of the chlorophyll estimation with the ICAM reached 0.2-0.5 mg m-3. The results of the ICAM application for the direct analysis of the natural phytoplankton and dissolved organic (“yellow“) matter in the Black Sea and the Sea of Japan are described.

Indirect and direct methods for measuring a dynamic throat diameter in a solid rocket motor

NASA Astrophysics Data System (ADS)

Colbaugh, Lauren

In a solid rocket motor, nozzle throat erosion is dictated by propellant composition, throat material properties, and operating conditions. Throat erosion has a significant effect on motor performance, so it must be accurately characterized to produce a good motor design. In order to correlate throat erosion rate to other parameters, it is first necessary to know what the throat diameter is throughout a motor burn. Thus, an indirect method and a direct method for determining throat diameter in a solid rocket motor are investigated in this thesis. The indirect method looks at the use of pressure and thrust data to solve for throat diameter as a function of time. The indirect method's proof of concept was shown by the good agreement between the ballistics model and the test data from a static motor firing. The ballistics model was within 10% of all measured and calculated performance parameters (e.g. average pressure, specific impulse, maximum thrust, etc.) for tests with throat erosion and within 6% of all measured and calculated performance parameters for tests without throat erosion. The direct method involves the use of x-rays to directly observe a simulated nozzle throat erode in a dynamic environment; this is achieved with a dynamic calibration standard. An image processing algorithm is developed for extracting the diameter dimensions from the x-ray intensity digital images. Static and dynamic tests were conducted. The measured diameter was compared to the known diameter in the calibration standard. All dynamic test results were within +6% / -7% of the actual diameter. Part of the edge detection method consists of dividing the entire x-ray image by an average pixel value, calculated from a set of pixels in the x-ray image. It was found that the accuracy of the edge detection method depends upon the selection of the average pixel value area and subsequently the average pixel value. An average pixel value sensitivity analysis is presented. Both the indirect method and the direct method prove to be viable approaches to determining throat diameter during solid rocket motor operation.

Development of an S-band cavity-type beam position monitor for a high power THz free-electron laser

NASA Astrophysics Data System (ADS)

Noh, Seon Yeong; Kim, Eun-San; Hwang, Ji-Gwang; Heo, A.; won Jang, Si; Vinokurov, Nikolay A.; Jeong, Young UK; Hee Park, Seong; Jang, Kyu-Ha

2015-01-01

A cavity-type beam position monitor (BPM) has been developed for a compact terahertz (THz) free-electron laser (FEL) system and ultra-short pulsed electron Linac system at the Korea Atomic Energy Research Institute (KAERI). Compared with other types of BPMs, the cavity-type BPM has higher sensitivity and faster response time even at low charge levels. When electron beam passes through the cavity-type BPM, it excites the dipole mode of the cavity of which amplitude depends linearly on the beam offset from the center of the cavity. Signals from the BPM were measured as a function of the beam offset by using an oscilloscope. The microtron accelerator for the KAERI THz FEL produces the electron beam with an energy of 6.5 MeV and pulse length of 5 μs with a micropulse of 10-20 ps at the frequency of 2.801 GHz. The macropulse beam current is 40 mA. Because the microtron provides multi-bunch system, output signal would be the superposition of each single bunch. So high output signal can be obtained from superposition of each single bunch. The designed position resolution of the cavity-type BPM in multi-bunch is submicron. Our cavity-type BPM is made of aluminum and vacuum can be maintained by indium sealing without brazing process, resulting in easy modification and cost saving. The resonance frequency of the cavity-type BPM is 2.803 GHz and the cavity-type BPM dimensions are 200 × 220 mm (length × height) with a pipe diameter of 38 mm. The measured position sensitivity was 6.19 (mV/mm)/mA and the measured isolation between the X and Y axis was -39 dB. By measuring the thermal noise of system, position resolution of the cavity-type BPM was estimated to be less than 1 μm. In this article, we present the test results of the S-band cavity-type BPM and prove the feasibility of the beam position measurement with high resolution using this device.

Development of an S-band cavity-type beam position monitor for a high power THz free-electron laser.

PubMed

Noh, Seon Yeong; Kim, Eun-San; Hwang, Ji-Gwang; Heo, A; Jang, Si won; Vinokurov, Nikolay A; Jeong, Young U K; Park, Seong Hee; Jang, Kyu-Ha

2015-01-01

A cavity-type beam position monitor (BPM) has been developed for a compact terahertz (THz) free-electron laser (FEL) system and ultra-short pulsed electron Linac system at the Korea Atomic Energy Research Institute (KAERI). Compared with other types of BPMs, the cavity-type BPM has higher sensitivity and faster response time even at low charge levels. When electron beam passes through the cavity-type BPM, it excites the dipole mode of the cavity of which amplitude depends linearly on the beam offset from the center of the cavity. Signals from the BPM were measured as a function of the beam offset by using an oscilloscope. The microtron accelerator for the KAERI THz FEL produces the electron beam with an energy of 6.5 MeV and pulse length of 5 μs with a micropulse of 10-20 ps at the frequency of 2.801 GHz. The macropulse beam current is 40 mA. Because the microtron provides multi-bunch system, output signal would be the superposition of each single bunch. So high output signal can be obtained from superposition of each single bunch. The designed position resolution of the cavity-type BPM in multi-bunch is submicron. Our cavity-type BPM is made of aluminum and vacuum can be maintained by indium sealing without brazing process, resulting in easy modification and cost saving. The resonance frequency of the cavity-type BPM is 2.803 GHz and the cavity-type BPM dimensions are 200 × 220 mm (length × height) with a pipe diameter of 38 mm. The measured position sensitivity was 6.19 (mV/mm)/mA and the measured isolation between the X and Y axis was -39 dB. By measuring the thermal noise of system, position resolution of the cavity-type BPM was estimated to be less than 1 μm. In this article, we present the test results of the S-band cavity-type BPM and prove the feasibility of the beam position measurement with high resolution using this device.

Development of an S-band cavity-type beam position monitor for a high power THz free-electron laser

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

Noh, Seon Yeong; Kim, Eun-San, E-mail: eskim1@knu.ac.kr; Hwang, Ji-Gwang

2015-01-15

A cavity-type beam position monitor (BPM) has been developed for a compact terahertz (THz) free-electron laser (FEL) system and ultra-short pulsed electron Linac system at the Korea Atomic Energy Research Institute (KAERI). Compared with other types of BPMs, the cavity-type BPM has higher sensitivity and faster response time even at low charge levels. When electron beam passes through the cavity-type BPM, it excites the dipole mode of the cavity of which amplitude depends linearly on the beam offset from the center of the cavity. Signals from the BPM were measured as a function of the beam offset by using anmore » oscilloscope. The microtron accelerator for the KAERI THz FEL produces the electron beam with an energy of 6.5 MeV and pulse length of 5 μs with a micropulse of 10-20 ps at the frequency of 2.801 GHz. The macropulse beam current is 40 mA. Because the microtron provides multi-bunch system, output signal would be the superposition of each single bunch. So high output signal can be obtained from superposition of each single bunch. The designed position resolution of the cavity-type BPM in multi-bunch is submicron. Our cavity-type BPM is made of aluminum and vacuum can be maintained by indium sealing without brazing process, resulting in easy modification and cost saving. The resonance frequency of the cavity-type BPM is 2.803 GHz and the cavity-type BPM dimensions are 200 × 220 mm (length × height) with a pipe diameter of 38 mm. The measured position sensitivity was 6.19 (mV/mm)/mA and the measured isolation between the X and Y axis was −39 dB. By measuring the thermal noise of system, position resolution of the cavity-type BPM was estimated to be less than 1 μm. In this article, we present the test results of the S-band cavity-type BPM and prove the feasibility of the beam position measurement with high resolution using this device.« less

PHYSICAL PROPERTIES OF LARGE AND SMALL GRANULES IN SOLAR QUIET REGIONS

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

Yu Daren; Xie Zongxia; Hu Qinghua

The normal mode observations of seven quiet regions obtained by the Hinode spacecraft are analyzed to study the physical properties of granules. An artificial intelligence technique is introduced to automatically find the spatial distribution of granules in feature spaces. In this work, we investigate the dependence of granular continuum intensity, mean Doppler velocity, and magnetic fields on granular diameter. We recognized 71,538 granules by an automatic segmentation technique and then extracted five properties: diameter, continuum intensity, Doppler velocity, and longitudinal and transverse magnetic flux density to describe the granules. To automatically explore the intrinsic structures of the granules in themore » five-dimensional parameter space, the X-means clustering algorithm and one-rule classifier are introduced to define the rules for classifying the granules. It is found that diameter is a dominating parameter in classifying the granules and two families of granules are derived: small granules with diameters smaller than 1.''44, and large granules with diameters larger than 1.''44. Based on statistical analysis of the detected granules, the following results are derived: (1) the averages of diameter, continuum intensity, and Doppler velocity in the upward direction of large granules are larger than those of small granules; (2) the averages of absolute longitudinal, transverse, and unsigned flux density of large granules are smaller than those of small granules; (3) for small granules, the average of continuum intensity increases with their diameters, while the averages of Doppler velocity, transverse, absolute longitudinal, and unsigned magnetic flux density decrease with their diameters. However, the mean properties of large granules are stable; (4) the intensity distributions of all granules and small granules do not satisfy Gaussian distribution, while that of large granules almost agrees with normal distribution with a peak at 1.04 I{sub 0}.« less

Thermal-Mechanical Study of 3.9 GHz CW Coupler and Cavity for LCLS-II Project

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

Gonin, Ivan; Harms, Elvin; Khabiboulline, Timergali

2017-05-01

Third harmonic system was originally developed by Fermilab for FLASH facility at DESY and then was adopted and modified by INFN for the XFEL project [1-3]. In contrast to XFEL project, all cryomodules in LCLS-II project will operate in CW regime with higher RF average power for 1.3 GHz and 3.9 GHz cavities and couplers. Design of the cavity and fundamental power coupler has been modified to satisfy LCLS-II requirements. In this paper we discuss the results of COMSOL thermal and mechanical analysis of the 3.9 GHz coupler and cavity to verify proposed modifica-tion of the design. For the dressedmore » cavity we present simulations of Lorentz force detuning, helium pressure sensitivity df/dP and major mechanical resonances.« less

Higher order mode couplers for normal conducting DORIS 5-cell cavities

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

Dewersteg, B.; Seesselberg, E.; Zolfaghari, A.

1985-10-01

The beam intensity of the DORIS e -e storage ring is limited to about 100 mA average circulation current as a result of instabilities driven by higher order rf cavity modes. Thus an investigation has been made of the higher order mode impedances of the DORIS rf accelerator cavities. These cavities are the same as the normally conducting inductively coupled 500 MHz 5-cell structures used in PETRA. The results of the investigation were applied for the construction of inductive and capacitive attenuation antennae corresponding to specific mode spectra and mode impedances. The antennae must fit into the existing 35 mmmore » pick up flanges of the cavities and in spite of these size and position limitations they must be efficient in reducing the shunt impedances of the dangerous modes.« less

Pressure loadings in a rectangular cavity with and without a captive store

DOE PAGES

Barone, Matthew; Arunajatesan, Srinivasan

2016-05-31

Simulations of the flow past a rectangular cavity containing a model captive store are performed using a hybrid Reynolds-averaged Navier–Stokes/large-eddy simulation model. Calculated pressure fluctuation spectra are validated using measurements made on the same configuration in a trisonic wind tunnel at Mach numbers of 0.60, 0.80, and 1.47. The simulation results are used to calculate unsteady integrated forces and moments acting on the store. Spectra of the forces and moments, along with correlations calculated for force/moment pairs, reveal that a complex relationship exists between the unsteady integrated forces and the measured resonant cavity modes, as indicated in the cavity wallmore » pressure measurements. As a result, the structure of identified cavity resonant tones is examined by visualization of filtered surface pressure fields.« less

Commercial mode-locked vertical external cavity surface emitting lasers

NASA Astrophysics Data System (ADS)

Lubeigt, Walter; Bialkowski, Bartlomiej; Lin, Jipeng; Head, C. Robin; Hempler, Nils; Maker, Gareth T.; Malcolm, Graeme P. A.

2017-02-01

In recent years, M Squared Lasers have successfully commercialized a range of mode-locked vertical external cavity surface emitting lasers (VECSELs) operating between 920-1050nm and producing picosecond-range pulses with average powers above 1W at pulse repetition frequencies (PRF) of 200MHz. These laser products offer a low-cost, easy-to-use and maintenance-free tool for the growing market of nonlinear microscopy. However, in order to present a credible alternative to ultrafast Ti-sapphire lasers, pulse durations below 200fs are required. In the last year, efforts have been directed to reduce the pulse duration of the Dragonfly laser system to below 200fs with a target average power above 1W at a PRF of 200MHz. This paper will describe and discuss the latest efforts undertaken to approach these targets in a laser system operating at 990nm. The relatively low PRF operation of Dragonfly lasers represents a challenging requirement for mode-locked VECSELs due to the very short upper state carrier lifetime, on the order of a few nanoseconds, which can lead to double pulsing behavior in longer cavities as the time between consecutive pulses is increased. Most notably, the design of the Dragonfly VECSEL cavity was considerably modified and the laser system extended with a nonlinear pulse stretcher and an additional compression stage. The improved Dragonfly laser system achieved pulse duration as short as 130fs with an average power of 0.85W.

[Oral health among adolescents: aspects relating to hygiene, dental cavities and periodontal disease in the cities of Recife and Feira de Santana, Brazil].

PubMed

Nogueira dos Santos, Nilton Cesar; Alves, Tecia Daltro Borges; Freitas, Valéria Souza; Jamelli, Silvia Regina; Cavalcanti Sarinho, Emanuel Sávio

2007-01-01

To characterize the oral health in adolescents in the cities of Recife and Feira de Santana, Northeast Brazil by assessment of personal hygiene and dental cavities and periodontal disease. Forty adolescents between ten and eighteen years old were assessed through an exploratory study run in Recife in 2005. In Feira de Santana, 971 adolescents (twelve years old) were examined through a cross section study in 2002. It was assessed cavity status through the number of cavitied, missing and filled teeth, visible dental plaque, bleeding gums and periodontal status. The analysis was based on Chi-Square, Kruskall-Wallis and Fisher tests, with a confidence interval of 95%. The most of adolescents followed oral hygiene practices three times a day. The DMTF values presented a median of 1.5 in Recife and averages of 1.89 in state schools, 2.17 in municipal schools and 2.39 in private schools in Feira de Santana. The bleeding gum in Recife presented a median of 27%, and in Feira de Santana the healthy sextant averages of 4.36, 4.08 and 5.16 in state, municipal and private schools respectively. The frequency of the dental cavities was low, with most of the adolescents reporting good habits of oral hygiene and favorable periodontal conditions.

Invertebrate enemies and nest associates of the leaf-cutting ant Atta texana (Buckley) (Formicudae, Attini)

Treesearch

D.A. Waller; John C. Moser

1990-01-01

The complex nests of leaf-cutting ants (Formicidae; Attini) provide rich habitats for ant associates. These mounds consist of interconnected subterranean cavities that average 0.002 m3 in volume (Waler et al. 1938) and extend to depths of 7 m (Moser 1963). Many cavities contain fungus gardens, cultivated on live plant material, frass and debris....

High-speed 850 nm VCSELs with 28 GHz modulation bandwidth for short reach communication

NASA Astrophysics Data System (ADS)

Westbergh, Petter; Safaisini, Rashid; Haglund, Erik; Gustavsson, Johan S.; Larsson, Anders; Joel, Andrew

2013-03-01

We present results from our new generation of high performance 850 nm oxide confined vertical cavity surface-emitting lasers (VCSELs). With devices optimized for high-speed operation under direct modulation, we achieve record high 3dB modulation bandwidths of 28 GHz for ~4 μm oxide aperture diameter VCSELs, and 27 GHz for devices with a ~7 μm oxide aperture diameter. Combined with a high-speed photoreceiver, the ~7 μm VCSEL enables error-free transmission at data rates up to 47 Gbit/s at room temperature, and up to 40 Gbit/s at 85°C.

Droplet Impact Sub-cavity Histories and PDPA Spray Experiments for Spray Cooling Modeling

NASA Astrophysics Data System (ADS)

Hillen, Nicholas Lee

Spray cooling is a topic of current interest for its ability to uniformly remove high levels of waste heat from densely packed microelectronics. It has demonstrated the ability to achieve very high heat fluxes, up to 500 W/cm2 with water as the coolant, making it an attractive active thermal management tool. Full Computational Fluid Dynamic (CFD) simulations of spray cooling are infeasible due to the complexity of the spray (drops fluxes of 106 drops/cm2-sec) and heater surface physics requiring impractical resources. Thus a Monte-Carlo (MC) spray cooling simulation model based on empirical data is under development to serve as a cost effective design tool. The initial MC model shows promise, but it lacks additional physics necessary to predict accurate heat fluxes based on nozzle conditions and heated surface geometry. This work reports spray and single drop experiments with the goal of computing the volume beneath a droplet impact cavity (the sub-cavity volume) created by a single impinging droplet on an initial liquid layer. A Phase Doppler Particle Analyzer (PDPA) was utilized to characterize a spray of interest in terms of integrated global Weber, Reynolds, and Froude numbers for varying flow conditions. Results showed that the spray droplet diameters decreased and velocities increased with increasing nozzle gage pressure. A relevant test plan for the single drop experiments has been created from the measured PDPA spray profiles combined with residual spray film thickness measurements from literature resulting in: 140≤We≤1,000, 1,200≤ Re≤3,300, and 0.2≤h0*≤1.0. Froude numbers were not able to be matched for the current single drop experiments (spray: 32,800≤Fr≤275,000). Liquid film thicknesses under the cavity formed by a single droplet have been measured versus radius and time via a non-contact optical thickness sensor for the selected range of dimensionless numbers (We, Re, and h0*). Sub-cavity radius histories have also been analyzed utilizing high-speed imagery techniques to create the cavity thickness traverse profiles. Time dependent sub-cavity volumes have been computed by integrating these subcavity liquid film thicknesses versus radius at various times. It is found that higher We and lower h0* result in a more radially uniform sub-cavity surface contour versus time, except for thinner liquid film regions which are observed near the outer bottom cavity radius. The subcavity volume was found to be nearly constant for a majority of the cavity lifetime and increased with We and h0*. These results will be incorporated into the MC model to improve its predictive capability in future work. In addition, splashed droplet diameters and velocities have been extracted from PDPA data for a spray impinging normal to a smooth surface. It was found that the splashed droplets had sizes which were similar to the impinging spray droplets, and had velocities that never exceeded 3 m/s. The splashed droplet results have a negligible contribution to cavity formations due to their low Weber number. This splashing data has been detailed for future implementation into the MC model in terms of mass conservation in the liquid film.

A 1.5 T transverse magnetic field in radiotherapy of rectal cancer: Impact on the dose distribution

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

Uilkema, Sander, E-mail: s.uilkema@nki.nl; Heide, Uulke van der; Sonke, Jan-Jakob

2015-12-15

Purpose: MRI guidance during radiotherapy has the potential to enable more accurate dose delivery, optimizing the balance between local control and treatment related toxicity. However, the presence of a permanent magnetic field influences the dose delivery, especially around air cavities. Here, electrons are able to return to the surface through which they entered the air cavity (electron return effect, ERE) locally resulting in dose hot- and cold-spots. Where RT of rectal cancer patients might benefit from MRI guidance for margin reduction, air cavities in and around the target volume are frequently present. The purpose of this research is to evaluatemore » the impact of the presence of a 1.5 T transverse magnetic field on dose delivery in patients with rectal cancer. Methods: Ten patients treated with 5 × 5 Gy RT having large changes in pelvic air content were selected out of a cohort of 33 patients. On the planning CT, a 1.5 T, 6 MV, 7-field intensity modulated radiotherapy (IMRT) plan was created. This plan was subsequently recalculated on daily CT scans. For each daily CT, the CTV V{sub 95%} and V{sub 107%} and bowel area V{sub 5Gy}, V{sub 10Gy}, V{sub 15Gy}, V{sub 20Gy}, and V{sub 25Gy} were calculated to evaluate the changes in dose distribution from fraction to fraction. For comparison, the authors repeated this procedure for the 0 T situation. To study the effect of changing air cavities separate from other anatomical changes, the authors also generated artificial air cavities in the CTV of one patient (2 and 5 cm diameter), in the high dose gradient region (2 cm), and in the low dose area (2 cm). Treatment plans were optimized without and with each simulated air cavity. For appearing and disappearing air cavities, the CTV V{sub 95%} and V{sub 107%} were evaluated. The authors also evaluated the ERE separate from attenuation changes locally around appearing gas pockets. Results: For the ten patients, at 1.5 T, the V{sub 95%} was influenced by both appearing and disappearing air, and dropped to <98% in 2 out of 50 fractions due a disappearing air cavity of 150 cm{sup 3}. V{sub 95%} differences between 0 and 1.5 T were all within 2%. The V{sub 107%} was below 1% in 46 out of 50 fractions, and increased to 3% in the remaining fractions due to appearing air of around 120 cm{sup 3}. For comparison, V{sub 107%} was <1% at 0 T for all fractions. In the bowel area, the V{sub 15Gy} varied strongest from fraction to fraction, but differences between 1.5 and 0 T were minimal with an average difference of 2.3 cm{sup 3} (SD = 18.7 cm{sup 3}, p = 0.38). For the simulated air cavities, the ERE resulted in cold-spots maximally 5% lower than prescribed and hot-spots maximally 6% higher than prescribed. Conclusions: The presence of a 1.5 T magnetic field has an impact on the dose distribution when the air content changes of within a few percent in these selected rectal cancer patients. The authors consider this influence of the transverse magnetic field on the dose distribution in IMRT for rectal cancer patients clinically acceptable.« less

Microendoscopy of the eustachian tube and the middle ear

NASA Astrophysics Data System (ADS)

Hopf, Juergen U. G.; Linnarz, Marietta; Gundlach, Peter; Scherer, Hans H.; Lutze-Koffroth, C.; Loerke, S.; Voege, Karl H.; Tschepe, Johannes; Mueller, Gerhard J.

1992-08-01

Progressive miniaturization of flexible fiberoptic instruments has made it possible to perform atraumatic endoscopy of the Eustachian tube and tympanic cavity with an intact ear drum. By means of a special set of carrier- and balloon-catheters which are partly actively steerable, flexible microendoscopes with outside diameters of 290 - 700 micrometers are inserted through the nasal cavity into the nasopharyngeal opening of the Eustachian tube and carefully advanced into the middle ear compartment under permanent direct visual control. Second generation microendoscopes with outside diameters of 750 to 1000 micrometers are equipped with a one- direction tip-steering mechanism which allows deflection up to 90 degrees. In addition to it, the use of two special types of four-function scopes (outside diameter: 1.6 mm and 1.8 mm) fitted with a one-lumen working channel are presented. This new technique of `Transnasal Tubo-Tympanoscopy' (TTT) only needs local anesthesia, normally is performed on an outpatient basis, and is indicated for the diagnosis of any disturbances of the sound conducting apparatus (ear drum and ossicular chain) like chronic otitis media and oto-sclerosis and of those sensorineural hearing disorders on which -- until today -- only the traditional surgical tympanoscopy could provide morphological information on the pathogenesis of the hearing loss, e.g., on assumed round window ruptures. By this minimal invasive and minimal traumatizing method pathological alterations of the ossicular chain as well as obstructions in the cartilaginous and the osseous part of the Eustachian tube can be directly visualized.

Counting Condensation Nuclei in the Antarctic Ozone Mission

NASA Technical Reports Server (NTRS)

Wilson, James Charles

1994-01-01

The work done on this grant primarily concerns the measurement of aerosol in the stratosphere from NASA ER-2 aircraft in studies of stratospheric ozone depletion in the northern and southern hemispheres. The ER-2 Condensation Nucleus Counter (CNC) measures the number concentration of particles in the diameter range of approximately 0.01 to 1 micron. The Passive Cavity Aerosol Spectrometer measures size distributions in the 0.17 to 3 micron diameter range. This instrument was upgraded during this grant period to a Focused Cavity Aerosol Spectrometer (FCAS). This upgrade permitted the instrument to measure particles as small as 0.05 micron in diameter. The inlet for the PCAS and FCAS was modified and characterized under this grant so that the modifications to the aerosol due to anisokinetic sampling and heating upon sampling and in transport to the measurement location were accounted for in the data analysis. These measurements permitted observations of particle production in the southern hemisphere winter polar vortex and observation of the impact of denitrification on the number concentration of the aerosol in the denitrified air. In the northern polar vortex, the measurements provided a characterization of the sulfate aerosol. Following the eruption of Mount Pinatubo in 1991, the measurements permitted an accurate characterization of the sulfate aerosol enhancements resulting from the eruption. This led to studies of the impact of heterogeneous chemistry on the partitioning of the partitioning of the reactive nitrogen species and the partitioning of the chlorine reservoir.

Superconducting radio-frequency cavities made from medium and low-purity niobium ingots

DOE PAGES

Ciovati, Gianluigi; Dhakal, Pashupati; Myneni, Ganapati R.

2016-04-07

Superconducting radio-frequency cavities made of ingot niobium with residual resistivity ratio (RRR) greater than 250 have proven to have similar or better performance than fine-grain Nb cavities of the same purity, after standard processing. The high purity requirement contributes to the high cost of the material. As superconducting accelerators operating in continuous-wave typically require cavities to operate at moderate accelerating gradients, using lower purity material could be advantageous not only to reduce cost but also to achieve higher Q 0-values. In this contribution we present the results from cryogenic RF tests of 1.3–1.5 GHz single-cell cavities made of ingot Nbmore » of medium (RRR = 100–150) and low (RRR = 60) purity from different suppliers. Cavities made of medium-purity ingots routinely achieved peak surface magnetic field values greater than 70 mT with an average Q 0-value of 2 × 10 10 at 2 K after standard processing treatments. As a result, the performances of cavities made of low-purity ingots were affected by significant pitting of the surface after chemical etching.« less

Preoperative progressive pneumoperitoneum and botulinum toxin type A in patients with large incisional hernia.

PubMed

Bueno-Lledó, J; Torregrosa, A; Ballester, N; Carreño, O; Carbonell, F; Pastor, P G; Pamies, J; Cortés, V; Bonafé, S; Iserte, J

2017-04-01

Combination of preoperative progressive pneumoperitoneum (PPP) and botulinum toxin type A (BT) has not been previously reported in the management of large incisional hernia (LIH). Observational study of 45 consecutive patients with LIH between June 2010 and July 2014. The diameters of the hernia sac, the volumes of the incisional hernia (VIH) and the abdominal cavity (VAC), and the VIH/VAC ratio were measured before and after PPP and BT using abdominal CT scan data. We indicated the combination of both techniques when the volume of the incisional hernia (VIH)/volume of the abdominal cavity (VAC) ratio was >20%. The median insufflated volume of air for PPP was 8.600 ± 3.200 cc (4.500-13.250), over a period of 14.3 ± 1.3 days (13-16). BT administration time was 40.2 ± 3.3 days (37-44). We obtained an average value of reduction of 14% of the VIH/VAC ratio after PPP and BT (p < 0.05). Complications associated with PPP were 15.5%, and with surgical technique, 26.6%. No complications occurred during the BT administration. Reconstructive technique was anterior CST and primary fascial closure was achieved in all patients. Median follow-up was 40.5 ± 19 months (12-60) and we reported 2 cases of hernia recurrence (4.4%). Preoperative combination of PPP and BT is feasible and a useful tool in the surgical management of LIH, although at the cost of some specific complications.

Acoustical transmission-line model of the middle-ear cavities and mastoid air cells.

PubMed

Keefe, Douglas H

2015-04-01

An acoustical transmission line model of the middle-ear cavities and mastoid air cell system (MACS) was constructed for the adult human middle ear with normal function. The air-filled cavities comprised the tympanic cavity, aditus, antrum, and MACS. A binary symmetrical airway branching model of the MACS was constructed using an optimization procedure to match the average total volume and surface area of human temporal bones. The acoustical input impedance of the MACS was calculated using a recursive procedure, and used to predict the input impedance of the middle-ear cavities at the location of the tympanic membrane. The model also calculated the ratio of the acoustical pressure in the antrum to the pressure in the middle-ear cavities at the location of the tympanic membrane. The predicted responses were sensitive to the magnitude of the viscothermal losses within the MACS. These predicted input impedance and pressure ratio functions explained the presence of multiple resonances reported in published data, which were not explained by existing MACS models.

Effect of aperture geometry on heat transfer in tilted partially open cavities

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

Elsayed, M.M.; Chakroun, W.

1999-11-01

Heat transfer in cavities is receiving increasing attention because of the various applications in engineering; e.g., passive solar heating, energy conservation in buildings, solar concentrating receivers, and electronic equipment. Here, convection from a square, tilted partially open cavity was investigated experimentally. The experiment was carried out to study the effect of the aperture geometry on the heat transfer between the cavity and the surrounding air. Four different geometrical arrangements for the opening were investigated: (1) high wall slit, (2) low wall slit, (3) centered wall slit, and (4) uniform wall slots. Each opening arrangement was studied at opening ratios (i.e.,more » ratio of opening height to cavity height) of 0.25, 0.5, and 0.75. The average heat transfer coefficient between the cavity and the surrounding air was estimated for each geometrical arrangement for tilt angles ranging from {minus}90 deg to +90 deg with increments of 15 deg and at a constant heat flux Grashof number of 5.5 x 10{sup 8}. The results showed that for tilt angles between 90 and 75 deg, the heat transfer coefficient has a small value that is independent of the geometrical arrangement of the opening. The value of the heat transfer coefficient increases sharply with decreasing tilt angle until an angle value of zero degrees is reached. The increase in the heat transfer coefficient continues in the negative range of tilt angle but not in the same rate as in the positive range of the tilt angle. The uniform slot arrangement gave in general higher heat transfer coefficient than the other three arrangements of the opening. Large differences in the heat transfer coefficient were observed between the high and the low wall slits where the high wall slit is found to transfer more heat to the surroundings than the low wall slit. Correlations were developed to predict the average Nusselt number of the cavity in terms of the opening ratio and the cavity tilt angle for cavities with high wall slit, low wall slit, centered wall slit, and the uniform wall slots.« less

Temperature and composition dependent density of states extracted using overlapping large polaron tunnelling model in MnxCo1-xFe2O4 (x=0.25, 0.5, 0.75) nanoparticles

NASA Astrophysics Data System (ADS)

Jamil, Arifa; Afsar, M. F.; Sher, F.; Rafiq, M. A.

2017-03-01

We report detailed ac electrical and structural characterization of manganese cobalt ferrite nanoparticles, prepared by coprecipitation technique. X-ray diffraction (XRD) confirmed single-phase cubic spinel structure of the nanoparticles. Tetrahedral (A) and octahedral (B) group complexes were present in the spinel lattice as determined by Fourier Transform Infrared Spectroscopy (FTIR). Scanning Electron Microscope (SEM) images revealed presence of spherical shape nanoparticles having an average diameter 50-80 nm. Composition, temperature and frequency dependent ac electrical study of prepared nanoparticles interpreted the role of cationic distribution between A and B sites. Overlapping large polaron tunnelling (OLPT) conduction mechanism was observed from 290 to 200 K. Frequency exponent s was fitted theoretically using OLPT model. High values of Density of States (DOS) of the order of 1022-1024 eV-1 cm-3 were extracted from ac conductivity for different compositions. We found that DOS was dependent on distribution of cations in the tunnel-type cavities along the a and b axis.

Nondestructive and in situ determination of graphene layers using optical fiber Fabry-Perot interference

NASA Astrophysics Data System (ADS)

Li, Cheng; Peng, Xiaobin; Liu, Qianwen; Gan, Xin; Lv, Ruitao; Fan, Shangchun

2017-02-01

Thickness measurement plays an important role for characterizing optomechanical behaviors of graphene. From the view of graphene-based Fabry-Perot (F-P) sensors, a simple, nondestructive and in situ method of determining the thickness of nanothick graphene membranes was demonstrated by using optical fiber F-P interference. Few-layer/multilayer graphene sheets were suspendedly adhered onto the endface of a ferrule with a 125 µm inner diameter by van der Waals interactions to construct micro F-P cavities. Along with the Fresnel’s law and complex index of refraction of the membrane working as a light reflector of an F-P interferometer, the optical reflectivity of graphene was modeled to investigate the effects of light wavelength and temperature. Then the average thickness of graphene membranes were extracted by F-P interference demodulation, and yielded a very strong cross-correlation coefficient of 99.95% with the experimental results observed by Raman spectrum and atomic force microscope. The method could be further extended for determining the number of layers of other 2D materials.

Properties of ordered titanium templates covered with Au thin films for SERS applications

NASA Astrophysics Data System (ADS)

Grochowska, Katarzyna; Siuzdak, Katarzyna; Sokołowski, Michał; Karczewski, Jakub; Szkoda, Mariusz; Śliwiński, Gerard

2016-12-01

Currently, roughened metal nanostructures are widely studied as highly sensitive Raman scattering substrates that show application potential in biochemistry, food safety or medical diagnostic. In this work the structural properties and the enhancement effect due to surface enhanced Raman scattering (SERS) of highly ordered nano-patterned titanium templates covered with thin (5-20 nm) gold films are reported. The templates are formed by preparation of a dense structure of TiO2 nanotubes on a flat Ti surface (2 × 2 cm2) and their subsequent etching down to the substrate. SEM images reveal the formation of honeycomb nanostructures with the cavity diameter of 80 nm. Due to the strongly inhomogeneous distribution of the electromagnetic field in the vicinity of the Au film discontinuities the measured average enhancement factor (107-108) is markedly higher than observed for bare Ti templates. The enhancement factor and Raman signal intensity can be optimized by adjusting the process conditions and thickness of the deposited Au layer. Results confirm that the obtained structures can be used in surface enhanced sensing.

Nanoporous distributed Bragg reflectors on free-standing nonpolar m-plane GaN

NASA Astrophysics Data System (ADS)

Mishkat-Ul-Masabih, Saadat; Luk, Ting Shan; Rishinaramangalam, Ashwin; Monavarian, Morteza; Nami, Mohsen; Feezell, Daniel

2018-01-01

We report the fabrication of m-plane nanoporous distributed Bragg reflectors (DBRs) on free-standing GaN substrates. The DBRs consist of 15 pairs of alternating undoped and highly doped n-type ([Si] = ˜3.7 × 1019 cm-3) GaN. Electrochemical (EC) etching was performed to convert the highly doped regions into a porous material, consequently reducing the effective refractive index of the layers. We demonstrate a DBR with peak reflectance greater than 98% at 450 nm with a stopband width of ˜72 nm. The polarization ratio of an incident polarized light source remains identical after reflection from the DBR, verifying that there is no drop in the polarization ratio due to the interfaces between the porous layers. We also quantify the porosity under various EC bias conditions for layers with different doping concentrations. The bias voltage controls the average pore diameter, while the pore density is primarily determined by the doping concentration. The results show that nanoporous DBRs on nonpolar free-standing GaN are promising candidates for high-reflectance, lattice-matched DBR mirrors for GaN-based resonant cavity devices.

End-compensated magnetostatic cavity for polarized 3He neutron spin filters.

PubMed

McIver, J W; Erwin, R; Chen, W C; Gentile, T R

2009-06-01

We have expanded upon the "Magic Box" concept, a coil driven magnetic parallel plate capacitor constructed out of mu-metal, by introducing compensation sections at the ends of the box that are tuned to limit end-effects similar to those of short solenoids. This ability has reduced the length of the magic box design without sacrificing any loss in field homogeneity, making the device far more applicable to the often space limited neutron beam line. The appeal of the design beyond affording longer polarized 3He lifetimes is that it provides a vertical guide field, which facilitates neutron spin transport for typical polarized beam experiments. We have constructed two end-compensated magic boxes of dimensions 28.4 x 40 x 15 cm3 (length x width x height) with measured, normalized volume-averaged transverse field gradients ranging from 3.3 x 10(-4) to 6.3 x 10(-4) cm(-1) for cell sizes ranging from 8.1 x 6.0 to 12.0 x 7.9 cm2 (diameter x length), respectively.

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

Kapp, O.H.; Mainwaring, M.G.; Vinogradov, S.N.

A fraction of the extracellular hemoglobin of Lumbricus terrestris, obtained by gel filtration at neutral pH subsequent to dissociation either at pH 9.8 or at pH 4.0 or at pH 7.0 in 10 mM sodium phosphotungstate, consisting of the three subunits D1 (31 kDa), D2 (37 kDa) and T (50 kDa), produced two peaks when subjected to FPLC on a Superose 6 column at neutral pH. Peak I, eluting at a slightly greater volume than the native hemoglobin, consisted of reassociated hexagonal bilayer structures when examined by scanning transmission electron microscopy. The dimensions of the three reassociated hexagonal bilayer structuresmore » were 25 nm x 16 nm. Although the latter are smaller than the dimensions of the native hemoglobin, 30 nm x 20 nm, the diameter of the central cavity remained unchanged. Subtraction of the digitized and averaged images of the reassociated forms from those of the native hemoglobin suggested that the spatial localization of the fourth subunit, subunit M (16.7 kDa), was limited primarily to the periphery of the molecule.« less

Proposed Cavity for Reduced Slip-Stacking Loss

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

Eldred, J.; Zwaska, R.

This paper employs a novel dynamical mechanism to improve the performance of slip-stacking. Slip-stacking in an accumulation technique used at Fermilab since 2004 which nearly double the proton intensity. During slip-stacking, the Recycler or the Main Injector stores two particles beams that spatially overlap but have different momenta. The two particle beams are longitudinally focused by two 53 MHz 100 kV RF cavities with a small frequency difference between them. We propose an additional 106 MHz 20 kV RF cavity, with a frequency at the double the average of the upper and lower main RF frequencies. In simulation, we findmore » the proposed RF cavity significantly enhances the stable bucket area and reduces slip-stacking losses under reasonable injection scenarios. We quantify and map the stability of the parameter space for any accelerator implementing slip-stacking with the addition of a harmonic RF cavity.« less

Ring Laser Gyro Resonator Design

DTIC Science & Technology

1994-06-20

vibration environment could cause errors in measured RLG rotation rates due to vibration (tilt) of the resonator mirrors . Vibration-induced mirror tilt...the RLG resonator design theoretically and calculated pertinent parameters such as the beam diameter at the aperture, cavity mirror alignment...sensitivities, and power loss due to aperture occlusion. The mirror vibration levels required to significantly affect the laser power were then calculated for

Thermal lens effect for optimizing a passively Q-switched 1064 nm laser

NASA Astrophysics Data System (ADS)

Xing, Enbo; Rong, Jiamin; Khew, Si Ying; Tong, Cunzhu; Hong, Minghui

2018-06-01

We demonstrate the improvement of pulse characteristics of a passively Q-switched laser by utilizing the thermal lens effect of a saturable absorber (SA) inside the cavity. The experimental results show that the SA should be considered as a convex lens inside the cavity, whose position strongly improves output performance. A fourfold enhancement of the average output power is obtained, and the peak energy increases from 8.2 to 25 µJ. Theoretically, we calculate the thermal lens effect of the SA and the optimal position inside the cavity, which agree with the experimental results.

Effects of Contamination by Hemostatic Agents and Use of Cleaning Agent on Etch-and-Rinse Dentin Bond Strength.

PubMed

Pucci, César Rogério; Araújo, Rodrigo Maximo de; Lacerda, Ana Julia Farias de; Souza, Mirella Anjos de; Huhtala, Maria Filomena Rocha Lima; Feitosa, Fernanda Alves

2016-01-01

The aim of this study was to evaluate the influence of contamination by hemostatic agents and rinsing with chlorhexidine on bond strength between dentin and resin composite. Ninety-six bovine teeth were sectioned to expose a flat dentin surface area. A standardized cavity with 2.0 mm in thickness, superficial diameter of 4.0 mm and bottom diameter of 3.0 mm was prepared with a diamond bur in each dentin specimen. The teeth were divided into four groups according to the hemostatic employed: G1: control; G2: use of ViscoStat, Ultradent; G3: Hemosthasegel, FGM; and G4: Hemostop, Dentsply. The groups were divided into two subgroups according to the cleaning protocol method (n=12): A: without any further cleaning; and B: cleaning with chlorhexidine at 0.2%. All cavities were filled using a dentin adhesive and a resin composite, following the manufacturer's instructions. After 24 h, the specimens were aged by thermal and mechanical cycling. The bond strength was determined by the push out bond test (MPa), Statistical analysis was performed using two-way ANOVA and Tukey test (p<0.05). Statistically significant differences were detected among all groups treated with hemostatic agents and the control group. The post-hoc test showed that cleaning the cavity with chlorhexidine significantly improves the bond strength between dentin and resin composite. Our results suggested that the use of chlorhexidine can reestablish the bond strength between dentin and resin composite when a hemostatic agent was applied.

A transparent model of the human scala tympani cavity.

PubMed

Rebscher, S J; Talbot, N; Bruszewski, W; Heilmann, M; Brasell, J; Merzenich, M M

1996-01-01

A dimensionally accurate clear model of the human scala tympani has been produced to evaluate the insertion and position of clinically applied intracochlear electrodes for electrical stimulation. Replicates of the human scala tympani were made from low melting point metal alloy (LMA) and from polymethylmeth-acrylate (PMMA) resin. The LMA metal casts were embedded in blocks of epoxy and in clear silicone rubber. After removal of the metal alloy, a cavity was produced that accurately models the human scala tympani. Investment casting molds were made from the PMMA scala tympani casts to enable production of multiple LMA casts from which identical models were fabricated. Total dimensional distortion of the LMA casting process was less than 1% in length and 2% in diameter. The models have been successfully integrated into the design process for the iterative development of advanced intracochlear electrode arrays at UCSF. These fabrication techniques are applicable to a wide range of biomedical design problems that require modelling of visually obscured cavities.

Flight tests of external modifications used to reduce blunt base drag

NASA Technical Reports Server (NTRS)

Powers, Sheryll Goecke

1988-01-01

The effectiveness of a trailing disk (the trapped vortex concept) in reducing the blunt base drag of an 8-in diameter body of revolution was studied from measurements made both in flight and in full-scale wind-tunnel tests. The experiment demonstrated the significant base drag reduction capability of the trailing disk to Mach 0.93. The maximum base drag reduction obtained from a cavity tested on the flight body of revolution was not significant. The effectiveness of a splitter plate and a vented-wall cavity in reducing the base drag of a quasi-two-dimensional fuselage closure was studied from base pressure measurements made in flight. The fuselage closure was between the two engines of the F-111 airplane; therefore, the base pressures were in the presence of jet engine exhaust. For Mach numbers from 1.10 to 1.51, significant base drag reduction was provided by the vented-wall cavity configuration. The splitter plate was not considered effective in reducing base drag at any Mach number tested.

Catheter guided by optical coherence domain reflectometry

DOEpatents

Everett, Matthew; Colston, Billy W.; Da Silva, Luiz B.; Matthews, Dennis

2002-01-01

A guidance and viewing system based on multiplexed optical coherence domain reflectometry is incorporated into a catheter, endoscope, or other medical device to measure the location, thickness, and structure of the arterial walls or other intra-cavity regions at discrete points on the medical device during minimally invasive medical procedures. The information will be used both to guide the device through the body and to evaluate the tissue through which the device is being passed. Multiple optical fibers are situated along the circumference of the device. Light from the distal end of each fiber is directed onto the interior cavity walls via small diameter optics (such as gradient index lenses and mirrored corner cubes). Both forward viewing and side viewing fibers can be included. The light reflected or scattered from the cavity walls is then collected by the fibers and multiplexed at the proximal end to the sample arm of an optical low coherence reflectometer. The system may also be implemented in a nonmedical inspection device.

Optical coherence domain reflectometry guidewire

DOEpatents

Colston, Billy W.; Everett, Matthew; Da Silva, Luiz B.; Matthews, Dennis

2001-01-01

A guidewire with optical sensing capabilities is based on a multiplexed optical coherence domain reflectometer (OCDR), which allows it to sense location, thickness, and structure of the arterial walls or other intra-cavity regions as it travels through the body during minimally invasive medical procedures. This information will be used both to direct the guidewire through the body by detecting vascular junctions and to evaluate the nearby tissue. The guidewire contains multiple optical fibers which couple light from the proximal to distal end. Light from the fibers at the distal end of the guidewire is directed onto interior cavity walls via small diameter optics such as gradient index lenses and mirrored corner cubes. Both forward viewing and side viewing fibers can be included. The light reflected or scattered from the cavity walls is then collected by the fibers, which are multiplexed at the proximal end to the sample arm of an optical low coherence reflectometer. The guidewire can also be used in nonmedical applications.

Paragnomoxyala gen. nov. (Xyalidae, Monhysterida, Nematoda) from the East China Sea.

PubMed

Jiang, Weijun; Huang, Yong

2015-11-05

A new genus, Paragnomoxyala gen. nov., and a new species, Paragnomoxyala breviseta sp. nov. are described from the East China Sea. Paragnomoxyala gen. nov. is characterized by having large funnel-shaped buccal cavity with cuticularized walls and extended anteriorly; lips very high; striated cuticle; four cephalic setae, absence of outer labial setae; circular amphidial fovea; straight spicules and absence of gubernaculum; tail conico-cylindrical with three terminal setae; female monodelphic with an anterior outstretched ovary. It differs from similar genera by having a large buccal cavity unique in Xyalidae, straight spicules, lacking gubernaculum, and conico-cylindrical tail with terminal setae. Paragnomoxyala breviseta sp. nov. is characterized by having a large funnel-shaped buccal cavity, with cuticularized walls and extended anteriorly, 1.6-1.8 hd long and 63-79% cbd wide; four cephalic setae 3-4 µm long; circular amphids 6-9 µm in diameter; spicules straight but slightly bent at both ends; absence of gubernaculum and precloacal supplement.

Berkeley Proton Linear Accelerator

DOE R&D Accomplishments Database

Alvarez, L. W.; Bradner, H.; Franck, J.; Gordon, H.; Gow, J. D.; Marshall, L. C.; Oppenheimer, F. F.; Panofsky, W. K. H.; Richman, C.; Woodyard, J. R.

1953-10-13

A linear accelerator, which increases the energy of protons from a 4 Mev Van de Graaff injector, to a final energy of 31.5 Mev, has been constructed. The accelerator consists of a cavity 40 feet long and 39 inches in diameter, excited at resonance in a longitudinal electric mode with a radio-frequency power of about 2.2 x 10{sup 6} watts peak at 202.5 mc. Acceleration is made possible by the introduction of 46 axial "drift tubes" into the cavity, which is designed such that the particles traverse the distance between the centers of successive tubes in one cycle of the r.f. power. The protons are longitudinally stable as in the synchrotron, and are stabilized transversely by the action of converging fields produced by focusing grids. The electrical cavity is constructed like an inverted airplane fuselage and is supported in a vacuum tank. Power is supplied by 9 high powered oscillators fed from a pulse generator of the artificial transmission line type.

Brownian escape and force-driven transport through entropic barriers: Particle size effect.

PubMed

Cheng, Kuang-Ling; Sheng, Yu-Jane; Tsao, Heng-Kwong

2008-11-14

Brownian escape from a spherical cavity through small holes and force-driven transport through periodic spherical cavities for finite-size particles have been investigated by Brownian dynamic simulations and scaling analysis. The mean first passage time and force-driven mobility are obtained as a function of particle diameter a, hole radius R(H), cavity radius R(C), and external field strength. In the absence of external field, the escape rate is proportional to the exit effect, (R(H)R(C))(1-a2R(H))(32). In weak fields, Brownian diffusion is still dominant and the migration is controlled by the exit effect. Therefore, smaller particles migrate faster than larger ones. In this limit the relation between Brownian escape and force-driven transport can be established by the generalized Einstein-Smoluchowski relation. As the field strength is strong enough, the mobility becomes field dependent and grows with increasing field strength. As a result, the size selectivity diminishes.

Optimization and characterization of high pressure homogenization produced chemically modified starch nanoparticles.

PubMed

Ding, Yongbo; Kan, Jianquan

2017-12-01

Chemically modified starch (RS4) nanoparticles were synthesized through homogenization and water-in-oil mini-emulsion cross-linking. Homogenization was optimized with regard to z-average diameter by using a three-factor-three-level Box-Behnken design. Homogenization pressure (X 1 ), oil/water ratio (X 2 ), and surfactant (X 3 ) were selected as independent variables, whereas z-average diameter was considered as a dependent variable. The following optimum preparation conditions were obtained to achieve the minimum average size of these nanoparticles: 50 MPa homogenization pressure, 10:1 oil/water ratio, and 2 g surfactant amount, when the predicted z-average diameter was 303.6 nm. The physicochemical properties of these nanoparticles were also determined. Dynamic light scattering experiments revealed that RS4 nanoparticles measuring a PdI of 0.380 and an average size of approximately 300 nm, which was very close to the predicted z-average diameter (303.6 nm). The absolute value of zeta potential of RS4 nanoparticles (39.7 mV) was higher than RS4 (32.4 mV), with strengthened swelling power. X-ray diffraction results revealed that homogenization induced a disruption in crystalline structure of RS4 nanoparticles led to amorphous or low-crystallinity. Results of stability analysis showed that RS4 nanosuspensions (particle size) had good stability at 30 °C over 24 h.

Effect of Reynolds and Grashof numbers on mixed convection inside a lid-driven square cavity filled with water-Al2O3 nanofluid

NASA Astrophysics Data System (ADS)

Jaman, Md. Shah; Islam, Showmic; Saha, Sumon; Hasan, Mohammad Nasim; Islam, Md. Quamrul

2016-07-01

A numerical analysis is carried out to study the performance of steady laminar mixed convection flow inside a square lid-driven cavity filled with water-Al2O3 nanofluid. The top wall of the cavity is moving at a constant velocity and is heated by an isothermal heat source. Two-dimensional Navier-stokes equations along with the energy equations are solved using Galerkin finite element method. Results are obtained for a range of Reynolds and Grashof numbers by considering with and without the presence of nanoparticles. The parametric studies for a wide range of governing parameters in case of pure mixed convective flow show significant features of the present problem in terms of streamline and isotherm contours, average Nusselt number and average temperature profiles. The computational results indicate that the heat transfer coeffcient is strongly influenced by the above governing parameters at the pure mixed convection regime.

Determining the average path length of amplified spontaneous emission in a four-level laser near the 1/3 mode-degeneracy cavity configurations

NASA Astrophysics Data System (ADS)

Chen, Ching-Hsu; Lu, Ming-Lun; Tai, Po-Tse

2015-08-01

We determine the average path length ls of amplified spontaneous emission (ASE) by comparing the numerical slope of a straight line with the experimental slope in the graph of the square of relaxation oscillation frequency versus normalized pump ratio. The simple method is applied in an end-pumped Nd:YVO4 laser with the 1/3 mode-degeneracy cavity having the transverse mode spacing equal to 1/3 of the longitudinal mode spacing. We find that ls is larger at the degeneracy than that far from the degeneracy. This result indicates the existence of stronger ASE at the degeneracy, which is confirmed below the threshold. This is because many spontaneous emission photons can undergo amplification not only before escaping from the gain medium but also after leaving the gain medium, owing to cavity reflection. Our method can be applied in the situations where the Auger upconversion effect is absent, weak, or well-known.

Shiitake mushroom production on small diameter oak logs in Ohio

Treesearch

S.M. Bratkovich

1991-01-01

Yields of different strains of shiitake mushrooms (Lentinus edodes) were evaluated when produced on small diameter oak logs in Ohio. Logs averaging between 3-4 inches in diameter were inoculated with four spawn strains in 1985.

Comparison of ballistic impact effects between biological tissue and gelatin.

PubMed

Jin, Yongxi; Mai, Ruimin; Wu, Cheng; Han, Ruiguo; Li, Bingcang

2018-02-01

Gelatin is commonly used in ballistic testing as substitute for biological tissue. Comparison of ballistic impact effects produced in the gelatin and living tissue is lacking. The work in this paper was aimed to compare the typical ballistic impact effects (penetration trajectory, energy transfer, temporary cavity) caused by 4.8mm steel ball penetrating the 60kg porcine hind limbs and 10wt% gelatin. The impact event in the biological tissue was recorded by high speed flash X-ray machine at different delay time, while the event in the gelatin continuously recorded by high speed video was compared to that in the biological tissue. The collected results clearly displayed that the ballistic impact effects in the muscle and gelatin were similar for the steel ball test; as for instance, the projectile trajectory in the two targets was basically similar, the process of energy transfer was highly coincident, and the expansion of temporary cavity followed the same pattern. This study fully demonstrated that choosing gelatin as muscle simulant was reasonable. However, the maximum temporary cavity diameter in the gelatin was a little larger than that in the muscle, and the expansion period of temporary cavity was longer in the gelatin. Additionally, the temporary cavity collapse process in the two targets followed different patterns, and the collapse period in the gelatin was two times as long as that in the muscle. Copyright © 2017 Elsevier Ltd. All rights reserved.

LEM Characterization of Synthetic Jet Actuators Driven by Piezoelectric Element: A Review

PubMed Central

Chiatto, Matteo; Capuano, Francesco; Coppola, Gennaro; de Luca, Luigi

2017-01-01

In the last decades, Synthetic jet actuators have gained much interest among the flow control techniques due to their short response time, high jet velocity and absence of traditional piping, which matches the requirements of reduced size and low weight. A synthetic jet is generated by the diaphragm oscillation (generally driven by a piezoelectric element) in a relatively small cavity, producing periodic cavity pressure variations associated with cavity volume changes. The pressured air exhausts through an orifice, converting diaphragm electrodynamic energy into jet kinetic energy. This review paper considers the development of various Lumped-Element Models (LEMs) as practical tools to design and manufacture the actuators. LEMs can quickly predict device performances such as the frequency response in terms of diaphragm displacement, cavity pressure and jet velocity, as well as the efficiency of energy conversion of input Joule power into useful kinetic power of air jet. The actuator performance is also analyzed by varying typical geometric parameters such as cavity height and orifice diameter and length, through a suited dimensionless form of the governing equations. A comprehensive and detailed physical modeling aimed to evaluate the device efficiency is introduced, shedding light on the different stages involved in the process. Overall, the influence of the coupling degree of the two oscillators, the diaphragm and the Helmholtz frequency, on the device performance is discussed throughout the paper. PMID:28587141

Dynamic water behaviour due to one trapped air pocket in a laboratory pipeline apparatus

NASA Astrophysics Data System (ADS)

Bergant, A.; Karadžić, U.; Tijsseling, A.

2016-11-01

Trapped air pockets may cause severe operational problems in hydropower and water supply systems. A locally isolated air pocket creates distinct amplitude, shape and timing of pressure pulses. This paper investigates dynamic behaviour of a single trapped air pocket. The air pocket is incorporated as a boundary condition into the discrete gas cavity model (DGCM). DGCM allows small gas cavities to form at computational sections in the method of characteristics (MOC). The growth of the pocket and gas cavities is described by the water hammer compatibility equation(s), the continuity equation for the cavity volume, and the equation of state of an ideal gas. Isentropic behaviour is assumed for the trapped gas pocket and an isothermal bath for small gas cavities. Experimental investigations have been performed in a laboratory pipeline apparatus. The apparatus consists of an upstream end high-pressure tank, a horizontal steel pipeline (total length 55.37 m, inner diameter 18 mm), four valve units positioned along the pipeline including the end points, and a downstream end tank. A trapped air pocket is captured between two ball valves at the downstream end of the pipeline. The transient event is initiated by rapid opening of the upstream end valve; the downstream end valve stays closed during the event. Predicted and measured results for a few typical cases are compared and discussed.

On the nature of cavities on protein surfaces: application to the identification of drug-binding sites.

PubMed

Nayal, Murad; Honig, Barry

2006-06-01

In this article we introduce a new method for the identification and the accurate characterization of protein surface cavities. The method is encoded in the program SCREEN (Surface Cavity REcognition and EvaluatioN). As a first test of the utility of our approach we used SCREEN to locate and analyze the surface cavities of a nonredundant set of 99 proteins cocrystallized with drugs. We find that this set of proteins has on average about 14 distinct cavities per protein. In all cases, a drug is bound at one (and sometimes more than one) of these cavities. Using cavity size alone as a criterion for predicting drug-binding sites yields a high balanced error rate of 15.7%, with only 71.7% coverage. Here we characterize each surface cavity by computing a comprehensive set of 408 physicochemical, structural, and geometric attributes. By applying modern machine learning techniques (Random Forests) we were able to develop a classifier that can identify drug-binding cavities with a balanced error rate of 7.2% and coverage of 88.9%. Only 18 of the 408 cavity attributes had a statistically significant role in the prediction. Of these 18 important attributes, almost all involved size and shape rather than physicochemical properties of the surface cavity. The implications of these results are discussed. A SCREEN Web server is available at http://interface.bioc.columbia.edu/screen. 2006 Wiley-Liss, Inc.

Donor states in inverse opals

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

Mahan, G. D.

We calculate the binding energy of an electron bound to a donor in a semiconductor inverse opal. Inverse opals have two kinds of cavities, which we call octahedral and tetrahedral, according to their group symmetry. We put the donor in the center of each of these two cavities and obtain the binding energy. The binding energies become very large when the inverse opal is made from templates with small spheres. For spheres less than 50 nm in diameter, the donor binding can increase to several times its unconfined value. Then electrons become tightly bound to the donor and are unlikelymore » to be thermally activated to the semiconductor conduction band. This conclusion suggests that inverse opals will be poor conductors.« less

Evacuated, displacement compression mold. [of tubular bodies from thermosetting plastics

NASA Technical Reports Server (NTRS)

Heier, W. C. (Inventor)

1974-01-01

A process of molding long thin-wall tubular bodies from thermosetting plastic molding compounds is described wherein the tubular body lengths may be several times the diameters. The process is accomplished by loading a predetermined quantity of molding compound into a female mold cavity closed at one end by a force mandrel. After closing the other end of the female mold with a balance mandrel, the loaded cavity is evacuated by applying a vacuum of from one-to-five mm pressure for a period of fifteen-to-thirty minutes. The mold temperature is raised to the minimum temperature at which the resin constituent of the compound will soften or plasticize and a pressure of 2500 psi is applied.

Simple and robust phase-locking of optical cavities with > 200 KHz servo-bandwidth using a piezo-actuated mirror mounted in soft materials.

PubMed

Goldovsky, David; Jouravsky, Valery; Pe'er, Avi

2016-12-12

We present an approach to locking of optical cavities with piezoelectric actuated mirrors based on a simple and effective mechanical decoupling of the mirror and actuator from the surrounding mount. Using simple elastic materials (e.g. rubber or soft silicone gel pads) as mechanical dampers between the piezo-mirror compound and the surrounding mount, a firm and stable mounting of a relatively large mirror (8mm diameter) can be maintained that is isolated from external mechanical resonances, and is limited only by the internal piezo-mirror resonance of > 330 KHz. Our piezo lock showed positive servo gain up to 208 KHz, and a temporal response to a step interference within < 3 μs.

Bi-material crystalline whispering gallery mode microcavity structure for thermo-opto-mechanical stabilization

NASA Astrophysics Data System (ADS)

Itobe, Hiroki; Nakagawa, Yosuke; Mizumoto, Yuta; Kangawa, Hiroi; Kakinuma, Yasuhiro; Tanabe, Takasumi

2016-05-01

We fabricated a calcium fluoride (CaF2) whispering gallery mode (WGM) microcavity with a computer controlled ultra-precision cutting process. We observed a thermo-opto-mechanical (TOM) oscillation in the CaF2 WGM microcavity, which may influence the stability of the optical output when the cavity is employed for Kerr comb generation. We studied experimentally and numerically the mechanism of the TOM oscillation and showed that it is strongly dependent on cavity diameter. In addition, our numerical study suggests that a microcavity structure fabricated with a hybrid material (i.e. CaF2 and silicon), which is compatible with an ultra-high Q and high thermal conductivity, will allow us to reduce the TOM oscillation and stabilize the optical output.

CT-Guided Placement of a Drainage Catheter Within a Pelvic Abscess Using a Transsacral Approach

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

Iguchi, Toshihiro; Asami, Shinya; Kubo, Shinichiro

2007-11-15

A 66-year-old man underwent CT-guided drainage catheter placement within a pelvic abscess with a diameter of 46 mm. We performed the drainage by a transsacral approach because it was considered the safest and most feasible approach. An 8G bone marrow biopsy needle was used to penetrate the sacrum to create a path for subsequent drainage catheter insertion. After withdrawal of the biopsy needle, a 6 Fr catheter was advanced into the abscess cavity through the path using the Seldinger technique. Except for bearable pain, no procedure-related complications occurred. Twenty-nine days after the placement, the catheter was withdrawn safely and themore » abscess cavity had shrunk remarkably.« less

Assessment of Flow Control Devices for Transonic Cavity Flows Using DES and LES

NASA Astrophysics Data System (ADS)

Barakos, G. N.; Lawson, S. J.; Steijl, R.; Nayyar, P.

Since the implementation of internal carriage of stores on military aircraft, transonic flows in cavities were put forward as a model problem for validation of CFD methods before design studies of weapon bays can be undertaken. Depending on the free-stream Mach number and the cavity dimensions, the flow inside the cavity can become very unsteady. Below a critical length-to-depth ratio (L/D), the flow has enough energy to span across the cavity opening and a shear layer develops. When the shear layer impacts the downstream cavity corner, acoustical disturbances are generated and propagated upstream, which in turn causes further instabilities at the cavity front and a feedback loop is maintained. The acoustic environment in the cavity is so harsh in these circumstances that the noise level at the cavity rear has been found to approach 170 dB and frequencies near 1 kHz are created. The effect of this unsteady environment on the structural integrity of the contents of the cavity (e.g. stores, avionics, etc.) can be serious. Above the critical L/D ratio, the shear layer no longer has enough energy to span across the cavity and dips into it. Although this does not produce as high noise levels and frequencies as shorter cavities, the differential pressure along the cavity produces large pitching moments making store release difficult. Computational fluid dynamics analysis of cavity flows, based on the Reynolds-Averaged Navier—Stokes equations was only able to capture some of the flow physics present. On the other hand, results obtained with Large-Eddy Simulation or Detached-Eddy Simulation methods fared much better and for the cases computed, quantitative and qualitative agreement with experimental data has been obtained.

Orthopedic stretcher with average-sized person can pass through 18-inch opening

NASA Technical Reports Server (NTRS)

Lothschuetz, F. X.

1966-01-01

Modified Robinson stretcher for vertical lifting and carrying, will pass through an opening 18 inches in diameter, while containing a person of average height and weight. A subject 6 feet tall and weighing 200 pounds was lowered and raised out of an 18 inch diameter opening in a tank to test the stretcher.

Accurate Size and Size-Distribution Determination of Polystyrene Latex Nanoparticles in Aqueous Medium Using Dynamic Light Scattering and Asymmetrical Flow Field Flow Fractionation with Multi-Angle Light Scattering

PubMed Central

Kato, Haruhisa; Nakamura, Ayako; Takahashi, Kayori; Kinugasa, Shinichi

2012-01-01

Accurate determination of the intensity-average diameter of polystyrene latex (PS-latex) by dynamic light scattering (DLS) was carried out through extrapolation of both the concentration of PS-latex and the observed scattering angle. Intensity-average diameter and size distribution were reliably determined by asymmetric flow field flow fractionation (AFFFF) using multi-angle light scattering (MALS) with consideration of band broadening in AFFFF separation. The intensity-average diameter determined by DLS and AFFFF-MALS agreed well within the estimated uncertainties, although the size distribution of PS-latex determined by DLS was less reliable in comparison with that determined by AFFFF-MALS. PMID:28348293

Accuracy of volumetric measurement of simulated root resorption lacunas based on cone beam computed tomography.

PubMed

Wang, Y; He, S; Guo, Y; Wang, S; Chen, S

2013-08-01

To evaluate the accuracy of volumetric measurement of simulated root resorption cavities based on cone beam computed tomography (CBCT), in comparison with that of Micro-computed tomography (Micro-CT) which served as the reference. The State Key Laboratory of Oral Diseases at Sichuan University. Thirty-two bovine teeth were included for standardized CBCT scanning and Micro-CT scanning before and after the simulation of different degrees of root resorption. The teeth were divided into three groups according to the depths of the root resorption cavity (group 1: 0.15, 0.2, 0.3 mm; group 2: 0.6, 1.0 mm; group 3: 1.5, 2.0, 3.0 mm). Each depth included four specimens. Differences in tooth volume before and after simulated root resorption were then calculated from CBCT and Micro-CT scans, respectively. The overall between-method agreement of the measurements was evaluated using the concordance correlation coefficient (CCC). For the first group, the average volume of resorption cavity was 1.07 mm(3) , and the between-method agreement of measurement for the volume changes was low (CCC = 0.098). For the second and third groups, the average volumes of resorption cavities were 3.47 and 6.73 mm(3) respectively, and the between-method agreements were good (CCC = 0.828 and 0.895, respectively). The accuracy of 3-D quantitative volumetric measurement of simulated root resorption based on CBCT was fairly good in detecting simulated resorption cavities larger than 3.47 mm(3), while it was not sufficient for measuring resorption cavities smaller than 1.07 mm(3) . This method could be applied in future studies of root resorption although further studies are required to improve its accuracy. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Hybrid Large Eddy Simulation / Reynolds Averaged Navier-Stokes Modeling in Directed Energy Applications

NASA Astrophysics Data System (ADS)

Zilberter, Ilya Alexandrovich

In this work, a hybrid Large Eddy Simulation / Reynolds-Averaged Navier Stokes (LES/RANS) turbulence model is applied to simulate two flows relevant to directed energy applications. The flow solver blends the Menter Baseline turbulence closure near solid boundaries with a Lenormand-type subgrid model in the free-stream with a blending function that employs the ratio of estimated inner and outer turbulent length scales. A Mach 2.2 mixing nozzle/diffuser system representative of a gas laser is simulated under a range of exit pressures to assess the ability of the model to predict the dynamics of the shock train. The simulation captures the location of the shock train responsible for pressure recovery but under-predicts the rate of pressure increase. Predicted turbulence production at the wall is found to be highly sensitive to the behavior of the RANS turbulence model. A Mach 2.3, high-Reynolds number, three-dimensional cavity flow is also simulated in order to compute the wavefront aberrations of an optical beam passing thorough the cavity. The cavity geometry is modeled using an immersed boundary method, and an auxiliary flat plate simulation is performed to replicate the effects of the wind-tunnel boundary layer on the computed optical path difference. Pressure spectra extracted on the cavity walls agree with empirical predictions based on Rossiter's formula. Proper orthogonal modes of the wavefront aberrations in a beam originating from the cavity center agree well with experimental data despite uncertainty about in flow turbulence levels and boundary layer thicknesses over the wind tunnel window. Dynamic mode decomposition of a planar wavefront spanning the cavity reveals that wavefront distortions are driven by shear layer oscillations at the Rossiter frequencies; these disturbances create eddy shocklets that propagate into the free-stream, creating additional optical wavefront distortion.

Waveguide Calibrator for Multi-Element Probe Calibration

NASA Technical Reports Server (NTRS)

Sommerfeldt, Scott D.; Blotter, Jonathan D.

2007-01-01

A calibrator, referred to as the spider design, can be used to calibrate probes incorporating multiple acoustic sensing elements. The application is an acoustic energy density probe, although the calibrator can be used for other types of acoustic probes. The calibrator relies on the use of acoustic waveguide technology to produce the same acoustic field at each of the sensing elements. As a result, the sensing elements can be separated from each other, but still calibrated through use of the acoustic waveguides. Standard calibration techniques involve placement of an individual microphone into a small cavity with a known, uniform pressure to perform the calibration. If a cavity is manufactured with sufficient size to insert the energy density probe, it has been found that a uniform pressure field can only be created at very low frequencies, due to the size of the probe. The size of the energy density probe prevents one from having the same pressure at each microphone in a cavity, due to the wave effects. The "spider" design probe is effective in calibrating multiple microphones separated from each other. The spider design ensures that the same wave effects exist for each microphone, each with an indivdual sound path. The calibrator s speaker is mounted at one end of a 14-cm-long and 4.1-cm diameter small plane-wave tube. This length was chosen so that the first evanescent cross mode of the plane-wave tube would be attenuated by about 90 dB, thus leaving just the plane wave at the termination plane of the tube. The tube terminates with a small, acrylic plate with five holes placed symmetrically about the axis of the speaker. Four ports are included for the four microphones on the probe. The fifth port is included for the pre-calibrated reference microphone. The ports in the acrylic plate are in turn connected to the probe sensing elements via flexible PVC tubes. These five tubes are the same length, so the acoustic wave effects are the same in each tube. The flexible nature of the tubes allows them to be positioned so that each tube terminates at one of the microphones of the energy density probe, which is mounted in the acrylic structure, or the calibrated reference microphone. Tests performed verify that the pressure did not vary due to bends in the tubes. The results of these tests indicate that the average sound pressure level in the tubes varied by only 0.03 dB as the tubes were bent to various angles. The current calibrator design is effective up to a frequency of approximately 4.5 kHz. This upper design frequency is largely due to the diameter of the plane-wave tubes.

Cavity-enhanced eigenmode and angular hybrid multiplexing in holographic data storage systems.

PubMed

Miller, Bo E; Takashima, Yuzuru

2016-12-26

Resonant optical cavities have been demonstrated to improve energy efficiencies in Holographic Data Storage Systems (HDSS). The orthogonal reference beams supported as cavity eigenmodes can provide another multiplexing degree of freedom to push storage densities toward the limit of 3D optical data storage. While keeping the increased energy efficiency of a cavity enhanced reference arm, image bearing holograms are multiplexed by orthogonal phase code multiplexing via Hermite-Gaussian eigenmodes in a Fe:LiNbO₃ medium with a 532 nm laser at two Bragg angles. We experimentally confirmed write rates are enhanced by an average factor of 1.1, and page crosstalk is about 2.5%. This hybrid multiplexing opens up a pathway to increase storage density while minimizing modification of current angular multiplexing HDSS.

Diagnostics Upgrades for Investigations of HOM Effects in TESLA-type SCRF Cavities

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

Lumpkin, A. H.; Edstrom Jr., D.; Ruan, J.

We describe the upgrades to diagnostic capabilities on the Fermilab Accelerator Science and Technology (FAST) electron linear accelerator that will allow investigations of the effects of high-order modes (HOMs) in SCRF cavities on macropulse-average beam quality. We examine the dipole modes in the first pass-band generally observed in the 1.6-1.9 GHz regime for TESLA-type SCRF cavities due to uniform transverse beam offsets of the electron beam. Such cavities are the basis of the accelerators such as the European XFEL and the proposed MaRIE XFEL facility. Preliminary HOM detector data, prototype BPM test data, and first framing camera OTR data withmore » ~20- micron spatial resolution at 250 pC per bunch will be presented.« less

STUDY OF THE 3D GEOMETRIC STRUCTURE AND TEMPERATURE OF A CORONAL CAVITY USING THE LIMB SYNOPTIC MAP METHOD

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

Karna, N.; Pesnell, W. Dean; Webber, S. A. Hess

2015-09-10

We present the three-dimensional geometric structure and thermal properties of a coronal cavity deduced from limb synoptic maps. The observations are extreme ultraviolet images from the Atmospheric Imager Assembly (AIA) and magnetic images from the Helioseismic Magnetic Imager instruments on board the Solar Dynamics Observatory. We describe a limb synoptic-map method used to effectively identify and measure cavities from annuli of radiance above the solar limb. We find that cavities are best seen in the 211, 193, and 171 Å passbands. The prominence associated with each cavity is best seen in the 304 Å synoptic maps. We also estimate themore » thermal properties of the cavity and surrounding plasma by combining the AIA radiances with a differential emission measure analysis. This paper focuses on one long cavity from a catalog of coronal cavities that we are developing. Cavities in this catalog are designated by a coded name using the Carrington Rotation number and position. Cavity C211347177N was observed during Carrington Rotation 2113 at the northwestern limb of the solar disk with an average latitude of 47° N and a central longitude of 177°. We showed the following. (1) The cavity is a long tube with an elliptical cross-section with ratios of the length to width and the length to height of 11:1 and 7:1, respectively. (2) The cavity is about 1360 Mm long, or 170° in longitude. (3) It is tilted in latitude. (4) And it is slightly hotter than its surroundings.« less

Systems and methods for determining strength of cylindrical structures by internal pressure loading

DOEpatents

DeTeresa, Steven John; Groves, Scott Eric; Sanchez, Roberto Joseph; Andrade, William Andrew

2015-08-04

In one embodiment, an apparatus, includes: a mandrel; an expansion cylinder, comprising: opposite first and second ends; an inner circumferential surface extending between the ends and characterized by an inner diameter, the inner circumferential surface defining a hollow cavity; an outer circumferential surface extending between the ends and characterized by an outer diameter that is greater than the inner diameter; and a plurality of slots extending from the inner circumferential surface to the outer circumferential surface and latitudinally oriented between the ends; and one or more base plates configured to engage one of the ends of the expansion cylinder. In another embodiment, a method includes: arranging an expansion cylinder inside a test cylinder; arranging a mandrel inside the expansion cylinder; applying a force to the mandrel for exerting a radial force on the expansion cylinder; and detecting one or more indicia of structural failure of the test cylinder.

Injection Molding Parameters Calculations by Using Visual Basic (VB) Programming

NASA Astrophysics Data System (ADS)

Tony, B. Jain A. R.; Karthikeyen, S.; Alex, B. Jeslin A. R.; Hasan, Z. Jahid Ali

2018-03-01

Now a day’s manufacturing industry plays a vital role in production sectors. To fabricate a component lot of design calculation has to be done. There is a chance of human errors occurs during design calculations. The aim of this project is to create a special module using visual basic (VB) programming to calculate injection molding parameters to avoid human errors. To create an injection mold for a spur gear component the following parameters have to be calculated such as Cooling Capacity, Cooling Channel Diameter, and Cooling Channel Length, Runner Length and Runner Diameter, Gate Diameter and Gate Pressure. To calculate the above injection molding parameters a separate module has been created using Visual Basic (VB) Programming to reduce the human errors. The outcome of the module dimensions is the injection molding components such as mold cavity and core design, ejector plate design.

Characterisation of the aerobic bacterial flora of boid snakes: application of MALDI-TOF mass spectrometry.

PubMed

Plenz, Bastian; Schmidt, Volker; Grosse-Herrenthey, Anke; Krüger, Monika; Pees, Michael

2015-03-14

The aim of this study was to identify aerobic bacterial isolates from the respiratory tract of boids with matrix-assisted laser desorption ionisation-time-of-flight mass spectrometry (MALDI-TOF MS). From 47 boid snakes, swabs from the oral cavity, tracheal wash samples and, in cases in which postmortem examination was performed, pulmonary tissue samples were taken. Each snake was classified as having inflammation of the respiratory tract and/or oral cavity, or without evidence of inflammation based on combination of clinical, cytological and histopathological findings. Samples collected from the respiratory tract and oral cavity were inoculated onto routine media and bacteria were cultured aerobically. All morphologically distinct individual colonies obtained were analysed using MALDI-TOF MS. Unidentified isolates detected in more than three snakes were selected for further 16S rDNA PCR and sequencing. Among all examined isolates (n=243), 49 per cent (n=119) could be sufficiently speciated using MALDI-TOF MS. Molecular biology revealed several bacterial species that have not been previously described in reptiles. With an average of 6.3 different isolates from the respiratory tract and/or oral cavity, boids with inflammatory disease harboured significantly more bacterial species than boids without inflammatory disease (average 2.8 isolates). British Veterinary Association.

The Effect of Density on the Height-Diameter Relationship

Treesearch

Boris Zeide; Curtis Vanderschaaf

2002-01-01

Using stand density along with mean diameter to predict average height increases the proportion of explained variance. This result, obtained from permanent plots established in a loblolly pine plantation thinned to different levels, makes sense. We know that due to competition, trees with the same diameter are taller in denser stands. Diameter and density are not only...

Characterization of ignition transient processes in kerosene-fueled model scramjet engine by dual-pulse laser-induced plasma

NASA Astrophysics Data System (ADS)

Li, Xipeng; Liu, Weidong; Pan, Yu; Yang, Leichao; An, Bin; Zhu, Jiajian

2018-03-01

Dual-pulse laser-induced plasma ignition of kerosene in cavity at model scramjet engine is studied. The simulated flight condition is Ma 6 at 30 km, and the isolator entrance has a Mach number of 2.92, a total pressure of 2.6 MPa and a stagnation temperature of 1650 K. Two independent laser pulses at 532 nm with a pulse width of 10 ns, a diameter of 12 mm and a maximum energy of 300 mJ are focused into cavity for ignition. The flame structure and propagation during transient ignition processes are captured by simultaneous CH* and OH* chemiluminescence imaging. The entire ignition process of kerosene can be divided into five stages, which are referred as turbulent dissipation stage, quasi-stable state, combustion enhancement stage, reverting stage and combustion stabilization stage. A local closed loop of propagations of the burning mixtures from the shear layer into the recirculation zone of cavity is revealed, which the large-scale eddy in the shear layer plays a key role. The enhancement of mass exchange between shear layer and the recirculation zone of cavity could promote the flame propagation process and enhance the ignition capability as well as extend the ignition limits. A cavity shear-layer stabilized combustion of kerosene is established in the supersonic flow roughly 3.3 ms after the laser pulse. Chemical reactions mainly occur in the shear layer and the near-wall zone downstream of the cavity. The distribution of OH* is thicker than CH* at stable combustion condition.

CFD analysis of a scramjet combustor with cavity based flame holders

NASA Astrophysics Data System (ADS)

Kummitha, Obula Reddy; Pandey, Krishna Murari; Gupta, Rajat

2018-03-01

Numerical analysis of a scramjet combustor with different cavity flame holders has been carried out using ANSYS 16 - FLUENT tool. In this research article the internal fluid flow behaviour of the scramjet combustor with different cavity based flame holders have been discussed in detail. Two dimensional Reynolds-Averaged Navier-Stokes governing(RANS) equations and shear stress turbulence (SST) k - ω model along with finite rate/eddy dissipation chemistry turbulence have been considered for modelling chemical reacting flows. Due to the advantage of less computational time, global one step reaction mechanism has been used for combustion modelling of hydrogen and air. The performance of the scramjet combustor with two different cavities namely spherical and step cavity has been compared with the standard DLR scramjet. From the comparison of numerical results, it is found that the development of recirculation regions and additional shock waves from the edge of cavity flame holder is increased. And also it is observed that with the cavity flame holder the residence time of air in the scramjet combustor is also increased and achieved stabilized combustion. From this research analysis, it has been found that the mixing and combustion efficiency of scramjet combustor with step cavity design is optimum as compared to other models.

Frequency-agile, rapid scanning spectroscopy: absorption sensitivity of 2 × 10-12 cm-1 Hz-1/2 with a tunable diode laser

NASA Astrophysics Data System (ADS)

Long, D. A.; Truong, G.-W.; van Zee, R. D.; Plusquellic, D. F.; Hodges, J. T.

2014-03-01

We present ultrasensitive measurements of molecular absorption using frequency-agile rapid scanning, cavity ring-down spectroscopy with an external-cavity diode laser. A microwave source that drives an electro-optic phase modulator with a bandwidth of 20 GHz generates pairs of sidebands on the probe laser. The optical cavity provides for high sensitivity and filters the carrier and all but a single, selected sideband. Absorption spectra were acquired by stepping the tunable sideband from mode-to-mode of the ring-down cavity at a rate that was limited only by the cavity decay time. This approach allows for scanning rates of 8 kHz per cavity resonance, a minimum detectable absorption coefficient of 1.7 × 10-11 cm-1 after only 20 ms of averaging, and a noise-equivalent absorption coefficient of 1.7 × 10-12 cm-1 Hz-1/2. By comparison with cavity-enhanced laser absorption spectrometers reported in the literature, the present system is, to the best of our knowledge, among the most sensitive and has by far the highest spectrum scanning rate.

Canopy structure and tree condition of young, mature, and old-growth Douglas-fir/hardwood forests

Treesearch

B.B. Bingham; J.O. Sawyer

1992-01-01

Sixty-two Douglas-fir/hardwood stands ranging from 40 to 560 years old were used to characterize the density; diameter, and height class distributions of canopy hardwoods and conifers in young (40 -100 yr), mature (101 - 200 yr) and old-growth (>200 yr) forests. The crown, bole, disease, disturbance, and cavity conditions of canopy conifers and hardwoods were...

Paclitaxel-loaded polymeric microparticles: Quantitative relationships between in vitro drug release rate and in vivo pharmacodynamics

PubMed Central

Tsai, Max; Lu, Ze; Wientjes, M. Guillaume; Au, Jessie L.-S.

2013-01-01

Intraperitoneal therapy (IP) has demonstrated survival advantages in patients with peritoneal cancers, but has not become a widely practiced standard-of-care in part due to local toxicity and sub-optimal drug delivery. Paclitaxel-loaded, polymeric microparticles were developed to overcome these limitations. The present study evaluated the effects of microparticle properties on paclitaxel release (extent and rate) and in vivo pharmacodynamics. In vitro paclitaxel release from microparticles with varying physical characteristics (i.e., particle size, copolymer viscosity and composition) was evaluated. A method was developed to simulate the dosing rate and cumulative dose released in the peritoneal cavity based on the in vitro release data. The relationship between the simulated drug delivery and treatment outcomes of seven microparticle compositions was studied in mice bearing IP human pancreatic tumors, and compared to that of the intravenous Cremophor micellar paclitaxel solution used off-label in previous IP studies. Paclitaxel release from polymeric microparticles in vitro was multi-phasic; release was greater and more rapid from microparticles with lower polymer viscosities and smaller diameters (e.g., viscosity of 0.17 vs. 0.67 dl/g and diameter of 5–6 vs. 50–60 μm). The simulated drug release in the peritoneal cavity linearly correlated with treatment efficacy in mice (r2>0.8, p<0.001). The smaller microparticles, which distribute more evenly in the peritoneal cavity compared to the large microparticles, showed greater dose efficiency. For single treatment, the microparticles demonstrated up to 2-times longer survival extension and 4-times higher dose efficiency, relative to the paclitaxel/Cremophor micellar solution. Upon repeated dosing, the paclitaxel/Cremophor micellar solution showed cumulative toxicity whereas the microparticle that yielded 2-times longer survival did not display cumulative toxicity. The efficacy of IP therapy depended on both temporal and spatial factors that were determined by the characteristics of the drug delivery system. A combination of fast- and slow-releasing microparticles with 5–6 μm diameter provided favorable spatial distribution and optimal drug release for IP therapy. PMID:24056144

The densest loblolly pine stand and its silvicultural implications

Treesearch

Boris Zeide; John Stephens

2010-01-01

Estimation of stand density index has been based on the assumption that the only cause of mortality in fully stocked stands is diameter growth. For example, when average diameter increases by 1 percent, a fixed proportion (1.6 percent) of trees must die, regardless of age, average tree size, and other factors. This balance between growth and mortality entails the...

Polarization mode control of long-wavelength VCSELs by intracavity patterning

DOE PAGES

Long, Christopher Michael; Mickovic, Zlatko; Dwir, Benjamin; ...

2016-04-26

Polarization mode control is enhanced in wafer-fused vertical-cavity surface-emitting lasers emitting at 1310 nm wavelength by etching two symmetrically arranged arcs above the gain structure within the laser cavity. The intracavity patterning introduces birefringence and dichroism, which discriminates between the two polarization states of the fundamental transverse modes. We find that the cavity modifications define the polarization angle at threshold with respect to the crystal axes, and increase the gain anisotropy and birefringence on average, leading to an increase in the polarization switching current. As a result, experimental measurements are explained using the spin-flip model of VCSEL polarization dynamics.

Universal quantum gates for photon-atom hybrid systems assisted by bad cavities

PubMed Central

Wang, Guan-Yu; Liu, Qian; Wei, Hai-Rui; Li, Tao; Ai, Qing; Deng, Fu-Guo

2016-01-01

We present two deterministic schemes for constructing a CNOT gate and a Toffoli gate on photon-atom and photon-atom-atom hybrid quantum systems assisted by bad cavities, respectively. They are achieved by cavity-assisted photon scattering and work in the intermediate coupling region with bad cavities, which relaxes the difficulty of their implementation in experiment. Also, bad cavities are feasible for fast quantum operations and reading out information. Compared with previous works, our schemes do not need any auxiliary qubits and measurements. Moreover, the schematic setups for these gates are simple, especially that for our Toffoli gate as only a quarter wave packet is used to interact the photon with each of the atoms every time. These atom-cavity systems can be used as the quantum nodes in long-distance quantum communication as their relatively long coherence time is suitable for multi-time operations between the photon and the system. Our calculations show that the average fidelities and efficiencies of our two universal hybrid quantum gates are high with current experimental technology. PMID:27067992

Correlation between extraocular muscle size and motility restriction in thyroid eye disease.

PubMed

Dagi, Lora R; Zoumalan, Christopher I; Konrad, Hindola; Trokel, Stephen L; Kazim, Michael

2011-01-01

Evaluate the relationship between extraocular muscle (EOM) size, measured by computed tomography, and ocular motility in thyroid eye disease (TED). This case series is based on a retrospective review of the records of 54 patients (108 orbits) with TED. Main outcome measures included EOM size and degree of motility restriction. The average diameter of each rectus muscle was compared with published norms. Four subpopulations based on Age (< 40 or ≥ 40 years) and State of thyroid eye disease (active or stable) were studied. Versions were measured by the corneal light reflex method. The trend of muscle diameter versus motility restriction was evaluated. The average EOM diameter was greater than the norm in the study cohort and 4 subpopulations. The average diameter was largest in the Older and Active TED subpopulations. The inferior rectus and medial rectus were most frequently restricted in the study cohort and 4 subpopulations. The medial rectus had the strongest trend between increasing diameter and motility restriction, followed by the inferior rectus and the superior muscle group (comprised of the superior rectus and levator palpebrae superioris). However, there was a general lack of strong correlation between the diameter of the rectus muscles and their respective motility, especially in the Younger subpopulation. EOM diameters are larger and have more restricted motility in the Older and Active TED subpopulations. Contrary to prior publications, the correlation between EOM diameters and motility was weak, especially in the Younger subpopulation. These findings suggest that the pathophysiology of EOM enlargement is different based upon the age of the patient and the activity of the orbitopathy.

Sexual dimorphism of the suprascapular notch – morphometric study

PubMed Central

Jędrzejewski, Kazimierz S.; Topol, Mirosław

2013-01-01

Introduction The concept of the study was to compare the morphometry of the suprascapular notch (SSN) in females and males because its size and shape may be a factor in suprascapular nerve entrapment. Material and methods The measurements of 81 scapulae included morphological length and width, maximal width and length projection of the scapular spine, and width and length of the glenoid cavity. The width-length scapular and glenoid cavity indices were calculated. In addition to standard anthropometric measurements three other dimensions were defined and collected for every SSN: maximal depth (MD), superior (STD) and middle (MTD) transverse diameters. Results The analysis of the measurements allowed us to distinguish five types of SSN. Type I (26%) had longer maximal depth than superior transverse diameter. Type II (3%) had equal MD, STD and MTD. In type III (57.6%) superior transverse diameter was longer than maximal depth. In type IV (7.4%) a bony foramen was present. Type V (6%) was without a discrete notch. Types I and III were divided into two subtypes: A (MTD was longer than STD) and B (MTD < STD). Distribution of the suprascapular notch types in both sexes was similar. However, MD, STD and MTD were significantly higher in males. The superior transverse suprascapular ligament was completely and partially ossified in 7.4% and 24.7% respectively. Conclusions The presented classification of the suprascapular notch is simple, easy to use, and based on specific geometric parameters which allow one to clearly distinguish five types of these structures. All dimensions of SSN were significantly higher in males than in females. PMID:23515320

Height-diameter equations for thirteen midwestern bottomland hardwood species

Treesearch

Kenneth C. Colbert; David R. Larsen; James R. Lootens

2002-01-01

Height-diameter equations are often used to predict the mean total tree height for trees when only diameter at breast height (dbh) is measured. Measuring dbh is much easier and is subject to less measurement error than total tree height. However, predicted heights only reflect the average height for trees of a particular diameter. In this study, we present a set of...

WE-DE-BRA-10: Development of a Novel Scanning Beam Low-Energy Intraoperative Radiation Therapy (SBIORT) System for Pancreatic Cancer

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

Wears, B; Mohiuddin, I; Flynn, R

2016-06-15

Purpose: Developing a compact collimator system and validating a 3D surface imaging module for a scanning beam low-energy x-ray radiation therapy (SBIORT) system that enables delivery of non-uniform radiation dose to targets with irregular shapes intraoperatively. Methods: SBIORT consists of a low energy x-ray source, a custom compact collimator module, a robotic arm, and a 3D surface imaging module. The 3D surface imaging system (structure sensor) is utilized for treatment planning and motion monitoring of the surgical cavity. SBIORT can deliver non-uniform dose distributions by dynamically moving the x-ray source assembly along optimal paths with various collimator apertures. The compactmore » collimator utilizes a dynamic shutter mechanism to form a variable square aperture. The accuracy and reproducibility of the collimator were evaluated using a high accuracy encoder and a high resolution camera platform. The dosimetrical characteristics of the collimator prototype were evaluated using EBT3 films with a Pantak Therapax unit. The accuracy and clinical feasibility of the 3D imaging system were evaluated using a phantom and a cadaver cavity. Results: The SBIORT collimator has a compact size: 66 mm diameter and 10 mm thickness with the maximum aperture of 20 mm. The mechanical experiment indicated the average accuracy of leaf position was 0.08 mm with a reproducibility of 0.25 mm at 95% confidence level. The dosimetry study indicated the collimator had a penumbra of 0.35 mm with a leaf transmission of 0.5%. 3D surface scans can be acquired in 5 seconds. The average difference between the acquired 3D surface and the ground truth is 1 mm with a standard deviation of 0.6 mm. Conclusion: This work demonstrates the feasibility of the compact collimator and 3D scanning system for the SBIORT. SBIORT is a way of delivering IORT with a compact system that requires minimum shielding of the procedure room. This research is supported by the University of Iowa Internal Funding Initiatives.« less

10 kHz ps 1342 nm laser generation by an electro-optically cavity-dumped mode-locked Nd:YVO4 laser

NASA Astrophysics Data System (ADS)

Chen, Ying; Liu, Ke; He, Li-jiao; Yang, Jing; Zong, Nan; Yang, Feng; Gao, Hong-wei; Liu, Zhao; Yuan, Lei; Lan, Ying-jie; Bo, Yong; Peng, Qin-jun; Cui, Da-fu; Xu, Zu-yan

2017-01-01

We have demonstrated an electro-optically cavity-dumped mode-locked (CDML) picosecond Nd:YVO4 laser at 1342 nm with 880 nm diode-laser direct pumping. At a repetition rate of 10 kHz, an average output power of 0.119 W was achieved, corresponding to a pulse energy of 11.9 μJ. Compared with the continuous wave mode-locking pulse energy of 17.5 nJ, the CDML pulse energy was 680 times higher. The pulse width was measured to be 33.4 ps, resulting in the peak power of 356 kW. Meanwhile, the beam quality was nearly diffraction limited with an average beam quality factor M2 of 1.29.

Diode-side-pumped intracavity frequency-doubled Nd:YAG/BaWO4 Raman laser generating average output power of 3.14 W at 590 nm.

PubMed

Li, Shutao; Zhang, Xingyu; Wang, Qingpu; Zhang, Xiaolei; Cong, Zhenhua; Zhang, Huaijin; Wang, Jiyang

2007-10-15

We report a linear-cavity high-power all-solid-state Q-switched yellow laser. The laser source comprises a diode-side-pumped Nd:YAG module that produces 1064 nm fundamental radiation, an intracavity BaWO(4) Raman crystal that generates a first-Stokes laser at 1180 nm, and a KTP crystal that frequency doubles the first-Stokes laser to 590 nm. A convex-plane cavity is employed in this configuration to counteract some of the thermal effect caused by high pump power. An average output power of 3.14 W at 590 nm is obtained at a pulse repetition frequency of 10 kHz.

Hot interstellar tunnels. 1: Simulation of interacting supernova remnants

NASA Technical Reports Server (NTRS)

Smith, B. W.

1976-01-01

The theory required to build a numerical simulation of interacting supernova remnants is developed. The hot cavities within a population of remnants will become connected, with varying ease and speed, for a variety of assumed conditions in the outer shells of old remnants. Apparently neither radiative cooling nor thermal conduction in a large-scale galactic magnetic field can destroy hot cavity regions, if they grow, faster than they are reheated by supernova shock waves, but interstellar mass motions disrupt the contiguity of extensive cavities necessary for the dispersal of these shocks over a wide volume. Monte Carlo simulations show that a quasi-equilibrium is reached in the test space within 10 million yrs of the first supernova and is characterized by an average cavity filling fraction of the interstellar volume. Aspects of this equilibrium are discussed for a range of supernova rates. Two predictions are not confirmed within this range: critical growth of hot regions to encompass the entire medium, and the efficient quenching of a remnant's expansion by interaction with other cavities.

Observation of Schumann Resonances in the Earth's Ionosphere

NASA Technical Reports Server (NTRS)

Simoes, Fernando; Pfaff, Robert; Freudenreich, Henry

2011-01-01

The surface of the Earth and the lower edge of the ionosphere define a cavity in which electromagnetic waves propagate. When the cavity is excited by broadband electromagnetic sources, e.g., lightning, a resonant state can develop provided the average equatorial circumference is approximately equal to an integral number of wavelengths of the electromagnetic waves. This phenomenon, known as Schumann resonance, corresponds to electromagnetic oscillations of the surface-ionosphere cavity, and has been used extensively to investigate atmospheric electricity. Using measurements from the Communications/Navigation Outage Forecasting System (C/NOFS) satellite, we report, for the first time, Schumann resonance signatures detected well beyond the upper boundary of the cavity. These results offer new means for investigating atmospheric electricity, tropospheric-ionospheric coupling mechanisms related to lightning activity, and wave propagation in the ionosphere. The detection of Schumann resonances in the ionosphere calls for revisions to the existing models of extremely low frequency wave propagation in the surface-ionosphere cavity. Additionally, these measurements suggest new remote sensing capabilities for investigating atmospheric electricity at other planets.

Subsurface Cavity Detection by Using Integrated Geophysical Methods

NASA Astrophysics Data System (ADS)

Aykaç, Sinem; Rezzan Ozerk, Zeynep; Işıkdeniz Şerifoǧlu, Betül; Bihter Demirci, Büşra; Timur, Emre; Çakir, Korhan

2016-04-01

Global warming experienced in recent years in Turkey has led to a severe drought around the Konya Plain in central Anatolia .As a result, excessive amount of ground water was drawn in the region for the sustainability of agricultural activities. So, five small-scale shallow depth sinkholes have occured at different times, at an average interval between 400-450 m. in the study area; Konya-Atlantı. Generally, sinkholes formation occurres among natural processes has turned into disasters caused by humans due to excessive use of groundwater. Consequently, investigations were carried out within a partnership research programme on cavity detection and ground penetration radar, microgravity and multi-frequency electromagnetic methods were jointly utilized. . Exact locations and dimensions of two possible hidden cavities were determined by using these multidisciplinary methods. Keywords: Cavity;Ground-penetrating radar;Konya;Microgravimetry;Multi-frequency electromagnetic method.

Multiple bunch HOM evaluation for ERL cavities

DOE PAGES

Xu, Chen; Ben-Zvi, I.; Blaskiewicz, Michael M.; ...

2017-06-15

In this paper we investigate the effect of the bunch pattern in a linac on the Higher Order Mode (HOM) power generation. The future ERL-based electron–ion collider eRHIC at BNL is used as an illustrative example. This ERL has multiple high current Superconducting Radiofrequency (SRF) 5-cell cavities. The HOM power generated when a single bunch traverses the cavity is estimated by the corresponding loss factor. Multiple re-circulations through the Energy Recovery Linac (ERL) create a specific bunch pattern. In this case the loss factor can be different than the single bunch loss factor. HOM power can vary dramatically when themore » ERL bunch pattern changes. The HOM power generation can be surveyed in the time and frequency domains. We estimate the average HOM power in a 5-cell cavity with different ERL bunch patterns.« less

Multiple bunch HOM evaluation for ERL cavities

NASA Astrophysics Data System (ADS)

Xu, Chen; Ben-Zvi, I.; Blaskiewicz, Michael M.; Hao, Yue; Ptitsyn, Vadim

2017-09-01

In this work we investigate the effect of the bunch pattern in a linac on the Higher Order Mode (HOM) power generation. The future ERL-based electron-ion collider eRHIC at BNL is used as an illustrative example. This ERL has multiple high current Superconducting Radiofrequency (SRF) 5-cell cavities. The HOM power generated when a single bunch traverses the cavity is estimated by the corresponding loss factor. Multiple re-circulations through the Energy Recovery Linac (ERL) create a specific bunch pattern. In this case the loss factor can be different than the single bunch loss factor. HOM power can vary dramatically when the ERL bunch pattern changes. The HOM power generation can be surveyed in the time and frequency domains. We estimate the average HOM power in a 5-cell cavity with different ERL bunch patterns.

Multiple bunch HOM evaluation for ERL cavities

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

Xu, Chen; Ben-Zvi, I.; Blaskiewicz, Michael M.

In this paper we investigate the effect of the bunch pattern in a linac on the Higher Order Mode (HOM) power generation. The future ERL-based electron–ion collider eRHIC at BNL is used as an illustrative example. This ERL has multiple high current Superconducting Radiofrequency (SRF) 5-cell cavities. The HOM power generated when a single bunch traverses the cavity is estimated by the corresponding loss factor. Multiple re-circulations through the Energy Recovery Linac (ERL) create a specific bunch pattern. In this case the loss factor can be different than the single bunch loss factor. HOM power can vary dramatically when themore » ERL bunch pattern changes. The HOM power generation can be surveyed in the time and frequency domains. We estimate the average HOM power in a 5-cell cavity with different ERL bunch patterns.« less

Genetic divergence among accessions of melon from traditional agriculture of the Brazilian Northeast.

PubMed

Aragão, F A S; Torres Filho, J; Nunes, G H S; Queiróz, M A; Bordallo, P N; Buso, G S C; Ferreira, M A; Costa, Z P; Bezerra Neto, F

2013-12-06

The genetic divergence of 38 melon accessions from traditional agriculture of the Brazilian Northeast and three commercial hybrids were evaluated using fruit descriptors and microsatellite markers. The melon germplasm belongs to the botanic varieties cantalupensis (19), momordica (7), conomon (4), and inodorus (3), and to eight genotypes that were identified only at the species level. The fruit descriptors evaluated were: number of fruits per plant (NPF), fruit mass (FM; kg), fruit longitudinal diameter (LD; cm), fruit transversal diameter (TD; cm), shape index based on the LD/TD ratio, flesh pulp thickness, cavity thickness (CT; cm), firmness fruit pulp (N), and soluble solids (SS; °Brix). The results showed high variability for all descriptors, especially for NPF, LD, and FM. The grouping analysis based on fruit descriptors produced eight groups without taxonomic criteria. The LD (22.52%), NPF (19.70%), CT (16.13%), and SS (9.57%) characteristics were the descriptors that contributed the most to genotype dissimilarity. The 17 simple sequence repeat polymorphic markers amplified 41 alleles with an average of 2.41 alleles and three genotypes per locus. Some markers presented a high frequency for the main allele. The genetic diversity ranged from 0.07 to 0.60, the observed heterozygosity had very low values, and the mean polymorphism information content was 0.32. Molecular genetic similarity analyses clustered the accessions in 13 groups, also not following taxonomic ranks. There was no association between morphoagronomic and molecular groupings. In conclusion, there was great variability among the accessions and among and within botanic groups.

Design of high-brightness TEM00-mode solar-pumped laser for renewable material processing

NASA Astrophysics Data System (ADS)

Liang, D.; Almeida, J.

2014-08-01

The conversion of sunlight into laser light by direct solar pumping is of ever-increasing importance because broadband, temporally constant, sunlight is converted into laser light, which can be a source of narrowband, collimated, rapidly pulsed, radiation with the possibility of obtaining extremely high brightness and intensity. Nonlinear processes, such as harmonic generation, might be used to obtain broad wavelength coverage, including the ultraviolet wavelengths, where the solar flux is very weak. The direct excitation of large lasers by sunlight offers the prospect of a drastic reduction in the cost of coherent optical radiation for high average power materials processing. This renewable laser has a large potential for many applications such as high-temperature materials processing, renewable magnesium-hydrogen energy cycle and so on. We propose here a scalable TEM00 mode solar laser pumping scheme, which is composed of four firststage 1.13 m diameter Fresnel lenses with its respective folding mirrors mounted on a two-axis automatic solar tracker. Concentrated solar power at the four focal spots of these Fresnel lenses are focused individually along a common 3.5 mm diameter, 70 mm length Nd:YAG rod via four pairs of second-stage fused-silica spherical lenses and third-stage 2D-CPCs (Compound Parabolic Concentrator), sitting just above the laser rod which is also double-pass pumped by four V-shaped pumping cavities. Distilled water cools both the rod and the concentrators. 15.4 W TEM00 solar laser power is numerically calculated, corresponding to 6.7 times enhancement in laser beam brightness.

Understanding the breathing phenomena in nano-ZIF-7 upon gas adsorption

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

Cuadrado-Collados, Carlos; Fernández-Català, Javier; Fauth, François

For this research, synchrotron X-ray diffraction and inelastic neutron scattering measurements have been applied to evaluate the breathing phenomena in small nanocrystals of ZIF-7 upon gas adsorption. The experimental results show that an extended solvent exchange process with methanol is crucial to get a solvent-free narrow pore structure. Under these conditions, nano-ZIF-7 is indeed able to adsorb N 2 with a total BET surface area of around 380 m 2 g -1, in close agreement with theoretical predictions. The breathing phenomenon upon nitrogen adsorption is accompanied by a phase-to-phase transition, from a narrow-pore (phase II) to a large-pore (phase I)more » structure and a suppression of the cooperative deformation of the framework involving mainly the flapping motion of the benzimidazolate (bIm) ligand with the 4- and 6-membered rings. Whereas nitrogen requires temperature and pressure conditions close to condensation (close to 1 bar and 77 K) to induce the breathing in ZIF-7, CO 2 can do it under milder conditions (at room temperature and low relative pressures). These results reflect that the nature of the adsorptive probe and the gas–framework interactions, rather than the molecular diameter and/or shape, play a crucial role in defining the pressure and temperature conditions required to induce the breathing. Lastly, the presence of two different cavities in ZIF-7 as suggested by theoretical predictions, one with a window diameter of below 0.4 nm (cavity A) and the other with a pore size of around 0.6 nm (cavity B), has been confirmed experimentally using immersion calorimetry.« less

Understanding the breathing phenomena in nano-ZIF-7 upon gas adsorption

DOE PAGES

Cuadrado-Collados, Carlos; Fernández-Català, Javier; Fauth, François; ...

2017-09-11

For this research, synchrotron X-ray diffraction and inelastic neutron scattering measurements have been applied to evaluate the breathing phenomena in small nanocrystals of ZIF-7 upon gas adsorption. The experimental results show that an extended solvent exchange process with methanol is crucial to get a solvent-free narrow pore structure. Under these conditions, nano-ZIF-7 is indeed able to adsorb N 2 with a total BET surface area of around 380 m 2 g -1, in close agreement with theoretical predictions. The breathing phenomenon upon nitrogen adsorption is accompanied by a phase-to-phase transition, from a narrow-pore (phase II) to a large-pore (phase I)more » structure and a suppression of the cooperative deformation of the framework involving mainly the flapping motion of the benzimidazolate (bIm) ligand with the 4- and 6-membered rings. Whereas nitrogen requires temperature and pressure conditions close to condensation (close to 1 bar and 77 K) to induce the breathing in ZIF-7, CO 2 can do it under milder conditions (at room temperature and low relative pressures). These results reflect that the nature of the adsorptive probe and the gas–framework interactions, rather than the molecular diameter and/or shape, play a crucial role in defining the pressure and temperature conditions required to induce the breathing. Lastly, the presence of two different cavities in ZIF-7 as suggested by theoretical predictions, one with a window diameter of below 0.4 nm (cavity A) and the other with a pore size of around 0.6 nm (cavity B), has been confirmed experimentally using immersion calorimetry.« less

Simulation optimization of spherical non-polar guest recognition by deep-cavity cavitands

PubMed Central

Wanjari, Piyush P.; Gibb, Bruce C.; Ashbaugh, Henry S.

2013-01-01

Biomimetic deep-cavity cavitand hosts possess unique recognition and encapsulation properties that make them capable of selectively binding a range of non-polar guests within their hydrophobic pocket. Adamantane based derivatives which snuggly fit within the pocket of octa-acid deep cavity cavitands exhibit some of the strongest host binding. Here we explore the roles of guest size and attractiveness on optimizing guest binding to form 1:1 complexes with octa-acid cavitands in water. Specifically we simulate the water-mediated interactions of the cavitand with adamantane and a range of simple Lennard-Jones guests of varying diameter and attractive well-depth. Initial simulations performed with methane indicate hydrated methanes preferentially reside within the host pocket, although these guests frequently trade places with water and other methanes in bulk solution. The interaction strength of hydrophobic guests increases with increasing size from sizes slightly smaller than methane to Lennard-Jones guests comparable in size to adamantane. Over this guest size range the preferential guest binding location migrates from the bottom of the host pocket upwards. For guests larger than adamantane, however, binding becomes less favorable as the minimum in the potential-of-mean force shifts to the cavitand face around the portal. For a fixed guest diameter, the Lennard-Jones well-depth is found to systematically shift the guest-host potential-of-mean force to lower free energies, however, the optimal guest size is found to be insensitive to increasing well-depth. Ultimately our simulations show that adamantane lies within the optimal range of guest sizes with significant attractive interactions to match the most tightly bound Lennard-Jones guests studied. PMID:24359375

[A parallel-plate small volume chamber for dosimetry of fast electrons and its use].

PubMed

Markus, B

1976-12-01

The ionization chamber described is designed for dosimetry of electron radiation above ca. 100 keV. It is used for the measurement of the cavity ion dose and of the absorbed dose within solid or water phantoms. Its construction corresponds to a flat chamber in accordance with DIN 6800. The cylindric main body is made of plexiglass (diameter 30 mm, height 14 mm) and encompasses the measuring volume being flush with the surface (diameter 5 mm, height 2 mm; chamber window 2.3 mg/cm2; build up cap for measurements in water 236 mg/cm2). The chamber is constructed with regard to its independency on energy and direction of the incidence as well as to the minimization of the remaining influence quantities, thus answering for the accuracy class "reference-class instrument" (+/- 0.5%). The polarity effect and field perturbation effect are to be neglected, the displacement comes to 0.1 mm, the statistical inaccuracy of measurement to 0.1%. The calibration for the chamber was obtained with a 15 MeV electron beam. The calibration factor for the cavity ion dose is constant, not being related to energy, at least in the range of performance from 2 to 15 MeV according to the primary standard used for calibration (graphic double extrapolation chamber). The overall uncertainty of the calibration factor amounts to +/- 1.5% for the cavity ion dose and to +/- 1.8% for the energy dose. Numerical values of all characteristic quantities and influence quantities which correspond to DIN 6817 and also measurement results for the determination of dose and energy are reported.

[Exploration of three-dimensional biometric measurement of emmetropic adult eye-ball by using magnetic resonance imaging technology].

PubMed

Xu, Hai-Ming; Zhou, Yun-Xin; Shi, Ming-Guang

2008-11-01

To study biometric measurements of emmetropic adult eyes with magnetic resonance imaging technology (MRI). MRI technology, with super-resolution, hyper-speed imaging and the integration of the thin-scanning layer, is applied to measure the three-dimensional biometric parameters of the eyeball. From January to December, 2003, emmetropic eyes from 31 normal Chinese adults (16 males and 15 females) aged from 18 to 32 years old (23.32 +/- 3.32) were successfully measured to obtain the volume of the eyeball and vitreous cavity; inner dimensions of the eye, including the anterior-posterior, vertical and horizontal diameters. The length of ocular axis was measured by A-echo too. Data was analyzed by SPSS 11.0 statistical software. The volume of the eyeball, anterior chamber, lens and the vitreous cavity is (6.013 +/- 0.449) ml, (0.348 +/- 0.020) ml, (0.183 +/- 0.015) ml, and (5.482 +/- 0.440) ml, respectively. The length of anterior-posterior diameter of the vitreous cavity is (16.008 +/- 0.707) mm. The ocular inner dimensions of horizontal, vertical and anterior-posterior planes were (22.455 +/- 0.983) mm, (23.290 +/- 0.815) mm and (22.619 +/- 0.912) mm, respectively. The length of the ocular axis is (23.10 +/- 0.92) mm (with MRI & Orbscan II) and (23.67 +/- 0.82) mm (with A-echo). The value of the ocular length in emmetropic eye measured with both MRI + Orbscan II and the (A-echo) in the present study is very close to the value of the Bennett-Rabbitts schematic eye (24.09 mm). MRI technology is valuable for obtaining more reliable and precise data in the study of ocular physiology and clinical ophthalmology.

Apparatus for connecting aligned abutted tubes

DOEpatents

Williams, R.E.

1984-11-29

An apparatus for connecting abutted tubes and for maintaining their rotary alignment during connection. The apparatus comprises first and second tubes, a rotation prevention element, a collar and a retainer. Each tube has inside and outside walls, and first and second ends, each end having an inside and outside edge. The first tube has portions defining a first plurality of cavities located at the outside edge of its first end. An external threaded portion is on the outside wall of the first tube and next to the first plurality of cavities. The second tube has portions defining a second plurality of cavities located at the outside edge of its first end. The first plurality has a different number than the second plurality. The first ends of the first and second tubes have substantially the same outside diameter and are abutted during connection so that an orifice is formed whenever first and second tube cavities substantially overlap. A rotation prevension element is placed in the orifice to prevent rotation of the first and second tubes. A collar with an internal threaded portion is slidably disposed about the second tube. The internal threaded portion engages the external threaded portion of the first tube to connect the tubes. A lip connected to the collar prevents separation of the collar from the second tube.

Servo scanning 3D micro EDM for array micro cavities using on-machine fabricated tool electrodes

NASA Astrophysics Data System (ADS)

Tong, Hao; Li, Yong; Zhang, Long

2018-02-01

Array micro cavities are useful in many fields including in micro molds, optical devices, biochips and so on. Array servo scanning micro electro discharge machining (EDM), using array micro electrodes with simple cross-sectional shape, has the advantage of machining complex 3D micro cavities in batches. In this paper, the machining errors caused by offline-fabricated array micro electrodes are analyzed in particular, and then a machining process of array servo scanning micro EDM is proposed by using on-machine fabricated array micro electrodes. The array micro electrodes are fabricated on-machine by combined procedures including wire electro discharge grinding, array reverse copying and electrode end trimming. Nine-array tool electrodes with Φ80 µm diameter and 600 µm length are obtained. Furthermore, the proposed process is verified by several machining experiments for achieving nine-array hexagonal micro cavities with top side length of 300 µm, bottom side length of 150 µm, and depth of 112 µm or 120 µm. In the experiments, a chip hump accumulates on the electrode tips like the built-up edge in mechanical machining under the conditions of brass workpieces, copper electrodes and the dielectric of deionized water. The accumulated hump can be avoided by replacing the water dielectric by an oil dielectric.

Hydraulic Jumps on Superhydrophobic Surfaces Exhibiting Ribs and Cavities

NASA Astrophysics Data System (ADS)

Johnson, Michael; Russell, Benton; Maynes, Daniel; Webb, Brent

2009-11-01

We report experimental results characterizing the dynamics of a liquid jet impinging normally on superhydrophobic surfaces spanning the Weber number (based on the jet velocity and diameter) range from 100 to 1400. The superhydrophobic surfaces are fabricated with both silicon and PDMS surfaces and exhibit micro-ribs and cavities coated with a hydrophobic coating. In general, the hydraulic jump exhibits an elliptical shape with the major axis being aligned parallel to the ribs, concomitant with the frictional resistance being smaller in the parallel direction than in the transverse direction. When the water depth downstream of the jump was imposed at a predetermined value, the major and minor axis of the jump increased with decreasing water depth, following classical hydraulic jump behavior. When no water depth was imposed, however, the total projected area of the ellipse exhibited a nearly linear dependence on the jet Weber number, and was nominally invariant with varying hydrophobicity and relative size of the ribs and cavities. For this scenario the Weber number (based on the local radial velocity and water depth prior to the jump) was of order unity at the jump location. The results also reveal that for increasing relative size of the cavities, the ratio of the ellipse axis (major-to-minor) increases.

A new model for the characterization of infection risk in gunshot injuries:Technology, principal consideration and clinical implementation

PubMed Central

2011-01-01

Introduction The extent of wound contamination in gunshot injuries is still a topic of controversial debate. The purpose of the present study is to develop a model that illustrates the contamination of wounds with exogenous particles along the bullet path. Material and methods To simulate bacteria, radio-opaque barium titanate (3-6 μm in diameter) was atomized in a dust chamber. Full metal jacket or soft point bullets caliber .222 (n = 12, v0 = 1096 m/s) were fired through the chamber into a gelatin block directly behind it. After that, the gelatin block underwent multi-slice CT in order to analyze the permanent and temporary wound cavity. Results The permanent cavity caused by both types of projectiles showed deposits of barium titanate distributed over the entire bullet path. Full metal jacket bullets left only few traces of barium titanate in the temporary cavity. In contrast, the soft point bullets disintegrated completely, and barium titanate covered the entire wound cavity. Discussion Deep penetration of potential exogenous bacteria can be simulated easily and reproducibly with barium titanate particles shot into a gelatin block. Additionally, this procedure permits conclusions to be drawn about the distribution of possible contaminants and thus can yield essential findings in terms of necessary therapeutic procedures. PMID:22032229

Heavy hydrocarbon main injector technology program

NASA Technical Reports Server (NTRS)

Arbit, H. A.; Tuegel, L. M.; Dodd, F. E.

1991-01-01

The Heavy Hydrocarbon Main Injector Program was an analytical, design, and test program to demonstrate an injection concept applicable to an Isolated Combustion Compartment of a full-scale, high pressure, LOX/RP-1 engine. Several injector patterns were tested in a 3.4-in. combustor. Based on these results, features of the most promising injector design were incorporated into a 5.7-in. injector which was then hot-fire tested. In turn, a preliminary design of a 5-compartment 2D combustor was based on this pattern. Also the additional subscale injector testing and analysis was performed with an emphasis on improving analytical techniques and acoustic cavity design methodology. Several of the existing 3.5-in. diameter injectors were hot-fire tested with and without acoustic cavities for spontaneous and dynamic stability characteristics.

Sensitivity enhancement of fiber loop cavity ring-down pressure sensor.

PubMed

Jiang, Yajun; Yang, Dexing; Tang, Daqing; Zhao, Jianlin

2009-11-10

We present a theoretical and experimental study on sensitivity enhancement of a fiber-loop cavity ring-down pressure sensor. The cladding of the sensing fiber is etched in hydrofluoric acid solution to enhance its sensitivity. The experimental results demonstrate that the pressure applied on the sensing fiber is linearly proportional to the difference between the reciprocals of the ring-down time with and without pressure, and the relative sensitivity exponentially increases with decreasing the cladding diameter. When the sensing fiber is etched to 41.15 microm, its sensitivity is about 36 times that of nonetched fiber in the range of 0 to 32.5 MPa. The measured relative standard deviation of the ring-down time is about 0.15% and, correspondingly, the least detectable loss is about 0.00069 dB.

Static latching arrangement and method

DOEpatents

Morrison, Larry

1988-01-01

A latching assembly for use in latching a cable to and unlatching it from a given object in order to move an object from one location to another is disclosed herein. This assembly includes a weighted sphere mounted to one end of a cable so as to rotate about a specific diameter of the sphere. The assembly also includes a static latch adapted for connection with the object to be moved. This latch includes an internal latching cavity for containing the sphere in a latching condition and a series of surfaces and openings which cooperate with the sphere in order to move the sphere into and out of the latching cavity and thereby connect the cable to and disconnect it from the latch without using any moving parts on the latch itself.

830-nm Polarization Controlled Lasing of InGaAs Quantum Wire Vertical-Cavity Surface-Emitting Lasers Grown on (775)B GaAs Substrates by Molecular Beam Epitaxy

NASA Astrophysics Data System (ADS)

Higuchi, Yu; Osaki, Shinji; Sasahata, Yoshifumi; Kitada, Takahiro; Shimomura, Satoshi; Ogura, Mutsuo; Hiyamizu, Satoshi

2007-02-01

We report the first demonstration of room temperature (RT) current injection lasing of vertical-cavity surface-emitting lasers (VCSELs), with self-organized InGaAs/(GaAs)6(AlAs)1 quantum wires (QWRs) in their active region, grown on (775)B-oriented GaAs substrates by molecular beam epitaxy. A (775)B InGaAs QWR-VCSEL with an aperture diameter of 4 μm lased at a wavelength of 829.7 nm and a threshold current of 0.7 mA at RT. The light output was linearly polarized in the direction parallel to the QWRs due to optical anisotropy of the self-organized (775)B InGaAs QWRs.

Expulsion of Fibroids to the Endometrial Cavity after Magnetic Resonance Imaging-guided High Intensity Focused Ultrasound Surgery (MRgFUS) Treatment of Intramural Uterine Fibroids

PubMed Central

Jeong, Jae-Hyeok; Hong, Gil Pyo; Kim, Yu-Ri; Hong, Da Gyo; Ha, Jae-Eun; Yeom, Jung In; Kim, Eun-Jeong; Kim, Hyung-Il

2016-01-01

Objectives This report seeks to introduce some cases of the patients who received magnetic resonance imaging (MRI)-guided high intensity focused ultrasound (HIFU) surgery (MRgFUS)-based intramural uterine fibroids treatment where the post-MRgFUS intramural uterine fibroids decreased in its volume and protruded towards the endometrial cavity to be expelled by hysteroscopy. Methods Of the 157 patients who had received MRgFUS treatment in the Obstetrics and Gynecology of the Hospital from March, 2015 to February, 2016; this study examined 6 of the cases where, after high intensity focused ultrasound treatment, intramural uterine fibroids protruded towards the endometrial cavity to be removed by hysteroscopic myomectomy. The high intensity focused ultrasound utilized in the cases were Philips Achieva 1.5 Tesla MR (Philips Healthcare, Best, The Netherlands) and Sonalleve HIFU system. Results The volume of fibroids ranged from 26.0 cm3 to 199.5 cm3, averaging 95.6 cm3. The major axis length ranged from 4.0 cm to 8.2 cm, averaging 6.3 cm. Fibroid location in all of the patients was in intramural uterine before treatment but after the high intensity focused ultrasound treatment, the fibroids were observed to protrude towards the endometrial cavity in at least Day 5 or up to Day 73 to allow hysteroscopic myomectomy. Conclusions In some cases, after an intramural uterine fibroid is treated with MRgFUS, fibroid volume is decreased and the fibroid protrudes towards the endometrial cavity. In this case, hysteroscopic myomectomy can be a useful solution. PMID:28119893

[INVITED] Sensing properties of micro-cavity in-line Mach-Zehnder interferometer enhanced by reactive ion etching

NASA Astrophysics Data System (ADS)

Janik, Monika; Koba, Marcin; Celebańska, Anna; Bock, Wojtek J.; Śmietana, Mateusz

2018-07-01

In this work, we discuss an application of reactive ion etching (RIE) for enhancing the sensing properties of a micro-cavity in-line Mach-Zehnder interferometer (μIMZI). The μIMZI was fabricated using femtosecond laser micromachining in a standard single-mode fiber as a circular hole with a diameter of 54 μm. Next, the structures underwent two kinds of RIE using as reactive gases: sulfur hexafluoride (SF6) and oxygen (O2) mixtures (SF6/O2) or O2 itself. When RIE with SF6/O2 was applied, it allowed for an efficient and well-controlled etching of the fabricated structure at nanometers level observed as an increase in spectral depths of the minima in the μIMZI transmission spectrum. A similar RIE process with O2 alone was ineffective. The well-defined minima obtained with the SF6/O2 RIE significantly improved the resolution of measurements made with the μIMZI. The effect was demonstrated for high-resolution refractive index (RI) measurements of liquids in the cavity. The result of the RIE process was to clean the micro-cavity bottom, increase its depth, and smooth its sidewalls. As an additional effect, the wettability of the micro-cavity surface was improved, making the RI measurements faster and more repeatable. Moreover, we demonstrated that RIE with SF6/O2 results in more stable wettability improvement than when O2 is applied as a reactive gas.

Origin of microplasma instabilities during DC operation of silicon based microhollow cathode devices

NASA Astrophysics Data System (ADS)

Felix, Valentin; Lefaucheux, Philippe; Aubry, Olivier; Golda, Judith; Schulz-von der Gathen, Volker; Overzet, Lawrence J.; Dussart, Rémi

2016-04-01

The failure mechanisms of micro hollow cathode discharges (MHCD) in silicon have been investigated using their I-V characteristics, high speed photography and scanning electron microscopy. Experiments were carried out in helium. We observed I-V instabilities in the form of rapid voltage decreases associated with current spikes. The current spikes can reach values more than 100 times greater than the average MHCD current. (The peaks can be more than 1 Ampere for a few 10’s of nanoseconds.) These current spikes are correlated in time with 3-10 μm diameter optical flashes that occur inside the cavities. The SEM characterizations indicated that blister-like structures form on the Si surface during plasma operation. Thin Si layers detach from the surface in localized regions. We theorize that shallow helium implantation occurs and forms the ‘blisters’ whenever the Si is biased as the cathode. These blisters ‘explode’ when the helium pressure inside them becomes too large leading to the transient micro-arcs seen in both the optical emission and the I-V characteristics. We noted that blisters were never found on the metal counter electrode, even when it was biased as the cathode (and the Si as the anode). This observation led to a few suggestions for delaying the failure of Si MHCDs. One may coat the Si cathode (cavities) with blister resistant material; design the MHCD array to operate with the Si as the anode rather than as the cathode; or use a gas additive to prevent surface damage. Regarding the latter, tests using SF6 as the gas additive successfully prevented blister formation through rapid etching. The result was an enhanced MHCD lifetime.

High frame rate synthetic aperture vector flow imaging for transthoracic echocardiography

NASA Astrophysics Data System (ADS)

Villagómez-Hoyos, Carlos A.; Stuart, Matthias B.; Bechsgaard, Thor; Nielsen, Michael Bachmann; Jensen, Jørgen Arendt

2016-04-01

This work presents the first in vivo results of 2-D high frame rate vector velocity imaging for transthoracic cardiac imaging. Measurements are made on a healthy volunteer using the SARUS experimental ultrasound scanner connected to an intercostal phased-array probe. Two parasternal long-axis view (PLAX) are obtained, one centred at the aortic valve and another centred at the left ventricle. The acquisition sequence was composed of 3 diverging waves for high frame rate synthetic aperture flow imaging. For verification a phantom measurement is performed on a transverse straight 5 mm diameter vessel at a depth of 100 mm in a tissue-mimicking phantom. A flow pump produced a 2 ml/s constant flow with a peak velocity of 0.2 m/s. The average estimated flow angle in the ROI was 86.22° +/- 6.66° with a true flow angle of 90°. A relative velocity bias of -39% with a standard deviation of 13% was found. In-vivo acquisitions show complex flow patterns in the heart. In the aortic valve view, blood is seen exiting the left ventricle cavity through the aortic valve into the aorta during the systolic phase of the cardiac cycle. In the left ventricle view, blood flow is seen entering the left ventricle cavity through the mitral valve and splitting in two ways when approximating the left ventricle wall. The work presents 2-D velocity estimates on the heart from a non-invasive transthoracic scan. The ability of the method detecting flow regardless of the beam angle could potentially reveal a more complete view of the flow patterns presented on the heart.

Laser processing with specially designed laser beam

NASA Astrophysics Data System (ADS)

Asratyan, A. A.; Bulychev, N. A.; Feofanov, I. N.; Kazaryan, M. A.; Krasovskii, V. I.; Lyabin, N. A.; Pogosyan, L. A.; Sachkov, V. I.; Zakharyan, R. A.

2016-04-01

The possibility of using laser systems to form beams with special spatial configurations has been studied. The laser systems applied had a self-conjugate cavity based on the elements of copper vapor lasers (LT-5Cu, LT-10Cu, LT-30Cu) with an average power of 5, 10, or 30 W. The active elements were pumped by current pulses of duration 80-100 ns. The duration of laser generation pulses was up to 25 ns. The generator unit included an unstable cavity, where one reflector was a special mirror with a reflecting coating. Various original optical schemes used were capable of exploring spatial configurations and energy characteristics of output laser beams in their interaction with micro- and nanoparticles fabricated from various materials. In these experiments, the beam dimensions of the obtained zones varied from 0.3 to 5 µm, which is comparable with the minimum permissible dimensions determined by the optical elements applied. This method is useful in transforming a large amount of information at the laser pulse repetition rate of 10-30 kHz. It was possible to realize the high-precision micromachining and microfabrication of microscale details by direct writing, cutting and drilling (with the cutting width and through-hole diameters ranging from 3 to 100 µm) and produce microscale, deep, intricate and narrow grooves on substrate surfaces of metals and nonmetal materials. This system is used for producing high-quality microscale details without moving the object under treatment. It can also be used for microcutting and microdrilling in a variety of metals such as molybdenum, copper and stainless steel, with a thickness of up to 300 µm, and in nonmetals such as silicon, sapphire and diamond with a thickness ranging from 10 µm to 1 mm with different thermal parameters and specially designed laser beam.

Nb{sub 2}O{sub 5} hollow nanospheres as anode material for enhanced performance in lithium ion batteries

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

Sasidharan, Manickam; Gunawardhana, Nanda; Yoshio, Masaki, E-mail: yoshio@cc.saga-u.ac.jp

2012-09-15

Graphical abstract: Nb{sub 2}O{sub 5} hollow nanosphere constructed electrode delivers high capacity of 172 mAh g{sup −1} after 250 cycles and maintains structural integrity and excellent cycling stability. Highlights: ► Nb{sub 2}O{sub 5} hollow nanospheres synthesis was synthesized by soft-template. ► Nb{sub 2}O{sub 5} hollow nanospheres were investigated as anode material in Li-ion battery. ► Nanostructured electrode delivers high capacity of 172 mAh g{sup −1} after 250 cycles. ► The electrode maintains the structural integrity and excellent cycling stability. ► Nanosized shell domain facilitates fast lithium intercalation/deintercalation. -- Abstract: Nb{sub 2}O{sub 5} hollow nanospheres of average diameter ca. ∼29 nmmore » and hollow cavity size ca. 17 nm were synthesized using polymeric micelles with core–shell–corona architecture under mild conditions. The hollow particles were thoroughly characterized by transmission electron microscope (TEM), X-ray diffraction (XRD), infrared spectroscopy (FTIR), thermal (TG/DTA) and nitrogen adsorption analyses. Thus obtained Nb{sub 2}O{sub 5} hollow nanospheres were investigated as anode materials for lithium ion rechargeable batteries for the first time. The nanostructured electrode delivers high capacity of 172 mAh g{sup −1} after 250 cycles of charge/discharge at a rate of 0.5 C. More importantly, the hollow particles based electrodes maintains the structural integrity and excellent cycling stability even after exposing to high current density 6.25 A g{sup −1}. The enhanced electrochemical behavior is ascribed to hollow cavity coupled with nanosized Nb{sub 2}O{sub 5} shell domain that facilitates fast lithium intercalation/deintercalation kinetics.« less

End-to-end test of spatial accuracy in Gamma Knife treatments for trigeminal neuralgia

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

Brezovich, Ivan A., E-mail: ibrezovich@uabmc.edu; Wu, Xingen; Duan, Jun

2014-11-01

Purpose: Spatial accuracy is most crucial when small targets like the trigeminal nerve are treated. Although current quality assurance procedures typically verify that individual apparatus, like the MRI scanner, CT scanner, Gamma Knife, etc., are meeting specifications, the cumulative error of all equipment and procedures combined may exceed safe margins. This study uses an end-to-end approach to assess the overall targeting errors that may have occurred in individual patients previously treated for trigeminal neuralgia. Methods: The trigeminal nerve is simulated by a 3 mm long, 3.175 mm (1/8 in.) diameter MRI-contrast filled cavity embedded within a PMMA plastic capsule. Themore » capsule is positioned within the head frame such that the location of the cavity matches the Gamma Knife coordinates of an arbitrarily chosen, previously treated patient. Gafchromic EBT2 film is placed at the center of the cavity in coronal and sagittal orientations. The films are marked with a pinprick to identify the cavity center. Treatments are planned for radiation delivery with 4 mm collimators according to MRI and CT scans using the clinical localizer boxes and acquisition protocols. Shots are planned so that the 50% isodose surface encompasses the cavity. Following irradiation, the films are scanned and analyzed. Targeting errors are defined as the distance between the pinprick, which represents the intended target, and the centroid of the 50% isodose line, which is the center of the radiation field that was actually delivered. Results: Averaged over ten patient simulations, targeting errors along the x, y, and z coordinates (patient’s left-to-right, posterior-to-anterior, and head-to-foot) were, respectively, −0.060 ± 0.363, −0.350 ± 0.253, and 0.348 ± 0.204 mm when MRI was used for treatment planning. Planning according to CT exhibited generally smaller errors, namely, 0.109 ± 0.167, −0.191 ± 0.144, and 0.211 ± 0.094 mm. The largest errors along individual axes in MRI- and CT-planned treatments were, respectively, −0.761 mm in the y-direction and 0.428 mm in the x-direction, well within safe limits. Conclusions: The highly accurate dose delivery was possible because the Gamma Knife, MRI scanner, and other equipment performed within tight limits and scans were acquired using the thinnest slices and smallest pixel sizes available. Had the individual devices performed only near the limits of their specifications, the cumulative error could have left parts of the trigeminal nerve undertreated. The presented end-to-end test gives assurance that patients had received the expected high quality treatment. End-to-end tests should become part of clinical practice.« less

Part I. Mechanisms of injury associated with extracorporeal shock wave lithotripsy; Part II. Exsolution of volatiles

NASA Astrophysics Data System (ADS)

Howard, Danny Dwayne

Part I - Shock waves are focused in extracorporeal shock wave lithotripsy (ESWL) machines to strengths sufficient to fracture kidney stones. Substantial side effects-most of them acute-have resulted from this procedure, including injury to soft tissue. The focusing of shock waves through various layers of tissue is a complex process which stimulates many bio-mechano-chemical responses.This thesis presents results of an in vitro study of the initial mechanical stimulus. Planar nitrocellulose membranes of order 10 um thick were used as models of thin tissue structures. Two modes of failure were recorded: Failure due to cavitation collapsing on or near the membranes, and failure induced by altering the structure of shock waves. Tests were done in water at and around F2 to characterize the extent of cavitation damage, and was found to be confined within the focal region, 1.2 cm along the axis of focus.Scattering media were used to simulate the effects of acoustic nonuniformity of tissue and to alter the structure of focusing shock waves. 40 um diameter (average) hollow glass spheres were added to ethylene glycol, glycerine and castor oil to vary the properties of the scattering media. Multiple layer samples of various types of phantom tissue were tested in degassed castor oil to gauge the validity of the scattering media. The scattering media and tissue samples increased the rise time decreased strain rate in a similar fashion. Membranes were damaged by the decreased strain rate and accumulated effects of the altered structure: After about 20 or so shocks immersed in the scattering media and after about 100 shocks behind the tissue samples. The mode of failure was tearing with multiple tears in some cases from about .1 cm to about 3 cm depending of the number of shocks and membrane thickness.Part II - This work examines the exsolution of volatiles-carbon dioxide from water-in a cylindrical test cell under different pressure conditions. Water was supersaturated with carbon dioxide under various pressures (620 to 1062 kPa), and depressurized rapidly to investigate how carbon dioxide is undissolved, exsolution, and its effects on the surrounding environment. Cavities grow as a result of convective diffusion: They move before depleting carbon dioxide in a given region. The radius of a cavity in this environment grows at a faster rate [...] than that of a cavity at rest [...]. Bubble growth rates were inferred by measuring the bulk liquid using high speed motion pictures. Water in the test-cell is accelerated as a result of buoyancy induced by cavity growth. Cavities are elliptical in shape and grow until mutual interaction causes them to fragment. Accelerations range from 10 to 100 g were measured with velocities ranging from 7 to 13 m/s.

A New Impact Crater

NASA Image and Video Library

2018-05-29

NASA's Mars Reconnaissance Orbiter (MRO) keeps finding new impact sites on Mars. This one occurred within the dense secondary crater field of Corinto Crater, to the north-northeast. The new crater and its ejecta have distinctive color patterns. Once the colors have faded in a few decades, this new crater will still be distinctive compared to the secondaries by having a deeper cavity compared to its diameter. https://photojournal.jpl.nasa.gov/catalog/PIA22462

In Situ Steam Fracture Experiments.

DTIC Science & Technology

1984-12-31

pressure and tempera- ture data for use in validation of multi-phase flow models describing - condensation/vaporization, heat-transfer, and fluid/vapor...provide an excellent base for development and/or verification of steam-fracture models for low- permeability materials where heat transfer is significant...representative of post-shot cavity conditions. Steam flow tests have been performed at S-CUBED in a 3-meter long by 20-centimeter diameter sand column. In

Ultrasonic Attenuation in Normal and Superconducting Indium.

DTIC Science & Technology

1980-05-22

dimension x space coordinate, dislocation displacement dislocation displacement y space coordinate.1z space coordinate x ACKNOWLEDGMENTS The author...The driving force on the dislocation is given by: F=bO (2.7) In general, the dislocation displacement will be a function of three space coordinates...mm diameter, 50 Q impedance coaxial conductors 47 * made of stainless steel and teflon . The cavity button is soldered * directly to the rigid

Seasonal morphological changes in the ovary of the Jungle crow (Corvus macrorhynchos).

PubMed

Islam, Muhammad Nazrul; Zhu, Xiao Bo; Aoyama, Masato; Sugita, Shoei

2010-12-01

Morphometric and histological studies were conducted to examine the seasonal ovarian changes in the Jungle crow of the Kanto area, Japan, from December to June. The ovary weights, largest diameters and atresias of the ovarian follicles and steroid-producing cells were examined. Hematoxylin and eosin-stained ovary sections and ImageJ software were used. The most developed ovary weight increased 373-fold in April, compared to those in December, followed by a 29-fold decrease in June. The average largest follicle diameter of the December and the January ovaries were 1.03 ± 0.35 and 1.05 ± 0.3 mm, respectively. The average largest follicle diameter increased by 2-fold in February, 4-fold in March and 8-fold in April, compared to those of December and January. Thereafter, the average largest follicle diameter declined by 6-fold in June. The average ovary weight and the largest follicle diameter in April increased significantly (P < 0.05) compared to those of December and January, followed by a significant decrease (P < 0.05) in June. The ovary weight correlated well with the expansion of the largest follicular diameter. Non-bursting and bursting atresias of smaller follicles were more common in the December, January, February and June ovaries, and bursting atresias of larger follicles were more common in the March, April and May ovaries. Ovarian steroidogenic cells became heavily charged with lipids in December, January, February and June, and they depleted their lipids in March and April, which might be due to steroid synthesis. Our results indicate that there are significant seasonal histomorphologic variations in the Jungle crow ovary.

Plasma processing of superconducting radio frequency cavities

NASA Astrophysics Data System (ADS)

Upadhyay, Janardan

The development of plasma processing technology of superconducting radio frequency (SRF) cavities not only provides a chemical free and less expensive processing method, but also opens up the possibility for controlled modification of the inner surfaces of the cavity for better superconducting properties. The research was focused on the transition of plasma etching from two dimensional flat surfaces to inner surfaces of three dimensional (3D) structures. The results could be applicable to a variety of inner surfaces of 3D structures other than SRF cavities. Understanding the Ar/Cl2 plasma etching mechanism is crucial for achieving the desired modification of Nb SRF cavities. In the process of developing plasma etching technology, an apparatus was built and a method was developed to plasma etch a single cell Pill Box cavity. The plasma characterization was done with the help of optical emission spectroscopy. The Nb etch rate at various points of this cavity was measured before processing the SRF cavity. Cylindrical ring-type samples of Nb placed on the inner surface of the outer wall were used to measure the dependence of the process parameters on plasma etching. The measured etch rate dependence on the pressure, rf power, dc bias, temperature, Cl2 concentration and diameter of the inner electrode was determined. The etch rate mechanism was studied by varying the temperature of the outer wall, the dc bias on the inner electrode and gas conditions. In a coaxial plasma reactor, uniform plasma etching along the cylindrical structure is a challenging task due to depletion of the active radicals along the gas flow direction. The dependence of etch rate uniformity along the cylindrical axis was determined as a function of process parameters. The formation of dc self-biases due to surface area asymmetry in this type of plasma and its variation on the pressure, rf power and gas composition was measured. Enhancing the surface area of the inner electrode to reduce the asymmetry was studied by changing the contour of the inner electrode. The optimized contour of the electrode based on these measurements was chosen for SRF cavity processing.

Influence of rainfall microstructure on rainfall interception

NASA Astrophysics Data System (ADS)

Zabret, Katarina; Rakovec, Jože; Mikoš, Matjaž; Šraj, Mojca

2016-04-01

Rainfall interception is part of the hydrological cycle. Precipitation, which hits vegetation, is retained on the leaves and branches, from which it eventually evaporates into the atmosphere (interception) or reaches the ground by dripping from the canopy, falling through the gaps (throughfall) and running down the stems (stemflow). The process is influenced by various meteorological and vegetation parameters. Often neglected meteorological parameter influencing rainfall interception is also rainfall microstructure. Rain is a discrete process consisting of various numbers of individual raindrops with different sizes and velocities. This properties describe rainfall microstructure which is often neglected in hydrological analysis and replaced with rainfall intensity. Throughfall, stemflow and rainfall microstructure have been measured since the beginning of the year 2014 under two tree species (Betula pendula and Pinus nigra) on a study plot in Ljubljana, Slovenia. The preliminary analysis of the influence of rainfall microstructure on rainfall interception has been conducted using three events with different characteristics measured in May 2014. Event A is quite short with low rainfall amount and moderate rainfall intensity, whereas events B and C have similar length but low and high intensities, respectively. Event A was observed on the 1st of May 2014. It was 22 minutes long and delivered 1.2 mm of rainfall. The average rainfall intensity was equal to 3.27 mm/h. The event consisted of 1,350 rain drops with average diameter of 1.517 mm and average velocity of 5.110 m/s. Both Betula pendula and Pinus nigra intercepted similar amount of rainfall, 68 % and 69 %, respectively. Event B was observed in the night from the 7th to 8th of May 2014, it was 16 hours and 18 minutes long, and delivered 4.2 mm of rainfall with average intensity of 0.97 mm/h. There were 39,108 raindrops detected with average diameter of 0.858 mm and average velocity of 3.855 m/s. Betula pendula (23 %) has intercepted significantly less rainfall than Pinus nigra (85%). Event C was also observed in the night time between 11th and 12th of May 2014, it lasted 4 hours and 12 minutes and delivered 34.6 mm of rainfall with an average intensity equal to 8.24 mm/h. During the event 147,236 raindrops with average diameter of 1.020 mm and average velocity of 4.078 m/s were detected. Betula pendula has intercepted only 6 % of rainfall whereas Pinus nigra intercepted majority of rainfall, namely 85 %. In case of B. pendula rainfall interception is increasing with higher velocity whereas it is lower for medium diameters than for smaller or larger diameters. Rainfall interception under P. nigra is decreasing with higher velocities and behaving similar as under B. pendula for different diameters but with less obvious difference between diameter classes. We will continue with the measurements and further analysis of several rainfall events will be prepared.

Noise-immune cavity-enhanced optical frequency comb spectroscopy: a sensitive technique for high-resolution broadband molecular detection

NASA Astrophysics Data System (ADS)

Khodabakhsh, Amir; Johansson, Alexandra C.; Foltynowicz, Aleksandra

2015-04-01

Noise-immune cavity-enhanced optical frequency comb spectroscopy (NICE-OFCS) is a recently developed technique that utilizes phase modulation to obtain immunity to frequency-to-amplitude noise conversion by the cavity modes and yields high absorption sensitivity over a broad spectral range. We describe the principles of the technique and discuss possible comb-cavity matching solutions. We present a theoretical description of NICE-OFCS signals detected with a Fourier transform spectrometer (FTS) and validate the model by comparing it to experimental CO2 spectra around 1,575 nm. Our system is based on an Er:fiber femtosecond laser locked to a cavity and phase-modulated at a frequency equal to a multiple of the cavity free spectral range (FSR). The NICE-OFCS signal is detected by a fast-scanning FTS equipped with a high-bandwidth commercial detector. We demonstrate a simple method of passive locking of the modulation frequency to the cavity FSR that significantly improves the long-term stability of the system, allowing averaging times on the order of minutes. Using a cavity with a finesse of ~9,000, we obtain absorption sensitivity of 6.4 × 10-11 cm-1 Hz-1/2 per spectral element and concentration detection limit for CO2 of 450 ppb Hz-1/2, determined by multiline fitting.

Nondestructive Evaluation (NDE) for Characterizing Oxidation Damage in Cracked Reinforced Carbon-Carbon

NASA Technical Reports Server (NTRS)

Roth, Don J.; Jacobson, Nathan S.; Rauser, Richard W.; Wincheski, Russell A.; Walker, James L.; Cosgriff, Laura A.

2010-01-01

In this study, coated reinforced carbon-carbon (RCC) samples of similar structure and composition as that from the NASA space shuttle orbiter's thermal protection system were fabricated with slots in their coating simulating craze cracks. These specimens were used to study oxidation damage detection and characterization using nondestructive evaluation (NDE) methods. These specimens were heat treated in air at 1143 C and 1200 C to create cavities in the carbon substrate underneath the coating as oxygen reacted with the carbon and resulted in its consumption. The cavities varied in diameter from approximately 1 to 3mm. Single-sided NDE methods were used because they might be practical for on-wing inspection, while X-ray micro-computed tomography (CT) was used to measure cavity sizes in order to validate oxidation models under development for carbon-carbon materials. An RCC sample having a naturally cracked coating and subsequent oxidation damage was also studied with X-ray micro-CT. This effort is a follow-on study to one that characterized NDE methods for assessing oxidation damage in an RCC sample with drilled holes in the coating.

Nondestructive Evaluation (NDE) for Characterizing Oxidation Damage in Cracked Reinforced Carbon-Carbon (RCC)

NASA Technical Reports Server (NTRS)

Roth, Don J.; Rauser, Richard W.; Jacobson, Nathan S.; Wincheski, Russell A.; Walker, James L.; Cosgriff, Laura A.

2009-01-01

In this study, coated reinforced carbon-carbon (RCC) samples of similar structure and composition as that from the NASA space shuttle orbiter's thermal protection system were fabricated with slots in their coating simulating craze cracks. These specimens were used to study oxidation damage detection and characterization using nondestructive evaluation (NDE) methods. These specimens were heat treated in air at 1143 and 1200 C to create cavities in the carbon substrate underneath the coating as oxygen reacted with the carbon and resulted in its consumption. The cavities varied in diameter from approximately 1 to 3 mm. Single-sided NDE methods were used since they might be practical for on-wing inspection, while x-ray micro-computed tomography (CT) was used to measure cavity sizes in order to validate oxidation models under development for carbon-carbon materials. An RCC sample having a naturally-cracked coating and subsequent oxidation damage was also studied with x-ray micro-CT. This effort is a follow-on study to one that characterized NDE methods for assessing oxidation damage in an RCC sample with drilled holes in the coating.

Measurements of the frequency stability of ultralow thermal expansion glass ceramic optical cavity lasers

NASA Astrophysics Data System (ADS)

Oram, R. J.; Latimer, I. D.; Spoor, S. P.

1997-05-01

This paper reports on a technique for providing a frequency-stabilized helium - neon gas laser by using inherently stable ultralow thermal expansion optical cavities. Four longitudinal monoblock cavity lasers were constructed and tested. These had their laser mirrors optically contacted to the bulk material. A 1 mm diameter hole along the axis of the block served as the discharge channel with electrodes optically contacted to the sides of the block. One of these lasers had a glass capilliary for the discharge channel. A fifth laser had a gain tube with Brewster angle windows fixed in a Zerodur box with the mirrors contacted to the ends. The warm-up characteristics of the five different lasers have been obtained and a theoretical model using finite element analysis was developed to determine the thermal expansion during warm-up. Using this computer model the thermal expansion coefficient of the material Zerodur was obtained. The results suggest that monoblock lasers can produce a free-running laser frequency stability of better than 10 MHz and show a repeatable warm-up characteristic of 100 MHz frequency drift.

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

Brezovich, I; Wu, X; Popple, R

Purpose: To test spatial and dosimetric accuracy of small cranial target irradiation based on 1.5 T MRI scans using static arcs with MLC-defined fields Methods: A plastic (PMMA) phantom simulating a small brain lesion was mounted on a GammaKnife headframe equipped with MRI localizer. The lesion was a 3 mm long, 3.175 mm diameter cylindrical cavity filled with MRI contrast. Radiochromic film passing through the cavity was marked with pin pricks at the cavity center. The cavity was contoured on an MRI image and fused with CT to simulate treatment of a lesion not visible on CT. The transfer ofmore » the target to CT involved registering the MRI contrast cannels of the localizer that were visible on both modalities. Treatments were planned to deliver 800 cGy to the cavity center using multiple static arcs with 5.0×2.4 mm MLC-defined fields. The phantom was aligned on a STx accelerator by registering the conebeam CT with the planning CT. Films from coronal and sagittal planes were scanned and evaluated using ImageJ software Results: Geographic errors in treatment based on 1.5 T scans agreed within 0.33, −0.27 and 1.21 mm in the vertical, lateral and longitudinal dimensions, respectively. The doses delivered to the cavity center were 7.2% higher than planned. The dose distributions were similar to those of a GammaKnife. Conclusion: Radiation can be delivered with an accelerator at mm accuracy to small cranial targets based on 1.5 MRI scans fused to CTs using a standard GammaKnife headframe and MRI localizer. MLC-defined static arcs produce isodose lines very similar to the GammaKnife.« less

Shrinkage of Dental Composite in Simulated Cavity Measured with Digital Image Correlation

PubMed Central

Li, Jianying; Thakur, Preetanjali; Fok, Alex S. L.

2014-01-01

Polymerization shrinkage of dental resin composites can lead to restoration debonding or cracked tooth tissues in composite-restored teeth. In order to understand where and how shrinkage strain and stress develop in such restored teeth, Digital Image Correlation (DIC) was used to provide a comprehensive view of the displacement and strain distributions within model restorations that had undergone polymerization shrinkage. Specimens with model cavities were made of cylindrical glass rods with both diameter and length being 10 mm. The dimensions of the mesial-occlusal-distal (MOD) cavity prepared in each specimen measured 3 mm and 2 mm in width and depth, respectively. After filling the cavity with resin composite, the surface under observation was sprayed with first a thin layer of white paint and then fine black charcoal powder to create high-contrast speckles. Pictures of that surface were then taken before curing and 5 min after. Finally, the two pictures were correlated using DIC software to calculate the displacement and strain distributions. The resin composite shrunk vertically towards the bottom of the cavity, with the top center portion of the restoration having the largest downward displacement. At the same time, it shrunk horizontally towards its vertical midline. Shrinkage of the composite stretched the material in the vicinity of the “tooth-restoration” interface, resulting in cuspal deflections and high tensile strains around the restoration. Material close to the cavity walls or floor had direct strains mostly in the directions perpendicular to the interfaces. Summation of the two direct strain components showed a relatively uniform distribution around the restoration and its magnitude equaled approximately to the volumetric shrinkage strain of the material. PMID:25079865

Very high repetition-rate electro-optical cavity-dumped Nd: YVO4 laser with optics and dynamics stabilities

NASA Astrophysics Data System (ADS)

Liu, Xuesong; Shi, Zhaohui; Huang, Yutao; Fan, Zhongwei; Yu, Jin; Zhang, Jing; Hou, Liqun

2015-02-01

In this paper, a very high repetition-rate, short-pulse, electro-optical cavity-dumped Nd: YVO4 laser is experimentally and theoretically investigated. The laser performance is optimized from two aspects. Firstly, the laser resonator is designed for a good thermal stability under large pump power fluctuation through optics methods. Secondly, dynamics simulation as well as experiments verifies that cavity dumping at very high repetition rate has better stability than medium/high repetition rate. At 30 W, 880 nm pump power, up to 500 kHz, constant 5 ns, stable 1064 nm fundamental-mode laser pulses can be obtained with 10 W average output power.

Compact near-IR and mid-IR cavity ring down spectroscopy device

NASA Technical Reports Server (NTRS)

Miller, J. Houston (Inventor)

2011-01-01

This invention relates to a compact cavity ring down spectrometer for detection and measurement of trace species in a sample gas using a tunable solid-state continuous-wave mid-infrared PPLN OPO laser or a tunable low-power solid-state continuous wave near-infrared diode laser with an algorithm for reducing the periodic noise in the voltage decay signal which subjects the data to cluster analysis or by averaging of the interquartile range of the data.

Hierarchically assembled Au microspheres and sea urchin-like architectures: formation mechanism and SERS study

NASA Astrophysics Data System (ADS)

Wang, Xiansong; Yang, Da-Peng; Huang, Peng; Li, Min; Li, Chao; Chen, Di; Cui, Daxiang

2012-11-01

The hierarchically assembled Au microspheres/sea urchin-like structures have been synthesized in aqueous solution at room temperature with and without proteins (bovine serum albumin, BSA) as mediators. The average diameter of an individual Au microsphere is 300-600 nm, which is composed of some compact nanoparticles with an average diameter of about 15 nm. Meanwhile, the sea urchin-like Au architecture exhibits an average diameter of 600-800 nm, which is made up of some nanopricks with an average length of 100-200 nm. These products are characterized by means of scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electronic microscopy (TEM). It is found that the BSA and ascorbic acid (AA) have great effects on the morphology of the resulting products. Two different growth mechanisms are proposed. The study on surface enhanced Raman scattering (SERS) activities is also carried out between Au microspheres and Au sea urchin-like architectures. It is found that Au urchin-like architectures possess much higher SERS activity than the Au microspheres. Our work may shed light on the design and synthesis of hierarchically self-assembled 3D micro/nano-architectures for SERS, catalysis and biosensors.The hierarchically assembled Au microspheres/sea urchin-like structures have been synthesized in aqueous solution at room temperature with and without proteins (bovine serum albumin, BSA) as mediators. The average diameter of an individual Au microsphere is 300-600 nm, which is composed of some compact nanoparticles with an average diameter of about 15 nm. Meanwhile, the sea urchin-like Au architecture exhibits an average diameter of 600-800 nm, which is made up of some nanopricks with an average length of 100-200 nm. These products are characterized by means of scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electronic microscopy (TEM). It is found that the BSA and ascorbic acid (AA) have great effects on the morphology of the resulting products. Two different growth mechanisms are proposed. The study on surface enhanced Raman scattering (SERS) activities is also carried out between Au microspheres and Au sea urchin-like architectures. It is found that Au urchin-like architectures possess much higher SERS activity than the Au microspheres. Our work may shed light on the design and synthesis of hierarchically self-assembled 3D micro/nano-architectures for SERS, catalysis and biosensors. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr32405a

The effect of no naked pancreatic surface in the cavity of jejunum on pancreaticojejunostomy in 132 consecutive cases.

PubMed

Zhang, Fumin; Jin, Jichun; Jiang, Hao; Wang, Shiyang; Gu, Hanbao; Jin, Xinglin

2015-01-01

To prevent the pancreatic fistulas, we designed a technique termed "no naked pancreatic surface in the cavity of jejunum" on pancreaticojejunostomy. We adopted pancreatic exocrine secretions following the pancreatic duct by drainage; there was no naked pancreatic surface in the cavity of jejunum, and entail 2-3 cm sheath of the jejunum to the pancreatic stump. Only 3 (2.27%) cases developed pancreatic fistulas, 1 patient had a grade A leak, and 2 patients had grade B leakage. The overall morbidity was 25.76%. There was no dilatation of pancreatic duct or pancreatic enzyme deficiency shown during followed-up. The duration for accomplishing the anastomosis was 20 minutes averagely. The technique of no naked pancreatic surface in the cavity of jejunum can be routinely used in any case with pancreaticojejunostomy. It is a safe, simple, and effective technique that avoids the primary complication of anastomotic leakage.

Fabrication of Microfibrous and Nano-/Microfibrous Scaffolds: Melt and Hybrid Electrospinning and Surface Modification of Poly(L-lactic acid) with Plasticizer

PubMed Central

Yoon, Young Il; Park, Ko Eun; Lee, Seung Jin; Park, Won Ho

2013-01-01

Biodegradable poly(L-lactic acid) (PLA) fibrous scaffolds were prepared by electrospinning from a PLA melt containing poly(ethylene glycol) (PEG) as a plasticizer to obtain thinner fibers. The effects of PEG on the melt electrospinning of PLA were examined in terms of the melt viscosity and fiber diameter. Among the parameters, the content of PEG had a more significant effect on the average fiber diameter and its distribution than those of the spinning temperature. Furthermore, nano-/microfibrous silk fibroin (SF)/PLA and PLA/PLA composite scaffolds were fabricated by hybrid electrospinning, which involved a combination of solution electrospinning and melt electrospinning. The SF/PLA (20/80) scaffolds consisted of a randomly oriented structure of PLA microfibers (average fiber diameter = 8.9 µm) and SF nanofibers (average fiber diameter = 820 nm). The PLA nano-/microfiber (20/80) scaffolds were found to have similar pore parameters to the PLA microfiber scaffolds. The PLA scaffolds were treated with plasma in the presence of either oxygen or ammonia gas to modify the surface of the fibers. This approach of controlling the surface properties and diameter of fibers could be useful in the design and tailoring of novel scaffolds for tissue engineering. PMID:24381937

Compact spectrometer for precision studies of multimode behavior in an extended-cavity diode laser

NASA Astrophysics Data System (ADS)

Roach, Timothy; Golemi, Josian; Krueger, Thomas

2016-05-01

We have built a compact, inexpensive, high-precision spectrometer and used it to investigate the tuning behavior of a grating stabilized extended-cavity diode laser (ECDL). A common ECDL design uses a laser chip with an uncoated (partially reflecting) front facet, and the laser output exhibits a complicated pattern of mode hops as the frequency is tuned, in some cases even showing chaotic dynamics. Our grating spectrometer (based on a design by White & Scholten) monitors a span of 4000 GHz (8 nm at 780 nm) with a linewidth of 3 GHz, which with line-splitting gives a precision of 0.02 GHz in determining the frequency of a laser mode. We have studied multimode operation of the ECDL, tracking two or three simultaneous chip cavity modes (spacing ~ 30 GHz) during tuning via current or piezo control of the external cavity. Simultaneous output on adjacent external cavity modes (spacing ~ 5 GHz) is monitored by measuring an increase in the spectral linewidth. Computer-control of the spectrometer (for line-fitting and averaging) and of the ECDL (electronic tuning) allows rapid collection of spectral data sets, which we will use to test mathematical simulation models of the non-linear laser cavity interactions.

Active measurement-based quantum feedback for preparing and stabilizing superpositions of two cavity photon number states

NASA Astrophysics Data System (ADS)

Berube-Lauziere, Yves

The measurement-based quantum feedback scheme developed and implemented by Haroche and collaborators to actively prepare and stabilize specific photon number states in cavity quantum electrodynamics (CQED) is a milestone achievement in the active protection of quantum states from decoherence. This feat was achieved by injecting, after each weak dispersive measurement of the cavity state via Rydberg atoms serving as cavity sensors, a low average number classical field (coherent state) to steer the cavity towards the targeted number state. This talk will present the generalization of the theory developed for targeting number states in order to prepare and stabilize desired superpositions of two cavity photon number states. Results from realistic simulations taking into account decoherence and imperfections in a CQED set-up will be presented. These demonstrate the validity of the generalized theory and points to the experimental feasibility of preparing and stabilizing such superpositions. This is a further step towards the active protection of more complex quantum states than number states. This work, cast in the context of CQED, is also almost readily applicable to circuit QED. YBL acknowledges financial support from the Institut Quantique through a Canada First Research Excellence Fund.

Dosimetric response of variable-size cavities in photon-irradiated media and the behaviour of the Spencer-Attix cavity integral with increasing Δ.

PubMed

Kumar, Sudhir; Deshpande, Deepak D; Nahum, Alan E

2016-04-07

Cavity theory is fundamental to understanding and predicting dosimeter response. Conventional cavity theories have been shown to be consistent with one another by deriving the electron (+positron) and photon fluence spectra with the FLURZnrc user-code (EGSnrc Monte-Carlo system) in large volumes under quasi-CPE for photon beams of 1 MeV and 10 MeV in three materials (water, aluminium and copper) and then using these fluence spectra to evaluate and then inter-compare the Bragg-Gray, Spencer-Attix and 'large photon' 'cavity integrals'. The behaviour of the 'Spencer-Attix dose' (aka restricted cema), D S-A(▵), in a 1-MeV photon field in water has been investigated for a wide range of values of the cavity-size parameter ▵: D S-A(▵) decreases far below the Monte-Carlo dose (D MC) for ▵ greater than  ≈  30 keV due to secondary electrons with starting energies below ▵ not being 'counted'. We show that for a quasi-scatter-free geometry (D S-A(▵)/D MC) is closely equal to the proportion of energy transferred to Compton electrons with initial (kinetic) energies above ▵, derived from the Klein-Nishina (K-N) differential cross section. (D S-A(▵)/D MC) can be used to estimate the maximum size of a detector behaving as a Bragg-Gray cavity in a photon-irradiated medium as a function of photon-beam quality (under quasi CPE) e.g. a typical air-filled ion chamber is 'Bragg-Gray' at (monoenergetic) beam energies  ⩾260 keV. Finally, by varying the density of a silicon cavity (of 2.26 mm diameter and 2.0 mm thickness) in water, the response of different cavity 'sizes' was simulated; the Monte-Carlo-derived ratio D w/D Si for 6 MV and 15 MV photons varied from very close to the Spencer-Attix value at 'gas' densities, agreed well with Burlin cavity theory as ρ increased, and approached large photon behaviour for ρ  ≈  10 g cm(-3). The estimate of ▵ for the Si cavity was improved by incorporating a Monte-Carlo-derived correction for electron 'detours'. Excellent agreement was obtained between the Burlin 'd' factor for the Si cavity and D S-A(▵)/D MC at different (detour-corrected) ▵, thereby suggesting a further application for the D S-A(▵)/D MC ratio.

Supercritical multicomponent solvent coal extraction

NASA Technical Reports Server (NTRS)

Corcoran, W. H.; Fong, W. S.; Pichaichanarong, P.; Chan, P. C. F.; Lawson, D. D. (Inventor)

1983-01-01

The yield of organic extract from the supercritical extraction of coal with larger diameter organic solvents such as toluene is increased by use of a minor amount of from 0.1 to 10% by weight of a second solvent such as methanol having a molecular diameter significantly smaller than the average pore diameter of the coal.

One new genus and three new species of deep-sea nematodes (Nematoda: Microlaimidae) from the Southwest Pacific Ocean and Ross Sea.

PubMed

Leduc, Daniel

2016-02-11

New deep-sea nematodes of the family Microlaimidae are described from the Southwest Pacific Ocean and Ross Sea. Microlaimus korari n. sp. is characterised by annulated cuticle with longitudinal bars, round amphideal aperture slightly smaller than the cryptospiral amphideal fovea, spacious and heavily cuticularised buccal cavity with large dorsal tooth and right subventral tooth situated anteriorly relative to left subventral tooth, slender spicules 4.4 cloacal body diameters long, and gubernaculum 1.2 cloacal body diameters long with laterally curved distal end and swollen proximal end. Bolbolaimus tongaensis n. sp. is characterised by annulated cuticle with longitudinal bars, oval amphideal aperture and cryptocircular amphideal fovea situated between cephalic setae and only partially surrounded by cuticle annulations, and short spicules cuticularised along dorsal edge and at proximal end and with swollen portion near proximal end. Maragnopsia n. gen. is characterised by a minute, non-cuticularised mouth cavity without teeth, an elongated posterior pharyngeal bulb more than twice as long as it is wide, a single outstretched testis, and a conico-cylindrical tail 13-16 anal body diameters long. A list of all 83 valid Microlaimus species is provided. The present study provides the first microlaimid species records from deep-sea habitats (> 200 m depth) in the Southwest Pacific and Ross Sea. The presence of M. korari n. sp. on both the continental slope of New Zealand and Ross Sea abyssal plain suggests that this species has a wide geographical and depth distribution. However, molecular analyses will be required to confirm the identity of these two geographically disparate populations.

A 300m-width sinkhole threatens the stability of the embankment of a saltpan in Jordan, Dead Sea Region

NASA Astrophysics Data System (ADS)

Closson, Damien; Abou Karaki, Najib; Pasquali, Paolo; Riccardi, Paolo

2013-04-01

Since the 1980s, the Dead Sea coastal zone is affected by sinkholes. The dynamic of the salt karst system is attested by a drastic increase of collapse events. The energy available for sub-surface erosion (or cavities genesis) is related to the head difference between the water table and the lake level which drop down at an accelerating rate of more than 1 m/yr. In the region of Ghor Al Haditha, Jordan, the size of the craters increased significantly during the last decade. Up to now, the greatest compound structure observed (association of metric subsidence, decametric sinkholes, and landslides) was about 150-200 m in diameter. End of December 2012, a single circular structure having 250-300 m in diameter was identified within a 10 km x 1.5 km saltpan of the Arab Potash Company. This finding raises questions regarding the origin of the underlying cavity and the capability of prediction of all models developed up to now in Israel and Jordan regarding the Dead Sea sinkholes. The analysis of satellite images of the past shows that the appearance of this unique depression is very recent (probably less than 5 years). Cosmo-SkyMed radar images have been processed to map the associated deformation field. Ground motions attest that the overall diameter could be around 600 m. Currently, this sinkhole is threatening the stability of more than one kilometer of a 12 km long dike holding 90 million m3 of Dead Sea brine. This case study underlines the great fragility of the Dead Sea salt karst and demonstrates the need for the setting up of an early warning system.

Carbon Dioxide Laser Fiber Optics In Endoscopy

NASA Astrophysics Data System (ADS)

Fuller, Terry A.

1982-12-01

Carbon dioxide laser surgery has been limited to a great extent to surgical application on the integument and accessible cavities such as the cervix, vagina, oral cavities, etc. This limitation has been due to the rigid delivery systems available to all carbon dioxide lasers. Articulating arms (series of hollow tubes connected by articulating mirrors) have provided an effective means of delivery of laser energy to the patient as long as the lesion was within the direct line of sight. Even direct line-of-sight applications were restricted to physical dimension of the articulating arm or associated hand probes, manipulators and hollow tubes. The many attempts at providing straight endoscopic systems to the laser only stressed the need for a fiber optic capable of carrying the carbon dioxide laser wavelength. Rectangular and circular hollow metal waveguides, hollow dielectric waveguides have proven ineffective to the stringent requirements of a flexible surgical delivery system. One large diameter (1 cm) fiber optic delivery system, incorporates a toxic thalliumAbased fiber optic material. The device is an effective alternative to an articulating arm for external or conventional laser surgery, but is too large and stiff to use as a flexible endoscopic tool. The author describes the first highly flexible inexpensive series of fiber optic systems suitable for either conventional or endoscopic carbon dioxide laser surgery. One system (IRFLEX 3) has been manufactured by Medlase, Inc. for surgical uses capable of delivering 2000w, 100 mJ pulsed energy and 15w continuous wave. The system diameter is 0.035 inches in diameter. Surgically suitable fibers as small as 120 um have been manufactured. Other fibers (IRFLEX 142,447) have a variety of transmission characteristics, bend radii, etc.

Segmentation of multiple heart cavities in 3-D transesophageal ultrasound images.

PubMed

Haak, Alexander; Vegas-Sánchez-Ferrero, Gonzalo; Mulder, Harriët W; Ren, Ben; Kirişli, Hortense A; Metz, Coert; van Burken, Gerard; van Stralen, Marijn; Pluim, Josien P W; van der Steen, Antonius F W; van Walsum, Theo; Bosch, Johannes G

2015-06-01

Three-dimensional transesophageal echocardiography (TEE) is an excellent modality for real-time visualization of the heart and monitoring of interventions. To improve the usability of 3-D TEE for intervention monitoring and catheter guidance, automated segmentation is desired. However, 3-D TEE segmentation is still a challenging task due to the complex anatomy with multiple cavities, the limited TEE field of view, and typical ultrasound artifacts. We propose to segment all cavities within the TEE view with a multi-cavity active shape model (ASM) in conjunction with a tissue/blood classification based on a gamma mixture model (GMM). 3-D TEE image data of twenty patients were acquired with a Philips X7-2t matrix TEE probe. Tissue probability maps were estimated by a two-class (blood/tissue) GMM. A statistical shape model containing the left ventricle, right ventricle, left atrium, right atrium, and aorta was derived from computed tomography angiography (CTA) segmentations by principal component analysis. ASMs of the whole heart and individual cavities were generated and consecutively fitted to tissue probability maps. First, an average whole-heart model was aligned with the 3-D TEE based on three manually indicated anatomical landmarks. Second, pose and shape of the whole-heart ASM were fitted by a weighted update scheme excluding parts outside of the image sector. Third, pose and shape of ASM for individual heart cavities were initialized by the previous whole heart ASM and updated in a regularized manner to fit the tissue probability maps. The ASM segmentations were validated against manual outlines by two observers and CTA derived segmentations. Dice coefficients and point-to-surface distances were used to determine segmentation accuracy. ASM segmentations were successful in 19 of 20 cases. The median Dice coefficient for all successful segmentations versus the average observer ranged from 90% to 71% compared with an inter-observer range of 95% to 84%. The agreement against the CTA segmentations was slightly lower with a median Dice coefficient between 85% and 57%. In this work, we successfully showed the accuracy and robustness of the proposed multi-cavity segmentation scheme. This is a promising development for intraoperative procedure guidance, e.g., in cardiac electrophysiology.

Fiber inhalability and head deposition in rats and humans. ...

EPA Pesticide Factsheets

Due to their dimensions and long durability, inhaled asbestos fibers clear slowly from lung airways. Retained fibers may injure the epithelium, interact with macrophages, or translocate to the interstitium to result in various respiratory diseases. Therefore, calculations of fiber inhalability, deposition, and retention in respiratory tract regions of both rats and humans are crucial, both to assess the health risk of fiber exposures and to facilitate inferences from rat inhalation studies. Rat inhalation experiments are underway at the EPA and NIEHS. A model of fiber inhalability and initial deposition in the human and rat nasal cavity was developed. Existing models for particles were extended to fibers by replacing particle diameter with an equivalent fiber diameter. Since fiber inhalability into the respiratory tract and deposition in the extra thoracic airways depended mainly on its inertia, equivalent impaction diameters were derived and substituted in expressions for spherical particle diameter to determine fiber inhalability and nasal losses. Fiber impaction diameter depended strongly on its orientation in the air. Highest inhalability was obtained when fibers were aligned perpendicular to the flow streamlines in the inhaled air. However, detailed calculations of fiber transport in slow moving air such as that in the atmosphere and in lung airways showed that fibers stayed primarily aligned (parallel) to the flow. Therefore, for inhalability calculations,

Nd:YAG laser in endodontics: filling-material edge bordering on a root channel laser cavity

NASA Astrophysics Data System (ADS)

Belikov, Andrei V.; Sinelnik, Yuri A.; Moroz, Boris T.; Pavlovskaya, Irina V.

1997-12-01

For the very first time it is represented a study of filling material edge bordering upon root channel cavity modified with a laser. As a filling material it is used a glass ionomer cement. It is demonstrated that Nd:YAG laser radiation effects on increase of grade of edge bordering on the average of 20 - 30% at temperature rise of no more than 2 - 3 degrees in periodontium area in a period of operation.

Optomechanical entanglement via non-degenerate parametric interactions

NASA Astrophysics Data System (ADS)

Ahmed, Rizwan; Qamar, Shahid

2017-10-01

We present a scheme for the optomechanical entanglement between a micro-mechanical mirror and the field inside a bimodal cavity system using a non-degenerate optical parametric amplifier (NOPA). Our results show that the introduction of NOPA makes the entanglement stronger or more robust against the mean number of average thermal phonons and cavity decay. Interestingly, macroscopic entanglement depends upon the choice of the phase associated with classical field driving NOPA. We also consider the effects of input laser power on optomechanical entanglement.

Plasmon resonant cavities in vertical nanowire arrays

DOEpatents

Bora, Mihail; Bond, Tiziana C.; Fasenfest, Benjamin J.; Behymer, Elaine M.

2014-07-15

Tunable plasmon resonant cavity arrays in paired parallel nanowire waveguides are presented. Resonances can be observed when the waveguide length is an odd multiple of quarter plasmon wavelengths, consistent with boundary conditions of node and antinode at the ends. Two nanowire waveguides can satisfy the dispersion relation of a planar metal-dielectric-metal waveguide of equivalent width equal to the square field average weighted gap. Confinement factors of over 10.sup.3 are possible due to plasmon focusing in the inter-wire space.

Principles of quasi-equivalence and Euclidean geometry govern the assembly of cubic and dodecahedral cores of pyruvate dehydrogenase complexes.

PubMed

Izard, T; Aevarsson, A; Allen, M D; Westphal, A H; Perham, R N; de Kok, A; Hol, W G

1999-02-16

The pyruvate dehydrogenase multienzyme complex (Mr of 5-10 million) is assembled around a structural core formed of multiple copies of dihydrolipoyl acetyltransferase (E2p), which exhibits the shape of either a cube or a dodecahedron, depending on the source. The crystal structures of the 60-meric dihydrolipoyl acyltransferase cores of Bacillus stearothermophilus and Enterococcus faecalis pyruvate dehydrogenase complexes were determined and revealed a remarkably hollow dodecahedron with an outer diameter of approximately 237 A, 12 large openings of approximately 52 A diameter across the fivefold axes, and an inner cavity with a diameter of approximately 118 A. Comparison of cubic and dodecahedral E2p assemblies shows that combining the principles of quasi-equivalence formulated by Caspar and Klug [Caspar, D. L. & Klug, A. (1962) Cold Spring Harbor Symp. Quant. Biol. 27, 1-4] with strict Euclidean geometric considerations results in predictions of the major features of the E2p dodecahedron matching the observed features almost exactly.

Gravity Field of the Orientale Basin from the Gravity Recovery and Interior Laboratory Mission

NASA Technical Reports Server (NTRS)

Zuber, Maria T.; Smith, David E.; Neumann, Gregory A.; Goossens, Sander; Andrews-Hanna, Jeffrey C.; Head, James W.; Kiefer, Walter S.; Asmar, Sami W.; Konopliv, Alexander S.; Lemoine, Frank G.;

Cryo-transmission electron tomography of native casein micelles from bovine milk

PubMed Central

Trejo, R.; Dokland, T.; Jurat-Fuentes, J.; Harte, F.

2013-01-01

Caseins are the principal protein components in milk and an important ingredient in the food industry. In liquid milk, caseins are found as micelles of casein proteins and colloidal calcium nanoclusters. Casein micelles were isolated from raw skim milk by size exclusion chromatography and suspended in milk protein-free serum produced by ultrafiltration (molecular weight cut-off of 3 kDa) of raw skim milk. The micelles were imaged by cryo-electron microscopy and subjected to tomographic reconstruction methods to visualize the 3-dimensional and internal organization of native casein micelles. This provided new insights into the internal architecture of the casein micelle that had not been apparent from prior cryo-transmission electron microscopy studies. This analysis demonstrated the presence of water-filled cavities (~20 to 30 nm in diameter), channels (diameter greater than ~5 nm), and several hundred high-density nanoclusters (6 to 12 nm in diameter) within the interior of the micelles. No spherical protein submicellar structures were observed. PMID:22118067

Highly efficient solar-pumped Nd:YAG laser.

PubMed

Liang, Dawei; Almeida, Joana

2011-12-19

The recent progress in solar-pumped laser with Fresnel lens and Cr:Nd:YAG ceramic medium has revitalized solar laser researches, revealing a promising future for renewable reduction of magnesium from magnesium oxide. Here we show a big advance in solar laser collection efficiency by utilizing an economical Fresnel lens and a most widely used Nd:YAG single-crystal rod. The incoming solar radiation from the sun is focused by a 0.9 m diameter Fresnel lens. A dielectric totally internally reflecting secondary concentrator is employed to couple the concentrated solar radiation from the focal zone to a 4 mm diameter Nd:YAG rod within a conical pumping cavity. 12.3 W cw laser power is produced, corresponding to 19.3 W/m(2) collection efficiency, which is 2.9 times larger than the previous results with Nd:YAG single-crystal medium. Record-high slope efficiency of 3.9% is also registered. Laser beam quality is considerably improved by pumping a 3 mm diameter Nd:YAG rod.

Vertical-Cavity Surface-Emitting 1.55-μm Lasers Fabricated by Fusion

NASA Astrophysics Data System (ADS)

Babichev, A. V.; Karachinskii, L. Ya.; Novikov, I. I.; Gladyshev, A. G.; Blokhin, S. A.; Mikhailov, S.; Iakovlev, V.; Sirbu, A.; Stepniak, G.; Chorchos, L.; Turkiewicz, J. P.; Voropaev, K. O.; Ionov, A. S.; Agustin, M.; Ledentsov, N. N.; Egorov, A. Yu.

2018-01-01

The results of studies on fabrication of vertical-cavity surface-emitting 1.55-μm lasers by fusing AlGaAs/GaAs distributed-Bragg-reflector wafers and an active region based on thin In0.74Ga0.26 As quantum wells grown by molecular-beam epitaxy are presented. Lasers with a current aperture diameter of 8 μm exhibit continuous lasing with a threshold current below 1.5 mA, an output optical power of 6 mW, and an efficiency of approximately 22%. Single-mode lasing with a side-mode suppression ratio of 40-45 dB is observed in the entire operating current range. The effective modulation frequency of these lasers is as high as 9 GHz and is limited by the low parasitic cutoff frequency and self-heating.

Pathological features of olfactory neuroblastoma in an axolotl (Ambystoma mexicanum).

PubMed

Shioda, Chieko; Uchida, Kazuyuki; Nakayama, Hiroyuki

2011-08-01

A one-year-old, female Mexican axolotl (Ambystoma mexicanum) had a rough-surfaced, polypoid, pink tumor mass of approximately 10 mm in diameter in the oral cavity. Histologically, the tumor extended from the ethmoturbinate region and into the oral cavity and had replaced some of the maxillary bone tissue. The tumor mass was composed of a lobular architecture of small round-shaped tumor cells with occasional Flexner-Wintersteiner-like rosette formation. There were no metastatic lesions in the other organs. Immunohistochemically, the tumor cells were partly positive for several neural markers (class III beta-tubulin, S-100 protein, and doublecortin) and intensely positive for an epithelial marker (cytokeratin AE1/AE3). These results suggest that the present tumor originated from neuroectodermal tissue. Considering the location and histological and immunohistochemical features of the tumor, a diagnosis of olfactory neuroblastoma was made.

Approach to high quality GaN lateral nanowires and planar cavities fabricated by focused ion beam and metal-organic vapor phase epitaxy.

PubMed

Pozina, Galia; Gubaydullin, Azat R; Mitrofanov, Maxim I; Kaliteevski, Mikhail A; Levitskii, Iaroslav V; Voznyuk, Gleb V; Tatarinov, Evgeniy E; Evtikhiev, Vadim P; Rodin, Sergey N; Kaliteevskiy, Vasily N; Chechurin, Leonid S

2018-05-08

We have developed a method to fabricate GaN planar nanowires and cavities by combination of Focused Ion Beam (FIB) patterning of the substrate followed by Metal Organic Vapor Phase Epitaxy (MOVPE). The method includes depositing a silicon nitride mask on a sapphire substrate, etching of the trenches in the mask by FIB with a diameter of 40 nm with subsequent MOVPE growth of GaN within trenches. It was observed that the growth rate of GaN is substantially increased due to enhanced bulk diffusion of the growth precursor therefore the model for analysis of the growth rate was developed. The GaN strips fabricated by this method demonstrate effective luminescence properties. The structures demonstrate enhancement of spontaneous emission via formation of Fabry-Perot modes.

Growth of GaN micro/nanolaser arrays by chemical vapor deposition.

PubMed

Liu, Haitao; Zhang, Hanlu; Dong, Lin; Zhang, Yingjiu; Pan, Caofeng

2016-09-02

Optically pumped ultraviolet lasing at room temperature based on GaN microwire arrays with Fabry-Perot cavities is demonstrated. GaN microwires have been grown perpendicularly on c-GaN/sapphire substrates through simple catalyst-free chemical vapor deposition. The GaN microwires are [0001] oriented single-crystal structures with hexagonal cross sections, each with a diameter of ∼1 μm and a length of ∼15 μm. A possible growth mechanism of the vertical GaN microwire arrays is proposed. Furthermore, we report room-temperature lasing in optically pumped GaN microwire arrays based on the Fabry-Perot cavity. Photoluminescence spectra exhibit lasing typically at 372 nm with an excitation threshold of 410 kW cm(-2). The result indicates that these aligned GaN microwire arrays may offer promising prospects for ultraviolet-emitting micro/nanodevices.

Room temperature lasing of GaAs quantum wire vertical-cavity surface-emitting lasers grown on (7 7 5) B GaAs substrates by molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Higuchi, Y.; Osaki, S.; Kitada, T.; Shimomura, S.; Takasuka, Y.; Ogura, M.; Hiyamizu, S.

2006-06-01

Self-organized GaAs/(GaAs) 4(AlAs) 2 quantum wires (QWRs) grown on (7 7 5) B-oriented GaAs substrates by molecular beam epitaxy have been applied to an active region of vertical-cavity surface-emitting lasers (VCSELs). The (7 7 5) B GaAs QWR-VCSEL with an aperture diameter of 3 μm lased at a wavelength of 765 nm with a threshold current of 0.38 mA at room temperature. This is the first demonstration of laser operation of the QWR-VCSEL by current injection. The light output was linearly polarized in the direction parallel to the QWRs due to the optical anisotropy of the self-organized (7 7 5) B GaAs QWRs.

TEM00 mode Nd:YAG solar laser by side-pumping a grooved rod

NASA Astrophysics Data System (ADS)

Vistas, Cláudia R.; Liang, Dawei; Almeida, Joana; Guillot, Emmanuel

2016-05-01

A simple TEM00 mode solar laser system with a grooved Nd:YAG rod pumped through a heliostat-parabolic mirror system is reported here. The radiation coupling capacity of a fused silica tube lens was combined with the multipass pumping ability of a 2 V-shaped cavity to provide efficient side-pumping along a 4.0 mm diameter grooved Nd:YAG single-crystal rod. TEM00 mode solar laser power of 3.4 W was measured by adopting an asymmetric large-mode laser resonant cavity. Record TEM00 mode solar laser collection efficiency of 3.4 W/m2and slope efficiency of 1.9% was achieved, which corresponds to 1.8 and 2.4 times more than the previous TEM00 mode Nd:YAG solar laser using the PROMES-CNRS heliostat-parabolic mirror system, respectively.

Intermittent burst of a super rogue wave in the breathing multi-soliton regime of an anomalous fiber ring cavity.

PubMed

Lee, Seungjong; Park, Kyoungyoon; Kim, Hyuntai; Vazquez-Zuniga, Luis Alonso; Kim, Jinseob; Jeong, Yoonchan

2018-04-30

We report the intermittent burst of a super rogue wave in the multi-soliton (MS) regime of an anomalous-dispersion fiber ring cavity. We exploit the spatio-temporal measurement technique to log and capture the shot-to-shot wave dynamics of various pulse events in the cavity, and obtain the corresponding intensity probability density function, which eventually unveils the inherent nature of the extreme events encompassed therein. In the breathing MS regime, a specific MS regime with heavy soliton population, the natural probability of pulse interaction among solitons and dispersive waves exponentially increases owing to the extraordinarily high soliton population density. Combination of the probabilistically started soliton interactions and subsequently accompanying dispersive waves in their vicinity triggers an avalanche of extreme events with even higher intensities, culminating to a burst of a super rogue wave nearly ten times stronger than the average solitons observed in the cavity. Without any cavity modification or control, the process naturally and intermittently recurs within a time scale in the order of ten seconds.

Repetitively Mode-Locked Cavity-Enhanced Absorption Spectroscopy (RML-CEAS) for Near-Infrared Gas Sensing

PubMed Central

Zheng, Chuantao; Wang, Yiding

2017-01-01

A Pound-Drever-Hall (PDH)-based mode-locked cavity-enhanced sensor system was developed using a distributed feedback diode laser centered at 1.53 µm as the laser source. Laser temperature scanning, bias control of the piezoelectric ceramic transducer (PZT) and proportional-integral-derivative (PID) feedback control of diode laser current were used to repetitively lock the laser modes to the cavity modes. A gas absorption spectrum was obtained by using a series of absorption data from the discrete mode-locked points. The 15 cm-long Fabry-Perot cavity was sealed using an enclosure with an inlet and outlet for gas pumping and a PZT for cavity length tuning. The performance of the sensor system was evaluated by conducting water vapor measurements. A linear relationship was observed between the measured absorption signal amplitude and the H2O concentration. A minimum detectable absorption coefficient of 1.5 × 10–8 cm–1 was achieved with an averaging time of 700 s. This technique can also be used for the detection of other trace gas species by targeting the corresponding gas absorption line. PMID:29207470

Effects of cavity size on the control of transonic internal flow around a biconvex circular arc airfoil

NASA Astrophysics Data System (ADS)

Rahman, M. Mostaqur; Hasan, A. B. M. Toufique; Rabbi, M. S.

2017-06-01

In transonic flow conditions, self-sustained shock wave oscillation on biconvex airfoils is initiated by the complex shock wave boundary layer interaction which is frequently observed in several modern internal aeronautical applications such as inturbine cascades, compressor blades, butterfly valves, fans, nozzles, diffusers and so on. Shock wave boundary layer interaction often generates serious problems such as unsteady boundary layer separation, self-excited shock waveoscillation with large pressure fluctuations, buffeting excitations, aeroacoustic noise, nonsynchronous vibration, high cycle fatigue failure and intense drag rise. Recently, the control of the self-excited shock oscillation around an airfoil using passive control techniques is getting intense interest. Among the passive means, control using open cavity has found promising. In this study, the effect of cavity size on the control of self-sustained shock oscillation was investigated numerically. The present computations are validated with available experimental results. The results showed that the average root mean square (RMS) of pressure oscillation around the airfoil with open cavity has reduced significantly when compared to airfoil without cavity (clean airfoil).

Modeling the size of the very dynamic diamagnetic cavity of comet 67P/Churyumov-Gerasimenko

NASA Astrophysics Data System (ADS)

Timar, Aniko; Nemeth, Zoltan; Madanian, Hadi; Glassmeier, Karl-Heinz; Goetz, Charlotte; Richter, Ingo; Szego, Karoly

2017-04-01

After the first detection of the diamagnetic cavity of comet 67P/Churyumov-Gerasimenko (Goetz et al. 2015) it became apparent that the boundary of this plasma region is very dynamic. To date hundreds of short cavity crossing events were detected (Nemeth et al. 2016, Goetz et al. in press), none lasting longer than an hour. This intermittent set of short crossing events is very different from the classical cavity observation near 1P/Halley, where Giotto remained for a long time continuously inside the cavity. The distance of the boundary is larger than that predicted by recent models, so it was not clear whether these short cavity-like regions are connected to a global diamagnetic cavity, or they are due to some local effects causing similar magnetic and plasma signatures. Here we revisit the neutral-drag model of Cravens 1986 to provide a very good phenomenological approximation for the highly variable size of this dynamic region. The model uses the cometary neutral production rate and the solar wind dynamic pressure as inputs. For the production rate we use averaged and detrended data derived from ROSINA neutral density measurements (Hansen et al. 2016). The solar wind pressure comes from space weather models and independently from the magnetic field measurements of MAG derived by using a method proposed by Madanian et al. 2016. The changes in the production rate and the dynamic pressure allows us to accurately predict the size of the cavity. In addition we show that instead of the local neutral pressure, the global production rate drives the size of the cavity. We can also explain the observed asymmetry between inbound and outbound crossings of the cavity boundary.

A new algorithm for stand table projection models.

Treesearch

Quang V. Cao; V. Clark Baldwin

1999-01-01

The constrained least squares method is proposed as an algorithm for projecting stand tables through time. This method consists of three steps: (1) predict survival in each diameter class, (2) predict diameter growth, and (3) use the least squares approach to adjust the stand table to satisfy the constraints of future survival, average diameter, and stand basal area....

High-performance coaxial EPR cavity for investigations at elevated temperatures and pressures

NASA Astrophysics Data System (ADS)

Goldberg, Ira B.; McKinney, Ted M.

1984-07-01

A microwave cavity suitable for heating a sample to temperatures above 800 °C within 15 s at gas pressures above 17.5 MPa is reported. The cavity is coaxial and operates in the TE011 mode at frequencies between 9 and 10 GHz. The heating element is constructed of nickel-chromium (i.e., Chromel) wire. It consists of two concentric helices wound in opposite senses (directions) and connected in series so as to minimize the magnetic field generated by the heater current. The heater is potted in magnesium oxide-phosphate ceramic and placed inside of a cylinder made from 50-μm copper foil which provides uniform temperature distribution and shields the heater from the microwave field. This assembly then serves as the heating element and the coaxial conductor of the cavity. The diameter of the coaxial heater assembly is approximately 7 mm. The sample is confined by a cylindrical quartz cuvette which surrounds the coaxial conductor. Sample thicknesses of 0.2 to 1.0 mm can be used. Heating from room temperature to 800 °C requires between 15 and 20 s. Operating pressures up to 17 MPa have been used, although the structural design limit of the brass or beryllium copper walls is greater than 22 MPa. Modulation coils are placed in recessed areas of the cavity walls and covered with a thin layer of copper. Cooling water flows through channels cut into the walls to maintain constant microwave parameters. Q factors of 8000 -12 000 can be obtained depending on the sample.

Mucoceles of the oral cavity in pediatric patients.

PubMed

Wu, Chung Wei; Kao, Yu-Hsun; Chen, Chao-Ming; Hsu, Han Jen; Chen, Chun-Ming; Huang, I-Yueh

2011-07-01

Mucoceles are quite common in the oral cavity, but reports on pediatric patients are very rare. The aims of this study were to present our data and experience in the treatment of mucoceles of the oral cavity in pediatric patients, to compare them with those of other countries, and to remind the pediatric physician to devote much attention to lesions of the oral cavity in children. This retrospective study is based on the record of the patients who received surgical treatment for mucoceles of the oral cavity with pathologic confirmation at the Department of Dentistry, Kaohsiung Medical University Hospital, Taiwan, between 2000 and 2004. Patients younger than 18 years were included in this study. The analyzed data included age, gender, site, size, histopathologic findings, surgical methods, and complications. There were a total of 289 patients with mucoceles confirmed by histopathologic examination. As many as 64 patients were younger than 18 years. Of the 64, 34 were girls and 30 were boys; 89.1% of the lesions were in the lower lip; and 48.4% of the lesions were less than 5mm in diameter. Histopathologic findings showed that all mucoceles were of the extravasation type. As many as 30 patients were treated by carbon dioxide laser vaporization, and two cases recurred (6.67%); 34 patients were treated by surgical excision, and the recurrence rate (5.88%) was not statistically different for the treatment methods. The laser vaporization has the advantage of less bleeding, no sutures, and saving time, especially suitable for children with oral mucocele. Copyright © 2011 Elsevier Taiwan LLC. All rights reserved.

RF Design of a High Average Beam-Power SRF Electron Source

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

Sipahi, Nihan; Biedron, Sandra; Gonin, Ivan

2016-06-01

There is a significant interest in developing high-average power electron sources, particularly in the area of electron sources integrated with Superconducting Radio Frequency (SRF) systems. For these systems, the electron gun and cathode parts are critical components for stable intensity and high-average powers. In this initial design study, we will present the design of a 9-cell accelerator cavity having a frequency of 1.3 GHz and the corresponding field optimization studies.

Efficient Scheme for Perfect Collective Einstein-Podolsky-Rosen Steering

PubMed Central

Wang, M.; Gong, Q. H.; Ficek, Z.; He, Q. Y.

2015-01-01

A practical scheme for the demonstration of perfect one-sided device-independent quantum secret sharing is proposed. The scheme involves a three-mode optomechanical system in which a pair of independent cavity modes is driven by short laser pulses and interact with a movable mirror. We demonstrate that by tuning the laser frequency to the blue (anti-Stokes) sideband of the average frequency of the cavity modes, the modes become mutually coherent and then may collectively steer the mirror mode to a perfect Einstein-Podolsky-Rosen state. The scheme is shown to be experimentally feasible, it is robust against the frequency difference between the modes, mechanical thermal noise and damping, and coupling strengths of the cavity modes to the mirror. PMID:26212901

Compact, thermal-noise-limited reference cavity for ultra-low-noise microwave generation.

PubMed

Davila-Rodriguez, J; Baynes, F N; Ludlow, A D; Fortier, T M; Leopardi, H; Diddams, S A; Quinlan, F

2017-04-01

We demonstrate an easy-to-manufacture 25-mm-long ultra-stable optical reference cavity for transportable photonic microwave generation systems. Employing a rigid holding geometry that is first-order insensitive to the squeezing force and a cavity geometry that improves the thermal noise limit at room temperature, we observe a laser phase noise that is nearly thermal noise limited for three frequency decades (1 Hz to 1 kHz offset) and supports 10 GHz generation with phase noise near -100  dBc/Hz at 1 Hz offset and <-173  dBc/Hz for all offsets >600  Hz. The fractional frequency stability reaches 2×10^-15 at 0.1 s of averaging.

Design and analysis of photonic crystal micro-cavity based optical sensor platform

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

Goyal, Amit Kumar, E-mail: amitgoyal.ceeri@gmail.com; Dutta, Hemant Sankar, E-mail: hemantdutta97@gmail.com; Pal, Suchandan, E-mail: spal@ceeri.ernet.in

2016-04-13

In this paper, the design of a two-dimensional photonic crystal micro-cavity based integrated-optic sensor platform is proposed. The behaviour of designed cavity is analyzed using two-dimensional Finite Difference Time Domain (FDTD) method. The structure is designed by deliberately inserting some defects in a photonic crystal waveguide structure. Proposed structure shows a quality factor (Q) of about 1e5 and the average sensitivity of 500nm/RIU in the wavelength range of 1450 – 1580 nm. Sensing technique is based on the detection of shift in upper-edge cut-off wavelength for a reference signal strength of –10 dB in accordance with the change in refractive index ofmore » analyte.« less

Seismic resonances of acoustic cavities

NASA Astrophysics Data System (ADS)

Schneider, F. M.; Esterhazy, S.; Perugia, I.; Bokelmann, G.

2016-12-01

The goal of an On-Site Inspection (OSI) is to clarify at a possible testsite whether a member state of the Comprehensive nuclear Test Ban Treaty (CTBT)has violated its rules by conducting a underground nuclear test. Compared toatmospheric and underwater tests underground nuclear explosions are the mostdifficult to detect.One primary structural target for the field team during an OSI is the detectionof an underground cavity, created by underground nuclear explosions. Theapplication of seismic-resonances of the cavity for its detection has beenproposed in the CTBT by mentioning "resonance seismometry" as possibletechnique during OSIs. We modeled the interaction of a seismic wave-field withan underground cavity by a sphere filled with an acoustic medium surrounded byan elastic full space. For this setting the solution of the seismic wave-fieldcan be computed analytically. Using this approach the appearance of acousticresonances can be predicted in the theoretical calculations. Resonance peaksappear in the spectrum derived for the elastic domain surrounding the acousticcavity, which scale in width with the density of the acoustic medium. For lowdensities in the acoustic medium as for an gas-filled cavity, the spectralpeaks become very narrow and therefore hard to resolve. The resonancefrequencies, however can be correlated to the discrete set of eigenmodes of theacoustic cavity and can thus be predicted if the dimension of the cavity isknown. Origin of the resonance peaks are internal reverberations of wavescoupling in the acoustic domain and causing an echoing signal that couples outto the elastic domain again. In the gas-filled case the amplitudes in timedomain are very low.Beside theoretical considerations we seek to find real data examples fromsimilar settings. As example we analyze a 3D active seismic data set fromFelsőpetény, Hungary that has been conducted between 2012 and 2014 on behalf ofthe CTBTO. In the subsurface of this area a former clay mine is situated, whichis connected to a karst cave of 30 m diameter in 70 m depth. Our aim is toinvestigate whether resonances predicted from theoretical models can be alsoobserved in data from such real experiments. Observation of spectral resonantpeaks could serve as the foundation of a cavity detection method that could beutilized for nuclear verification.

Efficient solar-pumped Nd:YAG laser by a double-stage light-guide/V-groove cavity

NASA Astrophysics Data System (ADS)

Almeida, Joana; Liang, Dawei

2011-05-01

Since the first reported Nd:YAG solar laser, researchers have been exploiting parabolic mirrors and heliostats for enhancing laser output performance. We are now investigating the production of an efficient solar-pumped laser for the reduction of magnesium from magnesium oxide, which could be an alternative solution to fossil fuel. Therefore both high conversion efficiency and excellent beam quality are imperative. By using a single fused silica light guide of rectangular cross section, highly concentrated solar radiation at the focal spot of a stationary parabolic mirror is efficiently transferred to a water-flooded V-groove pump cavity. It allows for the double-pass absorption of pump light along a 4mm diameter, 30mm length, 1.1at% Nd:YAG rod. Optimum pumping parameters and solar laser output power are found through ZEMAXTM non-sequential ray-tracing and LASCADTM laser cavity analysis. 11.0 W of multimode laser output power with excellent beam profile is numerically calculated, corresponding to 6.1W/m2 collection efficiency. To validate the proposed pumping scheme, an experimental setup of the double-stage light-guide/V-groove cavity was built. 78% of highly concentrated solar radiation was efficiently transmitted by the fused silica light guide. The proposed pumping scheme can be an effective solution for enhancing solar laser performances when compared to other side-pump configurations.

Centrifuge tests on simulation of the ''cookie cutter'' mechanism of chimney collapse into underground openings: Final report

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

Kutter, B.L.; Chang, Ging-Song

The underground testing of nuclear devices causes the formation of large underground cavities which eventually may be filled by rubble and soil falling from the roof of the cavity. The zone of collapsing soil progresses upward toward the ground surface to form a ''chimney.'' The mechanisms of chimney collapse are important to understand for two important reasons. (1) A devastating and sudden propagation of the collapse may result in the formation of a surface crater which may threaten personnel and equipment in the vicinity of the crater. (2) Different collapse patterns are known to occur in the field and somemore » of these collapse patterns are known to be associated with leakage of radioactive wastes to the ground surface. A number of centrifuge tests were conducted by Kutter et al. (1988), to study the collapse of cavities in uniform dry sands. In these materials, the chimney collapse patterns were found to involve continuous, smoothly varying shear strain patterns in the chimney. The pattern of collapse in one of the tests is shown in figure 1. Figure 1a shows the surface crater that formed on the ground surface due to the collapse of a 6 inch diameter cavity buried 18'' beneath the ground surface. This result was obtained by draining fluid out of a 6'' rubber bag while the centrifuge was spinning at 11 g.« less

Intrauterine endometrial cyst after low uterine incision: A case report with literature review.

PubMed

Yin, Weiyao; Zhang, Jiawen; Xu, Liangzhi; Luo, Li

2018-04-01

During the surgical procedure, endometrial cells can be seeded into the wound edge of the uterine wall, developing into scar endometriosis. Due to the extremely low incidence, estimation of its prevalence is still unavailable. Even rarer might be the scar endometriosis in uterine cavity, to our best knowledge, a situation has not been reported yet. A 37-year-old woman complained of heavier and prolonged menstruation as well as pelvic pain during menses for more than 4 months. An endometrial cyst in diameter of 6 cm in uterine cavity was revealed by transvaginal ultrasound. Her surgical history was significant for 1 caesarean section and 1 abdominal myomectomy through transverse incision of lower uterine segment. Space-occupying lesions in uterine cavity, moderate anemia and scar uterus. The hysteroscopy was performed and a multilocular cyst full of chocolate-like fluid was removed. Pathological examination confirmed endometrial glands in the removed cyst tissue. During the follow-up visits at 1 and 6 months after surgery, the patient denied any special discomfort. Her postoperative transvaginal ultrasound showed an enlarged uterus with no lesion in uterine cavity. To achieve a better surveillance, a 3-year period of follow-up after surgery at a 6-month interval was suggested. Intrauterine endometriosis should be considered in patients of pelvic surgery history with pelvic pain, menstrual disorder, and intrauterine cystic mass.

Simultaneous imaging electron- and ion-feature Thomson scattering measurements of radiatively heated Xe.

PubMed

Pollock, B B; Meinecke, J; Kuschel, S; Ross, J S; Shaw, J L; Stoafer, C; Divol, L; Tynan, G R; Glenzer, S H

2012-10-01

Uniform density and temperature Xe plasmas have been produced over >4 mm scale-lengths using x-rays generated in a cylindrical Pb cavity. The cavity is 750 μm in depth and diameter, and is heated by a 300 J, 2 ns square, 1054 nm laser pulse focused to a spot size of 200 μm at the cavity entrance. The plasma is characterized by simultaneous imaging Thomson scattering measurements from both the electron and ion scattering features. The electron feature measurement determines the spatial electron density and temperature profile, and using these parameters as constraints in the ion feature analysis allows an accurate determination of the charge state of the Xe ions. The Thomson scattering probe beam is 40 J, 200 ps, and 527 nm, and is focused to a 100 μm spot size at the entrance of the Pb cavity. Each system has a spatial resolution of 25 μm, a temporal resolution of 200 ps (as determined by the probe duration), and a spectral resolution of 2 nm for the electron feature system and 0.025 nm for the ion feature system. The experiment is performed in a Xe filled target chamber at a neutral pressure of 3-10 Torr, and the x-rays produced in the Pb ionize and heat the Xe to a charge state of 20±4 at up to 200 eV electron temperatures.

A NEW CONCEPT FOR HIGH POWER RF COUPLING BETWEEN WAVEGUIDES AND RESONANT RF CAVITIES

DOE PAGES

Xu, Chen; Ben-Zvi, Ilan; Wang, Haipeng; ...

2017-01-01

Microwave engineering of high average-power (hundreds of kilowatts) devices often involves a transition from a waveguide to a device, typically a resonant cavity. This is a basic operation, which finds use in various application areas of significance to science and industry. At relatively low frequencies, L-band and below, it is convenient, sometimes essential, to couple the power between the waveguide and the cavity through a coaxial antenna, forming a power coupler. Power flow to the cavity in the fundamental mode leads to a Fundamental Power Coupler (FPC). High-order mode power generated in the cavity by a particle beam leads tomore » a high-order mode power damper. Coupling a cryogenic device, such as a superconducting cavity to a room temperature power source (or damp) leads to additional constraints and challenges. We propose a new approach to this problem, wherein the coax line element is operated in a TE11 mode rather than the conventional TEM mode. We will show that this method leads to a significant increase in the power handling capability of the coupler as well as a few other advantages. As a result, we describe the mode converter from the waveguide to the TE11 coax line, outline the characteristics and performance limits of the coupler and provide a detailed worked out example in the challenging area of coupling to a superconducting accelerator cavity.« less

Pressure Gradient Effects on Hypersonic Cavity Flow Heating

NASA Technical Reports Server (NTRS)

Everhart, Joel L.; Alter, Stephen J.; Merski, N. Ronald; Wood, William A.; Prabhu, Ramadas K.

2006-01-01

The effect of a pressure gradient on the local heating disturbance of rectangular cavities tested at hypersonic freestream conditions has been globally assessed using the two-color phosphor thermography method. These experiments were conducted in the Langley 31-Inch Mach 10 Tunnel and were initiated in support of the Space Shuttle Return-To-Flight Program. Two blunted-nose test surface geometries were developed, including an expansion plate test surface with nearly constant negative pressure gradient and a flat plate surface with nearly zero pressure gradient. The test surface designs and flow characterizations were performed using two-dimensional laminar computational methods, while the experimental boundary layer state conditions were inferred using the measured heating distributions. Three-dimensional computational predictions of the entire model geometry were used as a check on the design process. Both open-flow and closed-flow cavities were tested on each test surface. The cavity design parameters and the test condition matrix were established using the computational predictions. Preliminary conclusions based on an analysis of only the cavity centerline data indicate that the presence of the pressure gradient did not alter the open cavity heating for laminar-entry/laminar-exit flows, but did raise the average floor heating for closed cavities. The results of these risk-reduction studies will be used to formulate a heating assessment of potential damage scenarios occurring during future Space Shuttle flights.

Pressure Gradient Effects on Hypersonic Cavity Flow Heating

NASA Technical Reports Server (NTRS)

Everhart, Joel L.; Alter, Stephen J.; Merski, N. Ronald; Wood, William A.; Prabhu, Ramdas K.

2007-01-01

The effect of a pressure gradient on the local heating disturbance of rectangular cavities tested at hypersonic freestream conditions has been globally assessed using the two-color phosphor thermography method. These experiments were conducted in the Langley 31-Inch Mach 10 Tunnel and were initiated in support of the Space Shuttle Return-To-Flight Program. Two blunted-nose test surface geometries were developed, including an expansion plate test surface with nearly constant negative pressure gradient and a flat plate surface with nearly zero pressure gradient. The test surface designs and flow characterizations were performed using two-dimensional laminar computational methods, while the experimental boundary layer state conditions were inferred using the measured heating distributions. Three-dimensional computational predictions of the entire model geometry were used as a check on the design process. Both open-flow and closed-flow cavities were tested on each test surface. The cavity design parameters and the test condition matrix were established using the computational predictions. Preliminary conclusions based on an analysis of only the cavity centerline data indicate that the presence of the pressure gradient did not alter the open cavity heating for laminar-entry/laminar-exit flows, but did raise the average floor heating for closed cavities. The results of these risk-reduction studies will be used to formulate a heating assessment of potential damage scenarios occurring during future Space Shuttle flights.

Microstructure evolution during helium irradiation and post-irradiation annealing in a nanostructured reduced activation steel

NASA Astrophysics Data System (ADS)

Liu, W. B.; Ji, Y. Z.; Tan, P. K.; Zhang, C.; He, C. H.; Yang, Z. G.

2016-10-01

Severe plastic deformation, intense single-beam He-ion irradiation and post-irradiation annealing were performed on a nanostructured reduced activation ferritic/martensitic (RAFM) steel to investigate the effect of grain boundaries (GBs) on its microstructure evolution during these processes. A surface layer with a depth-dependent nanocrystalline (NC) microstructure was prepared in the RAFM steel using surface mechanical attrition treatment (SMAT). Microstructure evolution after helium (He) irradiation (24.8 dpa) at room temperature and after post-irradiation annealing was investigated using Transmission Electron Microscopy (TEM). Experimental observation shows that GBs play an important role during both the irradiation and the post-irradiation annealing process. He bubbles are preferentially trapped at GBs/interfaces during irradiation and cavities with large sizes are also preferentially trapped at GBs/interfaces during post-irradiation annealing, but void denuded zones (VDZs) near GBs could not be unambiguously observed. Compared with cavities at GBs and within larger grains, cavities with smaller size and higher density are found in smaller grains. The average size of cavities increases rapidly with the increase of time during post-irradiation annealing at 823 K. Cavities with a large size are observed just after annealing for 5 min, although many of the cavities with small sizes also exist after annealing for 240 min. The potential mechanism of cavity growth behavior during post-irradiation annealing is also discussed.

A NEW CONCEPT FOR HIGH POWER RF COUPLING BETWEEN WAVEGUIDES AND RESONANT RF CAVITIES

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

Xu, Chen; Ben-Zvi, Ilan; Wang, Haipeng

Microwave engineering of high average-power (hundreds of kilowatts) devices often involves a transition from a waveguide to a device, typically a resonant cavity. This is a basic operation, which finds use in various application areas of significance to science and industry. At relatively low frequencies, L-band and below, it is convenient, sometimes essential, to couple the power between the waveguide and the cavity through a coaxial antenna, forming a power coupler. Power flow to the cavity in the fundamental mode leads to a Fundamental Power Coupler (FPC). High-order mode power generated in the cavity by a particle beam leads tomore » a high-order mode power damper. Coupling a cryogenic device, such as a superconducting cavity to a room temperature power source (or damp) leads to additional constraints and challenges. We propose a new approach to this problem, wherein the coax line element is operated in a TE11 mode rather than the conventional TEM mode. We will show that this method leads to a significant increase in the power handling capability of the coupler as well as a few other advantages. As a result, we describe the mode converter from the waveguide to the TE11 coax line, outline the characteristics and performance limits of the coupler and provide a detailed worked out example in the challenging area of coupling to a superconducting accelerator cavity.« less

Numerical analyses of ventilated cavitation over a 2-D NACA0015 hydrofoil using two turbulence modeling methods

NASA Astrophysics Data System (ADS)

Yang, Dan-dan; Yu, An; Ji, Bin; Zhou, Jia-jian; Luo, Xian-wu

2018-04-01

The present paper studies the ventilated cavitation over a NACA0015 hydrofoil by numerical methods. The corresponding cavity evolutions are obtained at three ventilation rates by using the level set method. To depict the complicated turbulent flow structure, the filter-based density corrected model (FBDCM) and the modified partially-averaged Navier-Stokes (MPANS) model are applied in the present numerical analyses. It is indicated that the predicted results of the cavitation shedding dynamics by both turbulence models agree fairly well with the experimental data. It is also noted that the shedding frequency and the super cavity length predicted by the MPANS method are closer to the experiment data as compared to that predicted by the FBDCM model. The simulation results show that in the ventilated cavitation, the vapor cavity and the air cavity have the same shedding frequency. As the ventilated rate increases, the vapor cavity is depressed rapidly. The cavitation-vortex interaction in the ventilated cavitation is studied based on the vorticity transport equation (VTE) and the Lagrangian coherent structure (LCS). Those results demonstrate that the vortex dilatation and baroclinic torque terms are highly dependent on the evolution of the cavitation. In addition, from the LCSs and the tracer particles in the flow field, one may see the process from the attached cavity to the cloud cavity.

Impact of Upheaval Dome, Utah

NASA Technical Reports Server (NTRS)

Shoemaker, E. M.; Herkenhoff, K. E.

1984-01-01

Reexamination of Upheaval Dome in the Canyonlands National Park, Utah, shows that the structure of this remarkable feature conforms with that expected for a deeply eroded astrobleme. The structure is definitely not compatible with an origin due simply to plastic flowage of salt and other rocks in the underlying Paradox Formation. The most strongly deformed rocks are bounded by a series of circumferential listric faults. The convergent displacement of the rocks corresponds to the deformation that results from collapse of a transient cavity produced by high speed impact. From considerations of the probable depth of exposure of the impact structure and upward extrapolation of the listric faults, the final collapsed crater is estimated to be about 8 to 10 km in diameter; the impacting body was on the order of 0.5 km in diameter.

Transverse Coefficient of Thermal Expansion Measurements of Carbon Fibers Using ESEM at High Temperatures

NASA Technical Reports Server (NTRS)

Ochoa, O.; Jiang, J.; Putnam, D.; Lo, Z.; Ellis, A.; Effinger, Michael

2003-01-01

The transverse coefficient of thermal expansion (CTE) of single IM7, T1000, and P55 carbon fibers are measured at elevated temperatures. The specimens are prepared by press-fitting fiber tows into 0.7mm-diameter cavity in a graphite disk of 5mm in diameter and 3mm high. The specimens are placed on a crucible in an ESEM, and images of the fiber cross section are taken as the fibers are heated up to 800 C. Holding time, heating and cool down cycles are also introduced. The geometrical changes are measured using a graphics tablet. The change in area/perimeter is calculated to determine the strain and transverse CTE for each fiber. In a complimentary computational effort, displacements and stresses are calculated with finite element models.

Solar-Pumped TEM₀₀ Mode Nd:YAG laser.

PubMed

Liang, Dawei; Almeida, Joana

2013-10-21

Here we show a significant advance in solar-pumped laser beam brightness by utilizing a 1.0 m diameter Fresnel lens and a 3 mm diameter Nd:YAG single-crystal rod. The incoming solar radiation is firstly focused by the Fresnel lens on a solar tracker. A large aspheric lens and a 2D-CPC concentrator are then combined to further compress the concentrated solar radiation along the thin laser rod within a V-shaped pumping cavity. 2.3 W cw TEM₀₀ (M² ≤ 1.1) solar laser power is finally produced, attaining 1.9 W laser beam brightness figure of merit, which is 6.6 times higher than the previous record. For multimode operation, 8.1 W cw laser power is produced, corresponding to 143% enhancement in collection efficiency.

Picosecond laser with 11 W output power at 1342 nm based on composite multiple doping level Nd:YVO4 crystal

NASA Astrophysics Data System (ADS)

Rodin, Aleksej M.; Grishin, Mikhail; Michailovas, Andrejus

2016-01-01

We report results of design and optimization of high average output power picosecond and nanosecond laser operating at 1342 nm wavelength. Developed for selective micromachining, this DPSS laser is comprised of master oscillator, regenerative amplifier and output pulse control module. Passively mode-locked by means of semiconductor saturable absorber mirror and pumped with 808 nm wavelength Nd:YVO4 master oscillator emits 12.5 ps pulses at repetition rate of 55 MHz with average output power of ∼100 mW. The four-pass confocal delay line forms a longest part of the oscillator cavity in order to suppress thermo-mechanical misalignment. Picked from the train seed pulses were injected to the cavity of regenerative amplifier based on composite Nd:YVO4 crystal with diffusion-bonded segments of multiple Nd doping concentration end-pumped at 880 nm wavelength. Laser produces pulses of ∼13 ps duration at 300 kHz repetition rate with average output power of 11 W and nearly diffraction limited beam quality of M2∼1.03. Attained high peak power ∼2.8 MW facilitates conversion to the 2nd, 3rd and 6th harmonics at 671 nm, 447 nm and 224 nm wavelengths with 80%, 50% and 15% efficiency respectively. Without seeding the regenerative amplifier transforms to electro-optically cavity-dumped Q-switched laser providing 10 ns output pulses at high repetition rates with beam propagation factor of M2∼1.06.

Preoperative combination of progressive pneumoperitoneum and botulinum toxin type A in patients with loss of domain hernia.

PubMed

Bueno-Lledó, José; Torregrosa, Antonio; Jiménez, Raquel; Pastor, Providencia García

2018-02-15

Preoperative progressive pneumoperitoneum (PPP) and botulinum toxin type A (BT) are tools in the surgical preparation of patients with loss of domain hernias (LODH). The aim of this paper is to report our experience with these preoperative techniques in 70 patients with LODH. Observational study of 70 consecutive patients with LODH was conducted between May 2010 and May 2016. Diameters of the hernia sac, incisional hernia (VIH), and abdominal cavity (VAC) volumes, and VIH/VAC ratio were measured before and after PPP and BT, using abdominal CT scan data. Combination of both techniques was performed when the VIH/VAC ratio was > 20%. Median insufflated volume of air for PPP was 8450 ± 3400 cc (4500-13,450), over a period of 11.3 ± 2.3 days (9-16). BT administration time was 38.1 ± 3.7 days (35-44). An average reduction of 16.6% of the VIH/VAC ratio after PPP and BT was obtained (p < 0.05). Complications associated with PPP were 20%, and with surgical technique 29.6%. No complications occurred during the BT administration. Reconstructive technique was anterior CST in 54 patients, TAR in 14 cases and Rives-Stoppa technique in two patients. Median follow-up was 34.5 ± 22.3 months (12-60) and four cases of hernia recurrence (5.7%) were reported. Using a CT volumetric protocol, combination of PPP and BT decreases the VIH/VAC ratio and hernia defect diameters, which constitutes a key factor in the treatment of LODH.

Consideration of growth (age)-related effects on globe size and corneal thickness in ovine eyes for use in laboratory studies.

PubMed

Doughty, Michael J

2017-07-01

The aim was to assess differences in eyeball mass, corneal diameter and central corneal thickness in slaughterhouse-procured ovine eyes. Over a 12-year period, measurements of eye globe mass, horizontal corneal diameter and central corneal thickness were routinely undertaken within two hours post-mortem. Only eyes free of obvious mechanical damage or disease were used. From measurements on 736 quality-selected and trimmed eyes, globe wet mass ranged from 10.4 to 25.2 g, horizontal corneal diameter from 19.0 to 26.5 mm and central corneal thickness measured by ultrasonic pachymetry from 0.543 to 0.836 mm (with an overall average of 690 ± 0.056 mm). The ocular globe mass was strongly correlated to horizontal corneal diameter (r 2  = 0.829). Central corneal thickness correlated with globe mass (r = 0.543) and to horizontal corneal diameter (r = 0.402). Based on the different anatomical measurements, a lamb's eye would be expected to have a thinner cornea (average 0.640 mm) than that of an adult outbred ewe (average 0.730 mm). In freshly procured eyes showing signs of slight corneal oedema, central corneal thickness was greater (average 0.856 ± 0.052 mm) and up to 24 hours of cold storage resulted in predictable increases in central corneal thickness of six to 24 per cent, especially in eyes showing signs of corneal oedema before storage. Based on the correlations obtained, differences in ovine eyes can be attributed to growth-related differences in the animals and thus, indirectly to their expected ages. A simple measure of the horizontal corneal diameter in ovine eyes used for laboratory studies would be a useful indicator in reporting these studies. © 2016 Optometry Australia.

Updating Indiana Annual Forest Inventory and Analysis Plot Data Using Eastern Broadleaf Forest Diameter Growth Models

Treesearch

Veronica C. Lessard

2001-01-01

The Forest Inventory and Analysis (FIA) program of the North Central Research Station (NCRS), USDA Forest Service, has developed nonlinear, individual-tree, distance-independent annual diameter growth models. The models are calibrated for species groups and formulated as the product of an average diameter growth component and a modifier component. The regional models...

Axially uniform resonant cavity modes for potential use in electron paramagnetic resonance spectroscopy

NASA Astrophysics Data System (ADS)

Mett, Richard R.; Froncisz, Wojciech; Hyde, James S.

2001-11-01

This article is concerned with cylindrical transverse electric TE011 and rectangular TE102 microwave cavity resonators commonly used in electron paramagnetic resonance (EPR) spectroscopy. In the cylindrical mode geometry considered here, the sample is along the z axis of the cylinder, dielectric disks of 1/4 wavelength thickness are placed at each end wall, and the diameter of the cylinder is set at the cutoff condition for propagation of microwave energy in a cylindrical waveguide at the desired microwave frequency. The microwave magnetic field is exactly uniform along the sample in the region between the dielectric disks and the resonant frequency is independent of the length of the cylinder without limit. The rectangular TE102 geometry is analogous, but here the microwave magnetic field is exactly uniform in a plane. A uniform microwave field along a line sample is highly advantageous in EPR spectroscopy compared with the usual sinusoidal variation, and these geometries are called "uniform field" modes. Extensive theoretical analysis as well as finite element calculation of field patterns are presented. The perturbation of field patterns caused by sample insertion as functions of the overall length of the resonator and diameter of the sample is analyzed. The article is intended to provide a basis for design of practical structures in the range of 10 to 100 GHz.

Effects of injection pressure variation on mixing in a cold supersonic combustor with kerosene fuel

NASA Astrophysics Data System (ADS)

Liu, Wei-Lai; Zhu, Lin; Qi, Yin-Yin; Ge, Jia-Ru; Luo, Feng; Zou, Hao-Ran; Wei, Min; Jen, Tien-Chien

2017-10-01

Spray jet in cold kerosene-fueled supersonic flow has been characterized under different injection pressures to assess the effects of the pressure variation on the mixing between incident shock wave and transverse cavity injection. Based on the real scramjet combustor, a detailed computational fluid dynamics model is developed. The injection pressures are specified as 0.5, 1.0, 2.0, 3.0 and 4.0 MPa, respectively, with the other constant operation parameters (such as the injection diameter, angle and velocity). A three dimensional Couple Level Set & Volume of Fluids approach incorporating an improved Kelvin-Helmholtz & Rayleigh-Taylor model is used to investigate the interaction between kerosene and supersonic air. The numerical simulations primarily concentrate on penetration depth, span expansion area, angle of shock wave and sauter mean diameter distribution of the kerosene droplets with/without evaporation. Validation has been implemented by comparing the calculated against the measured in literature with good qualitative agreement. Results show that the penetration depth, span-wise angle and expansion area of the transverse cavity jet are all increased with the injection pressure. However, when the injection pressure is further increased, the value in either penetration depth or expansion area increases appreciably. This study demonstrates the feasibility and effectiveness of the combination of Couple Level Set & Volume of Fluids approach and an improved Kelvin-Helmholtz & Rayleigh-Taylor model, in turn providing insights into scramjet design improvement.

Calibration of Radiation Thermometers up to : Effective Emissivity of the Source

NASA Astrophysics Data System (ADS)

Kozlova, O.; Briaudeau, S.; Rongione, L.; Bourson, F.; Guimier, S.; Kosmalski, S.; Sadli, M.

2015-08-01

The growing demand of industry for traceable temperature measurements up to encourages improvement of calibration techniques for industrial-type radiation thermometers in this temperature range. High-temperature fixed points can be used at such high temperatures, but due to the small diameter of apertures of their cavities (3 mm), they are not adapted for the large field-of-views commonly featured by this kind of radiation thermometers. At LNE-Cnam, a Thermo Gauge furnace of 25.4 mm source aperture diameter is used as a comparison source to calibrate customers' instruments against a reference radiation thermometer calibrated according to the ITS-90 with the lowest uncertainties achievable in the Laboratory. But the furnace blackbody radiator exhibits a large temperature gradient that degrades its effective emissivity, and increases the calibration uncertainty due to the lack of information on the working spectral band of the industrial radiation thermometer. In order to estimate the corrections to apply, the temperature distribution (radial and on-axis) of the Thermo Gauge furnace blackbody radiator was characterized and the effective emissivity of the Thermo Gauge cavity was determined by three different methods. Because of this investigation, the corrections due to different fields of view and due to the different spectral bands of the reference pyrometer and the customer's pyrometer were obtained and the uncertainties on these corrections were evaluated.

Optimal Design of an Hourglass in-Fiber Air Fabry-Perot Microcavity—Towards Spectral Characteristics and Strain Sensing Technology

PubMed Central

Wang, Qi; Yan, Dongchao; Cui, Binbin; Guo, Zixuan

2017-01-01

An hourglass in-fiber air microcavity Fabry-Perot interferometer is proposed in this paper, and its second reflecting surface of in-fiber microcavity is designed to be a concave reflector with the best curvature radius in order to improve the spectral characteristics. Experimental results proved that the extinction ratio of Fabry-Perot interferometer with cavity length of 60 μm and concave reflector radius of 60 μm is higher than for a rectangular Fabry-Perot interferometer with cavity length of 60 μm (14 dB: 11 dB). Theory and numerical simulation results show that the strain sensitivity of sensor can be improved by reducing the microcavity wall thickness and microcavity diameter, and when the in-fiber microcavity length is 40 μm, the microcavity wall thickness is 10 μm, the microcavity diameter is 20 μm, and the curvature radius of reflective surface II is 50 μm, the interference fringe contrast of is greater than 0.97, an Axial-pull sensitivity of 20.46 nm/N and resolution of 1 mN can be achieved in the range of 0–1 N axial tension. The results show that the performance of hourglass in-fiber microcavity interferometer is far superior to that of the traditional Fabry-Perot interferometer. PMID:28587221

Tortuosity correction of Kozeny's hydraulic diameter of a porous medium

NASA Astrophysics Data System (ADS)

Shin, C.

2017-02-01

The hydraulic diameter of a porous medium is the most important characteristic parameter governing porous flow aspects. Kozeny's hydraulic diameter has been used as the representative definition ever since he proposed it in 1927. However, it seems likely that this definition does not perfectly reflect the porous flow features even if the geometric relations of porous media are reasonably considered. Here we reviewed its definition by introducing Darcy's friction flow relation, and discovered that the term "tortuosity" should be included in the definition to more accurately characterize porous flows. Thus, the definition of "Tortuous Hydraulic Diameter (THD)," which corrects Kozeny's hydraulic diameter using tortuosity, is newly presented. Moreover, computational fluid dynamics simulations were performed to check the validity and applicability of the THD approach. As a result, it is seen that the THD demonstrates very low errors, with an average of 1.67%, whereas Kozeny's definition has relatively large errors, with an average of 12.8%. Accordingly, it is confirmed that the THD relation is the more accurate hydraulic diameter definition for a porous medium. Ultimately, the corrected definition can contribute to more reliable determinations of the other characteristic parameters and more reasonable porous flow analyses.

Enhanced dynamical stability with harmonic slip stacking

DOE PAGES

Eldred, Jeffrey; Zwaska, Robert

2016-10-26

We develop a configuration of radio-frequency (rf) cavities to dramatically improve the performance of slip-stacking. Slip-stacking is an accumulation technique used at Fermilab to nearly double proton intensity by maintaining two beams of different momenta in the same storage ring. The two particle beams are longitudinally focused in the Recycler by two 53 MHz 100 kV rf cavities with a small frequency difference between them. We propose an additional 106 MHz 20 kV rf cavity with a frequency at the double the average of the upper and lower main rf frequencies. We show the harmonic rf cavity cancels out themore » resonances generated between the two main rf cavities and we derive the relationship between the harmonic rf voltage and the main rf voltage. We find the area factors that can be used to calculate the available phase space area for any set of beam parameters without individual simulation. We establish Booster beam quality requirements to achieve 99\\% slip-stacking efficiency. We measure the longitudinal distribution of the Booster beam and use it to generate a realistic beam model for slip-stacking simulation. In conclusion, we demonstrate that the harmonic rf cavity can not only reduce particle loss during slip-stacking, but also reduce the final longitudinal emittance.« less

Enhanced dynamical stability with harmonic slip stacking

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

Eldred, Jeffrey; Zwaska, Robert

We develop a configuration of radio-frequency (rf) cavities to dramatically improve the performance of slip-stacking. Slip-stacking is an accumulation technique used at Fermilab to nearly double proton intensity by maintaining two beams of different momenta in the same storage ring. The two particle beams are longitudinally focused in the Recycler by two 53 MHz 100 kV rf cavities with a small frequency difference between them. We propose an additional 106 MHz 20 kV rf cavity with a frequency at the double the average of the upper and lower main rf frequencies. We show the harmonic rf cavity cancels out themore » resonances generated between the two main rf cavities and we derive the relationship between the harmonic rf voltage and the main rf voltage. We find the area factors that can be used to calculate the available phase space area for any set of beam parameters without individual simulation. We establish Booster beam quality requirements to achieve 99\\% slip-stacking efficiency. We measure the longitudinal distribution of the Booster beam and use it to generate a realistic beam model for slip-stacking simulation. In conclusion, we demonstrate that the harmonic rf cavity can not only reduce particle loss during slip-stacking, but also reduce the final longitudinal emittance.« less

Computational Study of an Axisymmetric Dual Throat Fluidic Thrust Vectoring Nozzle for a Supersonic Aircraft Application

NASA Technical Reports Server (NTRS)

Deere, Karen A.; Flamm, Jeffrey D.; Berrier, Bobby L.; Johnson, Stuart K.

2007-01-01

A computational investigation of an axisymmetric Dual Throat Nozzle concept has been conducted. This fluidic thrust-vectoring nozzle was designed with a recessed cavity to enhance the throat shifting technique for improved thrust vectoring. The structured-grid, unsteady Reynolds- Averaged Navier-Stokes flow solver PAB3D was used to guide the nozzle design and analyze performance. Nozzle design variables included extent of circumferential injection, cavity divergence angle, cavity length, and cavity convergence angle. Internal nozzle performance (wind-off conditions) and thrust vector angles were computed for several configurations over a range of nozzle pressure ratios from 1.89 to 10, with the fluidic injection flow rate equal to zero and up to 4 percent of the primary flow rate. The effect of a variable expansion ratio on nozzle performance over a range of freestream Mach numbers up to 2 was investigated. Results indicated that a 60 circumferential injection was a good compromise between large thrust vector angles and efficient internal nozzle performance. A cavity divergence angle greater than 10 was detrimental to thrust vector angle. Shortening the cavity length improved internal nozzle performance with a small penalty to thrust vector angle. Contrary to expectations, a variable expansion ratio did not improve thrust efficiency at the flight conditions investigated.

Development of high repetition rate nitric oxide planar laser induced fluorescence imaging

NASA Astrophysics Data System (ADS)

Jiang, Naibo

This thesis has documented the development of a MHz repitition rate pulse burst laser system. Second harmonic and third harmonic efficiencies are improved by adding a Phase Conjugate Mirror to the system. Some high energy fundamental, second harmonic, and third harmonic burst sequences consisting of 1--12 pulses separated in time by between 4 and 12 microseconds are now routinely obtained. The reported burst envelopes are quite uniform. We have also demonstrated the ability to generate ultra-high frequency sequences of broadly wavelength tunable, high intensity laser pulses using a home built injection seeded Optical Parametric Oscillator (OPO), pumped by the second and third harmonic output of the pulse burst laser. Typical OPO output burst sequences consist of 6--10 pulses, separated in time by between 6 and 10 microseconds. With third harmonic pumping of the OPO system, we studied four conditions, two-crystal Singly Resonant OPO (SRO) cavity, three-crystal OPO cavity, single pass two-crystal Doubly Resonant OPO (DRO) cavity and double pass two-crystal OPO cavity. The double pass two-crystal OPO cavity gives the best operation in burst mode. For single pass OPO, the average total OPO conversion efficiency is approximately 25%. For double pass OPO, the average total OPO conversion efficiency is approximately 35%. As a preliminary work, we studied 532nm pumping of a single crystal OPO cavity. With single pulse pumping, the conversion efficiency can reach 30%. For both 355nm and 532nm pumping OPO, we have demonstrated injection seeding. The OPO output light linewidth is significantly narrowed. Some preliminary etalon traces are also reported. By mixing the OPO signal output at 622nm with residual third harmonic at 355nm, we obtained 226nm burst sequences with average pulse energy of ˜0.2 mJ. Injection seeding of the OPO increases the energy achieved by a factor of ˜2. 226nm burst sequences with reasonably uniform burst envelopes are reported. Using the system we have obtained, for the first time by any known optical method, Planar Laser Induced Fluorescence (PLIF) image sequences at ultrahigh (≥100kHz) frame rates, in particular NO PLIF image sequences, have been obtained in a Mach 2 jet. We also studied the possibility of utilizing a 250 kHz pulsed Nd:YVO 4 laser as the master oscillator. 10-pulse-10-mus spacing burst sequences with reasonably uniform burst envelope have been obtained. The total energy of the burst sequence is ˜2.5J.

Characterization of fiber diameter using image analysis

NASA Astrophysics Data System (ADS)

Baheti, S.; Tunak, M.

2017-10-01

Due to high surface area and porosity, the applications of nanofibers have increased in recent years. In the production process, determination of average fiber diameter and fiber orientation is crucial for quality assessment. The objective of present study was to compare the relative performance of different methods discussed in literature for estimation of fiber diameter. In this work, the existing automated fiber diameter analysis software packages available in literature were developed and validated based on simulated images of known fiber diameter. Finally, all methods were compared for their reliable and accurate estimation of fiber diameter in electro spun nanofiber membranes based on obtained mean and standard deviation.

High-Average Power Broadband 18-Beam Klystron Circuit and Collector Designs

DTIC Science & Technology

2008-04-01

high -average power S - band multiple-beam klystron are presented. The klystron will be powered by the recently completed 41.6 A, 42...al., “ High - power Four-cavity S - band multiple-beam klystron design,” IEEE Trans. Plasma Science, vol. 33, pp. 1119-1135, April 2005. [3] D.K Abe, et...APR 2008 2. REPORT TYPE 3. DATES COVERED 00-00-2008 to 00-00-2008 4. TITLE AND SUBTITLE High -average Power Broadband 18-beam

Influence of time off feed on broiler viscera weight, diameter, and shear.

PubMed

Buhr, R J; Northcutt, J K; Lyon, C E; Rowland, G N

1998-05-01

The influence of time off feed on broiler viscera weight, intestinal diameter, and shear was studied by subjecting market-age male broilers (42, 44, or 48 d) to incremental feed withdrawal periods (0, 6, 12, 18, or 24 h). Body weight was determined prior to feed withdrawal and at the time of processing. After slaughter, scalding, and defeathering, the abdominal cavity was opened. Diameter and shear of the proventriculus-ventriculus junction, jejunum, and ileum segments were measured, as were gallbladder length and width. Thoracic and abdominal viscera, liver, and ventriculus weights were determined, and liver surface color was measured. Percentage body weight loss increased with longer feed withdrawal periods, as viscera, liver, and ventriculus weights decreased. Gallbladder length increased with time off feed, whereas its width did not change. Diameter of the proventriculus-ventriculus junction, jejunum, and ileum decreased with longer feed withdrawal periods. Shear values for the proventriculus-ventriculus junction, jejunum, and ileum were not influenced by time off feed. Positive correlations (P < 0.05 and r > 0.4) between viscera weight and intestinal diameter were detected. Correlations between all measured parameters and shear values were not significant. Liver color measurements indicated that longer feed withdrawal periods resulted in significant linear decreases in L* (lightness), +a* (redness), and +b* (yellowness). Longer feed withdrawal periods decreased viscera weight and intestinal diameter, which would lower the potential for cutting the intestine during automated evisceration. However, the resulting greater gallbladder length (5 mm) would increase the possibility of bile contamination during evisceration.

Investigation of the relationship of crater depths and diameters in selected regions of Mars

NASA Astrophysics Data System (ADS)

Hsu, Hsin-Jen

2013-03-01

Impact craters are common geomorphological features on Mars. The density of craters is different among various regions. Higher crater density means older terrain. Craters can be divided into two types by the interior morphology: simple and complex. The cavity of Simple craters is bowl-shape, and complex craters display various interior features, such as central peaks. The depth/diameter ratio (d/D) of simple craters is larger than that of complex craters. The transition diameter from simple to complex morphologies ranges between 5 and 10 km, and is commonly cited to be about 7 km in the equatorial regions and 6 km near the poles, but the exact value also could vary with terrain type. In this research, seven regions, Amazonis Planitia, Arabia Terra, Chryse Planitia, Hesperia Planum, Isidis Planitia, Solis/Syria/Sinai Planum, and Terra Sirenum, were selected to investigate the onset diameter of complex craters and the relationship of crater diameter and depth in these regions on Mars in order to understand how the geology affects crater d/D. The analysis revealed that the slopes of the d/D relations are different, and these are linked to the surface material in different regions. The onset diameters in young volcanic regions with stronger material are slightly higher than older volcanic regions, and much higher than that of volatile regions. The research proves the different geological units can affect the morphology and morphometry of craters.

Highly uniform residual layers for arrays of 3D nanoimprinted cavities in Fabry-Pérot-filter-array-based nanospectrometers

NASA Astrophysics Data System (ADS)

Memon, Imran; Shen, Yannan; Khan, Abdullah; Woidt, Carsten; Hillmer, Hartmut

2016-04-01

Miniaturized optical spectrometers can be implemented by an array of Fabry-Pérot (FP) filters. FP filters are composed of two highly reflecting parallel mirrors and a resonance cavity. Each filter transmits a small spectral band (filter line) depending on its individual cavity height. The optical nanospectrometer, a miniaturized FP-based spectrometer, implements 3D NanoImprint technology for the fabrication of multiple FP filter cavities in a single process step. However, it is challenging to avoid the dependency of residual layer (RL) thickness on the shape of the printed patterns in NanoImprint. Since in a nanospectrometer the filter cavities vary in height between neighboring FP filters and, thus, the volume of each cavity varies causing that the RL varies slightly or noticeably between different filters. This is one of the few disadvantages of NanoImprint using soft templates such as substrate conformal imprint lithography which is used in this paper. The advantages of large area soft templates can be revealed substantially if the problem of laterally inhomogeneous RLs can be avoided or reduced considerably. In the case of the nanospectrometer, non-uniform RLs lead to random variations in the designed cavity heights resulting in the shift of desired filter lines. To achieve highly uniform RLs, we report a volume-equalized template design with the lateral distribution of 64 different cavity heights into several units with each unit comprising four cavity heights. The average volume of each unit is kept constant to obtain uniform filling of imprint material per unit area. The imprint results, based on the volume-equalized template, demonstrate highly uniform RLs of 110 nm thickness.

Syringe injectable electronics

PubMed Central

Hong, Guosong; Zhou, Tao; Jin, Lihua; Duvvuri, Madhavi; Jiang, Zhe; Kruskal, Peter; Xie, Chong; Suo, Zhigang; Fang, Ying; Lieber, Charles M.

2015-01-01

Seamless and minimally-invasive three-dimensional (3D) interpenetration of electronics within artificial or natural structures could allow for continuous monitoring and manipulation of their properties. Flexible electronics provide a means for conforming electronics to non-planar surfaces, yet targeted delivery of flexible electronics to internal regions remains difficult. Here, we overcome this challenge by demonstrating syringe injection and subsequent unfolding of submicrometer-thick, centimeter-scale macroporous mesh electronics through needles with a diameter as small as 100 micrometers. Our results show that electronic components can be injected into man-made and biological cavities, as well as dense gels and tissue, with > 90% device yield. We demonstrate several applications of syringe injectable electronics as a general approach for interpenetrating flexible electronics with 3D structures, including (i) monitoring of internal mechanical strains in polymer cavities, (ii) tight integration and low chronic immunoreactivity with several distinct regions of the brain, and (iii) in vivo multiplexed neural recording. Moreover, syringe injection enables delivery of flexible electronics through a rigid shell, delivery of large volume flexible electronics that can fill internal cavities and co-injection of electronics with other materials into host structures, opening up unique applications for flexible electronics. PMID:26053995

Syringe-injectable electronics.

PubMed

Liu, Jia; Fu, Tian-Ming; Cheng, Zengguang; Hong, Guosong; Zhou, Tao; Jin, Lihua; Duvvuri, Madhavi; Jiang, Zhe; Kruskal, Peter; Xie, Chong; Suo, Zhigang; Fang, Ying; Lieber, Charles M

2015-07-01

Seamless and minimally invasive three-dimensional interpenetration of electronics within artificial or natural structures could allow for continuous monitoring and manipulation of their properties. Flexible electronics provide a means for conforming electronics to non-planar surfaces, yet targeted delivery of flexible electronics to internal regions remains difficult. Here, we overcome this challenge by demonstrating the syringe injection (and subsequent unfolding) of sub-micrometre-thick, centimetre-scale macroporous mesh electronics through needles with a diameter as small as 100 μm. Our results show that electronic components can be injected into man-made and biological cavities, as well as dense gels and tissue, with >90% device yield. We demonstrate several applications of syringe-injectable electronics as a general approach for interpenetrating flexible electronics with three-dimensional structures, including (1) monitoring internal mechanical strains in polymer cavities, (2) tight integration and low chronic immunoreactivity with several distinct regions of the brain, and (3) in vivo multiplexed neural recording. Moreover, syringe injection enables the delivery of flexible electronics through a rigid shell, the delivery of large-volume flexible electronics that can fill internal cavities, and co-injection of electronics with other materials into host structures, opening up unique applications for flexible electronics.

Syringe-injectable electronics

NASA Astrophysics Data System (ADS)

Liu, Jia; Fu, Tian-Ming; Cheng, Zengguang; Hong, Guosong; Zhou, Tao; Jin, Lihua; Duvvuri, Madhavi; Jiang, Zhe; Kruskal, Peter; Xie, Chong; Suo, Zhigang; Fang, Ying; Lieber, Charles M.

2015-07-01

Seamless and minimally invasive three-dimensional interpenetration of electronics within artificial or natural structures could allow for continuous monitoring and manipulation of their properties. Flexible electronics provide a means for conforming electronics to non-planar surfaces, yet targeted delivery of flexible electronics to internal regions remains difficult. Here, we overcome this challenge by demonstrating the syringe injection (and subsequent unfolding) of sub-micrometre-thick, centimetre-scale macroporous mesh electronics through needles with a diameter as small as 100 μm. Our results show that electronic components can be injected into man-made and biological cavities, as well as dense gels and tissue, with >90% device yield. We demonstrate several applications of syringe-injectable electronics as a general approach for interpenetrating flexible electronics with three-dimensional structures, including (1) monitoring internal mechanical strains in polymer cavities, (2) tight integration and low chronic immunoreactivity with several distinct regions of the brain, and (3) in vivo multiplexed neural recording. Moreover, syringe injection enables the delivery of flexible electronics through a rigid shell, the delivery of large-volume flexible electronics that can fill internal cavities, and co-injection of electronics with other materials into host structures, opening up unique applications for flexible electronics.

Deviations from plane-wave Mie scattering and precise retrieval of refractive index for a single spherical particle in an optical cavity.

PubMed

Mason, Bernard J; Walker, Jim S; Reid, Jonathan P; Orr-Ewing, Andrew J

2014-03-20

The extinction cross-sections of individual, optically confined aerosol particles with radii of a micrometer or less can, in principle, be measured using cavity ring-down spectroscopy (CRDS). However, when the particle radius is comparable in magnitude to the wavelength of light stored in a high-finesse cavity, the phenomenological cross-section retrieved from a CRDS experiment depends on the location of the particle in the intracavity standing wave and differs from the Mie scattering cross-section for plane-wave irradiation. Using an evaporating 1,2,6-hexanetriol particle of initial radius ∼1.75 μm confined within the 4.5 μm diameter core of a Bessel beam, we demonstrate that the scatter in the retrieved extinction efficiency of a single particle is determined by its lateral motion, which spans a few wavelengths of the intracavity standing wave used for CRDS measurements. Fits of experimental measurements to Mie calculations, modified to account for the intracavity standing wave, allow precise retrieval of the refractive index of 1,2,6-hexanetriol particles (with relative humidity, RH < 10%) of 1.47824 ± 0.00072.

Static Performance of a Fixed-Geometry Exhaust Nozzle Incorporating Porous Cavities for Shock-Boundary Layer Interaction Control

NASA Technical Reports Server (NTRS)

Asbury, Scott C.; Hunter, Craig A.

1999-01-01

An investigation was conducted in the model preparation area of the Langley 16-Foot Transonic Tunnel to determine the internal performance of a fixed-geometry exhaust nozzle incorporating porous cavities for shock-boundary layer interaction control. Testing was conducted at static conditions using a sub-scale nozzle model with one baseline and 27 porous configurations. For the porous configurations, the effects of percent open porosity, hole diameter, and cavity depth were determined. All tests were conducted with no external flow at nozzle pressure ratios from 1.25 to approximately 9.50. Results indicate that baseline nozzle performance was dominated by unstable, shock-induced, boundary-layer separation at over-expanded conditions. Porous configurations were capable of controlling off-design separation in the nozzle by either alleviating separation or encouraging stable separation of the exhaust flow. The ability of the porous nozzle concept to alternately alleviate separation or encourage stable separation of exhaust flow through shock-boundary layer interaction control offers tremendous off-design performance benefits for fixed-geometry nozzle installations. In addition, the ability to encourage separation on one divergent flap while alleviating it on the other makes it possible to generate thrust vectoring using a fixed-geometry nozzle.

Electromagnetic microforging apparatus for low-cost fabrication of molds for microlens arrays

NASA Astrophysics Data System (ADS)

Pribošek, Jaka; Diaci, Janez

2015-06-01

This study addresses the problem of low-cost microlens fabrication and outlines the development of a novel microforging apparatus for microlens mold fabrication. The apparatus consists of an electromagnetic impact tool which strikes a piston with a hardened steel ball into a workpiece. The impact creates a spherical indentation which serves as a lens cavity. The microforging apparatus is controlled by a microprocessor control unit communicating with a personal computer and enables on-the-fly variation of electromagnetic excitation to control the microforging process. We studied the effects of process parameters on the diameter of the fabricated lens cavities inspected by a custom automatic image processing algorithm. Different microforging regimes are analyzed and discussed. The surface quality of fabricated cavities has been inspected by confocal microscopy and the influence of fill factor on sphericity error has been studied. The proposed microforging method enables the fabrication of molds with 100% fill factor, surface roughness as low as Ra 0.15 µm and sphericity error lower than 0.5 µm. The fabricated microlens arrays exhibit nearly diffraction-limited performance, offering a wide range of possible applications. We believe this study provides access to microoptical technology for smaller optical and computer vision laboratories.

Femtosecond laser for cavity preparation in enamel and dentin: ablation efficiency related factors.

PubMed

Chen, H; Li, H; Sun, Yc; Wang, Y; Lü, Pj

2016-02-11

To study the effects of laser fluence (laser energy density), scanning line spacing and ablation depth on the efficiency of a femtosecond laser for three-dimensional ablation of enamel and dentin. A diode-pumped, thin-disk femtosecond laser (wavelength 1025 nm, pulse width 400 fs) was used for the ablation of enamel and dentin. The laser spot was guided in a series of overlapping parallel lines on enamel and dentin surfaces to form a three-dimensional cavity. The depth and volume of the ablated cavity was then measured under a 3D measurement microscope to determine the ablation efficiency. Different values of fluence, scanning line spacing and ablation depth were used to assess the effects of each variable on ablation efficiency. Ablation efficiencies for enamel and dentin were maximized at different laser fluences and number of scanning lines and decreased with increases in laser fluence or with increases in scanning line spacing beyond spot diameter or with increases in ablation depth. Laser fluence, scanning line spacing and ablation depth all significantly affected femtosecond laser ablation efficiency. Use of a reasonable control for each of these parameters will improve future clinical application.

Oxidation Microstructure Studies of Reinforced Carbon/Carbon

NASA Technical Reports Server (NTRS)

Jacobson, Nathan S.; Curry, Donald M.

2006-01-01

Laboratory oxidation studies of reinforced carbon/carbon (RCC) are discussed with particular emphasis on the resulting microstructures. This study involves laboratory furnace (500-1500 C deg) and arc-jet exposures (1538 C deg) on various forms of RCC. RCC without oxidation protection oxidized at 800 and 1100 C deg exhibits pointed and reduced diameter fibers, due to preferential attack along the fiber edges. RCC with a SiC conversion coating exhibits limited attack of the carbon substrate at 500, 700 and 1500 C deg. However samples oxidized at 900, 1100, and 1300 C deg show small oxidation cavities at the SiC/carbon interface below through-thickness cracks in the SiC coating. These cavities have rough edges with denuded fibers and can be easily distinguished from cavities created in processing. Arc-jet tests at 1538 C deg show limited oxidation attack when the SiC coating and glass sealants are intact. When the SiC/sealant protection system is damaged, attack is extensive and proceeds through matrix cracks, creating denuded fibers on the edges of the cracks. Even at 1538 C deg, where diffusion control dominates, attack is non-uniform with fiber edges oxidizing in preference to the bulk fiber and matrix.

Aperture averaging in strong oceanic turbulence

NASA Astrophysics Data System (ADS)

Gökçe, Muhsin Caner; Baykal, Yahya

2018-04-01

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

Recent Progress on High-Current SRF Cavities at Jlab

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

Robert Rimmer, William Clemens, James Henry, Peter Kneisel, Kurt Macha, Frank Marhauser, Larry Turlington, Haipeng Wang, Daniel Forehand

2010-05-01

JLab has designed and fabricated several prototype SRF cavities with cell shapes optimized for high current beams and with strong damping of unwanted higher order modes. We report on the latest test results of these cavities and on developments of concepts for new variants optimized for particular applications such as light sources and high-power proton accelerators, including betas less than one. We also report on progress towards a first beam test of this design in the recirculation loop of the JLab ERL based FEL. With growing interest worldwide in applications of SRF for high-average power electron and hadron machines, amore » practical test of these concepts is highly desirable. We plan to package two prototype cavities in a de-mountable cryomodule for temporary installation into the JLab FEL for testing with RF and beam. This will allow verification of all critical design and operational parameters paving the way to a full-scale prototype cryomodule.« less

Cavity enhanced eigenmode multiplexing for volume holographic data storage

NASA Astrophysics Data System (ADS)

Miller, Bo E.; Takashima, Yuzuru

2017-08-01

Previously, we proposed and experimentally demonstrated enhanced recording speeds by using a resonant optical cavity to semi-passively increase the reference beam power while recording image bearing holograms. In addition to enhancing the reference beam power the cavity supports the orthogonal reference beam families of its eigenmodes, which can be used as a degree of freedom to multiplex data pages and increase storage densities for volume Holographic Data Storage Systems (HDSS). While keeping the increased recording speed of a cavity enhanced reference arm, image bearing holograms are multiplexed by orthogonal phase code multiplexing via Hermite-Gaussian eigenmodes in a Fe:LiNbO3 medium with a 532 nm laser at two Bragg angles for expedited recording of four multiplexed holograms. We experimentally confirmed write rates are enhanced by an average factor of 1.1, and page crosstalk is about 2.5%. This hybrid multiplexing opens up a pathway to increase storage density while minimizing modifications to current angular multiplexing HDSS.

Design study of an S-band RF cavity of a dual-energy electron LINAC for the CIS

NASA Astrophysics Data System (ADS)

Lee, Byeong-No; Park, Hyungdal; Song, Ki-baek; Li, Yonggui; Lee, Byung Cheol; Cha, Sung-su; Lee, Jong-Chul; Shin, Seung-Wook; Chai, Jong-seo

2014-01-01

The design of a resonance frequency (RF) cavity for the dual-energy S-band electron linear accelerator (LINAC) has been carried out for the cargo inspection system (CIS). This Standing-wave-type RF cavity is operated at a frequency under the 2856-MHz resonance frequency and generates electron beams of 9 MeV (high mode) and 6 MeV (low mode). The electrons are accelerated from the initial energy of the electron gun to the target energy (9 or 6 MeV) inside the RF cavity by using the RF power transmitted from a 5.5-MW-class klystron. Then, electron beams with a 1-kW average power (both high mode and low mode) bombard an X-ray target a 2-mm spot size. The proposed accelerating gradient was 13 MV/m, and the designed Q value was about 7100. On going research on 15-MeV non-destructive inspections for military or other applications is presented.

Numerical modeling of Stokes flows over a superhydrophobic surface containing gas bubbles

NASA Astrophysics Data System (ADS)

Ageev, A. I.; Golubkina, I. V.; Osiptsov, A. N.

2017-10-01

This paper continues the numerical modeling of Stokes flows near cavities of a superhydrophobic surface, occupied by gas bubbles, based on the Boundary Element Method (BEM). The aim of the present study is to estimate the friction reduction (pressure drop) in a microchannel with a bottom superhydrophobic surface, the texture of which is formed by a periodic system of striped rectangular microcavities containing compressible gas bubbles. The model proposed takes into account the streamwise variation of the bubble shift into the cavities, caused by the longitudinal pressure gradient in the channel flow. The solution for the macroscopic (averaged) flow in the microchannel, constructed using an effective slip boundary condition on the superhydrophobic bottom wall, is matched with the solution of the Stokes problem at the microscale of a single cavity containing a gas bubble. The 2D Stokes problems of fluid flow over single cavities containing curved phase interfaces with the condition of zero shear stress are reduced to the boundary integral equations which are solved using the BEM method.

Unsteady Analysis of Turbine Main Flow Coupled with Secondary Air Flow

NASA Technical Reports Server (NTRS)

Hah, Chunill

2006-01-01

Two numerical approaches are used to model the interaction between the turbine main gas flow and the wheelspace cavity seal flow. The 3-D, unsteady Reynolds-averaged Navier-Stokes equations are solved with a CFD code based on a structured grid to study the interaction between the turbine main gas flow and the wheelspace cavity seal flow. A CFD code based on an unstructured grid is used to solve detailed flow feature in the cavity seal which has a complex geometry. The numerical results confirm various observations from earlier experimental studies under similar flow conditions. When the flow rate through the rim cavity seal is increased, the ingestion of the main turbine flow into the rim seal area decreases drastically. However, a small amount of main gas flow is ingested to the rim seal area even with very high level of seal flow rate. This is due to the complex nature of 3-D, unsteady flow interaction near the hub of the turbine stage.

Mirror Birefringence in a Fabry-Perot Cavity and the Detection of Vacuum Birefringence in a Magnetic Field

NASA Technical Reports Server (NTRS)

Chui, T. C. P.; Shao, M.; Redding, D.; Gursel, Y.; Boden, A.

1995-01-01

We discuss the effect of mirror birefringence in two optical schemes designed to detect the quantum-electrodynamics (QED) predictions of vacuum birefringence under the influence of a strong magnetic field, B. Both schemes make use of a high finesse Fabry-Perot cavity (F-P) to increase the average path length of the light in the magnetic field. The first scheme, which we called the frequency scheme, is based on measurement of the beat frequency of two orthogonal polarized laser beams in the cavity. We show that mirror birefringence contributes to the detection uncertainties in first order, resulting in a high susceptibility to small thermal disturbances. We estimate that an unreasonably high thermal stability of 10-9 K is required to resolve the effect to 0.1%. In the second scheme, which we called the polarization rotation scheme, laser polarized at 45 relative to the B field is injected into the cavity.

Optical feedback cavity-enhanced absorption spectroscopy with a 3.24 μm interband cascade laser

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

Manfred, K. M.; Ritchie, G. A. D.; Lang, N.

2015-06-01

The development of interband cascade lasers (ICLs) has made the strong C-H transitions in the 3 μm spectral region increasingly accessible. We present the demonstration of a single mode distributed feedback ICL coupled to a V-shaped optical cavity in an optical feedback cavity-enhanced absorption spectroscopy (OF-CEAS) experiment. We achieved a minimum detectable absorption coefficient, α{sub min}, of (7.1±0.2)×10{sup −8} cm{sup −1} for a spectrum of CH{sub 4} at 3.24 μm with a two second acquisition time (100 scans averaged). This corresponds to a detection limit of 3 ppb CH{sub 4} at atmospheric pressure, which is comparable to previously reported OF-CEAS instruments with diodemore » lasers or quantum cascade lasers. The ability to frequency lock an ICL source in the important 3 μm region to an optical cavity holds great promise for future spectroscopic applications.« less

Numerical studies of the fluid and optical fields associated with complex cavity flows

NASA Technical Reports Server (NTRS)

Atwood, Christopher A.

1992-01-01

Numerical solutions for the flowfield about several cavity configurations have been computed using the Reynolds averaged Navier-Stokes equations. Comparisons between numerical and experimental results are made in two dimensions for free shear layers and a rectangular cavity, and in three dimensions for the transonic aero-window problem of the Stratospheric Observatory for Infrared Astronomy (SOFIA). Results show that dominant acoustic frequencies and magnitudes of the self excited resonant cavity flows compare well with the experiment. In addition, solution sensitivity to artificial dissipation and grid resolution levels are determined. Optical path distortion due to the flow field is modelled geometrically and is found to match the experiment. The fluid field was computed using a diagonalized scheme within an overset mesh framework. An existing code, OVERFLOW, was utilized with the additions of characteristic boundary condition and output routines required for reduction of the unsteady data. The newly developed code is directly applicable to a generalized three dimensional structured grid zone. Details are provided in a paper included in Appendix A.

High temperature electrically conducting ceramic heating element and control system

NASA Technical Reports Server (NTRS)

Halbach, C. R.; Page, R. J.

1975-01-01

Improvements were made in both electrode technology and ceramic conductor quality to increase significantly the lifetime and thermal cycling capability of electrically conducting ceramic heater elements. These elements were operated in vacuum, inert and reducing environments as well as oxidizing atmospheres adding to the versatility of the conducting ceramic as an ohmic heater. Using stabilized zirconia conducting ceramic heater elements, a furnace was fabricated and demonstrated to have excellent thermal response and cycling capability. The furnace was used to melt platinum-20% rhodium alloy (melting point 1904 C) with an isothermal ceramic heating element having a nominal working cavity size of 2.5 cm diameter by 10.0 cm long. The furnace was operated to 1940 C with the isothermal ceramic heating element. The same furnace structure was fitted with a pair of main heater elements to provide axial gradient temperature control over a working cavity length of 17.8 cm.

Comparison of advanced engines for parabolic dish solar thermal power plants

NASA Technical Reports Server (NTRS)

Fujita, T.; Bowyer, J. M.; Gajanana, B. C.

1980-01-01

A paraboloidal dish solar thermal power plant produces electrical energy by a two-step conversion process. The collector subsystem is composed of a two-axis tracking paraboloidal concentrator and a cavity receiver. The concentrator focuses intercepted sunlight (direct, normal insolation) into a cavity receiver whose aperture encircles the focal point of the concentrator. At the internal wall of the receiver the electromagnetic radiation is converted to thermal energy. A heat engine/generator assembly then converts the thermal energy captured by the receiver to electricity. Developmental activity has been concentrated on small power modules which employ 11- to 12-meter diameter dishes to generate nominal power levels of approximately 20 kWe. A comparison of advanced heat engines for the dish power module is presented in terms of the performance potential of each engine with its requirements for advanced technology development. Three advanced engine possibilities are the Brayton (gas turbine), Brayton/Rankine combined cycle, and Stirling engines.

Nuclear reactor vessel fuel thermal insulating barrier

DOEpatents

Keegan, C. Patrick; Scobel, James H.; Wright, Richard F.

2013-03-19

The reactor vessel of a nuclear reactor installation which is suspended from the cold leg nozzles in a reactor cavity is provided with a lower thermal insulating barrier spaced from the reactor vessel that has a hemispherical lower section that increases in volume from the center line of the reactor to the outer extent of the diameter of the thermal insulating barrier and smoothly transitions up the side walls of the vessel. The space between the thermal insulating harrier and the reactor vessel forms a chamber which can be flooded with cooling water through passive valving to directly cool the reactor vessel in the event of a severe accident. The passive inlet valve for the cooling water includes a buoyant door that is normally maintained sealed under its own weight and floats open when the cavity is Hooded. Passively opening steam vents are also provided.

Wear model simulating clinical abrasion on composite filling materials.

PubMed

Johnsen, Gaute Floer; Taxt-Lamolle, Sébastien F; Haugen, Håvard J

2011-01-01

The aim of this study was to establish a wear model for testing composite filling materials with abrasion properties closer to a clinical situation. In addition, the model was used to evaluate the effect of filler volume and particle size on surface roughness and wear resistance. Each incisor tooth was prepared with nine identical standardized cavities with respect to depth, diameter, and angle. Generic composite of 3 different filler volumes and 3 different particle sizes held together with the same resin were randomly filled in respective cavities. A multidirectional wet-grinder with molar cusps as antagonist wore the surface of the incisors containing the composite fillings in a bath of human saliva at a constant temperature of 37°C. The present study suggests that the most wear resistant filling materials should consist of medium filling content (75%) and that particles size is not as critical as earlier reported.

Acoustic Liner Drag: A Parametric Study of Conventional Configurations

NASA Technical Reports Server (NTRS)

Howerton, Brian M.; Jones, Michael G.

2015-01-01

Interest in the characterization of the aerodynamic drag performance of acoustic liners has increased in the past several years. This paper details experiments in NASA Langley's Grazing Flow Impedance Tube to quantify the relative drag of several conventional perforate-over-honeycomb liner configurations. For a fixed porosity, facesheet hole diameter and cavity depth are varied to study the effect of each. These configurations are selected to span the range of conventional liner geometries used in commercial aircraft engines. Detailed static pressure and acoustic measurements are made for grazing flows up to M=0.5 at 140 dB SPL for tones between 400 and 2800 Hz. These measurements are used to calculate a resistance factor (?) for each configuration. Analysis shows a correlation between perforate hole size and the resistance factor but cavity depth seems to have little influence. Acoustic effects on liner drag are observed to be limited to the lower Mach numbers included in this investigation.

Fabrication and room temperature operation of semiconductor nano-ring lasers using a general applicable membrane transfer method

NASA Astrophysics Data System (ADS)

Fan, Fan; Yu, Yueyang; Amiri, Seyed Ebrahim Hashemi; Quandt, David; Bimberg, Dieter; Ning, C. Z.

2017-04-01

Semiconductor nanolasers are potentially important for many applications. Their design and fabrication are still in the early stage of research and face many challenges. In this paper, we demonstrate a generally applicable membrane transfer method to release and transfer a strain-balanced InGaAs quantum-well nanomembrane of 260 nm in thickness onto various substrates with a high yield. As an initial device demonstration, nano-ring lasers of 1.5 μm in outer diameter and 500 nm in radial thickness are fabricated on MgF2 substrates. Room temperature single mode operation is achieved under optical pumping with a cavity volume of only 0.43λ03 (λ0 in vacuum). Our nano-membrane based approach represents an advantageous alternative to other design and fabrication approaches and could lead to integration of nanolasers on silicon substrates or with metallic cavity.

Study of parametric instability in gravitational wave detectors with silicon test masses

NASA Astrophysics Data System (ADS)

Zhang, Jue; Zhao, Chunnong; Ju, Li; Blair, David

2017-03-01

Parametric instability is an intrinsic risk in high power laser interferometer gravitational wave detectors, in which the optical cavity modes interact with the acoustic modes of the mirrors, leading to exponential growth of the acoustic vibration. In this paper, we investigate the potential parametric instability for a proposed next generation gravitational wave detector, the LIGO Voyager blue design, with cooled silicon test masses of size 45 cm in diameter and 55 cm in thickness. It is shown that there would be about two unstable modes per test mass at an arm cavity power of 3 MW, with the highest parametric gain of  ∼76. While this is less than the predicted number of unstable modes for Advanced LIGO (∼40 modes with max gain of  ∼32 at the designed operating power of 830 kW), the importance of developing suitable instability suppression schemes is emphasized.

650-nJ pulses from a cavity-dumped Yb:fiber-pumped ultrafast optical parametric oscillator

NASA Astrophysics Data System (ADS)

Lamour, Tobias P.; Reid, Derryck T.

2011-08-01

Sub-250-fs pulses with energies of up to 650 nJ and peak powers up to 2.07 MW were generated from a cavity-dumped optical parametric oscillator, synchronously-pumped at 15.3 MHz with sub-400-fs pulses from an Yb:fiber laser. The average beam quality factor of the dumped output was M2 ~1.2 and the total relative-intensity noise was 8 mdBc, making the system a promising candidate for ultrafast laser inscription of infrared materials.